Challenges for Achieving Automotive Grade 1/0 Reliability in FCBGA and fcCSP Packages

Achieving the Automotive Electronics Council (AEC) Q-100 specification for Grade 1 and 0 reliability introduces unique challenges as thermal cycling (TC) and high temperature storage (HTS) requirements increase. New automotive packages require increased integration of device functionality for sensors, driver assistance systems, infotainment and in-vehicle networking which pushes demand for larger package sizes. This increase in package size and thermal cycling over a large temperature range (from -55 to 150°C) introduces high thermomechanical stress to the package. Additionally, high operating temperatures and the need for 15-year reliability with zero-defect quality are driving qualifications that extend beyond the AEC Q-100 specification conditions. These factors present material challenges such as intermetallic compound (IMC) growth, degradation of organic materials and increased likelihood of wear-out failures from thermomechanical stresses.

This presentation provides an update on flip chip Chip Scale Packaging (fcCSP) and Flip Chip ball grid array (FCBGA) material and package development to achieve Grade 1/0 reliability. Simulation of key mechanical properties such as the modulus of elasticity and the coefficient of thermal expansion (CTE) and material aging experiments have highlighted the need to identify substrate materials, underfills and epoxy molding compounds (EMCs) that can withstand harsh TC and HTS conditions up to 175°C. To reduce thermomechanical stress in TC, low CTE substrate materials are needed. Results from prior experiments and current work have identified a robust bill of materials (BOM) for a 35 mm body size FCBGA and 12 mm body fcCSP package capable of achieving Grade 1 reliability. The remaining challenges and potential solutions are discussed for selecting materials capable of reaching Grade 0 and extended qualifications.