| XIAO Jin,TIAN Xuefeng,FENG Xiaojie,LIU Zhiming,XU Chuang.Solid-phase Transient Soldering Method Based on Au/Ni-W Composite Thin-film-modified Copper-based Micro-nano Hierarchical Structures[J],53(12):260-267 |
| Solid-phase Transient Soldering Method Based on Au/Ni-W Composite Thin-film-modified Copper-based Micro-nano Hierarchical Structures |
| Received:December 26, 2023 Revised:March 17, 2024 |
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| DOI：10.16490/j.cnki.issn.1001-3660.2024.12.022 |
| KeyWord:micro-nano hierarchical structure thin films soldering diffusion |
| Author | Institution |
| XIAO Jin |
School of Advanced Manufacturing, Guangdong Songshan Polytechnic, Guangdong Shaoguan , China |
| TIAN Xuefeng |
School of Advanced Manufacturing, Guangdong Songshan Polytechnic, Guangdong Shaoguan , China |
| FENG Xiaojie |
School of Advanced Manufacturing, Guangdong Songshan Polytechnic, Guangdong Shaoguan , China |
| LIU Zhiming |
School of Advanced Manufacturing, Guangdong Songshan Polytechnic, Guangdong Shaoguan , China |
| XU Chuang |
School of Advanced Manufacturing, Guangdong Songshan Polytechnic, Guangdong Shaoguan , China |
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| Abstract: |
| A copper-based micro-nanostructure with special morphology is used as the substrate to coat Ni-W alloy layer and Au nanolayer sequentially. Instantaneous soldering with tin-based solder is realized under ultrasonic energy and room temperature conditions, solving the thermal shock and thermal damage caused by the high melting point of lead-free solder on thin chips and thermal devices. This method ensures device safety and performance reliability. Electrochemical deposition of copper-based micro-nano-graded structures with special morphology was carried out. An amorphous Ni-W alloy layer with a thickness of 180 nm was deposited on the Cu-based micro-nano-graded structures by adjusting the atomic ratio of the plating solution. Since the Ni-W layer was easily oxidized, an Au layer with a thickness of 50 nm was electrodeposited on it to prevent oxidation. The obtained Au/Ni-W composite film-modified Cu-based micro-nano-graded structures were solid-phase transiently soldered with a commercial solder (SAC305) under a soldering pressure of 98 N(20 MPa), a soldering time of 3 s, and an ultrasonic vibration of 3 s. The copper-based micro-nano-graded structures with different surface modification layers were subject to destructive shear testing with solder balls. The soldered samples were aged at 180 ℃ for 10, 30, and 60 min, respectively. Scanning electron microscopy and X-ray fluorescence thickness gauge were used to study the microstructure, thickness of intermetallic compound composition, and properties at the soldered interface. The copper-based micron-scale protrusion structure had a height of 2-4 μm and a base size of 800-1 200 nm, which had a sharp tip, excellent protruding structure density and aspect ratio. The solder interface formed by the Au/Ni-W modified Cu-based micro-nano-graded structure and the SAC305 solder ball was well embedded without any hole. The average shear strength of the soldered interface was 43.06 MPa. The fracture surface of Au/Ni-W modified Cu-based micro-nano-graded structure basically occurred inside the solder ball matrix, which was a pure ductile fracture. The copper-based micro-nano-graded structure is inserted into the inside of the solder ball to form an inlay, which produces mechanical interlocking. The Au/Ni-W alloy modification layer can effectively improve the surface hardness of copper-based micro-nano-graded structure. It forms a large hardness difference with tin solder, which reduces the formation of holes in the insertion soldering. The soldering effect is excellent. The amorphous Ni-W alloy is prone to form a dense oxide film during the ultrasonic process. Its modification by Au film prevents the oxidation of Ni-W alloy layer. Moreover, Au has a high activation energy and reacts quickly with tin to generate intermetallic compounds, obtaining a stable bonding interface and improving the soldering shear strength. The presence of Ni-W alloy layer retards the interdiffusion between Cu-Sn and blocks the growth of Cu-Sn intermetallic compounds. This reduces the reliability problems due to interfacial failure. |
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