High-reliability low-temperature curing conductive adhesive and preparation method thereof

Abstract

The application discloses a high-reliability low-temperature curing conductive adhesive, which contains the following components in mass fractions: mixed resin, conductive filler, toughening agent, curing agent, coupling agent, thixotropic agent, active diluent and non-active diluent. The application also discloses a preparation method of the high-reliability low-temperature curing conductive adhesive, which comprises the following steps: S100, according to the formula weight fraction, the toughening agent, the curing agent, the coupling agent, the thixotropic agent, the active diluent and the non-active diluent are sequentially added into the mixed resin to prepare a resin matrix; S200, the conductive filler is added into the resin matrix to prepare a premix liquid; S300, the premix liquid is subjected to roller grinding to prepare a grinding liquid; and S400, the grinding liquid is subjected to vacuum stirring to prepare the high-reliability low-temperature curing conductive adhesive. The application realizes the use of the mixed resin to give the conductive adhesive high bonding performance and high environmental reliability, and the use of the active diluent and the non-active diluent in combination to effectively reduce the viscosity of the system.

Description

Technical Field

[0001] This invention relates to the field of conductive adhesive technology, specifically to a high-reliability low-temperature curing conductive adhesive and its preparation method. Background Technology

[0002] With the rapid development of high-density, miniaturization, micro-miniaturization, high integration, and three-dimensional packaging in electronic packaging, conductive adhesives are now required to have good adhesion and high reliability, as well as low curing temperature to protect the material from thermal aging damage. They also need to reduce their viscosity to adapt to new machine dispensing methods and rapid operation.

[0003] Existing low-temperature curing conductive adhesives can cure at relatively low temperatures, and can cure even faster as the temperature increases. However, most existing conductive adhesives have problems such as high viscosity and poor long-term bonding reliability.

[0004] When a dispensing machine performs machine dispensing operations, highly viscous adhesives are prone to stringing, which can easily cause misalignment and blockage of the dispensing nozzle. Therefore, in the existing technology, when using machine dispensing, a large amount of thinner needs to be added to reduce the viscosity of the conductive adhesive system, but this will inevitably lead to a decrease in bonding strength.

[0005] Therefore, existing low-temperature curing conductive adhesives are difficult to simultaneously meet the requirements of machine dispensing and high bonding strength. Summary of the Invention

[0006] The purpose of this invention is to provide a high-reliability low-temperature curing conductive adhesive and its preparation method, so as to solve the technical problem that the low-temperature curing conductive adhesive prepared by the prior art is difficult to simultaneously meet the requirements of machine dispensing and high bonding strength.

[0007] To solve the above-mentioned technical problems, the present invention specifically provides the following technical solution:

[0008] This invention provides a high-reliability low-temperature curing conductive adhesive and its preparation method. By weight, it contains the following components: 8-15 parts of mixed resin, 70-80 parts of conductive filler, 1-3 parts of toughening agent, 1-8 parts of curing agent, 0-0.2 parts of coupling agent, 0-0.2 parts of thixotropic agent, 3-5 parts of reactive diluent, and 1-5 parts of non-reactive diluent.

[0009] The mixed resin is a mixture of three resins: bisphenol epoxy resin, alicyclic epoxy resin, and phenolic epoxy resin, in a ratio of 1:0.2 to 0.5:1 to 3.

[0010] In a preferred embodiment of the present invention, the conductive filler is a mixture of flake silver powder and spherical silver powder;

[0011] The particle size of the flake silver powder and the spherical silver powder is 1-15 μm.

[0012] In a preferred embodiment of the present invention, the flake silver powder and the spherical silver powder are mixed in a ratio of 1:0.1 to 0.5.

[0013] In a preferred embodiment of the present invention, the toughening agent is at least one of carboxyl-terminated butadiene-acrylonitrile rubber, core-shell toughening agent, and polysulfide rubber.

[0014] As a preferred embodiment of the present invention, the curing agent is any one of modified imidazole fixatives and modified amine curing agents.

[0015] As a preferred embodiment of the present invention, the coupling agent is at least one of silane coupling agents, titanate coupling agents, and aluminate coupling agents.

[0016] The thixotropic agent is at least one of fumed silica and organobentonite.

[0017] As a preferred embodiment of the present invention, the active diluent is one or more of p-tert-butylphenyl glycidyl ether, resorcinol glycidyl ether, and 1,4-butanediol diglycidyl ether.

[0018] As a preferred embodiment of the present invention, the inactive diluent is at least one of low-boiling-point inactive diluents such as propylene glycol methyl ether acetate, ethylene glycol ethyl ether, ethyl acetate, and acetone.

[0019] This invention also provides a method for preparing a high-reliability low-temperature curing conductive adhesive, comprising the following steps:

[0020] S100. According to the formula by weight, toughening agent, curing agent, coupling agent, thixotropic agent, reactive diluent and non-reactive diluent are added to the mixed resin in sequence, and high-speed planetary stirring is carried out to obtain resin matrix.

