In the field of modern electronic manufacturing, high-density interconnect (HDI) technology has become a key factor driving the development of electronic products towards miniaturization and higher performance. The core of HDI technology lies in its unique stacked design, which not only greatly improves the space utilization of circuit boards, but also significantly enhances electrical performance and signal integrity.
The stacked-up design of HDI PCB allows multiple circuit layers to be connected through precisely controlled blind and buried holes, which have much smaller diameters than traditional PCB through holes. This connect method not only reduces the volume of the circuit board, but also increases the trace density, so that more and more electronic components can be integrated into a limited space.
In addition, the stacked design of HDI also optimizes the path of signal transmission. Due to the shorter signal transmission distance and the avoidance of unnecessary bends and corners, signal delay and loss have been effectively controlled. This is crucial for high-speed electronic devices as they require fast and accurate processing of large amounts of data.
In the manufacturing process, the stacked design of HDI also brings many challenges. In order to achieve high-precision buried/blind hole machining and interlayer registration, manufacturers must adopt advanced laser drilling technology and precision etching equipment. At the same time, in order to ensure the reliability and stability of the circuit board, strictly testing and verification of materials and processes are also required.
So what are the HDI stacking structures? This article will take you into an incredibly wonderful worldâŚ
1+N+1 Stack Up
1. Here, “1” (including the following “1”) refers to the layer number of blind holes (Blind via/ micro-via). And one layer blind hole always called a first step.
N refers to the number of non-blind hole layers in the inner layer (not necessarily just the Core), such as 4 layers, combined with 1, which is a 1-4-1 stacked structure. At the same time, if the N-layer is laminated, then this 1-4-1 laminated structure is called first-step-second-lamination (1 times N-layer lamination + 1 times outer layer lamination = 2 times, so it is called second lamination).
Does it make sense? If you have any questions, feel freely to leave a message or contact us at sales@bestpcbs.com.
2. Typical 1+N+1 stack-up
This kind of stack up shown as following is made by laminate a CCL sheet into 4 layers firstly and then laminate into 6 layers. It is also a common product on the market at present.
2+N+2 Stack Up
1. Here, 2 and N have the same meaning as 1-N-1, it will not be repeated again.
2. Typical 2+N+2 stack-up:
There are two types of second-step stack-up: stacked via and staggered via, which have different levels in difficulty, cost, and process.
2.1 Staggered via
Here is a stack-up of a staggered vias, this kind of structure has relatively lower cost and good reliability.
2.2 Stacked via
From the stack-up, it is not difficult to see the difference with staggered vias. This stacking structure requires drilling another blind hole on top of the blind hole, and the previous blind hole needs to be filled with copper or a material that can conduct electricity and resist laser drilling. This gives a rise to another technology, we will introduce in the later HDI electroplating process.
N+N Stack Up
1. Here, the âNâ and the âNâ in 1-N-1 or 2-N-2 have the same meaning.
2. Typical N+N stack-up
Although N+N stacking may not have blind holes, due to the special process and strict registration requirements, the actual production difficulty is no less than HDI technology.
Anylayer for Any Interconnection
1. The Any-layer means it can conduct at any layer, so how to achieve it?
2. Typical stack-up of Any-layer
From the section of the PCB as following, it can also be seen that how to stack each layer together to form a straight line is also a challenge, so the Anylayer process good or not depends on the registration ability of the manufacturer. Of course, the circuit uses this technology will definitely be very dense and fine, which gives rise to an advanced PCB process called MSAP.
So in summary, despite facing many challenges, HDI’s stacked design has become a key part of high-end electronic products. From smartphones to wearable devices, from high-performance computers to advanced communication systems, HDI technology is playing a crucial role. With the continuous advancement of technology and the increasing demand from consumers, we have reason to believe that HDI’s stacking will continue to lead the innovation trend in the field of electronic manufacturing.
First Article Inspection (FAI) refers to the inspection of the first or several products produced at the beginning of production (such as every day, every shift or the beginning of each production batch) to confirm whether the production conditions (such as equipment, process, materials, environment, etc.) meet the technical and quality requirements. This is a preventive quality control measure designed to prevent batch defects by early detection of possible problems in the production process.
The first inspection usually includes the following steps:
1. Preparation stage: clear inspection standards, inspection methods, inspection tools and equipment, and prepare relevant inspection records and forms.
2. Production preparation: Check whether the production equipment is in good condition, whether the process parameters are set correctly, and whether the raw materials or parts meet the requirements.
3. Production of the first piece: Start production according to the production plan, and make the first piece or the first few products as the first piece.
4. First inspection: Detailed inspection of the first product, including inspection of appearance, size, performance, function, etc., to ensure that the product meets the design requirements and quality standards.
5. Result judgment: According to the inspection results, determine whether the first piece is qualified. If qualified, mass production can continue; If it is not qualified, it is necessary to analyze the cause, adjust the production conditions, and re-make the first part for inspection until it is qualified.
6. Record and feedback: Record the results of the first inspection, and feedback the results to relevant departments and personnel in order to take timely measures to solve the problem.
Why Need to Perform a FAI?
â The first inspection in the production process is mainly to prevent the product from a batch of out-of-quality, repair, scrap. It is a means to control the product production process in advance, is an important method of product process quality control. It is an effective and essential method for enterprises to ensure product quality and improve economic efficiency.
â The first inspection is to find the factors affecting product quality in the production process as early as possible to prevent bad batch or scrap.
â The first piece can be entered into formal production after passing the inspection, mainly to prevent the occurrence of batch unqualified products.
â Long-term practical experience has proved that the first inspection system is an effective measure to detect problems as early as possible and prevent products from being scrapped in batches. Through the first piece inspection, it can be found that systematic causes such as severe wear of the fixture or installation positioning errors, poor accuracy of the measuring instrument, incorrect reading of the drawing, feeding or formulation errors exist, so that corrective or improvement measures can be taken to prevent the occurrence of batch nonconforming products.
What Happens if a Component Passes or Fails the FAI?
If a component passes the FAI, full-scale production can proceed to next stage. Because knowing that the process yields parts that match design criteria. Meanwhile, it builds confidence and reduces the likelihood of future issues.
If a component fails, corrective action is necessary. This means process, parameters, or used tools, materials are not suitable or with poor quality. After modifications, a new FAI may be needed to verify the adjustments work as expected.
When Should a First Article Inspection Occur?
Knowing the right time for a 1st article inspection is crucial to avoid production issues and ensure highest quality. But when exactly should this process take place? Let me tell you:
Initial Production Run
Picture this – youâre ready to kick off a new product line or start manufacturing a brand-new part. This is the perfect time for an FAI. Performing it at this stage helps catch any potential problems right from the start. Itâs like giving your process a test drive before you commit to full-scale production.
Process Changes
Changes are inevitable in manufacturing. Maybe thereâs an upgrade to your equipment or youâre switching up the method used to produce parts. Any significant change to the process means itâs time for a new FAI. Why? Because even small adjustments can lead to unexpected differences in the final product.
Supplier Changes
If you decide to switch to a different supplier for critical components, you shouldnât skip an FAI. Even if the new supplier promises the same specifications, differences in materials or production methods can impact the final product. An FAI here ensures that what youâre getting from the new supplier matches your quality expectations.
Design Modifications
Tweaking a design might seem minor, but it can change everything from part fit to performance. Any time thereâs an update or redesign, running an FAI confirms that the modified product still aligns with the original quality standards.
What is the Difference Between PPAP and First Article Inspection?
You might hear the terms PPAP (Production Part Approval Process) and FAI thrown around in manufacturing discussions. While they share a goal of ensuring quality, they are different in their approach, scope, and where they are commonly used.
