Urea epoxy curing accelerator, epoxy conductive silver glue and preparation method

Abstract

The present invention discloses a urea-type epoxy curing accelerator, an epoxy conductive silver paste and a preparation method thereof, and relates to the technical field of chip packaging materials. The present invention comprises a urea-type epoxy curing accelerator prepared by an esterification reaction between a diisocyanate compound and a secondary amine compound, an epoxy conductive silver paste comprising the urea-type epoxy curing accelerator and a preparation method thereof. In the present invention, the urea-type epoxy curing accelerator is prepared, and the epoxy conductive silver paste comprising the urea-type epoxy curing accelerator is prepared. The secondary amine released by the prepared organic urea has a boiling point greater than that of dimethylamine or diethylamine, and most of it participates in the curing reaction, with very little gas volatilization. Therefore, no voids are detected in the adhesive layer below the chip edge. By reducing the amount of gas generated during the high-temperature curing process of the substituted urea, the purpose of reducing voids in the adhesive layer and improving chip bonding reliability is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of chip packaging materials, in particular to a urea-based epoxy curing accelerator, epoxy conductive silver glue and a preparation method thereof. Background Art

[0002] Conductive adhesive is a material that plays an important role in integrated circuit packaging. It enables the process of fixing the integrated circuit chip to the packaging substrate or lead frame chip carrier. Conductive adhesive is generally composed of resin, conductive filler, additives, etc. It has the advantages of low production cost, environmental friendliness, low curing temperature, and high line resolution. It can meet the current production demand for highly integrated devices.

[0003] Currently, many preparation technologies, new systems and methods for improving the performance of conductive silver paste have been disclosed;

[0004] Publication No. CN1931946A discloses a single-component silver-filled conductive adhesive that can be stored and transported at room temperature. The adhesive is made primarily of silver powder with auxiliary materials added. The curing accelerator is an organic urea, and the diluent is a mixture of dimethyl adipate, dimethyl glutarate, and dimethyl succinate. The adhesive is suitable for replacing solder as a connecting material on printed circuit boards and for bonding SMT, quartz resonators, chips, and the like. It exhibits good conductivity and high adhesion.

[0005] Publication No. CN102127386B discloses a light-curing and heat-curing conductive adhesive and a preparation method thereof, using urea formed by the reaction of a halogenated aromatic isocyanate with dimethylamine or diethylamine as a curing accelerator;

[0006] Publication No. CN105255385A discloses a one-component high-performance conductive silver paste and its preparation method using UR300 as a curing accelerator;

[0007] The above-mentioned patent uses urea formed by the reaction of a low-boiling-point solvent and an aromatic isocyanate with dimethylamine or diethylamine as a curing accelerator. However, in the chip mounting process, the urea-type epoxy curing accelerator used in the above-mentioned patent decomposes into the corresponding isocyanate and low-boiling-point dimethylamine or diethylamine at high temperatures to promote the ring-opening polymerization reaction of the epoxy group. The released low-boiling-point dimethylamine or diethylamine and the low-boiling-point solvent in the formula form bubbles under the external high temperature and disperse around. During the baking process, the curing fluidity of the epoxy resin deteriorates, resulting in an inability to fill the gaps generated by gas diffusion, and voids will appear at these locations. Under the condition that there are voids in the adhesive layer, the heat distribution of the power semiconductor chip is uneven, and excessive thermal stress will cause the chip to automatically debond and cause chip deformation, resulting in cracks and charge accumulation in the device, affecting device performance, yield rate and reliability.

[0008] In response to the above problems, the inventors proposed a urea-based epoxy curing accelerator, epoxy conductive silver glue and a preparation method to solve the above problems. Summary of the Invention

[0009] In order to solve the problem in the prior art that the epoxy resin curing fluidity in the conductive adhesive for chip packaging deteriorates, resulting in the inability to fill the gaps caused by gas diffusion; the purpose of the present invention is to provide a urea epoxy curing accelerator, epoxy conductive silver glue and a preparation method.

[0010] In order to solve the above technical problems, the present invention adopts the following technical solution: a urea-based epoxy curing accelerator, the structural formula of the urea-based epoxy curing accelerator is as follows:

[0011]

[0012] The urea epoxy curing accelerator is prepared by esterification reaction of a diisocyanate compound and a secondary amine compound.

[0013] Preferably, the diisocyanate compound is 1,4-tetramethylene diisocyanate, dimer diisocyanate (DDI), hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), methylene diphenyl diisocyanate (MDI), toluene diisocyanate (TDI), toluidine diisocyanate (TODI), trimethylhexamethylene diisocyanate (TMDI), 2,5- or 2,6-bis-(isocyanatomethyl)-bicyclo[2.2.1]heptane, 1,5-naphthalene diisocyanate (NDI), dicyclohexylmethyl diisocyanate (H12MDI), p-phenylene diisocyanate (PPDI), m-tetramethylxylylene diisocyanate (TMXDI) and dimers thereof;

[0014] The secondary amine compound is any one of dipropylamine, dibutylamine, dipentylamine, dihexylamine, dicyclopentylamine, dicyclohexylamine, diphenylamine and dibenzylamine, which have a boiling point greater than that of dimethylamine and diethylamine at normal pressure.

[0015] The present invention also provides an epoxy conductive silver paste, which is composed of the following components in percentage:

[0016] 10% to 20% epoxy resin, 0.5% to 3% epoxy curing agent, 0.4% to 3% urea epoxy curing accelerator, 2% to 9% epoxy diluent, 45% to 85% silver powder, 0% to 10% reinforcing agent, 0.05% to 1% silane coupling agent and 0.01% to 1% conductive promoter.

