JPH0618121B2 - Chip resistor - Google Patents

Description

Detailed Description of the Invention

[0001]

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.

[0002]

2. Description of the Related Art Conventionally, in a chip resistor, a resistor formed on a substrate is subjected to resistance value trimming with a laser or the like, and then a glass coat is printed and baked on the resistor surface.

[0003]

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

Further, since the chip resistor is heated by solder reflow when it is mounted on the circuit board, sufficient thermal resistance is required.

Further, the chip resistor is inspected when it is commercialized, and marking characters such as ratings are attached to the outer surface of the chip resistor, and the chip resistor is not mounted when the circuit board is mounted. Since it is identified by the resistor itself or its marking character, the distinguishability is required in the miniaturized chip resistor.

Therefore, an object of the present invention is to provide a chip resistor which enhances resistance value resistance, enhances resistance value accuracy, and is excellent in discrimination during mounting and inspection.

[0007]

That is, the chip resistor of the present invention comprises a substrate (2) made of an insulating material and a pair of primary electrodes (4, 6) formed on the substrate so as to face each other. )
A resistor (8) formed on the substrate over the primary electrodes, and a green translucent first glass layer (10) provided so as to cover the surface of the resistor. , A black second glass layer (14) formed on the first glass layer so as to cover the trimming mark (notch 12) formed on the resistor, and the primary electrode electrically. And secondary electrodes (16, 18) connected to the substrate and formed on the edge of the substrate.

[0008]

The resistor on the substrate is covered with the first and second glass layers and is protected by the glass layer having the two-layer structure. Further, the trimming traces of the laser trimming applied to the chip resistor are covered with the second glass layer, and the deterioration of the resistor due to the oxidation or the like from the trimming traces is prevented. Further, since the resistor is covered with the green translucent first glass layer, the resistor is protected from the thermal influence of the firing process when forming the second glass layer, and the resistance value change is prevented. be able to.

Further, since the second glass layer is black, when a mark character indicating the rating or the like is attached to the second glass layer with a paint such as white, the mark character and the second glass layer are separated from each other. Since sufficient contrast can be obtained, the identification becomes easy.

Further, in the case of a small chip resistor, the identification of the chip 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 is black. Can be easily identified, and the visibility such as confirmation of the mounting position can be improved.

[0011]

1 shows an embodiment of the chip resistor of the present invention. A rectangular substrate 2 made of an insulating material such as alumina.
Is formed, and a pair of primary electrodes 4 and 6 are formed with a constant interval between the opposite 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 treatment. A first glass layer 10 is formed on the surface of the resistor 8 so as to entirely cover the surface.
The glass layer 10 covers almost the entire surface of the resistor 8 and part of the primary electrodes 4 and 6, and 12 is a notch 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 which covers the glass layer 10 and the resistor 8 as a whole is formed by printing and baking treatment. A second glass layer 14 is embedded in the notch 12,
The surface of the resistor 8 forming the wall surface of the notch 12 has a glass layer 14
Is covered by.

Then, secondary electrodes 16 and 18 electrically connected to the primary electrodes 4 and 6 are formed on the end face of the substrate 2 by printing or the like for convenience of soldering processing to a printed wiring board or the like. Is formed by means.

A method of manufacturing this chip resistor will be described with reference to FIG. 2 in the order of manufacturing steps. As shown in FIG. 2A, the rectangular substrate 2 is made 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 resistor 8 is fired by covering the surface of the substrate 2 between the primary electrodes 4 and 6 with a part of the surface of the primary electrodes 4 and 6. To do. The resistor 8 is electrically connected between the primary electrodes 4 and 6, and the primary electrodes 4 and 6 serve as external terminals directly connected to a conductor such as a circuit board.

Next, as shown in FIG. 2C, the first glass layer 10 covering the resistor 8 is printed and baked to form the first glass layer 10. The glass layer 10 is formed of boric acid glass or the like, and is set to a semitransparent green 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 to a specified value. Resistor 8 and glass layer 10
The notch 12 formed in 1 shows a trimming mark.

In such a chip resistor, the glass layer 1
Since the resistance value 8 covered with 0 is subjected to resistance value trimming and the glass layer 14 is fired thereon, the glass layer 14
The glass layer 10 functions as a heat shield for the resistor 8 when firing. Therefore, the firing of the glass layer 14 can suppress the thermal shock of the resistor 8 and contribute to the reduction of the resistance value change, as compared with the conventional case. Therefore, the resistance value accuracy of the chip resistor can be improved, the yield is improved, and the resistance value is easily managed. Although the glass layer 10 causes a change in the resistance value of the resistor 8 as in the conventional case, the glass layer 10 is formed before trimming, and the change is in the process of manufacturing. Does not happen.

Since most of the resistor 8 is covered with the glass layer 10, the second glass layer 14 can be thinly formed, and by forming the glass layer 14, the thickness of the resistor can be increased. There is no.

[0019]

As described above, according to the present invention, the following effects can be obtained. a. The resistor placed on the board is green when trimming
Since the resistor is protected by the translucent first glass layer, is covered by the first and second glass layers, and is protected by the glass layer forming the two-layer structure, mechanical damage and soldering are prevented. The thermal resistance at the time of attachment is enhanced, and the change in resistance value can be prevented. b. Since the first glass layer is green translucent , the accuracy of laser trimming during manufacturing can be increased, and a highly accurate resistance value can be set. That is, since the first glass layer is semi-transparent, the resistor under the first glass layer can be seen through and its position can be confirmed, and the operator can perform the first glass layer during laser trimming. The starting position of laser trimming of the resistor can be easily set from above, and laser trimming accuracy can be improved. c. Since the first glass layer is translucent green , it is easy to confirm the trimming trace through the first glass layer after laser trimming, and the trimming failure can be visually recognized. That is, since the first glass layer is semi-transparent, the cutting state of the resistor and the conductor by laser trimming can be easily confirmed from the top of the first glass layer, and the trimming failure can be visually detected and the reliability can be improved. A high chip resistor can be provided. d . Since the second glass layer is black, the inside of the resistor can be concealed by the second glass layer, and at the same time, it is possible to enhance the visibility of the marking characters indicating the rating printed on the resistor and the resistor itself. . That is, when a mark character made of white or the like is attached on the second glass layer which is black, a sufficient contrast can be generated between the mark character and the second glass layer. The identification becomes easy, and the visual processing such as the confirmation of the mounting position and the inspection of the resistance value becomes easy, and the inspection accuracy and the inspection efficiency can be improved.

[Brief description of drawings]

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

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

[Explanation of symbols]

 2 Substrate 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] 1. A substrate formed of an insulating material, a pair of primary electrodes formed facing each other on the substrate, and a resistor formed on the substrate across the primary electrodes. And the first translucent green that is placed over the surface of this resistor.
A second glass layer formed on the first glass layer so as to cover the trimming mark formed on the resistor, and electrically connected to the primary electrode. And a secondary electrode formed on an edge of the substrate.