JP2818489B2 - Resistor trimming method for thin film thermal head - Google Patents

Resistor trimming method for thin film thermal head

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Publication number
JP2818489B2
JP2818489B2 JP2418994A JP41899490A JP2818489B2 JP 2818489 B2 JP2818489 B2 JP 2818489B2 JP 2418994 A JP2418994 A JP 2418994A JP 41899490 A JP41899490 A JP 41899490A JP 2818489 B2 JP2818489 B2 JP 2818489B2
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trimming
resistance value
pulse
resistance
heating
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JPH04298360A (en
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士郎 田中
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京セラ株式会社
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Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a trimming method for adjusting a resistance value of a resistor of a thin film thermal head manufactured by using a thin film technique.

[0002]

2. Description of the Related Art In a thermal head used in various printing output devices, a plurality of heating resistors are linearly arranged on an electrically insulating head substrate, and a row of the heating resistors is selectively energized. , Thermal printing is performed. At this time, in order to realize the designed printing density, the resistance value of each heating resistor is:
It is necessary that the heating resistor is uniform. Therefore, a pulse trimming technique of adjusting a resistance value by applying a voltage pulse to the heating resistor after the formation of the heating resistor is adopted.

A typical conventional example is disclosed in, for example,
20363. In this conventional example, in a thick-film thermal head, a plurality of heating resistors serving as samples are selected from within a thermal head to be trimmed, and voltage pulses are sequentially applied to the heating resistors from a relatively low voltage. At this time, a calibration curve indicating the relationship between the applied voltage and the change in resistance value is created, and an approximate expression representing the curve is calculated. Next, the applied voltage of the test pulse is determined based on the approximate expression, and the test pulse is applied to the sample resistor.

[0004] The obtained change in the resistance value is measured to judge the acceptability of the approximate expression, and if it is acceptable, the pulse condition is determined by the approximate expression as it is, and the trimming process is performed over all the heating resistors. If the determination result of the approximate expression is negative, the approximate expression is corrected based on the measurement result of the resistance change due to the test pulse application, or another sample resistor is selected separately, as described above. Voltage pulses are applied sequentially from a relatively low voltage, and the approximation formula is calculated again.

[0005] In this way, an approximate expression with the highest possible accuracy is calculated, and then the actual trimming process is performed. In addition, even in the same head substrate, in consideration of a situation in which the obtained optimum approximation formula is locally changed, a single thermal head is divided into a plurality of blocks, and the approximation formula is corrected for each block. A trimming method has also been proposed.

[0006] Such a conventional example is based on the following premise.

(1) When a trimming pulse of a specific voltage is applied once and when a trimming pulse whose voltage is sequentially increased from a relatively low voltage is applied one by one until the specific voltage is reached. Is equivalent for the amount of change in resistance value.

(2) When the trimming pulse is applied, the resistance value of the heating resistor changes from the initial resistance value R0 to the resistance value R. The rate of change of the resistance value (R-R0) / R0 is the initial resistance value. Regarding the boundary value V0 of the applied voltage and the increment voltage ΔV, which are independent of the value R0 and the resistance value starts to change,

[0009]

(R−R0) / R0 = −α {(V−V0) / ΔV} a

Α, β: approximated by an equation determined by the voltage V, such as a constant determined by the structure of the thermal head.

[0011]

However, the inventor of the present invention has proposed a thin film thermal head manufactured by thin film technology, that is, a resistor layer constituting a heating resistor is formed by a thin film technology such as sputtering or vapor deposition to have a thickness of several hundreds of mm. In the case of the thermal head formed as described above, it was confirmed that the premise of the above-mentioned items 1 and 2 was not satisfied. That is, in the thin-film thermal head, even when the voltage of the applied pulse is the same, the amount of change in the resistance value after trimming differs depending on the initial resistance value R0.

Further, the voltage is sequentially increased from a relatively low voltage,
It was confirmed that the resistance value change did not match between the case where the trimming pulse was applied once until reaching the specific voltage and the case where the trimming pulse of the specific voltage was applied only once. Therefore, the above-mentioned conventional example cannot be applied to a thin-film thermal head, and a trimming processing technique which has high controllability and can perform the trimming processing in a relatively short time is desired for the above-described thin-film thermal head.

An object of the present invention is to solve the above-mentioned technical problems and to provide a method of trimming a thin film thermal head which has high controllability and can speed up the trimming process.

[0014]

According to the present invention, a plurality of heating resistor elements linearly arranged on an electrically insulating substrate of a thin-film thermal head are divided into a plurality of groups, and these heating resistor elements are grouped. In trimming each time, a voltage pulse is applied to the heating resistor of the thermal head of the same standard as the thin film thermal head, and the resistance value of the heating resistor corresponding to the pulse width of the voltage pulse and the applied power is applied. In the thin-film thermal head resistor trimming method of preliminarily storing the relationship of the change of the decrease or the rise as a calibration curve and determining the applied power of the trimming pulse for each group based on the calibration curve, the average resistance of the heating resistor element is determined. Trimming was started from the group with the smallest value, and the heating resistor elements in each group were trimmed. Calculate the deviation between the actual resistance change amount and the calibration curve, and apply the voltage pulse applied to the group to be trimmed in the second and lower stages. A resistor trimming method for a thin-film thermal head, wherein a calibration curve is corrected, and a determination is made based on the corrected calibration curve.