[0017] Preferably, the epoxy resin is any one of bisphenol A epoxy resin, bisphenol F epoxy resin, bisphenol S epoxy resin, phenol novolac epoxy resin, methylphenol novolac epoxy resin, bisphenol A linear novolac epoxy resin, biphenyl epoxy resin, naphthalene epoxy resin, aralkyl epoxy resin, alicyclic epoxy resin, trifunctional epoxy resin and tetrafunctional epoxy resin, or a combination of at least any two thereof, and the halogen content of the epoxy resin is less than 100 ppm;

[0018] The epoxy curing agent is an aromatic diprimary amine, and the aromatic diprimary amine is p-phenylenediamine, 2,6-dimethyl-p-phenylenediamine, 2,5-di-tert-butyl-p-phenylenediamine, 2,3-dimethyl-p-phenylenediamine, 2,3,5-trimethyl-p-phenylenediamine, m-phenylenediamine, 3,5-diaminotoluene, 3,5-diaminotrifluorotoluene, 2,6-diaminotoluene, 2,6-diaminotrifluorotoluene, o-phenylenediamine, 4,4'-diaminodiphenylmethane, 3,3'-dimethyl-4,4'-diaminodiphenylmethane, 3,3',5,5'-tetramethyl-4,4'-diaminodiphenylmethane, 2,2-bis(4-aminophenyl)propane, 2,2-bis(4-amino-3,5-dimethylphenyl)propane, 2,2-bis(4-aminophenyl) Hexafluoropropane, 2,2-bis(4-amino-3,5-dimethylphenyl)hexafluoropropane, 4,4'-diaminodiphenyl sulfone, 3,3'-diaminodiphenyl sulfone, 4,4'-diamino-3,3',5,5'-tetramethyldiphenyl sulfone, 4,4'-diaminobenzophenone, 3,3'-diaminobenzophenone, 4,4'-diaminodiphenyl ether, 3,3'-diaminodiphenyl ether, 3,4'-diaminodiphenyl ether, 4,4'-diaminodiphenyl sulfide, 3,3'-diaminodiphenyl sulfide, 3,4'-diaminodiphenyl sulfide, 4,4'-diaminobiphenyl, 3,3'-dimethyl-4,4'-diaminobiphenyl, 3,3'- Dimethoxy-4,4'-diaminobiphenyl, 3,3'-bis(trifluoromethyl)-4,4'-diaminobiphenyl, 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl, 3,3'-dimethoxy-4,4'-diaminobiphenyl, 3,3'-bis(trifluoromethoxy)-4,4'-diaminobiphenyl, 2,2'- Dimethyl-4,4'-diaminobiphenyl, 2,2'-dimethoxy-4,4'-diaminobiphenyl, 2,2'-bis(trifluoromethyl)-4,4'-diaminobiphenyl, 3,3'-dimethoxy-4,4'-diaminodiphenylmethane, 1,3-bis(4-aminophenoxy)benzene, 1,2-bis(4-aminophenoxy)benzene, 1,4-bis(4-aminophenoxy)benzene, 1,3-bis(3-aminophenoxy)benzene, 1,2-bis(3-aminophenoxy)benzene, 1,4-bis(3-aminophenoxy)benzene, 1,3-bis(2-aminophenoxy)benzene, 1,2-bis(2-aminophenoxy)benzene benzene, 1,4-bis(2-aminophenoxy)benzene, 2,6-bis(4-aminophenoxy)toluene, 2,6-bis(3-aminophenoxy)toluene, 2,6-bis(2-aminophenoxy)toluene, 2,6-bis(4-aminophenoxy)benzotrifluoride, 2,6-bis(3-aminophenoxy)benzotrifluoride, 2,6-bis(2-aminophenoxy)benzotrifluoride, 1,4-bis(4-aminophenoxy)-2,6-dimethylbenzene, 1,4-bis(3-aminophenoxy)-2,6-dimethylbenzene, 1,4-bis(2-aminophenoxy)-2,6-dimethylbenzene, 1,4-bis(3-aminophenoxy)-2,6-bis(trifluoromethyl)benzene, 1,4-bis(2-aminophenoxy)-2,6-bis(trifluoromethyl)benzene, 1,4-bis(4-aminophenoxy)-2,6-bis(trifluoromethyl)benzene, 1,4-bis(4-aminophenoxy)-2,5-di-tert-butylbenzene, 1,4-bis(3-aminophenoxy)-2,5-di-tert-butylbenzene, 1,4-bis(2-aminophenoxy)-2,5-di-tert-butylbenzene, 1,4-bis(4-aminophenoxy)-2,6-bis(trifluoromethyl)benzene 1,4-bis(3-aminophenoxy)-2,3-dimethylbenzene, 1,4-bis(2-aminophenoxy)-2,3-dimethylbenzene, 1,4-bis(4-aminophenoxy)-2,3-bis(trifluoromethyl)benzene, 1,4-bis(3-aminophenoxy)-2,3-bis(trifluoromethyl)benzene, 1,4-bis(2-aminophenoxy)-2,3-bis(trifluoromethyl)benzene, 1,4-bis(4-aminophenoxy)-2,3,5-trimethylbenzene, 1,4-bis(3-aminophenoxy)-2,3,5-trimethylbenzene, 1,4-bis(2-aminophenoxy)-2,3,5-trimethylbenzene, 3,5-bis(4-aminophenoxy)toluene, 3,5-bis(3-aminophenoxy)toluene, 3,5-bis(2-aminophenoxy)-2,3,5-trimethylbenzene 4,4'-bis(4-aminophenoxy)diphenylmethane, 4,4'-bis(3-aminophenoxy)diphenylmethane, 4,4'-bis(2-aminophenoxy)diphenylmethane, 4,4'-bis(4-aminophenoxy)-3,3',5,5'-tetramethyldiphenylmethane, 4,4'-bis(4-aminophenoxy)diphenyl ether, 4,4'-bis(3-aminophenoxy)diphenyl ether, 4,4'-bis(4-aminophenoxy)diphenylmethane, 4,4'-bis(4-aminophenoxy)-3,3',5,5'-tetramethyldiphenylmethane, 4,4'-bis(4-aminophenoxy)diphenyl ether, 4,4'-bis(3-aminophenoxy)diphenyl ether, 4,4'- Bis(2-aminophenoxy)diphenyl ether, 4,4'-bis(4-aminophenoxy)diphenyl sulfone, 4,4'-bis(3-aminophenoxy)diphenyl sulfone, 4,4'-bis(2-aminophenoxy)diphenyl sulfone, 4,4'-bis(4-aminophenoxy)-3,3',5,5'-tetramethyl diphenyl sulfone, 4,4'-bis(3-aminophenoxy)-3,3',5,5'-tetramethyl diphenyl sulfone, 4,4'-bis(2-aminophenoxy)-3,3',5,5'-tetramethyl diphenyl sulfone, 4,4'-bis(4-aminophenoxy)diphenyl sulfide, 4,4'-bis(3-aminophenoxy)diphenyl sulfide, 4,4'- Bis(2-aminophenoxy)diphenyl sulfide, 4,4'-bis(4-aminophenoxy)-3,3',5,5'-tetramethyldiphenyl sulfone, 4,4'-bis(4-aminophenoxy)biphenyl, 4,4'-bis(3-aminophenoxy)biphenyl, 4,4'-bis(2-aminophenoxy)biphenyl, 4,4'-bis(4-aminophenoxy)-3,3',5,5'-tetramethyldiphenyl sulfone5'-tetramethylbiphenyl, 4,4'-bis(3-aminophenoxy)-3,3',5,5'-tetramethylbiphenyl, 4,4'-bis(2-aminophenoxy)-3,3',5,5'-tetramethylbiphenyl, 2,2-bis[4-(4-aminophenoxy)phenyl]propane, 2,2-bis[4-(3-aminophenoxy)phenyl]propane, 2,2-bis[4-(2-aminophenoxy)phenyl]propane, 2,2-bis[4-(4-aminophenoxy)-3,5-dimethylphenyl]propane, 2,2-bis[4-(3-aminophenoxy)-3,5-dimethylphenyl]propane, 2,2-bis[4-(2-aminophenoxy)-3,5-dimethylphenyl]propane, 2,2-bis[4-(4-aminophenoxy)phenyl]hexafluoropropane, 2,2- Bis[4-(3-aminophenoxy)phenyl]hexafluoropropane, 2,2-bis[4-(2-aminophenoxy)phenyl]hexafluoropropane, 2,2-bis[4-(4-aminophenoxy)phenyl-3,5-dimethylphenyl]hexafluoropropane, 2,2-bis[4-(3-aminophenoxy)phenyl-3,5-dimethylphenyl]hexafluoropropane, 2,2-bis[4-(2-aminophenoxy)phenyl-3,5-dimethylphenyl]hexafluoropropane, 3,5-diaminobenzoic acid, 3,5-diaminophenol, 1,5-diaminonaphthalene, 1,7-diaminonaphthalene, 2,3-diaminonaphthalene, 2,7-diaminonaphthalene, 1,4-diaminonaphthalene, 1,2-diaminonaphthalene, 1,3-diaminonaphthalene, 1,6-diaminonaphthalene, 1,8-diaminonaphthalene, 2,4-diaminonaphthalene, 2,5-diaminonaphthalene, One or a mixture of any of 2,6-diaminonaphthalene, 2,8-diaminonaphthalene, 2,5-diaminopyridine, 2,6-diaminopyridine and 3,4-diaminopyridine;

