JPH07201502A - Board mounding type electronic component - Google Patents

Abstract

PURPOSE:To eliminate high-temperature treating and long time complicated steps to apply fluorine resin to a board mounting type electronic component. CONSTITUTION:An entire surface of a main part except a connecting part (terminal, etc.) of a board-mounting type electronic component such as a read switch 2, a resistor, a capacitor, etc., to a board is covered with porous PTFE1, and, as required, the component is further shielded from the atmosphere by using a solvent soluble fluorine resin.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a board-mounted electronic component, and more particularly to improvement of an insulating and sealing structure for a board-mounted electronic component such as a reed switch, a resistor and a capacitor.

[0002]

2. Description of the Related Art Electronic components such as reed switches, diodes and ICs are insulated and sealed with synthetic resin for the purpose of improving electrical insulation performance and mechanical and chemical protection. In particular, since fluororesin is excellent in electrical insulation, heat resistance, corrosion resistance, etc., a method of heat-shrinking a fluororesin tube such as FEP and PTFE, a method of baking a fluororesin dispersion such as FEP and PTFE, and a solvent solubility Attempts have been made to insulatively seal electronic components using a fluororesin by a fluororesin coating method or the like.

[0003]

Each of the above methods of insulating and sealing using a fluororesin has the following drawbacks.
The method of heat-shrinking the fluororesin tube requires a heat-shrink step at a high temperature of 300 ° C. or higher. At this time, the element is destroyed and the surface of the metal conductor wire is oxidized, and the shrink step at a low temperature is sufficient. Can not be obtained.

In the method of baking a dispersion of fluororesin, adhesion can be obtained, but since it is baked at a high temperature of 360 ° C. or higher, the elements and terminals are destroyed, and this step takes a long time (about 20 hours). Is required, which causes a problem in the process. Furthermore, the thickness that can be coated with one coating is small, and it is usually necessary to repeat about three times to obtain a coating thickness of about 60 μm.

The solvent-soluble fluororesin coating method can be dried at a relatively low temperature of 150 ° C. and causes little damage to the elements and terminals, but the thickness of one coating is about 5 μm, which is usually 10. It is necessary to repeat the coating-> drying process up to 12 times. Also, this type of resin is generally expensive and not suitable for forming the entire encapsulant. Further, it is difficult to arrange the shape, and waviness and unevenness on the surface become a problem in the subsequent steps.

Therefore, the present invention has the drawback that the elements and terminals are deteriorated during the high-insulation sealing step in the conventional method as described above, and the electrical characteristics (insulating property) resulting from low adhesion after sealing. SUMMARY OF THE INVENTION It is an object of the present invention to solve the drawback that it is not sufficiently obtained, thereby providing an electronic component (reed switch, resistance, etc.) excellent in insulation and reliability. As an invention related to the present invention, JP-A-4-149252 discloses a porous body obtained by impregnating a surface portion of a continuous porous porous tetrafluoroethylene resin base material with a fluoropolymer, Although an electric insulating material is described as the use, the specific use is only an electric wire and an insulator of a printed circuit board.

Japanese Patent Laid-Open No. 2-216854 discloses that
Although it is disclosed that an electronic component is sealed and molded with a polyarylene sulfide resin composition containing 1 to 5% by volume of independent pores, the resin is not a fluororesin, and its object is also different from the present invention.

[0008]

In order to achieve the above object, the present invention provides a board-mounted electronic component such as a reed switch, a resistor, a capacitor, etc. In a board-mounted electronic component characterized in that the entire surface is covered with porous polytetrafluoroethylene, and in a board-mounted electronic component such as a reed switch, a resistor and a capacitor, a connection part between the electronic component and the substrate The entire surface of the main part except for is covered with porous polytetrafluoroethylene, and the main part except the connection part of the electronic component with the substrate is blocked from contact with the outside air by the solvent-soluble fluororesin. A board-mounted electronic component is provided.

The board-mounted electronic parts refer to electronic parts mounted on a board and used, for example, reed switches, capacitors, resistors, diodes, transistors, ICs, LSIs, etc., but the present invention particularly refers to insulating properties. This is effective for further enhancing the insulating property of the glass-sealed reed switch. The connection portion of the electronic component with the substrate refers to a portion such as a terminal (lead) or a solder bump that electrically connects the electronic component to the substrate. Usually, a part of the terminal is also covered.

In the present invention, electronic parts are coated with porous polytetrafluoroethylene (PTFE). Porous PTF
E is much more flexible than the PTFE tube of the actual filling material, and it is good for the glass portion and the terminal portion on the surface of the reed switch, and no gap is formed. Further, in particular, expanded porous PTFE such as GORE-TEX registered trademark has a large heat shrinkage ratio,
Even at a comparatively low temperature (260 ° C. or less) that does not deteriorate the element part of the electronic component such as the reed switch, it sufficiently contracts, and the gap between the electronic component and the PTFE portion is further less likely to occur. An example of the coating is shown in FIG. 1, and FIG.
FIG. 1 (a) is a longitudinal section, but in the figure, 1 is porous PTF.
E, 2 are reed switches (glass-sealed parts), 3 are terminals (solder plating, Cu wire), and 4 are element parts. Further, according to the present invention, as shown in this figure, the porous PTFE covers even a part of the terminal well, so that the insulating characteristic is further improved.

