METHOD FOR DEPOSITING THICK COPPER LAYERS ONTO SINTERED MATERIALS
The present invention relates to a method for electrodepositing a thick copper layer onto an electrically conductive, sintered layer. The thick copper layer has a high adhesion strength, is poor in defects and internal stress, and has high electrical and thermal conductivity. The thick copper layer on the sintered layer is suited for printed circuit boards for high power electronic applications.
1 . A method for electrodepositing at least one copper layer onto an electrically conductive, sintered layer, the method comprising the steps of
(i) providing at least one electrically conductive, sintered layer,
(i.a) pre-treating the at least one electrically conductive, sintered layer,
(ii) contacting the sintered layer with an electrolytic copper plating solution and applying an electrical current between the sintered layer and at least one anode, and
(iii) thereby depositing a copper layer onto the sintered layer,
wherein the pre-treating of the at least one electrically conductive, sintered layer comprises a step (i.aa):
(i.aa) contacting the at least one electrically conductive, sintered layer with a micro etchant comprising a sulfuric solution and at least one peroxo compound as oxidizing agent.
2 . The method according to claim 1 wherein the micro etchant according to method step (i.aa)
further comprises at least one source of a halogenide ion.
3 . The method according to claim 1 wherein the at least one electrically conductive, sintered layer comprises a metal selected from the group of copper, titanium, silver, aluminum, tungsten, silicon, nickel, tin, palladium, platinum, and mixtures thereof.
4 . The method according to claim 1 wherein the at least one electrically conductive, sintered layer is provided on a substrate.
5 . The method according to claim 4 wherein the substrate is made of a material selected from ceramics, glass, enamel, and quartz.
6 . The method according to claim 1 wherein the electrolytic copper plating solution is acidic.
7 . The method according to claim 1 wherein the electrolytic copper plating solution comprises an inorganic matrix comprising copper ions, chloride ions and sulphuric acid.
8 . The method according to claim 1 wherein the electrolytic copper plating solution further comprises organic additives selected from brightening agents, leveling agents, carriers, wetting agents and mixtures thereof.
9 . The method according to claim 1 wherein the electrolytic copper plating solution contains a low concentration of a leveling agent and a high concentration of a carrier.
10 . The method according to claim 1 wherein the electrical current is either a direct current, an alternating current or a pulsed current.
11 . The method according to claim 1 wherein the applied electrical current has an average current density higher than 3 A/dm 2 .
12 . The method according to claim 1 wherein the copper layer is a thick copper layer having a thickness ranging from 100-600 μm.
13 . The method according to claim 2 wherein the at least one electrically conductive, sintered layer comprises a metal selected from the group of copper, titanium, silver, aluminum, tungsten, silicon, nickel, tin, palladium, platinum, and mixtures thereof.