Epoxy Adhesive Compositions and Their Preparation Methods, Preforming Materials and Cavity Encapsulation Structures

Abstract

This invention relates to an epoxy adhesive composition, its preparation method, preformed material, and cavity encapsulation structure. The epoxy adhesive composition comprises the following raw materials in parts by weight: 100 parts liquid epoxy resin; 20 to 300 parts thermoplastic resin powder; a latent curing agent, wherein the ratio of the active hydrogen equivalent of the latent curing agent to the sum of the epoxy equivalents of the liquid epoxy resin and the thermoplastic resin powder is 0.6 to 1.4; and 0.1 to 5 parts adhesion promoter. The softening point of the liquid epoxy resin is T1, the softening point of the thermoplastic resin powder is T2, and the curing temperature of the latent curing agent is T3, satisfying T3 > T2 ≥ (T1 + 30°C). This epoxy adhesive composition can be preformed, exhibits excellent high-temperature resistance, and demonstrates good adhesion. Products bonded with this epoxy resin exhibit good airtightness.

Description

Technical Field

[0001] This invention relates to the technical field of adhesives, and in particular to an epoxy adhesive composition, its preparation method, preform material, and cavity encapsulation structure. Background Technology

[0002] One-component epoxy adhesives are a type of engineering adhesive formulated from epoxy resin, latent curing agents, and other additives. They have advantages such as good adhesion, simple bonding process, low curing shrinkage, good fatigue resistance, and relatively low price. They are also easier to use than two-component epoxy resins, can be stored for a long time, and are widely used in industries such as machinery manufacturing, electronic equipment, building decoration, and aerospace.

[0003] Cavity packaging is a widely used chip packaging structure, consisting of a base and a cap. While ensuring hermeticity and stability, the base and cap are bonded together using adhesives. To improve the throughput and yield of cavity packaging structures and reduce the impact of adhesive curing on the quality of the packaged product, the adhesive is typically applied to the cap, pre-formed, and then stored. After other processes are completed, the stored cap with adhesive is then bonded to the base. Therefore, the pre-forming properties of the adhesive have a decisive influence on the appearance and quality of the product under conditions of touch, vacuum, refrigeration, transportation, and storage.

[0004] Furthermore, after encapsulation, the cavity packaging structure needs to be reflow soldered onto printed circuit boards and other electronic devices. Therefore, this structure requires a high degree of airtightness, maintaining good airtightness even after multiple reflow soldering cycles. However, cavity packaging structures using pre-formed one-component epoxy adhesives are prone to airtightness issues after reflow soldering, with frequent air leaks at the adhesive bonding seals, severely impacting the product's airtightness yield. Summary of the Invention

[0005] Therefore, it is necessary to provide an epoxy resin composition that can be preformed and encapsulated with good airtightness, as well as its preparation method, preformed material, and cavity encapsulation structure.

[0006] The above-mentioned objective of this invention is achieved through the following technical solution:

[0007] In a first aspect, the present invention provides an epoxy adhesive composition comprising the following raw materials in parts by weight:

[0008] 100 parts of liquid epoxy resin; 20 to 300 parts of thermoplastic resin powder; a latent curing agent, wherein the ratio of the active hydrogen equivalent of the latent curing agent to the sum of the epoxy equivalents of the liquid epoxy resin and the thermoplastic resin powder is 0.6 to 1.4; and 0.1 to 5 parts of adhesion promoter.

[0009] The softening point of the liquid epoxy resin is T1, the softening point of the thermoplastic resin powder is T2, and the curing temperature of the latent curing agent is T3, and the conditions T3>T2≥(T1+30℃) are met.

[0010] In one embodiment, the softening point of the thermoplastic resin powder satisfies: 60℃≤T2≤120℃.

[0011] In one embodiment, one or more of the following conditions are met:

[0012] 1) The particle size of the thermoplastic resin powder satisfies: 2μm≤D50≤30μm;

[0013] 2) The particle size of the latent curing agent satisfies: D90≤30μm;

[0014] 3) The viscosity of the epoxy adhesive composition at 25°C and 6 rpm is ≤150 Pa·s.

[0015] In one embodiment, the thermoplastic resin powder is one or more of epoxy resin powder, polyurethane powder, polyacrylic acid powder, and polyamide powder.

[0016] In one embodiment, the latent curing agent is one or more of the following: aromatic polyamine latent curing agents, dicyandiamide latent curing agents, organic hydrazide latent curing agents, organic acid anhydride latent curing agents, imidazole latent curing agents, and Lewis acid latent curing agents.

[0017] In one embodiment, the adhesion promoter is selected from one or more of organosilane adhesion promoters, titanate adhesion promoters, zirconate adhesion promoters, phosphate adhesion promoters, and chromium complex adhesion promoters.

[0018] In one embodiment, the liquid epoxy resin is selected from one or more of bisphenol A epoxy resin, bisphenol F epoxy resin, hydrogenated bisphenol A epoxy resin, hydrogenated bisphenol F epoxy resin, phenolic epoxy resin, o-cresol type epoxy resin, hydantoin epoxy resin, allyl glycidyl ether type epoxy resin, glycidyl amine type epoxy resin, and glycidyl ester type epoxy resin.

[0019] In a second aspect, the present invention provides a method for preparing an epoxy adhesive composition, comprising the following steps: mixing the liquid epoxy resin, the thermoplastic resin powder, the latent curing agent and the adhesion promoter, and stirring at a temperature at least 30°C below T2.