[0021] S200. The conductive filler is added to the resin matrix and subjected to low-speed planetary stirring to obtain a premixed solution.

[0022] S300. The premixed liquid is subjected to roller milling to obtain a grinding liquid;

[0023] The fineness of the grinding slurry is less than 20 μm;

[0024] S400. Vacuum stir the grinding slurry to obtain a high-reliability low-temperature curing conductive adhesive.

[0025] As a preferred embodiment of the present invention, the high-speed planetary mixer satisfies the following conditions: the revolution speed is 1000-2000 rpm, the rotation speed is 500-1000 rpm, and the mixing time is 60-120 s;

[0026] The low-speed planetary mixer meets the following conditions: revolution speed of 500-1000 rpm, rotation speed of 800-1500 rpm, and mixing time of 60-150 s;

[0027] The vacuum stirring is a planetary vacuum stirring, and meets the following conditions: vacuum degree of 1.3-1.5 kPa, revolution speed of 500-1000 rpm, rotation speed of 800-1500 rpm, and stirring time of 60-150 s.

[0028] Compared with the prior art, the present invention has the following advantages:

[0029] 1. The present invention uses a certain proportion of mixed resin as the conductive adhesive matrix, which can reduce the viscosity of the system and maintain the high adhesion performance and high environmental reliability of the conductive adhesive.

[0030] 2. This invention combines reactive and non-reactive diluents to effectively further reduce the viscosity of the system without affecting the bonding effect, thus meeting the needs of machine dispensing.

[0031] 2. In preparing the conductive adhesive, this invention combines high-speed planetary stirring with low-speed planetary stirring, which reduces the stirring time required during the preparation process and reduces the contact time between the solution and air under violent vibration, which helps to reduce bubbles and improve its homogenization effect; and during the planetary stirring process, the speed and time of rotation and revolution are controlled within a certain range to avoid internal heating of the colloid. Attached Figure Description

[0032] To more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are merely exemplary, and those skilled in the art can derive other embodiments based on the provided drawings without creative effort.

[0033] Figure 1 This invention provides a schematic flowchart of a method for preparing a highly reliable low-temperature curing conductive adhesive. Detailed Implementation

[0034] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0035] This invention provides a high-reliability low-temperature curing conductive adhesive, which contains the following components by weight: 8-15 parts of mixed resin, 70-80 parts of conductive filler, 1-3 parts of toughening agent, 1-8 parts of curing agent, 0-0.2 parts of coupling agent, 0-0.2 parts of thixotropic agent, 3-5 parts of reactive diluent, and 1-5 parts of non-reactive diluent.

[0036] The mixed resin is a mixture of three resins: bisphenol epoxy resin, alicyclic epoxy resin, and phenolic epoxy resin, in a ratio of 1:0.2 to 0.5:1 to 3.

[0037] The bisphenol epoxy resin is bisphenol A or bisphenol F epoxy resin, wherein bisphenol A or bisphenol F epoxy resin is at least one of E51, NPEL-128, and NPEL-127.

[0038] The alicyclic epoxy resin is at least one of CELLOXIDE 2021P, TDE-85, and S-06E.

[0039] The phenolic epoxy resin is at least one of EPALLOY 8230, EPALLOY 8240, and NPPN-631.

[0040] In conductive adhesives, conductive fillers provide electrical properties, while the resin matrix provides physical and mechanical properties. Generally, the resin materials used in production are relatively simple, resulting in poor stability.

[0041] Among them, bisphenol A epoxy resin cured products have strong adhesion, high mechanical strength and strong stability. It is the most widely used and has the largest amount of usage among epoxy resins. Therefore, bisphenol A epoxy resin is often used as a base resin. However, conductive adhesives prepared using only bisphenol A epoxy resin have a large viscosity, generally higher than the standard value of 8000cps@25℃, which is not conducive to machine dispensing operations.

[0042] Alicyclic epoxy resins have a viscosity range of 200–5000 cps at 25°C. Compared with bisphenol A, they are easier to thermocure. Their cured products have excellent heat and weather resistance and high mechanical strength, but their viscosity range is wide and unstable.

[0043] Phenolic epoxy resin, with a viscosity range of 2000-8000cps@25℃, has superior curing and heat resistance properties compared to bisphenol A, and is more suitable for low-temperature curing.

[0044] The three resins have a certain viscosity gradient. Mixing them together in a certain proportion can reduce the viscosity of the system and improve the bonding performance, while also possessing a variety of excellent properties.

[0045] This invention achieves low system viscosity, excellent low-temperature curing performance and adhesive properties, and excellent anti-crystallization properties by mixing three types of resins in a certain ratio (1:0.2-0.5:1-3).

