Pouring sealant and potting method

Abstract

The invention provides a pouring sealant and a pouring method. The pouring sealant comprises a sealant A and a sealant B, the adhesive A comprises the following components in percentage by mass: 45%-55% of heat-conducting silicone grease; 30%-40% of epoxy resin; 7% to 11% of toluene diisocynate; 2.5% to 3.5% of dibutyl phthalate; 0.8% to 1.2% of an epoxy diluent; 1.5%-2.5% of a black paste; the glue B comprises the following components in percentage by mass: 10%-14% of silicon dioxide; 75%-85% of a modified amine curing agent; and 1%-5% of black paste. According to the pouring sealant and the pouring method provided by the invention, the mechanical property, the physical property and the durability and the reliability of the functionality of a product can be protected; and the product is prevented from being detached and copied, the core technology of the product is effectively protected, and the pouring sealant performance is excellent.

Description

Technical Field

[0001] The present invention belongs to the field of communication electronics technology, and particularly relates to a potting adhesive and a potting method. Background Art

[0002] In the field of electronic communication, during the use of products, due to uncontrollable environmental impacts, over time, products will be eroded, corroded, damaged by mechanical shock and vibration of components caused by environmental factors such as dust, humidity, and external stress. To reduce or delay the erosion damage of environmental factors to products and improve product life, a relatively effective method is to pour and seal key parts such as circuits, magnetic rings, inductors, baluns, and cable connectors in the product cavity with a colloid, which plays a role in protecting electronic circuits, preventing dust, moisture, and water, resisting impact, and improving mechanical strength and stability.

[0003] Among potting adhesives, epoxy potting adhesives have a wide range of applications. Room-temperature curing epoxy potting adhesives are generally two-component. After potting, they can be cured without heating, have low requirements for equipment, and are easy to use. The disadvantages are that the compound has a high working viscosity, poor impregnation performance, a short pot life, is difficult to achieve automated production, and the cured product has not very high heat resistance and electrical properties. It is generally used for potting low-voltage electronic devices or in occasions where heating curing is not suitable. Compared with two-component heat-curing potting adhesives, the prominent advantages are that the required potting equipment is simple, easy to use, and the quality of the potting adhesive is less dependent on equipment and processes.

[0004] However, the existing room-temperature curing epoxy potting adhesives have insufficient thermal conductivity, and insufficient low-temperature resistance and thermal shock resistance, resulting in a lower service life. Therefore, it is necessary to develop a potting adhesive. Summary of the Invention

[0005] In order to solve the problems of insufficient thermal conductivity of the potting adhesive, insufficient low-temperature resistance and thermal shock resistance, resulting in a lower service life, the present invention proposes a potting adhesive. The present invention is implemented by the following technical solutions:

[0006] A potting adhesive, comprising A glue and B glue;

[0007] The A glue comprises the following components by mass fraction:

[0008] 45% - 55% of thermal conductive grease;

[0009] 30% - 40% of epoxy resin;

[0010] 7% - 11% of toluene diisocyanate;

[0011] 2.5% - 3.5% of dibutyl phthalate;

[0012] 0.8% - 1.2% of epoxy diluent;

[0013] 1.5% to 2.5% of black pigment;

[0014] The B glue comprises components in the following mass fractions:

[0015] 10% to 14% of silicon dioxide;

[0016] 75% to 85% of modified amine curing agent;

[0017] 1% to 5% of black pigment.

[0018] Optionally, the thermal conductive silicone grease comprises 10 - 25 parts by weight of silicone ketone and 75 - 90 parts by weight of thermal conductive filler;

[0019] Preferably, the thermal conductive filler is at least one of alumina, boron nitride, zinc oxide, silver powder, and copper powder. Optionally, the epoxy diluent is alkylene glycidyl ether;

[0020] The modified amine curing agent is diaminodiphenylmethane.

[0021] Optionally, the accelerator in the B glue is one of dibutyltin dilaurate or stannous octoate; the content of the accelerator in the B glue is 2% - 7%.