[0019] The urea epoxy curing accelerator is prepared by esterification of a diisocyanate compound with a secondary amine having a boiling point greater than that of dimethylamine and diethylamine at normal pressure;

[0020] The epoxy diluent is 1,6-hexanediol diglycidyl ether, neopentyl glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, ethylene glycol diglycidyl ether, polyethylene glycol diglycidyl ether, the purity of the epoxy diluent is greater than 90%, and the halogen content is not greater than 200 ppm;

[0021] The silver powder is one or a combination of spherical, flake, rod-shaped and dendritic metal silver powders, the metal silver powder is a combination of flake metal silver powder and spherical metal silver powder, and the size of the metal silver powder is 0.1-10 μm;

[0022] The reinforcing agent is bismaleimide, and the bismaleimide is 4,4'-bismaleimidodiphenylmethane, 4,4'-bismaleimidodiphenyl ether, 4,4'-bismaleimidodiphenyl sulfone, 1,3-bismaleimidobenzene, p-phenylene bismaleimide, 2,6-dimethyl-p-phenylene bismaleimide, 2,5-di-tert-butyl-p-phenylene bismaleimide, 2,3-dimethyl-p-phenylene bismaleimide, 2,3,5-trimethyl-p-phenylene bismaleimide, 3,5-bismaleimidotoluene, 3,5-bismaleimidotrifluorotoluene, 2,6-bismaleimidotoluene, 2,6-bismaleimidotrifluorotoluene, o-phenylene bismaleimide, 3,3'-dimethyl-4,4'- Bismaleimidodiphenylmethane, 3,3'-dichloro-4,4'-bismaleimidodiphenylmethane, 3,3',5,5'-tetramethyl-4,4'-bismaleimidodiphenylmethane, 2,2-bis(4-maleimidophenyl)propane, 2,2-bis(4-maleimidophenyl)propane, dimethylphenyl)propane, 2,2-bis(4-maleimidophenyl)hexafluoropropane, 2,2-bis(4-maleimido-3,5-dimethylphenyl)hexafluoropropane, 3,3'-bismaleimidodiphenyl sulfone, 4,4'-bismaleimido-3,3',5,5'-tetramethyldiphenyl sulfone, 4,4'-bismaleimidobenzophenone, 3,3'-bismaleimidobenzophenone, 3,3'-bismaleimidodiphenyl ether, 3,4'-bismaleimidodiphenyl ether, 4,4'-bismaleimidodiphenyl sulfide, 3,3'-bismaleimidodiphenyl sulfide, 3,4'-bismaleimidodiphenyl sulfide, 4,4'-bismaleimidobiphenyl, 3,3'-dimethyl-4,4'- Bismaleimidobiphenyl, 3,3'-dimethoxy-4,4'-bismaleimidobiphenyl, 3,3'-bis(trifluoromethyl)-4,4'-bismaleimidobiphenyl, 2,2'-bis(trifluoromethyl)-4,4'-bismaleimidobiphenyl, 3,3'-dimethoxy-4,4'-bismaleimidobiphenyl, 3,3'-bis(trifluoromethoxy)-4,4'-bismaleimidobiphenyl, 2,2'-dimethyl-4,4'-bismaleimidobiphenyl, 2,2'-dimethoxy-4,4'-bismaleimidobiphenyl, 2,2'-bis(trifluoromethyl)-4,4'- Bismaleimidobiphenyl, 3,3'-dimethoxy-4,4'-bismaleimidodiphenylmethane, 1,3-bis(4-maleimidophenoxy)benzene, 1,2-bis(4-maleimidophenoxy)benzene, 1,4-bis(4-maleimidophenoxy)benzene, 1,3-bis(3-maleimidophenoxy)benzene, 1,2-bis(3-maleimidophenoxy)benzene, 1,4-bis(3-maleimidophenoxy)benzene, 1,3-bis(2-maleimidophenoxy)benzene, 1,2-bis(2-maleimidophenoxy)benzene, 1,4-bis(2-maleimidophenoxy)benzene, 2,6-bis(4-maleimidophenoxy)toluene, 2,6-bis(3-maleimidophenoxy)toluene, 2,6-bis(2-maleimidophenoxy)toluene, 2,6-bis(4-maleimidophenoxy)trifluorotoluene, 2,6-bis(3-maleimidophenoxy)trifluorotoluene, 2,6-bis(2- 1,4-bis(3-maleimidophenoxy)-2,6-dimethylbenzene, 1,4-bis(2-maleimidophenoxy)-2,6-dimethylbenzene, 1,4-bis(3-maleimidophenoxy)-2,6-dimethylbenzene, 1,4-bis(3-maleimidophenoxy)-2,6-bis(trifluoromethyl)benzene, 1,4-bis(2-maleimidophenoxy)- 2,6-bis(trifluoromethyl)benzene, 1,4-bis(4-maleimidophenoxy)-2,6-bis(trifluoromethyl)benzene, 1,4-bis(4-maleimidophenoxy)-2,5-di-tert-butylbenzene, 1,4-bis(3-maleimidophenoxy)-2,5-di-tert-butylbenzene, 1,4-bis(2-maleimidophenoxy)-2,5-di-tert-butylbenzene, 1,4-bis(4-maleimidophenoxy) 1,4-bis(3-maleimidophenoxy)-2,3-dimethylbenzene, 1,4-bis(2-maleimidophenoxy)-2,3-dimethylbenzene, 1,4-bis(4-maleimidophenoxy)-2,3-bis(trifluoromethyl)benzene, 1,4-bis(3-maleimidophenoxy)-2,3-bis(trifluoromethyl)benzene, 1,4-bis(2-maleimidophenoxy)-2,3-bis(trifluoromethyl)benzene, 1,4-bis(4-maleimidophenoxy)-2,3,5-trimethylbenzene, 