Reveal the advantages of PCB rigid-flex board! Why choose PCB rigid-flex board?

/in /by

In recent years, with the continuous development of science and technology, the demand for electronic products has become more and more diversified. As one of the core components of electronic products, PCB (Printed Circuit Board) rigid-flexible board has received widespread attention due to its unique advantages.

First, let us understand the definition of PCB rigid-flexible board. PCB rigid-flexible board is a circuit board that combines rigid and flexible characteristics. By stacking rigid boards and flexible circuit boards together, it achieves both rigid and flexible characteristics on one circuit board. This design can not only meet the requirements for high-density wiring and three-dimensional space layout, but also adapt to the needs of products for bending and folding.

So, what are the advantages of PCB rigid-flexible boards compared to traditional rigid boards?

PCB rigid-flexible board has high reliability and stability. Due to the existence of flexible circuit boards, PCB rigid-flexible boards can better absorb external shock and vibration, reducing the risk of circuit board damage and breakage. At the same time, the use of rigid boards also ensures the stability and reliability of the circuit board, allowing it to work normally in various harsh environments.
Secondly, rigid-flexible boards have a higher degree of design freedom. Traditional rigid board wiring is limited by plane layout, while rigid-flexible boards can arrange more components and lines in three-dimensional space through the bending and folding of flexible circuit boards, improving the wiring density and functional integration of circuit boards. , providing greater space for innovative product design.
Rigid-flex boards also have lower costs and fast production cycles. Compared with the traditional method of separate design and manufacturing of rigid boards and flexible circuit boards, the integrated design and manufacturing process of PCB rigid-flexible boards can greatly shorten the production cycle and reduce labor and material costs in the manufacturing process, thereby reducing the overall cost.
So, why choose PCB rigid-flex board?
Rigid-flexible boards can meet more application needs. Whether in the fields of consumer electronics, medical equipment, aerospace equipment or smart wearable devices, rigid-flexible boards can provide better performance and reliability and meet the special needs of different products for circuit boards.
Secondly, rigid-flexible boards have higher adaptability and scalability. Due to the existence of flexible circuit boards, rigid-flexible boards can better adapt to the shape, size and functional requirements of the product, and can be easily expanded and upgraded later, providing greater space for product development and improvement.

PCB rigid-flex board has become an important choice in the field of electronic product design and manufacturing due to its advantages of high reliability, design freedom, low cost and fast production cycle. Whether you are pursuing innovative design, improving product performance or reducing manufacturing costs, choosing PCB rigid-flexible board is a wise decision. It is believed that with the continuous advancement of technology, PCB rigid-flexible boards will play an important role in more fields and bring more convenience and possibilities to our lives.

Interpretation of the advantages and disadvantages of high-frequency pcb and ordinary pcb, which one is more suitable for your project?

/in /by

In the development of today’s electronics industry, PCB boards play a vital role. When choosing a suitable PCB board, we often face a question: should we choose high-frequency board or ordinary board? What are the pros and cons between the two? Which one is more suitable for your project?

Compared with ordinary boards, PCB high-frequency sheets have the following advantages in high-frequency circuit design:

1. Low loss: High-frequency plates have lower dielectric constant and loss factor, which can reduce energy loss during signal transmission and improve the stability and speed of signal transmission.

2. Strong anti-interference ability: High-frequency plates have good anti-interference performance, which can reduce the impact of external electromagnetic interference on the circuit and ensure the accuracy and stability of the signal.

3. High-speed transmission capability: High-frequency boards can support higher signal transmission rates and are suitable for high-frequency and high-speed data transmission application scenarios.

4. Good thermal stability: High-frequency plates have good thermal stability and can maintain good performance in high-temperature environments. They are suitable for occasions that require heat dissipation and high-temperature operation.

Ordinary boards have the following advantages in general circuit design:

1. Lower cost: Compared with high-frequency boards, ordinary boards are more economical and suitable for general electronic products.

