Reflow soldering is a common SMT reflow soldering defect. After reflow soldering, it seems that the front and rear are soldered together, but in fact the smt components have not reached the level of integration, the strength of the joint surface is very low, and the welding seam has to go through various complex processes on the production line, especially through The high-temperature furnace zone and the high-tension tension-correction zone, so the false welding seam is very easy to cause electrical defects on the production line, which will have a great impact on the normal operation of the production line. Guang Shengde here to share the four major reasons for reflow soldering failure.

Reflow soldering

1. Defects in the design of the circuit board pads cause reflow soldering

The existence of through-holes on the circuit board pads is a major defect in PCB design. If it is less than absolutely necessary, do not use it. The through-holes will cause solder loss and insufficient solder; the pad spacing and area also need to be standardized, otherwise the design should be corrected as soon as possible.

2. Oxidation of the circuit board causes false soldering in reflow soldering

The circuit board is oxidized, that is, the pad is black and does not shine. If there is oxidation, you can use an eraser to remove the oxide layer to reproduce the bright light. If the circuit board is damp, it can be dried in a drying box if suspected. The PCB board is polluted by oil stains, sweat stains, etc. At this time, it should be cleaned with absolute ethanol.

3. there is less solder paste on the circuit board printed with solder paste, resulting in reflow soldering

On circuit boards that have been printed with solder paste, the solder paste is scratched and rubbed, which reduces the amount of solder paste on the relevant pads, resulting in insufficient solder. It should be made up in time. The method of making up can be made up with a dispenser or pick a little with bamboo sticks.

4. surface mount components are of poor quality, expired, oxidized, and deformed, resulting in false reflow soldering

This is a more common reason. The quality department must strictly control the inspection, and strictly control the feeding and storage of surface mount components to avoid component quality problems.