Archive for the ‘FAQ’ Category

How to clean the PCB assembled boards after soldering?

Friday, June 19th, 2020

Best Technology is a full turn-key assembly service company, we can supply the assembled board with very nice and clean surface.

Do you want to know how we control the cleaning process of PCBA? We would like to share the full cleaning process.

As we know, flux is used when soldering electrical components to a printed circuit board.

After assembly process finished, we need to remove all the unnecessary flux paste or other solder flux/ residue in order to avoid any quality issue.

Although it is a simple work, but to prepare some tools and preparation is necessary and important. Like wash board water, dust-free cloth, brush,Tweezers, static bracelets, finger gloves

Here is the how the cleaning process we made:

Step1:  

Use brush to brush the solder joint and solder flux on the soldered PCB. Applying some alcohol or acetone onto the brush, do not use too much pressure, as this may cause the solder point to break. Repeat the procedure as necessary, to remove remaining flux residue on the PCBA.

PCB assembly
Step1: Brush the solder joint and solder flux on the soldered PCB

Step2:

Wipe with a clean dust-free cloth to clean the assembled PCB.

Keep board clean and tidy to make sure no impurities and finger marks. Do the same process for bottom side.

PCB assembly
Step2:Wipe with a clean dust-free cloth to clean the assembled PCB.

Step3:

When above step finished, keep the board for an extra day to let the board dry enough before packing. Best QC guys will do final inspection for the finger prints under light. this will be helpful to check the cleaning result further.

PCB assembly
Step3:  final inspection for the finger prints under light

Step4:

Finally, use dust-free cloth to do the final cleaning and let the board dry and clean enough before package.

PCBA Cleaning process
Step4: use dust-free cloth to do the final cleaning.

Above are the process for how we clean the assembled boards.

Best Tech is a very professional manufacturer in printed circuit board and assembly. We clean each of assembled boards as the procedure we showed above.

If you are interesting to know more process for how we control the quality for the PCB assembled boards, contact us at any time, we will show you more.

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What kind of finishing recommended for the extra thin FR4 PCB

Thursday, June 18th, 2020

As we know, the extra thin PCB means the thickness of printed circuit board is more thin than normal PCB, which is refer to a thickness smaller than 0.4mm for 1L/ 2L & 4L PCB. For extra thin PCB, we know they are all very thin and are easily to be broken, so the option for the surface treatment of the extra thin PCB is very crucial.

So, what kind of finishing to be recommended for the extra thin Rigid PCB?

extra thin FR4 PCB
0.15mm extra thin FR4 PCB_Best Technology

Generally, there are 3 kinds finishing can be recommended for the extra thin PCB. It is OSP, ENIG (Electroless Nickel Immersion Gold), and ENEPIG.

extra thin pcb finishing
extra thin pcb finishing

But you may want to ask that lead-free Tin is also a common finishing for the PCB. Why not recommend LF HASL? 

That’s because while LF HASL Process, the PCB will be easy to be blew away, people will use heated compressed air to leveling (blowing) on the coating molten tin (lead) solder, during this process, the traces will be easy to be broken as well.

So normally, we will not recommend the LF HASL finishing for an ultra thin FR4 PCB.

HASL lead-free is only suitable for a board with minimum thickness of 0.6mm, while the standard gold immersion surface coating can support PCB with a minimum thickness of 0.2mm. For the surface treatment of ENEPIG , which plate only needs to be about 0.1 microns for palladium and about 0.1 microns for gold, (palladium is a precious metal that is much harder than gold), so for board with ENEPIG finishing, its surface will looks more smooth, that’s also why it is the most recommended surface treatment for an extra thin PCB.

extra thin PCB
0.13mm extra thin Rigid FR4 PCB_Best Technology

If you are searching for an extra thin PCB, feel freely to ask or send your inquiry to us. We will be pleased to share you more information regarding the extra thin PCB.

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What is SinkPad PCB?

