|
Despite the electronic manufacturing is well-established mass production process for a long time, the problem of
reworking, i.a. reject and replace of defect components, still exists. The rework operations (soldering, replacement and
desoldering) are performed in most cases manually. However, this practice is characterized by an inconsistent quality of
the reworked solder joints and a high degree of physiological stress for the employees.
In this paper, we propose a novel full-automated laser based soldering and rework process. Our developed soldering
system is a pick-and-place unit with an integrated galvanometer scanner, a fiber coupled diode laser for quasi-simultaneous
soldering and a pyrometer-based process control. The developed system provides soldering and reworking
processes taking into account a kind of defect, a type of electronic component and quality requirements from the IPC-
610 norm.
The paper spends a great deal of efforts to analyze quality of laser reworked solder joints. The quality depends mainly
on the type and thickness of intermetallic phases between solder, pads and leads; the wetting angles between pad, solder
and lead; and finally, the joint microstructure with its mechanical properties. The influence of the rework soldering on
these three factors is discussed and compared to conventional laser soldering results. In order to optimize the quality of
reworked joints, the different strategies of energy input are applied.
|