[0020] In a third aspect, the present invention provides a preform material, which is prepared by heating the epoxy resin composition described above at a temperature higher than T2 and lower than T3 for at least 0.5 h and then cooling it.

[0021] In a fourth aspect, the present invention provides a cavity encapsulation structure comprising a lid and a base, wherein the lid is fixedly connected to the base by the epoxy adhesive composition described above.

[0022] This invention, through a rational formulation of liquid epoxy resin, thermoplastic resin powder, latent curing agent, and adhesion promoter, yields an epoxy adhesive composition with excellent high-temperature resistance and good adhesion. The composition is liquid at room temperature. When heated to a temperature higher than the softening point of the thermoplastic resin powder but lower than the curing temperature of the latent curing agent, the thermoplastic resin powder gradually softens and dissolves in the liquid epoxy resin. The linear molecules flow and entangle with each other, but no chemical cross-linking occurs. After heating for a period and then cooling to room temperature, the entangled thermoplastic resin re-hardens and mixes with the liquid epoxy resin to form an elastomer or become a rigid state, thus obtaining a preformed material with good storage stability. Heating this preformed material above the curing temperature of the latent curing agent causes the liquid epoxy resin and the latent curing agent to undergo a cross-linking reaction and gradually cure. Furthermore, the thermoplastic resin can continuously penetrate the epoxy resin network to form a semi-interpenetrating network polymer, thereby improving the adhesion, thermal stability, and toughness of the cured product.

[0023] Compared to solid epoxy resins, the liquid epoxy resin used in this invention contains more adsorption active groups per unit mass, which is beneficial for forming more adhesive bonds at the bonding interface and significantly enhances the interfacial adhesive strength. The introduction of thermoplastic resin powder further enhances the adhesive strength and thermal stability of the colloid itself. Furthermore, the introduction of an adhesion promoter improves the bonding ability of the composition with various substrates, thereby ensuring good airtightness of the epoxy adhesive composition after high-temperature heat treatment such as reflow soldering. At room temperature, no chemical reaction occurs between the components, nor does it undergo layering or agglomeration, exhibiting excellent storage stability. In addition, this composition does not contain any volatile organic compounds, making it environmentally friendly, and it has good flowability, enabling smooth dispensing. Detailed Implementation

[0024] To make the above-mentioned objects, features, and advantages of the present invention more apparent and understandable, specific embodiments of the present invention are described in detail below. Many specific details are set forth in the following description to provide a thorough understanding of the present invention. However, the present invention can be practiced in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of the present invention. Therefore, the present invention is not limited to the specific embodiments disclosed below.

[0025] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains. The terminology used herein in the specification of this invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0026] Terms and definitions:

[0027] One-component epoxy adhesive: also known as one-component epoxy resin adhesive, refers to epoxy resin adhesive in which epoxy resin, latent curing agent and other additives are formulated into the same component. The raw materials do not need to be packaged separately and do not need to be mixed before use.

[0028] Epoxy equivalent: refers to the number of grams of epoxy resin containing 1 equivalent of epoxy groups, that is, the average molecular weight of epoxy resin divided by the number of epoxy groups contained in each molecule, and the unit is g / mol; the amount of curing agent required for epoxy resin curing can be calculated based on the epoxy equivalent.

[0029] Latent curing agents: These are curing agents that, when mixed with epoxy resin, have a certain storage stability at room temperature, but can rapidly undergo a curing reaction under conditions such as heating, light, humidity, and pressure.

[0030] Adhesion promoters: Additives that improve the adhesion between resin and substrate.

[0031] Thermoplastic resins are linear or slightly branched polymers with no intermolecular cross-linking, attracting each other only through van der Waals forces or hydrogen bonds. They have the properties of softening when heated and hardening when cooled. They are solid at room temperature, softening and flowing after being heated under pressure, but do not undergo chemical cross-linking, and their molecular structure remains essentially unchanged during repeated heating. Examples of thermoplastic resins include polyethylene, polypropylene, polyvinyl chloride, polystyrene, polyamide, polyoxymethylene, polycarbonate, polyphenylene ether, and polysulfone.

[0032] Thermosetting resins are high molecular polymer materials whose molecular chains are cross-linked together through chemical reactions to form a rigid three-dimensional network structure. This cross-linked structure cannot be repeatedly processed and molded during the polymerization process. Thermosetting resins include epoxy resins, phenolic resins, unsaturated polyester resins, and silicone resins. Among them, epoxy resin itself is a linear thermoplastic resin, and the cured product obtained by reacting with a curing agent is a thermosetting resin.

[0033] Softening point: This mainly refers to the temperature at which an amorphous polymer begins to soften, and it is related to the polymer's structure and molecular weight.

[0034] D50: Also known as median particle size or median particle size, it refers to the particle size corresponding to the cumulative particle size distribution percentage of a solid material reaching 50%.

[0035] D90: The particle size corresponding to the cumulative particle size distribution number of a solid material reaching 90%.

[0036] The viscosity of the adhesive was determined in accordance with the standard GB / T2794-2013, "Determination of Viscosity of Adhesives by Single-Cylinder Rotation Viscometer". The viscosity of the adhesive at 25°C and 6 rpm was tested using a DV2TRV rotation viscometer (rotor model RV7).

