Conductive adhesive for epoxy mounting and preparation method thereof

Abstract

The invention discloses a conductive adhesive for epoxy mounting and a preparation method of the conductive adhesive. The conductive adhesive comprises the following raw material components in percentage by mass: 10-15% of epoxy resin; 0.7 to 1% of a blocked isocyanate prepolymer; 2-5% of an amine curing agent; 1-5% of a silane coupling agent; and 75-85% of an inorganic conductive filler. By accurately controlling the proportion of the components and strictly selecting the types of the components, the structural adhesive can keep higher adhesive strength, excellent conductivity, sufficient operation time and good chip bonding strength in a working environment, and can meet the use requirements of the current chip bonding process.

Description

Technical Field

[0001] The invention belongs to the technical field of adhesives and relates to a conductive adhesive, in particular to a conductive adhesive for epoxy mounting and a preparation method thereof. Background Art

[0002] Epoxy patch is to form an interconnection, electrical and thermal conductor between the chip and the carrier through epoxy resin conductive glue (conductive glue doped with gold or silver). The metal content of the doped glue determines the quality of its electrical and thermal conductivity. Silver-doped epoxy resin pasting method is the most widely used chip mounting method today. Silver-doped conductive glue is an adhesive with certain conductive properties after curing or drying. It usually has a base resin and a conductive filler (i.e., conductive particles) as the main components. The conductive particles are combined together through the bonding effect of the base resin to form a conductive path and realize the conductive connection of the bonded materials. Bare chip mounting refers to a method of forming a firm, conductive or insulating connection between a semiconductor chip and a carrier (package shell or substrate). Its purpose is to achieve physical positioning, electrical connection, and provide heat dissipation channels for components, and to achieve mechanical and electrical interconnection between the wafer and the substrate. It is the core process of micro-assembly technology.

[0003] Currently, the commonly used chip mounting methods include epoxy mounting, chip eutectic and flip chip soldering. Silver-containing conductive epoxy resin is widely used to bond transistors, integrated circuit chips, capacitors to substrates and to bond substrates to package shells. In most cases, adhesives are used as the main heat dissipation channel from chip to substrate and substrate to package shell.

[0004] The Chinese invention patent with application number 200910236312.1 discloses an epoxy conductive adhesive and a preparation method thereof. The components of the epoxy conductive adhesive and their mass percentages are: metal particles: 68-72%, promoter: 1-1.5%, epoxy resin: 22-25%, curing agent: 1-2%, coupling agent: 2-3% and antioxidant: 1-2%. The antioxidant is first dissolved and dispersed in a mixture of coupling agent and promoter, then added to epoxy resin and stirred evenly, metal particles are added and dispersed evenly, and finally curing agent is added and stirred evenly to obtain epoxy conductive adhesive. The conductive adhesive obtained has good bonding performance, conductive performance and wet heat stability. However, the operating time of the epoxy conductive adhesive is relatively short (usually within 8 hours), and it is not suitable for adhesive requirements of complex size, multi-layer stacking and other variable processes. Summary of the invention

[0005] In order to solve the above technical problems, the purpose of the present invention is to provide a conductive adhesive for epoxy mounting, which improves the operation time of epoxy resin conductive adhesive and has excellent conductive properties and shear strength after curing.

[0006] In order to achieve the above object, the present invention provides a conductive adhesive for epoxy mounting, which comprises the following raw material components in percentage by mass:

[0007]

[0008]

[0009] Optimally, the epoxy resin is a mixture of one or more selected from bisphenol A epoxy resin, bisphenol F epoxy resin, naphthalene epoxy resin, aminophenol epoxy resin and siloxane epoxy resin. Further, the epoxy resin is a mixture of one or more selected from YDF8170, YDF870GS, EXA-850CRP, 828, HP4032D, JER630, JER630LSD, TSL9906 and ZX1658GS.

