JPH0590753A - Ceramic wiring board with projecting through-holes - Google Patents

Abstract

PURPOSE:To allow the ceramic section not to be exposed even when the conductor metal of through-hole sections is exposed on the grinding surface during grinding for glazing by forming all through-holes so as to project from the surface of ceramic board when firing them on the exposed surface of the ceramic wiring board. CONSTITUTION:All through-holes 1 on the exposed surface where a ceramic wiring board is fired are formed so as to project from the surface of board ceramic 4. The contraction amount of conductor paste during firing is controlled to regulate the projection amount by adjusting the grain size of metallic powder of the conductor paste to be filled in the through-holes 1 of which green sheet becomes front/back face when piling up layers. Therefore, when the contraction ratio of the conductor paste is smaller than that of the green sheet, the through- holes 1 are formed to project from the surface 4 corresponding to the difference of contraction ratio. Furthermore, even when the conductor metal of through- hole section is exposed on the grinding surface during grinding for glazing treatment, a ceramic section 2 is not exposed.

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, and more particularly to a ceramic wiring board suitable for forming thin films on the front and back surfaces of the board.

[0002]

2. Description of the Related Art A ceramic wiring board is used as a board for mounting a semiconductor chip or a small electronic component because it can be miniaturized and has high reliability, and is incorporated in a computer, a communication device, a home electric appliance or the like. There is.

Among the ceramic wiring boards, a wet type ceramic wiring board using a green sheet is often used because it is advantageous for high density wiring. The method of manufacturing this wet ceramic wiring board is as follows. First, a ceramic green sheet (hereinafter referred to as a green sheet) in which ceramic raw material powders are combined with an organic resin is prepared, and then a through hole is formed in the green sheet, and then a wiring pattern is formed using a conductor paste, and each sheet is formed. The conductor paste is also filled in the through holes that connect the wiring patterns. next,
A predetermined number of green sheets having the wiring pattern thus formed are stacked, laminated, pressure-bonded, and then fired to produce a ceramic wiring board.

Next, Nikkei Electronics, 1985
On June 17, 2014, a wiring pattern is formed by a thin film method on the front and back surfaces of the ceramic wiring board that has been fired as described in P243 to 266 "Water cooling the multi-chip package".
Since flatness of the surface is required when forming a thin film, it is necessary to perform a glaze treatment to smooth the surface.

In the glaze treatment, glass powder is applied to the surface of the ceramic substrate after firing, and then heat treatment is performed at a temperature at which the glass melts and comes into close contact with the surface of the ceramic substrate. Subsequently, since minute irregularities are present on the glass surface after the heat treatment, polishing treatment is performed to smooth the surface. At this time,
The conductive metal in the through-hole portion on the surface of the ceramic wiring board is exposed on the polished surface so that the thin film wiring can be electrically connected.

[0006]

However, the above-mentioned prior art has a problem in that a perfectly smooth surface cannot be obtained even after polishing, since no consideration is given to minute undulations on the surface of the ceramic wiring board.

That is, in the cross section of the ceramic wiring board after firing, the conductor metal portion of the through hole portion only slightly protrudes from the ceramic portion, and therefore the conductor metal portion of the through hole portion is polished by the polishing after the glaze treatment. When exposed to the surface, the ceramic is partially exposed. This is shown in FIG. Since the exposed ceramic surface has voids, it is unsuitable as a thin film forming surface. Therefore, in order to avoid this, a method of grinding and polishing the ceramic wiring substrate to make it flat before the glaze treatment is adopted. When such a method is adopted, it is necessary to grind and polish the ceramic wiring substrate and then perform plating to raise the through-hole portion by grinding and polishing.

However, when plating is performed, the number of steps is not only increased, but the glaze method is restricted by the plating material, and the plated portion on the through-hole portion appearing on the polished surface after the glaze treatment is plated by the through-hole. Since the thickness is increased by the thickness, there arises a problem that the miniaturization of the through hole portion is prevented.

An object of the present invention is to provide a ceramic wiring board suitable for glazing.

[0010]

The above object is to provide a ceramic wiring board that is fired so that all the through holes on the exposed surface of the board project from an imaginary plane in contact with the ceramic surface of the board. Is achieved by

[0011]

If the through-holes on the exposed surface of the ceramic wiring board during firing are shaped so as to project from the virtual plane in contact with the ceramic surface of the substrate, the ceramic surface of the substrate will remain even after polishing after the glaze treatment. Never exposed. This is shown in FIG.

Here, in order to form a shape in which all the through holes on the exposed surface of the ceramic wiring board during firing protrude from the virtual surface of the substrate ceramic, the following may be done.
This is because the shrinkage amount of the conductor paste in the through holes during firing is controlled by adjusting the particle size of the metal powder of the conductor paste filled in the through holes of the green sheets that are the front and back surfaces during stacking, and at the same time the protrusion amount is also controlled. Controlled. That is,
If the contraction rate of the conductor paste in the through hole is the same as that of the green sheet, the substrate ceramic surface and the surface of the through hole are the same surface. When the contraction rate of the conductor paste is smaller than that of the green sheet, the through holes have a shape protruding from the substrate ceramic surface in accordance with the difference in contraction rate. Conversely,
When the contraction rate of the conductor paste is larger than that of the green sheet, the through holes have a shape recessed from the ceramic surface of the substrate.

