A silicone potting compound for high precision voltage sensors and a method for producing the same

Abstract

The application belongs to the technical field of materials, and relates to a siloxane potting glue for a high-precision voltage sensor and a preparation method thereof. Under the action of a platinum-gold catalyst in the system, Si-H of methyl hydrogen silicone oil in component B is combined with active vinyl Si-C=C of methyl vinyl silicone oil in component A to generate a high-molecular-weight three-dimensional network structure elastomer through a silicon hydrogen addition reaction and a polymerization reaction. No by-product is generated in the polymerization reaction process. The heat-conducting filler (high-purity quartz powder) in the system does not participate in the above reaction and is merely wrapped therein. The polymerization reaction product has the advantages of small overall volume shrinkage before / after a curing reaction, good overall dimensional stability, small internal stress of a prepared cured product and the like, is very suitable for packaging of precise electronic components and parts, and plays an insulating, sealing and protecting role on the parts to be potted.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of materials, and relates to a siloxane pouring sealant for a high-precision voltage sensor and a preparation method thereof. BACKGROUND

[0002] For a high-precision voltage sensor, the current ways to improve the reliability of the device are as follows: using a military standard device of a higher reliability level; enhancing the integration level of the device to realize functions by using more integrated circuits; and improving the protection level of a power port. The first two ways often put forward higher requirements for device selection and circuit design capability, and the material cost will also increase accordingly. The third way has the least change in principle circuit and functional implementation device, and the corresponding cost is also the most economical.

[0003] The protection level is mainly realized by means of a pouring sealant, but in a harsh working environment, especially under certain environmental temperature conditions, higher requirements are put forward for the stability and reliability of the pouring sealant used for the high-precision voltage sensor, especially in the technical field of existing rail transit electrical equipment and new energy electrical equipment.

[0004] A flexible epoxy pouring sealant is provided in a Chinese patent application file (publication number: CN 110699026A), a pouring sealant and a preparation method and application thereof are provided in a Chinese patent application file (publication number: CN 110699036A), and a Chinese patent application file (publication number: CN 110484025A). The technical solutions provided in the above existing inventions cannot meet the requirements of the current updated transportation industry, especially the stability and reliability requirements of the high-precision voltage sensor under harsh environmental temperature. SUMMARY

[0005] The purpose of the present application is to provide a siloxane pouring sealant for a high-precision voltage sensor, which has low internal stress, low volatility and high thermal conductivity.

[0006] The purpose of the present application can be achieved by the following technical solution: a siloxane pouring sealant for a high-precision voltage sensor, characterized in that the raw material of the siloxane pouring sealant is composed of component A and component B, wherein component A comprises the following raw materials in mass fraction: 95-115 parts of methyl vinyl silicone oil, 180-210 parts of thermal conductive filler, and 1-5 parts of platinum gold catalyst.

[0007] Component B comprises the following raw materials in mass fraction: 85-95 parts of methyl vinyl silicone oil, 8-12 parts of mixed silicone oil, and 180-210 parts of thermal conductive filler.

[0008] The silicone pouring sealant of the present application has low stress in the fixed and shaped glue body after being applied in its use environment, and the total amount of small molecule substances remaining in the shaped glue body is small, the volatile amount of the final product is less, and the process requirements of high-precision voltage sensors are fully met. Especially in harsh working environments, especially under certain environmental temperature conditions, the high stability and high reliability requirements of the pouring sealant used for electrical products, especially suitable for application in the technical field of existing rail transit electrical equipment and new energy electrical equipment.

[0009] As preferred, the methyl vinyl silicone oil has a molecular formula of (CH2=CH)SiO[Si(CH3)2SiO] n Si(CH=CH2), wherein n is 175-190.

[0010] In the above-mentioned silicone pouring sealant for high-precision voltage sensors, the heat-conducting filler is high-purity quartz powder.

