Interactions at the planar Ag3Sn/liquid Sn interface under ultrasonic irradiation

Abstract

The interactions at the interface between planar AgSn and liquid Sn under ultrasonic irradiation were investigated. An intensive thermal grooving process occurred at AgSn grain boundaries due to ultrasonic effects. Without ultrasonic application, planar shape of AgSn layer gradually evolved into scalloped morphology after the solid-state Sn melting, due to a preferential dissolution of the intermetallic compounds from the regions at grain boundaries, which left behind the grooves embedding in the AgSn layer. Under the effect of ultrasonic, stable grooves could be rapidly generated within an extremely short time (<10s) that was far less than the traditional soldering process (>10min). In addition, the deepened grooves leaded to the formation of necks at the roots of AgSn grains, and further resulted in the strong detachment of intermetallic grains from the substrate. The intensive thermal grooving could promote the growth of AgSn grains in the vertical direction but restrain their coarsening in the horizontal direction, consequently, an elongated morphology was presented. All these phenomena could be attributed to the acoustic cavitation and streaming effects of ultrasonic vibration.

Effect of ultrasonic vibration on interfacial reaction of Ni/Sn/Ni soldered joint

“…In addition, a few Ni 3 Sn 4 chunks were distributed in the joint (marked by yellow circles). Shao et al (2017) observed the same appearance of grooves at the planar Ag 3 Sn layer under the effect of USV. They suggested that the formation of grooves may have been mainly attributable to acoustic cavitation and streaming effects on the accelerated dissolution of Ag 3 Sn at grain boundaries.…”

“…Therefore, the Ni particles in the joint could completely react with Sn for a short time to produce a complete IMC joint. Shao et al (2017) and Li et al (2017) also fabricated sole IMC joints in a short time using an ultrasound-induced transient liquid phase bonding process. These studies indicated that the rapid formation of sole IMC joints was attributable to the accelerated dissolution of the substrate into the liquid solder, which was induced by complex sonochemical effects (ultrasonic cavitation and ultrasonic streaming) on the substrate.…”

Effect of SiO2 nanoparticle addition on growth of interfacial Ag3Sn intermetallic compound layers between lead-free solder and silver conductor

“…7c). It is believed that the formation of the groove is due to IMC dissolution at Ag 3 Sn grain boundaries; the IMC at grain boundaries continually dissolved into the molten solder, deepening the grooves and inducing silver leaching [14,15]. The silica NPs located at grain boundaries can hinder the dissolution of the IMC by the molten solder along grain boundaries and hence retard silver leaching.…”