Analysis of Ni-coating's influence on wetting of Ag solder
Ni-coating's influence on the wetting progress in metal-ceramic bonding was analysed in this paper. Firstly Ag's contact angle was measured through high-temperature experiments, which turned out to be 100° and 25° on non-coated and Ni-coated ceramic substrates, respectively. Then a mathematical model was originally built up to catch the phase interface's motion on different substrates, considering fluid dynamics, melting and solidification, surface tension and liquid-solid heat transfer. Results indicated that Ni-coating affected the angle α directly and could reduce abnormity of joint structure through enhancing Ag solder's wettability on ceramic.
Wettability of SnCuNi-xEu solders and mechanical properties of solder joints
Abstract Wettability balance method was used to investigate the wetting performance of SnCuNi-xEu on Cu substrate, and the mechanical properties and the fracture morphology were studied. The results indicated that the addition of Eu could enhance the properties of solder and solder joints, with the increase of Eu content, tendency of first increase and then decrease could be found in the wetting time, wetting force and the mechanical properties of SnCuNi-xEu, and the optimal content was 0.039%. For SnCuNi-0.039Eu solder joints, the optimum mechanical properties could be found, and the amplitude increased was 20%, with the observation of the fracture morphology, it was found that small dimples could be seen, the toughness fracture for SnCuNi and mixture fracture for SnCuNi-0.039Eu could be demonstrated. And thermal fatigue behavior of SnCuNi solder joints could be enhanced obviously with the 0.039%Eu addition.
Preparation and properties of pressureless infiltrated SiC and AlN particulate reinforced metal ceramic composites based on bronze and iron alloys
Abstract Metal ceramic composites were prepared from SiC and G–CuAl10Ni, AlN and G–CuAl10Ni, as well as AlN and GGG–NiSiCr 35 5 2 by a pressureless melt infiltration process starting from porous ceramic preforms and the mentioned alloys. Titanium was used to improve wetting of the ceramic materials by the liquid metals. The microstructure and mechanical properties (density, Young's modulus, bending strength and fracture toughness) were characterised and prototypic parts prepared. With increasing SiC particle size, the amount of metal in the matrix of the SiC containing composites increases. A correlation between the microstructure and the mechanical properties was observed. The matrix of the AlN containing composites consists mainly of the residual alloy, whereas the matrix of the SiC containing composites contains also silicides, which were formed during the infiltration process. A comparison between preforms consisting either of milled AlN powder or porous AlN granulate and their infiltration with GGG–NiSiCr 35 5 2 shows, that the decomposition of granulate hinders further infiltration in these preforms. The deformation behaviour of the materials, obtained from bending strength measurements, indicates a failure tolerant behaviour for composites with a high amount of metal in the matrix.