[0022] Optionally, the diluent in the B glue is one of alkylene glycidyl ether or phenyl glycidyl ether; the content of the accelerator in the B glue is 2% - 7%.

[0023] Optionally, the A glue comprises components in the following mass fractions:

[0024] 50% of thermal conductive silicone grease;

[0025] 35% of epoxy resin;

[0026] 9% of toluene diisocyanate;

[0027] 3% of dibutyl phthalate;

[0028] 1% of epoxy diluent;

[0029] 2% of black pigment.

[0030] Optionally, the B glue comprises components in the following mass fractions: 12% of silicon dioxide; 80% of modified amine curing agent; 3% of black pigment.

[0031] The black pigment used in the present invention is a black pigment, and the component showing black is carbon black. The black pigment adopted in the present invention contains 2% to 50% by mass of carbon black.

[0032] Optionally, the weight ratio of the adhesive A to the adhesive B is 6:1 to 2;

[0033] Preferably, the weight ratio of the adhesive A to the adhesive B is 6:1.5;

[0034] Preferably, the viscosity of the adhesive A at 25 °C is 4 to 7 Pa·s;

[0035] The viscosity of the adhesive B at 25 °C is 0.5 to 1 Pa·s.

[0036] A potting method includes the following steps:

[0037] Step 1) Mix the adhesive A and the adhesive B in claim 1 evenly to obtain a mixed adhesive solution;

[0038] Step 2) Clean and remove moisture from the workpiece to be potted;

[0039] Step 3) Coat a 0.2 - 0.5 mm thick mixed adhesive solution on the surface of the workpiece to be potted;

[0040] Step 4) Pot the workpiece to be potted with the mixed adhesive solution;

[0041] Step 5) After potting, conduct vacuum defoaming treatment on the mixed adhesive solution;

[0042] Step 6) After the defoaming treatment, dry and cure the mixed adhesive solution to complete the potting.

[0043] The present invention has the following technical effects

[0044] The present invention provides a potting adhesive and a potting method. The potting adhesive of the present invention can simultaneously play the roles of flame retardancy, heat conduction, electrical insulation, enhance environmental adaptability, effectively extend the service life of the product, and also play the role of preventing product disassembly, preventing the leakage of product technology, and effectively protecting the core technology of the product. The potting adhesive of the present invention has excellent performance. After potting, the test shows that the electrical insulation and flame retardancy performance can reach UL94V0 level; the temperature test passes the heat and humidity test at 85 °C, humidity 85% and low temperature -70 °C test and high and low temperature shock -50 °C - 160 °C, with no cracking and structural changes after 2000 hours, and can work for more than 20000 hours through the aging and weather resistance test; the heat conduction performance can reach 3 W / mk. Description of the Drawings

[0045] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for use in the description of the specific embodiments or the prior art. Obviously, the following drawings are some embodiments of the present invention. For those of ordinary skill in the art, other drawings can be obtained based on these drawings without creative efforts.

[0046] Figure 1 It is the potting flow chart in the embodiment. Detailed implementation manners

[0047] Now, various exemplary implementation manners of the present invention will be described in detail. This detailed description should not be regarded as a limitation on the present invention, but should be understood as a more detailed description of certain aspects, characteristics and implementation schemes of the present invention. It should be understood that the terms described in the present invention are only used to describe specific implementation manners and are not used to limit the present invention. In the following embodiments, unless otherwise specified, the experimental methods used are all conventional methods, and the materials, reagents, etc. used can be purchased from biological or chemical reagent companies.

[0048] In addition, for the numerical ranges in the present invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any intermediate value within any stated value or stated range, as well as each smaller range between any other stated value or intermediate value within the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded from the range.

[0049] Regarding the use of "comprising", "including", "having", "containing", etc. in this article, they are all open-ended terms, that is, they are meant to include but not be limited to.

[0050] Unless otherwise specified, all technical and scientific terms used in this article have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention pertains. Although the present invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described in this article can also be used in the implementation or testing of the present invention.

