JPH0682919B2 - Conductor paste filling method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method suitable for filling a through-hole of a green sheet with a conductor paste when manufacturing a ceramic multilayer wiring board.

[Conventional technology]

As a substrate for mounting semiconductor parts in high density, 20 ~
Attention has been paid to a ceramic multilayer wiring board having 30 layers of multilayer wiring. The electrical connection between the layers of the substrate is performed by filling the through holes formed in the green sheet with a conductor paste.

A screen printing method is generally used to fill the through-hole with the conductive paste, but as described in Japanese Patent Publication No. 56-25789, there are very severe restrictions in terms of pattern dimensions and alignment accuracy. , A special printing machine is needed.

[Problems to be solved by the invention]

Although the above-mentioned publicly known example does not describe the paste composition and the printing conditions, when the through hole 4 of the green sheet 3 is filled with the conductive paste 8 as shown in FIG.
Generally, the printing method as shown in FIG. 3, that is, the green sheet 3 is placed on the upper surface portion 1'provided with a large number of suction holes 9 of the table 1 on which the green sheet is placed, and the green sheet 3 is fixed to fix it. A method is used in which the through holes 4 are exhausted from the exhaust port 10 to be vacuum-adsorbed, and then the through holes 4 are filled with the conductive paste by using the screen plate 5. However, in this case, if no special paste is used, as shown in FIG. 4, the conductive paste 8 filled in the through holes 4 adheres to the upper surface portion 1 ′ of the base 1 on which the green sheet is placed, and after filling, the green paste is formed. When the sheet is taken out, a part 12 of the filled conductor paste remains on the table side. For this reason, the recess 11 is formed in the conductor paste in the through hole, which causes a connection failure or a plating failure in the subsequent steps of stacking, plating, and mounting of semiconductor components. As a method for solving this problem, as shown in FIG. 5, a hole 9'having a diameter larger than the through hole is provided at a position corresponding to the through hole 4 formed in the green sheet 3 of the base 1 on which the green sheet is placed. There is also a method of preventing the conductor paste 8 filled in the holes 4 from adhering to the upper surface portion 1'of the stand. However, in this case, there is a difference in the amount of conductor paste extruded from the through holes due to differences in the diameter of the through holes formed on the screen and the green sheet, uneven printing pressure, changes in the viscosity of the conductor paste, etc. No. 6 by crushing by hot pressing
As shown in the figure, there is a problem in that the size of the through-hole pattern (8 ', 8 ") on the extruding side (base side) is likely to vary significantly.

An object of the present invention is to provide a conductor paste filling method that solves the above problems.

[Means for solving problems]

In the method of filling the through holes formed in the green sheet with the conductor paste by screen printing, a plastic sheet to which regenerated cellulose is attached is sandwiched between the green sheet and the base on which the green sheet is placed, and the recycled sheet is regenerated. This is achieved by filling the conductor paste with the cellulose-adhering surface facing the through hole portion of the green sheet.

[Action]

The present inventors solve the problems of the prior art by interposing a material that absorbs the solvent in the conductor paste and has good releasability with the conductor paste between the green sheet and the table on which the green sheet is placed. We thought that it might be possible to solve the problem, and as a result of examining the method, we decided to insert regenerated cellulose in a flat sheet shape by adhering regenerated cellulose to the plastic sheet in consideration of the exchangeability of the material. That is, by absorbing the solvent in the conductor paste during printing with regenerated cellulose having good absorptivity, the packing density of the conductor paste in the through holes is increased, and regenerated cellulose has good releasability from the conductor paste. After that, when the green sheet is taken out, a part of the conductor paste remains on the base side, and the through-hole conductor is not dented. Moreover, the regenerated cellulose adhesion surface is smooth and has good adhesion to the green sheet, so the filled conductor paste does not ooze out between the regenerated cellulose adhesion surface and the green sheet, which allows dimensional accuracy in the through hole. The conductor paste can be filled well. The plastic sheet holds the regenerated cellulose and serves as a stiffener to prevent the regenerated cellulose from partially breaking and adhering to the surface of the through-hole conductor. Further, as the plastic sheet, a porous body that allows gas and liquid to pass therethrough, a so-called filter can be used, and the solvent absorbed by the regenerated cellulose during printing can be further sucked by an exhaust pump.

〔Example〕

 Hereinafter, examples of the present invention will be described in detail.

FIG. 1 shows an outline of an apparatus for carrying out the present invention. Similar to a commonly used screen printer, the upper surface 1'of the base 1 on which the green sheet is placed has a diameter of 1-2 mm by a drilling machine or an electric discharge machine for fixing the green sheet.
A large number of suction holes 9 are formed, or a sintered metal plate having air permeability is provided. On the upper surface 1'of this stand, a plastic sheet 2 having an outer dimension of 10 to 30 mm smaller than that of the green sheet and having regenerated cellulose attached thereon is placed, and φ0.
A green sheet 3 with a thickness of 0.23 to 0.27 mm and an outer dimension of 200 x 200 mm, which is a through hole 4 of 13 to 0.15 mm formed by an NC boring machine and has a thickness of 0.23 to 0.27 mm, is a recycled plastic sheet 2. The green sheet 3 is fixed by accurately positioning it with a guide pin (not shown) so that it overlaps with the surface on which cellulose is attached, and then vacuum-sucking it with an exhaust pump connected to the exhaust port 10 of the base 1. Then, after accurately aligning the screen plate 5 in which the pattern holes 6 of φ0.1 to 0.13 mm are formed by photoetching at the positions corresponding to the through holes 4 of the green sheet 3, the conductive paste 8 having the following composition is squeegeeed. Was used under the following printing conditions.

