JPH11138585A - Sealing method by rubber composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a sealing method by a rubber composition wherein an article to be sealed such as an electronic part can be efficiently sealed by the rubber composition of a fixed shape. SOLUTION: A forming material is prepared by mixing fine hollow bodies 22 in a liquid-form rubber material 21. As the fine hollow body 22, a fine hollow body comprising a shell made of a plastic is used, and the material for the shell made of the plastic is an acrylonitrile polymer, and the thickness of the shell which constitutes the fine hollow body 22 is 0.2 μm or higher, and the liquid-form rubber material 21 is a silicone resin. In a die 1 holding an electronic part 10, the forming material 20 is injected and arranged around the electronic part 10, and the rubber component is hardened in the die 1, and the die is removed, and a formed article which is sealed by a rubber composition wherein the fine hollow bodies 22 are dispersed, is taken out.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sealing method for sealing an object such as an electronic component with a rubber composition.

[0002]

2. Description of the Related Art Conventionally, rubber materials have been applied to various uses due to their excellent properties. For example, a lightening material, a heat insulating material, and the like. In addition, a compressible rubber material, for example, a rubber material in which bubbles are dispersed, has a compressibility because the volume of the contained bubbles shrinks when an external force is applied, and is used for stress relaxation.

As an example of the use of such a compressible rubber material, as shown in FIG. 17, it is conceivable to coat an electronic component 100 with a compressible rubber material 101 and embed it in a potting material 102. With such a structure, the built-in electronic component 100 can be protected from contraction stress by the potting material 102 due to the stress relaxation effect of the compressible rubber material 101.

In such an application, the compressible rubber material 10
If 1 is thinner and has a constant shape, it can be arranged in a narrower space when installing a product (electronic component 100 after coating), which can contribute to miniaturization of the entire apparatus. As a method of manufacturing the rubber-sealed product, the electronic component 100 is dipped or spray-coated in a liquid rubber material (101) mixed with a plastic hollow body, and then heat-cured to thereby compress the rubber material 101. Can be arranged around the electronic component 100. However, these methods have the disadvantage that the outer shape of the compressible rubber material 101 is not constant and the film thickness is not uniform.

[0005] Therefore, as a method of forming a fixed shape, for example, a method of preparing a sheet material made of compressible rubber in advance and using the sheet material in an appropriate shape can be considered. Object (electronic component 100 in FIG. 17)
Considering the ease of wrapping, it is considered that the method of molding using a mold is most suitable. That is, after inserting an object to be sealed (for example, an electronic component) into a mold, a liquid rubber material is injected,
Heat and cure.

On the other hand, as a method of forming air bubbles in rubber in order to obtain a rubber material having compressibility, for example, (i) an organic foaming agent is mixed with a rubber material and foamed by heating the rubber material. Method (JP-A-7-247436),
(Ii) a method of injecting a gas component into a liquid rubber material (Japanese Patent Laid-Open No. 5-31814); (iii) mixing a plastic micro hollow body containing a foaming gas therein and expanding by heat into a rubber material; A method of foaming with heat at the time of rubber curing (JP-A-5-209080), a method of (iv) mixing microballoons (specifically, a balloon in which a liquid is sealed) with a powdered resin material, and heating and curing the mixture (particularly). No. 6-157808).

However, according to the study of the present inventors,
It has been found that when these are applied to manufacturing with a mold having a constant shape, there are the following problems. First, (i)
In the case of using an organic foaming agent of (3) or a plastic minute hollow body which expands due to the heat of (iii), these expand in volume in the mold and press the rubber material against the wall of the mold, making it extremely difficult to release. Become. In addition, after the mold is released, the part that cannot be expanded in the mold and is compressed causes volume expansion, so that the stability of the outer shape cannot be secured. In the method (ii) of injecting gas into the liquid rubber, a special device for introducing gas is required.

Further, the method (iv) of mixing microballoons with a powdered resin is intended to obtain a high compression ratio.
The content of the powdered resin decreases, and it becomes difficult for them to dissolve each other, and the strength of the cured product (molded product) decreases.

