Q: Working panel vs. shipping panel, the different size during PCB production.

« What's the main element defines PCB's size and shape?» PCB comes in all kinds of sizes and shapes. It might be round, rectangle or irregular shape. The various PCB shape is customized for its mechanism. About the PCB size, it could be as small as nail size or as big as lighting bar in department store. Here we’re talking about per unit of PCB. However, PCB manufacturers usually deliver PCB in panel size which composes of multiple units. Have you wondered the reason behind it? « High Usage Rate of Working panel could decrease selling price» In most of cases, the bare PCB will be mounted after arrival. And the panel size designs for the SMT equipment. If delivering in unit size, it’s difficult for clients or PCBA suppliers to mount components by using SMT equipment because the SMT track is fixed and usually per unit of PCB will be too small to fit into the SMT track. However, if the bare PCB don’t need to be assembled by SMT equipment, sometimes the clients will ask to deliver in unit size. The panel size we called here also known as shipping panel. During PCB production, the PCB manufactures will panelize various shipping panels into one working panel for its efficiency. When the usage rate of PCB working panel is high then it could also save the production cost because fewer raw material is wasted. Which means it could help to bring down the selling price. Once it enters CNC phase, the working panel will be routed into shipping panel. And it’ll become the panel that clients received.

Q: Basic methods of PCB assembly: THM & SMT

W hen it comes to the PCB assembly, there are two type of components that can be placed on a printed circuit board (PCB). The first one is Through-Hole Mounting (THM) and the Surface Mount Technology (SMT). You can make a decision on which one to use, even more, you can use both two of it on your designed PCB. Double-sided reflow requires two reflows, and have you ever wondered which side should pass through the reflow oven first? In general, the side with small components on it will pass through first. First of all, because the first reflow will not cause too much deformation to the PCB, the solder paste printing is relatively accurate, and the probability of small parts dislocation is small. Secondly, during the second reflow, the small components are facing up and will not come off due to the high temperature and gravity. Both methods have its Pros & Cons. We will go through this topic in the future articles.

Q: What is the purpose of using Nickel in PCB surface finish ENIG?

First, let's take a look at the characteristics of nickel. In addition to anti-oxidation, nickel can enhance the following mechanical properties. 1. Tensile strength 2. Elongation 3. Hardness 4. Internal 5. Fatigue life 6. Hydrogen embrittlement What role does nickel play in ENIG? The main purpose of using nickel in surface finish ENIG is to avoid the migration and diffusion between Cu and Ag, and play role as a barrier layer and protect copper layer from oxidation, furthermore, the nickel can also prevent poor conductivity and poor solderability. And in order to smooth the PCB assembly process, components are sometimes plated with a layer of nickel as a barrier layer.

Question 1

What is impedance control? - Part.1

Accepted Answer

If you have ever seen a printed circuit board, it may be aware that it has many conductors on it.
And in these conductors will have different types of signal transmission. Such signal will be changed or even distorted according the trace width and spacing, which may be affected by the etching, stack thickness, and other factors.

Therefore, especially PCBs with high speed and high frequency, the impedance value of the conductors should be controlled within a certain range, referred to as “impedance control”.

Question 2

The introduction of the aspect ratio of the PCB

Accepted Answer

The aspect ratio of PCB is the ratio of the hole depth to the hole diameter of the PCB. The main purpose is to quantify the plating difficulty of through-holes in PCB. The aspect ratio is the board thickness/aperture; for example, if the board thickness is 100 mil and the aperture is 10 mil, the aspect ratio is 10.

The larger the aspect ratio, the more difficult the plating is. This is because capillary action is likely to occur, making the plating thicker at the edge of the copper tube, resulting in a thinner center. If the center of the plated hole is too thin, the structural integrity of the plated hole will be compromised and it will crack under thermal or mechanical stress.

When we talk about aspect ratio, we will think about the conductive vias in a PCB that connect multiple layers together. However, if we plan to have plated to the mounting holes, it is important to pay attention to the value of the aspect ratio.

