Formula design method of single-layer heat-conducting wave-absorbing gasket

Abstract

The invention discloses a formula design method of a single-layer heat-conducting wave-absorbing gasket. The formula design method comprises the following steps: establishing a powder parameter database; establishing a two-dimensional matrix related to a series formula ratio of all powder to a resin matrix in the database; calculating the theoretical heat conductivity coefficient kc of the gasket prepared under the series formula; inputting a formula with a qualified heat conductivity coefficient to calculate theoretical electromagnetic parameters; calculating the reflectivity of the gasket according to a transmission line theory and a set gasket thickness; and a formula conforming to heat-conducting and wave-absorbing properties is output. By introducing calculation of the heat conductivity coefficient and an equivalent medium theory, the heat conductivity coefficient of the single-layer wave-absorbing gasket and electromagnetic parameters under different electromagnetic wave frequencies and different powder proportions can be simulated and calculated, and the output electromagnetic parameters are substituted into a transmission line theory to simulate and calculate the reflectivity. Compared with a traditional design method of the single-layer heat-conducting wave-absorbing material, the design scheme meeting the requirements can be obtained without repeated tests, the consumed time is short, the cost is low, and the accuracy rate is high.

Description

Technical Field

[0001] The invention belongs to the preparation of a heat-conducting and wave-absorbing gasket, and in particular relates to the formula design of a single-layer heat-conducting and wave-absorbing gasket. Background Art

[0002] With the rapid development of electronic equipment, local area networks and communication facilities, it is becoming increasingly important to develop miniaturized and functional electronic devices, and the demand for anti-electromagnetic interference and heat dissipation is also increasing. As an important component of device packaging interface materials, silicone gaskets with thermal conductivity and wave absorption properties provide more options for electromagnetic compatibility and thermal management design of electronic devices. The silicone single-layer thermally conductive and wave-absorbing gasket is obtained by mixing thermally conductive fillers and wave-absorbing fillers into the silicone substrate. Since there is a maximum limit on the amount of functional fillers added to the resin matrix, the addition mode of the two powders has the characteristics of one increase and the other decrease in product performance, and it is difficult to achieve a synergistic improvement of the two properties. To adjust both properties to meet the standards, multiple formula adjustments are required, and the experimental cycle is too long. Therefore, necessary simulation calculations can effectively reduce the workload.

[0003] At present, there is already a lot of research foundation in the calculation of thermal conductivity and absorbing performance. For example, patent number CN108760800 B provides a method for calculating the equivalent thermal conductivity of hollow glass microspheres, which is simple in principle, easy to use, and has high calculation accuracy. Patent number CN 103399975 B provides an optimization method for calculating the absorbing impedance of metal-backed electromagnetic absorbing materials. The matching thickness model is combined with the transmission line theory to make the impedance matching optimization of electromagnetic wave absorbing materials more efficient, so that the preparation of absorbing materials can be completed quickly and accurately, and it is applicable to a variety of electromagnetic wave absorbing composite materials. However, the above-mentioned public technologies only involve a single calculation of thermal conductivity or absorbing performance, and cannot realize the overall design of a single-layer thermal conductive absorbing gasket. In order to solve this problem, the present invention has developed a matlab program that can calculate a suitable gasket formula design based on thermal conductivity and absorbing performance. Summary of the invention

[0004] The purpose of the present invention is to overcome the deficiencies of the prior art and provide a method for designing a formula of a single-layer heat-conducting and wave-absorbing gasket.

[0005] The technical solution of the present invention is: a formula design method for a single-layer heat-conducting and wave-absorbing gasket, and the calculation method comprises the following steps: Step 1: Establish a powder parameter database, including electromagnetic parameters, thermal conductivity, and specific gravity; Step 2: Establish a two-dimensional matrix to list all the series of formula ratios of powder and resin matrix involved in the database; Step 3: Calculate the theoretical thermal conductivity k of the gasket prepared under the series of formulations c , kc The calculation formula is: log k c =V*(X1*C1*log k1+X2*C2*log k2+...+X a *C a *log k a )+(1-V)*log(C*k p ); Step 4: Automatically calculate the theoretical electromagnetic parameters of the prepared gasket for the formula with qualified thermal conductivity; Step 5: Calculate the reflectivity of the gasket based on the transmission line theory and the set gasket thickness; Step 6: Output the formula that meets the thermal conductivity and wave absorption performance.

