FR2551091A1 - MELT METAL SUPPLY VESSEL FOR ELECTRON BEAM EVAPORATOR CUP - Google Patents

Abstract

TO AVOID THAT, WHEN THE COPPER WIRE 31 COMES TO FEED THE BATH CONTAINED IN THE CRUCIBLE 23 OF THE EVAPORATOR, COPPER DROPS FROM BEING PROJECTED OUTSIDE THE EVAPORATOR, ON ONE OF THE SIDES OF THE CRUCIBLE 23 IS EXTENDED BY A TANK 34 WHICH RECEIVES THE SOLID WIRE AND THE ZONE FOR PENETRATION OF THE WIRE 31 IN THE MELTED COPPER BATH IS COVERED WITH A SCREEN 36 WHICH STOPPES ANY PROJECTIONS. THE INVENTION IS APPLICABLE TO THE MANUFACTURING OF LAMINATE PRODUCTS FORMED BY DEPOSIT IN THE VAPOR PHASE.

Description

The present invention relates to high vacuum coating systems

  using electron beam technology and, more particularly, it relates to the construction of electron beam evaporation sources used in this technology.

  In general, these systems comprise a vacuum chamber, in which are housed the devices adapted to the presentation of the substrate to be coated and the electron beam evaporator In the vicinity of this chamber, but outside, are located The vacuum pump system and the valves and control devices desired for the operation of the overall system. Usually, the electron beam evaporator consists of a crucible adapted to contain the molten material to be evaporated, the generator An electron beam beam, and a deflection system by which the electron beam from the generator can be directed at a target zone in the crucible. The kinetic energy transformation of the accelerated electrons heats the source material into the electron beam. crucible until the evaporation temperature is reached and the source material is entrained as a vapor L The electron beam itself is generated by heating a cathode filament held at a high voltage negative potential. The electron beam deflection capability using a magnetic field makes it possible to dispose the cathode in a place where it is not at risk.

  to be coated by the material of the vaporized source.

  Such a vacuum coating system is one that can be used when copper is deposited directly onto a chemically clean aluminum foil support surface by vapor deposition while controlling the magnitude of adhesion. The copper coating applied to the aluminum backing sheet has a thickness usually of less than about 16 microns and, more generally, less than about 5 microns. It is desirable that this copper coating be uniformly thick, continuous, smooth and devoid of pinholes at about 100% of its theoretical density -2 Similarly, under the usual copper deposition conditions, the coating has a discernable columnar structure The combination of copper film / aluminum support is a precursor in the production of copper-clad assemblies especially useful in the manufacture of copper plates. printed copies of

strong resolution.

  During the copper deposition production cycles, it is necessary to evaporate the copper from the crucible at high speeds and, since very high purity copper having a very low content of copper is used. gas, the vapor deposition does not pose any particular problem. It would be desirable to use copper of lower purity (with respect to its gas content) to reduce the cost of the copper / carrier material material. However, when using copper having impurities ( for example, a significant gas content), the gas evolution that occurs in the crucible frequently projects small molten copper bodies out of the crucible. The contacting of these melts, generally about 50-70 microns in diameter, on the aluminum foil support surface results in some defects in the resulting laminate. These defects are of two types: if the copper melt strikes the copper surface of an already coated backing sheet, it shrinks on cooling and tears the copper film; if the melt strikes the uncoated backing, it forms a fairly large bump that can not be caught on the high resolution circuit boards for the preparation of

  laminated precursors copper-aluminum support.

  The device according to the invention limits any release of gas from the copper being melted and any mass ejection of molten copper into the enclosure of a chamber, whereby the molten copper can be retained and

  prevented from coming into contact with the support sheet.

  The conventional crucible constructions used in the electron beam evaporator include a longitudinal vessel in communication with the bottom of the crucible and disposed in alignment with automatic feed means. The distal end of the vessel, at less, is covered with a screen or lid cooled by a liquid which, together with the tank, forms a closed chamber for supplying molten metal into the tank. Feeding solid metal wire, leaving the feed means in wire at a set speed, passes under the lid, enters the metal contained in the tank (kept molten by the heat supplied from the crucible) and is melted. The lid is sized in section so as to be small enough to allow an efficient melting while being large enough to allow gas evolution from the molten metal feed and exhaust of gaseous products in a manner that does not t no harmful Any mass of molten metal ejected hits the inner wall of the screen and is condensed The screen is removed, cleaned and

  replaced when the need arises.

