Time- and temperature-dependent wetting behavior of eutectic SnPb on Cu leadframes plated with Pd/Ni and Au/Pd/Ni thin films

This study provides a comparison of the influence of Pd(P) thickness on reactions during soldering with the Sn-3Ag-0.5Cu alloy. Soldering was carried out in an infrared-enhanced conventional reflow oven, and a multiple reflow test method (up to ten cycles) was performed. With increasing Pd(P) thickness, the (Cu,Ni) 6 Sn 5 grew more slowly at the solder/Ni(P) interface, while the Ni 2 SnP/Ni 3 P bilayer became predominant after the first reflow. These three intermetallics, i.e., (Cu,Ni) 6 Sn 5 , Ni 2 SnP, and Ni 3 P, gradually coarsened as the number of reflow cycles increased. Furthermore, an additional (Ni,Cu) 3 Sn 4 layer appeared between (Cu,Ni) 6 Sn 5 and Ni 2 SnP, especially for the case of a thicker Pd(P) layer (0.2 lm). The attachment of the (Ni,Cu) 3 Sn 4 to the Ni 2 SnP, however, was fairly poor, and a series of microcracks formed along the (Ni,Cu) 3 Sn 4 /Ni 2 SnP interface. To quantify the mechanical response of the interfacial microstructures, shear testing was conducted at two different shear speeds (0.0007 m/s and 2 m/s). The results indicated that the interfacial strength and the Pd(P) thickness were strongly correlated.

Section: Discussionmentioning

confidence: 98%

Section: Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Influence of Palladium Thickness on the Soldering Reactions Between Sn-3Ag-0.5Cu and Au/Pd(P)/Ni(P) Surface Finish

Lin

Huang

et al. 2010

“…As a consequence, surface Au/Pd finishes can be removed very quickly through dissolution/reaction when they contact a molten solder. [13][14][15] It was found that, immediately after the topmost Au is removed, the Pd of the Pd(P) layer converts into the PdSn 4 [or (Pd,Ni)Sn 4 ] phase, which in turn spalls into the molten solder. 15 The remaining P further reacts with Ni and Sn and crystallizes into the Ni 2 SnP phase.…”

Section: Introductionmentioning

confidence: 99%

Solid–Solid Reaction Between Sn-3Ag-0.5Cu Alloy and Au/Pd(P)/Ni(P) Metallization Pad with Various Pd(P) Thicknesses

Hsu

et al. 2011

The effect of Pd(P) thickness on the solid-solid reaction between Sn-3Ag-0.5Cu and Au/Pd(P)/Ni(P) at 180°C was investigated in this study. The reaction was conducted after reflow, thereby removing the Au/Pd finish before the solidstate reaction. The reaction products included (Cu,Ni) 6 Sn 5 , Ni 2 SnP, and Ni 3 P, and their growth strongly depended on the Pd(P) thickness, especially for the former phases [i.e., (Cu,Ni) 6 Sn 5 and Ni 2 SnP]. As the Pd(P) thickness increased from 0 lm, to 0.1 lm, to 0.22 lm, the (Cu,Ni) 6 Sn 5 exhibited a needle-like dense layer, chunk-like morphology, and discontinuous morphology, respectively. The alternative phase (Ni 2 SnP) behaved in a manner opposite to that of (Cu,Ni) 6 Sn 5 , growing with a discontinuous morphology to a dense layer with increasing Pd(P) thickness. However, this strong dependence disappeared when the solder joints were subsequently subjected to solid-state aging. The (Cu,Ni) 6 Sn 5 and Ni 2 SnP both became layered structures for all cases examined. A high-speed ball shear (HSBS) test was conducted to quantify the mechanical response of the interfacial microstructures. The HSBS test results showed that any initial difference in shear strength caused by the various Pd(P) thicknesses could be reduced after the solid-state aging, which is consistent with the microstructural evolution observed. The mechanical strength of the solder joints was decreased due to the presence of a bi-intermetallic structure of (Cu,Ni) 6 Sn 5 /Ni 2 SnP at the interface. Detailed analysis of the growth of (Cu,Ni) 6 Sn 5 and Ni 2 SnP is also provided.

“…4,5 The Pd film is customarily deposited within a thickness range of 0.05 lmÀ0.3 lm 1,6 and can quickly alloy with molten solder at an early stage of soldering. [7][8][9] Removal of the Pd exposes the underlying Ni(P) to the solder, which might contain various Pd concentrations. The Pd concentration in the solder varies as a function of joint size and Pd thickness.…”

Section: Introductionmentioning

confidence: 99%

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

Hsu

Lin

et al. 2011

The interfacial reaction between Ni and Sn-3Ag-0.5Cu-xPd alloys (x = 0 wt.% to 1 wt.%) at 250°C and the mechanical reliability of the solder joints were investigated in this study. The reaction and the resulting mechanical properties were both strongly dependent on the Pd concentration. When x was low (£0.2 wt.%), the reaction product at the Ni/Sn-Ag-Cu-xPd interface was a layer of (Cu,Ni) 6 Sn 5 . An increase of x to 0.3 wt.% produced one additional (Pd,Ni)Sn 4 compound that was discontinuously scattered above the (Cu,Ni) 6 Sn 5 . When x was relatively high (0.5 wt.% to 1 wt.%), a dual layer of (Pd,Ni)Sn 4 -(Cu,Ni) 6 Sn 5 developed with the reaction time. The results of the high-speed ball shear (HSBS) test showed that the mechanical strength of the Ni/Sn-3Ag-0.5Cu-xPd joints degraded with increasing x, especially when x reached a high level of ‡0.3 wt.%. This degradation corresponded to the growth of (Pd,Ni)Sn 4 at the interface, and joints easily failed along the boundaries of solder/(Pd,Ni)Sn 4 and (Pd,Ni)Sn 4 /(Cu,Ni) 6 Sn 5 in the HSBS test. The (Pd,Ni)Sn 4 -induced joint failure (Pd embrittlement) was alleviated by doping the solder with an appropriate amount of Cu. When the Cu concentration increased to 1 wt.% and the Pd concentration did not exceed 0.5 wt.%, the growth of (Pd,Ni)Sn 4 could be thoroughly inhibited, thereby avoiding the occurrence of Pd embrittlement in the solder joints.