[0010] Optimally, the blocked isocyanate prepolymer is prepared according to the following steps:

[0011] Add 2-phenylimidazole and 1,6-hexamethylene diisocyanate into a nitrogen-protected reaction device, then add an organic solvent for stirring, and react at 80°C to 100°C for 3 to 5 hours; when the temperature is lowered to 50°C to 60°C, add an appropriate amount of anhydrous methanol to obtain a first mixture; the molar ratio of the imidazole to the 1,6-hexamethylene diisocyanate is 1.8 to 2.2:1;

[0012] The first mixture is subjected to rotary evaporation to obtain the blocked isocyanate prepolymer; the rotary evaporation temperature is 50° C. to 60° C., and the vacuum degree is -0.2 to 0 MPa.

[0013] Furthermore, the organic solvent is cyclohexane.

[0014] Optimally, the amine curing agent is a latent amine curing agent, which is selected from a mixture of one or more of a dicyandiamide curing agent and a modified aliphatic amine curing agent.

[0015] Furthermore, the amine curing agent is a mixture of one or more selected from EH-226A, EH-257S, EH-433S-4, EH-451K, EH-3895L, EH-485 and Dyhard 100S.

[0016] Optimally, the silane coupling agent is a mixture of one or more selected from coupling agents KH540, KH560, KH570, KH580 and KH792.

[0017] Optimally, the inorganic conductive filler is silver powder, which is a mixture of one or more of irregular-shaped silver powder, spherical silver powder, flaky silver powder and linear silver powder, among which the spherical silver powder K-7418P produced by Metalor is preferred.

[0018] Another object of the present invention is to provide a method for preparing the above-mentioned conductive adhesive for epoxy mounting, comprising the following steps:

[0019] Stirring and mixing the raw material components according to the formula ratio to obtain a preliminary mixed slurry;

[0020] The preliminarily mixed slurry is transferred to a planetary machine for dispersion treatment to obtain a uniform slurry;

[0021] The uniform slurry is subjected to vacuum degassing to obtain the conductive adhesive.

[0022] The conductive adhesive for epoxy mounting of the present invention can improve the structural adhesive to maintain high colloid strength, excellent conductivity, sufficient operating time and good chip bonding strength in a working environment by accurately controlling the ratio of each component and strictly selecting the type of each component, and can meet the use requirements of the current chip bonding process. DETAILED DESCRIPTION

[0023] The conductive adhesive for epoxy mounting of the present invention comprises the following raw material components in percentage by weight: 10-15% epoxy resin; 0.7-1% blocked isocyanate prepolymer; 2-5% amine curing agent; 1-5% silane coupling agent; 75-85% inorganic conductive filler. By accurately controlling the proportion of each component and strictly selecting the type of each component, the structural adhesive can maintain high colloid strength, excellent conductivity, sufficient operating time and good chip bonding strength in the working environment, and can meet the use requirements of the current chip bonding process.

[0024] The epoxy resin is a mixture of one or more selected from bisphenol A epoxy resin, bisphenol F epoxy resin, naphthalene epoxy resin, aminophenol epoxy resin and siloxane epoxy resin. Specifically, it is a mixture of one or more selected from YDF8170, YDF870GS, EXA-850CRP, 828, HP4032D, JER630, JER630LSD, TSL9906 and ZX1658GS. The blocked isocyanate prepolymer is prepared according to the following steps: 2-phenylimidazole and 1,6-hexamethylene diisocyanate are added to a nitrogen-protected reaction device, and then an organic solvent is added for stirring, and the reaction is carried out at 80°C to 100°C for 3 to 5 hours; when the temperature is lowered to 50°C to 60°C, an appropriate amount of anhydrous methanol is added to obtain a first mixture; the molar ratio of the 2-phenylimidazole to the 1,6-hexamethylene diisocyanate is 1.8 to 2.2:1; the first mixture is subjected to rotary evaporation to obtain the blocked isocyanate prepolymer; the rotary evaporation temperature is 50°C to 60°C, and the vacuum degree is -0.2 to 0 MPa. The organic solvent is preferably cyclohexane.

