JP2007324522A - Method of manufacturing metallized ceramic substrate - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of manufacturing a metallized ceramic substrate having high reliability and adequate adhesion strength, by forming a metal film directly on a ceramic substrate through electroless plating. <P>SOLUTION: A method of manufacturing a metallized ceramic substrate comprises a process (A) of preparing a material substrate, consisting of a ceramic substrate that may have a conductive layer or a conductive paste layer on its surface; a process (B) of forming a ceramic paste layer on the material substrate and of baking the ceramic paste layer to form a sintered ceramic layer; and a process (C) of forming a metal film on the sintered ceramic layer through electroless plating. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method of manufacturing a metallized ceramic substrate.

  As a method of manufacturing a metallized ceramic substrate for forming a metal film on the surface of the ceramic substrate, a method of forming a metal film on the surface of the ceramic substrate by a dry thin film method (evaporation method, etc.) or a method of performing an electroless plating process has been proposed. Yes. There is also a method of obtaining a metal film by applying a thick film paste by screen printing or the like and baking it.

  Among these methods, the electroless plating method has the advantage that it can be automated and does not require expensive equipment, and can be formed into a complicated shape, and is practically used industrially. ing.

When a metal film is directly formed on the surface of a ceramic substrate by electroless plating, pretreatment is important to improve the adhesion of the metal film, especially roughening the surface is an essential pretreatment. It has become. As a surface roughening method, generally, a strong alkaline solution such as NaOH or KOH, a weak alkaline solution such as Na ₂ CO ₃ , K ₂ CO ₃ or NH ₃ or an acidic solution such as H ₂ SO ₄ , HCl or HF is used. There are chemical processing methods for etching and physical processing methods such as rubbing using honing and abrasive grains, and pretreatment methods suitable for each type of ceramic substrate have been developed.

For example, when electroless plating is performed on the surface of an aluminum nitride sintered body substrate that is useful as a wiring board material because of its high thermal conductivity, etching using a NaOH solution is performed as a pretreatment, thereby Grain boundaries are preferentially eluted to roughen the surface, and the adhesion of the plating layer is enhanced by the anchoring effect (anchor effect) (Non-Patent Document 1)
2 and Patent Document 1).
J. Electrochem. Soc., 133, p.2345 (1986) Tetsuaki Osaka, Toshiaki Asada, Eiji Nakajima, Ichiro Koiwa, Kazuaki Utsumi: Abstracts of the 76th Annual Conference of the Metal Surface Technology Association, p. 176 (1988) JP-A-9-184076

  As described above, the surface roughening treatment is necessary when the metal film is directly formed on the surface of the ceramic substrate by electroless plating. Either the chemical treatment or the physical treatment can be used as the surface roughening treatment. Even if is adopted, the ceramic substrate is damaged. For this reason, if the conditions of the roughening treatment are too severe, damage to the substrate will increase and problems such as reduction in mechanical strength will occur. On the other hand, if the roughening treatment is insufficient, adhesion between the ceramic and the plating film cannot be obtained sufficiently.

In particular, when a substrate mainly composed of aluminum nitride that easily undergoes a chemical reaction with a basic aqueous solution and is easily decomposed is etched with the basic aqueous solution, the following problems may occur.
1) Mechanical properties such as bending strength decrease due to damage to the substrate due to etching (this problem is remarkable when the substrate is thin).
2) Due to the preferential dissolution of the aluminum nitride crystal grain boundaries, the aluminum nitride crystal grains underlying the plating film (metal film) fall off when used for a long time after the plating film is formed. Peeling occurs,
3) The surface becomes too rough by etching, and the surface of the exposed ceramic (aluminum nitride) surface on which the plating film (metal film) is not formed becomes rough.
4) In the case of 3), the surface roughness of the formed plating film (metal film) is also increased. For example, when a semiconductor element is bonded directly or indirectly on this plating film, the element is bonded well. Difficult to do,
5) The aluminum nitride substrate usually contains a sintering aid phase such as yttrium oxide, but depending on the firing conditions, mainly the firing atmosphere, the aid may or may not cover the surface, and the same etching conditions. Even when etching is performed, a constant plating film strength cannot always be obtained.

  In addition, as a method of roughening the surface without damaging the ceramic surface, a method of baking a surface modifier made of special glass powder on the ceramic surface is also known, but depending on the type of ceramic substrate, baking is performed. There arises a problem that the adhesion strength between the formed glass layer and the ceramic substrate becomes insufficient. Further, when such a surface modifier is used, it is necessary to accurately control the baking temperature, and it is difficult to obtain a ceramic substrate having a good surface state with high reproducibility and high yield. For example, when trying to obtain good bonding strength when baking glass on a ceramic substrate, it is often preferable to increase the baking temperature, but generally glass has a remarkably low melting point compared to ceramic, and thus baking is performed. If the temperature is too high, the surface of the baked glass layer becomes smooth and a sufficient roughening effect cannot be obtained.

  The present invention is intended to solve such problems of the prior art. That is, the present invention can produce a metallized ceramic substrate with high reliability and sufficient adhesion strength in a method for producing a metallized ceramic substrate by directly forming a metal film on the ceramic substrate by electroless plating. It aims to provide a method.