[0006] Preferably, the powder in step 1 is carbonyl iron powder, sendust aluminum alloy powder, ferrite, iron powder, aluminum oxide, zinc oxide, aluminum nitride, boron nitride, aluminum hydroxide, or magnesium hydroxide.

[0007] Preferably, the powder parameters in step 1 include electromagnetic parameters, thermal conductivity, and specific gravity.

[0008] Preferably, the powder in step 1 is spherical in shape and has a particle size D50 of 1-150 μm.

[0009] Preferably, the resin matrix in step 2 is one of silicone oil, epoxy resin, polyurethane resin, phenolic resin, polystyrene and rubber.

[0010] Preferably, the two-dimensional matrix in step 2 is a mass ratio of the resin matrix to the powder, and the mass ratio of the resin matrix to the powder is 100:0-1500.

[0011] Preferably, the theoretical thermal conductivity k in step 3 is c In the calculation formula: k c is the thermal conductivity of the gasket, k1, k2, ..., k a is the thermal conductivity of the filler particles, k p is the thermal conductivity of the resin matrix; V is the volume fraction of the filling powder; C1, C2, ..., C a is the coefficient of the difficulty of the powder conductive chain formation, C is the coefficient that affects the crystallinity and crystal size of the polymer; X1, X2, ..., X a It is the percentage of particles in the filling powder.

[0012] Preferably, the volume fraction V of the filling powder in step 3 is calculated as follows: V = (m1 + m2 + ... + m a ) / (m1 / ρ1+m2 / ρ2+...+m a / ρa +m p / ρ p ), where m1, m2, ..., m a is the mass of the filling powder, ρ1, ρ2, ..., ρ a are the specific gravity of the filling powder, m p is the mass of the resin matrix, ρ p is the specific gravity of the resin matrix.

[0013] Preferably, the number of particles of the filling powder in step 3 accounts for X1, X2, ..., X a The calculation formula is: j =m j / ρ j (D j ) 3 / (m1 / ρ1(D1) 3 +m2 / ρ2(D2) 3 +...m j / ρ j (D j ) 3 ...+m a / ρ a (D a ) 3 ), where m1, m2, ..., m a is the mass of the filling powder, ρ1, ρ2, ..., ρ a Specific gravity of filling powder, D1, D2, ..., D a is the particle size of the filling powder.

[014] Preferably, the difficulty coefficients C1, C2, ..., C a The calculation formula for the coefficient C of polymer crystallinity and crystal size is: log k c =V*(C1*log k1)+(1-V)*log(C*k p ); Among them, the filling powder is limited to one kind, and gaskets with two different filling fractions of the same matrix resin are made. The thermal conductivity coefficient is tested, and the measured thermal conductivity and the calculated volume fraction are substituted into the formula to obtain two linear equations of two variables. Solving the equations can obtain the difficulty coefficient of the formation of the filler conductive chain and the coefficient affecting the crystallinity and crystal size of the polymer.

[0015] Preferably, the calculation formula of the theoretical electromagnetic parameters (ε, μ) of the gasket in step 4 is: Among them, ε j 、v j represents the dielectric constant and volume fraction of the jth filler powder in the composite system, ε mis the dielectric constant of the resin matrix; according to the duality principle of electromagnetic theory, ε=μ, ε j =μ j , ε m =μ m .μ j represents the magnetic permeability of the jth filling powder in the composite system, μ m is the magnetic permeability of the resin matrix.

[0016] Preferably, the volume fraction in step 4 is calculated as follows: V j =m j / (m1 / ρ1+m2 / ρ2+...+m a / ρ a +m p / ρ p ), where m1, m2, ..., m a are the masses of the filling particles, ρ1, ρ2, ..., ρ a are the specific gravity of the filling particles, m p is the mass of the resin matrix, ρ p is the specific gravity of the resin matrix.

