JPS6313397A - Thick film circuit board with built-in capacitor - 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 comprises forming a dielectric glass layer on a conductor layer formed on an insulating substrate, and further forming an upper conductor layer on the dielectric glass layer. This invention relates to a thick film circuit board with a built-in capacitor.

Conventional technology In recent years, it has become an effective means of downsizing electronic devices.

``Hybrid ICs for various electronic circuits are becoming very active, and research and development into incorporating passive components (resistors, capacitors, coils, etc.) using thick film technology is active. Among them, regarding thick film circuit boards with built-in capacitors,
Further progress and applications are expected in the future.

The conventional thick film circuit board with a built-in capacitor as described above will be explained below. FIG. 5 shows an example of a conventional thick film circuit board with a built-in capacitor. In FIG. 5, 1 is an insulating substrate, and 2 is a lower conductor layer formed on the insulating substrate. 3 is an insulating glass layer, which is generally made of crystallized glass having a dielectric constant of about 8 to 12. 4 is a dielectric glass layer;
Crystallized glass doped with various crystalline materials having a dielectric constant of about 8 to 1000 is used depending on the required capacitance value range. Reference numeral 5 denotes an upper conductor layer formed on the insulating glass layer 3 and the dielectric glass layer 4, forming a cross-over structure in the insulating glass layer 3', and forming a cross-over structure on the dielectric glass layer 4, the lower conductor layer 2 , a dielectric glass layer 4, and an upper conductor layer 5 forming a sandwich structure to form a capacitor. Reference numeral 6 denotes a contact portion that electrically connects the lower conductor layer 5 and the upper conductor layer 2. FIG. 6 shows a cross section of FIG. 5. In Fig. 3, 7 is an overcoat glass layer for improving moisture resistance, and has a softening point of 450 to 550°C.
It is common to use glass with a low melting point. Although FIGS. 5 and 6 show a thick film circuit board with a built-in capacitor that includes a crossover structure, there is also a case where the thick film circuit board with a built-in capacitor does not include the insulating glass layer 3, that is, a crossover structure.

The thick film circuit board with a built-in capacitor constructed as described above is generally formed in the following order. That is, firstly, the lower conductor layer 2 is printed and fired on the insulating substrate 1, and secondly, the insulating glass layer 3 is printed and fired. Third, dielectric glass M4 is printed and fired. Fourthly, the insulating glass M3
Then, an upper conductor layer 5 is printed and fired on the dielectric glass layer 4 to form a capacitor and a crossover structure.

Further, in a circuit incorporating a resistor element, a resistor layer is printed and fired as a fifth step, and finally an overcoat glass layer 7 is printed and fired.

Problems to be Solved by the Invention In the thick film circuit board with a built-in capacitor constructed as described above, the thickness of the dielectric glass layer 4 is 40 mm as shown in FIG.
It is generally designed to have a thickness of about 50 μm. The above-mentioned film thickness is the film thickness necessary to ensure the initial insulation characteristics, withstand voltage, etc. of the capacitor, and is an important factor determining the performance of the capacitor.

However, due to the difference in film thickness of the dielectric glass layer 4,
When printing the overcoat glass layer 7, a uniform film thickness cannot be obtained, and defects such as pinholes and print blurring are likely to occur, especially in the vertically steep portions of the pattern edges of the dielectric glass layer 4. The moisture resistance effect of layer 7 is not sufficiently obtained.

Generally, dielectric constant 8 to 1 used for crossover etc.
Insulating crystalline glass materials with grade 2 have a very dense film cross section and have excellent moisture resistance even without overcoat glass, so they are susceptible to insulation deterioration and short circuits due to migration between the upper and lower conductor layers. On the other hand, among dielectric glasses, dielectric glass materials that have a crystalline component such as barium titanate, which has a high dielectric constant, have a very porous film cross section and many voids and pinholes. As a result, migration easily progresses between the upper and lower conductor layers due to moisture absorption, resulting in insulation deterioration and short circuit failure.

In order to ensure the reliability of the built-in capacitors in thick film circuit boards, overcoat glass is used. It is important to form a coating that is uniform and free of defects.

However, in the cross-sectional structure shown in FIG. 6, it is very difficult to form a uniform and defect-free overcoat glass layer due to the difference in the thickness of the dielectric glass layer as described above.

For the above reasons, conventional thick film circuit boards with built-in capacitors have insufficient capacitor reliability, especially moisture load resistance, so despite their usefulness, their application range is limited to some electronic devices. It was limited.

The present invention is intended to solve these problems, and aims to provide a thick film circuit board with a built-in capacitor that has significantly improved moisture resistance and load characteristics.

Means for Solving the Problems In order to solve the above problems, the present invention includes a lower conductor layer formed on an insulating substrate, a layer covering the insulating substrate and the lower conductor layer, and a layer on the lower conductor layer. an insulating glass layer provided with an opening in the insulating glass layer, a dielectric glass layer filled in the opening in the insulating glass layer, and an upper conductor layer formed on the insulating glass layer and the dielectric glass layer; The structure includes an overcoat glass layer that covers the entire surface.