1. Industries and Common Use
FAI is used across various industries, and it especially popular in fields like aerospace and defense. Itâs typically a requirement when introducing a new part or process. PPAP, on the other hand, is most commonly linked to the automotive industry. Itâs a standard method required by major automotive manufacturers to ensure that their suppliers can consistently meet production quality standards.
2. Range and Detail
FAI is about confirming that one specific piece meets all the design and specification requirements. The process involves checking the dimensions, materials, and other key aspects to ensure everything matches up before moving forward with full-scale production.
PPAP, however, takes a broader approach. Instead of just focusing on one component, PPAP is like an in-depth audit of the entire production process. It includes elements like process flow diagrams, control plans, and even failure mode and effects analysis (FMEA). PPAP doesnât just ask, âDoes this part meet the specs?â but goes further to check if the entire production line can consistently produce parts that meet quality requirements over time. A PPAP file like as below:
3. Level of Documentation
FAI has its documentation, but itâs more straightforward. You get a detailed report of the inspected part, including dimensions and results from any tests performed. With PPAP, the documentation is more comprehensive and multi-layered. It often involves around 18 sheets, including a sample production run, process validation reports, and customer-specific requirements.
First Article Inspection in Best Technology
At Best Technology, we believe that FAI is more than a formalityâitâs a guarantee of reliability and quality. So, we pay more attention to the first article inspection, from every step, every operator, every report. We have a 1st article inspection tester in our factory, for each prototype, we can finish the FAI inspection quickly and effectively.
As an advanced PCB and PCBA manufacturer, we have more than 18 years experiences in this industry. We have served over 5000 customers with 98% satisfied comments. All of them are amazed with our one-stop service and quick delivery.
During the PCB board manufacturing, there is an important process called surface treatment. This is mainly used to protect the board surface from oxidation, corrosion, and good electricity. Gold plating, also is a popular surface finishing method, which commonly used in the industry. As a professional PCB fabricator, here Best Team would like to introduce some key points about gold plating that customers always pay more attention to. Letâs keep reading!
What is Gold Plating in PCB?
Firstly, letâs know what is a gold plating. Gold plating on PCBs refers to a layer of gold applied over specific areas of a circuit board. This gold coating is typically applied on the connectors, pads, and edge contacts of a PCB to improve electrical conductivity and provide better resistance against wear and oxidation. Gold plating protects these sensitive areas, which are critical for the performance and reliability of the PCB.
The principle of gold plating is to dissolve nickel and gold (commonly known as gold salt) in the chemical solution. And then the circuit board is immersed in the electroplating cylinder and the current is passed on the copper foil surface of the circuit board to generate nickel gold coating. Due to the electric nickel gold has good hardness, wear resistance, and not easy to oxidization, it is widely used in the electronics.
Does Gold Plating Process Use Real Gold?
âThe gold plating in PCB is not really pure gold, but a gold alloy (has gold and some other metals in it). â
In PCB manufacturing, gold-plating is usually not done using pure gold, but by compression and treatment of gold alloys. Such alloys often contain small amounts of metals such as silver, nickel, and copper to reduce costs and meet specific performance requirements.
The role of gold plating in PCB is mainly to enhance electrical conductivity and chemical stability. Gold has good electrical conductivity and oxidation resistance, which can provide stable signal transmission and reliable connections in electronic devices. In addition, gold does not discolor or corrode, making it an ideal material for electronic applications.
In general, there are two main gold-plating processes: electrolytic gold-plating and brush gold-plating. Electrolytic gold plating is the deposition of metal on the circuit board through chemical bath and electrolytic process, which has higher cost but better quality. Brush gold plating, by depositing metal particles onto a conductive substrate via electronic devices, is cheaper but of poorer quality.
Why Use Gold in PCB?
May somebody curious about why use gold in PCB? To make the PCB surface more beautiful? Let me tell you why.
1. Improve electrical conductivity
Metals such as gold have good electrical conductivity. Through gold plating, a metal conductive layer can be formed at the circuit connection of the PCB board, thus significantly improving the electrical conductivity of the circuit. This helps to reduce the resistance at the circuit connection, reduce signal loss.
2. Prevent oxidation and corrosion
The gold coating has excellent chemical stability and can resist oxidation and corrosion. This can protect the PCB board from the erosion of harmful substances in the external environment, such as humidity, salt spray, chemical gases, etc., thereby extending its service life.
3. Improve welding performance
Oxidized layer may be formed on the metal surface during welding, affecting welding quality. The gold coating can reduce the thickness of the surface oxide layer, thereby improving the reliability and robustness of the welding. In addition, gold plating can also provide better welding contact, reduce thermal stress during welding, and reduce the occurrence of welding defects.
4. Enhance the appearance
Gold plating can give the PCB surface metallic luster, improve the appearance texture and product grade, and increase the market competitiveness of the product. To be honest, gold appearance indeed gives a better appearance.
5. Meet specific needs
In some high-end electronic products, there are higher requirements for the electrical conductivity, corrosion resistance, welding performance and appearance texture of PCB boards. Gold plating, as an effective surface treatment technology, can meet these specific needs.
6. Meet welding quality challenges
With the improvement of integration of electronic products, IC feet are becoming more and more dense, and traditional vertical tin injection technology is difficult to meet the welding challenges of thin pads. Gold plating technology can provide better welding performance and reliability, and reduce the occurrence of welding quality problems such as virtual welding.
How Thick is Gold Plating on Circuit Boards?
The thickness of gold plating on PCBs depends on the type and application. Generally, PCB gold plating thickness ranges from 0.1-1.27um. For standard PCBs, a gold layer thickness of 0.03 to 0.05 microns is common, especially for immersion gold. However, thicker plating is applied for connectors or contacts exposed to frequent wear and tear, as these areas need more protection.
Hard gold, used for high-wear applications like edge connectors, typically has a greater thickness than immersion gold. The thickness is carefully controlled because too thin a layer might fail to provide effective protection, while an excessively thick layer could lead to wasted materials and unnecessary expense. The goal is to strike a balance that delivers durability without incurring excessive costs.
What is the Difference Between Immersion Gold and Hard Gold PCB?
Hard gold plating âis by electroplating, so that the gold particles are attached to the âPCB board, so it is also called electric gold. Because of its strong adhesion, hard gold plating is also called hard gold, which is often used for â memory bar â gold finger and other parts that need wear-resistant.
âImmersion gold â is through the â chemical reaction, the gold particles crystallization and attached to the PCB â pad, so it is also known as â soft gold. Due to the weak adhesion, the sinking gold is mainly used for the surface treatment of the pad, and the weldability is good. The difference between hard gold plating and immersion gold are including:
Color: Immersion gold is more yellow, while gold plating is more white.
Crystal structure: Immersion gold has a denser crystal structure.
Thickness: Immersion gold has a thicker layer of gold.
Wear resistance: Gold plating is harder and more resistant to wear and tear.
Solderability: Immersion gold is easier to solder.
Short circuits: Gold plating is more likely to cause short circuits.
Oxidation resistance: Immersion gold is less prone to oxidation.
Cost: Immersion gold is more expensive.
Deposition process: Gold plating uses an external electric current, while immersion gold is a chemical process.
Suitability: Gold plating is better for environments with high mechanical stress, while immersion gold is better for movable contacts.
PCB Applications of Gold Plating
Gold-plated PCBs are popular in industries where reliability and durability are essential. Some typical applications include:
Aerospace and Defense
Medical Devices
Telecommunications
Consumer Electronics
High power electronics
High current electronics
Low voltage digital logic electronics
As a PCB and PCBA manufacturer, we provide various surface treatment options for customers, including: ENIG, ENEPIG, OSP, HASL-LF, Immersion gold, hard gold (up to 50uââ). We offer customized PCB service tailored to customerâs requirements, we will try our best to meet the demands of surface treatment. Welcome to contact us if you have any questions.
