JPS62283602A - Method of trimming thick film resistance array - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] 3. Detailed Description of the Invention [Field of Industrial Application] This invention relates to a trimming method for setting each resistor of a resistor array to a predetermined resistance value without changing its shape, and in particular, More specifically, the present invention relates to a method of controlling voltage values when applying high voltage pulses to a resistor array for trimming.

[Technical Background of the Invention] For example, in a thermal printer, when a head is configured with a thick film resistor array, trimming is performed to set the resistance to a predetermined value without changing the shape of each resistor in the resistor array. There is. In other words, in a resistor array used in a thermal print head, the maximum temperature and heat generation temperature such as heat generation area are problematic, so a trimming method such as laser trimming that changes the shape of the resistor cannot be adopted.

Generally, a trimming method is used to lower the resistance value by applying a high voltage pulse to electrostatically break down the glassy barrier between the conductive particles of the thick film resistor and causing a short circuit. It is difficult to uniformly define trimming characteristics and subsequent resistance stability, which vary depending on the thick film resistor paste, conductive paste, and firing conditions used.

That is, the resolution of thermal print heads has recently increased, and many have resistor arrays with a density of 8/- or more. For example, in an A4 size print head, a resistor array has a resistor array with a density of 1,700 or more resistors. By the way, the initial resistance value varies by about ±15%, and in order to keep this within ±3%, it is necessary to
It is necessary to trim more than 1700 resistive elements per head.

Now, to explain the conventional trimming method with reference to FIGS. 1 and 2, each resistor element 2 of the resistor array 1 of the thermal print head is connected to a common electrode 4 provided on a substrate 3 and a drive circuit, etc. The probe 6 which is provided between the electrode 5 and the common electrode 4 and the probe 7 which is applied to the electrode 5 first
Measure the initial resistance value. This measurement is performed using selector switch 8.
This is done by switching to the resistance measuring device 9 side. The measurement results are sent to the control device 10, which controls the program power supply 11.
Then, the pulse generating circuit 12 is driven to first set the high voltage A. Here, the changeover switch 8 is switched to the pulse application side, and the voltage A pulse is applied to the first resistance element via the probe 6.7. Switch the selector switch 8 to the resistance measuring device 9 side again.

The resistance value of the first resistance element 2 is measured, the measurement result is sent to the control bag @ 10, and the control device 10
Then, the pulse generating circuit 12 is driven to set the high voltage B. The voltage pulse B caused by this high voltage B is applied again to the first resistance element 2 by switching the changeover switch 8. Then, the resistance value of the first resistance element 2 is measured again, and the voltage pulse C of the high voltage C is applied to the first resistance element 2 again based on the measurement result. Thereafter, the same operation is generally repeated six or more times by gradually increasing the applied voltage until the resistance value reaches the desired value. When the desired resistance value is reached, the second resistance element 2 is connected to the probe 6°. 7 will be moved. This basic procedure is shown in FIG.

This method takes too much time to trim more than 1,700 resistive elements. Therefore, a method of performing parallel processing using a large number of probes has also been proposed. Parallel processing methods can be broadly classified into the following two methods.

The first method is to prepare a large number of steps in advance, corresponding to each step in FIG. For example, high voltage A, B, C
... are separated into separate probes, that is, separate processes, and when voltage pulse A (e.g., 350 V) has been applied, the stage is moved one step and voltage pulse B (e.g., 400 V) is applied. . After the application of voltage pulse B is completed, the stage is moved one step further, voltage pulse C (for example, 450 V) is applied, and then voltage pulse D is applied. In this case, when the stage moves, each probe moves at the same time, so if one moves the high voltage setting from A to B, the other steps will also move. For example, move the high voltage setting from B to C, and from C to It can be moved to D. This method has the advantage of making the system hardware single-function, such as using a fixed-voltage power supply for each process rather than a programmable high-voltage pulse power supply. Since time-consuming probe movement time is required for each processing step, the trimming time cannot be reduced as much as expected. Furthermore, since the initial resistance values in the array vary, it becomes difficult to develop software for controlling the resistance value, which is the absolute value, rather than the resistance change, in separate resistance measurement steps. Furthermore, due to variations in initial values, it is necessary to increase the number of high voltage setting stages.

