JPH02230790A - Manufacture of ceramics circuit board - Google Patents

Abstract

PURPOSE:To improve the reproducibility and dimensional precision of a circuit pattern by a method wherein a copper circuit board directly bonded to a ceramics board is provided with an outer frame surrounding a part turning to a circuit, and said circuit part and the outer frame are linked and retained by forming a bridge part. CONSTITUTION:On a copper circuit board 1, the following are formed; a specified island part 2, a bridge part 3 which is linked with said island part 2 and stretches toward the outer periphery of the copper board, and an outer frame 4 which is linked with the island part 2 via the bridge part 3 and retains the island part. On a ceramics board 7, this island part of the copper circuit board 1 is arranged so as to contact with the board. The copper circuit board 1 and the ceramics board 7 are bonded with each other by heating them in a nitrogen gas atmosphere. After that, by using hands, vertical force is applied to the ceramics board 7, thereby cutting the bridge part 3 at the part linking with the island part. On the ceramics board 7, only the island part is left in the bonded state, and constitutes a circuit pattern.

Description

[Detailed description of the invention] [Purpose of the invention] (Industrial application field) The present invention relates to a method of manufacturing a ceramic circuit board.

(Prior Art) As a circuit board such as a power transformer module board or a switching power supply module board, a circuit board in which a metal plate such as a copper plate is bonded to a ceramic board is often used.

In manufacturing such ceramic circuit boards, the method of bonding a copper circuit board onto a ceramic board is to place the copper circuit board in contact with a ceramic board made of sintered aluminum oxide or sintered aluminum nitride. A direct bonding copper method (DBC method) in which a ceramic substrate and a copper circuit board are directly bonded by heating is often used.

Ceramic circuit boards produced by this DBC method have the advantages of strong bonding strength between the ceramic board and copper circuit board, a simple structure that allows for small size and high packaging, and shortened work processes. There is.

In addition, methods for forming a circuit on a copper plate include first bonding the copper plate to a ceramic substrate and then etching the desired shape on the copper plate to form the circuit, or attaching the copper plate to the ceramic substrate in advance. There is a method in which a circuit pattern is formed by punching or the like, and a circuit is formed by bonding this copper circuit board to a ceramic substrate.

When a copper circuit board is fabricated first and then bonded to a ceramic substrate, a bridge section is placed between each island section to make it easier to handle the copper circuit board, which is made up of multiple island sections that form a pattern. or provide an outer frame around the outer periphery of the copper circuit board,
This outer frame and each island-like part are connected by a bridge part, and they are connected so that they are integrated into one copper circuit board, and after bonding the island-like part of this copper circuit board to the ceramic substrate. Finally, the bridge portion is cut and removed to form a circuit pattern.

An example of such a conventional method of manufacturing a ceramic circuit board is shown in FIG.

In the same figure, (a) is a front view of a copper circuit board, in which a plurality of island-like parts 2 and a bridge part 3 connecting these island-like parts 2 are formed on the copper circuit board 1 by press working. The bridge portion 3 has a structure in which it is curved upward so that the bridge portion 3 is not bonded to the ceramic substrate during bonding (FIG. 5-a).

Next, this copper circuit board 1 is placed in contact with a ceramic substrate and bonded by heating (FIG. 1b).

Then, the bridge portion 3 is cut and removed using a plane cutter (FIG. 1C).

In this way, a ceramic circuit board using the DBC method is produced.

(Problems to be Solved by the Invention) When forming a ceramic circuit board using green rollers using the DBC method, if the circuit is formed by etching after bonding the copper plates by heating, the pattern accuracy increases, but the ceramic circuit board There is a problem in that some materials are corroded by the etching solution.

In addition, with the method of providing a bridge, when cutting and removing the bridge, it is difficult to effectively remove only the bridge, and chips may remain or the cut end of the cut portion may stand up and form a burr, and this burr may leak. There was a problem in that this caused a drop in withstand voltage.

For this reason, post-processing called deburring is required, and as the number of work steps increases, dimensional accuracy decreases and costs increase.

On the other hand, although the method of providing an outer frame can reduce the number of bridges between the island-like parts, it is difficult to completely remove the outer frame, and when removing the outer frame, the outer frame and the island-like parts must be connected. There have been problems in that a part of the bridge part connected to the ceramic substrate is bonded to the ceramic substrate, and uncut portions of the bridge part are left at the ends of the island parts. This also hindered cost reduction.

The present invention was made in response to these problems, and it provides a ceramic material whose outer frame can be easily removed to reduce costs, which has high dimensional accuracy, and which allows circuit formation to be performed with good reproducibility. The purpose of the present invention is to provide a method for manufacturing a circuit board.

