JPH068056B2 - Method of manufacturing thermal head - Google Patents

Description

The present invention relates to a method for manufacturing a thick film type thermal head, and more particularly to uniforming the resistance value of its heating resistor.

[Conventional technology]

In the thick film type thermal head, a heating resistor is formed by printing a paste-like resistance material in a predetermined pattern by a screen printing method or the like and then firing it. Therefore, the thick film type thermal head can be manufactured at a low cost by a relatively short manufacturing process, but has a drawback that the resistance value of the heating resistor varies greatly. Since the variation in the resistance value of the heating resistor directly affects the quality of printing etc., it is an extremely important factor to make the resistance value of the heating resistor uniform in the production of the thick film type thermal head. . To make the resistance values of the heating resistors uniform, there is a trimming process utilizing the phenomenon that the resistance value decreases when a relatively high voltage pulse is individually applied to each heating resistor after the heating resistors are formed. .

FIG. 4 is a flow chart showing a conventional method for manufacturing a thermal head disclosed in, for example, Japanese Patent Laid-Open No. 61-83053. In the figure, ST1 is the default step,
ST2 is a prober and switching step following step ST1, ST3 is a voltage pulse application step following step ST2, and ST4 is the step ST.
3 is a resistance value measurement step, ST5 is a step of comparing with previous data following step ST4, ST6 is a step of detecting a resistance value decrease following step ST5,
ST7 is a step for detecting the end of all the trimming dots following step ST6, ST8 is a probe step branched from step ST5, and ST9 is a step for voltage adjustment of the voltage pulse branched from step ST6. From the branch, step ST2
The processing is returned from step ST8 to step ST4, and from step ST9 to step ST3.

Next, the operation will be described. First, in step ST1, initial conditions such as an initial value of a voltage pulse applied to a heating resistor to be trimmed and a trimming target value are set. Next, in step ST2, the thermal head is probed, the dot to be trimmed is selected, and the heating resistor is connected to the voltage pulse generating means.
At T3, the voltage pulse having the initial value set in the step 1 is applied. Next, in step ST4, the resistance value of the heating resistor is measured, and in step ST5 it is discriminated whether or not the resistance value has decreased. If not, it is considered that the probe has a poor contact, and the probing is repeated in step ST8. After returning to step ST4, the resistance value is measured again. If the resistance value has decreased, it is compared with the trimming target value set in step ST1 in step ST6. If it is not smaller than the target value, the voltage value of the voltage pulse is increased by ΔV in step ST9. Step S
Returning to T3, the voltage pulse is reapplied. This process is repeated until the resistance value of the heating resistor becomes smaller than the target value, and when it becomes smaller than the target value, trimming of the dot heating resistor is finished and the process proceeds to step ST7.
In step ST7, it is identified whether or not the trimming of all the dots has been completed. If the trimming of all the dots has not been completed, the process returns to step ST2. Step ST
In step 2, a new dot is selected, the heating resistor is connected to the voltage pulse generating means, and the same process is repeated until the trimming of all dots is completed.

FIG. 5 is a diagram showing a decrease in the resistance value of the heating resistor, and the resistance value, which largely varies from R ₁ , R ₂ , and R ₃ before trimming, is slightly lower than the target value R ₀ . It is homogenized within a narrow range. In the figure, V _s is the initial value of the voltage pulse, and is set to, for example, 25 V because the boundary voltage at which the resistance value of the heating resistor begins to decrease due to the application of the voltage pulse is usually around 25 V. Further, ΔV is an increment of the voltage value of the voltage pulse by step ST9, and is set to, for example, 2.5 V so that the resistance value of the heating resistor does not decrease too much, and the resistance value is gradually decreased.

[Problems to be solved by the invention]

Since the conventional thermal head manufacturing method is configured as described above, it takes two steps to trim a one-dot heating resistor.
The voltage pulse must be applied 0 to 30 times and the resistance value must be measured, which requires a great deal of time to equalize the resistance value of the heating resistor.

The present invention has been made to solve the above problems, and an object thereof is to obtain a method for manufacturing a thermal head that does not require a large amount of time to equalize the resistance value of the heating resistor. To do.

[Means for solving problems]

The manufacturing method of the thermal head according to the present invention is such that some samples are selected from the thermal head dots and several voltage pulses having different voltage values are sequentially applied to the samples from the lower one, and the resistance of the heating resistor is changed each time. Measure the change to approximate the resistance drop curve, and when trimming each dot, first measure the resistance value of the heating resistor and apply it based on the resistance drop curve from the required resistance drop amount. The voltage value of the voltage pulse to be applied is determined.

