GB1570380A

GB1570380A - Electroless plating

Info

Publication number: GB1570380A
Application number: GB23935/78A
Authority: GB
Original assignee: Standard Telephone and Cables PLC
Current assignee: STC PLC
Priority date: 1978-05-30
Filing date: 1978-05-30
Publication date: 1980-07-02
Also published as: DE2920633C2; DE2920633A1

Description

(54) ELECTROLESS PLATING (71) We, STANDARD TELE PHONES AND CABLES LIMITED a British Company, of 190 Strand, London W.C.2. England, do hereby declare the invention, for which we pray that a patent may be granted to us, and the method by which it is to be performed, to be particularly described in and by the following statement: This invention relates to processes for the deposition of metal coatings on to plastic surfaces, and in particular to plasma treatment of such surfaces prior to deposition.

It is frequently necessary to provide metal coatings deposited on to plastics materials. Typically the surface of the plastics material is given a wet chemical treatment prior to electroless nickel plating.

The nickel surface then forms a 'key' and an electrical conductor for subsequent electroplating of a further metal layer.

Special grades of plastics materials are necessary for successful pretreatment prior to electroless nickel plating as the adhesion of the plated metal largely depends on the successful production of surface cavities during the pre-treatment process.

Conventional wet chemical pretreatments are designed to condition the surface of the plastics material for subsequent sensitising processes and at the same time to produce cavities either by the removal of a dispersed phase or by surface swelling.

The quality of the cavities produced in this way is critically dependent on the quality of the plastics material.

The object of the invention is to minimize or to overcome this disadvantage.

According to one aspect of the invention there is provided a process for providing an activated surface on a plastics body, the process including exposing the body to a low pressure radio-frequency plasma, the nature of the plasma being such that the plastics surface is etched and roughened.

According to another aspect of the invention there is provided a process for providing a metal surface coating on a plastics body, including exposing the surface to a low pressure radio-frequency plasma so as to etch and roughen the surface, providing the treated surface with an electroless coating of nickel, and electroplating the metal on to the nickel coating.

An embodiment of the invention will now be described with reference to the accompanying drawing in which the single Figure is a schematic view of an apparatus for plasma pre-treatment of plastics materials.

Referring to the drawing, plastics work-pieces 11 are provided with a plasma surface pretreatment in a high frequency plasma maintained in a vacuum chamber 12 via an external ring electrode 13 coupled to a radio frequency generator. To enhance coupling into the discharge the workpieces 11 are supported each on an insulating stand 14 on an earthed metal plate 15, the upper surface of the plate 15 being covered by an insulating, e.g. glass, plate 16. Conveniently a gas inlet to the vacuum chamber 12 may be provided through an opening 17 in the centre of the metal plate 15 and a corresponding opening 18 in the insulating plate 16. It has been found that such an arrangement of a conductive and an insulating plate enhances coupling of the work pieces into the discharge.

Surface roughening of the plastics workpieces 11 are exposed to a low pressure oxygen plasma which modifies the plastics surface forming a dense pattern of cavities.

Typically, the workpieces are exposed for 10 minutes to an oxygen plasma at a pressure of 0.15 torr and a radio frequency input power of 200 watt. Such treatment leaves the surface in a very activated state which enhances wetting and adhesion if the workpieces are processed immediately after the plasma treatment. In some applications an inert gas plasma, e.g. nitrogen, argon or helium, may be employed to attack the plastics surface so as to provide for purely mechanised keying of a subsequent surface treatment.

In further applications the workpieces may be exposed e.g. to a hydrogen discharge in the presence of a heavy metal such as nickel or palladium. Such metals are transported via the plasma to the plastics surface where they act as sensitizers for subsequent surface treatment.

Typically, the plasma-treated plastics workpieces may be provided with a coating of nickel by a conventional electroless plating process. In a particularly advantageous embodiment, plastics piece parts, e.g. moulded ABS water faucet fittings may be plasma treated by a process described herein followed by nickel and then chromium electroplating to produce the finished article.

WHAT WE CLAIM IS: 1. A process for providing an activated surface on a plastics body, the process including exposing the body to a low pressure radio-frequency plasma, the nature of the plasma being such that the plastics surface is etched and roughened.

2. A process as claimed in claim 1, and in which the plasma is an oxygen plasma.

3. A process as claimed in claim 1, and in which the plasma is a hydrogen plasma containing one or more heavy metals.

4. A process as claimed in claim 2, and in which the heavy metal is nickel or palladium.

5. A process as claimed in claim 1, and in which the plasma is a nitrogen, argon or helium plasma.

6. A process for surface activation of a plastics body substantially as described herein with reference to the accompanying drawing.

7. A process for providing a metal surface coating on a plastics body, including exposing the surface to a low pressure radio-frequency plasma so as to etch and roughen the surface, providing the treated surface with an electroless coating of nickel, and electroplating the metal on to the nickel coating.

8. A process as claimed in claim 7, and in which the electroplated metal is chromium.

9. A process as claimed in claim 7 or 8, and in which the plasma is an oxygen plasma.

10. A metal coating process substantially as described herein with reference to the accompanying drawing.

11. A water faucet plastics fitting provided with a metal coating bv a process claimed in any one of claims 7 to 10.

**WARNING** end of DESC field may overlap start of CLMS **.

Claims

**WARNING** start of CLMS field may overlap end of DESC **. which enhances wetting and adhesion if the workpieces are processed immediately after the plasma treatment. In some applications an inert gas plasma, e.g. nitrogen, argon or helium, may be employed to attack the plastics surface so as to provide for purely mechanised keying of a subsequent surface treatment. In further applications the workpieces may be exposed e.g. to a hydrogen discharge in the presence of a heavy metal such as nickel or palladium. Such metals are transported via the plasma to the plastics surface where they act as sensitizers for subsequent surface treatment. Typically, the plasma-treated plastics workpieces may be provided with a coating of nickel by a conventional electroless plating process. In a particularly advantageous embodiment, plastics piece parts, e.g. moulded ABS water faucet fittings may be plasma treated by a process described herein followed by nickel and then chromium electroplating to produce the finished article. WHAT WE CLAIM IS:

1. A process for providing an activated surface on a plastics body, the process including exposing the body to a low pressure radio-frequency plasma, the nature of the plasma being such that the plastics surface is etched and roughened.