Strong effect of Pd concentration on the soldering reaction between Ni and Sn–Pd alloys

Abstract

The effect of Pd concentration on the soldering reaction between Ni and Sn–xPd alloys (x = 0–0.5 wt%) was investigated in this study. When the Pd concentration was low (x ≤ 0.05 wt%), the predominant reaction product was a layer of Ni3Sn4. In contrast, an additional (Pd,Ni)Sn4 layer deposited over the Ni3Sn4 in the case of above 0.2 wt%. This microstructure evolution significantly weakened the strength of the interface, deteriorating the reliability of solder joints. A Pd–Ni–Sn isotherm simulated by the CALPHAD method was used to rationalize the above transition in the reaction product(s).

Influence of Pd Concentration on the Interfacial Reaction and Mechanical Reliability of the Ni/Sn-Ag-Cu-xPd System

“…The formation of the (Pd,Ni)Sn 4 -Ni 3 Sn 4 structure together with the voiding in between the layers seriously deteriorated the mechanical strength of the Ni/SnPd interface, affecting the reliability of the solder joints. 10,11 This Pd-concentration-dependent reaction can be explained based on the Sn corner of the Pd-Ni-Sn isotherm (250°C), and more details can be found in the literature. 10,11 The goal of this study is to investigate the influence of Pd concentration on the Ni/Sn-Ag-Cu-xPd system.…”

“…10,11 This Pd-concentration-dependent reaction can be explained based on the Sn corner of the Pd-Ni-Sn isotherm (250°C), and more details can be found in the literature. 10,11 The goal of this study is to investigate the influence of Pd concentration on the Ni/Sn-Ag-Cu-xPd system. Unlike the previously reported Ni/Sn-xPd reaction, 10,11 Cu itself is also very active in the reaction between Ni and solders, [12][13][14] even though the Cu concentration in the Sn-Ag-Cu alloy family is minor (typically ranging from 0 wt.% to 1 wt.%).…”

“…The Pd concentration in the solder varies as a function of joint size and Pd thickness. 10 For instance, in the case of soldering a 200-lmdiameter solder sphere to a 150-lm-diameter metallization pad, the resultant Pd concentration is $0.14 wt.% if a 0.2-lm-thick Pd layer is deposited and all of the Pd dissolves into the solder during soldering. This value increases inversely with joint size and becomes double (i.e., 0.28 wt.%) with the use of the same film with a joint of half the size.…”

“…The influence of Pd concentration on the reaction between Ni and Sn-xPd alloys (where x = 0.05 wt.% to 1 wt.%) at 250°C was recently examined by Ho et al 10,11 The reaction depended strongly on the Pd concentration, and the reaction product could become completely different, even with a 0.1 wt.% variation in the Pd concentration. When x was low (£0.05 wt.%), the reaction product was a single Ni 3 Sn 4 .…”

“…10,11 The goal of this study is to investigate the influence of Pd concentration on the Ni/Sn-Ag-Cu-xPd system. Unlike the previously reported Ni/Sn-xPd reaction, 10,11 Cu itself is also very active in the reaction between Ni and solders, [12][13][14] even though the Cu concentration in the Sn-Ag-Cu alloy family is minor (typically ranging from 0 wt.% to 1 wt.%). A translation from one compound (Ni 3 Sn 4 ) into another [(Cu,Ni) 6 Sn 5 ] might occur when the Cu concentration increases from 0.3 wt.% to 0.5 wt.% (250°C).…”