Growth of an intermetallic compound layer with Sn-3.5Ag-5Bi on Cu and Ni-P/Cu during aging treatment

Abstract

Growth kinetics of intermetallic compound (IMC) layers formed between the Sn-3.5Ag-5Bi solder and the Cu and electroless Ni-P substrates were investigated at temperatures ranging from 70°C to 200°C for 0-60 days. With the solder joints between the Sn-Ag-Bi solder and Cu substrates, the IMC layer consisted of two phases: the Cu 6 Sn 5 (η phase) adjacent to the solder and the Cu 3 Sn (ε phase) adjacent to the Cu substrate. In the case of the electroless Ni-P substrate, the IMC formed at the interface was mainly Ni 3 Sn 4 , and a P-rich Ni (Ni 3 P) layer was also observed as a by-product of the Ni-Sn reaction, which was between the Ni 3 Sn 4 IMC and the electroless Ni-P deposit layer. With all the intermetallic layers, time exponent (n) was approximately 0.5, suggesting a diffusion-controlled mechanism over the temperature range studied. The interface between electroless Ni-P and Ni 3 P was planar, and the time exponent for the Ni 3 P layer growth was also 0.5. The Ni 3 P layer thickness reached about 2.5 µm after 60 days of aging at 170°C. The activation energies for the growth of the total Cu-Sn compound layer (Cu 6 Sn 5 ϩ Cu 3 Sn) and the Ni 3 Sn 4 IMC were 88.6 kJ/mol and 52.85 kJ/mol, respectively.

Investigation on the intermetallic compound layer growth of Sn–0.5Ag–0.7Cu–xGa/Cu solder joints during isothermal aging

“…However, as the aging time prolongs, Cu 3 Sn was found as well (easier to be observed at larger magnification shown in Fig. 5) and the solder structure from solder to substrate is SAC solder/Cu 6 Sn 5 /Cu 3 Sn/Cu, which is in accordance with the previous studies [18]. Laurila et al [19] pointed out that in high-temperature conditions (close to 220°C), the Cu-Sn interface reaction is based on the diffusion of Sn, thus presenting a thick Cu 6 Sn 5 interface layer.…”

Interfacial reactions and shear strengths between Sn-Ag-based Pb-free solder balls and Au/EN/Cu metallization

“…The electroless Ni-P layer contained about 15at.%P and had an amorphous structure. 17 The electroless Ni-P plating deposits a mixture of Ni and phosphorous (P), because of the use of hypophosphite in the chemical reaction for reducing Ni ions. These solder balls were bonded to the BGA substrate in a reflow process employing rosin mildly activated flux in a reflow machine (SAT-5100 ϩ profile temperature raise heater, Rhesca Co., Hino City, Japan) with a maximum temperature of 255°C for 1 sec (Fig.…”

“…Advantages of the electroless Ni plating such as low stress, excellent corrosion resistance, uniform thickness, and selective deposition make the electroless Ni plating more suitable to be a diffusion barrier than the electroplated Ni and expensive vacuum deposition of Ni. 11,17 However, it has been reported that reliability degradation occurs at the interface between plated electroless Ni layer and solder when a P-enriched (Ni 3 P) layer is formed on the interface during soldering. 18,19 In this study, the reaction of three Pb-free solder alloys (Sn3.5Ag, Sn3.5Ag0.75Cu, and Sn3Ag6Bi2In) on electroless Ni-P layer is characterized.…”

Diffusion Behavior of Zn During Reflow of Sn-9Zn Solder on Ni/Cu Substrate

“…3,4 Therefore, Ni is used as a diffusion barrier over copper. 5 Many studies have been performed on the interfacial reactions between Sn-Zn solder and Ni/Cu substrate during reflow and aging. [6][7][8][9][10] It has been observed that Ni prefers to react with Zn over Sn, and forms Ni-Zn compounds in the IMC.…”