Microstructural evolution in the Sn-Cu-Ni and Pb-Sn solder joints with Cu and Pt-Ag metallized Al2O3 substrate

Abstract

Special Issue PaperThe growth mechanism of intermetallics between solders and metallized substrates, after thermal aging, are investigated. The solders used in this study are unleaded Sn-Cu-Ni solder and eutectic Pb-Sn solder. The Pt-Ag/Al 2 O 3 , Cu block and the electroless Cu/Pt-Ag/Al 2 O 3 are employed as the metallized substrates. Microstructure evolution of the interfacial morphology, elemental, and phase distribution are probed with the aid of electron-probe microanalyzer (EPMA) and x-ray diffractometry. Two kinds of intermetallics, Cu 3 Sn and Cu 6 Sn 5 , are formed at the solder/Cu interface. However, for the solder/Pt-Ag system, only Ag 3 Sn is observed at the interface. The thickness of Cu 3 Sn, Cu 6 Sn 5 , and Ag 3 Sn compound layers for all solder/metallized substrate systems shows a t 0.5 dependence at 100, 125, 150 and 170∞C. According to the calculated activation energy and diffusion constant, the growth rate of Cu 3 Sn and Cu 6 Sn 5 intermetallics in the electroless Cu metallized substrate is relatively higher than that for Cu block one at the range of 100∞C to 170∞C. However, the growth rate of Cu 6 Sn 5 and Ag 3 Sn is reduced in the Sn-Cu-Ni solder with respect to the eutectic Pb-Sn solder. On the other hand, the Sn-Cu-Ni solder system exhibits a thicker Cu 3 Sn intermetallic layer than the eutectic Pb-Sn solder after various aging times at 100∞C. The thickness of Cu3Sn in the eutectic Pb-Sn solder is, however, thicker than that for Sn-Cu-Ni solder at 170∞C.

Intermetallic compound layer growth at the interface between Sn–Cu–Ni solder and Cu substrate

“…They reported that Ni on the substrate side could diffuse across the entire solder joint and formed the (Cu,Ni) 6 Sn 5 ternary phase on top of the Ni(V) UBM on the chip side during reflow cycles. However, Young et al [15] reported that two kinds of intermetallics (Cu 6 Sn 5 and Cu 3 Sn) are formed at a Sn-2.7 wt.% Cu-0.2 wt.% Ni/Cu interface, which is different from our result. The Cu-Ni binary system forms a complete solid solution.…”

Phase transformation and morphology of the intermetallic compounds formed at the Sn–9Zn–3.5Ag/Cu interface in aging

“…Therefore, many researchers have engaged in investigating the interface reactions between solder alloys and Cu substrate or other under bump metallization (UBM) layers [2][3][4][5]. -Cu 6 Sn 5 is the most often observed IMC formed at the Sn-base solder/Cu interface and has a hexagonal structure [6][7][8][9][10].…”

Effect of adding 1wt% Bi into the Sn–2.8Ag–0.5Cu solder alloy on the intermetallic formations with Cu-substrate during soldering and isothermal aging

“…Sn-lead (Sn-Pb) solders are most prominent interconnect materials for soldering the electronic components with the circuit boards [1]. However, nowadays, the use of this solder is so far restricted due to the environmental and health concern [2][3][4].…”