In the process of PCBA processing and production, some errors in operation may lead to poor patch phenomenon. So, what are the undesirable phenomena in PCBA processing?
1, stand upright
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; The 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 placement offset Lead to short circuit; poor stencil opening (too thick thickness, too long pin opening, too large opening) lead to short circuit, etc.
3, offset
Causes of : 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 clamp of the circuit board in the printing machine is loose, and the positioning thimble is not in place, etc.
4, missing parts
Causes of : The vacuum pump is not good enough, 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 not detected properly or the detector is bad; the mounting height is not set properly, etc.
5, empty 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.