JPH0799380A - Pattern formation of ceramic-metal bonded body - Google Patents

Abstract

PURPOSE:To provide a method of forming the pattern of a ceramicmetal bonded body, which makes it possible to form a pattern, which has a narrow line width and the narrow interval is fine and is complicated, on a metal plate with good reproducibility and easily. CONSTITUTION:A ceramic plate 1 and a metal plate 2 are bonded together via an active metal-containing brazing metal layer 3, for example. The plate 2 subsequent to the bonding is subjected to etching treatment into the form of a desired pattern. A layer 3a remaining in a part 2a removed from the plate 2 on the plate 1 by this etching treatment is removed by a forning treatment or laser machining.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for forming a desired pattern on a metal plate of a ceramic-metal bonded body.

[0002]

2. Description of the Related Art Ceramic substrates have been put to practical use as substrates for mounting electronic components such as semiconductor elements because they have characteristics such as high electrical insulation, high thermal conductivity and low thermal expansion. By the way, when the ceramic substrate is used for the above-mentioned applications, it is indispensable to first bond it to a metal plate for the purpose of forming a circuit pattern or the like.

As a method of joining the ceramic substrate and the metal plate as described above, a so-called DBC method (direct bonding copper method) of directly joining a copper circuit board of a required shape and the ceramic substrate, or a Group 4A element And 5A
An active metal method using an active metal such as a group element is known. The active metal method is a joining method that utilizes the fact that metal elements such as Ti, Zr, Hf, and Nb easily wet and react with the ceramic material.Specifically, a brazing material containing an active metal is used. The brazing method is commonly used.

By the way, as a method of forming (patterning) a circuit on a copper plate or the like joined by the above-mentioned DBC method or active metal method, (1) after joining a solid copper plate, patterning is carried out by an etching treatment, (2) For example, a copper plate that has been patterned in advance may be joined.

[0005]

However, in the above-mentioned patterning method (1), although the copper plate can be satisfactorily removed by the etching treatment, the reaction layer existing at the interface between the copper plate and the ceramic substrate is removed. However, there is a problem that the reaction layer remains and adversely affects the circuit characteristics and the circuit shape. In particular, when the active metal method is applied, the reaction product of the active metal and the ceramics substrate is firmly bonded on the ceramics substrate, and it takes a lot of man-hours to remove this reaction layer, and the manufacturing cost is low. There is a problem in that as the cost increases, overetching and the like are likely to occur. Furthermore, the reaction product of the active metal and the ceramic substrate is often a conductive substance, and there is a problem that a circuit defect is likely to occur due to the conductive substance slightly remaining after the etching treatment.

Further, in the patterning method (2) described above, when a pattern having a narrow line width is formed, if such a pattern is formed in advance on the copper plate, the bonding itself becomes difficult and the positional accuracy is lowered. However, there is a problem that a fine pattern cannot be formed with good reproducibility.

The present invention has been made in consideration of such a problem, and easily forms a fine and complicated pattern having a narrow line width and a space between lines on a metal plate with good reproducibility. It is an object of the present invention to provide a method for forming a pattern of a ceramic-metal bonded body that enables the above.

[0008]

Means for Solving the Problems Ceramics of the Present Invention
Pattern formation of the metal bonded body, a step of bonding the ceramics plate and the metal plate, in forming a desired pattern on the metal plate after the bonding, etching the metal plate after the bonding into a desired pattern shape, and And a step of removing a layer remaining on a portion of the ceramic plate where the metal plate is removed by the etching treatment, by a honing treatment or a laser processing.

[0009]

In the method for forming a pattern of a ceramic-metal bonded body according to the present invention, after the metal plate is patterned in advance by etching treatment or the like, the layer remaining on the ceramic plate is removed by honing treatment or laser processing. A complicated and fine pattern can be formed with good reproducibility without leaving a reaction layer or the like made of an organic substance. Further, in the etching process, since at least only the metal plate is dissolved and removed, overetching or the like is not caused and sagging or the like is not caused on the side surface of the pattern portion.

