PCBA Tech - Analysis of the problem of solder point sharpening in PCBA welding?

Analysis of the problem of solder point sharpening in PCBA welding?
Recently, a customer asked a question about the straight-through rate of PCBA processing. The straight-through rate is actually the time it takes for the product to go from the previous process to the next process. Then the less time, the higher the efficiency and the higher the yield rate., After all, only when there is no problem with your product can you move on to the next step. With this question, let’s talk about the generation and solution of solder joints in PCBA soldering:

1. In the preheating stage, the temperature of the PCB circuit board is too low and the preheating time is too short, which makes the temperature of the PCB and the components low, and the components and the PCB absorb heat during soldering to produce a convex tendency.
2. The temperature of SMT chip soldering is too low or the conveyor speed is too fast, so that the viscosity of the molten solder is too large.
3. The wave crest height of the electromagnetic pump wave soldering machine is too high or the pin is too long, so that the bottom of the pin cannot touch the wave crest. Because the electromagnetic pump wave soldering machine is a hollow wave, the thickness of the hollow wave is 4~5mm.
4. Poor flux activity.
5. The ratio of the lead diameter of the DIP plug-in component to the plug-in hole is incorrect, the plug-in hole is too large, and the large pad absorbs a large amount of heat.
The above problems are the most important factors that cause the solder joints to sharpen, so we should make corresponding optimizations and adjustments to the above problems in the smt patch processing, solve the problems before they occur, and ensure the yield and delivery speed of the products. .
1. The tin wave temperature is 250 degree Celsius±5 degree Celsius, and the welding time is 3~5s; when the temperature is slightly lower, the speed of the conveyor belt will be slower.
2. The height of the wave crest is generally controlled at 2/3 of the thickness of the printed board. The lead forming of the plug-in component requires that the lead of the component be exposed to the printed circuit 3, and the welding surface of the board is 0.8mm~3mm.
4. Replace the flux.
5. The aperture of the insertion hole is 0.15~0.4mm larger than the diameter of the lead (the thin lead is removed, and the thick lead is the upper limit)