2. Wide range of applications: Ordinary boards are suitable for various general electronic products, such as household appliances, computers, communication equipment, etc.

When selecting the right panels for your project, you need to evaluate and select based on specific project needs and performance requirements. If the project has higher requirements for high-frequency transmission, anti-interference ability, thermal stability, etc., then PCB high-frequency boards may be more suitable; if the project pays more attention to cost control and general performance requirements, then ordinary boards may be more suitable.

The final choice also needs to comprehensively consider the specific requirements of the project, cost budget, production cycle and other factors. It is recommended that you consult a professional PCB manufacturer or engineer when selecting board materials for more accurate advice and help.

What matters need to be paid attention to during wave soldering operations in PCBA processing?

/in /by

In PCBA processing and production, we often encounter situations where there are a lot of post-soldering materials. At this time, wave soldering is needed for post-soldering processing. So what should we pay attention to during wave soldering operations? Today I will talk to you about wave soldering:

We all know that the wave surface is covered by a layer of oxide scale, which remains almost static along the entire length of the solder wave. During the wave soldering process, the PCB contacts the front surface of the tin wave, and the oxide scale breaks. The tin wave is pushed forward without wrinkles? This shows that the entire oxide scale and PCB move at the same speed.

Generally, in order to avoid poor wave soldering, the following methods can be used: use components/PCBs with good solderability, increase the activity of the soldering flux, increase the preheating temperature of the PCB, increase the wetting performance of the pad, and increase the temperature of the solder. , Remove harmful impurities and reduce the cohesion of the solder to facilitate the separation of the solder between the two solder joints.

Common preheating methods in wave soldering machines: air convection heating, infrared heater heating, heating by a combination of hot air and radiation; wave soldering process curve analysis: the wetting time refers to the time when the wetting starts after the solder joint comes into contact with the solder Time and residence time refer to the time from when a certain solder joint on the PCB contacts the wave crest surface to leaving the wave crest surface. Preheating temperature refers to the temperature reached before the PCB contacts the wave crest surface. Welding temperature refers to the soldering temperature. Important welding parameters. Usually 50°C ~60°C higher than the melting point of the solder (183°C). In most cases, it refers to the temperature of the soldering furnace. The temperature of the PCB solder joints soldered during actual operation is lower than the furnace temperature. This is because the PCB absorbs heat.

Why choose high-precision HDI circuit board? Comprehensive analysis!

/in /by

HDI, or High Density Interconnector, is an advanced printed circuit board (PCB) manufacturing technology. Its design and manufacturing process undergoes precise calculations and fine processing, and has many advantages, so it is very popular. Next, we will comprehensively analyze the reasons for choosing high-precision HDI circuit boards.
1. High-density wiring: HDI circuit boards have higher circuit density and smaller size, allowing denser wiring and more compact designs. This makes them particularly suitable for small devices or electronic products that require a high degree of integration, such as smartphones, tablets, etc.
2. Higher performance: HDI circuit boards can provide higher signal transmission speeds and lower signal delays because they can use shorter signal paths and smaller wiring spacing. This makes them ideal for high-speed digital signal transmission or high-frequency applications.
3. Enhanced signal integrity: HDI circuit boards can reduce signal crosstalk and signal attenuation, and improve signal integrity and stability. This is very important for complex circuit designs and applications requiring high performance.
4. Higher reliability: HDI circuit boards usually use more advanced manufacturing processes and materials, such as microvia technology, blind and buried via technology, etc., making them more reliable and stable. This can reduce product failure rates and extend product life.
5. Reduced costs: Although the manufacturing cost of HDI circuit boards may be slightly higher than traditional circuit boards, the overall product cost can be reduced due to its more compact design and higher performance. For example, HDI circuit boards can reduce the use of external connectors and components, thereby saving space and material costs.
6. Increased design freedom: HDI circuit boards enable more flexible and innovative designs because they enable more complex wiring and more compact component layouts. This allows designers to better realize their design concepts and meet clients’ specific needs.
Choosing high-precision HDI circuit boards can bring higher performance, better reliability and greater design freedom to product design, especially for applications that require high-density wiring, high-speed signal transmission and high-performance requirements. It is a very ideal choice.