[Structure of the Invention] (Means for Solving the Problems) The method for manufacturing a ceramic circuit board of the present invention includes: a plurality of island-like portions; a bridge portion connected at least to the island-like portions; A step of forming a copper circuit board consisting of an outer frame holding a plurality of island-like parts, and placing the plurality of island-like parts of the copper circuit board in contact with a ceramic substrate, and also placing the bridge part on the ceramic substrate. After tilting upward with respect to the surface at an angle in the range of IO° to 90'', or interposing a substance at the contact portion between the bridge portion and the ceramic substrate to prevent bonding between the bridge portion and the ceramic substrate. After that, there is a step of thermally bonding the island-shaped portion and the ceramic substrate, and a connecting portion between the island-shaped portion of the copper circuit board and the bridge portion is cut to remove the bridge portion and the outer frame together. It is characterized by having a process.

Further, the method for manufacturing a ceramic circuit board of the present invention includes a plurality of island-like parts, an outer frame that integrally holds the plurality of island-like parts, and a plurality of island-like parts that connect the plurality of island-like parts and the outer frame. a step of forming a copper circuit board consisting of a bridge portion of the copper circuit board; a step of placing a plurality of island-like portions of the copper circuit board in contact with a ceramic substrate and heat-bonding the same; The bridge part and the outer frame are removed together by cutting the connection part with the bridge part.

Ceramic substrates used in the present invention include sintered ceramics of oxides such as alumina and silicon oxide,
Examples include ceramic substrates made of non-oxide ceramic sintered bodies such as aluminum nitride and silicon carbide. In addition, when using a non-oxide ceramic substrate, it is preferable to oxidize the bonding surface with the copper circuit board beforehand.

In the present invention, the copper plate for forming the copper circuit board contains 100 to 3000 p of oxygen such as tough pitch copper.
It is preferable to use rolled copper containing approximately pm.

In order to produce a steel circuit board by forming island-shaped parts, bridge parts, and an outer frame on such a copper plate, there are methods such as etching to dissolve and remove the copper plate into a desired pattern shape, or punching to form a circuit pattern. is used.

Further, it is preferable that the bridge portion of the steel circuit board is inclined upwardly at an angle in the range of IO@ to 90@ with respect to the ceramic substrate to be bonded.

By raising the bridge part from the ceramic substrate with the inclined C in this way, it is possible to prevent the copper plate, that is, the conductive substance, from remaining on the ceramic substrate when bonding the copper circuit board and the ceramic substrate by heating, and furthermore, This makes it easier to remove the outer frame in later steps.

If the inclination angle of the bridge part is less than IO1, the bridge will collapse due to its own weight during the manufacture of ceramic circuit boards.
This is not preferable because the sloped shape cannot be maintained. Further, if the inclination angle of the bridge portion exceeds 906, it will be easy to break at the connecting portion with the island portion.

Also, the bridge. In the case where the portion is not inclined, it is preferable to interpose a substance in the contact portion between the bridge portion and the ceramic substrate to prevent bonding between the bridge portion and the ceramic substrate.

Examples of such a bonding prevention substance include organic substances such as acrylic and 7-enol, and non-oxide ceramics such as BNS813 N 4 and SIC.

Particularly preferred as the material to be interposed in the contact portion between the bridge portion and the ceramic substrate is non-oxide ceramic. This non-oxide ceramic takes away the oxygen in the copper circuit board and oxidizes it when the ceramic substrate and the copper circuit board are bonded together. No eutectic is generated, which is effective in preventing the bridge portion from bonding to the ceramic substrate.

Furthermore, it is also possible to use two methods in combination: giving the bridge part an inclined shape as described above, and arranging the bonding prevention substance on the ceramic substrate corresponding to the lower surface of the bridge part. This makes it possible to more completely prevent excess copper pieces, ie, conductive material, from adhering to the surface of the ceramic substrate.

Further, the bridge portion preferably has a tapered shape that becomes wider from the island portion toward the outer frame.

With such a tapered shape, the bridge portion can be easily cut.

And, in the connection part on the island-like part side of the bridge part,
Making cuts on both sides of the bridge not only further improves cutting performance, but also prevents the bridge from remaining cut on the outside of the island, improving the shape accuracy of the island that remains on the ceramic substrate and is bonded. can be improved.

In the ceramic circuit board of the present invention, the island portion of the copper circuit board described above is placed in contact with the ceramic substrate and bonded by heating, and then the bridge portion is cut at the connection portion with the island portion. Remove the above outer frame along with the bridge part,
It can be manufactured by leaving only the island-like portions forming the circuit on the ceramic substrate.