[0037] Reflow soldering: refers to the technique of using solder paste to connect electronic components to contact pads, and then melting the solder paste by controlling the temperature to achieve a permanent bond. It is the most commonly used method in surface mount technology (SMT) to bond electronic components to printed circuit boards. During the entire process, the devices will reach a high temperature of 270°C in a short time.

[0038] Thermal shock test: also known as temperature shock test or high and low temperature shock test, is used to determine the resistance of components to exposure to extreme high and low temperatures, as well as to alternating shocks from extreme high and low temperatures; the test is conducted in accordance with the "Test Methods for Electronic and Electrical Components: Temperature Shock Test" (GJB360.7-87). In cavity packaged applications, the thermal shock test is performed at a test temperature of -65℃ to 150℃ for 1000 cycles.

[0039] Air tightness test: Used to test the sealing effect of the cavity encapsulation structure. The following two test methods can be used: 1) Immerse the cavity encapsulation structure in an oil bath and observe whether bubbles are generated in the oil bath; 2) Add an appropriate amount of red ink to the glue bonding seal and observe whether red ink seeps into the cavity encapsulation structure.

[0040] The cap of a cavity encapsulation structure is typically made of liquid crystal polymer (LCP) material. This material has excellent mechanical strength, can withstand the high-temperature heat treatment of reflow soldering, and has little impact on the electrical performance of the chip. However, LCP material is difficult to bond, which can easily affect the hermeticity of the bond. Furthermore, the cavity encapsulation structure needs to be reflow soldered onto electronic devices after encapsulation, with the highest soldering temperature reaching 270°C. Traditional pre-formable one-component epoxy resins have poor bonding performance and high-temperature resistance, leading to potential hermeticity problems. Based on this, in a first aspect, the present invention provides an epoxy adhesive composition comprising the following raw materials in parts by weight:

[0041] 100 parts of liquid epoxy resin; 20 to 300 parts of thermoplastic resin powder; a latent curing agent, wherein the ratio of the active hydrogen equivalent of the latent curing agent to the sum of the epoxy equivalents of the liquid epoxy resin and the thermoplastic resin powder is 0.6 to 1.4; and 0.1 to 5 parts of adhesion promoter.

[0042] The softening point of the liquid epoxy resin is T1, the softening point of the thermoplastic resin powder is T2, and the curing temperature of the latent curing agent is T3, and the conditions T3>T2≥(T1+30℃) are met.

[0043] This invention, through a rational formulation of liquid epoxy resin, thermoplastic resin powder, latent curing agent, and adhesion promoter, yields an epoxy adhesive composition with excellent high-temperature resistance and good adhesion. The composition is liquid at room temperature. When heated to a temperature higher than the softening point of the thermoplastic resin powder but lower than the curing temperature of the latent curing agent, the thermoplastic resin powder gradually softens and dissolves in the liquid epoxy resin. The linear molecules flow and entangle with each other, but no chemical cross-linking occurs. After heating for a period and then cooling to room temperature, the entangled thermoplastic resin re-hardens and mixes with the liquid epoxy resin to form an elastomer or become a rigid state, thus obtaining a preformed material with good storage stability. Heating this preformed material above the curing temperature of the latent curing agent causes the liquid epoxy resin and the latent curing agent to undergo a cross-linking reaction and gradually cure. Furthermore, the thermoplastic resin can continuously penetrate the epoxy resin network to form a semi-interpenetrating network polymer, thereby improving the adhesion, thermal stability, and toughness of the cured product.

[0044] The liquid epoxy resin used in this invention has a lower epoxy equivalent than the solid epoxy resin, and contains more adsorption active groups per unit mass, which is beneficial for forming more adhesive bonds at the bonding interface, significantly enhancing the interfacial adhesive strength. The introduction of thermoplastic resin powder further enhances the adhesive strength and thermal stability of the colloid itself. Furthermore, the introduction of an adhesion promoter improves the bonding ability of the composition with various substrates, thereby ensuring good airtightness of the epoxy adhesive composition after high-temperature heat treatment such as reflow soldering. At room temperature, no chemical reaction occurs between the components, nor does it undergo layering or agglomeration, exhibiting excellent storage stability. In addition, this composition does not contain any volatile organic compounds, making it environmentally friendly, and it has good flowability, enabling smooth dispensing.

[0045] Understandably, liquid epoxy resin is an epoxy resin that is a viscous liquid at room temperature, typically with an epoxy equivalent of ≥40 g / mol.

[0046] Understandably, room temperature refers to room temperature or general temperature, which ranges from 20℃ to 30℃.

[0047] In some embodiments, the epoxy equivalent of the liquid epoxy resin is 160 g / mol to 300 g / mol.

[0048] Because liquid epoxy resin has a lower epoxy equivalent, it means that for the same mass, liquid epoxy resin has more epoxy groups than solid epoxy resin, resulting in more adsorption active groups exposed at the bonding interface. This facilitates the formation of more adhesion bonds at the bonding interface, significantly enhancing the bonding strength of the interface.

[0049] In some embodiments, the softening point of the thermoplastic resin powder satisfies: 60℃≤T2≤120℃.

[0050] When the softening point of the thermoplastic resin powder is between 60℃ and 120℃, the raw materials can be mixed at room temperature or low temperature to obtain a composition in which the thermoplastic resin powder, latent curing agent and adhesion promoter are uniformly dispersed in liquid epoxy resin. The composition can also be heated at medium temperature to preform the epoxy resin composition. This is beneficial to improve the production capacity and yield of the product and reduce the energy consumption in the preparation and preforming process of the epoxy resin composition.

