Process for treating copper surface

• US 4,902,551 A
• Filed: 07/27/1988
• Issued: 02/20/1990
• Est. Priority Date: 12/14/1987
• Status: Expired due to Term

• Current Assignee: Hitachi Chemical Company Limited (Resonac Holdings Corp.)
• Original Assignee: Hitachi Chemical Company Limited (Resonac Holdings Corp.)
• Inventors: Watanabe, Tomoko, Kimura, Yuko, Ogino, Haruo, Nakaso, Akishi, Okamura, Toshiro
• Primary Examiner(s): Gallagher, John J.
• Application Number:
  US07/224,911
• Time in Patent Office: 573 Days
• Field of Search: 156/151, 156/314, 156/253, 156/630, 156/281, 156/902, 148/6.14 R, 148/269, 148/272, 204/27, 204/38.1, 428/137, 428/901, 29/852
• US Class Current: 428/137
• CPC Class Codes: B32B 15/04 comprising metal as the main or only constituent of a layer, which is next to another layer of the same or of a different material next to a bituminous or tarry layer B32B11/08; next to a water-setting substance layer B32B13/06; next to a glass layer B32B17/061; next to a cellulosic plastic layer B32B23/042
• CPC Class Codes: B32B 15/08 of synthetic resin
• CPC Class Codes: B32B 15/092 comprising epoxy resins
• CPC Class Codes: B32B 15/098 comprising condensation resins of aldehydes, e.g. with phenols, ureas or melamines
• CPC Class Codes: B32B 15/12 of paper or cardboard
• CPC Class Codes: B32B 15/14 next to a fibrous or filamentary layer
• CPC Class Codes: B32B 15/20 comprising aluminium or copper B32B15/016 and B32B15/017 take precedence
• CPC Class Codes: B32B 2311/12 Copper
• CPC Class Codes: B32B 2457/08 PCBs, i.e. printed circuit boards
• CPC Class Codes: B32B 27/281 comprising polyimides
• CPC Class Codes: B32B 27/38 comprising epoxy resins
• CPC Class Codes: B32B 27/42 comprising condensation resins of aldehydes, e.g. with phenols, ureas or melamines
• CPC Class Codes: C23C 18/40 using reducing agents
• CPC Class Codes: C23C 22/63 Treatment of copper or alloys based thereon
• CPC Class Codes: C23C 22/83 Chemical after-treatment
• CPC Class Codes: H05K 1/0366 reinforced, e.g. by fibres, fabrics H05K1/036 takes precedence
• CPC Class Codes: H05K 1/0393 Flexible materials H05K1/038 takes precedence; specific organic compositions are classified in H05K1/0313 and subgroups
• CPC Class Codes: H05K 2201/0355 Metal foils
• CPC Class Codes: H05K 2203/0315 Oxidising metal
• CPC Class Codes: H05K 2203/1157 Using means for chemical reduction
• CPC Class Codes: H05K 3/022 : Processes for manufacturing precursors of printed circuits, i.e. copper-clad substrates
• CPC Class Codes: H05K 3/281 : by means of a preformed insulating foil H05K3/284 takes precedence
• CPC Class Codes: H05K 3/385 : by conversion of the surface of the metal, e.g. by oxidation, whether or not followed by reaction or removal of the converted layer
• CPC Class Codes: H05K 3/427 : initial plating of through-holes in metal-clad substrates
• CPC Class Codes: H05K 3/4652 : Adding a circuit layer by laminating a metal foil or a preformed metal foil pattern H05K3/4647 takes precedence
• CPC Class Codes: Y10S 428/901 : Printed circuit
• CPC Class Codes: Y10T 156/1057 : Subsequent to assembly of laminae
• CPC Class Codes: Y10T 29/49165 : by forming conductive walled aperture in base
• CPC Class Codes: Y10T 428/24322 : Composite web or sheet

Abstract

Adhesion of copper to a resin layer is improved by reducing a copper oxide layer with an aqueous aldehyde solution (a) while applying a potential of -1000 mV to -400 mV to the copper oxide layer, (b) after contacting with a metal piece made of copper or a metal nobler than copper, or (c) after contacting with an aqueous solution of alkali borohydride.

Claims

1. A process for treating a copper surface which comprises

forming a copper oxide layer on a copper surface by treating with an aqueous solution containing an oxidizing agent, and

treating the copper oxide layer with an aqueous aldehyde solution having a pH of 9.0 or higher to reduce the copper oxide,

said treatment of the copper oxide layer being carried out

(a) while applying a potential of -1000 mV to -400 mV in terms of Ag-AgCl electrode to the copper oxide layer, or

(b) after contacting the copper oxide layer with a contacting piece made of copper or a metal nobler than copper, or

(c) after contacting the copper oxide layer with an aqueous solution containing an alkali borohydride so as to make the potential of copper in the range of -1000 mV to -400 mV in terms of Ag-AgCl electrode.

2. A process according to claim 1, wherein the treatment of the copper oxide layer is carried out while applying a potential of -1000 mV to -400 mV in terms of Ag-AgCl electrode to the copper oxide layer.

