Unusual Void Formation at the Anode-Side Interface of a Cu/Snagcubi/Cu Solder Stripe under Current Stressing

Abstract

Unusual void formation is found at the anode-side interface of a Cu/solder/Cu stripe under current stressing with a density of 3.0 × 10^4 A/cm^2 at 120℃, where the solder is Sn-3 wt.%Ag-0.5 wt.%Cu added with 10 wt.%Bi. A network structure composed of major Cu6Sn5 particles is formed first at the anode-side interface as a result of Cu dissolution from the cathode-side Cu electrode due to electromigration. This Cu6Sn5 network structure hinders the inward atomic diffusion. Imbalance of atomic fluxes occurs at the anode-side interface, resulting in solder depletion and void formation.

添加10 wt.%鉍的錫-3 wt.%銀-0.5 wt.%銅銲料與兩端的銅電極組成銅／銲料／銅線型樣品，在120℃的溫度下通以3.0 × 10^4 A/cm^2的電流密度，在陽極的銅／銲料界面處發現不尋常的孔洞生成。實驗的觀察顯示，在電遷移影響下，陰極端的銅電極會溶解進入銲料中，並在陽極端的界面處生成大量的Cu6Sn5顆粒，形成一網絡結構，此一網絡結構不利於原子繼續往內擴散，導致原子補充不及，造成原子通量的不平衡，因而在此區域（陽極端的界面）發現銲料消耗與孔洞生成的現象。