[0009]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a sealing method using a rubber composition capable of efficiently sealing an object to be sealed such as an electronic component with a rubber composition having a predetermined shape. It is in.

[0010]

According to the first aspect of the present invention, a composition obtained by mixing a liquid rubber material and a minute hollow body is injected into a mold holding an object to be sealed. Place around the seal. Then, the rubber component of the composition is cured in a mold. Further, it is released as a molded product sealed with a rubber composition in which minute hollow bodies are dispersed.

Therefore, the use of the liquid rubber material facilitates the filling of the rubber material into the mold. That is, if it is a liquid, a liquid ejection device (dispenser device) or generally a reactive injection molding (RIM) is used.
g) Alternatively, liquid injection molding (LIM; Liquid Inject)
A manufacturing facility for automatically injecting a liquid into a mold, which is called oin molding, can be used. Therefore, the present invention
This is a suitable method for automation.

Further, by mixing a minute hollow body into a liquid rubber material, the rubber has a compressibility, and does not expand due to heat. As a result, the volume does not expand significantly during the heating step for curing after being injected into the mold, and as a result, the mold release becomes extremely easy.

That is, as shown in FIG. 15, a liquid sealing balloon 81 (a liquid 81b sealed in a shell 81a) is scattered in a liquid rubber material 80, and the liquid resin
When the liquid resin 8 in the mold 83 is injected and heated,
In 2, the liquid 81b of the liquid-filled balloon 81 evaporates and the shell 81a expands to form a hollow body. At this time, the liquid resin 82 in the mold 83 has a volume expansion in a state of being placed in the airtight container. It is extremely difficult to release the resin by pressing the liquid resin 82 against the wall surface of the mold 83, and it is not possible to expand in the mold 83 after the mold is released and the part which has been compressed is expanded in volume and the stability of the outer shape cannot be secured. . On the other hand, in the present invention, as shown in FIG. 16, a gas-filled balloon 90 (a gas 90b is sealed in a shell 90a) is scattered in a liquid rubber material 80, and this liquid resin 92 is placed in a mold 83. To the liquid resin 92 in the mold 83
The desired molding can be performed by suppressing the inflation of the gas-filled balloon 90 at the time.

As described above, the external dimensions after release are stable, which is particularly advantageous when the rubber-sealed product (molded product) is arranged in a narrow space. Further, a compressible rubber material can be easily prepared without using a gas introducing device for forming a hollow portion. Furthermore, since the micro-balloons are mixed with the liquid rubber material instead of mixing the micro-balloons with the powder resin, the powders dissolve each other even if the mixing ratio of the micro-hollows is increased to obtain high compressibility. Inconvenience such as a decrease in strength due to non-compliance hardly occurs.

In this manner, an object to be sealed such as an electronic component can be efficiently sealed with the rubber composition having a predetermined shape. Here, as described in claim 2, when the mold is provided with a pressure release portion in a part thereof, pressure is less applied to the molding material in the mold, and the compression characteristics of the minute hollow body are reduced. Does not impair.

Further, as described in the third aspect, the pressure relief portion can also serve as an injection port. Further, as described in claim 4, an injection mold can be used as the mold, and the injection port and the pressure relief portion can be separately provided in the mold.

Further, as described in claim 5, the pressure relief portion is constituted by a gap formed in a mold split surface of a mold, and after molding, the rubber composition that has entered the gap is removed. It is good to do so.

Further, when the micro hollow body having a plastic shell is used, high compressibility can be secured. Here, as described in claim 7, when the plastic shell is made of a fine hollow body made of an acrylonitrile polymer, the plastic shell is excellent in compressibility, heat resistance, and corrosion resistance.

Further, as set forth in claim 8, when the thickness of the shell constituting the minute hollow body is 0.1 μm or more,
It is possible to avoid the problem that the shell of the minute hollow body is broken when pressure for injection is applied.