Wednesday, June 17th, 2020

SinkPad PCB, also called Heat Sink or DTP (direct thermal path) PCB, it is a type of Copper base PCB used in thermoelectric separation application. It generally used for high power LED, the pad of LED touch the copper base directly, so that the heat generated by LED will dissipate quickly, which can achieve the best heat dissipation and conduction.

SinkPad PCB
SinkPad PCB

Thermoelectric separation technology is based on the higher heat dissipation requirements of high power electronic products, which needs to meet two basic conditions:

1.LED pad touches the base substrate directly.

It means we need to increase the path of the LED pad to the base substrate to accelerate the heat emission from the base material.

Two layers SinkPad PCB Stack up
Two layers SinkPad PCB Stack up

2.Higher heat dissipation substrate materials

Copper has a thermal conductivity of 401W/m·K, while aluminum has a thermal conductivity of 237W/m·K. Obviously, copper has better thermal conductivity because of its high density, high mass. Therefore, a SinkPad PCB usually means a SinkPad copper base PCB.

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Why do High Power LED mostly use COB light sources? What are the advantages?

Tuesday, June 16th, 2020

If we observe carefully, we will find that most of the high-quality surface light lamps in the market use COB light source, such as LED spotlights, Automotive, LED Backlight for LED TV, etc. What are the advantages of such choice?

Automotive
Automotive
LED Backlight for LED TV
LED Backlight for LED TV
LED spotlights
LED spotlights

First of all, we need to how the COB differ from the common MCPCB. “Chip-On-Board” Metal Core PCB is a type of MCPCB used in thermoelectric separation application. By using COB, the micro-chip (also known as “die”) directly touch the metal core where the heat dissipate, and electrically interconnect the trace of circuit board (wire-bonding) so that power supply can be provided.

Stack up
Stack up

Advantages of utilizing COB MCPCB over common MCPCB:

  1. High thermal conductivity(137W/m.K), High insulation, High pressure resistance
  2. High reflectivity: mirror aluminum≄98% (The reflectivity of Taiyo Soldermask used in common MCPCB is 75-80%, the highest is only 90%)
aluminum pcb
BAS15191
metal core pcb
BAS15192

Since the COB is packaged directly on the MCPCB, it’s easy assembly for high powers LED, direct heat dissipation through the substrate can not only reduce the manufacturing process and cost of the bracket, but also have the advantage of reducing heat dissipation resistance. So the spotlight produced by COB technology will be lighter, more flexible and able to realize more possibilities on the stage.

If you are also interested in COB, please feel free to contact me, I’m looking forward to communicating more with you.

You’re welcome to visit our website to learn more about us. https://www.bestpcbs.com/products/COB-MCPCB.htm

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What is high Tg PCB (fr4-170TG, TG 130-140, FR4 Tg150)

Thursday, June 11th, 2020

In recent years, there are more and more customers request to manufacture PCB with high Tg, in the following we would like to describe what is high Tg PCB.

fr4 170tg
fr4 170tg

Normally high Tg refers to high heat resistance in PCB raw material, the standard Tg for copper clad laminate is between 130 – 140℃, High Tg is generally greater than 170℃, and middle Tg is generally greater than 150℃. Basically the printed circuit board with Tg≄170℃, we call high Tg PCB. As the rapid development of electric industry, especially for the computer as the representative of electronic products, developing toward the high performance, high multilayer requires PCB substrate material with higher heat resistance to ensure high reliability. On the other hand, as a result of development of SMT, CMT with high density pcb assembly technology, the PCB manufacturing with small hole size, fine lines and thin thickness are more and more inseparable from the support of high heat resistance.

fr4 170tg
fr4 170tg

If the Tg of PCB substrate is increased, the heat resistance, moisture resistance, chemical resistance and stability of printed circuit boards will be improved as well. The high Tg applicates more in the lead free pcb manufacturing process.

Therefore, the difference between general FR4 and high Tg FR4 is, in the hot state, especially in the heat absorption with moisture, the high Tg PCB substrate will perform better than general FR4 in the aspects of mechanical strength, dimensional stability, adhesiveness, water absorption and thermal decomposition.

