JP2006196483A - Wiring board and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a wiring board whose thermal resistance is sufficient and which is superior in productivity although a metal plate is used for a substrate. <P>SOLUTION: A stainless steel plate 1 which is formed of a stainless steel plate of a Fe-Cr-Al system and in which a whole surface is coated with an aluminum oxide coat by thermal treatment after the steel is worked into a desired shape is set to be the substrate. Wiring 3 is formed on the aluminum oxide coat 2 in the substrate. A protection film 4 is formed if necessary. Since the aluminum oxide coat formed by heat treatment with respect to the stainless steel plate of the Fe-Cr-Al system is used as an insulating layer, resin in adhesive use is not required as in a conventional case. Thus, thermal resistance of the substrate is sufficient and correspondence is possible to the trouble of heat or to an environment that it is used under a high temperature condition. The aluminum oxide film on a surface of the substrate is formed by diffusion from an inner side of the steel plate. Thus, bonding strength of the insulating layer and the metal plate is large and mechanical strength of the wiring board itself is sufficient. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a wiring board in which a wiring having a desired pattern is formed on a base material processed into a desired shape, such as a wiring board constituting a printed wiring board, a semiconductor package, various sensors and the like.

  Conventionally, as this type of wiring substrate, a resin substrate is often used as a base material for mounting the wiring. However, recently, there is a demand for wiring boards with better environmental performance, such as the problems of heat caused by high performance, miniaturization, and high density of electronic devices, and when used under high temperature conditions. Therefore, instead of a resin base material that is weak against heat, a metal plate such as aluminum having good thermal conductivity and excellent heat dissipation is used as the base material.

  As described above, when a metal plate is used as the substrate of the wiring board, since the metal is an electric conductor, it is necessary to coat the surface with an insulating film such as alumina and to apply a thin film wiring thereon. However, when an alumina film is formed on a metal, a stress due to a difference in thermal expansion coefficient is generated, causing a problem that the alumina film is peeled off. Or the problem that the insulation defect of a pin pole etc. arises in an insulating film also generate | occur | produces. Accordingly, various methods for manufacturing a metal plate with an insulating film in consideration of these problems have been proposed.

  For example, Japanese Patent Application Laid-Open No. 5-42627 and Japanese Patent Application Laid-Open No. 5-74251 disclose that the adhesion to a metal is improved by spraying ceramic on a sheet-like carrier made of a metal foil such as aluminum or copper. After forming the layer and removing the carrier from the ceramic layer to obtain a ceramic sheet, the ceramic sheet is impregnated with an insulating agent to obtain a ceramic prepreg, and then the insulating impregnated ceramic prepreg and a metal plate are bonded together to insulate A method for producing a metal plate with a film is disclosed.

Japanese Patent Application Laid-Open No. 5-295518 discloses a method of reducing the number of insulation defects by dry-coating an alumina film on a stainless steel plate and subsequently heat-treating it at a temperature of 600 ° C. or higher in a non-oxidizing atmosphere. JP-A-5-306460 discloses a method of reducing the holes and improving the insulating properties. Japanese Unexamined Patent Publication (Kokai) No. 5-306460 dry-coats an alumina film on a stainless steel plate, and subsequently continues in an oxidizing atmosphere at 500 ° C. or higher. An electrical insulation property is improved by performing a heat treatment at the above temperature.
Japanese Patent Laid-Open No. 5-42627 JP-A-5-74251 Japanese Patent Laid-Open No. 5-295518 JP-A-5-306460

  In the former, the adhesion of the insulating layer to the metal is improved, but a resin is used for bonding the metal base and the ceramic insulating layer, and the heat resistance temperature of the substrate itself is the heat resistance temperature of the resin. This is equivalent to the case of using a conventional resin base material. In addition, since the resin used as the adhesive layer is inferior in thermal conductivity compared to metal, there is a problem that the thermal conductivity of the entire substrate is deteriorated.

  In the latter case, insulation defects such as pinholes are reduced, but production efficiency is poor because dry coating such as sputtering is used as a process for forming an alumina film on a metal substrate. Moreover, if the metal substrate after film formation must be heat-treated in an oxidizing atmosphere, there is a problem that the number of processes is increased and productivity is deteriorated.

  The present invention has been made in view of such problems. The object of the present invention is to use a metal plate as a base material, while having good heat resistance and excellent productivity. And a manufacturing method thereof.

  A wiring board as a wiring according to claim 1 is made of a Fe-Cr-Al-based stainless steel plate, and a stainless steel plate whose entire surface is coated with an aluminum oxide film by heat treatment after being processed into a desired shape. The substrate is characterized in that a wiring is formed on the aluminum oxide film on the substrate.