3. A process according to claim 2, wherein the potential is applied by contacting with copper or a metal nobler than copper.

4. A process according to claim 1, wherein the treatment of the copper oxide layer is carried out after contacting the copper oxide layer with a contacting piece made of copper or a metal nobler than copper.

5. A process according to claim 4, wherein the contacting piece is made in the form of roll covered with a copper layer or a layer of a metal nobler than copper.

6. A process according to claim 1, wherein the treatment of the copper oxide layer is carried out after contacting the copper oxide layer with an aqueous solution containing an alkali borohydride so as to make the potential of copper in the range of -1000 mV to -400 mV in terms of Ag-AgCl electrode.

7. A process according to claim 6, wherein the alkali borohydride is sodium borohydride.

8. A copper-clad laminate obtained by

subjecting one or both surfaces of copper foil to the surface treatment process of claim 1,

laminating one or more of the surface treated copper foils and one or more sheets of glass cloth or paper impregnated with an epoxy resin, a phenol resin or a polyimide resin or one or more sheets of an epoxy resin, a phenol resin or a polyimide resin mixed with glass fibers, or laminating one or more of the thus surface treated copper foils coated with an epoxy resin, and

subjecting the resulting multiple layers to heating and pressing treatment to form a laminated unit having copper layers on the outermost surfaces.

9. A copper-clad flexible film obtained by

subjecting one or both surfaces of copper foil to the surface treatment process of claim 1, and

bonding a flexible resin film to the resulting copper foil using an adhesive of epoxy resin or acrylic resin so as to have copper layers on the outermost surfaces.

10. A copper-clad flexible film according to claim 9, wherein the flexible resin film is made from polyimide, polyester, polytetrafluoroethylene, polysulfone, or polyether ether ketone.

11. A multi-layer wiring board obtained by

laminating one or more copper foils and one or more sheets of glass cloth or paper impregnated with an epoxy resin, a phenol resin or a polyimide resin or one or more sheets of an epoxy resin, a phenol resin or a polyimide resin mixed with glass fibers, or laminating one or more copper foils coated with an epoxy resin, a phenol resin or a polyimide resin,

subjecting the resulting multiple layers to heating and pressing treatment to form a copper-clad laminate,

removing unnecessary portions from the copper foil of the laminate by etching to form a circuit pattern for an internal layer,

subjecting the copper foil thus treated to the surface treatment process of claim 1,

laminating on the resulting copper surface an epoxy resin, a phenol resin or a polyimide resin, or a glass cloth or paper impregnated with an epoxy resin, a phenol resin or a polyimide resin, or laminating a sheet of an epoxy resin, a phenol resin or a polyimide resin mixed with glass fibers, with repetition of laminating to form multiple layers and a copper foil as an outermost layer,

subjecting the multiple layers and copper foil to heating and pressing treatment to form a laminated unit having copper layers on the outermost surfaces,

drilling through-holes in the laminated unit,

metallizing inner walls of the through-holes, and

removing unnecessary portions from the outermost copper layers by etching to form circuits.

12. A multi-layer wiring board obtained by

laminating one or more copper foils and one or more sheets of glass cloth or paper impregnated with an epoxy resin, a phenol resin or a polyimide resin or one or more sheets of an epoxy resin, a phenol resin or a polyimide resin mixed with glass fibers, or laminating one or more copper foils coated with an epoxy resin, a phenol resin or a polyimide resin,

subjecting the resulting multiple layers to heating and pressing treatment to form a copper-clad laminate,

removing unnecessary portions from the copper foil of the laminate by etching to form a circuit pattern for an inner layer,

subjecting the copper foil thus treated to the surface treatment process of claim 1,

laminating on the resulting copper surface an epoxy resin, a phenol resin or a polyimide resin, or a glass cloth or paper impregnated with an epoxy resin, a phenol resin or a polyimide resin, or laminating a sheet of an epoxy resin, a phenol resin or a polyimide resin mixed with glass fibers, with repetition of laminating to form multiple layers and a copper foil subjected to the surface treatment process of claim 1 as an outermost layer,

subjecting the multiple layers and copper foil to heating and pressing treatment to form a laminated unit having copper layers on the outermost surfaces,

drilling through-holes in the laminated unit,

metallizing inner walls of the through-holes, and

removing unnecessary portions from the outermost copper layers by etching to form circuits.

13. A flexible wiring board obtained by

bonding a copper foil to a flexible resin film using an adhesive of epoxy resin or acrylic resin to form a copper-clad flexible film,

removing unnecessary portions from the copper foil by etching to form a circuit pattern for an inner layer,

subjecting the copper foil thus treated to the surface treatment process of claim 1, and

bonding a flexible resin film from which necessary portions for connection are removed to the thus treated copper surface with an adhesive of epoxy resin or acrylic resin.

14. A flexible wiring board according to claim 13, wherein the flexible resin film is made from polyimide, polyester, polytetrafluoroethylene, polysulfone, or polyether ether ketone.