Means for solving the above problems provided by the present invention are as follows.
(1) Step (A) of preparing a raw material substrate made of a ceramic substrate that may have a conductive layer or a conductive paste layer on the surface;
Forming a ceramic paste layer on the raw material substrate, firing the ceramic paste layer to form a ceramic sintered body layer; and
And (C) forming a metal film on the ceramic sintered body layer by electroless plating.
(2) The manufacturing method as described in (1) which does not include the process of etching a raw material board | substrate with basic aqueous solution as a pre-process of a process (C).
(3) The production method according to (2), further including a step (D) of coating the metal by electroplating on the electroless plating metal film formed in the step (C).
(4) A metallized ceramic substrate obtained by the production method of any one of (1) to (3) above. (5) A metallized ceramic substrate having a laminated structure comprising at least one ceramic sintered body layer and an electroless plating metal film directly formed thereon on the ceramic sintered body substrate, The ceramic sintered body layer forming the laminated structure is made of a ceramic sintered body of the same type as the ceramic constituting the ceramic sintered body, and the average particle diameter of the ceramic particles constituting the ceramic sintered body layer is A metallized ceramic substrate which is 10 to 80% of the average particle size of ceramic particles constituting the sintered body substrate.
(6) The metallized ceramic substrate according to (5), wherein the ceramic particles forming the ceramic sintered body layer have an average particle size of 0.1 μm to 5 μm.
(7) The metallized ceramic substrate according to (5) or (6), wherein the average roughness of the ceramic sintered body layer surface is 0.1 μm to 3 μm.
(8) The metallized ceramic substrate according to any one of (5) to (7), wherein the ceramic sintered body substrate and the ceramic sintered body layer are made of aluminum nitride.

  The metallized ceramic substrate of the above (5) or (6) is one aspect of the metallized ceramic substrate of the above (4), and any of them can be manufactured by the manufacturing method of the present invention. In particular, in the production method of the present invention, when a ceramic paste prepared using the same kind of ceramic powder having an average particle diameter equal to or smaller than that of the ceramic powder used in manufacturing the ceramic sintered body substrate is used ( The metalized ceramic substrate of 5) is obtained.

  In general, when a sintered ceramic substrate is produced by firing a green sheet or when a metallized substrate is produced by the co-fire method, the green sheet shrinks during the firing process, so that the ceramic particles therein are fused together. Whereas grain growth occurs, in the above manufacturing method, shrinkage of the raw material substrate (ceramic sintered body substrate) does not occur during firing, so the ceramic paste layer formed thereon, particularly with a thickness of 1 to 50 μm. The ceramic particles in the ceramic paste layer are limited in movement and do not cause sufficient grain growth. For this reason, in the metallized substrate of the present invention manufactured by the method as described above, the average particle size of the ceramic particles constituting the ceramic sintered body layer (a layer formed by firing the ceramic paste layer) is 10 to 80% of the average particle size of the ceramic particles constituting the sintered substrate, and the surface has fine irregularities, a peculiarity not found in the substrates obtained by the conventional postfire method and cofire method Will have a structure.

  For this reason, the ceramic substrate made by the above method has a moderately roughened surface without performing etching treatment, and plating with high adhesion even when direct catalytic contact and plating treatment are performed. A metal layer can be formed.

  Whether or not the substrate is obtained by the method as described above, the average particle size of the ceramic particles in the vicinity of the joint portion with the metallized layer and the average particle size of the ceramic particles in the vicinity of the center portion of the metallized ceramic substrate. It can be confirmed by examining whether the former is 80% or less of the latter, more surely 60% or less.

  If the manufacturing method of this invention is used, the metal film which adhere | attached firmly on the ceramic substrate surface directly by the electroless-plating method can be formed without performing an etching process. For this reason, since the substrate is not damaged in the film forming process (including pretreatment), a metallized ceramic substrate in which a highly reliable metal film is coated on the ceramic substrate without impairing the mechanical strength of the substrate. It can be manufactured at low cost.

  In particular, when a metal layer is directly formed on the surface of a ceramic substrate mainly composed of aluminum nitride by an electroless plating method, when etching is performed using a basic aqueous solution as a roughening treatment as in the past, While problems as shown in 1) to 4) may occur, such a problem does not occur when the method of the present invention is employed.

The method for producing a metallized ceramic substrate according to the present invention includes:
A step (A) of preparing a raw material substrate made of a ceramic substrate which may have a conductive layer or a conductive paste layer on the surface;
Forming a ceramic paste layer on the raw material substrate, firing the ceramic paste layer to form a ceramic sintered body layer; and
The method includes a step (C) of forming a metal film on the ceramic sintered body layer by electroless plating.

  In the production method of the present invention, first, as a step (A), a raw material substrate made of a ceramic substrate which may have a conductive layer or a conductive paste layer on its surface is prepared. As the ceramic substrate used here, a substrate made of a known ceramic can be used without particular limitation.

  Examples of the ceramic as a constituent material of the ceramic substrate include (i) oxide ceramics such as aluminum oxide ceramics, silicon oxide ceramics, calcium oxide ceramics, and magnesium oxide ceramics; (ii) aluminum nitride ceramics and nitrides Nitride-based ceramics such as silicon-based ceramics and boron nitride-based ceramics; (iii) beryllium oxide, silicon carbide, mullite, borosilicate glass, and the like can be used. Among these, (ii) nitride ceramics are preferred, and aluminum nitride ceramics are particularly preferred because of their high thermal conductivity.

  The ceramic substrate used in the production method of the present invention is an average of the ceramic sintered body substrate, particularly the ceramic particles constituting the sintered body substrate, because it is easily available and can be obtained in a desired shape. It is preferable to use a ceramic sintered body substrate having a particle size of 0.5 to 20 μm, more preferably 1 to 15 μm. In addition, such a ceramic sintered compact board | substrate can be obtained by baking the green sheet which consists of ceramic raw material powder whose average particle diameter is 0.1-15 micrometers, Preferably it is 0.5-5 micrometers.

