JP4484676B2 - Ceramic circuit board and manufacturing method thereof - Google Patents

Description

  The present invention relates to a ceramic circuit board in which a metal circuit board is bonded to a ceramic board.

  In recent years, as circuit boards such as power module boards and switching module boards, an active metal brazing material in which at least one of titanium, zirconium, hafnium and hydrides thereof is added to a silver-copper alloy on a ceramic board is used. A ceramic circuit board formed by bonding a metal circuit board made of copper, aluminum or the like, or a ceramic circuit board formed by bonding a metal circuit board made of copper, aluminum or the like directly to a ceramic board without using a brazing material is used. ing.

  Such a ceramic circuit board is generally made of an electrically insulating ceramic material such as an aluminum oxide sintered body, an aluminum nitride sintered body, a silicon nitride sintered body, or a mullite sintered body. For example, when the ceramic substrate is made of an aluminum oxide sintered body and the bonding is performed via a brazing material, the ceramic substrate is manufactured by the method described below.

  First, an active metal brazing paste is prepared by adding an organic solvent and a solvent to an active metal powder obtained by adding at least one of titanium, zirconium, hafnium and hydrides thereof to a silver-copper alloy.

  Next, a ceramic raw material powder such as aluminum oxide, silicon oxide, magnesium oxide, and calcium oxide is mixed with an appropriate organic binder, plasticizer, solvent, etc. to form a slurry, and this is made into a conventionally known doctor blade method or calendar. A plurality of ceramic green sheets are obtained by employing a tape forming technique such as a roll method.

  After this ceramic green sheet is formed to a predetermined size, it is fired at a temperature of about 1600 ° C. in a reducing atmosphere and sintered and integrated to form a ceramic substrate made of an aluminum oxide sintered body.

  Next, after applying an active metal brazing paste in a circuit shape on the ceramic substrate in advance, a metal plate made of copper, aluminum or the like is placed thereon.

  Next, the active metal brazing paste disposed between the ceramic substrate and the metal plate is heated to a temperature of about 900 ° C. in a non-oxidizing atmosphere to bond the metal plate to the ceramic substrate.

  Next, an etching resist ink is applied to the surface of the metal plate in a circuit form using a technique such as screen printing, and the metal plate is etched with a ferric chloride, cupric chloride solution, or the like. A ceramic circuit board is manufactured by forming a circuit-like metal circuit board.

  The ceramic circuit board thus manufactured becomes a semiconductor module by mounting electronic components such as IC and IGBT elements via solder.

A conventional ceramic circuit board is shown in FIG. As shown in FIG. 4, 41 is a ceramic substrate, 42 is an active brazing material, and 43 is a metal circuit board.
JP 2002-246717 A

  However, in a conventional ceramic circuit board, when an etching resist ink is applied by a screen printing method and a metal circuit board is formed by an etching process, the etching process etches the width direction as well as the depth direction of the metal circuit board. The dimension B that is the etching amount in the width direction of FIG. 3 is about ½ of the dimension A that is the thickness of the metal circuit board 33.

  Therefore, when the upper width of the metal circuit board 33 is etched below the thickness of the metal circuit board 33, the upper width of the metal circuit board 33 is reduced to the metal circuit because the shape of the upper part of the metal circuit board 33 cannot be processed into a desired shape. Etching below the thickness of the plate 33 was not performed. FIG. 3 shows a cross-sectional shape of the metal circuit board after the etching process, and 33 is a metal circuit board.

  In addition, in order to make the upper portion of the line conductor that does not flow a large current partially less than the thickness of the metal circuit board, the metal circuit board may be completely removed and only the active metal layer may be used as the line conductor. Since only the wiring has a high resistance value and a large calorific value, there is a problem that the Si chip mounted on the substrate is damaged. In addition, the wiring with only the active metal layer has a problem that the brazing material is peeled off when the metal circuit board is eroded by etching, resulting in disconnection. In addition, even if the metal circuit board can be formed in a portion where the width of the line conductor is narrow, if the metal circuit board is rectangular and the thickness is the same as that of the ground conductor, the ceramic and metal circuit board are joined. Since the width is narrow and the thickness of the metal circuit board is large, stress is applied to the active metal layer, causing the active metal layer to peel off, resulting in poor reliability.

  Accordingly, the ceramic circuit board of the present invention has been completed in view of the above-mentioned problems, and the purpose thereof is to reduce the pitch of a part of the line conductor so that a grounding conductor that allows a large current and a line that allows a small current to flow. An object of the present invention is to provide a highly reliable ceramic circuit board that realizes miniaturization by mixing conductors at high density and that does not break by reducing the resistance value in a line conductor through which a small current flows.

Ceramic circuit board of the present invention, and the circuit board metal circuit plate is bonded to the main surface of the ceramic substrate, the metal circuit board, and the vertical sectional shape trapezoidal ground conductor, the vertical cross section in a triangular shape A line conductor having a height at the top portion lower than the upper surface of the ground conductor is provided.

