JP4629356B2 - Manufacturing method of ceramic heater - Google Patents

Description

The present invention relates to a method for manufacturing a ceramic heater. More specifically, the present invention produces a plurality of unfired ceramic heaters using unfired ceramic sheets provided with a plurality of unfired conductor patterns, for example, 5 to 500 unfired conductor patterns. The present invention relates to a method for manufacturing a ceramic heater in which the line width of an unfired conductor pattern is adjusted in advance so that the electrical resistance of the conductor pattern falls within a design value range when the ceramic heater is manufactured by firing.
The present invention can be used in applications such as various sensors for vehicles, heating sources such as heating of glow plugs of diesel engines and heating of semiconductor substrates.

  Conventionally, ceramic heaters are made by applying a conductive paste containing conductive powder such as platinum powder to an unfired ceramic sheet made of highly insulating ceramic such as alumina by screen printing or the like, drying, and then firing integrally. It is manufactured by

  Ceramic heaters are manufactured using unfired ceramic sheets and conductor pastes as described above. Especially, heaters used for various sensors for vehicles, etc., are not prepared individually. It cannot be manufactured efficiently. Therefore, an efficient method is proposed in which a large number of unfired conductor patterns are formed on an unfired ceramic sheet that is large enough to be picked, and then a small piece having each unfired conductor pattern is cut out and then fired. (See, for example, Patent Document 1).

  However, in the method in which a large number of unfired ceramic heaters are cut out from the unfired ceramic sheet and formed simultaneously, the electrical resistance of the conductor pattern of the heater after firing is reduced when repeatedly producing (in other words, mass production) the same number of ceramic heaters. There was a problem (a first problem) that the green ceramic sheets varied. As described above, the electrical resistance of the conductor pattern of the heater obtained varies among the unfired ceramic sheets mainly due to subtle variations in the properties that occur between the raw ceramic sheets and the raw material lots constituting the conductor paste. This is thought to be a major factor. The raw material lot referred to here is a group (unit) prepared by collecting a predetermined amount of raw materials to be an unfired ceramic sheet or an unfired conductor paste for the purpose of producing a plurality of ceramic heaters having the same product number. Further, in the method in which a large number of unfired ceramic heaters are cut out from the unfired ceramic sheet and simultaneously formed, the electrical resistance of the conductor pattern of each heater after firing varies within the same unfired ceramic sheet (second) Problem). This is because it is practically difficult to form a plurality of unfired conductor patterns uniformly at a time when a plurality of unfired conductor patterns are formed on the unfired ceramic sheet by screen printing or the like using a conductor paste. This is due to the fact that

  When the resistance value of the conductor pattern of the heater may be out of the design value range due to the above-described factors, the yield decreases. Therefore, conventionally, an unfired conductor pattern is formed in advance so that the resistance value is lower than the design value, and after firing, the conductor pattern is cut with a YAG laser or the like, and the resistance value is adjusted until it is within the design value range. A so-called trimming method is known.

JP 2000-58237 A

  However, in the trimming method, since a part of the conductor pattern is cut, the resistance value in the vicinity thereof becomes high, and when the conductor pattern is energized, the conductor pattern may be disconnected due to local heat generation. In addition, this trimming method must be performed individually for a large number of small pieces (ceramic heaters), and it takes time to produce ceramic heaters of the same product number, which is preferable in terms of manufacturing efficiency. It was difficult.

  The present invention solves the above-described conventional problems, and manufactures the ceramic heater by adjusting the line width of the unfired conductor pattern for each raw material lot so that the electric resistance of the conductor pattern becomes a set value. An object of the present invention is to provide a method for manufacturing a ceramic heater.