PCB antennas are crucial in todayâs compact wireless devices. These antennas are directly integrated into the PCB board, providing an efficient way to transmit and receive signals. They have become more and more important in IoT devices, smartphones, and many other electronic products.
What is a PCB Antenna?
A PCB antenna is an antenna built directly onto the printed circuit board, often as a conductive trace or embedded component. By integrating it directly onto the PCB, the antenna becomes a seamless part of the overall design, eliminating the need for separate antennas. The design principle of PCB antenna is based on electromagnetic field theory. By arranging a specific metal conductor pattern on the PCB board, an effective electromagnetic radiation and receiving structure can be formed, so as to achieve the transmission and reception of wireless signals.
This antenna uses PCB as the medium, through the PCB process to achieve, no need to assemble the antenna separately, testing and use are very convenient. PCB antenna can be directly integrated on the circuit board, easy to touch and damage, and easy to assemble.
PCB Antenna Types
PCB antennas come in different types, each suited to specific applications and requirements. The most common types include:
Monopole Antennas
These antennas are simple, consisting of a single conductor. Theyâre straightforward to design and offer decent performance for applications with limited space. Monopole antennas are ideal for Bluetooth and Wi-Fi applications, where simplicity is needed without compromising basic functionality.
Dipole Antennas
Known for their balanced design, dipole antennas use two conductors, often resulting in improved radiation patterns. They are commonly used in environments where the antenna needs to work effectively in multiple directions. Dipole antennas are popular in high-frequency applications.
Inverted-F Antennas (IFA)
This type features a ground plane and a radiating element shaped like an âF.â IFAs are compact and provide a stable, omnidirectional pattern, making them suitable for Wi-Fi and cellular applications. The structure of IFA antennas helps achieve good efficiency even in confined spaces.
Patch Antennas
These antennas are flat and rectangular, making them excellent for devices with strict space limitations. Often used in GPS and RFID applications, patch antennas offer directional radiation patterns, allowing them to focus energy toward specific areas, enhancing range and strength.
Slot Antennas
Slot antennas consist of a slot cut out of a conductive surface, with electromagnetic fields radiating from the slot. They are typically more directional, so they are suitable for specific point-to-point applications or where the signal needs to be targeted.
What is the Frequency Range of a PCB Antenna?
The frequency range of a PCB antenna depends on the design and intended application. Most PCB antennas operate within common wireless communication bands, such as 2.4 GHz for Wi-Fi, Bluetooth, and other short-range communications. However, they can be designed for various ranges, including sub-1 GHz bands (for long-range IoT applications) and frequencies as high as 5 GHz for Wi-Fi 6 and other high-speed networks.
Higher frequencies typically require smaller antennas, which aligns well with compact devices but may also affect range. Low-frequency antennas, on the other hand, are larger but provide greater coverage and are less affected by obstacles.
PCB antenna’s Basic Formulas
1. Wavelength Calculation
The wavelength (Îť) of the signal is an essential parameter in designing antennas, especially for determining the length of a PCB trace antenna.
Where:
c = Speed of light (approximately 3Ă10^8m/s)
f = Frequency in Hz
For example, at 2.4 GHz (a common frequency for Wi-Fi and Bluetooth), the wavelength is around 12.5 cm.
2. Length of a Monopole Antenna
For a monopole antenna on a PCB, the length (L) of the antenna is typically set to one-quarter of the wavelength. This is known as a quarter-wave monopole antenna, which is commonly used in PCB designs.
This length provides a good balance of efficiency and compact size.
3. Length of a Dipole Antenna
A dipole antenna is usually designed to have a length of half the wavelength. The total length L for a dipole is:
Each “arm” of the dipole would then be a quarter-wavelength. This structure is well-suited for many applications due to its balanced design.
4. Inverted-F Antenna (IFA) Length Calculation
For an Inverted-F Antenna, the length of the main resonant arm is usually close to a quarter of the wavelength. This helps the IFA to maintain a compact form while still achieving effective performance:
Since IFAs often include a grounding element, they may be slightly shorter than traditional quarter-wave monopoles.
5. Impedance Matching
The impedance (Z) of the antenna needs to match the transmission line (typically 50 ohms) to maximize power transfer. For a basic dipole or monopole antenna, the impedance can be approximated with empirical formulas. For instance, a free-space dipole impedance is around 73 ohms, but this value changes on a PCB.
To achieve matching, adjustments can be made by changing the length or width of the antenna trace or by using matching networks with inductors or capacitors.
6. Resonant Frequency Calculation
The resonant frequency (f) of a PCB trace antenna depends on its physical length. Rearranging the wavelength formula allows you to solve for f if you know the length:
Where L would typically be one-quarter of the wavelength for a monopole or half for a dipole.
7. Effective Dielectric Constant Adjustments
PCB antennas are affected by the PCB materialâs dielectric constant (Ďľr). This changes the effective wavelength (Îť):
Using this adjusted wavelength improves accuracy in trace length calculations for PCB antennas, especially when working with substrates with a high dielectric constant.
8. Bandwidth Calculation
The bandwidth of a PCB antenna can be approximated using the Quality Factor (Q) of the antenna:
Where Q is influenced by factors such as antenna length, material, and layout. Lower Q values usually provide broader bandwidth, which can be achieved through specific design choices like wider traces or shorter antennas.
9. Gain Estimation
The gain of a PCB antenna depends on its radiation pattern and efficiency. Although gain is typically measured rather than calculated, some estimates can be made based on the type of antenna and its efficiency. For simple PCB antennas, a rough gain value might range from 0 dBi (isotropic) for omnidirectional designs to 3â5 dBi for directional designs.
Are PCB Antennas Directional?
PCB antennas can be directional or omnidirectional, depending on their type and design. Directional antennas focus the energy in a specific direction, which increases range in that direction while reducing it in others. Omnidirectional antennas, in contrast, distribute the signal evenly in all directions, which is beneficial for applications where the device orientation may vary.
Patch antennas and slot antennas are generally more directional, suitable for point-to-point communication or when a targeted signal path is needed. Monopole and dipole antennas, however, are typically omnidirectional, making them ideal for devices like smartphones and IoT gadgets, where a consistent signal is required from various angles.
The choice between directional and omnidirectional antennas should align with the specific needs of the application. For example, in a warehouse, an omnidirectional antenna might be preferred for broad coverage, while a directional antenna could be beneficial for a remote control application.
What Are the Applications of PCB Antenna?
PCB antennas are used in a wide range of applications, including:
Consumer Electronics: PCB antennas are essential in smartphones, tablets, and laptops for Wi-Fi, Bluetooth, and cellular connectivity.
IoT Devices: Many IoT devices use PCB antennas for wireless data transmission, making them integral in smart homes, agriculture, and industrial monitoring.
Automotive: In vehicles, PCB antennas enable GPS, remote keyless entry, and other connectivity features, enhancing both functionality and user experience.
Medical Devices: PCB antennas are used in medical equipment for wireless communication, which enables real-time monitoring and diagnostics.
Wearables: PCB antennas are commonly found in wearable tech like fitness trackers and smartwatches, where compactness is a priority.
Industrial Equipment: Many industrial machines rely on PCB antennas for remote monitoring and control, helping to streamline operations and improve efficiency.
When choosing a PCB antenna, consider the application requirements, including size constraints, frequency range, and directional needs. PCB antennas bring numerous advantages to electronics, from consumer gadgets to industrial equipment. With the right antenna, you can achieve reliable wireless communication, keeping your designs efficient and effective in todayâs connected world.
