RU2163424C1 - Device for dynamic plasma treatment of articles - Google Patents

Abstract

FIELD: plasma engineering, in particular, devices with an indirect heating by arc discharge, applicable as a source of linear thermal radiation at a dynamic plasma treatment of surfaces of non-metallic materials, in particular, electronic integrated circuits. SUBSTANCE: the device uses a water-cooled anode and cathode pressed in whose end piece is an insert of refractory metal, body, nozzle, magnetic control winding, oscillator, regulated DC source, as well as water and gas lines; in the initial section the electrodes are diverging ones, and in the working area - parallel ones, an insert of refractory metal is pressed in the end piece of each electrode in its length, each electrode is enveloped by a clamp, and the plates of the magnetic core coupled to the magnetic control winding, and the holders with blanks are positioned in planes that are parallel to the plane of the electrodes. Besides, an arc chute with a grate of metal plates is positioned between the working area and the nozzle. Relative position of the electrodes and the magnetic control coil makes it possible to treat the surface of a non-metallic article by means of a source of linear thermal radiation, in the given case it is an arc moving in a transverse magnetic field, which provides for a uniform heating of the surface of the article being treated. To provide a uniform movement of the arc, use is made of the magnetic control winding, as well as the clamps of their magnetic material enveloping the electrodes in the working area in their section. Reduction of arc contraction is ensured due to the presence of an insert of refractory metal with an electron output potential lower than that of the electrode base material in the end piece of each electrode in its length, as well as due to the shape of the electrode end piece. Provision of the arc chute facilitates are extinction after it passes the working area, which reduces the thermal load on the device components. EFFECT: uniform heating of the surface of article being treated. 2 cl, 2 dwg

Description

 The invention relates to the field of plasma technology, and more specifically to devices with indirect heating by an arc discharge, and can be used as a source of linear thermal radiation during dynamic plasma processing of surfaces of non-metallic materials, in particular electronic circuits.

 Known direct current plasmatrons with an indirect arc (see Esibyan EM Plasma-arc equipment. - Kiev: Technique, 1971. - 164 pp.), Which have found application in various technologies for plasma processing of materials. The plasma torch closest to the proposed device and adopted as a prototype contains a water-cooled anode made in the form of a nozzle, a rod-shaped water-cooled cathode, an electrode insert, a housing, a magnetic control coil, as well as water and gas communications. The plasma torch power supply includes an oscillator and an adjustable current source. The stabilization of the arc in such a plasma torch is ensured by the longitudinal magnetic field generated by the magnetic control winding, as well as by tangential gas injection into the working chamber, and the reduction of arc contraction is achieved by using a zirconium insert pressed into the end tip of the cathode. This is due to the fact that zirconium oxide formed on the surface of the insert during operation in oxygen-containing media has a significantly lower electron yield potential compared to the cathode main material (copper, brass), and therefore the cathode spot moves mainly along the surface of the zirconium insert . When working in an environment of inert and neutral gases, a tungsten insert can be used instead of zirconium.

 The advantages of this plasma torch design are its simplicity, high efficiency of converting electrical energy into heat and a relatively simple power supply circuit.

 When using such plasmatrons to implement the technology of dynamic plasma processing of materials (see Danilin BS, Kireev V.Yu. Application of low-temperature plasma for cleaning and etching of materials. - M.: Energoatomizdat, 1987. - 264 p.) The thermal action of the plasma the arcs on the surface to be treated are heterogeneous due to changes in the temperature profile along the cross section of the arc column. This drawback can be partially overcome by moving the workpiece or the plasma torch itself, however, in this case, achieving a high quality of processing is not entirely possible. In addition, the devices necessary for such a movement reduce reliability and increase the cost of the technological installation.

 The proposed device allows to obtain a new technical result, which consists in uniform heating of the surface of the workpiece.

 This is achieved by the fact that in a device for dynamic plasma processing of products containing a water-cooled anode and cathode, a refractory metal insert, a housing, a nozzle, a magnetic control winding, an oscillator, an adjustable direct current source, and also water and gas communications are pressed into the tip, the electrodes are made diverging in the initial section, and parallel in the working area, an insert of refractory metal is pressed along the length of each electrode along its length, each electrode is covered with the wallpaper, and the magnetic plate, the magnetic coil associated with the control and the holder with workpieces arranged in planes parallel to the plane of the electrodes. In addition, between the working area and the nozzle there is an arcing chamber with a grating of metal plates. The mutual arrangement of the electrodes and the magnetic control coil allows you to process the surface of a non-metallic product using a linear source of thermal radiation, which in this case is an arc moving in a transverse magnetic field, which ensures uniform heating of the surface of the workpiece. In this case, to ensure uniform arc movement, a magnetic circuit connected to the core of the magnetic control winding, as well as staples made of magnetic material, covering the electrodes in the working area along their cross section, are used. The reduction of arc contraction is ensured by the presence of a tip from each refractory metal in the tip of each electrode along its length with a lower electron exit potential than the main electrode material, as well as the shape of the electrode tip. The presence of a discharge chamber is designed to facilitate the extinction of the arc after it passes through the working area, which reduces the thermal load on the elements of the device. Together, the features of the proposed device are essential to achieve the specified technical result.

