JP7621650B2 - Fixed Structure - Google Patents

Description

The present invention relates to a fixing structure with excellent vibration-proofing properties.

In recent years, as the functionality of electronic devices has improved, the electronic circuit boards installed in these electronic devices have come to be equipped with a greater number of precision components with higher accuracy. The manufacture of such electronic devices requires stable quality and uninterrupted supply, and as part of the manufacturing process, it has been common to use metal screws or bolts in the process of fixing the electronic circuit board to the base (for example, Patent Document 1).

Patent No. 5936313

However, with conventional fixing structures using metal screws or bolts, the energy of externally applied shocks or vibrations is not attenuated, or in some cases is amplified and transmitted to the electronic board, causing problems such as malfunctions during manufacturing or product use. In the process of fixing the electronic board to the base, a reliable fixing method using metal screws or bolts or other fasteners has been used, but no measures have been taken to protect against external shocks and vibrations.

The problem that this invention aims to solve is to provide a fixing structure that suppresses the energy of external shocks and vibrations and does not transmit them to the electronic board.

The fixing structure of the present invention, which has solved the above problem, comprises an electronic board having at least one or more first mounting holes, a base having at least one or more second mounting holes with a female thread structure on the inside, and a resin mounting tool for fixing the electronic board to the base. The mounting tool has a head having an outer diameter larger than the inner diameter of at least the first mounting hole, and an axial leg extending from the head in one direction and capable of being pressed into the second mounting hole, and the leg has a plurality of elastic fins formed on the leg such that the angle between the extension direction starting from the axial surface and the press-in direction of the leg is an obtuse angle. The leg can be pressed into the second mounting hole by the elastic deformation of the elastic fin, and can be fixed to the second mounting hole by the elastic fin being caught in the female thread structure by the restoration of the elastic deformation. In addition, the fixing structure of the present invention is configured such that the fixed leg can be detached from the second mounting hole by pulling the head with a force of 550 N.

The present invention may further include the following configurations or characteristics.
An elastomer member may be provided, disposed between the electronic board and the base, and having a third mounting hole through which the leg can pass. The elastomer member may be cylindrical, the diameter of the third mounting hole may be 3 to 9 mm, the outer diameter of the elastomer member may be 5 to 20 mm, and the thickness of the elastomer member in the cylindrical axial direction may be 1 to 6 mm. The mounting tool is made of polyamide resin, and the elastomer member comprises a styrene-based elastomer or an acrylic-based elastomer, a paraffin-based process oil, an olefin-based resin, a crosslinking agent made of an organic peroxide, a crosslinking aid, an antioxidant, and magnesium hydroxide treated with a higher fatty acid, and 400 to 485 parts by mass of the paraffin-based process oil, 9 to 13 parts by mass of the olefin-based resin, 5 to 7 parts by mass of the crosslinking agent, 13 to 16.9 parts by mass of the crosslinking aid, 3 to 4 parts by mass of the antioxidant, and 15 to 25 parts by mass of the magnesium hydroxide are blended with respect to 100 parts by mass of the styrene-based elastomer or the acrylic elastomer, and the JIS A hardness of the elastomer member may be 0 to 37 when the styrene-based elastomer is blended, and 32 to 64 when the acrylic elastomer is blended. The elastomer member may also be disposed between the electronic board and the head of the mounting tool.

The present invention is a structure that can fix an electronic board to a base by penetrating and pressing the leg of the mounting fixture into the first mounting hole of the electronic board and the second mounting hole of the base, respectively. When the leg of the shaft-shaped mounting fixture penetrates the first mounting hole and is pressed into the second mounting hole, the multiple elastic fins formed so that the angle between the direction in which the leg extends from the shaft surface as a starting point and the direction in which the leg is pressed into is an obtuse angle are elastically deformed so that their tips approach the shaft surface. This allows the leg of the mounting fixture to penetrate and press into the first mounting hole and the second mounting hole, respectively. In addition, after penetrating and pressing into the first mounting hole and the second mounting hole, the elastically deformed elastic fins try to restore their shape before penetrating and pressing. Due to this shape restoration, the tip of the elastic fin gets caught in the female thread structure on the inside of the second mounting hole. Therefore, unless the mounting fixture is pulled with a strong force, the mounting fixture will not be pulled out of the first mounting hole and the second mounting hole, and it is possible to maintain the electronic board attached to the base. This method of fixing by a series of elastic deformations and restorations can be performed easily and stably by simply pressing the mounting fixture into each mounting hole on the electronic board and base.

