DE3805076A1 - Etching system - Google Patents

Abstract

The invention relates to an etching system, especially for etching printed circuit boards, in which the etching liquid is circulated by means of a pump. A motor-driven screw is provided as the pump. The invention also relates to the arrangement of the feed and return of the etchant, as well as to the arrangement of partitions which favour a uniform flow through the etching chamber.

Description

Etching systems, for example for etching printed circuit boards for the electronics indu strie, work with different processes. In industrial plants spraying the etchant on the circuit boards through nozzles under large Usual pressure.

Other methods involve turbulent rinsing of the etched material the etching liquid or, especially in smaller systems, the movement of the etchant generated by blowing air.

All procedures have in common that the required liquid or air pumps are complex and are therefore not suitable for use in small Etching systems, for example for hobby electronics, are suitable.

According to the invention, a simple solution is proposed which consists in circulating the etching liquid ( 2 ) in the etching chamber ( 1 ) by using a motor-driven screw spindle ( 3 ) in a housing ( 4 ) arranged next to the etching chamber ( 1 ) as the pump. One or more propeller-like propellers are to be regarded as equivalent in terms of patent law.

Such a construction can be extremely efficient and inexpensive build up.

Such a screw spindle ( 3 ) works particularly effectively when it pumps the etching liquid ( 2 ) from top to bottom. As a result, air and gas bubbles are entrained from the space above the etching liquid and increase the etching effect of the etching liquid ( 2 ).

A special embodiment of the housing ( 4 ) consists in the fact that there is only one run ( 5 ) at the top and one return ( 6 ) at the bottom to the etching chamber. This ensures better fluid flow and better circulation.

An embodiment of such an etching system as a common container which contains both the etching chamber ( 1 ) and the housing ( 4 ) and a common partition wall ( 7 ) which has openings as inlet ( 5 ) and return ( 6 ) is cost-saving. having.

An etching system according to the invention can be combined with an electrolysis cell to regenerate the etching liquid in a particularly efficient and cost-saving manner. For such a system, it is recommended to also arrange the electrolysis cell ( 8 ) in the same container and to use the anode plate ( 9 ) of the electrolysis cell ( 8 ) as a partition. With such a construction, the flow through the electrolytic cell ( 8 ) with the etching liquid ( 2 ) can be achieved by the fact that the anode plate ( 9 ) does not sit on the bottom at the bottom or other openings ( 10 ) are present which allow the etching flows to flow in liquid ( 2 ) in the lower region of the electrolytic cell ( 8 ).

The return flow of the etching liquid ( 2 ) is advantageously carried out via an overflow ( 11 ) into the etching chamber ( 1 ) and / or the housing ( 4 ).

The great advantages of the design of an etching system according to the invention become apparent if both the etching chamber ( 1 ) and the pump housing ( 4 ) and the electrolysis cell ( 8 ) are accommodated in a common container ( 16 ). This container ( 16 ) does not require any connections to the outside and can therefore be made tight in a simple manner. The circulation of the etching liquid ( 2 ) from the etching chamber ( 1 ) through the pump housing ( 4 ) and through the electrolysis cell ( 8 ) inevitably takes place within the container ( 16 ).

In Figs. 1, 2 and 3, a schematic example of a erfindungsge MAESSEN etching system is shown.

Fig. 1 is a view from above,

Fig. 2 is a view from the front and

Fig. 3 is a view from the side of the etching system.

The etching chamber ( 1 ) is divided by the pump housing ( 4 ) through the partition ( 7 ), the partition ( 7 ) above having an inlet ( 5 ) from the etching chamber into the pump housing ( 4 ) and a return ( 6 ) below through which the Ätzflüs liquid ( 2 ) can circulate. The direction of rotation of the screw ( 3 ) is expediently chosen so that the etching liquid ( 2 ) is pressed downwards, causing a level difference of the etching liquid ( 2 ) in the etching chamber ( 1 ) and in the pump housing ( 4 ), as in Fig FIG. 2 is produced. At the inlet ( 5 ) will form a kind of waterfall at the point ( 11 ), which still has the great advantage that air and gas particles with the turbulent flow around the screw benspindel ( 3 ) are torn into the liquid and carried along.

This is particularly important when the etchant ( 2 ) is regenerated in cooperation with an electrolysis cell ( 8 ). When using, for example, ammonium sulfate as the etchant, oxygen and ammonia are released in the electrolytic cell ( 8 ), and this gas mixture is returned to the etchant ( 2 ) in the pump housing ( 4 ), thereby promoting the regeneration of the etchant.