The present invention is as follows.
1. An unsintered ceramic layer comprising a non-sintered ceramic sheet and a plurality of unsintered conductor patterns disposed on the unsintered ceramic sheet is produced, and then the unsintered ceramic layer is formed from the unsintered substrate for the ceramic heater. A plurality of unfired ceramic heaters, and then firing each unfired ceramic heater, and then firing each unfired conductor pattern. Is measured, and then the average value of the electrical resistance of each conductor pattern is calculated. Thereafter, the difference between the average value and the design value of the electrical resistance is reduced. An unfired ceramic substrate for a ceramic heater comprising a plurality of line width adjusted unfired conductor patterns with adjusted line widths From the same raw material lot as the raw material lot from which the green conductor pattern was manufactured, and then from the green substrate for the ceramic heater, the green ceramic layer and the line width disposed on the green ceramic layer Cutting out a plurality of line width adjusted unfired ceramic heaters with adjusted unfired conductor patterns, and then firing each line width adjusted unfired ceramic heater to obtain a ceramic heater,
In obtaining the ceramic heater of the same product number using a plurality of raw material lots, the average value is calculated every time the raw material lots are changed, and thereafter, the difference between the average value and the design value of the electric resistance is reduced. A method of manufacturing a ceramic heater, comprising: forming a plurality of line width adjusted unfired conductor patterns with adjusted line widths to obtain a ceramic heater.
2. From the area of the conductor pattern and the average value, an area where the average value becomes the design value is calculated, and the adjustment value of the line width is set based on the calculated area. A method for producing the ceramic heater according to 1.

According to the ceramic heater manufacturing method of the present invention, a plurality of unfired ceramic heaters are prepared in advance using a specific raw material lot, and the unfired ceramic heaters are fired to measure the average value of the conductor pattern. Using the same raw material lot as the unfired ceramic sheet and the unfired conductor pattern of the unfired ceramic heater prepared in advance, the line width was adjusted so that the difference between the average value and the design value was reduced. An unsintered ceramic heater is prepared after adjusting the line width with the sintered conductor pattern. That is, according to the method for manufacturing a ceramic heater of the present invention, prior to producing an unfired ceramic heater using a specific raw material lot, the average value of the conductor pattern formed when using the raw material is determined in advance. The green ceramic heater is prepared after adjusting the line width so as to reduce the difference between the average value and the design value. This enables the electrical resistance of each ceramic heater to be adjusted to or close to the design value for each raw material lot even if the raw material lots are different when producing the same part number ceramic heater. Variations between raw material lots at the time can be reduced. In addition, each time a raw material lot is changed in this way, the electrical resistance of the conductor pattern is grasped in advance, and the variation between the raw material lots can be reduced simply by producing an unfired ceramic heater after adjusting the line width suitable for the raw material lot. Therefore, it is excellent from the viewpoint of manufacturing efficiency as compared with the case of using the conventional trimming method.
Also, when calculating the area where the average value is the design value from the area of the conductor pattern and the average value, and setting the adjustment value of the line width of the unfired conductor pattern based on the calculated area, a simple method Thus, a ceramic heater having a conductor pattern having a predetermined resistance can be easily obtained. Since the line width of the unfired conductor pattern usually has a size of 10 times or more with respect to the thickness (film thickness), the adjustment of the line width is finer than the adjustment of the film thickness. Adjustment can be performed easily, and consequently the electrical resistance of the conductor pattern can be adjusted easily.

Furthermore, the line width of the unfired conductor pattern provided on both ends is increased and the unfired line width is adjusted so that the difference in electrical resistance between the conductor patterns on the center and both ends on the width direction is reduced. According to the method for manufacturing a ceramic heater of the reference invention obtained by firing the ceramic heater, the resistance of the conductor pattern on both end sides where the electrical resistance tends to increase can be reduced, and the occurrence of defective products can be prevented, or At least, the difference in resistance between the conductor patterns can be reduced.
Also, when the unfired conductor pattern and the line width adjusted unfired conductor pattern are provided by the screen printing method or the sputtering method, the unfired conductor pattern and the line width adjusted unfired conductor pattern on both ends are thin. Therefore, the action and effect of reducing the difference in electrical resistance of the conductor pattern between the center part and both end parts by increasing the line width of the unfired conductor pattern on both ends are more remarkable. is there.

Hereinafter, the present invention will be described in detail.
The “unfired ceramic sheet” is prepared by mixing a ceramic powder, an organic binder, a plasticizer, a solvent, etc., and preparing a slurry by using this slurry, forming a sheet by a doctor blade method or the like, and then drying to form a solvent. Then, it can be formed by a method such as heating to remove the organic binder. Examples of the ceramic powder include alumina, mullite, spinel and the like, and alumina having excellent insulating properties and sufficient heat resistance and mechanical strength is particularly preferable. The slurry may contain a sintering aid. Examples of the sintering aid include silica, calcia, magnesia, and calcium carbonate and magnesium carbonate that become oxides when heated. Only one kind of sintering aid may be used, or two or more kinds may be used.

