JPH05135861A - Heating unit in surface form - Google Patents

Abstract

PURPOSE:To enhance reliability as a heating unit in a surface form by bonding the heating unit with a heated section with air bubbles excluded. CONSTITUTION:A pattern 13 is formed over a flexible substrate by the use of copper foil, a nickel plating layer 15 is provided over the copper foil pattern 13, and furthermore carbon paste 17 is applied on the nickel plating layer 15 so as to be sintered, so that a heating unit is thereby formed. And it is finally formed into a heating unit 18 in a surface form provided with a plural number of air venting holes 19 over the flexible substrate.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flexible sheet heating element, and more particularly to a sheet heating element which improves the reliability of the sheet heating element.

[0002]

2. Description of the Related Art Conventionally, as shown in FIG. 4, a planar heating element of this type has an electrode pattern 53 formed on a flexible insulating film 51 and the electrode pattern 53 straddling each electrode pattern 53. The carbon paste 57 was applied and fired to form the heat generating portion. The carbon paste 57 is prepared by kneading carbon powder with a phenol resin as a binder. In such a configuration,
The thinner the flexible insulating film 51, the more efficiently heat can be transferred, which is very convenient. Therefore, the thickness of the flexible insulating film 51 is usually about 30 μm.

Further, the flexible insulating film 51
A heat-resistant double-sided tape 59 is attached to the back surface of the.
When the sheet heating element 61 is attached to the heated portion 63, the release paper of the double-sided tape 59 attached to the back surface of the flexible insulating film 51 is peeled off, and the heated portion 63 is heated.
Was pasted on.

[0004]

However, when such a flexible sheet heating element 61 is attached to the heated portion 63 with the double-sided tape 59, as shown in FIG. 5, the double-sided tape 59 and the non-heated portion 63 are used. Bubbles 65 may enter between and. Similarly, air bubbles 65 may also enter between the flexible insulating film 51 and the double-sided tape 59. Since the flexible insulating film 51 is very thin and has elasticity, when the air bubble 65 is contained under the sheet heating element 61, the sheet heating element 6 is
As 1 is heated, the bubble 65 expands and the sheet heating element 5
An action force acts to greatly inflate 9 in the direction opposite to the non-heated portion 63.

On the other hand, since the fired carbon paste 57 has poor elasticity, the fired carbon paste 57 is likely to crack due to the acting force applied to the sheet heating element 61. If the sheet heating element 61 having a crack in one place is energized, the crack portion causes an electrical short, and the crack portion emits high heat. Then, due to the high temperature heat generation at the time of short circuit, the phenol resin becomes hard and brittle, and cracks are more likely to occur. As a result, the crack further grows, the resistance value of the sheet heating element 61 increases, and in the end, a sufficient amount of heat cannot be obtained, so that the sheet heating element 61 may not function.

Further, the bubble 65 expands and the sheet heating element 61 is expanded.
The bulging portion has poorer thermal conductivity than the other portions in contact with the body 63 to be heated, and the surface temperature of the planar heating element 61 is locally twice as high as that of the other portions. Become.
As a result, the phenolic resin becomes hard, brittle, and easily cracked. As a result, similarly, the sheet heating element 6
The function as 1 will not be fulfilled.

The present invention has been made to solve the above-mentioned problems, and since the planar heating element is provided with an air vent hole, air bubbles are generated when the planar heating element is attached to the heated portion. An object of the present invention is to provide a sheet-like heat generating element which can surely adhere the sheet-like heat generating element to a heated portion without forming it and can satisfy reliability.

[0008]

In order to achieve this object, the sheet heating element of the present invention has a plurality of conductive paths formed of a metal foil on a flexible insulating film and straddles the plurality of conductive paths. A heating element portion formed by applying a conductive coating material and baking the coating material, and a plurality of air vent holes provided on a flexible insulating film are provided.

[0009]

Since the sheet heating element of the present invention having the above-mentioned structure has a large number of air vent holes formed on the flexible insulating film, the sheet heating element can be applied to the heated portion when the sheet heating element is attached. The air existing between the heating element and the heated portion escapes from the air vent hole, and the planar heating element can surely adhere to the heated portion.

[0010]

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

FIG. 1 is a diagram showing the structure of a sheet heating element according to the present invention. Since the sheet heating element of the present invention is always used as a heater at a high temperature, it is difficult to maintain the adhesive strength with an adhesive used for a general substrate. Therefore, the flexible printed board of the sheet heating element according to the present invention uses a flexible printed board that does not use an adhesive between the heat resistant resin film 11 and the copper foil pattern 13.

The copper foil patterns 13 are formed so as to face each other as shown in FIG. 1, and a nickel plating layer 15 is formed on the copper foil patterns 13. Furthermore, a carbon paste agent 17 prepared by kneading carbon powder with a phenol resin as a binder is applied at intervals so as to extend between the two copper foil patterns 13 provided with the nickel plating layer 15.
A plurality of heating elements 18 are formed. As shown in FIG. 1, a place where the carbon paste agent 17 is not applied,
That is, the air vent holes 19 are arranged in the gaps between the heating elements 18. As shown in FIG. 2, the air vent hole 19 is formed by penetrating the heat resistant resin film 11, the double-sided tape 21 and the release paper 23 attached to the lower surface thereof.

