JPH06413B2 - Thermal head resistance adjustment device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a resistance adjusting device for a thick film type thermal head, and more particularly to uniforming the resistance of a heating resistor.

[Conventional technology]

The thick film type thermal head forms a heating resistor 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 or the like, it is an extremely important factor to make the resistance value of the heating resistor uniform in the manufacture 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. 5 is a flow chart showing a conventional method of manufacturing a thermal head disclosed in, for example, Japanese Patent Laid-Open No. 61-83053. In the figure, ST1 is an initial setting step,
ST2 is a step of prober and switching following the step ST1, ST3 is a step of applying a voltage pulse following the stap ST2, and ST4 is the step ST.
3 is a resistance value measuring step, ST5 is a step of comparing with previous data following step ST4, ST6 is a step of detecting a resistance value decreasing following step ST5,
ST7 is a step of detecting a dot end before trimming following step ST6, ST8 is a step of reprobing branched from step ST5, ST9 is a step of voltage adjustment of the voltage pulse branched from step ST6, and step ST7 Step ST from branch
The processing is returned to step 2, 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 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 probing is performed again in step ST8. Returning to step ST4, the resistance value is measured again. If the resistance value has decreased, it is compared with the target value for trimming 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 ST
Returning to step 3, 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 heating resistor of the dot is completed and the process proceeds to step ST7. In step ST7, it is identified whether or not trimming of all dots has been completed. If trimming of all dots has not been completed, the process returns to step ST2. Step ST2
Then, a new dot is selected, the heating resistor is connected to the voltage pulse generating means, and the same processing is repeated until the trimming of all dots is completed.

FIG. 6 is a diagram showing a decrease in the resistance value of the heating resistor. The resistance value which was largely varied with R ₁ , R ₂ and R ₃ before trimming was 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. Also, ΔV
Is an increase 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.

[Problems to be solved by the invention]

Since the conventional method of manufacturing a thermal head is configured as described above, it is necessary to apply a voltage pulse 20 to 30 times and measure the resistance value in order to trim a heating resistor of one dot. There is a problem that it takes a lot of time to make the resistance value of the heating resistor uniform.

The present invention has been made to solve the above problems, and an object of the present invention is to obtain a resistance adjusting device for a thermal head that does not require a great deal of time to make the resistances of the heating resistors uniform. To aim.

[Means for solving problems]

A resistance adjusting device for a thermal head according to the present invention selects several samples from the dots of the thermal head and sequentially applies several voltage pulses having different voltage values to the heating resistors from the lowest one. The resistance change is measured, the resistance value starts to appear, and the representative value is fixedly given to the boundary value of the applied voltage to create a resistance vs. applied voltage table.
First, the resistance value of the heating resistor is measured, and the voltage value of the voltage pulse to be applied is determined using the resistance vs. applied voltage table from the required amount of drop in the resistance value.

[Action]

The resistance adjusting device of the thermal head in this invention is
Measure the sample dots in the thermal head,
A typical value is fixedly given in advance to the boundary value of the applied voltage at which the resistance value begins to change, and a resistance-to-applied voltage table is created to shorten the creation time. Using the voltage table,
The voltage value of the voltage pulse to be applied is determined from the measured resistance value of the heating resistor of the dot, and the resistance value of the heating resistor is made close to the target value by one application of the voltage pulse.

〔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 step ST11, ST13 is a step of creating a resistance vs. applied voltage table following step ST12, ST14 is a step of measuring resistance value following step ST13, and ST1.
5 is a step of determining an applied voltage following step ST14, ST16 is a step of applying a voltage pulse following step ST15, and ST17 is a step of detecting the end of all dots of trimming following step ST16. From the branch of step ST17. Returns to step ST14.

FIG. 2 is a block diagram showing an example of an apparatus for carrying out the method for manufacturing a thermal head according to the present invention.
Is a thermal head on which a trimming process 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, and the relay network 4 and the switch 4 constitute a switch circuit. 5 is a pulse generator which is connected to one of the switches 4 and sends out a voltage pulse of a designated voltage value, 6 is an ohmmeter connected to the other of the switches 4, 7 is an input / output unit 8, a central processing unit (hereinafter , A CPU) 9, a memory 10, a keyboard 11 and the like, and a printer 12 connected to the control operation unit 7, and a control operation unit 12 for controlling the above-mentioned various devices and performing necessary operation processing.

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 resistance change rate of the heating resistor due to the voltage pulse application. As a result of the experiment, when the vertical axis of FIG. 6 is taken as the resistance change rate and the% drop from the initial resistance value is plotted, 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).

In the formula (1), R ₀ is the initial resistance value of the heating resistor,
V ₀ is a boundary value of the applied voltage at which the resistance value starts to change, ΔV is a change step of the applied voltage, and α and β are constants determined by the structure of the thermal head, the 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
The resistance decrease rate when applied only once shows a value equivalent to that of the same voltage value when the voltage pulse is applied many times even if the voltage value is temporarily increased as shown in FIG. Boundary voltage value V _{0 of} applied voltage at which change in value begins to appear
Is different for each thermal head,
It was also found that the value was concentrated around 25V and there was no large variation. The present invention is based on the results of these experiments.

