JPH05246065A - Heating control structure of heating element - Google Patents

Abstract

(57) [Summary] [Object] To provide a heating element control structure capable of limiting the temperature rise of a heating element within a predetermined range while simplifying an electric control circuit. [Structure] A supporting metal body 7 made of Pb or the like having a large thermal expansion coefficient is arranged substantially in the center of the lower surface side of the heating element 11, and grounding side conductors 10 are arranged on both sides thereof so as to contact the heating element 11. There is. The supporting metal body 7 is connected to the live side conductor 6, and when a current is supplied through the live side conductor 6, a current flows toward the ground side conductor 10 and the heat generating element 11 generates heat. .. When heat generation continues and the temperature of the heating element 11 rises, the supporting metal body having a large coefficient of thermal expansion thermally expands and pushes up the heating element 11. Due to this rise of the heating element 11, the ground-side conductor 10 that has been in contact with the heating element 11 is separated from the heating element 11. As a result, the current path to the heating element 11 is cut off, the temperature of the heating element 11 starts to drop, and the temperature rise is limited within the predetermined range.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat generation control structure for a heat generating element used in a thermal head or the like.

[0002]

2. Description of the Related Art Conventionally, a method of heating a heating element used in a thermal head or the like has been described by selectively applying a voltage from a driving circuit section to a large number of heating elements provided on a substrate. An electric current is passed through to generate heat, and the heat is used for thermal recording. In this case, the voltage applied to the heating element is applied in pulses from the drive circuit to the heating element, and the heating temperature of the heating element is controlled by controlling the time during which the current flows through the heating element with this pulse. ing.

[0003]

However, in the heat generation control method for the heat generating element used in the thermal head or the like, when printing continuous characters, the temperature of the heat generating element is different at the beginning and end of printing. As a result, variations in printing density occur. This is because the temperature of the heating element is room temperature (room temperature) at the start of printing, but at the end of printing, the temperature changes from room temperature to the printing temperature depending on the frequency of use of the heating element. In order to cope with this and perform heat-sensitive recording with uniform print density, it is necessary to control the time and timing of passing current through the heating element according to the frequency of use, which makes the control circuit extremely complicated and expensive. There was a problem. An object of the present invention is to provide a heating element control structure capable of limiting the temperature rise of the heating element within a predetermined range while simplifying the electric control circuit.

[0004]

In order to achieve the above-mentioned object, the present invention supports a heating element in contact with a live side conductor and a ground side conductor with a metal body having a large thermal expansion coefficient,
The metal body expands due to the heat generated by the heating element, so that the contact with the conductor is cut off when the heating element reaches a certain temperature or higher.

[0005]

According to the heat generation control structure of the heat generating element of the present invention,
When the heating element in contact with the live conductor and the ground conductor frequently generates heat and its temperature exceeds a predetermined value, the metal body supporting the heating element thermally expands due to the heat of the heating element, The thermal expansion of the metal body interrupts the contact between the heating element and the conductor. Therefore, the heating element is de-energized and the temperature rise of the heating element can be suppressed. Moreover, because the thermal expansion of the metal body automatically cuts off the power supply to the heating element,
It is not necessary to electrically control the time, timing, and the like of flowing a current through the heating element according to the frequency of use, and the electrical control of the heating element can be simplified.

[0006]

