Metal coating on ceramic substrates

Abstract

A method for producing metal coatings on ceramic substrates for establishing electrical contact, and ceramic substrates having metal coatings. More particularly, the invention relates to the production of weldable and solderable metal coatings on ceramic substrates.

Claims

1. A method for producing an electrically conducting metal coating on ceramic substrates, wherein the metal coating is in direct contact with the ceramic substrate and is solderable and/or weldable, the method comprising the steps of: a) producing a metal-coating paste comprising at least one metal selected from the group consisting of a conducting metal, a solderable metal and weldable metal; b) applying the metal-coating paste to the ceramic substrate; c) baking-on of the metal-coating paste; wherein the metal coating does not contain a noble metal selected from the group consisting of platinum, gold, palladium and silver, wherein the metal-coating paste further comprises at least one additive, wherein the additive comprises an element of the transition groups IVB, VB and VIB of the periodic table.

2. A method for producing an electrically conducting metal coating on ceramic substrates, wherein the metal coating is in direct contact with the ceramic substrate and is solderable and/or weldable, the method comprising the steps of: a) producing a metal-coating paste comprising at least one metal selected from the group consisting of a conducting metal, a solderable metal and weldable metal; b) applying the metal-coating paste to the ceramic substrate; c) baking-on of the metal-coating paste; wherein the metal coating does not contain a noble metal selected from the group consisting of platinum, gold, palladium and silver, wherein the metal-coating paste further comprises at least one additive, wherein the additive comprises at least one member selected from the group consisting of Ti, Zr, W and Al, or compounds thereof.

3. A method for producing an electrically conducting metal coating on ceramic substrates, wherein the metal coating is in direct contact with the ceramic substrate and is solderable and/or weldable, the method comprising the steps of: a) producing a metal-coating paste comprising at least one metal selected from the group consisting of a conducting metal, a solderable metal and weldable metal; b) applying the metal-coating paste to the ceramic substrate; c) baking-on of the metal-coating paste; wherein the metal coating does not contain a noble metal selected from the group consisting of platinum, gold, palladium and silver, wherein the metal-coating paste further comprises at least one additive, wherein the metal-coating paste further comprises a glass.

4. A method for producing an electrically conducting metal coating on ceramic substrates, wherein the metal coating is in direct contact with the ceramic substrate and is solderable and/or weldable, the method comprising the steps of: a) producing a metal-coating paste comprising at least one metal selected from the group consisting of a conducting metal, a solderable metal and weldable metal; b) applying the metal-coating paste to the ceramic substrate; c) baking-on of the metal-coating paste; wherein the metal coating does not contain a noble metal selected from the group consisting of platinum, gold, palladium and silver, wherein the metal-coating paste further comprises an oxidic glass.

5. The method according to claim 3, wherein the glass comprises at least one member selected from the group consisting of SiO.sub.2, Bi.sub.2O.sub.3, ZnO, TiO.sub.2, MnO, an alkali metal oxide and an oxide from the main group III of the periodic table.

6. The method according to claim 2, wherein the metal-coating paste comprises a pasting medium which is a solution of 5 to 25% w/w a) ethyl cellulose in either terpineol or polyvinyl butyral; or a polyacrylate in either Texanol or butyl carbitol.

7. The method according to claim 2, wherein the application of the metal-coating paste to the ceramic substrate is carried out by immersing the substrate in the metal-coating paste or by applying the metal-coating paste by means of a screen printing or pad printing method or by spraying.

8. The method according to claim 2, wherein the baking-on is carried out at a temperature between 800 and 900 C.

9. The method according to claim 2, wherein the baking-on is carried out in a gas atmosphere.

10. The method according to claim 2, wherein a further layer comprising Ni, or Au, is applied over the electrically conducting metal coating.

11. The method according to claim 2, wherein the metal coating comprises at least one conducting metal selected from the group consisting of iron, cobalt and nickel.

12. The method according to claim 3, wherein the metal coating comprises at least one member selected from the group consisting of iron, cobalt, nickel and copper.

13. The method according to claim 3, wherein the metal coating further comprises a member selected from the group consisting of Ti, Zr and W, or a compounds thereof.

14. The method according to claim 3, wherein the glass is selected from the group consisting of SiO.sub.2, Bi.sub.2O.sub.3, ZnO, TiO.sub.2, an alkali metal oxide and an oxide of the main group III of the periodic table, or mixtures of these compounds.

15. The method of claim 3, wherein the metal is selected from the group consisting of Ni and Cu.

16. The method according to claim 15, wherein the metal is Ni.

Description

EXAMPLES

(1) A U-shaped oxide-ceramic coil body is metal-coated by immersing the ends in a paste made of Ni, Fe, Cu and possibly further materials and also glass. By way of example, the metal-coating paste can have the following composition: 50% w/w Ni, 0 to 20% w/w Fe and/or 0 to 20% w/w Ti and/or 0 to 20% w/w Al, 10 to 20% w/w Cu and/or 0 to 20% w/w CuO and/or 0 to 20% w/w Cu.sub.2O, 10% w/w of a MnOSiO.sub.2Al.sub.2O.sub.3 glass.

(2) In the exemplary embodiment, the paste comprises 50% fine nickel powder (d50=5 m), 20% iron powder (d50=5 m), 20% copper powder (d50=5 m) and 10% of a glass powder MnO (50% w/w)-SiO.sub.2 (40% w/w)-Al.sub.2O.sub.3 (10% w/w, in each case referred to the total mass of glass), pasted in a solution of 10% w/w ethyl cellulose in terpineol, with a viscosity of 30 Pa*s.

(3) The copper powder can partially or completely be replaced by copper oxide, CuO or Cu.sub.2O.

(4) The iron can partially or completely be replaced by titanium powder and/or aluminum powder.

(5) In a further example, the metal-coating paste is produced from a mixture of Ni, W, W(VI) oxide and glass and the pasting medium described above. 70% w/w Ni, 15% w/w W, 5% w/w W(VI) oxide and 10% w/w glass as a powder (d50=5 m) are mixed together and pasted on. The glass has the composition 50% w/w MnO, 40% w/w SiO.sub.2 and 10% w/w Al.sub.2O.sub.3. The metal-coating paste is sintered on for 30 min at 1100 C. in moist hydrogen with a dew point of 20 C.

(6) A mixture of ZnOSiO.sub.2B.sub.2O3-Al.sub.2O3-TiO.sub.2ZrO.sub.2 can also be used as the glass powder, for example: 35% w/w ZnO, 35% w/w SiO.sub.2, 20% w/w B.sub.2O.sub.3, 5% w/w Al.sub.2O.sub.3, remainder TiO.sub.2 and ZrO.sub.2.