  The “unfired conductor pattern” has an unfired heat generating portion and unfired lead portions connected to the unfired heat generating portion. The unfired heat generating portion is a portion that becomes a heat generating portion after firing and generates heat when energized. Further, the unfired lead portion becomes a lead portion after firing and is a portion connected to the heater terminal. The unsintered heat generating part and the unsintered lead part may be formed integrally, or each may be formed separately. This unfired conductor pattern can be formed by applying a paste for conductor containing at least a conductive powder on the surface of an unfired ceramic sheet by a screen printing method or the like. The conductive powder is not particularly limited, and examples thereof include platinum, gold, tungsten, and molybdenum. The unfired conductor pattern can also be formed by sputtering or the like using platinum, gold, tungsten, molybdenum, or the like.

  This unfired conductor pattern can also be formed using a paste containing conductive powder and a ceramic component contained in the unfired ceramic sheet. The ceramic component contained in the unfired ceramic sheet is preferably 1 to 30 parts by weight, particularly 3 to 20 parts by weight, when the unfired conductor pattern is 100 parts by weight. If content of a ceramic component is 1-30 mass parts, after baking, a ceramic layer and a conductor pattern will fully adhere | attach, and it can be set as a highly durable ceramic heater.

  The green ceramic sheet is provided with a plurality of green conductor patterns. The number of the unfired conductor patterns is not particularly limited, but may be 5 to 500, particularly 10 to 200. Further, the arrangement of the unfired conductor pattern on the surface of the unfired ceramic sheet is not particularly limited, but usually unfired conductor patterns having the same shape and dimensions are arranged at equal intervals in the vertical direction and the horizontal direction. By doing so, ceramic heaters of the same standard can be mass-produced efficiently.

  The “unfired ceramic heater” is produced by cutting out individual pieces having an unfired ceramic layer and each unfired conductor pattern from an unfired ceramic sheet on which a plurality of unfired conductor patterns are arranged. be able to. This unfired ceramic heater has an unfired ceramic layer and an unfired conductor pattern provided in contact with the surface of the unfired ceramic layer, and firing each unfired ceramic heater to produce a plurality of ceramic heaters Can be manufactured at the same time.

  A plurality of manufactured ceramic heaters measure the electric resistance of the conductor pattern of each ceramic heater, and then calculate the average value of the electric resistance of each conductor pattern, and then the average value and the design of the electric resistance The resistance value is corrected by adjusting the line width of at least the unfired heat generating portion of the unfired conductor pattern so as to make the above-mentioned “line width adjusted unfired conductor pattern” so that the difference from the value becomes small Can do. At this time, the non-fired ceramic heater after the line width adjustment including the line width-adjusted unfired conductor pattern is obtained by measuring the average value of the electrical resistance of the conductor pattern in advance. It is important to produce using the same raw material lot as the conductor paste. In this way, the line width is adjusted, and thereafter the line width adjustment unfired conductor pattern having the adjusted line width is used to adjust the line width and the like of each ceramic heater conductor pattern after firing. As compared with the above, the resistance value of the ceramic heater can be set within the range of the design value very easily, or at least the number of heaters that deviate from the design value can be reduced, and the yield can be improved. In addition, when manufacturing ceramic heaters of the same product number using a plurality of raw material lots, the resistance value of the conductor pattern between the raw material lots is formed by forming the above-described line width adjusted unfired conductor pattern for each raw material lot. Can be effectively suppressed.

  The method of adjusting the line width is not particularly limited, but the area of the conductor pattern of the ceramic heater (the design value of the area of the conductor pattern may be used, or the area of each conductor pattern may be measured and the average calculated from each area value. And an average value of the resistance value, an area where the average value is a design value of the resistance value is calculated, and the line width adjustment value of the unfired conductor pattern is adjusted based on the calculated area Can be set. In this method, the electrical resistance of the conductor pattern of each ceramic heater is shifted upward or downward as a whole, thereby eliminating or at least reducing the ceramic heater having a conductor pattern whose resistance value is out of the design value range. be able to.