The fixing structure of the present invention uses the above-mentioned mounting fixture, and is different from conventional fixing structures that use metal screws or bolts, in that the elastic fins of the legs of the mounting fixture hook onto the female thread structure of the second mounting hole, thereby fixing the mounting fixture. Therefore, the mounting fixture attached to the electronic board and base can be removed by pulling the mounting fixture with a strong force.

In the fixing structure of the present invention, there is a large gap between the inner wall of the second mounting hole and the legs or elastic fins of the mounting fixture, compared to conventional fixing structures that use metal screws or bolts. Although the details are unknown, it is believed that when an external shock or vibration is applied, the legs or elastic fins of the mounting fixture will swing within this gap, generating friction at the points of contact between the mounting fixture and the inner wall of the second mounting hole. In the fixing structure of the present invention, it is believed that such swinging and friction of the mounting fixture have a positive effect on the vibration-proofing effect.

1 is a schematic cross-sectional view showing the state of a fixture, an electronic board, a base body, and an elastomer member in embodiment 1. FIG. 2A is a diagram showing the female thread structure of the second mounting hole, and FIG 2B is a diagram showing the structure of the mounting fixture. 1 is a graph comparing the vibration-proofing effect of the first embodiment with that of the first embodiment in which the mounting fixture is made of a conventional metal (metal screw). 11 is a graph comparing vibration test results when the thickness of the elastomer member in the first embodiment is changed. FIG. 11 is a schematic cross-sectional view showing the state of a fixture, an electronic board, and a base body in a second embodiment. 13 is a graph comparing vibration test results between the second embodiment and the second embodiment in which the fastener is made of metal (metal screw). 10 is a schematic cross-sectional view showing the state of a fixture, an electronic board, a base body, and an elastomer member in Modification 1. FIG. 11 is a schematic cross-sectional view showing the state of a fixture, an electronic board, and a base body in Modification 2. FIG.

[Embodiment 1]
FIG. 1 is a schematic cross-sectional view showing the state of a fixture, an electronic board, a base body, and an elastomer member in a first embodiment of the present invention.

As shown in FIG. 1, the fixing structure 1 of this embodiment includes an electronic board 3, a base 5, an elastomer member 7, and a mounting fixture 9. The electronic board 3 has a first mounting hole 31, and the base 5 has a second mounting hole 51. The second mounting hole 51 has an internal thread structure. The elastomer member 7 is disposed between the electronic board 3 and the base 5, and has a third mounting hole 71. The mounting fixture 9 has a leg 91 and a head 93, and an elastic fin 91A is formed on the axial surface of the leg 91.

Examples of styrene-based elastomers selected as one of the substrates of the elastomer member used in the present invention include polystyrene-poly(ethylene-ethylene/propylene) block-polystyrene block copolymer (SEEPS), polystyrene-poly(ethylene/propylene)-polystyrene block copolymer (SEPS), polystyrene-poly(ethylene/propylene)-polystyrene block copolymer (SEBS), polystyrene-polybutadiene block copolymer (SBC), polystyrene-polyisoprene-polystyrene block copolymer (SIS), etc. These may be used alone or in combination of two or more.

Examples of styrene-based elastomers (e.g., SEEPS) on the market include products under the trade names "Septon 4055" (manufactured by Kuraray Co., Ltd.), "Septon 4077" (manufactured by Kuraray Co., Ltd.), and "Septon 4099" (manufactured by Kuraray Co., Ltd.).

