JP2627283B2 - Thermal head and method of manufacturing the same - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal head having a resistance display function and a method of manufacturing the same.

[Summary of the Invention]

The present invention has a heating resistor and an electrode for supplying power to the heating resistor, and in order to simplify the act of setting a voltage and a pulse width for appropriately driving the heating resistor,
In a thermal head having a resistance value display circuit for displaying a resistance value of the heating resistor, the resistance value display circuit is provided on a heating element forming substrate, and at least a resistance made of the same material as the heating resistor is set to the resistance value. Be a component of the display circuit. Further, in order to selectively cut off the circuit of the heating resistor in accordance with the resistance value in order to display the resistance value by a binary value or the like, the cut-off portion is a resistor in the circuit.
The cutting means is characterized by resistance burning due to Joule heat generated by laser irradiation or application of a voltage to a resistor in the circuit.

With the above structure and manufacturing method, the manufacturing complexity and labor are greatly simplified as compared with the resistance value display circuit having the conventional structure, and therefore, a low-cost and easy-to-use thermal head can be provided.

[Conventional technology]

In the thermal head, the resistance value of the heat generating resistor causes some variation between individuals in manufacturing.

On the other hand, the amount of heat generated by the heating resistor changes depending on the resistance value. Therefore, in order to keep the above-mentioned heat amount constant, that is, to keep print quality from varying, the voltage or pulse applied to the heating resistor according to the resistance value is changed. It is necessary to adjust the width of each thermal head one by one.

Conventionally, for the purpose of simplifying the above adjustment work,
As a method of displaying the average resistance value of the heating resistor of each thermal head as a binary value, as shown in FIG. 6, a bit switch 22 of several bits is provided on a printed circuit board 23 connected to a heating element forming board 21. There is an example in which the height of the average resistance value of the heating resistor is indicated by a code using the bit switch. As another conventional example, as shown in FIG. 7, wirings 43-1 and 43- for code identification provided on a flexible printed circuit 42 connected to a heating element forming substrate 41 are provided.
Disclosed is a method of displaying the average resistance value of the heating resistor in a code by cutting 2 at the line a or b, similarly to the example using the bit switch. (For example, JP-A-62-90264) [Problems to be Solved by the Invention] In the above-described conventional example, a resistance value display circuit for displaying the code of the resistance value of the heating resistor is provided outside the heating element forming substrate. Therefore, the codes cannot be displayed unless the manufacturing process of the thermal head is advanced until the codes can be displayed as shown in FIGS. 6 and 7. Generally, the measurement of the resistance value of the heating resistor of the thermal head is performed at least in the state of the heating element forming substrate, and a plurality of other steps are performed between the measurement of the resistance value and the step of displaying the code of the resistance value. Will exist. That is, if the result of the resistance value measurement is used for the code display, it is necessary to record the resistance value corresponding to the heating element forming substrate on a one-to-one basis. Even if the recording is performed, it is an extremely complicated operation to make the correspondence between the recording and the heating element forming substrate without error. Further, it is apparent that the automation of the setting work of the bit switch and the cutting of the flexible printed circuit is not easy.

[Means for solving the problem]

According to the present invention, there is provided a resistance display circuit for displaying the resistance value of a heating resistor on a heating element forming substrate, and using a resistor made of the same material as the heating resistor as a component of the resistance display circuit. The code display of the resistance value of the heating resistor is performed by the selective cutting of.

[Action]

In a general thermal head manufacturing process in which a plurality of thermal heads are formed on most wafers by providing the resistance value display circuit on the heating element forming substrate, the wafer is divided into individual thermal heads. Before the separation, the resistance value of the heating resistor can be displayed in code. That is, it is possible to perform the above-described code display operation subsequent to the generally performed measurement operation of the resistance value in the wafer state. Therefore, it is possible to easily and without error to record or store the measurement result of the resistance value of the heating resistor, which is conventionally complicated, and to correspond to each thermal head.

On the other hand, by providing a resistor made of the same material as the heating resistor as a component of the resistance display circuit provided on the heating element forming substrate, it becomes easy to cut a circuit for code display. That is, the heating resistor is generally made of a dark color material that easily absorbs light, and as a result, can be easily heated and cut by a light beam having a high energy density such as a laser beam. Also, by appropriately applying a voltage to both ends of the resistor, resistance burning due to Joule heat generated in the resistor, that is, cutting can be easily realized.

