Archive for the ‘SMT Technology’ Category

Understanding Counterbore and Countersunk Holes in PCB Design

星期六, 8 7 月, 2023

When we talking about the holes in PCBs (Printed Circuit Boards), may somebody always curious about two special holes: Counterbore hole and Countersunk hole. They are easy to be confused and easy to misunderstanding if you are a layman of PCB. Today, we will introduce the differences between counterbore and countersunk for details, let’s keep reading!

What is a Counterbore Hole?

A counterbore hole is a cylindrical recess on a PCB that has a larger diameter at the top surface and a smaller diameter at the bottom. The purpose of a counterbore hole is to create space for a screw head or a bolt’s flange, allowing it to sit flush with or slightly below the PCB surface. The larger diameter at the top accommodates the head or flange, while the smaller diameter ensures that the fastener’s shaft or body fits snugly.

What is a Countersunk Hole?

On the other hand, a countersunk hole is a conical recess on a PCB that allows the head of a screw or bolt to sit flush with the PCB surface. The shape of a countersunk hole matches the profile of the fastener’s head, creating a seamless and level surface when the screw or bolt is fully inserted. Countersunk holes typically have an angled side, often 82 or 90 degrees, which determines the shape and size of the fastener head that will fit into the recess.

Counterbore VS Countersunk: Geometry

While both counterbore and countersunk holes serve the purpose of accommodating fasteners, their main difference lies in their geometry and the types of fasteners they accommodate.

Counterbore holes have a cylindrical recess with two different diameters, while countersunk holes have a conical recess with a single diameter.

Counterbore holes create a stepped or raised region on the PCB surface, whereas countersunk holes result in a flush or recessed surface.

Counterbore VS Countersunk: Fastener Types

Counterbore holes are primarily used for fasteners with a head or flange, such as bolts or screws that require a solid mounting surface.

Countersunk holes are designed for fasteners with a conical head, such as flathead screws or countersunk bolts, to achieve a flush surface.

Counterbore VS Countersunk: Drill angles

Different sizes and drilling angles of drill bits are offered for producing countersinks, depending on the intended use. These angles can include 120°, 110°, 100°, 90°, 82°, and 60°. However, the most frequently employed drilling angles for countersinking are 82° and 90°. For optimal outcomes, it is essential to align the countersink angle with the tapered angle on the underside of the fastener head. On the other hand, counterbore holes feature parallel sides and do not necessitate tapering.

Counterbore VS Countersunk: Applications

The choice between counterbore and countersunk holes depends on the specific requirements of the PCB design and the components being used.

Counterbore holes find applications in situations where a secure and flush fastening of components or mounting plates is necessary. They are commonly used to fasten connectors, brackets, or PCBs to an enclosure or chassis.

Countersunk holes are often employed when aesthetic considerations are important, as they provide a sleek and level surface. They are frequently used for mounting PCBs to surfaces where a flush finish is desired, such as in consumer electronics or decorative applications.

Counterbore and countersunk holes are important features in PCB design, enabling efficient component mounting and secure fastening. Understanding the differences between these two types of holes allows designers to select the appropriate option based on the specific requirements of their circuit board applications. Whether it’s ensuring a secure connection or achieving a visually pleasing finish, the choice between counterbore and countersunk holes plays a crucial role in the overall functionality and aesthetics of a PCB assembly.

What is BGA Soldering?

BGA soldering is a technique that involves the attachment of integrated circuit packages to a PCB using an array of solder balls. These solder balls are typically made of lead-based or lead-free alloys, depending on environmental regulations and specific requirements. The BGA package consists of a substrate, which acts as a carrier for the integrated circuit, and the solder balls that form the electrical and mechanical connections between the package and the PCB.

The Importance of BGA Soldering in Electronics Manufacturing

BGA soldering plays a critical role in the manufacturing of various electronic devices such as computers, smartphones, and gaming consoles. The increased demand for smaller and more powerful electronics has driven the adoption of BGA packages. Their compact size and high pin density make them suitable for advanced applications where space is limited.

Challenges Faced in BGA Soldering

Component Alignment and Placement

One of the primary challenges in BGA soldering is ensuring accurate component alignment and placement on the PCB. The small size of the solder balls and the dense layout of the BGA package make it difficult to achieve precise positioning. Misalignment during the assembly process can result in solder bridges, open connections, or mechanical stress on the package.

To address this challenge, manufacturers employ advanced technologies such as Automated Optical Inspection (AOI) and X-ray Inspection. AOI systems use cameras and image processing algorithms to verify the correct alignment and placement of BGA components. X-ray inspection, on the other hand, allows manufacturers to see beneath the surface of the PCB and detect any misalignment or defects that may not be visible to the naked eye.