  The green sheet may contain a sintering aid, an organic binder, and the like. As the sintering aid, a sintering aid commonly used according to the type of ceramic raw material powder can be used without any particular limitation. Furthermore, as the organic binder, polyvinyl butyral, ethyl celluloses and acrylic resins are used, and poly n-butyl methacrylate and polyvinyl butyral are particularly preferably used because the green sheet has good moldability.

  From the viewpoint of thermal conductivity of the obtained sintered body, a nitride ceramic green sheet formed by using a nitride ceramic powder containing a sintering aid as a ceramic raw material powder, particularly a sintering aid (for example, yttrium oxide or It is preferable to use a green sheet for aluminum nitride using an aluminum nitride powder containing calcium oxide as a raw material powder.

  The shape of the ceramic substrate (raw material substrate) used in the present invention is not particularly limited as long as it has a surface on which a ceramic sintered body layer and a metal film can be formed. A plate or plate It is also possible to use a substrate obtained by cutting or drilling a part of the substrate or a substrate having a curved surface. The ceramic substrate may have a via hole (that is, a through hole filled with a conductor or a conductive paste) or an inner layer wiring. Such a raw material substrate can be easily manufactured by a cofire method using a green sheet having the structure as described above.

  The magnitude | size of a raw material board | substrate is not specifically limited, What is necessary is just to determine suitably according to a use. For example, when the application is a substrate for mounting an electronic component, the substrate thickness is generally 0.1 to 2 mm, preferably about 0.2 to 1 mm. When a raw material substrate having such an extremely thin thickness is used, the method of the present invention is very valuable because it is easily damaged by etching.

In the production method of the present invention, the ceramic substrate may be used as a raw material substrate as it is. Further, a metallized substrate in which a conductive layer or a conductive paste layer is previously formed on the surface of the ceramic substrate by a conventional method, and further a metallized ceramic substrate obtained by the production method of the present invention can be used as a raw material substrate. By using such a metallized substrate as a raw material substrate, the conductive layer is multi-layered, the degree of freedom in device design is improved, and the device can be miniaturized.

  In the manufacturing method of the present invention, following the step (A), a ceramic paste layer is formed on the raw material substrate prepared in the step, and the ceramic paste layer is fired to form a ceramic sintered body layer (step (B )). As described above, when the ceramic paste layer applied on the raw material substrate that has already been sintered is fired, the shrinkage of the raw material substrate does not occur at the time of firing, so the movement of the ceramic particles in the ceramic paste layer is limited. Therefore, the average particle size of the ceramic particles constituting the layer formed by firing the ceramic paste layer is 10 to 80% of the average particle size of the ceramic particles constituting the raw material substrate, and the surface is fine. Unevenness can be made. The anchor effect is obtained when electroless plating is applied due to this unevenness, so the metal layer formed by electroless plating can be firmly bonded to the ceramic substrate even if the etching treatment as a pretreatment of electroless plating is omitted. Is possible.

  The average particle diameter D (μm) of the ceramic particles constituting the ceramic sintered body (the raw material substrate or the ceramic paste applied thereon) is determined by the following method (code method). Means the average particle diameter.

  That is, first, a scanning electron micrograph is taken of the cross section of the ceramic sintered body. The magnification at this time is in the direction perpendicular to the thickness direction of the ceramic sintered body in the photograph (when the ceramic sintered body is a plate-like body, the direction parallel to the main surface) When a straight line having an arbitrary specific length L (mm) {usually the same length as the width of the photograph} is drawn, the number of intersections between the straight line and the grain boundaries of the ceramic particles is 10 to 50. Magnification {normally 1000-5000 times}. Then, the length U (mm) on the photograph corresponding to the actual length 1 (μm) is obtained from the magnification. Next, n straight lines having a length L parallel to the straight line are drawn on the photograph at a predetermined interval (usually 3 to 7 mm, particularly 5 mm). At this time, the number n of straight lines is set so that the total number ε of intersections with the grain boundaries of the ceramic particles in all the straight lines is 100 to 300. When n straight lines are drawn, marks are made at the intersections between the straight lines and the grain boundaries, and the total number ε of the marks is obtained. And D is calculated | required by the following formula based on L, n, U, and (epsilon) at this time.

D = (1.57 × L × n) / (U × ε)
Formation of the ceramic paste layer in the step (B) is performed by applying the ceramic paste on the raw material substrate and drying it as necessary. At this time, when the raw material substrate has a conductive layer or a conductive paste layer on the surface, a ceramic paste may be applied on these layers.

  As the ceramic paste, a known ceramic paste composed of components such as ceramic powder, a sintering aid, an organic binder, an organic solvent, a dispersant, and a plasticizer can be used without any particular limitation.

  As the ceramic powder contained in the ceramic paste, a known powder can be used without any particular limitation. For example, various ceramic powders exemplified in the description of the ceramic substrate can be used. Among these, as the ceramic powder, it is preferable to use the same ceramic powder as the material of the raw material substrate from the viewpoint of adhesion to the ceramic substrate after firing. Even if different types of ceramics are used, a sufficient bonding strength can be obtained depending on the combination. For example, even when different types of ceramics are used, high bonding strength can be obtained when the types of the cationic components (metal atoms or metalloid atoms) contained are the same. For example, when the ceramic substrate is an aluminum nitride sintered substrate, aluminum nitride powder, aluminum oxide powder, or a mixture thereof can be used.