In addition, since the resistance value display circuit provided on the heating element forming substrate is composed of a resistive material and a conductor, which are all unacceptable elements of the Samar head, other special materials,
It is reasonable because no processing step is required.

〔Example〕

Hereinafter, some embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a plan view of a main part of a serial thermal head in which a heating resistor and an electrode have already been formed during a manufacturing process. Generally, a pattern of a thermal head illustrated on a larger-sized wafer, for example, a 100 mm × 200 mm wafer is shown. Are repeatedly formed. On the heating element forming substrate 1, the heating resistors 4-1 to 4-6 and the selection electrodes 3-1 to 3-6 connected to the heating resistors and the common electrode are formed by vapor deposition or sputtering of a resistance material. It is formed through a filming process by vapor deposition or sputtering of a conductor and a patterning process by photolithography or a manufacturing process using a screen printing method or the like.

Reference numerals 6-1 and 6-2 and 5-1 and 5-2 denote resistors and conductor paths that constitute the resistance value display circuit according to the present invention, and constitute a resistance value display circuit together with the common electrode 2. The two resistors 6-1 and 6-2 are connected in parallel to the common electrode 2, and conductor paths 5-1 and 5-1 are provided on the side facing the common electrode 2, respectively.
Connected to 5-2.

The material of the heating resistor is generally Ta if it is a thin film.
-N, a Ta-Si, Ta-SiO ₂ or the like, the thickness of the thin film 300Å
~ 4000Å. For a thick film, use 5 resistive materials such as Ru-O.
The heating resistor is formed with a thickness of about 30 μm.
Further, as a material for the common electrode and the selection electrode, generally, Au, Cu, Al having a thickness of 0.5 to 3 μm is used, and a Ni—Cr or Cr layer is provided below the metal layer as necessary. I have.

The resistors 6-1 and 6-2 and the conductor paths 5-1 and 5-2 which constitute the resistance display circuit together with the common electrode are made of the same material as the heating resistor and the same material as the electrode, respectively. The electrodes are formed simultaneously with the patterning or printing of the heating resistor and simultaneously with the patterning or printing of the electrodes. The above-described simultaneous formation is possible by providing a pattern of the resistor or the conductor path in advance on a photomask or a screen mask used for forming a pattern of the heating resistor or the electrode.

In FIG. 1A, the circuit including the heating resistors 4-1 to 4-6 and the resistance value display circuit are connected by the common electrode 2. However, as shown in FIG. The circuit may be formed separately. In this case, the resistance display circuit
A common conductor track 7 is formed.

In the above-described thermal head, the heating resistors 4-1 to 4-1
It is assumed that the product standard of the average resistance value of 4-6 is 90Ω or more and 110Ω or less. In order to reduce individual differences in the density of printing by the thermal head, in the printer, the energy consumed by the heating resistor is adjusted according to the average resistance value. Usually, the average resistance value of the thermal head is classified into ranks of about 3 to 4 within the product standard, and energy adjustment corresponding to the rank classification is performed in advance on the thermal head driving circuit side of the printer. In this embodiment, assuming that the average resistance value is classified into four ranks A to D as shown in a table (hereinafter, referred to as Table 1) shown on page 11 of the specification, the rank is determined by 2-bit coating. Can be expressed. In order to display the code of the rank, the resistors 6-1 and 6-2 may be selectively cut off in the resistance value display circuit according to the average resistance value of the heating resistor as shown in Table 1. For example, 103
In a thermal head having an average resistance of Ω, the second
What is necessary is just to make the resistance value display circuit as shown in the figure.

Next, an embodiment of the cutting means of the resistance value display circuit will be described.

FIG. 4 shows a wafer on which a plurality of thermal heads shown in FIG. 1 are formed.
-Vacuum adsorbed on Y table. Above the table, there is a laser oscillation source such as YAG, and it is possible to irradiate the laser on any part of the wafer by moving the table. Using such a laser irradiation apparatus, code display processing in the resistance display circuit is performed from the resistance value measurement in the procedure of the flowchart shown in FIG.
That is, in the wafer state, the resistance values of the individual heating resistors of each wafer-shaped thermal head are measured by a resistance measuring device having an auto-probing function. The arithmetic unit of the measuring device calculates the average resistance value of each of the thermal heads. Next, the wafer is moved to a laser irradiator, and the resistance constituting the resistance value display circuit of each thermal head is sequentially accessed from the wafer angle by the movement of the XY table holding the wafer, and the average resistance value is calculated. Based on the 01 code corresponding to the ranks A to D that were originally classified, laser irradiation and non-irradiation of the laser to the resistance unit are performed. The resistor irradiated with the laser is cut like a resistor 6-2 shown in FIG.