Solder Paste Application

Another significant challenge in BGA soldering is achieving precise and consistent solder paste application. Solder paste, a mixture of solder alloy and flux, is applied to the PCB pads before placing the BGA package. Inadequate or excessive solder paste can lead to solder defects such as insufficient solder joints, solder voids, or solder bridging.

To overcome this challenge, careful attention must be given to stencil design and aperture selection. Stencils with appropriate thickness and properly sized apertures ensure accurate solder paste deposition. Additionally, manufacturers can employ Solder Paste Inspection (SPI) systems to verify the quality and consistency of the solder paste applied. The solder paste that Best Technology uses is SAC305 solder paste, which has good printability and excellent stability.

Temperature Profiling

Temperature profiling, or we can say the thermal management, it is crucial in BGA soldering to ensure proper reflow of the solder paste. The reflow process involves subjecting the PCB to a carefully controlled temperature profile, allowing the solder paste to melt, form a reliable joint, and solidify. Inadequate temperature profiling can lead to insufficient solder wetting, incomplete reflow, or thermal damage to components.

Manufacturers must optimize the reflow oven setup and calibration to achieve the correct temperature profile. Thermal profiling techniques, such as the use of thermocouples and data loggers, help monitor and control the temperature during the reflow process.

Reflow Process

The reflow process itself presents challenges in BGA soldering. The soak zone, ramp rates, and peak temperature must be carefully controlled to prevent thermal stress on the components and ensure proper solder reflow. Inadequate temperature control or improper ramp rates can result in solder defects such as tombstoning, component warpage, or voids in the solder joints.

Manufacturers need to consider the specific requirements of the BGA package and follow recommended reflow profiles provided by component suppliers. Proper cooling after reflow is also essential to prevent thermal shock and ensure the stability of the solder joints.

Inspection and Quality Control

Inspection and quality control are critical aspects of BGA soldering to ensure the reliability and performance of the solder joints. Automated Optical Inspection (AOI) systems and X-ray inspection are commonly used to detect defects such as misalignment, insufficient solder wetting, solder bridging, or voids in the solder joints.

In addition to visual inspection techniques, some manufacturers may perform cross-section analysis, where a sample solder joint is cut and examined under a microscope. This analysis provides valuable information about the quality of the solder joint, such as solder wetting, void formation, or the presence of intermetallic compounds.

In a word, BGA soldering presents unique challenges in electronics manufacturing, primarily related to various factors. By addressing these challenges effectively, manufacturers can ensure the reliability and performance of BGA solder joints, contributing to the production of high-quality electronic devices. Best Technology has rich experience in PCBA assembly and we mounted thousands PCBs for our customers, whatever it is simple design or complex design, all the products are assemble perfect and work well in customer side. Please feel free to contact us for any questions about PCBA.

Stack up of 2L MCPCB and Double Sided MCPCB

For a 2L MCPCB, the metal core is positioning on the bottom side of the MCPCB as a cooling carrier to the whole MCPCB, while the metal base of double sided MCPCB is located in the middle of two copper trace. In generally, some PTH (plated-through-hole) vias are needed to designed to connect the bottom and top traces.

Below are the stack ups of these two kinds of products, from the structure, we can easily distinguish which one is 2L MCPCB and which one is double sided MCPCB.

Heat dissipation of 2L MCPCB and Double Sided MCPCB

Due to the different structure of the two products, their heat dissipation performance is also different. The main reason is the heating of double-sided metal core circuits can be spread out through both top and bottom side, while the heating generate by SMD components of 2 layers circuit only can be dissipated through bottom (metal) side and the heat need to go down layer by layer. In addition to this, the dissipation of FR4 is not good than metal materials, so double-sided metal core printed circuits perform better heat dissipation performance than 2 layers MCPCB.

Surface mounted locations (SMD populate)

Nowadays, surface mounted technology (SMT) is widely used in printed circuit board industry, more and more designers prefer to populate electronic components of the circuit surface to achieve high density, stable electrical performance and high reliability. 2L metal core circuit boards and double-sided metal core circuits also show their different mounted locations in this aspect.

The populate location of a 2L MCPCB only available on copper trace side, that is top side. And a double-sided metal core PCB can mount components on both top and bottom side, because both of them exist copper trace on it.

Manufacturing technology

May somebody will curious about “Are these two products produced in the same process/technology?”

The answer is obvious “NO, they have a different laminate process when fabricating.”

Different with single layer MCPCB, double sided MCPCB requires an additional pressing step to laminate the thermal conductive layer and metal core together. But sometimes, some raw Metal Clad material vendor will supply board material which already laminated.

