Evaluation of solder joints formed by different Vapour Phase Soldering systems

As Vapour Phase Soldering (VPS) has become a significant alternative method for reflow soldering, several investigations started to determine the possibilities of the re-introduced technology. In this particular case, experiments were made using two different offline VPS systems - Oven A and Oven B - in order to determine differences in soldering quality. The main aim of the experiments was to produce samples using the default linear soldering profile of each machine. The default settings are not only reflecting the different setup of the control parameters, but the differences in the oven constructions as well. The results were compared based on the quality of the joints. Additionally, plateau shaped soldering profiles were set up for Oven B. Test boards containing 0603 sized chip resistors and fine pitch BGAs were soldered using each heating profile. The mechanical quality of the solder joints was investigated with shear tests. X-ray inspection was used to determine the tendency of voiding regarding BGAs, while cross sections of each sample were analysed by SEM. The results show that there is significant difference between the mechanical qualities of samples soldered with different VPS machines. Correlation was found between the shape and parameters of the reflow profile and solder joint quality. The paper also highlights the importance of possible non-linear reflow profiles during vapour phase soldering.