Method of manufacturing a ceramic circuit board of the present invention, the forming a circuit pattern of the active metal layer on the main surface of the ceramic substrate, the metal circuit through the active metals layer on the main surface of the ceramic circuit board A step of joining a metal plate to be a plate, and an upper surface of the metal plate having a width equal to or smaller than a pattern corresponding to the line conductor of the active metal layer in the circuit pattern shape . A step of forming a second resist layer having a width larger than a pattern corresponding to the ground conductor among the one resist layer and the active metal layer having a circuit pattern, and etching the metal plate to obtain a vertical cross-sectional shape. trapezoidal vertical cross section and the ground conductor shape to and forming with said line conductor have lower than the top surface of the ground conductor height and apex triangular simultaneously And wherein the Rukoto.

Ceramic circuit board of the present invention is a circuit board that metal circuit plate is bonded to the main surface of the ceramic substrate, the metal circuit board, and the vertical sectional shape trapezoidal ground conductor, a longitudinal cross section triangular and the top portion by height it is made on-site and lower line conductor than the upper surface of the ground conductor, a portion of the line conductor pitch reduction, miniaturization accompanying Oyo Bisore be realized. And in low cost or One small, not broken by reducing the resistance in the ground conductor and the small current can be mixed at high density line conductor to flow, or One small current line conductor flowing a large current to flow through , it is possible to provide what one reliable ceramic circuit board. Also, the height of the line conductor longitudinal cross section and a top section a triangular shape and lower castings than the upper surface of the ground conductor, it is possible to reduce the stress at the junction between the metal circuit plate and the ceramic substrate , without generating troubles peeling of the active metal layer, it is possible to improve the reliability of the ceramic circuit board.

  Also, since the ground conductor is thicker than the line conductor, the side of the ground conductor surrounds the line conductor with a larger area, the capacitive coupling between the line conductor and the ground conductor is better, and transmission characteristics are further improved. Can do.

The method for manufacturing a ceramic circuit board according to the present invention includes a step of forming an active metal layer having a circuit pattern shape on a main surface of a ceramic substrate, and a metal plate that becomes a metal circuit plate on the main surface of the ceramic circuit board via the active metal layer A first resist layer and a circuit pattern having a width smaller than that of a pattern corresponding to a line conductor of a circuit pattern- like active metal layer or smaller than a pattern corresponding to a line conductor, on the upper surface of the metal plate A step of forming a second resist layer having a width larger than the pattern corresponding to the ground conductor in the active metal layer , and etching the metal plate results in a trapezoidal ground conductor and a longitudinal cross-sectional shape by triangular and high of the top portion is provided with a step of simultaneously forming a low There ray path conductor than the upper surface of the ground conductor, resist layer formed one major surface Once the resist layer forming against a grounding conductor longitudinal sectional shape of the trapezoidal in one etching regard etching process, the vertical cross-sectional shape and height of the top portion is triangular and the lower line conductor than the upper surface of the ground conductor Can be obtained.

  Next, the ceramic circuit board of the present invention will be described in detail with reference to the accompanying drawings.

  FIG. 1 is a cross-sectional view for each process showing an example of an embodiment of a ceramic circuit board of the present invention. As shown in FIG. 1, 1 is a ceramic substrate, 2 is an active metal layer, 3 is a metal circuit board, 4 is a ground conductor, and 5 is a line conductor. FIG. 2 shows a cross-sectional shape of an example of the method for producing a ceramic circuit board according to the present invention. As shown in FIG. 2, 21 is a ceramic substrate, 22 is an active metal layer, 23 is a metal circuit board, 23 'is a metal plate to be a metal circuit board, 24 is a ground conductor, 25 is a line conductor, and 26 is a resist ink. is there.

Ceramic circuit board of the present invention, the circuit board where the metal circuit plate 3 is bonded to the main surface of the ceramic substrate 1, the metal circuit plate 3, a longitudinal cross-sectional shape is trapezoidal ground conductor 4 of the shape, the vertical cross section triangular And a line conductor 5 having a top portion whose height is lower than that of the upper surface of the ground conductor 4.

  The ceramic circuit board of the present invention can be produced as follows. First, an active metal brazing material paste that becomes an active metal layer 22 by adding an organic solvent and a solvent to an active metal powder in which titanium, zirconium, hafnium, hydrides thereof, etc. are added to a brazing material such as a silver-copper alloy. To prepare.

  Next, for example, aluminum oxide powder is selected from ceramic raw material powders such as aluminum oxide, silicon oxide, magnesium oxide, calcium oxide, etc., and an appropriate organic binder, plasticizer, solvent, etc. are added and mixed to form a slurry. A plurality of ceramic green sheets are obtained by adopting a conventionally known tape forming technique such as a doctor blade method or a calender roll method and formed into a predetermined size, and then the ceramic green sheet is formed in a reducing atmosphere at a temperature of about 1600 ° C. The ceramic green sheet is formed by sintering and integrating the ceramic green sheets.

