Mechanical Properties of Cu-Core Solder Balls with ENEPIG Surface Finish
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https://doi.org/10.1007/s11664-020-08338-w 2020 The Minerals, Metals & Materials Society
Mechanical Properties of Cu-Core Solder Balls with ENEPIG Surface Finish HAKSAN JEONG,1 CHOONG-JAE LEE,1 KYUNG DEUK MIN,1 JAE-YEOL SON,1,2 and SEUNG-BOO JUNG 1,3 1.—School of Advanced Materials Science and Engineering, Sungkyunkwan University, 2066 Seobu-ro, Jangan-gu, Suwon 16419, South Korea. 2.—MK Electronics, 316-2, Kumeuri, Pogok-eup, Cheoin-gu, Yongin, Gyeonggi-do 449-812, South Korea. 3.—e-mail: [email protected]
The development of ball grid array (BGA) packages, such as the chip scale package, wafer level package and package on package, has focused on creating electronics packages that are smaller, thinner, higher-performance and capable of higher functionality, among other desirable traits. Among the interconnection materials used in BGA packages, the Cu-core solder ball (CCSB) has many advantages, such as the use of finer pitch, improved electrical conductivity and better controllability of the coplanarity of the chip. In this study, we evaluated the mechanical properties of the CCSB and Sn-3.0Ag0.5Cu (SAC) by low-speed shear tests, and the von Mises stress distribution and plastic strain distribution were simulated using a finite element method. The diameter of each solder ball was 280 lm, and the outer layer of the CCSB was a plated SAC layer. The shear strength of the CCSB was about 10% greater than that of SAC. The maximum value of the simulated von Mises stress for the CCSB was higher than that of SAC because the Cu-core is stiffer than SAC. The fracture energy of the CCSB decreased by about 50% compared to that of SAC. The maximum value of simulated plastic strain, which is associated with fracture surfaces, was higher with the CCSB than with SAC. We can thus conclude that the Cu-core in the CCSB affects the shear strength and fracture behavior of solder joints. Key words: Cu-core solder ball, Sn-3.0Ag-0.5Cu, low-speed shear test, finite element method, ENEPIG
INTRODUCTION Next-generation electronic devices for mobile and Internet of Things (IoT) applications require higher performance, higher functionality, and smaller and thinner device dimensions. Among advanced packages, ball grid array (BGA) packages, such as the chip scale package (CSP), wafer level package (WLP) and package on package (PoP), have been used as microelectronic packages because of their high input/output (I/O) density, ability to be miniaturized, multi-functionalization, and high
(Received March 23, 2020; accepted July 16, 2020)
reliability. The solder balls of the BGA package are one of the interconnection methods used to form electrical pathways and mechanical supports between the chip and the substrate.1–3 Package life is affected by solder reliability, which depends on properties such as strength, thermomechanical fatigue behavior, creep resistance and void rate.4–7 Package life is especially affected by tilted die, which occurs during the reflow process. Solder alloy is fully melted during reflow, so the die can be tilted if the di
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