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-
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.
Aluminum combines comparably good thermal and electrical properties with a low price and a low material weight. These properties make aluminum a promising alternative to copper for a large number of electronic applications, especially when manufacturing high volume components. However, a main obstacle for a wide use of this material is the lack of a reliable joining process for the interconnection of copper and aluminum. The reasons for this are a large misalignment in the physical properties and even more a poor metallurgical affinity of both materials that cause high crack sensitivity and the formation of brittle intermetallic phases during fusion welding. This paper presents investigations on laser micro welding of copper and aluminum with the objective to eliminate brittle intermetallic phases in the welding structure. For these purposes a combination of spot welding, a proper beam offset and special filler material are applied. The effect of silver, nickel and tin filler materials in the form of thin foils and coatings in a thickness range 3-100 μm has been investigated. Use of silver and tin filler materials yields to a considerable improvement of the static and dynamic mechanical stability of welded joints. The analysis of the weld microstructure shows that an application even of small amounts of suitable filler materials helps to avoid critical, very brittle intermetallic phases on the interface between copper and solidified melt in the welded joints.