JP2021193710A - Thick film resistor and manufacturing method thereof - Google Patents

Abstract

To provide a thick resistor which can be miniaturized with almost no deterioration in withstand voltage characteristics and surge resistance characteristics, and which has a desired value of resistance and temperature coefficient of resistance and hardly causes the disconnection by sulfurization of an electrode.SOLUTION: A thick film resistor suitably having the form of a square chip resistive body includes: an insulation substrate 21; a thick film resistive body 22 formed on at least one surface of the insulation substrate 21; an electrically insulating first coat layer 23 coating the surface of the thick film resistive body 22 excluding electrode connection surfaces 22a on both ends of the thick film resistive body; and a pair of surface electrodes 24 connected to the electrode connection surfaces 22a on both ends of the thick film resistive body 22 not coated with the first coat layer 23, respectively. The pair of surface electrodes 24 preferably coat surfaces partially on respective both ends of the first coat layer 23.SELECTED DRAWING: Figure 2

Description

The present invention relates to a thick film resistor formed by printing and firing a paste and a method for producing the same.

Chip resistors are widely used in various electronic devices as surface mount type fixed resistors. The chip resistor generally has a rectangular insulating substrate in a plan view, a pair of surface electrodes provided at both ends of the surface of the insulating substrate so as to be separated from each other, and these surface electrodes. It is mainly composed of the provided resistor and the coat layer covering the resistor, and the resistor is formed with a trimming groove for adjusting the resistance value. Further, the chip resistor includes a thin film resistor having a thickness of about 0.001 to 1 μm formed by a thin film forming method such as sputtering, and a resistor having a thickness of about 1 to 20 μm formed by a printing method. It can be roughly classified into a thick film resistor having.

In the latter manufacturing of thick film resistors, a method of simultaneously manufacturing a plurality of thick film resistors from one large insulating substrate is adopted in order to increase productivity. For example, in Patent Document 1, a plurality of pairs of front surface electrodes and a plurality of pairs of back surface electrodes are formed by printing, drying, and firing of an electrode paste on the front surface and the back surface of a ceramic substrate on which division slits extending vertically and horizontally are formed in advance. After that, a resistor paste is printed, dried, and fired so as to straddle the pair of surface electrodes to form a thick film resistor group, and a glass paste is printed on the surface of the obtained thick film resistor group. An undercoat layer group is formed by drying and firing. A trimming groove is formed with a laser beam together with an undercoat layer on each thick film resistor formed above, and then a resin paste is printed and heat-cured to form an overcoat layer group. After that, it is divided into individual chips along the division slit, and a side electrode connecting the front surface electrode and the back surface electrode and a plating layer covering these electrodes are formed to collectively manufacture a plurality of square chip resistors. The method is disclosed.

Japanese Unexamined Patent Publication No. 2015-023095

In recent years, electronic devices have become smaller, lighter, and have higher performance, and along with this, further miniaturization and higher performance are required for thick film resistors, which are one of the main electronic components. .. However, the withstand voltage and surge resistance, which are the electrical characteristics of thick film resistors, are generally superior to those having a resistor with a long effective length, so that the distance between the pair of surface electrodes facing each other is large. The longer one is more advantageous. Therefore, if the thick film resistor is miniaturized, it works disadvantageously on the withstand voltage characteristic and the surge withstand characteristic.

Therefore, in order to prevent the withstand voltage and surge resistance from deteriorating as much as possible when the thick film resistor is miniaturized, the size of the pair of surface electrodes is reduced to make the distance between them as long as possible, and the resistor is a resistor. It is conceivable to secure the above effective length of. However, in the manufacture of a thick film resistor, there is a trimming step of forming a trimming groove by a laser beam in order to correct the resistance value of the resistor, and at that time, the probe is brought into contact with the surface electrode to measure the resistance value. Therefore, if the size of the surface electrode is reduced as described above, the area for contacting the probe becomes smaller, which makes it difficult to measure the resistance value.

Further, in the firing step of the electrode and the resistor in the previous step of the trimming step, a diffusion phenomenon in which the electrode component and the resistor component migrate beyond their boundaries is likely to occur, and this changes the original component composition of the resistor. There will be an area where it will be done. When the thick film resistor is miniaturized, the ratio of the region where the original component composition of the resistor changes increases to the whole resistor, and as a result, the resistance value and the temperature coefficient of resistance (TCR) of the resistor become higher. There may be a problem that the Cofficient of Resistance) fluctuates from the target value. Further, in a chip resistor using Ag or Pd-Ag alloy as the material of the surface electrode, external atmospheric gas containing sulfur (S) may enter from the gap between the coat layer and the plating layer, and as a result. , The surface electrode may undergo sulfide corrosion, leading to disconnection.

