JP2001274548A - Manufacturing method of ceramic wiring substrate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent breaking or peeling of a thin-film wiring conductor 3. SOLUTION: A metallized via conductor 2 is provided with a vacancy 4 having the maximum opening diameter of 20 μm or over, and a depth of 10 μm or over on its edge plane is derived to the main plane of a ceramic substrate 1 which is almost flat plate shaped. At the same time, an edge plane of the metallized via conductor 2 is coated with an electroless plated film 5 of 5-10-μm thick, after which the top plane of the electroless plated film 5 is polished mechanically along the main plane of the ceramic substrate 1 to be made level with the main plane of the ceramic substrate 1. Then, the main plane of the ceramic substrate 1 is coated with a thin-film wiring conductor 3 which is to be connected to the metallized via conductor 2. The vacancy 4 formed on the edge plane of the metallized via conductor 2 is filled partly with the electroless plated film 5 and its maximum opening diameter becomes under 20 μm, or its depth becomes under 10 μm. Accordingly, breaking and peeling of the thin-film wiring conductor 3 can be prevented and also the metallized via conductor 2 can be connected well with the thin-film wiring conductor 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a ceramic wiring board in which metallized via conductors are led out to the main surface of a ceramic base and thin-film wiring conductors are formed on the main surface.

[0002]

2. Description of the Related Art Conventionally, as a ceramic wiring substrate capable of high-density wiring, a metallized via conductor is led out on a main surface of a substantially flat ceramic base, and a thin film wiring conductor is adhered and formed on the main surface. Wiring boards are known. According to this ceramic wiring board, since the wiring conductor is formed by the thin film forming technique, fine wiring is possible, and the metallized via conductor enables three-dimensional wiring and conduction between the front and back main surfaces of the ceramic substrate. Such a ceramic wiring board is prepared by preparing a substantially flat ceramic base on which a metallized via conductor is led out on the main surface and applying a thin metal film on the main surface of the ceramic base by using a thin film forming technique such as a sputtering method. Thereafter, the metal thin film is manufactured by etching the metal thin film into a desired pattern by using a photolithography technique.

In such a ceramic wiring board, the main surface of the ceramic base and the end surface of the metallized via conductor are required to be smooth and flat in order to accurately form the thin film wiring conductor. Therefore, usually, the main surface of the ceramic base and the exposed surface of the metallized via conductor are simultaneously polished by a mechanical polishing method before the metal thin film is applied.

[0004]

However, in general, holes having a maximum diameter of about 30 μm or less are formed in the metallized via conductor during the manufacturing process of the metallized via conductor. Then, when the end face of the metallized via conductor is polished by a mechanical polishing method, these holes are exposed on the end face of the metallized via conductor and the maximum opening diameter is 30 μm.
In some cases, a recess having a depth of about 15 μm may be formed. The hole exposed at the end face of such a metallized via conductor has a maximum opening diameter of 20 μm or more and a depth of
When the thickness is 10 μm or more, when a thin film wiring conductor is formed on the thin film wiring conductor, the thin film wiring conductor is liable to be disconnected or peeled. Therefore, for example, in Japanese Patent Application Laid-Open No. 3-80596, after an electrolytic plating film is applied to the end face of a polished metallized via conductor so as to project from the main surface of the ceramic substrate as a whole, A method is disclosed in which a portion which has been polished and removed is made flat. However, when the electrolytic plating film is applied to the end face of the metallized via conductor, the electrolytic plating electric field does not easily reach the inside of the hole opened on the end face of the metallized via conductor. Without this, pores remain under the electrolytic plating film. When holes are left under the electrolytic plating film in this way, for example, when heat is applied in a thin film forming step or the like, moisture or the like in the holes is likely to vaporize and expand to cause voids or peeling in the plating film. Had problems. Further, in order to apply the electrolytic plating film to a thickness projecting entirely from the main surface of the ceramic base, the thickness of the electrolytic plating film needs to be extremely thick exceeding at least 10 μm. The problem is that the stress generated in the electroplating film becomes extremely large and the electrolytic plating film is easily peeled off by external force or the like.
Further, there is a problem that productivity is extremely low because it takes a long time to form a thick electrolytic plating film exceeding at least 10 μm.

