JPH03261566A - Manufacture of thermal head - Google Patents

Abstract

PURPOSE:To make large the maximum rate of resistance change of a heating resistor in order to attain the target value of its resistance by setting at not more than a specific second the width of trimming pulse generated at the time of trimming the heating resistor. CONSTITUTION:On the surface of an insulating substrate 2, a plurality of separate electrodes 4 are provided and a plurality of common electrodes 3 are also provided, each facing the end part of each of the separate electrodes, and heating resistor 5 are formed connecting the separate and common electrodes 4 and 3 together. In a case where the initial resistance value Ri of the heating resistor 5 is greater than a predetermined target resistance value R0, a trimming pulse is applied to trim the resistance value of the heating resistor 5 within a predetermined range of the target resistance value R0. At this time, if the width of the trimming pulse is set at not more than 200 nanoseconds, the maximum rate of resistance change of the heating resistor becomes large.

Description

DETAILED DESCRIPTION OF THE INVENTION A0 Object of the Invention 0 Industrial Application Field The present invention relates to a method of manufacturing a thermal head used in a thermal printer, facsimile, etc. as an output device of a word processor, a personal computer, etc.

2) Conventional technology Conventionally, the thermal head has low noise during printing.
In addition, it has the advantage of being easy to handle because it does not require a developing/fixing process, and is widely used.

In such a thermal head, a heating resistor is formed between a plurality of individual electrodes arranged in a row on an insulating substrate and a common electrode arranged corresponding to the tips of these electrodes. Then, power is supplied between the selected individual electrode and the common electrode to cause the heating resistor in that area to generate heat, thereby performing thermal recording (printing).

By the way, if the resistance values of the heating resistors disposed between the individual electrodes and the common electrode (that is, the heating resistors corresponding to each dot) are not uniform, there will be a difference in the temperature of the heating resistors when they generate heat. occurs. In this case, when printing is performed on thermal transfer paper or the like, density unevenness occurs in the printed "characters" or "figures".

In order to prevent the density unevenness from occurring, conventionally, the resistance values of the heating resistors corresponding to the respective dots are made uniform. This utilizes the property that when an electric field of a predetermined intensity is applied to the heating resistor within a range that does not cause resistance breakdown, the resistance value of the heating resistor decreases in accordance with the electric field strength.

As a conventional technique for making the resistance value of such a heating resistor uniform, for example, Japanese Patent Application Laid-open No. 83053/1983 is known.

What is described in this publication is a trimming pulse with a constant width and a different voltage value applied to each of a plurality of heat generating resistors whose tips are arranged to face each other and which individually connect a plurality of individual electrodes and a common electrode, or Different numbers of trimming pulses are applied with constant radiation and voltage values. The publication describes an example in which trimming pulses having a constant width and different voltage values are applied to a heating resistor.

The method described in the example of the publication measures the initial resistance value of the heat generating resistor corresponding to each dot on the insulating substrate, and if the initial resistance value is larger than the target resistance value RO, A trimming pulse of a predetermined voltage vO is applied to the resistor to reduce the resistance value of the heating resistor. If this decreased resistance value is still larger than the target resistance value RO, a voltage VO+ which is the predetermined voltage VO plus ΔV
A trimming pulse of ΔV is applied to further reduce the resistance value of the heating resistor. If this further reduced resistance value is still larger than the target resistance value RO, a trimming pulse of a voltage VO+2ΔV, which is the predetermined voltage VO plus 2ΔV, is applied to further reduce the resistance value of the heating resistor. In this way, the voltage is increased by ΔV until the resistance value of the heating resistor falls below the target resistance value RO.
A trimming pulse of 0+nΔV is applied.

The pulse width of the trimming pulse is 1 to several μs.
It is set to about ec.

3) Problems to be Solved by the Invention As mentioned above, in conventional trimming of the resistance value of a heating resistor, it was common to apply a voltage pulse of a predetermined magnitude to the heating resistor for 1 μsec or more. .

By the way, there are conventionally various shapes and resistance values of heating resistors of thermal heads.

For example, the alternating lead type electrode 03. shown in FIG. 15A.
The shape and resistance value of the heating resistor 05a corresponding to 1 bit (heating unit) of the band-shaped heating resistor 05 connecting between the electrodes 03.
The shapes and resistance values of the individual heat generating resistors 05 connecting between the heat generating resistors 04 and 04 are considerably different. The alternating lead type electrode 83
．． The spacing between the electrodes 04 is often about 30 μm, and the spacing between the opposing electrodes 03 and 04 is about 130 μm.

For example, a heating resistor 0 as shown in FIG. 15A
When the pulse width of the trimming pulse for trimming 5a is 1 μsec, a sufficiently large resistance change rate can be obtained with an electric field strength of about 5 × 10'V/m, as shown in the qualitative trend in Fig. 16. .

