JPH03212901A - Square board type chip resistor - Google Patents

Abstract

PURPOSE:To reduce irregularities of a glass surface and to realize high precision of packaging without increasing dispersion of resistance values and deteriorating oxide resistance of glass by providing a specified three layer glass layer of specified softening point and linear expansion coefficient on a thick film resistance layer. CONSTITUTION:An upper surface electrode 2 is formed on 96 alumina substrate 1 and a thick film resistance layer 4 mainly composed of RuO2 is formed partially overlapping thereon. A first glass layer 5 is formed thereon, whose glass softening point is 550 to 570 deg.C and linear expansion coefficient is 69X10<-7> to 7<5>X10<-7>/ deg.C. An imprinting glass layer 6 having a softening point of 550 to 570 deg.C and linear expansion coefficient of 68X10<-7> to 74X10<-7>/ deg.C and a second glass layer 7 having a softening point of 580 to 630 deg.C and linear expansion coefficient of 62X10<-7> to 68X10<-7>/ deg.C are formed thereon. An edge surface electrode layer 3 is formed, which partially overlaps with the layer 7 and the electrode layer 2. Since a softening point of the first glass layer 5 is lower than that of the second glass layer 7, the imprinting glass layer 6 sinks to the layer 5 and irregularities of a surface reduce, thereby preventing development of cracks on the surface.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a square plate type chip resistor that is mainly mounted on a high-density wiring circuit (hybrid IC, etc.) by an automatic mounting machine.

Conventional technology In recent years, as the demand for lighter, thinner, and smaller electronic devices continues to increase, very small square plate-type chip resistors are increasingly being used as resistance elements in order to increase the wiring density of circuit boards. It has become.

Moreover, in order to mount this square plate type chip resistor on a printed circuit board at high speed, it is almost always mounted using an automatic mounting machine. For this reason, there is an increasing demand for improving the mounting quality of square plate type chip resistors.

The structure of a conventional square plate type chip resistor is shown in FIG.

A conventional high-power square plate type chip resistor includes a 96 alumina substrate 11, a top electrode layer 12 and an end electrode layer 13 made of a silver-based thick film electrode, a resistance layer 14 made of a ruthenium-based thick film resistor, and a resistance layer 14 made of a ruthenium-based thick film resistor. It is composed of a first glass layer 15 made of lead borosilicate glass, a stamping glass layer 16, and a second glass layer 17 that cover the glass. Incidentally, in order to improve the properties of the solder material, a Ni plating layer 18 and a 5n-Pb plating layer 19 are applied to the exposed electrode surface by electrolytic plating.

Problems to be Solved by the Invention However, in order to ensure reliability, the protective layer of the resistor of the conventional square plate chip resistor has a three-layer glass structure. - Consists of a second glass layer. This glass has a glass softening point of 590℃~
Linear expansion coefficient at 610℃ is 64X10-7 to 66X1
0-7/'C, and is formed by firing at a temperature of 580°C to 600°C. In this case, a raised part of the stamped glass layer remains on the glass surface, about 2
Unevenness of 0 to 30 μm will occur.

This is thought to be because the protective glass is fired near the glass softening point, so the glass is not sufficiently melted and a bulge of the stamped glass layer remains.

When trying to mount a square plate type chip resistor with an uneven surface on a printed circuit board etc. using an automatic mounting machine, when the square plate type chip resistor is picked up with the suction pin of the automatic mounting machine,
Due to the unevenness of the glass surface, the suction bottle and the square plate chip resistor often come into point contact, causing the square plate chip resistor to rotate, causing the square plate chip resistor to rotate diagonally as shown in Figure 3. The problem was that it could not be mounted accurately on a printed circuit board. In addition, 20 is a printed circuit board, 21 is a conductor part, and 22 is a square plate type chip resistor.

Conventional measures to solve this problem include: (1) firing the glass at a high temperature of 640°C or higher to sufficiently melt the protective glass and reducing surface irregularities; (2) raising the softening point of the protective glass to 550°C. Consideration has been given to lowering the firing temperature to a certain degree, thereby sufficiently melting the glass at the conventional firing temperature and reducing surface irregularities. However, when the firing temperature is raised as shown in (2), the variation in resistance increases, and when the softening point of the glass is lowered as shown in (2), the linear expansion coefficient increases and the acid resistance of the glass also deteriorates. For this reason, stress tends to remain inside the glass due to the difference in thermal expansion coefficient between the glass and the alumina substrate, and the acid resistance deteriorates, so when electroplating is applied to the exposed electrode surface, the glass surface is easily attacked by acid. However, there was a problem in that internal stress tried to dissipate, causing cracks to occur on the glass surface.

The present invention solves these problems all at once, and is a corner that does not increase the variation in resistance value, does not deteriorate the acid resistance of the glass, and further reduces the unevenness of the glass surface and achieves high mounting accuracy. The present invention provides a plate-type chip resistor.