AOI, or Automated Optical Inspection, is a process in PCB manufacturing that utilizes advanced imaging technology to inspect PCBs for potential defects. During the inspection, cameras capture detailed images of the PCB at different stages, comparing them against predefined standards to ensure every component is correctly placed and connected. AOI serves as a crucial step, helping detect manufacturing flaws that could lead to functional issues.
What is an AOI Machine in PCB?
AOI machine is a kind of inspection equipment based on optical principle, mainly used to detect various defects on a PCB board. The AOI device automatically scans the PCB through a high-definition CCD camera, acquires images, and compares the tested solder joints with qualified parameters in the database. After image processing, the defects on the PCB are checked, and the defects are displayed through the display or automatic signs for repair personnel to correct.
AOI detection is mainly composed of light source and its control subsystem, digital imaging and its control subsystem (including CCD/CMOS camera, image acquisition), image scanning motion mechanism and its control subsystem, image processing and optimization subsystem, image feature recognition and defect recognition subsystem, HMI and main control subsystem. These subsystems work together to scan the PCB and obtain the PCB image by controlling the light source, digital imaging, scanning and other subsystems, and then register the processed PCB image with the PCB standard image, extract features and compare and analyze the processed PCB image to determine whether the PCB has defects and the type of defects, and identify the location of defects.
What is the Basic Principle of AOI?
The principle behind AOI is quite straightforward: it illuminates the PCB through the light source, uses the optical lens to collect the reflected light of the PCB into the computer, and analyzes the color difference or gray ratio of the PCB information through the computer software, so as to judge the solder paste printing on the PCB, component placement, solder joint welding quality and so on. The AOI system can also analyze and count the defects to provide a basis for adjusting the process parameters of the manufacturing process.
In another word, it relies on optical imaging and pattern recognition to detect defects. AOI machines are programmed with reference images of a perfect PCB layout. They then scan each PCB, capturing images and comparing them pixel-by-pixel to the reference model. Variations between the scanned image and the reference indicate potential defects, prompting the machine to flag these areas for further review.
What are the Benefits of an AOI Machine?
1. Accuracy in Detection
AOI machines can identify defects that might be overlooked by manual inspection. The precision with which they analyze each PCB ensures high-quality output, reducing errors in the final product.
2. Speed and Efficiency
Automated inspection greatly speeds up the inspection process, especially valuable in large-scale manufacturing. With AOI, hundreds of PCBs can be checked in a fraction of the time required for manual inspection.
3. Cost Reduction
Early detection of defects prevents costly rework or scrap, saving both time and resources. By addressing issues during the early stages, AOI contributes to a smoother production process.
4. Consistency and Reliability
Unlike human inspection, which can vary, AOI provides consistent results every time. It applies the same criteria to every PCB, ensuring uniformity and quality across all batches.
5. Enhanced Quality Control
In a competitive market, high-quality products build trust with clients. AOI enables manufacturers to deliver high-standard PCBs, maintaining quality and reducing potential returns.
What Kinds of Defects Can Be Checked During AOI?
1. Soldering Issues
AOI machines are highly effective in identifying soldering defects, such as insufficient solder, excess solder, or bridging, which can interfere with connectivity.
2. Misalignment of Components
AOI can detect misaligned components or misplaced parts, which might cause issues in functionality or even physical interference on the PCB.
3. Component Presence and Orientation
The machine checks if all components are present and correctly oriented. Missing or rotated parts can lead to non-functioning circuits.
4. Short Circuits and Opens
AOI identifies unwanted connections (shorts) and incomplete circuits (opens), ensuring each connection is accurate and functional.
5. Surface Defects
Surface issues, including scratches, contamination, or other irregularities, are also detectable through AOI, contributing to the visual quality of the board.
6. Polarity and Value Verification
Some AOI systems can check component polarity and values, confirming that each component matches the required specifications for the PCB design.
AOI Applications
1. Consumer Electronics Manufacturing
Given the high volume of consumer electronics, AOIâs speed and accuracy are essential for maintaining efficiency without sacrificing quality. It is used for inspecting products like smartphones, laptops, and household appliances.
2. Automotive Industry
In automotive electronics, reliability is critical. AOI helps ensure that safety and performance-related components are defect-free, such as sensors, control units, and in-car entertainment systems.
3. Medical Devices
Medical equipment relies on precision and reliability. AOI in PCB inspection for medical devices ensures that these life-saving tools meet strict standards, minimizing risks in critical applications.
4. Aerospace and Defense
For aerospace and defense, where reliability and durability are paramount, AOI supports quality assurance in sensitive equipment, such as navigation systems and communication devices.
5. Telecommunications
In telecommunications, AOI assists in inspecting high-frequency PCBs, ensuring that communication devices remain operational and effective over long periods.
To ensure high quality of PCBA, Best Technology equipped with 3D online AOI to detect PCB defectives from all aspects. Contact us if you have any questions.
PCB rework is a delicate yet vital process for restoring functionality to circuit boards with flaws or damages. It involves methodically removing, replacing, or modifying components to correct issues. Whether itâs due to design alterations, assembly errors, or minor repairs, PCB rework can save costs and prevent discarding entire units
What is the Process of PCB Rework?
The process of PCB rework generally follows a series of careful steps. Technicians start by inspecting the board to identify the defective areas. For rework, precise tools like soldering irons, hot air rework stations, or BGA rework machines are typically used.
Once heated, damaged or defective components are removed. A flux application ensures that the solder flows cleanly, which reduces the risk of bridging or insufficient connections. The next step is carefully placing a new component in place, using a microscope to ensure accuracy, particularly for small parts like surface-mount components. Finally, the connections are resoldered, and the board undergoes cleaning and testing.
What is the Difference Between Repair and Rework in PCB?
PCB repair and rework, though closely related, serve unique purposes within electronics manufacturing and servicing. Rework refers specifically to correcting issues in a PCB due to assembly errors or modifications required before the board is shipped to the customer. This process should be operated very carefully, including during removing, adjusting, or replacing components. For instance, rework might be needed if components were placed incorrectly, solder joints are weak, or the board has minor assembly defects.
Repair, however, addresses boards that have become faulty or non-functional after use. Repair focuses on bringing a board back to working condition, whether due to physical damage, such as broken traces or burnt components, or due to environmental factors like corrosion. While rework ensures the board meets its initial design intent, repair aims to recover a boardâs functionality after it has failed. Both repair and rework require precise techniques and skilled technicians, but repair can be more complex due to the nature of post-production or operational damages.
In summary:
Rework: Fixing pre-delivery assembly issues to align the board with its intended design.
Repair: Restoring functionality to a damaged or non-functional board, often due to wear, damage, or environmental exposure.
How Many Times Can You Rework a PCB?
The number of rework attempts a PCB can safely endure depends on factors like the materials used in the board, the board’s structure (e.g., number of layers), and the rework methods applied. Typically, each rework cycle subjects the board to a heating process, which can wear down solder joints and laminate strength over time. For most PCBs, rework should be limited to two or three cycles to avoid degradation, as repeated heating can lead to pad lifting, warping, or delamination of the substrate, especially with multi-layer boards.
Multilayer PCBs with multiple embedded connections are particularly sensitive, as excessive heating can damage internal layers. High-temperature cycles weaken solder joints, increasing the risk of electrical faults. Some high-quality boards, particularly those designed for critical applications like aerospace or medical devices, may tolerate additional rework if built with durable materials, but general guidance suggests minimal rework attempts. Careful planning and accurate diagnostics are essential for minimizing rework cycles, ensuring the boardâs lifespan is preserved.
Can a Damaged PCB Be Repaired?
Yes, in many cases, a damaged PCB can be repaired.
