As an electronic engineer, designing circuits is a necessary and hard skill, but no matter how perfect the principle design is, if the circuit board design is unreasonable, the performance will be greatly reduced, and in serious cases, it may not even work properly.

No matter what software is used, there is a general procedure for PCB design. Going in order will save time and effort, so I will introduce it according to the production process. (Because the Protel interface style is close to that of Windows, the operating habits are also similar, and it has powerful simulation functions, so many people use it, so this software will be used as an explanation.)

Schematic design is the preliminary preparation work. It is often seen that beginners directly draw the PCB board to save trouble. This will not be worth the gain. For simple boards, if you are familiar with the process, you may as well skip it. But for beginners, they must follow the process. On the one hand, they can develop good habits. On the other hand, this is the only way to avoid making mistakes with complex circuits.

When drawing schematic diagrams, when designing hierarchies, attention should be paid to the final connection of each file into a whole, which is also of great significance for future work. Due to differences in software, some software may appear to be connected but actually not connected (in terms of electrical performance). If you don’t use relevant testing tools to detect it, if something goes wrong, it will be too late until the board is ready. Therefore, I have repeatedly emphasized the importance of doing it in order, hoping to attract everyone’s attention.

The schematic diagram is based on the designed project. As long as the electrical connections are correct, there is nothing much to say. Below we focus on discussing the specific issues in the board making process.

1. Make physical borders

The closed physical border is a basic platform for future component layout and wiring, and also constrains automatic layout. Otherwise, the components coming from the schematic diagram will be at a loss. But you must pay attention to accuracy here, otherwise you will be in trouble if there are installation problems in the future. In addition, it is best to use arcs at corners. On the one hand, it can avoid sharp corners from scratching workers, and at the same time, it can reduce stress. In the past, one of my products always had the case PCB board broken during transportation. It was fine after using arc.

2. Introduction of components and networks

It should be very simple to introduce components and networks into the drawn borders, but problems often arise here. You must carefully follow the errors prompted to solve them one by one, otherwise you will have to spend more effort later. The problems here generally include the following:

The packaging form of the component cannot be found, there is a component network problem, there are unused components or pins, the comparison prompts that these problems can be solved quickly.

3． Component layout

The layout and wiring of components have a great impact on the product’s life, stability, and electromagnetic compatibility, and should be paid special attention to. Generally speaking, there should be the following principles:

(1) Placement order

First place the fixed-position components related to the structure, such as power sockets, indicator lights, switches, connectors, etc. After placing these components, use the LOCK function of the software to lock them so that they will not be moved accidentally in the future. Then place special components and large components on the circuit, such as heating components, transformers, ICs, etc. Place the widget last.

(2) Pay attention to heat dissipation

The component layout should also pay special attention to heat dissipation issues. For high-power circuits, heating components such as power tubes and transformers should be placed as far apart as possible to facilitate heat dissipation. Do not concentrate them in one place, and do not have high capacitances too close to avoid premature aging of the electrolyte.

4． wiring

Wiring principles

The knowledge of routing is very profound, and everyone will have their own experience, but there are still some general principles.

◆It is better for high-frequency digital circuit traces to be thinner and shorter.

◆Attention should be paid to the isolation between large current signals, high voltage signals and small signals (the isolation distance is related to the withstand voltage to be withstood. Normally at 2KV, the distance between the boards should be 2mm, and the distance above this should be increased proportionally. , for example, if it wants to withstand the 3KV withstand voltage test, the distance between high and low voltage lines should be more than 3.5mm. In many cases, in order to avoid creepage, slots are also made between high and low voltage on the printed circuit board.)

◆When wiring two panels, the wires on both sides should be routed perpendicularly, obliquely, or bent to avoid being parallel to each other to reduce parasitic coupling; printed wires used as input and output of the circuit should avoid adjacent parallel lines as much as possible. , to avoid feedback, it is best to add a ground wire between these wires.

◆Make the wiring corners larger than 90 degrees as much as possible, avoid corners below 90 degrees, and use 90-degree corners as little as possible

◆If they are both address lines or data lines, the length of the lines should not be too different, otherwise the short lines will need to be artificially bent to compensate.

◆Try to run the traces on the welding surface as much as possible, especially for PCBs with through-hole technology

◆Use as few vias and jumpers as possible

◆The soldering pads of single-sided panels must be large, and the wires connecting the pads must be thick. Use teardrops if you can. The quality of ordinary single-sided panel manufacturers will not be very good, otherwise there will be problems with welding and RE-WORK.

