JPS6359552A - Manufacture of thermal head - Google Patents

Abstract

PURPOSE:To uniformize the resistances of heat generating resistors without requiring much time, by determining a voltage value of a voltage pulse to be applied based on a resistance fall curve approximated by using trimming constants. CONSTITUTION:Voltage pulses are applied to selected samples of dots in a thermal head, in the order of increasing voltage, and the changes in the resistances of heat generating resistors are measured on each application of the voltage pulse to obtain trimming constants alpha, beta. A plot of beta on the ordinate against alpha on the abscissa conforms substantially to a fixed curve Z. When deviations of the constants alpha, beta are within the range of + or -5% of Z, a resistance fall curve Y representing the relationship between resistance change rate DELTAR and applied voltage V is approximated. The resistance of the dot for which trimming it to be carried out is measured. Then, the resistance change rate DELTARn for lowering the resistance to a target value is calculated, and a voltage value Vn of a voltage pulse to be applied is determined by using the curve Y, whereby the resistance of the relevant heat generating resistor is lowered to a value approximate to the target value.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method of manufacturing a thick film thermal head, and particularly to making the resistance value of a heating resistor thereof uniform.

[Conventional technology]

In the thick film type thermal head, a heat generating resistor is formed by printing a paste-like resistive material into a predetermined pattern by screen printing or the like, and then firing it. Therefore, although the thick film type thermal head can be manufactured at low cost through a relatively short manufacturing process, it has the disadvantage that the resistance value of the heating resistor varies widely. Variations in the resistance value of the heating resistor directly affect the quality of printing, so uniformity of the resistance value of the heating resistor is an extremely important factor in the manufacture of thick-film thermal heads. . To make the resistance values of the heating resistors uniform, there is a trimming process that utilizes the phenomenon that after the heating resistors are formed, when a relatively high voltage pulse is applied to each heating resistor individually, the resistance value decreases. .

FIG. 5 is a flowchart showing a conventional method of manufacturing a thermal head disclosed in, for example, Japanese Patent Application Laid-Open No. 61-83053. In the figure, STI is the initial setting step,
Sr1 is the prober and switching step following step ST1, Sr1 is the voltage pulse application step following step ST2, and Sr1 is the step ST
Sr1 is a step of comparing with the previous data following step ST4, Sr6 is a step of detecting a decrease in resistance value following step ST5,
Sr1 is a step for detecting the end of all trimming dots following step ST6, Sr1 is a step branching from step ST5 or a probe step, Sr1 is a step for voltage adjustment of a voltage pulse branching from step ST6, and step ST7 is From the branch of step ST
2, from step ST8 to step ST4, and from step ST9 to step ST3.

Next, the operation will be explained. First, in step ST1, initial conditions such as the initial value of the voltage pulse applied to the heating resistor to be trimmed and the target value for trimming are set.Next, in step ST2, the thermal head is probed and a dot to be trimmed is selected. Then connect the heating resistor to voltage pulse generating means, and step ST
In step 3, a voltage pulse having the initial value set in step 1 is applied.Next, in step ST4, the resistance value of the heating resistor is measured, and in step ST5, it is determined whether or not the resistance value has decreased. If not, it is assumed that the contact of the probe is poor and the probing is repeated in step ST8.
Return to step ST4 and measure the resistance value again. If the resistance value has decreased, proceed to step ST6 and measure the resistance value again.
Compare with the trimming target value set in I, and if it is not smaller than the target value, increase the voltage value of the voltage pulse by ΔV in step ST9, return to step ST3, and reapply the voltage pulse. This process is repeated until the resistance value of the heating resistor becomes smaller than the target value, and when the resistance value of the heating resistor becomes smaller than the target value, the trimming of the heating resistor of the dot is completed and the process moves to step ST7. In step ST7, it is determined whether or not all dots have been trimmed. If all dots have not been trimmed, the process returns to step ST2. In step ST2, a new dot is selected and its heating resistor is is connected to the voltage pulse generating means, and the same process is repeated until all dots are trimmed.

