CN113789058B - Low-stress heat-conducting silica gel, preparation method thereof and electronic instrument - Google Patents

Abstract

The application provides low-stress heat-conducting silica gel, a preparation method thereof and an electronic instrument. The low-stress heat-conducting silica gel comprises the following components in parts by weight: 87.5 to 90 portions of modified heat-conducting filler; 8.7 to 11 portions of alpha-hydrogen-omega-hydroxy-polydimethylsiloxane; 0.5-0.8 part of methyl end-capped polydimethylsiloxane; 0.5-1 part of cross-linking agent; 0.2 to 0.3 portion of coupling agent; 0.1 to 0.2 portion of catalyst. Wherein the modified heat-conducting filler is a heat-conducting filler treated by a low-stress treatment agent; the crosslinking agent contains two reactive functional groups. Carrying out first mixing on the raw materials except for the catalyst to obtain a mixed base material; and adding a catalyst for second mixing to obtain the low-stress heat-conducting silica gel. The heat-conducting silica gel has ultralow hardness, and can effectively package and protect electronic instruments from mechanical stress caused by thermal cycling and stress caused by external force.

Description

Low-stress heat-conducting silica gel, preparation method thereof and electronic instrument

Technical Field

The application relates to the field of heat-conducting silica gel, in particular to low-stress heat-conducting silica gel, a preparation method thereof and an electronic instrument.

Background

With the increasing density and high performance of the assembly of integration technology and microelectronics, the electronic components and circuit boards are also mounted in a miniaturized and high-density manner along with the development requirements, but the requirement on the heat dissipation function of the device is higher, otherwise, the generated heat is not dissipated when the device works, and the working efficiency and the service life are greatly influenced. Further, since electronic components or semiconductor devices mounted at high density are easily damaged by external force in terms of strength, electrical or thermophysical properties, etc., a material having a low elastic modulus and an ultra-low stress is required to be packaged to relieve stress caused by a change in internal and external environments and stress caused by internal heat generation.

Therefore, in order to ensure that the electronic device can continuously and stably work with high performance in the use environment, it is necessary to develop a heat-conducting and ultra-low stress packaging material to protect the electronic device from the mechanical stress caused by thermal cycling and the stress caused by external force. The heat-conducting silica gel has heat-conducting property, excellent cold and hot alternation resistance, aging resistance and electric insulation property, can avoid risks such as short circuit of a circuit and the like, and has good adhesion to most of metals and non-metals, so that the heat-conducting silica gel can be used as a packaging protection material in an electronic instrument. However, the hardness of the traditional heat-conducting silica gel product on the market is very high, and the stress in an electronic instrument cannot be well relieved. Therefore, it is urgently required to develop a heat conductive silicone rubber which is low in stress and has excellent heat conductive performance.

Disclosure of Invention

The application aims to provide low-stress heat-conducting silica gel, a preparation method thereof and an electronic instrument.

In order to achieve the above purpose, the specific technical scheme of the application is as follows:

a low-stress heat-conducting silica gel comprises the following components in parts by weight:

87.5 to 90 portions of modified heat-conducting filler;

8.7 to 11 portions of alpha-hydrogen-omega-hydroxy-polydimethylsiloxane;

0.5-0.8 part of methyl end-capped polydimethylsiloxane;

0.5-1 part of cross-linking agent;

0.2-0.3 part of coupling agent;

0.1 to 0.2 portion of catalyst;

the modified heat-conducting filler is a heat-conducting filler treated by a low-stress treating agent;

the crosslinking agent contains two reactive functional groups.

Preferably, the low stress treatment agent comprises octadecyl methyl diethoxysilane;

the heat conducting filler comprises at least one of aluminum oxide, zinc oxide, magnesium oxide, aluminum hydroxide and magnesium hydroxide.

Preferably, the kinematic viscosity of the α -hydro- ω -hydroxy-polydimethylsiloxane is from 500mPa · s to 10000mPa · s at 25 ℃;

the kinematic viscosity of the methyl-terminated polydimethylsiloxane is 50-200 mPas at 25 ℃.

Preferably, the crosslinking agent comprises at least one of dimethyldimethoxysilane, methylvinyldimethoxysilane, dimethyldiethoxysilane and ethylphenyldimethoxysilane.

