Effects of Minor Elements in Cu Leadframe on Whisker Initiation From Electrodeposited Sn/Cu Coating

Properties and Whisker Formation Behavior of Tin‐Based Alloy Finishes

“…Hence, Sn-Cu finishes are often used in combination with other mitigation practices such as heat treatment [16] or base material selection [45][46][47][48][49][50][51][52]. The whisker mitigation effectiveness of the heat-treated Sn-Cu finish was shown earlier (Figs.…”

“…It also introduces metallurgical techniques studied by Kato et al [45][46][47][48][49][50][51][52] in order to illuminate the mechanisms of the formation and suppression of whisker growth from the Sn-Cu coating.…”

“…In studies by Kato et al [45][46][47][48][49][50][51][52] of the effects of long-term storage at room temperature, whiskers did not grow from the Sn-Cu coating on the CUCR lead frame, whereas long whiskers, up to about 200 μm long, grew from that on the CUFE lead frame.…”

“…Observation of IMCs by Kato et al [45][46][47][48] showed that the cross-sectional morphology of the LGIMC is a wedge-shaped structure for an Sn-Cu-coated CUFE lead-frame sample and a comb-tooth structure for an Sn-Cu-coated CUCR lead-frame sample, as described in Section 4.4.4. This section describes how minor elements in the lead frames affect the formation morphology of the IMCs.…”

“…Given the formation morphology of LGIMC Cu 6 Sn 5 , the difference between the whisker-initiation tendencies of the two sample types (Sn-Cu/CUFE and Sn-Cu/CUCR) was attributed to the difference in the compressive stresses in their coatings. The stresses in the coatings were therefore measured by XRD [45][46][47][48], and the results are presented and discussed here. The XRD measurements confirmed that there is a correlation between whisker initiation, LGIMC formation morphology, and compressive stress.…”