Vapor Deposition Apparatus With Rotating Drum Mask

Abstract

Apparatus and method for depositing a stripe of metal on a metallic strip, comprising a peripherally slitted wheel or drum enclosing a vaporizing boat into which the metal to be deposited is fed and heated to vaporization. A strip of metal of resistance material which is to be coated along its central portion is entrained and moved along the outer periphery of the slitted wheel or drum so that the edges of the slit define the limits of the coating to be deposited onto the metal strip. Both the slit wheel and vaporizing boat are water cooled. The entire assembly comprising the slit wheel, vaporizer and wire feeder are contained within an evacuated container. A heating current is passed through a length of the strip to heat it before it is coated. A modification is to provide a wheel with peripheral holes for depositing longitudinally spaced spots of metal, instead of a strip of metal, onto a metallic base strip. A plurality of such wheels may be used for simultaneously depositing metallic spots onto a plurality of metal strips disposed side-by-side.

Description

This invention relates to apparatus for coating a strip of metal onto a base metallic strip, such as one of resistance material, or, in the alternative, for coating a series of metallic spots thereon.

In the past, the common way of applying a coated strip of metal onto a base strip has been by an electrolytic method by first masking the sides of the strip and, after the electrolytic process, dissolving the masking strips and then finally washing out the resulting liquid. This involves considerable apparatus, chemicals, large tanks of water and extended time for manufacture that have made the cost of the process exhorbitant.

An object of the present invention is to overcome the abovenamed disadvantages and high costs by eliminating the necessity of masking the strip and using solutions for dissolving the masking material.

An object of the present invention is to overcome the abovenamed disadvantages and high costs by eliminating the necessity of masking the strip and the masking material.

A more specific object of my invention is to provide a novel apparatus for applying a strip or spots of vaporized metal to the strip after electrically heating a portion of the strip in a vacuum chamber.

Other objects and advantages will become more apparent from a study of the following description taken with the accompanying drawings wherein:

FIG. 1 is an elevational view, with the cover removed, of apparatus for depositing vaporized metal in the form of a central strip portion onto a metallic base strip, in accordance with the present invention;

FIG. 2 is a side view thereof, reduced in size and showing the cover in place, which cover is shown partly cut-away to expose the interior parts;

FIG. 3 is an enlarged, vertical, cross-sectional view of the slit wheel and vaporizer shown in FIGS. 1 and 2;

FIG. 4 is an enlarged, fragmentary view of a portion of the strip 9 illustrated in FIGS. 1 and 2, showing the deposited central strip portion 36 thereon;

FIG. 5 is a vertical, plan view, partly in cross-section, showing a modification wherein radial holes are provided to apply a series of longitudinally spaced spots, instead of a strip, on the base metallic strip;

FIG. 6 is an elevational view, partly in vertical cross-section, as viewed from the left of FIGS. 5;

FIG. 7 is an enlarged, fragmentary view of a portion of the spotted strip 61 illustrated in FIGS. 5 and 6;

FIG. 8 is a further modification showing multiple slit wheels for applying central coated strips to a plurality of base metallic strips, simultaneously; and,

FIG. 9 is a cross-sectional view taken along line IX--IX of FIG. 8.

Referring more particularly to FIGS. 1, 2 and 3, of the drawing, numeral 1 generally denotes apparatus for vaporizing metal and depositing it in the form of a strip along a central portion of a base metallic strip of electrical resistance material. The apparatus is mounted on a back plate or support 2 and is enclosed by a cover 3 which may be either round, to form a bell jar, or rectangular in shape and sealed to the back plate 2 by a sealing strip 6 of neoprene rubber or other suitable material to enable retention of a vacuum in the space enclosed by the cover 3. The cover 3 is hingedly mounted on back plate 2 by a double hinge 4, 5 and may be sealed tightly thereagainst by seal 6 and by a handle and cam lock (not shown), such as commonly used in the past on iceboxes and the like. An evaporation boat 23 heats to vaporization a strip of aluminum 24 or other metal to form the coating or stripe 36.

The space within cover 3 is evacuated by a mechanical pump driven by a motor, generally denoted by numeral 8, and a diffusion pump 7 of any well known type with suitable controls for allowing roughing, that is, partial evacuation by the mechanical pump and further evacuation by the diffusion pump. The diffusion pump has an outlet leading through a hole 7' in the back plate 2 to evacuate the space covered by sealed cover 3. A gate valve 46a is supported on the back plate for controlling the flow of air exhausted from the space in cover 3.

