Preparation And Properties Of High Compliant Low Exudation Silica Gel For Thermal Interface Materials

Thermal Interface Material(TIM)is a kind of material widely used in IC packaging and electronic heat dissipation.It is the key material to ensure the safe heat dissipation of all kinds of microelectronic products and equipment,reliable and stable long-term work.With the rapid development of contemporary electronic technology,electronic components and integrated circuits tend to be more integrated and miniaturized.For the elastomer TIM which assists in heat dissipation,high thermal conductivity,electrical insulation,high flexibility,low leakage and other performance requirements are put forward.Silica gel has high flexibility and excellent electrical properties.It is the preferred substrate for elastomeric TIM.It can give high thermal conductivity to materials with thermal conductive fillers.However,the addition of high content thermal conductive fillers will affect the flexibility of materials.The existing commercial products are generally improved by adding small molecular plasticizers,but this leads to the migration and exudation of plasticizers in the later use process and affects the use of plasticizers.Therefore,in order to improve the flexibility and reduce exudation of elastomeric TIM matrix,a series of high compliance and low exudation TIM silica gels were prepared by hydrosilation.The main contents and conclusions are as follows:(1)(Corresponding to the third chapter of the paper,system 1)Silicone gel and composite materials were prepared based on low viscosity divinyl vinyl terminated methyl silicone oil(VS 100 or VS50)based silicone oil,double silicon hydroterminated methyl hydrogen silicone oil CE4 as chain extender,and side chain containing hydrogenated silicone hydrogen XL17 as crosslinking agent.The crosslinking density of silica gel was characterized by equilibrium swelling method,GPC was used to characterize the molecular weight distribution of silica gel,and the migration characteristics of silica gel were studied by weight loss and exudation.The results show that the prepared silicone gel has good flexibility and the crosslinking density can reach 10-5 order of magnitude.The exudation performance of the composite can be improved when the amount of chain extender is reduced and the amount of crosslinking agent is increased.(2)The effect of different silicone oil on the flexibility of silicone gel and the hardness of composite materials was studied.Because of the shorter VS50 chain,the crosslinking point formed more dense,and the crosslinking density of silicone gel increased.The hardness of composite material also increased and the flexibility became worse.By reducing the amount of Si-H and crosslinking agent,the hardness of silica gel and composites can be adjusted and the silicone rubber matrix with high flexibility can be obtained.(3)(Corresponding to the fourth chapter of this paper,system2)By step reaction,the vinyl silicone oil and hydrogen silicone oil prepolymer with branched structure were prepared by side chain polyvinyl silicone oil VDM500 reacting with monohydrosilicone oil(H3000,H5000),polyhydrosilicone oil(XL 13,XL 17)reacting with monovinyl silicone oil(MCR-V21).The second step was to prepare vinyl silicone oil and hydrogen silicone oil prepolymer with different vinyl(Vi)and silicone hydrogen bond(Si-H).The preparation of different structures of silicone gel is based on the variable ratio.The crosslinking density measured by equilibrium swelling method ranges from 10-6 to 10-5,and because the molecular weight of the sol molecule in this system is more than 100,000,the friction between the sol molecule and the crosslinking network is large,and it is not easy to migrate to the surface of the material,so the exudation performance is excellent.(4)The samples were characterized by low field solid-state nuclear magnetic resonance(NMR).It was found that the relaxation of the sample 1 of the system tended to be 0,while the relaxation of the sample 2 of the system had some allowance,indicating that the system 2 successfully prepared the silicone gel with a suspended tail structure to give the material some flexibility.