Paste compound Tungsten powder …… 100g Sintering aid …… 2g Vehicle …… 15g Gelling agent …… 1.5g Printing conditions Squeegee attack angle …… 30 to 45 ° Squeegee speed …… 30mm / sec Squeegee load …… 10kg / 140mm (Squeegee length) 10 to 30 green sheets with the conductor paste filled in the through holes in this way are pressed with a hot press at a pressure of 120k.
After laminating at g / cm ² and a temperature of 150 ° C., it was sintered in a hydrogen reducing atmosphere furnace at 1580 to 1660 ° C. for 1 hour to manufacture a ceramic multilayer wiring board. As a result, the through hole dimensional accuracy after firing was as good as 110 ± 3 μm, and the yield of through hole connection, plating, and mounting of semiconductor components was very good.

The plastic sheet to be sandwiched between the pedestals for mounting the green sheet was selected from various materials shown in FIG. In other words, various materials including breathable materials (various filtering materials) and materials that are easily released (polyester sheet coated with silicone resin, Teflon sheet) are evaluated, and plastics to which regenerated cellulose is adhered are selected from these materials. Sheets (including films) were selected.

According to the evaluation results, the filter paper, Japanese paper, and Teflon filters have large surface irregularities, so the conductor paste oozes out between these materials and the green sheet, resulting in a very large variation in the through-hole size and poor shape. . In a polyester sheet and a filter made of vinyl chloride, the conductor paste adheres to the surface of these materials, and after filling, the conductor paste in the through hole has a recess.

A filter made only of regenerated cellulose has poor mechanical strength, and the portion facing the through hole is broken and adheres to the surface of the through hole conductor. Further, although the Teflon sheet and the polyester sheet coated with the silicone resin can be used for filling the through holes of φ150 μm, the conductor paste cannot be sufficiently filled in the through holes of φ130 μm. That is, it has poor solvent absorption.

On the other hand, plastic sheet (including filter)
Regenerated cellulose reinforced with is excellent in absorbability and releasability,
It was possible to satisfactorily fill the φ130 μm and φ150 μm through holes without being broken at the through holes. Here, the regenerated cellulose is used by applying it to a plastic sheet (including a filter) in a thickness of 0.03 to 0.1 mm. As the base material, various plastic sheets (including filters) such as polyester, nylon and vinylon having a thickness of 0.05 to 0.1 mm can be used.

〔The invention's effect〕

As described above, according to the present invention, it is possible to fill the through holes of the green sheet with the conductor paste with high dimensional accuracy and high yield without using a special printing machine or a special paste.

[Brief description of drawings]

FIG. 1 is a schematic sectional view showing an embodiment of the present invention, and FIGS. 2 (a) and 2 (b) are typical plan views of a green sheet filled with a conductor paste and its AA ′ sectional view, and FIG. FIG. 4 is a schematic sectional view showing an example of a conventional technique, FIG. 4 is a schematic sectional view showing a filled state of a conductor paste in the conventional technique of FIG. 3, and FIG. 5 is a schematic sectional view showing another example of the conventional technique. FIGS. 6 (a) and 6 (b) are plan views showing a state after lamination of the green sheets filled with the conductor paste according to the prior art of FIG. 5 and their BB ′ sectional views, and FIG. 7 shows the present invention. It is a figure showing the evaluation result of various sheet materials for explaining. Explanation of code 1 …… Green sheet mounting base 2 …… Regenerated cellulose attached plastic sheet 3 …… Green sheet 4 …… Through hole 5 …… Screen plate 6 …… Screen pattern hole 7 …… Squeegee 8 …… … Conductor paste 9 …… Green sheet adsorption hole 10 …… Exhaust hole

Front page continuation (72) Inventor Seiichi Mitsuda, 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa, Ltd., Production Engineering Laboratory, Hitachi, Ltd. (72) Inventor Tatsuji Noma, 292 Yoshida-cho, Totsuka-ku, Yokohama, Kanagawa Production Engineering Research Laboratory, Hitachi, Ltd.

Claims (2)

[Claims] 1. A method of filling a through-hole formed in a green sheet with a conductive paste by screen printing, wherein a plastic sheet having regenerated cellulose adhered is sandwiched between a green sheet and a base on which the green sheet is placed. A conductor paste filling method, which comprises filling a conductor paste with a surface of a regenerated cellulose facing a through hole portion of a green sheet. 2. The conductive paste filling method according to claim 1, wherein the plastic sheet is a porous body that allows gas and liquid to pass therethrough.