JPS5986292A - Method of producing ceramic 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 the Invention The present invention relates to a method for forming vias in a ceramic multilayer wiring board for electrically connecting wiring conductor portions located above and below across an insulating layer.

Conventional technology The formation of vias is divided into a pier hole process, in which an opening is formed in an insulating layer, and a via fill process, in which a conductor layer is formed in this opening.

A typical conventional method for forming vias is the so-called thick film screen printing method, in which a thick film paste is printed, dried, and fired using a previously patterned screen. This method has been widely used because it allows an insulating layer with pier holes to be formed by screen printing, fired, and then formed on the pier holes using a screen. However, in this method, the pattern is formed by the screen. Therefore, it is unsuitable for forming minute via patterns.When considering the mass production level, the size of the pier hole and via fill is 250 μm0 (micron square).
This is almost the limit. As a method of forming smaller vias, photosensitive resist C0NFERENCECIPl
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T-ATEJ describes a method in which a photosensitive resist is applied onto an insulating paste, a pier hole is formed in the insulating paste and the photosensitive resist φ by exposure and development, and then a conductive paste is filled in as a via fill.

This method is suitable for small vias, as it uses a full-length vagina keg 2-fi technique to form the pier hole, and a self-alignment technique that embeds conductive paste in the pier hole. Although it depends on the volatiles of the resist and the thickness of the insulating layer, it is 100μm0.
It is possible to form up to a certain degree. The problem with this method is that the allowable range of adhesion between the insulating paste and the photosensitive resist formed thereon is narrow. If the adhesion is too weak, the gap between the photosensitive resist and the insulating paste will peel off during development of the photosensitive resist. Furthermore, if the VJ adhesion is too strong, when the photosensitive resist is peeled off from the insulating paste after embedding the conductive paste, it may not be easily peeled off, or a portion of the insulating paste may also be peeled off. Therefore, controlling this adhesion is both important and difficult. Furthermore, in order to form a photosensitive resist on the insulating layer, steps such as coating, exposure, development, and peeling are added for the resist, making the process complicated.

Object of the Invention The object of the invention is to provide a method of forming a pier hole using a photo-curable insulating paste, filling the pier hole with a conductive paste from above to form a via fill, and then removing excess conductive paste remaining on the insulating paste. It is an object of the present invention to provide a method that solves the above-mentioned drawbacks and makes it possible to form vias in simple steps.

Another object of the present invention is to provide a method in which the conductive paste on the insulating paste can be easily removed using a Q, +CF4 plasma asher.

Another object of the present invention is 100 μm0 (micron square)
It is an object of the present invention to provide the following method for forming minute vias.

Structure of the Invention The method of the present invention includes a first step of printing and drying a photocurable insulating paste on the surface of a ceramic substrate, and a desired portion of the photocurable insulating paste by exposure and development. a second step of forming a peep opening; a third step of filling the opening with conductive paste using a stencil screen that covers the periphery of the substrate; A fourth step of removing the conductive paste, and a fifth step of firing the photocurable insulating paste and the conductive paste embedded in the opening to form an insulating layer and a conductive layer. shall be.

In the method as an embodiment of the present invention, in the fourth step of the above invention, 0. +CF gas plasma asher
The present invention is characterized in that it includes a method in which the organic binder component of the conductive paste is burned to facilitate removal of the conductive paste from the insulating paste.

Examples of the invention Next, the present invention will be explained in detail with reference to the drawings.

Referring to FIG. 1, a photocurable insulating paste 2 is printed and dried on the surface of an alumina substrate 1. As shown in FIG.

The photocurable insulation paste contains alumina particles AI, 0. and,
An inorganic component consisting of glass particles mainly composed of silicon dioxide SiO
G) and other organic components.

Next, referring to FIG. 2, the photocurable insulation paste 2
An opening 3 is formed by removing the paste at a desired portion of the hole 9. This is called a peer hole.

