Addressing the sample preparation challenges in failure analysis of wafer level chip scale package mounted inside a customer camera module

One significant application of Wafer Level Chip Scale Package (WLCSP) is in opto-electronics and CCD image processing. This includes cellphone camera module, notebook or computer camera module, video telephone and many more. Its package size represents a real advantage for designers of camera modules and is the ideal choice for highly space-constrained camera applications. One complex part though, is when the WLCSP unit failed during customer electrical testing or in the field. Failure analysis of the failing WLCSP unit mounted inside a camera module will be very challenging. The camera module needs to be opened to gain access on the WLCSP part, demount it and proceed to reballing process to enable further electrical verification and fault isolation analysis. This paper discusses the evaluations done in demounting the WLCSP unit mounted inside a customer camera module. Combinations of thermo-mechanical process and parallel lapping were used to demount the WLCSP unit. The established process enabled the electrical verification, fault isolation and further destructive analysis of WLCSP customer return mounted inside a camera module.