A strip 9 of metal, particularly metal having high electrical resistance, such as an alloy of iron, nickel and cobalt sold under the trademarks KOVAR and FERNICO, is unwound from a feed spool 10, passed over a guide spool 11 and thence over a centrally slitted drum or wheel generally denoted by numeral 15. A stripe 36 (see FIG. 4) of aluminum or of other vaporized metal is deposited on strip 9 through a slit in the wheel, thereafter the strip is passed over a second guide spool 12 and finally wound onto a take-up spool 13. The slit wheel assembly comprises three essential parts: an inner wheel 20 an outer wheel 21, and a spindle 16 on which both are rigidly mounted and spaced apart by slit 9. This assembly is water cooled.

The spindle 16 is essentially a piece of pipe threaded at one end and with a flange 34 with recessed O ring attached. A small pipe 42 located concentrically carries cooling water to the inner and outer slit wheels. The inner wheel 20 is permanently attached to the spindle.

Both slit wheels 20 and 21 have cavities through which cooling water flows. It enters the spindle via a rotating seal 18 outside the vacuum chamber, and flows into a cavity in the inner slit wheel 20 through a hole 38 in the spindle. When the cavity is full the water flows out through a radially located inlet pipe 40 connected to the pipe 42 concentric with the spindle. Inlet pipe 37 and outlet pipe 43 are provided for water flow.

The outer wheel 21 is similar to the inner and has a water cavity, the chief difference being that it is drilled and tapped to fit onto the threaded end of the spindle. By this means, the wheel is pulled up tightly against the O ring in the spindle flange, thus sealing in the cooling water. The outer slit wheel 21 differs in that it has an additional water cavity 41a supplied by a radial pipe 41 thence flowing into the pipe 42 concentric with the spindle. Water flows into the main cavity through holes 39 drilled in the threaded portion of the spindle. The water cavities of the inner and outer split wheels are thus in parallel. Before taking off the outer slit wheel 21, the water is removed by so positioning the wheel that the radial pipe is vertically below the spindle and applying a few pounds of pressure of compressed air.

Provision is made for adjusting the width of the aluminum stripe by inserting washer of appropriate thickness between the outer slit wheel 21 and the spindle flange 19. An additional O ring to that shown is let into the outer slit wheel 21 to effect a water seal. The spindle is supported by ball races 17 (not self-aligning) and is insulated electrically from the back plate 2 in much the same way as the outer spindles. The spindle is held in position by a ring 18 on a threaded portion of the spindle outside the vacuum chamber. A window 45 is provided to enable viewing of the interior of the space or chamber enclosed by lid 3. A graphite brush assembly is located on the spindle next to the rotating water seal.

The feeder for the aluminum wire 24 consists of four separate assemblies: (1) knurled wheel assembly; (2) Wilson seal assembly); (3) Motor and gearbox; and (4) spool support and guide tube.

The knurled wheel assembly 30 for feeding aluminum wire into evaporating boat 23 comprises two bars 30a, 30b, each carrying a knurled wheel 22a on a shaft inserted in small ball races pressed into opposite sides of the bars, which are clamped to a pivot 33 by means of two tie rods located at opposite ends of the bars. By adjusting the nuts on the tie rods, suitable clearance between the knurled wheels may be obtained. The pivot 33 is extended to serve as a support for the knurled wheel assembly and is terminated at the end by a flange bolted to the back plate 2.

The boat 23 is preferably made of boron nitride or other conducting material. The aluminum strip is electrically heated in the boat by power lead-ins comprising copper bars 28 extending through and insulated to back plate 2 and connected to the boat through copper delivery tubes 26, 27 which are constricted at the point of entry 35 through the slit between wheels 20 and 21. The bars 28 are cooled by passing cooling water in pipes 26, 27 therethrough.

A length of strip 34 between idler wheel 11 and drum 15 may be electrically preheated by a source of voltage V connected to their shafts through brushes B. Such preheating improves adherence of stripe 36.

FIGS. 5, 6 and 7 show a modification for applying spaced spots of vaporized metal, instead of a strip of metal, onto the base metallic strip 61. Numeral 1' denotes a back plate on which is mounted apparatus generally denoted by numeral 50 for depositing spots of vaporized metal onto strip 61, such as an electrical heater strip, for example, one of an iron, nickel cobalt alloy, such as KOVAR. The wheel or drum 51 is rotatably mounted on a tubular shaft or pipe 52 by means of a pipe flange 53 bolted to the drum 51. A plurality of sprockets 54 project radially outwardly from the peripheral surface of the drum for guiding the strip 61, that is, by projecting sprockets 54 through holes 54' extending along the edges of the strip. A plurality of circumferentially spaced holes 55 are provided through which vaporized metal is passed and deposited on strip 61 in the form of spots, such as 60, shown in FIG. 7.

