JPH0669370A - Manufacture of multilayer circuit board - Google Patents

Abstract

PURPOSE:To raise the reliability on electric connection as compared with the case of bringing a film-shaped metallic foil into contact with it, by providing an electrically conductive solution-form paste layer on a signal takeout part or a surface conductor layer, and supplying power through this paste layer. CONSTITUTION:This board comprises a ceramic board 1, a conductor layer 3, which is formed on the surface of the ceramic board 1 or on the surface through an insulating layer, and a signal takeout part, which is connected electrically to the conductor layer 3. What is more, the signal takeout part is provided with a signal takeout pin 2. Moreover, the signal takeout part is provided with a paste layer by applying electrically conductive paste 4, and electrolytic plating is performed by supplying the conductor layer 3 with power through the paste layer and the signal takeout part. And, the thickness of the conductor layer 3 is controlled by forming a plated layer on the surface of the conductor layer 3, and then the paste layer is removed. Hereby, favorable electrolytic plating of the signal takeout part can be performed.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing a multilayer circuit board, and more particularly to a method for electrolytically plating a conductor layer (or a signal extraction portion) provided on a ceramic board.

[0002]

2. Description of the Related Art Conventionally, a ceramic substrate, a conductor layer formed on the surface of a ceramic substrate or an insulating layer, and a signal extracting pin formed on the surface of a ceramic substrate and electrically connected to the conductor layer. Various methods are known as a method for electrolytically plating a signal extraction part such as a signal extraction pin formed on the surface or a conductor layer exposed on the surface in a multilayer circuit board including a signal extraction part including There is. As an example, as shown in FIG. 8, for example, the conductor layer 2 exposed on the surface of the ceramic substrate 21.
2. A dummy electrode 25 electrically connected to the internal conductor layer 23 and the pin 24 serving as a signal extraction portion is formed on an unnecessary portion such as a side surface of the ceramic substrate 21, and power is supplied from the dummy electrode 25 for electrolytic plating. It is known how to do it.

[0003]

However, in the method described above, the dummy electrode 25 is finally cut off, but the internal wiring remains and cannot be completely removed. There was an unfavorable problem that it became a source of. In order to solve this problem, when supplying power to the surface conductor from the pin side, a method of contacting an electrically conductive metal foil such as aluminum foil to the pin and supplying power through the metal foil,
When power is supplied to the pin from the surface conductor side, power is supplied through the conductor layer formed on the entire surface of the substrate before wiring the conductor layer, and when the power is supplied to the pin from the surface processed conductor side. A method has been considered in which an electrically conductive metal foil such as an aluminum foil is brought into contact with a conductor layer on which wiring has been processed, and power is supplied through the metal foil.

However, even with these methods, when power is first supplied to the surface conductor from the pin side, the metal foil cannot be brought into contact with all 100 or more pins with a completely uniform force, and good power is supplied. There is a problem that if the force is too weak, the contact becomes poor, and if it is too strong, the pin bends. Further, when power is supplied to the pin from the surface conductor side, there is a problem that there is no degree of freedom in process design because there is a limiting condition that power can be supplied to the pin side but before the conductor layer is processed. Furthermore, when power is supplied to the pin from the surface conductor side where wiring is processed, it is not possible to completely contact the metal foil with all of the plurality of electrically independent wiring conductors, and it is also impossible to perform good power supply. was there.

The object of the present invention is to solve the above problems,
An object of the present invention is to provide a method for manufacturing a multilayer circuit board, which is capable of performing excellent electrolytic plating of a conductor layer exposed on the surface of a ceramic substrate and a signal extraction portion such as a pin.

[0006]

A method of manufacturing a multilayer circuit board according to the present invention comprises a ceramic board, a conductor layer formed on the surface of the ceramic board or on a surface with an insulating layer interposed therebetween, and on the surface of the ceramic board. A method for manufacturing a multilayer circuit board comprising a conductor layer and a signal take-out portion electrically connected, wherein a paste layer is provided by applying an electrically conductive paste to the signal take-out portion (or the conductor layer). And the signal extraction part (or the conductor layer) to supply power to the conductor layer (or the signal extraction part) to perform electrolytic plating, and form a plating layer on the surface of the conductor layer (or the signal extraction part) to form the conductor layer (or The feature is that the paste layer is removed after controlling the thickness of the signal extraction portion).

[0007]

In the above structure, when a signal-extracting portion or a surface conductor layer is provided with a paste layer on an electrically conductive solution and power is supplied through this paste layer, when a film-like metal foil is brought into contact The reliability of the electrical connection can be improved as compared with. In addition, since the dummy electrode for plating is not required, the wiring for electrolytic plating is not left in the multilayer circuit board, the performance of the multilayer circuit board is improved, and the peelable paste is used for power supply. Therefore, the work of removing the electric power feeding portion after the electrolytic plating can be facilitated.

