The embrittlement mechanism and improvement of impact strength for lead-free solder joints in BGA packaging using electrolytic Ni/Au plating |
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Authors: | Kenichi Yamamoto Takahiko Kato Toshinori Kawamura Hiroshi Nakano Masahiro Koizumi Haruo Akahoshi |
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Affiliation: | 1. Renesas Technology Corporation , Tokyo, Japan;2. Material Research Laboratory, Hitachi Ltd , Tokyo, Japan;3. Hitachi Research Laboratory, Hitachi Ltd , Tokyo, Japan |
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Abstract: | Impact strength evaluation and fracture mechanism analysis in board level of Sn–3mass%Ag–0.5mass%Cu solder joints of ball grid arrays (BGA) using electrolytic Ni/Au plating were performed. The cause of impact strength degradation of BGA solder ball joints is the existence of low density defects, which contain organic materials, in the (Cu,Ni)6Sn5 intermetallic compound grain boundary formed in the solder joints. These organic materials are taken in by the nickel plating film at the time of nickel plating. To improve the impact strength of the Sn–3mass%Ag–0.5mass%Cu solder joint of the BGA, it is necessary to lower the concentration of these organic materials. The contamination prevention and nickel plating bath sanitization, solder mask material selection (to minimize nickel plating bath contamination) and higher current density of nickel plating are effective to keep a lower concentration of organic materials in nickel plating film. |
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Keywords: | lead free solder Sn–Ag–Cu BGA intermetallic compound impact load electroplated Ni/Au plating solder mask |
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