Abstract
Graphene nanosheets (GNSs) have an extensive application in materials modification. In this study, the effects of graphene nanosheets on the wettability of Sn-20Bi lead-free solder on copper (Cu) substrate and the growth behavior of intermetallic compound (IMC) layers at Sn-20Bi-xGNS/Cu solder joints were investigated. The experimental results indicate that the wettability of Sn-20Bi solder firstly diminished and then increased by the addition of GNSs. Meanwhile, a prism-shaped and scallop-shaped Cu6Sn5 IMC layer was clearly observed at the interface of the solder/substrate system. Moreover, it was found that a small amount of GNS addition can significantly inhibit the growth of the IMC layer at the interface as well as refine the microstructure. Additionally, by nano-indentation apparatus, it can be concluded that the hardness and elastic module of IMCs show the same variation trend, which firstly decreased and then increased. Besides, to intuitively demonstrate the reliability of IMCs, the relationship between the hardness and elastic module was established, and the ratio of hardness/elastic module (H/E) was adopted to characterize the reliability of IMCs. The results show that when the addition of GNSs was 0.02 wt%, the value of H/E is the minimum and the solder joint has the highest reliability.
Highlights
In the microelectronic packaging industries, traditional Sn-Pb solder alloys were widely used due to the low melting temperature, low cost and high mechanical properties [1]
The results show that the wettability of solder improves with the addition of In, and the wettability is the best when the addition amount is 4 wt%, and it decreased with further addition because Cu-Sn-In intermetallic compound (IMC) formed at the interface
It was confirmed that both spreading area and spreading ratio were decreased with Graphene nanosheets (GNSs) addition until 0.06 wt% GNSs
Summary
In the microelectronic packaging industries, traditional Sn-Pb solder alloys were widely used due to the low melting temperature, low cost and high mechanical properties [1]. The research work on lead-free Sn-based solders has been carried out extensively Composite solder, such as Sn-Bi [2], Sn-Ag [3], Sn-Cu [4,5], Sn-Ag-Cu [6] and Sn-Zn [7], etc., are employed to improve the reliability of solder joints to extend the service life of electronic products. Many studies have been published about the wettability, microstructural development and mechanical properties of Sn-Bi solder alloy. Sn-20Bi-xGNS/Cu solder joints was investigated and the mechanical properties of IMCs at the interface were determined
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