The acrylic elastomer selected as one of the base materials for the elastomer member used in the present invention is a composition containing at least an acrylic polymer obtained by polymerizing one or more (meth)acrylates, and one or more (meth)acrylates. Examples of the (meth)acrylate include ethyl (meth)acrylate, n-propyl (meth)acrylate, i-propyl (meth)acrylate, n-butyl (meth)acrylate, i-butyl (meth)acrylate, n-pentyl (meth)acrylate, i-pentyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-hexyl (meth)acrylate, n-octyl (meth)acrylate, i-octyl (meth)acrylate, n-nonyl (meth)acrylate, i-nonyl (meth)acrylate, i-decyl (meth)acrylate, lauryl (meth)acrylate, tridecyl (meth)acrylate, i-myristyl (meth)acrylate, stearyl (meth)acrylate, i-stearyl (meth)acrylate, etc. The acrylic elastomer contains (meth)acrylate as a monomer together with the acrylic polymer. In addition, (meth)acrylates as monomers may be used alone or in combination of two or more types.

Examples of acrylic elastomers on the market include the product name "Acrycure (registered trademark)" (manufactured by Nippon Shokubai Co., Ltd.; HD-A series).
The paraffin-based process oil used in the present invention is one of the main materials constituting the elastomer member, and imparts flexibility to the elastomer member, etc. As the paraffin-based process oil, for example, one having a kinetic viscosity (40° C.) of 300 to 400 mm ² /s is used.

The olefin resin used in the present invention is composed of a homopolymer or copolymer of olefins such as ethylene, propylene, butene, or a copolymer of these olefins and a monomer component copolymerizable therewith. Specific examples include polyethylene, polypropylene, ethylene-vinyl acetate copolymer, ethylene-ethyl acrylate copolymer, ethylene-acrylic acid copolymer, ethylene-methyl methacrylate copolymer, ethylene-α-olefin copolymer, ethylene-propylene copolymer, ethylene-butene copolymer, etc. These may be used alone or in combination of two or more.

The olefin resin used in the present invention is blended in a ratio of 9 to 13 parts by mass per 100 parts by mass of the elastomer member. If the blended amount of olefin resin is too high, there is a risk of losing properties such as mixability (mold releasability). Also, if the blended amount of olefin resin is too low, there is a risk of losing properties such as heat resistance.

The crosslinking agent used in the present invention is made of an organic peroxide, which generates radicals when heated to a predetermined temperature or higher, thereby partially crosslinking the elastomers. Examples of crosslinking agents include 1,1-bis(t-butylperoxy)-3,5,5-trimethylcyclohexane, 2,5-dimethylhexane-2,5-dihydroperoxide, di-t-butyl peroxide, t-butylcumyl peroxide, dicumyl peroxide, α,α-bis(t-butylperoxy)-p-diisopropylbenzene, 2,5-dimethyl-2,5-di(t-butylperoxy)hexane, 2,5-dimethyl-2,5-di(t-butylperoxy)-hexyne-3, benzoyl peroxide, t-butylperoxybenzene, t-butylperoxymaleic acid, t-butylperoxyisopropylcarbonate, and t-butylperoxybenzoate. These may be used alone or in combination of two or more.

The cross-linking agent is mixed in a ratio of 5 to 7 parts by mass per 100 parts by mass of the elastomer member. If too much cross-linking agent is mixed, the elastomer member may become too hard and may not be able to be molded. If too little cross-linking agent is mixed, properties such as heat resistance may be lost.

