Typical surface mount PCB. (Courtesy Wireline Technologies Ltd)
Bore hole data loggers are required to operate at temperatures around 150°C and withstand storage at -40°C with high levels of shock/vibration loading. These conditions place considerable demands on the solder joints ofthe monitoring/signal processing printed circuit boards (PCBs) within them. Pressure to reduce bore hole size and increase logger functionality demands smaller electronic packing using surface mounted devices (SMDs); these haveinherently smaller/weaker solder joints.
Wireline Technologies Ltd was engaged in a new product development programme and was concerned to ensure the highest reliability for the new SMD PCBs. A Product and Process Review followed by a Feasibility Study was undertaken byTWI through the Joining Forces programme. The company was advised on possible choices for solders and PCB materials/finishes and subsequently set up in-house trials to evaluate various materials, including those recommended by TWI.
Survey tool. (Courtesy Wireline Technologies Ltd)
Once sufficient testing had been done to identify statistically reliable trends, TWI was asked to analyse samples of failed materials. This analysis was performed using x-ray diffraction and scanning electron microscopy and helpedconfirm the nature and cause of the failures thereby assisting Wireline Technologies to choose the most appropriate materials for their application.
