Abstract
In this work, the effects of electroplated Cu (EP Cu) and Cu addition (0.7%) in Sn solder on the intermetallic compounds (IMCs) growth and void formation were clarified by comparison with solder joints comprising of high purity Cu (HP Cu) substrate and pure Sn solder. After aging processes, a new IMC, Cu3Sn, was formed at the interface, in addition to Cu6Sn5 formed in the as-soldered joints. The EP Cu and Cu addition (0.7%) both had limited effects on the total IMCs thickness. However, the effects varied on the growth behaviors of different IMCs. Comparing to the void-free interface between Sn and HP Cu, a large number of voids were observed at the Cu3Sn/Cu interface in Sn/EP Cu joints. The formation of these voids may be induced by the impurities and fine grain, which were introduced during the electroplating process. The addition of Cu suppressed the inter-diffusion of Cu and Sn at the interface. Consequently, the growth of the Cu3Sn layer and formation of voids were suppressed.
Highlights
Intermetallic compounds (IMCs) and voids that form at the interface between solder and copper joints have been given great attention, because the existence of these interfacial intermetallic compounds (IMCs) and voids are crucial to several reliability concerns [1,2]
Sn was formed at the interface, and no void was the as-reflowed Sn/electroplated Cu (EP Cu) joint, a thin layer of Cu66Sn55 was formed at the interface, and no void was
The results indicated that the EP Cu substrate promotes growth of the Cu3 Sn layer, and Cu addition (0.7%) is beneficial in retarding the growth of the Cu3 Sn layer
Summary
Intermetallic compounds (IMCs) and voids that form at the interface between solder and copper joints have been given great attention, because the existence of these interfacial IMCs and voids are crucial to several reliability concerns [1,2]. Sn-based solder could suppress the formation of voids and retard the growth of IMCs [10,11,12,13,14,15]. As we the in solders/Cu joint is made bybeen the electroplating process It is retarding theknow, growth ofCu thesubstrate. Extensive research done on the effect ofCu impurities of EP Cu formation of KVs [17–. Extensive research has been done on the effect of impurities of EP Cu on the formation of electroplated. [19], proceeding from the source of impurities, systematically studied the electroplated Cu UBM (under ball metal) on the void formation, and especially studied the effect of electroplating parameters onthe void formation at the interface. Sn0.7Cu solder were to interface growth and void formation were analyzed. The interface evolution, especially the Kirkendall voiding level, was discussed
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