By the way, when a large number of unfired conductor patterns are arranged in parallel in the width direction of the unfired ceramic sheet, and this unfired conductor pattern is provided by the screen printing method and the sputtering method, in the central portion in the width direction. The film thickness of the unfired conductor pattern has a predetermined thickness, and tends to be thinner than the predetermined thickness on both ends. Therefore, in the method of this reference invention, the line width of the unfired conductor pattern on both ends in the width direction of the unfired ceramic sheet is made larger than the line width of the unfired conductor pattern in the center, and this adjustment was performed thereafter. A line width adjusted unfired conductor pattern having a line width is used. As a result, the resistance value of the ceramic heater can be made within the range of the design value very easily compared with the case where the line width of the conductor pattern of each ceramic heater is adjusted after firing, or at least the design value of It is possible to reduce the number of heaters that are out of range, and it is possible to effectively suppress variation in the electric resistance of the conductor pattern in the same unfired ceramic sheet. The interval between adjacent unfired conductor patterns and line width adjusted unfired conductor patterns may or may not be constant, but in order to mass-produce ceramic heaters of more stable quality efficiently and easily. Is preferably constant. Further, the method for adjusting the line width of the unfired conductor pattern on both ends in the width direction of the unfired ceramic sheet is the same as the above-described line width adjustment method.

In any of the manufacturing method of the ceramic heater of the present invention and the manufacturing method of the ceramic heater of the reference invention, it is preferable to adjust the line width at least in the unfired heat generating portion. Since the unfired lead part does not affect the heat generation, it is not necessary to adjust the line width, but when the unfired heat generation part and the unfired lead part are formed integrally, the shape of the mask hole of the screen mask is easy For example, the line width of the unfired lead portion can also be adjusted at the same time. On the other hand, when each of the unfired heat generating portion and the unfired lead portion is formed as a separate body, only the line width of the unfired heat generating portion needs to be adjusted.
Note that the resistance measurement of the conductor pattern of the ceramic heater can be performed by a measuring instrument such as a milliohm high tester.

Hereinafter, the present invention will be described in detail by way of examples.
[1] Manufacture of ceramic heater (1) Production of unfired ceramic sheet 97% by mass of alumina powder, 2% by mass of silica powder as a sintering aid and 1% by mass of calcium carbonate powder (the blending amount of the following other components is And 10 parts by mass of polyvinyl butyral as an organic binder, 5 parts by mass of dibutyl phthalate as a plasticizer, methyl ethyl ketone and toluene as a solvent (methyl ethyl ketone / mass by mass ratio). Toluene = 3/2) 50 parts by mass were mixed by a ball mill to prepare a slurry. Then, this was degassed under reduced pressure, and then an unfired alumina sheet having a thickness of 0.6 mm was prepared by a doctor blade method using the slurry depressurized under reduced pressure.

(2) Preparation of Conductive Paste Containing Platinum and Alumina 95% by mass of platinum powder and 5% by mass of alumina powder were mixed with cobblestone and a pot using acetone as a solvent. Thereafter, 10 parts by mass of ethylcellulose and 10 parts by mass of butyl carbitol (100 parts by mass of platinum powder and alumina powder) were blended as an organic binder and further mixed. Subsequently, degassing was performed under reduced pressure, and acetone was volatilized to prepare a conductor paste containing platinum and alumina.

(3) Formation of unsintered conductor pattern and unsintered through-hole conductor From the unsintered alumina sheet prepared in (1) above, as shown in part in FIG. A sheet) 21 is cut out, and the unfired conductor pattern 1 for the unfired ceramic heaters for a total of 80 unfired ceramic heaters is formed on the portion excluding the peripheral portion of the sheet 21 in the horizontal direction and two rows in the vertical direction (2 It was formed by the screen printing method using the conductor paste prepared in (1). In addition, a total of 160 through holes for 80 unfired ceramic heaters are provided in the sheet 21 in advance, and the conductor paste is filled in the through holes together with the formation of the unfired conductor pattern 1, and the unfired through holes are formed. A conductor (this unfired through-hole conductor 13 shown in FIG. 4 constitutes the through-hole conductor after firing) was formed. In addition, the line width of the unsintered heat generating part 11 of the unsintered conductor pattern 1 is 300 μm, the thickness is 20 μm, the line width of the unsintered lead part 12 is 500 μm, and the thickness is 20 μm.