[0010]

EXAMPLES Next, examples of the present invention will be described.

FIG. 1 is a diagram sequentially showing a pattern forming process of an embodiment in which the present invention is applied to a circuit pattern formation of a ceramic circuit board. First, the metal plate 2 is bonded onto the ceramic substrate 1 (FIG. 1A). As the ceramics substrate 1, various ceramics substrates can be used, from oxide-based ceramics substrates such as aluminum oxide to non-oxide ceramics substrates such as aluminum nitride, silicon nitride and silicon carbide. This is effective when using an aluminum nitride substrate, a silicon nitride substrate, or the like, which has a low wettability with respect to a brazing material or the like and which is effective in using an active metal. Further, the material of the metal plate 2 may be appropriately selected from various metal materials according to the application, for example, Cu, Cu
Alloys, Ni, Ni alloys, W, Mo, etc. are used.

The above-mentioned ceramic substrate 1 and the metal plate 2 can be joined by applying various joining methods such as an active metal method and a DBC method. Particularly in the case of the active metal method, the ceramics can be joined. The present invention is particularly effective when the active metal method is applied because it forms a reaction layer that is strongly bonded to the substrate 1 and has conductivity.

In this embodiment, an example of the active metal method to which a joining method using a brazing filler metal containing an active metal is applied will be described. Specifically, a paste containing an active metal-containing brazing material is applied to the ceramic substrate 1 or the metal plate 2 by applying, for example, a screen printing method. Here, as the bonding paste, for example, a eutectic composition of Ag-Cu or a composition in the vicinity thereof is mainly used, and an active metal-containing brazing material in which an appropriate amount of an active metal component such as Ti, Zr, Hf, or Nb is mixed To
A paste prepared by using an appropriate resin binder and a dispersion medium is used. The amount of active metal added to the brazing material is
For example, it is about 1 to 10% by weight. The main component of the brazing material is not limited to the above Ag-Cu eutectic brazing material, but various brazing materials such as Cu can be used.

Next, the ceramic substrate 1 and the metal plate 2 are laminated with a paste coating layer containing the active metal-containing brazing material interposed therebetween. Then, heat treatment is performed under conditions (atmosphere, temperature, time, etc.) according to the active metal-containing brazing material used,
The ceramics substrate 1 and the metal plate 2 are joined via the brazing material layer 3 (FIG. 1A).

Next, after forming a resist layer (not shown) on the metal plate 2 after bonding so as to cover a desired circuit shape, the metal plate is formed by using an etchant suitable for the material of the metal plate 2. 2 is etched. As the etchant, for example, when the metal plate 2 is a copper plate, ferric chloride solution or the like is used. By this etching process, as shown in FIG. 1B, the unnecessary portion 2a of the metal plate 2 is removed, and the metal plate 2 is removed.
Is patterned into a desired shape. Further, of the brazing material layer 3, a layer mainly composed of a brazing material component such as Ag-Cu is dissolved and removed by the above etching treatment, but a reaction product of the ceramic substrate 1 and the active metal, that is, a conductive material. The layer 3a mainly containing the interface product having is not dissolved and removed by the above-mentioned etchant, but remains on the ceramic substrate 1. That is, in the case of the active metal method, a reaction product of the active metal component and the ceramic substrate 1, for example, an interface product such as TiN is generated at the bonding interface on the ceramic substrate 1 side. On the other hand, the etchant selected according to the material of the metal plate 2 cannot dissolve and remove the interface product. Since the interface product containing the active metal is generally conductive, it cannot be used as a circuit board if it remains on the ceramic substrate 1.

Therefore, the layer 3a mainly composed of the interface product remaining after the etching process is removed by the honing process or the laser processing, so that each pattern portion 2b of the metal plate 2 is formed as shown in FIG. 1 (c). The target ceramics circuit board 4 in which insulation between 2 and 2b is ensured
Is obtained. As the honing process, a process using a general liquid honing device or the like can be applied. For laser processing, CO ₂ gas laser, YAG laser, etc. are used to form a layer 3 mainly composed of interface products.
It is only necessary to dissolve and remove a.