[0011] In the above-mentioned silicone pouring sealant for high-precision voltage sensors, the platinum-gold catalyst is Pt3000 platinum-gold catalyst. Under the action of the platinum-gold catalyst in the system, the Si-H group of the methyl hydrogen silicone oil in component B reacts with the active vinyl group Si-C=C of the methyl vinyl silicone oil in component A to form a high-molecular-weight three-dimensional network structure elastomer through a silicon-hydrogen addition reaction and a polymerization reaction. No by-products are generated in the polymerization reaction process. The heat-conducting filler (high-purity quartz powder) in the system does not participate in the above-mentioned reaction and is only wrapped therein. The product of the polymerization reaction has the advantages of small overall volume shrinkage before / after the curing reaction, good overall dimensional stability, small internal stress of the prepared cured product, and the like, and is very suitable for packaging precision electronic components and parts, and plays an insulating, sealing, and protective role on the encapsulated parts.

[0012] In the above-mentioned silicone pouring sealant for high-precision voltage sensors, the mixed silicone oil is composed of methyl hydrogen silicone oil a and methyl hydrogen silicone oil b in a mass ratio of 1:(5-15).

[0013] In the above-mentioned silicone pouring sealant for high-precision voltage sensors, the methyl hydrogen silicone oil a has a molecular formula of (CH3)3SiO[(CH3)(H)SiO] n [(CH3)2SiO] m Si(CH3)3, wherein m=5-10 and n=35-45.

[0014] In the above-mentioned silicone pouring sealant for high-precision voltage sensors, the methyl hydrogen silicone oil b has a molecular formula of HSiO[Si(CH3)2SiO]nSiH, wherein n=35-45.

[0015] The application further provides a preparation method of the silicone potting compound for the high-precision voltage sensor.

[0016] S1, preparation of component A: methyl vinyl silicone oil is purified and refined, then mixed with a heat-conducting filler, and after cooling, a platinum-gold catalyst is added for vacuum stirring to obtain component A;

[0017] S2, preparation of component B: methyl vinyl silicone oil and mixed silicone oil are purified and refined respectively, then the methyl vinyl silicone oil is mixed with the heat-conducting filler, and after cooling, the mixed silicone oil is added for vacuum stirring to obtain component B;

[0018] S3, components A and B are uniformly mixed, and finally vacuum debubbling and room temperature curing are performed to obtain the silicone potting compound.

[0019] The novel potting compound prepared in the application can improve the protection strength of the power port, ensure the heat dissipation requirement of the circuit by the high heat-conducting performance, reduce the influence of power consumption heat on the temperature drift of the device, and thus realize the stability and reliability requirement of the high-precision voltage sensor under harsh environmental temperature, and is particularly suitable for application in the fields of rail transit and new energy.

[0020] In the preparation method of the silicone potting compound for the high-precision voltage sensor, the purification and refining are performed by rotary film evaporation, specifically, vacuum distillation is performed at a temperature of 180-230 DEG C and a pressure of 1-200 Pa for 10-20 h.

[0021] The main impurities in the raw material are cyclic siloxanes [(CH3)2SiO] n n=3, 4, 5, 6; and free small molecule linear or branched silicone oil with a molecular weight of less than 500, which can ensure that the total content of impurities is less than 500 ppm after rotary film evaporation.

[0022] In the preparation method of the silicone potting compound for the high-precision voltage sensor, the heating and mixing temperature is 80-120 DEG C, and the time is 1-3 h.

[0023] As preferred, the temperature after cooling is 40-80 DEG C.

[0024] After heating and mixing, the platinum-gold catalyst is added after cooling, which can avoid oxidation failure of the platinum-gold catalyst caused by high temperature, and affect the curing speed.

[0025] After heating and mixing, the mixed silicone oil is added after cooling, which can avoid the high-temperature dehydrogenation of methyl hydrogen-containing silicone oil, resulting in the imbalance of component ratio, and further affecting the physical properties such as the strength of the cured product.

[0026] In the preparation method of the silicone potting glue of the high-precision voltage sensor, the mass ratio of component A to component B in step S3 is 1:(0.5-1.5).