◆Large areas of copper should be covered in a grid pattern to prevent the board from generating bubbles and bending due to thermal stress during wave soldering. However, in special occasions, the flow direction and size of the GND must be considered, and it cannot simply be filled with copper foil. , but need to route

◆Components and wiring should not be placed too close to the edge. Common single panels are mostly made of paper boards, which are easy to break after being stressed. If you connect wires or place components at the edge, they will be affected.

◆The convenience of production, debugging and maintenance must be considered

It is very important to deal with ground issues for analog circuits. Noise generated on the ground is often unpredictable, but once it occurs, it will cause great trouble and should be avoided. For power amplifier circuits, extremely small ground noise will have a significant impact on the sound quality due to the amplification of the subsequent stages; in high-precision A/D conversion circuits, if there are high-frequency components on the ground line, there will be a certain temperature drift, which will affect the sound quality. Amplifier work. At this time, you can add decoupling capacitors to the 4 corners of the board, connect one leg to the ground on the board, and connect the other leg to the mounting hole (connected to the chassis through screws), so that this component can be eliminated, and the amplifier and AD can also It’s stable.

In addition, the issue of electromagnetic compatibility has become even more important now that people are paying more attention to environmentally friendly products. Generally speaking, there are three sources of electromagnetic signals: signal source, radiation, and transmission line. Crystal oscillator is a common high-frequency signal source. In the power spectrum, the energy value of each harmonic of the crystal oscillator will be significantly higher than the average value. A feasible approach is to control the amplitude of the signal, ground the crystal oscillator shell, shield the interference signal, and use special filter circuits and devices.

What needs special explanation is the snake-shaped wiring, because its functions are different depending on the application. It is used on some clock signals in the computer motherboard, such as PCIClk and AGP-Clk. It has two functions: 1. Impedance matching 2. Filter inductor.

For some important signals, such as the HUBLink in the INTELHUB architecture, there are 13 wires in total and the frequency can reach 233MHZ. They must be strictly equal in length to eliminate the hidden dangers caused by time lag. At this time, snake wiring is the only solution.

Generally speaking, the line spacing of snake-shaped traces is >= 2 times the line width; if it is used in an ordinary PCB board, in addition to having the function of a filter inductor, it can also be used as an inductor coil of a radio antenna, etc.

5. Adjustment and improvement

After completing the wiring, all that needs to be done is to make some adjustments to the text, individual components, and wiring and apply copper (this work should not be done too early, otherwise it will affect the speed and cause trouble to the wiring), also for the convenience of production, Debugging and maintenance.

Copper coating usually refers to filling the blank area left after wiring with a large area of copper foil. You can lay GND copper foil or VCC copper foil (but this will easily burn the device in the event of a short circuit. It is best to ground it unless you have to. To increase the conduction area of the power supply to withstand larger current, connect to VCC). Ground wrapping usually refers to wrapping a bunch of signal lines with special requirements with two ground wires (TRAC) to prevent them from being interfered by or interfering with others.

If you use copper instead of ground wire, you must pay attention to whether the entire ground is connected, the current size, flow direction, and whether there are any special requirements to ensure that unnecessary mistakes are reduced.

6. Check the network

Sometimes due to misoperation or negligence, the network relationship of the drawn board is different from the schematic diagram. In this case, it is necessary to check. Therefore, after finishing the painting, you must not rush to hand it over to the plate maker. You should check it first and then proceed with the follow-up work.

7. Use the simulation function

After completing these tasks, if time permits, software simulation can also be performed. Especially for high-frequency digital circuits, some problems can be discovered in advance and greatly reduce the workload of debugging in the future.

As an electronic engineer, designing circuits is a necessary and hard skill, but no matter how perfect the principle design is, if the circuit board design is unreasonable, the performance will be greatly reduced, and in serious cases, it may not even work properly. Based on my experience, I have summarized the following things that should be paid attention to in PCB design. I hope it can inspire you.

No matter what software is used, there is a general procedure for PCB design. Going in order will save time and effort, so I will introduce it according to the production process. (Because the Protel interface style is close to that of Windows, the operating habits are also similar, and it has powerful simulation functions, so many people use it, so this software will be used as an explanation.)

Schematic design is the preliminary preparation work. It is often seen that beginners directly draw the PCB board to save trouble. This will not be worth the gain. For simple boards, if you are familiar with the process, you may as well skip it. But for beginners, they must follow the process. On the one hand, they can develop good habits. On the other hand, this is the only way to avoid making mistakes with complex circuits.

