JP3592634B2 - Resistance heating element - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a resistance heating element used for a heating element for erasing characters printed on a rewrite card.
[0002]
[Prior art]
Japanese Laid-Open Patent Publication No. 11-138881 discloses a resistance heating element having a resistance heating part on the surface of an insulating substrate and a thermistor component fixed to the back surface of the insulating substrate. Here, to explain with reference to FIG. 6, a surface mount type chip thermistor 22 is first mounted (fixed with solder) on a pair of electrodes 21 formed at the center of the back surface 20 of the substrate. Next, the lands 23 formed integrally with the electrodes 21 and the electric wires 24 are soldered 25. In this manner, the chip thermistor 22 is fixed to the back surface 20 of the substrate and the chip thermistor 22 and the electric wire 24 are connected.
[0003]
[Problems to be solved by the invention]
Applications of the resistance heating element include inputting information into a so-called rewrite card or deleting information from the rewrite card. In such an application, the resistance heating element repeats rapid heating to about 100 to 170 ° C. by energization and natural cooling to room temperature by stopping energization many times. On the other hand, the thermistor is usually arranged in a high temperature region in order to sense the temperature of the resistance heating element. Therefore, it has been clarified that if the resistance heating element having the above-described configuration of the related art is continuously used in the above-mentioned usage pattern, a problem of disconnection of the connection portion between the electrode and the lead terminal occurs. That is, the electrical connection between the thermistor terminal and the electrical wire connected therewith becomes insufficient, and it becomes impossible to grasp the electrical characteristics of the thermistor.
[0004]
Therefore, the problem to be solved by the present invention is to provide a resistance heating element that can grasp the electrical characteristics of the thermistor even in a usage pattern in which the temperature rise / fall is repeated many times.
[0005]
[Means for Solving the Problems]
In order to solve the above problems, the resistance heating element of the present invention has a resistance heating part on the surface of the insulating substrate 4, and the thermistor element and the lead 2 are electrically connected to the back surface of the insulating substrate 4 by welding or pressure welding. A resistance heating element to which a thermistor with a lead 1 in which a connecting portion is encapsulated in glass is fixed. The fixing is performed by bending a metal plate welded to a conductor disposed on the back surface of the insulating substrate 4. It is characterized by holding .
[0006]
As described above, since the thermistor 1 senses the temperature of the resistance heating element, it is necessary to receive the heat of the resistance heating element directly as much as possible and not to prevent the heating of the object to be heated. Accordingly, the thermistor 1 is disposed on the back surface of the insulating substrate 4 via the insulating substrate 4 having the resistance heating portion disposed on the front surface.
[0007]
In addition, the resistance heating portion includes, for example, a resistor 7 and a pair of electrodes 5 arranged so as to be in contact with both ends thereof as shown in FIG. It is something that emits.
[0008]
The reason why the thermistor 1 with leads 2 is used in the resistance heating element of the present invention will be described below.
The disconnection of the connection part between the electrode and the lead terminal due to the continuous use of the resistance heating element in the conventional usage pattern in which the temperature is increased and decreased a great number of times is considered to be caused by the solder used for the connection. It is done. For example, when solder with a melting point of about 180-200 ° C is placed in an environment where the temperature of about 100-170 ° C required for erasing information on the rewrite card and the ordinary temperature is repeated many times, the solder structure becomes enlarged and only the solder Then, even if the holding force of the object to be held (the chip thermistor 22, the electrode 21, the land 23, and the electric wire 24 in FIG. 6) can be kept high, a sufficiently stable connection state may not be obtained for the electric connection. .
[0009]
On the other hand, solder is not used for electrical connection between the thermistor element in the normal thermistor 1 with the lead 2 and the lead 2, and for example, welding is often performed by pressure welding. Furthermore, a strong connection portion is formed by sealing the electrical connection portion with glass or the like. Here, the connection reinforcing / maintaining means such as the glass sealing is indispensable for maintaining the pressure contact state.
[0010]
That is, the components of the normal thermistor 1 with the lead 2 do not use a material such as solder that easily changes in structure due to heat change, and therefore, the cycle between a temperature of about 100 to 170 ° C. and a normal temperature is repeated many times. Even when placed in the environment, the electrical connection between the thermistor element and the lead 2 is unlikely to deteriorate. Thus, even in a usage form in which the temperature rise / fall is repeated, it is possible to provide a resistance heating element that can grasp the electrical characteristics of the thermistor 1 by using the thermistor 1 with leads 2. Accordingly, the thermistor 1 with leads 2 is used as the temperature sensing means of the resistance heating element of the present invention.