  Next, as shown in FIG. 21), an active metal brazing paste is applied on the ceramic substrate 21 in advance by a known method such as screen printing so as to form a desired pattern of the line conductor 25 and the ground conductor 24. After that, a metal plate 23 ′ to be a metal circuit plate 23 such as copper is placed.

  Next, as shown in FIG. 22), by heating the active metal brazing paste disposed between the ceramic substrate 21 and the metal plate 23 ′ to a temperature of about 900 ° C. in a non-oxidizing atmosphere, The metal plate 23 ′ is bonded to the ceramic substrate 21 through the active metal layer 22.

Next, as shown in FIG. 23), a resist ink is printed on the surface of the metal plate 23 'by applying a technique such as a screen printing method in a circuit form. Pattern resist ink to print the coating, in the ground conductor 24 portion of the longitudinal cross-section trapezoidal, the resist pattern width not less than the thickness of the metal plate 23 ', the height of the vertical cross section and top triangular ground In a portion formed on the line conductor 25 lower than the upper surface of the conductor 24, the resist pattern width is set to be equal to or smaller than the thickness of the metal plate 23 ′ and equal to or larger than ½ of the thickness of the metal plate 23 ′.

Next, the metal plate 23 ′ is etched with , for example, a ferric chloride solution. During the etching process, so that the vertical cross-section the portion height and apex triangular forms the lower line conductor 25 than the upper surface of the ground conductor 24 is shaped to a desired, by adjusting the etching time, It adjusts so that cutting etching may be carried out in the center vicinity of the thickness of mounted metal plate 23 '. Thereby, by performing the pitch of the line conductor 25, the line conductor 25 to flow to the ground conductor 24 a small current to flow a large current to achieve miniaturization by mixing a high density, flow or One small current without disconnection by reducing the resistance value in the line conductors 25, may be either one reliable ceramic circuit board.

Note that when cormorants etching row above method, the width of the resist ink, the width of the line conductor 25 to the desired, i.e. equal to the width of the active metal layer 22 formed in a pattern shape which is line conductor 25 to a desired or with smaller than, the width of the ground conductor 24 to the desired, i.e. by also increasing Ri by the width of the active metal layer 22 formed in a pattern shape having the ground conductor 24, the desired metal circuit board 23 vertical cross-sectional shape and height of the top triangular can be with lower line conductor 25 than the upper surface of the ground conductor 24 of the. Preferably, the width of the resist ink corresponding to the pattern to be the line conductor 25 is 3/4 or less of the width of the metal circuit board 23 as the desired line conductor 25. Thus, vertical cross-sectional shape of the metal circuit plate 23 is the angle of the inclined surface of the metal circuit plate 23 becomes smaller than the portion of the ground conductor 24 of the trapezoidal, it is possible to improve the reliability by more stress is relaxed it can.

  Note that the present invention is not limited to the above-described best modes and examples, and various modifications may be made without departing from the scope of the present invention.

It is a figure which shows an example of embodiment of the ceramic circuit board of this invention. It is sectional drawing for every process which shows an example of the manufacturing method of the ceramic circuit board of this invention. It is sectional drawing of the metal circuit board after an etching. It is sectional drawing of the conventional ceramic circuit board.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1,2: Ceramic substrate 2,22: Active metal layer 3,23: Metal circuit board 23 ': Metal plate used as a metal circuit board 4,24: Ground conductor 5,25: Line conductor

Claims (2)

In the circuit board metal circuit plate is bonded to the main surface of the ceramic substrate, the metal circuit board, and the vertical sectional shape trapezoidal ground conductor, the vertical cross section height the ground conductor and the top triangular A ceramic circuit board comprising a line conductor lower than the upper surface of the circuit board. A method of manufacturing a ceramic circuit substrate according to claim 1, wherein the steps of forming an active metal layer of the circuit pattern on the main surface of the ceramic substrate, through the active metals layer on the main surface of the ceramic circuit board A step of joining a metal plate to be the metal circuit plate, and a pattern corresponding to the pattern corresponding to the line conductor in the active metal layer of the circuit pattern on the upper surface of the metal plate or a pattern corresponding to the line conductor A step of forming a second resist layer having a width larger than a pattern corresponding to the ground conductor among the first resist layer having a small width and the active metal layer having a circuit pattern, and etching the metal plate, step longitudinal sectional shape vertical cross-section and the ground conductor of trapezoidal forming with said line conductor have lower than the top surface of the ground conductor height and apex triangular simultaneously Method of manufacturing a ceramic circuit board, characterized in that it comprises a.

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