Preferably, the coupling agent comprises at least one of 3-aminopropylmethyldimethoxysilane, 3-aminopropylmethyldiethoxysilane, N- (2-aminoethyl) -3-aminopropylmethyldimethoxysilane, and N- (2-aminoethyl) -3-aminoisobutylmethyldimethoxysilane.

Preferably, the catalyst comprises at least one of n-butyl titanate, tetraisobutyl titanate, n-propyl titanate, tetraisopropyl titanate, titanium complex of ethyl acetoacetate, and tert-butyl titanate.

The application also provides a preparation method of the low-stress heat-conducting silica gel, which comprises the following steps:

carrying out first mixing on raw materials including modified heat-conducting filler, alpha-hydrogen-omega-hydroxy-polydimethylsiloxane, methyl-terminated polydimethylsiloxane, a cross-linking agent and a coupling agent to obtain a mixed base material;

and adding a catalyst into the mixed base material for second mixing to obtain the low-stress heat-conducting silica gel.

Preferably, the preparation process of the modified heat-conducting filler comprises the following steps:

adding 90-110 parts by weight of distilled water into 9-11 parts by weight of heat-conducting filler, uniformly stirring, adding 0.25-0.35 part by weight of low-stress treatment agent octadecyl methyl diethoxy silane, continuously stirring to obtain slurry, and drying the slurry to constant weight to obtain the modified heat-conducting filler.

Preferably, the first mixing and the second mixing need to be stirred under a vacuum condition, wherein the vacuum condition is-0.1 MPa to-0.08 MPa;

the stirring time of the first mixing is 28 min-32 min, and the stirring time of the second mixing is 18 min-22 min.

The application also provides an electronic instrument which comprises the low-stress heat-conducting silica gel.

The beneficial effect of this application:

the low-stress heat-conducting silica gel provided by the application reduces the crosslinking density by using the crosslinking agent containing two reactive functional groups, so that the hardness of the heat-conducting silica gel product is reduced, and the stress is reduced. On one hand, the heat-conducting filler is treated by using the low-stress treating agent, so that the dispersing capacity of the filler can be improved, the heat-conducting property of a system is improved, and the influence of the heat-conducting filler on the hardness of a product is reduced by using the characteristics of long chain and large steric hindrance of the low-stress treating agent. The synergistic effect of filler is handled through cross-linking agent and low stress additive to this application for the heat conduction silica gel that final preparation obtained has ultralow hardness and ultralow stress, can protect sensitive electron device to avoid the mechanical stress that thermal cycle caused and the stress that external force caused. In addition, the low-stress heat-conducting silica gel has good heat-conducting property and room-temperature curing property, is simple and convenient to use, and the low-stress property of the low-stress heat-conducting silica gel cannot cause damage to electronic instruments, so that electronic devices and equipment are effectively protected.

The application also provides a preparation method of the low-stress heat-conducting silica gel, which is simple in process and easy to implement. Compared with double-component heat-conducting silica gel, the single-component condensed type heat-conducting silica gel greatly shortens the production period, and is simple in production process and high in production efficiency.

The application also provides an electronic instrument, and the low-stress heat-conducting silica gel prepared by the application can be applied to the electronic instrument, plays roles in heat conduction, packaging, protection and the like, and ensures the normal use of the electronic instrument.

Detailed Description

The terms as used herein:

"consisting of 8230%" \8230, preparation "and" comprising "are synonymous. The terms "comprises," "comprising," "includes," "including," "has," "having," "contains," "containing," or any other variation thereof, as used herein, are intended to cover a non-exclusive inclusion. For example, a composition, process, method, article, or apparatus that comprises a list of elements is not necessarily limited to only those elements but may include other elements not expressly listed or inherent to such composition, process, method, article, or apparatus.

The conjunction "consisting of 8230% \8230comprises" excludes any unspecified elements, steps or components. If used in a claim, the phrase is intended to claim as closed, meaning that it does not contain materials other than those described, except for the conventional impurities associated therewith. When the phrase "consisting of 8230' \8230"; composition "appears in a clause of the subject matter of the claims and not immediately after the subject matter, it defines only the elements described in the clause; other elements are not excluded from the claims as a whole.

When an amount, concentration, or other value or parameter is expressed as a range, preferred range, or as a range of upper preferable values and lower preferable values, this is to be understood as specifically disclosing all ranges formed from any pair of any upper range limit or preferred value and any lower range limit or preferred value, regardless of whether ranges are separately disclosed. For example, when a range of "1 to 5" is disclosed, the recited range should be interpreted to include ranges of "1 to 4," "1 to 3," "1 to 2 and 4 to 5," "1 to 3 and 5," and the like. When a range of values is described herein, unless otherwise stated, the range is intended to include the endpoints thereof and all integers and fractions within the range.

