JPH10256731A - Manufacture of ceramic multilayer circuit board - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate damages to a via by nucleating a plating nucleus on the via exposed with a surface of a ceramic board, then forming a metallic film on the via by an electroless plating method, and then roughing the surface of the ceramic board. SOLUTION: A plating nucleus is nucleated on a via, exposed with a surface of a baked ceramic board. Nucleating liquid used for this contains palladium, so that its pH is preferably 4 to 9. Then, after a metallic film is formed on the via by an electrolessly plating method, it is heat-treated at 300 to 450. Thereafter, the surface of the board formed with the metallic film is roughed by using hydrofluoric acid. Accordingly, since it is roughened after the film has been formed, elution of the glass component in the via is prevented so that no air gap is generated in the via.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] The present invention relates to an inner conductor circuit,
Ceramic multilayer wiring for manufacturing a multilayer wiring board by forming a thin film metal layer electrically connected to the via by a plating method on a surface of a ceramic substrate in which a via formed using a conductive paste is formed. The present invention relates to a method for manufacturing a plate.

[0002]

2. Description of the Related Art As electronic devices and the like have been reduced in size and advanced in function, ceramic multilayer wiring boards have been partially put into practical use as substrates for mounting electronic components such as ICs. As a method for manufacturing a ceramic multilayer wiring board, there is a method called a thick film multilayer method in which a conductor layer and an insulating layer are alternately printed and fired using a paste on a fired core substrate, and a conductor paste is applied to a green sheet. 2. Description of the Related Art There is known a method called a green sheet multi-layer method in which printed materials are stacked, pressed, and fired to produce them. In either case, the surface circuit is generally formed by a thick film method using a conductive paste, but has the drawback that it is difficult to form a fine pattern. After forming a conductor layer on the substrate surface by sputtering to enable the formation of a fine pattern,
Although formation of a surface circuit by a photo method has been studied, the sputtering method has a problem of inferior mass productivity, and its practical use is limited to a partial one.

Therefore, it is conceivable to form a conductor layer on a substrate surface by a plating method which is excellent in mass productivity and then form a surface circuit by a photo method. However, a ceramic multilayer wiring board is formed by forming a surface conductor layer by a plating method. There is a problem that needs to be solved even when trying to manufacture a hologram. In other words, when the surface conductor layer is formed by plating, the surface of the substrate is roughened before plating using a chemical such as hydrofluoric acid or molten alkali in order to secure the adhesion between the ceramic substrate and the conductor layer. In general, the plating is performed under conditions of high temperature and high alkali when plating by electroless plating. In this case, there is a problem that vias (conductors for connecting between conductive layers) exposed on the substrate surface are damaged, and connection reliability becomes insufficient. The reason for this is that the via is generally formed using a conductor paste containing a metal component and a glass component, so that when subjected to such severe processing, the glass component in the via elutes and the via It is considered that voids are generated therein, and plating solution components and the like in a later process enter and remain in the voids, so that connection reliability becomes insufficient.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to form an inner layer conductor circuit and a conductor paste containing a glass component. With a via in it
After roughening the surface of the fired ceramic substrate in which the ends of the vias are exposed, a thin-film metal layer electrically connected to the vias is formed on the surface of the ceramic substrate by plating. A method for manufacturing a ceramic multilayer wiring board, which manufactures a multilayer wiring board by using a method, wherein a via is less likely to be damaged, and therefore a ceramic multilayer wiring board having sufficient connection reliability can be manufactured. It is in.

[0005]

According to a first aspect of the present invention, there is provided a method for manufacturing a ceramic multilayer wiring board, wherein an inner-layer conductive circuit and a via formed by using a conductive paste containing a glass component are formed therein. Then, after roughening the surface of the fired ceramic substrate in which the ends of the vias are exposed on the surface, a thin-film metal layer electrically connected to the via by plating is formed on the surface of the ceramic substrate. In a method for manufacturing a ceramic multilayer wiring board for forming and manufacturing a multilayer wiring board, a nucleating process of a plating nucleus is performed on a via exposed on the surface of the ceramic substrate, and then a metal is formed on the via by an electroless plating method. After forming the coating, the surface roughening treatment is performed on the surface of the ceramic substrate.