[0051] The present invention provides a potting adhesive, comprising Component A and Component B; Component A comprises the following components by mass fraction: 45% - 55% of thermal conductive silicone grease; 30% - 40% of epoxy resin; 7% - 11% of toluene diisocyanate; 2.5% - 3.5% of dibutyl phthalate; 0.8% - 1.2% of epoxy diluent; 1.5% - 2.5% of black pigment; Component B comprises the following components by mass fraction: 10% - 14% of silicon dioxide; 75% - 85% of modified amine curing agent; 1% - 5% of black pigment.

[0052] Thermal conductive silicone grease is an efficient thermal conductive material, mainly used in the heat dissipation field of electronic devices. It is composed of organosiloxane and thermal conductive fillers with excellent heat resistance and thermal conductivity, and has high thermal conductivity and good electrical insulation. Thermal conductive silicone grease fills the tiny gaps between electronic components and heat sinks to form a thermal conductive network, improving the heat transfer efficiency. On a microscopic scale, thermal conductive silicone grease can fill the air gaps between surfaces, replacing air with a material with higher thermal conductivity, thereby improving the heat transfer efficiency. The matrix material of thermal conductive silicone grease is usually silicone oil, which is a long-chain silicon oxide polymer with good thermal stability and chemical inertness. The thermal conductive silicone grease used in the present invention contains 10-25 parts by weight of organosiloxane and 75-90 parts by weight of thermal conductive fillers; the thermal conductive fillers are at least one of alumina, boron nitride, zinc oxide, silver powder, and copper powder. In the present invention, thermal conductive silicone grease with other ratios and components can also be used as long as the thermal conductivity can be achieved.

[0053] Optionally, the epoxy diluent is alkylene glycidyl ether; the modified amine curing agent is diaminodiphenylmethane.

[0054] Optionally, the accelerator in the B glue is one of dibutyltin dilaurate or stannous octoate; the content of the accelerator in the B glue is 2%-7%. The diluent in the B glue is one of alkylene glycidyl ether or phenyl glycidyl ether; the content of the accelerator in the B glue is 2%-7%.

[0055] Optionally, the black pigment is a black paste containing 2% to 50% by mass of carbon black. The black paste is a commonly used black pigment in electronic technology, and the black paste in the present invention is the IC-Black 9000 black paste of Sinoma Science & Technology Co., Ltd.

[0056] Optionally, the weight ratio of the A glue to the B glue is 6:1 to 2;

[0057] Preferably, the weight ratio of the A glue to the B glue is 6:1.5; the viscosity of the A glue at 25°C is 4-7 Pa·s; the viscosity of the B glue at 25°C is 0.5-1 Pa·s.

[0058] The present invention also provides a potting method, which includes the following steps:

[0059] Step 1) Mix the above-mentioned A glue and B glue evenly to obtain a mixed glue solution;

[0060] Step 2) Clean and remove moisture from the workpiece to be potted;

[0061] Step 3) Coat 0.2-0.5 mm of the mixed glue solution on the surface of the workpiece to be potted;

[0062] Step 4) Pot the workpiece to be potted with the mixed glue solution;

[0063] Step V) After potting is completed, perform vacuum defoaming treatment on the mixed adhesive;

[0064] Step VI) After the defoaming treatment is completed, dry and cure the mixed adhesive to complete the potting.

[0065] Example 1

[0066] The present invention provides a potting adhesive, and the components of the potting adhesive are shown in Table 1

[0067] Table 1

[0068]

[0069] Preparation of Component A: Sequentially add thermal conductive silicone grease, epoxy resin, toluene diisocyanate, dibutyl phthalate, epoxy diluent, and black pigment into a batching container in proportion, and stir evenly to obtain a black viscous liquid, Component A, with a viscosity of 4 - 7 Pa·s at an environment of about 25°C. The weight ratio of the content of organosilicone in the thermal conductive silicone grease used to the alumina powder filler is 25:75.

[0070] Preparation of Component B: Sequentially add modified amine curing agent, silicon dioxide, accelerator, diluent, and black pigment into a batching container in proportion, and stir evenly to obtain a black liquid, Component B, with a viscosity of 0.5 - 1 Pa·s at an environment of about 25°C.

