JP2009188229A - Laminated ceramic substrate and manufacturing method thereof - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a laminated ceramic substrate which is enhanced in reliability by increasing fixing strength of a via pad for a ceramic base material. <P>SOLUTION: The laminated ceramic substrate comprises a ceramic base material 11 having a via hole 13, a via conductor 14 filling the via hole, and the via pad 16 made of a conductor connected to the via conductor and provided on a surface of the ceramic base material; and a groove 15 is formed on the surface of the ceramic base material at a periphery of the via hole and the via pad 16 is trenched in the groove 15 to be fixed to the surface of the ceramic base material. The anchor effect can enhance the fixing strength for the ceramic substrate, and the laminated ceramic substrate having high reliability is provided. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a multilayer ceramic substrate having a surface layer and a wiring pattern or the like formed therein by laminating and pressing a plurality of ceramic green sheets having a wiring pattern or the like and firing them.

  Conventionally, the laminated ceramic substrate has a via hole filled with a via conductor in a ceramic base formed from a green sheet, and the surface of the ceramic base provided with the via hole is connected to the via conductor. A via pad which is a conductor pattern is provided, and upper and lower wiring patterns are connected via the via conductor and the via pad.

The multilayer ceramic substrate is prepared by first preparing a ceramic green sheet, forming via holes in the green sheet by laser etching or punching as necessary, filling the via holes with a conductive material paste, and the surface of the green sheet around the via holes. A via pad pattern is formed using a conductive material paste, and a wiring pattern is formed by screen printing of the conductive material paste. Then, a plurality of ceramic green sheets are laminated and pressure-bonded to form a ceramic green sheet block, fired, and divided as necessary to perform terminal electrode plating treatment, etc., thereby completing a laminated ceramic substrate. .
JP-A 64-9691 Japanese Patent No. 3074728

  However, in the laminated ceramic substrate, there is a problem that sufficient adhesion strength of the via pad provided on the surface layer to the ceramic base material may not be ensured.

  The present invention has been made based on the above-described circumstances, and an object of the present invention is to provide a multilayer ceramic substrate that increases the adhesion strength of a via pad provided on a surface layer to a ceramic base material and has improved reliability.

  The multilayer ceramic substrate of the present invention includes a ceramic base material having via holes, a via conductor filled with the via holes, and a via pad connected to the via conductor and made of a conductor provided on the surface of the ceramic base material. A groove is formed around a via hole on the surface of the ceramic substrate, and the via pad bites into the groove and is fixed to the surface of the ceramic substrate.

  According to the present invention, since the outer peripheral portion of the via pad provided on the surface layer bites into the groove and is fixed to the surface of the ceramic substrate, the anchoring effect can enhance the fixing strength to the ceramic substrate. Thereby, a highly reliable laminated ceramic substrate can be provided.

  Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings. FIG. 1 shows a peripheral portion of a via of the multilayer ceramic substrate of the present invention. In addition, in each figure, the same code | symbol is attached | subjected and demonstrated to the same or equivalent member or element.

  In the illustrated example, the laminated ceramic substrate shows only two layers of the ceramic bases 11 and 12, but in actuality, 5 to 20 layers of ceramic bases (not shown) are laminated. The surface ceramic substrate 11 and the internal ceramic substrate 12 are each provided with a metal glaze wiring pattern, and the upper and lower wiring layers are conductively connected through the via holes 13. Here, the ceramic base materials 11 and 12 are formed by laminating, pressing and firing ceramic green sheets each having a wiring pattern formed of a conductive material paste.

  The via hole 13 of the surface ceramic base material 11 is filled with a via conductor 14 such as Ag, Ag—Pd, or Cu. The lower surface of the via conductor 14 is connected to a wiring layer 17 provided on the surface of the ceramic substrate 12. An upper portion of the via hole 13 includes a via pad 16 connected to the via conductor 14 and including a conductive material such as Ag, Ag—Pd, or Cu provided on the surface of the ceramic substrate 11. A concentric ring-shaped V-shaped groove 15 is formed around the via hole 13 on the surface of the ceramic substrate 11 along the outer peripheral portion of the via pad 16, and the outer peripheral portion of the via pad 16 is formed. The via pad 16 bites into the groove 15 and is firmly fixed to the surface of the ceramic substrate 11, and an anchor effect is obtained. Although not shown, a wiring layer provided on the surface of the ceramic substrate 11 is connected to the via pad 16. The diameter of the via hole 13 is about 30-100 μm, the diameter of the via pad 16 is about twice the diameter of the via hole, and the thickness of the green sheet is 30-150 μm.

