Trimming method for a resistor

Abstract

A resistor trimming method for irradiating a resistor (4) of a chip resistor (1) with laser light to form a trimming groove (7; 5, 6) in the resistor (4), thereby adjusting a resistance value of the resistor (4), the chip resistor (1) including an insulating substrate (2), a pair of front electrodes (3) provided on a front surface of the insulating substrate (2), and the resistor (4) connected to the pair of front electrodes (3), wherein: after the laser light has been applied linearly from a side surface of the resistor (4) which is not connected to the front electrodes (3) toward an opposite side surface of the resistor (4) to form a first trimming groove (5), a point returned to from an end point of the first trimming groove (5), the point being different from the end point, is used as a start position to thereby perform scanning with the laser light radiated in a direction intersecting with the first trimming groove (5), to thereby form a wide second trimming groove or second trimming groove (6) which includes at least the end point of the first trimming groove (5).

Description

Technical area

[0001] The present invention relates to a resistor trimming method for irradiating a resistor with laser light to form a trimming groove in the resistor, thereby adjusting a resistance value of the resistor. State of the art

[0002] A chip resistor is basically formed by a cuboid-shaped insulating substrate, a pair of front electrodes, a pair of rear electrodes, end-face electrodes, a resistor, a protective layer, etc. The pair of front electrodes are arranged on a front surface of the insulating substrate, and they face each other with a predetermined interval therebetween. The pair of rear electrodes are arranged on a rear surface of the insulating substrate, and they face each other with a predetermined interval therebetween. The electrodes on the end surface connect or bridge the front electrodes and the rear electrodes, respectively. The resistor bridges or connects the front electrodes that are paired with each other. The protective layer covers the resistor.

[0003] Generally, such a chip resistor is manufactured in the following manner. That is, electrodes, resistors, protective layers, etc., are assembled so that a large number of chip resistors are collectively formed on a large-sized aggregate substrate. Then, the aggregate substrate is divided along dividing lines (e.g., dividing grooves) arranged in a mesh-like pattern, so that the large number of chip resistors can be obtained. In such a chip resistor manufacturing method, a resistor paste is printed and sintered on a surface of the aggregate substrate to thereby form the large number of resistors. However, due to the influence of positional misalignment or blurring during printing or temperature unevenness in a sintering furnace, etc., it is difficult to avoid the formation of some variations in size or film thickness among the resistors.For this reason, it is necessary to perform a resistance value adjustment operation for forming trimming grooves or trenches in each resistor in the state of the aggregate substrate, so as to adjust a resistance value of the resistor to a desired one. The trimming groove or trench is a slit formed by irradiating laser light. Regarding the shape of the slit, it is common to use a trimming method called "L-cutting" or "straight cutting." However, a chip resistor has also been proposed that uses a trimming method called "scanning and cutting" to obtain a resistance value with high accuracy (e.g., see JP H04 168 702 A).

[0004] Fig. 5 is a plan view of a chip resistor 10 disclosed in the aforementioned JP H04 168 702 A. The chip resistor 10 is provided with a pair of front electrodes 12, a resistor 13, etc. The pair of front electrodes 12 are formed on an insulating substrate 11, and they oppose each other with a predetermined interval therebetween. The resistor 13 is shaped like a rectangle bridging the front electrodes. An inverted U-shaped trimming groove 14 is formed in the resistor 13. A resistance value of the chip resistor 10 is regulated by the resistor 13 in which the trimming groove 14 is formed. By the trimming groove 14, the resistor 13 is divided into two parts, that is, a body portion 13a and a cutout portion 13b.A method of forming the trim groove 14 having such a shape will be described below based on FIG. Fig. 6 described.