[First Embodiment] A first embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is an enlarged sectional view of an essential part showing a heat generation control structure of a heat generating element according to the present invention. The heat generation control structure of this heat generating element is applied to, for example, a thermal head for performing thermal recording, and a large number of heat generating components 2 and this heat generating component 2 are formed on a single crystal n-type silicon substrate (wafer) 1. It has a configuration in which driving elements such as the transistor element 3 for driving are collectively formed. A large number of heating components 2 are arranged on the silicon substrate 1. That is, the SiO ₂ insulating film 4 is formed on the upper surface of the silicon substrate 1 by thermal oxidation, and the insulating protective film 5 made of phosphosilicate glass (PSG) and having a high insulating property is formed on the insulating film 4. CVD (Chemical Vapor Depositio)
n) is formed by the method. On the upper surface of the insulating protective film 5, a wiring pattern (live-side conductor) 6 made of a low resistance metal such as Cu, Ti, or Mo is formed. On the upper surface of the wiring pattern 6, a supporting metal body 7 is formed. An insulating film 8 made of SiO ₂ , SiN or the like is formed over the insulating protective film 5 on the wiring pattern 6 except the supporting metal body 7. In this case, the supporting metal body 7 is made of a metal such as Pb having a large coefficient of thermal expansion, and is formed in a plurality of cylindrical arrangements. Then, it is configured so as to project upward from the upper surface of the insulating film 8 due to thermal expansion. Further, the insulating film 8 has a groove 9 extending from the inside of the supporting metal body 7 to the outside.
Is formed by half etching, and C is placed in the groove 9.
A ground line (ground-side conductor) 10 made of u, Ti, Mo, etc. is formed. The ground line 10 is protected by the insulating film 8 so as not to be electrically connected to the wiring pattern 6 and the supporting metal body 7 described above, is hardly affected by the temperature change, and its upper surface is flush with the upper surface of the insulating film 8. Has been formed. Then, the supporting metal body 7 including the ground line 10
A heat generating resistance element (heat generating element) 11 is provided on the upper side so as to be in close contact with the ground line 10 at room temperature. That is, the heating resistance element 11 is made of a material having a high electric resistance and a small coefficient of thermal expansion, for example, polycrystalline silicon. By doping the polycrystalline silicon with phosphorus (P) ions as impurities, a predetermined sheet resistance ( Tens of Ω / □). That is, the total resistance value of the heating resistance element 11 is determined by the concentration of P ions and the area thereof, and is finally adjusted to about several tens to several hundreds Ω. A protective film 12 made of SiO ₂ , SiN or the like is formed on the heating resistor element 11 and the insulating film 8 described above.

The transistor element 3 has a field effect (E
It is an FT) type n-MOS and is formed on the silicon substrate 1 in the vicinity of the heat generating component 2. That is, the p-type region 13 doped with B ions is formed inside the silicon substrate 1 at this portion, and the p-type region 13 is formed.
Inside, a pair of n-type regions 14 doped with P ions,
14 is formed. Then, in the p-type region 13 located between the n-type regions 14, 14, SiO ₂
A gate electrode 16 is formed via a gate insulating film 15 made of. The gate electrode 16 serves as the heating resistance element 11
Similarly to, the polycrystalline silicon is doped with P ions to have a low resistance, and the surface thereof is covered with the insulating protective film 5 described above. In addition, a pair of n-type regions 14,
Drain and source wiring patterns 6 and 17 are formed at locations corresponding to 14 so as to be electrically connected to the n-type regions 14 and 14, respectively. In this case, the drain wiring pattern 6
Are extended to the heat generating structure 2 as described above. Then, the insulating film 8 and the protective film 1 described above are formed on the upper surfaces thereof.
2 are sequentially stacked.

Next, with reference to FIG. 2, description will be made on the case of manufacturing the heat generating component 2 of the thermal head as described above. In this case, the thermal head is obtained by dividing one silicon substrate (wafer) 1 into a large number of blocks, simultaneously forming the required elements in each block, and finally cutting each block. Therefore, in the following description, only one block of the silicon substrate 1 will be described.

First, a single crystal n-type silicon substrate 1 is prepared, and the transistor element 3 is previously formed on the silicon substrate 1.
Drive elements are formed. And the transistor element 3
When the drain and source wiring patterns 6 and 17 are formed on the insulating film 4 and the insulating protective film 5, the heat generating component 2 is formed. That is, a low resistance metal such as Cu, Ti and Mo and a metal having a large coefficient of thermal expansion such as Pb are sequentially deposited on the upper surface of the insulating protective film 5 formed on the silicon substrate 1 with the insulating film 4 by vapor deposition or sputtering. After being formed, the laminated metal layers are sequentially etched from the top to
As shown in (A), the supporting metal body 7 is patterned on the wiring pattern 6. Then, an insulating film 8 made of SiO ₂ , SiN or the like is formed on the wiring pattern 6 except the supporting metal body 7, and the insulating film 8 is half-etched to form the supporting metal body 7.
The concave groove 9 is formed from the inside of the region to the outside.

After that, as shown in FIG. 2B, a low resistance metal such as Cu, Ti and Mo is formed in the groove 9 of the insulating film 8 by vapor deposition or sputtering. As a result, the ground line 10 is formed in the groove 9. And the silicon substrate 1
Is heated to an appropriate temperature, the supporting metal body 7 is thermally expanded as shown in FIG. 2C, and the upper end of the supporting metal body 7 is projected above the insulating film 8. The amount of protrusion is such that the heating resistor element 11 described later can be separated from the ground line 10. The protrusion amount is set to be small if the rigidity of the heating resistor element 11 is high, and set to be large if the rigidity is low. The heating temperature is determined by the rigidity of the heat generating resistance element 11 and the coefficient of thermal expansion of the supporting metal body 7.