Next, the sheet heating element 1 constructed as described above.
The work of attaching 8 to the heated portion 25 will be described with reference to FIG.

In FIG. 3, the sheet heating element 18 is provided with a heated portion 25.
FIG. 2 is a cross-sectional view showing a state in which the sheet-shaped heat generating element 18 is bonded to the sheet, and is a view showing the same state as the cross section taken along the line BB of the planar heating element 18 in FIG. 1.

When the sheet heating element 18 is attached to the heated portion 25, first, the release paper 23 on the back side of the sheet heating element 18 is attached.
A little, and the sheet-like heating element 18 at that part is removed from the heated portion 2
Press against 5. Then, the release paper 23 is gradually peeled off while the planar heating element 18 is pressed against the heated portion 25 with a finger or the like, and the planar heating element 18 is bonded to the heated portion 25. At that time, the air existing between the heated portion 25 and the double-sided tape 21 or between the double-sided tape 21 and the heat-resistant resin film 11 is expelled by a finger or the like and easily escapes through the air vent hole 19. Therefore, the sheet heating element 18 can be brought into close contact with the heated portion 25 without forming bubbles. As a result, the heat of the sheet heating element 18 is reliably transmitted to the heated portion 25, and no local heating portion is generated. Further, since there are no bubbles, the sheet heating element 18 does not swell. Therefore, the reliability of the sheet heating element 18 can be improved.

Next, an example of the manufacturing process of the sheet heating element 18 of the present invention will be described. A casting method is one of the methods for producing a flexible printed circuit board that does not use this adhesive. The casting method is a method in which a varnish is applied on a copper foil and a solution material is subjected to an imide reaction to form a film material.

The copper foil of the flexible printed circuit board produced by this casting method is selectively removed by etching to form copper foil patterns 13 facing each other. After the etching, the flexible printed circuit board is dipped in a nickel plating solution, and a nickel plating layer 15 having a thickness of about 2 μm is formed on the copper foil pattern 13 by electrolytic plating. The nickel plating layer 15 is for preventing the generation of copper oxide on the surface of the copper foil pattern 13. That is, in the absence of the nickel plating layer 15, when exposed to a high temperature and high humidity condition for a long time, a copper oxide layer grows on the copper foil pattern 13,
This will greatly change the resistance value of the entire heating element.

Further, a carbon paste agent 17 is applied by silk screen printing so as to extend between the copper foil patterns 13.
With a thickness of 15 μm. Carbon paste agent 17
Has a composition in which a thermosetting phenol resin and carbon powder are kneaded and dispersed. By baking the carbon paste agent 17, the phenol resin is hardened and the carbon powder is held at appropriate intervals, so that a stable sheet resistance value can be obtained. Carbon paste 17
It is possible to obtain a heating element portion having a stable sheet resistance value when the phenol resin contained in is heated at the maximum temperature that can withstand the temperature. Therefore, the firing in the case of the structure according to the present invention is performed at a firing temperature of 260 ° C. and a firing time of 5 minutes.

The sheet heating element 18 that has been fired is heated 25
To the heat-resistant resin film 11, the outer shape of the sheet heating element 18, the air vent hole 19, and other holes are punched with a Thomson type or a press type. The finished product.

The present invention is not limited to the embodiments described in detail above, and various modifications can be made without departing from the spirit of the invention.

For example, although polyimide is used for the heat resistant resin film 11 in this embodiment, a heat resistant material such as a flame retardant polyolefin resin may be used.
Further, an adhesive may exist between the heat resistant resin film 11 and the copper foil pattern 13, and the adhesive may be a heat resistant adhesive such as a heat resistant epoxy resin. Also, the nickel plating layer 15 is a copper foil pattern 13.
Any material can be used as long as it can prevent the oxidation of gold, such as gold plating. Further, the air vent hole 19 may have a slit shape.

[0022]

As is apparent from the above description, since the sheet heating element of the present invention has a large number of air vent holes formed on the flexible insulating film, the sheet heating element can be used as a heated portion. When pasting, the air existing between the sheet heating element and the heated portion can escape from the air vent hole, so it is possible to bond the sheet heating element to the heated portion without forming bubbles. it can. As a result, the reliability and function of the sheet heating element can be satisfied.

[Brief description of drawings]

FIG. 1 is a perspective view of a sheet heating element of the present invention.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is a cross-sectional view taken along the line BB in FIG. 1 of the planar heating element in a state of being bonded to a heated portion.

FIG. 4 is a perspective view of a conventional sheet heating element.

FIG. 5 is a diagram in which a conventional sheet heating element is bonded to a heated portion.

[Explanation of symbols]

 11 Heat Resistant Resin Film 13 Copper Foil Pattern 17 Carbon Paste Agent 19 Air Venting Hole

Claims (1)

[Claims] 1. A plurality of conductive paths formed of a metal foil on a flexible insulating film, and a heating element part formed by straddling the plurality of conductive paths, applying a conductive paint, and firing the conductive coating. A planar heating element comprising a plurality of air vent holes provided on the flexible insulating film.