17.Missing Component( 缺件 )

拒收 良好情r

缺c描述 :

Designated component are not at the determined pads & locations.

ACCEPTABILITY

It is not consider to be a defect if it is above the AQL level of 2.5%.

PROBABLE CAUSES

Insufficient tack characteristics of solder paste due to extreme temperature and humidity

Component placement inaccuracies
Too much movement of the assembly prior and during reflow

POSSIBLE PREVENTIONS

Abide by the recommended temperature and humidity requirement of the solder paste
Improve the accuracy of component placement

Minimize the amount of movement the unreflowed assembly sees
Usage of a more aggressive flux
Improve the solderability of the components and PCBs

REWORK

For multilead, fine-pitch component and IC :
The footprints are lightly fluxed before replacing the missing component. A chisel-shaped soldering iron is used to solder back the joint by placed it against the horizontal ends of the gullwing legs long enough such that the transfer of heat is sufficient enough before placing the solderwire close to the tip of the iron.

For SMD :
The missing component is place before it is soldered on with the help of a chisel-shaped soldering tip and solder iron.The soldering tip is placed against the joint long enough such that the transfer of heat is sufficient enough before placing the solderwire close to the tip of the iron.

For through-hole component :
Replace the missing component before using a chisel-shaped soldering iron to solder back the joint.It is placed against the joint long enough such that the transfer of heat is sufficient enough before placing the solderwire close to the tip of the iron.