[0017] Preferably, the calculation formula of the reflectivity R of the gasket in step 5 is as follows: z in =z c tanh(γd), w=2πf;where z in is the input impedance of the absorbing material, z c is the characteristic impedance of the absorbing material, f is the frequency of the electromagnetic wave, d is the thickness of the absorbing material, z0 is the characteristic impedance of the metal base plate, and z0=1.

[0018] The technical advantages of the present invention are as follows: The present invention calculates the thermal conductivity and reflectivity of a single-layer gasket through computer simulation, and can design a formula design that simultaneously meets the two performance indicators. A single-layer thermally conductive and absorbing gasket that meets the requirements can be obtained without repeated experiments. The electromagnetic parameters are calculated through the equivalent medium theory, which can better characterize the relationship between the change of the electromagnetic parameters and the frequency, so that the calculation result of the reflectivity is closer to the actual test, shortening the experimental cycle, and also reducing the loss of raw materials. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 This is a wave absorption characteristic curve diagram of specific embodiment 1.

[0020] Figure 2 This is a curve diagram of the absorption characteristics of specific embodiment 2.

[0021] Figure 3This is a curve diagram of absorption characteristics of specific embodiment 3.

[0022] Figure 4 This is a curve diagram of the absorption characteristics of specific embodiment 4. DETAILED DESCRIPTION

[0023] In order to better understand the invention, the content of the patent of the present invention is further explained below in conjunction with the implementation examples. However, the content of the patent of the present invention is not limited to the following implementation examples. Based on the embodiments of the present invention, other embodiments obtained by technicians in this field without creative work all fall within the scope of protection of the present invention.

[0024] The operating method of the present invention for obtaining the formula of a single-layer heat-conducting and wave-absorbing gasket is as follows: (1) Input the target thermal conductivity and wave absorption data of the gasket; (2) Set the gasket thickness, the thickness range is 0-20mm; (3) Call database data to set the type and particle size of filler; (4) Input the thermal conductivity and specific gravity of the resin matrix; (5) Generate a two-dimensional matrix to list the formulation designs with different mass ratios between the selected powder and the resin matrix; (6) Calculate the thermal conductivity of different formulations according to step 3 of the invention; (7) The reflectivity of the formula that meets the thermal conductivity is automatically calculated according to steps 4 and 5 of the invention content; (8) Select a formula that meets the set goals based on the calculation results.

[0025] The thermal conductive and wave absorbing materials are artificially prepared with the formula that meets the set target and tested to verify whether it achieves the expected set target performance.

[0026] The method for artificially preparing thermal conductive and wave absorbing materials is as follows: The output heat-conducting and wave-absorbing powder formula (containing no vinyl silicone oil) that meets the set target is preliminarily dispersed with 100g of mixed silicone oil, and then dispersed evenly using a vacuum mixer for 1.0h; the resulting paste is placed on a release film and then fed into a calender, and after calendering according to the set thickness, it is vulcanized at 150°C for 15min to obtain a heat-conducting and wave-absorbing gasket. The mixed silicone oil system is 100 parts of 500cP vinyl silicone oil + 4.0 parts of side hydrogen silicone oil + 0.33 parts of acetylene cyclohexanol inhibitor + 0.33 parts of platinum catalyst.

[0027] The performance test method of artificially prepared thermal conductive and wave absorbing materials is as follows: Wave absorption performance test: The coaxial method of the vector network analyzer is used to test its wave absorption performance, and its dielectric constant and magnetic permeability are tested to calculate its reflection loss (RL). The formula is as follows. The equipment model used is N5222B. z in =z c tanh(γd) Thermal conductivity test: refer to ASTM D5470 method to test the thermal conductivity of the sample.