  The features of this invention are defined

  in particular in the appended claims, while the arrangement, the mode of operation, as well as the objects and advantages of the invention will be better understood on reading the following description in connection with the accompanying drawings, in which:

  FIG. 1 is a schematic partial sectional view of a vacuum chamber showing the construction of the bowl crucible according to the invention disposed in operative relation with the remainder of the electron beam evaporator for depositing vapor phase of metal on a moving substrate; Figure 2 is an enlarged sectional view of the crucible bowl shown in Figure 1; FIG. 3 is a sectional view taken along line 3-3 of FIG. 2, and FIG. 4 is a sectional view showing a mode of

  modified embodiment according to the invention.

  Similar items in different views are -4

  designated by the same numerical reference.

  In the arrangement of FIG. 1, the vacuum chamber 11 of the vapor deposition coating system 12 contains an arrangement of components for depositing a metal on a moving support. An aluminum support sheet 13 moves from a feeding drum 14 on and in contact with the surface of a coating drum 16 to be received on a receiving drum 17, after the application of an ultra-thin copper film on said sheet of liquid refrigerant (no shown) flows within the coating drum 16 to adjust the temperature of the drum and the sheet 13 in contact with this drum during deposition processing. Other necessary components in a functional system, such as vacuum pumps, control members, energy sources, means for circulating the refrigerant through the electron beam evaporator, etc., do not form part of the invention and are not The electron beam evaporator 20 comprises, as an essential part, the electron source (the tungsten cathode filament 21), the permanent magnet 22 and the graphite crucible 23 The cathode 21 is heated for emitting electrons and the electron beam thus produced is deflected in a programmable manner by the magnet 22 (as well as permanent magnets and auxiliary electromagnets, not shown), so that the electron beam is directed along the general path represented by the dotted line 24 to strike a predefined target zone of the molten metal 26 contained in the crucible 23, which has a graphite liner in a water-cooled copper support block. molten metal - in this case, copper, is evaporated in the target area struck by the beam

  of electrons, and replaced by neighboring liquid copper.

  The resulting vapor comes into contact with the sheet 13 and is deposited thereon under the desired thickness and with the desired bond strength. The copper complementarization of the bath 26 is accomplished by a copper-wire feed. advancing -5 from the coil 32 via a motor drive mechanism 33 to come into contact with the already molten copper in the extension 26 a of the bath 26 contained in the

  tank 34, in communication with the crucible 23.

  As can be seen from FIGS. 1 and 2, the solid metal brought in the form of a wire passes, at a downward angle, under the screen 36 cooled by a liquid, so that its point of impact in the extension 26 The bath 31 is well below the area covered by the screen 36. When it comes into contact with the molten metal, the wire 31 melts and, if it emerges from the gas during this melting (c. that is, release of dissolved gaseous impurities, such as oxygen, nitrogen, carbon dioxide and / or the decomposition of certain oxide or nitride contaminants), this clearance remains below the screen Thus, any projection of molten metal mass caused by the evolution of gas strikes the underside of the screen 36 cooled by the circulation of the refrigerant in the coils 36 fixed to the screen 36. moves from the location where the merge to the target area occurs in the c 23, where the evaporation occurs, the degassing effect from the impurities is completely eliminated. In order not to modify the magnetic fields established for the desired operation of the evaporator 20, the screen 36 is made of a material which is not magnetisable, as

austenitic stainless steel.

  Tests on one embodiment have shown that copper can be successfully evaporated at speeds as high as 25 g / min without encountering the problem of ejection of molten copper from the evaporator. these tests, both the crucible and the bowl were 9.53 mm deep and were in graphite, the crucible having an internal diameter of 53.10 mm and the bowl, in one piece with the crucible, was about 88, 90 mm long and 9.53 mm wide The screen was in the form of a U-shaped lid and was cooled as shown in Figure 2. The condensed copper on the inner surface of the screen could easily be removed because the cooling of the surface prevents the formation

an inter-metallic layer.