[0051] In some preferred embodiments, the softening point of the thermoplastic resin powder satisfies: 90℃≤T2≤120℃.

[0052] In some implementations, one or more of the following conditions are met:

[0053] 1) The particle size of the thermoplastic resin powder satisfies: 2μm≤D50≤30μm;

[0054] 2) The particle size of the latent curing agent satisfies: D90≤30μm;

[0055] 3) The viscosity of the epoxy adhesive composition at 25°C and 6 rpm is ≤150 Pa·s.

[0056] The median particle size of the thermoplastic resin powder and the D90 particle size of the latent curing agent are both less than 30 μm, which is beneficial to improving its dispersion stability and dispersion uniformity in liquid epoxy resin. It can be stored at low temperature for 6 months without agglomeration and precipitation.

[0057] In some embodiments, the thermoplastic resin powder is one or more of epoxy resin powder, polyurethane powder, polyacrylic acid powder, and polyamide powder.

[0058] Epoxy resin powder can undergo a curing reaction with active hydrogen in a latent curing agent along with liquid epoxy resin at a certain temperature, which helps to improve the adhesion and flexibility of the cured product of the composition. Thermoplastics such as polyurethane, polyacrylic acid and polyamide can continuously penetrate the epoxy resin network to form a semi-interpenetrating network polymer, thereby improving the adhesion, thermal stability and toughness of the cured product of the composition.

[0059] In some preferred embodiments, the thermoplastic resin powder is bisphenol A epoxy resin powder.

[0060] In some embodiments, the latent curing agent is one or more of the following: aromatic polyamine latent curing agents, dicyandiamide latent curing agents, organic hydrazide latent curing agents, organic acid anhydride latent curing agents, imidazole latent curing agents, and Lewis acid latent curing agents.

[0061] Aromatic polyamine latent curing agents, dicyandiamide latent curing agents, organic hydrazide latent curing agents, organic acid anhydride latent curing agents, imidazole latent curing agents, and Lewis acid latent curing agents are all high-temperature curing agents, with curing temperatures all above 100℃. Among these high-temperature curing agents, latent curing agents with curing temperatures higher than T2 and suitable curing times can be selected.

[0062] In some embodiments, the latent curing agent is one or more of 2,4'-diaminodiphenylmethane, 4,4'-diaminodiphenyl sulfone, dicyandiamide, and sebacate dihydrazide.

[0063] In some preferred embodiments, the latent curing agent is 4,4'-diaminodiphenyl sulfone.

[0064] Among them, 4,4'-diaminodiphenyl sulfone is cured by heating at 110℃~200℃ for 2h~4h, and has excellent chemical and thermal stability.

[0065] In some embodiments, the adhesion promoter is selected from one or more of organosilane adhesion promoters, titanate adhesion promoters, zirconate adhesion promoters, phosphate adhesion promoters, and chromium complex adhesion promoters.

[0066] The introduction of adhesion promoters can significantly improve the adhesion between the adhesive and the substrate, solving the problem of poor adhesion of substrates such as LCP materials.

[0067] In some preferred embodiments, the adhesion promoter is 3-glycidyl etheroxypropyltrimethoxysilane and / or 3-(2,3-epoxypropoxy)propyltriethoxysilane.

[0068] In some embodiments, the liquid epoxy resin is selected from one or more of bisphenol A epoxy resin, bisphenol F epoxy resin, hydrogenated bisphenol A epoxy resin, hydrogenated bisphenol F epoxy resin, phenolic epoxy resin, o-cresol type epoxy resin, hydantoin epoxy resin, allyl glycidyl ether type epoxy resin, glycidyl amine type epoxy resin, and glycidyl ester type epoxy resin.

[0069] In some preferred embodiments, the liquid epoxy resin is bisphenol A epoxy resin and / or bisphenol F epoxy resin.

[0070] In some embodiments, the composition further includes one or more of a curing accelerator, filler, anti-settling agent, dispersant, and thixotropic agent.

[0071] In a second aspect, the present invention provides a method for preparing the epoxy adhesive composition described above, comprising the following steps: mixing the liquid epoxy resin, the thermoplastic resin powder, the latent curing agent and the adhesion promoter, and stirring at a temperature at least 30°C below T2.

[0072] In some embodiments, the stirring conditions satisfy one or more of the following conditions: 1) the rotation speed is 400 rpm to 1200 rpm; 2) the duration is 20 min to 5 h.

[0073] In a third aspect, the present invention provides a preform material prepared by heating the epoxy resin composition described above at a temperature higher than T2 and lower than T3 for at least 0.5 h.

[0074] In a fourth aspect, the present invention provides a cavity encapsulation structure comprising a lid and a base, wherein the lid is fixedly connected to the base by the epoxy adhesive composition described above.

[0075] In some embodiments, the method for preparing the cavity encapsulation structure is as follows:

[0076] The epoxy adhesive composition is applied to the cap, heated at a temperature higher than T2 and lower than T3 for at least 1 hour, and then cooled to obtain an adhesive cap.

[0077] The adhesive cap is placed on the base and heated at a temperature not lower than T3 for at least 20 minutes to obtain the cavity encapsulation structure.

[0078] The present invention will be further described in detail below with reference to specific embodiments.