The present invention has been made in view of the above circumstances, can be miniaturized with almost no deterioration in withstand voltage characteristics and surge withstand characteristics, has a desired resistance value and temperature coefficient of resistance, and is an electrode. It is an object of the present invention to provide a thick film resistor which is less likely to cause sulfide disconnection.

In order to achieve the above object, the thick film resistor according to the present invention includes an insulating substrate, a thick film resistor formed on at least one surface of the insulating substrate, and the surface of the thick film resistor. It is characterized in that it includes an electrically insulating first coat layer that covers a portion excluding the electrode connecting surfaces at both ends, and a pair of electrodes that are connected to the electrode connecting surfaces at both ends.

Further, the method for manufacturing a thick film resistor according to the present invention includes a thick film resistor forming step of printing a resistor paste on the surface of an insulating substrate and firing it at a predetermined firing temperature to form a thick film resistor. The first coat layer is formed by printing a glass paste on the surface of the thick film resistor excluding the electrode connection surfaces at both ends and firing at a temperature lower than the firing temperature in the thick film resistor forming step. The first coat layer forming step of forming the above and the electrode paste are printed so as to overlap the electrode connecting surfaces at both ends and fired at a temperature lower than the firing temperature of the thick film resistor forming step to form a pair. It is characterized by having a surface electrode forming step of forming a surface electrode.

According to the present invention, a thick film resistor which can be miniaturized without deteriorating the withstand voltage characteristics and surge resistance characteristics, has a desired resistance value and temperature coefficient of resistance, and is less likely to cause disconnection due to sulfide corrosion. Can be provided.

It is a schematic vertical sectional view of a conventional chip resistor. It is a schematic vertical sectional view of the chip resistor of one specific example of this invention. It is a partial cut-out perspective view of the chip resistor of FIG.

Hereinafter, a specific example of the thick film resistor of the present invention will be described by taking a square chip resistor as an example. The thick film resistor of a specific example of the present invention includes an insulating substrate having a rectangular shape in a plan view made of an insulating material such as ceramic, a thick film resistor formed on at least one surface of the insulating substrate, and the thick film resistor. An electrically insulating first coat layer that covers the surface of the body excluding the electrode connection surfaces at both ends in the voltage application direction (direction in which current flows), and the electrodes at both ends of the thick film resistor. It is provided with a pair of electrodes to be connected to each connection surface. With such a configuration, unlike a conventional thick film resistor, it is possible to suppress deterioration of withstand voltage characteristics and surge resistance even if the size is reduced, and it is possible to prevent disconnection due to sulfurization corrosion.

That is, in the conventional thick film resistor, for example, as shown in the square chip resistor of FIG. 1, a pair of surface electrodes provided so as to be separated from each other at both ends on the surface side of the insulating substrate 11 such as ceramic. It is composed of 14 and a thick film resistor 12 provided so as to straddle (cross over) these pair of surface electrodes 14, and both ends of the thick film resistor 12 in the voltage application direction are 1 respectively. It partially overlaps the surface of the pair of surface electrodes 14 on opposite sides.

The surface of the thick film resistor 12 is covered with a first coat layer 13 made of glass over the entire surface, and these thick film resistors are used for adjusting (trimming) the resistance value of the thick film resistor 12. The 12 and the first coat layer 13 are provided with groove-shaped notches (trimming portion 15) formed by laser light. The surface of the first coat layer 13 is entirely covered with the second coat layer 16 made of glass or resin.

A pair of backside electrodes 17 that are separated from each other are provided at both ends on the back side of the chip resistor to which the thick film resistor 12 is not provided, and the pair of backside electrodes 17 and the pair of backside electrodes 17 are separated from each other. A pair of terminal electrodes 18 are provided at both ends of the chip resistor so as to connect the surface electrodes 14 to each other. A plating layer 19 made of nickel plating or the like is formed at each end of the chip resistor so as to cover the front surface electrode 14, the back surface electrode 17, and the terminal electrode 18.

As described above, since the conventional chip resistor is formed so that both ends of the thick film resistor overlap each other on the surface of the pair of surface electrodes, the conventional chip resistor overlaps the surface electrode of the thick film resistor. The portion is not able to fully exert its role as a resistor, so that the effective length of the thick film resistor is shorter than the length from one end to the other in the voltage application direction of the thick film resistor.

