JPH0464198B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a hybrid integrated circuit board for high-density packaging circuit modules composed of thick film parts, chip parts, ICs, LSIs, and the like.

Conventional configurations and their problems In recent years, demands for smaller devices and multifunctionality have become stronger year by year, and in order to meet these demands, high-density mounting of circuit components has become an important technology. ing. In particular, with the development of ICs and LSIs, as well as the development of thick film components such as resistors and capacitors, the mounting density of circuit components is becoming increasingly dense. Furthermore, in recent years, as communication frequencies have become higher, the conductor resistance of the module wiring layer has become an important point. For example, in the case of alumina module, if the wiring conductor resistance is high in the high frequency range, phenomena such as oscillation and decrease in gain will occur, so it is currently difficult to put it into practical use with the conventional configuration of alumina module due to the high conductor resistance. It is. However, from the viewpoint of downsizing devices and streamlining the assembly process, there is a strong desire to modularize these high-frequency circuits using hybrid ICs.

In order to modularize the circuit and realize circuit implementation that also improves the characteristics in the high frequency range,
In addition to reducing the size of components, as mentioned above, it is necessary to lower the resistance of wiring conductors and improve wiring density. In order to increase the wiring density, it is generally considered that the wiring is multilayered, and efforts are being made actively in various fields. Conventionally, these multilayer substrates can be broadly classified into combinations of resin substrates and copper wiring, and combinations of alumina ceramics and Mo or W. Conventionally, boards with these configurations have had the following problems as boards for high-density mounting.

Combination of resin substrate and copper wiring (a) It is difficult to form connecting via holes between internal conductor layers, so through holes that penetrate both sides of the substrate are used to connect conductor layers. Therefore, when trying to mount many components, the area of the through-hole cannot be ignored, and as a result, the mounting density cannot be increased.

(b) It is impossible to form thick film parts on resin substrates, that is, thick film parts such as glaze resistors require 800
Since these parts are formed in air at ~900°C, it is not possible to form these parts on a resin substrate, and an integrated configuration of the substrate and resistor cannot be achieved.

Combination of Alumina and Mo or W (a) For solder connection of parts, it is necessary to plate the tungsten or molybdenum layer on the surface of the multilayer board with nickel, gold, etc.

(b) Glaze resistors and capacitors, which are thick-film components, must be formed in air at high temperatures, but if they are made of conductive materials that easily oxidize, such as tungsten or molybdenum, these thick-film components It is impossible to form such a material and is not suitable as an integrated circuit board with thick film components.

(c) High conductor resistance of Mo and W (20 to 30 mΩ/□) For the above reasons, it has sufficient functionality as a conventional resin multilayer board or ceramic multilayer board as a board for high-density mounting or a board for high-frequency modules. It can be said that there is no.

Purpose of the Invention In view of the above-mentioned drawbacks, the present invention provides a substrate for a hybrid integrated circuit in which the conductor resistance of the internal wiring layer is low and a thick film resistor is formed, and which enables modularization of high-frequency circuits and high-density component mounting. be.

Structure of the Invention The hybrid integrated circuit substrate including a copper wiring layer of the present invention is a laminate in which a copper wiring layer and a glass layer for electrical insulation are alternately formed on a polycrystalline substrate mainly composed of alumina. , a small hole is formed in the glass layer formed on the top layer so that the internal copper wiring layer is exposed, a filling material made of barium borosilicate glass and a noble metal is connected to this small hole portion, and the filling material on the top layer is connected. The present invention is made up of a silver-palladium conductor and a ruthenium-based glaze resistor, thereby providing an integrated circuit substrate with a resistor-integrated multilayer structure and low conductor resistance.

DESCRIPTION OF EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a cross-sectional view of a hybrid integrated circuit board in one embodiment of the present invention.
In Figure 1, 1 is an alumina substrate, 2 is a through hole made of copper material, 3 is a copper wiring formed on the alumina substrate, 4 is a glass layer formed for the purpose of insulating from the upper wiring layer, and 5 is a glass insulating layer. This is a filling part made of barium borosilicate glass and noble metal that fills the small holes formed in the.