The crosslinking aid used in the present invention is used in combination with a crosslinking agent and has the function of promoting crosslinking between elastomer members. Examples of crosslinking aids include triallyl cyanurate, trimethallyl isocyanurate, triacrylformal, triallyl trimellitate, N,N'-m-phenylene bismaleimide, dipropargyl terephthalate, diallyl phthalate, tetraallyl terephthalate amide, triallyl phosphate, bismaleimide, fluorinated triallyl isocyanurate (1,3,5-tris(2,3,3-trifluoro-2-propenyl)-1,3,5-triazine-2,4,6- trione), tris(diallylamine)-S-triazine, triallyl phosphite, N,N-diallylacrylamide, 1,6-divinyldodecafluorohexane, hexaallyl phosphoramide, N,N,N',N'-tetraallylphthalamide, N,N,N',N'-tetraallylmalonamide, trivinyl isocyanurate, 2,4,6-trivinylmethyltrisiloxane, tri(5-norbornene-2-methylene) cyanurate, triallyl phosphite, etc. These may be used alone or in combination of two or more.

The cross-linking aid is mixed in a ratio of 13 to 15 parts by mass per 100 parts by mass of the elastomer member. If the amount of cross-linking aid mixed is too high, moldability and other properties may be impaired. If the amount of cross-linking aid mixed is too low, properties such as heat resistance may be impaired.

The antioxidant used in the present invention is used in combination with a crosslinking agent or the like and has the function of suppressing oxidation of the elastomer member. The antioxidant also has the function of adjusting the amount of crosslinking of the elastomer member. As the antioxidant, for example, a phenol-based antioxidant containing a phenol-based hydroxyl group in the structure can be used, and a hindered phenol-based antioxidant is particularly preferred.

The antioxidant is mixed in a ratio of 3 to 4 parts by mass per 100 parts by mass of the elastomer component. If the amount of antioxidant mixed is too high, the crosslinking of the elastomer component may not be sufficiently formed, and heat resistance, etc. may be impaired. If the amount of antioxidant mixed is too low, there is a risk of problems such as oil bleeding occurring in the elastomer component.

The magnesium hydroxide used in the present invention is surface-treated (coated) with a higher fatty acid. Examples of higher fatty acids that coat the magnesium hydroxide include palmitic acid, stearic acid, oleic acid, and linoleic acid. The particle size of the magnesium hydroxide is preferably 0.5 to 1.5 μm in terms of the median (D50) determined by a laser diffraction method or the like.

Magnesium hydroxide is mixed in a ratio of 15 to 25 parts by mass per 100 parts by mass of the elastomer member. If the amount of magnesium hydroxide mixed is too high, the compression set value of the elastomer member will be high, and the hardness will also be high. If the amount of magnesium hydroxide mixed is too low, there is a risk of problems such as oil bleeding occurring in the elastomer member.

The elastomer member may contain other components as long as they do not impair the objective of the present invention. Examples of other components include colorants (pigments, dyes), carbon black, conductive fillers, UV absorbers, flame retardants, plasticizers, preservatives, solvents, etc.

The JIS A hardness of the elastomer member used in the present invention is preferably in the range of 0 to 37 when the base material is a styrene-based elastomer, and 32 to 64 when the base material is an acrylic elastomer. If the JIS A hardness is within these ranges, the elastomer member will easily deform and enter the gaps in the legs of the mounting fixture, providing a more suitable vibration-damping effect.

[Measurement of JIS A hardness]
For the elastomer member used in the present invention, a sheet-shaped test sample was prepared in order to measure the JIS A hardness. The test sample was subjected to measurement of the JIS A hardness in accordance with JIS K 6253-3 using an Asker Rubber Hardness Tester Type A (manufactured by Kobunshi Keiki Co., Ltd.) under the condition of 23±3° C.

2A and 2B are conceptual diagrams showing the names of dimensions of each part.
In the present invention, as shown in Fig. 2A, the narrower diameter of the female thread structure is defined as the "inner diameter" and the wider diameter is defined as the "root diameter." Also, as shown in Fig. 2B, the diameter of the leg 91 of the mounting tool 9 is defined as the "outer diameter."

