Effect of Ag, Fe, Au and Ni on the growth kinetics of Sn–Cu intermetallic compound layers (original) (raw)
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The effect of adding Zn into the Sn–Ag–Cu solder on the intermetallic growth rate
Journal of Materials Science: Materials in Electronics, 2014
Due to toxicity of lead in the commercial solder, lead-free solders were proposed. Among the potential leadfree solders, the SnAg -Cu solders were considered as a potential replacement. To further improve the solder properties, a fourth element was added into the SnAg -Cu solder. The present study investigates the effect of different weight percentage of Zn (up to 0.7 wt%) into the Sn-3.5Ag-1.0Cu solder on intermetallic and growth rate (k) after long time thermal aging. The solders were prepared using powder metallurgy method and X-ray diffraction analysis shows that there were Cu 6 Sn 5 , Cu 3 Sn, CuZn and Ag 3 Sn phases present after solder preparation. The solders were reacted with Cu substrate at 250°C for 1 min and aged at 150°C until 1,000 h. The morphology of the intermetallic was observed under scanning electron microscope and the elemental distribution was confirmed by energy dispersive X-ray. Intermetallic thickness and growth kinetic result show that the additions of 0.4 % zinc is sufficient in retarding the Cu 6 Sn 5 and Cu 3 Sn intermetallic growth.
Growth of Sn and intermetallic compounds in Sn-Ag-Cu solder
Journal of Electronic Materials, 2004
The microstructure of the SnAg -Cu solder is examined by optical microscopy and scanning electron microscopy (SEM) for various compositions near the ternary eutectic for different cooling rates from the solder melt. Focus is on the size and orientation of Sn grains as indicated by cross-polarized, light optical microscopy, and pole figures from x-ray diffraction. We find that both composition and cooling rate have strong influences on Sn grain size, with Sn grain size increasing an order of magnitude as Cu concentration increases from 0% to 1.1%. Cyclic growth twinning, with twinning angles near 60°, is observed in SnAg -Cu alloys near the composition Sn-3.9Ag-0.6Cu.
Solid state interaction between a Sn–Ag–Cu–In solder alloy and Cu substrate
Intermetallics, 2013
The solid-state reactions between the Sn-3.0Ag-0.4Cu-7.0In (wt%) solder and Cu substrate, at temperatures 100, 125, 150 and 180 C and for aging times up to 1506 h, are studied. The interfacial layers formed between solder and substrates are characterized using optical and scanning electron microscopy and electron microprobe analysis. Two ternary intermetallic layers Cu 6 (Sn,In) 5 (h-phase) and Cu 3 (Sn,In) (3-phase) are formed at the interface between the solder and Cu substrate. Kirkendall voids were observed at Cu/ 3 interface as well as inside the 3 layer. The growth kinetics of h and 3 phases and the activation energies for their growth are calculated and results are compared with growth kinetics of these phases in the case of SneAgeCu solders/Cu systems.
The effect of Ni addition on Cu-Sn intermetallic growth rate values in the SAC solder
2018
Due to environmental concerns, lead free solders were introduced in replacing the lead based solders in microelectronic devices technology. Among many lead-free solders, the Sn-3.5Ag-1.0Cu solder is the potential replacement for the Sn-Pb solder. This research was carried out to improve the properties of the Sn-3.5Ag-1.0Cu solder in terms of the reaction with copper substrate by adding small amount of Ni into the solder. The composite solders were synthesized via the powder metallurgy route, which consist of blending, compacting and sintering process. After soldering on copper substrate, the solder joint was aged at 150 o C for 1000 hours. The thickness of Cu 6 Sn 5 and Cu 3 Sn were measured and hence the growths kinetic of the intermetallics (k) were calculated. The results show that the SAC-0.05Ni solder has the lowest k value for Cu 6 Sn 5 intermetallic and SAC-0.5Ni has the lowest k value for Cu 3 Sn intermetallic.
Journal of Electronic Materials, 2006
Soldering with the lead-free tin-base alloys requires substantially higher temperatures (;235-250°C) than those (213-223°C) required for the current tin-lead solders, and the rates for intermetallic compound (IMC) growth and substrate dissolution are known to be significantly greater for these alloys. In this study, the IMC growth kinetics for Sn-3.7Ag, Sn-0.7Cu, and Sn-3.8Ag-0.7Cu solders on Cu substrates and for Sn-3.8Ag-0.7Cu solder with three different substrates (Cu, Ni, and Fe-42Ni) are investigated. For all three solders on Cu, a thick scalloped layer of h phase (Cu 6 Sn 5) and a thin layer of e phase (Cu 3 Sn) were observed to form, with the growth of the layers being fastest for the Sn-3.8Ag-0.7Cu alloy and slowest for the Sn-3.7Ag alloy. For the Sn-3.8Ag-0.7Cu solder on Ni, only a relatively uniform thick layer of h phase (Cu,Ni) 6 Sn 5 growing faster than that on the Cu substrate was found to form. IMC growth in both cases appears to be controlled by grain-boundary diffusion through the IMC layer. For the Fe-42Ni substrate with the Sn-3.8Ag-0.7Cu, only a very thin layer of (Fe,Ni)Sn 2 was observed to develop.