  As the sintering aid contained in the ceramic paste, those used as a sintering aid depending on the type of ceramic powder can be used without particular limitation. For example, when the ceramic powder is an aluminum nitride powder, a rare earth element oxide such as yttrium oxide, an alkaline earth metal oxide such as calcium oxide, or the like can be used.

  As the organic binder contained in the ceramic paste, known ones can be used without particular limitation. For example, acrylic resins such as polyacrylic acid esters and polymethacrylic acid esters, cellulose resins such as methyl cellulose, hydroxymethyl cellulose, nitrocellulose, and cellulose acetate butyrate, vinyl group-containing resins such as polyvinyl butyral, polyvinyl alcohol, and polyvinyl chloride, polyolefins Hydrocarbon resins such as polyethylene oxide, oxygen-containing resins such as polyethylene oxide, and the like can be used singly or in combination. Among these, acrylic resins and cellulose resins are preferable because they are easily dissolved in a solvent and easily absorb a solvent contained in a conductive paste such as a tungsten paste.

  As the organic solvent contained in the ceramic paste, known ones can be used without particular limitation. For example, toluene, ethyl acetate, terpineol, butyl carbitol acetate, texanol and the like can be used.

  A well-known thing can be especially used as a dispersing agent contained in a ceramic paste without a restriction | limiting. For example, a phosphate ester-based or polycarboxylic acid-based dispersant can be used.

  As the plasticizer contained in the ceramic paste, known ones can be used without particular limitation. For example, dioctyl phthalate, dibutyl phthalate, diisononyl phthalate, diisodecyl phthalate, dioctyl adipate and the like can be used.

  The mixing ratio of the raw material components in the ceramic paste is not particularly limited, but the sintering aid is 0.1 to 15 parts by weight, the organic binder is 6 to 20 parts by weight, the organic solvent, and the plasticizer with respect to 100 parts by weight of the ceramic powder. And at least one selected from the group consisting of dispersants is preferably 10 to 60 parts by mass. Moreover, at least one selected from the group consisting of 1 to 10 parts by mass of a sintering aid, 6 to 15 parts by mass of an organic binder, an organic solvent, a plasticizer and a dispersant is 15 to 100 parts by mass of the ceramic powder. The amount of 50 parts by mass is particularly suitable.

  The method for preparing the ceramic paste is not particularly limited as long as various components can be mixed to obtain a paste having a uniform composition. For example, a known kneading method such as a three-roll mill or a planetary mixer can be employed.

  In the manufacturing method of the present invention, the ceramic paste thus prepared is applied to the entire surface of the raw material substrate or to a predetermined location. The application shape and size of the ceramic paste applied at this time are not particularly limited as long as a metal film having a predetermined pattern can be formed on the sintered ceramic layer after firing. However, when the source substrate has a via hole (that is, a through hole filled with a conductor or a conductive paste) and the via hole is electrically connected to the metal film to be formed, the conductor or the conductive paste and It is necessary not to apply ceramic paste to the joints. The ceramic paste can be applied by a known method such as screen printing, calendar printing, or pad printing.

The thickness of the ceramic paste layer to be formed is not particularly limited, but it is 1 to 20 μm from the viewpoint of obtaining sufficient adhesion by coating the ceramic sintered body layer with a metal film and productivity. In particular, the thickness is preferably 2 to 10 μm, and most preferably 3 to 5 μm. If the ceramic paste layer is too thin, the resulting ceramic sintered body layer becomes thin, and a sufficient anchor effect with the metal film cannot be obtained, so that the adhesion with the metal film may be insufficient. On the other hand, if the ceramic paste layer is too thick, an unnecessary amount of the ceramic paste is used, which is uneconomical, and the thickness may become uneven or distortion may occur after firing.

  The surface average roughness of the formed ceramic sintered body layer (specified by JISB0601 in terms of centerline average roughness (Ra)) is preferably 0.1 μm to 3 μm. Considering that sufficient adhesion strength with the metal film to be coated can be obtained and that the metal film is finely processed, the surface average roughness is preferably 0.5 to 2 μm. Furthermore, from the viewpoint of bondability when a semiconductor element is bonded directly or indirectly onto a metal layer formed by electroless plating, the average surface roughness (Ra) of the ceramic sintered body layer is 0.1. It is preferably ˜1 μm.

  The average particle diameter of the ceramic particles constituting the ceramic sintered body layer is preferably in the range of 0.1 to 5 μm, more preferably 0.3 to 3 μm, and particularly preferably 0.5 to 2 μm. The average particle diameter of the ceramic particles constituting the ceramic sintered body layer is a guideline for achieving a predetermined surface average roughness. Generally, the larger the average particle diameter, the larger the surface average roughness.

  As described above, when firing the ceramic paste layer, the ceramic particles in the ceramic paste layer are restricted in movement and do not cause sufficient grain growth, so the particle size of the ceramic particles contained in the ceramic paste as the raw material Is substantially maintained after sintering. Therefore, the average particle diameter of the ceramic particles constituting the ceramic sintered body layer can be controlled by appropriately setting the particle diameter of the raw ceramic particles.