[0046] In this invention, the ratio of bisphenol A epoxy resin, alicyclic epoxy resin and phenolic epoxy resin is 1:0.2-0.5:1-3. According to multiple experiments, alicyclic epoxy resin and phenolic epoxy resin reduce the viscosity of the system and provide excellent temperature resistance and adhesion.

[0047] Furthermore, the addition of toughening agents to the formulation can improve the brittleness of the epoxy system, thereby achieving good mechanical strength and long-term bonding reliability. Moreover, the price of this formulation is relatively reasonable, which can reduce production costs.

[0048] Furthermore, by adding a small amount of both reactive and non-reactive diluents to the formulation, the system can be diluted by using a mixture of reactive and non-reactive diluents without significantly altering the system viscosity. This mixing method not only extends the pot life of the conductive adhesive but also does not affect its conductivity and bonding strength, and may even further improve them.

[0049] The addition of reactive diluents can effectively reduce the viscosity of the system and participate in the curing reaction. However, since the reactive diluents with good dilution effects are all monofunctional or difunctional epoxy diluents, when the amount added is large, the crosslinking density of the cured product decreases, which leads to an increase in volume resistivity and a decrease in conductivity.

[0050] This invention has found that by mixing non-active and active diluents in a certain proportion, the pot life of conductive adhesives can be increased and the viscosity of the system can be reduced without affecting conductivity and bonding strength.

[0051] Furthermore, in order to improve the conductivity of the filler in the conductive adhesive system, the conductive filler is preferably a mixture of flake silver powder and spherical silver powder.

[0052] When flake-shaped and spherical silver powder are mixed, they can fill and fill each other because of their different shapes, forming a more efficient overlapping pattern. If it is just flake-shaped or spherical silver powder, there will be more gaps between the particles, resulting in a higher resistance value.

[0053] This invention has found that by mixing two types of silver powder in a certain proportion, a more efficient bonding morphology and higher conductivity can be obtained.

[0054] In actual production, the preferred ratio of flaky silver powder to spherical silver powder in the conductive filler is 1:0.1 to 0.5. This ratio is also beneficial for quickly achieving the optimal fineness of the system during subsequent grinding, thereby improving the homogeneity of the system.

[0055] Furthermore, the particle size of the flake silver powder and the spherical silver powder is 1–15 μm.

[0056] Specifically, the particle size of flake-shaped and spherical silver powder is between 1 and 15 μm, which can improve the homogeneity of silver powder in the system, thereby improving the conductivity of the conductive adhesive system.

[0057] Furthermore, the toughening agent can be rotated within a wide range, but in order to improve the brittleness of the resin matrix, the toughening agent is at least one of carboxyl-terminated nitrile rubber, core-shell toughening agent, and polysulfide rubber.

[0058] Furthermore, the curing agent can be selected from a wide range, but in order to further reduce the curing heat of the conductive colloid, the curing agent is any one of modified imidazole fixatives and modified amine curing agents. Modified imidazole fixatives and modified amine curing agents have low curing heat and can achieve low-temperature curing without the use of accelerators. At the same time, the conductive colloid has stable storage performance, and the viscosity can be reduced and the pot life extended by using appropriate reactive and non-reactive diluents, which can meet the needs of machine dispensing.

[0059] The modified imidazole curing agent is at least one of PN-40, PN-40J, and PN23J.

[0060] The modified amine curing agent is at least one of Z04, HAA-1021, EH-5057P, and FXR-1020.

[0061] Furthermore, the coupling agent can be selected from a wide range of options. In this embodiment, the coupling agent is at least one of silane coupling agents, titanate coupling agents, and aluminate coupling agents.

[0062] Furthermore, the thixotropic agent can be selected from a wide range of options. In this embodiment, the thixotropic agent is at least one of fumed silica and organobentonite.

[0063] Furthermore, the reactive diluent can be selected from a wide range of options. In this embodiment, the reactive diluent is one or more of p-tert-butylphenyl glycidyl ether, resorcinol glycidyl ether, and 1,4-butanediol diglycidyl ether.

[0064] Furthermore, the inactive diluent can be selected from a wide range. In this embodiment, the inactive diluent is at least one of low-boiling-point inactive diluents such as propylene glycol methyl ether acetate, ethylene glycol ethyl ether, ethyl acetate, and acetone.

[0065] In existing technologies, using a planetary mixer to prepare conductive adhesives is a common method. However, since the viscosity of general conductive adhesives is high, they need to be stirred at high speed in a planetary mixer for a long time to make their texture uniform. However, long-term stirring makes it easier for the system to come into contact with air. Air enters the system and fills it with air bubbles, which are not easy to remove later.

[0066] Furthermore, during the planetary degassing process, the low-temperature curing conductive adhesive is susceptible to defects because its curing agent is highly sensitive to temperature. At higher temperatures, a reaction occurs inside the conductive adhesive, leading to product defects.