[0015]

According to the present invention, a trimming pulse is applied to a heating resistor element of a thermal head of the same standard as the thermal head to be trimmed, and a change in resistance value corresponding to the pulse width and the applied power is stored as a calibration curve. . Next, the heating resistor elements of the thermal head to be trimmed are divided into a plurality of groups, trimming starts from the group with the smallest average heating resistor element, and the actual resistance value when the heating resistor elements of each group are trimmed. If there is a deviation between the change amount and the calibration curve, calculate the deviation amount, apply the voltage pulse to be applied to the group to be subsequently trimmed, and apply the calibration curve used when trimming the previous group to the previous stage. When there is a difference between the deviation amounts of the groups, the correction amount is corrected by the deviation amount, a new calibration curve is determined, a new calibration curve is obtained, and the applied power of the applied trimming pulse is determined. Hereinafter, similar processing is repeated.

As described above, according to the present invention, trimming is started from the group having the smallest average resistance value. That is, since the average resistance value of this group is closest to the target resistance value,
When the required resistance value change amount is the smallest and the trimming process is performed based on the calibration curve, the applied voltage pulse is the smallest. Therefore, even if the resistance value change characteristic of this group greatly deviates from the calibration curve, the possibility that the applied voltage pulse becomes excessive and the heating element is destroyed can be reduced as much as possible. In addition, the calibration curve corrected for each group thereby basically comes close to the characteristics of the thin-film thermal head, so that the number of trimming pulses applied to the subsequent group can be reduced, and the speed of the trimming process can be increased. Can be contributed to.

[0017]

FIG. 1 is a sectional view for explaining the structure of a thin film thermal head (hereinafter abbreviated as thermal head) 21 manufactured by using the trimming method of the present invention. The thermal head 21 includes a heat radiating plate 22 made of a metal material such as aluminum, for example, and a head substrate 23 is fixed thereon with an adhesive layer 32. On the head substrate 23, a large number of heating resistance elements 24 are formed linearly in a direction perpendicular to the paper surface of FIG. 1, and are arranged in parallel with the arrangement direction of the heating resistance elements 24. A plurality of drive circuit elements 25 connected by electrodes are arranged. These drive circuit elements 25 are formed of a protective layer 2 made of a synthetic resin material.
6 coated.

On the head substrate 23, a heat storage layer 35 is formed by a thick film technique such as screen printing, and a thick film common electrode layer 27 is formed along the outer periphery of the head substrate 23. On the heat storage layer 35, a heating resistance element layer 34, a common electrode layer 36, and a plurality of individual electrodes 37 are formed, and a plurality of heating resistance elements 24 on a straight line are configured. The heating resistance element 24 is connected to a platen roller 31 via a wear-resistant layer 39 formed by a thin film technique such as sputtering.
Then, thermal printing is performed on the thermal paper 32. The heating resistance element 24 is controlled by a driving circuit element 25 realized as an integrated circuit element. The drive circuit element 25 is connected to the individual electrode 37 covered with the insulating layer 28, and inputs a signal for driving the heating resistor element 24 to the drive circuit element 25, and the external connection covered with the insulating layer 28 The terminal 29 is connected, and a protective layer 26 made of a synthetic resin material or the like is formed to cover the drive circuit element 25 and its periphery. In the present invention, the heating resistance element layer 3 is formed on the head substrate 23.
4. At the stage when the common electrode 36 and the plurality of individual electrodes 37 are formed, the resistance value of each of the plurality of heating resistance elements 24 defined by the common electrode 36 and the plurality of individual electrodes 37 is to be trimmed and made uniform. As a result of conducting an experiment on the thermal head 21, the following facts were found.

(1) Before forming the wear-resistant layer 39, a trimming pulse is applied in the air atmosphere. At this time, by appropriately selecting the pulse width, the resistance value of the heating resistance element 24 can be increased as well as reduced. A summary of the experimental results is shown in the graph of FIG. That is, the horizontal axis represents the applied power, and the vertical axis represents the resistance value change rate Δ of the heating resistance element 24.
It has been confirmed that when R / R is taken, the obtained characteristic curve greatly changes by changing the pulse width of the applied trimming pulse. Lines L1 and L shown in FIG.
2, L3 indicate cases where the pulse widths are different from each other, and when the corresponding pulse widths are represented by WL1, WL2, WL3 (collectively referred to as WL if necessary), these relationships are

[0020]

## EQU2 ## WL1> WL2> WL3.

That is, when the pulse width WL is relatively long, the resistance value increases when the applied power is increased as shown by the line L1. On the other hand, when the pulse width WL is relatively short, the resistance value does not change in the range A less than the threshold power Pth as indicated by the line L3, but the threshold power Pth
When the applied power is increased to the above range B, the resistance value decreases. In addition, an intermediate pulse width W of the pulse widths WL1 and WL3
In L2, both the rising phenomenon and the falling phenomenon of the resistance value appear depending on the degree of the applied power P as shown in the line L2. That is, in the range A of the applied power that is less than the threshold power Pth with respect to the applied power, the resistance value decreases as the applied power increases, and the rate of decrease initially increases, but gradually decreases from 0 to negative (that is, increases). )become. At the threshold power Pth, the resistance value returns to the original value. In the range B, the resistance value gradually increases as the applied power P increases.

