JP2737893B2 - Chip resistor - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a chip resistor having a resistor formed on an insulating substrate. Conventionally, in a chip resistor, a resistor formed on a substrate is subjected to resistance trimming with a laser or the like, and then a glass coat is printed and fired on the surface of the resistor. [0003] By the way, a glass coat is applied to the chip resistor, and since the glass coat is formed by a baking treatment, the resistor is also heated during the treatment. Such heating of the resistor, even if the angle resistance value is adjusted with high precision by laser trimming, causes a change in the resistance value after the adjustment, thereby lowering the resistance value accuracy of the manufactured chip resistor. There was a disadvantage. [0004] Further, since the chip resistor is heated by solder reflow when mounted on a circuit board, a sufficient thermal resistance is required. [0005] Further, chip resistors are inspected when they are commercialized, marked with markings such as ratings on the outer surface, and when mounted on a circuit board, the resistors themselves are used. In addition, since the chip resistor is identified by the mark character, the chip resistor which is miniaturized is required to have the distinguishing property. SUMMARY OF THE INVENTION It is an object of the present invention to provide a chip resistor which enhances the protection of the resistor, improves the resistance value accuracy, and has excellent discrimination at the time of mounting and inspection. That is, as shown in FIG. 1, a chip resistor according to the present invention comprises a substrate (2) made of an insulating material and having a plate shape, and a chip resistor on the substrate. A pair of primary electrodes (4, 6) formed on opposing edge portions and facing each other at a fixed interval, and covering a part of the surface of these primary electrodes and printing on the substrate between the primary electrodes; A resistor (8) formed by sintering, and a first resistor that is formed of an insulating material that can be seen through and that covers the surface of the resistor.
And an insulating layer (glass layer 10) formed of a black insulating material formed on the first insulating layer and covering traces of trimming applied to the resistor from above the first insulating layer . 2 insulating layers (glass layers 14), formed on the edge of the substrate from the upper surface of the first electrode to the end surface of the substrate and the back surface thereof, and electrically connected to the primary electrode. And secondary electrodes (16, 18). The resistor on the substrate is covered with the first and second insulating layers and protected by the two-layer insulating layer. In addition, the trimming mark by laser trimming applied to the chip resistor is covered with a black second insulating layer made of an insulating material, thereby preventing deterioration of the resistor due to oxidation or the like from the trimming mark. Since the resistor is covered with the first insulating layer which can be seen through, the resistor is protected from the thermal influence of the baking process when forming the second insulating layer, and the resistance value is prevented from changing. can do. Secondary electrode is 1
Formed on the substrate and the back side from the upper surface of the next electrode
And the secondary electrode is placed on the base from the top of the primary electrode.
Because it is formed on the plate and its back side, the installation strength of the electrodes
And the primary electrode covers the primary electrode.
The pole is protected by the secondary electrode. Moreover, the secondary electrode
Since it is provided on the upper surface, end surface, and back surface of the primary electrode,
Ensure the connection between the resistor and the mounting board to ensure accurate resistance
You can set the value. Further, since the second insulating layer formed of a black insulating material is literally black, if a marking character indicating a rating or the like is given thereon with white paint or the like, the marking character is Sufficient contrast is obtained with the black layer to facilitate identification. In the case of a small chip resistor, identification of the chip resistor itself poses a problem in handling. However, the chip resistor is formed of a second insulating layer made of black insulating material,
Since the insulating layer is black, it is easy to determine the chip resistor, and the visibility such as confirmation of the mounting position is improved. FIG. 1 shows an embodiment of a chip resistor according to the present invention. Rectangular substrate 2 made of insulating material such as alumina
Are formed, and a pair of primary electrodes 4 and 6 are formed at regular intervals between opposing edges of the surface of the substrate 2. On the substrate 2 between the primary electrodes 4 and 6, a resistor 8 is formed across the primary electrodes 4 and 6 by printing and firing. On the surface of the resistor 8, a glass layer 10 as a first insulating layer that covers the entire surface is formed. The glass layer 10 covers almost the entire surface of the resistor 8 and a part of the primary electrodes 4 and 6, and 12 is a cutout formed on the resistor 8 from above the glass layer 10 by laser trimming. . Then, on the upper surface of the glass layer 10, a second glass layer 14 as a protective film that entirely covers the glass layer 10 and the resistor 8 is formed by printing and firing. A glass layer 14 serving as a second insulating layer is embedded in the notch 12, and the surface of the resistor 8 forming a wall surface of the notch 12 is covered with the glass layer 14. The glass layer 14 is made of boric glass or the like, and is set to black or the like. On the end surface of the substrate 2, secondary electrodes 16 and 18 electrically connected to the primary electrodes 4 and 6 are formed by printing or the like for convenience of soldering to a printed wiring board or the like. It is formed by means. The method of manufacturing the chip resistor will be described in the order of manufacturing steps with reference to FIG. 2. As shown in FIG. 2A, the rectangular substrate 2 is formed of an insulating material such as alumina. A pair of primary electrodes 4 and 6 are formed on opposite edges of the surface of the substrate 2. Next, as shown in FIG. 2B, the surface of the substrate 2 between the primary electrodes 4 and 6 is partially covered with the surface of the primary electrodes 4 and 6, and the resistor 8 is fired. I do. The resistor 8 is electrically connected between the primary electrodes 4 and 6, and the primary electrodes 4 and 6 become external terminals directly connected to a conductor such as a circuit board. Next, as shown in FIG. 2C, a glass layer 10 covering the resistor 8 is formed by printing and firing. The glass layer 10 is formed of a borate glass or the like, and is set to a translucent green or the like in order to improve laser absorption. Therefore, the resistor 8 can be visually recognized through the glass layer 10. Next, as shown in FIG. 2D, the resistor 8 is subjected to laser trimming on the glass layer 10 from above.
