Board level reliability of automotive eWLB (embedded wafer level BGA) FOWLP

Abstract

With shrinking chip sizes, Wafer Level Packaging (WLP) is becoming an attractive packaging technology with many advantages in comparison to standard Ball Grid Array (BGA) packages. With the advancement of various fan-out Wafer Level Packaging (FOWLP) designs, this advanced technology has proven to be a more optimal and promising solution compared to fan-in WLP because of the greater design flexibility in having more input/output (I/O) and improved thermal performance. In addition, FOWLP shows superior high-frequency performance with its shorter and simpler interconnection compared to flip chip packaging. eWLB (embedded wafer level BGA) is a type of FOWLP that enables applications requiring smaller form factor, excellent heat dissipation and thin package profiles. It also has the potential to evolve into various configurations with proven yields and manufacturing experience based on over 8 years of high volume production. This paper discusses the recent advancements in robust board level reliability performance of eWLB for automotive applications. A Design of Experiment (DOE) study will be reviewed which demonstrates improved Temperature Cycle on Board (TCoB) performance with experimental results. Several DOE studies were planned and test vehicles were prepared with the variables of solder materials, solder mask opening/Cu pad size of redistribution layer (RDL) design, copper (Cu) RDL thickness and under bump metallurgy (UBM), and Cu pad design (NSMD, SMD) on a printed circuit board (PCB). With these parametric studies and TCoB reliability tests, the test vehicle passed 1000x temperature cycles (TC). Daisy chain test vehicles were used for TCoB reliability performance in industry standard test conditions.