SMTA International Conference Proceedings

Effect of Board Thickness, Temperature Range, and Dwell Time on Solder Joint Reliability of FCBGA Packages Based on IPC9701 Characterization

Authors: Olivia H. Chen, Jagadeesh Radhakrishnan and Al Molina
Company: Intel Corporation
Date Published: 9/28/2014   Conference: SMTA International

Abstract: To understand the long term reliability of Flip Chip Ball Grid Array (FCBGA) packages with SAC405 lead-free solder balls, a study was conducted to focus on the effect of printed circuit board thickness, temperature cycle range (delta T) and temperature dwell time on the accelerated temperature cycling performance of two different types of FCBGA packages (cavity packages with center depopulation of ball grid array and non-cavity packages with fully populated ball grid array) based on IPC9701 characterization methodology [1].

The time-to-failure (TTF) and acceleration factor (AF) at 1% and 63.2% failure rate will be discussed in this paper with the following test conditions: two different temperature ranges (delta T = 100C and 140C), two different board thicknesses (40mils and 125mils) and three dwell times (5 min, 15min, and 60min). The results will be summarized based on Cavity vs. Non-cavity package case studies with different ball pitches (ranging from 0.673mm to 1.01mm). In addition to calculating the AF from experimental results, the time-to failure data will also be fit with Norris Landzberg (N-L) model to understand whether the model will predict comparable AFs at the given test conditions. Finally, finite element analysis (FEA) will be used, with the support of failure analysis (FA) data, to correlate to experimental data.

Based on the results of this study, increasing board thickness leads to decreasing temp cycle performance in both cavity and non-cavity packages. Also, larger temperature range leads to decreasing temp cycle performance in both cavity and non-cavity packages. Longer dwell time leads to decreasing temp cycle performance in both cavity and non-cavity packages. From the package geometry standpoint, non-cavity packages with showed better reliability results when compared to cavity packages. When comparing failure location, die shadow solder joints failed before package corner and edge solder joints for both cavity and non-cavity packages under the given temp cycle conditions. A fit of N-L model to experimental test results showed that a range of values found in literature for model exponents didn’t yield good trend prediction of the AF, thus highlighting the gap in N-L model due to the effect of geometric parameters (such as board thickness, package sizes and package types) for FCBGA packages under study.

An FEA analysis showed good trend to experimental results when comparing Inelastic Strain Energy Density (ISED) for various testing conditions, thus showing promise to fill in the gaps identified by N-L model.

Key Words: 

IPC9701, SAC405, FCBGA, Solder Joint Reliability (SJR), FEA

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