Suppressing Ni–Sn–P growth in SnAgCu/Ni–P solder joints

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: Resultssupporting

confidence: 77%

Section: Resultsmentioning

confidence: 92%

Section: Resultsmentioning

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

“…Because Ni 13 Sn 8 P 3 has a higher Sn content than the Ni-Sn-P deposit, it is speculated that transformation of the Ni-Sn-P deposit into the Ni 13 Sn 8 P 3 compound requires Sn supply from the solder, which is similar to the formation of Ni 2 SnP during the Ni-P/Sn-3.5Ag interfacial reaction. 6,[21][22][23][24] On the basis of these arguments, we believe that polycrystalline Ni 13 Sn 8 P 3 is formed by transformation of amorphous Ni-Sn-P metallization with outward diffusion of Ni and inward diffusion of Sn during the soldering reaction.…”

Section: Discussionmentioning

confidence: 99%

Interface Reaction Between Electroless Ni–Sn–P Metallization and Lead-Free Sn–3.5Ag Solder with Suppressed Ni3P Formation

Yang

Balaraju

Huang

et al. 2014

The voids formed in the Ni 3 P layer during reaction between Sn-based solders and electroless Ni-P metallization is an important cause of rapid degradation of solder joint reliability. In this study, to suppress formation of the Ni 3 P phase, an electrolessly plated Ni-Sn-P alloy (6-7 wt.% P and 19-21 wt.% Sn) was developed to replace Ni-P. The interfacial microstructure of electroless Ni-Sn-P/Sn-3.5Ag solder joints was investigated after reflow and solid-state aging. For comparison, the interfacial reaction in electroless Ni-P/Sn-3.5Ag solder joints under the same reflow and aging conditions was studied. It was found that the Ni-Sn-P metallization is consumed much more slowly than the Ni-P metallization during soldering. After prolonged reaction, no Ni 3 P or voids are observed under SEM at the Ni-Sn-P/Sn-3.5Ag interface. Two main intermetallic compounds, Ni 3 Sn 4 and Ni 13 Sn 8 P 3 , are formed during the soldering reaction. The reason for Ni 3 P phase suppression and the overall mechanisms of reaction at the Ni-Sn-P/Sn-3.5Ag interface are discussed.

“…13 It was verified that the spalling phenomena was the result of Ni-Sn-P layer formation between the IMC and the Ni-P metallization. [12][13][14][15][16][17] However, limited data have been reported concerning the formation mechanism of the Ni-Sn-P layer. In this study, the formation of the Ni-Sn-P phase was systematically evaluated, and a description of the corresponding mechanism was proposed.…”

Section: Introductionmentioning

confidence: 99%

Detailed Phase Evolution of a Phosphorous-Rich Layer and Formation of the Ni-Sn-P Compound in Sn-Ag-Cu/Electroplated Ni-P Solder Joints

Lin

Wang

Duh

2009

Self Cite

The interfacial microstructure of Sn-3Ag-0.5Cu/Ni-P with various phosphorous contents was investigated by analytical transmission electron microscopy (TEM) and field-emission electron probe microanalysis (FE-EPMA). As the Ni-Sn-P compound was formed between the solder matrix and Ni-P under bump metallization (UBM), the so-called phosphorous-rich layer was transformed to a series of layer compounds, including Ni 3 P, Ni 12 P 5 , and Ni 2 P. The relationship between Ni-Sn-P formation and the evolution of P-rich layers was probed by electron microscopic characterization with the aid of the Ni-P phase diagram. In addition, the thickness of Ni-P UBM affects the Ni-Sn-P formation. Based on TEM, selected-area diffraction, as well as FE-EPMA, the detailed phase evolution of P-rich layers in the Sn-Ag-Cu/Ni-P joint was revealed. Moreover, in consideration of the mechanical properties of the joint, Ni-Sn-P phase formation, and fabrication feasibility of Ni-P UBM, the phosphorous content and suitable thickness of Ni-P UBM are discussed.