The second method for parallel processing is to extend the system based on FIGS. 1 and 2 to include adjacent resistive elements, and install n resistive elements. According to this method, other devices other than the control device 10, that is, the changeover switch 8, the resistance measurement bag w
9. Although there is a cost increase in preparing n program power supplies 11 and pulse generation circuits 12, trimming of n resistor elements can be completed at one probe position, so the movement of n probes can be completed in one probe position. Trimming can be done by moving the stage twice, and trimming time is the shortest.
It's practical. Also, since it is a parallel system of n pieces,
The contents of the system are simplified and easy to manufacture. When trimming is performed using this method, conventionally a method is used in which high voltage pulses are applied at regular intervals to obtain a target resistance value.

That is, 300V, 350V, 450V/750V
, 800V, 850V (7), high voltage bar) I/
X (7) The size was changed to keep it within the target resistance value (for example, ±3%). This requires multiple high voltage setting steps and increases pulse generation and measurement waiting time.

Many time-consuming processes such as setting high voltage are required.
Furthermore, since a large number of repeated man-hours are required, the time required for trimming becomes long.

[Objective of the Invention] The object of the present invention is to focus on the point that, as mentioned above, the conventional trimming method using parallel processing applies pulses with different voltage values many times, so that the overall trimming time cannot be shortened. Another object of the present invention is to provide a method for trimming a thick film resistor array, which can significantly reduce the number of pulse applications compared to the conventional method, shorten the overall trimming time, and set a desired resistance value.

[Structure of the invention] A method of trimming a thick film resistor array according to the present invention is as follows.

Measure in advance the curve data of the rate of change in the resistance value of the resistance element when high voltage pulses with different voltage values are applied to each resistance element, measure the initial resistance value of the resistance element to be processed, and calculate its resistance. In order to make the element a desired resistance value, find the rate of change in the first resistance that can correct the resistance value that requires correction by at least 50%, and calculate the rate of change in the first resistance corresponding to the rate of change in the first resistance from the curve data. Select one high voltage pulse, apply this first high voltage pulse multiple times, then calculate the uncorrected resistance in the first correction, and correct the calculated resistance value by at least 50% or more. Find the rate of change of the second resistance obtained, and select the second high voltage pulse corresponding to the new rate of change of resistance obtained by adding the rate of change of the second resistance to the rate of change of the first resistance from the curve data. , this second high voltage pulse is applied to the resistance element multiple times, and a third high voltage pulse corresponding to the rate of change in resistance required to achieve the desired resistance value is selected. This method is characterized in that the resistive element is trimmed by applying a high voltage pulse to the resistive element multiple times.

[Embodiment] Hereinafter, an embodiment of the present invention will be explained with reference to FIGS. 1 and 3 described above.
, 4 will be explained. Among the plurality of resistance elements 2 constituting the resistance array 1, one resistance element 2 is taken out and a high voltage pulse with a constant pulse width is applied to it within the range of Ov to 1000V, for example, as shown in FIG. The voltage is applied to this resistance element 2 in various ways. Curve data indicating the change in resistance value of the resistance element 2 at this time is obtained in advance. That is, for example 20
Data on the percentage change in the resistance value of the resistance element 2 when a high voltage pulse of 0V is applied is obtained in advance.

Specifically, the initial resistance value of the resistance element 2 of the resistance array 1 to be trimmed is measured using the probes 6 and 7 and the resistance measuring device 9. As a result, it is assumed that the target resistance value of the resistance element 2 is 127% of this initial resistance value. Therefore, based on the curve data in Figure 3, the resistance value to be corrected is 60 to 7.
Control bag [10, program power supply ■1 and pulse generation circuit 1]
2, the voltage is applied to the resistive element 2 at least twice, and -1
Trim to 8% 0 then 620 which corresponds to a rate of change of 60-70% of the remaining resistance that needs to be corrected
Apply the high voltage pulse (2) twice to the resistor element 2 in the same way to trim it to -24%, and finally, apply the high voltage pulse of 750V necessary to complete the correction twice to the resistor element 2. Apply the voltage twice to lower the resistance value to -27%. In this way, the resistance change rate due to the second and third trimming is successively reduced to 6% and 3%, so excessive trimming can be prevented, and even with safety in mind, it is much more effective than the conventional method. A desired resistance value can be set with a small number of trimming times (3 times).

