JPH04355901A - Chip resistor - Google Patents

Abstract

PURPOSE:To obtain a chip resistor having an excellent discriminating property when it is mounted and inspected by strengthening the protection of a resistor element and also by enhancing the accuracy of resistance value. CONSTITUTION:A substrate 2 formed by insulating material, a pair of primary electrodes 4 and 6 opposingly formed on the substrate, a resistor 8 formed on the substrate astriding the above-mentioned primary electrodes, and a first glass layer 10 constituting a semitransparent green provided covering the surface of the above-mentioned resistor, are provided on the title chip resistor. Also, a black-colored second glass layer 14, formed on a first glass layer covering the trace of trimming (a notch 12) provided on the resistor, and secondary electrodes 16 and 18, which are electrically connected to the primary electrode and formed on the edge part of the substrate, are provided in the title chip resistor.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a chip resistor in which a resistor is formed on an insulating substrate.

0002

2. Description of the Related Art Conventionally, chip resistors are manufactured by trimming the resistance value of a resistor formed on a substrate using a laser or the like, and then printing and baking a glass coat on the surface of the resistor.

0003

By the way, a chip resistor is coated with a glass, but since this glass coat is formed by a firing process, the resistor is also heated during the process. Such heating of the resistor causes the resistance value to change after adjustment, even if the resistance value is adjusted with high precision by laser trimming, and the resistance value accuracy of the manufactured chip resistor decreases. There was a drawback.

Furthermore, since chip resistors are heated by solder reflow when mounted on a circuit board, they are required to have sufficient thermal resistance.

Furthermore, chip resistors are inspected when they are manufactured into products, markings such as ratings are placed on their outer surfaces, and chip resistors are inspected when mounted on circuit boards. , because the resistor itself or its marking letters can be identified, so miniaturized chip resistors also require identifiability.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a chip resistor that enhances the protection of the resistor, improves resistance value accuracy, and has excellent identification during mounting and testing.

[0007]

[Means for Solving the Problems] That is, the chip resistor of the present invention includes a substrate (2) formed of an insulating material, and a pair of primary electrodes (4, 6) formed oppositely on this substrate. ), a resistor (8) formed on the substrate spanning between these primary electrodes, and a first glass layer (10) of translucent green disposed covering the surface of this resistor. ), a black second glass layer (14) formed on the first glass layer to cover the trimming marks (notches 12) made on the resistor, and a black second glass layer (14) on the primary electrode. secondary electrodes (16, 18) electrically connected and formed on the edge of the substrate;
It is characterized by having the following.

[0008]

[Operation] The resistor on the substrate is covered with first and second glass layers, and is protected by the two-layer glass layer. Further, the trimming marks caused by laser trimming applied to the chip resistor are covered with a second glass layer, thereby preventing deterioration of the resistor due to oxidation or the like from the trimming marks. Since the resistor is covered with the first glass layer, the resistor is protected from the thermal effects of the firing process when forming the second glass layer, and a change in resistance value can be prevented.

Furthermore, since the second glass layer is black, if a marking letter indicating the rating etc. is attached with white paint etc. on it, there will be a gap between the marking letter and the second glass layer. This provides sufficient contrast for easy identification.

[0010] Also, with small chip resistors, identification of the chip resistor itself becomes a problem in handling, but since the second glass layer forms the exterior of the chip resistor and this glass layer is black, the chip resistor cannot be easily identified. This makes it easier to identify and improve visibility, such as confirming the mounting position.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an embodiment of a chip resistor according to the present invention. A rectangular substrate 2 made of an insulating material such as alumina
A pair of primary electrodes 4 and 6 are formed at a constant interval between opposing edges of the surface of the substrate 2. A resistor 8 is formed on the substrate 2 between the primary electrodes 4 and 6 by printing and firing so as to span each of the primary electrodes 4 and 6. A first glass layer 10 is formed on the surface of this resistor 8, covering the entire surface thereof. This 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 notch formed in the resistor 8 from above the glass layer 10 by laser trimming. . A second glass layer 14 as a protective film that entirely covers the glass layer 10 and the resistor 8 is formed on the upper surface of the glass layer 10 by printing and firing. A second glass layer 14 is embedded in the notch 12 , and the surface of the resistor 8 forming the wall surface of the notch 12 is covered with the glass layer 14 .

A primary electrode 4 is provided on the end surface of the substrate 2.
, 6 are formed by printing or other means to facilitate soldering to a printed wiring board or the like.