Further, when the liquid rubber material is a silicone resin, flexibility can be maintained over a wide temperature range and the curing time can be shortened. Further, when the viscosity of the liquid rubber material is 700 poise or more as measured at a BH-type viscometer rotor No. 7 at 20 revolutions / minute, the liquid rubber material and the minute hollow body are separated from each other. Can be avoided.

According to the present invention, if the shell is made of plastic and an inorganic substance is adhered to the surface of the shell, the hollow body is made of a liquid rubber material. And the separation can be avoided.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS (First Embodiment) An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a molding apparatus according to the present embodiment using a casting method. In FIG. 1, a mold 1
And an electronic component 10 as an object to be sealed. In FIG. 1, a mold 1 includes a first mold 2 and a second mold 3. The cavity 4 is formed in a state where the first mold 2 and the second mold 3 are in contact with each other. The electronic component 10 is arranged in the cavity 4, and the cavity 4 is open from the upper surface of the mold 1. The electronic component 10 can be inserted through the opening 5.

The electronic component 10 comprises a lead frame 11 on which a silicon chip 12 is mounted,
And silicon chip 12 with molding material (primary sealing resin) 1
Covered with 3. A part of the lead frame 11 is exposed as a terminal for making an electrical connection.

In the dies 2 and 3, small holding projections 6 for holding the electronic component 10 in fixed positions are provided. The holding projections 6 make the rubber film thickness of each part of the molded product constant.
Next, a molding procedure (sealing method) using the mold 1 will be described.

As shown in FIG. 1, the electronic component 10 is set in the dies 2 and 3. At this time, since the molds 2 and 3 are partially open, the electronic component 10 can be easily inserted. Then, as shown in FIG. 2, a predetermined amount of a molding material (liquid resin) 20 is injected from the opening 5 of the mold by a liquid ejection device. This molding material 20, as shown in FIG.
1 and the minute hollow body 22 are mixed and further stirred by a stirrer 23 to disperse the minute hollow bodies 22 in the liquid rubber material 21. Here, a silicone resin is used for the liquid rubber material 21. As shown in FIG. 5, a plastic shell (skin) 2 is used as the minute hollow body 22.
A micro hollow body made of 2a is used. More specifically,
The material of the plastic shell 22a is an acrylonitrile polymer, and the outer diameter D of the shell 22a is about 80 μm.

In the step of injecting the molding material (liquid resin) 20, the molds 2 and 3 are partly open, so that they can be easily injected. In addition, in the manufacturing method of the present embodiment, since the molds 2 and 3 are partially open, the liquid level fluctuates depending on the injection amount. However, when the accuracy of the rubber material thickness at this portion is not so required. Can be injected using a relatively simple dispenser device.

In this way, the molding material (composition obtained by mixing the liquid rubber material 21 with the minute hollow body 22) is placed around the electronic component 10 in the mold 1 of FIG. Subsequently, the rubber component of the molding material 20 is cured by heating in this state. More specifically, 120-150 ° C, 30-6
Place in high temperature oven for 0 minutes to cure. At this time, since the molds 2 and 3 are partially open, even if the liquid rubber material (silicone resin) 21 expands due to thermal expansion during heating, the molds 2 and 3 are partially opened. When this part (the resin in the opening 5) expands, pressure is less applied to the molding material 20 in the molds 2 and 3, and the compression characteristics of the minute hollow body 22 are impaired (the hollow body is crushed). Absent.

After curing, the molds 2 and 3 are opened and the molded product 25 is taken out as shown in FIG. This molded product 25 is sealed with a rubber coating material 26 in which minute hollow bodies 22 are scattered. As shown in FIG. 17, the molded article 25 manufactured in this manner receives contraction stress caused by the potting material 102 when placed in the potting material 102, but the rubber coating material 26 ( By utilizing the compressibility of the electronic component 10 (see FIG. 3), the electronic component 10 can be protected.

Further, since the periphery of the electronic component 10 is coated with the rubber coating material 26 by molding using the mold 1, the rubber coating material 26 can be made thinner and have a uniform shape. Therefore, when the electronic component 10 (molded article 25) is arranged in a limited space, the electronic component 10 (molded article 25) can be arranged in a narrower space, which can contribute to downsizing of the entire device.