It depends on the type and extent of the damage. For example, broken traces, lifted pads, and minor component failures are often fixable. Using epoxy, technicians can repair lifted pads, while trace repair kits can restore broken connections. However, severe burns or extensive damage to multiple layers can make repairs impractical or costly. The best approach is to assess each situation individually and determine if repair is viable.
What Wire is Best for PCB Rework?
Using the right wire during PCB rework is crucial for achieving reliable connections. For rework, thin, lead-free solder wire with a flux core is often recommended. A wire diameter of 0.5mm to 0.8mm provides better control and precision, making it suitable for both small and large components. Lead-free solder is preferred in many industries due to environmental regulations, but it requires higher temperatures than traditional lead-based solders, so itâs essential to have proper temperature control.
Flux-core solder wire is essential as it allows for smoother, more reliable connections by promoting better solder flow and reducing oxidation at solder joints. Rosin-core flux is commonly used because it provides a strong bond and requires minimal cleaning. Additionally, if jumper wires are needed to bridge broken traces, insulated 30 AWG wire is ideal due to its fine gauge.
What is the IPC Standard for PCB Rework?
The IPC standards for PCB rework and repair are widely recognized and adhered to within the electronics industry to ensure quality and reliability. IPC-7711 and IPC-7721 specifically address rework, modification, and repair of printed circuit boards.
IPC-7711 provides guidelines for reworking and modifying electronic assemblies. This includes instructions on tools, temperature control, and safety practices necessary for removing and replacing components while preserving the boardâs structure. It offers details on soldering and desoldering techniques that ensure high-quality connections after rework.
IPC-7721 focuses on the repair aspect, covering methods for handling damaged components and structural faults like broken traces, lifted pads, and substrate repair. This standard is critical for technicians performing repairs, as it outlines best practices for restoring physical and electrical integrity without compromising board function.
What is the Main Cause of PCB Failure?
PCB failures may cause from a variety of factors, with design flaws, manufacturing errors, and environmental stresses among the primary culprits. Hereâs a closer look at some of the main causes:
Design Flaws: Poorly optimized PCB layouts can lead to issues like excessive heat buildup, inadequate trace width for current capacity, or improper component spacing.
Manufacturing Errors: Mistakes during the assembly process, such as improper soldering temperatures or placement inaccuracies, can lead to weak solder joints or misaligned components. These issues may not be apparent initially but can result in premature board failure.
Environmental Stress: PCBs exposed to extreme temperatures, humidity, or corrosive environments are at risk of damage. Moisture can cause short circuits or corrosion on solder joints and traces, while high temperatures may warp the board or degrade the substrate. Boards used in outdoor or industrial settings are especially vulnerable.
Electrostatic Discharge (ESD): Sensitive components can fail if exposed to static electricity.
Aging and Wear: Over time, boards and components naturally wear out. Solder joints may crack, components degrade, and thermal cycles lead to material fatigue.
If your PCB or PCBA canât work, and donât know where is the problem. You can contact Best Team to ask for help, we are professional in this industry.
Laser Direct Imaging (LDI) is a technology that uses a laser beam emitted by an ultraviolet laser to image directly on a PCB (printed circuit board). Compared to traditional exposure techniques, LDI has higher image quality, precision traces and real-time adjustment.
The LDI technology achieves pattern transfer by projecting the line image directly onto the PCB coated with photoresist through the laser beam emitted by the laser diode. This method eliminates the use of negatives in the traditional exposure process, reduces the time and cost of loading and unloading negatives, and avoids deviations caused by negative growing. The image resolution of LDI technology is high, and the fine wire can reach about 20um, which is suitable for the production of fine wire and improves the yield of PCB production.
Working Principle of LDI Technology
The principle of laser imaging is to acquire and present images based on the characteristics of laser beam. As we know, a laser is a highly focused, high-brightness, monochromatic beam that can therefore produce high-quality images. The laser imaging system mainly consists of laser, lens, scanning device and receiver. The laser is used to generate the laser beam, the lens is used to focus the beam, the scanning device is used to change the path of the beam on the object, and the receiver is used to receive the light signal and convert it into an image.
In the imaging process, the laser beam is focused from the laser through the lens, and then the path of the beam on the object is controlled by the scanning device. When the laser beam hits the surface of an object, it interacts with the surface. This interaction causes light to scatter and reflect, with scattered light diffusing in different directions and reflected light remaining in its original direction of propagation. The receiver receives the light scattered and reflected by the object and converts it into an electrical signal. The receiver converts the signal into a digital image signal, which is then processed and displayed on the screen to form an image. In the processing process, the received signal can be filtered, amplified and other operations to improve the quality and clarity of the image.
As PCB manufacturing processes continue to advance, LDI technology is also evolving. At present, the mainstream light source in the industry is the 405nm laser diode produced by Nichiya, Panasonic, and it is expected that the optical power requirements for exposure will be further improved in the future, and the optical power of a single device may develop to 100W. Nowadays, LDI technology is not only used in PCB manufacturing process, but also in high-end applications like medical imaging, industrial detection, remote sensing.
Advantages of Laser Direct Imaging Over Photo Exposure
The advantages of laser direct imaging (LDI) compared with traditional exposure machines mainly include the following aspects:
1. Eliminating the negative process in the exposure process
The LDI technology eliminates the step of making the negative in the traditional exposure process, thereby saving the time and cost of loading and unloading the negative, and reducing the deviation caused by the negative growth and contraction.
2. High resolution
The image resolution of LDI technology is very high, which is suitable for some very fine line production, especially for multi-layer PCB, which greatly improves the yield of PCB production.
3. High quality and precision
LDI is contactless operation, reducing the chance of miscontact, the closed operating environment reduces the influence of temperature and humidity, the image quality is high and fine, eliminating many defects in the traditional process.
4. Reduce errors and improve alignment
LDI technology improves alignment by eliminating alignment problems that often exist in photographic plates, especially the anisotropic movement of photographic plates caused by changes in temperature and humidity. High-precision alignment is achieved by using a charge-coupled device (CCD) camera system and a reference target to line up printed images and panels.
5. Shorten the production process and reduce costs
Because there is no need to have a negative production process, LDI technology shortens the production process, reduces the call of personnel, and reduces the production cost. In addition, the LDI system can lay more devices in the same environment, enabling two-way scanning and further savings.
6. Adapt to a variety of production needs
LDI technology has a flexible manufacturing route, which can meet various production needs without affecting the output. Once the data is delivered to the engineering department, production can begin, reducing product delivery time.
The image quality of LDI technology is clearer than that of traditional exposure technology, and it has obvious advantages in mid-to-high-end PCB manufacturing. With the transfer of global PCB production capacity to China and the high-end development of the electronics industry, the demand for LDI equipment continues to grow, and it is expected that the future will gradually replace traditional exposure equipment in the field of low-end PCB.
What is the Process of Direct Imaging?
Direct imaging with LDI involves several steps that ensure precise layer creation:
Design Preparation: The digital circuit design is prepped for imaging, with adjustments made to accommodate laser processing specifics.
Photoresist Coating: The PCB is coated with a light-sensitive photoresist material, which reacts chemically when exposed to the laser.
Laser Imaging: The laser projects the circuit pattern directly onto the photoresist. Adjustments can be made mid-process, allowing for precise alignment.
Developing: After exposure, the board is treated with a developer to reveal the circuit paths. Unexposed areas are removed, leaving only the intended design.
Etching or Plating: Depending on the PCB type, the board undergoes etching or plating to define the copper traces, completing the imaging process.
Difference Between Positive and Negative Images in PCB
In PCB photo exposure, the terms âpositiveâ and ânegativeâ refer to how the photoresist reacts to the laser exposure:
Positive Image: Here, the laser exposes areas intended to be removed. During development, the exposed regions dissolve, leaving behind the unexposed areas as the design.