[0071] Mixing and using: Weigh Components A and B according to a weight ratio of A:B = 6:1.5, stir evenly, and after degassing treatment, it can be poured and used for potting.

[0072] The method of potting using the above potting adhesive is as Figure 1 shown, and specifically includes the following steps:

[0073] The mixing ratio of Component A and Component B of the potting adhesive is 6:1.5.

[0074] Stir Components A and B of the potting material evenly, and scoop the stirred Components A and B of the potting material into a round container or cup according to the ratio.

[0075] Stir the proportioned Components A and B of the potting material in the same direction evenly for 10 - 15 minutes until Components A and B are in a fully molten state.

[0076] Place the prepared potting adhesive into a vacuum defoaming device to eliminate bubbles.

[0077] Step II) Pretreatment of the workpiece before potting:

[0078] Clean the inside of the workpiece. Use tweezers to hold dust-free paper or dust cloth and a small amount of anhydrous ethanol to wipe the inside of the workpiece. Hold the workpiece at an angle of 45 degrees and blow it from top to bottom with 0.3-0.5Mpa dry compressed gas 2-3 times.

[0079] After dehumidification, put the cleaned workpiece to be potted into a baking oven and bake it at 70±3℃ for 2 hours.

[0080] Cool for 30 minutes in an environment with a temperature of 22±3℃ and a humidity of 20-60%.

[0081] Step 3) Workpiece coating

[0082] Use a brush to apply a layer of potting glue about 0.2-0.5mm thick on the circuits, magnetic rings, inductors, baluns, transformers and other circuit components of the cleaned and dehumidified workpieces to form a continuous protective film to prevent moisture from invading.

[0083] Step 4) Pouring and potting:

[0084] Put the prepared potting glue into the needle copper, and use the glue dripping machine to evenly pour the potting glue into the product cavity. Use the copper needle to eliminate the surface bubbles and lumps while pouring. The pouring depth should be 0.3-1mm above the surface height of the device.

[0085] After pouring, the potting glue can be leveled with a scraper to ensure a smooth surface.

[0086] After the product is potted, air bubbles will remain in the glue. The presence of bubbles in the glue will affect the overall effect of the potting, resulting in poor air tightness, weakened insulation and flame retardant effects, lower strength and thermal conductivity, and air and water vapor will invade through the bubbles, shortening the service life of the product, etc. Therefore, defoaming treatment is required after potting and leveling.

[0087] In the present invention, the vacuum defoaming device consists of a 15L defoaming barrel (304 stainless steel pressure barrel), an acrylic transparent sealing cover, a vacuum negative pressure gauge, an inlet and outlet valve switch, and a filter shockproof vacuum pump. The vacuum degree of the vacuum pump is -100Kpa, and the vacuum negative pressure gauge and the air valve are installed on the acrylic sealing cover.

[0088] Step 5) Defoaming treatment after potting of the workpiece. The defoaming process is as follows:

[0089] Open the acrylic sealing cover and put the workpiece after potting and leveling into the barrel. The diameter of the barrel bottom is 500mm. Depending on the size of the workpiece, one or more workpieces can be placed at a time. When placing, they should be moved in parallel and slowly, and should not be tilted or vibrated to avoid lateral flow of the potting glue. After installation, cover the sealing cover and tighten it.

[0090] Connect the vacuum pump suction pipe to the air inlet of the defoaming barrel, open the air inlet valve in the defoaming barrel, and close the air outlet valve.

[0091] Turn on the power switch of the vacuum pump to evacuate and defoam. Observe the vacuum negative pressure gauge on the defoaming bucket cover. It takes about 45S to evacuate to the minimum value of 0.1Mpa. Keep pumping for 3 - 5 minutes. Through the transparent cover, the workpiece glue liquid should be smooth, uniform, without other impurities and bubble holes, and the defoaming is completed.