1,4-bis(3-maleimidophenoxy)-2,3,5-trimethylbenzene, 1,4-bis(2-maleimidophenoxy)-2,3,5-trimethylbenzene, 3,5-bis(4-maleimidophenoxy)-2,3,5-trimethylbenzene, 3,5-bis(3-maleimidophenoxy)toluene, 3,5-bis(2-maleimidophenoxy)toluene, 3,5-bis(4-maleimidophenoxy)-trifluorotoluene, 3,5-bis(3-maleimidophenoxy)-trifluorotoluene, 3,5-bis(2-maleimidophenoxy)-trifluorotoluene, 4,4'-bis(4-maleimidophenoxy)diphenylmethane, 4,4'-bis(3-maleimidophenoxy)diphenylmethane, 4,4'-bis(2-maleimidophenoxy)diphenylmethane, 4,4'-bis(4-maleimidophenoxy)-3,3',5,5'-tetramethyldiphenylmethane, 4,4'-bis(4-maleimidophenoxy)diphenyl ether, 4,4'-bis(4-maleimidophenoxy)diphenyl ether, 4,4'-bis(4-maleimidophenoxy)diphenyl ether, 4,4'-bis(4-maleimidophenoxy)diphenyl ether, 4,4'-bis(4-maleimidophenoxy)diphenyl ether, 4,4'-bis(4-maleimidophenoxy)diphenyl ether, 4,4'-bis(4-maleimidophenoxy)diphenyl ether, 4,4'-bis(4-maleimidophenoxy)diphenyl ether, 4,4'-bis(4-maleimidophenoxy)diphenyl ether, 4,4'-bis(4-maleimidophenoxy)diphenyl ether, 4,4'-bis(4-maleimidophenoxy)diphenyl ether, 4,4'-bis(4-maleimidophenoxy)diphenyl4'-bis(3-maleimidophenoxy)diphenyl ether, 4,4'-bis(2-maleimidophenoxy)diphenyl ether, 4,4'-bis(4-maleimidophenoxy)diphenyl sulfone, 4,4'-bis(3-maleimidophenoxy)diphenyl sulfone, 4,4'-bis(2-maleimidophenoxy)diphenyl sulfone, 4,4'-bis(4-maleimidophenoxy)-3,3',5,5'-tetramethyl diphenyl sulfone, 4,4'-bis(3-maleimidophenoxy)-3,3',5,5'-tetramethyl diphenyl sulfone, 4,4'-bis(2-maleimidophenoxy)diphenyl sulfone phenyl sulfone, 4,4'-bis(4-aminophenoxy)diphenyl sulfide, 4,4'-bis(3-aminophenoxy)diphenyl sulfide, 4,4'-bis(2-maleimidophenoxy)diphenyl sulfide, 4,4'-bis(4-maleimidophenoxy)-3,3',5,5'-tetramethyldiphenyl sulfone, 4,4'-bis(4-maleimidophenoxy)biphenyl, 4,4'-bis(3-maleimidophenoxy)biphenyl, 4,4'-bis(2-maleimidophenoxy)biphenyl, 4,4'-bis(4-maleimidophenoxy)biphenyl, phenyl]propane, 2,2-bis[4-(3-maleimidophenoxy)phenyl]propane, 2,2-bis[4-(2-maleimidophenoxy)phenyl]propane, 2,2-bis[4-(4-maleimidophenoxy)phenyl]propane, 2,2-bis[4-(3-maleimidophenoxy)phenyl]propane, 2,2-bis[4-(2-maleimidophenoxy)phenyl]propane, 2,2-bis[4-(4-maleimidophenoxy)phenyl]propane, 2,2-bis[4-(4-maleimidophenoxy)phenyl]propane 5-dimethylphenyl]propane, 2,2-bis[4-(3-maleimidophenoxy)-3,5-dimethylphenyl]propane, 2,2-bis[4-(2-maleimidophenoxy)-3,5-dimethylphenyl]propane, 2,2-bis[4-(4-maleimidophenoxy)phenyl]hexafluoropropane, 2,2-bis[4-(3-maleimidophenoxy)phenyl]hexafluoropropane, 2,2-bis[4-(2-maleimidophenoxy)phenyl]hexafluoropropane, 2,2-bis[4-(4-maleimidophenoxy)phenyl-3,5-dimethylphenyl]propane Hexafluoropropane, 2,2-bis[4-(3-maleimidophenoxy)phenyl-3,5-dimethylphenyl]hexafluoropropane, 2,2-bis[4-(2-maleimidophenoxy)phenyl-3,5-dimethylphenyl]hexafluoropropane, 3,5-bismaleimidobenzoic acid, 3,5-bismaleimidophenol, 1,5-bismaleimidonaphthalene, 1,7-bismaleimidonaphthalene, 2,3-bismaleimidonaphthalene, 2,7-bismaleimidonaphthalene, 1,4-bismaleimidonaphthalene, 1,2-bismaleimidonaphthalene, 1,3-bismaleimidonaphthalene, 1,6-bismaleimidonaphthalene, 1,8-bismaleimidonaphthalene, 2,4-bismaleimidonaphthalene, 2,5- Bismaleimidonaphthalene, 2,6-bismaleimidonaphthalene, 2,8-bismaleimidonaphthalene, 1,3-bismaleimidonaphthalene-2-carboxylic acid, 1,4-bismaleimidonaphthalene-2-carboxylic acid, 1,5-bismaleimidonaphthalene-2-carboxylic acid, 1,6-bismaleimidonaphthalene-2-carboxylic acid, 1,5-dihydroxy-2,4-bismaleimidobenzene, 2,3-bismaleimidopyridine, 1,4-bismaleimidonaphthalene-2-carboxylic acid, 1,5-bismaleimidonaphthalene-2-carboxylic acid, 1,6-bismaleimidonaphthalene-2-carboxylic acid, 2,5- Bismaleimidopyridine, 2,6-bismaleimidopyridine, 3,4-bismaleimidopyridine, 3,5-bismaleimidopyridine, 2,2-bis(3-maleimido-4-hydroxyphenyl)propane, 2,2-bis(3-maleimido-4-hydroxyphenyl)hexafluoropropane, 3,3'-dihydroxy-4,4'-bismaleimidobiphenyl, 4,4'-dihydroxy-3,3'-bismaleimidobiphenyl, 4,4'-bismaleimido-4"-hydroxytriphenylmethane, or any mixture thereof;

