JPH09207368A - Thermal head and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize a head, which can be used not as a defective head but as a normal head even when a heating resisting element, the resistive value of which does not reach the predetermined value, develops by a method wherein a corrective resistor is connected with the lead conductor parts of separate electrodes for correcting the calorific value of the heating resisting element. SOLUTION: Lead conductors 31 opposite to the connecting terminals 92 of a corrective resistor 91 are connected with respective bonding wires BW through window parts 93 to the terminals 92. The resistive value of the corrective resistor 91 is property selected and set in response to the resistive value of a heating resisting element to be connected so as to constitute to correct the calorific value of the heating resisting element having lower resistive value at energizing by connecting the corrective resistor 91. After the finish of a corrective resistor connecting process, a driving control circuit 5 is mounted on an insulating substrate 1 so as to connect each connecting terminal of the driving control circuit 5 to each connecting pad 32 of the separate electrode part 3 and a connecting pattern with a bonding wire BW.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a thermal head used in a recording device.

[0002]

2. Description of the Related Art FIG. 3 is a diagram showing a main structure of a thermal head of this type. In FIG. 3, 1 is an insulating substrate made of ceramic or the like, 2 is a heating resistor formed in the longitudinal direction of the insulating substrate 1, Reference numeral 3 is an individual electrode portion that is connected to each of the heating resistors 2, 4 is a common electrode portion that is connected to the heating resistor 2 between adjacent individual electrodes, and that is also connected to a power supply, and 5 is that the individual electrode 3 is selectively grounded Then, a drive control circuit portion for energizing and driving the heat generation resistance element formed by being divided by each individual electrode, 6 is a connection pattern portion connected to the control circuit of the recording apparatus and the ground, and 7 is a protective layer. .

The individual electrode portion 3 is connected to the heating resistor 2 and is connected to the lead conductor portion 31 formed so as to be drawn out in the vicinity of the drive control circuit portion 4 and the connection pad portion provided in the vicinity of the drive control circuit portion 4. Individual electrodes composed of 32 are arranged in the longitudinal direction of the insulating substrate 1 at a predetermined interval, and the connection pad portions 32 of the individual electrode portions are mounted on the insulating substrate 1 so as to face the individual pad portions 32. And is connected to the corresponding connection terminals of the drive control circuit IC5 by bonding wires BW. Further, the drive IC 5 is connected to the bonding wire BW on the connection pattern 6 formed on the insulating substrate 1, whereby the drive IC 5 is formed.
Will be connected to the control device and the ground of the recording device (not shown) via the connection pattern 6.

As a method of driving this thermal head,
A power source is connected to the common electrode 4, and a drive control signal is input to the connection pattern portion 6 to which the drive IC 5 is connected to control the drive IC 5, and the desired lead conductor 31 is grounded based on the recording data. A potential difference is generated between the grounded lead conductor 31 and the adjacent common electrode 4, and a current flows through the heating resistance element formed between them to generate heat.

As a method of manufacturing this thermal head,
First, the individual electrode pattern 3, the common electrode pattern 4 and the connection pattern 6 are formed by the printing method on the insulating substrate 1 made of ceramic or the like whose surface is smoothed, and the heating resistor 2 is formed by the printing method or the dispensing method. Form. Next, the heating resistor 2, the common electrode 4 and the individual electrode portion 3
The protective layer 7 is formed by overcoating the lead conductor portion 31 with a glass material. At this time, the protective layer 7 is not formed on the connection pad portion 32 of the individual electrode pattern 3 and is kept exposed.

When the heating resistor 2, the individual electrode pattern 3, the common electrode pattern 4, the connection pattern 6 and the protective layer 7 are formed on the insulating substrate 1, the heating resistor elements are electrically connected,
Resistance value measurement and resistance value adjustment are performed. That is, in this resistance value measuring step, a probe of the measuring device is brought into contact with the connection pad portion 32 of the individual electrode pattern 3 to cause a current to flow, and the lead conductor 31 adjacent to the lead conductor 31 carrying the current is connected. By detecting this current from the pad portion 32 for use, conduction and resistance value measurement of the heating resistance element formed by being partitioned by the lead conductors 31 are performed. As a result of this measurement, if there is an element whose resistance value exceeds the average resistance value of the heating resistor 2 by a predetermined value or more, the resistance value of the element is adjusted. In this resistance value adjusting step, a predetermined voltage is applied to the heating resistor 2 having a characteristic that its resistance value is reduced by applying a high voltage to change the resistance value (so-called trimming method), Adjust so that the resistance values of all heating resistor elements are uniform.