[0025] The amine curing agent is a latent amine curing agent, which is a mixture of one or more selected from dicyandiamide curing agent and modified aliphatic amine curing agent; specifically, a mixture of one or more selected from EH-226A, EH-257S, EH-433S-4, EH-451K, EH-3895L, EH-485 and Dyhard 100S. The silane coupling agent is a mixture of one or more selected from coupling agents KH540, KH560, KH570, KH580 and KH792. The inorganic conductive filler is silver powder, which is a mixture of one or more selected from irregular silver powder, spherical silver powder, flaky silver powder and linear silver powder, wherein the spherical silver powder K-7418P produced by Metalor is preferred.

[0026] The preparation method of the above-mentioned conductive adhesive for epoxy mounting comprises the following steps: stirring and mixing the raw material components according to the formula ratio to obtain a preliminary mixed slurry; transferring the preliminary mixed slurry to a planetary machine for dispersion treatment to obtain a uniform slurry; and vacuum degassing the uniform slurry to obtain the conductive adhesive.

[0027] In order to enable those skilled in the art to better understand the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below in conjunction with the embodiments. Obviously, the described embodiments are only embodiments of a part of the present invention, rather than all embodiments. Based on the embodiments of the present invention, all other embodiments obtained under the premise of equivalent changes and modifications made by ordinary technicians in the field should belong to the scope of protection of the present invention.

[0028] Example 1

[0029] This embodiment provides a blocked isocyanate prepolymer and a preparation method thereof, which are specifically as follows:

[0030] Add 2-phenylimidazole (28.8 g) and 1,6-hexamethylene diisocyanate (16.8 g, purchased from Anaiji) into a nitrogen-protected reaction device (the molar ratio of 2-phenylimidazole to 1,6-hexamethylene diisocyanate is 2:1), add solvent cyclohexane (50 ml), stir evenly, and react at 80°C to 100°C (this numerical range has little effect on the performance of the product, the same below) for 3 to 5 hours;

[0031] When the reaction temperature is controlled to drop to 50°C to 60°C, an appropriate amount of anhydrous methanol (100 ml) is added dropwise to the aforementioned reaction device to ensure that all isocyanate groups react completely to obtain a first mixture;

[0032] The first mixture was transferred to a rotary evaporator, and under the conditions of a vacuum degree of -0.1 MPa (measured by a commercial vacuum gauge) and 60° C., excess solvents of cyclohexane and methanol were removed, the vacuum was removed, and the temperature was lowered to obtain a blocked isocyanate prepolymer.

[0033] Comparative Example 1

[0034] This example provides a blocked isocyanate prepolymer and a preparation method thereof, which is basically the same as that in Example 1, except that 2-phenylimidazole is not used.

[0035] Example 2

[0036] This embodiment provides a conductive adhesive for epoxy mounting (specifically, a conductive adhesive with a long operating time applied to epoxy mounting (Die Attach)) and a preparation method thereof, as follows:

[0037] 11.3 g of epoxy resin (YDF870GS (Nippon Steel)), 0.7 g of blocked isocyanate prepolymer (in Example 1), 2 g of amine curing agent (Dyhard 100S), 1 g of silane KH560 coupling agent and 85 g of spherical silver powder (Metall, spherical silver powder K-7418P) were preliminarily mixed to obtain a preliminarily mixed slurry;

[0038] The preliminary mixed slurry is transferred to a planetary machine for dispersion treatment to obtain a uniform slurry; then vacuum degassing and cooling are performed.

[0039] Example 3

[0040] The present embodiment provides a conductive adhesive for epoxy mounting (specifically, a conductive adhesive with a long operating time used for epoxy mounting (Die Attach)) and a preparation method thereof, which is basically the same as that in Example 2, except that: 14g of epoxy resin, 1g of blocked isocyanate prepolymer, 5g of amine curing agent, 5g of KH560 silane coupling agent and 75g of silver powder filler are preliminarily mixed.