[0079] Example 1

[0080] Please refer to Table 1. The epoxy adhesive composition of this embodiment includes the following raw materials in parts by weight: 100 parts of liquid bisphenol A epoxy resin with an epoxy equivalent of 185 g / mol; 50 parts of bisphenol A epoxy resin powder with a softening point of 105 °C and D50 = 5 μm; 33 parts of 4,4'-diaminodiphenyl sulfone with a particle size of 9 μm; and 0.5 parts of 3-(2,3-epoxypropoxy)propyltriethoxysilane.

[0081] The epoxy adhesive composition is prepared as follows: at room temperature, liquid bisphenol A epoxy resin, bisphenol A epoxy resin powder, 33 parts of 4,4'-diaminodiphenyl sulfone and 0.5 parts of 3-(2,3-epoxypropoxy)propyltriethoxysilane are added to a clean dispersion dish, and the mixture is stirred at 1000 rpm for 2 hours to obtain the epoxy adhesive composition.

[0082] Table 1. Raw materials and content of epoxy resin compositions in Examples 1-4

[0083]

[0084] This epoxy adhesive composition exhibits a long shelf life, remaining stable for 6 months under low-temperature conditions ranging from 2℃ to 8℃. The viscosity of this epoxy adhesive composition at 25℃ and 6 rpm, measured using a rotational viscometer, is 120 Pa·s, indicating low viscosity and good flowability under rapid shear. Dispensing performance tests were conducted using a dispensing machine with an LCP cap (Polyplastics E130i) as the substrate. The dispensing machine achieved a capacity of 6 pcs / min, demonstrating smooth dispensing of the epoxy adhesive composition.

[0085] The cap after dispensing the adhesive is heated at 110°C for 1 hour to pre-form the epoxy resin composition. After cooling, the cap with adhesive is obtained. This cap with adhesive can be stored for 1 month at low temperatures of 2°C to 8°C.

[0086] The adhesive cap was fixed to the heat sink base and heated at 5 psi pressure and 180°C for 30 minutes to complete the bonding, thus obtaining the cavity encapsulation structure. The cavity encapsulation structure was then subjected to three reflow soldering cycles, followed by a thermal shock test. The airtightness of the cavity encapsulation structure was tested before, after, and after both the reflow soldering and thermal shock tests. Forty-five cavity encapsulation structures were tested for each airtightness test, and the results of the airtightness yield are shown in Table 2. Table 2 shows that the airtightness yield of the cavity encapsulation structure was 100% before and after reflow soldering, and 98% after both the reflow soldering and thermal shock tests. This indicates that the epoxy adhesive composition has good bonding performance and excellent high-temperature resistance, and the cavity encapsulation structure bonded using this epoxy adhesive composition has good airtightness.

[0087] Table 2. Hermeticity test results of the cavity packaging structures prepared in Examples 1-4 and Comparative Examples 1-3

[0088] Serial Number Before reflow soldering After reflow soldering After reflow soldering and thermal shock testing Example 1 100％ 100％ 98％ Example 2 100％ 95％ 95％ Example 3 100％ 98％ 90％ Example 4 100％ 100％ 90％ Comparative Example 1 99％ 66.7％ 50％ Comparative Example 2 99％ 25％ 15％ Comparative Example 3 99％ 90％ 85％

[0089] Example 2

[0090] The formulation and preparation method of the epoxy adhesive composition in this embodiment are basically the same as those in Example 1, except for the composition and content of the thermoplastic powder. Please refer to Table 1. The epoxy adhesive composition in this embodiment includes the following raw materials in parts by weight: 100 parts of liquid bisphenol A epoxy resin with an epoxy equivalent of 185 g / mol; 100 parts of polyurethane powder with a softening point of 80℃ and D50 = 6 μm; 33 parts of 4,4'-diaminodiphenyl sulfone with a particle size of 9 μm; and 0.5 parts of 3-(2,3-epoxypropoxy)propyltriethoxysilane.

[0091] This epoxy adhesive composition exhibits a long shelf life, remaining stable for 6 months under low-temperature conditions ranging from 2℃ to 8℃. The viscosity of this epoxy adhesive composition at 25℃ and 6 rpm, measured using a rotational viscometer, is 60 Pa·s, indicating low viscosity and good flowability under rapid shear. Dispensing performance tests were conducted using a dispensing machine with an LCP cap (Polyplastics E130i) as the substrate. The dispensing machine achieved a capacity of 6 pcs / min, demonstrating smooth dispensing of the epoxy adhesive composition.

[0092] The cap after dispensing the adhesive is heated at 110°C for 1 hour to pre-form the epoxy resin composition. After cooling, the cap with adhesive is obtained. This cap with adhesive can be stored for 1 month at low temperatures of 2°C to 8°C.

[0093] The adhesive cap was fixed to the heat sink base and heated at 5 psi pressure and 180°C for 30 minutes to complete the bonding, thus obtaining the cavity encapsulation structure. The cavity encapsulation structure was then subjected to three reflow soldering cycles, followed by a thermal shock test. The airtightness of the cavity encapsulation structure was tested before, after, and after both the reflow soldering and thermal shock tests. Forty-five cavity encapsulation structures were tested for each airtightness test, and the results are shown in Table 2. Table 2 shows that the airtightness yield of the cavity encapsulation structure was 100% before reflow soldering, 95% after reflow soldering, and 95% after both the reflow soldering and thermal shock tests. This indicates that the epoxy adhesive composition prepared by blending liquid epoxy resin and polyurethane powder also has good adhesive properties and excellent high-temperature resistance, and the cavity encapsulation structure bonded using this epoxy adhesive composition has good airtightness.