(4) Production of unsintered heater electrode pad Unsintered through-hole conductor 13 on the surface opposite to the surface on which unsintered conductor pattern 1 is formed of sheet 21 on which unsintered conductor pattern 1 is formed as described in (3) above. Using the conductor paste prepared in (2) above, a non-fired heater electrode pad 14 having a length of 1000 μm, a width of 500 μm, and a thickness of 20 μm is formed using the conductor paste prepared in (2) above, as shown in FIG. did.

(5) Fabrication and firing of unfired ceramic heater The sheet 21 on which the unfired conductor pattern 1 was formed as described in (3) above was fabricated in (1) above on the surface on which the unfired conductor pattern 1 was formed. A sheet (non-sintered ceramic sheet) 22 having a size of 300 × 150 mm cut out from the unsintered ceramic sheet was bonded together, and was pressure-bonded while being heated by a pressure-bonding device, thereby producing a laminate having a part shown in FIG. Thereafter, 80 unfired ceramic heaters H (see FIG. 4) are cut out from the laminated body along the cut line 23 shown with the aid of FIGS. , 22 ′, each of the unfired ceramic heaters H provided with the unfired conductor pattern 1 is heated at 400 ° C. for 4 hours in an air atmosphere to remove the organic binder, and then at 1520 ° C. in an air atmosphere. Hold for 2 hours and fire.

[2] Measurement of electric resistance of ceramic heater and adjustment of resistance (1) Method of adjusting resistance by changing line width of all unfired conductor patterns As in (1) to (5) of [1] above The electrical resistance of the 480 ceramic heater conductor patterns manufactured in the above was measured with a milliohm high tester. In this measurement, the probe is brought into contact with a pair of heater electrode pads formed on the ceramic heater, a current of 1 mA is passed through the conductor pattern at room temperature, and the voltage at both ends is measured after 1 second from the start of power supply. This was done by measuring the electrical resistance from the energization current and the voltage at both ends. As a result, the design value is 3.70 ± 0.30Ω (3.40 to 4.00Ω), whereas the minimum value is 3.68Ω, the maximum value is 4.03Ω, and the average value is 3. It was 86Ω. The defective rate was 1%, and the process capability cpk was 0.71.

  The average value of the measured value of electrical resistance is 3.86Ω, which is the central value of the design value, that is, the resistance value is decreased by 4.15% [{(3.86-3.70) / 3. .86} × 100 = 4.15], the area of the unfired conductor pattern may be increased by 4.15%. In the case of this example, calculating based on the shape and area of the unsintered heat generating portion of the unsintered conductor pattern, the line width is increased by 20 μm over the entire length of the unsintered heat generating portion to 320 μm. The area can be increased by 4.15%. Therefore, a ceramic heater was manufactured in the same manner as (1) to (5) of [1] above, except that the line width of the portion corresponding to the unfired heat generating portion of the screen mask used for screen printing was set to 320 μm. The electrical resistance of 480 ceramic heaters was measured in the same manner as in the above (1). As a result, while the design value is 3.70 ± 0.30Ω (3.40 to 4.00Ω), the minimum value is 3.62Ω and the maximum value is 3.91Ω as shown in FIG. The average value was 3.71Ω. Thus, there was no defective product whose resistance value was outside the allowable range, and the process capability cpk was 1.34.

(2) Method of adjusting resistance by increasing the line width of the unfired conductor pattern on both ends The line width of the entire unfired conductor pattern (unfired heat generating part and unfired lead part) is 300 μm, and the thickness is A ceramic heater was manufactured in the same manner as in (1) to (5) of [1] except that the thickness was 25 μm, and the electrical resistance of 80 ceramic heaters was measured in the same manner as in (1) above. As a result, the design value is 2.85 ± 0.20Ω (2.65 to 3.05Ω), whereas the minimum value is 2.68Ω, the maximum value is 3.13Ω, and the average value is 2.2. It was 87Ω. The defect rate was 10% and the process capability cpk was 0.79.

