US 2401220 A
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May 28, 1946. w. F. BONNER I 2,401,220
METHOD OF FORMING SPRAYED LAYERS Filed May 27, 1942 I 16 I v VENTOR.
/ BONNER Patented May 28, 1946 UNlTED SAT E METHOD OF FORMING SPRAYED LAYERS Walter F. Bonner, Glen Itldge. N.
Federal Telephone and Radio corporation of Delaware J., asslgnor to- Corporation, a
Application May 27, 1942, Serial No. 444,721
This invention relates to means for assuring deposit of matter on a predetermined area and more particularly to means fordepositing a counter-electrode over a small. areafor productionof small rectifiers.
It sometimes occurs that it is desirable to deposit a thin layer of matter over a small area of a base plate, the area of deposit to be substantially constant. Such a problem is encountered in the application of counter-electrodes to small rectiflers, such as instrument rectifiers.
It has been proposed to assure that the desired area be covered by use of a template serving as a stencil with openings of the desired size. and shape. However, this is not found satisfactory in the making of small rectifiers such as instrument rectifiers since the metal forming the counter-electrode tends to adhere to the template so that when it is removed the metal deposit may be disturbed or lifted entirely oil the rectifier layer. This leads to lack of uiformity in the rectifiers produced and to generally unsatisfactory results.
It is an object of my invention to avoid the dificulties which arise from matter deposited through atemplate sticking thereto.
It is a further object of my invention to provide apparatus for the production of rectiilers of small size so that the individual re'ctifiers will be substantially uniform.
According to a feature of my invention I provide a template with an opening or openings through which matter to be deposited on a plate supported therebelow may be applied over the dea flare -toward the lower'side of the template so that sired area. The openings are made with matter deposited through the holes will not contact the template and will therefore not be disturbed upon removal of the template from the base plate.
Preferably my invention applies to production of selenium rectifiers and deposit of the counter-electrode is made by spraying moltenmetal from above the upper surface of the template through the openings.
A better understanding of my invention and the objects and feature thereof may be had from the particular description thereof made with reference to the accompanying drawing the singlev figure of which illustrates an enlarged scale apparatus for practicing my invention. The figure of the drawing shows by way of example in exaggerated scalean arrangement for practicing my invention. In this figure a supporting plate or table It is shown on which is to the selenium layer.
placed a. strip or plate ll" forming the base plate of rectifier units. On'this plate II is a further layer I! which may be a thin layer of selenium or in the case of other rectifiers, a suitable semiconducting oxide. In order to complete a rec tifier unit counter-electrodes I3 must be applied In the case of instrument rectifiers which are very small in size, this thin Z counter-electrode layer may be easily stripped flaring out the hole 15 below point metal coated with selenium.
from the selenium if it is permitted to stick to any portion of the template through which it is deposited. To'avold this difficulty I provide a template I of special form, which is arranged over the coated strip H so that holes or open- IS in the template'are directly above seleni-' ings um layer l2. Each hole is reduced in diameter so that at point It the substantially ofa size to correspond to the desired area of counter-electrode layer l3. The
metal forming the counter-electrode l3 may be applied by means of a metal spray gun indicated at B1 by the nozzle. When this molten metal is sprayed over the upper surface of template I so as to feed through the hole IE, it will then deposit a thin layer 13 over a small area of the selenium coated surface. In accordance with my invention the difllculty caused by metal of the thin layer sticking to the template is avoided by cated at E8, So that the sprayed metal deposited on the selenium layer I2 is at no point in contact with the template. As a consequence when template It is removed, the deposited metal is not disturbed.
A plurality of holes l5 may be provided in ternplate It so that the counter-electrode for many rectifiers may beapplied to a strip or plate of After deposit of the counter-electrode the strip may be cut up to form the individual rectifier units. By using apparatus as outlined in accordance with my invention, a uniformity of the rectifier product is achieved. This is of rectifiers, for example, in instrument rectifier ts. While I have described my invention as particularly applied to the production of small rectifier units, it should be distinctly understood that this method may be applied in any case where it is necessary to deposit matter over a predetermined area. Whenever the problem of preventing the deposited matter sticking to the template or stencil sheet arises, my invention will be found useful. It is, therefore, clear that the principles of my invention may be appliedgenerdiameter'of the hole is l6, as indiextreme importance in small ally to the deposit of thin layers of fixed area and need not be limited to th specific purpose outlined above.
What is claimed is: In a method of spraying a thin layer of ma terial on a predetermined area of a flat surface by means of a template having holes therethrougb, said holes being divided into two continuous zones, said zones having a relatively small common cross-section and each zone increasing in cross-section to its outer end at the surface and the said two zonesforming a sharp template.
angle at their meeting point in an axial section through the said hole, comprising the steps of applying said template to said flat surface around the area of the latter to be sprayed, spraying said material through the holes of said template on I an area smaller than the end of said hole adjacent to said flat surface, and removing said template from said fiat surface, thereby preventing that a part of said layer is removed with said WALTER F. BONNER.