The Package Of Semiconductor Lasers And Fluxless Reflow Soldering Technology Using Formic Acid

The semiconductor laser has more and more attention since the invention of it, because it has a small size, light weight, long life and high conversion efficiency. It has been widely used in the military and civilian areas. However, in terms of current domestic situation, packaging technology which determines the reliability and life of semiconductor lasers has a big gap with foreign countries. The soldering level of chip, main process of semiconductor laser package, has an important influence on the performance of the semiconductor laser. In the soldering of chip, the most complicated and most difficult to achieve is how to remove the oxide film on the surface of the solder layer, so that the solder, the chip and the heat sink achieve the best wettability.This paper introduces briefly the packaging type and packaging process of the semiconductor laser, and researches the influence of the silver layer and the gold layer on the performance of indium solder, what’s more, it also researches the effect of void and intermetallic compound on solder. After much of literature survey, this paper describes the principle of fluxless reflow soldering technology using formic acid and its specific soldering process, and a lot of experiments have been done to study the effects of fluxless reflow soldering technology using formic acid on the performance of solder from different sides as follows.(1) Indium solder was prepared using Si as the substrate, and the samples had been soldered using formic acid. The specific reaction process of formic acid and indium oxide in different stage was analyzed by XRD patterns. It was confirmed that the formic acid could remove effectively the oxide film of solder surface through setting a suitable reflow profile.(2) Through the comparison of two methods soldering SEM images, it was found that solder particles uniformity using formic acid was much better than the soldering in the air. The EDS test of solder surface also confirmed the reaction of formic acid and indium oxide.(3) Through measuring solder shear strength of fluxless reflow soldering using formic acid and direct soldering in the air, the influence of fluxless reflow soldering technology using formic acid on solder wettability was discussed.(4) Through the study of indium dropped formic acid solution, observing SEM images of the samples and analyzing XRD patterns of the samples, we concluded: although formic acid solution can remove the oxide film of the solder, it will cause residual solution, and reduce the performance of the solder.