JPH03215902A - Square plate chip resistor - Google Patents

Abstract

PURPOSE:To make it possible to prevent a printed substrate from scorching by a method wherein a resistance layer and the like are formed on the heat- resisting insulated substrate of 0.7mm or more in thickness. CONSTITUTION:The title chip resistor is composed of a heat-resisting insulating layer of 0.7mm or more in thickness, a thick silver film upper electrode layer 2 to be formed on the insulated substrate, a thick ruthenium film resistor layer 4 which will be overlapped on a part of the upper electrode layer, an overcoat glass layer 5 with which the resistor layer 4 will be covered completely, and a thick silver film edge-face electrode layer 3 which is overlapped on a part of the upper surface electrode layer. Accordingly, even when the resistor is mounted on a printed substrate snd high power is applied, heat-rediating effect is enhanced due to the increase in thickness of the substrate 1 of a square- shaped chip resistor, and as a result, the heat generated on the surface of the chip resistor is hardly transferred directly below. Consequently, the scorching of the printed substrate can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a square plate type chip resistor used in high-density wiring circuits.

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.

In addition, there has been an increasing demand for higher power for this square plate type chip resistor in recent years.

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

The thickness (1) of conventional high-power square plate chip resistors is 0.
．． A base material made of a fired 96 alumina substrate 9 of around 5wun, a top electrode layer 10 and an end electrode layer 11 made of a silver-based thick film electrode, and a resistance layer 12 made of a ruthenium-based thick film resistor.
and an overcoat glass layer 13 made of glass that covers the resistance layer 12. Note that the exposed electrode surface is coated with a Ni plating layer 14 and a Sn plating layer to improve solderability.
-Pb plating layer 15 is applied by electrolytic plating.

Problems to be Solved by the Invention However, conventional high-power square plate chip resistors are mounted on printed circuit boards made of glass epoxy material or paper phenolic material, and suffer from the heat generated when high power is applied. but,
There is a problem in that the heat is transmitted directly under the square plate type chip resistor and the printed circuit board in that area is burnt.

Also, the thickness is 0. When using a 96 alumina substrate with a thickness of around 5 mm, there was a problem in that cracks would occur in the solder joints due to internal stress when mounted on a printed circuit board and subjected to temperature changes such as thermal shock.

Means for Solving the Problems The square plate type chip resistor of the present invention has a thickness of 0. 7 m
an insulating substrate with heat resistance of m or more, a top electrode layer of a silver-based thick film formed on the insulating substrate, a resistance layer of a ruthenium-based thick film overlapping a part of the top electrode layer, and the resistance layer. It is composed of an overcoat 1 glass layer that completely covers the electrode layer, and an end electrode layer made of a silver-based thick film that partially overlaps the two-sided electrode layer.

As a result, even when the square plate type chip resistor of the present invention is mounted on a printed circuit board and high power is applied, the heat dissipation effect is enhanced by increasing the thickness of the board of the square plate type chip resistor. Therefore, the heat generated on the surface of the chip resistor is difficult to be transmitted directly below, and it is possible to eliminate burning of the printed circuit board.

Furthermore, when mounted on a printed circuit board and subjected to temperature changes such as thermal shock, the internal stress that occurs in the solder joint is reduced (especially the stress that occurs when trying to peel a square chip resistor from the board is reduced). Problems such as cracks and cracks can also be solved.

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.

First, in FIG. 1, the square plate type chip resistor of the present invention has a thickness of 1. ．． A 96 alumina substrate 1 with a thickness of 0 mm, a top electrode layer 2 and an end electrode layer 3 made of silver-based thick film electrodes,
It is composed of a resistance layer 4 made of a ruthenium-based thick film resistor, and an overcoat 1/glass layer 5. Note that a Ni plating layer 6 is provided on the exposed electrode surface to improve solderability.
A Sn--Pb plating layer 7 is applied by electrolytic plating.

Next, details of the embodiment of the present invention shown in FIG. 1 will be explained. First, the thickness has excellent heat resistance and insulation].
．． A 96 alumina substrate 1 of O mm is accepted. This alumina substrate 1 has grooves for dividing it into strips and individual pieces (molded with a mold during green sheeting).
6. 3mm and 3. They are formed at a pitch of 2 mm. Next, a thick film silver paste 1 was screen-printed on the 96 alumina substrate 1, and a belt-type continuous firing furnace was used to heat the film at a temperature of 850°C for a peak time of 6 minutes.
The upper surface electrode layer 2 is formed by baking according to the profile for 45 minutes. Next, R
A thick film resistor paste containing uO2 as a main component is screen printed and fired in a belt-type continuous firing furnace at a temperature of 850°C according to a profile of a peak time of 6 minutes and an IN-OUT of 45 minutes to form a resistance layer 4. Next, the upper surface electrode layer 2
In order to equalize the resistance value of the resistance layer 4 between the two, a portion of the resistance layer 4 is destroyed by laser light to correct the resistance value. Furthermore, a lead borosilicate glass paste was screen printed so as to completely cover the resistance layer 4, and the firing profile was set at a temperature of 590°C using a belt-type continuous firing furnace, with a peak time of 6 minutes and an IN-OUT of 50 minutes. 5 to form an overcoat 1 and a glass layer 5. Next, as a preparatory step for forming the end electrodes, the alumina substrate 1 is divided into strips to expose the end electrodes, thereby obtaining strip-shaped alumina substrates. A thick film silver paste was applied to the side surface of the rectangular alumina substrate by a roller so as to overlap a part of the single-sided electrode layer 2, and was heated in a belt-type continuous firing furnace at a temperature of 600'C for a peak time of 6. The end electrode layer 3 is formed by firing according to a firing profile of 45 minutes IN-OUT and 45 minutes IN-OUT. Next, as a preparation step for electrode plating, a secondary substrate division is performed in which the rectangular alumina substrate on which the end surface electrode layer 3 has already been formed is divided into individual pieces to obtain individual piece-shaped alumina substrates. Finally, in order to prevent the exposed top electrode layer 2 and end electrode layer 3 from being eaten away during soldering and to ensure soldering reliability, electrolytic plating is applied to the Ni plating layer 6 and Sn-Pb. A plating layer 7 is formed.

