Failure prediction of the solder joints in the ball-grid-array package under thermal loading

Abstract

This paper studies the numerical failure mechanism of the solder joints in the ball grid array (BGA) package under thermal reliability process. The package consists of the silicon die, the Flame Retardant 4 (FR-4) substrate and the FR-4 printed circuit board (PCB). A total of 64 95.5Sn-4.0Ag-0.5Cu (SAC405) solder joints with a diameter of 0.46 mm are arranged together in area array fashion with a pitch distance of 0.8 mm. Only a quarter-model of the package is simulated since all the geometry, loading and boundary conditions (BC) is symmetry at the centre of the package. The package is exposed with thermal loading, initially at the liquidus temperature of 220°C to room temperature (25°C). Then, it follows with 3 additional thermal cycles between 125°C and -40°C with a ramp rate of 11°C/min and 15 minutes dwell time, respectively. Unified inelastic strain model (Anand model) was used to compute the inelastic behaviour of the solder joints. Results show that the stress level at the critical solder joints and the corresponding inelastic strain are 39.91 MPa of 0.2083%, respectively after the end of the solder reflow cooling process. As predicted, the inelastic strains accumulate continuously in the solder joint throughout the temperature cycles. Additionally, in the critical solder joint, both high stress and inelastic strain gradients are localized near to the solder-IMC interfaces. Prolong the thermal cycles can extensively accumulate the inelastic strains which lead to fatigue crack and subsequently crack propagation in the solder joints. After the end of the FE simulation, the highest stress and inelastic strain predicted are 57.96 MPa and 0.5781%, respectively.

Effect of Solder Ball Geometry on Solder Joint Reliability under Solder Reflow Cooling Process

“…At the same time, it slowly fades and declines to the center of the solder ball, where it remains elastic. The finding obtained from the simulation shows a similar result to those obtained by Yamin et al [16]. As for the bottom part, the NSMD pad experiences lesser inelastic strain throughout the whole surface than the SMD pad.…”

Determination of the Anand Parameters for SAC405 Solders Through the Use of Stress-Strain Data

“…The Anand model's ability to forecast plasticity and creep, as well as its incorporation into a number of commercial finite element software packages, have made it an appealing option among engineers working with Tin-Lead and lead-free solders. Developed by Anand and Brown, the Anand model is one of the most popular constitutive models used to de-scribe the mechanical properties of solder [8]. The Anand model is typically employed to represent solder deformation in electronic packages [9].…”