According to a second aspect of the present invention, there is provided a method of manufacturing a ceramic multilayer wiring board according to the first aspect, wherein a metal film is formed on the via by electroless plating.
After the ceramic substrate is subjected to a heat treatment, a roughening treatment is performed.

According to a third aspect of the present invention, there is provided the method for manufacturing a ceramic multilayer wiring board according to the first or second aspect, wherein the pH of the nucleating solution used for nucleating the plating nucleus is 4 or more. -9.

In the method for manufacturing a ceramic multilayer wiring board according to the first to third aspects of the present invention, a plating nucleus is nucleated on a via exposed on the surface of the ceramic substrate,
Then, after forming a metal film on the via by electroless plating, the surface of the ceramic substrate is subjected to a surface roughening treatment, so that the glass component in the via is prevented from being eluted during the surface roughening treatment. Therefore, no void is generated in the via, and the connection reliability of the obtained ceramic multilayer wiring board is sufficient.

In the method for manufacturing a ceramic multilayer wiring board according to the second aspect of the present invention, after forming a metal film on the via,
Heat treatment is preferable because a diffusion phenomenon occurs between the conductor of the via and the metal film formed by the electroless plating method, so that the conductor of the via and the metal film can be firmly bonded. In addition,
To ensure that the diffusion phenomenon occurs, this heat treatment should be performed for 30 minutes.
The heat treatment is preferably performed at 0 to 450 ° C.

In the method for manufacturing a ceramic multilayer wiring board according to the third aspect of the present invention, since the pH of the nucleating solution used for the nucleating process of the plating nucleus is 4 to 9, Since the glass component in the via is prevented from being eluted, the generation of voids in the via is more reliably prevented.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION A fired multilayer in which an inner conductor circuit and a via formed using a conductor paste containing a glass component are formed therein, and the end of the via is exposed on the surface. A ceramic substrate is used. The ceramic substrate material is not particularly limited,
A glass ceramic material such as borosilicate glass that can be co-fired with the conductive paste forming the via is preferred. Also,
Examples of the conductor component contained in the conductor paste include silver, palladium, and copper, but it is preferable that silver is the main component in terms of electric resistance. The conductive paste contains a glass component in order to enhance the adhesion to the ceramic during firing. Further, the inner conductor circuit is preferably formed by a thick film method using a conductor paste, but may be formed by a thin film method such as a sputtering method or a plating method.

The plating nucleus is nucleated on the via exposed on the surface of the fired ceramic substrate. The nucleating liquid used for the nucleating treatment contains palladium, and the pH of the nucleating solution is palladium. It is preferably from 4 to 9. pH
Is within the range of 4 to 9, elution of the glass component in the via at the time of the nucleating process is suppressed. When performing the nucleating process of the plating nucleus on the via, it is preferable to use a nucleating process that can selectively nucleate only on the via, since the plating nucleus does not adhere to the surface of the ceramic substrate other than the via. However, nucleation may be performed only on the via by using a resist or the like to expose only the via portion so that nucleation is not performed on the surface of the ceramic substrate other than the via.

Next, after forming a metal film only on the via by electroless plating, the surface of the ceramic substrate is subjected to a surface roughening treatment. Examples of the material of the metal film formed by the electroless plating method include nickel and palladium. After forming such a metal film, 30
When a heat treatment of 0 to 450 ° C. is performed, a diffusion phenomenon occurs between the conductor of the via and the metal film formed by the electroless plating method,
It is preferable because the conductor of the via and the metal film can be firmly bonded.

