Thin-film resistor element and manufacturing method thereof

Abstract

To provide a thin-film resistor element that is set at a high resistance value, and a manufacturing method thereof capable of improving productivity by improving the efficiency of resistance measurement required in a laser trimming process.SOLUTION: The manufacturing method of the thin-film resistor element includes the steps: forming a trimming groove in a thin film resistive layer that is placed on the top surface of an insulating circuit board, and adjusting the resistance value. The manufacturing method also includes the following steps: dividing the thin film resistive layer into multiple successive sections; measuring the resistance value of each section; calculating the resistance of the thin film resistive layer based on the measured values; and feeding back the same for forming a laser trimming groove.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present disclosure relates to a thin-film resistor element having a thin-film resistor pattern formed thereon and a manufacturing method thereof, and more particularly to a thin-film resistor element in which a laser trimming groove is formed in the thin-film resistor pattern to adjust the resistance value to a desired value, and a manufacturing method thereof. [Background technology]

[0002] As electronic devices become smaller and their performance improves, there is a growing demand for smaller and more functional electronic components. Resistive elements are also becoming smaller, and as the power requirements of electronic devices increase, they are being required to have high precision.

[0003] In the past, thin-film resistors using thin-film resistors have been developed to manufacture highly accurate resistors. In these thin-film resistors, the resistor is adjusted to the desired resistance value through a trimming process in which trimming grooves are formed in the thin-film resistor.

[0004] However, among thin film resistor elements, there is a problem in that it is difficult to ensure the precision of the resistor element itself in products with high resistance values.

[0005] Patent Document 1 discloses that in order to provide a resistance element having a high resistance value and improved accuracy, a configuration is adopted in which two resistors, a thick film resistor and a thin film resistor, are connected in series between external terminals, and the thin film resistor region is trimmed to adjust the resistance value to a desired value. [Prior art documents] [Patent documents]

[0006] [Patent Document 1] Japanese Patent Application Publication No. 2018-133554 Summary of the Invention [Problem to be solved by the invention]

[0007] In the trimming process, after forming the resistive layer, grooves (hereinafter referred to as trimming grooves) are formed in the thin-film resistor by fine cutting using a laser (hereinafter referred to as laser trimming) to partially remove the thin-film resistor in order to adjust the resistance value to the desired value.

[0008] To manufacture a high-precision thin-film resistor element, laser trimming is usually performed while measuring the resistance value of the thin-film resistor, and trimming grooves are formed. In this process, when the measured resistance value reaches the target value, the formation of the trimming grooves is stopped, thereby producing a thin-film resistor element with the desired resistance value.

[0009] In thin-film resistor elements set to a high resistance value, when the resistance value is measured in the trimming process, the measured current value varies greatly due to the influence of disturbance factors such as noise, leakage current, etc. For this reason, measures have been introduced to minimize the influence of disturbance factors and leakage current, but these methods result in problems such as the complication of the manufacturing process and redundancy.

[0010] The present invention has been made to solve at least part of the above-mentioned problems, and has an object to realize a manufacturing method that improves productivity in thin-film resistor elements set to a high resistance value. [Means for solving the problem]

[0011] The thin-film resistor according to one embodiment of the present disclosure includes a rectangular substrate, a a thin-film resistor element comprising a pair of upper surface electrodes formed at both ends of the substrate, a thin-film resistor electrically connected to each upper surface electrode and formed on the upper surface of the substrate, and a resin protective film formed to cover the thin-film resistor, wherein the thin-film resistor forms a resistor pattern, and the pattern further forms a conductive path connecting the upper surface electrodes and at least one connection pad portion extending from the conductive path.