A water cooling pipe 57 is provided with an inlet pipe 58 to allow the flow of cooling water through boat 56 which contains the vaporizing metal, such as gold, which is fed into vaporizing boat 56 in the form of a strip through tube 58. A masking strip 59, entrained about idler wheels 64 and 65, will mask the sides of the strip (or any other portion).

FIG. 7 shows the resultant design. The strip 61 is entrained about guide spools 62 and 63 and underneath arcuate guide 66 so as to be laid onto masking tape 59 before vaporized metal is deposited thereon. The iron-nickel stamped lead frame strip 61 may have cut-out portions such as 61a which provide inwardly projecting fingers 61b whose inner extremities would be coated with gold spots, -- four in number, corresponding to the peripheral portions of a single spot 60.

FIGS. 8 and 9 show a modification of the invention illustrated in FIGS. 1 to 4 inclusive for depositing a stripe of metal 36 onto a metallic strip 9, preferably of resistance material. As shown in FIGS. 8 and 9, a plurality of wheels 70 may be provided with V-shaped slots and arranged side-by-side and guided by locating wheels 74 and a spring loaded locating wheel 73. A supply spool feeds aluminum wire 77 into a evaporating boat 76 serving all of the slit wheels. A water cooled shield is provided between each slit wheel. Radiation shields 78 are provided on the outside of the slit wheels at the ends of the gang assembly. Thus a plurality of metal strips 9, when entrained about the slits between the respective wheels, will be coated simultaneously with stripes 36 centrally and longitudinally of the strip, as shown in FIG. 4.

Such deposited stripes may be used for numerous purposes, including the making of a bimetallic strip, such as, by depositing a silver-copper eutectic stripe on a strip 9 of 0.01 inch iron-nickel cobalt alloy. This comprises a significant improvement over the common method of bonding by rolling a silver-copper eutectic foil about 2 mils thick onto a nickel-iron strip. Foil is difficult to roll, particularly thinner than 1 mil.

It will be readily apparent to those skilled in the art that variations may be made in the illustrative embodiments heretofore described. For example, instead of putting the vaporization boat inside the slit wheel, it may be put on the outside and under it while passing the metallic strip 9 inside the wheel adjacent the periphery. A plurality of such units may be provided side-by-side, as illustrated in FIGS. 8 and 9.

Claims

1. Apparatus for depositing vaporized metal along the intermediate longitudinal portion of an elongated base strip, comprising a drum having central opening means extending along the entire periphery, means for rotating said drum about its axis, a source of metallic vapor on one side of said opening means, means for longitudinally moving a base strip entrained on the other side of the drum overlying said opening immediately adjacent said opening means, said source of metallic vapor being contained within said drum and comprising a boat-like container which is heated to vaporization temperature of a strip of metal progressively fed into said container, and said base strip being longitudinally driven along a portion of the outer periphery of said drum so that the inner surface exposed to said slit will become coated with said vaporized metal, the edges of the slit defining the boundaries of the coated strip, said base strip being driven by a motor and further entrained about a plurality of idler wheels, a source of potential being applied between a brush which contacts the shaft of one of said idler wheels and a brush which contacts the shaft of said drum so as to provide electric heating current to a portion of said base strip extending between the periphery of one of said idler wheels and of said drum, to effect preheating of said portion before deposition of vaporized metal thereon through said slit, and means contacting said drum beyond the area of strip contact whereby to remove excess deposited metal

2. Apparatus as recited in claim 1, together with a back plate rotatably mounting said drum, and together with a pivotally mounted cover having a flexible sealing gasket about the mouth of said cover for engaging and forming a seal with said back plate, and evacuating means for evacuating

3. Apparatus as recited in claim 1 together with water cooling conduits extending through a spindle on which said drum is rigidly connected and through interior portions of said drum and back plate on which said

4. Apparatus as recited in claim 3 together with a pair of electrical, water-cooled terminals extending through said back plate and to the ends of said container for passing electric heating current through said

5. Apparatus as recited in claim 1 together with a supply roll of strip material and means for longitudinally moving said strip material into said

6. Apparatus as recited in claim 1 wherein said opening means is in the form of a plurality of holes extending along the entire periphery of said

7. Apparatus as recited in claim 6 wherein a masking strip is longitudinally moved between the periphery of said drum and the base strip

8. Apparatus as recited in claim 1 comprising a plurality of drums in side-by-side relationship with said drum, each having a circumferential slit and a plurality of base strips simultaneously moved longitudinally outside said slits, whereby the base strips which are moved along said

9. Apparatus as recited in claim 1 wherein said means to remove excess deposited metal comprises knife means projecting into the sides of said slit.