Negative Image: In a negative image process, the laser exposes the regions meant to remain on the board. These exposed parts resist the developer, protecting the underlying material, while unexposed regions dissolve away.
The choice between positive and negative imaging depends on the photoresist type and the specific design requirements. Both methods offer high accuracy, but each has unique benefits based on the intended application.
Why LDI Process Less Cost-effective than Phototool?
While LDI offers many advantages, it often requires a higher initial investment than phototools:
1. Equipment Costs: LDI machines are sophisticated and costly, requiring a significant investment in laser technology and imaging systems.
2. Maintenance: High-precision lasers and optics demand regular maintenance and calibration to ensure consistent performance, which adds to operational costs.
3. Speed on Larger Runs: For high-volume production, phototools may still be more cost-effective. Phototools offer rapid replication without the need for repeated laser exposure, lowering costs for large-scale production.
These cost factors make LDI more suitable for specialized, lower-volume, or high-precision applications rather than large-batch productions.
How is Layer Registration in LDI?
Layer registration is crucial in PCB manufacturing, especially for multilayer boards where each layer must align precisely. LDI excels in this aspect:
1. Automated Alignment: LDI systems come with advanced alignment software that adjusts each laser exposure to match the existing layer positions.
2. Reduced Human Error: Since the process is largely automated, human handling is minimal, reducing the risk of alignment issues.
3. Dynamic Adjustment: With real-time feedback systems, LDI machines adjust alignment during the process, maintaining tight registration tolerances.
If youâre seeking high-quality PCB manufacturing, consider choosing a provider skilled in LDI processes like Best Technology. Our company combines expertise with cutting-edge technology to ensure your boards are produced to exact specifications, delivering the durability and performance you need in todayâs advanced electronics.
Printed Circuit Boards (PCBs) are the backbone of modern electronics. To ensure optimal performance and durability, PCBs undergo various surface treatments. These treatments protect the copper traces from corrosion, enhance solderability, and improve the overall reliability of the circuit board. In this article, we’ll explore the most common PCB surface treatments and their applications.
1. HASL (Hot Air Solder Leveling)
Principle
HASL is a traditional surface treatment that involves immersing the PCB in a bath of molten solder. After the solder solidifies, hot air is used to level the surface and remove excess solder.
Features
â˘Material: Lead-tin alloy (for traditional HASL) or lead-free solder (for LF HASL).
â˘Process: Immersion in molten solder followed by hot air leveling.
Advantages
â˘Excellent solderability.
â˘Cost-effective for large volumes.
â˘Good mechanical strength.
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2. OSP (Organic Solderability Preservatives)
Principle
OSP involves applying a thin layer of organic material (usually a rosin-based compound) to the copper surface, which protects it from oxidation.
Features
â˘Material: Organic preservatives.
â˘Process: Application of organic film.
Advantages
â˘Environmentally friendly.
â˘Good solderability.
â˘Suitable for rework.
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3. ENIG (Electroless Nickel Immersion Gold)
Principle
ENIG involves depositing a layer of nickel followed by a thin layer of gold on the copper surface. This provides a robust barrier against corrosion and ensures good solderability.
Features
â˘Material: Nickel and gold.
â˘Process: Electroless nickel deposition followed by immersion gold plating.
ENEPIG is similar to ENIG but adds a palladium layer between the nickel and gold. This improves the resistance to wear and tear.
Features
â˘Material: Nickel, palladium, and gold.
â˘Process: Electroless nickel deposition, electroless palladium, and immersion gold plating.
Advantages
â˘Superior wear resistance.
â˘Excellent solderability.
â˘Long-term reliability.
Applications
â˘High-reliability military and aerospace applications.
â˘High-frequency applications.
â˘Wire bonding
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5. Gold Immersion (Direct Gold Plating)
Principle
Gold immersion directly deposits a layer of gold onto the copper surface without a nickel underlayer.
Features
â˘Material: Gold.
â˘Process: Direct gold plating.
Advantages
â˘High conductivity.
â˘Excellent solderability.
Silver Immersion
Principle
Silver immersion involves depositing a layer of silver onto the copper surface.
Features
â˘Material: Silver.
â˘Process: Immersion silver plating.
Advantages
â˘High conductivity.
â˘Low cost compared to gold.
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6. Hard Gold (Selective Gold Plating)
Principle
Hard gold is a thicker and harder layer of gold, typically applied selectively to contact areas.
Features
â˘Material: Gold.
â˘Process: Selective gold plating.
Advantages
â˘High wear resistance.
â˘Good electrical contact properties.
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7. Tin Immersion
Principle
Tin immersion deposits a layer of tin onto the copper surface.
Features
â˘Material: Tin.
â˘Process: Immersion tin plating.
Advantages
â˘Good solderability.
â˘Low cost.
Applications
â˘Cost-sensitive applications.
â˘General-purpose electronics.
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Choosing the right surface treatment for your PCB depends on several factors, including the application environment, cost considerations, and performance requirements. Each treatment has its own set of advantages and limitations. Understanding these treatments will help you make informed decisions that enhance the performance and longevity of your electronic devices.
I hope this guide helps you understand the different surface treatments used in PCB manufacturing and their applications. If you have any questions or need further clarification, feel free to reach out!
The full form of ICT is In-Circuit Testing. It is a method that always used to test assembled circuit board during manufacturing.
What is ICT in PCB?
In-circuit testing (ICT) is a method used to test assembled circuit boards during production. It ensures that every component on the PCB functions as expected. By applying electrical signals to the board, it checks for faults like open circuits, shorts, and wrong component values.
In PCB assembly, ICT is used for final testing after surface-mount components and through-hole components have been soldered onto the board. This test is highly effective in identifying assembly defects that might compromise the functionality of the final product.
ICT vs. FCT
Although ICT and FCT look similar, their purposes and focus are different.
In-Circuit Testing (ICT) is like a thorough quality check for individual components. It tests each resistor, capacitor, inductor, and IC on the board to make sure theyâre installed and working as expected. ICT does this without focusing on the PCB’s complete function as a whole; instead, it looks for manufacturing faults or placement errors on each part of the circuit. This is perfect for catching problems before the PCB reaches final assembly.
Functional Circuit Testing (FCT), on the other hand, looks at the bigger picture. FCT checks if the assembled board works as intended in a simulated working environment. It mimics the real-world conditions the PCB will face once in use, testing the board as a whole rather than individual components. FCT aims to ensure that all parts are correctly interacting and that the board behaves as it should under operating conditions.
Together, ICT and FCT form a powerful duo: ICT focuses on each componentâs accuracy, while FCT ensures that all the elements work smoothly as a cohesive unit. Using both tests provides a comprehensive check, enhancing the PCB’s overall quality and reliability before it reaches the end-user.
What Items Does ICT Test for on a PCBA?
When ICT tests a PCBA, itâs really looking for any faults or failures in the components and connections that could cause problems later on. Hereâs what ICT commonly checks:
Resistors â It verifies that each resistor has the right resistance value and is correctly placed. If a resistor value is wrong, it can disrupt the whole circuit.
Capacitors â ICT checks capacitance levels and polarity (in specific cases) to make sure each capacitor is installed properly. Incorrect capacitors can lead to unstable performance.
Inductors â The test examines if inductors have the correct inductance values. Faulty inductors can cause power issues or signal problems.
Integrated Circuits (ICs) â ICT verifies that ICs are in the right orientation and connected properly to avoid shorts or opens, both of which can make the board malfunction.
Transistors â By checking transistor functionality, ICT ensures they wonât cause signal or power issues within the PCB.
Diodes â ICT makes sure diodes have correct polarity and work properly. Misplaced or faulty diodes can impact the flow of current, leading to circuit failure.
