Effect of Additive Elements Bi/Ni/Ge on Crack Initiation and Propagation for Low-Ag Solders

Noritake Hiyoshi,Mitsuo Yamashita,Hiroaki Hokazono

doi:10.3221/igf-esis.46.03

Abstract

This study discusses an effect of additive elements on crack propagation behaviour for low-Ag contain Sn1.0Ag0.7Cu lead-free solders at high temperature. A cyclic push-pull loading tests for four kinds of Sn1.0Ag0.7Cu solders were conducted at 313 K with a single hole specimen. Stress amplitude of solders containing additive element Bi were bigger than that of Bi-free solders. Crack initiation cycle of solders containing Bi were earlier than that of Bi-free solders. Low-Ag solders containing Bi had shorter crack propagation cycles than that of Bi-free solders. These results indicate that the additive element Bi have the effects on the crack initiation and propagation cycles, that is, Bi accelerates the crack propagation rate. We also discuss the adaptation of J-integral range parameter to the crack propagation rate evaluation for solders. J-integral range parameter evaluates the crack propagation rate for low-Ag solders independent of the additive elements.

Highlights

S oldering is an important and a fundamental technique for electronic device mounting
Crack propagated in the maximum shear direction for SnAgCu+BiNiGe in the smaller strain range (photo (g)), but crack propagation direction of one side for SnAgCu+BiNiGe in the larger strain range was changed from the principal direction to the maximum shear direction (photo (h))
The crack propagation direction difference and the direction changing behaviour among the low-Ag solders might depend on the existence of Bi element

Summary

Introduction

S oldering is an important and a fundamental technique for electronic device mounting. The solder joints have lots of stress concentration parts, so that it is useful for fatigue life estimation of electronic devices to make clear the cyclic crack initiation and propagation behaviour of solders from the stress concentration part at commercial operating temperature. Sn-3.0Ag-0.5Cu lead-free solder is widely used solder all over the world, there are some issues for the solder One of these issues is that high material cost due to it contains Ag element. The melting point temperature of Sn-low-Ag-Cu solders is 500 K and the material cost is about 4,800JPY (Japanese Yen) per 1kg while Sn-3.0Ag-0.5Cu solder costs about 7,500JPY It is important for commercial safety products design to clarify tensile strength and mechanical properties and fatigue life of the electronic materials, there is little experimental research paper on Sn-low-Ag-Cu solders. This study discusses the adaptation of J-integral range parameter for the crack propagation rate evaluation

Methods

Results

Conclusion