Is the circuit board covered with grid copper or solid copper?

/in /by

The so-called copper pouring is to use the idle space on the circuit board as the reference plane and then fill it with solid copper. These copper areas are also called copper filling.

The significance of copper coating is to: reduce the impedance of the ground wire and improve the anti-interference ability; reduce the voltage drop and improve the power efficiency; and connect to the ground wire to reduce the loop area.

Also for the purpose of keeping the PCB from deforming as much as possible during welding, most PCB manufacturers will also require PCB designers to fill the open areas of the PCB with copper or grid-like ground wires. If the copper is not handled properly, it will The gain outweighs the loss. Does copper coating have “more pros than cons” or “does more cons than pros”?

Everyone knows that at high frequencies, the distributed capacitance of the wiring on the printed circuit board will work. When the length is greater than 1/20 of the corresponding wavelength of the noise frequency, the antenna effect will occur, and the noise will be emitted outward through the wiring. If there is poorly grounded copper in the PCB, the copper becomes a tool for transmitting noise.

Therefore, in high-frequency circuits, do not think that the ground wire is connected to the ground somewhere. This is the “ground wire”. You must drill holes in the wiring with a spacing of less than λ/20, and connect it to the ground. The ground plane of the shelf is “well grounded”. If the copper coating is handled properly, the copper coating not only increases the current, but also plays the dual role of shielding interference.

There are generally two basic methods of copper pouring, namely large-area copper pouring and grid copper pouring. People often ask whether it is better to pour copper pouring over a large area or with grid copper pouring. It is difficult to generalize.

why? Covering a large area with copper has the dual functions of increasing current and shielding. However, if a large area of copper is covered with wave soldering, the board may warp or even blister. Therefore, when covering a large area with copper, several grooves are usually opened to alleviate blistering of the copper foil.

Simple grid copper coating mainly has a shielding effect, and the effect of increasing current is reduced. From the perspective of heat dissipation, the grid is beneficial (it reduces the heating surface of copper) and plays a certain role in electromagnetic shielding.

It should be pointed out that the grid is composed of traces in staggered directions. We know that for circuits, the width of the traces has its corresponding “electrical length” for the operating frequency of the circuit board (the actual size divided by The digital frequency corresponding to the working frequency is available, please refer to relevant books for details).

When the operating frequency is not very high, perhaps the role of the grid lines is not very obvious. Once the electrical length matches the operating frequency, it is very bad. You will find that the circuit cannot work properly at all, and interference is being emitted everywhere. signal of.

The suggestion is to choose based on the working conditions of the designed circuit board, and don’t stick to one thing. Therefore, high-frequency circuits have multi-purpose grids that require high interference resistance, and low-frequency circuits have high-current circuits and other circuits that commonly use complete copper laying.

Layout and routing of PCB components.

/in /by

PCB design is 90% in device layout and 10% in wiring. If the PCB is designed well, it can get twice the result with half the effort and also improve the electrical characteristics of the PCB.

For example, if you want to improve work efficiency, you need to pay attention to the space for wiring to prevent re-routing due to lack of space; or if you don’t want to find that it cannot be soldered when soldering the board, you need to pay attention to the placement of components and consider the edges of the board. Distance and other factors; and if you want a PCB board that looks good and is easy to debug, you need to pay more attention to the overall layout of the PCB. These must be planned in advance to make the PCB board symmetrical, clean and beautiful.

Of course, for the same circuit diagram, 100 electronic engineers will have 1,000 wiring schemes. Because designing a circuit board is also a process of artistic creation, and different people have different aesthetic standards, so we do not define fixed PCB layout wiring standards. But I will provide you with a basic idea, based on which designers can design the most beautiful PCB board in their mind.

