JPS61230391A - Manufacture of 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 Application of the Invention] The present invention relates to a method for manufacturing a thick film multilayer wiring board, and particularly to a method for manufacturing a multilayer wiring board by a laminated printing method using a clean sheet.

[Background of the invention]

Recently, ICs and LSIs have come to be mounted on thick-film multilayer wiring circuit boards, and ceramic thick-film circuit boards cannot be used simply by crossing over some of the wiring. Therefore, multilayer circuit boards that form an insulating layer between circuit layers and establish conduction between the eyebrows using via holes (conducting paths in the downward direction filled with conductive paste) within the insulating layer have been created and used in various ways. A typical example is heat-resistant insulating inorganic powder such as alumina.
1~Q, 5tnnt thick green sheets are made, via holes, wiring, terminals, etc. are formed by printing conductive paste through a screen mask, a predetermined number of sheets are laminated and crimped, and heat treated (approximately 80~120℃). Sheet lamination method (for example, IEEE 198
0p283-295 A Multi-Laye
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A green sheet of mmt alumina etc. is used as the printing substrate,
A wet printing method (e.g. ISHM1983 p616-620 A) is used to alternately print a conductive paste and a heat-resistant insulating paste made of alumina or the like on the surface of this substrate to create a multilayer circuit board, and then heat-treat it to form a multilayer circuit board.
new Multilayer Printgct
Subztr-ata For Eight Free
Quency Dgvicaz T, Nomura,
T.

After printing and firing (heat treatment) a conductive paste on a substrate such as sintered alumina (Nonon+ura, SoMayumi), printing and firing (heat treatment) an insulating paste.
There is a dry printing lamination method in which this process is repeated alternately.

In the above-mentioned sheet stacking method, holes are punched to form through holes in the green sheet, so punch equipment and punch molds are required, and changing the through hole position due to changes in circuit configuration requires the use of a mold. It requires modification, is costly and time-consuming, and has the drawback of not being able to respond to urgent requests. On the other hand, in the printing lamination method, when forming an interlayer insulating layer by printing, an insulating layer with through holes can be formed with just one printing mask, and changing the through holes can be done by simply changing the negative pattern used to create the printing mask. It has the advantage of being much cheaper and shorter in terms of cost and repair time than mold repair using the sheet lamination method. However, since the printing lamination method also sequentially stacks circuit layers by printing, a step difference due to the thickness of the lower layer (usually 10 to 20 μm) occurs as unevenness on almost the entire surface of the insulating layer to be coated. Furthermore, since the insulating paste is printed through a mesh mask, surface roughness due to fine mesh marks appears on the entire surface. Therefore, when printing the upper layer circuit, a gap is created between the printing screen mask and the surface of the insulating layer, causing the conductive paste to sag,
Bleeding occurred, making it impossible to form the desired fine wiring, and sometimes causing short circuits between lines.

[Purpose of the invention]

The purpose of the present invention is to improve the flatness of the surface to be printed with a conductive paste in the production of multilayer circuits by the printed lamination method,
The present invention provides a method for manufacturing a multilayer circuit that prevents dripping and bleeding of printed conductive paste, enables formation at a high yield, and also enables fine circuits.

[Summary of the invention]

In the present invention, when a multilayer body consisting of a plurality of circuit layers or insulating layers is created by a wet printing lamination method, the surface to which the conductive paste is applied is prepared before the process of printing a conductive paste for forming an upper layer circuit. This is a method for manufacturing a multilayer circuit board, in which an insulating layer is printed, dried, and then flattened to make the surface of the insulating layer flat, and then a conductive paste is printed on this surface layer to form a circuit layer. .

In the present invention, the connection between the lower layer circuit and the newly printed upper layer circuit is made by via holes. In the present invention, at the time of forming this via hole, the surface of the insulating layer is flattened and pressed.The via hole may be formed later, but if the through hole is small, the through hole may be closed during the flattening press. Therefore, it is desirable to perform the flattening press after forming the via holes.

[Embodiments of the invention]

The present invention will be explained in more detail by way of examples.

1 to 4 show the process of forming a multilayer circuit on the surface of the green sheet.

Figure 1 shows a green sheet with a thickness of 1 stitch and a width of 50 m.

The green sheet that becomes the printing board is made by mixing alumina powder, talc, and clay in a weight ratio of 100:5:2, and adding polyvinyl butyral resin as a binder to this powder, and butyl glycol phthalate and trichloride as plasticizers. It was made into a slurry by adding a mixed solution of renalbutanol, and then formed by a normal sheet forming method using a doctor blade method.

