JPH05226108A - Rectangular chip resistor and its manufacture - Google Patents

Abstract

PURPOSE:To contrive to surely mount a chip resistor on a printed board by suppressing the inclination of the resistor in longitudinal and transverse directions through providing parts, in which the height of an electrode is made higher than a protective layer, in four corners of the top-face part of the chip resistor. CONSTITUTION:After top-face electrode layers 2 are formed on the surface of 96 alumina substrate 1 by the use of a thick-film silver paste, a thick-film resistive paste mainly composed of RuO2 is used in the manner of overlapping with a part of the top-face electrode layer 2 so that a resistive layer 4 is formed. Then, after an overcoat glass layer 6 is formed in the manner of completely covering the resistive layer 4, the thick-film silver paste is used in the manner of overlapping with a part of the top-face electrode layer 2 so that two pairs of top-face electrode layers 5 are formed. Subsequently, the alumina substrate 1 is divided into strips and the thick-film silver paste is used in the manner of overlapping with parts of the top-face electrode layers 2, 5 so that end-face electrode layers 3 are formed in the side of the strip-shaped alumina substrate. After that, the secondary-substrate division of the strip-shaped alumina substrate is performed so that Ni plating layer and Sn-Pb plating layer are formed in the electrode layers 2, 3, 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rectangular chip resistor used in a high density wiring circuit and a method for manufacturing the same.

[0002]

2. Description of the Related Art In recent years, with the ever-increasing demand for smaller, lighter, smaller electronic devices, in order to increase the wiring density of circuit boards, very small resistors have become widely used as resistive elements. Came. In addition, in recent years, in addition to the conventional one-by-one mounting machine, a collective mounting machine having a higher mounting speed has been widely used in high-density mounting.

An example of the structure of a conventional thick film type rectangular chip resistor is shown in FIGS. 3 (a), 3 (b) and 3 (c). Figure 3
3A is a top view, FIG. 3B is a sectional view taken along the line AA ′ in FIG. 3A, and FIG. 3C is a sectional view taken along the line BB ′ in FIG.

The conventional rectangular chip resistor is a resistor formed by a pair of thick film electrodes formed on a 96 alumina substrate 10 and a ruthenium-based thick film resistor formed so as to be connected to the upper electrode layer 11. It comprises a layer 12, a glass layer 14 covering the resistance layer, and an end face electrode layer 13 overlapping a part of the upper face electrode layer. A Ni plating layer and a solder plating layer are formed on the exposed electrode surface by electrolytic plating to ensure solderability. However, this prismatic chip resistor has a step difference of about 50 μm between the upper electrode layer and the glass layer.

[0005]

Further, when this chip resistor is automatically mounted on a printed circuit board by a collective mounting machine, the chip resistor is mounted so that the front surface side (glass surface side) of the chip resistor is in contact with the printed circuit board. In this case, the probability of occurrence is about 50%. However, if the land pattern and the chip resistor are misaligned at this time, the chip resistor is vertically and horizontally displaced as shown in FIGS. 4 (a) and 4 (b). There is a problem that the tilt occurs, and in the worst case, only one terminal is soldered.

The present invention solves such a problem, and an object of the present invention is to suppress the inclination of the chip resistor even when the chip resistor is mounted face down, and to surely mount the chip resistor on the printed circuit board. ..

[0007]

In order to achieve the above object, a pair of first upper surface electrode layers formed on an insulative substrate, and a resistance layer overlapping a part of the first upper surface electrode layers. A pair of end face electrode layers formed on the end faces of the substrate connected to the first top face electrode layer, and a protective layer that completely covers the resistance layer, and formed so as to partially overlap the first top face electrode layer. The two pairs of second upper surface electrode layers thus formed are characterized in that the upper surfaces thereof project beyond the upper surface of the protective layer.

[0008]

According to the present invention, by providing the upper portion of the chip resistor with the electrode height higher than that of the protective layer at the four corners, even when the chip resistor is mounted face down, By suppressing the inclination of the chip resistor in the direction, the chip resistor is surely mounted on the printed circuit board.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A rectangular chip resistor according to an embodiment of the present invention and a method of manufacturing the same will be described below with reference to the drawings.