  The conventional sizing of the components according to the invention is as follows: Tank: width of about 12.70 mm to about

31.75 mm.

  depth of about 6.35 mmn to about

, 4 mm.

  length from about 50.80 mm to about 127 mm total Crucible: inner diameter from about 9.53 mm to about 50.80 mm depth from about 6.35 mm to about 25.4 min. wall thickness from about 3.18 mm to about

19.05 mm.

  Although the dimensions given above are for a unitary crucible structure with tank having (a) a uniform thickness, (b) a crucible whose general shape is that of a right circular cylinder and (c) a rectangular tank in In cross-section, other shapes, cross-sections and other volumes could be used to achieve comparable volumetric relationships between the volume of the crucible and that of the vessel. In this way, the heat capacity of the molten copper in the crucible maintains in the liquid state the copper lying

in the tank.

  Fig. 4 shows a cooled flat screen 40, requiring separate support means (not shown) and also the use of a slag stop 41 for preventing any slag forming in the vessel 34 from entering the crucible Means 42 adapted to circulate the refrigerant in the copper support block 43 are partially shown. The screen 40 is sized (i.e., in length and width) so as to stop any direct ejection of molten copper from the bath 27a and preventing it from coming into contact with the aluminum support. The use of a flat plate screen is preferred in apparatus using more than one evaporator and the units are mounted side by side, and covered with a single screen. The liner of the crucible may be made of graphite or other material inert to molten copper, such as magnesia or alumina. Other material may be used for the screen material than steel austenitic stainless steel as long as it is non-magnetic and is not damaged by exposure to the conditions

  of operation during vapor deposition.

  The stop for slag must be mounted across the top surface of the tank and flush this upper part or be slightly recessed. Its conventional dimensions should be between approximately 6, 35 mm.

  x 6.35 mm and 25.4 mm x 25.4 mm in cross section.

  It can thus be seen that the device according to the invention which isolates the metal feed during melting and degassing by means of a structure which interrupts any in-line movement of the molten copper ejected during degassing from the copper bath to the substrate to be coated, greatly improves the implementation of the coating operation as well as the quality of the product. Thus, by virtue of this arrangement, a metal feed having a purity significantly lower than that of the previously used metal sources can be used, both as regards the dissolved gas content and the content of other impurities emitting gaseous products. during the decomposition It is therefore possible to realize savings both in terms of material costs and in

the use of the equipment.

-8

Claims (8)

  1 Apparatus for the metered metal supply of a crucible belonging to an electron beam evaporator arranged in a vacuum chamber, in which, during operation, the wire is fed at a regulated feed speed from a source via wire drive means and is introduced in the solid state into the molten metal contained in said crucible, characterized in that it comprises: a vessel-shaped vessel (34) extending longitudinally, communication with said crucible (23) at one end of said container, said container being closed at the opposite end and having volumetric dimensions with respect to the volumetric dimensions of said crucible such that the heat capacity of the molten copper contained in said crucible maintains the copper contained in said container, non-magnetic screen means (36) juxtaposed with said container and spaced therefrom at least a distance sufficient to allow the wire (31) directed to said vessel by said wire drive means (33) to pass under said screen means (36) and into said vessel, and means (36a) for cooling said screen means (36), whereby the melted copper masses ejected from said container by the gas evolution occurring upon entry of the wire into the molten copper contained in said container and during its merger come up against the   lower face of said screen means.   2 Device according to claim 1, characterized in that the crucible (23) and the container (34) are graphite. 3 Device according to claim 1, characterized in that it comprises stop means (41) disposed on the container (34) in the vicinity of the crucible (23) to prevent slag floating on the surface of the molten copper in the   container to enter said crucible.   4 Device according to claim 1, characterized in that the screen means (36) are steel austenitic stainless.   Device according to Claim 4, characterized in that the screen means (40) are in the form of shape of a flat plate.   Device according to claim 4, characterized in that the screen means (36) have a U-shaped cross-section in that they overlap said container. and in that they are removed from it.   7 Device according to claim 1, characterized in that the crucible (23) and the container (34) are of a single plece. 8 Device according to claim 7, characterized in that the crucible (23) is circular in shape, has an internal radius of between about 9.53 mm and about 50.80 mm and that it is one piece with a tub having a width of between about 12.70 mm and about 31.75 mm and a length of about 50.80 mm and about 127 mm.