Solid-state reactions between Ni and Sn–Ag–Cu solders with different Cu concentrations
Materials Science and Engineering: A, 2005
It had been reported that, during the reflow of the Sn-Ag-Cu solders over the Ni-bearing surface finishes, a slight variation in Cu concentration produced different reaction products at the interface. In this study, we extended our earlier efforts to investigate whether this strong Cu concentration dependency also existed for the solid-state aging reaction between the Sn-Ag-Cu solders and Ni. Specifically, five Sn-3.9Ag-xCu solders (x = 0.2, 0.4, 0.5, 0.6, and 0.8) were reacted with Ni at 180 • C. It was found that the strong Cu concentration dependency disappeared after the solid-state aging at high temperatures for sufficient periods of time. For all the Cu concentrations studied, the same intermetallic compounds, a layer of (Cu 1 − y Ni y ) 6 Sn 5 and a layer of (Ni 1 − x Cu x ) 3 Sn 4 , formed at the interface after aging. This study showed that the initial difference in the intermetallic compounds right after reflow could be aged out at high temperatures. The growth mechanisms for (Cu 1 − y Ni y ) 6 Sn 5 and (Ni 1 − x Cu x ) 3 Sn 4 were different, and were pointed out in this study.
A study on the reaction between Cu and Sn3.5Ag solder doped with small amounts of Ni
Journal of Electronic Materials, 2003
The reaction between Cu and the Sn-Ag solders doped with different amounts of Ni is studied. Four different solders with the Ag concentration fixed at 3.5 wt.% and Ni concentrations varied between 0.0 wt.% and 1.0 wt.% are used. In contrast to the reaction between Ni and the Sn-Ag solders doped with different amounts of Cu, the type of intermetallic compound formed does not depend on the Ni concentration. The compound Cu 6 Sn 5 forms for all the Ni concentrations used. For the Ni-doped solders, the Cu 6 Sn 5 phase contains a small amount of Ni. The compound Cu 3 Sn appears subsequently between Cu 6 Sn 5 and Cu as the reaction time increases. The addition of Ni has the effect of substantially increasing the amount of intermetallic compound at the interface. The addition of Ni also produces two distinct Cu 6 Sn 5 regions at the interface. The outer region contains more Ni, and the inner region contains less Ni. This study also finds that, during solid-state aging, the growth of Cu 3 Sn becomes slower when Ni is added to the solder. The findings of this study are rationalized using the Cu-Ni-Sn isotherm.
Journal of Alloys and Compounds, 2005
Sn-based lead-free solders have a high melting temperature, which often cause excessive interfacial reactions at the interface. A small amount of In is added to reduce the melting temperature and to change the intermetallic compound (IMC) phases. Sn3.5Ag0.5Cu and Sn3.5Ag0.5Cu9In lead-free solder alloys have been used to identify its interfacial reactions with 2-metal layer flexible substrates. In this paper we investigate the effect of 9 at.% In addition to Sn3.5Ag0.5Cu solder during extended reflow. During reflow, Au diffuses rapidly in the molten Sn Ag Cu solder and forms AuSn 4 IMC but in the case of In-containing solder, In Sn Au IMCs form and are uniformly distributed in the solder. Some In Sn Au IMCs have been entrapped in the Sn Cu Ni In quaternary intermetallic compounds (QIMCs) due to lower diffusion rate of Au in the In-containing solder. Initially Sn Cu Ni ternary intermetallic compounds (TIMCs) and Sn Cu Ni In QIMCs form at the interface, which have higher growth rate and consume more of the NiP layer. Low-Cu QIMCs are found in the In-containing solder after 30 min reflow which are more stable in the P-rich Ni layer and significantly reduce the dissolution rate of the NiP layer. The spalling of Sn Cu Ni TIMCs in the Sn Ag Cu solder increases the diffusion rate of Sn atoms and as a consequence both the TIMCs growth rate and dissolution rate of the NiP layer also increases. In-containing solder have lower growth rate of the QIMCs and lower dissolution rate of the NiP layer than the Sn Ag Cu solder. Consumption of the NiP layer can be reduced by adding In, because of the formation of QIMCs at the interface, QIMCs are stable and are well adhering to the P-rich Ni layer during reflow.
Journal of Electronic Materials, 2003
Intermetallic-layer formation and growth in Pb-free solder joints, during solder reflow or subsequent aging, has a significant effect on the thermal and mechanical behavior of solder joints. In this study, the influence of initial intermetallic morphology on growth rate, and kinetics were examined in a Sn-3.5Ag solder reflowed on Cu. The initial morphology of the intermetallic was tailered by cooling in water, air, or furnace conditions. Solder aging was conducted at 100°C, 140°C, and 175°C and aged for 0-1,000 h. Cooling rate, aging temperature, and aging time played an important role on microstructure evolution and growth kinetics of Cu 6 Sn 5 (η) and Cu 3 Sn (ε) intermetallic layers. Prior to aging, faster cooling rates resulted in a relatively planar Cu 6 Sn 5 layer, while a nodular Cu 6 Sn 5 morphology was present for slower cooling. Intermetallic-growth rate measurements after aging at various times, indicated a mixed growth mechanism of grain-boundary and bulk diffusion. These mechanisms are discussed in terms of the initial intermetallic thickness and morphology controlled by cooling rate, diffusion kinetics, and the competition between Cu 6 Sn 5 and Cu 3 Sn growth.