[0067] Solution: During planetary mixing, control the speed and time of rotation and revolution within a certain range to avoid internal heating of the colloid.

[0068] To reduce air ingress and prevent internal heating of the colloid, this invention addresses the aforementioned conductive adhesive, such as... Figure 1 As shown, the present invention also provides a method for preparing a high-reliability low-temperature curing conductive adhesive, comprising the following steps:

[0069] S100. According to the formula by weight, toughening agent, curing agent, coupling agent, thixotropic agent, reactive diluent and non-reactive diluent are added to the mixed resin in sequence, and the mixture is stirred at high speed in a planetary mixer with a revolution speed of 1000-2000 rpm and a rotation speed of 500-1000 rpm for 60-120 s to obtain the resin matrix.

[0070] S200. The conductive filler is added to the resin matrix and stirred at low speed in a planetary mixer. The revolution speed is 500-1000 rpm and the rotation speed is 800-1500 rpm. The stirring time is 60-150 s to obtain a premixed liquid.

[0071] S300. The premixed liquid is subjected to roller milling to obtain a grinding liquid;

[0072] The fineness of the grinding slurry is less than 20 μm;

[0073] S400. The grinding slurry is vacuum stirred in a planetary vacuum mixer, and the vacuum degree is adjusted to 1.3-1.5 kPa, the revolution speed is 500-1000 rpm, and the rotation speed is 800-1500 rpm, so as to obtain a high-reliability low-temperature curing conductive adhesive.

[0074] The preparation method can be rotated within a wide range. However, in order to improve the conductivity, stability and reliability of the conductive adhesive during the preparation process, a method is provided in which toughening agent, curing agent, coupling agent, thixotropic agent, reactive diluent, non-reactive diluent and mixed resin are mixed evenly, and then conductive filler is added and ground. That is, the stability of the resin matrix is ​​ensured by toughening agent, and the solution containing conductive material is ground to make its fineness less than 20μm, thereby improving its uniformity and conductivity.

[0075] In particular, in S100, since the conductive adhesive matrix is ​​a mixed resin with low viscosity and active and inactive diluents are added, the viscosity of the mixed system is greatly reduced. During vigorous shaking, air bubbles are more easily expelled. Therefore, when using a planetary mixer, the stirring speed can be appropriately increased and the stirring time can be reduced accordingly. This helps to improve production efficiency, reduce the time of vigorous contact between the system and air, and reduce the generation of air bubbles.

[0076] In S200, after the system is stirred at high speed, conductive filler is added and stirred at low speed. This step helps the system to expel gas. In S300, the system is further purged by roller milling to remove air bubbles, improve the homogenization effect of the system, prevent the generation of air bubbles, and enhance its homogenization effect.

[0077] Furthermore, the speed of the high-speed planetary mixer can be selected within a wide range to ensure that the resin matrix is ​​stirred evenly. However, in order to increase the stirring effect, reduce the stirring time, and improve the stirring efficiency, the high-speed planetary mixer must meet the following conditions: the revolution speed is 1000-2000 rpm, the rotation speed is 500-1000 rpm, and the stirring time is 60-120 s.

[0078] Planetary stirring involves mixing the solution under centrifugal force that changes direction but remains on the same horizontal plane. This constant change in centrifugal force promotes mixing between solutions. Furthermore, this method eliminates the need for stirring rods or similar devices, effectively preventing the solution from mixing with air and avoiding impurities such as air bubbles in the conductive adhesive.

[0079] Furthermore, the low-speed planetary mixer can rotate within a wide range, but in order to improve the homogeneity of the conductive filler and make its composition singular, the low-speed planetary mixer meets the following conditions: revolution speed of 500-1000 rpm, rotation speed of 800-1500 rpm, and mixing time of 60-150 s.

[0080] Furthermore, the vacuum stirrer can rotate within a wide range, but in order to prevent air from entering the solution during stirring, the vacuum stirrer is a planetary vacuum stirrer and meets the following conditions: vacuum degree of 1.3-1.5 kPa, revolution speed of 500-1000 rpm, rotation speed of 800-1500 rpm, and stirring time of 60-150 s.

[0081] Specifically, a planetary mixer only has a centrifugal separation effect when its revolution is 0; and only a vacuum degassing effect when its rotation is 0.

[0082] Between high-speed revolution and rotation, the material exhibits stratified convection, with more intense movement on the upper surface. At the same time, this convection, under the action of centrifugal force, generates internal circulation, allowing each particle of the material to uniformly repeat this movement process. The air bubbles present inside can be carried to the upper layer and released by this circulation, and the material can also be effectively mixed.

[0083] Therefore, in practice, high-speed planetary stirring is generally used for mixing. However, this method can affect the quality of conductive adhesives during the preparation of low-temperature curing conductive adhesives.

