JPS61159792A - Making ceramic wiring 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 [Technical Field] The present invention relates to a method for manufacturing a ceramic wiring board used as an electronic base material.

[Background technology]

Conventional methods for making circuit boards made of inorganic wiring boards such as ceramics include drawing circuits on alumina green ceramic sheets before firing with tungsten slurry and firing them together in a reducing atmosphere; Pd
, Ag/Pt, Au.

A common method is to mix fine metal powder such as Cu with glass frit and an organic vehicle to form a paste, screen print it on a ceramic substrate, and then bake it at a temperature that melts the glass frit to the ceramic substrate to form a circuit. It is. These methods are unsuitable for fine wiring due to high wiring resistance, and are difficult to form fine patterns.
Furthermore, since it contains glass, it has disadvantages such as poor solder adhesion, a tendency to produce defective products, and a tendency to break down during use.

A ceramic substrate and a copper foil are bonded together using an adhesive to form an etching resist film on a predetermined circuit portion. There is also a method of forming a circuit by removing the etching resist film after etching away parts other than the predetermined circuit parts. However, at present, this method is not generally used because there is no good inorganic adhesive and organic adhesives are inferior in properties such as heat resistance, chemical resistance, and one-dimensional stability.

Other methods for manufacturing ceramic wiring boards include PV deposition, sputtering, and ion plating.
There is a method of forming a circuit using the D method. Since the PVD method does not have the above-mentioned drawbacks, it can be said to be a highly practical method. However, it is difficult to obtain strong adhesion between the substrate and the metal layer, and it is also very difficult to increase the film thickness.

Generally, the first element required for a wiring board is good adhesion between the board material and the wiring metal. Therefore, the above-mentioned drawbacks of the PVD method can be said to be serious problems in putting this method into practical use. For organic wiring board materials such as glass epoxy, one way to increase this adhesion is to roughen the board surface and then metalize it to physically bond the board and metal layer using the so-called anchor effect. However, for inorganic wiring boards such as ceramics, there is a practical method that improves adhesion by roughening the board surface and then metalizing it. There are no examples. That is, although NaOH melt, HF, etc. have been considered as methods for roughening the surface of a ceramic substrate, it is impossible to uniformly and finely roughen the surface.

[Purpose of the invention]

The present invention was made in view of the current situation, and provides a ceramic wiring board in which even fine patterns can be formed using base metal conductors with low wiring resistance, and in which the adhesion between the ceramic and the conductor is stable and strong. Our goal is to provide the following.

[Disclosure of the invention]

Conventionally, solutions and melts of H3PO4, borax, V2O5, etc. have been used for chemical processing methods of ceramics including glass, and
It is used as a chemical polishing method. Among these chemical methods, the inventors came up with the idea that a method using phosphoric acid could be used to roughen the surface of a ceramic substrate, and after conducting various experimental studies, they found that it could be used. Furthermore, we learned that adjusting the crane size of the board is also important. And here we have completed this invention.

Therefore, the present invention provides a method in which the average crane size of a ceramic substrate is set to 8 μm or less, the surface is roughened with phosphoric acid, and the roughened surface is subjected to only PVD, and after PVD is performed, electrolysis is performed. The gist of the present invention is a method for manufacturing a ceramic wiring board, characterized in that a metal layer is formed by any one of plating methods.

The manufacturing process of the ceramic wiring board according to the present invention is shown in FIG. 1, and the manufacturing process will be described in detail below with reference to this figure.

■ Prepare a sintered ceramic substrate. During sintering, the crane size of the substrate is controlled to be 8 μm or less. As the material of the substrate, oxide-based ceramics such as alumina, forsterite, steatite, zircon, mullite, cordierite, zirconia, and titania are mainly considered, and carbide-based and nitride-based ceramics can also be used.

■ Roughen the surface of the ceramic substrate. As for the etching agents used in the surface roughening method, we have experimented with all conventionally known etching agents, and found that they can uniformly roughen a large area and do not reduce the adhesion even if the etching agent remains. First, it was found that phosphoric acid solutions such as orthophosphoric acid, pyrophosphoric acid, metaphosphoric acid, etc., or molten salts are etching agents that do not adversely affect the metal film that will be formed on the substrate later. Adopted.

By the way, it is possible to roughen the ceramic surface layer by etching with the well-known HF at 90°C, but if HF remains, etching may progress gradually and the ceramic substrate may deteriorate. In addition to corroding the metal film layer, fine and uniform roughening is impossible.

Further, phosphoric acid has a low etching ability at a processing temperature of 250° C. or lower, and decomposes or condenses rapidly at a processing temperature of 360° C. or higher, so the etching ability is also low. 250～
At a treatment temperature of 360°C, 1 to 30 minutes, preferably 3 to 1
When treated for 0 minutes, a surface-roughened substrate with no deterioration in strength can be obtained. Note that the roughening with phosphoric acid does not need to be done by immersion.