[0012] Also, a method for manufacturing a thin-film resistor element includes the steps of forming a rectangular substrate and top electrodes at either end of the top surface of the substrate, forming a pattern of a thin-film resistor so as to be electrically connected to the top electrodes, forming laser trimming grooves in the pattern of the thin-film resistor for adjusting the resistance value, and forming a resin protective film so as to cover the thin-film resistor, wherein the step of forming the laser trimming grooves includes the steps of: arranging a resistance measurement terminal for measuring the resistance value at at least one location in the pattern of the thin-film resistor; measuring the resistance value between one of the top electrodes and the resistance measurement terminal closest to the electrode; measuring the resistance value between the other top electrode and the resistance measurement terminal closest to the other electrode, and forming the laser trimming groove based on the total resistance value of the thin-film resistor obtained by adding up this measurement value and each measurement value in the steps prior to this step.

[0013] In the above-described manufacturing method, it is preferable that the pattern of the thin-film resistor has a conductive path connecting a pair of upper electrodes and at least one connection pad portion extending from this conductive path, and that a resistance measurement terminal is disposed on this connection pad portion.

[0014] According to the above-described thin-film resistor element and method for manufacturing the same, the resistance value of the thin-film resistor, which is essential in the process of forming the laser trimming groove, is measured with high precision, and the process of forming the trimming groove by laser trimming is controlled based on the measurement results.

[0015] Typically, in the manufacturing process of chip resistors set to high resistance values, measurements are performed by applying a small current to the high-resistance resistor. When this occurs, if small noise is introduced into the measurement environment or if leakage current occurs in the pattern or top electrode of the thin-film resistor, it can adversely affect the measurement results of the resistor and the accuracy of the resistor itself. Conversely, to eliminate these disturbance factors, a method has been proposed in which measurements are continued until a stable measurement value is reached. However, this leads to redundancy in the measurement process and increases the lead time of the entire element manufacturing process.

[0016] Furthermore, when measuring resistors, increasing the measurement current causes the resistor itself to heat up during resistance measurement, which causes the resistance value to fluctuate due to the resistor's temperature characteristics. This adversely affects the measurement results of the resistor and becomes a factor that hinders the improvement of the precision of resistor elements.

[0017] In a method for manufacturing a thin-film resistor according to one aspect of the present disclosure, at least one resistance measurement terminal is disposed in the pattern of the thin-film resistor, the resistance value of the thin-film resistor is divided into a plurality of sections, the resistance value of each section is measured in sequence, and the measured resistance values ​​are summed up to measure the entire thin-film resistor. With this method, even for a thin-film resistor with a high resistance overall, the resistance value of each section can be measured with high accuracy by reducing the resistance value of each measurement section, thereby achieving high-accuracy measurement of the entire resistor element.

[0018] The pattern of the thin-film resistor preferably forms a conductive path connecting a pair of upper electrodes and at least one connection pad portion extending from this conductive path. In this pattern, the resistance measurement terminal placed in the trimming process is placed on the connection pad portion, not on the conductive path between the upper electrodes, and measures the resistance value of the thin-film resistor layer in the trimming process. By placing the resistance measurement terminal on the connection pad portion, it is no longer necessary to contact the terminal with the conductive path, This contact can prevent minute scratches from occurring in the conductive path, making it possible to measure the resistance value of the thin-film resistive layer precisely.

[0019] Furthermore, the step of creating the laser trimming groove involves adding up the measurement value of the thin-film resistor between one top electrode and the resistance measurement terminal closest to this electrode on the conductive path, and if resistance measurement terminals are placed in two or more locations, the measurement values ​​of the thin-film resistor between each terminal, and further adding up the measurement value of the thin-film resistor between the other top electrode and the resistance measurement terminal closest to this electrode on the conductive path, and controlling the creation of the laser trimming groove based on the difference between these sum values ​​and the desired resistance value.

[0020] By employing the above-described method for fabricating laser trimming grooves, it is possible to minimize measurement errors in the resistance value of the thin-film resistor and form the laser trimming grooves with fine control, thereby enabling the fabrication of highly accurate thin-film resistor elements.