In this example, three different high voltage pulses are applied twice each, as shown in Figure 4.
The rate of change in resistance value when the same voltage pulse (400V in this case) is applied to a resistive element multiple times is that most of the trimming effect is obtained when the first high voltage pulse is applied, and saturates after that. The focus is on Therefore, to ensure safety, two pulses are applied to a high voltage that has been set once to completely saturate the trimming, and any subsequent irregular changes in trimming are removed.

In order to select a pulse voltage, determine the number of pulses, and control a series of sequences in accordance with the curve shown in FIG. 3, a microcomputer may be provided in the control device 10, and the control may be performed using the microcomputer.

[Effects of the Invention] As described above, the thick film resistor array trimming method of the present invention applies high voltage pulses with different voltage values to each resistor element to adjust the rate of change in the resistance value of the resistor element. A first resistor that can be measured in advance and corrected by at least 50% or more of the resistance value that is requested to be corrected in order to measure the initial resistance value of the resistance element to be processed and make the resistance element a desired resistance value. Find the rate of change in the first resistance, select a first high voltage pulse corresponding to the rate of change in the first resistance from the curve data,
The first high voltage pulse is applied a plurality of times, the uncorrected resistance is calculated in the first correction, and the change/rate of the second resistance is such that the calculated resistance value can be corrected by at least 50% or more. , select a second high voltage pulse corresponding to a new resistance change rate obtained by adding the second resistance change rate to the first resistance change rate from the curve data, and select this second high voltage pulse. is applied to the resistance element multiple times, and a third high voltage pulse corresponding to the rate of change in resistance required to achieve the desired resistance value is selected, and this third high voltage pulse is applied to the resistance element. The resistive element is trimmed by applying it multiple times.

Therefore, the number of times of trimming can be reduced compared to conventional trimming methods, and the time required for trimming the entire thermal print head can be significantly reduced. Furthermore, an apparatus for carrying out this method can be used by simply modifying a conventional apparatus by changing its sequence.

[Brief explanation of the drawing]

Figure 1 is a diagram schematically showing the basic trimming system, Figure 2 is a diagram showing the basic trimming procedure, and Figure 3 is a diagram showing the basic trimming procedure.
The figure is a graph showing a curve of the rate of change in resistance value with respect to high voltage pulses, and FIG. 4 is a graph showing the change in resistance value with respect to the number of applied pulses. In the drawing, 1 is a resistance array, 2 is a resistance element, 6.7 is a probe, 9 is a resistance measuring device, and 12 is a pulse generation circuit. Patent Applicant: Fujitsu General Co., Ltd. Representative, Patent Attorney: Takuya Ohara Figure 1: Figure 3: Pulse Size (V) Figure 4

Claims (2)

[Claims] (1) In a trimming method in which a predetermined resistance value is set by applying a high voltage pulse to each of the resistive elements of a thick film resistor array in which a plurality of resistive elements are provided on a substrate by thick film printing, the resistive elements are The curve data of the rate of change in the resistance value of the resistor element when high voltage pulses with different voltage values are applied to the resistor element is measured in advance, and the initial resistance value of the resistor element to be processed is measured. To achieve the desired resistance value, the resistance value that requires modification must be at least 5
The rate of change in the first resistance that can be corrected by 0% or more is determined, and the rate of change in the first resistance that corresponds to the rate of change in the first resistance is determined from the curve data.
Select a high voltage pulse of , apply this first high voltage pulse multiple times, then calculate the uncorrected resistance in the first correction, and correct the calculated resistance value by at least 50% or more. A second high voltage pulse corresponding to a new resistance change rate obtained by adding the second resistance change rate to the first resistance change rate from the curve data. This second high voltage pulse is applied to the resistor element multiple times, and a third high voltage pulse is selected that corresponds to the rate of change in resistance required to achieve the desired resistance value. A method for trimming a thick film resistor array, characterized in that the third high voltage pulse is applied to the resistor element multiple times to trim the resistor element. (2) In claim 1, the rate of change in resistance for setting the first and second high voltage pulses is set to a rate of change in resistance of 60 to 70% of the resistance value that requires correction. A method for trimming a thick film resistor array.