Solder Joints â ICT evaluates each solder joint, checking for breaks or poor connections. Bad solder joints lead to unstable electrical contact, which could cause intermittent issues or complete failure.
What is an ICT Machine?
An ICT machine is a specialized piece of equipment designed to perform in-circuit tests on PCBs. You can see it from below picture. The ICT machine uses a test fixture, also called a “bed of nails,” containing numerous tiny probes or pins. Each probe aligns with a specific point on the PCB, making contact with various circuit points to evaluate the electrical connections.
Once a PCB is placed in the test fixture, the machine applies signals through the probes to test individual components. It checks electrical properties such as resistance, capacitance, and voltage at each node. If a component is misplaced, missing, or faulty, the machine flags it immediately.
With its speed and precision, an ICT machine is an invaluable tool in high-volume production lines. While setting up an ICT machine requires creating a test fixture for each PCB, they save much time and human during the manufacturing process, make sure a fast delivery.
What Are the 7 Types of PCB Testing Methods?
In addition to ICT testing, there are other 6 types of PCB testing methods that widely used. Letâs talk about them one by one.
1. Flying Probe Testing
A testing method mainly used for prototypes or small/low volume orders. In Flying Probe Testing, multiple movable probes make contact with test points on the board. Unlike ICT, it doesnât require a fixture, making it highly flexible and cost-effective for small production runs. However, compared with ICT testing, itâs relatively slower than ICT because it tests points sequentially.
2. Functional Circuit Testing (FCT)
FCT is a method that check whether PCBA works correctly. It is typically come after ICT, and in almost factory, it is the last process to confirm that every component works together correctly.
3. Burn-In Testing
Burn-in Testing (also called aging test) pushes the board to its limits by applying high temperatures, loads, or voltages for extended periods. It can spot failures in components that might not withstand the stress of real-world conditions. Burn-in testing is often used for products that need high reliability, such as aerospace and medical devices.
4. X-Ray Inspection
For multilayer or densely packed PCBs, X-ray inspection is must to do. It helps visualize hidden solder joints and component placements that inspectors canât found by naked eyes. X-ray inspection is invaluable for boards with fine-pitch components such as BGAs, QFNs, or those where hidden joints canât be inspected visually.
5. Automated Optical Inspection (AOI)
AOI uses cameras to visually inspect the board for common issues like misalignment, missing components, or faulty solder joints. This is a quick and effective way to catch visible defects. AOI is widely used in automated production lines, as it quickly flags any boards that require closer examination. To get highest quality and no-defect products, Best Technology equipped with online dual track AOI to inspect PCBA.
6. Boundary Scan Testing
Boundary Scan Testing is particularly useful for complex boards where physical probing is challenging. It involves using ICs that support scan testing, so that engineers to check connectivity between ICs and other critical points. Boundary scan is common in high-density boards like those found in telecommunications.
Each method brings a unique advantage to PCB testing. In-Circuit Testing (ICT) is highly effective for large-scale quality control, while Flying Probe Testing is better suited for prototypes and smaller batches. Together, these tests form a complete strategy for delivering reliable, high-quality PCBs across various production needs.
How does ICT Testing?
ICT works by using a bed-of-nails (BON) tester or test probes to connect to specific test points on a PCB. Electrical signals are then sent through the board, and the responses are analyzed. Here’s how it works in simple steps:
Connection: The PCB is placed on the ICT machine, where test pins contact the board at designated points.
Signal Application: The ICT machine applies electrical signals to test the components individually or in groups.
Data Collection: The responses from each component are recorded to determine if it matches the expected output.
Fault Identification: Any deviations from expected responses are flagged, identifying potential defects like soldering errors, component failures, or incorrect placements.
FAQs about ICT
Q: What is ICT?
A: ICT (In-Circuit Test System), commonly known as online tester In Chinese, is mainly used for the test of assembled Circuit boards (PCBA).
Q: Which components can ICT basic functions measure?
A: On, short circuit, resistance, capacitance, inductance, diode, IC protection diode test, etc.
Q: Why use ICT?
A: According to the statistical data of the circuit board assembly industry, assembly defects are mainly reflected in the welding open circuit, short circuit, offset, missing parts and other aspects, accounting for more than 90%, so the principle of online testing technology application is to quickly detect faulty components or assembly defects, and can accurately locate defects and defect classification.
Q: Can ICT be regarded as a universal meter?
A: ICT can be regarded as an automated high-level multipurpose meter, and because it has the function of circuit isolation, it can accurately measure the actual value of each component in the circuit.
Q: What is the relationship between ICT and AOI?
A: ICT is mainly carried out by electrical measurement methods, while AOI is carried out by optical image processing technology. Both have their own strengths and complement each other. In the process arrangement, AOI is generally the first, then ICT.
In the PCB design and testing, there is a common term be mentioned frequently, that is EMI and EMC. Some people may ask that âwhat is EMI/EMC, why is it be mentioned every time?â Today, BEST team will take you to understand what are they and how to test them. Letâs keep reading.
What are EMI and EMC in PCB?
Before diving into, we should know both EMI and EMC are important elements during the PCB design. Some new PCB projects are failed during testing, because EMI and EMC design is not reasonable.
EMC is short for electromagnetic compatibility. EMC in a PCB is the ability of the PCB to operate in its electromagnetic environment without creating unbearable electromagnetic interference to other devices around it. In general, to achieve an EMC compliant design, engineers need to consider three basic aspects:
Generating unwanted electromagnetic radiation and its propagation.
The vulnerability of designs or components to electromagnetic interference (EMI).
PCB design should not cause intolerable electromagnetic interference on its own.
EMI is short for electromagnetic interference. EMI is unwanted noise or signals generated by electronic devices, which can disrupt other nearby equipment. PCBs, being central to electronics, are often both sources and victims of EMI. Every engineer should follow EMC configuration standards to minimize the total amount of EMI and its impact.
In a word, EMI refers to the generation of electromagnetic interference, while EMC refers to electromagnetic compatibility, that is, how well a device blocks EMI. EMI originates from electromagnetic equipment, and EMC involves equipment that is both anti-interference and non-interference with other equipment.
What Is the Difference Between EMI and EMC Testing?
EMI testing focuses on measuring the interference a device generates. It aims to ensure that the PCB doesnât emit electromagnetic waves that can interfere with other devices. EMC testing, on the other hand, checks the deviceâs ability to withstand electromagnetic interference from its environment without losing functionality. Both tests are essential to make sure that your PCB not only works well but also doesnât cause problems for other systems.
The main difference between EMC tests and EMI is their purpose and method of testing. â
Test purpose
âEMC testing focus on the equipment or system will function properly in an electromagnetic environment and will not cause intolerable electromagnetic disturbance to other equipment. EMC testing includes two aspects: electromagnetic immunity (the ability to resist interference) and electromagnetic emission (not to interfere with other equipment).
âHowever, EMI testing focuses on unwanted electromagnetic energy emitted by a device or system that may interfere with the normal operation of other nearby equipment. The purpose of EMI testing is to identify and reduce these sources of interference to prevent interference with other equipment â
Testing method
âEMC test usually includes shielding, grounding, and filtering methods. Shielding is surrounding devices or systems by using conductive materials to reduce leakage of electromagnetic radiation. Grounding is connecting the metal housing and ground to provide a safe electrical circuit loop. Filtering is to reduce unnecessary electromagnetic signal transmission through PCB circuit design.
âEMI test mainly measuring by the conducted interference and radiation interference of the devices. Conducted interference is interference that travels through a conductive medium (such as a wire), while radiative interference refers to the interference that travels through space.
What Are the Testing Standards for EMI/EMC?
Several global standards guide the EMI/EMC testing process. These include:
IEC 61000 series: This is the most common EMC test standard, covering EMI and EMS (Electromagnetic sensitivity) test methods, limits and units of measure.
