During the last period of newly assembled electrical devices (pcbs), new component types like LGA and QFN were also qualified as well as smaller passive components with reliability requirements based on the automotive and industrial industry. In the narrow gaps under components, residues can accumulate more by the capillary forces. This is not that much a surface resistance than an interface issue.
Also that the flux residues under such types of components creates interaction with the solder resists from the pcb, as well as the component body was not completely described in the standard SIR measurement. On the other hand also, 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 cannot analyze those combinations. The paper discusses the requirements for a measurement process, and will give results. The influences of the pcb and component quality will also be discussed. Furthermore it will describe requirements for nc solder paste to increase the chemical/thermal/electrical reliability for whole devices.
Different single tests were already addressed for understanding the new requirements by electrical and environmental properties for new requirements on electrical devices. To make it easier and practical for future qualifications it should start a multifunctional project which includes experts and user for all single influences.
