| As a new phase-change heat transfer device, vapor chamber has become a significantconsideration of thermal management of high-power LED and electronic circuit and so on forits excellent heat transfer performance. However, the vapor chamber performance is limitedby the packaging technology, especially the sealing connection technology. In order to meetthe requirements of high heat transfer performance and long service life of the vapor chamber,it requires high finish of the surface, high purity of the material, low deformation and highconnected strength etc. for the bonding technology. In this analysis, a new type sinteringdiffusion bonding technology which is different from the conventional diffusion bonding hasbeen proposed, and the main research contents are as follows:(1)The distinction and relation between the new sintering diffusion bonding technologyand the conventional technologies such as powder sintering, diffusion bonding and othersealing connection technologies have been compared and analyzed. Technological process ofthe sintering diffusion bonding is protocoled based on the diffusion bonding technology. Thesimplified experimental scheme has been designed for studying the sintering diffusionbonding mechanism of the vapor chamber. And then, the appropriate choices of theexperimental material, equipment and performance testing method have been conducted.(2)The deformation and the stress distribution of the bonded sample and the mold underpreload have been simulated by adopting finite element software (ANSYS Workbench), andthe range of initial compress for sintering diffusion bonding is determined. The results showthat: macroscopic plastic deformation of the sample and the mold takes place due to themaximum s仕ess of them exceeding the yield strength when the preload is over3kN; when thepreload reaches the value of6.5kN，plastic deformation of the sample and the mold occursand the initial pressure of sintering difRision bonding should not be more than60MPa.(3)The macrohardness and tensile shear strength of the diffusion bonding sampleprepared by sintering process have been tested and the technological parameters for sinteringdiffusion bonding process have been preliminarily determined by analyzing and comparingthe mechanical property of the bonded joint under different bonding parameters. Metallurgicalmicroscope is adopted for studying the microstructure on the bonded joint under different bonding parameters. It is found that there exists a phenomenon of grain growth in the basemetal under bonding temperature of900°C and holding time for60min. Shear fracturemorphology of the bonding samples is characterized by using scanning electron microscope(SEM). It is found that fracture mechanism is ductile fracture and the essential reason for thisis the formation of inclusion due to uncompleted clearance of the oxidation film or oil stain onthe surface of the sample to be bonded. The results show that the optimum technologicalparameters for sintering diffusion bonding process are initial pressure of25MPa-50MPa，bonding temperature of800°C and holding time for30min.(4) Sintering diffusion bonding samples prepared by using base metal with differentsurface roughness have been tested for the tensile shear strength. It is found that the tensileshear strength of the bonded joint increases with decrease of the surface roughness of the basemetal. Diffusion bonding samples with better shear performance can be obtained when thesurface roughness-Ra is lower than0.64[im. In order to pre-detecting the sample to be bonded,surface roughness of it is characterized by using infra-red technology. It reaches the bettercondition for conducting diffusion bonding process when the surface emissivity is lower than0.131. |
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