As described above, the pulse width W of the trimming pulse
The phenomenon that the resistance value of the heating resistance element 24 can change either upward or downward due to L is described as follows with reference to FIG. That is, the change in the resistance value of the heating resistor element 24 due to the application of the trimming pulse is due to the annealing effect due to the heating of the heating resistor layer 34 itself, that is, the crystallization of the heating resistor layer 34 and the heating of the heating resistor layer 34 itself. Oxidation. Among these, the annealing effect appears as a phenomenon in which the resistance value decreases at the point where the crystallization of the heating resistance element layer 34 progresses,
Oxidation also appears as an increase in resistance.

As shown in FIG. 3A, when the pulse width WL1 of the applied trimming pulse is set relatively long and the applied voltage is set low, the heating resistor element layer 34 applies the applied voltage V1
Is relatively low, the temperature does not show a rapid and significant rise, while the relatively long pulse width WL1 results in a relatively low temperature for a long time. The progress of the annealing effect in the heating resistance element layer 34 is determined by the temperature. In this case, the temperature T1 does not reach the temperature Ta at which the annealing effect is generated, and the resistance value decreases due to the annealing effect. Does not occur. However, since the temperature is equal to or higher than the temperature Tox at which the oxidation phenomenon occurs, and this state is continued for a relatively long time, the heating resistance element layer 3
Oxidation proceeds to 4, and the resistance value increases.

On the other hand, the applied trimming pulse is shown in FIG.
As shown in (1), when the pulse width WL3 is relatively short and the applied voltage V2 is relatively high, the heating resistance element layer 3
4 changes to the state shown in FIG. 4 (2). That is, the temperature of the heating resistance element layer 34 rapidly rises to reach a temperature T2 exceeding the temperature Ta at which the annealing effect occurs. On the other hand, since the pulse width WL3 is relatively short, the temperature T2 hardly lasts, and quickly returns to room temperature. In this case, the temperature T
2, the annealing effect progresses, and the heating resistance element layer 3
The resistance value of 4 drops. On the other hand, the temperature T at which the oxidation occurs
Since the period exceeding ox is relatively short, almost no oxidation occurs and no increase in resistance occurs. That is, by appropriately selecting the pulse width WL of the trimming pulse and the applied power, it is possible to control which of the above-described annealing effect and oxidation becomes the dominant phenomenon. That is, control for increasing or decreasing the resistance value of the heating resistance element layer 34 can be performed.

(2) As shown in FIG. 3A, when a trimming pulse having a pulse width WL1 that causes only a rise in the resistance value in the heating resistor element layer 34 is applied, the pulse width WL1 of the trimming pulse is fixed. Even if the resistance value before the application of the trimming pulse is different for each heating resistance element 24, each heating resistance element 24 exhibits a substantially constant resistance value change rate by applying the same applied power.
On the other hand, the same applies to the case where a trimming pulse having a pulse width WL3 that causes only a decrease in the resistance value as shown in FIG. 4A is applied. Even if the resistance is different for each element 24, it shows a substantially constant resistance value change rate.

The present inventor has proposed a heating resistor element 2 shown in FIG.
4, the width of the heating resistor is 151 μm in the left-right direction in FIG. 1 and the width is 105 μm in the direction perpendicular to the plane of FIG. 1. Was measured. The relationship between the applied voltage and the change in the resistance value is shown by lines L6 and L7 in FIG.
Shown in As described above, it is understood that the state of the resistance value change is significantly different from the relationship with the applied voltage.

On the other hand, the relationship between the applied power and the change in the resistance value is shown in lines L8 and L9 in FIG. As shown in the figure, if the applied power is the same, it is understood that the same resistance value change is exhibited regardless of the difference in the initial resistance value before trimming. When these are combined, the line L shown in FIG.
It can be concluded that the characteristic curves of 1 and L3 do not depend on the resistance value of each heating resistance element 24.

The above phenomenon is explained as follows. As described above, the progress of the annealing effect and oxidation, which are factors that change the resistance value of the heating resistance element layer 34, are as shown in FIG. 3 (2) of the heating resistance element layer 34 itself corresponding to the state of the applied trimming pulse. ) And the characteristics of the temperature change as shown in FIG. 4 (2). Therefore, if the pulse width WL and the applied power P are the same, even if the resistance values of the heating resistance elements 24 are different from each other, the characteristics of the time change of the temperature of each heating resistance element 24 are as follows.
It becomes the same between the respective heating resistance elements 24, and a substantially constant resistance value change rate is obtained as described above.