As described above, it is advantageous that the effective length of the thick film resistor is long for the surge resistance and withstand voltage characteristics of the resistor. Therefore, the conventional chip resistor having the structure shown in FIG. 1 has the surge resistance and withstand voltage. It was difficult to improve the characteristics. Further, in the conventional chip resistor having the structure of FIG. 1, after forming the surface electrode, the resistor paste is fired at a high temperature to form a thick film resistor, so that the components constituting the surface electrode are transferred to the resistor. (Diffusion) or conversely, the transfer (diffusion) of the components constituting the resistor to the surface electrode may cause the resistance value and temperature coefficient of resistance (TCR) of the thick film resistor to fluctuate from the target values. there were.

On the other hand, the thick film resistor of one specific example of the present invention has a thickness on the surface side of the insulating substrate 21 such as ceramic represented by alumina, as shown in the square chip resistors of FIGS. 2 and 3. The film resistor 22 is provided so as to be in contact with the insulating substrate 21 from one end to the other in the voltage application direction, except for the electrode connection surfaces 22a at both ends of the thick film resistor 22 in the voltage application direction. A pair of surface electrodes 24 are electrically connected to the electrode connection surface 22a, which is not covered with the first coat layer 23 and is covered with an electrically insulating first coat layer 23. ..

The resistance value of the thick film resistor 22 and the first coat layer 23 is adjusted (trimmed) by making a notch with a laser beam, whereby the trimming portion 25 having a substantially L-shaped groove in a plan view 25 is formed. Is provided. Then, the surface of the first coat layer 23 is covered, and the second coat layer 26 made of resin or glass is provided so as to straddle (cross over) the pair of surface electrodes 24.

A pair of back surface electrodes 27 are provided at both ends of the back surface side of the chip resistor to which the thick film resistor 22 is not provided in the voltage application direction, and the pair of back surface electrodes 27 and the above pair are provided. A pair of terminal electrodes 28 are provided at both ends of the chip resistor so as to connect the surface electrodes 24 of the above. At each end of the chip resistor, a plating layer 29 made of nickel plating or the like is formed so as to cover the front surface electrode 24, the back surface electrode 27, and the terminal electrode 28.

As described above, in the thick film resistor of one specific example of the present invention, the stacking order at both ends in the voltage application direction is different from the structure of FIG. Since the layers are laminated from the insulating substrate 21 side in the order of 24, the effective length of the thick film resistor 22 can be made longer than that of the structure of FIG. 1, so that even if the size is the same as that of the conventional chip resistor, it is more excellent. It is possible to provide a chip resistor having electrical characteristics such as surge resistance characteristics and withstand voltage characteristics. In other words, since the size can be reduced without deteriorating the electrical characteristics such as surge resistance and voltage resistance, it is possible to achieve both the miniaturization of the thick film resistor and the high electrical characteristics.

Further, in the thick film resistor of one specific example of the present invention, a pair of surface electrodes 24 are formed on the surface of the thick film resistor 22 at both ends in the voltage application direction, so that the second coat layer is formed. The surface area of the pair of surface electrodes 24 exposed in the state before forming 26 can be made larger than that of the conventional chip resistor having the structure of FIG. 1. As a result, when trimming with laser light, it is possible to secure a sufficient electrode area for abutting the probe for measuring the resistance value. The pair of surface electrodes 24 is not only the electrode connection surfaces 22a at both ends of the thick film resistor 22 in the voltage application direction, but also the surface of the first coat layer 23 in the voltage application direction. Both ends may be partially covered, whereby the surface area of the pair of surface electrodes 24 can be further increased.

Further, in the thick film resistor of one specific example of the present invention, the firing temperature of the electrode paste is set to the firing temperature of the resistor paste in the step of forming the pair of surface electrodes 24 after the formation of the thick film resistor 22 as described later. By lowering the firing temperature below the firing temperature, the components constituting the pair of surface electrodes 24 are transferred (diffused) to the thick film resistor 22, and conversely, the surface of the pair of components constituting the thick film resistor 22. The migration (diffusion) to the electrode 24 can be suppressed. As a result, a chip resistor composed of a pair of surface electrodes 24 and a thick film resistor 22 having desired component compositions can be produced.

