JPH0380358B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a multilayer circuit board on which a large number of active elements and passive elements such as ICs, capacitors, and resistors are mounted.

Conventionally, when forming an insulating layer to insulate between the multilayer conductor circuits of this type of multilayer circuit board by screen printing, the shape of the via hole was not printed on the screen due to the influence of the underlying circuit conductor. It was difficult to print according to the formed pattern. In addition, the recent need for high-density multilayer circuit boards for high-speed calculations requires physical properties such as low dielectric constant, high thermal conductivity, and high mechanical strength as materials for insulating layers, so glass powder and A mixture of inorganic oxide powders such as , alumina, etc. has been used. Therefore, the insulating layer after formation contains many pores. If there are many pores, the plating solution will seep in during the plating process and metal will precipitate, causing a short circuit between the upper and lower conductor layers and degrading the insulation.

The present invention eliminates the above-mentioned drawbacks, prevents deterioration of insulation properties by reducing pores, increases mechanical strength, and provides a multilayer circuit that secures via holes to ensure reliable connection with upper and lower layer conductors. A method for manufacturing a substrate is provided.

The method for manufacturing a multilayer circuit board of the present invention includes the steps of forming a first conductor pattern on a ceramic substrate;
A first insulating paste containing high melting point glass powder and inorganic oxide powder is screen printed on the surface of the ceramic substrate including the first conductor pattern using a screen having a pattern for forming via holes, and the high melting point glass is softened. forming a first insulating layer having a via hole on the first conductive pattern by firing at a temperature between a melting point and a melting point; and a first insulating layer including a first conductive pattern exposed in the via hole. forming a second insulating layer by applying a second insulating paste containing a low melting point glass powder thereon and firing it at a temperature slightly higher than the softening point of the low melting point glass; and applying the screen on the second insulating film. screen printing the first insulating paste to form a coating film having a pattern that matches the pattern of the first insulating layer, and forming a coating film having a pattern between the softening point and the melting point of the high melting point glass of the first insulating paste. At the same time, the second insulating layer is melted to form a third insulating layer at a temperature of the first in the via hole.
The method includes the steps of exposing the surface of the conductive pattern, and forming a second conductive pattern connected to the first conductive pattern on the surface including the via hole.

Next, embodiments of the present invention will be described using the drawings.

1 to 6 are cross-sectional views showing main manufacturing steps for explaining an embodiment of the present invention.

First, as raw materials, a ceramic substrate made of alumina etc., a thick film conductor forming paste containing noble metals such as Au and Ag/Pd, a softening point of 800℃ and a softening point of 1000℃.
a first insulating paste comprising a first glass powder and an alumina powder having a melting point of 500°C and a softening point of 850°C;
A second insulating paste is provided that includes a second glass powder having a melting point of °C.

Next, as shown in FIG.
A first conductor pattern 2 is formed thereon by a screen printing method using a paste for forming a thick film. A first insulating paste is printed on this by a screen printing method and dried to form a first insulating paste coating layer 3. At this time, a screen having via holes 7 for connecting the second conductor pattern formed in a later step to the first conductor pattern 2 is used.

Next, as shown in FIG. 2, the first insulating paste coating layer 3 is fired together with the substrate 1 at 850° C. to form a first insulating layer 4. A large number of pores 5 are generated in the first insulating layer 4 by this firing.

Next, as shown in FIG. 3, a second insulating paste is applied to the entire surface and fired at 530° C. to form a second insulating layer 6 filling the via holes 7.

Next, as shown in FIG. 4, the same pattern as the first insulating paste coating layer 3 is formed using the screen and the first insulating paste used when forming the first insulating paste coating layer 3 shown in FIG. A third insulating paste coating layer 3' and a via hole 7 are formed.

Next, as shown in FIG. 5, the third insulating paste coating layer 3' is fired together with the substrate 1 at 850° C. to form a third insulating layer 9. At this time, since the second insulating layer 6 has a melting point of 850°C, it melts during firing and is absorbed into the pores 5 and 10 of the first and third insulating layers 4 and 9, so that the via hole Most of the second insulating layer 6 on the first conductor pattern 2 in 7 is removed, and the conductor surface is exposed.

Next, as shown in FIG. 6, a second conductor pattern 11 is formed by screen printing, drying, and baking using a paste for forming a thick film conductor.

A multilayer circuit board can be obtained by repeating the above steps a necessary number of times. As shown in this example, by using two types of insulating pastes with different softening and melting points, via holes can be printed according to the pattern without clogging, and the pores can be closed to provide insulation by absorbing moisture, etc. A multilayer circuit board that prevents deterioration can be obtained.

As explained above, by forming a dense insulating layer using two types of insulating paste and two different firing temperatures, the present invention secures the connection between the upper and lower layer conductors through fine via holes, and also provides insulation. This has the effect of obtaining a multilayer circuit board with excellent characteristics.

[Brief explanation of drawings]

1 to 6 are cross-sectional views for explaining one embodiment of the present invention. 1... Ceramic substrate, 2... First conductor pattern,
3... First insulating paste coating layer, 3'... Third insulating paste coating layer, 4... First insulating layer, 5... Pore, 6...
2nd insulating layer, 7... via hole, 8... second insulating layer, 9... third insulating layer, 10... pore, 11... second conductor pattern.

Claims (1)

[Claims] 1. Forming a first conductor pattern on a ceramic substrate, and using a screen having a pattern for forming via holes on the surface of the ceramic substrate including the first conductor pattern, using a high melting point glass powder and an inorganic oxide powder. forming a first insulating layer having via holes on the first conductor pattern by screen printing a first insulating paste and baking at a temperature between the softening point and melting point of the high melting point glass; A second insulating paste containing low melting point glass powder is applied on the first insulating layer including the first conductor pattern exposed in the hole, and is fired at a temperature slightly higher than the softening point of the low melting point glass to form a second insulating layer. forming a coating film having a pattern matching the pattern of the first insulating layer by screen printing the first insulating paste on the second insulating film using the screen; The insulating paste is fired at a temperature between the softening point and the melting point of the high melting point glass to form a third insulating layer, and at the same time, the second insulating layer is melted to form a second insulating paste on the first conductor pattern in the via hole. a step of absorbing an insulating layer into bubbles generated in the first and third insulating layers to expose the surface of the first conductive pattern in the via hole, and forming the first conductive pattern on the surface including the via hole. A method for manufacturing a multilayer circuit board, comprising the step of forming a second conductor pattern to be connected.