  According to a second aspect of the present invention, there is provided a wiring board as a wiring according to the first aspect, wherein the wiring is formed on an aluminum oxide film covering a side surface of a cavity formed by processing.

  The wiring board according to claim 3 is characterized in that, in the wiring board according to claim 1, the wiring is formed on the aluminum oxide film covering the inner surface of the through hole formed by processing. .

  The wiring board according to claim 4 is the wiring board according to any one of claims 1 to 3, wherein a film element is formed on the aluminum oxide film, and the film element is connected to the wiring. It is characterized by.

  The wiring board according to claim 5 is the wiring board according to any one of claims 1 to 4, wherein an insulating protective film is formed to cover the wiring formed on the aluminum oxide film. It is characterized by.

  The method for manufacturing a wiring board according to the present invention according to claim 6 includes a processing step of processing a Fe-Cr-Al stainless steel plate into a desired shape, and a stainless steel whose entire surface is coated with an aluminum oxide film by firing. It includes a heat treatment step for obtaining a base material made of a steel plate and a wiring formation step for forming a wiring on an aluminum oxide film on the base material.

  According to a seventh aspect of the present invention, there is provided a method for manufacturing a wiring board, comprising: performing a film element forming step of forming a film element connected to the wiring after the wiring forming step in the manufacturing method according to the sixth aspect. It is said.

  The method for manufacturing a wiring board according to an eighth aspect of the present invention includes a protective film forming step for forming an insulating protective film covering the wiring after the wiring forming step in the manufacturing method according to the sixth or seventh aspect. It is characterized by doing.

  Since the wiring board of the present invention uses an aluminum oxide film formed by heat treatment on an Fe—Cr—Al stainless steel plate as an insulating layer, it does not require a resin for adhesive use as in the prior art. The heat resistance of the material is good, it can cope with the environment where there is a problem of heat or it is used under high temperature conditions, and the aluminum oxide film on the surface of the base material is formed by diffusion from inside the steel material Therefore, the adhesive strength between the insulating layer and the metal plate is high, and the mechanical strength of the wiring board itself is also good.

  Further, according to the method for manufacturing a wiring board of the present invention, a strong insulating layer can be formed on the entire surface of the stainless steel plate only by heat treatment, and it is only necessary to form a wiring on the insulating layer. Since dry coating and subsequent heat treatment are not required, the process is simplified and productivity is improved.

  1 is a plan view showing an example of a wiring board according to the present invention, FIG. 2 is a cross-sectional view taken along the line AA in FIG. 1, FIG. 3 is a cross-sectional view taken along the line BB in FIG. FIG. 5 and FIG. 5 are DD sectional views of FIG.

  In these drawings, 1 is an Fe—Cr—Al-based stainless steel plate 1 processed into a desired shape, 2 is an aluminum oxide coating covering the entire surface of the stainless steel plate 1, and 3 is an aluminum oxide coating 2. A wiring 4 and 4 are insulating protective films formed to cover the wiring. Further, 5 is a film element such as a resistor or thermistor, 6 is a film element constituting a capacitor, 7 is a semiconductor element, 8 is a cavity, and 9 is a through hole. In FIG. 1, an insulating protective film (described later) is formed so as to cover the wiring 3, but the illustration is omitted.

  The Fe—Cr—Al-based stainless steel plate 1 is made of a material containing aluminum in an amount of about 8% or less in stainless steel (for example, Fe: 75%, Cr: 20%, Al: 5%). Thus, a film made of aluminum oxide (alumina) is formed on the entire surface by performing a heat treatment of firing in an appropriate atmosphere. Therefore, after the stainless steel plate 1 is processed into a desired shape, heat treatment is performed to obtain a metal plate whose entire surface including the processed surface is covered with the insulating layer made of the aluminum oxide film 2.

  Then, using the stainless steel plate 1 with the insulating film 2 as a base material, the wiring 3 is formed on the aluminum oxide film 2 on the base material, and then the film elements 5 and 6 are formed or the semiconductor element 7 is mounted. After passing through the steps such as, a protective film 4 covering the wiring 3 is formed as necessary to obtain the wiring substrate shown in FIG.

  After forming the wiring 3, in order to form a resistor with the film element 5 as shown in FIG. 3, a resist is formed on the entire surface with only the region where the resistor is formed exposed, and then reactive sputtering is performed. To form tantalum nitride and further remove the resist. Thereby, the resistor body by the film element 5 can be formed. In addition, a thermistor used for a temperature sensor due to a large change in resistance value depending on the temperature is the same as that of the resistor described above by reactive sputtering, as disclosed in, for example, JP-A-2004-319737. The film element 5 can be formed.