Further, the chip resistor of one specific example of the present invention partially covers the surface of each of the pair of surface electrodes 24 in the second coat layer 26 that coats the thick film resistor 22 and the first coat layer 23. Since the thickness of the formed portion can be made thinner than that of the conventional chip resistor having the structure shown in FIG. 1, as a result, it is plated with the second coat layer 26 which is in contact with the surface of each surface electrode 24. The difference in thickness from the layer 29 can be made smaller than that of the conventional chip resistor. As a result, a gap between the second coat layer 26 and the plating layer 29 is less likely to occur.

That is, in the conventional chip resistor having the structure shown in FIG. 1, the second coat layer 16 and the plating layer 19 which are in contact with each other on the surface of each of the pair of surface electrodes 14 have a large difference in thickness. Gap is likely to occur between them, and gas containing sulfur may enter from there, causing sulfur corrosion of the surface electrode 14 and leading to disconnection. On the other hand, in the chip resistor of one specific example of the present invention, the problem of sulfide corrosion is less likely to occur, and thus the surface electrode 24 is less likely to be disconnected, so that the reliability of the chip resistor can be improved.

The thick film resistor 22 constituting the above-mentioned chip resistor contains a solvent and a binder resin as a main component composed of a ruthenium oxide, a conductive powder such as Ag, Pd, and Cu, and an inorganic additive such as glass powder. The resistor paste produced by mixing can be formed by screen-printing, drying if necessary, and then firing. The firing temperature of this resistor paste is preferably 820 to 880 ° C. The glass powder, which is the main component of the above-mentioned resistor paste, preferably has a softening point of 620 ° C. or higher, and more preferably 620 ° C. or higher and 820 ° C. or lower. The film thickness of the thick film resistor 22 is preferably about 1 to 20 μm.

The first coat layer 23 plays a role of insulating the thick film resistor 22 from the surface electrode 24 by covering the surface of the thick film resistor 22 except for the electrode connecting surfaces 22a at both ends thereof. A glass paste prepared by mixing glass powder as the main component, additives such as pigments to be added as appropriate, a solvent and a binder resin is screen-printed, dried as necessary, and then fired to form the paste. Can be done. The firing temperature of this glass paste is preferably 580 to 620 ° C. By lowering the firing temperature when forming the first coat layer 23 to be lower than the firing temperature of the resistor paste described above, it is possible to prevent the original characteristics of the thick film resistor from being impaired. The film thickness of the first coat layer 23 is preferably about 3 to 10 μm.

The pair of surface electrodes 24 are a powdery metal material having a low specific resistance as a main component represented by Au, Ag, Pd, Cu and alloys thereof, a glass powder for bonding to a ceramic substrate, and an inorganic compound. It can be formed by screen-printing an electrode paste prepared by mixing the additives, the solvent and the binder resin of the above, and then firing the electrode paste. As the metal material of the pair of surface electrodes 24, a Pd-Ag alloy containing 0.5 to 20% by mass of Pd and the balance being Ag is generally used.

The firing temperature of the above electrode paste is preferably 580 to 620 ° C. In this way, by lowering the firing temperature when forming the pair of surface electrodes 24 to the firing temperature of the resistor paste described above, the components constituting the pair of surface electrodes 24 can be transferred to the thick film resistor 22. It is possible to suppress migration (diffusion) and conversely, migration (diffusion) of the components constituting the thick film resistor 22 to the surface electrode 24. As described above, the firing temperature at which the first coat layer 23 and the pair of surface electrodes 24 described above are formed by setting the softening point of the glass powder, which is the main component of the resistor paste, to 620 ° C. or higher. In the above, it is possible to suppress the components constituting the pair of surface electrodes 24 from softening to the extent that they diffuse into the inside of the thick film resistor 22.

In the chip resistor of one specific example of the present invention, a pair of backside electrodes 27 are formed on the lower surface side of the insulating substrate 21, and this shape is generally widely adopted. The pair of backside electrodes 27 can be formed by screen-printing an electrode paste containing a powdery metal material having a low specific resistance as a main component, a solvent, and a binder resin, and then firing the electrodes. Ag is the most suitable as the metal material of the back surface electrode 27. By forming the pair of backside electrodes 27 before the step of forming the thick film resistor 22, the firing temperature of the electrode paste at the time of forming the pair of backside electrodes 27 is 820 to 880. Can be ℃.

The second coat layer 26, which covers almost the entire thick film resistor 22 covered with the first coat layer 23 and the pair of surface electrodes 24, serves as an insulating protective layer, and screen-prints the resin paste. It can be formed by heat-curing the glass paste or by screen-printing the glass paste and then firing the glass paste. When it is formed of the former resin paste, it is preferably heat-cured at 150 to 200 ° C. On the other hand, when it is formed of the latter glass paste, it is preferable to carry out the firing treatment at a firing temperature of 580 to 620 ° C. The second coat layer 26 also plays a role of protecting the thick film resistor 22 and the trimming portion 25 of the first coat layer 23.