FIG. 1A is a top view showing an embodiment of the present invention, and FIG. 1B is a sectional view taken along the line AA 'in FIG.
FIG. 1C is a cross-sectional view taken along the line BB ′ of FIG.

1 (a), 1 (b) and 1 (c), a rectangular chip resistor according to the present invention comprises a 96 alumina substrate 1 and a pair of first silver-based thick films on the 96 alumina substrate 1. A top surface electrode layer 2, a ruthenium-based thick film resistance layer 4 overlapping a portion of the first top surface electrode layer 2, a glass layer 6 that completely covers the resistance layer 4, and a top surface of the first top surface electrode layer 2. Two pairs of the second upper surface electrode layer 5, the first upper surface electrode layer 2, and the second upper surface electrode layer 5 that are formed and are arranged at the four corners of the rectangular chip resistor.
Of the end face electrode layer 3 made of a silver-based thick film that partially overlaps with. The exposed electrode surface is electrolytically plated with a Ni plating layer and a Sn-Pb plating layer in order to improve solderability. Here, the height of the upper surface electrode portion is configured to be higher than the height of the glass portion, and even when the chip resistor is mounted face down, inclination of the chip resistor in the vertical and horizontal directions can be suppressed.

Next, a manufacturing method of the first embodiment of the present invention shown in FIG. 1 will be described. First, the 96 alumina substrate 1 having excellent heat resistance and insulating properties is received. In order to divide the alumina substrate 1 into strips and individual pieces, grooves for division (molding at the time of green sheet) are formed. Next, a thick film silver paste was screen-printed on the surface of the 96 alumina substrate 1 and dried, and a belt type continuous firing furnace was used at a temperature of 850 ° C. for a peak time of 6 minutes, I.
The first upper surface electrode layer 2 was formed by firing according to the profile of N-OUT 45 minutes. Next, a thick film resistance paste containing RuO ₂ as a main component is screen-printed so as to overlap a part of the first upper surface electrode layer 2, and the thick film resistance paste is formed by a belt-type continuous firing furnace.
The resistance layer 4 was formed by firing at a temperature of 50 ° C. according to a profile with a peak time of 6 minutes and IN-OUT 45 minutes. Next, in order to make the resistance value of the resistance layer 4 between the first upper surface electrode layers 2 uniform, a part of the resistance layer 4 is destroyed by laser light to correct the resistance value (L cut, 100 mm / sec, 12
KHZ, 5W). Subsequently, a lead borosilicate glass paste was screen-printed so as to completely cover the resistance layer 4, and a belt-type continuous firing furnace was used to perform a firing profile at a temperature of 590 ° C. for a peak time of 6 minutes and IN-OUT 50 minutes. Firing was performed to form the overcoat glass layer 6. Next, a thick film silver paste is screen-printed and dried so as to overlap a part of the upper electrode layer 2, and the temperature is set to 600 ° C. in a belt-type continuous firing furnace for a peak time of 6 minutes.
Two pairs of second upper surface electrode layers 5 were formed by firing according to the profile of IN-OUT 45 minutes. Next, as a preparatory step for forming the end face electrodes, the alumina substrate 1 was divided into strips to expose the end face electrodes to obtain strip-shaped alumina substrates. A thick film silver paste is applied to the side surface of the strip-shaped alumina substrate by a roller so as to partially overlap the first upper surface electrode layer 2 and the second upper surface electrode layer 5, and the temperature is set to 600 ° C. by a belt-type continuous firing furnace. Then, the end face electrode layer 3 was formed by firing according to a firing profile with a peak time of 6 minutes and IN-OUT 45 minutes. Next, as a preparatory step for electrode plating, the strip-shaped alumina substrate on which the end face electrode layer 3 had been formed was divided into individual secondary substrates to obtain individual alumina substrates. Finally, in order to prevent electrode erosion during soldering of the exposed first upper surface electrode layer 2, second upper surface electrode layer 5, and end surface electrode layer 3 and to secure reliability of soldering, electrolytic plating is performed. Ni plating layer and Sn
-Pb plating layer was formed.