The elastic fin 91A functions when the leg 91 of the mounting fixture 9 is pressed into and fixed in the second mounting hole 51. The outer diameter of the leg 91 before pressing is larger than the second mounting hole 51, but by pressing the leg 91 into the second mounting hole 51, the elastic fin 91A is elastically deformed and the outer diameter of the leg 91 is reduced until it can be pressed into. After the leg 91 is pressed into the second mounting hole 51, the elastically deformed elastic fin 91A tries to restore its original shape. Due to this shape restoration, the elastic fin 91A comes into pressure contact with the inner wall of the second mounting hole 51 and gets caught, so that the leg 91 is fixed in the second mounting hole 51.

[Tension and compression test]
For the fixing structure 1 of the first embodiment of the present invention in which the leg 91 of the mounting fixture 9 penetrates the first mounting hole 31 of the electronic board 3 and is press-fitted and fixed into the second mounting hole 51, a tension and compression testing machine (TCM-50 manufactured by MinebeaMitsumi Inc.) was used to pull the head 93 of the press-fitted and fixed mounting fixture 9, and measure the force (removal force) required to remove the leg 91 from the second mounting hole 51. The measurement conditions were a room temperature of 25° C., a humidity of 45% RH, and a pulling speed of 10 mm/min.

As a result of the tension and compression test, the leg 91 of the mounting fixture 9 could be completely removed from the second mounting hole 51 by pulling the head 93 with a force of 458 to 541 N. A similar test was also conducted on a fixing structure using a conventional metal mounting fixture instead of the mounting fixture 9, but the leg of the metal mounting fixture could not be removed from the second mounting hole 51 with a force of 458 to 541 N. In other words, it was found that the mounting fixture 9 is fixed with a weaker force than the metal mounting fixture.

[Vibration test (measurement of vibration-proofing effect)]
The vibration isolation effect of the fixture 9 was measured using a fully automatic vibration tester (F-300BM/A manufactured by EMIC Co., Ltd.). More specifically, the base 5 was used as the vibration device of the fully automatic vibration tester, the electronic board 3 was used as a mounting plate for mounting the vibration device, and the mounting plate was fixed to the vibration device by the fixture 9. An accelerometer was installed on the surface of the mounting plate opposite the vibration device, and it was possible to measure the vibration transmission coefficient, which is the degree to which the vibration applied by the vibration device is transmitted to the mounting plate relative to the frequency. A mounting plate weighing 600 g was used.

The vibration transmission coefficient represents the ratio of the vibration transmitted to the mounting plate when the vibration applied by the vibration device is set to 1. When the vibration transmission coefficient exceeds 1, it indicates that the vibration applied by the vibration device is amplified and transmitted to the mounting plate. Conversely, when the vibration transmission coefficient is less than 1, it indicates that energy loss occurs during transmission, and the vibration applied by the vibration device is suppressed and transmitted to the mounting plate.

FIG. 3 is a graph comparing the results of a vibration test between the first embodiment of the present invention and a case in which the fastener of the first embodiment is replaced with a conventional metal fastener (metal screw).
The vibration test shown in Fig. 3 was carried out with the thickness of the elastomer member 7 sandwiched between the electronic board 3 and the base body 5 set to 5 mm. As shown in Fig. 3, it was found that in the first embodiment, the resonance frequency (the peak frequency at which the vibration transmissibility greatly exceeds 1) is shifted to the lower frequency side compared to the case where a conventional metal screw is used.

The frequency bands where vibration countermeasures are necessary vary depending on the electronic device and its usage, but it is necessary to avoid amplifying the energy of shocks and vibrations given to the electronic device in those frequency bands. In that regard, as shown in Figure 3, when a conventional metal screw is used, the vibration transmission coefficient of the peak that occurs in the frequency band of approximately 300 to 400 Hz is 1 or more, and it can be seen that the applied vibration energy is amplified. In contrast, with fixed structure 1, in the frequency band of approximately 90 Hz and above, there is no amplification of energy in any specific frequency band, and the vibration transmission coefficient can be suppressed to 1 or less, so that a stable vibration-proofing effect can be obtained for various electronic devices in a wide frequency band. Furthermore, measurements were taken with different masses of the mounting plate, and it was found that the desired vibration-proofing effect could be obtained with a mounting plate weighing 2 kg or less.