(3) After a trimming pulse of a predetermined applied power P0 is applied to the heating resistor element 24, a trimming pulse in which the applied power is increased by an increment ΔP of the applied power is applied from the second time onward to gradually increase the applied power. The resistance value can be reduced. The inventor of the present invention has determined that the heating resistor element 24 shown in FIG. 1 has a length of 151 μm in the left-right direction in FIG. 1 and a 105 μm width in a direction perpendicular to the plane of FIG. After a pulse was applied to reduce the resistance value, a change in resistance value when the applied power was increased by an increment ΔP from the second time onward was measured. The result is shown in lines L10 and L11 in FIG. The manner in which the resistance value decreases as described above depends on the applied power of the first pulse, but in any case, the resistance value decreases.

(4) In the description of the third item, by setting the second and subsequent trimming pulses to be trimming pulses having a relatively long pulse width as shown in FIG.
The resistance value can be gradually increased. The present inventor:
With respect to the plurality of heating resistance elements 24 having different resistance values in the description of the third section, a change in resistance value when a trimming pulse having a pulse width of, for example, 50 ms is applied for the second time or later is measured. This state is shown in FIG.
12, L13. It is understood that the resistance value can be gradually increased as shown in FIG. At this time, the line L12 shows a case where the applied power is higher than that of the line L13. In addition, as shown by the line L13 in the case where the applied power is set lower, the change in the resistance value in one application of the trimming pulse can be set relatively small. This makes it possible to control the resistance value of the heating resistance element 24 by trimming with extremely high precision.

(5) The annealing effect that causes the resistance value of the heating resistor layer 34 to decrease as described above promotes rearrangement and crystallization of constituent molecules in the heating resistor layer 34. Therefore, the durability of the heating resistance element 24 to applied pulses (such as a trimming pulse and a driving pulse accompanying use) is improved. On the other hand, an oxidation phenomenon that causes an increase in the resistance value narrows the region of the heating resistance element 24 having a predetermined resistance value, and thus substantially reduces the film thickness. Therefore, the durability against the applied pulse is deteriorated. That is, the process of greatly increasing the resistance value of the heating resistance element 24 deteriorates the heating resistance element 24 and shortens the life.

(6) In the case where the heating resistance element 24 is a tantalum Ta type, the present inventor has confirmed that the resistance value can be reduced to about -70% with a pulse width of 1 ms or less. However, if the resistance value is excessively reduced, the heat-generating resistance element 24 aggregates, and the heat-generating resistance element 24
May be destroyed due to heat. In view of these points, the present inventor has determined that the maximum trimming amount −D which can maintain the reliability of the thermal head 21 is the limit.
It was confirmed that R1 was, for example, about -40% as shown in FIG.

(7) As described above, when the trimming is performed by increasing or decreasing the resistance value, when the resistance value decrease due to the application of the trimming pulse is excessive, the trimming pulse having a relatively long pulse width is used as described above. It is necessary to oxidize the heating resistance element 24 to increase the resistance value. Due to this oxidation, as described above, the heating resistance element 24
The reliability of the device decreases. In addition, in the case of performing control to further decrease the resistance value by increasing the applied power, when the change in the resistance value is excessively large in the down direction due to the first trimming pulse application, a trimming pulse for further reducing the resistance value is applied. However, it has been confirmed that the resistance value may be increased without being reduced, or may be significantly reduced in excess of a previously calculated reduction amount. In such a case, the heating resistance element 24 may be broken. According to such an experiment, in the case of performing the above-described increase or decrease control of the resistance value, the change in the resistance value is, for example, about -30% of the limit value -D
It was confirmed that R2 or more could not be achieved.

(8) Further, it was confirmed that the resistance value of the heating resistor element 24 was reduced by, for example, about 2 to 3% with the use of the thermal head 21 when the trimming was not performed. This is the heating resistance element 2 that has been trimmed.
In No. 4, the reliability with respect to the applied pulse is improved by the above-described annealing effect, and therefore, the resistance does not decrease during use. On the other hand, the resistance value of the heating resistance element 24 that has not been subjected to the trimming treatment is reduced because it does not have the annealing effect. For this reason, in a single thermal head 21, the amount of heat generation varies with use, resulting in uneven density. Therefore, all the heating resistance elements 24 of the thermal head 21
For example, it is necessary to perform a trimming process by a minimum trimming amount DR4 of about -3%.

Based on the above-described conditions, a description will be given of a method for applying the above-described phenomenon of increasing and decreasing the resistance value to the adjustment of the resistance value of the heating resistance element 24. FIG.
As shown in (1), when a trimming pulse having a relatively short pulse width WL3 is applied and the pulse width WL3 is kept constant, the relationship between the applied power and the rate of change in resistance value is reduced as described above. Although the resistance value does not depend on the resistance value, the resistance value change rate actually varies due to unevenness of the heat storage layer 35 and dimensional variation of the heating resistance element 24.

Therefore, the applied power P and the rate of change in resistance value ΔR
As shown in FIG. 9, the graph showing the relationship between the line L4 and the line L4 shows the ideal correspondence.
a, L4b. Therefore, as described as the prior art, when the thermal head is manufactured, a trimming pulse is applied to the head substrate 23 in the same lot or the heating resistance element 24 in the same head substrate 23, and the calibration curve of the line L4 in FIG. Then, the pulse width and applied power of the trimming pulse are determined based on the calibration curve, and even if such a trimming pulse is applied to each heating resistor element 24, the lines L4a and L4a shown in FIG.
Due to the variation between L4b, it is impossible to control the rate of change of the resistance value with high accuracy.