The porous PTFE coating is tape wound only,
Alternatively, after tape winding, heat shrinkage is performed at about 50 to 260 ° C. When a porous PTFE tube is used, 50 to 260 after inserting the electronic component into the porous PTFE tube.
It is desirable to heat-shrink at about ℃. As the porous polytetrafluoroethylene (PTFE) that covers the electronic parts, those produced as a continuous porous body such as a film or a tube are used. The continuous porous body is produced by the elution method,
Although it may be a sintering method, a stretching method, or the like, the stretching method is preferable, and for example, it is produced by the method described in JP-B-51-18991 and JP-B-56-17216. That is, a liquid lubricant, for example, hydrocarbon oil such as solvent naphtha, white oil, petroleum ether, etc. is added to and mixed with a polytetrafluoroethylene resin having a crystallinity of about 95% or more to prepare a preform. The mixing ratio in this case is, for example, polytetrafluoroethylene 80 and liquid lubricant 20. Next, this preform is extruded into a sheet shape, a tube shape, or the like using an extruder to obtain a formed article. The obtained molded product is stretched at a high speed of 10% or more per second in a non-sintered state at 327 ° C. or less with or without removing the liquid lubricant. Next, this stretched product is heat-treated in a stretched state at 200 to 390 ° C. to prevent shrinkage and obtain a desired continuous polytetrafluoroethylene resin porous body. A uniaxially stretched film is obtained by performing the stretching operation in one direction in the stretching step, and a biaxially stretched film is obtained by performing the stretching operation in two directions.

The thickness of the continuous porous body is preferably 5 to 30 μm. If it exceeds 30 μm, it is unsuitable for electronic parts, while if it is less than 5 μm, the number of windings increases and the manufacturing process becomes complicated. The pore size of the porous body is generally 0.1 to 1 μm.
Use m. This is because the solvent-soluble fluororesin can easily penetrate into the porous space. The porosity of the porous body is preferably 70 to 95%. If it is less than 70%, the conformability (flexibility) to the shape of the electronic component is insufficient, and if it exceeds 95%, the strength becomes weak.

When coating porous PTFE, a total coating thickness of at least 60 μm is required. This is because if it is thinner than this, the insulating property will not be sufficiently high. By the way, for electronic components used in fields requiring ultra-high insulation of 1 fA level, which is particularly small at 1 pA or less, current flows even by air flowing inside the porous body as shown in FIG. To meet such ultra high insulation,
Referring to the reed switch shown in FIG. 1, it is necessary to attach a solvent-soluble fluororesin to the reed switch excluding a part of the terminal to block the contact between this part and the outside air.
This mode is shown in FIG. 3, in which 1, 2, 3 are the same as in FIG. 1, and 6 is a solvent-soluble fluororesin.

In addition, a structure in which the outer surface of the porous PTFE is coated with a solvent-soluble fluororesin to stop the flow of air, and a structure in which pores are filled in the entire porous PTFE (thickness direction) (impregnation method of solvent-soluble fluororesin) The same effect can be obtained. For example, in FIG.
In the former example, 7 is a resistance element and 8 is porous PTFE.
A tube, 9 is a solvent-soluble fluororesin, and 3 is a terminal.

As such a solvent-soluble fluororesin, a fluororesin soluble in a solvent can be used. For example, perfluoro-2,2-dimethyl-disclosed in JP-A-58-38707 and JP-A-3-502585.
Amorphous dioxole copolymer (Teflon AF1600, Teflon AF2400, trade name, manufactured by DuPont), or a fluorine-containing thermoplastic resin-like polymer disclosed in JP-A-1-131215 (trade name, Cytop, manufactured by Asahi Glass Co., Ltd.) However, CYTOP has good adhesiveness to glass and is preferable in this respect. Further, JP-A-4-149252 also includes examples of solvent-soluble fluororesins and fluorine-based solvents that dissolve such fluororesins. As the fluorine-based solvent, for example, perfluoroalkane such as perfluorohexane, perfluorocycloalkane,
Examples thereof include perfluoroalkenes, perfluorocyclic ethers such as perfluorotetrahydrofuran, and perfluoroalkylamines.

When the contact between the electronic component and the outside air is blocked by using the solvent-soluble fluororesin, it is not necessary to fill all the pores of the porous polytetrafluoroethylene, and only the contact portion with the electronic component or the outer peripheral portion. Only the holes may be filled, or all the holes may be filled.

[0017]

By coating with porous PTFE, since it has flexibility, it fits well to the outer shape of the electronic component, and the coating operation is simple and can be completed in a short time. In addition, since the heat shrinkage can be performed at a relatively low temperature, the electronic components are not damaged. Thus, a practicable electronic component that is insulated and sealed using highly insulating PTFE is provided, which also contributes to miniaturization of the component. When ultra high insulation is required, a solvent-soluble fluororesin can be used to block the contact between the electronic component and the outside air.