The absorption of ammonia also causes an odor nuisance considerably reduced.

The turbulence of a screw pump according to the invention and the mixing the transported liquid with gas bubbles is a major advantage ner such arrangement.

The screw ( 3 ) is driven by a high-speed motor ( 15 ) ben, wherein, as shown in Fig. 3, the motor ( 15 ) is directly connected to the cathode connection ( 13 ) and the anode connection ( 14 ).

This arrangement has the advantage that only an operating voltage for the electro lysis cell and for the motor ( 15 ) has to be supplied. This also ensures that the electrolysis cell is always switched on together with the motor during the etching.

In the example shown, the etching chamber ( 1 ) is separated from the electrolytic cell ( 8 ) only by the anode ( 9 ), so that a special partition in the container ( 16 ) can be saved.

The flow through the electrolytic cell ( 8 ) with the etchant ( 2 ) is given by the fact that openings ( 10 ) are provided at the lower end of the anode ( 9 ) and, on the other hand, the upper edge ( 21 ) of the anode ( 9 ) does not reach the surface of the Etchant ( 2 ) in the etching chamber ( 1 ) is sufficient.

The circulation of the etching liquid ( 2 ) in the electrolysis cell ( 8 ) takes place not only under the influence of the pump flow of the screw spindle ( 3 ), but also through the heat flow which forms when the voltage is applied to the electrolysis cell ( 8 ), but also additionally through the emergence of z. B. of oxygen and ammonia, which rises in the form of gas bubbles and favors the flow.

The copper etched away in the etching chamber ( 1 ) is deposited on the cathode ( 12 ).

A simple and reliable design of a holder for the printed circuit boards ( 18 ) is of particular importance. In the example described, round material is bent as a handle ( 17 ) and as guide rods ( 20 ). Notches ( 19 ), in which the printed circuit board ( 18 ) is held, run on the guide rods ( 20 ).

Of course, it is also possible to provide several such holders ( 19 ) in order to hold several smaller circuit boards. It is also advisable, for. B. rigidly attach the lower bracket ( 19 ) to the guide rods ( 20 ).

It is obvious that this embodiment is only schematically the Er thought ideas and this example in many points and details can be designed differently.

Therefore, this embodiment is only to be understood as such to the Ge thank to describe a simple etching system according to the invention. The advantages are obvious and the absence of any connection lines is not only inexpensive, but also ensures trouble-free work.

Claims (9)

1. Etching system, in particular for etching printed circuit boards, consisting of an etching chamber ( 1 ) which is filled with etching liquid ( 2 ), which is circulated by means of a pump, characterized in that as a pump a motor-driven screw spindle ( 3 ) in a housing ( 4 ) arranged next to the etching chamber ( 1 ) is present. 2. Etching system according to claim 1, characterized in that the screw spin del ( 3 ) pumps the etching liquid ( 2 ) from top to bottom. 3. Etching system according to claim 1 and 2, characterized in that the Ätzkam mer ( 1 ) and the housing ( 4 ) with an inlet ( 5 ) above and a return ( 6 ) are connected below. 4. Etching system according to claim 3, characterized in that the etching chamber ( 1 ) and the housing ( 4 ) have a common partition ( 7 ) which has openings as the inlet ( 5 ) and return ( 6 ). 5. Etching system according to claim 1, characterized in that in addition to the etching chamber ( 1 ) there is an electrolysis cell ( 8 ) which is also flowed through by the etching liquid ( 2 ) under the influence of the screw spindle ( 3 ). 6. Etching system according to claim 1, characterized in that the anode plate ( 9 ) is arranged as a partition between the etching chamber's ( 1 ) and the electrolytic cell ( 8 ). 7. etching system according to claim 6, characterized in that the anode plate ( 9 ) does not sit on the bottom at the bottom or other openings ( 10 ) are present which allow the inflow of the etching liquid ( 2 ) into the electrolysis cell ( 8 ). 8. Etching system according to claim 6, characterized in that the electrolytic cell ( 8 ) has an overflow ( 11 ) for the return of the etching liquid ( 2 ) in the etching chamber ( 1 ) and / or the housing ( 4 ). 9. etching system according to one or more of the preceding claims, characterized in that the etching chamber ( 1 ), the electrolytic cell ( 8 ) and the Ge housing ( 4 ) are arranged in a common container.