Effect: With the above structure, the pattern edge portion of the dielectric glass layer is in close contact with the dense and moisture-resistant insulating glass layer, and moisture absorption from the lateral direction with respect to the cross section of the capacitor is eliminated. Furthermore, since the dielectric glass layer is printed so as to fill the openings in the insulating glass layer, the thickness of the dielectric glass layer and the insulating glass layer can be controlled to be approximately equal. Therefore, since the surface of the substrate around the capacitor formation area is smooth, the overcoat glass layer is formed with a uniform function with few defects, and moisture absorption from the direction perpendicular to the capacitor cross section is prevented. It will be significantly improved.

EXAMPLE An example of the present invention will be described below based on the drawings. 1st
The figure shows a cross section of a thick film circuit board with a built-in capacitor according to an embodiment of the present invention. In FIG. 1, 8 is an insulating substrate, 9 is a lower conductor layer formed on this insulating substrate 8, and 1
0 is an insulating glass layer that covers the insulating substrate 8 and the lower conductor layer 9 and has an opening in a part of the lower conductor layer 9. 11 is a dielectric glass layer filled in the opening in the insulating glass layer 10 by printing, 12 is an upper conductor layer formed on the insulating glass layer 10 and dielectric glass J'1511, and 13 is a lower conductor layer 9. The contact portion 14 that electrically connects the upper conductor layer 12 is an overcoat glass layer that covers the entire contact portion.

In the thick film circuit board with a built-in capacitor of this embodiment, the pattern edge portion of the dielectric glass ff1l is protected by the insulating glass [12], and the film thicknesses of the dielectric glass layer 11 and the insulating glass layer 10 are approximately equal. Therefore, the upper overcoat glass layer 14 is formed uniformly and with few defects, and the moisture resistance is greatly improved.

The second @ shows an embodiment in which the insulating glass layer 10 is limited only to the periphery of the capacitor forming part in the first invention.

However, it has the same effect as the embodiment shown in FIG. FIG. 3 shows a cross section of FIG.

FIG. 4 is a sectional view of another embodiment of the present invention in a thick film multilayer circuit board. In FIG. 4, 15 is an insulating substrate;
6 is a first conductor layer, 17 is a first insulating glass layer with an opening formed in a part of the first conductor layer 16, 18 is a dielectric glass layer filled in the opening, and 19 is a second conductor layer. Up to this point, the configuration is similar to that of the embodiment shown in FIG. In this embodiment, a second insulating glass layer 20 is formed on the second conductor layer 19, a third conductor layer 21 is provided on the second insulating glass layer 20, and a resistor is provided between the third conductor layers 21. A layer 23 is provided, and an overcoat glass layer 24 covering the entire surface thereof is formed. Note that 22a and 22b are contact portions between the second conductor layer and the third conductor layer 21.

In this embodiment, by forming the insulating glass layer into two layers, the upper part of the dielectric glass layer is covered with an insulating glass layer instead of the overcoat glass layer, and the effect is equivalent to that of the embodiment shown in FIG. It also improves moisture resistance.

Effects of the Invention According to the present invention, by filling the openings in the insulating glass layer with a dielectric glass layer, it is possible to prevent moisture from entering from the lateral direction and to form a uniform film of O-A-coated glass. This makes it easier to prevent moisture from entering from the vertical direction. This effect prevents insulation deterioration and short circuit failure due to migration even in thick film capacitors using relatively porous dielectric glass materials, making it possible to obtain a capacitor-embedded thick film circuit board with excellent moisture load resistance. , its practical effects are great.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a thick film circuit board with a built-in capacitor according to an embodiment of the present invention, FIG. 2 is a plan view of a thick film circuit board with a built-in capacitor according to another embodiment of the present invention, and FIG. cross section,
FIG. 4 is a sectional view of still another embodiment of the thick film multilayer board of the present invention, FIG. 5 is a plan view of a conventional thick film circuit board with a built-in capacitor, and FIG. 6 is a sectional view of the same board. 8.15... Insulating substrate, 9... Lower conductor layer, 10.
...Insulating glass layer, 11.18...Dielectric glass layer,
12... Upper conductor layer, 13.22a, 22b--contact part, 14.24-... Overcoat glass layer, 16... First conductor layer, 17... First insulating glass layer, 19...・Second conductor layer, 20...Second insulating glass layer, 21...33rd body layer, 23...Resistance layer agentヰman / θ - - Power to ask "2nd layer 11 -1 - ψ pu 1 habitual force" Uno / 2 ++ 1
-Immediate ship crushing /3---Congut section/4-over)-) 77" intrusion layer @2 Figure S Figure 4 is-,, zQ4 grave 222.2 and 02. Conductive Mantle 23-Pull 1 24-X-Nogu-〕-Toka''woi Fig. 5 Fig. 2

Claims (1)

[Claims] 1. a lower conductor layer formed on an insulating substrate; an insulating glass layer covering the insulating substrate and the lower conductor layer and having an opening in a part of the lower conductor layer; A thick film circuit board with a built-in capacitor, comprising: a dielectric glass layer filled in an opening of the insulating glass layer, an upper conductor layer formed on the insulating glass layer and the dielectric glass layer, and an overcoat glass layer covering the entirety.