[0028] Example 1 1. The method for obtaining the formula of a single-layer heat-conducting and wave-absorbing silicone gasket using the present invention is as follows: (1) Input gasket target thermal conductivity 1-1.2W / (m*k), reflectivity <-10dB within 7-10GHz, reflectivity peak <-10dB, peak frequency 7.5-8.5GHz; (2) Set the gasket thickness to 2 mm; (3) Calling the database data, selecting fillers, 1 μm spherical zinc oxide, 5 μm spherical carbonyl iron powder, 20 μm spherical alumina, 40 μm spherical alumina and 14 μm spherical sendust powder; (4) Input resin matrix vinyl silicone oil with thermal conductivity of 0.15-0.20 W / (m*k) and specific gravity of 1.005; (5) Generate a two-dimensional matrix to list the formulation designs with different mass ratios between powders; (6) Calculate the thermal conductivity of different formulations according to step 3 of the invention; (7) The reflectivity of the formula that meets the thermal conductivity is automatically calculated according to steps 4 and 5 of the invention content; (8) Select a formula that meets the set goals based on the calculation results. 2. The output results of Example 1 are as follows: Output result 1: Part of the data of the two-dimensional matrix generated in step (5) during the execution of the program of Example 1 is shown in Table 1 (mass ratio). Table 1: One of the formulas that meet the set target output by the program running in Example 1 is selected to prepare an organic silicone thermal conductive wave absorbing gasket. The test results of the prepared organic silicone thermal conductive wave absorbing gasket are compared with the expected set target performance as shown in Table 2. Table 2:

[0029] Example 2 Same as Example 1 1. The method for obtaining the formula of a single-layer heat-conducting and wave-absorbing silicone gasket using the present invention is as follows: (1) Input gasket target thermal conductivity 3-3.2W / (m*k), reflectivity <-10dB within 7-10GHz, reflectivity peak <-10dB, peak frequency 7.5-8.5GHz; (2) Set the gasket thickness to 2 mm; (3) Calling database data, Example 2 selects fillers, 1 μm spherical zinc oxide, 5 μm spherical carbonyl iron powder, 40 μm spherical aluminum oxide and 14 μm spherical sendust powder; (4) Input the thermal conductivity of vinyl silicone oil 0.15-0.20 W / (m*k) and specific gravity 1.005. (5) Generate a two-dimensional matrix to list the formulation designs with different mass ratios between powders; (6) Calculate the thermal conductivity of different formulations according to step 3 of the invention; (7) The reflectivity of the formula that meets the thermal conductivity is automatically calculated according to steps 4 and 5 of the invention content; (8) Select a formula that meets the set goals based on the calculation results. 2. The output results of Example 2 are as follows: Output result 2: Part of the data of the two-dimensional matrix generated in step (5) during the execution of the program in Example 2 is shown in Table 3 (mass ratio). Table 3: Among the formulas that meet the set target output by the program running in Example 2, one is selected to prepare an organic silicone thermal conductive wave absorbing gasket. The test results of the prepared organic silicone thermal conductive wave absorbing gasket are compared with the expected set target performance as shown in Table 4. Table 4:

[0030] Example 3 Same as Example 1 1. The method for obtaining the formula of a single-layer heat-conducting and wave-absorbing silicone gasket using the present invention is as follows: (1) Input gasket target thermal conductivity 1.5-1.7W / (m*k), reflectivity <-10dB within 12-15GHz, reflectivity peak <-10dB, peak frequency 14.0-14.5GHz; (2) Set the gasket thickness to 2 mm; (3) Calling database data, selecting fillers, 1 μm spherical zinc oxide, 5 μm spherical manganese zinc ferrite, 40 μm spherical aluminum oxide, 10 μm spherical boron nitride and 14 μm spherical iron silicon aluminum powder; (4) Input resin matrix vinyl silicone oil with thermal conductivity of 0.15-0.20 W / (m*k) and specific gravity of 1.005; (5) Generate a two-dimensional matrix to list the formulation designs with different mass ratios between powders; (6) Calculate the thermal conductivity of different formulations according to step 3 of the invention; (7) The reflectivity of the formula that meets the thermal conductivity is automatically calculated according to steps 4 and 5 of the invention content; (8) Select a formula that meets the set goals based on the calculation results. 2. The output results of Example 3 are as follows: Output result 3: Part of the data of the two-dimensional matrix generated in step (5) during the execution of the program in Example 3 is shown in Table 5 (mass ratio). Table 5: Among the formulas that meet the set target output by the program running in Example 3, one is selected to prepare an organic silicone thermal conductive wave absorbing gasket. The test results of the prepared organic silicone thermal conductive wave absorbing gasket are compared with the expected set target performance as shown in Table 6. Table 6

