SMTA International Conference Proceedings

Effect of Tim Compression Loads on BGA Reliability

Authors: Nicholas Graziano, Harry Schoeller, Ph.D., Lars Bruno
Company: Department of Mechanical Engineering, Binghamton University, Universal Instruments Corporation and Ericsson AB
Date Published: 10/14/2018   Conference: SMTA International

Abstract: Compressive loads are often applied to Thermal Interface Materials (TIMs) to improve their thermal performance and this stress must be accommodated by the underlying solder joints. The effect of compressive loads on BGA reliability has been analyzed for SAC305 solder in thermal shock (-40/125 °C with 15 minutes dwells).

Assemblies were temperature cycled using two different simulated heat sinks with multiple load magnitudes. One delivered the load directly to the die while the other loaded the outer BGA rows through contact on the substrate. Die loaded samples were tested with and without a backplate. Additionally, two sets of samples were pre-aged for up to 1000 hours at 125 °C under compression prior to solder collapse measurements or thermal shock.

BGA thermomechanical reliability, under different loading configurations and magnitudes, was compared using Weibull failure rate distribution plots. Cross sectioning and dye and pry analyses were performed to identify the location and mode of failure. This work aims to provide guidance for the potential trade-offs between thermal performances and second level interconnect reliability.

Key Words: 

TIM, compression, SAC 305, thermal reliability

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