[0011]
Next, means for fixing the thermistor 1 with leads 2 to the back surface of the insulating substrate 4 will be described.
In FIG. 1, the fixing member 3 is simply shown. The fixing member 3 does not require a special function such as the purpose of serving as a connection, and is merely for fixing, and therefore, there is no strict restriction on the means. For example, without using the fixing member 3, the elasticity of the lead 2 of the thermistor 1 may be used to press against the back surface of the insulating substrate 4. Further, in this case, a recess may be provided on the back surface of the insulating substrate 4 so that the thermistor 1 with the leads 2 is accommodated in the recess, and the resistance heating element may be fixed in a predetermined position. In addition, the resistance heating portion is fixed first, and the thermistor is fixed separately, and the positions of the back surface of the insulating substrate 4 and the thermistor 1 are adjusted, respectively, so that the thermistor 1 with leads 2 is fixed to the back surface of the insulating substrate 4. It can also be. These are resistance heating elements capable of grasping the electrical characteristics of the thermistor 1 even when the temperature rise and fall are repeated.
[0012]
However, it is preferable to integrally fix the insulating substrate 4 and the thermistor 1 because it contributes to downsizing of the device in which the insulating substrate 4 is incorporated and improvement of the efficiency of assembling the resistance heating element. An example of means for realizing such a configuration is that the thermistor 1 is fixed to the back surface of the insulating substrate 4 by holding the thermistor component of the metal plate 9 welded to the conductor 6 disposed on the back surface of the insulating substrate 4. It is a means by bending. In this case, the fixing member 3 in FIG.
[0013]
FIG. 2 shows an example of how the lead 2 is fixed to the back surface of the insulating substrate 4 when a metal plate 9 such as copper is used. As shown in FIG. 2A, first, a conductor 6 is disposed on the back surface of the insulating substrate 4 by a technique such as screen printing. Then, the metal plate 9 is placed on the conductor 6, and the conductor 6 and the metal plate 9 are integrated by spot welding or the like. The welding mark 10 is shown in the same figure. Next, as shown in FIG. 2B, the metal plate 9 is bent so that the lead 2 of the thermistor 1 is inserted. Since the copper plate or the like hardly undergoes elastic deformation and is difficult to restore to the original shape once bent, the lead 2 can be sufficiently fixed. Thus, the back surface of the insulating substrate 4 and the lead 2 can be fixed using the conductor 6 and the metal plate 9.
[0014]
1 and 2, the lead 2 portion of the thermistor 1 is fixed to the back surface of the insulating substrate 4. However, the present invention is not limited to this, and it goes without saying that the portion other than the lead 2 of the thermistor 1 may be fixed to the back surface of the insulating substrate 4. Yes. In this case, for example, a means such as bonding a portion other than the lead 2 of the thermistor 1 and the back surface of the insulating substrate 4 with a glass paste, and then heat-curing the glass substrate can be considered.
[0015]
However, the fixing means can be varied by making the portion related to the fixing of the thermistor 1 with the lead 2 the lead 2 portion. The first reason is that the lead 2 portion is a conductor and the portions other than the lead 2 portion are non-conductive materials. In the case of a conductor, welding or soldering can be employed as the fixing means in addition to the fixing means using an adhesive or the like as the fixing means. Here, FIG. 2 shows a means for fixing the lead 2 to the insulating substrate 4 via the metal plate 9, but it is also possible to directly weld the lead 2 and the conductor 6 without the metal plate 9. is there. The second reason is that the lead 2 portion is a deformable metal wire. Utilizing this property, fixing can be performed by tying or entwining with the back surface of the insulating substrate 4, a part having a three-dimensional shape, etc. existing on the other members and related members close thereto.
