Preparation Of High Heat-resistant Electronic Packaging Material Based On Bismaleimide Resin

With the continuous development of the third generation semiconductor industry,wide bandgap semiconductor materials represented by silicon carbide and gallium nitride are widely used in electronic components.In order to adapt to the long-term work in high frequency,high temperature and high power environment,it is necessary to put forward higher performance requirements for electronic packaging materials for packaging electronic components.At present,the most widely used epoxy molding compound（EMC）is used at a low temperature（below 200°C）,which is not suitable for the high temperature working environment of the third generation semiconductor devices.Therefore,the development of an electronic packaging material with excellent heat resistance and other related properties that can be used for a long time in high temperature working environment has become an urgent need in the third generation semiconductor packaging field.Bismaleimide resin（BMI）is a difunctional compound with maleimide group as the terminal group.The cured product of BMI has excellent heat resistance,aging resistance and electrical insulation,and has similar moldability to epoxy resin.In this paper,2E4MZ is used as the curing accelerator of the resin.In the first part of this paper,crystalline bismaleimide resin（BMI-70）,multi-functional epoxy resin（EPPN-501H）and allyl modified phenolic resin（PA）are used as matrix resins.In the second part,BMI-70,EPPN-501H and 2,2’-diallylbisphenol A（DBA）were used as matrix resins.In the third part,oligomeric BMI resin（BMI-2300）and EPPN-501H were used as matrix resins,and 4,4’-diaminodiphenylmethane（DDM）was used as curing agent.The gelation time,curing behavior and mechanism of the three parts were discussed.The resin formula was applied to the field of electronic packaging to prepare the corresponding electronic packaging molding compounds.The processing formability,thermal properties,dielectric properties,aging resistance and thermal conductivity were evaluated.The specific research contents are as follows:（1）Allyl modified phenolic resin（PA）was synthesized by nucleophilic substitution of arylalkyl phenolic resin（MEH-78004S）with allyl bromide.It was used as a chain extender of BMI-70 and pre-mixed according to a certain proportion to obtain BMI/PA premix.Its structure and allyl substitution degree were characterized by ¹H NMR and FT-IR spectra.Then,BMI/PA/EP（BEP）resin blends were obtained by melt blending BMI/PA,EPPN-501H resin and 2E4MZ according to a certain formula ratio.The effects of BMI content on the gel time,curing behavior and thermal stability of BEP resin system were studied by non-isothermal DSC and TGA.The curing mechanism of BEP resin was summarized.Finally,the BEP resin system was used as a matrix to prepare a BEP resin-based electronic packaging molding compound.Compared with commercial EMC,the processability of the obtained electronic packaging molding compound and the thermal properties,bending properties,dielectric properties,thermal conductivity,moisture resistance and aging resistance of the cured molding compound were systematically evaluated.The experimental results show that the allyl substitution rate of PA is 27%,and the first curing exothermic peak temperature of BEP resin system is about140°C,which can meet the curing temperature requirements of electronic packaging molding compound.The thermal decomposition temperature(T_5%)of the cured BEP resin is always higher than 400°C,and the thermal stability is excellent.The gel time of BEP molding compound is within 18 s,and the spiral flow length is higher than 30 inch,which has good processability.The T_g of the cured BEP molding compound can reach 193°C,the flexural strength at room temperature can reach 162 MPa,and the flexural modulus can reach 17.88GPa,which is comparable to commercial EMC and has good thermal and mechanical properties.（2）On the basis of the above research conclusions,2,2’-diallyl bisphenol A（DBA）was selected to replace PA.The allyl and phenolic hydroxyl groups in DBA can react with BMI-70and epoxy resin to form a crosslinking network,respectively.MEH-78004S was selected as another curing agent of epoxy resin to further improve the curing performance of the system.Firstly,BMI-70 and DBA were pre-mixed and chain-extended at 130°C to obtain BMI/DBA chain-extended premix,and its viscosity at 110°C was tested by cone-plate viscometer.Then,BMI/DBA,EPPN-501H resin,MEH-78004S resin and 2E4MZ were blended by melting method to obtain BMI/DBA/EP/PF（BDEP）resin blends.The effects of BMI content on the gelation time,curing behavior,curing mechanism and thermal stability of BDEP resin were investigated by non-isothermal DSC,FT-IR and TGA.Finally,BDEP resin system was applied to the formulation of molding compound to prepare BDEP resin-based electronic packaging molding compound.Compared with the performance results of commercial EMC,the related properties of BDEP molding compound were systematically evaluated.The results show that the softening point of BMI/DBA chain extender premix obtained at 130°C for 1 hour is between80°C and 100°C,and the viscosity at 110°C is 616 m Pa·s.It can be fully melt kneaded with matrix resin and filler in screw extruder.When the addition amount of curing accelerator is 1wt%,the curing exothermic peak temperature of BDEP resin is up to 154.04°C and the lowest is 148.60°C,which can be cured at a lower temperature.The T_5%of the cured BDEP resin is up to 410°C,showing excellent thermal stability.The gel time of BDEP molding compound is up to 39 s,and the spiral flow length is up to 45 inch,which has good processability.The T_g of the cured BDEP molding compound is up to 242°C,which is better than that of commercial EMC.The flexural strength and flexural modulus of the cured BDEP molding compound at room temperature are up to 145 MPa and 20.26 GPa,which are comparable to those of commercial EMC.The highest flexural strength and flexural modulus at 200°C are 47.5 MPa and 8.46 GPa,which are much higher than those of commercial EMC,showing excellent thermal and mechanical properties.（3）Based on the above conclusions,in order to further simplify the process flow and improve the performance,BMI-70 resin was replaced by oligomeric BMI resin（BMI-2300）,and 4,4’-diaminodiphenylmethane（DDM）was used as curing agent.The primary amine group in the molecular structure of DDM can react with the double bond of BMI and the epoxy group of epoxy resin to form a dense cross-linked network structure.BMI/DDM/EP（BED）resin blends with different BMI contents were obtained by blending BMI-2300 resin,DDM,EPPN-501H resin and 2E4MZ by solvent method.The effects of different BMI contents on the gelation time,curing behavior and thermal stability of BED resin system were studied by non-isothermal DSC,TGA and FT-IR,and the curing mechanism of BED resin was analyzed.The BED resin formula with suitable gel time was selected and applied to the molding formula as a matrix resin to prepare the BED resin-based electronic packaging molding compound,and its related properties were evaluated compared with commercial EMC.The results showed that when the addition amount of curing accelerator was 1 wt%,the curing exothermic peak temperature of BED resin was within 160°C,which could meet the curing temperature requirements of molding plastics production.The T_5%of the cured BED resin is up to 388°C,showing excellent thermal stability.The gel time and spiral flow length of BED molding compound are 41 s and43 inch,respectively,which are higher than those of commercial EMC,but still meet the processing requirements of molding compound.It is worth noting that the cured BED molding compound has extremely high T_g,up to 363°C,and its flexural strength at room temperature is up to 138 MPa,and the flexural modulus is up to 20.95 GPa,which is slightly lower than commercial EMC.However,at high temperature（250°C）,the cured BED molding compound can still maintain a flexural strength of up to 68.7 MPa and a flexural modulus of 12.97 GPa,which is far superior to commercial EMC,showing extremely excellent thermal and high temperature mechanical properties.