How to Detect Faulty Soldering on Circuit Board

1. Manual detection method

The problem of false soldering and false soldering of circuit boards is completely detected manually. First, workers should observe and knock the solder joints with problematic traces with the naked eye. Then, conduct live test, find the hot solder joint, and then test whether it is false welding. After busy, a person can't test a few boards in most of the day, and there may be missed detection.

2. X-ray detection

Irradiate and image the circuit board under X-ray to find the void point of false welding. This method seems to be very effective, but it also has several great disadvantages. 1) Low efficiency, long imaging time during testing, and observation of each solder joint, which takes a long time. 2) Although X-rays are well protected and have little impact on human body, there is still radiation pollution. Therefore, this method is not a safe and economic method.

3. AOI detection

This is an intelligent detection method, rich in high-tech elements. One thing is certain that the cost of this method is too high. Moving one machine will cost hundreds of thousands. Another point is that this method tests false welding and false welding through image comparison. If the circuit board is placed in different positions, resulting in inconsistent light irradiation angles or color pollution of the circuit board, the test effect will be greatly reduced. Moreover, this method only compares the surface images of the solder joint, and can not go deep into the interior of the solder joint, and can not find the false welding inside the solder joint. So it is an expensive way to cure the symptoms.

4. Electromagnetic vibration test bench test method

This method uses the resonance principle of shaking table to damage the false solder joints in the process of vibration, so as to find the false solder joints quickly and efficiently. When testing with this method, we should pay attention to several key points: 1) the tested circuit board and PCB board should be fixed on the table of the shaking table with a fixture. Generally, there are 25 M8 screw holes on the shaking table, which is convenient to fix the fixture on the shaking table with screws. 2) When the electromagnetic vibration table vibrates, it shall be set to sweep frequency vibration. If it is not set to sweep frequency, the vibration table will not be able to find the resonance point of the circuit board, so even if the vibration time is longer, it will not find the resonance point. The advantages of this test method are also obvious. First, it is efficient. Generally, the table width of the vibration test bench is 50x50cm, so multiple circuit boards or PCB boards can be fixed and tested on the table at one time. Secondly, the detection time is short. Generally, a detection cycle takes only dozens of minutes to quickly detect multiple circuit boards. If the circuit board has the problem of false soldering, the false soldering point will either fall off or the gap of false soldering can be seen at a glance.

In fact, in the detection of false soldering of circuit boards and PCB boards, we should adhere to the principle of low cost and high efficiency, reject low-cost and inefficient methods, and reject high-cost and inefficient methods. As a story tells, in order to pick out the empty boxes without soap on the assembly line, a doctoral student spent hundreds of thousands on a perfect scheme through rigorous calculation and exquisite design. The workers on the assembly line brought an electric fan and blew it against the assembly line. The boxes without soap were blown off one by one. This tells us a simple truth. Sometimes the most effective method is often the most reliable method. Therefore, we recommend that it is the most economical and effective to use electromagnetic vibration test-bed in the process of false welding and similar welding detection of circuit board and PCB.