For example, in order to change the resistance value by -n%, data of the corresponding applied power P0 (-n%) was obtained from the calibration curve of line L4 in FIG. 9, and a trimming pulse having this applied power was applied. In this case, the resistance value change rate actually varies in the range of the width δ shown in FIG. Therefore, the obtained rate of change in resistance is −nd−2% at the lower limit and −n + at the upper limit.
It will vary between d1% (d1 + d2 = δ).

Therefore, in trimming the heating resistance element 24, once a trimming pulse is applied,
Further, it is necessary to increase or decrease the resistance value by applying a trimming pulse. It has been confirmed that such processing can be realized by the following method.

First, when the resistance value is further decreased after the first trimming pulse application, only the annealing effect described above needs to be advanced. Therefore, a trimming pulse having the same pulse width as the first trimming pulse and having the applied power increased by the predetermined power ΔP is applied. As a result, the heating resistance element 24 reaches a higher temperature than when the first trimming pulse is applied, so that the annealing effect further proceeds and the resistance value further decreases.

In order to further reduce the resistance value, the power may be further increased by the applied power ΔP to apply the trimming pulse. At this time, since the pulse width is set to be relatively short, the above-described oxidation phenomenon hardly occurs. However, when the applied power ΔP is too small, the oxidation phenomenon cannot be ignored, and conversely, the resistance value may increase. Therefore, the predetermined applied power ΔP is determined in consideration of such conditions comprehensively.

When the resistance value is increased after the first trimming pulse application, only the oxidation phenomenon described above needs to proceed, and FIG. 3 (1) showing a characteristic like line L1 in FIG.
As shown, a trimming pulse having a relatively long pulse width WL1 is applied. As a result, the heating resistance element 24 basically cools down from the temperature after the first trimming pulse application, and the annealing effect hardly progresses, and only the oxidation phenomenon progresses. Thereby, the resistance value of the heating resistance element 24 can be reliably increased. Further, by selecting the applied power P1 at this time to be relatively small, the rate of increase of the resistance value every time the trimming pulse is applied can be changed little by little, for example, about +0.1 to 0.2%. 2
4 can be controlled with high precision.

FIG. 10 shows a trimming device 41 according to the present invention.
It is a block diagram of. The trimming device 41 is mounted on the head substrate 23 of the thermal head 21 and
The heating resistor element 2 is connected to the common electrode 36 and the individual electrode 37 on
A probing device 42 is provided for bringing the probe into contact with each of the probes 4 individually. The probing device 42 is connected to a resistance value meter 44 and a trimming pulse generator 45 via a switching unit 43. The resistance value measured by the resistance value meter 44 is input to a calibration curve creation unit 47 that creates and stores a calibration curve in the control device 46. The head substrate 23 has X
The XY stage 52 is mounted on a Y stage 52, and the XY stage 52 is moved by the positioning mechanism 53 controlled by the controller 46.
Positioning 3 is performed.

The trimming pulse generating section 45 includes a reference pulse generating section 48. The generated reference pulse passes through a pulse width adjusting section 49 and a voltage adjusting section 50.
It is output as a trimming pulse as described later, and is applied to the selected heating resistor element 24 via the switching circuit 43 and the probing device 42.

FIG. 11 is a process chart for explaining the entire process of manufacturing the thermal head 21. In step a1 of FIG. 11, a thick film common electrode layer 27 and a heat storage layer 35 are formed on the thermal head 21. In step a2, the heating resistor layer 34 is formed on the thermal head 21. In step a3, the common electrode 36 and the individual electrode 37 are formed on the heating resistor layer 34. In step a4, a trimming process, which will be described in detail later, is performed to adjust the resistance value of each heating resistance element 24 to be uniform.
Is formed. Thereafter, through other processing, the thermal head 21 is completed.

FIG. 12 is a process chart for explaining a trimming processing method of a configuration which is a basis of the present invention, and FIG.
FIG. 7 is a process chart for explaining a method of generating a calibration curve and other pulse condition determination processing during the process of FIG. In step b1 in FIG. 12, a sample head in which the heating resistance elements 24 are arranged as shown in FIG. 1 is prepared, and the pulse conditions as described above are obtained.

The details of this process will be described with reference to a process chart for creating a calibration curve shown in FIG. That is, a sample head substrate is set, and a trimming pulse application test is performed on the sample head substrate using the trimming device 41 shown in FIG. 10 to obtain the following pulse conditions 1 to 3.

(Condition 1) When one pulse is applied, a pulse width WLd at which the resistance value decreases is obtained in step c1, and a test pulse is applied by changing the applied power variously in the pulse width WLd. The resistance change rate due to the application of the test pulse is measured to obtain a calibration curve shown by a line L4 in FIG. From the calibration curve, the resistance value change rate ΔR / R is −1%, −2%,.
% Applied power P0 (-1%), P0 (-2%),
, P0 (-n%) are obtained in step c2.