When drawing schematic diagrams, when designing hierarchies, attention should be paid to the final connection of each file into a whole, which is also of great significance for future work. Due to differences in software, some software may appear to be connected but actually not connected (in terms of electrical performance). If you don’t use relevant testing tools to detect it, if something goes wrong, it will be too late until the board is ready. Therefore, I have repeatedly emphasized the importance of doing it in order, hoping to attract everyone’s attention.

The schematic diagram is based on the designed project. As long as the electrical connections are correct, there is nothing much to say. Below we focus on discussing the specific issues in the board making process.

1. Make physical borders

The closed physical border is a basic platform for future component layout and wiring, and also constrains automatic layout. Otherwise, the components coming from the schematic diagram will be at a loss. But you must pay attention to accuracy here, otherwise you will be in trouble if there are installation problems in the future. In addition, it is best to use arcs at corners. On the one hand, it can avoid sharp corners from scratching workers, and at the same time, it can reduce stress. In the past, one of my products always had the case PCB board broken during transportation. It was fine after using arc.

2. Introduction of components and networks

It should be very simple to introduce components and networks into the drawn borders, but problems often arise here. You must carefully follow the errors prompted to solve them one by one, otherwise you will have to spend more effort later. The problems here generally include the following:

The packaging form of the component cannot be found, there is a component network problem, there are unused components or pins, the comparison prompts that these problems can be solved quickly.

3． Component layout

The layout and wiring of components have a great impact on the product’s life, stability, and electromagnetic compatibility, and should be paid special attention to. Generally speaking, there should be the following principles:

(1) Placement order

First place the fixed-position components related to the structure, such as power sockets, indicator lights, switches, connectors, etc. After placing these components, use the LOCK function of the software to lock them so that they will not be moved accidentally in the future. Then place special components and large components on the circuit, such as heating components, transformers, ICs, etc. Place the widget last.

(2) Pay attention to heat dissipation

The component layout should also pay special attention to heat dissipation issues. For high-power circuits, heating components such as power tubes and transformers should be placed as far apart as possible to facilitate heat dissipation. Do not concentrate them in one place, and do not have high capacitances too close to avoid premature aging of the electrolyte.

4． wiring

Wiring principles

The knowledge of routing is very profound, and everyone will have their own experience, but there are still some general principles.

◆It is better for high-frequency digital circuit traces to be thinner and shorter.

◆Attention should be paid to the isolation between large current signals, high voltage signals and small signals (the isolation distance is related to the withstand voltage to be withstood. Normally at 2KV, the distance between the boards should be 2mm, and the distance above this should be increased proportionally. , for example, if it wants to withstand the 3KV withstand voltage test, the distance between high and low voltage lines should be more than 3.5mm. In many cases, in order to avoid creepage, slots are also made between high and low voltage on the printed circuit board.)

◆When wiring two panels, the wires on both sides should be routed perpendicularly, obliquely, or bent to avoid being parallel to each other to reduce parasitic coupling; printed wires used as input and output of the circuit should avoid adjacent parallel lines as much as possible. , to avoid feedback, it is best to add a ground wire between these wires.

◆Make the wiring corners larger than 90 degrees as much as possible, avoid corners below 90 degrees, and use 90-degree corners as little as possible

◆If they are both address lines or data lines, the length of the lines should not be too different, otherwise the short lines will need to be artificially bent to compensate.

◆Try to run the traces on the welding surface as much as possible, especially for PCBs with through-hole technology

◆Use as few vias and jumpers as possible

◆The soldering pads of single-sided panels must be large, and the wires connecting the pads must be thick. Use teardrops if you can. The quality of ordinary single-sided panel manufacturers will not be very good, otherwise there will be problems with welding and RE-WORK.

◆Large areas of copper should be covered in a grid pattern to prevent the board from generating bubbles and bending due to thermal stress during wave soldering. However, in special occasions, the flow direction and size of the GND must be considered, and it cannot simply be filled with copper foil. , but need to route

◆Components and wiring should not be placed too close to the edge. Common single panels are mostly made of paper boards, which are easy to break after being stressed. If you connect wires or place components at the edge, they will be affected.

