JPS6155988A - Multilayer circuit board - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a multilayer wiring board that can be used in general electronic circuits requiring a low resistance in the range of O, S to 3Ω.

Conventional configurations and their problems In recent years, as electronic devices have become more highly integrated and reliable, the wiring boards used inside them are also becoming more integrated and reliable. is required.

DESCRIPTION OF THE PREFERRED EMBODIMENTS A conventional multilayer wiring board used in electronic circuits requiring a low resistance in the range of 0.5 to 3 Ω will be described below with reference to the drawings. FIG. 1 is a cross-sectional view of the conventional multilayer wiring board, in which 1 is the AJI' 203 board after firing, 2 is the AJI' 203 board after firing;
is a conductor wiring formed of Ag-PdK, 3 is an insulating layer formed of crystalline glass, and 4 is RuO□
The resistor 5 is an overcoat for protecting the resistor 4, and like the insulating layer 3, it is made of crystalline glass. Moreover, FIG. 2 is an enlarged view of the cross section of the RuO2 resistor printed on the crystalline glass after firing.
6Vi crystalline glass after firing, 7 RuO2 paste,
8 is a printing sag portion of the RuO2 paste 7.

The multilayer wiring board configured as described above will be explained. Conductive wiring 2 is formed on the λg203 substrate 1 by printing, dried and fired at about SOO''C, and an insulating layer 3 is formed by printing, dried and fired at about 500''C.

By repeating the above steps, a multilayer wiring board can be created, and at the locations where resistance values are required,
The wiring section is drawn out to the top layer of the multilayer wiring board.

AI wired in this way? 20. In order to provide a resistance on the board 1, a resistance is formed in the wiring section drawn out to the top layer of the multilayer wiring board, but if a low resistance value of about 0.5 to 3 Ω is required, a step resistor is used. In order to create this resistance value, it is necessary to use a chip resistor with a large shape, so RuO2 paste is usually printed on wiring parts that require low resistance, and then baked at about 500"C after drying. , then printed crystalline glass as an overcoat to protect the RuO2,
After drying, it is fired at about 500'C.

However, in the above configuration, after the multilayer wiring board is completed, RuO2 is printed, dried, and fired, and crystalline glass is printed as an overcoat.

Since the steps of drying and firing are added, this becomes a factor that increases the cost per low resistor when only a relatively small number of low resistors are formed.

Furthermore, the RuO2 resistor is printed on the surface of the fired crystalline glass, which is an insulating layer, and in FIG. 3, the surface of the fired crystalline glass 6 is in a very dense state. The RuO2 paste 7 printed on the surface flows out of the surface of the crystalline glass 6 and the width of the formed wiring varies, so the resistance value R expressed by the following formula is R=ρT ρ: Sheet resistance L of the RuO2 paste:
RuO2 wiring length W: // Wiring width varies greatly due to variations in wiring width K.

The normal variation in resistance value is about ±3Q to 50%.

Therefore, in circuits that require low resistance with relatively little variation (about ±2 or 3), after the RuO□ resistor 7 is formed, trimming is performed using a laser or the like.
Since the accuracy of the resistance value is increased, the number of man-hours increases, leading to further increases in costs. and,
During trimming, the overcoat 6 was also removed at the same time, exposing a part of the RuO□ resistor, and using the RuO2 paste 7, which had imperfect reliability, a particularly low resistance was formed. When doing so, there were a number of problems as described above.

Purpose of the Invention The present invention aims to provide a highly reliable and low-cost multilayer wiring board incorporating the above-mentioned low resistance, which can be used in general electronic circuits requiring a low resistance in the range of 0.5 to 3Ω. This is the purpose.

Structure of the Invention In order to achieve the above object, the multilayer wiring board of the present invention has the following features:
Tungsten powder constituting 10 parts by weight of tungsten paste is 2 to 8 parts by weight, i20. With tungsten base containing 8 to 2 parts by weight of powder,
5e20. Form a wiring and a resistor in the range of Q.6Ω to 3Ω on the substrate, and the resistor is then connected to the wire e20. Being covered with paste, the above wiring and resistor, and A4205
The substrate and the Ae205 paste are fired at the same time, and from this K it is possible to create a highly reliable, low-cost, multilayer substrate with built-in low resistance.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings, FIG. 3, and FIG. 4. FIG. 3 shows a cross section of the multilayer wiring board of the present invention, where 9 is an A1205 substrate, 1o is a conductor wiring made of tungsten, and 11 is an insulating layer made of e205.

