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Crystals 2017, 7(8), 255;

Evaluation of Thin Copper Wire and Lead-Free Solder Joint Strength by Pullout Tests and Wire Surface Observation

Graduate School of Natural Science and Technology, Okayama University, Okayama 700-8530, Japan
Author to whom correspondence should be addressed.
Received: 13 July 2017 / Revised: 13 August 2017 / Accepted: 18 August 2017 / Published: 20 August 2017
(This article belongs to the Special Issue Advance in Crystalline Thin Wires)
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Copper wires have been attracting much attention for Large Scale Integration (LSI) bonding because of their excellent mechanical and electrical properties, in addition to their low material cost. The ends of these wires are usually joined to pads or through-holes on a printed circuit board, and lead-free soldering is one of the popular bonding methods. Since the deformation resistance of solder is lower than that of copper, especially in slow deformation due to creep, the strain tends to be increased in the solder and concentrated near the copper/solder joint interface. Thus, fracture frequently occurs at this interface and may influence the quality of the product. It is therefore important to evaluate the bonding strength of thin copper wire and lead-free solder. In this paper, pullout tests of thin copper wire from lead-free solder were carried out, and the pullout behavior of the wires was observed. The bonding strength was evaluated based on the actual bonded area on the copper wire surface. Finally, the strength of the thin copper wire/solder joint was summarized using the shear and tensile strengths of the copper/solder interface as well as the tensile strength of the copper wire. View Full-Text
Keywords: copper wire; lead-free solder; bonding strength; pullout test copper wire; lead-free solder; bonding strength; pullout test

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Tada, N.; Tanaka, T.; Uemori, T.; Nakata, T. Evaluation of Thin Copper Wire and Lead-Free Solder Joint Strength by Pullout Tests and Wire Surface Observation. Crystals 2017, 7, 255.

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