[0021] In the manufacturing method according to claim 4, in the step of arranging the resistance measurement terminal, the resistance measurement terminal is arranged at only one connection pad portion in the pattern of the thin-film resistor. In this manufacturing method, the thin-film resistor is divided into two sections, namely, between one top electrode and the resistance measurement terminal and between the resistance measurement terminal and the other top electrode, and the resistance value of the thin-film resistor as a whole is measured by summing the measured values ​​of the thin-film resistor in each section. Furthermore, a laser trimming groove is formed while measuring the latter section.

[0022] Furthermore, this manufacturing method makes it possible to simplify the equipment and minimize the time required for resistance measurement compared to when resistance measurement terminals are arranged in multiple locations, and has the unique effect of enabling high-precision thin-film resistance elements to be efficiently manufactured.

[0023] In addition to the step of forming the laser trimming grooves, a manufacturing method according to claim 5 compares the resistance value measured between one upper surface electrode and the resistance measurement terminal with a preset specified resistance value, and forms the laser trimming grooves based on the comparison result, and in this trimming groove forming step, the specified resistance value is determined based on the resistance value between the resistance measurement terminal and the other upper surface electrode. In other words, a laser trimming groove is formed in each measurement section of the resistor divided into two parts as described in claim 4.

[0024] According to the manufacturing method of claim 5, it is possible to optimally arrange the trimming grooves over the entire thin film resistor, which optimizes the conductive path in the thin film resistor and makes it possible to prevent cracks from occurring in the thin film resistor, thereby improving the reliability of the thin film resistor. [Effects of the Invention]

[0025] According to one aspect of the present disclosure, a thin-film resistor element and a manufacturing method thereof can be realized, which can be a highly accurate thin-film resistor element, even if the thin-film resistor element has a particularly high resistance value, and furthermore, can be manufactured efficiently. [Brief explanation of the drawings]

[0026] [Figure 1] FIG. 1 is a cross-sectional view of a thin-film resistor element according to the present invention. [Figure 2] 2A and 2B are schematic diagrams of the upper surface of a rectangular substrate and the upper surface of a substrate on which a conductive layer is formed, respectively. [Figure 3] 3A is a schematic diagram of the upper surface of a substrate on which a thin-film resistor is formed, and FIG. 3B is a schematic diagram of the upper surface of a substrate on which a laser trimming groove is formed in a thin-film resistor layer. DETAILED DESCRIPTION OF THE INVENTION

[0027] A method for manufacturing a thin film resistor element according to an embodiment of the present invention will now be described with reference to the drawings.

[0028] FIG. 1 is a cross-sectional view of a thin-film resistor element according to one embodiment of the present invention. In this figure, a rectangular substrate 11 is formed from an insulating material such as 96-alumina with a purity of approximately 96%. A pair of upper electrodes 12 are formed on both ends of the upper surface of the substrate 11, and are generally arranged on the shorter sides of the upper surface of the rectangular substrate 11. A thin-film resistor 14 covers at least a portion of the upper electrode 12 and is electrically connected to this upper electrode 12. The material and method of forming the thin-film resistor will be described later.

[0029] A resin protective film 16 is formed to cover the thin-film resistor 14. A pair of rear electrodes 17 are formed facing each other at both ends of the rear surface of the substrate 11. A pair of end electrodes 18 are electrically connected to the top electrode 12 and the rear electrode 17, and are formed on the short side surfaces of the rectangular substrate 11. A nickel plating layer 19 covers the surfaces of the top electrode 12, the rear electrode 17, and the end electrodes 18, and a tin plating layer 20 further covers the surface of the nickel plating layer 19.

[0030] Next, a method for manufacturing a thin film resistor element according to one embodiment of the present invention will be described with reference to the cross-sectional view of Figure 1 and the schematic views of Figures 2 and 3. These figures show the top surface of the substrate.