[Action]

The manufacturing method of the thermal head in this invention approximates the resistance drop curve by measuring the sample dots in the thermal head, and uses this resistance drop curve during trimming to measure the heating resistor of the dot. The voltage value of the voltage pulse to be applied is determined from the resistance value, and the resistance value of the heating resistor is made close to the target value by applying the voltage pulse once.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. First
In the figure, ST11 is an initial setting step, ST12
Is a step of measuring the resistance change of the sample following the step ST11, ST13 is a step of approximating a resistance drop curve following the step ST12, ST14 is a step of measuring the resistance value following the step ST13, and ST15 is an application following the step ST14. Voltage determination step, ST
Reference numeral 16 is a step of applying a voltage pulse following the step ST15, ST17 is a step of detecting all dot end of trimming subsequent to the step ST16, and the processing is returned from the branch of the step ST17 to the step ST14.

FIG. 2 is a block diagram showing an example of an apparatus for carrying out the thermal head manufacturing method of the present invention.
Is a thermal head on which trimming processing is performed, 2 is a probing device for pressing a probe against the terminals of each heating resistor of the thermal head 1, and 3 is a probing device 2.
A relay network which is connected to and selects the heating resistor,
A switch 4 is connected to the relay network 3 and switches between application of a voltage pulse and measurement of a resistance value. Reference numeral 5 is a pulse generator connected to one of the switches 4 for sending a voltage pulse of a specified voltage value. An ohmmeter connected to the other side of the switch 4, an input / output unit 8, a central processing unit (hereinafter referred to as CPU) 9, a memory 10, a keyboard 11 and the like are provided to control the above-mentioned various devices and perform necessary calculations. A control calculation unit 12 for performing processing is a printer connected to the control calculation unit 7.

Next, the operation will be described. FIG. 3 is a diagram showing an example of the resistance drop curve. The solid line Y in the figure is the resistance drop curve, and the horizontal axis shows the applied voltage value by the voltage pulse.
The vertical axis shows the rate of change in resistance of the heating resistor due to the application of a voltage pulse. As a result of the experiment, when plotting the percentage change from the initial resistance value by plotting the resistance change rate on the vertical axis of FIG. 3, as shown by the broken line in FIG. 3, it is almost constant regardless of the initial resistance value. It was found that the curve Y can be approximated by the equation (1) by tracing the curve Y of

In the equation (1), R ₀ is the initial resistance value of the heating resistor,
V ₀ is the boundary value of the applied voltage at which the resistance value starts to change, ΔV is the step of changing the applied voltage, and α and β are constants determined by the thermal head structure, dot density, and the like.

In addition, as a result of another experiment, a voltage pulse of a predetermined voltage value is set to 1
It was also known that the resistance reduction rate when applied only once showed a value equivalent to that of the same voltage value when the voltage pulse was applied many times while temporarily increasing the voltage value as shown in FIG. The present invention is based on the results of these experiments.

In this embodiment, first, the initial setting is performed in step 11, and then the resistance change measurement of the sample is performed in step 12. That is, the relay network 3 is controlled to select the dot heating resistor designated as the sample of the thermal head 1, the switch 4 is switched and the resistance value is measured by connecting to the resistance meter 6, and the measured value is controlled. The data is sent to the calculation unit 7, and the CPU 9 of the control calculation unit 7 stores it in the memory 10. Next, the switch 4 is switched to apply a voltage pulse of a predetermined voltage value from the pulse generator 5 to the resistance heating element. Here, this voltage pulse is, for example, one pulse having a width of 2 μsec.
It is a pulse train that is continuous with five 50 μsec cycles. next,
Switching the switch 4 again, the heating resistor to which this voltage pulse is applied is connected to the resistance meter 6, and the resistance value is measured.
It is sent to the control calculation unit 7. The CPU 9 of the control calculation unit 7 stores it in the memory 10 together with the voltage value of the applied voltage pulse. Thereafter, similarly, these processes are repeated while appropriately increasing the voltage value of the voltage pulse. This process is repeated at least three times, switching the relay network 3 and executing for some samples.

