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Published on: June 2, 2017
Microstructural and Mechanical Characterization of Cu/SnAg Pillar Bumps with Ni-Less Surface Finish Utilizing
Sang-Eun Han1,2, Dong-Gyu Choi1,3, Seonghui Han1,4
1Regional Industry Innovation Department (Growth Engine), Korea Institute of Industrial Technology, Incheon 21999, Republic of Korea.
Materials (Basel, Switzerland)
|May 7, 2025
Summary
Laser-assisted bonding (LAB) creates strong Cu/SnAg interconnections with minimal intermetallic compound (IMC) growth. Optimized LAB conditions surpass traditional methods, though high laser power can cause solder splashing.
Area of Science:
- Materials Science
- Surface Engineering
- Joining Technologies
Background:
- Reliable interconnections are crucial for advanced electronic packaging.
- Traditional bonding methods like thermo-compression bonding (TCB) and mass reflow (MR) have limitations.
- Ni-less copper pads present unique bonding challenges.
Purpose of the Study:
- To investigate the feasibility and characteristics of laser-assisted bonding (LAB) for Cu/SnAg pillar bump to Ni-less Cu pad interconnections.
- To evaluate the influence of laser irradiation time and power density on bond quality and mechanical strength.
- To compare LAB performance against conventional TCB and MR processes.
Main Methods:
- Formation of Cu/SnAg pillar bump to Ni-less Cu pad interconnections using LAB.
- Systematic variation of laser irradiation time and laser power density.
- Analysis of intermetallic compound (IMC) growth using Field Emission Scanning Electron Microscopy (FE-SEM).
- Evaluation of bonding strength and failure modes.
Main Results:
- Optimized LAB conditions yielded minimal IMC growth and superior bonding strength compared to TCB and MR.
- Increased laser irradiation time and power density led to solder splashing above 300 °C, attributed to rapid flux vaporization.
- Higher laser power density shifted the failure mode from solder to the IMC interface.
Conclusions:
- Laser-assisted bonding (LAB) offers a promising alternative for high-performance electronic interconnections.
- Precise control over LAB parameters is essential to optimize bond quality and prevent defects like solder splashing.
- LAB demonstrates potential for achieving robust joints with reduced IMC formation in advanced packaging applications.
