Extending Board Level Reliability(BLR) of a Wafer Level Fanout 4D Digital Radar Chiplet Package

Adoption of Fanout Wafer Level Packages (FO-WLP) for automotive Radar chips became common with the introduction of 76GHz to 80GHz systems almost 10 years ago. Early systems using small 36mm2 packages had partitioning separating the transmit and receive functions into separate packages or integrating a few transceivers in the same package. Many system realizations took two to six FO-WLP packages per radar system and did not include the compute function. In this paper, we will present board level reliability (BLR) data from a 105mm2 single FO-WLP chiplet package integrating transmit, receive, and compute radar functions for automotive applications. This 8.2mm x 12.8mm FO-WLP integrates two die of different technology nodes in a multi-layer RDL AEC-Q104 qualified package. Board level reliability is studied using empirical methods for two high frequency low CTE board materials and multiple stack construction choices. Dominate features influencing the BLR results such as metal density, board material and board thickness are identified and explored. Edge bond materials are introduced as a method of extending board life. Two materials are explored. One industry standard material and one custom formulated material tuned to the application. This package contains up to 12 transmit and 16 receiver channels. Due to the nature of the high frequency transmit and receiver functions, traditional edge bond dispense patterns may be problematic in some applications which fan-out signals on the top layer of the printed circuit board. This paper compares the effect of a traditional and a non-traditional dispense pattern on BLR results.