[0031] First, as shown in FIG. 2A , a metal-organic paste containing a precious metal material, such as gold, that is resistant to oxidation in air is screen-printed and dried on both ends of the short sides of the top surface of an insulating substrate 11 made of alumina or the like with a purity of approximately 96%. The organic components of the metal-organic paste are then removed and the metal components are baked onto the substrate 11 at 600–900°C in a belt-type continuous firing furnace, thereby forming top electrodes 12. FIG. 2A shows a rectangular substrate 11 that is the size of a thin-film resistor element, and the following description of the manufacturing process will also use this individual-sized substrate 11. However, in actual manufacturing processes, a sheet-like insulating substrate is used that can be used to obtain multiple individual-sized substrates 11 in the vertical and horizontal directions. The sheet-like insulating substrate is then divided into strips or individual pieces before the end electrode formation process described below.

[0032] The material for forming the upper electrode 12 is not limited to gold-based materials, and other noble metal materials that are resistant to oxidation in air, such as silver, platinum, iridium, and alloys thereof, may also be used.

[0033] 2B, a pattern of thin-film resistors 14 is formed over almost the entire upper surface of substrate 11. In this process, a conductor layer 13 made of a nickel-chromium alloy or the like is formed using a thin-film process such as sputtering, and then unnecessary portions of conductor layer 13 are removed using a photolithography process to form a pattern of thin-film resistors 14 as shown in FIG.

[0034] The pattern of this thin-film resistor 14 has a conductive path connecting one upper surface electrode 121 and the other upper surface electrode 122, and at least one connection pad 15 extending from this conductive path, and a resistance measurement terminal is disposed on this connection pad. Note that, although the pattern in Fig. 3A has only one connection pad 15 formed, multiple connection pads may be provided extending from the conductive path.

[0035] Here, the pattern of the thin film resistor 14 shown in FIG. 3A has a narrow line width of 10 to 20 μm and a complex shape that combines a ladder area (coarse adjustment area) and a fine adjustment area, so it is difficult to form it by a mask sputtering method. Therefore, the thin film resistor 14 is formed by photolithography. It is preferable to form it using a process.

[0036] The material constituting this thin film resistor 14 is not limited to nickel-chromium alloys, and other materials, such as tantalum nitride, chromium silicon, tantalum oxide, or other metal alloys that can be used as resistors, may be used depending on the required characteristics.

[0037] Furthermore, in the above-described embodiment of the present invention, a method has been described in which, after forming top electrode 12, the pattern of thin-film resistor 14 is formed so as to partially overlap top electrode 12. However, this order of steps may be reversed; that is, after forming the pattern of thin-film resistor 14 over the entire top surface of substrate 11, top electrodes 12 may be formed on both ends of the short sides of the top surface of substrate 11.

[0038] Subsequently, a laser trimming process is carried out to form trimming grooves in the thin film resistor 14. This process involves irradiating the thin film resistor 14 with a laser to form trimming grooves and adjust the resistance value of the thin film resistor 14. In detail, this process comprises at least the following steps:

[0039] As a first step, a resistance measurement terminal for measuring the resistance value is disposed on the connection pad portion 15 of the thin-film resistor pattern. In Fig. 3A, the connection pad portion 15 pattern is formed approximately at the center in the longitudinal direction of the thin-film resistor layer formed on the upper surface of the substrate, and the resistance measurement terminal is disposed on this pad portion 15.

[0040] In the second step, a resistance measurement terminal is disposed on the connection pad portion 15, and the resistance value between one of the upper surface electrodes and the resistance measurement terminal is measured in the path of the thin-film resistor 14. In Fig. 3A, the resistance value of the thin-film resistor is measured between one upper surface electrode 121 of the upper surface electrode 12 and the connection pad portion 15 (hereinafter referred to as the first section).

[0041] In this second step, if the resistance value in the first section is close to a preset resistance value, i.e., is within a range that can be adjusted by fine-tuning the resistance value using laser trimming performed in the third step described below, there is no need to perform laser trimming on the first section in this step.

