Inhibition of grainboundary cacking in copper-base alloys used in electronic industries

2002 Fiscal Year Final Research Report Summary

• Project/Area Number: 13555185
• Research Category: Grant-in-Aid for Scientific Research (B)
• Allocation Type: Single-year Grants
• Section: 展開研究
• Research Field: Structural/Functional materials
• Research Institution: The University of Tokyo
• Principal Investigator: KANNO Kanno The University of Tokyo, Graduate School of Engineering, Professor, 大学院・工学系研究科, 教授 (60011128)
• Co-Investigator(Kenkyū-buntansha): NISHI Seiji Kobe Steel, LTD., Technical Development Group, Manufacture Technology Laboratory, Director, 技術開発本部生産技術研究所, 所長(研究職)
• Project Period (FY): 2001 – 2002
• Keywords: Ch-Ni-Si alloy / grain boundary cracking / trace impurity / intermediate temperature embrittlement / sulfur / hydrogen

Research Abstract

Age-hardenable Cu-Ni-Si alloys, which have been used as lead-frame materials in electronic industries, often show grain boundary cracking during hot-wokring. In addition, it is known that these alloys also show an intermediate temperature embrittlement accompanied by grain boundary cracking. This work was undertaken to make clear the cause of the grain boundary cracking and to inhibit the cracking, paying attention to sulfur and hydrogen which are believed to cause grain boundary cracking in copper base alloys.
Since magnesium and zirconium are reported to have high affinity between sulfur and hydrogen, a Cu-Ni-Si alloy and the alloys added magnesium or zirconium were used in this study. Thermal desorption hydrogen analysis showed a hydrogen emission peak appeared at around 4500 in the ternary and in the Mg-bearing alloy, but a new peak appeared in addition to the above peak in the Zr-bearing alloy, suggesting that there appeared new trapping sites for hydrogen atoms. In the Zr-bearing alloy, reduction in area increased to a small extent. compared to that of the ternary alloy accompanied by dynamic recrystallization, showing that Zr addition might be effective to reduce grain boundary cracking. Since grain boundary cracking is still present in the quaternary alloys, there might be other factors in addition to sulfur and hydrogen which enhances grain boundary cracking. Further study is being made to inhibit grain boundary cracking in these alloys.