IC Substrate - Why SMT solder joint is not full how to check short circuit

As we all know in the PCB industry, soldering tin on PCB circuit board is a very important work link in SMT technology patch processing, which is related to the service performance and beautiful appearance of PCB circuit board. In the actual PCB Factory production patch processing link, poor soldering tin will occur due to some reasons, such as: the solder joint of PCB circuit board is not full, Will directly affect the quality of SMT patch processing, so what is the reason why the tin on SMT patch processing is not full?

Let's explain it in detail.

1. The wetting property of the flux in the solder paste is not good, which can not meet the requirements of good SMT patch tin application.

2. The activity of the flux in the solder paste is not enough to remove the oxidizing substances in the PCB pad or SMD welding position.

3. The expansion rate of flux in solder paste is too high, which is prone to voids.

4. PCB pad or SMD welding position has serious oxidation, which affects the tin loading effect.

5. The amount of solder paste at the solder joint is not enough, resulting in insufficient tin and vacancy.

6. If the tin on some solder joints of PCB circuit board is not full, the reason may be that the solder paste is not fully stirred before use, and the flux and tin powder cannot be fully integrated.

7. Too long preheating time or too high preheating temperature during machine reflow soldering of PCB board will lead to the failure of flux activity in solder paste. At present, SMT patch processing manufacturers mostly use imported advanced testing equipment to monitor the quality of the production process. During the reflow soldering process of PCB board, The SMT technology of PCB manufacturers generally uses AOI testing equipment to control the quality of SMT patches of PCB circuit board components. Due to the high cost, the automatic parameter adjustment and feedback in the quality control process still need to be set manually. Generally, in this case, the electronic patch enterprises of PCB manufacturers need to formulate some practical and effective specifications and systems, In the formulation of quality control specifications for electronic patch price, the coping ability of SMT technical operators and equipment control are very important.

In the manual PCBA circuit board welding process of SMT processing plant, short circuit is a common poor processing. In order to achieve the same effect of manual SMT patch and machine patch, short circuit is a problem that must be solved. Short circuit PCBA can not be used. There are many methods to solve short circuit in SMT patch processing.

1. The manual welding operation shall form a good habit, and use a multimeter to check whether the key circuits are short circuited. Each time an IC foundry completes manual SMT placement, it is necessary to use a multimeter to measure whether the power supply and ground are short circuited.

2. Light up the short circuit network on the PCB, find the place on the PCB where the short circuit is most likely to occur, and pay attention to the internal short circuit of the IC.

3. If the same batch of short circuits occur in the PCBA processing of SMT chip, take a PCB board to cut the line, and then energize each part to check the short circuit part.

4. Check with short circuit positioning analyzer.