Finite Element Analysis on Soldered Joint Reliability of Ball Grid Array Device Under Thermal Shock

Abstract

AbstractIn this paper, finite element analysis with the constitutive relationships described by Anand model, is used to simulate thermally induced stresses distributions on the ball grid array (BGA) packages under thermal cycling. The maximum stress locates on the top surface of the outmost corner of the soldered joint with FR-4 substrate. The stress relaxation is observed and the stress accumulated enhancement exists under thermal cycling. The effects of stresses on the solder joints are studied as a function of height, diameter and pitch of solder joint. The maximum stress decreases with the height increase of soldered joints, and increases monotonously with the increasing pitch of solder joints. The diameter of solder joints plays an important role in the reliability of soldered joints. The soldered joint with the diameter of 0.41 mm has minimum stress when the height of solder joints is 0.20 mm. In addition, the reliability on soldered joints with different substrate materials is also studied. It is indicated that the maximum stress of soldered joint locates on the sharp corner of exterior part of the joint with PTFE substrate, similar to the case with Roges6002 substrate, and the maximum stress focuses on the sharp corner of interior part of the joint with CLTE substrate. The soldered joints with PTFE substrate have the maximum stress, and the soldered joints have minimum stress when the substrate material is CLTE by contrast. The stress relaxation is observed in the Roges6002 and CLTE substrate, which is not found in the PTFE substrate. The conclusions obtained may provide theoretical guidance for the designation of electronic packages and improve the soldered joint reliability of BGA device under thermal shock.KeywordsFinite element analysisAnand modelThermal cyclingStress relaxation