For 2 layers metal core PCB, due to it is made of a single MCPCB and a double-sided FR4 PCB, the first thing we should make a double sided FR4 PCB, then laminate the PCB together with the single MCPCB. But due to the thermal conductive layer (pure adhesive) is easy to overflow during laminating process, which will cause the poor adhesion and crack between metal core and FR4 PCB. In the meantime, to avoid such problem, an experienced operator is needed to proceed the laminated process. That is why the lead time and cost of a 2 layers metal core circuit is much longer and expensive.

This is the end of this post, if you still have some questions or difficulties about the metal core PCB, welcome to contact us at sales@bestpcbs.com, our professional sales team and engineering team will give you a best solution for free.

HASL Surface Finish

HASL (Hot Air Solder Level) can be known as tin-lead HASL and lead-free HASL, it was the mainstream surface treatment technology in the 1980s, but with the increased of “small and high density” demands in PCB, there are less and less circuit boards use the HASL technology because it will cause the defective products due to the solder point are easy to leave on the board surface during SMT process. In view of this situation, some PCB board manufacturers or designers prefer use OSP or immersion gold to ensure the good quality products as well as smooth production process.

Tin-lead HASL

Advantages:

1） Economical and widely available.

2） Excellent solderability.

3）Better mechanical strength & lustrousness than lead-free HSAL.

Disadvantages: it is harmful to environment and violates RoHS compliance.

Lead-free HASL

Advantages: low cost, good solder performance and environmental.

Disadvantages: mechanical strength & lustrousness are not good than lead HASL.

In additional, due to the poor surface flatness of HASL circuit boards, neither leaded nor lead-free HASL is not suitable for soldering fine-pitch components or plated through-holes, because it will cause the short circuits and poor welding during the assembly process.

OSP

OSP (Organic Solderability Preservatives) also named as pre flux, the working principle is to generate a layer of organic film chemically on the copper surface to protect the surface from oxidation or vulcanization in the room environment. Meanwhile, OSP also can increase the oxidation resistance, heat shock resistance and moisture resistance of a PCB.

OSP is equivalent to an anti-oxidation treatment, the protective thin film can be easily removed by the flux quickly under the high soldering temperature, then it makes the exposed copper surface immediately combined with the molten solder in a very short time to become a solid solder spot.

At present, the usage of OSP surface finishing process has increased significantly because it is appropriated for both low and high-end products. If your application has no surface connection functional requirements or storage life limitations, the OSP process is the most desirable surface treatment process.

Advantage:

1）With all the advantages of bare copper soldering, expired (more than 3 months) boards can also be resurfaced, but one time is better.

2）Good for fine-pitch, BGA and smaller components.

3）Low cost and easy to rework.

4）Simple process and easy to ensure quality.

Disadvantage:

1）OSP is easily affected by acid and humidity, so must be packed with vacuum.

2）Need to do surface treatment again if storage time more than 3 months.

3）It should be used within 24 hours after unpacking.

4）OSP is an insulating layer, so the test point must be printed with solder paste to remove the original OSP layer for electrical testing.

ENIG

ENIG (Electroless Nickel/Immersion Gold) is one of a chemical nickel gold deposition method, the working principle is to generate a layer of coating by chemical REDOX reaction to get a thicker gold layer. Currently, ENIG is mainly used in the surface of the circuit board with connection functional requirements and long storage life.

Advantage:

1）Can be stored long time as well as no oxidation.

2）Good flatness surface and suitable for small solder point components.

3）Good solderability.

4）Can be used as the base material for COB wire bonding.

Disadvantage:

1）High cost than other two surface treatments.

2）Easy to exist black-pad issue during production process.

As we can know from above information, each PCB surface treatment has its own merit and demerit, you can choose the one according to the effect you want to reach, as well as your cost.

If you don’t know which is best for you, you can send inquiry to us, our professional engineering team and PCB sales will choose the suitable one for you. Welcome to contact us if you have any other questions.

What are Printed Circuit Boards?

A printed circuit board also known as PCB for short, is an electronic board for connecting metal circuits by mounting different electronic components in a device and have it do its functions.

PCB is made of fiberglass and laminate materials or a composite epoxy with conductive, it can be made to varies shapes and sizes depends on what applications it will be used for—some have many holes on it while some only have several pads or traces.

In most of devices, we can see there are many components or wires mounted or connected on the surface of PCB, which comes into two different pathways –surface mount and through-hole. Surface mount is a technology that can be abbreviated as SMT, it is a famous technical that mount electronic components (typically SMDs) attached on top of a pad by melted solder paste. Through-hole generally refers to components that have wires through the plated-through-holes that drilled into the circuit board. Both ways are commonly use, but currently with the fast development of the technology advance, surface mount is more popular than through-hole as it is more convenient for production.

What the Functions of Printed Circuit Boards?

The main functions of a PCB is to connect different components and achieve a communication between components and devices, that can be used for everywhere you can think of – Computer, phones, televisions, tablets, cameras, projectors, and so on….