A pair of terminal electrodes 28 formed in a substantially U-shape in cross section at both ends of the insulating substrate 21 in the voltage application direction serve as a base for the pair of plating layers 29. The pair of terminal electrodes 28 is formed by a thick film film forming method in which the electrode paste is screen-printed and then heat-cured, or the electrode paste is screen-printed and then fired, or a thin film formed by sputtering Ni—Cr or the like. It can be formed by the membrane method. The pair of terminal electrodes 28, the pair of front electrode 24, and the pair of plating layers 29 covering the pair of backside electrodes 27 can be formed by electrolytic plating.

Next, an embodiment of the method for manufacturing a thick film resistor of the present invention will be described by exemplifying a case where the thick film resistor is a square chip resistor shown in FIG. 2. In the manufacture of a square chip resistor as shown in FIG. 2, in general, a plurality of thick film resistors, a plurality of pairs of electrodes, and the like are formed on one large insulating substrate made of ceramic to form a plurality of resistors. A method is adopted in which a large-sized insulating substrate in which body elements are arranged in a matrix is produced, and then the large-sized insulating substrate is divided vertically and horizontally for each of the resistor elements, and a terminal electrode and a plating layer are formed on each of the resistor elements.

That is, in the method for manufacturing a thick film resistor according to the embodiment of the present invention, an insulating substrate preparation for forming a pair of backside electrodes by printing an electrode paste on the back surface of the insulating substrate and firing at a firing temperature of 820 to 880 ° C. A step of forming a thick film resistor by printing a resistor paste on the surface of an insulating substrate and firing at a predetermined firing temperature, and a thick film resistor forming step of forming a thick film resistor, and both ends of the surface of the thick film resistor. A first coat layer forming step of forming a first coat layer by printing a glass paste on a portion excluding the electrode connection surface of the portion and firing at a temperature lower than the firing temperature of the thick film resistor forming step, and the step of forming the first coat layer. A surface electrode that forms a pair of surface electrodes by printing an electrode paste so that it overlaps the electrode connection surfaces at both ends of the thick film resistor and firing at a temperature lower than the firing temperature in the thick film resistor forming step. The forming step, the resistance value adjusting step of trimming the thick film resistor with a laser, the second coat layer forming step of forming the second coat layer covering the first coat layer, and the paired surface. A terminal electrode forming process for forming a pair of terminal electrodes connecting the electrodes and the paired back surface electrodes, and a pair covering the paired front surface electrodes, the paired back surface electrodes, and the paired terminal electrodes, respectively. It has a plating process for forming a plating layer. Hereinafter, each of these steps will be described.

In the insulating substrate preparation step, Ag, Cu, and alloys thereof are formed at positions corresponding to a plurality of thick film resistors formed on the front side of the large rectangular insulating substrate made of ceramic in the subsequent step. The paste is screen-printed and fired at a firing temperature of 820-880 ° C. to form a plurality of pairs of backside electrodes.

In the thick film resistor forming step, a conductive material powder such as ruthenium oxide, Ag, Pd, or Cu, and a glass powder are applied to the front surface side of a large insulating substrate in which the above-mentioned plurality of pairs of back surface electrodes are formed on the back surface side. The resistor paste as the main component is screen-printed, dried as necessary to volatilize the solvent component contained in the resistor paste, and then fired at a firing temperature of 820 to 880 ° C. to obtain a plurality of thick films. Form a resistor.

In the first coat layer forming step, a glass paste containing glass particles as a main component is screened on the surface of each of the plurality of thick film resistors except for the electrode connecting surfaces located at both ends in the voltage application direction. The first coat layer is formed by printing, drying if necessary, and then firing at a firing temperature of 580 to 620 ° C. The firing of the glass paste for forming the first coat layer or the glass paste dry film obtained by drying the glass paste may be performed before printing the electrode paste in the surface electrode forming step of the next step, and will be described later. As described above, the electrode paste printed in the surface electrode forming step or the electrode paste dried film obtained by drying the same may be fired at the same time.