[0092] Turn off the power of the vacuum pump, close the intake valve, open the outlet valve, observe the vacuum gauge, and let the gas in the defoaming bucket slowly discharge. When the pointer returns to the atmospheric pressure value, open the defoaming bucket cover and gently take out the workpiece horizontally.

[0093] Step (VI) Potting glue curing:

[0094] Let it stand in an environment with a temperature of 22 ± 3°C and a humidity of 20 - 60% for 2 hours, then transfer it to a baking at 70 ± 3°C for 3 hours. Take it out when it returns to room temperature, and the workpiece potting process is completed.

[0095] Example 2

[0096] Replace the components in Example 1 with the components shown in Table 2, and the remaining steps are the same as those in Example 1.

[0097] Table 2

[0098]

[0099] The weight ratio of the content of silicone ketone to the alumina powder filler in the thermal conductive silicone grease used is 25:75.

[0100] Example 3

[0101] Replace the components in Example 1 with the components shown in Table 3, and the remaining steps are the same as those in Example 1.

[0102] Table 3

[0103]

[0104]

[0105] The weight ratio of the content of silicone ketone to the alumina powder filler in the thermal conductive silicone grease used is 25:75.

[0106] Comparative Example 1

[0107] Adjust the components of Component A as shown in Table 4, and the remaining steps are the same as those in Example 1.

[0108] Table 4

[0109] Formulation ingredients Ingredient ratio Thermal grease 34％ Epoxy resin 60％ Dibutyl phthalate 3％ Epoxy diluent 1％ Black pigment 2％

[0110] Comparative Example 2

[0111] Adjust the components of Adhesive A as shown in Table 5, and the remaining steps are the same as those in Example 1.

[0112] Table 5

[0113] Formulation ingredients Ingredient ratio Thermal grease 31％ Epoxy resin 57％ Toluene diisocyanate 9％ Epoxy diluent 1％ Black pigment 2％

[0114] Comparative Example 3

[0115] Adjust the components of Adhesive A as shown in Table 6, and the remaining steps are the same as those in Example 1.

[0116] Table 6

[0117] Formulation ingredients Ingredient ratio Thermal grease 30％ Epoxy resin 55％ Toluene diisocyanate 9％ Dibutyl phthalate 3％ Epoxy diluent 1％ Black pigment 2％

[0118] Comparative Example 4

[0119] Adjust the components of Adhesive A as shown in Table 7, and the remaining steps are the same as those in Example 1.

[0120] Table 7

[0121]

[0122]

[0123] Perform performance tests on the potted products obtained from the above examples and comparative examples. Performance test methods:

[0124] Flame retardancy performance: Oxygen index test method, referring to GB / T 18483-2008 "Test Method for Combustion Performance of Electrical and Electronic Products"; Thermal conductivity performance: Heat flow meter test method, and the test standard refers to ASTM D5470;

[0125] Aging and weather resistance performance: UV radiation test for 500 hours;

[0126] Damp heat resistance test: Temperature 40°C, humidity 95% RH, duration 168 hours;

[0127] Low temperature resistance test: Temperature -40°C, humidity 50% RH, duration 168 hours;

[0128] High and low temperature shock test: Temperature range -40°C to +160°C, cycle 3 times, and each cycle time is 8 hours.

[0129] The performance test results are shown in Table 8:

[0130] Table 8

[0131]

[0132]

[0133] From the comparison between the comparative examples and the examples, it can be seen that the lack of toluene diisocyanate in the potting adhesive will lead to a significant decrease in crosslinking density and chemical stability, thereby resulting in insufficient mechanical properties, possible reduction in tensile strength and elasticity, and affecting the protective effect. The adhesiveness is weakened, the adhesion to the substrate is insufficient, and delamination is likely to occur. The chemical resistance is poor, the ability to resist solvents, oils, etc. decreases, and the heat resistance decreases, and the performance deteriorates at high or low temperatures. And the curing process of the potting adhesive will also be affected.

[0134] The lack of dibutyl phthalate in the potting adhesive will lead to a decrease in flexibility, weakening of the interfacial bonding force, and deterioration of low-temperature performance, etc.

