Controllable Preparation And Low Temperature Sintering Of Nano Silver/Copper And Its Interconnection Application In Microelectronic Packaging

With the rapid development of third-generation power semiconductor devices such as silicon carbide?SiC?and gallium nitride?GaN?,traditional chip-mount interconnect materials are difficult to meet the conditions of high-temperature operation,and it is urgent to find new alternative materials.However,due to the size effect of the metal nanomaterial,the melting point of the metal nanoparticle decreases as the size of the nanoparticle decreases,so that it can be sintered at a temperature much lower than the bulk melting point.At the same time,after sintering,nanomaterials can work stably at higher temperatures for a long time,which satisfies the requirements of low temperature sintering and high temperature service,and is an ideal chip interconnection material.Among metal nanoparticles,the interaction between copper and silver nanoparticles has received widespread attention.Silver has the highest conductivity in metal materials and has excellent properties.It is not easily oxidized in the air,which is conducive to transportation and storage.However,copper nanoparticles are easily oxidized in the air to generate copper oxide on the surface,which will increase the required sintering temperature and decrease the conductivity.The main research contents of this article are as follows:?1?Controllable preparation and low temperature sintering of dendritic silver and its interconnection application in microelectronic packagingSilver-based conductive paste is a new type of chip interconnect material.This chapter reports the synthesis of dendritic Ag and its application as a low temperature interconnect material for power semiconductors.Using silver nitrate as the precursor of silver and copper foil as the reducing agent,dendritic silver with stable size and morphology was synthesized under very mild conditions,and mixed with diethylene glycol monoethyl ether acetate solution to form the paste.,Properly optimized parameters?sintering time,temperature,and dendritic silver content?can produce weld joints with high shear strength,even after 1000 cold and hot shock cycles,it has excellent reliability,and the shear strength will not be obvious change.The shear strengths before and after 1000 thermal cycles at-55-125?were about 28 and 26 MPa,respectively.After sintering the paste at 300?for 30 minutes,we obtained a thermal conductivity of 78.9 Wm^-1K^-11 and a resistivity of 9.85x10^-6?.cm.?2?Controllable preparation and low temperature sintering of nano copper materials and its interconnection application in microelectronic packagingThis chapter reports the synthesis of dendritic copper and copper nanoplates and their applications as low temperature interconnect materials for power semiconductors.Optimize its sintering performance by adjusting the sintering time,sintering temperature,sintering pressure and other factors.Dendritic copper and copper nanoplates can obtain the best shear strength after sintering for 30 min and20 min,respectively.A welded joint of 20 MPa can be obtained after sinter 30 min,and the high shear strength of the bonded joint can be produced.Even after 1000thermal shock cycles,it has excellent reliability,and the shear strength will not decrease significantly.After the copper nanoplates were sintered at 300?for 20min,a welded joint with a shear strength of 29.1 MPa was obtained.Compared with copper nanoparticles,dendritic copper and copper nanosheets have better low-temperature sintering performance under the same conditions.?3?Controllable preparation and low temperature sintering of copper nanoparticles and its interconnection application in microelectronic packagingThis chapter reports the synthesis of different nanoparticles and their applications as low temperature interconnect materials for power semiconductors.Copper acetate was used as a precursor,ascorbic acid was used as a reducing agent,a mixed solution of ethylene glycol and toluene was used as a solvent,and different fatty acids and alkylamines were used as surfactants and co-surfactants to synthesize Cu nanoparticles with various particle sizes.Then,four kinds of Cu nanoparticles with relatively representative particle diameters were selected.The oxidation resistance test showed that the oxidation resistance of copper nanoparticles was related to the particle size and the content of surface coating agent.By adjusting the sintering parameters,the maximum value was reached after30 min of sintering.By comparing the shear strength of the four particle sizes,the relationship between the particle size and the surface coating content was explored.Its shear strength is 26.5 MPa after sintering at 350? for 30 min.