[0005] First, as in Fig. 6 (a), a location (starting point) S1 at a distance from the resistor 13 on the insulating substrate 11 is irradiated with laser light while measuring terminals (probes) are brought into contact with the pair of front electrodes 12 to measure a resistance value of the resistor 13. On this occasion, the starting point S1 is set at a location slightly spaced from the resistor 13, e.g., an intermittent portion (on a dividing line in Fig. 6) between the resistor 13 and a neighboring resistor 13 to prevent the resistor 13 from being accidentally damaged due to a positional misalignment. As in Fig. As shown in Figure 6(b), the location irradiated with the laser light is shown in the top right corner of Fig. 6(b) from the starting point S1 towards a side surface of the resistor 13. Then, as in Fig. As shown in Fig. 6(c), the location irradiated with the laser light is extended to the inside of the resistor 13 as it is. Consequently, a slit 15 shaped like a straight line perpendicular to a current direction is formed. The resistance value of the resistor 13 is gradually increased due to the slit 15. After the resistance value is increased until the measured resistance value is lower than a target resistance value by a certain degree, the direction of the slit 15 is changed by 90° at a first inflection point T1 so that the slit 15 can be extended in a direction parallel to the current direction, as shown in Fig. 6(c). Consequently, the resistance value is further increased. Then, as shown in Fig. 6(e), the direction of the slit 15 is changed by 90° at a second inflection point T2 and moved downward, thereby forming an inverted U-shaped trimming groove 14. Consequently, the resistor 13 is divided into two portions, i.e., a body portion 13a and a cut-out portion 13b. At this time, the resistance value of the resistor 13 is set to a value (approximately -1% to -5%) slightly lower than the target resistance value. Next, laser light is applied to the body portion 13a side of the trimming groove 14 to gradually trim the body portion 13a, as shown in Fig. 6(f). Consequently, the resistance value of the resistor 13 is adjusted relative to the target resistance value with extremely high accuracy.

[0006] According to such a trimming method, the cutout portion 13b trimmed in an inverted U-shape is provided in a portion of the resistor 13, thereby roughly adjusting the resistance value. Therefore, a time required to perform coarse adjustment of the resistance value can be shortened. In addition, the slit having the inverted U-shape is scanned and gradually linearly cut to be widened. Consequently, the roughly adjusted resistance value is accurately adjusted. Accordingly, the resistance value of the resistor 13 can be quickly and accurately adjusted.

[0007] JP 2001-307912 A describes a method for trimming electronic circuits by which trimming with high accuracy, high productivity, and high yield can be realized, and an electronic circuit device. At the time of fine adjustment of the electronic circuit by cutting the portions to be trimmed by changing the cutting direction from a first direction that crosses the direction of electric current flow to a second direction after coarse adjustment by cutting the portions in the first direction, the electronic circuit is adjusted by starting the fine adjustment trimming cut from a position on the initial end side to which the trimming work has returned from the final end T2 of the coarse adjustment trimming cut.

[0008] DE 198 43 699 A1 describes a chip resistor and methods for adjusting its resistance. The chip resistor consists of a substrate with a pair of electrodes attached to it and a resistor connected to the electrodes. The resistor is formed on the substrate using laser trimming to create grooves that provide the desired pattern and resistance. The pattern itself has a long branch extending from an intermediate point on the resistor to an electrode, and a shorter branch extending between the intermediate point and the longer branch. Citation listPatent literature Patent literature 1: JP H04 168 702 A Patent literature 2: JP 2001-307 912 A Patent literature 3: DE 198 43 699 A1 Summary of the inventionTechnical problem

[0009] In the trimming method known from the prior art from the technical background, which is disclosed in JP H04 168 702 A, the slit of inverted U-shape is formed in the resistor. In this way, the resistance value is roughly adjusted to a value (approximately -1% to -5%) slightly lower than the target resistance value. Then, the slit is scanned and cut to be widened. In this way, the resistance value is finely adjusted to match the target resistance value. Therefore, when trimming is performed, it is necessary to extend the slit in the direction perpendicular to the current direction from the one side surface of the resistor.To extend the resistance, it is necessary to change the direction of the slit at the first inflection point T1 after trimming is performed to increase the resistance value up to approximately -10% with respect to the target resistance value, considering an amount of change (increase amount) of the resistance value caused by the slit behind the first inflection point T1. Accordingly, if the resistance value (initial resistance value) before formation of the trimming groove is lower than -1% with respect to the target resistance value (e.g., -20%), trimming may be performed to form the inverted U-shaped slit in the resistor to roughly adjust the resistance value up to approximately -1% to -5%. Then, the slit may be scanned and cut, thereby adjusting the resistance value with ultra-high accuracy.

[0010] However, since resistors are formed in a large number of chip resistors collectively on a large-sized aggregate substrate, the initial resistance values ​​of all of the resistors are not always lower than -10% with respect to the target resistance value. Due to variations in printing conditions, sintering conditions, etc., the initial resistance values ​​of some of the resistors on the aggregate substrate may be higher than -10% with respect to the target resistance value. In the case where the resistance value of such a resistor is adjusted, the first inflection point T1 coincides with the starting point S1. As shown in Fig. 7(a), no inverted U-shaped slit is formed in the resistor, but scanning and cutting are started suddenly at the starting point S1. Accordingly, a substrate portion from which the resistor is absent is also cut as shown in Fig. 7(b), and the scanning and cutting time required for resistor trimming becomes very long. Accordingly, even if only one resistor like this is present on this substrate, the standby time until the next step on the aggregate substrate as a whole becomes very long, even though the other resistors can be quickly trimmed. Therefore, a problem arises that production efficiency may be affected.