  For one of each sheet from which 80 unfired ceramic heaters can be cut, the correlation between the position of each unfired ceramic heater on the sheet and the electrical resistance of the conductor pattern after firing was examined. As a result, as shown in FIG. 6, the unfired conductor pattern located at the center in the width direction of the unfired ceramic sheet was fired in both cases of 40 in the first row and 40 in the second row. The electrical resistance of the conductor pattern is close to the design value and was not located on both ends (1 to 10, 31 to 40 in the first row, 41 to 50 in the second example, 71 to 80 in FIG. 6). It was found that the electrical resistance of the conductor pattern formed by firing the fired conductor pattern was larger than the design value.

  Therefore, in each of the 40 unfired conductor patterns arranged in the 1st row and the 2nd row of the unfired ceramic sheets, 10 on the right end side (31 to 40, 71 to 80 in FIG. 7) and the left end portion The above (1) to [1] except that a screen mask having mask holes in which the line widths of the 10 unfired conductor patterns on the side (1 to 10, 41 to 50 in FIG. 7) are each increased by 10 μm is used. Ceramic heaters were produced in the same manner as in (5), and the electrical resistance of 80 ceramic heaters was measured in the same manner as in (1) above. As a result, as shown in FIG. 7, the design value is 2.85 ± 0.20Ω (2.65-3.05Ω), whereas the minimum value is 2.70Ω and the maximum value is 2.95Ω. The average value was 2.81Ω. Thus, there was no defective product whose resistance value was outside the allowable range, and the process capability cpk was 1.24.

It is a schematic diagram which shows a part of one surface of the unfired ceramic sheet in which the unfired conductor pattern was formed. It is a schematic diagram which shows the cross section in AA of FIG. It is a schematic diagram which shows a part of other surface of the non-fired ceramic sheet | seat in which the non-fired heater terminal was provided. It is a perspective view of the unfired ceramic heater cut out from the unfired ceramic sheet in which the unfired conductor pattern and the unfired heater terminal were formed. It is a graph which compares and shows the measurement result of the electrical resistance of the ceramic heater manufactured by the normal method, and the ceramic heater manufactured by the method of this invention, and the electrical resistance was adjusted. It is a graph which shows the dispersion | variation in the electrical resistance in the width direction of the unfired ceramic sheet | seat of the ceramic heater manufactured by the normal method. It is a graph which shows the dispersion | variation in the electrical resistance in the width direction of the unfired ceramic sheet | seat of the ceramic heater manufactured by the method of the reference invention, and the electrical resistance was adjusted.

Explanation of symbols

  H: Unsintered ceramic heater, 1; Unsintered conductor pattern, 11; Unsintered heat generating part, 12; Unsintered lead part, 13; Unsintered through-hole conductor, 14; Unsintered heater electrode pad, 21, 22; Ceramic sheets, 21 ', 22'; unfired ceramic layer, 23;

Claims (2)

An unsintered ceramic layer comprising a non-sintered ceramic sheet and a plurality of unsintered conductor patterns disposed on the unsintered ceramic sheet is produced, and then the unsintered ceramic layer is formed from the unsintered substrate for the ceramic heater. A plurality of unfired ceramic heaters, and then firing each unfired ceramic heater, and then firing each unfired conductor pattern. Is measured, and then the average value of the electrical resistance of each conductor pattern is calculated. Thereafter, the difference between the average value and the design value of the electrical resistance is reduced. An unfired ceramic substrate for a ceramic heater comprising a plurality of line width adjusted unfired conductor patterns with adjusted line widths From the same raw material lot as the raw material lot from which the green conductor pattern was manufactured, and then from the green substrate for the ceramic heater, the green ceramic layer and the line width disposed on the green ceramic layer Cutting out a plurality of line width adjusted unfired ceramic heaters with adjusted unfired conductor patterns, and then firing each line width adjusted unfired ceramic heater to obtain a ceramic heater,
In obtaining the ceramic heater of the same product number using a plurality of raw material lots, the average value is calculated every time the raw material lots are changed, and thereafter, the difference between the average value and the design value of the electric resistance is reduced. A method of manufacturing a ceramic heater, comprising: forming a plurality of line width adjusted unfired conductor patterns with adjusted line widths to obtain a ceramic heater.   2. The ceramic according to claim 1, wherein an area where the average value becomes the design value is calculated from the area of the conductor pattern and the average value, and the adjustment value of the line width is set based on the calculated area. A method for manufacturing a heater.

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