[0031] Example 4 Same as Example 1 1. The method for obtaining the formula of a single-layer heat-conducting and wave-absorbing silicone gasket using the present invention is as follows: (1) Input gasket target thermal conductivity 0.8-0.9W / (m*k), reflectivity <-10dB within 5-8GHz, reflectivity peak <-10dB, peak frequency 6.5-7GHz; (2) Set the gasket thickness to 2 mm; (3) Calling the database data, selecting fillers, 1 μm spherical aluminum hydroxide, 5 μm spherical manganese-zinc ferrite, 40 μm spherical alumina and 14 μm spherical iron-silicon-aluminum powder; (4) Input resin matrix vinyl silicone oil with thermal conductivity of 0.15-0.20 W / (m*k) and specific gravity of 1.005; (5) Generate a two-dimensional matrix to list the formulation designs with different mass ratios between powders; (6) Calculate the thermal conductivity of different formulations according to step 3 of the invention; (7) The reflectivity of the formula that meets the thermal conductivity is automatically calculated according to steps 4 and 5 of the invention content; (8) Select a formula that meets the set goals based on the calculation results. 2. The output results of Example 4 are as follows: Output result 4: Part of the data of the two-dimensional matrix generated in step (5) during the execution of the program in Example 4 is shown in Table 7 (mass ratio). Table 7: Among the formulas that meet the set target output by the program running in Example 4, one is selected to prepare an organic silicone thermal conductive wave absorbing gasket. The test results of the prepared organic silicone thermal conductive wave absorbing gasket are compared with the expected set target performance as shown in Table 8. Table 8:

[0032] Combining the data of Examples 1-4 and Tables 2, 4, 6, and 8, it can be seen that the MATLAB program designed in the present application can design the formula of the thermally conductive and absorbing gasket according to the target thermal conductivity and absorption values, and the thermal conductivity and absorption performance of the gasket actually made by the output formula can meet the set target, and the error with the set target is small and the accuracy is high.

Claims

1. A method for designing a formula of a single-layer heat-conducting and wave-absorbing gasket, characterized in that: The following steps are involved: Step 1: Establish a powder parameter database, including electromagnetic parameters, thermal conductivity, and specific gravity; Step 2: Establish a two-dimensional matrix to list all the series of formula ratios of powder and resin matrix involved in the database; Step 3: Calculate the theoretical thermal conductivity k of the gasket prepared under the series of formulations c , k c The calculation formula is: log k c =V*(X1*C1*log k1+X2*C2*log k2+...+X a *C a *log k a )+(1-V)*log(C*k p ); Step 4: Automatically calculate the theoretical electromagnetic parameters of the prepared gasket for the formula with qualified thermal conductivity; Step 5: Calculate the reflectivity of the gasket based on the transmission line theory and the set gasket thickness; Step 6: Output the formula that meets the thermal conductivity and wave absorption performance.

2. The method for designing a formula of a single-layer heat-conducting and wave-absorbing gasket according to claim 1, characterized in that: The powder described in step 1 is carbonyl iron powder, sendust aluminum alloy powder, ferrite, iron powder, aluminum oxide, zinc oxide, aluminum nitride, boron nitride, aluminum hydroxide, and magnesium hydroxide.

3. The method for formula design of a single-layer heat-conducting and wave-absorbing gasket according to claim 1, characterized in that: The electromagnetic parameters, thermal conductivity and specific gravity of the powder parameters described in step 1. The method for designing a formula of a single-layer thermally conductive and wave-absorbing gasket according to claim 1 is characterized in that the powder morphology described in step 1 is spherical; and the powder particle size D50 is 1-150 μm.

4. The method for designing a formula of a single-layer heat-conducting and wave-absorbing gasket according to claim 1, characterized in that: In step 2, the resin matrix is ​​one of silicone oil, epoxy resin, polyurethane resin, phenolic resin, polystyrene, and rubber.

5. The method for designing a formula of a single-layer heat-conducting and wave-absorbing gasket according to claim 1, characterized in that: The two-dimensional matrix described in step 2 is the mass ratio of the resin matrix to the powder, and the mass ratio of the resin matrix to the powder is 100:0-1500.