The ceramic sintered body layer is formed by firing a ceramic paste layer.
If necessary, degreasing may be performed before firing.
Degreasing is performed in a ceramic paste layer in a humidified gas atmosphere in which an oxidizing gas such as oxygen or air, a reducing gas such as hydrogen, an inert gas such as argon or nitrogen, carbon dioxide, and a mixed gas or water vapor thereof is mixed. This is performed by heat-treating the ceramic substrate (hereinafter, sometimes referred to as “ceramic substrate precursor”). The heat treatment conditions may be appropriately selected from the range of temperature: 250 ° C. to 1200 ° C. and holding time: 1 minute to 1000 minutes according to the type and amount of the organic component contained in the ceramic substrate precursor.

  In the firing performed subsequent to the degreasing treatment, normally employed conditions are appropriately employed depending on the type of ceramic paste used (more specifically, the type of ceramic powder used as the raw material). For example, when the ceramic powder contained in the ceramic paste layer is made of an aluminum nitride-based ceramic, it is 1600 to 2000 ° C., preferably 1700 to 1850 ° C. for 1 hour to 20 hours, preferably 2 to 10 hours. It may be fired for the time. As an atmosphere at the time of firing, it may be performed at normal pressure in an atmosphere of non-oxidizing gas such as nitrogen gas.

Through the step (B), a ceramic sintered body layer is formed on the raw material substrate.
Next, a metallized ceramic substrate is obtained by forming a metal film on the ceramic sintered body layer by electroless plating (step (C)). Here, electroless plating is also referred to as chemical plating, and is a plating method in which metal is deposited without using an external power source. A plating method in which metal ions are deposited by a chemical reduction action in a solution containing a reducing agent. means.

In the manufacturing method of the present invention, a good plating film can be formed even if the activation process is performed without performing the etching process after the substrate cleaning. Of course, if damage to the substrate is not a problem, an etching process may be performed. However, when using a substrate mainly composed of aluminum nitride, it is preferable not to perform the etching treatment with a basic aqueous solution. By doing so, it is possible to prevent the problems described in 1) to 4) from occurring.

  In order to perform electroless plating directly on the surface of the ceramic substrate, it is necessary to activate the surface of the portion of the ceramic substrate to be plated. The activation of the surface is performed by attaching a catalyst serving as a reaction initiator for electroless plating. (It is also referred to as catalyst application.) The method of catalyst application is not particularly different from the conventional catalyst application in electroless plating of ceramics. After immersion in a reducing ion solution called sensitizer, catalyst application called activator is applied. After the substrate is immersed in a catalyst solution or suspension (also referred to simply as catalyst solution) called catalyst and the catalyst is attached, the catalyst is added to an acid or alkali solution called accelerator treatment as necessary. It is carried out by immersing the substrate on which the catalyst adheres and activating the catalyst.

  The catalyst application method may be appropriately determined according to the type of plating metal, the plating solution, and the type of substrate. A stannous chloride solution is used as a sensitizer, a palladium solution is used as an activator, and palladium is used as a catalyst. And a solution containing tin. Among them, the method using an accelerator may easily remove the catalyst adhering to the substrate during acid treatment or alkali treatment, and may cause non-deposition in a subsequent plating step (such a phenomenon is In particular, a process using a sensitizer and an activator is more preferable because it is likely to occur when an aluminum nitride substrate is used.

  The activation conditions are not particularly different from those in the prior art, but typical activation conditions are as follows. That is, the immersion in the sensitizer may be performed for 5 seconds to 10 minutes while maintaining the liquid temperature at 20 to 60 ° C. Further, the immersion in the activator may be performed by maintaining the liquid temperature at 20 to 60 ° C. for 5 seconds to 10 minutes, and these operations may be repeated. In these activation treatments, an acidic solution or an alkaline solution may be used. However, since the immersion conditions in these activation processes are milder than the etching treatment conditions, the substrate damage received at this time is It is much smaller than the damage received during the etching process.

  It is preferable to clean the substrate before performing the activation treatment. The substrate can be suitably cleaned by cleaning using an organic solvent such as alcohol, acid cleaning such as hydrochloric acid, or a cleaning solution containing a surfactant.

  In the method of the present invention, a desired portion of the ceramic substrate can be selectively coated with metal by adopting the following method. That is, before applying electroless plating, a resist is formed on a portion other than the portion to be coated with metal, or resist is formed before pretreatment such as activation treatment, and after the pretreatment, the resist is removed and then electroless plating is performed. A desired portion of the ceramic substrate can be selectively coated with a metal by adopting a method for performing electroless plating or a method for performing electroless plating after performing a pretreatment for electroless plating.

  In the method of the present invention, electroless plating is performed subsequent to the catalyst application treatment and then the water washing treatment performed as necessary. Electroless plating can be performed by immersing a pretreated ceramic substrate as an object to be plated in an electroless plating solution containing a reducing agent in the same manner as conventional electroless plating.

Here, the electroless plating solution is composed of a solution containing at least ions of a metal (plating metal) to be plated on the object to be processed, a reducing agent, and a complexing agent. The plating metal is not particularly limited as long as it can be electrolessly plated. Copper, nickel (Ni—P, Ni—B, Ni—
Co or Ni-W), tin, gold, or a combination thereof can be used, but soldering may be performed on the wiring at the time of mounting, and it is difficult to melt into the solder and copper or nickel from the viewpoint of conductivity Preferably there is. These plating metals are usually added to the electroless plating solution as a salt. Examples of the counter ion of the metal ion in the salt at this time include mineral acid ions such as sulfate ion, nitrate ion and chlorine ion, cyan ion and pyrophosphate ion. For example, in the case of Cu ions, it is added as copper sulfate, copper nitrate, copper chloride salt, copper cyanide, or copper pyrophosphate, but other copper compounds such as metal copper and copper oxide are added to a mineral acid solution such as sulfuric acid. It may be solubilized and supplied in the case of other metal ions. The concentration of metal ions in the electroless plating solution is generally about 1 g / liter to 10 g / liter.

