Research On Integrated Packaging Technology Of Transient Electronic Devices

Transient electronic device is a new kind of advanced electronic devices which can run stably during the using stage and trigger automatic destruction or degradation under specific conditions.In the present stage,the development of transient electronic technology is in the primary stage.There are also many problems,such as the slow material degradation rate,the inconvenient trigger mode,the imperfect manufacturing process and the difficulty in large-scale integration,which limit the application fields of transient electronic devices and hinder its engineering application.Therefore,this thesis studies the integrated packaging technology of transient electronic devices,designs two encapsulation schemes suitable for two different scenarios,samples are prepared,and the feasibility of the scheme is verified through experiments.The main research contents of this thesis are as follows:1.Polyvinyl alcohol and magnesium metal are used as materials for degradable packaging design in a solution environment.The applicability of the material is analyzed.The results show that polyvinyl alcohol with a thickness of 1.8mm can be degraded within10h,and the degradation rate is about 3?m·min^-1.Besides,it can be assembled with ceramics,silicon wafers,conductive adhesives and insulating adhesives.The package pins made of gold-plated magnesium materials can be degraded within 6h.The degradation rate of polyvinyl alcohol is positively related to the volume and temperature of the solution,and it is not sensitive to p H.The degradation rate of gold-plated magnesium pins is positively correlated with temperature and negatively correlated with p H,and is not sensitive to the volume of the solution.The test results of the materials show that polyvinyl alcohol and gold-plated magnesium have good degradation properties and can meet the design index requirements,but polyvinyl alcohol is not resistant to high temperatures,and the technological process need to be optimized.2.After completing the applicability analysis of the material,a degradable packaging structure is designed.Using the principle that polyvinyl alcohol is soluble in water and silicon and magnesium can react with water,the device can be degraded and destroyed in the solution.This packaging design is mainly used in environments that can provide solutions,such as submarines,its application scenarios is limited.Therefore,a packaging technology that can achieve device destruction in a dry environment is designed.The Ni Cr film resistance and the energetic material is placed between the chip and the package.The resistance is heated by an electric current,causing the energetic material to expand and chip to broken.The information on the chip is destroyed,and the destruction can not be recovered.The slotting method of chip is optimized by finite element simulation.The circular groove with a depth of 0.1mm and an area of 1mm²is used to fill the energetic material.3.In order to realize the preparation of transient integrated package samples,we have studied chip thinning,chip transfer,packaging process compatibility and so on.The silicon films whose thickness is 5?m and 10?m are separately obtained by peeling off the oxide layer selectively and temporarily bonding the support substrate.It is convenient for the temporarily bonded substrate to transfer the ultrathin chip to a polyvinyl alcohol substrate,meanwhile,the separation is achieved by acetone.That the ultrathin chip is fragile and the polyvinyl alcohol is not resistant to high temperature processing are solved by laser cutting,sacrificial layer transfer,conductive plastic adhesive bonding wire and so on.4.The transient integrated package sample of degradable is prepared.The device function is fail after 20min and completes degradation after 10h in aqueous solution.The sample that can be destroyed makes the chip function invalid in about 6ms,realizing the rapid destruction of the chip.