Stock material or miscellaneous articles – Structurally defined web or sheet – Continuous and nonuniform or irregular surface on layer or...
Patent
1988-08-31
1990-09-25
Robinson, Ellis P.
Stock material or miscellaneous articles
Structurally defined web or sheet
Continuous and nonuniform or irregular surface on layer or...
428141, 428145, 428212, 428220, 428325, 428328, 428332, 428409, 428426, 428432, 428698, 428901, B32B 310
Patent
active
049592556
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Technical Field
The present invention relates to a ceramic substrate being subjected at its surface to an electroless plating, and a method of manufacturing the ceramic substrate.
2. Background Art
Heretofore, when a metallic film for joining a different metal or as a conductor is formed on the surface of the ceramic substrate, the following have been used as a process for direct electroless plating:
(a) a process in which the surface of the ceramic substrate is subjected to a surface roughening treatment with an etching solution containing an alkali metal compound, adsorbed with a catalyst for an electroless plating and then subjected to the electroless plating;
(b) a process in which an activated paste is applied to the surface of the ceramic substrate and baked to form a plated layer and then an electroless plating is applied to the plated layer;
(c) a process in which a resin sheet whose surface has been roughened is adhered to the surface of the ceramic substrate, and then a catalyst for an electroless plating is adsorbed on the resin sheet, which is subjected to the electroless plating; and
(d) a process in which an alumina paste containing an excessive amount of an organic binder than normal is print-applied onto a part or a whole surface of a green (ceramic) sheet and then simultaneously fired to form a ceramic substrate having a porous surface, and thereafter the surface of the ceramic substrate is subjected to an electroless plating (Japanese Patent laid open No. 59-161,896).
DISCLOSURE OF INVENTION
The above described processes, however, have the following problems:
Case of item (a)
(i) The etching solution is apt to remain in accordance with the state of the roughened surface, so that a corrosion phenomenon is liable to result at a boundary between the electrolessly plated layer and the ceramic substrate after the electroless plating;
(ii) In the well-known etching method using, for example, a high-temperature alkali metal compound, especially a hydroxide or the like of an alkali metal dissolved at about 400.degree. C., it is difficult to conduct a uniform etching due to uneven heating, so that scattering in the bonding force between the electrolessly, plated layer and the ceramic substrate is likely to occur.
Case of item (b)
Since the bonding strength by the activated paste is dependent upon the bonding force of the activated paste, it is necessary to conduct a high-temperature sintering at about 600.degree. C. in order to increase the bonding strength. However, when the ceramic substrate is used as a substrate for an electronic circuit, if resistors, magnetic materials, dielectrics and so on are provided as functional parts of the electronic circuit under the baking conditions different from those for the formation of conductors before the electroless plating, these parts are exposed to the aforementioned high-temperature sintering. As a result, the characteristics of the functional parts are changed by such a high-temperature sintering, so that it is difficult to ensure stable characteristics.
Case of item (c)
Since the resin sheet is interposed between the electrolessly plated layer and the ceramic substrate, the heat characteristics such as heat resistance, high-thermal conductivity of ceramic as the substrate are damaged due to the resin sheet.
Case of item (d)
(i) For example, when copper plating is applied as an electroless plating, the bonding force between the copper plated layer and the ceramic substrate is only obtained in about 1.2.about.2 times as compared with a ceramic substrate having no porous structure, which is still insufficient.
(ii) When the surface roughness of the porous layer after the firing is considerably roughened by adding an excess amount of the organic binder to increase the viscosity of the alumina paste in order to provide the bonding force, it is difficult to form finer wiring patterns on the electrolessly plated layer due to the high degree, of surface roughness.
Also, in a step for forming the wiring pattern by etching, i
REFERENCES:
patent: 4055451 (1977-10-01), Cockbain et al.
patent: 4484972 (1984-11-01), Ebata et al.
patent: 4615763 (1986-10-01), Gelorme et al.
patent: 4684446 (1987-08-01), Charles et al.
NGK Insulators Ltd.
Robinson Ellis P.
Turner Archene A.
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