[0027] The silicone potting glue prepared finally in the application is a "jelly-like" elastic substance, has very low mechanical strength, has certain adhesion, is easy to construct, and can replace various existing potting glues used in various scenes for sealing various electronic components.

[0028] Compared with the prior art, the application has the following beneficial effects:

[0029] 1. The silicone potting glue provided by the application is soft and elastic, can provide insulation protection and vibration buffering for a printed circuit board, and thus ensures that the printed circuit board is not affected by thermal stress and mechanical stress during use.

[0030] 2. The silicone potting glue provided by the application has very low content of low-molecular-weight cyclic siloxane, greatly reduces the concentration of small-molecule volatile substances in the potting system during use, and reduces the risk of increasing the surface contact resistance of components due to small-molecule volatile substances.

[0031] 3. The silicone potting glue provided by the application has a relatively high thermal conductivity, greatly accelerates heat dissipation of the circuit board during operation, and reduces the influence of power consumption heat on device temperature drift.

[0032] 4. The silicone potting glue provided by the application has adhesion, the glue layer is well combined with the surface of a printed circuit board, a magnetic assembly and the like inside a sensor, reduces the possibility of deposition of free small molecules on the surface of components of the printed circuit board, and thus reduces the risk of increasing the surface contact resistance of components due to small-molecule volatile substances.

[0033] 5. The silicone potting glue can ensure stable and reliable measurement accuracy of a high-precision voltage sensor, can enable the sensor to meet 1000-hour high-temperature and high-humidity double 85 and 1000-cycle high-low temperature impact test requirements, and greatly improves the environmental application reliability of the high-precision voltage sensor. DETAILED DESCRIPTION

[0034] The following is a specific embodiment of the application, which further describes the technical solutions of the application, but the application is not limited to these embodiments.

[0035] Methyl vinyl silicone oil:

[0036] Manufacturer: Shanghai Jingri New Material Technology Co., Ltd., model (VS500L), molecular weight (about 13000), the methyl vinyl silicone oil component contains about 100 ppm of low molecular weight cyclosiloxane, and the methyl vinyl silicone oil has a suitable viscosity of 100-1000 mPa·s to ensure that the subsequent obtained formula has suitable fluidity and prevents powder from settling;

[0037] Thermally conductive filler high-purity quartz powder:

[0038] Manufacturer: Shanghai Silibico Mining Co., Ltd., model (Silver Bond 606);

[0039] Platinum-based catalyst Kastner platinum-based complex:

[0040] Manufacturer: Shanghai Jingri New Material Technology Co., Ltd., model (Pt3000);

[0041] Methyl hydrogen-containing silicone oil a:

[0042] Manufacturer: Shanghai Jingri New Material Technology Co., Ltd., model (H020), molecular weight (about 3000), the methyl hydrogen-containing silicone oil component contains about 500 ppm of low molecular weight cyclosiloxane, and the methyl hydrogen-containing silicone oil has a suitable viscosity of 20-120 mPa·s; (CH3)3SiO[(CH3)(H)SiO] n [(CH3)2SiO] m Si(CH3)3, wherein m=8, n=40.

[0043] Methyl hydrogen-containing silicone oil b:

[0044] Manufacturer: Shanghai Jingri New Material Technology Co., Ltd., model (DH006), molecular weight (about 3300), the methyl hydrogen-containing silicone oil component contains about 500 ppm of low molecular weight cyclosiloxane, and the methyl hydrogen-containing silicone oil has a suitable viscosity of 20-120 mPa·s; HSiO[Si(CH3)2SiO]nSiH, wherein n=40.