In the surface electrode forming step, both electrode connecting surfaces located at both ends of each of the plurality of thick film resistors in the voltage application direction, and preferably the first coat layer or the dry film before firing thereof in the voltage application direction. A plurality of electrode pastes containing Au, Ag, Cu or alloy powders thereof as main components are screen-printed so as to cover both ends, dried as necessary, and then fired at a firing temperature of 580 to 620 ° C. Form a pair of surface electrodes. As described above, the firing of the electrode paste or the dried film of the electrode paste obtained by drying the electrode paste may be performed separately from the firing of the glass paste or the dried film thereof, or at the same time as the glass paste or the dried film thereof. It may be baked.

In the resistance value adjusting step, in order to adjust the resistance value of each thick film resistor to a desired value, a laser beam is irradiated from above the first coat layer for trimming, and the shape is preferably approximately L-shaped in plan view. A trimming portion consisting of a groove is formed. At the time of this trimming, the resistance value is measured by bringing the probe into contact with the corresponding pair of surface electrodes. If it is not necessary to adjust the resistance value, this resistance value adjustment step is omitted.

In the second coat layer forming step, the heat-curable resin paste or glass paste is screen-printed so as to cover (cross over) the paired surface electrodes while covering the first coat layer, and if it is a heat-curable resin paste, 150 The second coat layer is formed by heat-curing at ~ 200 ° C., and if necessary, drying the glass paste and then firing at a firing temperature of 580 to 620 ° C. As shown in FIG. 2, the second coat layer does not cover both ends of the surface of the paired surface electrodes in the voltage application direction of the chip resistor.

In the terminal electrode forming step, a large insulating substrate is divided into individual thick film resistor elements, and then the paired front electrode and the paired back electrode are connected to each of them. The electrode paste is screen-printed on both ends of the divided insulating substrate in the voltage application direction and heat-cured at 150 to 200 ° C., or fired at a firing temperature of 580 to 620 ° C. A pair of terminal electrodes is formed by a film film forming method or a thin film forming method of sputtering Ni—Cr or the like.

In the plating step, a plating layer is formed by electrolytic plating on the terminal electrodes, the exposed portions of the front surface electrodes not covered with the second coat layer, and the back surface electrodes at both ends of each of the divided resistor elements. In the formation of this plating layer, nickel plating is applied as a base to protect the above three types of electrodes of the thick film resistor, and then tin plating, which is familiar with the solder used for mounting, is applied to the surface of the nickel plating. It is preferable to apply. Through the above series of steps, it is possible to manufacture a plurality of thick film resistors with little variation in quality with high productivity.

[Example 1]
By forming a thick film resistor, a first coat layer, and a surface electrode on the surface of the insulating substrate using the following three types of pastes in the order described, a plurality of thick film resistors for evaluation were produced. Their characteristics were evaluated.

(1) Resistor paste A
The resistor paste for forming the thick film resistor includes R-13U (manufactured by Sumitomo Metal Mining Co., Ltd.), which is a resistor paste with a nominal area resistance of 1000 Ω, and R, which is a resistor paste with a nominal area resistance of 10000 Ω. A mixed resistance paste A having an area resistance value of about 3300 Ω, which was prepared by mixing with -14U (manufactured by Sumitomo Metal Mining Co., Ltd.), was used. The reason for mixing in this way is that, as described later, when a thick film resistor having a distance between electrodes of 0.6 mm and a resistor width of 0.3 mm is manufactured, the resistance value between the electrodes is 6700 Ω. Is. These R-13U, R-14U, and mixed resistor paste A are all resistance pastes suitable for firing treatment performed in an atmospheric atmosphere at a firing temperature of a peak temperature of 850 ° C. over 9 minutes.

(2) Glass paste for the first coat layer The glass paste for forming the first coat layer is Sumitomo Metal Mining Co., Ltd., which is a glass paste suitable for firing treatment performed at a firing temperature of 600 ° C. for 5 minutes in an air atmosphere. I-9760 manufactured by the company was used.

(3) Ag-Pd paste for surface electrodes The electrode paste for forming a pair of surface electrodes is Sumitomo, which is an Ag-Pd paste suitable for firing treatment performed at a firing temperature of 600 ° C. for 5 minutes in an air atmosphere. C-4420 manufactured by Metal Mining Co., Ltd. was used.

The film thickness, area resistance value, and surge characteristics shown below were adopted as the evaluation items of the thick film resistor for evaluation.

(1) Film thickness For each of the five thick film resistors manufactured under the same conditions, the film thickness was measured with a stylus thickness roughness meter (manufactured by Tokyo Precision Co., Ltd., model number: Surfcom 480B). The film thickness was determined by arithmetically averaging the obtained measured values.