Ta-N, Ta-S used as a material of the heating resistor
i, since Ta-SiO _2, Ru-O, etc. reflectance of a material of a dark based color visible light wavelength region is at most about 10%, Au used as the electrode material, Al, reflectance such as Cu As compared with a material having a high melting point, the heating efficiency by laser irradiation is much higher, and even if there is a difference in the melting point of the material, evaporation or cutting is easy. For example, 10
When compared with a Ta-N thin film having a thickness of 00 mm and a Cu thin film having the same thickness, when a 0.8 KW power is output for 1 msec with a YAG laser having a beam diameter of 200 μm, the Ta-N thin film has almost a beam diameter. Showed 100% evaporation, but no trace was observed on the Cu thin film. If the resistance value display circuit is composed entirely of electrode materials, in addition to the above-mentioned difficult to evaporate, since the thickness as an electrode is about 0.5 to 3 μm even in a thin film, cutting is not possible unless a laser device with extremely high output is used. Seems difficult.

In cutting the resistor by the laser irradiation, it is desirable to reduce the shape of the resistor in order to perform the cutting reliably. If a small laser device is used, it is desirable that the laser beam diameter be reduced to about 200 μm or less, and more preferably about 100 μm. But,
When narrowing down the beam diameter here, narrowing down using a lens system should not be performed too much due to the depth of focus of the lens system. This is because the distance between the lens system and the surface of the wafer to be irradiated with the laser beam may vary due to the warpage of the wafer or the mechanical accuracy of the apparatus. By the way, if it is intended to reliably cut the resistor by a single laser irradiation, the laser beam must cross the resistor. If the beam diameter is φ100 μm, a resistor having a width smaller than that is required. Further, the relative position accuracy between the laser beam and the wafer is determined by the mechanical reproduction accuracy of the laser device, the repetitive imposition accuracy of the thermal head pattern in the wafer, and the positioning of the wafer on the laser device. Due to the positioning accuracy described above, a variation of about ± 30 μm should be considered in advance. That is, the resistance width is set to several tens μ
m. On the other hand, if the resistance width is to be finely processed to several μm or less, it is not preferable because chances of occurrence of defects such as open at the time of the processing increase. Therefore, the actual resistance width is several tens of μm, and the laser beam diameter should be set in consideration of the relative positional accuracy, and the beam diameter will be about φ100 μm or more.

Next, an embodiment of the second cutting means of the resistance value display circuit will be described.

In general, the resistance of the heating resistor is measured by applying probe pins to the terminals of the common electrode 2 and the selection electrodes 3-1 to 3-6 shown in FIG. 1, and applying a small current between the two electrodes. In such a resistance value measuring method, as shown in FIG. 3, the probes 12-1 to 12-12 required for the above-described resistance value measurement are used.
In addition to -6 and the common probe 13, probes 10-1 and 10-2 that are in contact with conductor paths of the resistance value display circuit are provided. On the probe side, a switch 11-1, which can turn on and off the current,
11-2 and a power supply 14 capable of applying a voltage to the resistors 6-1 and 6-2 by turning on the switch.

Turning on the switch 11-1 or 11-2 in the probing state shown in FIG.
At -2, Joule heat is generated. If the voltage of the power supply 14 is appropriately increased, the resistor is burned, that is, cut off by the Joule heat.

Using the above-described cutting principle, in one probing operation as shown in FIG. 3, measurement of the resistance value of the heating resistor, calculation of the average resistance value based on the measurement, rank classification of A to D, and 2-bit encoding of the rank, selective ON operation of switches 11-1 and 11-2 based on the code, that is, resistor 6
A series of operations such as selective cutting of -1, 6-2 can be continuously performed.