In the above-described embodiment, the layer 3a mainly composed of the interface product remaining after the etching process is removed by the honing process or the laser processing, so that the space between the pattern portions 2b and 2b of the metal plate 2 is removed. Can be reliably separated. Therefore, it is possible to easily and electrically obtain an electrically isolated pattern with good reproducibility. Further, since patterning is performed by a combination of etching processing, honing processing and laser processing, it is possible to accurately reproduce a fine and complicated pattern shape. For example, according to this embodiment, it is possible to stably reproduce a fine circuit pattern having a line width of 0.3 mm and a line spacing of about 0.3 mm (in the case of a copper plate thickness of 0.3 mm). Furthermore, the etching process
Since only the main components of the metal plate 2 and the brazing material layer 3 need to be removed, overetching or the like does not occur, and thus, sagging or the like does not occur on the side surface of the circuit portion. This also makes it possible to accurately reproduce a fine circuit pattern. Further, the settling of the etchant can be prevented.

Next, a specific example based on the above embodiment will be described.

Example 1 First, on a 63 × 29 × 0.3 mm aluminum nitride substrate, A
A paste containing an active metal-containing brazing material having a composition of g: Cu: Ti = 70.6: 27.4: 2.0 was applied, and a 59.2 × 25.6 × 0.3 mm copper plate was placed on the application layer of this paste. Next, this laminate was heat-treated in a vacuum of 1 × 10 ⁻⁴ Torr at 850 ° C. for 10 minutes to bond the aluminum nitride substrate and the copper plate.

Next, a resist was pattern-printed on the copper plate of the above-mentioned joined body, and then it was immersed in a FeCl ₃ solution at 40 ° C. for 10 minutes to carry out an etching treatment. The formed circuit pattern was a fine pattern with a minimum line width and a minimum line spacing of 0.3 mm.

Thereafter, the reaction layer remaining between the pattern portions on the aluminum nitride substrate, that is, TiN (AlN + Ti →
A layer mainly composed of a conductive layer produced by the reaction of TiN + Al) was removed by honing.

When the shape of the copper circuit layer of the ceramics circuit board thus obtained was visually observed, it was found that the minimum line width was 0.3 mm and the minimum line spacing was 0.3 mm, exactly as originally assumed. In addition, TiN was not left. Further, a good circuit pattern was obtained without any sagging or the like on the side surface of each pattern portion of the copper circuit layer.

Example 2 First, in the same manner as in Example 1, the copper plate of the joined body was subjected to etching treatment, and then CO ₂ was added to the layer mainly containing TiN remaining between the pattern portions on the aluminum nitride substrate. A gas laser was irradiated in an Ar atmosphere under the conditions of an output of 700 W and a speed of 2 m / min to dissolve and remove the layer mainly containing TiN. The laser irradiation was numerical control (NC).

The copper circuit layer of the ceramics circuit board thus obtained also had a good pattern shape and accuracy as in Example 1, and TiN did not remain.

In the above embodiment, the patterning of the metal plate bonded to the ceramics substrate by the active metal method has been described, but the present invention is not limited to this, and any patterning with the ceramics substrate may be used. It is effective when applying various bonding methods using reactions.

[0026]

As described above, according to the pattern forming method for a ceramic-metal bonded body of the present invention, a fine and complicated pattern having a narrow line width and a narrow space can be reproducibly formed on a metal plate, and It can be easily formed.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing a process of an embodiment in which the present invention is applied to manufacture of a ceramic circuit board.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Ceramic substrate 2 ... Metal plate 2a ... Etching removed portion 2b ... Pattern portion 3 ... Active metal containing brazing material layer 3a ... Layer mainly composed of interface products 4 ... Ceramic circuit board

Claims (1)

[Claims] 1. A step of etching a metal plate after the bonding into a desired pattern shape when the ceramic plate and the metal plate are bonded together and a desired pattern is formed on the metal plate after the bonding, And a step of removing a layer remaining on a portion of the plate where the metal plate is removed by the etching treatment, by a honing treatment or a laser processing.