◆The convenience of production, debugging and maintenance must be considered

It is very important to deal with ground issues for analog circuits. Noise generated on the ground is often unpredictable, but once it occurs, it will cause great trouble and should be avoided. For power amplifier circuits, extremely small ground noise will have a significant impact on the sound quality due to the amplification of the subsequent stages; in high-precision A/D conversion circuits, if there are high-frequency components on the ground line, there will be a certain temperature drift, which will affect the sound quality. Amplifier work. At this time, you can add decoupling capacitors to the 4 corners of the board, connect one leg to the ground on the board, and connect the other leg to the mounting hole (connected to the chassis through screws), so that this component can be eliminated, and the amplifier and AD can also It’s stable.

In addition, the issue of electromagnetic compatibility has become even more important now that people are paying more attention to environmentally friendly products. Generally speaking, there are three sources of electromagnetic signals: signal source, radiation, and transmission line. Crystal oscillator is a common high-frequency signal source. In the power spectrum, the energy value of each harmonic of the crystal oscillator will be significantly higher than the average value. A feasible approach is to control the amplitude of the signal, ground the crystal oscillator shell, shield the interference signal, and use special filter circuits and devices.

What needs special explanation is the snake-shaped wiring, because its functions are different depending on the application. It is used on some clock signals in the computer motherboard, such as PCIClk and AGP-Clk. It has two functions: 1. Impedance matching 2. Filter inductor.

For some important signals, such as the HUBLink in the INTELHUB architecture, there are 13 wires in total and the frequency can reach 233MHZ. They must be strictly equal in length to eliminate the hidden dangers caused by time lag. At this time, snake wiring is the only solution.

Generally speaking, the line spacing of snake-shaped traces is >= 2 times the line width; if it is used in an ordinary PCB board, in addition to having the function of a filter inductor, it can also be used as an inductor coil of a radio antenna, etc.

5. Adjustment and improvement

After completing the wiring, all that needs to be done is to make some adjustments to the text, individual components, and wiring and apply copper (this work should not be done too early, otherwise it will affect the speed and cause trouble to the wiring), also for the convenience of production, Debugging and maintenance.

Copper coating usually refers to filling the blank area left after wiring with a large area of copper foil. You can lay GND copper foil or VCC copper foil (but this will easily burn the device in the event of a short circuit. It is best to ground it unless you have to. To increase the conduction area of the power supply to withstand larger current, connect to VCC). Ground wrapping usually refers to wrapping a bunch of signal lines with special requirements with two ground wires (TRAC) to prevent them from being interfered by or interfering with others.

If you use copper instead of ground wire, you must pay attention to whether the entire ground is connected, the current size, flow direction, and whether there are any special requirements to ensure that unnecessary mistakes are reduced.

6. Check the network

Sometimes due to misoperation or negligence, the network relationship of the drawn board is different from the schematic diagram. In this case, it is necessary to check. Therefore, after finishing the painting, you must not rush to hand it over to the plate maker. You should check it first and then proceed with the follow-up work.

7. Use the simulation function

After completing these tasks, if time permits, software simulation can also be performed. Especially for high-frequency digital circuits, some problems can be discovered in advance and the future debugging workload can be greatly reduced.

In the world of electronics design, high-performance design has its own unique challenges.

1 The birth of high-speed design

In recent years, the increasing number of high-frequency signal designs has been closely linked to the steadily increasing performance of electronic systems.

As system performance improves, the challenges for PCB designers are increasing day by day: smaller chips, denser circuit board layout, and lower power consumption chip requirements.

With the rapid development of all technologies, we are at the core of high-speed design and need to consider its complexity and all factors.

2 review

PCB design has changed a lot over the past 30 years. In 1987, we thought 0.5 micron was the end of the technology, but today, 22nm has become the norm.

As shown in the figure below, the edge rate in 1985 promoted the increase in design complexity (typically 30 nanoseconds), and today the edge rate has become 1 nanosecond.

Changes in marginal rates over the past 30 years.

3 Technological progress is accompanied by various problems

The advancement of technology is always accompanied by a series of problems. As system performance increases and high-speed designs are adopted, some issues must be addressed in the design environment.

Below, we summarize the challenges faced:

Signal quality

IC manufacturers favor lower core voltages and higher operating frequencies, which results in sharply rising edge rates. Edge rates in unterminated designs will cause reflections and signal quality issues.

crosstalk

In high-speed signal designs, dense paths often lead to crosstalk—the phenomenon associated with electromagnetic coupling between traces on a PCB.

Crosstalk can be edge coupling of traces on the same layer or broadside coupling on adjacent layers.

The coupling is three-dimensional. Parallel paths and wide-side traces cause more crosstalk than side-by-side trace paths.

