Wunstorf, Germany - 1999-09-01. The current development of electronic devices and their application has resulted in a change of the requirements for connection technology. Simultaneously, in the United States, in the European Union, and in Japan the legislative pressure increases to eliminate the toxic lead from electronic devices. New soldering alloys, such as SnAg, SnCu and AuSn are probable solutions for a wide range of these connection problems, especially for applications that require higher temperature resistance. The customary tin-lead solders which have been applied and investigated for decades now have to be replaced by new alloys. This implies that the well-known process parameters for soldering have to be considered anew. Here the questions arises, whether lead-free solder joints can be inspected using X-ray techiques in the same way and with the same reliability as the PbSn solder joints. In particular, the tin alloys have been suspected to yield a low contrast in X-ray images due to the lower X-ray absorption of tin in comparison to the absorption of lead. phoenix|x-ray now has started a systematic study on the visualisation of lead-free solder joints. The first inspection results are very encouraging. As can be seen from the images the contrast for SMT SnAg solder joints is not worse than for standard PbSn. On the contrary, for many connection techniques such as BGA and µBGA the solder joints can be penetrated easier and, hence, their internal details can be displayed at lower voltage. As a consequence, saturation effects that might occur, e.g., in BGA inspections (i.e. the apparent shrinking of the solder balls during voiding inspection) are diminished and can be removed more conveniently. The lead-free soldered assembly was kindly provided by:
Fraunhofer Institut Siliziumtechnologie, Itzehoe, Germany.