Metalization of non-hermetic optical fibers

Details Metalization of non-hermetic optical fibers Metalization of non-hermetic optical fibers

1999-08-25

2001-06-26

Wong, Edna (Department: 1741)

Electrolysis: processes, compositions used therein, and methods

Electrolytic coating

Coating predominantly nonmetal substrate

C205S149000, C205S187000

Reexamination Certificate

active

06251252

ABSTRACT:

FIELD OF THE INVENTION
The present invention relates generally to metalization of an optical fiber. More particularly, the invention relates to metalization of non-hermetic optical fiber pigtails that are used in the Bragg grated optical industry.
BACKGROUND OF THE INVENTION
Optical fibers have been widely used for industrial communication systems. In optical devices such as lasers, photodetectors, feedthroughs and sensors, the optical fiber and other device components need to be joined. As a requisite step, the optical fiber needs to be first metalized. There exist several techniques in the prior art for metalization of the optical fibers. A conventional approach is to use a vacuum deposition technique such as sputtering. A metal layer is sputtered onto the optical fiber. The metal used for sputtering deposition includes titanium, platinum and gold. The sputtered metal has relatively good adhesion properties on the optical fiber. However, this approach is not only expensive but also produces a non-uniform coating. It also tends to weaken the optical fiber and puts limitations on the type of polymeric jacket that can be used in the vacuum of the sputtering chamber.
Another technique has been used in the past is electroless deposition of nickel to metalize the glass surface of the optical fiber. A glass surface of the optical fiber is prepared for the electroless deposition of nickel by applying onto the surface a sensitizer which acts to deposit a catalyst for the nickel reduction from an electroless nickel plating solution. U.S. Pat. No. 5,380,559 to Filas et al. discloses an electroless process to deposit nickel and gold onto an optical fiber using aqueous chemistry. The key to the process is a sensitization of the surface of the optical fiber using a dilute aqueous stannous fluoride solution in absence of oxygen. Stannous fluoride solution is prepared by dissolving crystalline SnF
2
in deionized water. Subsequent treatment includes immersion of sensitized optical fiber in a palladium chloride/HCl aqueous solution and commercially available electroless nickel and electroless gold solutions. Although it is possible to obtain reproducible plating of nickel on the surface of the optical fiber according to this approach, it is inconvenient and put a lot of restrictions on the process condition because the majority of process steps need to be performed in absence of oxygen. Thus, a simple and yet reproducible process for the electroless metalization of optical fibers is needed.
SUMMARY OF INVENTION
A method for metalizing a non-hermetic optical fiber having a bare silica surface is disclosed. According to the present invention, the method comprises the steps in the following order. The silica surface is sensitized with a stannous fluoride solution having a concentration of 0.1% by weight under ambient condition. The sensitized silica surface is catalyzed with a catalyzing solution comprising stannous chloride and hydrochloric acid under ambient condition. Then the catalyzed silica surface is activated with an activator solution comprising palladium chloride under ambient condition. A first nickel layer is deposited on the activated silica surface by immersing into an electroless nickel plating solution, and a second nickel layer is also deposited by immersing into an electrolytic nickel plating solution. Finally, a gold layer is deposited on the nickel layer by immersing into an electrolytic gold plating solution.
Preferably, the sensitizing step is conducted in the stannous fluoride solution at a temperature of 72 F. for 5 minutes. The catalyzing solution comprises 14.26% of Shipley Co.'s Sensitizer 471solution, and the activating solution comprises 5% of Shipley Co.'s Activator 472 solution. The electroless nickel plating solution has 1 part of sodium fluoride, 80 parts of sodium succinate, 100 parts of nickel sulfate and 169 parts of sodium hyprophosphite with 500 parts of deionized water. The temperature of the electroless nickel plating solution is about 130 F. The nickel deposition rate in the electroless nickel plating is about 1 &mgr;m per {fraction (1/2+L )} hour. The electrolytic nickel solution has 13 ounce/gallon nickel with pH between 3.5 to 4.5. The electrolytic gold plating solution has 0.5 Troy ounce/gal and pH of 4.0 to 4.8.


REFERENCES:
patent: 5380559 (1995-01-01), Filas et al.
patent: 5774615 (1998-06-01), Uda et al.

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