Next, the surface of the ceramic substrate on which the metal film has been formed is subjected to a surface roughening treatment using a chemical such as hydrofluoric acid, phosphoric acid, or a molten alkali. A thin-film metal layer to be electrically connected is formed on the surface of the ceramic substrate to manufacture a multilayer wiring board. After the metal film is formed on the via, the surface roughening treatment is performed, so that the glass component in the via is prevented from being eluted during the surface roughening treatment, and no void is generated in the via, and therefore, Thus, the connection reliability of the obtained ceramic multilayer wiring board becomes sufficient. Since hydrofluoric acid and molten alkali have a value of about 0 that elutes the glass component in the vias is larger than phosphoric acid, phosphoric acid is preferable as a chemical used for the surface roughening treatment. In addition, about the formation of the thin film metal layer after the surface roughening treatment, after forming a base metal layer having a thickness of not less than the thickness showing conductivity by electroless plating and not more than 3 μm, a predetermined thickness is formed by electrolytic plating. When the method of forming a thin film metal layer is performed, the electroless plating is completed in a short time, compared with the case where all of the formation of the thin film metal layer of a predetermined thickness are performed by electroless plating. Of the glass component is suppressed, and the generation of voids in the via is more reliably prevented.

[0015]

The present invention will be described below based on examples and comparative examples. In addition, this invention is not limited to a following example.

(Example 1) Via holes for connecting conductive layers were formed by punching a green sheet containing lead borosilicate glass and alumina powder as main components. Next, using a silver paste containing lead borosilicate glass, printing of the inner conductor circuit and filling of the paste into the via hole were performed on the green sheet. Next, four green sheets were laminated and pressed, and then fired in an oxidizing atmosphere at 900 ° C. to obtain an integrated ceramic substrate. A neutral type nucleating liquid (trade name Actus M, manufactured by Uemura Kogyo Co., Ltd.)
Using PD-38, pH 6.9), palladium nucleation treatment was performed at 70 ° C. for 5 minutes. When this nucleating solution was used, nucleation could be selectively performed only on the via.

After the nucleation treatment, a weakly acidic type electroless nickel plating solution (trade name Nimden NPR, manufactured by Uemura Kogyo Co., Ltd.)
Using a pH of 4.6), a 3 μm thick nickel plating film was formed on the via under plating conditions of 85 ° C. for 15 minutes.
The obtained ceramic substrate was immersed in hot phosphoric acid at 180 ° C. for 2 minutes to roughen the surface of the ceramic substrate. After this,
Catalyst treatment (Okuno Pharmaceutical Co., Ltd., product name OPC-80M) is performed on the surface of the ceramic substrate at room temperature for 5 minutes, followed by accelerator treatment (Okuno Pharmaceutical Co., Ltd., product name OPC50).
0MX1, 2) at 35 ° C. for 5 minutes to nucleate palladium, and then immersed in an electroless copper plating solution to form a base metal layer (thickness sufficient to show conductivity) with a film pressure of 1 μm. Thereafter, electrolytic copper plating was performed at a current density of 2 A / dm ² and a plating time of 15 minutes to form a thin metal layer (copper plated layer) having a total film thickness of 10 μm. Next, an outer conductor circuit was formed on the thin metal layer to obtain a ceramic multilayer wiring board. Observation of the cross section of the obtained ceramic multilayer wiring board showed no generation of voids in the vias. Therefore, it was evaluated that a ceramic multilayer wiring board with sufficient connection reliability could be manufactured.

Comparative Example 1 Same as Example 1 except that the surface of the ceramic substrate was roughened without forming a nickel plating film on the nucleated via. Thus, a ceramic multilayer wiring board was obtained. When the cross section of the obtained ceramic multilayer wiring board was observed, the occurrence of a void was observed at a depth of about 20 μm from the surface of the via, and it was confirmed that the via was damaged. Therefore, it was evaluated that only a ceramic multilayer wiring board having insufficient connection reliability could be manufactured.

(Example 2) The formation of a nickel plating film on a nucleated via was performed by using a neutral type electroless nickel plating solution (trade name: Top Chemical Alloy 66, manufactured by Okuno Pharmaceutical Co., Ltd., pH 6.5). ), A ceramic multilayer wiring board was obtained in the same manner as in Example 1 except that a nickel plating film having a thickness of 2 μm was formed under plating conditions of 65 ° C. for 15 minutes. Observation of the cross section of the obtained ceramic multilayer wiring board showed no generation of voids in the vias. Therefore, it was evaluated that a ceramic multilayer wiring board with sufficient connection reliability could be manufactured.