In these examples, parts and percentages are by weight unless otherwise indicated.

"parts by weight" means the basic unit of measure indicating the proportional relationship of the mass of the components, and 1 part may represent any unit mass, for example, 1g or 2.689 g. If the parts by weight of the component A are a parts and the parts by weight of the component B are B parts, the ratio of the mass of the component A to the mass of the component B, a: b. alternatively, the mass of the A component is aK and the mass of the B component is bK (K is an arbitrary number, and represents a multiple factor). It is not to be understood that, unlike the parts by weight, the sum of the parts by weight of all components is not limited to 100 parts.

"and/or" is used to indicate that one or both of the illustrated conditions may occur, e.g., a and/or B includes (a and B) and (a or B).

The application provides a low stress heat conduction silica gel, by weight, includes:

87.5 to 90 portions of modified heat-conducting filler (specifically, any value between 87.5 portions, 87.7 portions, 87.9 portions, 88 portions, 88.2 portions, 88.4 portions, 88.6 portions, 88.8 portions, 89 portions, 89.1 portions, 89.3 portions, 89.5 portions, 89.8 portions, 90 portions or 87.5 to 90 portions);

8.7 to 11 parts of alpha-hydrogen-omega-hydroxy-polydimethylsiloxane (which can be any value of 8.7 parts, 8.8 parts, 8.9 parts, 9 parts, 9.2 parts, 9.4 parts, 9.6 parts, 9.8 parts, 10 parts, 10.1 parts, 10.3 parts, 10.5 parts, 10.8 parts, 90 parts or 8.7 to 11 parts);

0.5 to 0.8 portion of methyl-terminated polydimethylsiloxane (specifically, 0.5 portion, 0.53 portion, 0.55 portion, 0.57 portion, 0.6 portion, 0.65 portion, 0.7 portion, 0.75 portion, 0.8 portion or any value between 0.5 and 0.8 portion);

0.5 to 1 part of a crosslinking agent (specifically, any value between 0.5, 0.55, 0.6, 0.65, 0.7, 0.75, 0.8, 0.85, 0.9, 0.95, 1 or 0.5 to 1 part of the crosslinking agent;

0.2 to 0.3 portion of coupling agent (specifically, any value between 0.2, 0.21, 0.22, 0.23, 0.24, 0.25, 0.26, 0.27, 0.28, 0.29, 0.3 or 0.2 to 0.3 portions);

0.1 to 0.2 portion of catalyst (specifically, 0.1 portion, 0.11 portion, 0.12 portion, 0.13 portion, 0.14 portion, 0.15 portion, 0.16 portion, 0.17 portion, 0.18 portion, 0.19 portion, 0.2 portion or any value between 0.1 and 0.2 portions);

wherein the modified heat-conducting filler is a heat-conducting filler treated by a low-stress treating agent; the crosslinking agent contains two reactive functional groups.

It is noted that in some embodiments of the present application, the thermally conductive filler includes at least one of aluminum oxide, zinc oxide, magnesium oxide, aluminum hydroxide, and magnesium hydroxide. Since the thermal conductivity of the polymer material is only 0.2 to 0.3W/(m.K), it is inevitable to select a filler having a high thermal conductivity. These heat conduction of this application are packed and are belonged to insulating type heat conduction and pack, mainly rely on the phonon to carry out heat-conduction, even under high addition, still can keep the excellent electrical insulation of silicon rubber, consequently the heat conduction silica gel of this application can be widely used as LED packaging material, the embedment material and the thermal interface material of IC chip in the electron electric field.

Generally, the morphology of the heat-conducting filler also affects the heat-conducting performance of the heat-conducting silica gel. The conventional heat-conducting filler has various shapes such as granular shape, sheet shape, fibrous shape and the like, and compared with a zero-dimensional material, a one-dimensional material (such as a fibrous material) and a two-dimensional material (such as a sheet material) with ultrahigh length-diameter ratio can form a larger contact area between the filler and the filler, thereby providing a wider path for phonon transmission, reducing interface contact thermal resistance and being beneficial to the construction of a heat-conducting network in a system. However, spherical fillers are most widely used in industry because they do not result in a sharp increase in viscosity at high loadings. In addition, the fillers with different powder particle sizes are matched for use, so that the stacking porosity of the fillers in the matrix can be reduced, a structure close to dense stacking is formed, and the heat-conducting property of the heat-conducting silicon rubber can be effectively improved. The use of a filler of a single particle size for filling silicone rubber often does not achieve a good effect.

