| Summary: | 碩士 === 國立中央大學 === 化學工程與材料工程研究所 === 97 === In the work, we study soldering reaction between Ni-Co alloy layer and Sn(Cu) Pb-free solders. Different Co concentrations in Ni-Co alloy layer were electroplated on Cu foils. Then, Sn(Cu) solders were reflowed on the Ni-Co alloy layers at 250 ℃ to investigate the growth situation and morphology of IMCs and to discuss the effect of Co concentration and Cu concentration on the reaction between Sn(Cu) and Ni-Co layer.
Experimental results show that when the composition of NiCo alloy are Ni, Ni-20at%Co, Ni-63at%Co and Co, the corresponding IMCs formed at the interface are Ni3Sn4, (Ni,Co)Sn2, (Ni,Co)Sn3 and CoSn3. We also observe that the consumption of Ni-63at%Co alloy is more serious than other NiCo alloys and it is due to the loose structure of IMCs.
In the case of Ni-20at%Co, after 300 seconds reflowing additional needle-like phase (Ni,Cu)3Sn4 was formed right above the continuous (Ni,Co)Sn2 layer when Cu concentration overs 0.2wt% and Cu addition enhance the growth rate of (Ni,Co)Sn2. In the case of Ni-63at%Co and Co, as Cu addition and increasing of Cu concentration are performed only CoSn3 formed at the interface, but these factors restrain the growth rate of CoSn3.
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