[0045] Example 1:

[0046] S1, the raw materials are configured as follows:

[0047] Component A: 100 parts of methyl vinyl silicone oil, 2 parts of Pt catalyst, and 200 parts of thermally conductive filler (high-purity quartz powder); Component B: 90 parts of methyl vinyl silicone oil, 10 parts of mixed silicone oil, and 200 parts of thermally conductive filler (high-purity quartz powder); the mass ratio of methyl hydrogen-containing silicone oil a and methyl hydrogen-containing silicone oil b in the mixed silicone oil is 1:10;

[0048] S2, the methyl vinyl silicone oil and methyl hydrogen silicone oil are respectively purified and refined twice, specifically, the rotary film evaporation method is adopted, under vacuum condition, the temperature is controlled in the range of 200°C, the pressure is 180 Pa, and distillation refining is performed for 15 h, so as to further remove low molecular weight impurities;

[0049] S2, component A is prepared in the following manner: the methyl vinyl silicone oil and the thermal conductive filler are fully premixed, heated to 100°C, the system pressure is kept at 800 Pa, moisture is removed, the reaction is kept for 2 h, cooled to 60°C, and then the platinum-gold catalyst is added to perform vacuum stirring for 15 min to obtain component A;

[0050] S3, component B is prepared in the following manner: the methyl vinyl silicone oil and the thermal conductive filler are fully premixed, heated to 100°C, the system pressure is kept at 800 Pa, moisture is removed, the reaction is kept for 2 h, cooled to 60°C, and then the mixed silicone oil is added to perform vacuum stirring to obtain component B;

[0051] S4, component A and component B are uniformly mixed in a mass ratio of 1:1, defoaming is performed under vacuum condition for 30 min, and then the mixture is placed at room temperature to cure for 24 h to obtain the silicone pouring sealant.

[0052] Table 1: physical property detection results of the silicone pouring sealant prepared in Example 1

[0053]

[0054]

[0055] Example 2:

[0056] S1, the following raw materials are configured in the following mass fractions:

[0057] Component A: 95 parts of methyl vinyl silicone oil, 1 part of Pt catalyst, and 180 parts of thermal conductive filler (high-purity quartz powder); component B: 85 parts of methyl vinyl silicone oil, 8 parts of mixed silicone oil, and 180 parts of thermal conductive filler (high-purity quartz powder); the mass ratio of methyl hydrogen silicone oil a and methyl hydrogen silicone oil b in the mixed silicone oil is 1:5;

[0058] S2, the methyl vinyl silicone oil and the methyl hydrogen silicone oil are respectively purified and refined twice, specifically, the rotary film evaporation method is adopted, under vacuum condition, the temperature is controlled in the range of 180°C, the pressure is 1 Pa, and distillation refining is performed for 10 h, so as to further remove low molecular weight impurities;

[0059] S2, component A is prepared in the following manner: the methyl vinyl silicone oil and the thermal conductive filler are fully premixed, heated to 80°C, the system pressure is kept at 800 Pa, moisture is removed, the reaction is kept for 1 h, cooled to 60°C, and then the platinum-gold catalyst is added to perform vacuum stirring for 15 min to obtain component A;

[0060] S3, Preparation of Component B: After methyl vinyl silicone oil and thermal conductive filler were pre-mixed, the system was heated to 80℃, and the pressure was kept at 800 Pa to remove moisture. The reaction was maintained for 1 h. After cooling to 60℃, mixed silicone oil was added for vacuum stirring to obtain Component B;

[0061] S4, Component A and Component B were uniformly mixed at a mass ratio of 1:0.5. After vacuum degassing for 30 min, the mixture was cured at room temperature for 24 h to obtain a silicone pouring sealant.

[0062] Example 3:

[0063] S1, the following raw materials were configured by mass fraction:

[0064] Component A: 115 parts of methyl vinyl silicone oil, 5 parts of Pt catalyst, 210 parts of thermal conductive filler (high-purity quartz powder); Component B: 95 parts of methyl vinyl silicone oil, 12 parts of mixed silicone oil, 210 parts of thermal conductive filler (high-purity quartz powder); the mass ratio of methyl hydrogen-containing silicone oil a and methyl hydrogen-containing silicone oil b in the mixed silicone oil was 1:15;

[0065] S2, methyl vinyl silicone oil and methyl hydrogen-containing silicone oil were respectively subjected to secondary purification and refining. Specifically, rotary thin film evaporation was adopted. The temperature was controlled in the range of 230℃ under vacuum condition, and the pressure was 200 Pa. Distillation refining was performed for 20 h to further remove low molecular weight impurities;

