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This article mainly explains the "common problems and solutions in PCB design". The content of the explanation is simple and clear, and it is easy to learn and understand. Please follow the editor's train of thought to study and learn "common problems and solutions in PCB design".

In the process of design and manufacture of PCB board, engineers not only need to prevent accidents in the manufacturing process of PCB board, but also need to avoid design errors.

Problem 1: short circuit of PCB board

This problem is one of the common faults that will directly cause the PCB board to fail to work, and there are many reasons for this problem, which we will analyze one by one.

The biggest cause of PCB short circuit is the improper design of the solder pad. At this time, the round solder pad can be changed into an oval to increase the distance between points to prevent short circuit.

The improper design of the direction of PCB parts will also cause the board to short circuit and fail to work. For example, if the foot of the SOIC is parallel to the tin wave, it is easy to cause a short circuit accident. At this time, the direction of the part can be appropriately modified to make it perpendicular to the tin wave.

There is another possibility that can also cause short-circuit failure of PCB, which is automatic plug-in foot bending. As the length of the wire foot stipulated by IPC is below 2mm and the parts will fall off when the bending angle is too large, it is easy to cause short circuit, so it is necessary to leave the solder joint above the line 2mm.

In addition to the three reasons mentioned above, there are some reasons that can also lead to short-circuit faults of the PCB board, such as too large hole in the substrate, too low temperature of the tin furnace, poor solderability of the plate surface, failure of the anti-welding film, surface contamination, etc., are the more common causes of faults, engineers can compare the above reasons and the occurrence of the fault one by one to eliminate and check.

Problem 2: dark and granular contacts appear on the PCB board

The joint problem of dark color or small particles on the PCB board is mostly due to the contamination of solder and too much oxide mixed in the dissolved tin, resulting in the brittle structure of the solder joint. Be careful not to be confused with the dark color caused by the use of solder with low tin content.

Another reason for this problem is that the composition of the solder used in the processing and manufacturing process changes, the content of impurities is too much, and pure tin or replacement of solder is needed. The physical changes of the fibrous layer of the spotted glass, such as the separation between layers. But this is not a bad solder joint. The reason is that the substrate is overheated, so it is necessary to reduce the preheating and solder temperature or increase the speed of the substrate.

Problem 3: the PCB solder joint turns golden

In general, the solder of the PCB board is silver gray, but occasionally golden solder joints appear. The main reason for this problem is that the temperature is too high, so it is only necessary to lower the temperature of the tin furnace.

Problem 4: the poor quality of the board is also affected by the environment

Due to the construction of PCB itself, it is easy to cause damage to PCB board when it is in an unfavorable environment. Other conditions such as extreme temperature or temperature variation, excessive humidity, high-intensity vibration and so on are all factors that lead to the decline of board performance or even scrap. For example, the change of ambient temperature will cause the deformation of the board. As a result, the solder joint will be damaged, the shape of the board will be bent, or the copper trace on the board may be broken.

On the other hand, moisture in the air can cause oxidation, corrosion and rust on metal surfaces, such as exposed copper traces, solder joints, pads, and component leads. The accumulation of dirt, dust or debris on the surface of components and circuit boards can also reduce the air flow and cooling of components, resulting in PCB overheating and performance degradation. Vibrating, dropping, hitting or bending PCB can deform it and cause cracks to be present, while high current or overvoltage can cause PCB board breakdown or lead to rapid aging of components and pathways.

Question 5: PCB opens the road

An open circuit occurs when the trace is broken, or when the solder is only on the pad and not on the component lead. In this case, there is no adhesion or connection between the component and the PCB. Just like a short circuit, these can occur during production or welding and other operations. Vibrating or stretching circuit boards, dropping them or other mechanical deformation factors can damage traces or solder joints. Similarly, chemical or moisture can cause wear and tear of solder or metal parts, causing assembly leads to break.

Problem 6: loosening or dislocation of components

During reflow soldering, the widget may float on the molten solder and eventually leave the target solder joint. The possible reasons for the shift or tilt include the vibration or bounce of the components on the welded PCB board due to insufficient support of the circuit board, setting of reflux furnace, solder paste problems, human error and so on.

Question 7: welding problem

Here are some problems caused by poor welding practices:

Disturbed solder joint: the solder moves before solidification due to external disturbance. This is similar to cold solder joints, but for different reasons, they can be corrected by reheating and ensure that solder joints are cooled without external interference.

Cold welding: this occurs when the solder does not melt correctly, resulting in rough surfaces and unreliable connections. Cold solder joints can also occur because excess solder prevents complete melting. The remedy is to reheat the joint and remove excess solder.

Solder bridge: this occurs when the solder crosses and physically connects the two leads together. These may form unexpected connections and short circuits, which may cause components to burn out or burn out wires when the current is too high.

Pad: insufficient wetting of pins or leads. Too much or too little solder. A pad that is raised due to overheating or rough welding.

Problem 8: human error

Most of the defects in PCB manufacturing are caused by human errors. In most cases, wrong production processes, misplacement of components and unprofessional manufacturing practices lead to up to 64% avoidable product defects. The possibility of defects increases with circuit complexity and the number of production processes due to the following: densely packaged components; multiple circuit layers; fine wiring; surface welding assemblies; power supplies and ground connections.

Although every manufacturer or assembler wants to produce PCB boards without defects, there are several difficulties in the design and production process that cause PCB board problems.

Typical problems and results include the following: poor welding will lead to short circuit, open circuit, cold solder joint, etc.; dislocation of the plate will lead to poor contact and poor overall performance; poor insulation of the copper trace will lead to an arc between the trace and the trace; if the copper trace is too tight between the path and the path, it is prone to the risk of short circuit; insufficient thickness of the circuit board will lead to bending and fracture.

Thank you for reading, the above is the content of "common problems and solutions in PCB design". After the study of this article, I believe you have a deeper understanding of the common problems and solutions in PCB design, and the specific use needs to be verified in practice. Here is, the editor will push for you more related knowledge points of the article, welcome to follow!

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