Broadside coupling (top) compared to edge coupling (bottom)

Fast edge rates in traditional designs can cause ringing on unterminated transmission lines, even when using the same frequency and trace length as before.

This essentially results in higher emissions, well in excess of the FCC/CISPR Class B limits for unterminated transmission lines.

Edge rate radiation at 10 nanoseconds (left) and 1 nanosecond (right).

4 Design Solutions

Signal and power integrity issues occur intermittently and are difficult to diagnose. Therefore, the best way is to find the root cause of the problem during the design process and eliminate it, rather than trying to solve it in the later stages and delaying production.

The stackup planning tool makes it easier to implement solutions to signal integrity issues in your design.

5 Circuit board stackup planning

The number one priority in high-speed design must be circuit board stackup. The substrate is the most important component of the assembly, and its specifications must be carefully planned to avoid discontinuous impedance, signal coupling, and excessive electromagnetic radiation.

When looking at the circuit board stackup for your next design, keep these tips and suggestions in mind:
All signal layers need to be adjacent and tightly coupled to an uninterrupted reference plane that creates a clear loop and eliminates broadside crosstalk.

The substrate of each signal layer is adjacent to the reference plane.

There are good planar capacitors to reduce AC impedance in high frequencies. The tightly coupled inner electrical layer plane reduces the AC impedance of the top layer and greatly reduces electromagnetic radiation.

Reducing the dielectric height significantly reduces crosstalk without impacting the available space on the board.

The substrate should be able to accommodate a range of different technologies. For example: 50/100 ohm digital, 40/80 ohm DDR4, 90 ohm USB.

6 Cabling and Workflow

With your stackup carefully planned, the next step is to focus on board routing. Based on design rules and careful configuration of your work area, you can route your board most efficiently and successfully.

These tips can help make your wiring easier and avoid unnecessary crosstalk, radiation, and signal quality problems:

Simplify the view to clearly see the split planes and current loops.

To do this, first determine which copper foil plane (ground or power) serves as the reference plane for each signal layer, and then open the signal layer and internal electrical layer planes to view them at the same time. This helps you more easily see the traces that split the plane.

Multiple signal layers (left), top and adjacent plane views (right)

If a digital signal must cross a power reference plane, you can place one or two decoupling capacitors (100nF) close to the signal. This provides a current loop between the two power supplies.

Avoid parallel routing and broadside routing, which can cause more crosstalk than side-by-side routing.

Unless you are using a synchronous bus, keep the parallel intervals as short as possible to reduce crosstalk. Leave room for signal groups so that their address and data spacing is three times the trace width.

Be careful when using combined microstrip layers on the top and bottom layers of the board. This can lead to crosstalk between traces on adjacent board layers, compromising signal integrity.

Routing the clock (or strobe) signal with the longest delay by signal group ensures that the data has been established before the clock is read.

Routing embedded signals between planes helps minimize radiation and provides ESD protection.

7 Signal clarity

In the future, the complexity of electronic design will undoubtedly continue to increase, which will bring a series of challenges to PCB designers that need to be solved. Ensuring the correct configuration of circuit board stackup, impedance, and current loops is the basis for design stability.

In the rapid development of modern electronic products, high-speed PCB proofing has become a key part of improving product performance. This article will introduce to you how to improve product performance through high-speed PCB proofing.

1. Understand the concept and significance of high-speed pcb prototyping
In electronic product design, high-speed PCB prototyping refers to the use of high-performance materials, precision processes and advanced equipment when designing and manufacturing PCB boards to meet high-speed signal transmission, anti-interference ability and stability requirements. Through high-speed PCB prototyping, signal transmission delay and signal distortion can be effectively reduced, and the reliability and stability of the product can be improved.

2. Choose suitable high-speed PCB materials
Choosing suitable high-speed PCB materials is an important step to ensure product performance improvement. Common high-speed PCB materials include FR-4, Rogers, PTFE, etc. According to the specific needs of the product, the dielectric constant, loss factor and thermal stability of the material are selected to meet the requirements of high-speed signal transmission.

3. Optimize PCB layout and routing
When performing high-speed PCB prototyping, reasonable layout and wiring design can significantly improve product performance. Try to shorten the signal transmission path as much as possible to reduce signal loss; avoid excessive plane layering to reduce signal crosstalk and interference. In addition, the ground wire and power wire should be properly set up to provide good ground potential and power supply stability.

