Research On Fabrication Process Of Copper Enhanced-boiling Heat Transfer Surface

In recent years,with the development of the chip technology,the integration density of chips has constantly increased.And the heat flux density of devices has also been increasing.Thus,the heat dissipating problem has become a prominent factor which restricts the development of the chip technology.The boiling heat transfer behavior has the characteristics of having large heat transfer coefficient in low wall superheat degree situations,which has great potentials in solving the heat dissipation problem of chips.Therefore,the fabrication process of structures which have enhanced-boiling heat transfer effects has become a hotspot in the field of heat dissipation.Based on the lithography of SU-8 photoresist and the microelectroforming technology,The metal surface of micro-columns array with enhanced-boiling heat transfer effect was fabricated on copper substrate.The main research contents include the following aspects :In this paper,in order to solve the removing problem of SU-8 photoresist,a new removal method using preset-swelling gap is proposed.This method utilizes the photolithography process to set gaps on the SU-8 photoresist,which divide the SU-8 photoresist into some independent units.In this way,the swelling behavior of SU-8 photoresist can be used to make the independent units automatically detach from the microstructure.In order to determine the appropriate SU-8 size,ABAQUS software was used to simulate the swelling behavior of SU-8 photoresist,in which 2D and 3D models were both established.The results show that the removing effect of the SU-8 photoresist meets the fabrication requirement when the width of the pattern is 14?m,16?m and 18?m.The swelling experiments were designed in consistent with the simulation results.The results show that the optimum removal effect of SU-8 photoresist is realized when the width of pattern was18 ?m.The problems of casting loss and casting layer shedding arising after the microelectroforming process were studied.Based on the analysis of the shed casting layer,it was found that the dirt and impurities attached to the surface of the substrate were the main reasons for the casting loss and casting layer shedding.In order to remove the dirt and impurities on the surface of the substrate,the methods of oxygen plasma treatment and weakly etched surface treatment were tried respectively.The cleanliness of the substrate was improved after the treatment,and the micro-columns array structure with intact morphology and full array was electroformed.The enhanced-boiling heat transfer metal surface was fabricated.The structural dimensions of the surface were measured.The results showed that the average height of the micro-columns array was 56.6?m,the average length of side was 47.7?m,and the average interval distance was 51.9?m.The actual size of the micro-columns array structure met the design requirements.In addition,the static contact angle of the metal surface was 135°,the surface was hydrophobic.The heat transfer performance test of the surface is completed.The heat transfer performance of the enhanced-boiling heat transfer surface and the common surface were tested using the boiling heat transfer experimental platform respectively.Under the same test environment,the heat flux density of the enhanced-boiling heat transfer surface is 5 times as much as the common surface,and the heat transfer coefficient is 4.18 times as much as the common surface.