Hereinafter, the minute hollow body 22 and the liquid rubber material 21
The selection of materials and the like will be described. It is important that the minute hollow body 22 has compressibility, and the shell (skin) 22 shown in FIG.
It is necessary to select a material having flexibility as the material of a. For example, a hollow body made of silica, which is a hard inorganic component (generally called a shirasu balloon), cannot achieve the desired compression characteristics even when blended with a liquid rubber material. Therefore, a flexible plastic shell (shell)
It is desirable to use 22a. Plastic shell 2
As a specific material of 2a, acrylonitrile, vinyl chloride, styrene, and a copolymer thereof can be generally obtained from the viewpoint of ease of production of the micro hollow body 22, but the condition that it is suitable for production in a mold is used. In order to be added, it is necessary to withstand heating (150 ° C.) during rubber curing and not to corrode the mold. In consideration of this, vinyl chloride has no heat resistance, and chlorine contained in the mold corrodes the mold. Not suitable. Also, a plastic shell 22a
As a result of a study by the present inventors regarding the specific material of the above, it was found that acrylonitrile was excellent in compressibility, heat resistance, and corrosion resistance, and was suitable for the present application (sealing with a rubber composition). Examples of such a minute hollow body 22 include a microballoon (product name: 091DE80, material: acrylonitrile, average particle size: 80 μm) manufactured by Expancel.

As for the material selection of the liquid rubber material 21, a general liquid rubber having a viscosity suitable for casting by a liquid discharging device can be used. A viscosity of 30 to 300 poise is suitable. What is important is that the hollow member 22 has a softness that does not impair the compression characteristics of the hollow body 22 and has a hardness that can withstand release from the mold. As a result of the study of the present inventors, it has been found that a rubber material having a JIS-A hardness in a range of 10 to 60 in JIS-A hardness in a state in which the minute hollow body 22 is not inserted is suitable for this use.

Further, in the use of wrapping the electronic parts 10 and the like, the liquid rubber material 21 needs to maintain this softness in a wide temperature range, and in view of production efficiency, a rubber material which cures quickly is desired. .

Silicone resin is suitable as a material having such characteristics relating to the material selection of the liquid rubber material 21. The silicone resin generally has stable softness in a wide temperature range from -40 ° C to 150 ° C, and the curing time can be shortened by using an addition reaction between a silanol group and a vinyl group. An example of such a silicone resin is KE1218 manufactured by Shin-Etsu Chemical Co., Ltd.

Further, referring to the amount of the minute hollow body 22 contained in the liquid rubber material 21, it may be adjusted according to the required compression characteristics. In this embodiment, the above-mentioned KE1218 manufactured by Shin-Etsu Chemical Co., Ltd. A 40% (vol%) volume content of Micro Balloon 091DE80 manufactured by Expancel Co., Ltd. is used.

The viscosity of the liquid rubber material 21 at the time of mixing the minute hollow body 22 needs to be about 300 poise or less so as to be applicable to a general dispenser device. However, with this viscosity, the minute hollow body 22 starts to float (separate) within a few hours and is not stable. Therefore, every time a product is manufactured, a step of mixing and stirring the minute hollow body 22 and the liquid rubber material 21 is inserted. There is a need.

In view of the above, in the present embodiment, the liquid rubber material 21 is KE1 manufactured by Shin-Etsu Chemical Co., Ltd.
218 and microballoon 091DE80 manufactured by Expancel Co., Ltd. as the minute hollow body 22 and mixed at 40 vol%, so that the minute hollow body 22 and the liquid rubber material 21 are mixed and stirred every time a product is manufactured. I have.

As described above, this embodiment has the following features. (A) As shown in FIG.
2 is injected into the mold 1 holding the electronic component 10 and is placed around the electronic component 10, and the rubber component of the molding material 20 is set in the mold 1. After being cured, as shown in FIG. 3, the molded product 25 was separated and released as a molded product 25 sealed with a rubber composition (rubber coating material 26) in which minute hollow bodies 22 were scattered.