EN 55014 series: This is the EU EMC test standard, including:
EN 55014-1: Radiation from household appliances
âEN 55014-2â: Radiation immunity of household appliances
âEN 55032â : Interference emission test for multimedia electronic products
âEN 55035â : Immune immunity test for multimedia electronic products
âGB/T17625 series â : This is China’s EMC test standard, including:
GB/T17625.1-2012â : EMC limits Harmonic current emission limits (Input current per phase â¤16A)
âGB/T17625.2-2007â : Limits on voltage variation, voltage fluctuation, and flicker (rated current of equipment per phase â¤16A)
âGB/T17625.7-2013â : Harmonic current limit for conditionally connected devices with rated current â¤75A in a common low-voltage power supply system
âGB/T17625.8-2015â : Harmonic current limit for devices connected to a common low-voltage system with input current greater than 16A but less than 75A per phase
âGB/T17625.9-2016â : Signal transmission emission levels, frequency bands and electromagnetic disturbance levels on low-voltage electrical installations
âGBZ17625.3-2000â : Limits on voltage fluctuations and flickers in low-voltage supply systems for devices with rated current >16A
âGBZ17625.6-2003â : Limits on harmonic currents produced by devices with rated current >16A in low-voltage power supply systems
âGBZ17625.13-2020â : Evaluation of emission limits for unbalanced installations connected to medium voltage, high voltage, and ultra-high voltage power systems
âGBZ17625.14-2017â : Evaluation of emission limits for harmonics, interharmonics, voltage fluctuations and unbalance of nuisance devices connected to low voltage power systems
âGBZ17625.15-2017â : Evaluation of low frequency electromagnetic immunity and emission requirements for distributed generation systems in low voltage power grids
These standards cover a wide range from household appliances to industrial equipment, you can follow one of them according to your specific applications and countries.
How to Conduct an EMI Test?
Before conduct a test, letâs know the testing method. EMI test methods mainly include the following â :
1. Pre-test: EMI testing performed during the design phase to detect and resolve EMI problems early in product design and development. Pre-test can be conducted using computer simulation, or by using actual test equipment.
2. Emission test: It is a test to measure whether electromagnetic waves emitted by equipment meet EMI standards. The emission test can be carried out by field test, half-time test, full-field test and other methods. Commonly used test equipment includes spectrum analyzer, scanning receiver, antenna, etc.
3. Sensitivity test: Common sensitivity testing methods include radiation sensitivity testing and conduction sensitivity testing. radiation sensitivity testing uses a signal generator to generate an electromagnetic field of a specific frequency and intensity. And conduction sensitivity testing involves injecting simulated electromagnetic interference signals on the power or signal lines of the equipment under test.
4â. Spectrum analysis: By measuring the spectrum of electromagnetic wave to analyze the characteristics of electromagnetic interference.
âAbove are the testing methods of EMI, and here is the steps that how to test it.
Select the right test method
First of all, select a right test method according to the specific test purpose and object. For example, if the emission characteristics of the equipment need to be evaluated, an emission test can be selected; If you need to evaluate the anti-interference capability of the equipment, you can choose sensitivity test.
Use professional equipment
Use professional test equipment, such as spectrum analyzer, signal generator, digital storage oscilloscope, etc., to ensure the accuracy of the test results.
Environment control
When performing sensitivity test, control the test environment to avoid the influence of other electromagnetic interference sources. Tests can be conducted in a shielded room to reduce outside interference.
Data analysis
Detailed analysis of the test data, identify potential sources of electromagnetic interference, and propose improvement measures. Methods such as difference method and potential zeroing method can be used to reduce the influence of interfering magnetic field on measurement results.
EMI/EMC PCB Design Guidelines
1. Ground plane
Because all circuits need to be grounded, the ground plane is the first line of defense against EMI. The following measures can be taken to reduce EMI:
Increase the ground area
Set up the ground plane
Each component should be connected to the ground plane
Each component should be connected to the ground plane or a ground point.
Decoupling capacitor
The ground plane is placed directly below the plane with the signal trace
Digital ground and analog ground should be separated
The ground wire should be as thick as possible
The length of the ground system should be kept to a minimum
2. Power supply design
Improper power supply design will result in greater noise and ultimately reduce product performance. Two main factors that lead to power supply instability:
1) Excessive transient AC current under high-speed switching
2) Inductance exists in the current loop Therefore, the integrity of the power supply should be fully considered in PCB design.
3. PCB layout
a) PCB size
PCB size must be considered. When it comes to oversized boards, the traces must go a long way as the impedance increases, the noise immunity decreases, and the manufacturing cost increases. When the board size is particularly small, it will cause heat dissipation problems and crosstalk is prone to occur between adjacent traces. The recommended PCB size is a rectangle with an aspect ratio of 3:2 or 4:3. In addition, when the board size exceeds 200mm*150mm, the mechanical strength of the board retraction should be considered.
b) Avoid right angles
This has been said many times. Avoid 45° to 90° for vias, traces, etc. When the trace reaches more than 45°, the capacitance will increase.
c) Keep signals separated
Digital circuits, analog circuits, and noise sources should be placed independently on the board, and high-frequency circuits should be isolated from low-frequency circuits. In addition, attention should be paid to the component distribution of strong and weak signals and the direction of signal transmission.
d) Increase the trace width as much as possible
e) Wider trace sizes can effectively reduce radiated emissions.
f) Make the return current path as short as possible and route along the path with the least resistance. The length of the return path should be roughly the same as or shorter than the length of the transmission trace.
4. Component placement
In general, it is best to completely separate analog and digital signals. Being too close can easily lead to problems such as crosstalk. In addition, compatible components should be placed independently to ensure that components do not interfere with each other in space.
5. PCB layer design
In terms of the number of layers, choose the appropriate number of layers. Single-layer PCBs and double-layer PCBs are suitable for medium and low-density wiring or low-integrity circuits. Based on manufacturing cost considerations, most consumer electronic products rely on single-layer PCBs or double-layer PCBs. However, due to their structural defects, they both generate a lot of EMI, and they are also sensitive to external interference. Multi-layer PCBs tend to be more used in high-density wiring and high-integrity chip circuits. Therefore, when the signal frequency is high and the electronic components are densely distributed, a PCB with at least 4 layers should be selected. In multi-layer PCB design, the power layer and the ground layer should be specially arranged, and the distance between the signal line and the ground line should be reduced.
6. EMI shielding
Shielding and filtering can minimize the impact of EMI. Some shielding and filtering options include:
Component and PCB shielding
Low-pass filtering
Cable shielding
7. Trace routing
Put the current signals with the same output but opposite directions in parallel to eliminate magnetic interference. Discontinuities in printed leads should be minimized. For example, the lead width should not change abruptly and the lead angle should not exceed 90°.
8. Routing design
The power line, ground line, and traces on the circuit board should maintain low impedance to high-frequency signals. When the frequency remains so high, the power line, ground line, and circuit board traces all become small antennas responsible for receiving and transmitting interference. To overcome this interference, it is more important to reduce the high-frequency impedance of the power line, ground line, and circuit board traces than to increase the filter capacitor. Therefore, the traces on the circuit board should be short, thick, and evenly arranged.
9. Decoupling and grounding
The proper placement of decoupling capacitors and the application of the inductor capacitor energy storage function make it possible to provide current to the device at the moment of switching. In a DC loop, load changes can cause power supply noise. The decoupling capacitor configuration can block the noise generated by load changes. For electronic equipment, grounding is a key method to control interference. If grounding is properly combined with shielding measures, most interference problems will be solved.
Above all are the key points when design pcb, hope you can take them in mind and use in your actual design phase.
