Surface properties and solderability behaviour of nickel–phosphorus and nickel–boron deposited by electroless plating

Abstract

X-ray photoelectron spectroscopy (XPS), scanning Auger microscopy (SAM), atomic force microscopy (AFM) and wetting force measurements have been applied to various nickel deposits prepared by standard electroless plating for probing the origins of solderability behaviour of 'electroless nickel'. By controlling the plating chemicals and plating conditions, three kinds of electroless nickel deposits have been prepared, namely electroless nickel-high phosphorus (EN-HP), electroless nickel-low phosphorus (EN-LP) and electroless nickel-boron (EN-B). Wetting balance measurements confirmed the solderability strength decreased in the order of EN − B > EN − LP > EN − HP. Unexpectedly, among the three EN deposits, EN-B was found by XPS to have the thickest surface oxide, which opposes the traditional correlation of good solderability with thin surface oxide. On the other hand, SAM and AFM studies showed that the average nodule size increased in the order of EN − B < EN − LP < EN − HP. Accordingly, there appeared to be a correlation of small nodule size with good solderability. Solderability of 'electroless nickel' thus depended more on surface morphology than on surface oxidation. Nevertheless, further studies of the wetting kinetics of the EN deposits revealed that among the three EN deposits EN-HP had the oxide structure that was most difficult to penetrate and thus the slowest to 'wet'. The structure of the surface oxide therefore was found to affect the wetting kinetics of 'electroless nickel'.

Phase analysis and kinetics of solid‐state ageing of Pb‐free Sn3.5Ag solder on electroless NiP substrate

“…5,6 However, still to be understood is the mechanism of interfacial reaction during reflow and information on the interfacial reaction product at the solder joint is still needed. An electronic package is generally subjected to different thermal and mechanical loads during manufacturing, storage, transport and operation.…”

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

“…[5][6][7][8][9][10] Especially, Sn-Ag system solder alloys are recognized as the first choice for Pb-free solder. [11][12][13] Copper has been widely used in the under bump metallurgy (UBM) of chip and substrate metallization for chip packaging. However, due to the rapid formation of Cu-Sn intermetallic compound (IMC) at the Sn-based solder/Cu interface during soldering reaction, the reliability of this solder joint has been a serious concern.…”

Effect of Ni-P Plating Temperature on Growth of Interfacial Intermetallic Compound in Electroless Nickel Immersion Gold/Sn-Ag-Cu Solder Joints

“…Many researchers have reported that increasing the pH of the Ni-P plating solution increases the nodule size of the Ni-P layer. 10,26,27 However, Chow et al 28 reported that increasing the pH decreased the nodule size of Ni-P. In fact, their plating temperature was 88°C at pH of 4.8 and 44°C at pH of 8.5, Effect of Ni-P Plating Temperature on Growth of Interfacial Intermetallic Compound in Electroless Nickel Immersion Gold/Sn-Ag-Cu Solder Joints thus Chow et al decreased the plating temperature when they increased the pH.…”

“…[10][11][12] The P content in the Ni-P layer affects the interfacial IMC thickness, joint strength, and solder wettability. [10][11][12] These properties of the Ni-P layer depend on the Ni-P electroless plating conditions, including temperature, pH, additives, etc. Hence, the effects of these conditions on the properties of the Ni-P layer and the solder joint must be evaluated.…”