[0084] When the orbital speed is constant, increasing the rotational speed enhances the internal circulation of the material particles and promotes the mixing of the materials. When the rotational speed reaches a certain critical value, the material particles are over-mixed, and friction between the particles generates heat, causing the curing agent to react at a certain temperature, resulting in the deterioration of the conductive adhesive quality.

[0085] Therefore, through research, this invention has found that using a combination of high-speed rotation and revolution can reduce the stirring time required during the preparation process and reduce the contact time between the solution and air under violent vibration, which is beneficial to reduce bubbles and improve its homogenization effect; and during planetary stirring, controlling the speed and time of rotation and revolution within a certain range can prevent the colloid from heating up inside.

[0086] This invention provides comparative experiments to verify the above conclusions, wherein the following materials are used:

[0087] Mixed Resin No. 1: Composed of 128 Bisphenol A Epoxy Resin, TDE-85 Alicyclic Epoxy Resin, and 8230 Phenolic Epoxy Resin in a mixing ratio of 1:0.2:1;

[0088] No. 2 Mixed Resin: Composed of E51 bisphenol A epoxy resin, TDE-85 alicyclic epoxy resin, and 8230 phenolic epoxy resin in a mixing ratio of 1:0.3:2;

[0089] Mixed resin No. 3: Composed of 170 bisphenol F epoxy resin, TDE-85 alicyclic epoxy resin, and 8240 phenolic epoxy resin in a mixing ratio of 1:0.4:3;

[0090] Conductive filler No. 1: Conductive filler No. 1 is composed of flake silver powder and spherical silver powder in a mixing ratio of 1:0.1;

[0091] Conductive filler No. 2: Conductive filler No. 2 is composed of flake silver powder and spherical silver powder mixed in a ratio of 1:0.3;

[0092] Conductive filler No. 3: Conductive filler No. 3 is composed of flake silver powder and spherical silver powder mixed in a ratio of 1:0.5;

[0093] All curing agents are Z04 curing agents; toughening agents are MX-125 core-shell toughening agents; coupling agents are titanate coupling agents; thixotropic agents are all fumed silica; reactive diluents are all p-tert-butylphenyl glycidyl ether; and non-reactive diluents are propylene glycol methyl ether acetate.

[0094] Example 1:

[0095] 1. Material preparation: Take 100 parts of raw materials, each part of material is in g, including: 8 parts of No. 1 mixed resin, 1.8 parts of toughening agent, 2.5 parts of curing agent, 0.1 parts of coupling agent, 0.1 parts of thixotropic agent, 80 parts of No. 1 conductive filler, 4 parts of reactive diluent and 3.5 parts of non-reactive diluent;

[0096] 2. Add the No. 1 mixed resin, toughening agent, curing agent, coupling agent, thixotropic agent and diluent to the mixing chamber of the planetary mixer according to the formula, and carry out planetary mixing for 60 seconds. The revolution speed is 1500 rpm and the rotation speed is 800 rpm. Mix and stir evenly to obtain the resin matrix.

[0097] 3. Add the rated amount of No. 1 silver powder to the resin matrix obtained in step 2 in batches, start the planetary mixer, and stir for 80 seconds. The revolution speed is 600 rpm and the rotation speed is 900 rpm to obtain a premixed liquid.

[0098] 4. Place the premixed liquid into a three-roll mill and grind it twice until the fineness is less than 20μm to obtain the grinding liquid;

[0099] 5. Add the grinding slurry to the planetary vacuum mixer and stir under planetary vacuum for 80 seconds. The vacuum degree is 1.3 kPa, the revolution speed is 600 rpm, and the rotation speed is 900 rpm.

[0100] 6. After mixing evenly, pack the mixture into tubes to obtain Example 1.

[0101] The conductive adhesive prepared in Example 1 was used to measure the volume resistivity and chip shear strength after curing at 80℃, 100℃, 120℃, 150℃ and 175℃ for a certain period of time. The results are shown in Table 1.

[0102] Table 1 Performance parameters of Example 1 under different curing conditions

[0103] Curing conditions Volume resistivity (Ω·cm) Chip shear strength (kgf) 80℃ / 2h <![CDATA[3.1×10 -4 ]]> 10.1 100℃ / 1h <![CDATA[2.4×10 -4 ]]> 10.5 120℃ / 15min <![CDATA[3.0×10 -4 ]]> 11.4 150℃ / 5min <![CDATA[2.2×10 -4 ]]> 12.8

[0104] Analysis of Table 1 leads to the following conclusions: 1. The conductive adhesive of the present invention can be cured in 1-2 hours at a relatively low temperature of 80-100℃, and can be rapidly cured at a relatively high temperature of 120-150℃, with a low curing temperature; 2. The volume resistivity of the conductive adhesive of the present invention is at a low level, thus exhibiting good conductivity; 3. The conductive adhesive of the present invention has high chip shear strength, high adhesion, meets adhesion requirements, and is not prone to cracking.