Resistances 6-1 and 6 by turning on the switches 11-1 and 11-2
There may be conditions under which the burnout of -2 can be reliably performed within a time of 10 msec or less, and even if the number of bits of the code display of the average resistance value of the heating resistor increases, the resistance cutting corresponding to each bit can be performed at the same time. Therefore, the work of measuring the resistance value itself is not complicated at all.

In order to burn out the resistor, the shape, size, resistance value, applied voltage, and voltage application time of the resistor may be appropriately determined. The resistors 6-1 and 6- as shown in FIG. In the shape of No. 2, when a voltage that gives a power of 200 W per 1 mm ^{2 in} the area of the resistor is applied for 5 msec, 100% sure resistance burnout can be realized. For example, if the resistor is formed of 1000 ° Ta-N and the resistor shape is 100 μm in length and 25 μm in width, the resistance value in the length direction of the resistor is about 100Ω. 7 in the length direction of the resistor
As a result of applying a voltage of V, a voltage of 3 msec or more resulted in a 100% disconnection state at the center of the resistor. Further, as shown in FIG. 5, in the shape obtained by adding a cut-out pattern such as 17, 18 to the resistors 16-1, 16-2, current concentration occurs at the constricted portions 17, 18 of the resistors. As a result, the disconnection state could be realized with a voltage application time that is half that of the above-described example.

In a thermal head using a resistive film having a high sheet resistance, a higher voltage is required to obtain the same power density. Resistance cutting at
Desirable for cutting circuit design.

As described above, if the method of cutting the resistance value display circuit using Joule heat is used, the code display of the average resistance value can be performed with almost no influence on the throughput in the measurement of the resistance value of the heating resistor. It can be easily realized by adding a circuit having a simple mechanism to the resistance measuring device.

Next, a description will be given of a method of increasing the cutting efficiency in common with the above-described resistance cutting method using laser irradiation and the above-described resistance cutting method using Joule heat.

The thermal head generally uses a glazed ceramics substrate in which a glaze layer, which is a thermally defective conductor, is formed with a thickness of about 50 μm on an alumina ceramics substrate having good thermal conductivity. In the serial type thermal head, the glaze layer is formed by the heating resistors 4-1 to 4--4 as shown in FIG.
Generally, a partial glaze provided in the lower layer of 6 and in the vicinity thereof is provided. In recent years, the partial glaze has been adopted in a line thermal head used in a thermal facsimile or the like. The substrate surface other than the portion where the partial glaze is provided has a ceramic ground, and the electrodes are formed directly on the ceramic ground.

When the resistors 6-1 and 6-2 constituting the resistance value display circuit are formed directly on the ceramic ground and when they are formed on the island-like glaze 31, two of the above-described resistance cutting are performed.
It was found that the cutting efficiency was different in both kinds of means, namely, cutting by laser irradiation and cutting by Joule heat.

In the case of resistance cutting by laser irradiation, there are many parts where the laser incident angle becomes small microscopically due to the influence of the porous surface of the ceramics ground, and although the reflection is irregular, the reflectance increases and the thermal energy for resistance evaporation The conversion efficiency to heat is reduced, and the energy converted to heat is also diffused to the ceramic substrate having good heat conduction. However, when the resistors 6-1 and 6-2 to be cut are formed on the island-shaped glaze 31 shown in FIG. 9, the laser beam can be incident almost perpendicularly to the resistors. Since the island-like glaze serves as a diffusion barrier for heat, the evaporation efficiency of the resistor irradiated with the laser increases with respect to the output energy of the laser light. By providing the island glaze,
It was confirmed that the cutting energy efficiency was improved by 30 to 50% as compared with the case where no provision was made.

On the other hand, in the case of resistance cutting by Joule heat, since the island glaze also serves as a diffusion barrier of Joule heat, an improvement in cutting energy efficiency of 30 to 50% has been confirmed as compared with the case where the island glaze is not provided. I have. In particular, when the resistance cutting is performed by generating the Joule heat for a longer time, the difference in the cutting energy efficiency becomes remarkable. This is due to the difference in the thermal diffusion time constant.

In addition, in addition, in both of the two types of cutting means described above, the resistance to be cut may be determined by cutting before the surface protective layer of the thermal head is coated, or by coating the surface protective layer. If cutting is to be performed after cutting, it is preferable that the surface of the resistor to be cut is not coated with the surface protective layer.