[0023] The silane coupling agent is one or any combination of KH-550, KH-560, KH-570 and KH792;

[0024] The conductive promoter is any one of succinic acid, glutaric acid and adipic acid, or a mixture in which the sum of the components of succinic acid, glutaric acid and adipic acid is 100%.

[0025] The present invention also provides a method for preparing epoxy conductive silver paste, comprising the following steps:

[0026] S1. Evenly mix epoxy resin, diluent, and reinforcing agent according to a formula ratio to obtain a mixture A;

[0027] S2. Adding a curing agent, a urea epoxy curing accelerator, a conductive accelerator, and a silane coupling agent to the mixture A in order according to the formula ratio to obtain a colloid B;

[0028] S3. Add metallic silver powder to the obtained colloid B, stir evenly, and then disperse, grind, filter, vacuum degas, and package to obtain epoxy conductive silver glue.

[0029] Preferably, in S3, the metallic silver powder is added in batches or all at once, the dispersion and grinding process is carried out in a three-roll mill, and the preparation environment temperature of S1, S2 and S3 is room temperature.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] In the present invention, a urea-based epoxy curing accelerator is prepared, and an epoxy conductive silver adhesive containing the urea-based epoxy curing accelerator is prepared. The dicyclohexylamine released by the organic urea has a higher boiling point than dimethylamine, and most of it participates in the curing reaction, with very little gas volatilization. Therefore, no voids are detected in the adhesive layer below the chip edge. By reducing the amount of gas generated during the high-temperature curing process of the substituted urea, the purpose of reducing voids in the adhesive layer and improving chip bonding reliability is achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0033] Figure 1 Schematic diagram of an X-ray photograph of Example 1 of the present invention.

[0034] Figure 2 This is a schematic diagram of an X-ray photograph of Example 2 of the present invention.

[0035] Figure 3 This is a schematic diagram of an X-ray photograph of Example 3 of the present invention.

[0036] Figure 4 Schematic diagram of an X-ray photograph of Comparative Example 1 of the present invention.

[0037] Figure 5 Schematic diagram of an X-ray photograph of comparative example 2 of the present invention.

[0038] Figure 6 Schematic diagram of the X-ray photograph of comparative example 3 of the present invention. DETAILED DESCRIPTION

[0039] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0040] like Figures 1-6 As shown, the present invention provides a urea epoxy curing accelerator, and the structural formula of the urea epoxy curing accelerator is as follows:

[0041]

[0042] Urea epoxy curing accelerators are prepared by esterification reaction of diisocyanate compounds and secondary amine compounds.