[0094] Example 3

[0095] Please refer to Table 1. The epoxy adhesive composition of this embodiment includes the following raw materials in parts by weight: 100 parts of liquid bisphenol F epoxy resin with an epoxy equivalent of 170 g / mol; 200 parts of polyacrylic acid powder with a softening point of 100°C and D50 = 6 μm; 36 parts of 4,4'-diaminodiphenyl sulfone with a particle size of 9 μm; and 0.5 parts of 3-(2,3-epoxypropoxy)propyltriethoxysilane.

[0096] The composition is prepared as described in Example 1.

[0097] This epoxy adhesive composition exhibits a long shelf life, remaining stable for 6 months under low-temperature conditions ranging from 2℃ to 8℃. The viscosity of this epoxy adhesive composition at 25℃ and 6 rpm, measured using a rotational viscometer, is 90 Pa·s, indicating low viscosity and good flowability under rapid shear. Dispensing performance tests were conducted using a dispensing machine with an LCP cap (Polyplastics E130i) as the substrate. The dispensing machine achieved a capacity of 6 pcs / min, demonstrating smooth dispensing of the epoxy adhesive composition.

[0098] The cap after dispensing the adhesive is heated at 110°C for 1 hour to pre-form the epoxy resin composition. After cooling, the cap with adhesive is obtained. This cap with adhesive can be stored for 1 month at low temperatures of 2°C to 8°C.

[0099] The adhesive cap was fixed to the heat sink base and heated at 5 psi pressure and 180°C for 30 minutes to complete the bonding, thus obtaining the cavity encapsulation structure. The cavity encapsulation structure was then subjected to three reflow soldering cycles, followed by a thermal shock test. The airtightness of the cavity encapsulation structure was tested before, after, and after both the reflow soldering and thermal shock tests. Forty-five cavity encapsulation structures were tested for each airtightness test, and the results are shown in Table 2. Table 2 shows that the airtightness yield of the cavity encapsulation structure was 100% before reflow soldering, 98% after reflow soldering, and 90% after both the reflow soldering and thermal shock tests. This indicates that the epoxy adhesive composition prepared by blending liquid epoxy resin and polyacrylic acid powder also has good adhesive properties and excellent high-temperature resistance, and the cavity encapsulation structure bonded using this epoxy adhesive composition has good airtightness.

[0100] Example 4

[0101] The formulation and preparation method of the epoxy adhesive composition in this embodiment are basically the same as those in Example 3, except for the content of thermoplastic powder and adhesion promoter. Please refer to Table 1. The epoxy adhesive composition in this embodiment includes the following raw materials in parts by weight: 100 parts of liquid bisphenol A epoxy resin with an epoxy equivalent of 170 g / mol; 300 parts of polyacrylic acid powder with a softening point of 110℃ and D50 = 6 μm; 36 parts of 4,4'-diaminodiphenyl sulfone with a particle size of 9 μm; and 1 part of 3-(2,3-epoxypropoxy)propyltriethoxysilane.

[0102] This epoxy adhesive composition exhibits a long shelf life, remaining stable for 6 months at -20°C. The viscosity of this epoxy adhesive composition at 25°C and 6 rpm, measured using a rotational viscometer, is 140 Pa·s, indicating low viscosity and good flowability under rapid shear. Dispensing performance tests were conducted using a dispensing machine with an LCP cap (Polyplastics E130i) as the substrate. The dispensing machine achieved a capacity of 6 pcs / min, demonstrating smooth dispensing of the epoxy adhesive composition.

[0103] The cap after dispensing the adhesive is heated at 110°C for 1 hour to pre-form the epoxy resin composition. After cooling, the adhesive-coated cap is obtained. This adhesive-coated cap can be stored at a low temperature of -20°C for one month.

[0104] The adhesive cap was fixed to the heat sink base and heated at 5 psi pressure and 180°C for 30 minutes to complete the bonding, thus obtaining the cavity encapsulation structure. The cavity encapsulation structure was then subjected to three reflow soldering cycles, followed by a thermal shock test. The airtightness of the cavity encapsulation structure was tested before, after, and after both the reflow soldering and thermal shock tests. Forty-five cavity encapsulation structures were tested for each airtightness test, and the results are shown in Table 2. Table 2 shows that the airtightness yield of the cavity encapsulation structure was 100% before and after reflow soldering, and 90% after both the reflow soldering and thermal shock tests. This indicates that the epoxy adhesive composition prepared by blending liquid epoxy resin and polyacrylic acid powder also has good adhesive properties and excellent high-temperature resistance, and the cavity encapsulation structure bonded using this epoxy adhesive composition has good airtightness. Furthermore, increasing the content of polyacrylic acid powder is beneficial to improving the sealing effect of the cured product of the composition after reflow soldering.

[0105] Comparative Example 1

[0106] Please refer to Table 3. The epoxy adhesive composition of this comparative example comprises the following raw materials in parts by weight: 45 parts prepolymer, 30 parts bisphenol A epoxy resin with an epoxy equivalent of 172 g / mol to 176 g / mol, 15 parts cresol-formaldehyde epoxy resin, 14 parts 2-methoxyethanol, 0.75 parts organosilane ester, 0.9 parts polydimethylsiloxane defoamer, 37 parts quartz powder, 0.3 parts fumed silica, 2 parts dicyandiamide, and 0.2 parts rheology modifier. The above raw materials were mixed and stirred at 1000 rpm for 2 hours to obtain the epoxy adhesive composition.