[0016]
In order to further improve the fixing reliability, for example, as shown in FIG. 2C, while trying to fill at least a part of the gap between the metal plate 9 and the lead 2 from the state of FIG. 2B. Dispose molten solder and solidify. That is, the metal plate 9 and the lead 2 portion are fixed with the solder 11. In this state, the fixing member 3 in FIG. 1 is the metal plate 9 and the solder 11. When the solder 11 is used for the purpose of electrical connection, it is difficult to obtain a sufficiently stable connection state as described above, but using the solder 11 as the mere fixing member 3 is not a big problem. In addition, in this case, since the metal plate 9 is also the fixing member 3, the solder 11 functions as a fixing auxiliary member, so that there are still fewer problems.
[0017]
The lead 2 of the thermistor 1 with the lead 2 according to the present invention cannot be lengthened indefinitely. In addition, since the material of the lead 2 is generally poor in flexibility and difficult to handle, the lead 2 terminal portion and the electric wire 13 are usually connected and attached to various devices. FIG. 3 shows a state in which the lead 2 portion and the electric wire 13 are connected by the solder 11. It is preferable that at least the connection portion is covered and protected by the heat shrinkable tube 12 or the like. Further, when the downsizing of the device is required, problems such as contact between the leads 2 are likely to occur. Therefore, it is most preferable to cover the entire exposed portion of the lead 2 with the heat shrinkable tube 12.
[0018]
Here, solder is used as an electrical connection means. Therefore, there may be a concern that the tissue enlargement as described above may occur and a sufficiently stable electrical connection state cannot be obtained. However, unlike the conventional case shown in FIG. 6 in which the land 23 arranged on the back surface of the substrate having the resistance heating portion on the surface and the electric wire 24 are connected by the solder 25, the resistance is applied to the surface as shown in FIG. The solder 11 is used to connect the electric wire 13 to the lead 2 portion of the thermistor 1 with the lead 2 disposed on the back surface of the insulating substrate 4 having the heat generating portion. Therefore, the connecting portion, that is, the solder 11 can be present at a position sufficiently away from the resistance heating portion.
[0019]
In this case, it may be influenced by the ventilation environment of the place where the resistance heating element is attached to the device, but it is considered that the connection portion should be located at a distance of 2 mm or more from the insulating substrate 4 in the rear surface direction. Further, the melting point of the solder 11 used here is more preferably approximately 210 ° C. or higher. These reasons are for avoiding the enlargement of the structure of the solder 11 as described above as much as possible.
[0020]
Moreover, the preferable alloy of the solder 11 used here and the solder 11 shown in FIG.2 (c) used as needed is a tin-silver-bismuth type alloy, a tin-bismuth-silver-copper type alloy, a tin-silver-copper. Alloy, tin-silver-indium alloy, tin-silver-copper-antimony alloy, tin-silver alloy, tin-copper alloy, tin-antimony alloy, and the like. These do not contain lead and are excellent in environmental harmony. Here, the presence of lead that is mixed to the extent of impurities is negligible from the viewpoint of environmental harmony, and therefore a range that does not substantially contain lead is a preferable alloy. They also have the advantage that a wide range of alloy compositions having a melting point of 210 ° C. or higher can be selected, and various alloys can be selected.
[0021]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an example of an embodiment of the present invention will be described with reference to the drawings.
First, a conductive paste containing Ag—Pd alloy powder and glass frit is applied to the surface of an alumina plate as an insulating substrate 4 having a thickness of 0.8 mm shown in FIG. (Film thickness 10-12 μm). Next, the conductive paste is screen-printed and fired so as to extend in the vicinity of the periphery of the through hole 14 on the back surface of the alumina plate and in the center direction of the alumina plate surface, thereby forming the electrode 5. Thus, the electrode 5 formed on the surface of the alumina plate and the electrode 5 formed on the back surface of the alumina plate are connected via the through hole 14. Further, a conductor 6 for mounting a thermistor 1 with leads 2 to be described later on the back side of the alumina plate is also formed simultaneously.
[0022]
Next, a resistor paste mainly composed of Ag—Pd alloy powder is formed by screen printing and firing on the surface of the alumina plate. At this time, the resistor 7 is formed so that both ends of the resistor 7 partially overlap the previously formed electrode 5. This resistor 7 becomes the resistance heating part 4.
[0023]
Thereafter, a paste mainly composed of lead borosilicate glass is left on the entire surface of the resistor 7 and a part of the electrode 5, and the resistor 7 film and the electrode 5 film are made of glass by screen printing and baking on almost the entire surface of the electrode 5. Protect with 8 membranes.
