Method and apparatus for electrolytic plating of surface metals

• US 20040092136A1
• Filed: 10/14/2003
• Published: 05/13/2004
• Est. Priority Date: 08/30/2000
• Status: Abandoned Application

• Current Assignee: Micron Technology, Inc.
• Original Assignee: Micron Technology, Inc.
• Inventors: Farnworth, Warren M., Duesman, Kevin G.
• Application Number:
  US10/684,723
• Publication Number:
  US 20040092136A1
• Time in Patent Office: Days
• US Class Current: 439/55
• CPC Class Codes: H05K 1/0346 containing N
• CPC Class Codes: H05K 1/0373 containing additives, e.g. fillers H05K1/036 takes precedence
• CPC Class Codes: H05K 2201/0154 Polyimide
• CPC Class Codes: H05K 2201/0323 Carbon
• CPC Class Codes: H05K 2203/1142 Conversion of conductive material into insulating material or into dissolvable compound
• CPC Class Codes: H05K 3/242 characterised by using temporary conductors on the printed circuit for electrically connecting areas which are to be electroplated
• CPC Class Codes: H05K 3/243 characterised by selective plating, e.g. for finish plating of pads selective plating for making the circuit pattern H05K3/108, H05K3/182

Abstract

A method and apparatus for electrolytic plating of selected areas of printed circuit board traces is disclosed. The method is characterized by its elimination of the need for plating bus bars and plating contacts on the printed circuit board to facilitate a spot-plating process. In one embodiment, a printed circuit board substrate is provided which is at least partially conductive, such that a plating voltage may be applied to any one or more points on the substrate during a spot plating operation. In another embodiment, the substrate material is initially partially conductive, but following the spot-plating operation, is subjected to a curing treatment or the like to cause degeneration of the substrate'"'"'s conductivity. Carbon-impregnated polimid, partially-cured polyimid, FR4 or FR5, with appropriate contaminants introduced therein are contemplated as materials suitable for a printed circuit board substrate in accordance with the invention. In another embodiment, the traces are first applied to the partially conductive substrate by an electroplating operation wherein an electroplating voltage is applied to the substrate such that the substrate itself serves as one terminal of the electroplating system.

Claims

1. A method of spot-plating selected areas of metal traces on a printed circuit board, comprising:

(a) providing a partially-conductive printed circuit board substrate having said metal traces formed thereon;

(b) applying a plating voltage to said substrate; and

(c) performing an electrolytic plating operation on said substrate;

2. A method in accordance with claim 1, wherein said partially-conductive printed circuit board substrate has a conductivity in a range between 10⁶ and 10⁸ Ω

per square centimeter.

3. A method in accordance with claim 1, further comprising:

(d) heat-treating said substrate after said step (c) of electroplating, thereby reducing said conductivity of said substrate.

4. A method in accordance with claim 1, further comprising:

(d) curing said substrate with ultraviolet light after said step (c) of electroplating, thereby reducing said conductivity of said substrate.

5. A printed circuit board, comprising:

a substrate composed of a partially conductive material;

at least one metal trace formed on said substrate;

wherein said substrate is adapted have a plating voltage applied thereto to facilitate a spot-plating operation on said at least one metal trace.

6. A printed circuit board in accordance with claim 5, wherein said substrate is composed of a partially-cured material and is adapted to be subjected to a curing operation subsequent to said spot-plating operation.

7. A printed circuit board in accordance with claim 5, wherein said partially conductive material has a conductivity in a range between 10⁶ and 10⁸ Ω

per square centimeter.

8. A method of applying metal traces to a printed circuit board substrate, comprising:

(a) providing a partially conductive substrate;

(b) applying an electroplating voltage to said substrate;

(c) electroplating said metal traces to said substrate using said electroplating voltage.

9. A method in accordance with claim 8, further comprising:

(d) heat-treating said substrate, thereby reducing said partial conductivity thereof.

10. A method in accordance with claim 8, further comprising:

(d) curing said substrate, thereby reducing said partial conductivity thereof.

11. A method in accordance with claim 8, further comprising:

(d) while said electroplating voltage is applied to said substrate, performing an electrolytic spot-plating operation on said traces.