In some embodiments, the thermally conductive filler used is a spherical composition of varying particle sizes. Specifically, in a preferred embodiment of the present application, the heat conductive filler is a mixture of spherical alumina particles of 1 μm, 5 μm, and 20 μm, and the mass ratio of the particle sizes is preferably 2:3:5.

after the heat-conducting filler is added into the silicone rubber, the inorganic filler and the organic matrix are very different in physical form and molecular structure, so that an interface layer is generated in a composite system, the properties of all components cannot be combined favorably, and the heat-conducting property of the heat-conducting silicone rubber and other properties are influenced. After the surface treating agent acts on the surfaces of the filler particles, the surface polarity of the filler particles can be reduced, the dispersion degree is improved, inorganic and organic materials with large property difference can be coupled, and the heat conducting performance and the mechanical performance of the heat conducting silica gel are improved.

However, the inventors of the present invention found that the modification treatment of the heat conductive filler with a conventional silane coupling agent, such as KH550, a151, etc., can greatly improve the connection between the filler and the organic matrix, but the hardness of the obtained heat conductive silica gel product is too high to be well used for packaging and protecting electronic devices. The heat-conducting filler is treated by the low-stress treating agent, and the finally obtained silica gel product has low hardness by utilizing the long chain and the large steric hindrance of the low-stress treating agent, so that the low-stress heat-conducting silica gel is obtained.

In some embodiments, the low-stress treatment agent of the present application comprises octadecyl methyldiethoxysilane, and octadecyl in the treatment agent can provide long chain and large steric hindrance, so that the hardness of the finally prepared heat-conducting silica gel is smaller.

In some embodiments, the α -hydro- ω -hydroxy-polydimethylsiloxane of the present application has a kinematic viscosity at 25 ℃ of 500 to 10000 mPa-s (specifically 500 to 1000, 2000 to 3000, 5000, 6000 to 8000, 10000 or any value between 500 to 10000 mPa-s). The heat-conducting silica gel is prepared by taking alpha-hydrogen-omega-hydroxy-polydimethylsiloxane as a main material of the silica gel and then carrying out condensation reaction with a cross-linking agent, and if the kinematic viscosity of the alpha-hydrogen-omega-hydroxy-polydimethylsiloxane is too high, the hardness of the prepared silica gel is larger.

In some embodiments, the methyl-terminated polydimethylsiloxane of the present disclosure has a kinematic viscosity at 25 ℃ of 50mPa · s to 200mPa · s (specifically, any value between 50mPa · s,80mPa · s,100mPa · s,120mPa · s,150mPa · s,180mPa · s,200mPa · s, or 50mPa · s to 200mPa · s), and it functions mainly as a plasticizer in the thermally conductive silica gel, and can increase the plasticity of the thermally conductive silica gel product, impart better flexibility to the silica gel, can reduce the viscosity of the base polymer, and can further add more thermally conductive filler to increase the thermal conductivity of the silica gel.

In some embodiments, the crosslinking agent herein comprises at least one of dimethyldimethoxysilane, methylvinyldimethoxysilane, dimethyldiethoxysilane, ethylphenyldimethoxysilane. In a general one-component dealcoholized heat-conducting silica gel, the crosslinking agent is mostly selected from methyltrimethoxysilane, methyltriethoxysilane, vinyltrimethoxysilane and the like. However, when these crosslinking agents are subjected to condensation reaction with the host material, often three methoxy groups or three ethoxy groups participate in crosslinking together, and the crosslinking density of the finally prepared heat-conducting silica gel is very high. However, the cross-linking agent selected by the application contains two reactive functional groups, and only two methoxyl groups or two ethoxyl groups participate in the reaction when the cross-linking agent is subjected to cross-linking reaction with the main material, so that the cross-linking density of the silica gel is greatly reduced, and the hardness of the silica gel product is reduced.

In some embodiments, the coupling agent of the present application comprises at least one of 3-aminopropylmethyldimethoxysilane, 3-aminopropylmethyldiethoxysilane, N- (2-aminoethyl) -3-aminopropylmethyldimethoxysilane, N- (2-aminoethyl) -3-aminoisobutylmethyldimethoxysilane. The coupling agents can improve the adhesive property of the heat-conducting silica gel and can better package electronic devices.