[0105] Example 2:

[0106] 1. Material preparation: Take 100 parts of raw materials, each part of material is in g, including: 10 parts of No. 2 mixed resin, 2 parts of toughening agent, 3.2 parts of curing agent, 0.3 parts of coupling agent, 0.5 parts of thixotropic agent, 77 parts of No. 2 conductive filler, 4 parts of reactive diluent and 3 parts of non-reactive diluent.

[0107] Steps 2, 3, 4, and 5 are all produced according to the formula amount, and their production steps are the same as steps 2, 3, 4, and 5 in Example 1;

[0108] 6. After mixing evenly, pack the mixture into tubes to obtain Example 2.

[0109] Example 3:

[0110] 1. Material preparation: Take 100 parts of raw materials, each part of material is in g, including: 13 parts of No. 3 mixed resin, 2.5 parts of toughening agent, 2 parts of curing agent, 0.5 parts of coupling agent, 0.5 parts of thixotropic agent, 76 parts of No. 3 conductive filler, 3.5 parts of reactive diluent and 2 parts of non-reactive diluent;

[0111] Steps 2, 3, 4, and 5 are all produced according to the formula amount, and their production steps are the same as steps 2, 3, 4, and 5 in Example 1;

[0112] 6. After mixing evenly, pack the mixture into tubes to obtain Example 3.

[0113] Example 4:

[0114] 1. Material preparation: Take 100 parts of raw materials, each part is in g, including: 10 parts of E51 bisphenol A epoxy resin and TDE-85 alicyclic epoxy resin and epoxy resin with a mixing ratio of 1:0.3, 2 parts of toughening agent, 3.2 parts of curing agent, 0.3 parts of coupling agent, 0.5 parts of thixotropic agent, 77 parts of No. 2 conductive filler, 4 parts of reactive diluent and 3 parts of non-reactive diluent;

[0115] Steps 2, 3, 4, and 5 are all produced according to the formula amount, and their production steps are the same as steps 2, 3, 4, and 5 in Example 1;

[0116] 6. After mixing evenly, pack the mixture into tubes to obtain Example 4.

[0117] Example 5:

[0118] 1. Material preparation: Take 100 parts of raw materials, each part of the material is in g, including: 10 parts of E51 bisphenol A epoxy resin and 8230 phenolic epoxy resin mixed in a ratio of 1:2, 2 parts of toughening agent, 3.2 parts of curing agent, 0.3 parts of coupling agent, 0.5 parts of thixotropic agent, 77 parts of No. 2 conductive filler, 4 parts of reactive diluent and 3 parts of non-reactive diluent;

[0119] Steps 2, 3, 4, and 5 are all produced according to the formula amount, and their production steps are the same as steps 2, 4, and 5 in Example 1;

[0120] 6. After mixing evenly, pack the mixture into tubes to obtain Example 5.

[0121] Table 2 Comparison of conductive adhesive performance parameters in Examples 2, 4, and 5

[0122]

[0123]

[0124] As shown in Table 2, the performance standards of the conductive adhesives in different embodiments are compared. Compared with the two resins used in Examples 4 and 5, the bisphenol A epoxy resin, phenolic epoxy resin and alicyclic epoxy resin are mixed in a specific ratio to form a mixed resin, which reduces the viscosity of the system and improves its brittleness by adding toughening agents, so as to give the conductive adhesive good conductivity and long-term performance stability.

[0125] Example 6:

[0126] 1. Material preparation: Take 100 parts of raw materials, each part of material is in g, including: 10 parts of No. 2 mixed resin, 2 parts of toughening agent, 3.2 parts of curing agent, 0.3 parts of coupling agent, 0.5 parts of thixotropic agent, 77 parts of No. 2 conductive filler, 4 parts of reactive diluent and 3 parts of non-reactive diluent.

[0127] 2. Step 2 involves production according to the formula, and the production steps are the same as step 2 in Example 1;

[0128] 3. Add the rated amount of No. 2 silver powder to the resin matrix obtained in step 2 in batches, start the planetary mixer, and stir for 80 seconds. The revolution speed is 600 rpm and the rotation speed is 1600 rpm to obtain a premixed liquid.

[0129] Steps 4 and 5 are produced according to the formula amount, and the production steps are the same as steps 4 and 5 in Example 1.

[0130] 6. After mixing evenly, pack the mixture into tubes to obtain Example 6.

[0131] Example 7:

[0132] 1. Material preparation: Take 100 parts of raw materials, each part of material is in g, including: 10 parts of No. 2 mixed resin, 2 parts of toughening agent, 3.2 parts of curing agent, 0.3 parts of coupling agent, 0.5 parts of thixotropic agent, 77 parts of No. 2 conductive filler, 4 parts of reactive diluent and 3 parts of non-reactive diluent.