[0043] The diisocyanate compound is 1,4-tetramethylene diisocyanate, dimer diisocyanate (DDI), hexamethylene diisocyanate (HDI), isophorone diisocyanate (IPDI), methylene diphenyl diisocyanate (MDI), toluene diisocyanate (TDI), toluidine diisocyanate (TODI), trimethylhexamethylene diisocyanate (TMDI), 2,5- or 2,6-bis-(isocyanatomethyl)-bicyclo[2.2.1]heptane, 1,5-naphthalene diisocyanate (NDI), dicyclohexylmethyl diisocyanate (H12MDI), p-phenylene diisocyanate (PPDI), m-tetramethylxylylene diisocyanate (TMXDI) and dimers thereof;

[0044] The secondary amine compound is any one of dipropylamine, dibutylamine, dipentylamine, dihexylamine, dicyclopentylamine, dicyclohexylamine, diphenylamine and dibenzylamine, which have a boiling point greater than that of dimethylamine and diethylamine at normal pressure.

[0045] The esterification reaction preparation comprises the following steps:

[0046] A: Synthesis of 1,1'-(hexane-1,6-diyl)bis(3,3-diphenylurea)

[0047]

[0048] Dissolve 16.8 g of hexamethylene diisocyanate (0.1 mol) in 250 ml of toluene, add 33.8 g of diphenylamine (0.2 mol), and react at 100°C for 15 h. After the reaction, freeze the mixture and centrifuge to obtain a solid. Wash the solid with a small amount of ice toluene and dry it at about 10°C under vacuum for 2 h to obtain 40 g of a solid with a yield of 80%.

[0049] B: Synthesis of 1,1'-(methylenebis(4,1-phenylene))bis(3,3-dicyclohexylurea)

[0050]

[0051] 25 g of 4,4'-diphenylmethane diisocyanate (0.1 mol) was dissolved in 250 ml of toluene, and 36.2 g of dicyclohexylamine (0.2 mol) was added. The mixture was reacted at 100°C for 15 h. After the reaction, the mixture was frozen and centrifuged to obtain a solid. The solid was washed with a small amount of ice toluene and dried at about 10°C under vacuum for 2 h to obtain 54.9 g of a solid with a yield of 90%.

[0052] C: Synthesis of 1,1′-(methylenebis(4,1-phenylene))bis(3,3-dibutylurea);

[0053]

[0054] 25 g of 4,4'-diphenylmethane diisocyanate (0.1 mol) was dissolved in 250 ml of toluene, and 25.8 g of dibutylamine (0.2 mol) was added. The mixture was reacted at 100°C for 15 h. After the reaction, the mixture was frozen and centrifuged to obtain a solid. The solid was washed with a small amount of ice toluene and dried at about 10°C under vacuum for 2 h to obtain 45 g of a solid with a yield of 90%.

[0055] D: Synthesis of 1,1'-(4-methyl-1,3-phenylene)bis(3,3-dicyclohexylurea);

[0056]

[0057] 17.4 g of toluene-2,4-diisocyanate (0.1 mol) was dissolved in 250 ml of toluene, and 33.8 g of dicyclohexylamine (0.2 mol) was added. The mixture was reacted at 100°C for 15 h. After the reaction, the mixture was frozen and centrifuged to obtain a solid. The solid was washed with a small amount of ice toluene and dried at about 10°C under vacuum for 2 h to obtain 49.5 g of a solid with a yield of 90%.

[0058] E: Synthesis of 1,1'-(4-methyl-1,3-phenylene)bis(3,3-dibutylurea)

[0059]

[0060] 17.4 g of toluene-2,4-diisocyanate (0.1 mol) was dissolved in 250 ml of toluene solution, and 25.8 g of dibutylamine (0.2 mol) was added. The reaction was carried out at 100°C for 15 h. After the reaction, the mixture was frozen and centrifuged to obtain a solid. The solid was washed with a small amount of ice toluene and dried at about 10°C under vacuum for 2 h to obtain 34 g of a solid with a yield of 80%.

[0061] The present invention also provides an epoxy conductive silver paste, which is composed of the following components in percentage:

[0062] 10% to 20% epoxy resin, 0.5% to 3% epoxy curing agent, 0.4% to 3% urea epoxy curing accelerator, 2% to 9% epoxy diluent, 45% to 85% silver powder, 0% to 10% reinforcing agent, 0.05% to 1% silane coupling agent and 0.01% to 1% conductive promoter.

[0063] The present invention also provides a method for preparing epoxy conductive silver paste, comprising the following steps:

[0064] S1. Evenly mix epoxy resin, diluent, and reinforcing agent according to a formula ratio to obtain a mixture A;

[0065] S2. Adding a curing agent, a urea epoxy curing accelerator, a conductive accelerator, and a silane coupling agent to the mixture A in order according to the formula ratio to obtain a colloid B;

[0066] S3. Add metallic silver powder to the obtained colloid B, stir evenly, and then disperse, grind, filter, vacuum degas, and package to obtain epoxy conductive silver glue.

[0067] Example 1:

[0068] The preparation method of epoxy conductive silver paste comprises the following steps:

[0069] S1. Weigh 12 parts by weight of phenol novolac epoxy resin, 2 parts by weight of 4,4'-diaminodiphenyl sulfone, 8 parts by weight of 1,4-butanediol diglycidyl ether, and 2.1 parts by weight of 4,4'-bismaleimidodiphenylmethane in sequence and mix them uniformly in a planetary mixer to obtain a mixture A;

[0070] S2. Then, 0.6 parts by weight of 1,1'-(methylenebis(4,1-phenylene))bis(3,3-dicyclohexylurea), 0.1 parts by weight of KH-560, and 0.2 parts by weight of succinic acid were added to the obtained mixture A, and the mixture was mixed evenly in a planetary mixer to obtain a conductive silver glue matrix B.

[0071] S3. Finally, 75 parts by weight of flaky silver powder is added to the conductive silver paste matrix B prepared above in batches and stirred thoroughly. The mixture is then placed in a three-roll mill for grinding and dispersion. The epoxy conductive silver paste is obtained after filtering, vacuum degassing, and packaging.

