Preparation And Thermal Performance Test Of Diamond/Nano Silver Solder Paste

With the development of high-power intensive chip,the performance of sintered nano silver solder paste faces new challenges.The reinforced base nano silver solder paste not only has the high thermal conductivity and electrical conductivity of the silver-based material,but also compensates for the non-densification disadvantages such as holes and cracks in the sintered silver joint.At present,the addition of reinforcing groups has become a research hotspot to improve the performance of sintered nano silver solder paste.Therefore,this paper attempts to add diamond as a reinforcing phase in nano silver solder paste because diamond has higher thermal conductivity,lower thermal expansion coefficient and excellent mechanical properties.The diamond is modified and added to the nano silver solder paste to prepare a diamond/nano silver solder paste material with excellent performance,which can be effectively applied in the power device interconnection package.In this paper,large particle nano silver solder paste with silver particle size of 60~90nm was prepared by hydrazine method,and small particle nano silver solder paste with particle size of 25~45 nm was prepared by modified Carey Lea method,preparation of composite nano silver solder paste by 1:4 ratio of large and small size silver particles.At the same time,the diamond particles are subjected to electroless silver plating treatment to improve the interface between the nano silver particles and the diamond,and added to the composite nano silver solder paste in a proportion of 1 wt%,5 wt%,and 10 wt%,respectively,for preparing a diamond/nano silver solder paste.Thermogravimetric analysis of the diamond/nano silver solder paste revealed that its organic components evaporate at 350?.By TEM transmission electron microscopy observation of the particle morphology of the diamond/nano silver solder paste before sintering,it was found that there was no agglomeration between the silver particles of the large and small particles,and the dispersion was good.The morphology of the sintered diamond/nano silver solder paste was characterized by SEM scanning electron microscopy.It was found that a large number of sintered silver layers were formed on the surface of the diamond particles,and a dense sintered neck was formed between the nano silver particles.The diamond surface was around 300?.The nano silver particles are the most,and the sintered layer has the best compactness.The nano silver solder paste bonded silicon chip and silver-plated copper substrate with different proportions of diamond particles were observed by SAM ultrasonic microscope.It was found that the sintered silver layer had the lowest porosity at 5 wt%.The thermal conductivity and thermal diffusivity of the diamond/nano silver solder paste at different sintering temperatures were measured by a Hot Disk thermal constant analyzer.The thermal conductivity was up to 2.643 W/mK at a sintering temperature of350?.The amount of heat diffusion coefficient found at 5 wt%was 36.84 mm~2/s.5 wt%diamond/nano silver solder paste,silver silicide,HY500 thermal grease were applied to the interconnected LED chip and PCB substrate,and the interface thermal resistance was tested at different sintering temperatures.It was found that sintering at 50~200?.The interface thermal resistance of the 5 wt%diamond/nano silver solder paste is much lower than the other two,with a minimum of 0.4364 K/W,which is about 40%lower than the thermal resistance at normal temperature.