[0133] 2. Step 2 involves production according to the formula, and the production steps are the same as step 2 in Example 1;

[0134] 3. Add the rated amount of No. 2 silver powder to the resin matrix obtained in step 2 in batches, start the planetary mixer, and stir for 80 seconds. The revolution speed is 400 rpm and the rotation speed is 900 rpm to obtain a premixed liquid.

[0135] Steps 4 and 5 are produced according to the formula amount, and the production steps are the same as steps 4 and 5 in Example 1.

[0136] 6. After mixing evenly, pack the mixture into tubes to obtain Example 7.

[0137] Table 3 Comparison of conductive adhesive performance parameters in Examples 2, 6, and 7

[0138]

[0139]

[0140] As shown in Table 3, when comparing the performance standards of the conductive adhesives in different embodiments, Embodiment 2 uses a combination of high and low speed revolution and rotation for planetary degassing and stirring. Compared with Embodiments 6 and 7, which use different rotation and revolution stirring methods, Embodiment 2 has better conductivity and mechanical strength.

[0141] Example 8:

[0142] 1. Material preparation: Take 100 parts of raw materials, each part of the material is in g, including: 10 parts of No. 2 mixed resin, 2 parts of toughening agent, 3.2 parts of curing agent, 0.3 parts of coupling agent, 0.5 parts of thixotropic agent, 77 parts of flake silver powder, 4 parts of reactive diluent and 3 parts of non-reactive diluent.

[0143] Steps 2, 3, 4, and 5 are all produced according to the formula amount, and their production steps are the same as steps 2, 3, 4, and 5 in Example 1;

[0144] 6. After mixing evenly, pack the mixture into tubes to obtain Example 8.

[0145] Example 9:

[0146] 1. Material preparation: Take 100 parts of raw materials, each part of the material is in g, including: 10 parts of No. 2 mixed resin, 2 parts of toughening agent, 3.2 parts of curing agent, 0.3 parts of coupling agent, 0.5 parts of thixotropic agent, 77 parts of spherical silver powder, 4 parts of reactive diluent and 3 parts of non-reactive diluent.

[0147] Steps 2, 3, 4, and 5 are all produced according to the formula amount, and their production steps are the same as steps 2, 3, 4, and 5 in Example 1;

[0148] 6. After mixing evenly, pack the mixture into tubes to obtain Example 9.

[0149] Table 4 Comparison of conductive adhesive performance parameters in Examples 2, 8, and 9

[0150]

[0151] As shown in Table 4, when comparing the performance standards of the conductive adhesives in different embodiments, Example 2 uses a mixture of flake silver powder and spherical silver powder in a certain proportion, which makes the conductive adhesive achieve a more efficient overlapping shape, makes the silver powder stacking layers more dense, and effectively reduces the contact resistance of the silver powder. Compared with Examples 8 and 9, which use only one type of silver powder as a conductive filler, it has better conductivity.

[0152] Comparative Example 1:

[0153] 1. Material preparation: Take 100 parts of raw materials, each part of material is in g, including: 13 parts of E51 epoxy resin, 2.5 parts of toughening agent, 2 parts of curing agent, 0.5 parts of coupling agent, 0.5 parts of thixotropic agent, 76 parts of flake silver powder, 3.5 parts of reactive diluent and 2 parts of non-reactive diluent.

[0154] Steps 2, 3, 4, and 5 are all produced according to the formula amount, and their production steps are the same as steps 2, 3, 4, and 5 in Example 1;

[0155] 6. After mixing thoroughly, pack the mixture into tubes to obtain the comparative sample.

[0156] The conductive adhesives of each embodiment were subjected to the following performance tests, and the results are shown in Table 5.

[0157] Table 5. Performance parameters of conductive adhesives in each embodiment.

[0158]

[0159] As shown in Table 5, compared with Comparative Example 1 and the conductive adhesive dispensing performance standard, Examples 1, 2, and 3 all exhibit low viscosity (viscosity ≤ 8000 cps @ 10 rpm), high adhesive strength (chip shear strength ≥ 8 kgf), and high conductivity (volume resistivity ≤ 4 × 10⁻⁶). -4 Ω·cm), high environmental reliability (its electrical conductivity and mechanical properties still have good performance indicators after long-term temperature cycling, temperature shock and damp heat environmental tests).

[0160] As can be seen from the above, compared with conventional epoxy resins, the present invention uses phenolic epoxy resin and other epoxy resins in a specific ratio to form a mixed resin, and adds toughening agents to improve its brittleness, so as to give the conductive adhesive good mechanical properties and long-term performance stability.

[0161] This invention uses a mixture of reactive and non-reactive diluents in a certain proportion to reduce the viscosity of the system, extend the pot life, and improve conductivity and bonding strength.