The reducing agent is a compound that can reduce a metal ion to be plated in the electroless plating solution and deposit the metal on the surface of the object to be processed to form a metal film. Examples of the reducing agent that can be suitably used include formalin, paraformaldehyde, dimethylamine borane, hypophosphite, hydrazine, glyoxylic acid, KBH ₄ , NaBH ₄ , and Roschoel salt. These can be used alone or in combination. The concentration of the reducing agent in the electroless plating solution is usually about 0.1 g / liter to 50 g / liter.

  The complexing agent is a substance capable of forming a complex. Examples of complexing agents that can be suitably used include tartrate, EDTA (ethylenediaminetetraacetic acid), NTA (nitrilolic acid acetic acid), HEDTA (oxyethylethylenediamine). Triacetic acid), DHEDDA (dihydroxyethylethylenediaminediacetic acid), 1,3PDTA (1,3-propenediaminetetraacetic acid), DTPA (diethylenetriaminepentaacetic acid), TTHA (triethylenetetraminehexaacetic acid), HIMDA (hydroxyethyliminodiacetic acid) ), And a compound such as ammonia.

Further, an alkaline agent or an acid may be added to the electroless plating solution for pH adjustment. Further, a stabilizer may be added to the electroless plating solution. As a stabilizer used at this time,
DDCN (sodium diethyldithiocarbamate), KSCN (potassium thiocyanate), 2,2′-bipyridyl, 2,2′-dipyridine, nicotinic acid, thiourea, tetramethylthiourea, cupron, cuperone, thiazole, 2-mercaptobenzothiazole, Potassium ferrocyanide, potassium ferricyanide, sodium cyanide, pyrrole, pyrazole, imidazole, 1,2,4-triazole, 1,2,4-benzotriazole, thiophene, thiomelide, rhodanine, rubeanic acid, pyridine, triazine, methyl orange, benzo Cyan compounds such as quinoline, 2,2′-biquinoline, dithizone, diphenylcarbazide, nerocproine, 2 (2-pyridyl) imidazoline, 1,10-phenanthroline, nitrogen-based organic compounds, sulfur Mention may be made of the compound. These may be added alone or in combination. The concentration of the stabilizer in the electroless plating solution is usually 0.01 to
100 ppm.

  Various electroless plating solutions are commercially available depending on the plating metal, and any commercially available plating solution can be used in the present invention without limitation. The management of the plating solution and the plating conditions may be appropriately determined according to the type of the plating solution used.

  In addition, when performing electroless plating, a commercially available plating system can be used without limitation, and the plating conditions may be appropriately determined according to the system used, the type of plating solution, the type of ceramic substrate, and the like. .

For example, as an electroless nickel plating bath, an electroless Ni-P plating bath using sodium hypophosphite as a reducing agent, and an electroless Ni using dimethylaminoboron as a reducing agent.
A -B plating bath is generally used. Nickel plating conditions vary depending on the plating film thickness and nickel plating bath composition. For example, in the case of Ni-B plating, the Ni concentration is 4 to 10 g / liter and the reducing agent concentration is 0.1 to 20 g / liter. The bath temperature is 50 to 70 ° C., the pH is 5 to 8, and the treatment (immersion of the object to be plated) is 1 to 150 minutes. In the case of P-Ni, the Ni concentration is 4 to 10 g / liter, the reducing agent concentration is 10 to 40 g / liter, the bath temperature is 50 to 95 ° C., the pH is 3 to 10, and the treatment (immersion of the object to be plated) is 1 to 100 minutes. It is.

  In the method of the present invention, after the metal film is formed by electroless plating, the obtained metal film may be further coated with metal by electrolytic plating (step (D)). In general, electrolytic plating is faster than electroless plating, so when forming a thick metal layer, electrolysis is performed on the metal layer formed by electroless plating rather than by electroless plating of the entire layer. The film formation time becomes shorter when the layer is grown by plating. In addition, when the electroless plating is Ni plating, P and B are included in the plated metal layer, and the metal layer becomes hard. Therefore, a metal layer that does not include such a material is formed on the plated metal layer. By forming by electrolytic plating, a good metal layer as a whole can be obtained. At this time, the metal type of the metal layer formed by electrolytic plating may be the same as or different from the metal type of the metal layer formed by electroless plating.

  In the case of performing electroplating, a metal coated by electroless plating is used as a power line (also referred to as a seed layer) for the electroplating process. As the electrolytic plating method itself, a conventional method can be used without any particular limitation.

  In electrolytic plating, a circuit can be formed by a semi-additive method. The semi-additive method is a method in which a resist layer is formed on a region other than a portion where a circuit is to be formed on a substrate that has been electrolessly plated on the entire surface, and then electroplating is performed on an electroless plating layer that is not covered with a resist. In this method, an electrolytic plating layer is formed, and then an unnecessary electroless plating layer is removed by etching after resist stripping. In addition, a circuit pattern can also be formed by forming a resist pattern after electrolytic plating is performed on the entire surface of the electroless plating layer, removing an unnecessary metal layer by etching, and then removing the resist.

