S3MD, Stress Sensitive Surface Mounted Devices for in-situ monitoring of mechanical processes in PCB manufacturing

In the past, silicon based measurement system were used to characterize packaging induced stresses of electronic devices. In this paper a new approach for qualifying mechanical PCB manufacturing processes is presented. Silicon based package equivalents (S³MD; Stress Sensitive Surface Mounted Devices) are used instead of real devices at locations of expected dangerous mechanical impact. The silicon based package equivalents have strain sensitive structures implemented. These structures are formed by thin film processes and are designed as strain sensitive metal resistors. Therefore, the mechanical impact of the following steps in the PCB process chain can be monitored. The sensor devices are qualified in the AEC Q200 “board flex” test to get the limiting strain values. In the result, we show a new method to get in situ measured data of the mechanical impact of PCB manufacturing processes.