[0041] Example 4

[0042] This embodiment provides a conductive adhesive for epoxy mounting (specifically, a conductive adhesive with a long operating time used for epoxy mounting (Die Attach)) and a preparation method thereof, which is basically the same as that in Example 2, except that: 12.2 g of epoxy resin, 0.8 g of blocked isocyanate prepolymer, 4 g of amine curing agent, 3 g of KH560 silane coupling agent and 80 g of silver powder filler are preliminarily mixed.

[0043] Example 5

[0044] This embodiment provides a conductive adhesive for epoxy mounting (specifically, a conductive adhesive with a long operating time used for epoxy mounting (Die Attach)) and a preparation method thereof, which is basically the same as that in Example 2, except that the epoxy resin uses another brand, specifically EXA-850CRP (DIC Corporation).

[0045] Example 6

[0046] This embodiment provides a conductive adhesive for epoxy mounting (specifically, a conductive adhesive with a long operating time used for epoxy mounting (Die Attach)) and a preparation method thereof, which is basically the same as that in Example 2, except that the epoxy resin uses another brand, specifically JER630LSD (Mitsubishi Chemical).

[0047] Example 7

[0048] This embodiment provides a conductive adhesive for epoxy mounting (specifically, a conductive adhesive with a long operating time used for epoxy mounting (Die Attach)) and a preparation method thereof, which is basically the same as that in Example 2, except that the epoxy resin uses another brand, specifically TSL9906 (Momentive Performance).

[0049] Comparative Example 2

[0050] This example provides a conductive adhesive for epoxy mounting (specifically a conductive adhesive with a long operating time used for epoxy mounting (Die Attach)) and a preparation method thereof, which is basically the same as that in Example 2, except that the silver powder filler is excessive, reaching 100g.

[0051] Comparative Example 3

[0052] This example provides a conductive adhesive for epoxy mounting (specifically a conductive adhesive with a long operating time used for epoxy mounting (Die Attach)) and a preparation method thereof, which is basically the same as that in Example 2, except that the silver powder filler is insufficient, which is 60g.

[0053] Comparative Example 4

[0054] This example provides a conductive adhesive for epoxy mounting (specifically a conductive adhesive with a long operating time used for epoxy mounting (Die Attach)) and a preparation method thereof, which is basically the same as that in Example 2, except that the blocked isocyanate prepolymer in Comparative Example 1 is used.

[0055] Comparative Example 5

[0056] This example provides a conductive adhesive for epoxy mounting (specifically a conductive adhesive with a long operating time used for epoxy mounting (Die Attach)) and a preparation method thereof, which is basically the same as that in Example 2, except that no epoxy resin is used.

[0057] Example 6

[0058] This example provides a conductive adhesive for epoxy mounting, which is a mature product on the market, and its brand name is Loctite S84-1.

[0059] The conductive adhesives in Examples 2-7 and Comparative Examples 2-6 were subjected to various performance tests, and the results are shown in Table 1.

[0060] Table 1 Test results of conductive adhesive in Examples 2-7 and Comparative Examples 2-6 (curing conditions: 180°C x 10 min)

[0061]

[0062]

[0063] The conductive adhesives in the embodiments and comparative examples in Table 1 were tested as follows:

[0064] Viscosity (25°C, cps): Test standard ASTM D 2196-1999;

[0065] Hardness (25℃, g / cm 3 );Test standard GB / T 531-1999;

[0066] Operating time (25) days: ASTM D 2196-1999;

[0067] 50℃ surface drying time (h): Put 2g of glue in the egg tart cup and observe the gel time of the colloid at 50℃;

[0068] Wafer shear force (2×2mm Si die, kgf): test standard GB / T7124-08;

[0069] Shear strength (MPa): Test standard GB / T7124-08;

[0070] Volume resistivity (Ω·m): Test standard GB / T26074-2010.