Question 3

Where are printed circuit boards used? IV

Accepted Answer

PCBs are used in many different sectors. Today we are talking about some applications in automotive components. In earlier times, PCBs were only used for things like windshield wipers and headlight switches, but today they enable many advanced features that make driving safer and easier.

Depending on what part of the car a PCB is used for, it may need to be able to withstand extreme temperatures or vibrations. It’s also critical that they perform reliably if involved in a safety feature of the car. Because of these challenges, manufacturers may use high TG materials and will require IATF16949 certification. They also use flex-rigid PCBs because of their ability to withstand vibrations.

Entertainment and navigation systems: Stereos and systems that integrate navigation and entertainment.
Control systems: Engine management systems and fuel regulators.
Sensors and others: Blind spots sensor, monitor systems, tire gage

*Related Article:
Where are printed circuit boards used?
Where are printed circuit boards used? II
Where are printed circuit boards used? III

Question 4

Working panel vs. shipping panel, the different size during PCB production.

Accepted Answer

«What's the main element defines PCB's size and shape?»
PCB comes in all kinds of sizes and shapes. It might be round, rectangle or irregular shape. The various PCB shape is customized for its mechanism. About the PCB size, it could be as small as nail size or as big as lighting bar in department store. Here we’re talking about per unit of PCB. However, PCB manufacturers usually deliver PCB in panel size which composes of multiple units. Have you wondered the reason behind it?

ExPlus PCB_working panel

«High Usage Rate of Working panel could decrease selling price»
In most of cases, the bare PCB will be mounted after arrival. And the panel size designs for the SMT equipment. If delivering in unit size, it’s difficult for clients or PCBA suppliers to mount components by using SMT equipment because the SMT track is fixed and usually per unit of PCB will be too small to fit into the SMT track. However, if the bare PCB don’t need to be assembled by SMT equipment, sometimes the clients will ask to deliver in unit size. The panel size we called here also known as shipping panel. During PCB production, the PCB manufactures will panelize various shipping panels into one working panel for its efficiency. When the usage rate of PCB working panel is high then it could also save the production cost because fewer raw material is wasted. Which means it could help to bring down the selling price. Once it enters CNC phase, the working panel will be routed into shipping panel. And it’ll become the panel that clients received.

Question 5

Lamination is coming after Black Oxidation

Accepted Answer

When inner layer is done, no matter how many layers there are, we will have to have them all laminated together. The key elements which decide whether the lamination is good or bad are black oxidation and the precision of positioning.
To be briefly speaking, black oxidation is a process between inner layer and lamination that cleans PCB and make it sticky for better combination of copper and epoxy.

Having all inner layers lay-up and positioning well, lamination process is done to laminate them together to be one single compound.

Question 6

Basic methods of PCB assembly: THM & SMT

Accepted Answer

When it comes to the PCB assembly, there are two type of components that can be placed on a printed circuit board (PCB). The first one is Through-Hole Mounting (THM) and the Surface Mount Technology (SMT). You can make a decision on which one to use, even more, you can use both two of it on your designed PCB.

Double-sided reflow requires two reflows, and have you ever wondered which side should pass through the reflow oven first? In general, the side with small components on it will pass through first. First of all, because the first reflow will not cause too much deformation to the PCB, the solder paste printing is relatively accurate, and the probability of small parts dislocation is small. Secondly, during the second reflow, the small components are facing up and will not come off due to the high temperature and gravity.

Both methods have its Pros & Cons. We will go through this topic in the future articles.

Question 7

What is the purpose of using Nickel in PCB surface finish ENIG?

Accepted Answer

First, let's take a look at the characteristics of nickel.

In addition to anti-oxidation, nickel can enhance the following mechanical properties.

1. Tensile strength

2. Elongation

3. Hardness

4. Internal

5. Fatigue life

6. Hydrogen embrittlement

What role does nickel play in ENIG?

The main purpose of using nickel in surface finish ENIG is to avoid the migration and diffusion between Cu and Ag, and play role as a barrier layer and protect copper layer from oxidation, furthermore, the nickel can also prevent poor conductivity and poor solderability.