PCB layout tips

1. Understand the physical limitations of the circuit board

Before placing components, determine the mounting holes of the circuit board, the location of edge connectors, and the mechanical size constraints of the circuit board.

2. Understand the circuit board manufacturing process

The assembly process and testing process of the circuit, whether it is necessary to reserve space for the PCB V-shaped groove, the component welding process, etc.

3. Leave breathing space for integrated chips

When placing components, try to leave at least 350mil between them. For chips with many pins, the space needs to be larger.

4. The same device has the same direction

For identical devices, keep the formation as consistent as possible. It facilitates the later assembly, inspection and testing of circuit boards and ensures consistent high solder joints.

5. Reduce lead crossings

Reduce lead crossings by adjusting device position and orientation. It can save a lot of effort for later wiring.

6. Place circuit edge components first

For devices that cannot be moved arbitrarily due to mechanical restrictions, they must be placed first, such as external connectors, switches, USB ports, etc. on the circuit board.

7. Avoid conflicts between devices

Absolutely avoid overlapping and sharing the pads of devices or overlapping the edges of devices in order to route them in a small circuit board. It is best to maintain a distance of 40mil between all devices.

8. Place the devices on the same side as much as possible

The devices on the circuit board are completed by an automatic device placement machine. The devices are only on one side. The PCB production process only needs one pass. Otherwise, the devices will be placed twice, which wastes production time and costs.

9. Keep the polarity of chip pins and devices consistent

If the polarity and orientation of the components on the circuit board are messy, it will hinder the successful soldering of the circuit board.

10. The device location is similar to that on the schematic diagram

When designing the schematic diagram, the positional relationship between the devices has been optimized (the shortest connections and the least crossovers), so it will be more reasonable to place the PCB devices according to the device positions on the schematic diagram.

PCB routing rules

1. Routing direction control rules

That is, the wiring directions of adjacent layers form an orthogonal structure. Avoid running different signal lines in the same direction on adjacent layers to reduce unnecessary inter-layer interference; when it is difficult to avoid this situation due to board structure limitations (such as some backplanes), especially when the signal rate is high, Consider using ground planes to isolate wiring layers and ground signal lines to isolate signal lines.

2. Open-loop inspection rules for wiring

Generally, wiring with one end floating (Dangling Line) is not allowed, mainly to avoid the “antenna effect” and reduce unnecessary interference radiation and reception, otherwise it may bring unpredictable results.

3. Impedance matching check rules

The wiring width of the same network should be consistent. Changes in line width will cause uneven line characteristic impedance. When the transmission speed is high, reflection will occur. This situation should be avoided in the design.

4. Trace length control rules

That is, the short line rule. When designing, the wiring length should be kept as short as possible to reduce interference problems caused by too long wiring. Especially for some important signal lines, such as clock lines, the oscillator must be placed very close to the device. The place.

5. Chamfering rules

Sharp angles and right angles should be avoided in PCB design, which will produce unnecessary radiation and poor process performance.

6. Device decoupling rules

Add necessary decoupling capacitors to the printed plate to filter out interference signals on the power supply and stabilize the power supply signal.

7. Ground loop rules

The minimum loop rule means that the loop area formed by the signal line and its loop should be as small as possible. The smaller the loop area, the less external radiation and the smaller the external interference received.

8. Integrity rules for power and ground layers

For areas with dense via holes, care should be taken to avoid the holes connecting to each other in the hollowed-out areas of the power supply and ground layers, forming a division of the plane layer, thereby destroying the integrity of the plane layer, and thereby causing an increase in the loop area of the signal line in the ground layer. .

9. Shielding protection

The corresponding ground loop rule is actually to minimize the loop area of the signal, which is more common in some more important signals, such as clock signals and synchronization signals.

10. Cabling closed-loop inspection rules

Prevent signal lines from forming self-loops between different layers. Such problems are prone to occur in multilayer board designs, and self-loops will cause radiated interference.