The formation of this pier hole is performed by exposing the film to light through a glass mask (not shown) and then developing it using a 1-1-1) dichloroethane solution. The possible size of the peer hole formed at this time depends on the resolution of the photocurable insulating paste, but the one used in this example is
A minimum of 50 to 80 μm0 (micron square) can be formed. This is 1/4 to 1/4 compared to conventional screen printing methods or methods that combine insulating paste and photosensitive resist.
It is 1/2 the size. Referring to FIG. 3, a conductive paste is printed on the surface of the insulating paste 2 using a stencil screen (not shown). The conductor paste 4 is
Although a very thin layer remains on the surface of the insulating paste, it is embedded in the pier hole 3 and becomes the via fill 5. The surface of the photocurable insulating paste 2 is slightly smooth, and the amount of conductive paste 4 is small compared to the amount of paste in the via fill portion. Also, since the periphery of the board is covered with a stencil screen, no conductive paste is attached to it. In this way, by using the stencil screen, it becomes possible to fill the conductive paste only in the area where via filling is required.

Referring to FIG. 4, the conductor paste remaining on the surface of the photocurable insulation paste is removed. A polishing device using Scotch prite is used for this purpose. By removing the very surface of the photocurable insulating paste, the conductive paste can be completely removed.

Further, the conductive paste 5 embedded in the pier hole remains without being removed in the polishing process.

Referring to FIG. 5, the photocurable insulation paste 2 and the via fill conductor paste 5 are fired, and the insulation layer 2 is heated.
' and a conductor layer 5'. As explained above,
In the present invention, it is possible to easily form and form the piers without using a photosensitive resist, and it is also possible to form minute piers. Referring to FIG. 6, a second embodiment of the present invention is implemented as follows. That is, with the conductor paste 4 gradually spreading on the surface of the photocurable insulating paste 20, O,
Plasma ashing using +-CF4 mixed gas is performed.

The organic binder components of the conductor paste 4 and the surface portion 2' of the photocurable insulating paste are burned by the ashing process for about 10 minutes, and the paste loses its binding power to bind the inorganic component particles of the paste, so the paste is extremely weak. It can be easily removed by force. Removal methods include using a spin brush 2-bar device, in which the substrate is rotated and lightly scrubbed with a brush made of nylon, etc., and a method in which the substrate is blown with pure water using pressure. FIG. 7 shows the state after the surface portion of the photocurable insulating paste and the conductive paste have been removed. In the state shown in Fig. 6, the conductor paste 5 embedded in the pier hole has a hollow shape at the center, but in the process of removing the conductor paste 4 using a plus 1 asher, the surface part of the insulating paste 2'' Therefore, as shown in FIG. 7, the entire surface of the insulating paste 2 including the pier hole portion 5 becomes smooth.

Referring to FIG. 8, the insulating paste 2 and the peer-hole conductor paste 5 are then fired to form the insulating layer 2.
The conductor layer 5' is the same as in the first embodiment.

By using a plasma asher, the conductor paste can be removed very easily, and by changing 1uj during the plasma asher, the organophilic binder portion (2 in Figure 7) on the surface of the insulating layer can be removed. An advantage of this embodiment is that the thickness can be controlled to an arbitrary value.

Effects of the Invention The present invention provides a method in which a photo-curable insulating paste is used to form a pier hole, a conductive paste is filled into the pier hole from above to form a via fill, and then excess conductive paste remaining on the insulating paste is removed. By using this, there is an effect that fine vias can be formed in a simple process.

[Brief explanation of drawings]

1 to 5 show a first embodiment of the present invention. 6 to 8 are process sectional views showing a second embodiment of the present invention. In Figs. 1 to 8, 1... alumina substrate;
2 Photocurable insulation paste, 2′・Insulating layer, 2“
Photocurable insulation paste surface portion, 3 Pier hole, 4
... Conductor paste residue, 5 ... Via fill conductor paste, 5' conductor layer. Z7 figure, → Z 2 figure 3 figure y; 4 figure 6' Z5 times 6 figure S4 figure 7 5 box 6 figure ,・

Claims (1)

[Claims] (1) A first step of printing and drying a photocurable insulating paste on the surface of a ceramic substrate, and forming an opening through which a desired portion of the photocurable insulating paste is exposed by exposure light and development. a third step of filling the opening with a conductive paste using a stencil screen that covers the periphery of the substrate; A fourth step of removing the conductive paste; and a fifth step of firing the photocurable insulating paste and the conductive paste embedded in the opening to form an insulating layer and a conductive layer. A method for manufacturing a ceramic multilayer wiring board. (2) In the fourth step, the organic binder component in the conductive paste adhering to the surface of the photocurable insulating paste is easily removed by being burned by a mixed gas plasma of oxygen and fluorocarbon. A method for manufacturing a ceramic multilayer wiring board according to claim 1.