[0066] S2, Preparation of Component A: After methyl vinyl silicone oil and thermal conductive filler were pre-mixed, the system was heated to 120℃, and the pressure was kept at 800 Pa to remove moisture. The reaction was maintained for 3 h. After cooling to 60℃, platinum gold catalyst was added for vacuum stirring for 15 min to obtain Component A;

[0067] S3, Preparation of Component B: After methyl vinyl silicone oil and thermal conductive filler were pre-mixed, the system was heated to 120℃, and the pressure was kept at 800 Pa to remove moisture. The reaction was maintained for 3 h. After cooling to 60℃, mixed silicone oil was added for vacuum stirring to obtain Component B;

[0068] S4, Component A and Component B were uniformly mixed at a mass ratio of 1:1.5. After vacuum degassing for 30 min, the mixture was cured at room temperature for 24 h to obtain a silicone pouring sealant.

[0069] Comparative Example 1:

[0070] The difference from Example 1 is that only methyl hydrogen-containing silicone oil a is used as the mixed silicone oil. The silicone pouring sealant prepared by using only methyl hydrogen-containing silicone oil a is unqualified, and the product presents an "oil out" phenomenon for a long time, because the low molecular weight polymers or small molecule substances in the product volatilize for a long time.

[0071] Comparative Example 2:

[0072] The difference from Example 1 is that only methyl hydrogen silicone oil b is used as the mixed silicone oil. If only methyl hydrogen silicone oil a is used, the final silicone potting compound is unqualified, and the product surface presents an "oily" phenomenon for a long time. This is because the low molecular weight polymer or small molecule material in it volatilizes for a long time, and the potting compound product itself is low in strength and easy to break.

[0073] Comparative Example 3:

[0074] The difference from Example 1 is that no mixed silicone oil is added to component B. The lack of mixed silicone oil in the heat-conducting filler makes the component mixing difficult, and the stirring intensity and time are lengthened. Fine air bubbles are found in the material, and the final potting compound product is unqualified.

[0075] Comparative Example 4:

[0076] The difference from Example 1 is that no platinum catalyst is added to component A. Due to the lack of catalyst, the subsequent reaction is not completed, and the potting compound cannot be prepared.

[0077] Comparative Example 5:

[0078] The difference from Example 1 is that no platinum catalyst is added to component A, and no mixed silicone oil is added to component B. Due to the lack of catalyst, the subsequent reaction is not completed, and the potting compound cannot be prepared.

[0079] The silicone potting compounds prepared in Examples 1-3 and Comparative Examples 1-5 are respectively used for the same batch of high-precision voltage sensors, and then the high-precision voltage sensors are respectively subjected to high temperature and high humidity double 85 test and high and low temperature impact test.

[0080] The high temperature and high humidity double 85 test standard is as required by the People's Republic of China National Standard "GB / T 2423.50-2012 Environmental Test Part 2: Test Method Test Cy: Constant Temperature and Humidity Mainly for Accelerated Test of Components", the temperature is 85℃, and the relative humidity is 85%.

[0081] The high and low temperature impact standard is as required by the People's Republic of China National Standard "GB / T 2423.22-2012 Electronic and Electrical Product Application Environment Condition Test Part 2: Test Method Test N: Temperature Change", the temperature interval is -40-85℃.

[0082] Table 2: Performance detection results of silicone potting compounds prepared in Examples 1-3 and Comparative Examples 1-3 for high-precision voltage sensors

[0083]

[0084]

[0085] In summary, the prepared potting glue has a total content of residual volatile impurities (mainly low molecular weight cyclic siloxane) in the finished product of less than 500 ppm. When potting components, the amount of small molecule volatile substances in the potting system can be greatly reduced, the volatile substances adhering to the surface of the components are reduced, and the risk of increased surface contact resistance of the components is reduced, while meeting the stability of chemical properties and being more environmentally friendly.