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We will be exhibiting at electronica Munich 2020

Monday, June 8th, 2020

Best Technology, a China- based assembly manufacturer will be exhibiting at electronica Munich 2020 in Bavaria, Germany at booth No. 623(Hall B1) from November 10, 2020 to November 13, 2020(Western Time). Actually, we have participated in this exhibition for continuous 2 years. Here are some pictures for your reference.

pcb exhibition
pcb exhibition
pcb exhibition
pcb exhibition
pcb exhibition
pcb exhibition
pcb exhibition
pcb exhibition

At our exhibition booth, attendees will be able to learn more about our company for PCB manufacturing and PCB assembly technology.

For interested professionals, Best Technology had on hand experts to offer detailed insights and experience on PCB assembly, covering PCB prototype and low/high-volume production. For more information on PCB assembly and fabrication, welcome to visit our booth.

You will see 10mm to 1,500 mm flexible circuit board, from 2 layer rigid-flex circuit to 50 layers, 1/2 OZ copper to 3 OZ, 0.15mm extra thin FR4 PCB to 30 OZ heavy copper, turn-key service from components sourcing,board fabrication(FPC, PCB, MCPCB, Ceramic PCB) and final assembly with programming and testing and metal dome that is used in conjunction with a printed circuit board, flex circuit, or membrane, become normally-open tactile switches. we have four types of metal domes: four legs with size from 5mm-20mm; triangle with size 4mm-12mm; round dome with size 4-16mm, oblong dome with size 3.7mm-58.1mm, and we also make dome with adhesive, named dome array.

You are warmly welcome to see how we can manage the components wastage and efficiency to help save your time, money and energy.

About electronica Munich:

Electronica is the international trade show for electronic components, systems and applications and shows the full range in all its diversity in width and depth as the world’s leading trade fair. It reflects the high degree of innovation throughout the industry. Exhibitors and users in the areas of systems, applications and technologies of electronics can receive the information of the latest innovations and developments in the fields of system peripherals, power engineering to printed circuit boards or EMS.

Welcome to visit us at Booth 623 from November 10, 2020 to November 13, 2020(Western Time).

electronica 2020
electronica 2020

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HS Code and Import Tariff Rates of Face Mask in Some Major Countries

Tuesday, June 2nd, 2020

Regarding HS code and duty rate of face masks in some major countries, we collected some information in main trade partners (US, Japan, EU, Korea, Taiwan, Australia, New Zealand) of China. This is aimed at the face masks such as personal protective masks without special function components, including medical face masks and disposable face masks. All of below information were published by the custom officially.

US:

According to Harmonized Tariff Schedule of the United States, HTSUS, the HS code of face masks in the US is 6307909889. And the duty rate imported from China is 7%. Regarding tariff imposed, according to announcement from the United States Trade Representative on March 12, 2020, the tariff is excluded for the face masks belonging to this HS code since September 1, 2019. Since then, all the face masks imported from China has been exempted from tariff. You can refer to the below chart for more information.

face mask tariff
face mask tariff

Japan:

The HS code of face masks in Japan is 630790029. The duty rate imported from China is 4.7%. To learn more, see below:

face mask tariff
face mask tariff

EU:

The duty paragraph for face masks imported from China in EU is 6307909899 and the duty rate is 6.3%. You can see below for more information:

face mask tariff
face mask tariff

Korea:

The duty paragraph for face masks imported from China in Korea is 6307909000, and normally, the tariff is 10%. However, from March 18, 2020 to June 30, 2020, Korea has been suspending imposing tariff for face masks from China(0 tariff currently), see below for more information:

face mask tariff
face mask tariff

Taiwan, China:

The HS code(also referred to as duty paragraph) of face masks imported from China mainland in Taiwan is 63079050.