After the resistance value adjusting step is completed, the drive ICs 5 are mounted on the insulating substrate 1 and are connected to the corresponding connection pad portions 32 and the connection pattern portions 6 by the bonding wires BW.

Further, a sealing material 8 made of silicon or the like is applied and formed on the connection pattern portion 6 and the connection pad portion 32, which are connected to the drive control circuit portion 5 by the bonding wire BW, to form these connection portions. The cover prevents the occurrence of contact failure after connection.

Through the above steps, the substrate portion of the thermal head is completed, and thereafter, the insulating substrate 1 on the aluminum base as the base and the flexible substrate connected to the connection pattern portion 6 of the insulating substrate 1, A protective cover (head cover) for covering the connection pattern portion 6, the drive control circuit portion 5 and the connection pad portion 32 of the flexible substrate and the insulating substrate 1 is attached, and the thermal head is assembled.

[0010]

As described above, the heating resistor 2 made of a mixed material such as ruthenium oxide and glass has a characteristic that its resistance value is lowered by applying a high voltage, In the conventional thermal head, the resistance value was previously formed on the insulating substrate so that it was higher than the target value, and the resistance value was adjusted to the specified resistance value during the resistance adjustment process. Due to the influence of static electricity that occurs, a high voltage may be applied and the resistance value may be less than the default value.If such a resistance element appears, the resistance value cannot be adjusted and the head itself may be defective. There was a problem that it became.

The present invention has been made to solve these problems, and provides a thermal head that can be used without causing a defective head even when a heating resistance element that does not reach a predetermined resistance value is generated. The purpose is to

[0012]

In order to solve the above-mentioned problems, in a thermal head of the present invention, a heating resistor element is attached to a lead conductor portion of an individual electrode connected to a heating resistor element having a predetermined resistance value or less. It is configured by connecting a correction resistor for correcting the heat generation amount of.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION A thermal head and a manufacturing method thereof according to the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a structure of a thermal head of the present invention, and structures equivalent to or corresponding to the above-described conventional thermal head are indicated by the same symbols.

In the figure, reference numeral 9 denotes a correction resistor portion, which is a correction resistor 9 made of a chip resistor having a predetermined resistance value.
1, a connection terminal 92 provided on the correction resistor 91,
A window portion 93 provided on the protective layer 7 to expose the lead conductor portion 31 connected to the heating resistance element to be corrected.
The connection terminal 92 and the lead conductor 31
Are connected by a bonding wire BW.

Next, a method of manufacturing the thermal head of the present invention will be described. Also in the thermal head of the present invention, the individual electrode pattern 3, the common electrode pattern 4, the connection pattern 6 and the heat generating resistor 2 are formed on the insulating substrate 1 and then the heat generating resistor 2 as in the conventional one. , A protective layer is formed on the lead conductor portion 31 of the common electrode 4 and the individual electrode portion 3.

Next, the resistance value of the heating resistor element formed by dividing the heating resistor 2 by each individual electrode 3 is individually measured. In this resistance value measuring step, if there is an element having a resistance value that is more than a predetermined value away from the average resistance value of the heating resistor 2, the resistance value is adjusted. That is, with respect to the heating resistance element having a resistance value equal to or higher than the predetermined value, a predetermined voltage is applied to change the resistance value (a so-called trimming method), and the resistance value is adjusted to be uniform.

On the contrary, when there is a heating resistance element having a low resistance value less than the predetermined resistance value, the correction resistance portion 9 is connected to the lead conductor 31 connected to the heating resistance element. In this correction resistance connection step, first, the lead conductor 31 connected to the low resistance heating element is cut at a portion near the connection pad 32 by laser irradiation or the like (shown in FIG. 1B). Part A). Next, the protective layer 7 is removed at the two upper portions on both sides of the lead conductor 31 sandwiching the conductor cut portion A to form the window portions 93, and the lead conductor 31 is exposed. In this window portion forming step, the window portion 93 is formed by removing the protective layer 7 at a predetermined position by an etching step using hydrofluoric acid and a peeling step by laser irradiation.

Next, a correction resistor 91 composed of a chip resistor having a predetermined resistance value is mounted at an intermediate position between the two window portions 93 (upper part of the conductor cut portion A), and this correction resistor 91 is mounted.
The lead conductors 31 facing the connection terminals 92 are connected by the bonding wires BW through the window portions 93. The resistance value of the correction resistor 91 is appropriately selected and set according to the resistance value of the heating resistance element to be connected.
Is connected to correct the heat generation amount of the heat generation resistance element having a low resistance value during energization (heat generation drive).