However, the electrode 0 as shown in FIG. 15B, 100
When trimming the heating resistor 05 with a large interval of 3.04 mm, when a trimming pulse with a pulse width of 1 μsec is used, the electric field strength is, for example, 2×10' The maximum resistance change rate can be obtained at about V/m. This maximum resistance change rate is -50%
This value does not reach . However, when trimming the heating resistor of a thermal head, it may be necessary to reduce the resistance value by at most 50% or more. Therefore, it is advantageous for the maximum resistance change rate during trimming of the heating resistor to be large.

The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to increase the maximum rate of change in resistance during trimming of a heating resistor of a thermal head.

B1 Structure of the Invention l) Means for Solving the Problems In order to solve the above problems, the thermal head trimming method of the present invention includes a method for trimming a plurality of individual electrodes and tips of the individual electrodes on the surface of an insulating substrate. After forming a common electrode arranged with A method for manufacturing a thermal head, comprising the step of trimming the resistance value of the heating resistor to a value within a predetermined range of the target resistance value by applying a trimming pulse when the resistance value is larger than the resistance value, the trimming pulse The pulse width of 200 nanoseconds (n5
ec) It is characterized by the following settings.

2) Effect The method for manufacturing the thermal head of the present invention described above is such that the pulse width of the trimming pulse when trimming the heating resistor is set to 20
Since it is set to 0 n5ec or less, the maximum resistance change rate of the heating resistor becomes large.

3) Example Next, one embodiment of the present invention will be described with reference to the drawings.

FIG. 1 is an overall explanatory diagram of a thermal head manufactured by an embodiment of the thick-film thermal head manufacturing method of the present invention, and FIG.
The figure is a perspective view of the main part, Fig. 3 is an enlarged view of the part shown by the arrow ■ in Fig. 2, Fig. 4A is a view taken from the IVA arrow in Fig. 3, and Fig. 4B is a line taken along the TVB-IVB line in Fig. 4A. FIG.

As shown in FIG. 1, a thermal head H for performing thermal recording on a thermal recording paper P conveyed along the outer periphery of a platen roll R is provided with a support plate l. An insulating substrate 2 is attached to the surface of the support plate l on the right side in FIG. It is composed of a heat storage layer 2b made of In Figure 3,
The surface of the heat storage layer 2b has a common electrode main body part 3a extending along the main scanning direction Common electrode 3 and the tip portion (hereinafter referred to as “common electrode tip portion”) 3 of the plurality of common electrode connecting portions 3b
A large number of individual electrodes 4 are formed, each having an individual electrode tip 4a facing away from bl by about 130 μm, and the base end (left end in FIG. It is formed as an IC connection terminal 4b for connection to a driving IC. And the picture electrode tip portions 3bl, 4
a are individually connected by heating resistors 5.

The heating resistor 5 shown in Figures 3.4A and 4B is formed to have a height of approximately 10 μm and a width of approximately 90 μm, and the surfaces of the picture electrodes 3, 4, the heating resistor 5, etc. are coated with a glaze. It is coated with a wear-resistant layer 6 made of

A printed wiring board 7 is attached to the surface of the support plate 1 on the left side in FIG. 1 with an adhesive, and external connection wiring 8 is formed on the surface of the printed wiring board 7. This external connection wiring 8 is connected to its input end side (the first
It is connected to a socket 10 as a drive signal input terminal via a lead wire 9 passing through the printed wiring board 7 on the left side in the figure. A driving IC is disposed in a portion of the printed wiring board 7 near the insulating substrate 2, and this driving IC connects the bonding wires 11 and 12.
It is connected to the IC connection terminal 4b of the individual electrode 4 and the external connection wiring 8 by.

The IC and bonding wires 11, 12 are covered with a protective resin 13, and the protective resin 13 is further protected with a cover 14 made of aluminum.

The thermal head H of this embodiment has the above-mentioned symbols 1 to 1.
It is composed of the component indicated by 14 and the driving IC.

Next, the heating resistor 5 which is the main part of the thermal head H
, a method of manufacturing the common electrode 3, individual electrodes 4, etc. will be explained.

First, as shown in FIGS. 5A and 5B, the insulating substrate 2 is manufactured by forming a heat storage layer 2b made of glaze on the surface of the substrate main body 2a made of ceramic. Next, as shown in FIGS. 8A and 8B, gold is added to the surface of the heat storage layer 2b. After forming an electrode forming layer consisting of the following materials, a common electrode 3 and individual electrodes 4 are formed by photolithography. Next, 7A, 7
As shown in Figure B, a large number of island-shaped resistors are formed by applying a photoresist to the surface of the insulating substrate 2 on which the electrodes 3 and 4 are formed, covering it with a mask (not shown), and then exposing and developing it. A resist layer having a body forming opening La is formed. At that time, the resistor formation opening La is
The picture electrode tip portions 3bl and 4a are arranged inside the image electrode.

