US3690291A

US3690291A - Deposition apparatus

Info

Publication number: US3690291A
Application number: US138229A
Authority: US
Inventors: Joseph H Judd; Raymond L Clark
Original assignee: National Aeronautics and Space Administration NASA
Current assignee: National Aeronautics and Space Administration NASA
Priority date: 1971-04-28
Filing date: 1971-04-28
Publication date: 1972-09-12
Anticipated expiration: 1989-09-12

Abstract

Means feed wire to be evaporated into contact with a central portion of an evaporator-filament having an electric current passing therethrough. An electrical potential difference is maintained between the wire and one side of said filament whereby the vapor is ionized.

Description

121Q 121/I 55H 1 132912-1172 KR he m/291 United States Patent Judd et a1. Sept. 12, 1972 [54] DEPOSITION APPARATUS [56] References Cited [72] Inventors: Joseph H. Judd, Newport News; UNITED STATES PATENTS a Clark Hampton both 2,153,786 4/1939 Alexander etal ..ll8/49 x 2,444,763 7/1948 Alexander ..ll8/49 x [73] Assignee: The United States of Ameri a 3,045,642 7/1962 Auzolle eta] ..118/49 zfig fffizfg g gmmg g g FOREIGN PATENTS OR APPLICATIONS Administration 55,291 10/1943 Netherlands ..118/49 [22] Filed: April 1971 Primary Examiner-Morris Kaplan [21] App1.N0.: 138,229 Att0rneyHoward J. Osborn, William H. King and John R. Manning [521 US. Cl. ..l18/49.1, 204/298, mag/ 192,12 1; [57] ABSTRACT 51 Int. (:1 ..C23c 13/12 Means feed wire to be evaporated into Contact w a 58 Field at Search ..118/48-49.1; central Portion of an evaporator-WWW having electric current passing therethrough. An electrical potential difference is maintained between the wire 204/298 and one side of said filament whereby the vapor is ionized.

4 Claims, 2 Drawing Figures l8 I l3 9 POVbER 5 20 I2 1 I POWER SUPPLY 1 SUPPLY 2 POWER 3 24 SUPPLY M PATENTEDSEP 12 I972 3,690,291

sum 1 or 2 l4 7 i 2 22 |e l3 1 2o 1 POWER I I POWER SUPPLY I SUPPLY 23 POWER 24 v SUPPLY FIG l INVENTORS JOSEPH H. JUDD RAYMOND L. CLARK PATENTED E 2 3.690.291

sum 2 OF 2 FIG. 2

INVENTORS JOSEPH H. JUDD BYwD lfiLARK ATTORN S DEPOSITION APPARATUS ORIGIN OF THE INVENTION The invention described herein was made by employees of the United States Government and may be manufactured and used by or for the Government for governmental purposes without the payment of any royalties thereon or therefor.

BACKGROUND OF THE INVENTION The invention relates generally to material coating and more specifically concerns depositing a thin metallic film on nonmetallic materials.

In the past, vapor deposition techniques have been used wherein a coating material is vaporized by heat in a vacuum and'then condenses on the material to be coated. The primary disadvantages of these techniques in coating nonmetallic substrates with metallic films is that there is no adhesion between the metallic film and the nonmetallic substrate. Also, there is very little control of the coating thickness in these techniques.

Other techniques used in the past consists of the cold cathode generation of the metal vapor. The disadvantage of thistechnique is that it cannot be controlled either by electric potential or by anode geometry to supply a uniform metal vapor. The almost instantaneous consumption of the cathode in the cold cathode technique results in the generation of a mixture of metal droplets and vapor which produces unsatisfactory thin metallic films. Under microscopic examination, the films are found to be uneven and the condensed metal droplets are evident in the thicknesses of 100 to 500 angstroms.

It is therefore the primary purpose of this invention to provide apparatus for applying thin metallic films to nonmetallic materials in which the film thicknesses are even and in which adhesion exists between the metallic film and the nonmetallic materials.

SUMMARY OF THE INVENTION The invention includes a tungsten filament, a positive plate, a negative plate, and an electric motor located inside a vacuum bell jar. The tungsten fiIament, electric motor, and positive and negative plates are supplied by power supplies located outside the bell jar. Specimens of the nonmetallic material that are to be coated are attached to both the positive and the negative plates. The electric motor feeds the coating material into the tungsten filament so that it makes contact with the tungsten filament at about its central portion. As the coating material is being fed into the tungsten filament, it is electrically connected to one side of the filament. Hence, there is a voltage difference between the coating material and the central portion of the tungsten filament. As the coating material is fed into the tungsten filament, it is vaporized by the heat from the filament and at the same time due to the potential difference between the end of the coating material andthe central position of the filament a current exists. This results in a very fine ionized vapor of the coating material which is attracted to both the negative and the positive plates thereby coating the attached specimen.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a schematic drawing of an embodiment of this invention; and

FIG. 2 is a schematic drawing of the mechanism for feeding the coating material into the filament.