And in order to smooth the PCB assembly process, components are sometimes plated with a layer of nickel as a barrier layer.

Question 8

3 Key elements for PCBA(PCB Assembly) quotation

Accepted Answer

The advantage of having PCB produced and assembled at one vendor
Once the bare board is produced, various components such as IC, BGA and other Active/passive components will be mounted on the PCB. After the PCB is assembled, there’ll be EMS before the end product i.e. smart phone, computer etc. completes. Thus, it makes sense that the majority of PCB suppliers will provide turnkey solution which includes PCB production, component procurement, PCB assembly or even EMS service to attract clients. For clients, the advantage of having PCB produced and assembly at same PCB supplier will be quality control. WHY? After the PCB assembled, the vendor could conduct function test, ICT test and so on based on client’s request. If the testing result fails, the PCB supplier could conduct experiment try to find the root cause and even fix the problem. On the other hand, if PCB produced at one vendor and assembly conducted at another. Most of time it takes longer process to find the root cause because it involves various parties. Let alone to mention the hassle of shipping the board back to the supplier.

3 Key elements for PCBA(PCB Assembly) quotation
So ExPlus is one of PCB suppliers could provide client PCB and PCB assembly service. In previous article, we have mentioned about the required information for PCB quotation. Today, we’re discussing the information required for PCB Assembly quotation. We’ll divide into 3 sectors as below.

1st element of PCBA quotation – Bill of Material
First, the client shall provide the basic information of BOM a.k.a. bill of material. In the BOM list, it shall include complete part number, usage quantity for each component and mounting location. Especially the part number, it’s crucial to provide the full component number of original manufacturer. Incomplete part number not only prolongs the searching time but affects the component’s size, the working voltage/current of and working temperature.

2nd element of PCBA quotation – Gerber or product’s picture
Second, the Gerber file or product’s picture is also required. The purpose is to compare the component’s corresponding location and also evaluating work method.

3rd element of PCBA quotation – Special requirements
Last, the client shall inform the supplier is there any specific requirement for the project. If ICT or function test is required, the testing condition, equipment and tooling shall be provided to the suppler. Also, for certain active components such as IC, the IC manufacturer will request the client to share the end product’s details such as application, selling location, the current situation of product’s development, end customer, annual usage and so on.

Finally, don’t forget to share the required quantity or even the EAU.

Check below link for relevant articles
Some Ways to Produce PCBA from PCB
PCB quotation x Gerber file

Question 9

How is the inner layer produced?

Accepted Answer

The pre-treatment that we discussed in last article was mainly to enhance the adhesion to help following inner layer process.

The first step is dry film lamination. To attach trace image photoresist film with base material to protect needed copper on the PCB. Second step to have UL light exposure to polymerize the film. Then the final step is to develop the trace on the PCB and to do etching with alkaline solution to remove the unprotected copper.

After the inner layer is done, of course AOI inspection is conducted to check if the trace is applied well enough.

Question 10

The Gerber File of Printed Circuit Board (PCB)

Accepted Answer

The Gerber file is an open 2D vector image format. It is a standard file type used in the PCB industry to describe the layer of the Printed circuit board (PCB), e.g. copper layers, solder mask, legend…etc. For fabrication purpose, the Gerber files must be contained in one .zip or .rar archive with the following standard file extensions:

Extension	Layer
pcb.GTL	Top Layer
pcb.GTS	Top Solder
pcb.GTO	Top Overlay
pcb.GBL	Bottom Layer
pcb.GBS	Bottom Solder
pcb.GBO	Bottom Overlay
pcb.TXT	Drill file
pcb.GML/GKO	Outline
pcb.GL2	Inner layer 2 (for multi-layer PCB)
pcb.GL3	Inner layer 3 (for multi-layer PCB)

Missing any files of the above list will cause PCB supplier a huge challenge. Also note, for getting a quote from a PCB supplier, the more detailed Gerber file you provide, the more accurate quote you will get!

Want to learn more about the Gerber file format? Please read the below article.
☑ What format of Gerber are most commonly used in PCB industry?

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