(2) Area resistance value For each of the 25 thick film resistors manufactured under the same conditions, the resistance value was measured with a digital multimeter (manufactured by KEITHLEY, No. 2001), and the obtained measured value was obtained. The area resistance value was obtained by adding and averaging.

(3) Surge characteristics The surge characteristics were evaluated by ESD (electrostatic discharge). Specifically, after laser trimming each of the 10 thick film resistors manufactured under the same conditions, static electricity charged at a voltage of 2 KV is discharged to a 200 pF capacitor 5 times, and before and after that. The rate of change of the resistance value in was calculated, and the average value obtained by adding and averaging them was used for evaluation.

The thick film resistor for evaluation was prepared by the following method. First, a thick film resistor with a length of 0.8 mm, a width of 0.3 mm, and a thickness of about 7 μm after firing is formed on the surface of a plan-view square alumina substrate having a side length of 1 inch (25.4 mm) and a thickness of 1 mm. The mixed resistor paste A was screen-printed so as to form a pattern arranged in a matrix of 10 pieces × 3 rows. Next, the solvent contained in the mixed resistor paste A is removed by performing a drying treatment at an atmospheric temperature of 120 ° C. for 10 minutes, and then a baking treatment is performed under an atmospheric atmosphere at a firing temperature of a peak temperature of 850 ° C. for 9 minutes. did. From the 30 thick film resistors formed in this way, 5 were arbitrarily selected and their film thicknesses were measured.

Next, the glass paste for the first coat layer is screened so as to cover the region excluding the range of 0.1 mm from both ends of each of the 30 thick film resistors formed above in the longitudinal direction (voltage application direction). I printed it. At that time, the printing film thickness of the glass paste for the first coat layer was adjusted so that the film thickness after firing was 5 μm. After printing the glass paste for the first coat layer as described above, the glass paste was dried at an atmospheric temperature of 120 ° C. for 10 minutes.

Cover both ends in the longitudinal direction of each thick film resistor that is not covered with the dry film of the glass paste for the first coat layer formed above, and cover the region 0.1 mm from both ends of the first coat layer. Then, after screen printing the Ag-Pd paste for the surface electrode so as to form a pattern in which two squares having a side of 2.5 mm are lined up for each thick film resistor, the drying process is performed at an ambient temperature of 120 ° C. for 10 minutes. Was done.

The dried film of the Ag-Pd paste thus formed was fired together with the dried film of the glass paste for the first coat layer in an air atmosphere at a peak temperature of 600 ° C. for 5 minutes. As a result, a thick film having a thick film resistor electrically connected to a pair of surface electrodes on the electrode connection surface not covered with the first coat layer in the range of 0.1 mm from both ends in the longitudinal direction. Thirty resistors were made. The resistor of each thick film resistor has a length of 0.6 mm width excluding both ends in the longitudinal direction and a region of 0.3 mm covered with a first coat layer, and 1 at both ends in the voltage application direction. Since the pair of surface electrodes are connected at a distance of 0.6 mm between the electrodes, the effective length of the thick film resistor is 0.6 mm.

The resistance values of 25 arbitrarily selected from the 30 thick film resistors prepared above were measured. After measuring this resistance value, in order to adjust the resistance value to 10000Ω, a YAG laser with a wavelength of 1.06 μm is irradiated and laser trimming is performed to form a thick film resistor together with the first coat layer in a substantially L-shape in plan view. A trimming portion composed of grooves was formed. After this laser trimming, the surge characteristics were evaluated by ESD.

[Comparative Example 1]
30 pairs of surface electrodes are placed on the surface of the same alumina substrate as in Example 1, and C-4605, which is an Ag-Pd paste manufactured by Sumitomo Metal Mining Co., Ltd., is placed on one side so that the paired electrodes are separated from each other by 0.3 mm. After screen printing so as to form a pattern in which 2.5 mm squares are lined up in 10 × 6 rows, drying treatment was performed at an ambient temperature of 120 ° C. for 10 minutes. The dried film of Ag-Pd paste thus formed was fired in an air atmosphere at a firing temperature of a peak temperature of 850 ° C. for 9 minutes to form 30 pairs of surface electrodes. C-4605 is an Ag-Pd paste suitable for a baking treatment performed in an atmospheric atmosphere at a firing temperature of a peak temperature of 850 ° C. over 9 minutes.