[0135] When the content of thermal conductive silicone grease is too low, it will lead to an increase in thermal resistance, an increase in junction temperature, a yellowing of the color, and an acceleration of cracking after high-temperature aging.

[0136] When the content of thermal conductive silicone grease is too high, the excessive thermal conductive filler may increase the interfacial defects, resulting in easier degradation caused by ultraviolet rays, and at the same time may affect the dispersion of antioxidants and accelerate aging. And too much filler may form more water penetration channels, increasing the risk of hydrolysis, especially if the interfacial bonding between the filler and the resin is not good, it is easy to absorb water. Excessive high thermal conductive silicone grease will make the material brittle, reduce flexibility, and is easy to crack at low temperatures. And it exacerbates the mismatch of the coefficient of thermal expansion, resulting in greater stress during temperature changes, causing cracks or delamination.

[0137] Obviously, the above examples are only for clear illustration and are not limitations on the implementation manners. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation manners here. And the obvious changes or modifications derived therefrom are still within the protection scope of the present invention.

Claims

1. A potting glue, characterized in that: Including A glue and B glue; The A glue comprises the following components by mass fraction: 45% to 55% thermal conductive silicone grease; 30% to 40% epoxy resin; 7% to 11% toluene diisocyanate; 2.5% to 3.5% dibutyl phthalate; 0.8% to 1.2% epoxy diluent; 1.5% to 2.5% black pigment; The B glue comprises the following components by mass fraction: 10% to 14% silicon dioxide; 75% to 85% modified amine curing agent; 1% to 5% black pigment.

2. The potting compound according to claim 1, characterized in that: The thermally conductive silicone grease comprises 10 to 25 parts by weight of organic silicone and 75 to 90 parts by weight of thermally conductive filler; Preferably, the thermally conductive filler is at least one of aluminum oxide, boron nitride, zinc oxide, silver powder, and copper powder.

3. The potting compound according to claim 1, characterized in that: The epoxy diluent is alkylene glycidyl ether; the modified amine curing agent is diaminodiphenylmethane.

4. The potting compound according to claim 1, characterized in that: The accelerator in the B glue is one of dibutyltin dilaurate and stannous octoate; the content of the accelerator in the B glue is 2% to 7%.

5. The potting compound according to claim 1, characterized in that: The diluent in the B glue is one of alkylene glycidyl ether and phenyl glycidyl ether; the content of the accelerator in the B glue is 2% to 7%.

6. The potting compound according to claim 1, characterized in that: The A glue comprises the following components by mass fraction: 50% thermal conductive silicone grease; 35% epoxy resin; 9% toluene diisocyanate; 3% dibutyl phthalate; 1% epoxy diluent; 2% black pigment.

7. The potting compound according to claim 1, characterized in that: The B glue comprises the following components in mass fractions: 12% silicon dioxide; 80% modified amine curing agent; and 3% black pigment.

8. The potting compound according to claim 1, characterized in that: The potting compound according to claim 1, characterized in that the black pigment is a black paste containing 2% to 50% by mass of carbon black.

9. The potting compound according to claim 1, characterized in that: The weight ratio of the A glue to the B glue is 6:1-2; preferably, the weight ratio of the A glue to the B glue is 6:1.5; Preferably, the viscosity of the glue A is 4-7 Pa·s at 25°C; the viscosity of the glue B is 0.5-1 Pa·s at 25°C.

10. A potting method, characterized in that: The steps include: Step 1) Evenly mixing the A glue and the B glue of the potting glue according to any one of claims 1 to 9 to obtain a mixed glue solution; Step 2) Cleaning and dehumidifying the workpiece to be potted; Step 3) Apply 0.2-0.5mm of mixed glue on the surface of the workpiece to be potted; Step 4) using the mixed glue to pot the workpiece to be potted; Step 5) After potting is completed, the mixed glue solution is subjected to vacuum defoaming treatment; Step 6) After the defoaming treatment is completed, the mixed glue solution is dried and solidified to complete the potting.

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