6. The method for formula design of a single-layer heat-conducting and wave-absorbing gasket according to claim 1, characterized in that: The theoretical thermal conductivity k described in step 3 c In the calculation formula: k c is the thermal conductivity of the gasket, k1, k2, ..., k a is the thermal conductivity of the filler particles, k p is the thermal conductivity of the resin matrix; V is the volume fraction of the filling powder; C1, C2, ..., C a is the coefficient of the difficulty of the powder conductive chain formation, C is the coefficient that affects the crystallinity and crystal size of the polymer; X1, X2, ..., X a It is the percentage of particles in the filling powder.

7. The method for formula design of a single-layer heat-conducting and wave-absorbing gasket according to claim 1 and claim 6, characterized in that: The calculation formula of the volume fraction V of the filling powder in step 3 is as follows: V = (m1 + m2 + ... + m a ) / (m1 / ρ1+m2 / ρ2+...+m a / ρ a +m p / ρ p ), where m1, m2, ..., m a is the mass of the filling powder, ρ1, ρ2, ..., ρ a are the specific gravity of the filling powder, m p is the mass of the resin matrix, ρ p is the specific gravity of the resin matrix.

8. The method for designing a formula of a single-layer heat-conducting and wave-absorbing gasket according to claim 1 and claim 6, characterized in that: The number of particles of the filling powder in step 3 accounts for X1, X2, ..., X a The calculation formula is: j =m j / ρ j (D j ) 3 / (m1 / ρ1(D1) 3 +m2 / ρ2(D2) 3 +...m j / ρ j (D j ) 3 ...+m a / ρ a (D a ) 3 ), where m1, m2, ..., m a is the mass of the filling powder, ρ1, ρ2, ..., ρ a Specific gravity of filling powder, D1, D2, ..., D a is the particle size of the filling powder.

9. A method for designing a formula of a single-layer heat-conducting and wave-absorbing gasket according to claim 1 and claim 6, characterized in that: The difficulty coefficients C1, C2, ..., C of the powder conductive chain formed in step 3 are a The calculation formula for the coefficient C of polymer crystallinity and crystal size is: log k c =V*(C1*log k1)+(1-V)*log(C*k p ); Among them, the filling powder is limited to one kind, and gaskets with two different filling fractions of the same matrix resin are made. The thermal conductivity coefficient is tested, and the measured thermal conductivity and the calculated volume fraction are substituted into the formula to obtain two linear equations of two variables. Solving the equations can obtain the difficulty coefficient of the formation of the filler conductive chain and the coefficient affecting the crystallinity and crystal size of the polymer.

10. The method for formula design of a single-layer heat-conducting and wave-absorbing gasket according to claim 1, characterized in that: The calculation formula of the theoretical electromagnetic parameters (ε, μ) of the gasket in step 4 is: Among them, ε j 、v j represents the dielectric constant and volume fraction of the jth filler powder in the composite system, ε m is the dielectric constant of the resin matrix; according to the duality principle of electromagnetic theory, ε=μ, ε j =μ j , ε m =μ m ;μ j represents the magnetic permeability of the jth filling powder in the composite system, μ m is the magnetic permeability of the resin matrix.

11. The method for formula design of a single-layer heat-conducting and wave-absorbing gasket according to claim 1 and claim 10, characterized in that: The calculation formula of the volume fraction in step 4 is as follows: V j =m j / (m1 / ρ1+m2 / ρ2+...+m a / ρ a +m p / ρ p ), where m1, m2, ..., m a are the masses of the filling particles, ρ1, ρ2, ..., ρ a are the specific gravity of the filling particles, m p is the mass of the resin matrix, ρ p is the specific gravity of the resin matrix.

12. The method for formula design of a single-layer heat-conducting and wave-absorbing gasket according to claim 1, characterized in that: The calculation formula of the reflectivity R of the gasket in step 5 is as follows: z in =z c tanh(γd), w=2πf;where z in is the input impedance of the absorbing material, z c is the characteristic impedance of the absorbing material, f is the frequency of the electromagnetic wave, d is the thickness of the absorbing material, z0 is the characteristic impedance of the metal base plate, and z0=1.

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