In some embodiments, the catalyst of the present application comprises at least one of n-butyl titanate, tetraisobutyl titanate, n-propyl titanate, tetraisopropyl titanate, titanium complex of ethyl acetoacetate, tert-butyl titanate.

The application also provides a preparation method of the low-stress heat-conducting silica gel, which specifically comprises the following steps: firstly, treating the heat-conducting filler with a low-stress treating agent of octadecyl methyl diethoxysilane to obtain a modified heat-conducting filler; and then carrying out first mixing on raw materials including the modified heat-conducting filler, alpha-hydrogen-omega-hydroxy-polydimethylsiloxane, methyl-terminated polydimethylsiloxane, a cross-linking agent and a coupling agent to obtain a mixed base material, and then adding a catalyst into the mixed base material to carry out second mixing to obtain the low-stress heat-conducting silica gel.

In some embodiments, the modified thermally conductive filler of the present application is prepared by a process comprising: adding 90-110 parts by weight (specifically, 90 parts, 93 parts, 95 parts, 97 parts, 100 parts, 102 parts, 104 parts, 106 parts, 108 parts, 110 parts or any value between 90 parts and 110 parts) of distilled water into 9-11 parts by weight (specifically, 9 parts, 9.3 parts, 9.5 parts, 9.7 parts, 10 parts, 10.2 parts, 10.4 parts, 10.6 parts, 10.8 parts, 11 parts or any value between 9 parts and 11 parts) of heat-conducting filler, uniformly stirring, adding 0.25-0.35 part by weight (specifically, 0.25 part, 0.26 part, 0.27 part, 0.28 part, 0.29 part, 0.3 part, 0.31 part, 0.32 part, 0.33 part, 0.34 part, 0.35 part or any value between 0.25 part and 0.35 part) of low-stress treating agent, stirring and drying the obtained heat-conducting filler to obtain the constant-stress treating agent-octadecyl methyl diethoxy silane slurry.

Further, when the distilled water and the heat conductive filler are stirred, the distilled water and the heat conductive filler can be stirred for 10min at 500rpm, then the low-stress treating agent can be added into the heat conductive filler mixed with the water by a spraying device, and the mixture is stirred for 20min at 2000rpm to obtain slurry, so that the heat conductive filler can be uniformly modified by the low-stress treating agent with small mass. Before the slurry is dried, the distilled water can be filtered out by a filter screen, and then a vacuum drying oven is selected for drying at 105 ℃, so that the modified heat-conducting filler is finally obtained.

In some embodiments, the heat conductive silica gel raw material of the present application is stirred under a vacuum condition of-0.1 MPa to-0.08 MPa during the first mixing and the second mixing; the stirring time of the first mixing is 28 min-32 min, and the stirring time of the second mixing is 18 min-22 min. Specifically, the stirring time of the first mixing is 30min, and the stirring time of the second mixing is 20min.

Further, when the heat-conducting silica gel is prepared, a vacuum planetary stirrer can be used as production equipment, first mixing is carried out, the rotating speed of the vacuum planetary stirrer can be set to be 10rpm, and the stirring time is set to be 30min; and when the second mixing is carried out, the rotating speed is continuously kept at 10rpm, but the stirring time can be set to be 20min, and finally the single-component low-stress heat-conducting silica gel can be prepared.

The application also provides an electronic instrument, which comprises the low-stress heat-conducting silica gel. The heat-conducting silica gel prepared by the application can be used for LCD (liquid crystal display) glue sealing, IC (integrated circuit) packaging and bonding and the like in a dispensing mode, and can be particularly used for sensors, relays, power adapters, electronic components, household appliances, computer and mobile phone digital products, coil products and optical semiconductor products; the heat-conducting silica gel can be pressed into molded products with different shapes in a mold, and then applied to different electronic instrument products, and has the functions of heat transfer media and performances of shock resistance, moisture resistance, dust resistance, corrosion resistance and the like.

Embodiments of the present invention will be described in detail below with reference to specific examples, but it will be understood by those skilled in the art that the following examples are only illustrative of the present invention and should not be construed as limiting the scope of the present invention. The examples, in which specific conditions are not specified, were conducted under conventional conditions or conditions recommended by the manufacturer. The reagents or instruments used are conventional products which are not indicated by manufacturers and are commercially available.