The heating temperature is above the eutectic temperature of copper and copper oxide (1065°C) and below the melting point of copper (1083°C), and when using a copper circuit board containing oxygen, it is heated in an inert gas atmosphere. It is preferable to perform heating, and when using a copper circuit board that does not contain oxygen, it is preferable to perform heating in an atmosphere containing about 80 to 3900 ppm of oxygen.

After the island-shaped portion of the copper circuit board, in which the outer frame is provided surrounding the island-shaped portion, is bonded to the ceramic substrate, the bridge portion is cut and the outer frame is removed.

This bridge portion can be cut and removed by hand by applying force in a direction perpendicular to the ceramic substrate.

Note that, apart from removing the outer frame, the bridge portion connecting the island-like portions is cut and removed by a method suitable for the conditions at that time.

In this way, only the island-like portions having the desired circuit shape are bonded onto the ceramic substrate, and the ceramic circuit board is completed.

(Function) According to the method for manufacturing a ceramic circuit board of the present invention, the bridge portion that connects the island-like portion and the outer frame is inclined upward at an angle in the range of 10° to 90″ with respect to the ceramic substrate surface. The island-shaped portion and the ceramic substrate are bonded together by heating, or after a substance that prevents bonding between the bridge portion and the ceramic substrate is interposed at the contact portion between the bridge portion and the ceramic substrate.

Therefore, after the copper circuit board is heated and bonded to the ceramic substrate, the bridge portion is cut by applying force in the vertical direction to the ceramic substrate, and the outer frame can be easily removed at the same time as the bridge portion is cut. .

Further, by interposing a substance that prevents bonding between the bridge portion and the ceramic substrate at the contact portion between the bridge portion and the ceramic substrate, bonding between the two can be prevented.

Further, by connecting the bridge portions of the island portions only to the outer frame so as to hold the island portions of the copper concave road plate integrally, it is possible to eliminate the bridge portions between the respective island portions. Therefore, the number of manufacturing steps can be reduced.

For these reasons, it is possible to improve the shape accuracy of the island-like portions forming the circuit pattern, and it is possible to reduce costs.

(Example) Embodiments of the present invention will be described below with reference to the drawings.

Embodiment FIG. 1 is a front view of a copper circuit board used in this embodiment.
The copper circuit board 1 has a predetermined island-like part 2, a bridge part 3 connected to the island-like part 2 and extending in the direction of the outer circumference of the copper plate, and a bridge part 3 connected to the island-like part 2 through the bridge part 3 to hold it. Outer frame 4
is formed.

FIG. 2 is an enlarged view of the bridge portion 3 in the copper circuit board 1, and the bridge portion 3 extends from the island portion 2 to the outer frame 4.
It has a tapered shape that becomes wider towards the end.

Furthermore, the connecting portion between the bridge portion 3 and the island portion 2 is
Small incisions 5 are made on both sides of the bridge part on the island-like part 2 side.

FIG. 3 is a side view of the copper circuit board 1 described above, in which the bridge portion 3 is inclined upward with respect to the horizontal direction. This inclination angle 6 is preferably in the range of IO 6 to 90''.

A method of manufacturing a ceramic circuit board according to this embodiment using such a copper circuit board is shown in FIG.

First, as explained in FIGS. 1 to 3, a copper circuit board 1 having a bridge part 3 and an outer frame 4 is manufactured, and the island-shaped part of this copper circuit board 1 is made of ceramic mainly composed of alumina, for example. It is placed in contact with the substrate 7. At this time, the bridge portion 3 has an inclination of 30 degrees with respect to the ceramic substrate 7, and the outer frame 4 is located on the outer periphery of the ceramic substrate 7.

Alternatively, when the bridge portion 3 does not have an inclination, a paste of SIC as a non-oxide ceramic is applied to the portion where the bridge portion 3 contacts the ceramic substrate 7.

Next, the copper circuit board 1 and the ceramic substrate 7 are bonded together by heating at 1070° C. in a nitrogen gas atmosphere (FIG. 4 1a).

Thereafter, a force is manually applied to the bridge portion 3 of the copper circuit board 1 in a direction perpendicular to the ceramic substrate 7, and the bridge portion 3 is cut at the connection portion with the island portion.

As a result, the bridge portion 3 is removed from the ceramic substrate 7 along with the outer frame 4, and only the island portion remains bonded to the ceramic substrate 7, forming a circuit pattern (
Figure-b).

The ceramic circuit board thus produced not only had easy circuit formation, but also had high precision in circuit pattern shape and excellent reproducibility.

Further, by interposing the non-oxide ceramic, it was possible to prevent the bridge portion from adhering to the ceramic substrate, and a highly reliable ceramic circuit board could be obtained.

Comparative Example FIG. 5 is a diagram showing the conventional method of manufacturing the ceramic circuit board mentioned above.