[0162] This invention uses a mixture of flake silver powder and spherical silver powder in a certain proportion to achieve a more efficient bonding morphology in the conductive adhesive, making the silver powder stacking layers more dense and effectively reducing the contact resistance of the silver powder.

[0163] This invention uses modified imidazoles or modified amines as curing agents, which can be cured at 80-100℃ without the need for accelerators. This ensures the bonding strength of the conductive adhesive while also enabling low-temperature curing.

[0164] In summary, the conductive adhesive in the above formula is suitable for machine dispensing requirements, has excellent overall performance, good environmental reliability, and can meet the needs of actual production.

[0165] The above embodiments are merely exemplary embodiments of this application and are not intended to limit this application. The scope of protection of this application is defined by the claims. Those skilled in the art can make various modifications or equivalent substitutions to this application within its substance and scope of protection, and such modifications or equivalent substitutions should also be considered to fall within the scope of protection of this application.

Claims

1. A high reliability low temperature cure electrically conductive adhesive characterized by, According to the mass fraction, the following ingredients are contained: 8-15 parts of mixed resin, 70-80 parts of conductive filler, 1-3 parts of toughening agent, 1-8 parts of curing agent, 0-0.2 parts of coupling agent, 0-0.2 parts of thixotropic agent, 3-5 parts of active diluent, 1-5 parts of non-active diluent; The mixed resin is a mixture of bisphenol epoxy resin, alicyclic epoxy resin and phenolic epoxy resin in a ratio of 1:0.2-0.5:1-3; The bisphenol epoxy resin is bisphenol A or bisphenol F epoxy resin, wherein the bisphenol A or bisphenol F epoxy resin is at least one of E51, NPEL-128 and NPEL-127; The alicyclic epoxy resin is at least one of CELLOXIDE 2021P, TDE-85 and S-06E; The phenolic epoxy resin is at least one of EPALLOY 8230, EPALLOY 8240 and NPPN-631; The toughening agent is at least one of carboxyl-terminated butyl nitrile rubber, core-shell toughening agent and polysulfide rubber.

2. The high reliability low temperature cure electrically conductive adhesive of claim 1, wherein, The conductive filler is a mixture of flaky silver powder and spherical silver powder; The particle size of the flaky silver powder and the spherical silver powder satisfies 1-15 μm.

3. The high reliability low temperature cure electrically conductive adhesive of claim 2, wherein, The flaky silver powder and the spherical silver powder are mixed in a ratio of 1:0.1-0.

5.

4. The high reliability low temperature cure electrically conductive adhesive of claim 1, wherein, The curing agent is any one of modified imidazole curing agent and modified amine curing agent.

5. The high reliability low temperature cure electrically conductive adhesive of claim 1, wherein, The coupling agent is at least one of silane coupling agent, titanate coupling agent and aluminate coupling agent; The thixotropic agent is at least one of fumed silica and organic bentonite.

6. The high reliability low temperature cure electrically conductive adhesive of claim 1, wherein, The active diluent is one or more of p-tert-butyl phenyl glycidyl ether, resorcinol glycidyl ether and 1,4-butanediol diglycidyl ether.

7. The high reliability low temperature cure electrically conductive adhesive of claim 1, wherein, The non-active diluent is at least one of propylene glycol methyl ether acetate, ethylene glycol ethyl ether, ethyl acetate and acetone.

8. The method for preparing the high-reliability low-temperature curing conductive adhesive according to claims 1-7, characterized in that, The method comprises the following steps: S100, according to the formula weight parts, the toughening agent, the curing agent, the coupling agent, the thixotropic agent, the active diluent and the non-active diluent are sequentially added to the mixed resin, and high-speed planetary stirring is performed to obtain a resin matrix; S200, the conductive filler is added to the resin matrix, and low-speed planetary stirring is performed to obtain a premix liquid; S300, the premix liquid is roller ground to obtain a ground liquid; The fineness of the ground liquid is less than 20 μm; S400, the ground liquid is vacuum stirred to obtain a high-reliability low-temperature curing conductive adhesive.

9. The method for preparing a high-reliability low-temperature curing conductive adhesive according to claim 8, characterized in that, The high-speed planetary stirring satisfies the following conditions: the revolution speed is 1000-2000 rpm, the rotation speed is 500-1000 rpm, and the stirring time is 60-120 s; The low-speed planetary stirring satisfies the following conditions: the revolution speed is 500-1000 rpm, the rotation speed is 800-1500 rpm, and the stirring time is 60-150 s; The vacuum stirring is planetary vacuum stirring, and satisfies the following conditions: the vacuum degree is 1.3-1.5 kPa, the revolution rotation speed is 500-1000 rpm, the rotation rotation speed is 800-1500 rpm, and the stirring time is 60-150 s.

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