■ Rinse and dry. It is necessary to thoroughly wash and dry the metal film so as not to cause poor adhesion.

■ Form a metal layer by PVD method. This is vapor deposition,
A base metal layer such as copper or nickel is formed using commonly used methods such as sputtering and ion plating. With these methods, it is very difficult to form a thick metal layer.

■ Perform electrolytic plating if necessary. When the required thickness of the metal layer is large, electrolytic plating is performed by forming the metal layer on the substrate by the PVD method and then plating with copper or nickel.

■ If necessary, form a circuit by etching. P
In some cases, the necessary circuit is immediately formed by the VD method or electrolytic plating thereon, but in the case of full-surface plating, the circuit is formed by etching. The circuit formation method is a commonly used method.

According to this manufacturing method, it is possible to form fine patterns using base metal conductors with low wiring resistance, and the adhesion between the metal layer and the ceramic substrate is uniform, making it possible to create a stable and strong ceramic wiring board. can.

The average crane size of commercially available ceramic substrates is 8 to 30 μm, but the crane size is controlled by controlling sintering to produce a ceramic substrate with an average crane size of 8 μm or less, which is then roughened. When the surface roughness after roughening was measured, it was found that the surface roughness was uniformly finely roughened to Rmax 1 to IO μm. This is the reason why the average crane size of the ceramic substrate is adjusted to 8 μm or less in this invention.

When a sintered ceramic substrate with a large crane size is used, the surface roughness after roughening is also large. Surface roughness Rm aX is 1
It is necessary to make it 0 μm or less, preferably 5 μm or less. Using such a ceramic substrate will improve the adhesion between the ceramic substrate and the metal layer, the roughness of the metal surface, and the ability to form fine patterns. Excellent effects can be obtained in these respects. For example, the adhesion strength is 1.5 on average.
It has doubled and the variation has been halved. The roughness of the metal layer surface could also be improved by 2 to 3 times. Also, the yield is 2
This has doubled, making it possible to create fine patterns with line widths and line spacings of up to 30 μm.

The cause of this improvement in characteristics will be explained below. When roughening a ceramic substrate, the etching agent attacks grain boundaries and etches the substrate. If the average crane size of the sintered ceramic substrate is reduced, the number of holes per unit area increases, and even shallow holes can be drilled with ideal recesses. Therefore, the anchor effect is improved and the adhesion between the metal layer and the ceramic substrate is improved.

Note that the crane size (size of polycrystalline particles) of the sintered body is measured using an electron micrograph.

Examples according to the present invention will be described below.

(Example 1) Alumina, steatite, zirconia, mullite, etc.
A sintered ceramic substrate with a thickness of 1.0 to 2.0 mm and a crane size of 1 to 8 μm was prototyped. This substrate was soaked in phosphoric acid heated to 250 to 360°C for 1 to 30 minutes.
The surface was roughened by soaking it for a minute. After roughening, it was thoroughly washed with water and dried. This sample was metallized with copper or nickel by PVD methods such as vapor deposition, sputtering, and ion plating. Next, a copper or nickel metal layer is formed by electrolytic plating to a thickness of 35 μm.
Adjusted to m. Then, the surface roughness of the ceramic substrate and the adhesion strength between the metal layer and the ceramic (90° peel strength, L-shaped tensile strength) were measured. Further, as for fine patterns, it was possible to create a line width and a line spacing of up to 30 μm. The results are shown in Table 1 together with comparative examples. In the table, Comparative Examples 1 to 4 are non-roughened ceramic substrates, Comparative Example 5
゜6 is a commercially available ceramic substrate roughened with phosphoric acid,
PVD and electrolytic plating (below)
(Margin) [Effects of the Invention] The method for manufacturing a ceramic wiring board according to the present invention makes it possible to form a fine pattern using a base metal conductor with low wiring resistance, and also ensures uniform adhesion between the ceramic board and the metal layer. A stable and strong ceramic wiring board can be made with

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing the manufacturing process of a ceramic wiring board according to the present invention. Agent Patent Attorney Takehiko Matsumoto Figure 1

Claims (3)

[Claims] (1) A method in which the average crane size of the ceramic substrate is set to 8 μm or less, the surface is roughened with phosphoric acid, and only PVD is applied on the roughened surface, and P
A method for manufacturing a ceramic wiring board, characterized in that a metal layer is formed by any one of the following methods: VD and then electrolytic plating. (2) The method for manufacturing a ceramic wiring board according to claim 1, wherein PVD is one method selected from the group consisting of vapor deposition, sputtering, and ion plating. (3) The phosphoric acid according to claim 1 or 2, wherein the phosphoric acid is a solution or a molten salt of one phosphoric acid selected from the group consisting of orthophosphoric acid, pyrophosphoric acid, and metaphosphoric acid. Manufacturing method for ceramic wiring boards.