[0086] Secondly, the thermal conductivity of the potting glue can reach 0.8 W / m·K, greatly accelerating the heat dissipation of the circuit board during operation and reducing the influence of power consumption heat on the temperature drift of the components. At the same time, the potting glue has good elasticity and adhesion, and the prepared glue layer has good bonding performance with the surface of the printed circuit board, magnetic components and other elements inside the sensor, further reducing the possibility of deposition of volatile free small molecules on the surface of the components of the printed circuit board, thereby reducing the risk of increased surface contact resistance of the components, and ultimately ensuring the stable and reliable measurement accuracy of the high-precision voltage sensor. In addition, through the vacuum potting method, the potting glue can form a uniform glue layer inside the high-precision voltage sensor after curing, ensuring the consistency of the overall insulation and mechanical strength of the voltage sensor.

[0087] The embodiments of the present application do not exhaust the technical scope of the claimed technical range, and the new technical solutions formed by the same or multiple technical features in the embodiments of the technical solutions are also within the scope of the claimed technical range; at the same time, in all the enumerated or unenumerated embodiments of the present application, the parameters in the same embodiment only represent one example (i.e. a feasible scheme) of the technical solution, and there is no strict cooperation and limitation relationship between the parameters, except for the special declaration, wherein the parameters can be replaced with each other without violating the axioms and the claims of the present application.

[0088] The technical means disclosed in the present application is not limited to the technical means disclosed in the above technical means, but also includes the technical solutions composed of any combination of the above technical features. The above is the specific implementation of the present application, and it should be pointed out that for ordinary skilled persons in the art, without departing from the principles of the present application, a number of improvements and refinements can be made, which are also considered within the scope of protection of the present application.

[0089] The specific embodiments described herein are merely illustrative of the spirit of the present application. Those skilled in the art can make various modifications or supplements to the described specific embodiments or use similar ways to replace them, without deviating from the spirit of the present application or exceeding the scope defined by the appended claims.

Claims

1. A silicone potting compound for high-precision voltage sensors, characterized in that, The siloxane potting compound raw material is composed of component A and component B, wherein component A includes the following parts by weight: 95-115 parts methyl vinyl silicone oil, 180-210 parts thermally conductive filler, and 1-5 parts platinum-based catalyst; component B includes the following parts by weight: 85-95 parts methyl vinyl silicone oil, 8-12 parts mixed silicone oil, and 180-210 parts thermally conductive filler. The thermally conductive filler is high-purity quartz powder; The mixed silicone oil is composed of methyl hydrogen silicone oil a and methyl hydrogen silicone oil b in a mass ratio of 1:(5-15); The molecular formula of methyl hydrogen silicone oil a is (CH3)3SiO[(CH3)(H)SiO] n [(CH3)2SiO] m Si(CH3)3, where m = 5-10, n = 35-45; The molecular formula of methyl hydrogen silicone oil b is HSiO[Si(CH3)2SiO]nSiH, where n = 35-45; The preparation method of the siloxane potting compound includes the following steps: S1. Preparation of component A: Methyl vinyl silicone oil is purified and refined, then mixed with thermally conductive filler under heat, cooled, and then a platinum-based catalyst is added and stirred under vacuum to obtain component A; S2, Preparation of Component B: First, methyl vinyl silicone oil and mixed silicone oil are purified and refined separately. Then, methyl vinyl silicone oil is heated and mixed with thermally conductive filler. After cooling, mixed silicone oil is added and vacuum stirred to obtain component B. S3. Mix component A and component B evenly, and finally perform vacuum degassing and room temperature curing to obtain siloxane potting compound; The temperature after cooling is 40–80℃; The purification and refining process employs rotary thin-film evaporation, specifically vacuum distillation at a temperature of 180–230°C and a pressure of 1–200 Pa for 10–20 hours. The heating and mixing temperature is 80–120℃, and the time is 1–3 hours; In step S3, the mass ratio of component A to component B is 1:(0.5 to 1.5).

2. The silicone potting compound for a high-precision voltage sensor according to claim 1, characterized in that, The platinum-based catalyst is a Pt3000 platinum catalyst.

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