Next, as shown in Figures 8A and 8B, a resistor-forming paste M is printed in a band shape along the rows of the resistor-forming openings La so that the paste M is higher than the surface of the resist layer. Each resistor forming opening La is filled. Next, as shown in Nos. 9A and 9BvIJ, after drying the resistor forming paste (M), it is lapped (ground) until it is flush with the resist layer and placed inside the resistor forming opening La. An unsintered resistor 5B is formed. Next, this unsintered resistor 5a is fired at a peak temperature of 800''C to 900'C for a peak hold time of 8 to 10 minutes.
As shown in l0ByIJ, a large number of heat generating resistors 5 are formed to connect the picture electrodes 3.4, and a heat storage JI2 is also formed.
The resist WL on the surface a is removed by combustion. In this firing step, the thickness of the heating resistor 5 is several orders of magnitude larger than that of the unsintered resistor 5a depending on the components of the resistor forming paste M.
Decreased by 0%.

Therefore, the thickness of the unsintered resistor 5a, that is, the thickness of the resist layer, is adjusted so that the height of the heating resistor 5 after firing is an appropriate value (for example, 10 μm).

The process from the process of forming the resist film shown in FIGS. 7A and 7B to the process of forming the heating resistor 5 shown in FIGS. 10A and JOB is a lift-off process, which is a type of thick film technology.

Next, the picture electrode 3.4 formed on the surface of the heat storage J12b
When the surfaces of the heating resistor 5 and the like are coated with a wear-resistant layer 6 made of glaze, an insulating substrate 2 in which the heating resistor 5 is covered with a wear-resistant layer 6 as shown in FIGS. 4A and 4B is obtained. It will be done.

The resistance value of the heating resistor 5 of the insulating substrate 2 is trimmed by a trimming device shown in the block diagram of FIG.

In FIG. 11, the blow μ21 includes a probe 21a+21a that contacts the IC connection terminal 4b of the individual electrode 4;
It is equipped with... A multiplexer relay 22 is connected to the blow μ21, and these blow μ21 and multiplexer relay 22 are controlled by a computer 23 to connect the heating resistor 5, 51... is configured to select one bit.

The multiplexer relay 22 is connected to the computer 2
It is configured to be selectively connected to the output terminal of the pulse generator 25 or the input terminal of the resistance measuring device 26 via the changeover switch 24 controlled by the pulse generator 3.

Next, the operation of the trimming device shown in the block diagram of FIG. 11 mentioned above will be explained with reference to the flowchart of FIG. 12.

When a process (flow) for trimming a plurality of heating resistors 5 formed on the surface of the insulating substrate 2 is started, in step s1, the probes 21a, 21 of the blow μ21 are trimmed.
a,... in contact with the individual electrodes 4, 4°...,
Initial resistance value R of the number of heating resistors 5 corresponding to the number of probes 21
Measure 1.

Next, in step S2, n=1 is set.

Next, in step S3, the bit (
Select heating resistor 5).

Next, in step S4, it is determined whether the resistance value is within a predetermined range of the target value. If no (N), the process moves to step s5.

In step S5, the voltage value of the trimming pulse to be applied to the heating resistor 5 is calculated. As a method for calculating this voltage value, for example, the method described in the above-mentioned Japanese Patent Laid-Open No. 61-83053 or Japanese Patent Laid-Open No. 1-271262 is adopted.

Next, in step S6, a trimming pulse is applied to the heating resistor 5.

Next, in step S7, the resistance value of the heating resistor 5 is measured, and then the process returns to step S4.

If YES in step S4, the process moves to step S8.

In step S8, n==n+1 is set.

Next, in step S9, it is determined whether n=no. However, no is the number of probes 21a of the probe 21 that contact the individual electrodes 4 plus 1; for example, if the number of probes 21a is 128, n0=129
It is. If the answer is NO in this step S9, the process returns to step S3, and if the answer is YES, the heating resistor 5 connected to all the probes (for example, 128 probes) 21a
Assuming that the trimming has been completed, the next step SI
Move to O.

In step SIO, it is determined whether all the bits (heating resistor 5) on the surface of the insulating substrate 2 have been trimmed. If the answer is NO in step S10, the process returns to step S1, and the probe 21a of the proper 21 is brought into contact with the individual electrode 4 connected to the heating resistor 5 which has not been trimmed yet. Measure the initial resistance value R1. If YES in this step SIO, the heating resistor 5 on the surface of the insulating substrate 2
Finish the trimming flow.