For a simple example, a phone has a PCB that can connect screen, the buttons, cameras, and the circuits on the both sides. Without this board, those components wouldn’t be able to transmit signals and talk to each other and the phone would cease to function.

In addition, electronic equipment using printed board enable to avoid the error of manual wiring, and can realize the automatic insertion or installation of electronic components, automatic soldering, automatic detection by communicate with each other, to ensure the quality of electronic products, improve labor productivity, protect components from damaged, reduce costs, and easy to maintenance.

The advantages of Printed Circuit Boards

PCB performs a number of advantages in electronic industries, a most significant feature is they make products be smaller and more portable as its density circuits and components communication. The density circuits on PCB allows it take up much space for components so you can get a smaller product.

High density

Over the past decades, the high density of printed boards has been developed with the improvement of integrated circuits and the advancement of installation technology.

High reliability

Through a series of checks, tests and aging tests, the PCB can be guaranteed to work reliably for a long time (generally 20 years).

Designability

For various performance (electrical, physical, chemical, mechanical, etc.) requirements, can PCB be achieved to such requirements in short time and high efficiency according to design standard rules.

Maintainability

By means of standard PCB design rules, once the program or device failure, users fix the devices quickly.

Cooling abilities

Overheating is one of the biggest reasons of electronics failure, so by keeping them cool with a PCB, you can increase the lifetime of your product.

Types of Printed Circuit Boards

Best Technology provides different kinds of PCBs and PCBAs for our customers, for a quickly reviewing, we listing as below:

Rigid Printed Circuit Board (FR4-PCB)
Flex Printed Circuit Board (FPCB)
Rigid-Flex PCB
Metal Core Printed Circuit Board (MCPCB)
Ceramic Board
SinkPAD Board
Other special PCB such as heavy copper PCB, HDI PCB, RF PCB, and so forth
PCB assembly

In a word, with the development of electronics, it’s necessary to have a functional part like the PCB that can keep up with the demand. Next step, contact us if you have PCB demands.

Part 1: What is Solder Mask?

If you had ever seen a printed circuit board, you may see there is a layer of green ink cover on the PCB surface while some orange-yellow areas didn’t cover by ink. In PCB industry, the green ink we called Solder Mask, or abbreviated as S/M, and exposed area is copper, they were leave as GND plane or soldering pads to mount electronic components.

Solder mask is a liquid acrylic oligomer, which has variety of colors such as red, blue, green, white, black. Green is commonly used in the process of PCB manufacturing, so some professional engineers call it as green oil.

Solder mask applied on the PCB designed as a protection layer to avoid oxidation, corrosion and other environmental impacts when they leave production line. In addition, solder mask between solder pads also can help to prevent forming to solder bridge when assembly.

Below are some other functions of coating a layer solder mask:

Prevent physical line breaking of copper trace
Only weld in the area that must be soldered to avoid waste of soldering
Reduce copper pollution to soldering groove
Prevent insulation deterioration and corrosion caused by dust, moisture and other external environmental factors
With high insulation, so that the high-density circuit is possible

Part 2: What is Solder Paste?

Solder Paste also known as “Solder cream”, is a most important soldering material used in surface mount technology (SMT) process. Mainly function for soldering resistors, capacitors, ICs and other electronic components onto the PCB surface to form a permanent connection.

The solder particles are a mixture of solder formed by mixing solder powder, flux and other surfactants and thixotropic. Traditionally this used to be tin and lead, but with the legislation has been introduced around the world, to only use lead free solders. These may be made from a variety of mixtures, Best Technology commonly used is SAC305 which includes 96.5% tin, 0.5% copper and 3.0% silver, some manufacturers also use 99.7% tin and 0.3% copper, whereas there are other mixtures that include other metals including tin.

Due to the role of solder paste in assembly, solder paste storage is extremely important. However, solder paste got into drying during storing became a common problem faced by most PCBA manufacturers, so How to solve solder paste dry problem is premier.

Part 3: The Difference Between Solder Mask and Solder Paste

Solder mask is a formal part of PCB, but solder paste ONLY for PCB assembly.
Solder mask is not allowed on the solder pads while solder paste can be printed on the solder pads openings.
Solder mask is used for applying solder mask ink, but solder paste is used for applying paste.
Solder mask has many available colors, but paste mask visually gray.
Solder mask is coating during PCB fabrication, but solder paste is printing when PCB assembly.

With over 16 years in PCB industry, Best Technology is one of the most reliable PCB and PCBA supplier in Asia, we commit to provide high quality products with excellent service before and after sales, to take care our customers wholeheartedly, and to treat customers’ business as ours. At the same time, we keep learning and continually to improve ourselves so that we can catch up the latest technology trend and provide better and better service for our customers.