  Further, as shown in FIG. 3, the film element 6 constituting the capacitor has a structure in which two electrodes 3a and 3b which are a part of the wiring 3 are provided opposite to each other with the dielectric layer 4 ′ interposed therebetween. . The film element 6 can be realized by forming the dielectric layer 4 ′ and the electrode 3 b in order by sputtering or the like after forming the electrode 3 a as a part of the wiring 3.

  When the semiconductor element 7 is mounted on the substrate, the cavity 8 is formed by half-etching on the stainless steel plate 1 as shown in FIG. Then, a terminal of the wiring 3 connected to the semiconductor element 7 is formed in the cavity 8. When the wiring 3 is formed in the cavity 8, it is necessary to form an insulating layer on the side surface of the cavity 8, but the Fe—Cr—Al-based stainless steel plate 1 can be heated only by heating. Since the aluminum oxide film 2 is formed at the same time, a special process for forming an insulating film on the side surface is not required.

  When providing the through-hole 9 in a base material, as shown in FIG. 5, a through-hole is formed with respect to the stainless steel plate 1 by an etching. An insulating layer needs to be formed on the inner wall surface of the through-hole, but the Fe—Cr—Al-based stainless steel plate 1 is simply heated, so that the inner wall surface of the through-hole is made of aluminum oxide simultaneously with other surfaces. Since the film 2 is formed, a special process for forming an insulating film on the inner wall surface of the through hole is not required. There are various methods for forming the conductor in the through hole, but a typical method is a subtractive method by panel plating described later.

  The above-described method for manufacturing a wiring board is shown in FIG. 1 in section AA in FIG. 1, and the manufacturing procedure will be described in detail below with reference to this process diagram.

  First, as shown to Fig.6 (a), the Fe-Cr-Al type stainless steel plate 1 which comprises a base material is prepared. In this case, as the Fe-Cr-Al type stainless steel plate, there are various types such as 0.1 mm, 0.2 mm, 0.4 mm, etc., and those having a thickness corresponding to the application are selected from them. And as shown in FIG.6 (b), this stainless steel plate 1 is processed into the desired shape according to a use by an etching process, machining, etc. As shown in FIG. Here, the figure which processed the some through-hole 1a is shown.

  In the case of etching processing, a resist film such as a dry film resist is provided on one or both surfaces of a stainless steel plate, and after patterning the resist film by exposure and subsequent development process, the resist film on the stainless steel plate is formed using a predetermined etching solution. After etching the non-existing portion, the resist film is finally stripped using a stripping solution. In this case, either single-sided etching or double-sided etching is selected according to the opening shape to be formed. In the case of machining, the stainless steel plate is processed into a desired shape using appropriate means such as punching and cutting.

  Next, after cleaning the stainless steel plate 1 processed into a desired shape, an aluminum oxide film 2 is formed on the entire surface of the stainless steel plate 1 by a heat treatment step of firing in an appropriate atmosphere as shown in FIG. To do.

  The heat treatment applied to the stainless steel sheet is 800 ° C. or higher, preferably 900 to 1200 ° C. in the atmosphere for about 2 hours. By this heat treatment, the aluminum component diffuses from the inside of the steel sheet, and an aluminum oxide film is formed on the entire surface including the front and back surfaces and the side surfaces of the base material. The formed aluminum oxide film is in close contact with the surface of the stainless steel plate and serves as an insulating layer in the wiring board. This aluminum oxide film is easily peeled off when the thickness exceeds 1.5 μm. Therefore, the conditions are controlled so that the thickness is preferably about 0.1 to 1 μm when the aluminum oxide film is formed by heat treatment.

  Next, as shown in FIG. 6 (d), a wiring 3 is formed on the aluminum oxide film 2 formed on the stainless steel plate 1. The wiring 3 is formed by sputtering or electroless plating. For example, it is possible to form a circuit by a so-called lift-off method in which a resist image is formed on an aluminum oxide film, a metal thin film is formed by a sputtering method, and then a wiring pattern is formed by peeling the resist. As the wiring material, Au, Al, Cu, Cr, Ni, Pt or the like can be used. Note that when an Au wiring is formed on an aluminum oxide film, a contact metal layer such as Ni, Ti, W, or Ta is required.

  After the wiring 3 is formed on the aluminum oxide film 2 in this way, the film elements 5 and 6 are formed as described above and the semiconductor element 7 is mounted, and then, as shown in FIG. Thus, the insulating protective film 4 is formed so as to cover the wiring 3. The protective film 4 may be formed of a metal oxide (for example, sputtering of aluminum oxide) by a vacuum film forming method, or may be formed of an organic material such as polyimide or epoxy resin when the required heat-resistant temperature is low. Good.