[0008]

FIG. 1 is a diagram showing the structure of an example of a multilayer circuit board which is the subject of electrolytic plating in the manufacturing method of the present invention. In the example shown in FIG. 1, a conductor layer 3 is formed on the surface of a ceramic multilayer substrate 1 by sputtering, a copper film is formed, a photosensitive resist resist is applied, exposed and developed to pattern the resist, and then formed by etching. ,
On the surface opposite to the conductor layer 3, a pin 2 made of Kovar and electrically connected to the conductor layer 3 as a signal extracting portion is attached by silver brazing.

Next, electrolytic plating on the conductor layer 3 or the pin 2 as a signal takeout portion in the multilayer circuit board having the above-described structure will be described with reference to the flow chart shown in FIG. First, the pin 2 as the signal takeout part
(Or the conductor layer 3) is coated with an electrically conductive paste and dried to form a paste layer. The method of forming the paste layer will be described later. Next, power is supplied through the paste layer and the pin 2 (or the conductor layer 3). By electroplating in this state, a plating layer is formed on the surface of the conductor layer 3 (or the pin 2). Finally, the paste layer is peeled off and removed to obtain a multilayer circuit board.

3 to 5 show a method of molding the electrically conductive paste 4 on the pin 2 side when power is supplied to the conductor layer 3 from the pin 2 side as a signal take-out portion. FIG. 3 shows an example in which the entire pin 2 is embedded with an electrically conductive paste 4.
FIG. 4 shows an example in which the electrically conductive paste 4 is applied only to the tip portion of the pin 2 and attached to the metal foil 5. In the example shown in FIG. 4, power is supplied to the conductor layer 3 via the metal foil 5, the paste 4, the pins 2, and internal wiring (not shown). FIG. 5 shows an example in which the electrically conductive paste 4 is provided in a sheet shape only on the tip portion of the pin 2. The structure shown in FIG. 5 can be obtained by molding the paste 4 into a sheet and inserting the pin 2 into the paste 4 while the paste 4 is undried to dry.

FIG. 6 shows an example of a method of forming the electrically conductive paste 4 on the conductor layer 3 when power is supplied to the pin 2 from the conductor layer 3 side. In the example shown in FIG. 6, the entire conductor layer 3 is embedded with the electrically conductive paste 4. Since the flatness of the conductor layer 3 side is usually better than that of the pin 2 side, the electrically conductive paste layer 4 can be formed by screen printing.

Electrically conductive paste 4 used in the present invention
Is carbon, graphite, silver, gold, iron, copper, zinc,
Binder of organic resin such as vinyl, polyvinyl, epoxy, ethocelle, bismaleimide, polyester, phenol, melamine, acrylic, etc. whose electrically conductive solids such as nickel, chromium, titanium, aluminum, etc. And a solvent in which the organic resin is dissolved. The electrically conductive paste 4 is brushed, screen-printed, and troweled on a portion for supplying electricity, and then dried at a temperature of 80 to 150 ° C. to dry the material. Further, the thickness of the paste 4 is preferably 5 μm or more, because if the thickness of the paste 4 is too thin, the paste does not easily peel off as a film. Most of the electrically conductive paste 4 is preferably peeled off mechanically after plating, but a small amount of residue may be dissolved and removed with an organic solvent similar to the solvent in the paste.

The ceramic substrate 1 used in the present invention is composed of a multilayer body of ceramics and a wiring layer made of an electrically conductive conductor. Ceramic materials are alumina, mullite,
Examples include aluminum nitride and glass. The signal extraction unit attached to the ceramic substrate may or may not have pins attached. Pin mounting is
It is done by brazing. Pin material is stainless steel,
Kovar, aluminum alloy, brass, nickel, iron, etc.,
Nickel on the surface to ensure the reliability of the electrical connection
Plate gold, chrome, etc. When no pin is attached to the signal extraction portion, the signal extraction portion is provided with a metal layer of nickel, chromium, gold, platinum, copper or the like by plating. Further, the signal extracting portion is connected to the wiring inside the ceramic substrate in the form of a via hole or a through hole on the surface of the ceramic substrate.

An actual example will be described below. Example A conductor layer 3 is formed on the surface of a ceramic substrate 1 having the structure shown in FIG.
Is formed by forming a copper film having a thickness of 0.5 μm by sputtering, applying a photosensitive resist, exposing and developing to pattern the resist, and then etching. The conductor is made of Kovar on the side opposite to the conductor layer 3. Signal take-out pins 2 electrically connected to layer 3 were attached by silver brazing. Then, as shown in FIG. 4, the carbon paste 4 is applied to the tip of the pin 2 side, and the paste 4 is pressed against the surface of the aluminum foil 5 in an undried state, and dried at 120 ° C. for 2 hours. The aluminum foil 5 was attached to the tip of the pin 2.