Means for Solving the Problems The square plate type chip resistor of the present invention includes an insulating ceramic substrate, a top electrode layer made of a thick silver film formed on the ceramic substrate, and a part of the top electrode layer. A thick ruthenium-based resistance layer overlapping the resistance layer and a softening point of 5 that completely covers the resistance layer.
50℃~570℃ and linear expansion coefficient 69X10-7~
A first glass layer having a temperature of 75X10-7 layers and a sealing glass formed on the first glass layer having a softening point of 550C to 570C and a coefficient of linear expansion of 68X10-7 to 74X10-7C. layer formed on the first glass layer to completely cover the imprinting glass layer has a softening point of 580°C to 6.
At 30℃ and linear expansion coefficient of 62x10-7 to 68X
It is composed of a second glass layer having a temperature of 10-7 degrees Celsius, and an end electrode layer made of a silver-based thick film and partially overlapping the upper electrode layer.

Function According to this configuration, since the glass softening point of the first glass layer is lower than the firing temperature (590°C), the marking glass is
It sinks into the glass layer and can reduce surface irregularities, and the acid resistance of the second glass layer is not deteriorated, so the glass is not eroded during electroplating and no cracks are generated on the glass surface.

Furthermore, since the second glass layer has the smallest coefficient of linear expansion, internal stress is generated in a direction that compresses the second glass layer, making cracks less likely to occur.

As a result, it is possible to provide a square plate type chip resistor that does not increase the variation in resistance value, does not deteriorate the acid resistance of the glass, and further reduces the unevenness of the glass surface and enables high-precision mounting.

EXAMPLE Hereinafter, an example of the present invention will be described with reference to FIG.

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

In FIG. 1, the square plate type chip resistor of the present invention has 96
An alumina substrate 1, a top electrode layer 2 and an end electrode layer 3 made of silver-based thick film electrodes, a resistance layer 4 made of a ruthenium-based thick film resistor, and a first glass layer 5 made of lead borosilicate glass covering the resistance layer 4 are stamped. It consists of a glass layer 6 and a second glass layer 7. In order to improve solderability, a Ni plating layer 8 and a 5n-Pb plating layer 9 are applied to the exposed electrode surface by electrolytic plating.

The details of the embodiment of the present invention will be explained with reference to FIG. First, a large 96 alumina substrate with excellent heat resistance and insulation properties is inserted. In order to divide the alumina substrate into strips and individual pieces, grooves for dividing are formed (molded with a mold when forming a green sheet). Next, a thick film silver paste was screen printed on the 96 alumina substrate and fired in a belt type continuous firing furnace at a temperature of 850°C with a peak time of 6 minutes and a profile of lN-0UT of 45 minutes to form the top electrode layer 2. Form. Next, a thick film resistor paste containing RuO2 as a main component was screen printed so as to partially overlap the upper electrode layer 2, and a belt-type continuous firing furnace was used to heat the film at a temperature of 850°C for 6 minutes at a peak time of 1N-0.
The resistive layer 4 is formed by firing according to a profile with a UT time of 45 minutes. Next, in order to equalize the resistance value of the resistance layer 4 between the upper electrode layers 2, a portion of the resistance layer 4 is destroyed by laser light to correct the resistance value. Furthermore, the glass softening point is 560 to completely cover the resistance layer 4.
A first glass paste having a linear expansion coefficient of 72±2×10 −7 after firing at ±5° C. is screen printed and dried at 150° C. for 10 minutes in a near-infrared drying oven. Furthermore, on top of the dried first glass paste, a glass softening point of 560±
A stamped glass paste having a linear expansion coefficient of 71±2×10 −7 after firing at 5° C. is screen printed and dried at 110° C. for 10 minutes in a near-infrared drying oven. Furthermore, a second glass paste having a glass softening point of 603±15°C and a coefficient of linear expansion after firing of 65±2×10-7 is placed on top of the dried first glass paste to completely cover the dried stamping glass paste. was screen printed and dried for 10 minutes at 150°C in a near-infrared drying oven. After that, it was heated in a belt-type continuous firing furnace at a temperature of 590°C for a peak time of 6 minutes, IN=
Fired according to the firing profile of OUT 5C1,
A first glass layer 5, an imprint glass layer 6, and a second glass layer 7 are formed. Next, as a preparatory step for forming the end electrodes, the alumina substrate 1 was divided into strips to expose the end electrodes, and partial substrate division was performed to obtain strip-shaped alumina substrates. A thick film silver paste was applied to the side surface of the rectangular alumina substrate using a roller so as to partially overlap the upper surface electrode layer 2, and then heated for 600 minutes using a belt-type continuous firing furnace.
The end face conductor paste is printed and fired in order to form the end face electrode layer 3 by firing at a temperature of °C with a firing profile of 6 minutes peak time and 1N-0UT 45 minutes. Next, as a preparatory step for the electrode plating step J, a secondary substrate division is performed in which the strip-shaped alumina substrate on which the end face electrode layer 3 has already been formed is divided into individual pieces to obtain individual pieces of alumina substrate. Finally, the exposed top electrode layer 2 and end electrode layer 3 are soldered using electrolytic plating to prevent the electrodes from being eaten away and to ensure soldering reliability.
- Perform electrolytic plating to form a Pb plating layer 9.