Through the above steps, a rectangular chip resistor according to an embodiment of the present invention was prototyped. 2 (a) and 2 (b) show a state in which the rectangular chip resistor according to the embodiment of the present invention is mounted on the land pattern in a face down manner. It can be seen that the chip resistor has a small inclination and is reliably soldered to the printed circuit board, and the effect of the present invention is exhibited.

Further, by making the distance between one pair and the other pair of the second upper surface electrode layers 5 smaller than the outer diameter of the suction nozzle 7 of the mounting machine, as shown in FIG. The suction nozzle 7 of the machine does not directly hit the overcoat glass layer 6, and defective glass chips during mounting can be greatly reduced.

In the embodiment, the second upper electrode layer 5 is formed by firing at a temperature of 600 ° C. after forming the glass layer 6, but it may be fired at a temperature in the range of 580 ° C. to 640 ° C. ( The electrode strength deteriorates at 580 ° C or lower to 640 ° C.
With the above, the resistance characteristics deteriorate).

[0016]

As is apparent from the above description, according to the rectangular chip resistor of the present invention, the second upper surface electrode layer in which the height of the electrode is higher than that of the protective layer is provided at the four corners of the upper surface portion of the chip resistor. By providing the chip resistor, even if the chip resistor is mounted face down, it is possible to obtain the effect that the chip resistor can be reliably mounted on the printed circuit board by suppressing the inclination of the chip resistor in the vertical and horizontal directions.

Further, by making the distance between one pair and the other pair of the upper surface electrode layers smaller than the outer diameter of the suction nozzle of the mounting machine, the suction nozzle of the mounting machine does not directly contact the overcoat glass layer. , Glass chip defects during mounting can be greatly reduced.

[Brief description of drawings]

1A is a top view showing the structure of a rectangular chip resistor according to an embodiment of the present invention, FIG. 1B is the same sectional view, and FIG. 1C is the same sectional view.

FIG. 2 (a) is a side view showing a state where the equilateral chip resistors are mounted on the land pattern face down, and FIG. 2 (b) is a side view showing the equilateral chip resistors mounted on the land pattern face down. (C) is an explanatory view showing a state in which the equilateral rectangular chip resistor is adsorbed by the adsorption nozzle of the mounting machine.

3A is a top view showing the structure of a conventional rectangular chip resistor, FIG. 3B is the same sectional view, and FIG. 3C is the same sectional view.

FIG. 4 (a) is a lateral view showing a state where a conventional rectangular chip resistor is mounted on a land pattern face down. FIG. 4 (b) is a conventional rectangular chip resistor faced on the land pattern face down. Explanatory view seen from the vertical direction showing the mounted state

[Explanation of symbols]

 1 96 Alumina substrate 2 1st upper surface electrode layer 3 end surface electrode layer 4 resistance layer 5 2nd upper surface electrode layer 6 overcoat glass layer 7 adsorption nozzle

Claims (3)

[Claims] 1. A pair of first upper surface electrode layers formed on an insulative substrate, a resistance layer overlapping a part of the first upper surface electrode layer, and a substrate end surface connected to the first upper surface electrode layer. The pair of end surface electrode layers formed on the first surface electrode layer and the protective layer that completely covers the resistance layer, and the pair of second upper surface electrode layers formed so as to partially overlap the first upper surface electrode layer are A rectangular chip resistor having an upper surface protruding more than the upper surface of the protective layer. 2. The second upper surface electrode layer is formed of a glass layer 58 after formation of the glass layer.
The method for manufacturing a rectangular chip resistor according to claim 1, wherein the film is formed at a firing temperature of 0 ° C to 640 ° C. 3. The rectangular chip resistor according to claim 1, wherein a distance between one pair and the other pair of the second upper surface electrode layers is smaller than an outer diameter of the suction nozzle of the mounting machine.