The method for manufacturing this chip resistor will be explained in the order of manufacturing steps with reference to FIG. 2. As shown in FIG. 2(A), a rectangular substrate 2 is made of an insulating material such as alumina. A pair of primary electrodes 4 and 6 are formed on opposing edges of the surface of the substrate 2.

Next, as shown in FIG. 2B, a resistor 8 is baked on the surface of the substrate 2 between the primary electrodes 4 and 6, covering part of the surface of the primary electrodes 4 and 6. do. This resistor 8 is electrically connected between the primary electrodes 4 and 6, and the primary electrodes 4 and 6 serve as external terminals that are directly connected to a conductor such as a circuit board.

Next, as shown in FIG. 2C, a first glass layer 10 covering the resistor 8 is printed and fired. This glass layer 10 is formed of boric acid glass or the like, and is set to a translucent green color or the like in order to improve laser absorption.

Next, as shown in FIG. 2D, the resistor 8 is laser trimmed from above the glass layer 10.
Adjust the resistance value to a predetermined value. Resistor 8 and glass layer 10
Notches 12 formed in the cutouts 12 indicate trimming marks.

In such a chip resistor, the glass layer 1
Since the resistance value trimming is performed on the resistor 8 coated with 0 and the glass layer 14 is fired on it, the glass layer 14
The glass layer 10 functions as a heat shield for the resistor 8 during firing. Therefore, the firing of the glass layer 14 can suppress the thermal shock of the resistor 8 compared to the conventional case, and contributes to reducing the change in its resistance value. Therefore, the accuracy of the resistance value of the chip resistor can be improved, the yield is improved, and the resistance value can be easily managed. Note that the glass layer 10 causes a change in the resistance value of the resistor 8 as in the conventional case, but since the glass layer 10 is formed before trimming and the change occurs during the manufacturing process, there may be no inconvenience. Does not occur.

Furthermore, since most of the resistor 8 is covered with the glass layer 10, the second glass layer 14 can be formed thinly, and the thickness of the resistor can be increased by forming the glass layer 14. There isn't.

[0019]

[Effects of the Invention] As explained above, according to the present invention, the following effects can be obtained. a. The resistor installed on the board is the first one during trimming.
The resistor is protected by a glass layer, and is also covered with a first and second glass layer, making it a two-layer structure, which protects the resistor from mechanical damage and heat during soldering. resistance is enhanced and resistance changes can be prevented. b. Since the first glass layer is semitransparent, the accuracy of laser trimming during manufacturing can be improved, and a highly accurate resistance value can be set. That is, since the first glass layer is semi-transparent, the resistor located below the first glass layer can be seen through and its position can be confirmed, and the operator can see through the first glass layer during laser trimming. The laser trimming start position of the resistor can be easily set from above, and the laser trimming accuracy can be improved. b. Since the first glass layer is translucent, after laser trimming, trimming marks can be easily confirmed through the first glass layer, and trimming defects can be visually confirmed. In other words, since the first glass layer is semi-transparent, it is possible to easily check the cutting status of resistors and conductors by laser trimming from above the first glass layer, and it is possible to visually detect trimming defects, which improves reliability. High chip resistors can be provided. c. Since the second glass layer is black, it is possible to hide the inside of the resistor using the second glass layer, and it is also possible to improve the visibility of the markings printed on it that indicate the rating, etc., and of the resistor itself. . That is, when marking characters made of white or the like are attached on the second glass layer which is black, sufficient contrast can be created between the marking characters and the second glass layer. It becomes easier to identify them, and it also becomes easier to perform visual processing such as confirming the mounting position and inspecting the resistance value, thereby improving inspection accuracy and efficiency.

[Brief explanation of drawings]

FIG. 1 is a longitudinal sectional view showing an embodiment of a chip resistor of the present invention.

FIG. 2 is a perspective view showing an embodiment of the method for manufacturing the chip resistor shown in FIG. 1;

[Explanation of symbols]

2 Board 4, 6 Primary electrode 8 Resistor 10 First glass layer 12 Notch (trimming trace) 14 Second glass layer 16, 18 Secondary electrode

Claims (1)

[Claims] Claim 1: A substrate formed of an insulating material, a pair of primary electrodes formed oppositely on this substrate, and
a resistor formed on the substrate spanning between the next electrodes;
A translucent first glass layer is installed to cover the surface of the resistor, and a black second glass layer is formed on the first glass layer to cover the trimming marks made on the resistor. A chip resistor comprising: a glass layer; and a secondary electrode electrically connected to the primary electrode and formed on the edge of the substrate.