[0107] The prepolymer was prepared as follows: liquid elastomer-modified epoxy resin (Hanssen EPON 58008), solid bisphenol A epoxy resin (Hanssen EPON 1001F), and toluene diamine (Aladdin D103021) were mixed and heated to 65°C under stirring to form a bisphenol A nitrile rubber copolymer; wherein the mass ratio of elastomer-modified epoxy resin to solid bisphenol A epoxy resin was 2:1, and the ratio of active hydrogen equivalent of toluene diamine to epoxy equivalent was 0.2:1.

[0108] Table 3. Raw materials and content of epoxy resin composition in Comparative Example 1

[0109]

[0110] This epoxy adhesive composition exhibits a long shelf life, remaining stable for 6 months under low-temperature conditions ranging from 2℃ to 8℃. The viscosity of this epoxy adhesive composition at 25℃ and 6 rpm, measured using a rotational viscometer, is 45 Pa·s, indicating low viscosity and good flowability under rapid shear. Dispensing performance tests were conducted using a dispensing machine (Polyplastics E130i) with an LCP cap as the substrate. The dispensing machine achieved a capacity of 6 pcs / min, demonstrating smooth dispensing of the epoxy adhesive composition.

[0111] The cap after dispensing the adhesive is heated at 110°C for 1 hour to pre-form the epoxy resin composition. After cooling, the cap with adhesive is obtained. This cap with adhesive can be stored for 1 month at low temperatures of 2°C to 8°C.

[0112] The adhesive cap was fixed to the heat sink base and heated at 5 psi pressure and 180°C for 30 minutes to complete the bonding, thus obtaining the cavity encapsulation structure. The cavity encapsulation structure was then subjected to three reflow soldering cycles, followed by a thermal shock test. The airtightness of the cavity encapsulation structure was tested before, after, and after both the reflow soldering and thermal shock tests. Forty-five cavity encapsulation structures were tested in each airtightness test, and the results are shown in Table 2. Table 2 shows that the airtightness yield of the cavity encapsulation structure was 99% before reflow soldering, 66.7% after reflow soldering, and 50% after both the reflow soldering and thermal shock tests. This indicates that the adhesive performance of the composition significantly decreased after reflow soldering and thermal shock, resulting in a low airtightness yield of the cavity encapsulation structure.

[0113] Comparative Example 2

[0114] The formulation and preparation method of the epoxy adhesive composition in this comparative example are basically the same as those in Example 1, except that no thermoplastic resin powder is added in this comparative example.

[0115] This epoxy adhesive composition exhibits a long shelf life, remaining stable for 6 months under low-temperature conditions ranging from 2℃ to 8℃. The viscosity of this epoxy adhesive composition at 25℃ and 6 rpm, measured using a rotational viscometer, is 30 Pa·s, indicating low viscosity and good flowability under rapid shear. Dispensing performance tests were conducted using a dispensing machine with an LCP cap (Polyplastics E130i) as the substrate. The dispensing machine achieved a capacity of 6 pcs / min, demonstrating smooth dispensing of the epoxy adhesive composition.

[0116] The cap with adhesive was heated at 110°C for 1 hour and then cooled to room temperature to obtain an adhesive-coated cap. However, the epoxy composition on the adhesive-coated cap remained in a liquid state and could not be semi-cured to form a preformed material, indicating that without the addition of thermoplastic resin powder, the epoxy composition did not have a semi-cured state and could not be made into a preformed material.

[0117] The aforementioned preformable adhesive cap was fixed onto a heat sink base and heated at 5 psi pressure and 180°C for 30 minutes to complete the bonding, thus obtaining a cavity encapsulation structure. This cavity encapsulation structure underwent three reflow soldering cycles, followed by thermal shock testing. The airtightness of the cavity encapsulation structure was tested before, after, and after both reflow soldering and thermal shock tests. Forty-five cavity encapsulation structures were tested for each airtightness test, and the results are shown in Table 2. Table 2 shows that the airtightness yield of the cavity encapsulation structure was 99% before reflow soldering, 25% after reflow soldering, and 15% after both reflow soldering and thermal shock tests. This indicates that the epoxy adhesive composition not only cannot be used to create a preformed material, but also exhibits a sharp decline in adhesive performance under high-temperature conditions, resulting in extremely poor airtightness of the cavity encapsulation structure bonded using this epoxy adhesive composition.

[0118] Comparative Example 3

[0119] The formulation and preparation method of the epoxy adhesive composition in this comparative example are basically the same as those in Example 1, except that no adhesion promoter is added in this comparative example.

[0120] This epoxy adhesive composition exhibits a long shelf life, remaining stable for 6 months under low-temperature conditions ranging from 2℃ to 8℃. The viscosity of this epoxy adhesive composition at 25℃ and 6 rpm, measured using a rotational viscometer, is 120 Pa·s, indicating low viscosity and good flowability under rapid shear. Dispensing performance tests were conducted using a dispensing machine with an LCP cap (Polyplastics E130i) as the substrate. The dispensing machine achieved a capacity of 6 pcs / min, demonstrating smooth dispensing of the epoxy adhesive composition.

[0121] The cap after dispensing the adhesive is heated at 110°C for 1 hour to pre-form the epoxy resin composition. After cooling, the adhesive-coated cap is obtained. This adhesive-coated cap can be stored for 6 months at low temperatures of 2°C to 8°C.