Through the above steps, a rectangular plate-type thin film chip resistor according to the embodiment of the present invention was prototyped. Also, as Comparative Example 1, the first glass layer, the stamped glass layer, and the second glass layer had a glass softening point of 600±20°C. Using a glass paste with a linear expansion coefficient of 65±2×10-7 after firing, a square plate type chip resistor was prototyped and fired at 640°C. 2
The glass layer was made of glass with a glass softening point of 550±20°C and a coefficient of linear expansion after firing of 65±2X10-7.
A square plate type chip resistor fired at 90°C was prototyped.

Table 1 shows a performance comparison between this embodiment of the present invention, Comparative Example 1, and Comparative Example 2.

Characteristics not shown in Table 1 (resistance temperature characteristics, current noise characteristics, etc.) are those of the embodiment of the present invention, the conventional example, and comparative example 1. Comparative example 2
It was confirmed that the two had equivalent performance.

Furthermore, in the square plate type chip resistor of the present invention, the glass softening point of the first glass layer/imprint glass layer is about 30°C higher than the firing temperature.
Since the resistance is low, it is sufficiently softened and pinholes on the glass surface, which are often a problem with square plate type chip resistors, are also improved.

(Left below) As is clear from Table 1, the square plate type chip resistor of the embodiment of the present invention has excellent mounting performance (no oblique mounting) due to small irregularities on the glass surface, and has excellent acid resistance. It can be said that the resistance is good, and the resistance value variation is the same as that of conventional products, indicating excellent performance.

In addition, a glass paste with a glass softening point of 560±5°C and a linear expansion coefficient of 72±2×10−7 after firing was used as the first glass layer, and a glass paste with a glass softening point of 560±5°C was used as the imprinting glass layer.
A glass paste with a linear expansion coefficient of 71±2×10−7 after firing was used as the second glass layer, and a glass softening point of 603±
A glass paste with a linear expansion coefficient of 65 ± 2 × 10 after firing at 15 °C was used, but this does not limit the glass layer; this paste has a softening point of 550 °C to 570 °C (555
℃~565℃) and linear expansion coefficient of 69X10-
7~75X10'' 77℃ first glass layer and softening point 5
50°C to 570°C (optimally 555°C to 565°C) and linear expansion coefficient of 68X10-7 to 74X10-7/'
C imprinted glass layer and a softening point of 580°C to 630°C (5
88℃~618℃) and linear expansion coefficient of 62X1
The second glass layer may have a temperature of 0-7 to 68 x 10-7-/°C.

In addition, in the example, precoat glass was not formed to suppress resistance value drift before resistance value trimming, but trimming was performed after forming precoat glass.
It has been confirmed that equivalent performance can be obtained even if a square plate type chip resistor is prototyped.

Effects of the Invention As is clear from the above explanation, the square plate type chip resistor of the present invention does not increase the variation in resistance value, does not deteriorate the acid resistance of the glass, and also reduces the unevenness of the glass surface and has a high Excellent effects such as being able to provide a square plate type chip resistor that allows precision mounting can be obtained.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing the structure of a square plate chip resistor according to an embodiment of the present invention, FIG. 2 is a sectional view showing an example of the structure of a conventional square plate chip resistor, and FIG. 3 is a conventional one. FIG. 2 is an explanatory diagram of a state in which a rectangular plate type chip resistor is mounted diagonally. 1...96 alumina substrate, 2...Top electrode layer, 3...End electrode layer, 4...Resistance layer, 5... First glass layer, 6... Imprint glass layer, 7... Second glass layer, 8...
...Ni plating layer, 9...5n-Pb plating layer.

Claims (1)

[Claims] an insulating ceramic substrate, a top electrode layer made of a thick silver film formed on the ceramic substrate, a resistance layer made of a thick ruthenium film that partially overlaps the top electrode layer, and a resistance layer that completely covers the resistance layer. A first glass layer having a softening point of 550°C to 570°C and a linear expansion coefficient of 69 x 10^-^7 to 75 x 10^-^7/°C, and a softening point formed on the first glass layer. is 550℃ to 570℃ and linear expansion coefficient is 68×10
＾-＾7～74×10＾-＾7/℃ stamped glass layer,
Formed on the first glass layer so as to completely cover the marking glass layer, the softening point is 580°C to 630°C and the linear expansion coefficient is 62 x 10^-^7 to 68 x 10^-^7/ ℃
A square plate type chip resistor comprising: a second glass layer; and a silver-based thick film end electrode layer overlapping a part of the upper electrode layer.