Summary of the phenomenon of poor PCBA processing

Summary of the phenomenon of poor PCBA processing

In the process of PCBA processing and production, some errors in operation may lead to poor patch phenomenon.

1. stand up

Causes: uneven tension on both sides of copper and platinum; too fast preheating heating rate; machine placement offset; uneven thickness of solder paste printing; uneven temperature distribution in the reflow oven; solder paste printing offset; Machine track splint is not tight, resulting in placement offset, etc.

2. Short circuit

Causes: Too large distance between stencil and PCB board leads to too thick solder paste printing and short circuit; component mounting height is set too low to squeeze solder paste and cause short circuit; reflow oven heats up too fast, resulting in short circuit; component mounting offset Lead to short circuit; poor opening of steel mesh (thickness is too thick, pin opening is too long, opening is too large) leads to short circuit, etc.

3. Offset

Causes: The positioning reference point on the circuit board is not clear; the positioning reference point on the circuit board is not aligned with the reference point of the stencil; the fixed clamping of the circuit board in the printing machine is loose, and the positioning thimble is not in place, etc.

4. Missing parts

Causes: The vacuum pump carbon sheet is bad and the vacuum is not enough to cause missing parts; the suction nozzle is blocked or the suction nozzle is bad; the thickness of the component is improperly detected or the detector is bad; the mounting height is not set properly, etc.

5. Air welding

Causes: weak solder paste activity; poor stencil opening; too large copper-platinum spacing or large copper paste small components; too much scraper pressure; poor flatness of component feet (upset, deformation) The hot zone heats up too fast, etc.