[0122] The adhesive cap was fixed to the heat sink base and heated at 5 psi pressure and 180°C for 30 minutes to complete the bonding, thus obtaining the cavity encapsulation structure. The cavity encapsulation structure was then subjected to three reflow soldering cycles, followed by a thermal shock test. The airtightness of the cavity encapsulation structure was tested before, after, and after both the reflow soldering and thermal shock tests. Forty-five cavity encapsulation structures were tested in each airtightness test, and the results are shown in Table 2. Table 2 shows that the airtightness yield of the cavity encapsulation structure was 99% before reflow soldering, 90% after reflow soldering, and 85% after both the reflow soldering and thermal shock tests. This indicates that without adhesion additives, the adhesive ability of this epoxy composition decreased after high-temperature heat treatment and extreme high- and low-temperature shocks, and the airtightness of the cavity encapsulation structures bonded using this epoxy composition was significantly reduced.

[0123] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0124] The embodiments described above are merely illustrative of several implementations of the present invention, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these all fall within the protection scope of the present invention. Therefore, the protection scope of this invention patent should be determined by the appended claims, and the specification can be used to interpret the content of the claims.

Claims

1. A preformed material, characterized in that, It is prepared by heating an epoxy resin composition at a temperature higher than T2 and lower than T3 for at least 0.5 hours, followed by cooling. The epoxy resin composition comprises the following raw materials in parts by weight: 100 parts of liquid epoxy resin; 50 to 300 parts of thermoplastic resin powder; a latent curing agent, wherein the ratio of the active hydrogen equivalent of the latent curing agent to the sum of the epoxy equivalents of the liquid epoxy resin and the thermoplastic resin powder is 0.6 to 1.4; and 0.1 to 5 parts of adhesion promoter. Wherein, the softening point of the liquid epoxy resin is T1, the softening point of the thermoplastic resin powder is T2, and the curing temperature of the latent curing agent is T3, and T3>T2≥(T1+30℃). The softening point of the thermoplastic resin powder satisfies: 60℃≤T2≤120℃; The thermoplastic resin powder is one or more of epoxy resin powder, polyurethane powder, and polyamide powder; The latent curing agent is 4,4'-diaminodiphenyl sulfone.

2. The preformed material as described in claim 1, characterized in that, The softening point of the thermoplastic resin powder satisfies: 90℃≤T2≤120℃.

3. The preformed material as described in claim 1, characterized in that, One or more of the following conditions must be met: 1) The particle size of the thermoplastic resin powder satisfies: 2μm≤D50≤30μm; 2) The particle size of the latent curing agent satisfies: D90≤30μm; 3) The viscosity of the epoxy adhesive composition at 25°C and 6 rpm is ≤150 Pa·s.

4. The preformed material according to any one of claims 1 to 3, characterized in that, The thermoplastic resin powder is epoxy resin powder.

5. The preformed material as described in claim 4, characterized in that, The thermoplastic resin powder is bisphenol A epoxy resin powder.

6. The preformed material according to any one of claims 1 to 3, characterized in that, The adhesion promoter is selected from one or more of the following: organosilane adhesion promoters, titanate adhesion promoters, zirconate adhesion promoters, phosphate adhesion promoters, and chromium complex adhesion promoters.

7. The preformed material according to any one of claims 1 to 3, characterized in that, The liquid epoxy resin is selected from one or more of the following: bisphenol A epoxy resin, bisphenol F epoxy resin, hydrogenated bisphenol A epoxy resin, hydrogenated bisphenol F epoxy resin, phenolic epoxy resin, o-cresol type epoxy resin, hydantoin epoxy resin, allyl glycidyl ether type epoxy resin, glycidyl amine type epoxy resin, and glycidyl ester type epoxy resin.

8. The preformed material according to any one of claims 1 to 3, characterized in that, The preparation method of the epoxy adhesive composition includes the following steps: mixing the liquid epoxy resin, the thermoplastic resin powder, the latent curing agent and the adhesion promoter, and stirring at a temperature at least 30°C below T2.

9. A cavity encapsulation structure, characterized in that, The product includes a lid and a base, and is manufactured using the following method: An epoxy adhesive composition is applied to the cap, heated at a temperature higher than T2 and lower than T3 for at least 1 hour, and then cooled to obtain an adhesive cap. The adhesive cap is placed on the base and heated at a temperature not lower than T3 for at least 20 minutes to obtain the cavity encapsulation structure; The epoxy resin composition comprises the following raw materials in parts by weight: 100 parts of liquid epoxy resin; 50 to 300 parts of thermoplastic resin powder; a latent curing agent, wherein the ratio of the active hydrogen equivalent of the latent curing agent to the sum of the epoxy equivalents of the liquid epoxy resin and the thermoplastic resin powder is 0.6 to 1.4; and 0.1 to 5 parts of adhesion promoter. Wherein, the softening point of the liquid epoxy resin is T1, the softening point of the thermoplastic resin powder is T2, and the curing temperature of the latent curing agent is T3, and T3>T2≥(T1+30℃). The softening point of the thermoplastic resin powder satisfies: 60℃≤T2≤120℃; The thermoplastic resin powder is one or more of epoxy resin powder, polyurethane powder, and polyamide powder; The latent curing agent is 4,4'-diaminodiphenyl sulfone.

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