FIG. 2 shows the relationship between the cutting ratio of the groove 15 and the fixing strength. here,
Cutting ratio = (cutting depth / green sheet thickness) x 100 (%)
It is. Both the ball shear strength and the tensile strength are the bonding strength of the via pad bonding surface. The ball shear strength is the strength at which the joint surface breaks when a load is applied to the via pad parallel to the surface of the board, whereas the tensile strength is when the tensile force is applied to the via pad perpendicular to the surface of the board. The strength at which the joint surface breaks.

  As shown in the figure, it can be seen that when the cutting ratio is 10% or more, the ball shear strength is improved to about 200% and the tensile strength is improved to about 150%. This indicates that a firm anchor effect was obtained for the via pad 16 by fixing the outer peripheral portion of the via pad to the groove 15 provided in the ceramic substrate 11.

  Next, with reference to FIG. 3, the manufacturing method of the laminated ceramic substrate of this invention is demonstrated. First, ceramic powder and glass are blended at a certain ratio, mixed, and an organic binder and solvent are added to the mixed raw materials and dispersed until uniform to form a slurry. The slurry is applied on the PET film with a certain thickness using a film forming apparatus, and a green sheet 11a is formed through a drying process. Then, the green sheet 11a is cut into a specified size (see (a)).

  Next, in order to ensure conduction between the upper and lower layers, the via hole 13 is formed by laser etching or punching, and the groove 15 having a V-shaped cross section is laser etched at a position where the outer peripheral portion of the via pad around the via hole 13 is disposed. (See (b)). Then, a conductive material paste mainly composed of Ag, Ag-Pd, Cu or the like is filled in the via hole 13 to form the via conductor 14a, and the via pad pattern 16a in which the groove 15 is filled with the conductive material paste is formed as a screen mask. Etc. (see (c)). The formation of the via conductor 14a and the formation of the via pad pattern 16a may be performed simultaneously as described above or separately.

  Furthermore, a wiring pattern is formed by screen printing of a conductive material paste, and a green sheet for one layer is completed. The formation of the wiring pattern and the formation of the via conductor 14a and the via pad pattern 16a may be performed simultaneously or separately. In this way, a plurality of green sheets having a wiring pattern are prepared, and pressure is applied in the laminating process to laminate them to form a ceramic green sheet block (see (d)). Furthermore, after the firing process, the ceramic green sheet becomes a ceramic base material, the pattern formed by solidifying the conductive material paste becomes a metal glaze conductive material pattern, and the laminated ceramic substrate shown in FIG. Then, plating and division into individual pieces are performed to complete the laminated ceramic substrate.

  The via pad 16 can be used for a so-called low-temperature fired ceramic substrate (LTCC) using Ag as a wiring layer, and can exhibit an anchor effect to the ceramic substrate particularly effectively.

  Further, although the V-shaped groove has been described as the shape of the groove, it can be similarly applied to a U-shaped or U-shaped groove.

  Although one embodiment of the present invention has been described so far, it is needless to say that the present invention is not limited to the above-described embodiment, and may be implemented in various forms within the scope of the technical idea.

It is sectional drawing of the via periphery part of the multilayer ceramic substrate of one Embodiment of this invention. It is a graph which shows the relationship between the notch ratio of a groove | channel, and fixing strength. It is a figure which shows the manufacturing process of the said laminated ceramic substrate.

Explanation of symbols

11, 12 Ceramic substrate 13 Via hole 14 Via conductor 15 Groove 16 Via pad 17 Wiring layer

Claims (5)

A ceramic substrate having via holes;
A via conductor filling the via hole;
A via pad connected to the via conductor and made of a conductor provided on the surface of the ceramic substrate;
A laminated ceramic substrate, wherein a groove is formed around a via hole on the surface of the ceramic base material, and the via pad bites into the groove and is fixed to the surface of the ceramic base material.   The multilayer ceramic substrate according to claim 1, wherein the groove is formed along an outer periphery of the via pad.   The multilayer ceramic substrate according to claim 1, wherein the groove has a V-shaped cross section.   The multilayer ceramic substrate according to claim 1, wherein the groove has a cut depth of 10% or more of the thickness of the base material. In the ceramic green sheet, via holes and grooves are formed around the via holes,
Fill the via hole with a conductive paste,
Forming a via pad pattern with a conductive material paste in a region including a groove formed around the via hole;
A method for producing a laminated ceramic substrate, comprising laminating and firing a plurality of ceramic green sheets.

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