The present invention has been made in view of the above-mentioned conventional problems, and an object of the present invention is to prevent a thin film wiring conductor connected to an end face of a metallized via conductor from being disconnected or peeled off without causing metallization. It is an object of the present invention to provide a method of manufacturing a ceramic wiring board with high productivity, which enables good connection between a via conductor and a thin film wiring conductor.

[0006]

According to the method of manufacturing a ceramic wiring board of the present invention, a substantially flat ceramic base has, on its main surface, a hole having a maximum opening diameter of 20 μm or more and a depth of 10 μm or more at an end face. After the metallized via conductor is led out and an electroless plating film having a thickness of 5 to 10 μm is applied to the end face, the electroless plating film is mechanically polished along the main surface to form a top of the electroless plating film. The surface is the same as the main surface, and thereafter, a thin film wiring conductor to be connected to the metallized via conductor is attached to the main surface.

According to the method for manufacturing a ceramic wiring board of the present invention, the maximum opening diameter is 20 μm or more and the depth is 10 μm.
Since the electroless plating film is applied to the end face of the metallized via conductor in which the above holes are formed, the maximum opening diameter formed in the end face of the metallized via conductor is 20 μm or more and the depth is 10 μm or more. The electroless plating film can be satisfactorily adhered to the hole. In addition, the thickness of the electroless plating film deposited on the end face of the metallized via conductor is 5 to 10 μm.
m, the size of the hole should be sufficiently small by partially filling the hole with a maximum opening diameter of 20 μm or more and a depth of 10 μm or more formed at the end face of the metallized via conductor. Can be. Further, since the thickness of the electroless plating film is 5 to 10 μm, the stress generated in the electroless plating film is small and the formation of the electroless plating film does not require a long time. In addition, a thickness of 5 mm is applied to the end face of the metallized via conductor.
After depositing an electroless plating film of about 10 μm, the top surface of the electroless plating film is mechanically polished so as to be flush with the main surface of the ceramic substrate, and is connected to a metallized via conductor thereon. Since the thin film wiring conductor is attached, the metallized via conductor and the thin film wiring conductor can be connected well.

[0008]

Next, the present invention will be described with reference to the accompanying drawings. FIGS. 1 to 5 are cross-sectional views showing steps of an example of a manufacturing method according to the present invention, wherein 1 is a ceramic substrate, 2 is a metallized via conductor, and 3 is a thin film wiring conductor.

First, as shown in the sectional view of FIG. 1, a substantially square plate-shaped ceramic substrate 1 having a plurality of metallized via conductors 2 penetrating between upper and lower main surfaces is prepared.

The ceramic base 1 is made of a ceramic material such as an aluminum nitride sintered body, an aluminum oxide sintered body, a silicon carbide sintered body, a silicon nitride sintered body, a mullite sintered body, and a glass ceramic. For example, in the case of a sintered body made of aluminum nitride, an appropriate organic binder and a solvent are added to a raw material powder such as aluminum nitride, yttrium oxide, and calcium oxide to form a slurry, which is conventionally known. By using the doctor blade method and the calendar roll method to form a sheet, a plurality of ceramic green sheets are obtained,
It is manufactured by subjecting them to appropriate punching and cutting processes and laminating them vertically to form a ceramic green sheet laminate, and finally firing this ceramic green sheet laminate at a temperature of about 1700 ° C in a reducing atmosphere. Usually, the upper and lower main surfaces are rough surfaces having a center line average roughness Ra of Ra> 0.1 μm.

The metallized via conductor 2 penetrating between the upper and lower main surfaces of the ceramic substrate 1 is made of metal powder of metal such as tungsten, molybdenum, copper, silver or the like, and is electrically connected between the upper and lower main surfaces of the ceramic substrate 1. It functions as a conductive path for conducting. Such a metallized via conductor 2
A through hole for arranging the metallized via conductor 2 is formed in the ceramic green sheet for the ceramic substrate 1, and a metal paste for the metallized via conductor 2 is filled in the through hole. By firing together with the body, the ceramic substrate 1
In this case, a plurality of holes 4 having a maximum diameter of about 30 μm are formed therein.