Next, a mixed resistor paste B in which R-13U and R-14U were mixed so that the area resistance value was about 6600 Ω was prepared, and this was placed at the end of each pair of surface electrodes on opposite sides by 0.1 mm. After screen printing so that the strip-shaped pastes with a width of 0.3 mm are lined up in 10 x 3 rows so as to straddle (cross over) them by stacking them one by one, they are dried and baked in the same manner under the conditions of Example 1. The treatment was performed to form a thick film resistor. At the time of the screen printing, the film thickness after firing was set to about 7 μm.

The glass paste for the first coat layer was screen-printed so as to cover the entire surface of each of the obtained thick film resistors, and dried and fired under the same conditions as in Example 1. In this way, 30 thick film resistors of Comparative Example 1 were produced. The resistor of each thick film resistor has an effective length of 0.3 mm and a width of 0.3 mm because a pair of surface electrodes are connected to both ends in the voltage application direction at a distance between the electrodes of 0.3 mm. After that, in order to measure the resistance value in the same manner as in Example 1 and then adjust the resistance value to 10000Ω, a YAG laser having a wavelength of 1.06 μm is used to form a substantially L-shaped groove in the thick film resistor and the first coat layer. After forming the trimming portion made of, the surge characteristics were evaluated by ESD. The evaluation results are shown in Table 1 below together with the evaluation results of Example 1.

As can be seen from Table 1 above, in Example 1 and Comparative Example 1, the average resistance values after the formation of the first coat layer were almost the same. However, in the evaluation result of EDS after laser trimming, the rate of change of Example 1 is significantly smaller than that of Comparative Example 1, and from this, the thick film resistors of Examples satisfying the requirements of the present invention are compared. It can be seen that the electrical characteristics are superior to those of Example 1.

11, 21 Insulated substrate 12, 22 Thick film resistor 13, 23 First coat layer 14, 24 Front electrode 15, 25 Trimming part 16, 26 Second coat layer 17, 27 Back electrode 18, 28 Terminal electrode 19, 29 Plating Layer 22a Electrode connection surface

Claims (12)

An electrically insulating substrate, a thick film resistor formed on at least one surface of the insulating substrate, and an electrically insulating surface covering the surface of the thick film resistor excluding the electrode connecting surfaces at both ends thereof. A thick film resistor comprising a first coat layer and a pair of electrodes connected to the electrode connecting surfaces at both ends thereof. The thick film resistor according to claim 1, wherein the pair of electrodes partially covers the surfaces of both ends of the first coat layer. The thick film resistor according to claim 1 or 2, wherein the thick film resistor and the first coat layer have a trimming groove formed between the pair of electrodes. The thick film resistor according to any one of claims 1 to 3, wherein the material of the first coat layer is glass. The thick film resistance according to any one of claims 1 to 4, wherein the second coat layer covering the surface of the first coat layer is provided so as to straddle the pair of electrodes. vessel. The thick film resistor according to any one of claims 1 to 5, wherein the material of the second coat layer is glass. A pair of terminal electrodes covering the portion of the pair of electrodes not covered with the second coat layer and the end face of the insulating substrate are provided at both ends of the insulating substrate. , The thick film resistor according to claim 5 or 6. A chip resistor according to any one of claims 1 to 7, wherein the thick film resistor is a chip type. A thick film resistor forming step of printing a resistor paste on the surface of an insulating substrate and firing it at a predetermined firing temperature to form a thick film resistor.
The first coat layer is formed by printing glass paste on the surface of the thick film resistor except for the electrode connection surfaces at both ends and firing at a temperature lower than the firing temperature in the thick film resistor forming step. The first coat layer forming step to be formed and
A surface electrode forming step of forming a pair of surface electrodes by printing an electrode paste so as to overlap the electrode connecting surfaces at both ends and firing at a temperature lower than the firing temperature of the thick film resistor forming step. A method for manufacturing a thick film resistor, which comprises having a thick film resistor. The claim is characterized in that the firing temperature of the resistor paste is 820 to 880 ° C, the firing temperature of the glass paste is 580 to 620 ° C, and the firing temperature of the electrode paste is 580 to 620 ° C. 9. The method for manufacturing a thick film resistor according to 9. The method for manufacturing a thick film resistor according to claim 9 or 10, wherein the firing of the glass paste and the firing of the electrode paste are performed at the same time. Prior to the thick film resistor forming step, there is an insulating substrate preparation step of printing an electrode paste on the back surface of the insulating substrate and firing it at a firing temperature of 820 to 880 ° C. to form a paired back surface electrodes. The method for manufacturing a thick film resistor according to any one of claims 9 to 11, wherein the thick film resistor is manufactured.

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