SMTA International Conference Proceedings


Author: Armin Rahn
Company: SEHO consultant
Date Published: 9/12/1999   Conference: SMTA International

Abstract: Even though efforts are made to eliminate TH devices on SM products, some seem to be irreplaceable. There are two basic approaches to deal with this problem: either include them in reflow or choose one of the selective soldering processes. As many of these critical TH devices cannot tolerate the reflow environment, selective soldering is one of the attractive alternatives.

We will concentrate on two such selective processes: Laser soldering and mini-wave soldering. With the event of powerful diode lasers, laser soldering has become very alluring and cost effective. Known as the soldering method that can produce the most reliable joints, it exerts a minimum of stress on the surrounding area. Laser soldering is fast and offers a large amount of options: e.g. split beams and bars of light can be produced to simultaneously solder several joints. Allied with the proper robotic handling systems, laser soldering may be employed as stand-alone or an in-line equipment.

Mini-wave soldering has been known as a de-soldering tool for a long time. This system has matured and has become more sophisticated. New wave designs, wave-height control, several nitrogen options and pin-point accuracy makes mini-wave soldering a viable alternative. Dip versions as well as 'drag over the wave' are available and several arrangements have been designed: indexing rotary tables, in-line equipment and stand-alone units. The talk will conclude with a depiction of an actual in-line operation making use of reflow for SM and Laser as well as mini-wave technology for selective soldering.

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