  According to the manufacturing method of the present invention, the electroless plating can be performed by omitting the etching process, so that the metallized ceramic substrate obtained by the method of the present invention has a feature of high mechanical strength and high reliability. Have. In addition, the bonding strength of the electroless plating layer (metal layer formed by electroless plating) that is directly bonded onto the ceramic substrate is high even though the etching treatment is not performed. The metallized ceramic substrate obtained by the method of the present invention has such advantages as compared with the metallized ceramic substrate obtained by the conventional electroless plating method, but is caused by going through the step (B). In addition, structurally, those having characteristics not found in conventional metallized ceramic substrates are included.

  That is, the metallized ceramic substrate obtained by the method of the present invention includes “at least one ceramic sintered body layer on a ceramic sintered body substrate, and an electroless plating metal film directly formed thereon. The ceramic sintered body layer having the laminated structure is formed of a ceramic sintered body of the same type as the ceramic constituting the ceramic sintered body, and the ceramic sintered body layer The metallized ceramic substrate having the structural feature that the average particle size of the ceramic particles constituting the ceramic particles is 10 to 80% of the average particle size of the ceramic particles constituting the ceramic sintered substrate.

In addition, it can confirm that the metallized ceramic substrate of this invention has the ceramic sintered compact layer specified above by observing a cross section of a substrate with an electron microscope (for example, SEM). Moreover, it can be confirmed that the metal layer directly joined to the ceramic sintered body layer is a layer formed by electroless plating by examining its composition and microstructure. For example, in the case where the metal layer obtained by electroless plating is a Ni layer, the layer is obtained by electroless plating by containing elements according to the plating solution used such as P and B. Can be easily confirmed.
To give the device enough strength,

If the manufacturing method of this invention is used, the metal which has adhesive force can be directly coat | covered by the industrially excellent method called electroless plating, without damaging a ceramic substrate. Therefore, a highly reliable ceramic circuit board and a ceramic board having a fine circuit pattern can be manufactured.

<Example>
EXAMPLES The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

Example 1
Aluminum nitride powder having an average particle diameter of 1.5 μm on the surface of a raw material substrate made of an aluminum nitride sintered body substrate obtained by sintering by adding aluminum nitride powder having an average particle diameter of 1.5 μm and yttrium oxide as a sintering aid 100 parts by mass, 5 parts by mass of yttrium oxide powder having an average particle size of 0.5 μm, 9 parts by mass of ethyl cellulose, and 40 parts by mass of terpineol were screen-printed with an aluminum nitride paste adjusted to a viscosity of 3500 P at 25 ° C. Drying was performed for 5 minutes.

  The substrate obtained as described above was baked in nitrogen gas at 1800 ° C. for 4 hours to obtain a ceramic substrate having a ceramic sintered body layer. The surface (ceramic sintered body layer) of the obtained substrate was coated with copper using an electroless plating system, and further plated with copper having a thickness of 5 μm by electrolytic plating to obtain a metallized ceramic substrate.

  At this time, the electroless plating was performed as follows without performing an etching process as a pretreatment. That is, first, the substrate was ultrasonically cleaned with acetone and water, then immersed in an aqueous solution at 25 ° C. containing 1% stannous chloride and 2% hydrochloric acid (sensitizer), then washed with water, After immersing in an aqueous solution containing 0.1% palladium chloride and 2% hydrochloric acid at 25 ° C for 5 minutes (activator), wash with water, and again perform sensitizer treatment, water wash, activator treatment, and water wash under the same conditions. After that, electroless copper plating solution Novigant HC (manufactured by Atotech Japan) is immersed in 30 ° C. for 15 minutes to form an electroless plated copper film having a thickness of 0.3 μm. Copper plating was increased by 5 μm.

  Further, with respect to the obtained metallized ceramic substrate, the fracture surface of the portion where the aluminum nitride ceramic sintered body layer was bonded to the raw material substrate and the metallized layer was formed thereon was observed with a scanning electron microscope. . The photograph is shown in FIG. From FIG. 1, the thickness of the layer formed by sintering the aluminum nitride paste layer is 5 μm, and the average particle diameter of the aluminum nitride particles constituting the layer is 2.1 μm (determined by the code method). Further, it was found that the average particle diameter of the aluminum nitride particles constituting the aluminum nitride sintered body substrate used as the raw material substrate was 5.4 μm (obtained by the code method). The surface roughness of the aluminum nitride ceramic sintered body layer was 0.6 μm. Further, it was found that the plating was uniformly coated.

The adhesion strength between the aluminum nitride ceramic sintered body layer and the metal film copper was measured by a tensile test. Specifically, a 42 alloy φ1.1 mm nail head pin with Ni plating applied to the plating film is soldered with flux-containing Pb-Sn solder, and the pin is perpendicular to the substrate at a speed of 10 mm / min. A method of measuring the strength when pulled in the direction and peeled off was used. As a result, the adhesion strength was 45 MPa and the peeling mode was between material and plating.

Further, after the plated substrate was immersed in a ferric chloride aqueous solution and the plating film was completely removed, the three-point bending strength was measured. The bending strength of the substrate was 420 MPa.
(Example 2)
A metallized ceramic substrate was produced in the same manner as in Example 1 except that electroless Ni-B was applied to the substrate surface. The electroless plating treatment at this time was the same as that in Example 1 until the activator treatment step. Thereafter, the plating treatment was performed at a liquid temperature of 65 ° C. for 20 minutes using Okuno Seiyaku Top Chemi Alloy 66 as a plating solution. The obtained Ni—B film thickness was 2 μm.

  Thereafter, electrolytic copper plating was performed, and the plating film adhesion strength of the obtained metallized substrate was measured. As a result, the peeling mode was 82-MPa and the solder-to-solder mode. Moreover, it was 480 Mpa when the three-point bending strength after removing a plating film was measured.