Adjust the resistance to a predetermined value. Resistor 8 and glass layer 10
The notch 12 formed at the bottom shows a trimming mark. In such a chip resistor, the glass layer 1
0 is subjected to resistance trimming and the glass layer 14 is baked thereon.
When baking, the glass layer 14 functions as a heat shield for the resistor 8. Therefore, the baking of the glass layer 14 can suppress the thermal shock of the resistor 8 as compared with the conventional case, and contribute to reducing the change in the resistance value. Therefore, the resistance value accuracy of the chip resistor can be improved, the yield can be improved, and the resistance value can be easily managed. In the glass layer 10, as in the conventional case, a change in the resistance of the resistor 8 occurs. However, the glass layer 10 is formed before trimming, and the change is in the course of manufacturing. Does not occur. Further, since most of the resistor 8 is covered with the glass layer 10, the second glass layer 14 can be formed thin, and the thickness of the resistor can be increased by forming the glass layer 14. There is no. As described above, according to the present invention, the following effects can be obtained. a. A resistor placed on a flat substrate made of an insulating material is protected by a first insulating layer at the time of trimming, and is firmly provided with first and second insulating layers such as glass having a laminated structure. Therefore, the thermal resistance at the time of mechanical damage or soldering is enhanced, and a change in the resistance value can be prevented. b. Since the resistor is visible through the first insulating layer, the accuracy of laser trimming during the manufacturing process can be increased, and a highly accurate resistance value can be set.
That is, the position of the resistor can be checked through the first insulating layer through the lower resistor, and the operator can start the laser trimming of the resistor from above the first insulating layer during laser trimming. Can be easily set, and laser trimming accuracy can be increased. c. After the laser trimming, the trimming trace of the resistor can be easily confirmed through the first insulating layer, and the trimming failure can be visually recognized. That is, since the cutting state of the resistor and the conductor by laser trimming can be confirmed through the first insulating layer, a trimming defect can be easily found visually, and a highly reliable chip resistor can be provided. d. Since the first insulating layer is covered with the second insulating layer of black color, the inside of the resistor can be concealed with the second insulating layer, and marking characters indicating the rating and the like printed thereon can be used. The visibility of the resistor itself can be improved. That is,
When a marking character made of white or the like is provided on the black second insulating layer, a sufficient contrast can be generated between the marking character and the black insulating layer, so that the identification can be easily performed. In addition, visual processing such as confirmation of a mounting position and inspection of a resistance value is facilitated, and inspection accuracy and inspection efficiency can be improved. e. The secondary electrode is on the top and end faces of the primary electrode and on the back side of the substrate
Electrode, the electrode installation strength is high,
Also, the end face side of the primary electrode is covered by the secondary electrode
The primary electrode can be protected by the secondary electrode
it can. The secondary electrode is the top, end, and base of the primary electrode.
Since it is provided on the back side of the board, the resistor and the mounting board
The connection between the
And an accurate resistance value can be obtained.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a longitudinal sectional view showing one embodiment of a chip resistor according to the present invention. FIG. 2 is a perspective view showing an embodiment of a method of manufacturing the chip resistor shown in FIG. [Description of Signs] 2 Substrates 4, 6 Primary electrode 8 Resistor 10 Glass layer (first insulating layer) 12 Notch (trimming mark) 14 Glass layer (second insulating layer) 16, 18 Secondary electrode

Claims (1)

(57) [Claims] A flat substrate formed of an insulating material; a pair of primary electrodes formed on opposite sides of the substrate facing each other at a predetermined interval; and covering a part of the surface of the primary electrodes. And a resistor formed by printing and firing on the substrate between the primary electrodes, and a resistor formed of an insulating material that is visible through the resistor.
A first insulating layer covering the surface of the resistor; and a first insulating layer formed on the first insulating layer ,
A second insulating layer made of a black insulating material covering a trace of trimming applied to the resistor from above the insulating layer; and an end face of the substrate from an upper surface side of the first electrode on an edge side of the substrate; And a secondary electrode formed on the back side and electrically connected to the primary electrode.