[0042] 3A, i.e., when a ladder area (coarse adjustment area) is set in the first section, the resistance value of the first section is roughly adjusted by laser trimming the ladder area based on the resistance value measured in the first section. In this rough adjustment, laser trimming is performed while measuring the resistance values ​​of one upper surface electrode 121 and connection pad portion 15, and the resistance value is adjusted to fall within a preset range for rough adjustment.

[0043] Next, the third and final step in the laser trimming process is performed, in which the resistance value of the thin-film resistor layer is adjusted by laser trimming so that the resistance value of the thin-film resistor 14, i.e., the resistance value between one upper electrode 121 and the other upper electrode 122, becomes a preset resistance value.

[0044] This step will be described in detail with reference to Fig. 3B. First, in the second step, a resistance measurement terminal disposed on the connection pad 15 is used to measure the resistance between the connection pad 15 and the other upper surface electrode 122 (hereinafter referred to as the second section). The measured resistance value in the second section and the resistance value in the first section measured in the second step are summed, and it is determined whether the resistance value of the thin-film resistor 14 is at a predetermined value.

[0045] In this determination, if the total resistance value of the first section and the second section is different from the predetermined value, Laser trimming grooves are formed in the fine adjustment areas set in the second section, and the resistance value of the second section is adjusted so that the total resistance value reaches a predetermined value. This adjustment is the same as the process described for laser trimming in the second step. That is, as laser trimming progresses, the resistance value of the second section is measured to calculate the total resistance value, and a decision is made as to whether to continue forming laser trimming grooves based on the results of comparing this total resistance value with a predetermined value. When the predetermined value is reached, the laser trimming process is terminated.

[0046] In this embodiment, one connection pad 15 is provided on the pattern of the thin-film resistor 14, and a resistance measurement terminal is disposed to measure the resistance value. A measurement method using multiple connection pads 15 is also possible. For example, in a configuration where two connection pads 15 are provided, the resistance value between one top surface electrode 121 and the connection pad 15 closest to this electrode is measured, and then the resistance value between adjacent connection pads is measured. The sum of these resistance values ​​is calculated. Finally, the resistance value between the other top surface electrode 122 and the connection pad 15 closest to this electrode is measured, and laser trimming is performed based on this value combined with the sum.

[0047] 3A and 3B show a pattern of the thin-film resistive layer that connects the top surface electrodes in a straight line, but instead, in a meandering pattern in which the top surface electrodes are bent at multiple locations, efficient resistance value measurement becomes possible by adopting a configuration in which connection pads 15 are provided at multiple locations. Even with this configuration, the resistance measurement method is the same as the method described above, in which the resistance values ​​of the top surface electrode, connection pad, and two adjacent connection pads are measured sequentially.

[0048] In the above-mentioned laser trimming, sufficient laser power is required to cut off or eliminate the resistor pattern formed by the thin film resistor 14. For this reason, it is preferable to use a YAG laser as the laser for laser trimming, with a laser spot diameter of 20 to 30 μm and a laser output of 0.5 to 2.0 W.

[0049] Furthermore, before laser trimming the thin-film resistor 14, a mask sputtering method may be used to form an inorganic protective film (not shown) made of a highly insulating material such as silicon oxide or alumina to a thickness of 50 nm to 10 μm so as to cover the thin-film resistor 14. Furthermore, after the laser trimming step is completed, a cleaning step may be provided in which the substrate 11 is ultrasonically cleaned using a water-based or alcohol-based cleaning solution to remove scum generated in the laser trimming step. By providing such a cleaning step, scum that can reduce the adhesion of the resin protective film described below is removed, and this is expected to have the effect of further improving the adhesion of the resin protective film.

[0050] After adjusting the resistance value of the thin-film resistor in the laser trimming process, a protective film is formed to protect the thin-film resistor. As shown in Figure 1, a thermosetting resin paste is printed so as to completely cover at least the resistor pattern portion of the thin-film resistor 14, and then hardened to form a resin protective film 16. If necessary, this resin protective film 16 can be printed with a marking indicating characteristics such as the resistance value, or an identification mark used to identify the orientation of the thin-film chip resistor.