FIG. 4 is a graph comparing vibration test results when the thickness of the elastomer member is changed in the first embodiment of the present invention.
As shown in FIG. 4, it has been found that the thicker the elastomer member 7 disposed between the electronic substrate 3 and the base 5, the higher the vibration-proofing effect tends to be.

In the first embodiment, experiments were only conducted with an elastomer member thickness of 5 mm, but as shown in Figure 4, it is expected that the thicker the elastomer member is, the better the vibration-damping effect will be. However, for example, when comparing an elastomer member thickness of 4 mm with an elastomer member thickness of 5 mm, no significant difference in vibration-damping effect is observed. Therefore, it is not the case that the elastomer member can be made as thick as possible, and it is expected that with the fixing structure of the present invention, a good vibration-damping effect can be obtained if the elastomer member is made up of a thickness of up to about 8 mm, more preferably up to 6 mm.

[Embodiment 2]
FIG. 5 is a schematic cross-sectional view showing the state of a fixture, an electronic board, and a base body in the second embodiment of the present invention.

Figure 5 shows a fixing structure in which the electronic board 3 and the base 5 are in contact with each other without an elastomer member being disposed between them. The second embodiment shown in Figure 5 differs from the first embodiment only in that the elastomer member 7 is not disposed.

FIG. 6 is a graph comparing vibration test results between the second embodiment of the present invention and the second embodiment in which the fastener is made of metal (metal screws).
FIG. 6 shows that, although the vibration-damping effect (value of vibration transmission coefficient) is smaller in the fixing structure of the present invention than in the first embodiment, even in a fixing structure using only mounting fixture 9 without disposing an elastomer member, a vibration-damping effect can be obtained.

Compared to a fixing structure using metal screws, in the first and second embodiments of the present invention, there is a larger gap between the leg 91 of the mounting fixture 9 and the inner wall of the second mounting hole 51. Also, in the first and second embodiments of the present invention, it is considered that the tip of each elastic blade 91A of the leg 91 is in contact with the inner wall of the second mounting hole 51. Therefore, when an impact or vibration is applied to the mounting fixture 9, the tip of the elastic blade 91A rubs against the inner wall of the second mounting hole 51, and it is considered that the vibration-proofing effect is obtained mainly by the frictional force. The fixing structure of the present invention is a structure that is likely to have a large frictional force compared to a fixing structure using metal screws, and therefore it is considered that a higher vibration-proofing effect can be obtained.

The elastomer member 7 has a JIS A hardness of 0 to 37 when the base material is a styrene-based elastomer, and 32 to 64 when the base material is an acrylic-based elastomer, making it a highly flexible material. Therefore, when the leg 91 of the mounting fixture 9 penetrates the third mounting hole 71, it is thought that one end of the elastomer member 7 deforms and enters the gaps between the multiple elastic fins 91A of the leg 91. With this type of structure, the contact area of the elastomer member 7 with the member to which the shock or vibration is transmitted increases, resulting in a more suitable vibration-proofing effect.

FIG. 7 is a schematic cross-sectional view showing the state of a fixture, an electronic board, a base body, and an elastomer member in the first modified example of the present invention.
Fig. 7 shows a fixing structure in which an elastomer member is disposed not only between the electronic board 3 and the base 5, but also between the head 93 of the fixture 9 and the electronic board 3. The elastomer member disposed above the electronic board 3 in Fig. 7 is referred to as the upper elastomer 7A, and the elastomer member disposed below is referred to as the lower elastomer 7B, so that a vibration-proofing effect can be expected from both the top and bottom of the electronic board 3. Also, by appropriately adjusting the thickness of the upper elastomer 7A and the thickness of the lower elastomer 7B, a vibration-proofing effect can be expected in a wider variety of frequency bands.