Figure 6 is a diagram showing the decrease in the resistance value of this heating resistor. Before trimming, the resistance value varied widely as R1, R, , R, but within a narrow range slightly lower than the target value R0. homogenized within. In the figure, v5 is the initial value of the voltage pulse, and is set to, for example, 25V because the boundary voltage at which the resistance value of the heating resistor begins to decrease upon application of the voltage pulse is usually around 25V. Also, ΔV
is the increment in the voltage value of the voltage pulse in 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.

[Problem that the invention seeks to solve]

Since the conventional thermal head manufacturing method is configured as described above, it takes two steps to trim one dot of the heating resistor.
Application of 0-30 voltage pulses.

There is a problem in that it takes a lot of time to make the resistance values of the heating resistors uniform.

This invention was made to solve the above-mentioned problems, and its purpose is to provide 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. do.

[Means for solving problems] A method for manufacturing a thermal head according to the present invention.

Select several samples from among the dots of the thermal head, apply several voltage pulses with different voltage values to them in order from low to high, measure the resistance change of the heating resistor each time, and approximate the resistance drop curve. Find trimming constants α, β for When trimming each dot by approximating the value drop curve, first determine the resistance value of the heating resistor by 8u, and then calculate the voltage of the voltage pulse to be applied based on the required resistance value drop amount based on the resistance value drop curve. It determines the value.

[Effect]

The method of manufacturing a thermal head according to the present invention approximates a resistance drop curve by measuring sample dots in the thermal head, and in the approximation, tests trimming constants α and β to determine the approximated resistance drop. Make sure that the curve does not deviate greatly from the true curve, use this resistance value drop curve during trimming, and determine the voltage value of the voltage pulse to be applied from the measured resistance value of the heating resistor of that dot. The resistance value of the heating resistor is made close to the target value by applying the voltage pulse twice.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. 1st
In the figure, 5TII is the initial setting step, 5T12
5T13 is the step of calculating the trimming constants α and β following step 5T12, 5T14 is the step of detecting the trimming constants α and β following step 5T13, and 5T15 is the step of measuring the resistance change of the sample following step STI 1. The step 5T16 of approximating the resistance value drop curve following step 5T14 is the step 5T16 of approximating the resistance value drop curve following step 5T14.
Step 5T17 of measuring the resistance value following T15 is a step of determining the applied voltage following step 5T16.
8 is a step of applying a voltage pulse following step STI 7, 5T19 is a step of detecting the end of all trimming dots following step 5T18, 5T20 is a step of selecting another sample branched from step 5T14, and step 5T19 is a step of selecting another sample branched from step 5T14. From the branch, go to step 5T16, and from step 5T20 to step 5T12
The processing is returned to each.

FIG. 2 is a block diagram showing an example of an apparatus for carrying out the method of manufacturing a thermal head of the present invention, and in the figure, 1
2 is a thermal head where trimming processing is performed; 2 is a blowing device that presses a probe against the terminal of each heating resistor of this thermal head 1; 3 is a blowing device 2
a relay network connected to select the heating resistor;
4 is a switch that is connected to the relay network 3 and switches between applying a voltage pulse and measuring a resistance value; 5 is a pulse generator that is connected to one side of the switch 4 and sends out a voltage pulse of a specified voltage value; and 6 is a A resistance meter 7 connected to the other side of the switch 4 includes an input/output section 8, a central processing unit (hereinafter referred to as CPU) 9, a memory 10, a keyboard 11, etc., and controls the various devices mentioned above and performs necessary calculations. A control calculation unit 12 that performs processing is a printer connected to this control calculation unit 7.

Next, the operation will be explained. FIG. 3 is a diagram showing an example of the resistance value drop curve, and the solid line Y in the figure is the resistance value drop curve, and the horizontal axis shows the applied voltage value due to the voltage pulse.
On the vertical axis, the rate of change in resistance of the heating resistor due to voltage pulse application is scaled.