The functions of the hybrid integrated circuit board including the copper wiring layer of this embodiment configured as described above will be explained below.

The board constructed as shown in Fig. 1 is made by first applying copper paste to an alumina board 1 to form through holes 2 and wiring layer 3.
screen print. After drying this at a temperature of about 120° C., a glass powder paste is screen printed, and the printed glass paste is then dried to form a glass layer 4. At this time, small holes 4a are formed in the glass layer 4 at necessary locations to expose the lower conductor. This small hole 4
A is provided for the purpose of electrical connection with the uppermost layer later. After printing and drying the alumina substrate, copper paste, and glass paste in this way, they were fired at 900°C in a nitrogen atmosphere. The profile during firing was at a peak temperature of 900°C for about 10 minutes. Note that a small amount of oxygen of 10 ppm or less was mixed into the nitrogen gas during firing. After that, a paste of barium borosilicate glass powder and silver powder was screen printed in the small holes 4a where the copper wiring provided in the formed insulating glass layer 4 was exposed, and after drying at 850°C.
The film was passed through a conventional thick film furnace. The barium borosilicate glass powder used was prepared using raw materials such as BaCO ₃ ,
40g, 60g, 4g, 7g, 3g, and 3g of H ₃ BO ₃ , SiO ₂ , Al ₂ O ₃ , MgO, and CaCO ₃ were mixed, heated to 1200°C to melt the glass, and dropped into water, followed by a wet process. The crushed one was used. This glass is made by adding Al ₂ O ₃ , MgO, and CaO to barium borosilicate glass. The addition of Al ₂ O ₃ is used to control the glass softening point, CaO to control the thermal expansion coefficient, and MgO to improve moisture resistance.
were added and dissolved in appropriate amounts. When this board was left in the air at 850°C for 30 minutes, the internal copper conductor layer showed a conductor resistance of 2 to 3 mΩ without being oxidized. Further, when the resistance between the filler and the lower conductor layer was measured, it was 10 to 15 mΩ.

The principle of construction of the above embodiment will be briefly described below.

The most important point here is Figure 1, 5.
A filling material made of glass and precious metals that cannot be reduced to copper is formed in the filling material. This is because this structure allows electrical continuity with the surface layer through the lower conductor copper and the filler material.
This is because the lower conductor layer will not be oxidized even under high temperature conditions in the air through the filler. Of course, the copper conductor formed under the glass insulating layer will not be oxidized even during high-temperature air treatment because the glass acts as an air diffusion prevention material. Generally, by dispersing conductive particles in a fluid material, a structure is created in which a kind of agglomeration phenomenon occurs between the conductive particles and the particles maintain contact with each other. As a result, the conductive particle dispersion exhibits an electrical conduction phenomenon. Therefore, in the configuration of the present invention, the glass becomes fluid when it reaches a certain temperature, and electrical conductivity is obtained because the noble metal group is dispersed in the glass. The reason for using noble metals as the conductive particles is that they must not be oxidized even in high-temperature air. On the other hand, it will be described that the structure of the present invention prevents the internal copper wiring layer from being oxidized even at high temperatures in air.

In the present invention, the glass material is highly effective in preventing oxidation of the internal copper wiring layer. In other words, the glass layer of the filler material in the filling part 5 in Fig. 1 wets the glass insulating layer well after firing, and the area around the noble metal particles is filled with glass, so this glass layer provides airtightness to the inside. This is because the retained air does not reach the lower conductor layer. If we consider lead-based glass, which is commonly used as a glass material, the following reaction occurs between the glass and the copper of the lower conductor.