Example 1

Preparing a modified heat-conducting filler: 200g of 1-micron spherical alumina, 300g of 5-micron spherical alumina and 500g of 20-micron spherical alumina are mixed with 10kg of distilled water, the mixture is stirred for 10min at the rotating speed of 500rpm, 30g of low-stress treatment agent octadecyl methyl diethoxysilane is added by a spraying device, then the mixture is continuously mixed for 20min at the rotating speed of 2000rpm, the mixed material is filtered by a filter screen to remove moisture, the filtered material is placed in a vacuum oven, and the dried material is dried to constant weight at 105 ℃, so that the modified heat-conducting filler treated by the low-stress treatment agent octadecyl methyl diethoxysilane is obtained.

Preparing low-stress heat-conducting silica gel: 90g of alpha-hydro-omega-hydroxy-polydimethylsiloxane having a kinematic viscosity of 500 mPas (at 25 ℃), 5g of methyl-terminated polydimethylsiloxane having a kinematic viscosity of 100 mPas (at 25 ℃), 7g of dimethyldimethoxysilane as a crosslinking agent, 3g of 3-aminopropylmethyldiethoxysilane as a coupling agent, and 893g of the treated heat-conductive filler were put into a vacuum planetary gear and stirred at-0.08 MPa and 10rpm for 30 minutes; then 2g of diisopropyl bis (ethyl acetoacetate) titanate is added and stirred for 20min under the conditions of-0.08 MPa and 10rpm to obtain the low-stress heat-conducting silica gel.

Example 2

The same as example 1 except that the crosslinking agent was changed to dimethyldiethoxysilane.

Example 3

The same as in example 1, except that the coupling agent was changed to 3-aminopropylmethyldimethoxysilane.

Example 4

The same as in example 1 except that the catalyst was changed to n-butyl titanate.

Example 5

The same as in example 1, except that the kinematic viscosity of α -hydro- ω -hydroxy-polydimethylsiloxane became 1500 mPas at 25 ℃.

Example 6

The same as example 1, except that the amount of α -hydro- ω -hydroxy-polydimethylsiloxane was changed to 100g, and the amount of the treated heat conductive filler was changed to 883g.

Comparative example 1

The same as example 1 except that the crosslinking agent was changed to methyltrimethoxysilane.

Comparative example 2

The same as example 1, except that in treating the thermally conductive filler, the low-stress treating agent octadecylmethyldiethoxysilane was changed to conventional treating agent γ -aminopropyltriethoxysilane.

Comparative example 3

The same as example 1, except that in treating the thermally conductive filler, the low-stress treating agent octadecylmethyldiethoxysilane was changed to conventional treating agent γ -aminopropyltriethoxysilane, and the crosslinking agent was changed to methyltrimethoxysilane.

Comparative example 4

The procedure of example 1 was repeated, except that the heat conductive filler was not treated with the treating agent, and 178.6g of dried 1 μm spherical alumina, 267.9g of dried 5 μm spherical alumina, and 446.5g of dried 20 μm spherical alumina were directly weighed to prepare a heat conductive silica gel.

The heat conductive silica gels provided in examples 1 to 6 and comparative examples 1 to 4 were tested for various properties: testing the surface drying time according to a testing method described in GB/T13477.5-2002 test method for building sealing materials surface drying time; performing Shore hardness test on the cured heat-conducting silica gel according to the standard GB/T2411-2008; testing the dispensing rate of the extrusion nozzle according to the extrusion quality of 90psi,1mm and 1 min; the specific gravity after curing was measured according to the standards in ASTM D792-2007 test methods for Density and relative Density of plastics; the thermal conductivity after curing was measured according to the standard in ASTM D5470-2017; the volume resistivity after curing was measured according to the standard in ASTM D257; the breakdown voltage after curing was tested according to the standard in ASTM D149. The test results are shown in table 1.

TABLE 1 Performance data for thermally conductive silica gels provided in examples 1-6 and comparative examples 1-4

As can be seen from Table 1, the thermally conductive silica gels prepared in examples 1 to 6 of the present application have good thermal conductivity and room temperature curability. Compared with the hardness of comparative examples 1-4, the hardness of the product prepared by using the traditional crosslinking agent methyl trimethoxy silane with multiple reactive functional groups is higher, the hardness of the product prepared by using the untreated conductive filler or the filler treated by using the conventional coupling agent is higher, and the hardness of the heat-conducting silica gel prepared by the technical scheme is lower. Particularly, the test results of the example 1 and the comparative examples 1 to 3 show that the filler treated by the cross-linking agent with dual reactive functional groups and the low-stress treating agent have a synergistic effect, so that the finally prepared heat-conducting silica gel has ultralow hardness and ultralow stress, and can protect sensitive electronic devices from mechanical stress caused by thermal cycling and stress caused by external force.

Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and these modifications or substitutions do not depart from the spirit of the corresponding technical solutions of the embodiments of the present invention.

Furthermore, those skilled in the art will appreciate that while some embodiments herein include some features included in other embodiments, rather than other features, combinations of features of different embodiments are meant to be within the scope of the invention and form different embodiments. For example, in the claims above, any of the claimed embodiments may be used in any combination. The information disclosed in this background section is only for enhancement of understanding of the general background of the invention and should not be taken as an acknowledgement or any form of suggestion that this information forms the prior art already known to a person skilled in the art.

Claims (8)

1. A low-stress heat-conducting silica gel is characterized by comprising the following components in parts by weight:

87.5 to 90 portions of modified heat-conducting filler;

8.7 to 11 portions of alpha-hydrogen-omega-hydroxy-polydimethylsiloxane;

0.5 to 0.8 portion of methyl terminated polydimethylsiloxane;

0.5-1 part of cross-linking agent;

0.2 to 0.3 portion of coupling agent;

0.1 to 0.2 portion of catalyst;

the modified heat-conducting filler is a heat-conducting filler treated by a low-stress treating agent; the low stress treatment agent comprises octadecyl methyl diethoxysilane;

the crosslinking agent contains two reactive functional groups; the cross-linking agent comprises at least one of dimethyl dimethoxy silane, methyl vinyl dimethoxy silane, dimethyl diethoxy silane and ethyl phenyl dimethoxy silane;

the coupling agent comprises at least one of 3-aminopropylmethyldimethoxysilane, 3-aminopropylmethyldiethoxysilane, N- (2-aminoethyl) -3-aminopropylmethyldimethoxysilane and N- (2-aminoethyl) -3-aminoisobutylmethyldimethoxysilane.

2. The low stress thermally conductive silica gel of claim 1 wherein the thermally conductive filler comprises at least one of aluminum oxide, zinc oxide, magnesium oxide, aluminum hydroxide, magnesium hydroxide.

3. The low stress, thermally conductive silica gel of claim 1, wherein the α -hydro- ω -hydroxy-polydimethylsiloxane has a kinematic viscosity of 500 mPa-s to 10000 mPa-s at 25 ℃;

the kinematic viscosity of the methyl-terminated polydimethylsiloxane at 25 ℃ is 50mPa & s-200 mPa & s.

4. The low stress thermally conductive silica gel according to any one of claims 1 to 3, wherein the catalyst comprises at least one of n-butyl titanate, tetraisobutyl titanate, n-propyl titanate, tetraisopropyl titanate, titanium complex of ethyl acetoacetate, and tert-butyl titanate.

5. A method for preparing the low-stress heat-conducting silica gel according to any one of claims 1 to 4, comprising the following steps:

firstly mixing raw materials including modified heat-conducting filler, alpha-hydrogen-omega-hydroxyl-polydimethylsiloxane, methyl-terminated polydimethylsiloxane, a cross-linking agent and a coupling agent to obtain a mixed base material;

and adding a catalyst into the mixed base material for second mixing to obtain the low-stress heat-conducting silica gel.

6. The method according to claim 5, wherein the modified thermally conductive filler is prepared by the following steps:

adding 90-110 parts by weight of distilled water into 9-11 parts by weight of heat-conducting filler, uniformly stirring, adding 0.25-0.35 part by weight of low-stress treatment agent octadecyl methyl diethoxy silane, continuously stirring to obtain slurry, and drying the slurry to constant weight to obtain the modified heat-conducting filler.

7. The method for preparing low-stress heat-conducting silica gel according to any one of claims 5 to 6, wherein the first mixing and the second mixing require stirring under vacuum conditions, wherein the vacuum conditions are-0.1 MPa to-0.08 MPa;

the stirring time of the first mixing is 28 min-32 min, and the stirring time of the second mixing is 18 min-22 min.

8. An electronic device comprising the low stress thermally conductive silica gel according to any one of claims 1 to 4.