[0072] Example 2:

[0073] The preparation method of epoxy conductive silver paste comprises the following steps:

[0074] S1. Weigh 12 parts by weight of a methylphenol novolac epoxy resin, 2 parts by weight of 3,3'-dimethyl-4,4'-diaminobiphenyl, 8 parts by weight of 1,6-hexanediol diglycidyl ether, and 2.1 parts by weight of 4,4'-bismaleimidodiphenylmethane in sequence and mix them uniformly in a planetary mixer to obtain a mixture A.

[0075] S2. Then, 0.6 parts by weight of 1,1'-(hexane-1,6-diyl)bis(3,3-diphenylurea), 0.1 parts by weight of KH-560, and 0.2 parts by weight of adipic acid were added to the obtained mixture A, and the mixture was mixed evenly in a planetary mixer to obtain a conductive silver paste matrix B.

[0076] S3. Finally, 75 parts by weight of flaky silver powder is added to the conductive silver paste matrix B prepared above in batches and stirred thoroughly. The mixture is then placed in a three-roll mill for grinding and dispersion. The epoxy conductive silver paste is obtained after filtering, vacuum degassing, and packaging.

[0077] Example 3:

[0078] The preparation method of epoxy conductive silver paste comprises the following steps:

[0079] S1. Weigh 12 parts by weight of bisphenol A novolac epoxy resin, 2 parts by weight of 4,4'-bis(4-aminophenoxy)diphenyl ether, 8 parts by weight of 1,4-butanediol diglycidyl ether, and 2.1 parts by weight of 4,4'-bismaleimido diphenyl ether in sequence and mix them uniformly in a planetary mixer to obtain a mixture A.

[0080] S2. Then, 0.6 parts by weight of 1,1'-(methylenebis(4,1-phenylene))bis(3,3-dibutylurea), 0.1 parts by weight of KH-560, and 0.2 parts by weight of succinic acid were added to the obtained mixture A, and the mixture was further mixed in a planetary mixer to obtain a conductive silver paste matrix B.

[0081] S3. Finally, 75 parts by weight of flaky silver powder is added to the conductive silver paste matrix B prepared above in batches and stirred thoroughly. The mixture is then placed in a three-roll mill for grinding and dispersion. The epoxy conductive silver paste is obtained after filtering, vacuum degassing, and packaging.

[0082] Comparative Example 1:

[0083] The preparation method of epoxy conductive silver paste comprises the following steps:

[0084] S1. Weigh 12 parts by weight of phenol novolac epoxy resin, 2 parts by weight of 4,4'-diaminodiphenyl sulfone, 8 parts by weight of 1,4-butanediol diglycidyl ether, and 2.1 parts by weight of 4,4'-bismaleimidodiphenylmethane in sequence and mix them uniformly in a planetary mixer to obtain a mixture A;

[0085] S2. Then, 0.6 parts by weight of 1,1'-(4-methyl-m-phenylene)bis(3,3-dimethylurea), 0.1 parts by weight of KH-560, and 0.2 parts by weight of succinic acid were added to the obtained mixture A, and the mixture was further mixed in a planetary mixer to obtain a conductive silver glue matrix B.

[0086] S3. Finally, 75 parts by weight of flaky silver powder is added to the conductive silver paste matrix B prepared above in batches and stirred thoroughly. The mixture is then placed in a three-roll mill for grinding and dispersion. The epoxy conductive silver paste is obtained after filtering, vacuum degassing, and packaging.

[0087] Comparative Example 2:

[0088] The preparation method of epoxy conductive silver paste comprises the following steps:

[0089] S1. Weigh 12 parts by weight of phenol novolac epoxy resin, 2 parts by weight of 4,4'-diaminodiphenyl sulfone, 8 parts by weight of 1,4-butanediol diglycidyl ether, and 2.1 parts by weight of 4,4'-bismaleimidodiphenylmethane in sequence and mix them uniformly in a planetary mixer to obtain a mixture A;

[0090] S2. Then, 0.6 parts by weight of 1,1-dimethyl-3-phenylurea, 0.1 parts by weight of KH-560, and 0.2 parts by weight of succinic acid were added to the obtained mixture A, and the mixture was mixed evenly in a planetary mixer to obtain a conductive silver paste matrix B.

[0091] S3. Finally, 75 parts by weight of flaky silver powder is added to the conductive silver paste matrix B prepared above in batches and stirred thoroughly. The mixture is then placed in a three-roll mill for grinding and dispersion. The epoxy conductive silver paste is obtained after filtering, vacuum degassing, and packaging.

[0092] Comparative Example 3:

[0093] The preparation method of epoxy conductive silver paste comprises the following steps:

[0094] S1. Weigh 12 parts by weight of phenol novolac epoxy resin, 2 parts by weight of 4,4'-diaminodiphenyl sulfone, 8 parts by weight of 1,4-butanediol diglycidyl ether, and 2.1 parts by weight of 4,4'-bismaleimidodiphenylmethane in sequence and mix them uniformly in a planetary mixer to obtain a mixture A;

[0095] S2. Then, 0.6 parts by weight of 3-(3,4-dichlorobenzene)-1,1-dimethylurea, 0.1 parts by weight of KH-560, and 0.2 parts by weight of succinic acid were added to the obtained mixture A, and the mixture was mixed evenly in a planetary mixer to obtain a conductive silver glue matrix B.

[0096] S3. Finally, 75 parts by weight of flaky silver powder is added to the conductive silver paste matrix B prepared above in batches and stirred thoroughly. The mixture is then placed in a three-roll mill for grinding and dispersion. The epoxy conductive silver paste is obtained after filtering, vacuum degassing, and packaging.

[0097]

[0098] The epoxy conductive silver paste prepared in Examples 1, 2, and 3 of the present invention was subjected to a number of tests and analyses, including measuring its viscosity using a cone-plate viscometer at 5 rpm at 25°C, measuring horizontal shear force using a Dage 4000, measuring its volume resistivity using a four-probe method, measuring chloride ion content by ion chromatography, and testing for the presence of voids using an X-ray method.