11. Isolated copper zone control rules

The emergence of isolated copper areas will bring about some unpredictable problems. Therefore, connecting the isolated copper areas with other signals will help improve the signal quality. Usually, the isolated copper areas are grounded or deleted.

PCB wiring rules: What are the connector connection methods?

/in /by

Everyone knows about PCB, but do you know about its wiring? As an integral part of the whole machine, a PCB generally cannot constitute an electronic product, and there must be problems with external connections. For example, electrical connections are required between PCBs, between PCBs and off-board components, and between PCBs and equipment panels. PCB wiring can be said to be a basic course for every electronic engineer. The following is a brief analysis of the wiring of each PCB component for your reference.

In more complex instruments and equipment, plug-in connectors are often used. This “building block” structure not only ensures the quality of product mass production, reduces the cost of the system, but also provides convenience for debugging and maintenance. When equipment fails, maintenance personnel do not have to check to the component level (that is, check the cause of the failure and trace it back to the specific components. This work takes a lot of time), as long as they determine which board is abnormal. It can be replaced immediately, troubleshooting in the shortest possible time, shortening downtime and improving equipment utilization. The replaced circuit board can be repaired in ample time and used as spare parts after repair.

1. Standard pin connection

This method can be used for external connection of PCB, especially in small instruments, pin connection is often used. Two PCBs are connected through standard pins. The two PCBs are generally parallel or vertical, making it easy to achieve mass production.

2. PCB socket

This method is to make a printed plug from the edge of the PCB. The plug part is designed according to the size of the socket, the number of contacts, the contact distance, the position of the positioning holes, etc., so that it matches the dedicated PCB socket.

When making boards, the plug part needs to be gold-plated to improve wear resistance and reduce contact resistance. This method has simple assembly, good interchangeability and maintenance performance, and is suitable for standardized mass production. The disadvantage is that the PCB cost increases, and the PCB manufacturing accuracy and process requirements are higher; the reliability is slightly poor, and poor contact is often caused by the oxidation of the plug part or the aging of the socket reed. In order to improve the reliability of external connections, the same lead wire is often led out in parallel through the contacts on the same side or both sides of the circuit board.

PCB socket connection methods are often used in products with multi-board structures. There are two types of sockets and PCB or base plates: reed type and pin type.

PCB wiring rules

1. Cross circuits are not allowed in printed circuits. For lines that may cross, “drilling” and “winding” can be used to solve them. That is, let a certain lead “drill” through the gap at the foot of other resistors, capacitors, and transistors, or “wind” through one end of a lead that may cross. In special cases, the circuit is very complicated. To simplify the design, Wire jumpers are allowed to solve cross-circuit problems.

2. Resistors, diodes, tubular capacitors and other components can be installed in two ways: “vertical” and “horizontal”. The vertical type means that the component body is installed and welded perpendicularly to the circuit board. Its advantage is that it saves space. The horizontal type means that the component body is installed and welded parallel and close to the circuit board. Its advantage is that the mechanical strength of the component installation is better. For these two different mounting components, the component hole spacing on the printed circuit board is different.

3. The grounding points of circuits of the same level should be as close as possible, and the power supply filter capacitor of this level of circuit should also be connected to the grounding point of this level. In particular, the grounding points of the base and emitter of the transistor of this level cannot be too far apart, otherwise interference and self-excitation will occur because the copper foil between the two grounding points is too long. A circuit using such a “one-point grounding method” will work more slowly. Stable and not prone to self-excitation.

4. The general ground wire must be strictly arranged according to the principle of high frequency-medium frequency-low frequency in the order of weak current to strong current. It must not be randomly connected over and over again. It is better to have longer wiring between levels. Follow this rule. In particular, the requirements for the grounding wire arrangement of the frequency converter head, regeneration head, and frequency modulation head are more stringent. If there is any improper grounding wire arrangement, self-excitation will occur and the grounding wire will not work. High-frequency circuits such as FM heads often use large-area surrounding ground wires to ensure good shielding effects.