For the perforation of the through holes in the ceramic green sheet, for example, perforation by a punching die or perforation by a laser beam is employed. The metal paste for the metallized via conductor 2 is manufactured by adding and mixing an appropriate organic binder and a solvent to a metal powder such as tungsten and adjusting the viscosity to an appropriate viscosity. To fill the metal paste for the metallized via conductor 2 into the through-holes provided in the ceramic green sheet, for example, a metal mask having a through-hole corresponding to the through-hole provided in the ceramic green sheet is placed on the ceramic green sheet. A method is employed in which the metal paste is placed on the mask, the metal paste is supplied, and the squeegee is slid, and the metal paste is extruded into the through holes of the ceramic green sheet by the sliding pressure of the squeegee. Such punching and filling may be performed for each ceramic green sheet, or may be performed after laminating a plurality of ceramic green sheets.

Next, as shown in the sectional view of FIG. 2, the upper and lower main surfaces of the ceramic substrate 1 are polished by mechanical polishing so that the center line average roughness Ra becomes a smooth surface of 0.05 μm or less. . At this time, the holes 4 of the metallized via conductor 2 are exposed by polishing, and a concave portion having a maximum opening diameter of about 20 μm or more and a depth of about 10 μm or more is formed on the end face of the metallized via conductor 2. For such polishing, for example, a lapping machine or a surface grinder is used.

Next, as shown in an enlarged sectional view of a main part in FIG. 3, an electroless plating film 5 such as an electroless nickel-boron plating film or an electroless nickel-phosphorus plating film is formed on the end face of the metallized via conductor 2. Is applied so that its thickness is 5 to 10 μm. At this time, since the electroless plating film 5 has a property of being applied to a substantially uniform thickness regardless of the shape of the object to be plated, the maximum opening diameter formed on the end face of the metallized via conductor 2 is 20 μm or more, The hole 4 having a thickness of 10 μm or more is satisfactorily adhered so as to partially fill the hole 4. The electroless plating film 5 has a thickness of 5 mm.
Since the thickness is as small as 10 μm, the stress generated in the electroless plating film 5 when the electroless plating film 5 is formed does not become extremely large, so that the electroless plating film 5 hardly peels. Further, the electroless plating film 5 has a thickness of 5 mm.
Since it is as thin as 10 μm, it does not take a long time to apply the electroless plating film 5, so that the productivity of the ceramic wiring substrate is not greatly reduced. In order to apply the electroless plating film 5 to the end face of the metallized via conductor 2 to a thickness of 5 to 10 μm, for example, if the electroless plating film 5 is made of a nickel-boron plating film, for example, nickel supply Nickel sulfate as a source and dimethylamine borane as a reducing agent as main components, and as a complexing agent, 2 to 3 kinds of acetic acid / malonic acid / succinic acid / propionic acid or a sodium salt thereof; A plating solution prepared by adding and mixing ammonium chloride as a regulator and thiodiacetic acid or lead acetate as a stabilizer is used.
The metallized via conductor 2 is immersed in the plating solution for about 30 to 60 minutes at a pH of about 5 to 7 and a solution temperature of about 55 to 65 ° C. for about 30 to 60 minutes. The electroless plating film 5 can be applied to the end surface of the substrate with a thickness of 5 to 10 μm.

Next, as shown in an enlarged sectional view of a main part in FIG. 4, a portion of the electroless plating film 5 adhered to the end face of the metallized via conductor 2 protruding from the main surface of the ceramic base 1 is made of ceramic. Polishing is performed along the main surface of the base 1 so that the top surface is flush with the main surface of the ceramic base 1. As a result, a part of the electroless plating film 5 is prevented from protruding from the main surface of the ceramic base 1, and the cavity 4 has a small maximum opening diameter of less than 20 μm or a depth of less than 10 μm. Note that a lapping machine, a surface grinder, or the like is used for such polishing.

Finally, as shown in an enlarged sectional view of the main part in FIG. 5, a thin film wiring conductor 3 is formed on the main surface of the ceramic base 1 so as to be connected to the metallized via conductor 2. In this case, holes 4 having a maximum opening diameter of 20 μm or more and a depth of 10 μm or more formed on the end face of metallized via conductor 2 are partially filled with electroless plating film 5 so that the maximum opening diameter is reduced. Since the depth is less than 20 μm or less than 10 μm and the top surface of the electroless plating film 5 is the same as the main surface of the ceramic substrate 1, the thin film wiring conductor 3 No disconnection or peeling occurs in the metallized via conductor 2 and the thin film wiring conductor 3.
Are connected very well.

The thin-film wiring conductor 3 formed on the main surface of the ceramic substrate 1 so as to be connected to the metallized via conductor 2 is formed by, for example, laminating an adhesion layer, a barrier layer, and a main conductor layer from the ceramic substrate 1 side. Titanium, chromium, tantalum, niobium, nichrome, tantalum nitride, etc., as the adhesion layer, and platinum, molybdenum, palladium, rhodium, ruthenium, titanium-tungsten alloy, etc. as the barrier layer. As the body layer, copper or gold or the like is used, for example, titanium as the adhesion layer, platinum as the barrier layer, if using gold as the main conductor layer, a titanium layer having a thickness of about 100 to 2,000 angstroms, A platinum layer having a thickness of about 500 to 10,000 angstroms and a gold layer having a thickness of about 1,000 to 50,000 angstroms are formed on the main surface of the ceramic substrate 1. Ttaringu method or an ion plating method, together with the depositing by employing known thin film forming technique deposition method, is formed by etching a predetermined pattern using these known photolithography technique.

Thus, according to the method for manufacturing a ceramic wiring board of the present invention, a ceramic wiring board in which the metallized via conductors 2 and the thin film wiring conductors 3 are well connected without disconnection or peeling of the thin film wiring conductors 3 is produced. It can be manufactured with high efficiency.

[0019]

According to the method for manufacturing a ceramic wiring board of the present invention, the maximum opening diameter is 20 μm or more and the depth is 10 μm.
Since a thickness of 5 to 10 μm of the electroless plating film is applied to the end face of the metallized via conductor in which holes of m or more are formed, the maximum opening diameter formed on the end face of the metallized via conductor is 20 μm or more, and The electroless plating film is satisfactorily adhered to the holes having a depth of 10 μm or more to partially fill the holes, and the top surface of the electroless plating film is flush with the main surface of the ceramic substrate. By polishing, the maximum opening diameter can be reduced to less than 20 μm or the depth can be reduced to less than 10 μm, and the thin film wiring conductor to be connected to the metallized via conductor is deposited thereon, so that metallization is performed. The via conductor and the thin-film wiring conductor can be connected well. In addition, since the electroless plating film applied to the end face of the metallized via conductor has a small thickness of 5 to 10 μm, the electroless plating film does not peel off due to generation of a large stress. It doesn't take long. Therefore, according to the present invention, a ceramic wiring board in which the metallized via conductor and the thin film wiring conductor are well connected can be manufactured with high productivity without causing disconnection or peeling of the thin film wiring conductor.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view for explaining an example of an embodiment of a method for manufacturing a ceramic wiring board of the present invention.

FIG. 2 is a cross-sectional view for explaining an example of an embodiment of a method for manufacturing a ceramic wiring board according to the present invention.

FIG. 3 is an enlarged sectional view of a main part for explaining an example of an embodiment of a method for manufacturing a ceramic wiring board of the present invention.

FIG. 4 is an enlarged sectional view of a main part for describing an example of an embodiment of a method for manufacturing a ceramic wiring board of the present invention.

FIG. 5 is an enlarged sectional view of a main part for explaining an example of an embodiment of a method for manufacturing a ceramic wiring board of the present invention.

[Explanation of symbols]

 1 Ceramic substrate 2 Metallized via conductor 3 Thin film wiring conductor 4 Hole 5 Electroless plating film

Claims (1)

[Claims] 1. A metallized via conductor having a hole having a maximum opening diameter of not less than 20 μm and a depth of not less than 10 μm at an end face is derived from a main surface of a substantially flat ceramic base, and the end face has a thickness of 5 to 10 μm. After the electroless plating film is applied, the electroless plating film is mechanically polished along the main surface so that the top surface of the electroless plating film is flush with the main surface. A method of manufacturing a ceramic wiring board, comprising: attaching a thin film wiring conductor to be connected to the metallized via conductor to the main surface.