Thomas Heinrich

A novel drop test methodology for highly stressed interconnects in automotive electronic control units

Drop events are infrequent on Electronic Control Units (ECUs) such as powertrain control modules, however they can cause significant damage at interconnects due to high stress levels, as these ECU designs utilize heavy components onto Printed Circuit Boards (PCB) that are in return built onto larger size of electronic products in the automotive electronics. This paper introduces the efforts to develop a new drop test method for ECUs under high shock condition that reconciles expected PCB vibration observed in the myriad of different end-use applications that ECUs can experience. The test method attempts to replicate the PCB deflection and its inherent solder joint stress that have been shown by numerical and analytical studies. Additionally, the test method also considers the various types of loading conditions and component weight by characterizing changes in applied load (via shock pulse amplitude) at different heights and evaluating effect of gradual weight increase under constant shock test. The paper outlines the benefits of this new test method as it utilizes symmetric loading for equivalent component response and stresses; it also allows for different setups that represent end-use conditions better. Moreover, it provides versatility for customized weight placement (center to edge) for increased PCB deflection, and greater control on the PCB vibration behavior minimizing concerns with test site miscorrelations. The latter section of this study illustrates how the use of proper daisy-chain test vehicles can enhance the statistical output as greater resolution can be achieved via the quadrant concept. Results from numerous experiments and test characterization such as effect of pulse parameter, stress analysis via input-G, responses to drop height changes and weight shall be presented. Finally, the authors demonstrate how this test method can be universally applied for both automotive and consumer products; thereby effectively expanding the horizon of JEDEC handheld test (JESD22-B111).

Solder Joint Reliability Investigation of Chip Scale Package with Plastic Core Solder Balls on Thermomechanically Loaded PCBs

In this paper, solder joint reliability of a Chip Scale Package (CSP) with polymer core solder balls (PCSB) was evaluated. Temperature cycling data was obtained from both conventional and polymer core balls tested on chip scale package with pitch 0.5mm mounted on an 8 layers HDI board. FEM simulation was also performed to compare the polymer core balls with a conventional solder ball. This study has clearly shown that the reliability of polymer core solder balls is strongly dependent on manufacturing, method of assembly (balling), package type (BGA or WLP) and the solder joint shape. Polymer core solder balls may potentially improve solder joint fatigue life, but the significant effects of design variables define the achievable benefits.