5. High-current leads (public ground wires, power amplifier power leads, etc.) should be as wide as possible to reduce wiring resistance and voltage drop, and reduce self-excitation caused by parasitic coupling.

6. Keep high-impedance traces as short as possible, and low-impedance traces as long as possible, because high-impedance traces tend to emit and absorb signals, causing circuit instability. The power wire, ground wire, base wire of non-feedback components, emitter wire, etc. are all low-impedance wires. The base wire of the emitter follower and the ground wires of the two channels of the radio must be separated and formed into a separate path. , until the end of the function and then combined together. If the two ground wires are connected back and forth, it is easy to produce crosstalk and reduce the separation.

Explore the PCB rigid-flex board process: making electronic devices more flexible and adaptable!

/in /by

In today’s era of rapid technological advancement, the flexibility and adaptability of electronic devices have become people’s pursuit of products. As an advanced technology, PCB rigid-flex board technology is attracting more and more attention and applications. This article will analyze the PCB rigid-flex board process and explore its advantages in improving the flexibility and adaptability of electronic equipment.

PCB rigid-flex board technology is a manufacturing process that combines rigid boards and flexible boards. Through rigid-flex integration, electronic devices can have the stability of rigid boards and the bending of flexible boards. This process can realize the free change of electronic devices in different forms and environments, thereby better adapting to user needs.

PCB rigid-flex board technology can greatly reduce the size and weight of electronic equipment. Traditional rigid boards have certain design limitations, while flexible boards can bend and fold more flexibly. By combining the two, electronic devices can achieve smaller and lighter designs while maintaining stability, making them easy to carry and use.

The rigid-flex board process can also improve the durability and reliability of electronic equipment. Flexible boards have good earthquake resistance, impact resistance and high temperature resistance, and can effectively protect electronic components from the external environment. The rigid board can provide better support and fixation to prevent electronic components from loosening or being damaged. Through the combination of the two, electronic equipment can maintain stable performance and reliable working status in the face of various complex environments and working conditions.

In addition, the PCB rigid-flex board process can also improve the wiring density and performance of electronic equipment. Flexible boards have high bending ability and small thickness, which can achieve more compact wiring design and improve the connection efficiency between electronic components. Rigid boards, on the other hand, can provide better electrical performance and signal transmission quality. Through the combination of the two, electronic devices can achieve higher integration and better performance.

The emergence of PCB rigid-flex board technology provides a new solution for the flexibility and adaptability of electronic equipment. Through the combination of rigid and flexible, electronic devices can be further improved in terms of size, weight, durability and performance. In the future, with the continuous development and application of this technology, we have reason to believe that electronic devices will become more and more flexible and adaptable, bringing people a more convenient and comfortable technological experience!

Quickly understand the various types and uses of fpc!

/in /by

Flexible Printed Circuit Board (FPC) is a flexible electronic component that is widely used in various electronic devices. It is different from traditional rigid circuit boards. Its main feature is that it can be bent, folded and twisted to adapt to various complex shapes and space constraints. In the field of modern technology, FPC is used more and more widely. Today we will reveal the secrets of flexible circuit boards and quickly understand the various types and uses of FPC.
First, let us understand the basic structure of fpc. FPC consists of conductive layer, insulating layer and protective layer. The conductive layer is usually made of copper foil and is used to transmit current and signals. The insulating layer is made of materials such as flexible polyimide and serves to isolate the conductive layer. The protective layer is used to protect the FPC from the external environment, such as moisture, dust and mechanical damage.
According to different application requirements, FPC can be divided into many types.
Single-sided FPC is the simplest type, with only one conductive layer, so the wiring density is not high, but it has good flex resistance.
Double-sided FPC has conductive layers on both sides, which is suitable for some scenarios that require more complex circuit layouts, but its softness is worse than that of single-sided panels.
Multilayer FPC, which has multiple conductive layers embedded inside, is suitable for more complex electronic devices.
Rigid-flexible board combines the characteristics of rigid circuit board and flexible circuit board, which can not only meet the needs of rigid structure, but also adapt to certain bending.