Through the above steps, a square plate type chip resistor according to an embodiment of the present invention was prototyped (the size was 6.4 (L) mm6 x 3.2 (W) mm x 1.1 (t) mm).

Similarly, as examples of the present invention, square plate type chip resistors with aluminum substrate thicknesses of 0.7 mm and 1.5 mm were also prototyped.

Furthermore, as a comparative example (conventional example), the thickness of the alumina substrate was 0. A 5 mm square plate type chip resistor was also prototyped.

The square plate type chip resistor of this example was actually mounted on a printed circuit board (LOOX 1.00 t: 1.6 mm glass epoxy printed circuit board), and the temperature was measured one hour after applying IW power. Furthermore, at -55°C for 30 minutes,
A thermal shock test was conducted for 100 cycles at 125°C for 30 minutes. The results are summarized in Table 1.

(Left below) Table 1 As can be seen from Table 1, in all of the embodiments of the present invention, the surface temperature rise is 0. It can be seen that the temperature is more than 25°C lower than that of 5 mm. Also, the alumina substrate thickness was set to 0.
．． Even if it is made thicker than 7 mm, it will still be 0.7 m.
It can be seen that the temperature rise cannot be suppressed much compared to the temperature rise in the case of a thickness of m. Furthermore, the incidence of cracks in solder joints has been drastically reduced, especially cracks of 1.0 mm or more.
It was found that the occurrence rate was O when an 8 alumina substrate was used.

As a result of these effects, it was found that no scorching occurred on the printed circuit board, and the reliability of the solder joints was significantly higher than before.

However, if a 1.5 mm alumina substrate is used, it will be difficult to divide it due to the manufacturing method, so the optimal alumina substrate thickness is 0.
．． 9mm~1. It can be said that it is about 1 mm.

It was also confirmed that the resistance performance (resistance temperature characteristics, current noise characteristics, moisture resistance, etc.) is almost the same as that of conventional square plate chip resistors.

As is clear from the above explanation, it can be said that the square plate type chip resistor of the example has very excellent performance.

In addition, in the example, a 96 alumina substrate was used as the insulating sintered substrate, but this is not intended to limit the insulating sintered substrate.

In addition, we prototyped a square plate type chip resistor with a size of 6.4 x 9 3.2 x 1.1 mm, but this does not limit the size of the chip resistor (however, 6.4 x 3 mm).
2X1.1n+m is optimal).

Effects of the Invention As is clear from the above explanation, the square plate type chip resistor of the present invention includes a heat-resistant insulating substrate having a thickness of 0.7 ur or more, and a silver-based thick film formed on the insulating substrate. a top electrode layer, a ruthenium-based thick film resistance layer overlapping a part of the top electrode layer, an overcoat glass layer completely covering the resistance layer, and a silver-based thick film overlapping a part of the top electrode layer. Since it is composed of end face electrode layers, even when the square plate type chip resistor of the present invention is mounted on a printed circuit board and high power is applied, the thickness of the square plate type chip resistor substrate is increased. Because the heat dissipation effect is enhanced, the heat generated on the surface of the chip resistor is difficult to be transmitted directly below, making it possible to eliminate scorching of the printed circuit board and also prevent temperature changes such as thermal shock when mounted on a printed circuit board. When the internal stress is applied to the solder joint, the internal stress generated in the solder joint becomes smaller (particularly the stress that causes the square chip resistor to be peeled off from the substrate becomes smaller), which causes cracks to occur. This has the effect of solving the problem.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing the structure of a square plate type chip resistor according to an embodiment of the present invention, and FIG. 2 is a sectional view showing the structure of a conventional high power type square plate type chip resistor. 1...96 alumina substrate, 2...Top electrode layer, 4...Resistance layer, 5...Overcoat glass layer, 3...・End face electrode layer, 6...
...Ni plating layer, 7...Sn-Pb plating layer.

Claims (1)

[Claims] a heat-resistant insulating substrate with a thickness of 0.7 mm or more, a silver-based thick film top electrode layer formed on the insulating substrate, and a ruthenium-based thick film resistance layer overlapping a part of the top electrode layer;
A square plate type chip resistor comprising: an overcoat glass layer that completely covers the resistance layer; and a silver-based thick film end electrode layer that partially overlaps the upper electrode layer.