  7 and 8 are process diagrams showing another method for manufacturing a wiring board, and here, a process using a subtractive method by panel plating is shown. Hereinafter, the manufacturing method will be described in detail with reference to the process drawings. In this example, the wiring is made of copper.

  First, as shown to Fig.7 (a), the Fe-Cr-Al type stainless steel plate 1 which comprises a base material is prepared. And as shown in FIG.7 (b), this stainless steel plate 1 is processed into the desired shape according to a use by an etching process, machining, etc. As shown in FIG. Here, a resist is patterned on both surfaces of the stainless steel plate 1, the stainless steel plate 1 is etched and formed from both surfaces using an etching solution containing ferric chloride as a main component, and then the resist is peeled to remove a plurality of through holes 1 a. And a through hole 1b is also formed. A cavity for a semiconductor element is also formed at the same time by half etching.

  Next, the formed stainless steel plate 1 is heated in the air at 800 ° C. or higher, preferably in the range of 900 to 1200 ° C. for about 2 hours, and as shown in FIG. An aluminum oxide film 2 is formed.

  Next, a thin copper electroless plating layer having a thickness of about 0.3 to 3.0 μm is formed on the entire surface so as to cover the aluminum oxide film 2, and this copper electroless plating layer is used as a power feeding layer as shown in FIG. As shown, a copper electroplating layer 3 ′ having a necessary thickness (usually 10 to 50 μm) is formed. By performing panel plating in this way, a copper layer is formed not only on the surface of the substrate but also on the side wall of the through-hole 1b, thereby conducting.

  Subsequently, a dry film resist is laminated on the copper electroplating layer 3 ′, and after exposure and development, a resist 10 is formed corresponding to a portion where wiring is to be formed, as shown in FIG. . In this case, the through hole portion is filled with a resin in advance if necessary. And after removing the unnecessary part in the copper electroplating layer 3 'using the etching liquid which has ferric chloride as a main component, after peeling the resist 10, as shown in FIG. The wiring 3 is formed, and the through hole 9 and the terminal are completed.

  After the copper wiring pattern is formed in this way, a desired film element 5 is formed on the wiring 3 as necessary, for example, as shown in FIG. The film element can be formed by a method such as screen printing, vapor deposition, or sputtering depending on the type.

  And as shown in FIG.8 (d), the insulating protective film 4 is formed and it completes as a wiring board. Further, if necessary, a semiconductor element, a passive element or the like is mounted on the substrate before or after the protective film 4 is formed.

  Although the embodiments of the present invention have been described in detail above, the wiring board according to the present invention is not limited to the above-described embodiments, and various modifications are possible without departing from the spirit of the present invention. It is natural to be.

It is a top view which shows an example of the wiring board which concerns on this invention. It is AA sectional drawing of FIG. It is BB sectional drawing of FIG. It is CC sectional drawing of FIG. It is DD sectional drawing of FIG. It is process drawing which shows the manufacturing method of a wiring board. It is process drawing of the first half which shows another manufacturing method of a wiring board. It is process drawing of the latter half which shows another manufacturing method of a wiring board.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Stainless steel plate 2 Aluminum oxide film 3 Wiring 3a, 3b Electrode 3 'Copper electroplating layer 4 Protective film 4' Dielectric layer 5, 6 Film element 7 Semiconductor element 8 Cavity 9 Through hole 10 Resist

Claims (8)

  A stainless steel plate made of a Fe-Cr-Al-based stainless steel plate and coated with an aluminum oxide film on the entire surface by heat treatment after being processed into a desired shape is used as a base material. A wiring board having wiring formed thereon.   The wiring board according to claim 1, wherein wiring is formed on an aluminum oxide film covering a side surface of the cavity formed by processing.   The wiring board according to claim 1, wherein wiring is formed on an aluminum oxide film covering an inner surface of the through hole formed by processing.   The wiring board according to claim 1, wherein a film element is formed on the aluminum oxide film, and the film element is connected to the wiring.   The wiring board according to claim 1, wherein an insulating protective film is formed to cover the wiring formed on the aluminum oxide film.   A processing step for processing a Fe-Cr-Al type stainless steel plate into a desired shape, a heat treatment step for obtaining a base material made of a stainless steel plate whose entire surface is coated with an aluminum oxide film by firing, and an aluminum oxide film on the base material And a wiring forming step of forming a wiring on the wiring board.   A method for manufacturing a wiring board, comprising performing a film element forming step of forming a film element connected to the wiring after the wiring forming step in the manufacturing method according to claim 6. 8. A method for manufacturing a wiring board, comprising performing a protective film forming step of forming an insulating protective film covering the wiring after the wiring forming step in the manufacturing method according to claim 6 or 7.

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