Void-free interface between In and high-impurity Cu joint

Abstract

The effect of impurities in the Cu film on the void formation at the interface of the Sn-rich solder joint has been extensively studied. However, this has rarely been studied for In solder joints. In this study, Sn-3.0Ag-0.5Cu (SAC305) and In-solder/ Cu films with high impurities were aged at 150 °C to analyze the films at various aging times. A metastable CuIn₂ phase appeared and transformed into a stable Cu₁₁In₉ phase. Noticeable voids and cracks were observed at the SAC305/Cu interface during the solid-state aging. In contrast, there was a void-free interface between In and Cu-CP. This was primarily due to the difference in diffusion behaviour between In/Cu and SAC305/Cu. The mechanism of the above phenomenon was revealed.

KEYWORDS:

• Electroplated Cu
• In solder
• Kirkendall effect
• impurity
• aging

Acknowledgements

Yu-An Shen thanks the National Science and Technology Council under Project 112-2221-E-035-022- & 111-2221-E-035-054-. Chih-Ming Chen thanks the National Science and Technology Council under Project 110-2221-E-005-006-MY3. The support of Ultra HR SEM at National Yang Ming Chiao Tung University Instrument Resource Center (EM002800) under Project MOST 111-2731-M-A49-001 was appreciated. EPMA000200 of Instrumentation Center at National Tsing Hua University under Project Most 111-2731-M-007-001 is appreciated.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Author contributions

Jia-Yi Lee: Validation, Formal analysis, Investigation, Data Curation.

Yu-An Shen: Formal analysis, Investigation, Data Curation, Validation, Writing – Original Draft, Writing – Review & Editing, Project administration, Funding acquisition.

Chih-Ming Chen: Conceptualization, Methodology, Validation, Data Curation, Writing – Original Draft, Writing – Review & Editing, Supervision, Visualization, Project administration, Funding acquisition.

The manuscript was written through contributions of all authors. All authors have given approval to the final version of the manuscript.

Data availability statement

The datasets used and analyzed during the current study available from the corresponding author on reasonable request.

Additional information

Funding

This work was supported by National Science and Technology Council: [Grant Number 112-2221-E-035 -022-]; National Science and Technology Council: [Grant Number Project 110-2221-E-005 -006 -MY3]; National Science and Technology Council: [Grant Number 111-2221-E-035-054-].