During this trimming, the initial resistance value Ri of the heating resistor 5 changes as shown in FIG. 13, for example.

In this FIG. 13, the initial resistance value R of each heating resistor 5
1 is indicated by a 0 mark, and their average value is indicated by Rh. Further, in FIG. 13, the target resistance value RO of the heating resistor 5 after trimming is 1000Ω, and the actual resistance value after trimming is indicated by a 0 mark.

The pulse width of the trimming pulse used in this trimming is 40 n5ec. This trimming pulse with a pulse width of 40 nsec provides a resistance change rate of -60 to -70% at an electric field strength of about 8 x 10'V/m, as shown by the solid line in Fig. 14, and the two-dot chain line in Fig. It can be seen that a larger rate of resistance change can be obtained compared to the trimming pulse with a pulse width of 1 μsec shown in FIG.

Although the embodiments of the thermal head according to the present invention have been described in detail above, the present invention is not limited to the above-described embodiments, and various modifications can be made without departing from the scope of the present invention described in the claims. Design changes are possible.

For example, for trimming various heating resistors commonly used in thermal heads, a pulse width of 200
If a trimming pulse of n5ec or less is used, a sufficiently large resistance change rate can be obtained. Furthermore, the present invention provides the heat generating resistor which connects between the electrodes having the shape shown in the embodiment described above, that is, between the electrodes having the shape shown in FIG. 15B.

The present invention can also be applied to various heating resistors such as those shown in Fig. 100 and the like.

C1 Effect of the Invention In the method for manufacturing a thermal head of the present invention described above, the pulse width of the trimming pulse when trimming the heating resistor is set to 20
Since it is set to 0 n5ec or less, the maximum resistance change rate of the heating resistor is larger than when using a conventional trimming pulse with a pulse width of about 1 μsec for a general heating resistor used in a thermal head. Become.

Therefore, the range in which the resistance values of the heating resistors can be adjusted is widened, so that even if there are large variations in the initial resistance values of the heating resistors, it is possible to align the resistance values to a predetermined target value.

[Brief explanation of drawings]

Fig. 1 is an overall explanatory diagram of a thermal head manufactured by an embodiment of the method for manufacturing a thermal head according to the present invention, Fig. 2 is a perspective view of the main parts thereof, and Fig. 3 is a section viewed from the arrow ■ in Fig. 2. , FIG. 4A is a view taken along the TVA arrow in FIG. 3, FIG. 4B is a sectional view taken along the line TVB-IVB in FIG. 4A, and FIGS.
Figure B is an explanatory diagram of the manufacturing method of the main parts of the same thermal head, and is a fifth A diagram. 6A, 7A, 8A, 9A, and IOA are partial plan views of the main parts of the thermal head corresponding to each manufacturing process, and 5B, 8B, 7B, 8B, and 9B, respectively. and Fig. 108 are the VB-VB line of Fig. 5A, the VIB-VIB line of Fig. 6A +7), and the B- of Fig. 7A, respectively.
■B line, ■B- in Figure 8A ■B line, IXB- in Figure 9A
A sectional view taken along line IXB and line XB-XB in FIG. 10A, FIG. 11 is an explanatory diagram of a trimming device used in manufacturing the thermal head, and FIG. 12 is an explanation of the operation of the trimming device shown in FIG. 11. Flowchart for
Figure 3 is an explanatory diagram of the change in resistance value of the heat generating resistor during trimming, and Figure 14 shows the resistance when the pulse width of the trimming pulse is 40 n5ec and 1 μsec when trimming the heat generating resistor of the above embodiment. An explanatory diagram of the rate of change, Figures 15A to 15C are explanatory diagrams of different arrangement examples of electrodes and heating resistors, respectively, and Figure 16 is a trimming pulse when trimming the heating resistor arranged between electrodes of an alternating lead type. FIG. 3 is an explanatory diagram of the resistance change rate when the pulse width of is 1μ5IIC. R1...Initial resistance value, RO...Target resistance value after trimming, 2...Insulating substrate, 3...Individual electrode, 4...Common electrode, 5...Heating resistor, Patent applicant

Claims (1)

[Claims] A plurality of individual electrodes (4) and a common electrode (3) arranged on the surface of the insulating substrate (2) corresponding to the tips of the individual electrodes.
and a heat generating resistor (5) connecting between the individual electrodes (4) and the common electrode (3), and then forming a heat generating resistor connecting between each of the individual electrodes (4) and the common electrode (3). The initial resistance value (Ri) of the body (5) is set to the predetermined target resistance value (R0
), the method includes the step of applying a trimming pulse to trim the resistance value of the heating resistor (5) to a value within a predetermined range of the target resistance value (R0). A method for manufacturing a thermal head, characterized in that the pulse width of the trimming pulse is set to 200 nanoseconds or less.