[0011] The invention has been realized in view of the actual circumstances of such a prior art technique. An object of the invention is to provide a resistor trimming method capable of adjusting a resistance value with ultra-high accuracy and having excellent production efficiency. Solution to the problem

[0012] To achieve the above-mentioned object, the invention provides a method for trimming resistors having the features of claim 1 for irradiating a resistance of a chip resistor with laser light to form a trimming groove or a trimming groove in the resistor, thereby adjusting a resistance value of the resistor, the chip resistor including an insulating substrate, a pair of front electrodes provided on a front surface of the insulating substrate, and the resistor connected to the pair of front electrodes, wherein: after the laser light is linearly applied from a side surface of the resistor which is not connected to the front electrodes toward an opposite side surface of the resistor to form a first trimming groove, a point returning from an end point of the first trimming groove,wherein the point different from the end point is used as a starting position to perform scanning with the laser light radiated in a direction intersecting with the first trimming groove, thereby forming a wide second trimming groove or second trimming groove containing at least the end point of the first trimming groove.

[0013] In such a trimming resistance method, scanning and cutting are started at a location that returns by the predetermined amount from the end point of the first trimming groove, and the location is a portion that is small in view of an amount of change in the resistance value in an inter-electrode direction.

[0014] Accordingly, an increase in the resistance value after an inflection point that regulates the end point of the first trimming groove can be suppressed relative to a measured resistance value of the inflection point. Therefore, the resistance value at the inflection point can be brought closer to the resistance value (e.g., approximately -1% to -5% with reference to the target resistance value) at the starting point of scanning and cutting. Accordingly, even if the initial resistance value before starting trimming is relatively high (e.g., approximately -7% with reference to the target resistance value), scanning and cutting can be prevented from starting abruptly, and production efficiency can be made excellent, while the resistance value can be adjusted with very high accuracy by scanning and cutting. Advantageous effects of the invention

[0015] With the resistor trimming method according to the invention, the resistor can be scanned and cut to adjust the resistance value with very high accuracy. In addition, the processing time required for scanning and cutting is shortened, thus improving product effectiveness and efficiency. Brief description of the illustrations [ Fig. 1] A plan view of a resistor to which a trimming method according to a first embodiment of the invention is applied. [ Fig. 2] Explanatory views showing the trimming method according to the first embodiment. [ Fig. 3] Explanatory view showing a trimming method according to a second embodiment of the invention. [ Fig. 4] An explanatory view showing a trimming method according to a third embodiment of the invention. [ Fig. 5] A plan view of a chip resistor to which a trimming method according to a prior art example of the technological background is applied. [ Fig. 6] Explanatory views showing the trimming method according to the prior art example. [ Fig. 7] Explanatory views showing a problem inherent in the prior art example. Description of the embodiments

[0016] Embodiments of the invention will be described with reference to the drawings. As in Fig. 1, a chip resistor 1 to which a trimming method according to a first embodiment of the invention is applied is mainly formed by a cuboid-shaped insulating substrate 2, a pair of front electrodes 3, a rectangular resistor 4, a protective layer (not shown), etc. The pair of front electrodes 3 are provided on longitudinally opposite end portions of a front surface of the insulating substrate 2. The resistor 4 is connected to the pair of front electrodes 3. The protective layer covers the resistor 4. A T-shaped trimming groove 7 consisting of a first trimming groove 5 and a second trimming groove 6 is formed in the resistor 4. A resistance value of the resistor 4 is determined by the trimming groove 7.Incidentally, although not shown, a pair of rear electrodes is provided on a rear surface of the insulating substrate 2, corresponding to the front electrodes 3. End surface electrodes bridge the front electrodes and the rear electrodes, respectively, and are provided on longitudinally opposite end surfaces of the insulating substrate 2, respectively.

[0017] The insulating substrate 2 is made of ceramics, etc. When a large-sized aggregate substrate, which will be described later, is divided along primary division grooves and secondary division grooves extending vertically and horizontally, a large number of insulating substrates 2 can be obtained. The pair of front electrodes 3 is obtained by screen printing, drying, and sintering an Ag paste. The resistor 4 is obtained by screen printing, drying, and sintering a resistance paste made of ruthenium oxide, etc.

