Surface preparation of ceramic substrates for metallization

A process for producing a printed circuit on a surface of a ceramic substrate comprising:

• (a) contacting the ceramic surface, with a molten alkali metal composition comprised of an alkali metal compound and an inert solid material in finely divided form to adhesion promote the surface, the inert solid material remaining solid in the presence of the alkali metal composition in a molten state and preventing coalescence of the alkali metal compositions at least until the alkali metal composition wets the ceramic surface;
• (b) treating the ceramic surface to activate it for electroless metal deposition;
• (c) depositing metal onto the activated surface;
• and
• (d) removing portions of the deposited metal to produce a metal printed circuit conductor pattern adhering to the surface of the ceramic substrate.

A process for producing a metallized conductor pattern on a surface of a ceramic substrate having a surface roughness less than about 0.7 micrometers, the process comprising:

• contacting the surface with a molten alkali metal composition comprised of one or more alkali metal compounds and inert inorganic oxide particles in finely divided form for a time period sufficient to adhesion promote said surface, the inert inorganic oxide particles not being dissolved or melted by the molten alkali metal composition up to and during the adhesion promotion;
• rinsing said surface with an aqueous solution;
• neutralizing said surface with an acid;
• repeating said rinsing step;
• contacting said surface with an activator solution providing stannous tin ions and precious metal ions, to render said surface receptive to electroless deposition of a metal;
• and
• contacting said surface or selected parts thereof with a metal depositing solution for a time period sufficient to form a metal layer thereon.

A process for bonding a first ceramic article to a second ceramic article provided with metallization, or to a metal article, comprising the steps of:

• adhesion promoting at least a portion of the surface of the first ceramic article with a molten alkali metal composition comprising one or more alkali metal compounds and an inert solid material which is not dissolved or melted by the alkali metal composition up to and during the adhesion promotion;
• adsorbing catalyst on the treated surface of the first ceramic article;
• depositing a coating of metal on the treated surface with a metal depositing bath;
• and metallurgically joining the metal coated portion of the first ceramic article to a metallized portion of the second ceramic article or to the metal article.