2 is a circuit-forming conductive paste layer printed on the surface of the green sheet 10. The conductive paste used was prepared by adding and kneading an α-terpineol solution in which ethyl cellulose was dissolved into the above powder mixture consisting of tungsten powder, alumina powder, talc, and clay.

Reference numeral 3 denotes an insulating paste layer provided by printing, covering the circuit-forming conductive paste layer 2.

The printing paste for the insulating layer was prepared by adding and kneading α-terpineol m liquid prepared by bath-dissolving ethyl cellulose to the above-mentioned powder mixture.

Reference numeral 4 denotes a through hole formed at the same time as printing the insulating paste. This through hole is provided at a position where the terminal portion of the lower layer circuit and the terminal portion of the upper layer circuit are connected. At this time, the surface of the insulating layer 5 is undulated due to the thickness of the circuit layer of the lower circuit, so that the upper surface of the wiring forming part becomes convex, and the insulating paste is passed through a stainless steel mesh of 325 to 200 mesh and coated on the board. 40-100 to be worn
Shallow mesh traces 6 of μ-groove gratings are produced.

Thereafter, a conductive paste was printed and filled into the through hole 4 to form a via hole.

Next, the circuit board of FIG. 1 was heated to dry the printed insulating paste, and then the circuit board was pressed at 20 V- using a parallel plate press. As a result, as shown in FIG. 2, the surface 5 of the printed insulating film has no surface roughness and is made flat.

FIG. 27 shows a via hole formed by filling a through hole with conductive paste.

Next, as shown in FIG. 3, an slc conductive paste is printed on the surface of the flattened insulating paste layer to form an upper layer circuit 8. At this time, the lower layer circuit 2 and the upper layer circuit 8 are connected through a via hole 7. As in the previous step, insulating paste is printed on circuit layer 8, and conductive paste is filled into the through hole by printing to form via hole 9, which is then heated and dried. Thereafter, the surface is flattened by pressure pressing. Next, terminal lO for circuit elements such as IC, LSI, resistor, capacitor, etc.
Printing of conductive paste.

It is formed by heating (1600° C., 2 hours, in a normal atmosphere of N, +H, 0+H) and drying.

〔Effect of the invention〕

As understood from the embodiments of the present invention described above, in the present invention, the surface on which the circuit layer is formed is always flattened, so that dripping of the printed conductive paste, uneven thickness, disconnection, etc. are unlikely to occur. Therefore, the yield of products is high, and moreover, it is possible to miniaturize the circuits.

The present invention is not limited to the manufacturing method described in the Examples, and various changes can be made without departing from the gist of the present invention. For example, in this embodiment, alumina is used as the heat-resistant and insulating material, but in carrying out the present invention, it is also possible to use mullite or a glassy material in addition to alumina.

Further, the conductive material is not limited to tungsten, and other conductive materials can also be used.

[Brief explanation of the drawing]

FIGS. 1 to 4 are explanatory diagrams of embodiments of the present invention, and are enlarged longitudinal cross-sectional views of essential parts for explaining the manufacturing process of a multilayer circuit board. 1... Green sheet (printed board) 2.8... Printed circuit 3... Insulating layer 4...
Through hole 5... Insulating layer surface 6... Roughness of insulating layer surface 7, 9... Via hole 10... Circuit terminal representative patent attorney Katsuo Ogawa ゝ'-1-Figure 4 Procedure amendment (spontaneous) Name of the invention Person who amends the manufacturing method of multilayer circuit board
Agent Subject of amendment Contents of amendment in the scope of claims column of the specification and the detailed description of the invention column t% The scope of claims column will be corrected as shown in the attached sheet. 2. “Clean sheet” on page 1, line 15 of the specification
is corrected to "green sheet". (v) "0.5mnt J" on page 3, line 7 of the specification.
Q. Corrected to 3I. 4. Change "Green Sheet" on page 6, line 2 of the specification to "
Corrected to ``Green Sheet.'' 5. “Green sheet” on page 6 of the specification, line fa1a
is corrected to "green sheet". The above claims include a step of printing an insulating paste layer on the surface of a circuit board, a step of drying the insulating paste layer, a step of pressing and flattening the surface of the dried insulating paste layer, and a step of flattening the surface of the dried insulating paste layer. 1. A method for manufacturing a multilayer circuit board, comprising the step of printing a conductive paste layer on the surface of the insulating paste layer.

Claims (1)

[Claims] The process of printing an insulating paste layer on the surface of the circuit board,
a step of firing and drying the insulating paste layer; a step of pressing and flattening the surface of the dried insulating paste layer; and a step of printing a conductive paste layer on the flattened surface of the insulating paste layer. A method for manufacturing a multilayer circuit board, comprising: