Intermetallic Compounds Formed in Sn-20In-2.8Ag Solder BGA Packages with Ag/Cu Pads |
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Authors: | CC Jain SS Wang KW Huang TH Chuang |
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Affiliation: | (1) Department of Materials Science and Engineering, National Taiwan University, Taipei, 106, Taiwan |
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Abstract: | The interfacial reactions in a Sn-20In-2.8Ag solder ball grid array (BGA) package with immersion Ag surface finish are investigated.
After reflow, the Ag thin film dissolves quickly into the solder matrix, and scallop-shaped intermetallic layers, with compositions
of (Cu0.98Ag0.02)6(In0.59Sn0.41)5, appear at the interfaces between Sn-20In-2.8Ag solder ball and Cu pad. No evident growth of the (Cu0.98Ag0.02)6(Sn0.59In0.41)5 intermetallic compounds was observed after prolonged aging at 100 °C. However, the growth accelerated at 150 °C, with more
intermetallic scallops floating into the solder matrix. The intermetallic thickness versus the square root of reaction time
(t
1/2) shows a linear relation, indicating that the growth of intermetallic compounds is diffusion-controlled. Ball shear tests
show that the strength of Sn-20In-2.8Ag solder joints after reflow is 4.4 N, which increases to 5.18 N and 5.14 N after aging
at 100 and 150 °C, respectively. |
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Keywords: | BGA package immersion Ag surface finish interfacial reactions Sn-20In-2 8Ag |
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