With the supporting metal body 7 expanded as described above, a photoresist 18 is deposited on the insulating film 8 and the ground line 10 excluding the supporting metal body 7 as shown in FIG. 2D. Then, the surface of the photoresist 18 is subjected to a CVD method using a monosilane (SiH ₄ ) gas as shown in FIG.
As shown in (E), a polycrystalline silicon layer 19 is formed,
After implanting P ions into the polycrystalline silicon layer 19 to adjust its resistance value, the polycrystalline silicon layer 19 is formed into a size having a predetermined resistance value by plasma etching. As a result, as shown in FIG.
A heating resistance element 11 is formed on the supporting metal body 7 in a state where the ground line 10 is covered with the heating resistance element 11 interposed therebetween.

After that, when the photoresist 18 is completely removed by etching, the heating resistance element 11 is supported by the supporting metal body 7 without contacting above the ground line 10 as shown in FIG. It Then, if the whole is lowered to room temperature in this state, the supporting metal body 7 contracts as shown in FIG. 1, and the heating resistance element 11 comes into close contact with the ground line 10 therebelow. In this state, the protective film 12 is deposited on the entire surface. As a result, a thermal head is formed.

Next, the case of using the thermal head having such a structure will be described. First, when a drive signal is applied to the gate electrode 16 of the transistor element 3 of the silicon substrate 1, a current flows from the source side to the drain side, and this current flows from the wiring pattern 6 of the heat generating structure 2 through the supporting metal body 7. It flows into the heating resistance element 11. Therefore, the heat generating resistance element 11 generates heat, and this heat causes thermal recording. In this case, the current flowing through the heating resistance element 11 is grounded by the ground line 10. As described above, when the current flows through the heating resistor element 11 of the heating component 2 and heat generation is repeated frequently, the temperature of the heating resistor element 11 gradually rises. Moreover, the heat of the heat generating resistance element 11 also causes the supporting metal body 7 to gradually expand and gradually push up the heat generating resistance element 11. When the temperature rises above a certain level, the heating resistor element 1
1 is pushed up by the supporting metal body 7 and the ground line 10
The power supply is cut off. Therefore, the heating resistor element 1
In No. 1, the temperature does not rise anymore, but on the contrary, the temperature drops, so
Along with this, the supporting metal body 7 contracts, the heating resistance element 11 again contacts the ground line 10 and becomes conductive, and becomes a state capable of conducting electricity. As a result, even if the heating resistor element 11 is used frequently, it does not reach a certain temperature or higher, so that it is possible to perform heat-sensitive recording with a uniform print density, and moreover, the time, timing, etc. for flowing a current through the heating resistor element 11 are set. Since it is not necessary to electrically control the heating resistor element 11 according to the frequency of use, electrical control of the heating resistor element 11 can be simplified.

[0014]

Second Embodiment Next, referring to FIG. 3, the second embodiment of the present invention will be described.
An example will be described. In this case, the same parts as those in the first embodiment described above are designated by the same reference numerals, and the description thereof will be omitted. The heat generating structure 20 of the second embodiment has a structure in which a supporting metal body 7 is provided at a position corresponding to the center of the lower surface of the heat generating resistance element 11, and ground lines 10 are provided on both sides of the lower surface of the heat generating resistance element 11. .. That is, the supporting metal body 7 is made of a metal such as Pb having the same large thermal expansion coefficient as that of the above-mentioned embodiment, and is formed on the wiring pattern 6 so as to be conductive in a columnar shape. This supporting metal body 7 is similar to that of the above-described embodiment in that it is at room temperature.
As shown in FIG. 3A, the upper surface thereof is flush with the upper surfaces of the insulating film 8 and the ground line 10 formed on the wiring pattern 6, and when heated by the heating resistance element 11 to reach a certain temperature or higher, FIG. As shown in (B), the upper surface thereof protrudes above the ground line 10 and pushes up the heating resistance element 11. Further, the ground line 10 is formed by recessing the insulating film 8 formed on the wiring pattern 6 by half-etching in the same manner as in the above-described embodiment to form grooves 9 and 9, and Cu and T are formed in the grooves 9 and 9.
It is formed by depositing a low resistance metal such as i and Mo by vapor deposition or sputtering. This ground line 1
Similarly to the above-described embodiment, 0 is not affected by the temperature change, does not protrude upward from the concave grooves 9 of the insulating film 8, and is formed so as to maintain the same surface as the upper surface of the insulating film 8. Has been done. The protective film 12 formed on the insulating film 8 so as to cover the heat generating resistance element 11 is adhered in a state where the supporting metal body 7 is thermally expanded, as shown by a solid line in FIG. There is a gap s between the heating resistor element 11. However, the protective film 12 is pushed into the gap s by the pressure applied to the thermal head during printing as shown by the dotted line, and comes into contact with the heating resistance element 11. Therefore, as in the first embodiment, the protective film 12 may be formed from the beginning as indicated by the dotted line.