As a result of the experiment, the vertical axis in Figure 6 represents the rate of change in resistance.

When plotting the percentage drop from the initial resistance value, it follows a nearly constant curve Y regardless of the initial resistance value, as shown by the broken line in Figure 3, and the curve Y is approximated by equation (1). I found out that it can be done.

Ro ΔV In formula (1), Ro is the initial resistance value of the heating resistor,
vo is the boundary value of the applied voltage at which a change in resistance value begins to appear, ΔV is the change step of the applied voltage, and α and β are trimming constants determined by the structure of the thermal head, dot density, etc.

Furthermore, as shown in Figure 4, the relationship between the trimming constants α and β is plotted with α on the horizontal axis and β on the vertical axis. teeth(
It was found that it is a hyperbola that can be approximated by equation 2).

β=Ω・α... (2)
Note that in equation (2), Ω2m is a constant that takes a constant value regardless of the dot density.

Furthermore, as a result of another experiment, the resistance reduction rate when a voltage pulse of a predetermined voltage value is applied only once is the same as that when a voltage pulse is applied many times while increasing the voltage value as shown in Figure 3. It was also found that the value was equivalent to that of the same voltage value.

This invention is based on these experimental results.

In this embodiment, first, initial settings are performed in step 11, and then, in step 12, resistance change measurement of the sample is performed. That is, the relay network 3 is controlled to select the dot heating resistor designated as a sample of the thermal head 1, the switch 4 is switched to connect it to the resistance meter 6, the resistance value is measured, and the measured value is controlled. The CPU 9 of the control calculation unit 7 stores the voltage in the memory 10.The CPU 9 of the control calculation unit 7 then switches the switch 4 to apply a voltage pulse of a predetermined voltage value to the resistance heating element from the pulse generator 5. Here, this voltage pulse is, for example, a pulse with a width of 2 μsec.
Switch 4 is switched again after the 0th pulse, which is a series of five consecutive pulses with a period of 50 μsec.

The heating resistor to which this voltage pulse has been applied is connected to a resistance meter 6 to measure the resistance value and send it to the control calculation section 7. The CPU 9 of the control calculation section 7 stores it in the memory 10 together with the voltage value of the applied voltage pulse.

Thereafter, these processes are repeated in the same manner while appropriately increasing the voltage value of the voltage pulse. This process is repeated at least three times, and is executed for several samples by switching the relay network 3.

Next, in step 5T13, trimming constants α and β for approximating the resistance value drop curve are calculated based on the resistance change thus measured. That is, the CPU 9 of the control calculation unit 7 determines the rate of resistance change ΔR=(R-R,)/Re at each applied voltage due to the voltage pulse from the resistance change stored in the memory 10, and calculates this by the above (1). Substitute into the expression. This creates and solves equations with α, β, and v0 as unknowns for each sample. If there are four or more equations for three unknowns, they are statistically processed. and get the solution. The obtained solution is further statistically processed between each sample, and
The desired trimming constant α along with the applied voltage boundary value v0
, β are obtained.

In the trimming constants α and β obtained in this way, a deviation from the relationship expressed by equation (2) is then detected in step 5T14. That is, as shown by point A in Figure 4, if the deviation is outside a certain range, for example, the ±5% area hatched in the same figure, it is regarded as an erroneous measurement, and step 5 is performed.
If you want to re-measure the resistance change using T12, in that case,
Dots to which no voltage pulses have been previously applied are selected as new samples by step 5T20. As shown by point B in FIG. 4, if the deviation is within a certain range, the trimming constant α.

β is substituted into equation (1) together with the applied voltage boundary value v0 in step STI 5, and a resistance value drop curve showing the relationship between the resistance change rate ΔR and the applied voltage V is approximated.