After the correction resistance connection process is completed, the drive control circuit 5 is mounted on the insulating substrate 1, and the connection pad portions of the individual electrode portions 3 corresponding to the connection terminals of the drive control circuit 5 respectively. 32 and the connection pattern 6 are connected by a bonding wire BW.

After the connection of the drive control circuit 5 is completed, the connection pattern portion 6 and the connection pad portion 32, which are connected to the drive control circuit portion 5 by the bonding wires BW,
The correction resistor portion 9 provided on the protective layer 7 is sealed with the sealing material 8. That is, since the connecting portion and the correcting resistor portion 9 largely project on the insulating substrate 1, they are sealed by forming the sealing material 81 made of silicon or the like into a semicircular shape.

The substrate portion of the thermal head is completed by the above steps, and thereafter, like the conventional thermal head described above, the insulating substrate 1, the flexible substrate, the head cover, etc. are attached to the aluminum base to assemble the thermal head. I do.

FIG. 2 is a diagram showing a second embodiment of the present invention. The difference from the above-mentioned embodiment is that the protective layer 7 is provided with a heating resistor 2,
The first protection layer 71 formed on the common electrode 4 and the individual electrode 3 formed on the heating resistor 2 side, and the connection pad 32 side formed at a predetermined distance from the first protection layer 71 The point is that the second protective layer 72 is formed on the lead conductor 31.

In the thermal head of the second embodiment, a region for connecting the correction resistance portion 9 and the lead conductor 31 of the individual electrode portion 3 is provided in advance at the stage of forming the protective layer 7, and the resistance value is set. As a result of the measurement, if there is a heating resistance element having a low resistance value, the correction resistor 9 is provided on the second protective layer 72.
1 is mounted, and the connection between the correction resistor 91 and the connection terminal 92 is performed by exposing the lead conductor 31 and the second protective layer 72 from the region provided between the first protective layer 71 and the second protective layer 72. Lead conductor 31 in a region provided between connection pads 32
And the bonding wire BW. That is, in the second embodiment, the window 93
Since the region corresponding to is provided, the window forming step in the correction resistance connecting step is not necessary.

Further, in the second embodiment, the connection pattern portion 6 and the connection pad portion 32, which are connected to the drive control circuit portion 5 by the bonding wire BW, and the second protection layer 72 are provided. The correction resistor portion 9 and its connecting portion are sealed with the sealing material 8, and the region provided between the first protective layer 71 and the second protective layer 72 is also sealed. In the region between the first and second protective layers 71 and 72, a sealing tape made of an insulating material or a sealing material made of silicon similar to the above is formed in a flat shape and sealed.

In the above embodiment, an example in which the correction resistor of the present invention of the common electrode type thermal head is connected is shown, but the present invention is not limited to this, and for example,
It may be used for an alternating read type thermal head in which an individual electrode portion and a drive control circuit portion are provided on both sides of the heating resistor.

[0026]

As described above in detail, in the thermal head of the present invention, the amount of heat generated by the heat generating resistance element is corrected in the lead conductor portion of the individual electrode connected to the heat generating resistance element that does not reach the predetermined resistance value. Since it is configured by connecting a correction resistor for this, even if a heat generating resistance element having a resistance value equal to or less than a predetermined value occurs, it is possible to use it without a defective head. Play.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a configuration of a thermal head of the present invention.

FIG. 2 is a diagram showing a second embodiment of the present invention.

FIG. 3 is a diagram showing a configuration of a conventional thermal head.

[Explanation of symbols]

 1 Insulating Substrate 2 Heating Resistor 3 Individual Electrode Section 4 Common Electrode Section 5 Drive Control Circuit Section 6 Connection Pattern Section 7 Protective Layer 8 Encapsulation Material 9 Correction Resistor Section

Claims (2)

[Claims] 1. A heating resistor linearly formed on an insulating substrate, and a lead conductor portion formed so that one end is connected to the heating resistor and the other end is led out to the vicinity of the drive control circuit. , A separate heating element is formed by the individual electrodes adjacent to each other, and the heating resistance element is driven to generate heat by being selectively grounded by the drive control circuit. A thermal head, wherein a correction resistor is connected to a lead conductor portion of an individual electrode in order to correct the heat generation amount. 2. A step of forming, on an insulating substrate, a heating resistor and an individual electrode portion having a lead conductor portion, one end of which is connected to the heating resistor and the other end of which is brought out to the vicinity of the drive control circuit, and adjacent to each other. The step of measuring the resistance value of the unit heating resistance element formed by the matching individual electrodes, and the lead conductor of the individual electrode connected to the heating resistance element that does not reach the predetermined resistance value, corrects the heating value of the heating resistance element. And a step of connecting a correction resistor for the purpose of manufacturing the thermal head.