JPS61230392A - 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 circuit board suitable for high-density mounting of membrane circuit components, ICs, LSIs, and the like.

(Prior Art) In recent years, demands for smaller devices and multifunctionality have become stronger year by year, and in order to meet these demands, high-density packaging of single circuit components has become an important technology. Especially IC, LS
With the development of integrated circuits and thick film technology for resistors, capacitors, etc., the mounting density of circuit components is becoming increasingly high. In order to achieve high-density mounting of components, it is important to make the components smaller and to increase the wiring density of the board. A multilayer circuit board formed inside the board is most effective.

Conventional multilayer circuit boards include those in which insulator layers containing alumina as a main component and conductor layers of tungsten or molybdenum are alternately laminated. (For example, IEEE Tr
an@on CHMT CHMT-344p 634(
1980) r A Multi'1ayar Cer
amlc MultichipModule J) (Problems to be Solved by the Invention) However, the conventional multilayer circuit board does not include a tungsten or molybdenum conductor layer on the surface of the multilayer circuit board to enable soldering of components. It is necessary to plate with nickel, gold, etc., and in order to form glazed resistor elements and capacitor confectionery as thick film elements, there is a fee for high-temperature treatment at 800 to 900 degrees Celsius in air.
Conductive materials such as tungsten and molybdenum, which are easily oxidized, cannot be processed in an oxygen atmosphere;
There is a problem in that thick film elements cannot be directly formed on a multilayer circuit board.

(Means for Solving the Problems) In order to solve the above-mentioned problems, the present invention provides a laminate made of alternating layers of insulator layers mainly composed of alumina and conductor layers of tungsten metal. and a conductive coating material made of a low melting point glass that is not reduced to tungsten and a noble metal, which is formed on the exposed conductor part provided in the uppermost insulating layer of the & layer part so as to be electrically connected to the internal conductor layer. , a thick film resistor element provided on the uppermost insulating layer and having an extended portion of the conductive coating as an electrode; and a silver-noyaranoum for mounting electronic components electrically connected to the extended portion. The present invention provides a multilayer circuit board comprising a system conductor pad and a wiring pattern, and the thickness of the conductive coating material is in the range of 15 to 35 μm.

(Function) With the above configuration, the present invention uses a low melting glass that is not reduced to tungsten or molybdenum as the glass component of the conductive filler, so even when sintered at high temperature in air, the tungsten or molybdenum conductive layer Good electrical conductivity can be obtained without being oxidized, and thick film elements of resistors and capacitors can be formed in air on the surface of the uppermost insulating layer by using the conductive filler.
Further, trimming of the thick film resistor by radar can also be stably performed because the insulator layer has a high alumina component.

(Embodiment) FIG. 1 is a cross-sectional view of a multilayer circuit board according to an embodiment of the present invention.
Figure g2 shows an enlarged sectional view of the main parts of the substrate, where 1 is an alumina paste, 2 is a first alumina insulator layer, 3 is an uppermost alumina insulator layer, 4 is a tungsten or molybdenum conductor layer, 5 6 is a silver-palladium-based conductor film; 7 is a ruthenium-based thick film resistor element; 8 is a low-melting glass that is not reduced to tungsten or molybdenum; Indicates the purchase price particle.

Inorganic powder containing alumina as the main component and adding a sintering aid,
A green sheet made of polyvinyl butyral (PVB) and a plasticizer was produced using a doctor blade method. On the green sheet, a conductor paste made by adding and kneading an appropriate amount of ethcel-based vehicle to a conductor mixture containing tungsten or molybdenum as a main component and a conductor sintering aid, and alumina having the same mMiM and t as the green sheet. A laminated part is formed by alternately printing and laminating the paste and the laminated part, and a 300 μm square hole is provided in the uppermost alumina insulating layer 3 of the laminated part so as to expose a part of the tungsten or molybdenum conductor layer 4. Ta. The laminated portion constructed as described above was fired in a reducing atmosphere at 1550 to 1650°C. The shrinkage rate of the laminated portion after sintering was about 16%.

Next, a pattern is formed in the surface hole of the sintered laminated part so that it has an extended part that will become an electrode for the glass powder thick film resistor element 7, which has a softening point of about 540°C and whose main components are B2O3 and Ba0i. It has a bell-shaped temperature profile and is passed through a thick film firing furnace with a peak temperature of 850°C. Further, a ruthenium-based glaze resistor element (thick film resistor element) 7 and a silver-palladium thread conductor film 6 were printed in a required pattern and passed through a thick film firing furnace in the same manner as described above.

