The solder-joint interconnect between an IC component and the PCB (printed circuit board) is an important link in the overall reliability of automotive electronics. Market trends are driving increased focus on solder-joint performance: (1) increasing electronics content for new functions (ex. ADAS or advanced driver-assistance systems), (2) use in safety critical systems and sub-systems, (3) decreasing interconnect pitches which reduces the stand-off and available solder, (4) increasing industry reliability expectations, and (5) package variations (ex. flip chip). This paper summarizes -40°C to 125°C temperature cycle results from multiple controlled experiments on Pb-free BGA test vehicle packages with pitches from 0.50mm to 1.00mm. Body sizes ranged from 10mm to 45mm. In addition to these primary attributes, the influence of various other factors on solder-joint lifetimes was studied, including solder ball alloy, package type, BGA pad finish, die size, and PCB pad diameter. Mechanical simulations further enhanced understanding and predictions. In all cases, the POR (plan of record) package BOM (bill of materials) and design configurations passed the application requirements. Per standard practice for solder-joint reliability studies, tests were extended past the application requirements until at least 75% of the population failed in order to construct Weibull plots and perform crack propagation analysis. Multiple factors were observed to affect solder-joint reliability. Rules of thumb and high-level trends could be used for first order assessments only. For common body size, BGA pitch and solder alloy, no solder-joint lifetime dependence was observed for the different package types MAPBGA, TEPBGA and FCPBGA. The first solder-joints (die shadow vs. package edge) to fail were body size and die size dependent for wirebond packages. SnAg solderball alloy showed longer characteristic lifetime than the high Ag SAC alternatives SAC305, SAC405 and SAC387. Adding 3% Bi to the SAC solder alloy further increased lifetimes.
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