1、 Problem 1: PCB board short circuit
This problem is one of the common faults that directly cause the PCB board to not work, and there are many reasons for this problem. Below, we will analyze each one.
The biggest cause of PCB short circuit is improper solder pad design. In this case, the circular solder pad can be changed to an oval shape, increasing the distance between points to prevent short circuits.
Improper design of PCB component orientation can also cause board short circuits and malfunction. If the feet of a SOIC are 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 a short circuit fault in the PCB, which is the automatic plug-in bending. Due to IPC regulations that the length of the wire pin is less than 2mm and concerns that parts may fall off when the bending angle is too large, it is easy to cause short circuits. Therefore, it is necessary to remove the solder joint from the circuit by more than 2mm.
In addition to the three reasons mentioned above, there are also some reasons that can cause short circuit faults in PCB boards, such as large substrate holes, low tin furnace temperature, poor solderability of the board surface, solder mask failure, and board surface pollution. These are common causes of faults, and engineers can troubleshoot and inspect each of the above reasons and the occurrence of faults one by one.
2、 Problem 2: Dark and granular contacts appear on the PCB board
The appearance of dark or small granular contact points on PCB boards is mostly due to the contamination of solder and the excessive mixing of oxides in the molten tin, resulting in a brittle solder joint structure. Be careful not to confuse 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 manufacturing process has changed, resulting in excessive impurity content and the need to add pure tin or replace the solder. Spotted glass undergoes physical changes in the accumulation of fibers, such as separation between layers. But this situation is not a poor solder joint. The reason is that the substrate is too hot, so it is necessary to reduce the preheating and soldering temperatures or increase the substrate travel speed.
3、 Problem 3: PCB solder joints turn golden yellow
In general, the solder on PCB boards appears silver gray, but occasionally golden yellow solder joints appear. The main reason for this problem is that the temperature is too high, and at this point, only the tin furnace temperature needs to be lowered.
4、 Problem 4: Poor board performance is also affected by the environment
Due to the construction of the PCB itself, it is easy to cause damage to the PCB board when in an unfavorable environment. Extreme temperature or temperature fluctuations, high humidity, high intensity vibration, and other conditions are all factors that can lead to reduced or even scrapped board performance. For example, changes in environmental temperature can cause deformation of the board. Therefore, it will damage the solder joints, bend the shape of the board, or may also cause copper traces on the board to break.
On the other hand, moisture in the air can cause oxidation, corrosion, and rusting of metal surfaces, such as exposed copper traces, solder joints, solder pads, and component leads. Accumulating dirt, dust, or debris on the surface of components and circuit boards can also reduce the airflow and cooling of the components, leading to PCB overheating and performance degradation. Vibration, dropping, hitting or bending a PCB can cause it to deform and cause cracks, resulting in large