Cu+3PbO→CuO+3Pb In other words, copper, which is a conductor, is oxidized by lead oxide, which is the main component of glass, and the resistance at the contact area between the filler and copper increases. Therefore, it is important that the glass used in the present invention has a property that does not oxidize copper, or in other words, that it is a glass material that is not reduced by copper. Some glasses that satisfy these conditions include those whose main component is an alkaline earth metal oxide group metal oxide. Among them, the system using the barium borosilicate glass of the present invention does not oxidize the internal copper electrode and has good wettability with the noble metal to be dispersed. Therefore, the filled conductor has excellent reliability, especially moisture resistance.

As described above, by adopting the configuration of the present invention, it is possible to provide electrical continuity to the upper layer through the filling material formed in the small hole provided in the upper insulating layer at the same time as providing copper wiring in the lower part. In addition, the lower copper wiring layer of this board will not be oxidized even at high temperatures in the air. Therefore, the currently very developed thick film technology makes it possible to integrate a glaze resistor and a glaze dielectric on top of this substrate. Here, in the embodiment, each of the copper wiring layer and the glass insulating layer is one layer, but the number of layers can be increased by repeating the process. In other words, the board structure of the present invention allows for multi-layered internal wiring, which enables high-density component mounting, and also enables integration of thick-film components, further improving packaging density.

In addition, since copper wiring is provided as an internal conductor layer, the conductor resistance is low and it is suitable for high frequency circuit modules. There are advantages such as the ability to reduce the line width of the wiring.

Next, other embodiments of the present invention will be described with reference to the drawings.

FIG. 2 is a cross-sectional view of a hybrid integrated circuit board including copper wiring according to another embodiment of the present invention. In an embodiment of the present invention, a ruthenium oxide based glaze resistor 6 is formed on the substrate shown in embodiment 1 using a silver-palladium conductor 6 and a silver-palladium conductor as electrodes so as to be connected to a filler 5.

The silver-palladium conductor and the ruthenium oxide resistor were formed through the same steps as in the conventional method. That is, after printing and drying a silver-palladium paste, it was fired in a thick film oven at 850°C in the air, and then a ruthenium oxide paste was printed on it, and after drying.
Fired at 850℃ in air. The resistance value of the glazed resistor created in this way was slightly higher than that of a conventional glazed resistor formed on an alumina substrate, but for example, a 100KΩ/□ resistor has a temperature coefficient of 100 to 150 ppm, which is sufficient. Characteristics that can be used generally were obtained. As described above, according to this embodiment, by forming a conventional thick film resistor on the substrate of Embodiment 1 using a conventional method, a resistor-integrated substrate with a multilayer structure and low internal conductor resistance is realized. .

Effects of the Invention As is clear from the above description, the present invention uses a copper material as an internal conductor layer and a glass material as an insulating layer on an alumina substrate to form a multilayer structure, and electrically connects the surface layer with a filler made of a glass noble metal. It enables connection and is integrated with a thick film component formed on the upper layer.The internal conductor resistance is low, so high frequency characteristics can be improved and the conductor line width can be made thinner. The excellent effect of being able to integrate thick film parts formed at high temperatures in air can be obtained. Due to its effect,
This makes it possible to modularize circuits that will increasingly be used as information communication means in the future, and also enables miniaturization of circuit modules in the sense that high-density packaging is possible.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a hybrid integrated circuit board according to one embodiment of the invention, and FIG. 2 is a sectional view of a hybrid integrated circuit board according to another embodiment of the invention. 1...Alumina substrate, 2...Copper through hole, 3
... copper wiring layer, 4 ... glass insulating layer, 5 ... filling part, 6 ... silver-palladium conductor layer, 7 ... ruthenium oxide glaze resistor.

Claims (1)

[Claims] 1 A laminate in which copper wiring layers and glass layers for electrical insulation are alternately formed on a polycrystalline substrate mainly composed of alumina, and the internal copper wiring layer is exposed to the glass layer formed on the top layer. A hybrid conductor consisting of a small hole provided in the hole, a filling material made of barium borosilicate glass and a noble metal in the small hole portion, and a silver-palladium conductor and a ruthenium-based glaze resistor formed so as to be connected to this top layer filling material. Substrate for integrated circuits.