[0018] The first trim groove 5 is a narrow slot which extends linearly and outwards from one side surface (lower side in Fig. 1) of the resistor 4. The extending direction of the first trimming groove 5 is perpendicular to a direction of a current flowing in the resistor 4. The second trimming groove 6 is a wide slit extending in a direction parallel to the direction of the current. An end point of the first trimming groove 5 is positioned inside the second trimming groove 6. Although details will be described later, the resistor 4 is cut straight to thereby form the first trimming groove 5, and a wire, which includes scanning and cutting a front end portion of the first trimming groove 5 to thereby form the second trimming groove 6.

[0019] Next, a trimming method with respect to the trimming resistor 1 configured as described above will be described with reference to Fig. 2. Incidentally, although only the insulating substrate 2 is formed into a chip in Fig. 2, a large number of chip resistors 1 are actually manufactured simultaneously or collectively. Therefore, as many chip formation areas as the large number of chip resistors are provided on an aggregate substrate to obtain the large number of chip resistors. In addition, the arrows X1-X2 in Fig. 2 the direction of the current (ie, an inter-electrode direction) flowing in the resistor 4 and arrows Y1-Y2 indicate the direction perpendicular to the direction of the current.

[0020] First, as in Fig. 2(a), a location (starting point) S1 at a distance from the resistor 4 on the insulating substrate 2 is irradiated with laser light, while measuring terminals (probes) are brought into contact with the pair of front electrodes 3 to measure the resistance value of the resistor 4. As shown in Fig. As shown in Fig. 2(b), a location irradiated with the laser light is scanned upwards to the right (in a direction Y1) in Fig. 2(b) from the starting point S1 towards a side surface of the resistor 4. Then, as in Fig. As shown in Figure 2(c), the location irradiated with laser light extends to the inside of the resistor 4 as it is. Consequently, the first trimming groove 5 shaped like a straight line perpendicular to the current direction is formed. Incidentally, although not shown, the resistor 4 is covered with a primer layer (protective layer), and the first trimming groove 5 is formed by laser light applied to the resistor 4 through the primer layer.

[0021] Due to the first trimming groove 5 extending in the Y1 direction, the resistance value of the resistor 4 is gradually increased. After the resistance value is increased to a value (e.g., approximately -7%) lower than a target resistance value by a certain degree, an end point (front end) of the first trimming groove 5 is set as a first inflection point T1, and the location irradiated with the laser light is returned by a predetermined amount from the first inflection point T1 in a direction (Y2 direction) of the start point S1.

[0022] As in Fig. 2(b), the direction of scanning with the laser light is changed by 90° at the return location set as a second inflection point T2, to thereby form a second trimming groove 6 extending in a direction (X1-X2 direction) perpendicular to the first trimming groove 5. Then, scanning and cutting are performed to widen a slit width of the second trimming groove 6 in the Y1 direction. Consequently, as shown in Fig. As shown in Fig. 2(b), the wide second trimming groove 6 covering the end point (first inversion point T1) of the first trimming groove 5 is formed. When the irradiation with the laser light is stopped at a time when the resistance value is increased to match the target resistance value, the trimming groove 7 having the T-shape is formed in the resistor 4. Thus, the trimming process is completed.

[0023] The invention is to provide a resistor trimming method capable of adjusting a resistance value with very high accuracy and having excellent production efficiency. To achieve the object, a starting point at a distance from a resistor is irradiated with laser light, while probes are brought into contact with a pair of surface electrodes to measure a resistance value of the resistor. The location irradiated with the laser light is scanned so that a first trimming groove extending in a direction perpendicular to a current direction can be formed in the resistor. Then, the location irradiated with the laser light is returned to by a predetermined amount from an end point (first turning point) of the first trimming groove to be set as a second turning point.Using the second reversal point as a starting point, scanning and cutting are performed to create a second trim groove. Consequently, the resistance value of the resistor is adjusted to a target resistance value with high accuracy.