[0099] The results of X-ray void measurement showed that there were many voids in the glue in Comparative Examples 1, 2, and 3, while almost no voids were found in Examples 1, 2, and 3 of the present invention. The dimethylamine released by the organic urea in Comparative Examples 1, 2, and 3 at high temperature volatilized rapidly, forming a large number of voids. The uncured organic phase could fill some of the voids, while the cured organic phase lost its fluidity and could not fill the voids, forming voids. In the X-ray photographs of Comparative Examples 1, 2, and 3, several channels were punched out in the glue layer below the edges of the chip, and there were many voids. The dicyclohexylamine released by the organic urea in Examples 1, 2, and 3 of the present invention had a higher boiling point than dimethylamine, and most of it participated in the curing reaction, with very little gas volatilization. Therefore, no voids were detected in the glue layer below the edge of the chip.

[0100] Obviously, those skilled in the art may make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if such changes and modifications fall within the scope of the claims and their equivalents, the present invention is intended to include such changes and modifications.

Claims

1. A urea-based epoxy curing accelerator is used to reduce adhesive layer voids and improve chip bonding reliability in the preparation of epoxy conductive silver adhesive, characterized in that: The epoxy conductive silver paste is composed of the following components by mass percentage: 10% to 20% epoxy resin, 0.5% to 3% epoxy curing agent, 0.4% to 3% urea epoxy curing accelerator, 2% to 9% epoxy diluent, 75% to 85% silver powder, 0% to 10% reinforcing agent, 0.05% to 1% silane coupling agent and 0.01% to 1% conductive accelerator; the epoxy curing agent is an aromatic diprimary amine, and the reinforcing agent is bismaleimide; The reaction formula of the urea epoxy curing accelerator is as follows: The urea epoxy curing accelerator is prepared by esterification of a diisocyanate compound and a secondary amine compound; The secondary amine compound is any one of dipentylamine, dihexylamine, dicyclopentylamine, diphenylamine and dibenzylamine, which has a boiling point greater than that of dimethylamine and diethylamine at normal pressure; The diisocyanate compound is 1,4-tetramethylene diisocyanate, dimer acid diisocyanate, hexamethylene diisocyanate, isophorone diisocyanate, methylene diphenyl diisocyanate, tolidine diisocyanate, trimethyl hexamethylene diisocyanate, 2,5- or 2,6-bis-(isocyanatomethyl)-bicyclo[2.2.1]heptane, 1,5-naphthalene diisocyanate, dicyclohexylmethyl diisocyanate, p-phenylene diisocyanate, m-tetramethylxylylene diisocyanate and dimers thereof; The bismaleimide is one of 4,4'-bismaleimidodiphenylmethane and 4,4'-bismaleimidodiphenyl ether or a mixture of the two.

2. The use of a urea-based epoxy curing accelerator as claimed in claim 1 in the preparation of epoxy conductive silver adhesive to reduce adhesive layer voids and improve chip bonding reliability, characterized in that: The epoxy resin is any one of bisphenol A epoxy resin, bisphenol F epoxy resin, bisphenol S epoxy resin, phenol novolac epoxy resin, methylphenol novolac epoxy resin, bisphenol A linear novolac epoxy resin, biphenyl epoxy resin, naphthalene epoxy resin, aralkyl epoxy resin, alicyclic epoxy resin, trifunctional epoxy resin and tetrafunctional epoxy resin, or a combination of at least any two thereof, and the halogen content of the epoxy resin is less than 100 ppm.

3. The use of the urea epoxy curing accelerator according to any one of claims 1 to 2 in the preparation of epoxy conductive silver adhesive to reduce adhesive layer voids and improve chip bonding reliability, characterized in that: The epoxy diluent is 1,6-hexanediol diglycidyl ether, neopentyl glycol diglycidyl ether, 1,4-butanediol diglycidyl ether, ethylene glycol diglycidyl ether, and polyethylene glycol diglycidyl ether. The purity of the epoxy diluent is greater than 90%, and the halogen content is not greater than 200 ppm. The silver powder is a combination of flaky metal silver powder and spherical metal silver powder, and the size of the metal silver powder is 0.1-10 μm.

4. Use of the urea epoxy curing accelerator according to any one of claims 1 to 2 in the preparation of epoxy conductive silver adhesive to reduce adhesive layer voids and improve chip bonding reliability, characterized in that: The silane coupling agent is one or any combination of KH-550, KH-560, KH-570 and KH792.

5. Use of the urea epoxy curing accelerator according to any one of claims 1 to 2 in the preparation of epoxy conductive silver adhesive to reduce voids in the adhesive layer and improve chip bonding reliability, wherein the conductive accelerator is any one of succinic acid, glutaric acid, and adipic acid, or a mixture of succinic acid, glutaric acid, and adipic acid in an amount of 100%.

6. Use of the urea epoxy curing accelerator according to any one of claims 1 to 2 in preparing epoxy conductive silver paste to reduce voids in the adhesive layer and improve chip bonding reliability, wherein the preparation method of the epoxy conductive silver paste comprises the following steps: S1. Evenly mix epoxy resin, epoxy diluent, and reinforcing agent according to a formula ratio to obtain a mixture A; S2. Adding an epoxy curing agent, a urea epoxy curing accelerator, a conductive accelerator, and a silane coupling agent to the mixture A in order according to the formula ratio to obtain a colloid B; S3. Add metallic silver powder to the obtained colloid B, stir evenly, and then disperse, grind, filter, vacuum degas, and package to obtain epoxy conductive silver glue.

7. The use of the urea epoxy curing accelerator according to claim 6 in the preparation of epoxy conductive silver glue to reduce voids in the glue layer and improve chip bonding reliability, characterized in that: In S3 of the preparation method of the epoxy conductive silver paste, the metallic silver powder is added in batches or all at once, the dispersion and grinding process is carried out in a three-roller grinder, and the preparation environment temperature of S1, S2 and S3 is room temperature.

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