Therefore, the use of the liquid rubber material 21 facilitates the filling of the mold 1 with the rubber material, and allows the use of a manufacturing facility (in this example, a liquid discharge device) for automatically injecting a liquid into the mold. It becomes suitable for. In addition, since the rubber has compressibility by mixing the minute hollow body 22 into the liquid rubber material 21 and does not expand due to heat, it is hardened after being injected into the mold 1. Even during the heating step, the volume does not greatly expand, the mold release is extremely easy, and the external dimensions after the mold release are stable, which is advantageous particularly when the molded article 26 is arranged in a narrow space.

Further, a compressible rubber material can be easily prepared without using a gas introducing device for forming a hollow portion. Further, since the micro hollow body 22 is mixed with the liquid rubber material 21 instead of mixing the micro balloon with the powder resin, even if the mixing ratio of the fine hollow body 22 is increased in order to obtain high compressibility, the powders are not mixed. Are less likely to occur due to the fact that they do not dissolve each other.

In this manner, the electronic component 100 can be efficiently sealed with the rubber composition (molding material 20) having a predetermined shape. (B) The mold 1 was provided with a pressure relief part in a part thereof. That is, the opening 5 in FIG. 2 is a pressure release portion that also serves as an injection port. Therefore, pressure is less applied to the molding material 20 in the mold 1 and the compression characteristics of the minute hollow body 22 are not impaired. (C) Since the micro hollow body 22 of FIG. 5 is provided with the plastic shell 22a, high compressibility can be secured. (D) Further, since the material of the plastic shell 22a is an acrylonitrile polymer, it is excellent in compressibility, heat resistance and corrosion resistance. (E) Since the liquid rubber material 21 is a silicone resin,
Flexibility can be maintained over a wide temperature range, and the curing time can be shortened. (Second Embodiment) Next, a second embodiment will be described with reference to the first embodiment.
The following description focuses on the differences from this embodiment.

FIG. 6 shows a molding apparatus according to the present embodiment using LIM (liquid injection molding). This LIM is 2
This is a manufacturing method in which a liquid-mixing type thermosetting resin is automatically supplied, automatically mixed, and then injected into a mold with pressure, and can be produced more efficiently than in the first embodiment.

In FIG. 6, a raw material can 40 and a raw material can 41 are provided. The raw material can 40 is filled with the A agent 42 of the raw liquid silicone resin, and the raw material can 41 is filled with the raw liquid silicone resin. The B agent 43 is satisfied. Also,
Each of the A agent 42 and the B agent 43 is provided with the minute hollow body 22 (FIG. 5).
) Is mixed, and 30 vol% of the minute hollow body 22 is mixed with the liquid rubber material (silicone resin as a raw material). The raw material can 40 is connected to a measuring cylinder 45 by a raw material transport pipe 44, and the raw material can 41 is connected to a measuring cylinder 47 by a raw material transport pipe 46. Measuring cylinder 4
5, 47 can measure (pressure feed) a certain amount by the operation (reciprocation) of the pistons 45a, 47a.

The discharge sides of the measuring cylinders 45 and 47 are connected to a mixer 50 by transport pipes 48 and 49, and the mixer 50 is composed of a static mixer. The discharge side of the mixer 50 is connected to the injection port 51 a of the injection mold 51.

The mold 51 includes a first mold 52 and a second mold 5.
The mold 51 has a cavity 54 formed therein. As shown in FIG. 8, the cavity 54 is
The electronic component storage 55 has a holding projection 56 provided therein. In addition, a gap 57 extends from the electronic component storage 55 in the cavity 54 on the side opposite to the injection side (the right side in FIG. 8), and the gap 57 opens to the end surfaces of the molds 52 and 53. That is, a slight gap (about 0.5 mm or less) 57 is provided on the mold splitting surfaces of the dies 52 and 53, and the structure is not completely sealed.