 

So, what are the main applications of fpc? First of all, FPC is widely used in mobile devices, such as smartphones, tablets, etc. Because FPC has high flexibility and foldability, it can adapt to the needs of equipment of various shapes and sizes. Secondly, it is also widely used in the field of automotive electronics. In cars, FPC can connect various sensors, displays and control modules to realize vehicle intelligence and automation. In addition, it is also commonly used in medical equipment, aerospace, industrial control and other fields to provide reliable circuit connections for various electronic devices.
Flexible circuit boards are flexible and foldable electronic components that are widely used in various electronic devices. By understanding the types and uses of FPC, we can better understand and apply this advanced electronic component and promote the development and innovation of science and technology.

What is the science of plugging holes in PCB circuit boards?

/in /by

Conductive holes are also known as conductive holes. In order to meet customer requirements, circuit board via holes must be plugged. After a lot of practice, the traditional aluminum sheet plugging process was changed, and white mesh was used to complete the circuit board surface solder mask and plugging. hole. Stable production and reliable quality.

Via holes play the role of connecting circuits to each other. The development of the electronics industry also promotes the development of PCB and puts forward higher requirements for printed board manufacturing technology and surface mounting technology. Via hole plugging technology emerged as the times require, and it should meet the following requirements:

(1) There is only copper in the via hole, and the solder mask can be plugged or not;

(2) There must be tin-lead in the via hole, and there is a certain thickness requirement (4 microns). There must be no solder mask ink entering the hole, causing tin beads to be hidden in the hole;

(3) The via hole must be plugged with solder mask ink, opaque, and must not have tin rings, tin beads, and flatness.

As electronic products develop in the direction of “light, thin, short and small”, PCBs are also developing towards high density and difficulty. Therefore, a large number of SMT and BGA PCBs appear. Customers require plug holes when mounting components. The main ones are Five functions:

(1) Prevent tin from the via hole penetrating the component surface to cause a short circuit when the PCB is wave soldered; especially when we place the via hole on the BGA pad, we must first make a plug hole and then gold plating to facilitate the welding of the BGA.

(2) Avoid flux remaining in the via hole;

(3) After surface mounting and component assembly in the electronics factory are completed, the PCB must be vacuumed on the testing machine to form negative pressure before completion:

(4) Prevent surface solder paste from flowing into the holes, causing virtual soldering and affecting placement;

(5) Prevent tin beads from popping up during wave soldering and causing short circuits.

Implementation of conductive hole plugging process
For surface mount boards, especially the mounting of BGA and IC, the via holes must be flat, with a convexity of plus or minus 1 mil. There must be no red tinting on the edges of the via holes; tin beads are hidden in the via holes. In order to satisfy customers According to the requirements, the via hole plugging process can be described as diverse, the process flow is extremely long, and the process control is difficult. Problems such as oil leakage during hot air leveling and green oil solder resistance testing and oil explosion after curing often occur. Based on the actual production conditions, we will summarize various PCB hole plugging processes and make some comparisons and elaborations on the processes, advantages and disadvantages:

Note: The working principle of hot air leveling is to use hot air to remove excess solder from the surface and holes of the printed circuit board. The remaining solder is evenly covered on the pads, non-resisting solder lines and surface packaging points. It is a surface treatment method for printed circuit boards. one.

1. Hole plugging process after hot air leveling
This process flow is: board solder mask→HAL→hole plugging→curing. The non-hole plugging process is used for production. After hot air leveling, an aluminum sheet screen or an ink-blocking net is used to complete the via hole plugging of all fortresses required by the customer. The plugging ink can be photosensitive ink or thermosetting ink. Under the condition of ensuring that the color of the wet film is consistent, it is best to use the same ink as the board surface. This process can ensure that the via hole does not lose oil after hot air leveling, but it can easily cause the plug hole ink to contaminate the board surface and make it uneven. Customers can easily cause false soldering during mounting (especially in BGA). So many customers do not accept this method.