Next, in step ST13, an approximation of the resistance drop curve based on the resistance change thus measured is performed. That is, the CPU 9 of the control calculation unit 7 obtains the resistance change rate ΔR = (R−R ₀ ) / R ₀ at each applied voltage by the voltage pulse from the resistance change stored in the memory 10,
This is substituted into the equation (1). As a result, an equation with α, β, and V ₀ as unknowns is created for each sample and solved. Here, when there are four or more equations for three unknowns, these are statistically processed to obtain a solution. The obtained solution is further statistically processed between each sample, and the obtained constants α and β and the boundary voltage value V ₀ are (1)
Substituting into the equation, the resistance value drop curve showing the relationship between the resistance change rate ΔR and the applied voltage V is approximated.

This completes the preparatory stage and starts the trimming process from step ST14. First, in step ST14,
A dot to be trimmed is selected by the relay network 3 and is connected to the ohmmeter 6 by a switch to measure its resistance value. Next, in step ST15, the CPU 9 calculates the resistance change rate ΔRn for decreasing the obtained resistance value to the target value, and further uses the resistance value decrease curve Y to determine the applied voltage Vn of the voltage pulse. decide. The situation is shown in FIG. 3. Specifically, the applied voltage Vn is obtained by substituting the ΔRn into the relational expression in which the α, β and V ₀ are substituted.
To calculate. The obtained applied voltage Vn is sent from the control calculation unit 7 to the pulse generator 5. When the switch 4 is switched at step ST16, a voltage pulse having a voltage Vn is sent from the pulse generator 5 and applied to the dot heating resistor for trimming. As a result, the resistance value of the heating resistor drops to a value close to the target value. Thereafter, steps ST14 and subsequent steps are repeated until step ST17 detects the end of trimming of all dots.

In the above embodiment, the resistance value drop curve is approximated by applying the voltage pulse at least three times to one sample, but the boundary value of the applied voltage at which the resistance value starts to change. If V ₀ is fixedly set to 25 V, the resistance value drop curve can be approximated by applying the voltage pulse twice.

Further, in the above-described embodiment, a pulse train in which a predetermined number of continuous pulses are used is used, but it may be a single pulse, and the same effect as that of the above-described embodiment is obtained.

〔The invention's effect〕

As described above, according to the present invention, the resistance drop curve is approximated by measuring the resistance change of a small sampling, and at the time of trimming, the resistance value of the heating resistor of the dot is measured to reduce the resistance drop. Since the voltage value of the voltage pulse is determined using a curve, trimming is completed by applying the voltage pulse once for each dot.
This has the effect of significantly reducing the time required to equalize the resistance values of the heating resistors. This effect is particularly remarkable when applied to a multi-dot thermal head having a heating resistor of 1000 dots or more, such as a thermal head for facsimile.

[Brief description of drawings]

FIG. 1 is a flow chart showing a method of manufacturing a thermal head according to an embodiment of the present invention, FIG. 2 is a block diagram showing an example of an apparatus for carrying out the method, and FIG. 3 is an example of a resistance drop curve thereof. FIG. 4 is a flow chart showing a conventional method for manufacturing a thermal head, and FIG. 5 is a diagram showing a decrease in the resistance value of the heating resistor. 1 is a thermal head, 2 is a probing device, 3 is a relay network, 4 is a switch, 5 is a pulse generator, 6 is an ohmmeter,
7 is a control calculation unit.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Yu Ozaki 8-1-1 Tsukaguchi Honcho, Amagasaki City, Hyogo Prefecture Sanryo Electric Co., Ltd. Communication Machinery Works (72) Inventor Yahei Takase 8-chome, Tsukaguchi Honcho, Amagasaki City, Hyogo Prefecture No. 1-1 Sanryo Electric Co., Ltd. Communication Equipment Factory (56) Reference JP-A-61-131404 (JP, A)

Claims (1)

[Claims] 1. A thermal head having a plurality of dots of heating resistors, wherein a voltage pulse is applied to each of the dots of the heating resistors, and the resistance value of the dots of the heating resistors is lowered to be uniform. In the method for manufacturing a head, a sample dot is selected from among the heating resistors of the dots, and voltage pulses having different voltage values are sequentially applied to the heating resistors of the dots selected as the sample dots, and applied. Approximate the resistance drop curve showing the relationship between the voltage and the resistance change, the voltage value of the voltage pulse applied to the heating resistor of each dot, based on the initial resistance value of the heating resistor of the dot A method of manufacturing a thermal head, which is characterized in that it is determined using a resistance drop curve.