JPH0661646A - Circuit board and production thereof - Google Patents

Abstract

PURPOSE:To increase production yield by making grooves in the periphery of the lamination surface of a thin film circuit thereby preventing exfoliation of thin film part. CONSTITUTION:In a circuit board where a thin film circuit 2 is laminated on a hard board 1, a plurality of grooves 3, 3,... are made from the inside toward the outside in the periphery of the lamination surface of the thin film circuit 2. The circuit board is produced by laminating a plurality of green sheets printed with a wiring pattern, baking the laminate to obtain a ceramic multilayer board 1 where interlayer connection is made through VIAs, making a plurality of grooves 3, 3,... from the inside toward the outside in the periphery of the surface part of the ceramic multilayer board 1, and then forming a thin film circuit 2 on the grooved surface. This constitution absorbs residual stress in the dielectric layer of the thin film circuit 2 and the warping stress of the board 1 through the grooves 3 and prevents exfoliation of the thin film circuit 2 at the interface.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a circuit board and a method for manufacturing the same.

[0002]

2. Description of the Related Art FIG. 13 shows a conventional circuit board in which a thin film circuit is formed on a hard circuit board. In this conventional example,
A thin film circuit 2 is formed on the surface of a ceramic multilayer substrate (hard substrate 1) formed by firing a green sheet.

The thin film circuit 2 includes a polyimide resin as an insulating layer 4
Is formed by laminating a plurality of conductor layers.

[0004]

However, in the above-mentioned conventional example, the residual stress of the polyimide insulating layer 4 caused by the heating in the curing step of the polyimide insulating layer 4 or the stress due to the warp of the substrate 1 causes the problem shown in FIG. As shown in b), the polyimide insulating layer 4 may be peeled from the interface of the substrate 1 or the interface of the substrate 1 may be damaged.
It had a defect that the production yield was low.

The present invention has been made to solve the above drawbacks, and an object of the present invention is to provide a circuit board having a high manufacturing yield and a manufacturing method thereof.

[0006]

According to the present invention, the above-mentioned object is a circuit board in which a thin film circuit 2 is laminated on a hard substrate 1 as shown in FIG.
It is achieved by providing a circuit board in which a plurality of concave grooves 3, 3, ...

In the circuit board, a plurality of green sheets 6 each having a wiring pattern 5 printed thereon are laminated and then fired to obtain a ceramic multilayer board 1 which is interconnected by vias 7. Then, the ceramic multilayer board is obtained. Manufactured by a method for manufacturing a circuit board in which a plurality of recessed grooves 3, 3 ... To be done.

[0008]

The hard substrate 1 according to the present invention is provided with a plurality of concave grooves 3 extending from the inner side to the outer side at the peripheral edge of the surface, and the thin film circuit 2 is
It is formed on the surface provided with the concave groove 3.

In the process of forming the thin film circuit 2, the stress remaining in the insulating layer 4 of the thin film circuit 2 or the stress caused by the warp of the substrate 1 is absorbed by each groove 3 and separated from the boundary surface with the thin film circuit 2. Are reliably prevented.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will now be described in detail with reference to the accompanying drawings. A method of manufacturing a circuit board is shown in FIG. 3 and subsequent figures, FIGS. 3 to 5 show a manufacturing step of the ceramic multilayer board 1 (hard board 1), and FIG. 6 and subsequent figures show a manufacturing step of the thin film circuit 2.

First, a via hole 8 is bored in a green sheet 6 formed by kneading a ceramic powder and an appropriate binder in a slurry form, and the via hole 8 is filled with a conductive metal.

Thereafter, a conductor metal is screen-printed on the green sheet 6 to form predetermined wiring patterns 5, 5, ... (See FIG. 3). The plurality of green sheets 6, 6 ... Formed in this way are laminated and fired in a firing furnace. By firing, as shown in FIG. 4, a ceramic multilayer substrate 1 in which the conductor layers are properly connected by vias 7 is obtained.

.. are formed in the surface portion of the ceramic multi-layer substrate 1 formed as described above by using an appropriate cutting means, as shown in FIG. Groove 3
Are formed on the peripheral portion of the ceramic multilayer substrate 1 and are provided parallel to the direction from the inside to the outside.