The reason for providing the gap 57 is that a general LIM
In, the mold is sealed. However, in the study of the present inventors, when pressure is applied into a closed mold to inject a liquid rubber material containing a minute hollow body, the pressure inside the mold increases, and the minute hollow body is moved inside the mold. It has been found that a damaging phenomenon occurs. In order to avoid this, in the present embodiment, the gap 57 is provided as a pressure release portion.

A hemispherical resin reservoir 58 is provided in a part of the gap 57 in the cavity 54. In the present embodiment, a minute hollow body made of a plastic shell 22a is used as the minute hollow body 22 in FIG. 5, the material of the plastic shell 22a is an acrylonitrile polymer, and the thickness of the shell 22a is 0.1 μm. That is all. The viscosity of the silicone resin as the liquid rubber material 21 is 700 poise or more when measured with a BH type viscometer rotor 7 at 20 revolutions / minute.

Next, a manufacturing method will be described. As shown in FIG. 7, while holding the electronic component 10 in the mold 51, pressure is applied to the raw material cans 40 and 41, and the A and B liquids (liquid raw materials) 42 and 43 are pushed out to the raw material transport pipes 44 and 46. . This is measured in a fixed amount by the measuring cylinders 45 and 47 and is fed to a mixer (static mixer) 50 under pressure. In the mixer 50, the A agent 42 and the B agent 43 are mixed and stirred. Thus, the molding material (liquid silicone resin) composed of the agent A and the agent B
60 is mixed and stirred immediately before injection into the mold.

Thereafter, the molding material 60 is injected into the mold 51, and is fed to the cavity 54 as shown in FIG. At this time, the amount of the molding material (liquid silicone resin) 60 to be injected into the mold 51 is controlled such that the electronic component storage chamber 55 is completely filled, but the gap 57 is not completely filled. This makes it possible to control the pressure in the mold 51 so as not to increase. Also, at the time of injection, a molding material (liquid silicone resin) 60 is made to enter the resin reservoir 58 in the middle of the gap 57. By doing so, the control range of the injection amount can be expanded.

Subsequently, the rubber component of the molding material 60 is cured by heating with the mold 51. Further, as shown in FIG. 10, the mold is released, and a molded product 65 in which the periphery of the electronic component 10 is covered with the rubber coating material 61 is taken out. Then, unnecessary portions 62, 63, and 64 are removed to obtain a final product as shown in FIG. At this time, the resin material (unnecessary part) 64 left in the resin pool part 58 in the middle of the gap 57 can be grasped by hand, and the unnecessary part (protruding part) 63 left in the gap 57 can be easily removed.

In this way, a molded product 65 having a final shape is obtained. Hereinafter, the silicone resin 21 which is a liquid rubber material will be described.
A discussion and an experiment regarding the dispersion of the minute hollow body 22 in the inside have been performed, and will be described.

In the LIM molding, since the material is supplied and injected by pressure, the viscosity of the molding material can be increased as compared with the casting method shown in FIG. Therefore, the rising speed of the minute hollow body 22 can be reduced by increasing the viscosity of the molding material, and the rising of the minute hollow body 22 can be suppressed. As a result, compared to the casting method shown in FIG.
There is a possibility that the step of mixing the minute hollow body 22 for each production may be omitted.

According to the study of the present inventors, it was found that if the viscosity of the silicone resin (liquid rubber material) 21 was increased to 700 poise, the floating phenomenon of the minute hollow body 22 was almost eliminated and stable molding could be performed. .

FIG. 12 shows the floating phenomenon of the minute hollow body 22.
This is captured as a change in viscosity at the top of the liquid. That is,
As shown in FIG. 13, a B-type viscometer 70 is disposed on the surface of the molding material (injection material) 20, and when the minute hollow body 22 floats up in the molding material (injection material) 20, the minute The content of the hollow body 22 increases, and as a result, the viscosity increases. Using a B-type viscometer 70, the change in viscosity was measured over time while the viscosity measuring unit (rotor 70a) was placed above the liquid. The B-type viscometer was a BH-type viscometer and was measured at 2 revolutions / minute using a rotor No. 6.

That is, the horizontal axis of FIG. 12 shows the standing time after mixing and stirring the silicone resin (liquid rubber material) 21 and the minute hollow body 22, and the vertical axis shows the molding material (injection material).
Viscosity at the top of liquid 20 (relative value with initial value being 100)
Has taken. As the samples, (i) a raw material silicone having a viscosity of 100 poise, (ii) a raw silicone having a viscosity of 300 poise, and (iii)
) The raw material silicone had a viscosity of 700 poise. The viscosity of the raw material silicone is a value measured at a BH-type viscometer rotor 7 at 20 revolutions / minute.

In FIG. 12, as can be seen from the measurement result L1 corresponding to (i) and the measurement result L2 corresponding to (ii), after mixing, the hollow body floats on the liquid with time and the viscosity increases. Go. However,
In the measurement result L3 corresponding to (iii), the rise in the viscosity of the raw material is suppressed to be low even after a lapse of time after the mixing. As described above, by setting the viscosity of the raw material silicone to 700 poise or more, separation of the liquid rubber material 21 and the minute hollow body 22 in the molding material (injection material) 20 is avoided. The hollow bodies 22 can be evenly dispersed.

Further, the molding material 20 in the LIM molding is used.
The crack phenomenon of the minute hollow body 22 at the time of press-fitting will be described. In this example, "Pressurizing the raw material cans 40, 41, extruding the liquid raw material into the raw material transport pipes 44, 46, measuring a certain amount with the measuring cylinders 45, 47, pressure-feeding to the mixer 50, and then pressure-feeding to the cavity. It has been found that, because of the configuration of "do", a repetitive pressure is applied to the liquid raw material 60, and a phenomenon occurs in which a part of the minute hollow body 21 is broken on the downstream side of the measuring cylinders 45 and 47. Therefore,
As a result of various experiments, it was found that, in the case of the micro hollow body 22 using the acrylonitrile shell 22a, the shell 22 was formed under the pressure (at least about 10 kg / cm ² ) at which the LIM material could be generally fed.
It has been found that cracking can be prevented by setting the thickness of a to 0.1 μm or more.

As described above, this embodiment has the following features. (A) The injection mold 51 is used as the mold, and the injection port 51a and the pressure release portion (gap 5) are formed in the mold 51.
7) is separately provided, and the pressure release portion is constituted by the gap 57 formed on the mold cutting surface of the mold, and the rubber composition 63 that has entered the gap 57 after molding is removed. The desired final shape can be obtained, which is practically preferable. (B) The thickness of the shell 22a constituting the minute hollow body 22 is set to 0.
Since the thickness is 1 μm or more, it is possible to avoid a problem that the shell 22a of the minute hollow body is cracked when pressure for injection is applied. (D) Since the viscosity of the liquid rubber material 21 is 700 poise or more as measured at a BH type viscometer rotor No. 7 at 20 revolutions / minute, separation of the liquid rubber material 21 from the minute hollow body 22 is avoided. Becomes possible.

As an application example of the present embodiment, a case where a rubber coating material 61 having high compressibility (see FIG. 11) is described below. In applications where high compressibility is required, the amount of the fine hollow body 22 must be increased, and as a result, the viscosity of the raw material after mixing increases. Generally, in order to apply to LIM, it is necessary to suppress the viscosity to about 10,000 poise or less.

That is, as in the first embodiment, 4 micro hollow bodies 22 are added to 700 poise silicone resin.
When 0 vol% is mixed, the viscosity exceeds 10,000 poise, and it cannot be applied to LIM.

Therefore, various studies were conducted to perform the LIM molding and prevent the floating of the minute hollow body 22 and perform stable molding. As a result, as shown in FIG. It has been found that this object can be achieved by directly bonding the inorganic filler 75 to the polymer. Specifically, MFL100CA made by Matsumoto Yushi can be exemplified. This is obtained by binding calcium carbonate powder to the shell 22a of the minute hollow body 22, and the specific gravity of the minute hollow body 22 can be increased about three times.