In this embodiment, first, initial setting is 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 heating resistor of the designated dot as the sample of the thermal head 1, the switch 4 is switched to connect to the resistance meter 6, the resistance value is measured, 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,
Switch the switch 4 again, connect the heating resistor to which this voltage pulse is applied to the resistance meter 6, and measure the resistance value.
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, the resistance drop curve is first approximated based on the resistance change thus measured. That is, the CPU 9 of the control calculation unit 7 uses the resistance change stored in the memory 10 to calculate the resistance change rate ΔR = (R−R ₀ ) / R at each applied voltage due to the voltage pulse.
₀ is obtained and this is substituted into the above equation (1). At this time,
As the boundary voltage V _{0 at} which the resistance value starts to change, a typical value thereof, for example, 25 V is fixedly provided. This creates an equation with unknowns α and β for each sample and solves it. Here, when there are three or more equations for two unknowns, they are processed by statistical means to obtain a solution. This equation gives a solution in a much shorter time than the one in which three of α, β, and V ₀ are unknowns, and the solution is also large because the boundary voltage value V ₀ is concentrated near 25 V. There is no error. The obtained solution was further statistically processed between each sample, and the obtained constants α and β were substituted into the equation (1), and the origin moved to the position shown by the chain double-dashed line in FIG. The value drop curve is approximated to obtain an equation showing the relationship between the resistance change rate ΔR and the applied voltage V. Next, the specific value ΔRn of the resistance change rate is sequentially inserted into the obtained formula, the value of the applied voltage Vn at that time is calculated, and the two are arranged in association with each other to create a resistance vs. applied voltage table. . FIG. 4 is an explanatory diagram showing an example of the resistance vs. applied voltage table.

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 this 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 lowering the obtained resistance value to the target value, and further, from the resistance vs. applied voltage table, the resistance change rate close to the calculated resistance change rate. Δ
The applied voltage Vn corresponding to Rn is read and the applied voltage of the voltage pulse is determined. Specifically, the resistance vs. applied voltage table is read by, for example, a binary search method (intermediate comparison method) or the like, and the applied voltage is determined by proportional distribution or the like for an intermediate value of the resistance change rate ΔRn in the table. To do. Further, the read applied voltage Vn may be used as it is.

The obtained applied voltage is sent from the control calculation unit 7 to the pulse generator 5. When the switch 4 is switched in step ST16, a voltage pulse whose voltage is adjusted to the applied voltage is sent from the pulse generator 5 and applied to the heating resistor of the dot to be trimmed. As a result, the resistance value of the heating resistor drops to a value close to the target value. Thereafter, the processes after step ST14 are repeated until step ST17 detects the end of trimming of all dots.

Further, in the above-mentioned embodiment, the pulse train in which the predetermined number is continuous is used for the voltage pulse, but a single pulse may be used, and the same effect as that in the above-mentioned embodiment is obtained.

〔The invention's effect〕

As described above, according to the present invention, a plurality of samples are selected from the heating resistors, voltage pulses having different voltage values are sequentially applied to the sample from the lowest, and the data of the resistance change rate at each applied voltage is converted into a plurality of data. While detecting the sample, the resistance drop curve is calculated by statistically processing the multiple data, and the specific resistance change rate is sequentially penetrated into the resistance drop curve to calculate the value of the applied voltage and the applied voltage. A resistance vs. applied voltage table showing the relationship of the resistance change rate is created, and the voltage value of the voltage pulse applied to the heating resistor is calculated based on the initial resistance value of the heating resistor. Since it is configured to be used for determination, the resistance vs. applied voltage table can be created in a short time, and the trimming is completed by applying the voltage pulse once for each dot. Further determination of the voltage value of the voltage pulse is also troublesome calculations can be performed in a short time because it is not necessary to the, there is an effect that can greatly reduce the time required for homogenization of the resistance value of the heating resistor. 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 a 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. FIG. 4 is an explanatory diagram showing an example of the resistance vs. applied voltage table, FIG. 5 is a flow chart showing a conventional method of manufacturing a thermal head, and FIG. 6 is a graph showing a decrease in the resistance value of the heating resistor. It is a diagram showing. 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 resistance adjusting device for a thermal head, wherein a voltage pulse is applied to each heating resistor of a thermal head to lower and equalize the resistance value thereof, and a probing connected to each heating resistor. And a switch circuit connected to the probing device for selecting the heating resistor and switching between application of a voltage pulse to the heating resistor by a pulse generator and resistance measurement of the heating resistor by an ohmmeter. , A plurality of samples are selected from the heating resistors, voltage pulses having different voltage values are sequentially applied to the sample from the lowest, and the resistance change rate data at each applied voltage is detected for the plurality of samples, and The resistance drop curve is calculated by statistically processing the data, and the specific resistance change rate is sequentially inserted into the resistance drop curve. Create a resistance versus applied voltage table showing the relationship between the calculated applied voltage value of applied voltage resistance change rate,
The voltage value of the voltage pulse applied to the heating resistor,
A resistance value adjusting device for a thermal head, comprising: a control calculation unit that determines the resistance value based on the initial resistance value of the heating resistor using the resistance vs. applied voltage table.