2. Hole plugging process before hot air leveling
2.1 Plug the holes with aluminum sheets, solidify, and grind the plate for pattern transfer.

In this process, a CNC drilling machine is used to drill out the aluminum sheet that needs to be plugged, and the holes are made into a screen to plug the holes to ensure that the via holes are filled with plugging ink. The plugging ink can also be thermosetting ink, which must have high hardness. , the resin shrinkage changes little, and the bonding force with the hole wall is good. The process flow is: pre-processing → hole plugging → plate grinding → pattern transfer → etching → solder mask on the board surface

This method can ensure that the via hole plug hole is flat, and hot air leveling will not cause quality problems such as oil explosion and oil loss on the edge of the hole. However, this process requires one-time thickening of copper to make the hole wall copper thickness meet the customer’s standards. Therefore, there are very high requirements for copper plating on the entire board, and there are also high requirements for the performance of the plate grinding machine to ensure that the resin on the copper surface is completely removed and the copper surface is clean and not contaminated. Many PCB factories do not have a one-time copper thickening process, and the performance of the equipment does not meet the requirements, resulting in this process being rarely used in PCB factories.

2.2 Plug the holes with aluminum sheets and directly screen-print the solder mask on the board.

In this process, a CNC drilling machine is used to drill out the aluminum sheet that needs to be plugged, and the screen is made into a screen. It is installed on the screen printing machine to plug the holes. After the plugging is completed, it should not be parked for more than 30 minutes. A 36T screen is used to directly screen the board surface to resist soldering. The process flow is: pre-treatment – hole plugging – screen printing – pre-baking – exposure – development – curing

Using this process can ensure that the via holes are well covered, the plug holes are flat, and the wet film has the same color. After hot air leveling, it can ensure that the via holes are not tinned and there are no tin beads hidden in the holes. However, it is easy to cause the ink in the holes to be stained after curing. pad, resulting in poor solderability; after hot air leveling, the edges of the via holes bubble and oil is removed. Production control using this process is difficult, and process engineers must adopt special processes and parameters to ensure the quality of the plug holes.

2.3 After the aluminum sheet is plugged, developed, pre-cured, and ground, the board surface is soldered.

Use a CNC drilling machine to drill out the aluminum sheet that requires plugging holes, make a screen, install it on a shift screen printing machine to plug the holes, the plug holes must be full, preferably protruding on both sides, and then solidify and grind the plate for surface treatment. The process flow is: pre-processing – hole plugging – pre-baking – development – pre-curing – solder mask on the board

Since this process uses plug hole curing, it can ensure that the via holes do not lose oil or explode after HAL. However, after HAL, it is difficult to completely solve the problem of tin beads hiding in via holes and tin application on via holes, so many customers do not accept it.

2.4 The solder mask and plug holes on the board are completed at the same time.

This method uses a 36T (43T) screen, installed on the screen printing machine, using a backing plate or nail bed to plug all the via holes while completing the board. The process flow is: pre-processing – screen printing – -Pre-baking–exposure–development–curing.

This process takes a short time and has a high utilization rate of the equipment. It can ensure that no oil will fall out of the via holes after hot air leveling, and no tin will be applied to the conductive holes. However, due to the use of silk screen printing for plugging, there is a large amount of air in the via holes, which will cause a large amount of air in the via holes during curing. , the air expands and breaks through the solder mask, causing holes and unevenness. Hot air leveling will leave a small amount of tin hidden in the via holes. At present, after a lot of experiments, our company has selected different types of inks and viscosities, adjusted the pressure of screen printing, etc., and basically solved the voids and unevenness of the vias, and has adopted this process for mass production.