On-board Package Decapsulation Techniques for Failure Analysis

With the increasing demand for sleeker and light weight devices, printed circuit boards (PCBs) are getting very crowded due to numerous components mounted within a limited space. This also reduces the number of probing test points available for failure analysis/fault isolation (FA/FI) processes. Hence, FA engineers usually extrapolate conclusions about the missing signals without concrete evidence. In many cases, these analyses end with component level isolation, without deep dive investigation of the failure signature. In addition, package decapsulation is a commonly used technique for die level analysis but in the cases where package removal from the PCB destroys the failure signature, on-board decapsulation is more appropriate. On-board decapsulation allows precise system level FA/FI and gives engineers the ability to literally look inside the components by exposing the die and wire bonds of the component while they are still intact on the motherboard. In the present work, various on-board decapsulation techniques to remove package overmold while preserving wire bonds either gold (Au) or Copper (Cu) were evaluated. From an electrical FA standpoint, this technique allows precise FA execution by enabling in situ probing of the wire bonds. Hence, previously inaccessible data can be collected by simply using a microprobe station.