| Electronic devices gradually develop towards miniaturization and high integration,which leads to a sharp increase of the heat flux of electronic devices.Therefore,efficient heat dissipation has become a research hotspot in the field of electronics.Metal micro-channel heat sink has attracted more and more attention due to its excellent cooling performance.Based on SU-8 lithography and micro-electroforming,a mental micro-channel structure with 100?m in width and over 500?m in height was fabricated on copper substrate.Then the micro-channel structure was packaged with the cover plate to fabricate a heat sink.In this paper,the fabrication of a metal micro-channel and the packaging process of the heat sink were studied.The main research contents include the following aspects:The uneven deposition of SU-8 photoresist in ultra-thick layers was studied.The causes of poor uniformity of ultra-thick layers was analyzed and the influence of air gap resulting from the poor uniformity of SU-8 film on the accuracy of replication fidelity was researched.According to Fresnel diffraction theory,linewidth deviation of SU-8 film caused by different size of the air gap was simulated.The results show that when the air gap reaches 210?m,linewidth deviation between SU-8 film and the mask is 10.8?m.The non-uniformity of four photoresist coating methods was experimented—single photoresist coating,photoresist coating assisted with EBR,multiple photoresist coating and photoresist coating with auxiliary frame.According to the experimental results,photoresist coating with auxiliary frame is the best coating method in improving the uniformity.When a 560?m-thick SU-8 film is coated with auxiliary frame,the non-uniformity is only 4.0%.The sidewall angel of SU-8 film with thick layers and high aspect ratio was studied.Firstly,the cooling performance of micro-channels with a fixed top width and different bottom widths is simulated by COMSOL in order to analyze the influence of sidewall angle on the cooling performance of the heat sink.The simulation results show that the heat transfer coefficient increases as the sidewall angle rises.The undercutting phenomenon often occurs in the SU-8 film with thick layers and high aspect ratio after exposing,which means the width of the bottom film is relatively small and sidewall angle is poor.Aiming at improving the sidewall angle,a photolithography experiment was designed and conducted to analyze the effect of exposure dose on the sidewall angle.And the most suitable exposure dose parameters was selected.The experimental results show that the optimal exposure dose of SU-8 with around 560?m in thickness is about 1518mJ/cm~2.Two metal micro-channels were fabricated from two groups of parameters in the lithography experiment,and the sidewall angle was measured and compared.The measurement results show that the sidewall angle of the micro-channel fabricated with the optimal exposure dose is enhanced by 1.6°.Aiming at the problem of large air gap between micro-channel plate and the cover plate during packaging the micro-channel heat sink,a novel method based on transition layer compensation was proposed.In order to meet the requirements of air tightness,a shear experiment was carried out in which the shear strength of silver paste,epoxy resin and solder paste were compared.The result shows that the solder paste has the largest shear strength.and the effect of surface roughness on the bonding strength was further explored.Based on the above research results,the fabrication and packaging process of metal micro-channel heat sink were completed.The dimension of the micro-channel was measured,and the measurement results meet the fabrication requirements.There is no leakage in 2.0MPa hydraulic seal test,and no blocking through X-ray detection,which satisfies the application requirements. |
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