In the multilayer circuit board obtained as described above, the coating material 5 made of silver-galanu material firmly adheres to the surface of the core layer, and furthermore, the electrical conduction between the coating material 5 and the conductor layer 4 is sufficient. was secured. For example, the conductor layer 4 in FIG.
When the electrical resistance value Re between the palladium-based conductor film 6 was evaluated, it was about 3 to 5-. Furthermore, a ruthenium-based thick film resistor element 7 is formed using an extended portion of the covering material 5 as an electrode.
teeth.

It exhibited approximately the same resistance value as conventional silver-palladium electrodes, and exhibited extremely good matching properties. Furthermore, the electrical conductivity at the interface between the coating material 5 and the silver-palladium conductor film 6 showed extremely good characteristics, and no phenomenon in which the electrical resistance at the interface increased was observed.

Further, in order to investigate the stability of the coating material of the multilayer circuit board of the present invention, a Gretzscher-Cuckett test (abbreviated as PCT) was performed at 1210.2 atm, and the electrical resistance Re was measured after 48 hours had elapsed. . Sample coating material 5 is placed on the bottom of the kite.
The measurement results of the electrical resistance value Re measured by changing the film thickness are shown below.

As shown in the table, when coating material with a thickness of 12 μm for Sample No. 1 or 40 μm for Sample No. 5 is formed, conduction with low resistance is obtained initially, but after PCT, the resistance value decreases. The resistance increases, sometimes reaching a high resistance of several tens of ohms. This is because when the coating material 5 has a thickness of 15 μm or less, the coating with the low softening point glass is not complete and the conductor oxide layer becomes thick.
Among the resin components in the vehicle mixed with the low softening point glass and silver powder near the interface between the coating material 5 and the internal conductor layer to form a paste, after firing the glass softens and tends to burn and scatter. It is thought that the electrical resistance Re increases after PCT because many bores are generated inside the glass and the bores thicken the oxidation field near the interface under high temperature and high humidity.

In the multilayer circuit board according to the present invention, the coating material 5 has a thickness of 15 to
By forming the layer to have a thickness of 35 μm, the coating effect of the glass was increased and the internal conductor layer 4 was made resistant to oxidation. Therefore, even under harsh conditions such as PCT, the coating material 5
and the inner conductor layer 4 is maintained with good electrical conductivity.

The relationship between the film thickness of the coating material 5 and the electric resistance Re of the interface 48 hours after PCT is shown in the shaded range in FIG.

(Effects of the Invention) As described above, the present invention uses noble metal and glass materials that are stable even in high-temperature air as the conductive coating material formed on the exposed portion of the internal conductor layer. Thickness 15~35μ
Since the groove is formed of m, it forms a groove bottom that prevents air from penetrating into the internal conductor layer. Therefore, the present invention makes it possible to form thick-film resistor elements and capacitor clusters fired in air at high temperatures of 800 to 900°C on the topmost surface, and furthermore, the internal conductor layer is made of tungsten. Because of this, it is inexpensive and allows for high-density mounting of not only confectionery but also chip parts and ICs. especially,
In the present invention, since the internal conductor layer is stabilized, a highly reliable multilayer circuit board can be provided. In addition, as a board for high-density component mounting, it does not require plating of soldering electrode pads, and it has a structure that allows the formation of thick and thin elements such as glazed resistor elements, and simplifies the manufacturing process. This makes it possible to reduce costs.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a multilayer circuit board according to an embodiment of the present invention, FIG. 2 is an enlarged sectional view of the essential parts of the board, 31. Alumina paste, 2. First layer alumina insulator. Layer, 3...
・Top layer alumina insulator layer, 4... Tungsten or molybdenum conductor layer, 5... Material made of low-melting glass and noble metal that does not oxidize tungsten or molybdenum, 6... Silver-.9 Radium Thread conductor membrane, 7...
・Ruthenium-based thick film resistor element, 8...Low melting point glass that is not reduced to tungsten or molybdenum, 9...
・Precious metal particles. Patent applicant: Matsushita Electric Industrial Co., Ltd. Representative: Hisashi Hoshino 4. 'l,,',
',, ','gFigure 1Figure 2

Claims (2)

[Claims] (1) A laminated part formed by alternately laminating an insulating layer mainly composed of alumina and a conductive layer made of tungsten metal, and an internal layer on the exposed part of the conductive layer provided on the uppermost insulating layer of the laminated part. a conductive coating made of a low-melting glass and noble metal that is not reduced to tungsten and formed to be electrically conductive with the conductor layer; and an extended portion of the conductive coating provided on the uppermost insulating layer as an electrode. A conductive coating formed on the exposed portion of the conductor layer, comprising a thick film resistor element, a silver-palladium thread conductor pad for mounting an electronic component electrically connected to the extension portion, and a wiring pattern. The film thickness of the material is 15~
A multilayer circuit board characterized by having a thickness in the range of 35 μm. (2) Claim No. (2) using molybdenum for the conductor layer
1) The multilayer circuit board described in item 1).