FIG. 8 is a schematic cross-sectional view showing the state of a fixture, an electronic board, and a fixing member in the second modified example of the present invention.
Fig. 8 shows a fixing structure in which a metal collar 33 having an internal thread structure is embedded in a first mounting hole 31 provided in an electronic board 3. In the case of the structure shown in Fig. 8, the leg 91 of the mounting fixture 9 is fixed not only to the second mounting hole 51 but also to the internal thread structure of the metal collar 33 embedded in the first mounting hole 31. Therefore, even if the elastomer member 7 is not disposed, the mounting fixture 9 makes it possible to fix the electronic board 3 and the base 5 without them coming into contact with each other.

Although the preferred embodiment of the present invention has been described above, the present invention is not limited to the above embodiment, and includes all aspects included in the concept of the present invention and the scope of the claims. In addition, each configuration may be appropriately and selectively combined so as to achieve at least some of the above-mentioned problems and effects. In addition, for example, the shape, material, arrangement, dimensions, etc. of each component in the above embodiment may be appropriately changed depending on the specific usage mode of the present invention.

1...fixing structure, 3...electronic board, 5...base, 7...elastomeric member, 7A...upper elastomer, 7B...lower elastomer, 9...mounting fixture, 31...first mounting hole, 33...metal collar, 51...second mounting hole, 71...third mounting hole, 91...leg, 91A...elastic fin, 93...head.

Claims (4)

an electronic substrate having at least one first mounting hole;
a base body provided with at least one second mounting hole having an internal thread structure;
a resin mounting fixture for fixing the electronic board to the base,
The mounting fixture includes:
a head portion having an outer diameter greater than an inner diameter of at least the first mounting hole;
a shaft-shaped leg portion extending in one direction from the head portion and capable of being press-fitted into the second mounting hole;
A plurality of elastic fins are formed on the leg portion such that an angle between an extension direction starting from a shaft surface and a press-fit direction of the leg portion is an obtuse angle,
The leg portion can be press-fitted into the second mounting hole by the elastic fin being elastically deformed, and the elastic fin can be fixed to the second mounting hole by being caught in the female thread structure by the restoration of the elastic deformation,
the head is in contact with the electronic board at a position away from the first mounting hole,
the head does not contact the electronic board between a contact point between the electronic board and the head and the first mounting hole,
an elastomer member disposed between the electronic board and the base and having a third mounting hole through which the leg can pass;
Among the plurality of elastic fins, some of the elastic fins are disposed on the inner circumferential side of the elastomer member, and tips of some of the elastic fins are in contact with the elastomer member,
A fixing structure configured so that the fixed leg portion can be detached from the second mounting hole by pulling the head portion with a force of 550 N. the elastomeric member has a cylindrical shape;
The diameter of the third mounting hole is 3 to 9 mm.
The outer diameter of the elastomeric member is 5 to 20 mm;
2. The fixing structure according to claim 1 , wherein the thickness of the elastomer member in the cylindrical axial direction is 1 to 6 mm. The mounting tool is made of polyamide resin,
the elastomer member comprises a styrene-based elastomer or an acrylic-based elastomer, a paraffin-based process oil, an olefin-based resin, a cross-linking agent made of an organic peroxide, a cross-linking assistant, an antioxidant, and magnesium hydroxide surface-treated with a higher fatty acid;
Relative to 100 parts by mass of the styrene-based elastomer or acrylic-based elastomer,
400 to 485 parts by mass of the paraffinic process oil;
9 to 13 parts by mass of the olefin-based resin; 5 to 7 parts by mass of the crosslinking agent;
13 to 16.9 parts by mass of the crosslinking assistant;
3 to 4 parts by mass of the antioxidant;
and 15 to 25 parts by mass of the magnesium hydroxide,
3. The fixing structure according to claim 1 , wherein the elastomeric member has a JIS A hardness of 0 to 37 when a styrene-based elastomer is blended therein, and a JIS A hardness of 32 to 64 when an acrylic-based elastomer is blended therein. The fixing structure according to claim 1 , wherein the elastomer member is also disposed between the electronic board and the head of the mounting fixture.

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