Q: Drilling Hole for Different Layers Connection

Drilling Hole for Different Layers Connection After lamination, the inner layer is done. What follows next is to drill hole for connection of trace in different layers and also those components holes that will be mounted when assembly. To program the drilling machine as per PCB data from the OP, the drilling hole process begins. Drill Process After the drilling hole process is all done, it is all ready for the next PTH copper plating process.

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.

Question 1

What is Glass Transition Temperature, also known as TG?

Accepted Answer

Sometimes you can see TG150/TG170, etc. on the PCB material. What does this TG mean?

TG(Glass Transition Temperature) is one of the most important characteristics of all plastic and epoxy resin materials. In fact, TG(Glass Transition Temperature) value is also one of the quality indicators of glass fiber for PCB.
When the temperature is lower than the glass transition temperature (TG), the plastic enters glassy state which is rigid but with brittle characteristics. Just like the characteristics of glass, it is hard but easily brittle.
When the temperature is higher than the glass transition temperature (TG), the plastic parts will show a soft and flexible rubbery state. Therefore, the glass transition temperature (TG) is generally the temperature at which the plastics undergo a phase transition from the glassy state to the rubber state.

As PCB’s TG(Glass Transition Temperature) increasing, the heat resistance, moisture resistance, chemical resistance, and resistance stability characteristics of PCB prodution will be strengthened and improved. The higher the TG(Glass Transition Temperature) value, the higher temperature PCB can endure, especially in the lead-free manufacturing process, where there are more applications of high TG(Glass Transition Temperature).

High TG(Glass Transition Temperature) refers to high heat resistance. The development of high functionalization and high multi-layering requires higher heat resistance of PCB substrate materials as an important guarantee. The emergence and development of high-density mounting technologies represented by SMT and CMT have made PCBs increasingly require specifications with high heat resistance of substrates in terms of small apertures, fine lines, and thinning.

Thus, regards PCB production, the difference between FR-4 and high TG FR-4 is that in a high temperature state, especially when heated after moisture absorption, the material’s mechanical strength, dimensional stability, adhesiveness, water absorption, thermal decomposition, and thermal expansion.

Question 2

Where are printed circuit boards used? V

Accepted Answer

Today we are talking about some applications in military products. Military-grade PCBs carry stringent performance, sourcing, and manufacturing requirements that are encoded in a number of standards, such as IPC-A-610E Class 3, MIL-PRF-31032, MIL-PRF-55110, etc. These standards specify performance requirements for high-performance electronic products.

These military printed circuit boards will often be subjected to high pressures and stresses, meaning they will frequently require high-temperature substrates like temperature-resistant laminates, copper or aluminum. Military PCB manufacturers must produce PCBs that will resist heat-induced oxidation and effectively dissipate heat in a low-weight design.

• Auxiliary power units for radar control systems
• Radio communications systems
• Control tower systems
• LED lighting systems
• Underwater navigation systems
• Jet instrumentation
• Jamming systems

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

Question 3

Final step before PCB delivery for International shipment – Standard Packing Procedure at ExPlus

Accepted Answer

«Standard Packing Procedure at ExPlus»

After the PCB passed FQC inspection and OQC inspector confirmed O.K., the PCB will be transferred to the warehouse and waiting for packing. When the packing staff receive PCB, he or she will first check the part number and OP, and then follow client requirements if there’s any for packing.

«Reduce potential risks during International transportation»

Different from domestic delivery, the PCB manufacturer shall consider all kinds of risk such as bumpy, falling and so on during international shipping. To reduce the risk of PCB damage due to transportation, ExPlus’ standard packing procedure will be following. First, the carton shall be multiple layers waterproof carton. Second, before place PCB into the carton, the packing staff will put buffer packaging materials(at ExPlus we use wave board as below image shows) on the bottom of carton and then surround the PCB with more wave boards for protection. Once the packing staff ensure the board won’t slide due to any movement, he or she could seal the box and measure the weight. For safety concern, the Net weight of each carton won’t exceed 20 k.g.. On outside of carton, the details including part number, PO, D/C, quantity and weight shall be listed. Once the box is sealed, it’s all ready to go.

ExPlus package

Question 4

Drilling Hole for Different Layers Connection

Accepted Answer

Drilling Hole for Different Layers Connection

After lamination, the inner layer is done.

What follows next is to drill hole for connection of trace in different layers and also those components holes that will be mounted when assembly.

To program the drilling machine as per PCB data from the OP, the drilling hole process begins.

Drill Process

After the drilling hole process is all done, it is all ready for the next PTH copper plating process.

Question 5

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 6

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 7

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 8

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 9

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 10

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.

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