Among these, in the ceramic wiring board in which the through hole is projected from the ceramic surface of the substrate, the ceramic portion is not exposed even when the conductor metal of the through hole portion is exposed on the polished surface by polishing after the glaze treatment. Therefore, it is suitable for thin film formation.

[0014]

EXAMPLES Example 1 A case where a ceramic wiring board made of a mullite material is manufactured will be described. As the ceramic powder, mullite fine powder having a particle diameter of about 2.5 μm is used.
2 wt%, alumina, silica, magnesia as a sintering aid 28 wt%, polyvinyl butyral as an organic binder and butylphthalyl butyl glycolate as a plasticizer with respect to the above ceramic powder, 6 g and 2 respectively.
g, and a solvent of azeotrope composition consisting of trichloroethylene, tetrachloroethylene and butyl alcohol, and well mixed in a ball mill to prepare a slurry in which ceramic powder is uniformly dispersed. Subsequently, after degassing air bubbles while stirring the slurry under reduced pressure, a doctor blade type casting device was used to obtain a thickness of 0.25 m.
m green sheets were produced. The outer shape of the green sheet produced in this manner is cut into a predetermined size. Further, a through hole for establishing electrical continuity between the upper and lower wirings is formed using a punching die having a cemented carbide pin.

Next, a method for producing a tungsten paste for forming a wiring pattern will be described. First, a method of manufacturing a through-hole in the inner layer not exposed on the surface and a tungsten paste for a wiring pattern will be described. Average particle size is 2μ
80g tungsten fine powder in which m and 0.5μm were mixed at a ratio of 8: 2, 2g glass powder as a sintering aid, 3g ethyl cellulose, 15g diethylene glycol as an organic solvent were added together, and a raider and a triple roll After kneading, the viscosity is adjusted by adding n-butyl carbitol acetate. (Tungsten paste 1 below)
Similarly, the tungsten paste for the through-holes exposed on the surface was mixed with 80 μg of tungsten fine powder having an average particle size of 2 μm and 0.5 μm at a ratio of 9: 1. It was made. (Tungsten paste 2) Subsequently, the paste is filled in the through holes of the green sheet that has been subjected to through hole processing by using the tungsten pastes 1 and 2 by the screen printing method.
A wiring pattern is formed on the surface of the green sheet. Here, a tungsten paste 1 was filled in the through holes of the green sheet as the inner layer, and a tungsten paste 2 was filled in the through holes of the front and back green sheets. Next, the green sheets on which the predetermined wiring patterns are formed are stacked, and the temperature is 130 ° C. and the pressure is 100 kg.
The green sheets are adhered to each other and integrated with each other at / cm ² .
Then, the firing process is started. For firing, a ceramic raw wiring board is placed on a predetermined base plate, an electric furnace using molybdenum as a heating element is used, and the temperature is raised to a predetermined temperature in a mixed gas atmosphere of nitrogen, hydrogen and water vapor, and the ceramic is 100 mm square. A wiring board was produced.

(Comparative Example 1) Comparative Example 1 is different from Example 1 only in that tungsten paste 1 is used for both the front and back sides and the inner layer when filling the paste into the paste. A ceramic wiring board was produced in the same manner as in Example 1.

With respect to each of the ceramic wiring boards of Comparative Example 1 and Example 1 thus produced, the step difference from the ceramic portion of the conductor metal in the through hole portion was measured for each through hole exposed on the surface by the three-dimensional coordinate measuring machine. Amount (+ is a protrusion, -is a dent), and the amount of protrusion of the conductor metal surface of all through-holes from an imaginary plane in contact with the ceramic surface based on the height measurement on the entire surface of the ceramic part (+ is a protrusion, − is a dent) Was measured (FIG. 3). The results were as follows.

[0018]

[Table 1]

Subsequently, the surface of the ceramic wiring boards produced in Comparative Example 1 and Example 1 was subjected to glaze treatment. For the glaze glass, use a neutral and weakly reducing composition that can be used.After applying glass powder to the surface of the ceramic wiring board, use an electric furnace to melt the glass powder and apply it to the surface of the ceramic wiring board. A glass film was formed. Then, the surface of the glass after the heat treatment is smoothed by removing fine irregularities so as to be suitable for thin film formation (surface roughness:
(0.2 μm or less), and at the same time, the amount of glass to be polished was adjusted so that the conductive metal in the through-hole portion appeared on the polished glass surface. Regarding the polished surface of the ceramic wiring boards produced in Comparative Example 1 and Example 1 thus subjected to the glaze treatment, the ceramic portion of the ceramic wiring board (other than glaze glass) occupies the area excluding the conductor metal portion. The exposure rate was examined using an electron microscope.
As a result, the exposed area ratio of the ceramic part was 0% in Example 1,
In Comparative Example 1, it was 35%.