And, the duty rate for face masks imported from China mainland is 7.5%. However, from February 27, 2020 to May 26, 2020, provisional tax rates (also referred to as“flexible tax rate”in Taiwan area) for face masks was carried out in Taiwan area, i.e. the tariff is zero. You can see below for more information:

face mask tariff
face mask tariff

Australia:

The HS code of face masks imported from China in Australia is 63079099 and the duty rate is 5%. See below for more information:

face mask tariff
face mask tariff

New Zealand:

The HS code of face masks imported from China in New Zealand is 63079028. Zero tariff is applied to the face masks imported from China according to “New free trade agreement”. See below for more information:

face mask tariff
face mask tariff

To learn more, see below document:

face-mask-hs-code-and-tariff-in-some-countries

Hope the above information is useful to you. And if you have any queries, comments or suggestions, contact us anytime. We will be glad to help you.

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Can you tell the difference between PWB and PCB?

Wednesday, May 20th, 2020

The abbreviations PWB and PCB are very common, especially in the field of electronics manufacturing. Therefore it is necessary to gain a clear understanding of the meaning of each one and the differences between the two. On this article, we will help our readers to distinguish PWB from PCB.

pcb vs pwb
pcb vs pwb

 PCB: Based on insulating substrate, it means a kind of products on which the wires are connected and components are printed from point to point on a dielectric substrate in a predetermined design. It is the English abbreviation of Printed Circuit Board.In a word, PCB stands for printed circuit board, where the width, side to side and multi-layer relationship(spacing) of conductor runs has or is designed to have a specific effect on circuit operation other than just a point to point connection.

 PWB: Based on insulating substrate, it means a kind of products on which the wires are connected from point to point on a dielectric substrate in a predetermined design. However, there is no printed component on it. PWBs are the early name of the British, because at that time there were only circuit diagrams on the circuit board, but no printed components. So they belonged to the more primitive board. Under its effect, now many traditional British and some Hong Kong people still call the circuit board to be PWB, which is the English abbreviation of Printed Wire Board. In a word, PWB stands for printed wiring board, one of the first uses when the issue was only a point to point connection.

The PCBs are the boards already equipped with various components, however the PWB is just a designed substrate with no components.

pcb vs pwb
pcb vs pwb

Moreover, PWB vs PCB greatly varies from one region to the other. For example, in the United States of America, the term Printed Circuit Board is more common in use while the use of the name PWB is more commonly used in Japan. In Japan, PWB is more preferred that PCB because it prevents confusion with another name, polychlorinated biphenyls, which refers to a particular poison available in Japan.

For your more information, in approximately 1999 the IPC Technical Activities Executive Committee made a mandate to only use the term PCB for all new document development because more often than not the printed circuitry design will have an impact on function.

If you are still confused or have any queries or comments about PCB, do not hesitate to contact us. Our sales team can give you a reply at our soonest convenience.

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What needs to be paid attention during PCBA process?

Thursday, April 16th, 2020

PCB is an indispensable part for any electronic equipment in small toys or computers., etc. The complex interconnection components include resistor, diode and capacitor, which help components work normally in series. In a sense, it is similar to the “brain” of the system. PCB assembly process must be of no any mistakes. Here are some points that need to be paid attention:

1.Supply chain management: In order to create high quality PCB, the first thing needing consideration is supply chain. For the availability, both quality and price are important, so is delivery time of components.

pcbassembly
pcbassembly

2.PCB layout. The common question during manufacturing stage is pcb layout in minor differences. Even though various types of designs looks the same to outward seeming, the manufacturing processes are different. You need to ensure PCB layout is feasible during manufacturing process.

3.Test-test has to be conducted after PCB assembly. What needs to be done is to design test point. Some tests include:

Micro-section analysis-also referred to as cross section analysis. This test contributes to identifying components fault and thermal-mechanical faults.

pcbassembly
pcbassembly

Solderability test. This test contributes to testing reliability of PCB solder pad, to ensure a firm surface and a reliable soldering point. It also contributes to confirming if storage will have an effect on solder components.

PCB pollution test-This can test many issues, such as corrosion and degradation. Scaling powder residue will result in pollution and thereby case components failure. Pollution analysis is famous for its accuracy and preciseness.