(Condition 2) The pulse width W obtained under the above condition 1
In Ld, after one pulse is applied to lower the resistance value, an increase power ΔP required to further reduce the resistance value by d1% (for example, 2 to 3%) is obtained in step c3.

(Condition 3) The pulse width WLu at which the resistance value increases when one pulse is applied is determined in step c4.

(Condition 4) The pulse width W
In Lu, the resistance value is d2% (for example, 0.2 to 0.
3%), the applied power P1 required to increase the power is obtained in step c5.

In step b2 in FIG. 12, the calibration curve correction value Ph
= 0 is set. In step b3, the plurality of heating resistance elements 24 linearly arranged on the head substrate 23 are divided into a plurality of groups. In this configuration example, for example, FIG.
As shown in FIG. 7, a heating resistor array 55 formed of a plurality of heating resistors 24 is divided into, for example, eleven blocks B0, B1,..., B10.

Thereafter, the probing device 42 is mounted on the heating resistance element 24 of the block B0 shown in FIG.
Measure 0. In step b4, a necessary resistance value change amount -DR is calculated from the initial resistance value R0 and a predetermined target resistance value Rf.

[0053]

(Equation 3)

Is calculated. In step b5, the pulse width WLd corresponding to the required resistance change amount DR is determined, and the required applied power P0 (-DR%) is obtained from the calibration curve L4 in FIG. In step b6, the obtained applied power P0 (−DR
%) Is corrected by the calibration curve correction value Ph. That is,

[0055]

## EQU4 ## As shown by P0 (-DR%) = P0 (-DR%) + Ph, the applied power P0 (-
DR%) is replaced with P0 (−DR%) + Ph. The reason why such correction processing of the calibration curve is possible will be described below.

In step b7, the applied voltage V0 is determined based on the pulse width WLd and the applied power P0 (-DR%).

[0057]

(Equation 5)

After the reference pulse generated by the reference pulse generator 48 based on these data is adjusted by the pulse width adjuster 49 and the voltage adjuster 50, the reference pulse is transmitted through the switch 43 and the probing device 42. Is applied to the heating resistance element 24.

In step b8, the switching means 43 is switched to the resistance value measuring device 44 side, and the resistance value R after the first pulse application is measured by the resistance value measuring device 44. In step b9,
From the initial resistance value R0 and the measured resistance value R, the actual resistance value change amount -DR1

[0060]

(Equation 6)

Is calculated, and the corresponding applied power P0 (-DR
1%) is obtained from the line L15 in FIG. Step b11
Now, the deviation Ph from the calibration curve L15 in the heating resistance element 24 to which the probing device 41 is currently connected is shown.
i (i = 0, 1, 2,...)

[0062]

[Mathematical formula-see original document] Phi = P0i (-DR%)-P0i (-DR1%) is calculated, and the calculation result is used as a calibration curve correction value in the control device 4.
6 is stored. In step b12, it is determined whether or not the resistance value R measured in step b8 is within a range considered to be equal to the target resistance value Rf, that is,

[0063]

| R−Rf | / Rf ≦ εε: It is determined whether or not a predetermined minute amount is satisfied.

If the determination in step b12 is affirmative, step b1
Move to 7. If not, the process moves to step b13 to determine whether or not the measured resistance value R is larger than the target resistance value Rf. If this determination is negative, the process proceeds to step b14, in which the voltage is calculated as in the fifth equation using the relatively long pulse width WLu and the applied power P1 as described above for increasing the resistance value, and the applied power is calculated. Is applied, the process proceeds to step b15, the resistance value is measured again, and the process returns to step b12.

If the determination in step b13 is affirmative, the process proceeds to step b16, where a trimming pulse for decreasing the resistance value is applied in which the applied power is increased by the incremental power ΔP with the above-mentioned pulse width WLd for decreasing the resistance value. Then, the resistance value is measured in step 15, and the process returns to step b12.

If the determination in step b12 is affirmative, the process proceeds to step b17 to determine, for example, whether or not the trimming of all the heating resistance elements 24 in block B0 in FIG. 15 has been completed. If the processing has not been completed, the process returns to step b3, and the above-described processing is repeated for the remaining heating resistance elements 24 in this block. If the determination is affirmative, the process proceeds to step b1.
8 and the average Ph of the deviation amounts Phi of all the heating resistance elements 24 in this block.

[0067]

(Equation 9)

Is calculated, and the average deviation Ph is set, for example, as the deviation Ph of the block B0.

If the determination in the step b17 is negative, it means that the heating resistor element 24 whose resistance value is not within the target resistance value range exists in the block B0, and returns to the step b3 to repeat the above processing. .

In this way, for example, the block B0 shown in FIG. 15 performs trimming based on the calibration curve L15 shown in FIG. 16 so that all the heating resistance elements 24 fall within the target resistance value range.

