2004 Fiscal Year Final Research Report Summary
Nano-Scale Characterization of Bonding Interface in Electronics Package and Its Application to Evaluating Reliability of the Joints
| Project/Area Number |
14350386
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| Research Category |
Grant-in-Aid for Scientific Research (B)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
Material processing/treatments
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| Research Institution | Osaka University |
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Principal Investigator |
KOBAYASHI F.Kojiro Osaka University, Graduate School of Engineering, Professor, 大学院・工学研究科, 教授 (70026277)
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| Co-Investigator(Kenkyū-buntansha) |
HIROSE Akio Osaka University, Graduate School of Engineering, Associate Professor, 大学院・工学研究科, 助教授 (70144433)
UENISHI Keisuke Osaka University, Graduate School of Engineering, Associate Professor, 大学院・工学研究科, 助教授 (80223478)
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| Project Period (FY) |
2002 – 2004
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| Keywords | Lead-free solders / Electronics assembly / Interfacial reaction / Joint strength / Nano-scale characterization / QFP / BGA / CSP |
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| Research Abstract |
The present research aimed to nano-scale characterizations of the bonding interface in electronics assemblies that could be applied to evaluating reliability of the joints of the package. The solder joints for QFP, BGA and CSP packages were made using Sn-Ag, Sn-Ag-Cu, Sn-Zn-Bi and Sn-Ag-Bi-In solders with varying metallization of the Cu land. The detailed metallographic observations of the bonding interface and the measurements of the joint strength were performed in as-soldered condition and after a high-temperature storage. In soldering on the bare Cu land, although the growth of the Cu-Sn intermetallic reaction layer in the Sn-Ag, Sn-Ag-Cu and Sn-Ag-Bi-In solder joints caused no significant degradation of the joint strength, coexistence of the Cu-Sn and Cu-Zn intermetllic reaction layers in the Sn-Zn-Bi solder joint had a marked detrimental effect on the reliability of the joint after the high-temperature storage. In soldering on the Ni-P/Au plated Cu land, a P-rich layer formed bet
… More
ween Ni-Sn intermetallic reaction layer and Ni-P plating in the Sn-Ag solder joint and caused the decrease in the joint strength. Thick Au plating resulted in the further degradation of the joint strength. Since the Cu alloying to the Sn-Ag solder promoted the formation of the Cu-Sn type intermetallic layer instead of the Ni-Sn layer and suppressed the formation of the P-rich layer, the Sn-Ag-Cu solder joint had higher strength than the Sn-Ag solder joint. In the Sn-Zn-Bi solder joint, the joint strength was insufficient in the case of a lower reflow temperature less than 230℃, because the Au-Zn intermetallic reaction layer caused the fracture. Increasing the reflow temperature higher than 230℃ promoted the reaction between the solder and Ni-P plating and thereby improved the joint strength. On the contrary in Sn-Ag-Bi-In solder joint, lower reflow temperature, which prevented the formation of clumpy Cu-Sn intermetallic phase on the Ni-Sn layer, was beneficial to the joint strength. Moreover, the kinetics of the interfacial reaction in the above mentioned solder joints were evaluated. Based on these results we clarified appropriate reflow soldering conditions and combinations of the solders and the metallization to obtain sufficient reliability of the solder joints. Less
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Research Products
(54 results)