〔The invention's effect〕

As an example of a thermal head manufactured by the method described above, FIG. 10 shows a serial thermal head 32 to which a flexible printed circuit 33 is connected. The above connection can be made by the same method of soldering thermocompression bonding etc. as with a conventional thermal head without a code display, and the code information of the resistance value display circuit 34 can be flexibly printed without any special process. It can be extracted from the circuit.

FIG. 11 shows an example of a thermal head manufactured by applying the present invention to a line head, in which a resistance value display circuit 37 is provided in an empty space of a heating element forming substrate 35, and the thermal head is connected via a printed circuit board 36. The code information expressing the average resistance value is extracted. Also in the above thermal head, the code information of the resistance value display circuit 37 can be extracted only by the same assembling process as that of the conventional thermal head having no code display.

According to the manufacturing method of the present invention, the heating resistor is provided with a resistance value display circuit that approximately displays the resistance value of the heating resistor. The thermal head, which can easily adjust the applied energy, has almost the same processing steps and processing time as a thermal head that does not have a code display function, compared to a thermal head that has a conventional code display function. It can be manufactured with.

If the above easiness is specifically stated, 1. It is possible to perform processing for code display in the state of a wafer with multiple thermal heads. 2. Continuously perform the resistance measurement process and the processing process for code display. Can be provided simultaneously. 3. Code display processing is possible with a small laser irradiation device or a simple energizing circuit. 4. Creation of a resistance value display circuit must be performed at the same time as normal heating resistor and electrode formation. The above advantage is useful for eliminating the complexity of the steps and the error in the code display as seen conventionally. Therefore, it is possible to provide a thermal head capable of eliminating the operation of adjusting the applied energy of the thermal head at the same cost as a thermal head without a code display function.

[Brief description of the drawings]

1 (a), 1 (b) and 2 are plan views of essential parts of an example of a thermal head in the manufacturing method of the present invention, and FIGS.
5 is an explanatory view showing an embodiment relating to resistance cutting in the manufacturing method of the present invention, FIGS. 6 and 7 are perspective views showing a conventional thermal head, and FIG. 8 is resistance cutting in the manufacturing method of the present invention. Process flow chart illustrating an example of the process, ninth process
The figures are plan views of essential parts of an example of a thermal head in the manufacturing method of the present invention, and FIGS. 10 and 11 are plan views of an example of a completed thermal head manufactured by the method of the present invention. 1, 21, 32, 35 ... heating element forming substrate 4-1 to 4-6 ... heating resistor 5-1, 5-2 ... conductor path 6-1, 6-2, 16-1, 16- 2 ... resistance 7 ... common conductor path 10-1, 10-2, 13 ... probe 11-1, 11-2 ... switch 17, 18 ... constriction of resistance 31 ... glaze 34, 37 ... resistance Value display circuit

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-63-137860 (JP, A) JP-A-62-184865 (JP, A) JP-A-59-115871 (JP, A) JP-A-58-158 89386 (JP, A)

Claims (5)

(57) [Claims] 1. A thermal head comprising a resistance value display circuit for substantially displaying a rank of a resistance value of a heating resistor on a substrate on which a heating resistor and an electrode for supplying power to the heating resistor are formed. The resistance value display circuit includes a resistor formed of the same material as the heating resistor, and represents a rank of the resistance value of the heating resistor by selectively cutting and coding the resistor. A thermal head, characterized in that: 2. A thermal circuit having a resistance value display circuit on a substrate on which a heating resistor and an electrode for supplying power to the heating resistor are formed, the resistance value of the heating resistor being roughly displayed by a code. In the method for manufacturing a head, a step of forming a resistor in at least a part of the resistance value display circuit using the same material as the heating resistor; and, in accordance with a resistance value of the heating resistor, changing a resistance of the resistance display circuit. Selectively cutting, and a method for manufacturing a thermal head. 3. The method of manufacturing a thermal head according to claim 2, wherein in the step of selectively cutting the resistance of the resistance display circuit, the resistance is evaporated by condensing heating such as a laser to cut the resistance. . 4. The step of selectively cutting the resistance of the resistance display circuit, wherein the resistance is burned by Joule heat generated by applying a voltage to both ends of the resistance, and the resistance is cut. Item 3. A method for manufacturing a thermal head according to Item 2. 5. The thermal head according to claim 2, wherein the resistance of the resistance display circuit is formed on a glaze layer formed on the substrate. Production method.