[0071] By comparing the data of Examples 2-4 in Table 1, it can be seen that: when different contents of the raw materials are combined, the conductive adhesive has different performance parameters, and the product of Example 2 is better than the products of Examples 3 and 4. By comparing the data of Examples 2 and 5-7 in Table 1, it can be seen that: the type of epoxy resin will also have a great impact on the product performance of the conductive adhesive. When the product with the brand name EXA-850CRP is selected, the performance of the conductive adhesive is optimal. When the epoxy resin is missing and the blocked isocyanate prepolymer in Comparative Example 1 is used, the product cannot be cured. Compared with mature commercial products (Comparative Example 6), the performance of the product of this application is not inferior, and even has obvious advantages in some performance (such as PCB / PCB shear strength).

[0072] The above description is only a preferred embodiment of the present invention and is not intended to limit the scope of protection of the present invention. At the same time, the above description should be understandable and implementable for those with ordinary knowledge in the relevant technical field. Therefore, other equivalent changes or modifications that do not deviate from the concepts disclosed in the present invention should be included in the scope of protection of the present invention.

Claims

1. A conductive adhesive for epoxy mounting, characterized in that: It includes the following raw material components in percentage by mass: Epoxy resin 10~15%; Blocked isocyanate prepolymer 0.7~1%; Amine curing agent 2~5%; Silane coupling agent 1~5%; Inorganic conductive filler 75~85%.

2. The conductive adhesive for epoxy mounting according to claim 1, characterized in that: The epoxy resin is a mixture of one or more selected from bisphenol A epoxy resin, bisphenol F epoxy resin, naphthalene epoxy resin, aminophenol epoxy resin and siloxane epoxy resin.

3. The conductive adhesive for epoxy mounting according to claim 2, characterized in that: The epoxy resin is a mixture of one or more selected from YDF8170, YDF870GS, EXA-850CRP, 828, HP4032D, JER630, JER630LSD, TSL9906 and ZX1658GS.

4. The conductive adhesive for epoxy mounting according to claim 1, characterized in that: The blocked isocyanate prepolymer is prepared according to the following steps: Add 2-phenylimidazole and 1,6-hexamethylene diisocyanate into a nitrogen-protected reaction device, then add an organic solvent for stirring, and react at 80°C-100°C for 3-5 hours; when the temperature is lowered to 50°C-60°C, add an appropriate amount of anhydrous methanol to obtain a first mixture; the molar ratio of the 2-phenylimidazole to the 1,6-hexamethylene diisocyanate is 1.8-2.2:1; The first mixture is subjected to rotary evaporation to obtain the blocked isocyanate prepolymer; the rotary evaporation temperature is 50° C. to 60° C., and the vacuum degree is -0.2 to 0 MPa.

5. The conductive adhesive for epoxy mounting according to claim 4, characterized in that: The organic solvent is cyclohexane.

6. The conductive adhesive for epoxy mounting according to claim 1, characterized in that: The amine curing agent is a latent amine curing agent, which is selected from a mixture of one or more of a dicyandiamide curing agent and a modified aliphatic amine curing agent.

7. The conductive adhesive for epoxy mounting according to claim 6, characterized in that: The amine curing agent is a mixture of one or more selected from EH-226A, EH-257S, EH-433S-4, EH-451K, EH-3895L, EH-485 and Dyhard 100S.

8. The conductive adhesive for epoxy mounting according to claim 1, characterized in that: The silane coupling agent is a mixture of one or more selected from coupling agents KH540, KH560, KH570, KH580 and KH792.

9. The conductive adhesive for epoxy mounting according to claim 1, characterized in that: The inorganic conductive filler is silver powder, which is a mixture of one or more of irregular-shaped silver powder, spherical silver powder, flaky silver powder and linear silver powder.

10. The method for preparing the conductive adhesive for epoxy mounting according to any one of claims 1 to 9, characterized in that: The following steps are involved: Stirring and mixing the raw material components according to the formula ratio to obtain a preliminary mixed slurry; The preliminary mixed slurry is transferred to a planetary machine for dispersion treatment to obtain a uniform slurry; The uniform slurry is subjected to vacuum degassing to obtain the conductive adhesive.

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