Optical microscope-This can test the issues relevant to PCB and soldering as well as overall pcb assembly. The process is famous for its speed, as it involves using high-power microscope to inspect incorrect structure.

Best Technology specializes in PCB assembly solutions since 2006, and if you would like to know more about turnkey PCB services(one-stop solutions about PCB), contact us anytime.

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How to Choose Thick or Thin FR4 PCB?

Monday, March 30th, 2020

If you’ve ever made a pie with your kids, you know that the thickness of your crust is important. Too thin, and the pie falls apart into a mess of filling. Too thick, and you might as well be chewing on a loaf of bread. Getting the thickness just right is what makes a pie worth eating.

Even though PCB substrate materials are non-conductive and do not carry current, the board material still affects the electrical performance. FR4 PCB substrate is widely used, and a thorough understanding of this material is very necessary.

FR4 PCB
FR4 PCB

FR4 Thickness Design Considerations

If you start your design process by choosing the correct board thickness, you will avoid to redesign later. A number of factors are influenced by the board thickness. Before you start designing your board, think about the following design issues:

Form factor and flexibility: Does your PCB have a strict form factor requirement? Thinner boards tend to be used in smaller devices and can flex more than a thicker board. A more flexible board may be unusable with a pick & place machine. Electrical connections in flexible boards can also break unless they have some mechanical support.

Components and connections: Will the device have any components that require the Printed Circuit Board to have a specific thickness? Components like USB edge connectors and some through-hole components require PCB in correct thickness. BGA connectors generally require thicker boards.

FR4 PCB
FR4 PCB

Impedance matching: Traces on adjacent layers in multi-layer boards form a capacitor, and the layer thickness and its dielectric constant determines the equivalent capacitance. Impedance matching is critical, and the capacitance must be taken into consideration when designing the board. This is especially true in HDI PCB.

High-speed devices: If you are working with a high-speed device, FR4 is always not the best option, and some other material should be used instead. FR4 PCB could be used in high-speed devices when the layers are coated with high-speed laminates. These laminates offer significantly improved electrical performance over standard FR4, and generally a combination of FR4 and a high-speed laminate may be preferable to an alternative material.

RF losses: FR4 tends to have higher losses than other PCB materials that are specialized for RF applications. Traces on FR4 will have larger attenuation at RF frequencies than other specialized materials for a given board thickness. The board thickness also changes the effective dielectric constant of the board, which then changes the required impedance matching in RF circuits.

Thermal and Reliability Considerations

All materials expand at higher temperatures, and the thermal expansion coefficient must be taken into consideration when choosing the board thickness. The thermal expansion coefficient of FR4 changes drastically above the material’s glass transition temperature (140℃). The board can become electrically and mechanically unstable when the board operates above the glass transition temperature.

The reliability of the trace materials, laminate materials, and solder joints on a PCB laminate are determined by the resistance to thermal cycling. When the thermal expansion coefficients of the different materials are mismatched, fatigue occurs after repeated thermal cycling. Copper plating in vias and solder balls are especially vulnerable to damage under thermal cycling.

This is a greater problem in thick FR4 PCB with high aspect ratio vias. Plating damage in through-hole vias, lifted pads, and cracked surface resin can occur under the stress caused by thermal cycling. A thicker board will have a larger expansion magnitude for a given via aspect ratio, resulting in more damage to the board and the electronic components. Thermal stresses can be huge when an FR4 PCB runs above the glass transition temperature.

Volumetric expansion is also critical in rigid-flex FR4 PCB. Thermoplastic adhesives with low glass transition temperatures and high Z-direction expansion coefficients can exhibit very large volume expansion at high temperature. Z-direction expansion in these situations can be as large as 500 ppm/℃.

Even though a thicker FR4 PCB has greater thermal mass and can dissipate more heat from electronic components, there is also the potential for more damage due to thermal expansion. Therefore, how to choose between a thick and thin FR4 PCB that satisfies all other requirements, the thinner board may be a better choice if the FR4 PCB will undergo thermal cycling frequently.

If you have any comments. queries or suggestions on this, welcome to contact us.

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