(Example 3)
A metallized ceramic substrate was produced in the same manner as in Example 1 except that electroless Ni-P was applied to the substrate surface.

  The electroless plating process at this time was the same as that of Example 1 until the activator process, and thereafter, the plating process was performed at a liquid temperature of 85 ° C. for 10 minutes using ICP Nicolon USD manufactured by Okuno Pharmaceutical. The film thickness of the obtained Ni—P was 2 μm.

  Then, electrolytic copper plating was performed, and the plating film adhesion strength of the obtained metallized substrate was measured. As a result, the peeling mode was between the substrate and the substrate at 60 MPa. Moreover, it was 455 MPa when the three-point bending strength after removing the plating film was measured.

(Comparative Example 1 (physical polishing method))
The surface of the raw material substrate made of the aluminum nitride sintered body substrate used in Example 1 was polished by sand blasting (using alumina powder). The surface roughness at this time was 1.8 μm. This was subjected to electroless copper plating in the same manner as in Example 1 and further plated with 5 μm of electrolytic copper plating.

  The adhesion between ceramics and copper at this time was measured by the same method as in Example 1. The result was 30 MPa and the peeling mode was between ceramic and plating. Furthermore, when the bending strength was measured after removing the plating film in the same manner as in Example 1, it was 320 MPa.

(Comparative Example 2 (physical polishing method))
A metallized substrate was produced in the same manner as in Comparative Example 1 except that electroless Ni-B was applied to the substrate surface as in Example 2.

  When the adhesion strength of the plating film of the obtained metallized substrate was measured, it was 35 MPa and the peeling mode was between ceramic and plating. Moreover, it was 350 MPa when the three-point bending strength after removing the plating film was measured.

(Comparative Example 3 (physical polishing method))
A metallized substrate was produced in the same manner as in Comparative Example 1 except that electroless Ni—P was applied to the substrate surface in the same manner as in Example 3.

When the adhesion strength of the plating film of the obtained metallized substrate was measured, the peeling mode was between ceramic and plating at 30 MPa. Moreover, it was 330 MPa when the three-point bending strength after removing the plating film was measured.

(Comparative Example 4 (etching method))
The surface of the raw material substrate made of the aluminum nitride sintered substrate used in Example 1 was treated with a sodium hydroxide solution having a concentration of 20 wt% at 65 ° C. for 60 minutes. The average roughness of the ceramic surface at this time was 1.4 μm. Electroless copper plating was applied thereto, and electrolytic copper plating was further plated by 10 μm.

  The adhesion between ceramics and copper at this time was measured by the same method as in Example 1. The result was 33 MPa, and the peeling mode was between material and plating. Further, as in Example 1, after removing the plating film, the bending strength was measured and found to be 300 MPa.

(Comparative Example 5 (etching method))
A metallized substrate was produced in the same manner as in Comparative Example 4 except that electroless Ni-B was applied to the substrate surface as in Example 2. When the adhesion strength of the plating film of the obtained metallized substrate was measured, it was 58 MPa, and the peeling mode was a mixed mode between ceramics and ceramics and between plating and ceramics. Moreover, it was 350 MPa when the three-point bending strength after removing the plating film was measured.

(Comparative Example 6 (etching method))
A metallized substrate was produced in the same manner as in Comparative Example 4 except that electroless Ni-P was applied to the substrate surface in the same manner as in Example 3. The plating film adhesion strength of the obtained metallized substrate was measured. At 42 MPa, the peeling mode was a mixed mode between ceramics and ceramics and between plating and ceramics. Moreover, it was 350 MPa when the three-point bending strength after removing the plating film was measured.

This figure is a scanning electron micrograph of a cross section of “a ceramic substrate having a ceramic sintered body layer” formed in Example 1.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Ceramic sintered compact layer 2 ... Ceramic substrate

Claims (8)

A step (A) of preparing a raw material substrate made of a ceramic substrate which may have a conductive layer or a conductive paste layer on the surface;
Forming a ceramic paste layer on the raw material substrate, firing the ceramic paste layer to form a ceramic sintered body layer; and
And (C) forming a metal film on the ceramic sintered body layer by electroless plating.   The manufacturing method of Claim 1 which does not include the process of etching a raw material board | substrate with basic aqueous solution as a pre-process of a process (C).   The manufacturing method according to claim 2, further comprising a step (D) of coating a metal by electroplating on the electroless plating metal film formed in the step (C).   A metallized ceramic substrate obtained by the production method according to claim 1.   A metallized ceramic substrate having a multilayer structure comprising at least one ceramic sintered body layer and an electroless plating metal film directly formed thereon on a ceramic sintered body substrate, wherein the multilayer structure is The ceramic sintered body layer to be formed is composed of a ceramic sintered body of the same kind as the ceramic constituting the ceramic sintered body, and the average particle size of the ceramic particles constituting the ceramic sintered body layer is the ceramic sintered body. A metallized ceramic substrate which is 10 to 80% of an average particle diameter of ceramic particles constituting the substrate.   The metallized ceramic substrate according to claim 5, wherein an average particle diameter of ceramic particles forming the ceramic sintered body layer is 0.1 µm to 5 µm.   The metallized ceramic substrate according to claim 5 or 6, wherein the average roughness of the ceramic sintered body layer surface is 0.1 µm to 3 µm.   The metallized ceramic substrate according to any one of claims 5 to 7, wherein the ceramic sintered body substrate and the ceramic sintered body layer are made of aluminum nitride.