[0051] In a mass production line, the resin protective film 16 is not formed independently for each individual region of the substrate 11, but is formed continuously in the vertical direction of the substrate 11, that is, in the direction parallel to the short sides of the substrate 11. This further increases the adhesive strength with the substrate 11.

[0052] 1, a back electrode 17 is formed by screen printing a conductive paste on the back surface of the substrate 11. At this time, as in the above, in a mass production line, The substrate 11 is cut from a sheet state into strips using a dicing method or a breaking method.

[0053] 1, edge electrodes 18 are formed on both end surfaces of the strip-shaped substrate 11 so as to be electrically connected to the top electrode 12 and the back electrode 17, respectively. The edge electrodes 18 are formed by applying and curing a conductive resin paste made of a mixture of, for example, an epoxy-based resin and conductive particles of silver, nickel, carbon, etc. After the edge electrodes 18 are formed, the strip-shaped substrate 11 is divided into individual pieces using a dicing method or a breaking method.

[0054] Finally, as shown in FIG. 1, in order to ensure reliability during soldering, a nickel plating layer 19 is formed on the exposed electrode portions on the top surface, back surface, and end surfaces of the substrate 11, and a tin plating layer 20 is further formed to cover the nickel plating layer 19, thereby completing the thin-film resistor element.

[0055] As described above, the manufacturing method of the present invention not only achieves high precision as a thin-film resistor element, even for a thin-film resistor element set to a high resistance value, but also has the effect of efficiently manufacturing a highly reliable thin-film resistor element. [Explanation of symbols]

[0056] 11 Circuit Board 12 Top electrode 121 One of the upper electrodes 122 Other top electrode 13 Conductor layer 14 Thin film resistors 15 Connection pad section

Claims

1. A thin-film resistor element comprising: a rectangular substrate; a pair of upper surface electrodes formed on either end of the substrate; a thin-film resistor electrically connected to each upper surface electrode and formed on the upper surface of the substrate; and a resin protective film formed to cover the thin-film resistor, The thin film resistor forms a resistor pattern, and this pattern forms a conductive path connecting each upper surface electrode and at least one connection pad portion extending from this conductive path.

2. A method for manufacturing a thin film resistor element, comprising the steps of: forming a rectangular substrate and a pair of upper surface electrodes at either end of an upper surface of the substrate; forming a pattern of a thin film resistor so as to be electrically connected to the upper surface electrodes; forming a laser trimming groove in the pattern of the thin film resistor for adjusting a resistance value; and forming a resin protective film so as to cover the thin film resistor, The step of forming the laser trimming groove includes a step of arranging a resistance measurement terminal for measuring a resistance value at at least one location of the thin film resistor; measuring a resistance value between one of the upper surface electrodes and a resistance measurement terminal closest to the one upper surface electrode; A method for manufacturing a thin-film resistor element, comprising the steps of measuring the resistance between the other top electrode and the resistance measurement terminal closest to this electrode, and forming a laser trimming groove based on the total resistance value of the thin-film resistor obtained by adding up this measurement value and each measurement value in the steps prior to this step.

3. 3. The method for manufacturing a thin film resistor element according to claim 2, wherein the pattern of the thin film resistor has a conductive path connecting a pair of upper electrodes and at least one connection pad portion extending from the conductive path, and a resistance measurement terminal is disposed on the connection pad portion.

4. 4. The method for manufacturing a thin film resistor element according to claim 3, wherein the step of arranging the resistance measuring terminal comprises arranging the resistance measuring terminal at one of the connection pads in the pattern of the thin film resistor.

5. 3. A method for manufacturing a thin-film resistor element according to claim 2, wherein the resistance value measured between one of the upper electrodes and the resistance measurement terminal is compared with a predetermined specified resistance value, a laser trimming groove is formed based on the comparison result, and the resistance value between one of the upper electrodes and the resistance measurement terminal is set to the specified resistance value.

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