Finite element analysis of fleXBGA reliability

• Published in: Soldering & surface mount technology 2006-04, Vol.18 (2), p.46-53
• Main Authors: Chen, Gang, Chen, Xu
• Format: Article
• Language: English
• Subjects: Accuracy; Boundary conditions; Deformation; Electronics industry; Finite element analysis; Optimization techniques; Packaging; Printed circuit boards; Reliability engineering; Reliability management; Shear strain; Simulation; Soldering; Solders; Studies; Symmetry; Thermal cycling
• ISSN: 0954-0911; 1758-6836
• DOI: 10.1108/09540910610665134

Purpose - To provide an approach to fleXBGA design and reliability analysis.Design methodology approach - A two-dimensional (2D) plane strain finite element analysis model is established to simulate the thermo-mechanical behaviour of fleXBGAs which are subjected to thermo-cyclic loading under different temperature cycling conditions. The model has been used to consider the effects of printed circuit board (PCB) thickness, die size, package size, ball count, pitch and substrate configuration. The Anand constitutive model is adopted to simulate creep and plastic deformation of the solder joints. A fatigue life prediction model based on plastic shear strain range is then applied to predict the fatigue life of different kinds of fleXBGA.Findings - Comparison of fatigue life predictions and experiments show that the maximum prediction errors are mostly within ±50 per cent, and it can be concluded that a smaller die size, a thinner PCB, a smaller solder ball diameter, more balls, a smaller temperature range and a faster ramp rate are all helpful in improving the package fatigue life.Research limitations implications - Not all properties of the packaging materials are available for design and reliability analysis. Advanced research should be focused on determining the mechanical properties of the packaging materials to improve the analysis accuracy.Practical implications - Design optimisation was used to determine the effect of structural parameters for the fleXBGA assembly on the von Mises equivalent stresses in the solder joints, which is one of the most critical factors for package reliability. The calculation results indicate that the equivalent stress in solder joints can be decreased about 19.7 per cent comparing with the initial structure and the fatigue life can be greatly enhanced.Originality value - The suggested approach is very useful for fleXBGA assembly design. The reliability of the package can be greatly improved by using the modified geometric parameters.