Authors: Jörg Trodler and Mathias Nowottnick Date Published: 10/13/2013
Abstract: During the last period of new assembled electrical devices (pcbs) there were also qualified new component types like LGA and QFN as well as smaller passive components with reliability requirements based on the automotive and industrial specifications. In the narrow gaps under components, residues can accumulate more by the capillary forces. This is not so much a surface resistance than an interface issue. Due to that fact the flux residues under such type of components create interaction with the solder resists from the pcb as well as component body that was not completely described by the standard SIR measurement. On the other hand also to electrical influence with higher voltage creates new terms and conditions in particular the combination of power and logic in such devices. The standard SIR measurement is not able to analyze those combinations. That paper will discuss the requirements for a measurement process and will give results and possibilities for a no clean solder paste solution based on the flux formulation. On the other hand also the influences of the pcb and component quality will be discussed.