[0024] Here, the second return point T2 is a location returned by a predetermined amount from the end point (first return point T1) of the first trimming groove 5 in a direction toward the start point S1. The location is a portion that is small with respect to an amount of change in the resistance value in the inter-electrode direction. Accordingly, the end point of the first trimming groove 5 does not need to be set to approximately -10% with respect to the target resistance value as in the prior art, but the trimming of the first trimming groove 5 can be completed at a time when the measured resistance value is increased to a value up to greater than -10%, for example, up to approximately -7% with respect to the target resistance value, so that the process of scanning and cutting the second trimming groove 6 can be postponed or continued.Accordingly, even if the initial resistance value before the start of trimming is comparatively high, the scanning and cutting can be abruptly suppressed from the beginning, and the manufacturing efficiency can be made excellent while the resistance value can be adjusted with high accuracy by scanning and cutting.

[0025] Incidentally, after such a trimming process (adjustment work for the resistance value) has been performed on all of the resistors 4 on the aggregate substrate, a resin paste such as an epoxy resin-based paste is applied by screen printing and thermally baked to cover the above-indicated primer layer, the resistor 4 and the trimming groove 7, etc. Thus, a covering layer is formed so that the protective covering layer can be formed to have a two-layer structure. Next, the aggregate substrate is divided, primarily to obtain strip-shaped substrates. Then, electrodes are formed on the end faces on divided surfaces of the strip-shaped substrates to connect and bridge the front electrodes 3 and the rear electrodes, respectively. Then, secondarily, the strip-shaped substrates are divided, so that a larger number of chip resistors 1 shown in Fig. 1, can be obtained.

[0026] As described above, in the resistor trimming method according to the first embodiment of the invention, scanning and cutting of the second trimming groove 6 is started at the location (second inflection point T2) that returns by the predetermined amount from the end point (first inflection point T1) of the first trimming groove 5, and the location is a portion that is small in terms of the amount of change in the resistance value in the inter-electrode direction. Accordingly, an increase amount of the resistance value after the inflection point T1, which controls the end point of the first trimming groove 5, can be suppressed relative to a measured resistance value at the inflection point. Therefore, the resistance value at the inflection point can be brought close to the resistance value (e.g., approximately -1% to -5% with respect to the target resistance value) at the start point of scanning and cutting.Accordingly, even if the initial resistance value before the start of trimming is relatively high, for example, approximately -7% with respect to the target resistance value, scanning and cutting can be abruptly suppressed from the start, and production efficiency can be made excellent while the resistance value can be adjusted with very high accuracy by scanning and cutting. Moreover, irradiation of the laser light can be performed continuously from the linear cutting of the first trimming groove 5 to the scanning and cutting of the second trimming groove 6. Therefore, a processing time required for forming the trimming groove 7 can also be shortened from this point of view.

[0027] Incidentally, in the above-mentioned embodiment, a description has been given of the trimming method in which a location returned by the predetermined amount from the end point of the first trimming groove 5 is used as the starting point to perform scanning and cutting, thereby forming the trimming groove 7 having a T-shape as a whole. However, the entire shape of the first trimming groove 5 and the second trimming groove 6 constituting the trimming groove 7 need not always be T-shaped.

[0028] For example, a trim groove 7, as in a second embodiment according to Fig. 3, may be L-shaped overall, and may be formed in such a manner that a location returned to by a predetermined amount from an end point of a first trimming groove 5 is used as a starting point to perform scanning and cutting to form a second trimming groove 6 in an illustrated area on a right side of the first trimming groove 5. Alternatively, as in a third embodiment shown in Fig. 4, a trimming groove 7 may be formed in such a manner that a location returned to by a predetermined amount from an end point of a first trimming groove 5 is used as a starting point to perform scanning and sampling to form a second trimming groove 6 having a circular-arc shape. List of reference symbols 1 chip resistor 2 insulating substrate 3 front electrode 4 Resistance 5 first trim groove 6 second trim groove or trench 7 trim groove S1 starting point T1 first reversal or turning point T2 second reversal or turning point

Claims

A resistor trimming method for irradiating a resistor (4) of a chip resistor (1) with laser light to form a trimming groove (7; 5, 6) in the resistor (4), thereby adjusting a resistance value of the resistor (4), the chip resistor (1) including an insulating substrate (2), a pair of front electrodes (3) provided on a front surface of the insulating substrate (2), and the resistor (4) connected to the pair of front electrodes (3), wherein: after the laser light has been linearly applied from a side surface of the resistor (4) not connected to the front electrodes (3) toward an opposite side surface of the resistor (4) to form a first trimming groove (5), a point returned to from an end point of the first trimming groove (5), the point being different from the end point, is used as a start position,to thereby perform scanning with the laser light radiated in a direction intersecting with the first trimming groove (5), to thereby form a wide second trimming groove or second trimming groove (6) containing at least the end point of the first trimming groove (5).

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