4. Pay attention to the details in high-speed PCB proofing
When performing high-speed PCB prototyping, you also need to pay attention to some details to ensure the improvement of product performance. Choose the appropriate PCB manufacturer to ensure that it has advanced production equipment and rich experience; conduct strict process control, including controlling the accuracy of parameters such as board thickness, line width, line spacing; and conduct necessary testing and verification to ensure that the product The quality and performance meet expectations.

Using high-speed PCB proofing can significantly improve product performance, thereby achieving better user experience and market competitiveness. By choosing the right materials, optimizing layout and trace design, and paying attention to detail and process control, you can maximize product performance.

High-frequency microwave circuit board is a circuit board specially used for high-frequency microwave signal transmission, which has unique advantages and limitations. By understanding its advantages and disadvantages, we can better apply and optimize this circuit board and improve product quality and performance.

First, let us understand the advantages of high frequency microwave circuit boards. High-frequency microwave PCB circuit board has excellent high-frequency characteristics and can show lower signal loss and higher signal transmission efficiency in high-frequency microwave signal transmission. In addition, it also has good anti-interference performance and can effectively resist the impact of external interference on signal transmission. In addition, the manufacturing process of high-frequency microwave PCB circuit boards is relatively mature and can meet the needs of mass production.

However, high-frequency microwave circuit boards also have some limitations. First, its manufacturing process is relatively complex and requires highly precise processing and production equipment, so it is prone to process challenges during the production process. High-frequency microwave circuit boards have higher material requirements and require the use of specific high-frequency materials, which also increases the cost and manufacturing difficulty. In addition, high-frequency microwave PCB circuit boards need to consider more high-frequency characteristics in the design and layout, and the technical requirements for designers are also higher.

Understanding the advantages and disadvantages of high-frequency microwave PCB circuit boards is crucial for the electronics industry and communications field. Only by fully understanding its advantages and disadvantages can we better apply and optimize this circuit board and improve product quality and performance. Through targeted optimization and improvement, we can better meet the needs of high-frequency microwave signal transmission and provide more reliable technical support for development and innovation in the communications field.

1. Reduce the impact of temperature on circuit board stress

Since “temperature” is the main source of circuit board stress, as long as the temperature of the reflow oven is lowered or the speed of heating and cooling of the circuit board in the reflow oven is slowed down, the bending and warping of the board can be greatly reduced. occur. However, other side effects may occur, such as solder short circuits.

2. PCB uses high Tg board

Tg is the glass transition temperature, which is the temperature at which the material changes from glass to rubber. The lower the Tg value of the material, the faster the circuit board begins to soften after entering the reflow oven and becomes soft and rubbery. The time will also become longer, and the deformation of the circuit board will of course become more serious. Using a higher Tg board can increase its ability to withstand stress deformation, but the price of high Tg PCB boards is relatively high.

3. Increase the thickness of the circuit board

In order to make many electronic products thinner and lighter, the thickness of the circuit board has been reduced to 1.0mm, 0.8mm, or even 0.6mm. Such a thickness is really a bit difficult to keep the circuit board from deforming after passing through the reflow oven. It is difficult to force people to do so. It is recommended that if there is no requirement to be thin and light, the circuit board should be 1.6mm thick, which can greatly reduce the risk of board bending and deformation.

4. Reduce the size of the circuit board and reduce the number of panels

Since most reflow ovens use chains to drive the circuit board forward, circuit boards with larger PCB design sizes will be dented and deformed in the reflow oven due to their own weight, so try to treat the long side of the circuit board as the board edge. Putting it on the chain of the reflow furnace can reduce the dent deformation caused by the weight of the circuit board itself. This is also the reason for reducing the number of panels. That is to say, when passing through the furnace, try to use the narrow edge perpendicular to the furnace passing direction. Achieve the lowest amount of dent deformation.

5. Use oven tray jig

If the above methods are difficult to achieve, the last option is to use an oven tray to reduce the amount of deformation. The reason why the oven tray can reduce the bending of the board is because whether it is thermal expansion or cold contraction, the tray is expected to be able to fix the circuit board. When the temperature of the circuit board drops below the Tg value and begins to harden again, the original size can be maintained.

If the single-layer pallet cannot reduce the deformation of the circuit board, you must add a layer of cover and clamp the circuit board with the upper and lower pallets. This can greatly reduce the problem of deformation of the circuit board after passing through the reflow oven. However, these oven trays are quite expensive, and labor is required to place and recycle the trays.