FIG. 4 shows a low resistance built into the multilayer wiring board, and 12 is a low resistance portion made of tungsten.

The multilayer wiring board configured as above will be explained below.

When forming conductor wiring with tungsten paste, tungsten is λg20. 1700, which is the firing temperature of
Since the Ae203 substrate 9 that forms the multilayer wiring board is in a green sheet state before firing, the insulating layer 11 is also made of AJ203.
It is best to use 3 pastes. At this time, the ratio of tungsten paste nickel tungsten to human β 203 is changed depending on which tungsten paste is used for a wiring part that does not require a resistance value and a wiring part that requires a resistance value. Next, find the area resistance of the lingsten paste used in the wiring part that requires a resistance value, and determine the width and length of the wiring as shown in the low resistance part 12 in Figure 4. can have a value. The resistance value R can be calculated from R = ρ - ρ: Sheet resistance L: Wiring length W: Wiring width, but from the above formula, if the wiring width changes due to printing sag, etc., the resistance The value is Ru
As with the use of O2 paste, there will be a great deal of variation. However, when using tungsten as the conductor wiring 10, the unfired Al203 substrate 9 with coarse particles can be used, so the solvent, etc. contained in the internal pressure of the Tough Gesten base will penetrate into the unfired Ae2O3 substrate 9. Therefore, the surface of the board is not spread, so the fourth
As shown in the figure, by controlling the printing thickness without causing printing sag, it is possible to obtain a resistance value that is almost close to the calculated value obtained by the above formula. In the experiment, tungsten paste with a sheet resistance of 50 mΩ10 was used.
When I created a wiring with a width of 200μyn and a length of 411M to create a low resistance of Ω, the resistance was 0.80 to 1.20.
The variation could be suppressed to (1Ω±20%).

Furthermore, since tungsten paste can be fired simultaneously with Al120s, AA'20. Mu71!203 paste after firing has excellent airtightness, so it is also good in terms of moisture resistance, and there is almost no change in resistance value in evaluations such as moisture resistance tests. I couldn't find it. Since the tungsten paste used for Kirani1 conductor wiring is also used as a resistor, Al2O5 and tungsten can be fired at the same time, so the firing process only needs to be done once, reducing the number of processes. This also leads to lower costs.

Effects of the Invention As is clear from the above explanation, the present invention enables wiring and resistance within the range of O, SΩ, or 3Ω to be formed on a 6205 board using a tungsten paste containing 2 parts by weight of tan. , and the resistor is then covered with Al205 paste, and the wiring and resistor are covered with Al20.
Substrate and Al20. So that the pastes are fired at the same time +
? 7J, it is possible to obtain resistors from 0.5Ω to 30Ω with little variation and good reliability, and it is of great industrial value as it can reduce costs by reducing man-hours. It is.

[Brief explanation of the drawing]

Figure 1 shows person g2 who used conventional λg-Pd for conductor wiring.
03 is a cross-sectional view of the multilayer wiring board, FIG. 2 is an enlarged perspective view of the RuO2 resistor, and FIG. 3 is a cross-sectional view of the multilayer wiring board of the present invention.
FIG. 4 is a turn diagram for forming the same low resistance. 9...AIJ20. Substrate, 10...Conductor wiring, 11...Insulating layer, 12...Low resistance portion formed of tungsten paste. Name of agent: Patent attorney Toshio Nakao and 1 other person 1st
Figure 4

Claims (1)

[Claims] 10 parts by weight of tungsten paste contains 2 to 8 parts by weight of tungsten powder and 8 to 2 parts by weight of Al_2O_3 powder, which connects wiring on the Al_2O_3 substrate to 0.5Ω to 3Ω.
forming a resistance within the range of Al_2O
_3 Covered with paste, the above wiring and resistor and Al_2O
A multilayer wiring board characterized in that a _3 board and an Al_2O_3 paste are fired at the same time.