DE1193765B - Evaporator vessel for vacuum evaporation of movable substrates with aluminum and process for its production - Google Patents

Description

FEDERAL REPUBLIC OF GERMANY

GERMAN

PATENT OFFICE

EDITORIAL

Int. α .:

Number:
File number:
Registration date:
Display day:

C23c

German KL: 48 b -13/10

N18106VIb / 48b
March 31, 1960
May 26, 1965

The invention relates to a method for producing an evaporator vessel for vacuum evaporation of movable substrates with aluminum at evaporation temperatures from 1200 to 1350 ° C.

The aim of the invention is to extend the service life of such an evaporator vessel.

Previously, there was the deposition of aluminum vapor on a substrate in a vacuum chamber one of the main problems in keeping the molten aluminum at suitable evaporation temperatures attacked and destroyed the vessel, so that it was often necessary to stop operating interrupt and replace the vessel.

It is already known to use boron carbide for the surface of a vessel for liquid aluminum for evaporation purposes. It is also known to apply a coating of a boride to the surface of such a vessel.

Such vessels, d. H. Vessels with a coating of boron carbide or a coating of a Boride, but have the disadvantage that these two coating materials are exposed to molten aluminum Temperature range between 1100 and 1300 ° C are heavily wetted and therefore for the absorption of molten Aluminum to be evaporated are unusable. The molten aluminum would namely be on the inside of such a vessel with a coating of a boride or rise from boron carbide, spread over the top of the vessel and onto the outer surface of the vessel flow down again. However, this would not only result in a loss of molten aluminum mean, but also, for example, make induction heating of the vessel impossible, because the liquid aluminum getting onto the outside of the vessel not only provides the necessary Destroy support elements between the induction coil and the vessel, but also a short circuit the induction coil.

In addition, it was found that borides and boron carbide in the molten aluminum in its Evaporation temperature are soluble, so that the life of with borides or with boron carbide coated vessels would be limited.

The invention is based on the knowledge that a surface of the vessel made of boron nitride has an excellent resistance to molten aluminum, so that when heated and brought to a temperature of the order of 1350 ° C it is much longer than previously used for vacuum evaporation
movable pads with aluminum and
Process for its manufacture

Applicant:

National Research Corporation,
Cambridge, Mass. (V. St. A.)

ι «Representative:

Dr.-Ing. E. Sommerfeld and Dr. D. v. Bezold,
Patent Attorneys, Munich 23, Dunantstr. 6th

¹ S Named as inventor:

Charles Alvin Baer, Princeton, N. J .;

Philip James Clough, Reading, Mass .;

Robert Wesley Steeves, Nahant, Mass. (V. St. A.)

broke could be used for the production of coatings. The layer of boron nitride is preferred a surface layer attached to the refractory material, which is one of carbon existing material or some other refractory material.

The favorable experiences with the invention proposed material boron nitride have been shown to be reproducible, if only for the production of an evaporator vessel for vacuum evaporation of movable substrates with aluminum at evaporation temperatures from 1200 to 1350 ° C a protective layer of boron nitride is applied to the surface of the vessel became.

The refractory vessel can be a conductor or an insulator, depending on the method of heating of aluminum is used. The material for the vessel can be from a large number of Metals and compounds are chosen, the main requirement being that there is the increased Able to withstand temperatures required for the evaporation of aluminum, and that it has a vapor pressure of less than 0.1 micron Hg absolute at 1300 ° C.

If the vessel material is made of carbon, the boron nitride coating can thereby be applied be that one mechanically presses the powder into the carbon of the vessel body, or you can the boron nitride in the form of a paste or a

509 577/347

Apply flooding that is subsequently dried. If desired, mechanical ones can also be used Use agents to improve the boron nitride on the surface of the refractory vessel bind, for example by placing small clips, wire nets or the like on the surface of the refractory Attaches the vessel.

An embodiment of the method according to the invention is illustrated below described.

A slurry is first prepared by adding 5 g of powdered boron nitride a few drops of ethyl silicate are mixed and this slurry a drop of a commercially available Wetting agent is added. Enough water is then added to make a thick paste form. This paste is made from a mixture on the inside and on the top of one of them Graphite and charcoal made vessel applied. This coating is then left in air at 93.degree then dry and bake the thus coated vessel in a vacuum oven at 1300 ° C until none More gases are released. The thus coated vessel is then filled with aluminum in a High vacuum chamber attached below a pad to be covered with aluminum and serves as a Source of aluminum fumes at temperatures of the order of 1300 ° C. The so coated Vessel has excellent resistance to molten aluminum.

The embodiment described can be used in several ways within the scope of the invention Relationship differ. The boron nitride coating does not need to be thicker than a few millimeters, • although it can also be made much thicker. To create good mechanical adhesion, if the boron nitride can be mixed with the material of the vessel a little below the surface, see above that the vessel material consists of pure boron nitride on the surface in a mixture of boron nitride and vessel material passes below the surface and then into pure vessel material. So you can, for example build up the vessel from a layer of carbon forming the outer surface of the vessel an intermediate layer, which is a mixture of boron nitride and carbon, and one is the inside of the vessel forming layer made of pure boron nitride. After baking, this arrangement shows excellent results physical properties that make it particularly useful for evaporation of molten material Make aluminum suitable.

The support for the molten aluminum can be made by resistance heating, radiation, be heated by conduction and eddy currents. For example, a rod made of carbon, which is coated with boron nitride can be used as resistance heating elements.

Claims (1)

Patent claims: ίο 1. Method of making an evaporator vessel for vacuum evaporation of movable substrates with aluminum at evaporation temperatures from 1200 to 1350 ° C, with one opposite on the surface of the vessel liquid aluminum resistant protective layer is applied, characterized in that that on the surface of the evaporation vessel coming into contact with liquid aluminum, a layer of boron nitride is applied. 2. Evaporation vessel for performing the method according to claim 1, characterized in that that the base material of the evaporator vessel covered with the protective layer of boron nitride consists of carbon. 3. Evaporation vessel for performing the method according to claim 1, characterized in that that the evaporator vessel coated with the protective layer of boron nitride consists of a refractory oxide. 4. Evaporation vessel for performing the method according to claim 1, characterized in that that the evaporator vessel coated with the protective layer of boron nitride consists of a refractory metal. 5. Evaporation vessel for performing the method according to claim 1, characterized in that that the evaporator vessel coated with the protective layer of boron nitride consists of a such refractory material which has a vapor pressure of less than 0.1 micron Hg absolutely at 1300 ° C. Considered publications: German Patent No. 974 136;
German Auslegeschrift No. 1 078 401;
German Auslegeschrift D19878 VI / 48 b (published on May 17, 1956); Powell-Campell, "Vapor-Plating", 1955, p. 101, para. 4. 509 577B47 5.65 © Bundesdruckerei Berlin