DETAILED DESCRIPTION OF THE INVENTION Turning now to the embodiment of the invention selected for illustration in the drawings, the number 11 designates a vacuum bell jar. Inasmuch as the equip ment for the evacuation bell jars is well known the details of this equipment are not disclosed in the drawings. Located inside bell jar 11 is a tungsten filament 12 which is connected across a power supply 13 located outside the bell jar. Two places, 14 and 15, located inside the bell jar are connected to a power supply 15 outside the bell jar such that plate 14 is a negative plate and plate 15 is a positive plate. An electric motor 17 located in the bell jar is powered by a power supply 18 to feed the coating material 19 into the central portion of tungsten filament 12. The coating material 19 is fed into filament 12 by a feed mechanism 20. The details of feed mechanism 20 are disclosed in FIG. 2. The lower portion of filament 12 is connected through feed mechanism 20 to coating material 19 thereby creating a potential difference between the end of the coating material 19 and the central portion of the tungsten filament 12. A specimen 21 of the material to be coated is attached to plate 14 by a metal clip 22 and a specimen 23 of the material to be coated is attached to plate 15 by a metal clip 24. In addition to attaching the specimen to

plates

14 and 15, metal clips 22 and 24 dissipate any electric charge that might be formed on the face of the specimen.

The feed mechanism in FIG. 2 includes a teflon or nylon adapter 25 which is coupled to the output shaft 26 of motor 17 such that adapter 25 rotates as shaft 26 rotates. A hole 27 in adapter 25 allows a shaft 28 to move longitudinally in the hole. Two

slots

29 and 30 are in adapter 25 and a key 31 extends through shaft 28 into

slots

29 and 30. Hence shaft 28 rotates with adapter 25 and is free to move longitudinally with respect to the adapter. A support 32 is attached to motor 17 forsupprting a metal block 33. Shaft 28 has threads 34 which engage with female threads that extend through block 33. The end of shaft 28 has a chuck 35 attached to it. Chuck 35 holds the rod of plating material 19 that is fed into filament 12. Rod 19 is held off-center of shuck 35 so that rod 19 engages filament 12 once every revolution of the chuck. A wire 36 has one of its ends connected to block 33 and its other end connected to the bottom of filament 12. Hence there is a potential difference between the unattached end of rod 19 and the central portion of filament 12. In the operation of the feed mechanism, when motor 17 turns shaft 26, adapter 25 turns which turns shaft 28 causing it to thread through block 33. This causes chuck 35 to rotate and move away from block 33. Hence, with every revolution of chuch 35, rod 19 makes contact with filament 12. The length of rod 19 that makes contact with filament 12 is the distance that chuck 35 moves longitudinally during one revolution. To produce la a higher ratio of time with the anode not in contact with the filament to the time with the anode in contact, a time delay during motor rotation is introduced; in tests of the apparatus a mechanical brake on the motor was used.

The embodiment of the invention disclosed in the drawings has been used to obtain excellent metallic coatings on elastomers by applying the following procedure. Samples are cleaned to remove dust and film and then attached to both positive and

negative plates

14 and 15 by

metal clips

22 and 24. The vacuum system is then closed and pumped down to the torr range. Dry argon is used to backfill the system and a flow discharge is made in the chamber for corona scrubbing. Then the vacuum system is again evacuated and an electric potential is applied across the positive and negative plates. The tungsten filament is heated to the melting point of the rod and the rod is driven by the electric motor into the tungsten filament. For very thin metallic films, one revolution of chuck 35 is sufficient.

The advantage of this invention is that it provides the ability to produce metallic coatings with good adhesions on a wide range of nonmetallic materials that were impractical or impossible to coat by previous processes.

It is to be understood that the form of the invention herewith shown and described is to be taken as a preferred embodiment. Various changes may be made in the shape, size and arrangement of parts. For example, equivalent elements may be substituted for those illustrated and described herein, parts may be reversed, and certain features of the invention may be utilized independently of the use of other features all without departing from the spirit or scope of the invention as defined in the subjoined claims. Means other than electric motor 17 could be used to feed rod 19 of the coating material into the central portion of tungsten filament 12. Also, means other than what is shown could be used to create a potential difference between the end of rod 19 and the central portion of tungsten filament 12.

What is claimed as new and desired to be secured by Letters Patent of the United States is:

1. Apparatus for depositing a coating of metallic material on a nonmetallic substrate comprising: a plate with an electric potential applied to it and with the substrate attached to it; an electrically heated filament; a rod of the coating material electrically connected to one side of said filament; and means for striking said rod against the central portion of said filament to form a very fine ionized vapor of said coating material whereby said vapor is attracted by said plate and deposited on said substrate.

2. Apparatus according to claim 1 with two plates instead of one and with a positive potential applied to one plate and a negative potential applied to the other plate.

3. Apparatus according to claim 1 wherein said means for striking said rod against the central portion of said filament includes rotating means for holding said rod off-center of rotation of said rotating means; and means for moving said rotating means in the direction of the central portion of said filament while said rotating means is rotating whereby during each revolution of said rotating means said rod is wiped across the central portion of said filament.

4. Apparatus according to claim 3 wherein said means for moving said rotating means in the direction of the central portion of said filament includes a motor that rotates a threaded shaft that has said holding means attached to its end.