This completes the preparation stage and starts the trimming process from step 5T16. First, in step 5T16,
A dot to be trimmed is selected by the relay network 3, and connected to the resistance meter 6 by a switch to measure its resistance value. Next, in step 5T17, the CPU 9 calculates the resistance change rate ΔRn for lowering the obtained resistance value to the target value, and further determines the applied voltage Vn of the voltage pulse using the aforementioned resistance value drop curve Y. .

The situation is shown in FIG. 3, specifically the above-mentioned α.

The applied voltage Vn is calculated by substituting the ΔRn into the relational expression in which βt Va is substituted. The obtained applied voltage Vn is sent from the control calculation section 7 to the pulse generator 5. Step 5T
When the switch 4 is switched at 18, the pulse generator 5
A voltage pulse with a voltage of Vn is sent out from , and is applied to the heating resistor of the dot to be trimmed. As a result, the resistance value of the heating resistor falls to a value close to the target value.

Thereafter, the processing from step 5T16 onward is repeated until step 5T19 detects that all dots have been trimmed.

In addition, in the above embodiment, for one sample.

We have shown that the resistance value drop curve is approximated by applying voltage pulses at least three times, but if we fix the applied voltage boundary value v0 at which the resistance value begins to change at 25V to approximate the resistance value drop curve, we can apply voltage pulses at least three times. It is also possible to approximate the resistance value drop curve by applying a voltage pulse of .

Further, in the above embodiment, a predetermined number of continuous pulse trains are used as the voltage pulses, but a single pulse may be used.

The same effects as in the above embodiment are achieved.

〔Effect of the invention〕

As described above, according to the present invention, a resistance drop curve is approximated by measuring the resistance change of a small number of samples, and when trimming, the resistance value of the heating resistor of the dot is measured, and the resistance value drop is calculated by measuring the resistance value of the heating resistor of the dot. Since the voltage value of the voltage pulse is determined using a curve, trimming is completed by applying one voltage pulse to each dot, which greatly reduces the time required to equalize the resistance value of one heating resistor. Furthermore, since the trimming constants α and β are detected when approximating the resistance value drop curve, the approximated curve will not deviate greatly from the true resistance value drop curve, and the resistance value will be reduced to It is possible to obtain a method for manufacturing a thermal head that does not cause excessive trimming or destruction of the heating resistor due to an error in approximating the value drop curve, and does not cause insufficient trimming or non-trimming.

[Brief explanation of the drawing]

FIG. 1 is a flowchart showing a method for 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 value drop curve. 4 is a diagram showing the relationship between the trimming constants α and β, FIG. 5 is a flowchart showing the conventional method for manufacturing a thermal head, and FIG. 6 is a diagram showing the resistance value of the heating resistor. It is a line diagram showing a decrease. 1 is a thermal head, 2 is a probing device, 3 is a relay network, 4 is a switch, and 5 is a pulse generator. 6 is a resistance meter, and 7 is a control calculation section. Figure 1 Figure 2 Figure 4 Figure 5 Figure 6

Claims (1)

[Claims] In a method for manufacturing a thermal head in which a voltage pulse is applied to each of the heating resistors of a thermal head equipped with a plurality of heating resistors to lower and equalize the resistance value, a sample is selected from among the heating resistors. , a trimming constant α for approximating a resistance value drop curve showing the relationship between applied voltage and resistance change by sequentially applying voltage pulses with different voltage values to the heating resistor selected as the sample, starting from the lowest voltage pulse; β is determined, and assuming that the trimming constants α and β have a relationship expressed by a predetermined relational expression, the deviation between the obtained trimming constants α and β and the above relational expression is tested, and if the deviation is constant. If it is within the range, the resistance value drop curve is approximated based on the trimming constants α and β, and the voltage value of the voltage pulse applied to each heating resistor is adjusted to the initial resistance value of the heating resistor. A method for manufacturing a thermal head, characterized in that the determination is made using the resistance value drop curve based on the resistance value drop curve.