Interfacial reactions between Sn-2.5Ag-2.0Ni solder and electroless Ni(P) deposited on SiCp/Al composites

A novel Sn-2.5Ag-2.0Ni alloy was used for soldering SiCp/Al composites substrate deposited with electroless Ni(5%P) (mass fraction) and Ni(10%P) (mass fraction) layers. It is observed that variation of P contents in the electroless Ni(P) layer results in different types of microstructures of SnAgNi/Ni(P) solder joint. The morphology of Ni3Sn4 intermetallic compounds (IMCs) formed between the solder and Ni(10%P) layer is observed to be needle-like and this shape provides high speed diffusion channels for Ni to diffuse into solder that culminates in high growth rate of Ni3Sn4. The diffusion of Ni into solder furthermore results in the formation of Kirkendall voids at the interface of Ni(P) layer and SiCp/Al composites substrate. It is observed that solder reliability is degraded by the formation of Ni2SnP, P rich Ni layer and Kirkendall voids. The compact Ni3Sn4 IMC layer in Ni(5%P) solder joint prevents Ni element from diffusing into solder, resulting in a low growth rate of Ni3Sn4 layer. Meanwhile, the formation of Ni2SnP that significantly affects the reliability of solder joints is suppressed by the low P content Ni(5%P) layer. Thus, shear strength of Ni(5%P) solder joint is concluded to be higher than that of Ni(10%P) solder joint. Growth of Ni3Sn4 IMC layer and formation of crack are accounted to be the major sources of the failure of Ni(5%P) solder joint.     

Fabrication and thermal conductivity of near-net-shaped diamond/copper composites by pressureless infiltration

Near-net-shaped diamond/copper composites with a relative density of over 99% and thermal conductivity of over 350 Wm⁻¹ K⁻¹ are successfully fabricated by powder press-pressureless infiltration processing. The effects of infiltration temperature, infiltration time, interfacial thickness, and type of protective atmosphere on the thermal conductivity of the diamond/copper composites were investigated. The results showed that the diamond-copper composites with complicated shape exhibited better thermal properties, which can be widely used in electronic packaging field. It was found that the properties of diamond-copper composites infiltrated in high vacuum atmosphere were better than that of composites infiltrated in other atmospheres. The thickness of interface showed great effects on the properties of composites. The carbide interfaces were attributed to the decrease of interfacial thermal resistance and enhancement of wetting properties between the diamonds and copper.     

金刚石/铜复合材料与氧化铝陶瓷的Ag-Cu-Ti活性钎焊(英文)

金刚石/铜复合材料具有低膨胀系数和高热导率等优异性能,使其成为一种理想的电子封装材料。采用97%(72Ag-28Cu)-3%Ti活性钎料对金刚石/铜复合材料和氧化铝陶瓷进行钎焊。发现活性钎料在氧化铝陶瓷和金刚石薄膜表面均具有良好的润湿性,在两者表面的平衡润湿角均小于5°。讨论了主要钎焊条件(如钎焊温度和保温时间等)对接头性能的影响。发现钎焊过程中Ti元素聚集在金刚石颗粒的表面形成TiC化合物,且TiC化合物的形貌与钎焊接头的剪切强度具有紧密联系。推测合适的TiC化合物层厚度可改善钎焊接头的剪切强度,而颗粒状的TiC化合物及过厚的TiC化合物层却会损害钎焊接头的性能。获得的最大剪切强度为117MPa。     

Effect of Fe on the sintering and thermal properties of Mo–Cu composites

Effects of Fe on the sintering and thermal properties of Mo–Cu composites have been investigated. Mo–Cu–xFe composites are fabricated by powder metallurgy techniques with addition of various Fe contents ranging from 0.4 wt% to 2.2 wt%. The thermal properties and action mechanism of Fe to Mo–Cu composites are discussed. Results have indicated that the coefficient of thermal expansion (CTE) and thermal conductivity (TC) of Mo–Cu composites are greatly affected by the addition of Fe contents. It has also been observed that the fabricated composite powders with Fe additions exhibit high sinterability. Also, the inclusion of Fe can active the sintering course in shorter times and decline the sintering temperature thus also improving the physical properties of composites. Furthermore, it is also concluded that the utilization of steel kettle and steel balls for milling the Mo–Cu powders is also beneficial to improve the physical and thermal properties of Mo–Cu alloy.