Board-level characterization of 1.0 and 1.27 mm pitch PBGA for automotive under-hood applications

Ball grid array (BGA) has become the mainstream package of choice for devices with pin counts greater than 160. As such, the current generation of automotive engine and electronic transmission controllers for under-hood and on-engine mounting with pin counts in the 200 to 350 pin count range are being introduced by Motorola in BGA packaging. There is also a driving force to reduce the form factor of automotive electronics, both due to space constraints and to achieve lower material costs. All this is occurring while there is a shift to put more electronics under-hood and specifically on-engine, where temperatures can be greater than typical firewall mounting. One special concern with the BGA, therefore, is its ability to withstand the repeated cycling associated with these applications up to temperatures that can approach 150°C. This paper will outline testing and simulation using finite element analysis (FEA) that was performed to assess the board-level (i.e., package to board interconnect) reliability of both 1.0 and 1.27 mm pitch PBGAs for the severe automotive environment. Variables such as package body size, die size, ball size, package substrate thickness, solder ball pitch and the presence/absence of thermal balls will be addressed. Solder joint fatigue failure data from the commonly used -40 to 125°C automotive thermal cycling condition as well a more severe potentially required condition of -50 to 150°C will be presented to show the suitability of PBGA for the intended application from a solder joint reliability perspective