Therefore, such a heat generating structure 20 has the same effect as that of the first embodiment, and particularly the supporting metal member 7
By forming the protective film 8 in the state of being thermally expanded,
If the space s is formed between the heating resistor element 11 and the supporting metal body 7 thermally expands during use, the heating resistor element 11 can be smoothly pushed up, and the heating resistor element 11 can be energized reliably and satisfactorily. Can be cut off.

[0016]

Third Embodiment Next, referring to FIG. 4, a third embodiment of the present invention will be described.
An example will be described. Also in this case, the same parts as those in the first embodiment described above are designated by the same reference numerals, and the description thereof will be omitted.
The heat generating component 30 of the third embodiment is similar to the heat generating resistor element 11 in FIG.
A supporting metal body 31 is formed at a position corresponding to the center of the lower surface of the wiring pattern, and a wiring pattern (live side conductor) 32 is formed on the right end side of the lower surface.
Is formed, and the ground line (ground side conductor) 33 is formed on the left end side.
Are formed. That is, the supporting metal body 31, the wiring pattern 32, and the ground line 33 are formed in parallel on the insulating film 4 on the silicon substrate 1. In other words, the supporting metal body 31 is provided between the wiring pattern 32 and the ground line 33, and the insulating film 8 is formed between them. Also in this case, the supporting metal body 31 is made of a metal such as Pb having a large coefficient of thermal expansion as in the first embodiment, and the upper surface thereof has the wiring pattern 32 and the ground line as shown in FIG. When it is formed by the heating resistor element 11 and has the same surface as the upper surface of 33, FIG.
As shown in FIG. 3, the upper surface of the heating resistor element 1 projects upward from the upper surfaces of the wiring pattern 32 and the ground line 33.
Push up 1. Further, the wiring pattern 32 and the ground line 33 are not affected by temperature changes, respectively, such as Cu, Ti, and Mo.
The wiring pattern 32 is also used as the drain wiring pattern 6 of the transistor element 3 shown in FIG. The protective film 12 is deposited in the state where the supporting metal body 31 is thermally expanded, as in the second embodiment described above.
As shown in FIG. 4 (A), a gap s is formed between the heating resistor element 11.

Even such a heat generating structure 30 has the same effects as the second embodiment described above.

The present invention is not limited to the above-mentioned embodiments, and various application modifications are possible. For example, the substrate on which the heat generating component is mounted does not have to be a silicon substrate, but may be an insulating substrate such as glass or quartz. Further, the heat generating components may be arranged in a matrix type in addition to the line type and the serial type. Further, the ground-side conductor may be composed of a diode.

[0019]

As described above in detail, according to the heat generation control structure of the heat generating element of the present invention, the heat generating element in contact with the live conductor and the ground conductor is made of a metal having a large coefficient of thermal expansion. Since the metal body is supported by the body and expands due to the heat generated by the heating element, the contact with the conductor is cut off when the heating element reaches a certain temperature or higher, so that the temperature rise of the heating element is limited. In addition, the electric control circuit of the heating element can be simplified.

[Brief description of drawings]

FIG. 1 is an enlarged cross-sectional view of a main part of a first embodiment when a heat generation control structure for a heat generating element according to the present invention is applied to a thermal head.

2A to 2G are cross-sectional views showing a manufacturing process of the heat generating component shown in FIG.

3A and 3B are enlarged cross-sectional views of a main part showing a second embodiment of the heat generating component.

FIG. 4A and FIG. 4B are enlarged cross-sectional views of essential parts showing a third embodiment of the heat generating component.

[Explanation of symbols]

 2, 20, 30 Heat generating component 6, 32 Wiring pattern (live side conductor) 7, 31 Supporting metal body 10, 33 Ground line (ground side conductor) 11 Heat resistance element

Claims (1)

[Claims] 1. A heat generating element in contact with a live conductor and a grounding conductor is supported by a metal body having a large coefficient of thermal expansion, and the heat generated by the heat generating element causes the metal body to expand, A heating control structure for a heating element, characterized in that the contact with the conductor is cut off when the heating element reaches a certain temperature or higher.