 The drawing shows a device for dynamic plasma processing of products.

 The device contains an anode 1 with an insert 2 of refractory metal (for example, zirconium), a water-cooling channel 3 and a bracket 4, a cathode 5 with an insert 6 of refractory material (for example, zirconium), a water-cooling channel 7 and a bracket 8, case 9, a magnetic coil 10 control with the core 11 and the magnetic core 12, which covers the housing 9 from the outside, the oscillator 13 and an adjustable current source (the figure shows only its output terminals indicating the polarity). The clips 14 with blanks 15 of the workpiece are placed inside the housing 9. Structurally, the electrodes 1, 4 are completely identical and consist of two characteristic sections. In the first portion of the surface of the electrodes are made diverging. This is done in order to stretch the arc to the dimensions determined by the technology of product processing. In the second section, the surfaces of the electrodes are parallel. This section corresponds to the work area where the surface of the workpieces is processed 15. Directly behind the work area are an arcing chamber 16 with a grill 17 made of metal plates and an exhaust chamber 18 with a nozzle 19.

 The device operates as follows.

 When the oscillator 13 is turned on, a breakdown of the interelectrode gap and ignition of the working arc, powered by an adjustable current source, occurs. As a result of the interaction of the arc current with an external transverse magnetic field created by the winding 10, the arc begins to move along the diverging part of the electrodes 1, 5. Stabilization of the arc current is ensured by the corresponding adjustment of the adjustable current source, and the arc power increases. The arc movement in this section is not uniform, the arc column is convex and rigidly fixed in the plane of the electrodes, which is achieved due to the presence in each electrode along its length of an insert made of refractory metal with a lower potential than the main electrode material (copper, brass) electron exit.

 When the arc reaches the second (parallel) section of electrodes 1, 5, the speed of the arc and its geometric dimensions stabilize. This is due to the fact that when moving along parallel electrodes, the arc power is unchanged, the perturbation consisting in a constant increase in the length of the arc, which is characteristic of the first section, is absent, the speed of movement of the arc column at all its points is the same. This is achieved through the use of brackets 4, 8 made of magnetic material, covering the corresponding electrodes 1, 5 in such a way that the magnetic field is amplified near the surface of the electrodes, which compensates for the braking of the arc at its reference points. The uniformity of the transverse magnetic field in the interelectrode gap is ensured by the magnetic circuit 12, the plates of which are parallel to the plane of the electrodes 1, 5. The stabilization of the arc in the plane of the electrodes, as in the first section, is ensured by the presence of refractory metal inserts in each electrode 1, 5 along its length respectively 2, 6. In addition, the shape of the tip of the electrode (semicircle in section AA) contributes to this goal.

 After passing through the working area, the arc is drawn into the lattice 17 of the arcing chamber 16, where it is stretched, cooled, and extinguished. When it then enters the exhaust chamber 18, the exhaust gas flow is inhibited and exits through the nozzle 19.

 As a result of the application of these measures, the plasma arc, which in this case is a linear source of thermal radiation, in the working area has constant geometric dimensions, stable electrical characteristics and moves along the surface to be processed at a constant speed, due to which uniform heating of the product surface is achieved.

Claims (2)

 1. A device for dynamic plasma processing of products containing a water-cooled anode and cathode, the tip of which is pressed into an insert made of refractory metal, a housing, a nozzle, a magnetic control coil, an oscillator, an adjustable constant current source, and also water and gas communications, characterized in that the electrodes are made diverging in the initial section, and parallel in the working area, an insert of refractory metal is pressed along the length of each electrode along its length, each electrode is covered by staples oh, and the plates of the magnetic circuit associated with the magnetic control winding, and clips with blanks are located in planes parallel to the plane of the electrodes.  2. The device according to p. 1, characterized in that between the working area and the nozzle there is an arcing chamber.