The ceramic substrate 1 with the aluminum foil 5 is placed in a metal box 11 as shown in FIG.
By inserting a metal sponge 13 as a cushioning material between the metal box 11 and the metal box 11, the aluminum foil 5 and the metal box 11
And made an electrical connection with. As shown in FIG. 7, a sealing ring 12 is interposed between the metal box 11 and the ceramic substrate 1, and even if the ceramic substrate 1 is placed in a copper plating solution and plating is performed, a pin is formed. Since the plating solution is not supplied to the 2 side, the pin 2 side is not plated. At that time, power is supplied through the metal box 11 and the plating jig to which the metal box 11 is attached, and the thickness of the conductor layer 3 is set to 10 mm.
μm.

After that, the ceramic substrate 1 was taken out from the metal box 11 and the aluminum foil 5 was peeled off from the pins 2. At this time, the electrically conductive paste 4 was detached from the pin 2 and remained attached to the aluminum foil 5 side. As a result, there was no plating failure in the wiring patterns at 300 locations. For comparison, 10% of the wiring was not plated in the product in which the electroconductive paste 4 was not applied and the aluminum foil 5 was simply brought into contact with the pins 2 for plating.

The present invention is not limited to the above-described embodiments, but various modifications and changes can be made. For example, in the embodiment described above, one conductor layer is provided on the surface of the ceramic substrate, but even in the case of a multilayer structure in which conductor layers and insulating layers are alternately formed, the conductor layer exposed on the surface It is obvious that the present invention can be preferably applied. Further, in the above-mentioned embodiment, the example in which the pin is erected on the signal take-out portion has been described, but it is clear that the present invention can be suitably applied even in the case of only the electrode-like signal take-out portion without the pin being erected. .

[0018]

As is apparent from the above description, according to the present invention, a paste layer on an electrically conductive solution is provided in the signal extracting portion or the surface conductor layer, and power is supplied through this paste layer. Therefore, the reliability of the electrical connection can be improved as compared with the case where the film-shaped metal foil is contacted. Also, because no dummy electrode for plating is required, the wiring for electrolytic plating is not left in the multilayer circuit board, improving the performance of the multilayer circuit board and using a peelable paste for power supply. Therefore, the work of removing the electric power feeding portion after the electrolytic plating can be facilitated.

[Brief description of drawings]

FIG. 1 is a diagram showing a configuration of an example of a multilayer circuit board which is an object of electrolytic plating in a manufacturing method of the present invention.

FIG. 2 is a flow chart for explaining a method of electrolytic plating on a conductor layer or a signal extraction portion according to the present invention.

FIG. 3 is a diagram showing an example of a method for molding an electrically conductive paste when power is supplied to a conductor layer from a signal extracting portion according to the present invention.

FIG. 4 is a diagram showing another example of a method for molding an electrically conductive paste when power is supplied to a conductor layer from a signal extracting portion according to the present invention.

FIG. 5 is a diagram showing still another example of the method for molding the electrically conductive paste in the case where power is supplied to the conductor layer from the signal extracting portion according to the present invention.

FIG. 6 is a diagram showing an example of a method of molding an electrically conductive paste when power is supplied from a conductor layer to a signal extracting portion according to the present invention.

FIG. 7 is a diagram showing a state during electrolytic plating according to the present invention.

FIG. 8 is a diagram showing a state during conventional electrolytic plating.

[Explanation of symbols]

 1 Ceramic Substrate 2 Pin 3 Conductor Layer 4 Electrically Conductive Paste 5 Metal Foil 11 Metal Box 12 Metal Sponge 13 Ring

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁵ Identification code Internal reference number FI technical display location 9355-4M H01L 23/12 P

Claims (3)

[Claims] 1. A ceramic substrate, and a conductor layer formed on the surface of the ceramic substrate or on the surface via an insulating layer,
In a method for manufacturing a multilayer circuit board, which is formed on a surface of a ceramic substrate and includes a signal takeout portion electrically connected to a conductor layer, an electrically conductive paste is applied to the signal takeout portion (or the conductor layer). Providing a paste layer, supplying power to the conductor layer (or signal extraction part) through the paste layer and the signal extraction part (or conductor layer) to perform electroplating, and deposit a plating layer on the surface of the conductor layer (or signal extraction part). A method for manufacturing a multilayer circuit board, which comprises forming and controlling the thickness of a conductor layer (or a signal extraction portion), and then removing the paste layer. 2. The method for manufacturing a multilayer circuit board according to claim 1, wherein power is supplied to the conductor layer (or the signal extracting portion) by connecting the paste layer to an electrically conductive portion of a plating jig. 3. The method for manufacturing a multilayer circuit board according to claim 1, wherein the signal take-out portion is provided with a signal take-out pin.