Example 3 The formation of a metal film on a nucleated via by an electroless plating method was performed using a neutral type electroless palladium plating solution (Mudden Noble, product name, manufactured by Okuno Pharmaceutical Co., Ltd., pH 6.0). Using 5), a ceramic multilayer wiring board was obtained in the same manner as in Example 1, except that a 2 μm-thick palladium plating film was formed under the plating conditions of 55 ° C. and 20 minutes. Observation of the cross section of the obtained ceramic multilayer wiring board showed no generation of voids in the vias. Therefore, it was evaluated that a ceramic multilayer wiring board with sufficient connection reliability could be manufactured.

(Embodiment 4) After a metal film is formed on the nucleated via by an electroless plating method, and before the surface of the ceramic substrate is roughened, it is heated in a nitrogen atmosphere at 350.degree. A ceramic multilayer wiring board was obtained in the same manner as in Example 1 except that the annealing treatment was performed at ℃. Observation of the cross section of the obtained ceramic multilayer wiring board showed no generation of voids in the vias. XMA analysis confirmed the presence of a nickel and silver diffusion layer. Therefore, it was evaluated that a ceramic multilayer wiring board in which the conductor of the via was firmly bonded to the metal film and the connection reliability was sufficient was produced.

(Embodiment 5) After a metal film is formed on the nucleated via by an electroless plating method, and before the surface of the ceramic substrate is roughened, it is heated in a nitrogen atmosphere at 350.degree. A ceramic multilayer wiring board was obtained in the same manner as in Example 3 except that the annealing treatment was performed at ℃. Observation of the cross section of the obtained ceramic multilayer wiring board showed no generation of voids in the vias. In addition, XMA analysis confirmed the presence of a palladium and silver diffusion layer. Therefore, it was evaluated that a ceramic multilayer wiring board in which the conductor of the via was firmly bonded to the metal film and the connection reliability was sufficient was produced.

[0023]

In the method for manufacturing a ceramic multilayer wiring board according to the first to third aspects of the present invention, a nucleating treatment of a plating nucleus is performed on a via, and then a metal film is formed on the via by an electroless plating method. After the formation, the roughening treatment is performed, so that the glass component in the via is prevented from being eluted during the roughening treatment. Therefore, according to the method for manufacturing a ceramic multilayer wiring board according to the first to third aspects of the present invention, it is possible to manufacture a ceramic multilayer wiring board having no connection gap and excellent connection reliability. become.

In the method for manufacturing a ceramic multilayer wiring board according to the second aspect of the present invention, after forming a metal film on the via,
Since the heat treatment is performed, a diffusion phenomenon occurs between the conductor of the via and the metal film formed by the electroless plating method. Therefore, according to the method for manufacturing a ceramic multilayer wiring board of the invention according to claim 2, in addition to the above effects, it is possible to manufacture a ceramic multilayer wiring board in which the conductor of the via and the metal film are more firmly bonded. Will be possible.

In the method for manufacturing a ceramic multilayer wiring board according to the third aspect of the present invention, the pH of the nucleating solution used for the nucleating process of the plating nucleus is 4 to 9, so that the Elution of the glass component in the via is prevented.
Therefore, according to this manufacturing method, generation of a void in the via is more reliably prevented.

Claims (3)

[Claims] An internal conductor circuit and a via formed using a conductive paste containing a glass component are formed therein, and the end of the via is exposed on the surface of the fired ceramic substrate. A method for producing a multilayer wiring board, comprising: forming a thin-film metal layer electrically connected to the via by plating on the surface of the ceramic substrate after the surface is roughened; Performing a nucleating treatment of a plating nucleus on the via exposed on the surface of the substrate, and then forming a metal film on the via by an electroless plating method, and then performing the surface roughening treatment on the surface of the ceramic substrate. A method for manufacturing a ceramic multilayer wiring board, comprising: 2. After forming a metal film on the via by an electroless plating method, heat-treating the ceramic substrate,
2. The method for manufacturing a ceramic multilayer wiring board according to claim 1, wherein a roughening treatment is performed. 3. The method for producing a ceramic multilayer wiring board according to claim 1, wherein the pH of the nucleating solution used for the nucleating process of the plating nucleus is 4 to 9.