First, a copper circuit board 1 was produced by press working. This copper circuit board 1 has a plurality of island-shaped parts 2 forming a predetermined circuit.
and a bridge portion 3 that connects these island portions 2. Moreover, this bridge portion 3 has a curved shape at the top (Fig. 5 1a). Next, the copper circuit board 1 was placed in contact with the ceramic substrate and heat-bonded under the same conditions as in the example. (Figure-b).

Finally, the bridge portion 3 protruding from the surface of the copper circuit board 1 was cut out using a plane cutter, and the connected island portions 2 were separated to obtain a ceramic circuit board (Fig. 5-10). .

When the bridge portion 3 of the ceramic circuit board manufactured in this manner was cut out using a flat cutter, the cut edges were irregular and burrs were formed, and post-processing was required to remove the burrs.

In addition, the chips adhere to the ceramic substrate and are bonded.
There was also a decrease in the accuracy of circuit patterns.

As is clear from the above results, the method for manufacturing a ceramic circuit board described in this example did not require any extra work steps, and the circuit formation work was easy.

In addition, the bridge section is sloped upward relative to the ceramic substrate to which the copper circuit board is bonded, and the bridge section is tapered in shape, widening from the island section toward the outer frame, making it easy to cut the bridge section. As a result, the shape accuracy of the island-shaped portion has improved.

Furthermore, by interposing non-oxide ceramics in the contact area between the bridge part and the ceramic substrate,
It was possible to prevent excess copper pieces from adhering to the ceramic substrate.

[Effects of the Invention] As explained above, according to the method for manufacturing a ceramic circuit board of the present invention, an outer frame is provided in a shape surrounding a portion that will become a circuit on a copper circuit board that is directly bonded onto a ceramic substrate, circuit. The parts and the outer frame are connected and held by forming a bridge section, and finally the bridge section is cut to remove the bridge section and the outer frame at the same time.

This cutting is extremely easy, does not leave any excess copper powder, etc., and can improve the reproducibility and dimensional accuracy of the circuit pattern.

Therefore, it greatly contributes to improving the reliability of the obtained ceramic circuit board and reducing costs in the manufacturing process.

[Brief explanation of the drawing]

Figure 1 is a front view of the copper circuit board used in the present invention, Figure 2 is an enlarged view of the bridge portion of the copper circuit board shown in Figure 1, and Figure 3 is the front view of the copper circuit board shown in Figure 1. A side view, FIG. 4 is a diagram showing a manufacturing process of a ceramic circuit board according to an embodiment of the present invention, and FIG. 5 is a diagram showing a manufacturing process of a conventional ceramic circuit board. 1......Copper circuit board 2......Island portion 3...Bridge portion 4...Outer frame 5...... Cut depth 6... Inclination angle 7... Ceramic substrate applicant
Toshiba Corporation

Claims (5)

[Claims] (1) forming a copper circuit board comprising a plurality of island-shaped parts, a bridge part connected at least to the island-shaped parts, and an outer frame that holds the plurality of island-shaped parts via the bridge parts; After the plurality of island-shaped portions of the copper circuit board are placed in contact with a ceramic substrate and the bridge portion is tilted upward at an angle in a range of 10° to 90° with respect to the surface of the ceramic substrate, or a step of interposing a substance that prevents bonding between the bridge portion and the ceramic substrate at the contact portion between the bridge portion and the ceramic substrate, and then heating and bonding the island-like portion and the ceramic substrate; and the copper circuit. A method for manufacturing a ceramic circuit board, comprising the step of cutting a connecting portion between an island portion of a plate and a bridge portion, and removing both the bridge portion and the outer frame. (2) A copper circuit board consisting of a plurality of island-like parts, an outer frame that integrally holds these plurality of island-like parts, and a plurality of bridge parts that connect these plurality of island-like parts and the outer frame. a step of placing a plurality of island-shaped portions of the copper circuit board in contact with a ceramic substrate and heat-bonding them; and a step of cutting the connecting portions between the island-shaped portions of the copper circuit board and the bridge portions and connecting them to each other. A method for manufacturing a ceramic circuit board, comprising the step of removing both the bridge portion and the outer frame. (3) The method of manufacturing a ceramic circuit board according to claim 2, wherein the bridge portion is inclined upward at an angle in the range of 10° to 90° with respect to the bonding surface of the ceramic substrate. (4) At the contact part between the bridge part and the ceramic substrate,
3. The method of manufacturing a ceramic circuit board according to claim 2, wherein a substance is interposed to prevent bonding between the bridge portions and the ceramic substrate. (5) The method for manufacturing a ceramic circuit board according to claim 1 or 2, wherein the bridge portion has a tapered shape that becomes wider from the island portion toward the outer frame.