In step b19, it is determined whether trimming has been completed for all blocks B0 to B10 as shown in FIG. 15, and if completed, the trimming process is ended. If not completed, the process moves to another block, for example, block B1, which is continued in step b20, returns to step b3, and repeats the above-described processing. At this time, step b6
In FIG. 15, the deviation Ph obtained in step b18 is determined with respect to the calibration curve corrected at the time of trimming in block B0.
The calibration curve is further corrected as shown in the fifth equation. Using this corrected calibration curve, the block B1 is trimmed.

Thereafter, as the process proceeds to the blocks B2,..., B10, the calibration curve is sequentially corrected and used for trimming of the subsequent block. At the time of trimming of the subsequent block, the new deviation amount Ph is obtained.

Thus, blocks B0,..., B10
As the trimming process proceeds, the calibration curve matches the characteristics of the thermal head to be trimmed, and the resistance value of each heating resistor element 24 can be easily adjusted. Further, as the trimming for each block progresses, the number of times the trimming pulse is applied decreases. This makes it possible to increase the speed of the trimming process.

If the number of the heating resistance elements 24 constituting each of the blocks B0 to B10 is too small, there is no point in performing the averaging operation, and if the number is too large, there is no meaning in correcting the calibration curve. According to experiments, about 16 to 64 dots are appropriate. Needless to say, the number of dots does not need to match the number of probes of the probing device 41.

FIG. 17 is a process chart for explaining the trimming processing method according to the embodiment of the present invention. FIG. 17 steps d1, d
Steps 2 and 3 are the same as steps b1 to b3 of the basic configuration. In step d4 in FIG. 17, it is determined whether or not the measurement of the initial resistance value R0 has been completed for all the heating resistance elements 24, and the measurement is continued until the measurement is completed. When the process is completed, the process proceeds to step d5.
For example, as shown in FIG. 19B, when the heating resistor element row 55 is divided into blocks B0 to B10, an average resistance value is calculated for each block Bi (i = 0 to 10). Now, when the resistance distribution of the thermal head is shown by the line L16 in FIG.
The distribution of the average resistance value for each i is obtained as shown in the line L16a.

In step d6, the block having the minimum average resistance value is determined. In the example of FIG. 18A, the sixth block B5 corresponds to this. In step d7, the probe of the probing device 41 is moved to the block B5. The subsequent steps d8 to d21 correspond to the steps b4 to b17 in FIG. 12 for each step, and perform the same processing as described above. At this time, the trimming order for each block Bi in the heating resistance value row 55 is as shown in FIG. 18B, from the sixth block B5 to the blocks B6, B7,.
... The process proceeds as in block B10.

As described above, when the judgment in the step d21 is affirmative regarding the trimming processing in each block, the processing shifts to the step d22, and the rightmost or leftmost block in the heating resistor element row 55 in FIG. It is determined whether or not. If this determination is negative, the trimming process can be further advanced to the right or left block in accordance with the progress of the trimming, and the process shifts to step d23 to perform the same process as step b18 in FIG.

In the following step d24, the block currently being trimmed is the sixth block B
It is determined whether or not the block, such as 5, is the first block subjected to the trimming process. If this determination is affirmative, in step d25, the calibration curve correction value Ph is stored as the correction value Ph0. Thereafter, the process proceeds to step d26, and the probe is moved to, for example, the seventh block B6 adjacent to the right side. Thereafter, the process proceeds to step d8, and the above process is repeated.

If the determination in step d22 is affirmative, the process proceeds to step d27, where it is determined whether the trimming process has been completed for all blocks. If it has been completed, the trimming process for the thermal head ends, and the process moves to the next thermal head. If this determination is negative, for example, the sixth block B in the trimming order in FIG.
This means that the trimming process in 10 has been completed. At this time, in step d28, the first trimmed block B
To the fifth block B4 adjacent to the left side of No. 5
To move. In step d29, the calibration curve correction value Ph is set to Ph0 stored in step d25, the process proceeds to step d8, and the trimming process proceeds leftward in FIG. 19 as in the remaining blocks B4 to B0 shown in FIG. .

As described above, in this embodiment, the trimming is started from the block having the smallest average resistance value. That is, when the average resistance value is closest to the target resistance value and the trimming process is performed based on the calibration curve obtained from the sample head, the applied power obtained from the calibration curve becomes the smallest. Therefore, even if the resistance change characteristic of the thermal head to be trimmed greatly deviates from the calibration curve, even if the first pulse applied power becomes overpower, the possibility that the heating resistance element 24 is destroyed can be reduced as much as possible. it can.

On the other hand, in the basic configuration,
Trimming is started from the first block regardless of the magnitude of the average resistance value. For example, the distribution of the average resistance value is shown in FIG.
In the case shown by the line L16a of (1), the required resistance change amount is large, and the resistance change amount obtained by applying the first trimming pulse greatly deviates from the required resistance change amount. There is a high possibility that the heating resistance element 24 will be destroyed.

As a modification of the trimming processing procedure of this embodiment, as shown in FIG. 18C, the trimming processing is started from the block B5 where the trimming processing is performed first toward the left side of FIG. May be moved to the block B6 on the right side of the block B5, and the trimming process may proceed rightward in FIG.