[0024]
After that, the alumina plate is divided by applying stress so as to open the dividing groove 15 provided in advance in the alumina plate 5.
[0025]
In the energizing terminal shown in FIG. 5, a caulking portion that caulps and fixes the copper wire exposed portion of the fluorinated polyethylene vinyl-coated copper wire, a caulking portion that bundles and fixes the conducting wires, and a flat plate portion are integrated. It consists of the member. The flat plate portion is obtained by coating Ag on the surface of a copper plate having a thickness of 0.1 mm by plating. The Ag plating thickness is several μm.
[0026]
Next, two welding electrodes having a diameter of about 1 mm are brought into contact with only the flat plate portion while bringing the flat plate portion into contact with the exposed surface of the electrode 5 on the back surface of the insulating substrate 4 connected to the resistor. A current was applied between the electrodes to spot weld the current-carrying terminal and the electrode 5. As welding conditions, two pulses of 0.45 kW are applied every 15 milliseconds with a pause of 50 milliseconds. The pressing force applied to the energizing terminal by the welding electrode was such that the welding electrode trace after welding had a depth of about 0.1 mm. Since the thickness of the electrode 3 is 10 to 12 μm, it is considered that the flat portion of the energizing terminal is locally thinned and the welding electrode trace depth after welding is about 0.1 mm.
[0027]
Next, a 0.1 mm thick metal plate 9 shown in FIG. 2 is welded to the conductor 6 under the same conditions as the above welding conditions. Then, the lead 2 of the thermistor 1 with leads 2 is placed on the metal plate 9 as shown in FIG. Thereafter, the metal plate 9 is rubbed against the lead 2 as shown in FIG. Then, as shown in FIG. 2C, the metal plate 9 and the lead 2 portion are fixed by the solder 11.
For the thermistor 1 with leads 2, the thermistor element and the lead 2 were electrically connected by pressure welding and the electrical connection portion was sealed in glass.
[0028]
Next, as shown in FIG. 3, the lead 2 portion (terminal) and the electric wire 13 are connected by the solder 11 at a position 2 mm or more away from the insulating substrate 4 in the back surface direction.
The solder 11 used for these is a tin-silver-copper alloy, and its melting point is about 230 ° C.
In this way, the resistance heating element of the present invention can be obtained.
[0029]
【The invention's effect】
According to the present invention, it is possible to provide a resistance heating element capable of grasping the electrical characteristics of the thermistor even in a usage pattern in which the temperature rise / fall is repeated many times.
[Brief description of the drawings]
FIG. 1 is a diagram showing an outline of a resistance heating element of the present invention.
FIG. 2 is a diagram illustrating a state in which leads are fixed to the back surface of an insulating substrate.
FIG. 3 is a diagram illustrating a connection state between a lead and an electric wire.
FIG. 4 is a diagram showing a connection state between leads and electric wires.
FIG. 5 is a diagram showing an appearance of a current-carrying terminal.
FIG. 6 is a view showing a conventional thermistor of a resistance heating element and an attached state of electric wires.
[Explanation of symbols]
1. Thermistor 2. 2. Lead 3. Fixing member 4. Insulating substrate Electrode 6. Conductor 7. Resistor 8. Glass 9. Metal plate 10. Welding marks 11. Solder 12. Heat shrink tube 13. Electric wire 14. Through hole 15. Dividing groove 20. Substrate back surface 21. Electrode 22. Chip thermistor 23. Land 24. Electric wire 25. Solder

Claims (5)

Has a resistance heating portion surface of the insulating substrate, the insulating substrate back surface, the thermistor element and the lead are electrically connected by welding or pressure contact, and the resistance heating element with lead thermistor which the electrical connections are glass encapsulated Ru fixed Because
The resistance heating element characterized in that the fixing is holding the lead portion by bending a metal plate welded to a conductor disposed on the back surface of the insulating substrate . 2. The resistance heating element according to claim 1, wherein the metal plate and the lead portion are fixed with solder. 3. The resistance heating element according to claim 1, wherein the lead portion and the electric wire are connected by solder at a position 2 mm or more away from the insulating substrate in the back surface direction. The resistance heating element according to claim 2 or 3, wherein the solder does not substantially contain lead. The resistance heating element according to any one of claims 1 to 4, wherein the resistance heating element is a heating element for inputting information to the rewritable card or erasing information of the rewritable card.

Images