This will be described with reference to FIG.
In the above, as a sample, (iv) the raw material silicone viscosity is set to 300 poise, and the shell 22a of the minute hollow body 22 is prepared.
The case where the surface coated with an inorganic filler is used is shown. In the measurement result L4 corresponding to (iv), the rise in the viscosity of the raw material is suppressed to be low even after a lapse of time after the mixing. In this way, the floating of the minute hollow body 22 is prevented.

As described above, since the shell 22a of the micro hollow body 22 shown in FIG. 14 is made of plastic and the surface of the shell 22a to which the inorganic filler (inorganic substance) 75 is adhered is used, the liquid rubber material 21 This makes it difficult for the minute hollow body 22 to float, thereby avoiding separation.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a molding apparatus according to a first embodiment.

FIG. 2 is a cross-sectional view for explaining a molding step.

FIG. 3 is a cross-sectional view for explaining a forming step.

FIG. 4 is an explanatory view for explaining a molding step.

FIG. 5 is a sectional view of a minute hollow body.

FIG. 6 is a sectional view showing a molding device according to a second embodiment.

FIG. 7 is a sectional view for explaining a forming step.

FIG. 8 is a cross-sectional view for explaining a molding step.

FIG. 9 is a cross-sectional view for explaining a forming step.

FIG. 10 is a cross-sectional view for explaining a molding step.

FIG. 11 is a cross-sectional view for explaining a forming step.

FIG. 12 is a diagram showing a result of examining a relationship between a standing time and a viscosity of a liquid uppermost part.

FIG. 13 is a diagram for explaining a method of measuring the liquid top viscosity.

FIG. 14 is a diagram illustrating a minute hollow body.

FIG. 15 is a view for explaining molding.

FIG. 16 is a view for explaining molding.

FIG. 17 is a cross-sectional view illustrating a sealing structure using a rubber composition.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Die, 5 ... Opening part, 10 ... Electronic parts, 20 ... Molding material, 21 ... Liquid rubber material, 22 ... Micro hollow body, 22a ...
Shell, 25 Shell, 26 Rubber coating material, 51 Mold for injection molding, 51a Injection port, 67 Gap, 63 Unnecessary part, 64 Unnecessary part, 75 Inorganic filler

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI H01L 23/31 // B29K 83:00 B29L 31:34

Claims (11)

[Claims] 1. A step of injecting a composition obtained by mixing a minute hollow body into a liquid rubber material into a mold holding an object to be sealed and disposing the composition around the object to be sealed. A step of curing a rubber component of the composition within the composition; and a step of releasing the molded product as a molded product sealed with a rubber composition in which molds are separated and minute hollow bodies are dispersed. Sealing method. 2. The sealing method according to claim 1, wherein the mold has a pressure relief part in a part thereof. 3. The sealing method according to claim 2, wherein the pressure release portion also serves as an injection port. 4. The sealing method according to claim 2, wherein an injection mold is used as the mold, and the mold is provided with an injection port and the pressure relief portion individually. 5. The rubber according to claim 4, wherein the pressure release portion is formed by a gap formed in a mold parting surface of a mold, and the rubber composition that has entered the gap after molding is removed. A sealing method using the composition. 6. The method for sealing with a rubber composition according to claim 1, wherein the micro hollow body having a plastic shell is used. 7. The sealing method according to claim 6, wherein the material of the plastic shell is an acrylonitrile polymer. 8. The sealing method according to claim 1, wherein the shell constituting the micro hollow body has a thickness of 0.1 μm or more. 9. The method according to claim 1, wherein the liquid rubber material is a silicone resin. 10. The sealing method according to claim 1, wherein the viscosity of the liquid rubber material is 700 poise or more as measured at a BH-type viscometer rotor of 7 rotations at 20 rpm. 11. The micro hollow body, wherein a shell is made of plastic, and an inorganic substance is attached to a surface of the shell.
5. A sealing method using the rubber composition described in 1. above.