[0018]

EXAMPLES Example 1 A glass sealed reed switch as shown in FIG. 1 (outer diameter 2 m
m, length 13 mm), a stretched porous PTFE film having a thickness of 20 μm, a width of 17 mm, a porosity of 80%, and an average pore diameter of 0.1 μm was wound three times. At this time, the stretched porous PTFE film was wound about 1 mm longer on both sides than the size of the reed switch. Isopropyl alcohol (IP
It was soaked in A), pulled up, naturally dried, and then further heat-shrinked in an oven at 260 ° C. for 20 minutes.

In the reed switch thus obtained, as shown in FIG. 1, the porous PTFE fit well with the irregularities of the glass tube, and the terminals on both sides were also firmly sealed. The insulation resistance of this expanded porous PTFE film-sealed reed switch was as high as 10 ¹⁵ Ω. Note that the total thickness and porosity of PTFE are only reduced by about 10% after thermal contraction.

Example 2 A glass-sealed reed switch similar to Example 1 was used, and a thickness of 5 was used.
A rolled porous PTFE film having a thickness of 6 μm, a width of 17 mm, a porosity of 90%, and an average pore diameter of 0.2 μm is wound 12 times to form a thickness of 6
A cover of about 0 μm was provided. The thin porous film having a thickness of about 5 μm was supple and covered the unevenness of the terminal portion and the glass portion well.

The glass-sealed reed switch was further dipped in a solvent-soluble fluororesin (Cytop CTX) having a concentration of 2%, so that the Cytop CTX was formed on a part of the pores of the porous film and on the glass-porous film interface. It was soaked and attached. The thus-obtained PTFE film-sealed reed switch has a contact with air cut off except for a part of the terminal, and can stop the flow of air.
The insulation resistance was 10 ¹⁷ Ω, which was a very high value. The withstand voltage was also 500 V or more.

Example 3 A glass tube portion and a part of a terminal of a glass-sealed reed switch were coated with a 5% solution of a solvent-soluble fluororesin (Cytop CTX), and the thickness was set to 2 while the solvent was not vaporized.
0 μm, 80% porosity, 0.2 μm pore size stretched porous P
It was wrapped around the TFE film three times. As shown in FIG. 3, the glass-sealed reed switch thus obtained had high adhesion at the glass-porous film interface, was blocked from contact with the outside air, and obtained an insulation resistance of 10 ¹⁷ Ω.

Example 4 A resistance element as shown in FIG. 4 (outer diameter 1.5 mm, length 7 mm) was used, and inner diameter 1.7 mm, length 10 mm, wall thickness 0.1 mm, porosity 90%.
It was inserted into the expanded porous PTFE tube of and the tube was shrunk at 260 ° C. Since it is a flexible tube, it fits well on the unevenness of the element surface.

Further, as shown in FIG. 4, 5% solvent-soluble fluororesin (Teflon AF2400) is coated on the surface of the tube to seal a part of the terminal and the boundary between the tube and the terminal to prevent contact with the outside air. Shut off. Teflon AF2
400 also penetrated into the vicinity of the surface of the porous PTFE tube, and the coating layer of Teflon AF2400 was firmly bonded to the porous PTFE tube by the anchor effect.

The insulation resistance of the obtained PTFE sealed resistance element was high, and 10 ¹⁶ Ω was obtained.

[0026]

As described above, according to the present invention, the current flowing on the surface of the electronic component is sufficiently blocked by using the porous PTFE without increasing the bulk (without enlarging the outer shape of the electronic component). It is effective in improving the characteristics of the electronic device and making it compact.

[Brief description of drawings]

FIG. 1 shows a porous PTFE encapsulated reed switch.

FIG. 2 shows the air flow through a porous PTFE sealed reed switch.

FIG. 3 shows a porous PTFE sealed reed switch in which a solvent-soluble fluororesin is impregnated near the interface between the porous PTFE and the glass tube portion.

FIG. 4 shows a porous PTFE sealed resistance element in which a solvent-soluble fluororesin is coated on the outer surface of porous PTFE.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Porous PTFE 2 ... Reed switch (glass sealing part) 3 ... Terminal 4 ... Element part 5 ... Air flow 6 ... Solvent-soluble fluororesin 7 ... Resistor element 8 ... Porous PTFE tube 9 ... Solvent-soluble fluororesin

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Reference number within the agency FI Technical display location H01H 9/02 Z H01L 23/29 23/31 (72) Inventor Koichi Okino 1 Akatsumi, Setagaya-ku, Tokyo 42-5, Japan, within Japan Gore-Tex Co., Ltd.

Claims (2)

[Claims] 1. In a board-mounted electronic component such as a reed switch, a resistor, a capacitor, etc., the entire surface of a main part of the electronic component except a connecting portion with the substrate is covered with porous polytetrafluoroethylene. A board-mounted electronic component. 2. In a board-mounted electronic component such as a reed switch, a resistor, a capacitor, etc., the entire surface of a main part of the electronic component except a connecting portion with the substrate is covered with porous polytetrafluoroethylene, and A board-mounted electronic component, wherein a main part of the electronic component except a connection part with a substrate is blocked from contact with outside air by a solvent-soluble fluororesin.