[0083]

[0084]

As described above, according to the present invention, the resistance values of all the heating resistance elements of the thermal head to be trimmed are measured, the average resistance value is calculated for each set block, and the lowest average resistance value is calculated. Starts the trimming process from the group of. According to this, since the average resistance value of the group in which the trimming process is performed first is the lowest, the required resistance change amount with respect to the target resistance value of the group is the smallest, and the applied power obtained from the calibration curve obtained in advance. Is also the smallest. Therefore, even if the deviation between the trimming characteristic of the thermal head to be trimmed and the calibration curve is large,
When a trimming pulse is applied based on this calibration curve, it is possible to prevent a situation in which the power of the resistance element is degraded or destroyed due to overpower.

When trimming each heating resistance element to adjust the resistance value, the calibration curve is corrected for each group to be trimmed, and trimming is repeated. Therefore, the trimming is repeated according to the characteristics of the thin film thermal head to be trimmed. It is possible to execute a simple trimming process. Further, thereby, the calibration curve corrected for each group is basically close to the characteristics of the thin-film thermal head, so that it is possible to reduce the number of trimming pulses applied in the group to be trimmed in the subsequent stage. This can contribute to speeding up of the trimming process.

[Brief description of the drawings]

FIG. 1 is a sectional view of a thermal head 21 to which the present invention is applied.

FIG. 2 is a graph showing a relationship between applied power and a resistance value change rate when the pulse width of a trimming pulse is variously changed.

FIG. 3 is a graph showing a waveform of a trimming pulse having a relatively long pulse width and a temporal change in the temperature of a heating resistor element.

FIG. 4 is a graph showing a waveform of a trimming pulse having a relatively short pulse width and a temporal change of a temperature of a heating resistor element.

FIG. 5 is a graph illustrating the operation of the present invention.

FIG. 6 is a graph showing a calibration curve for explaining the operation of the present embodiment.

FIG. 7 is a graph illustrating the operation of the present invention.

FIG. 8 is a graph illustrating the operation of the present invention.

FIG. 9 is a graph showing the relationship between the applied power and the change in resistance when the pulse width is fixed.

FIG. 10 is a block diagram of a trimming device 41.

FIG. 11 is a process diagram for explaining the entire manufacturing process of the thermal head 21.

FIG. 12 is a process diagram illustrating a trimming process of a configuration serving as a basis of the present invention.

FIG. 13 is a process diagram illustrating a calibration curve creation process.

FIG. 14 is a graph showing the relationship between the applied power and the rate of change in resistance when the pulse width is constant.

FIG. 15 shows a heating resistor element array 5 having a configuration serving as a basis of the present invention.
FIG. 14 is a diagram showing an example of block division No. 5;

FIG. 16 is a graph illustrating the operation of the present invention.

FIG. 17 is a process diagram illustrating a trimming processing method according to one embodiment of the present invention.

FIG. 18 is a graph illustrating the operation of the present embodiment.

FIG. 19 is a diagram illustrating an example of a block division of a heating resistor element row 55 in the present embodiment.

[Explanation of symbols]

 21 Thermal Head 23 Head Substrate 24 Heating Element 41 Trimming Device 44 Resistance Measurement Meter 45 Trimming Pulse Generator 47 Calibration Curve Storage 49 Pulse Width Adjuster 50 Voltage Adjuster

Claims (1)

(57) [Claims]
1. A method according to claim 1, wherein a plurality of heating resistor elements linearly arranged on the electrically insulating substrate of the thin film thermal head are divided into a plurality of groups, and the heating resistor elements are sequentially trimmed for each group. A voltage pulse is applied to the heating resistor of the thermal head of the same standard as the thin-film thermal head, and the relationship between the pulse width of the voltage pulse and the change in the decrease or rise in the resistance of the heating resistor corresponding to the applied power is determined. In the thin-film thermal head resistor trimming method of storing the calibration curve in advance and determining the applied power of the trimming pulse for each group based on the calibration curve, trimming is performed from the group having the smallest average resistance value of the heating resistance element. Starting and trimming the heating resistance element of each group and the actual resistance change amount The deviation amount from the calibration curve is calculated, and the voltage pulse applied to the group to be trimmed in the second stage or lower is corrected. A resistor trimming method for a thin film thermal head, wherein the method is determined based on a calibration curve.
JP2418994A 1990-12-29 1990-12-29 Resistor trimming method for thin film thermal head Expired - Lifetime JP2818489B2 (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
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Application Number Priority Date Filing Date Title
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Cited By (1)

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Publication number Priority date Publication date Assignee Title
JP2010076157A (en) * 2008-09-24 2010-04-08 Toshiba Corp Method for manufacturing thermal head

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Publication number Priority date Publication date Assignee Title
AU2003291150A1 (en) * 2002-11-21 2004-06-18 Sanmina-Sci Corporation Laser trimming of resistors

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Publication number Priority date Publication date Assignee Title
JPH0667635B2 (en) * 1987-11-05 1994-08-31 三菱電機株式会社 Method of manufacturing thermal head

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
JP2010076157A (en) * 2008-09-24 2010-04-08 Toshiba Corp Method for manufacturing thermal head

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