Next, a thin film circuit 2 is formed on the ceramic multilayer substrate 1. That is, first, a conductor film (adhesion layer) is formed on the ceramic multilayer substrate 1 by a sputtering process (see FIG. 6). Then, a resist layer 10 is formed on the sputtered film 9 (see FIG. 7).

Next, when the ceramic multilayer substrate 1 on which the resist layer 10 is formed is plated, the portion where the sputtered film 9 is exposed is selectively plated with the conductive metal 11 as shown in FIG. The layer 10 is peeled off, and then the sputtered film 9 exposed by panel etching is etched to form a single-layer thin film circuit pattern 12 (see FIGS. 9 and 10).

The above-mentioned thin film circuit pattern 12 is formed by laminating a plurality of layers on the ceramic multilayer substrate 1. When laminating the second and subsequent layers, first, the photosensitive polyimide 13 is applied by spin coating over the entire lower layer. (Fig. 1
1).

After that, when the photosensitive polyimide 13 is selectively etched through the steps of exposure, development, and hard baking, the lower layer is insulated by the polyimide insulating layer 4 leaving the interlayer connection via 7 '(see FIG. 12), A circuit board shown in FIG. 2 is formed by laminating a plurality of layers of circuit patterns on the upper surface in the same procedure as described above.

In the above, the groove 3 is formed by a cutting process performed after firing the green sheet 6, but it is also possible to form the groove 3 when laminating and compressing the green sheet 6 in this case. If the protrusion corresponding to the concave groove 3 is provided in the compression mold, the concave groove 3 can be formed without requiring a special process.

Further, the hard substrate 1 can be applied not only to the ceramic multilayer substrate but also to a glass substrate or the like.

[0020]

As is apparent from the above description, according to the present invention, since the stress due to the warp of the substrate or the strain during the manufacturing of the insulating film is absorbed by the concave groove, the peeling of the thin film portion can be completed completely. Can be prevented and the manufacturing yield can be improved.

[Brief description of drawings]

FIG. 1 is a perspective view showing an embodiment of the present invention.

FIG. 2 is a cross-sectional view of FIG.

FIG. 3 is a diagram showing a stacking process of green sheets.

FIG. 4 is a cross-sectional view of a hard substrate.

FIG. 5 is a perspective view showing a state in which a groove is cut.

FIG. 6 is a cross-sectional view showing a step of forming a sputtered film.

FIG. 7 is a cross-sectional view showing a formation state of a resist film.

FIG. 8 is a cross-sectional view showing a conductive metal plating step.

FIG. 9 is a cross-sectional view showing a state in which a resist film is peeled off.

FIG. 10 is a cross-sectional view showing a thin film circuit pattern.

FIG. 11 is a cross-sectional view showing a polyimide coating step.

FIG. 12 is a cross-sectional view showing an exposed state of polyimide.

FIG. 13 is a view showing a conventional example, (a) is an overall perspective view,
(B) is a figure which shows the peeling state of a thin film circuit.

[Explanation of symbols]

 1 Hard Substrate 2 Thin Film Circuit 3 Recessed Groove 4 Insulating Layer 5 Wiring Pattern 6 Green Sheet 7 Via

Claims (4)

[Claims] 1. A circuit board in which a thin film circuit (2) is laminated on a hard substrate (1), the inside of the substrate (1) being directed from the inside to the outside of the periphery of the laminated surface of the thin film circuit (2). A circuit board with multiple recesses (3, 3, ...) 2. The circuit board according to claim 1, wherein the board (1) is a ceramic multilayer board, and the insulating layer (4) of the thin film circuit (2) is formed of a polyimide resin. 3. A via is formed by stacking a plurality of green sheets (6, 6 ...) On which a wiring pattern (5) is printed and then firing them.
A ceramic multilayer substrate (1) interconnected by (7) is obtained, and then a plurality of concave grooves (3, 3, ...) From the inside to the outside are formed on the peripheral edge of the surface of the ceramic multilayer substrate (1). A method of manufacturing a circuit board, which comprises grinding, and then forming a thin film circuit (2) on the surface of the groove (3) formed. 4. The method for manufacturing a circuit board according to claim 3, wherein the recessed groove (3) is formed in a green sheet (6) laminating step.