The filling of the through-holes exposed on the surface in Example 1 was carried out by using 2 μm of tungsten fine powder for the conductor paste and 0.
Although 5 μm was set to 9: 1, when the ratio is variously changed, the step amount, the protrusion amount, and the exposed ceramic area ratio change according to the ratio. This is shown in FIG.

<Embodiment 2> A case where the material of the ceramic wiring board is changed from the mullite-based material of Embodiment 1 to an alumina-based material will be described.

90 wt% of alumina fine powder having a particle diameter of several μm or less as a ceramic powder, and a mixed powder of talc and clay 1 having a cordierite composition as a sintering aid.
0 wt% was used. Further, in the tungsten paste for forming the wiring pattern, the through hole of the inner layer not exposed on the surface and the metal material powder for the wiring pattern have an average particle diameter of 2
Tungsten fine powder in which μm and 0.5 μm were mixed in a ratio of 8.5: 1.5, and for the through holes to be the front and back, the average particle size was 2 μm and 0.5 μm of 9.5: 0.5. Using the tungsten fine powder mixed in a ratio, the same procedure as in Example 1 and Comparative Example 1 was performed except that the ceramic wiring substrate (Example 2) in which the conductor metal in the through hole was projected and the conductor metal in the through hole were formed. A ceramic wiring board (Comparative Example 2) which did not project was produced. Then, similarly, with respect to these ceramic wiring boards, the step amount of the conductor metal in the through hole portion from the ceramic portion and the protrusion amount of the conductor metal surface of all the through holes from the virtual plane in contact with the ceramic surface were measured. As a result, the amount of step difference is 30 ± 3 μm in Example 2, and Comparative Example 2
Is 0 ± 3 μm, while the protrusion amount is 13 ± 3 in the second embodiment.
μm, and in Comparative Example 2 it was -17 ± 3 μm.

Then, the same glaze treatment as in Example 1 was performed, and the ceramic surface of the ceramic wiring board after polishing the ceramic wiring boards produced in Example 2 and Comparative Example 2 occupied the area excluding the conductor metal portion. The exposure ratio of the area was examined using an electron microscope. As a result, the exposed area ratio of the ceramic part was 0% in Example 2 and 25 in Comparative Example 2.
%Met.

In this way, by adjusting the grain size of the conductive metal powder for forming the wiring pattern used for the through holes exposed on the surface and the through holes of the inner layer not exposed on the surface, the exposed metal is exposed on the surface of the ceramic wiring substrate after firing. It is possible to adjust the level difference from the ceramic part of the conductor metal surface of the through hole
It can be seen that it is possible to form a protrusion shape or a dent shape, and by forming the protrusion shape, a ceramic wiring board suitable for glazing can be obtained. Furthermore, it is clear that this is effective for all ceramic wiring boards using the green sheet method and is independent of the types of ceramic materials and conductor materials.

[0025]

According to the present invention, all the through holes on the exposed surface of the ceramic wiring board during firing are formed to project from the ceramic surface of the substrate, so that the through hole portion can be formed by polishing after the glaze treatment. Since the ceramic part is not exposed even when the conductor metal of is exposed on the polished surface,
A ceramic wiring board suitable for thin film formation can be obtained.

[Brief description of drawings]

FIG. 1 is an explanatory view of a surface of a ceramic wiring board according to the present invention when it is subjected to glaze treatment,

FIG. 2 is an explanatory view when a ceramic wiring board according to a conventional technique is subjected to glaze processing,

FIG. 3 is an explanatory diagram of a step amount and a protrusion amount of a through hole exposed on the surface of a ceramic wiring board;

FIG. 4 is a step amount when the ratio of the particle size of the tungsten fine powder of the conductor paste for filling the through holes exposed on the surface is changed,
FIG. 6 is a characteristic diagram showing the amount of protrusion and the exposed area ratio of the ceramic portion.

[Explanation of symbols]

1 ... Through-hole conductor metal, 2 ... Ceramic portion of ceramic wiring board, 3 ... Glaze glass, 4 ... Virtual plane, 5 ... Through hole protrusion amount, 6 ... Through hole step amount.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Norihiro Ami, 292 Yoshida-cho, Totsuka-ku, Yokohama City, Hitachi, Ltd., Production Engineering Laboratory (72) Inventor Tatsuji Noma, 292 Yoshida-cho, Totsuka-ku, Yokohama Hitachi, Ltd. Production Technology Laboratory

Claims (2)

[Claims] 1. A ceramic wiring board in which a wiring pattern is formed on a ceramic green sheet with metal powder, and a plurality of green sheets are laminated and fired. All through holes on the exposed surface of the substrate are formed from the substrate ceramic surface. A ceramic wiring board characterized by being projected. 2. A ceramic wiring board in which a wiring pattern is formed on a ceramic green sheet with metal powder, a plurality of green sheets are laminated and fired, and the front and back surfaces of a substrate having through holes protruding from the ceramic surface are subjected to a glaze treatment. A ceramic wiring board, characterized in that the conductor metal of the through hole is exposed on the glaze surface.