EP0146732B1 - Process and apparatus for separating, for example, copper from a liquid electrolyte introduced into a pluricellular electrolyser - Google Patents

Description

The invention relates to a working method for the deposition of copper from a liquid electrolyte serving as etching liquid by guiding the liquid flow metered through an inlet into a multi-cell electrolysis container, from which it emerges after deposition of the copper from an outlet, the liquid flow in front of one under the Liquid level of the electrolysis container lying inlet passes through a liquid template formed by the liquid flow in a liquid buffer container in order to flow through the individual cells of the electrolysis container with a uniform distribution. The invention further relates to a device for the deposition of copper from a liquid electrolyte serving as an etching liquid using a multi-cell electrolysis container with an inlet below the liquid level to be formed in the electrolysis container for the entry of the liquid electrolyte and outlet for the discharge of the electrolyte as well as an inlet located in front of the inlet Buffer container which is formed by an intermediate wall arranged parallel to the inlet side of the electrolysis container, the lower edge and side edges of which are connected in a liquid-tight manner to the electrolysis container in the manner of a partition, the intermediate wall possibly being provided with inlet openings.

In the case of electrolysis plants which have a plurality of anode or cathode plates connected in series in a common container, the uniform supply or flow through the individual cells is of the greatest importance. Methods and devices for the deposition of copper from electrolytes are known from US Pat. Nos. 3,682,809, 3,558,466 and 4,023,022. are known, in which the electrolyte is evenly passed through a multi-cell electrolysis tank by the liquid stream passing through a liquid reservoir formed by the liquid stream in a liquid buffer tank before entering the electrolysis tank. Due to the uniform deposition of copper from the liquid electrolyte at the electrodes, the deposited copper can then immediately be used again in the etching process. So here it is a recycling process, which among other things should be achieved here.

In one of these known devices, a sensor was in the etching liquid, which is continuously circulated. Even if the sensor is brought into flow-reduced places in the etching container, the measurement result is still so imprecise that the purpose of the invention, namely to obtain an optimal etching speed, is not achieved. Dipping printed circuit boards into the etching liquid changes their physical and chemical composition. It has been found that certain parameters of the chemical and / or physical nature of the etching liquid must be present in order to have an optimal etching speed. The present method is an environmentally friendly etching, i.e. the etching liquid is continuously circulated. It is not replaced, as in known methods, when it is used up, but is regenerated or also contains additives which ensure that an optimal etching rate is always present.

The object of the invention is, based on an absolutely uniform distribution of the liquid electrolyte among the electrodes, to direct the working process and to design the device such that the liquid electrolyte serving as the etching liquid is optimally adjusted with regard to its chemical properties.

The solution to this problem is that, starting from the known working methods for the deposition of copper from a liquid electrolyte by guiding the liquid stream, metered through an inlet into a multi-cell electrolysis container, from which it emerges from an outlet after deposition of the copper, the liquid stream in front of an inlet below the liquid level of the electrolysis container, a liquid reservoir formed by the liquid flow passes through a liquid buffer container in order to flow through the individual cells of the electrolysis container with a uniform distribution, now according to the invention a sensor for adjusting the etching liquid in a bypass to a circulation line the etching liquid is arranged between an etching container and the electrolysis cell, which is connected at adjustable, time intervals via a valve to the circulation line, with a switching phase of the sensor when the valve is closed, i.e. when the etching liquid is at rest.

The device for the deposition of copper from a liquid electrolyte serving as etching liquid using a multi-cell electrolysis tank with an inlet below the liquid level to be formed in the electrolysis tank for the entry of the liquid electrolyte and outlet for the discharge of the electrolyte as well as a buffer tank in front of the inlet, which is connected by a parallel to the inlet side of the electrolysis container arranged partition is formed, the lower edge and side edges of which are connected in a liquid-tight manner to the electrolysis container in the manner of a partition, the partition being optionally provided with inlet openings, characterized in that a sensor in a bypass to one is set for setting the etching liquid Circulation line of the etching liquid is arranged between an etching container and the electrolysis cell, which can be adjusted with the circulation line via a valve time intervals is connectable.

In the new process, the liquid electrolyte enters the container via a liquid reservoir. This liquid charge ensures that the electrodes are acted upon by the liquid electrolyte in a very uniform manner. Since the speed of the liquid flow from the inlet to the outlet is very low, it is important at these low flow speeds to carry out the supply of the liquid flow very evenly on the inlet side and, analogously, also to discharge the liquid flow evenly on the outlet side, so that every square millimeter of the plates - and these are usually very many in such a container - is evenly acted upon by the liquid flow or then a very uniform precipitation occurs. The exact flow-independent measurement and setting of the etching liquid is carried out by a sensor, which is arranged in a bypass for the circulation of the etching liquid between the etching container and the electrolysis cell and is connected to the circulation line at adjustable, time intervals via a valve, the switching phase of the sensor when the valve is closed , ie in the bypass when the etching liquid is at rest.

One no longer measures continuously, as was customary in such processes, but at intervals. The time intervals result from the fact that a sample is taken from the measuring liquid, which is transferred into a measuring container and then this liquid can be measured very precisely, irrespective of the flow, when at rest. Depending on this measurement result, the etching liquid is then regenerated or modified by additives until an optimal etching speed is available.

An embodiment according to the invention is that the sensor is a known float with an inductive or capacitive tap.

It is also expedient for the sensor to be located in an overflow vessel arranged in the bypass line.

This overflow vessel ensures that the amount of sample liquid always remains exactly constant.

It is advisable to arrange the valve in the inlet to the overflow vessel.

In order to ensure automatic operation, it is important that the valve is an electromagnetic valve, the open and closed position of which is program-controlled.

In a preferred embodiment, in which the copper content in the etching liquid is adjusted to a certain level, it is important that the sensor, e.g. B. via an amplifier, the power supply to the electrolytic cell switches.

The electrolysis cell is used for copper deposition, and depending on a set value, one is then able to assign a certain specific weight to the etching liquid according to a certain copper content.

Another possibility is that the sensor, for. B. via a valve and an amplifier that controls the fluid supply to the electrolytic cell.

If you not only want to set the copper content through an electrolytic cell to be switched, but if you choose other reference values that you want to set to achieve an optimal etching speed, then a working method for etching printed circuit boards results from the fact that the etching liquid in the etching container is continuously monitored; The teaching of the invention then consists in that, depending on the number of etchings, additives are added to the etching liquid at intervals until an optimal etching rate is reached. The working method can only be carried out precisely by a sensor monitoring the condition of the etching liquid in a control vessel, the filling of which takes place at selectable, time intervals, and the measuring phase of the sensor being moved to the stationary phase of the measuring liquid in the control vessel.

A preferably used device for uniform distribution of the liquid electrolyte provides a liquid buffer container which is formed by an intermediate wall arranged parallel to the inlet side of the electrolysis container, the upper edge of which is below the liquid level of the electrolytic container, while the lower edge and the side edges of this intermediate wall are also liquid-tight the electrolysis container are connected in the manner of a partition.

You can work with very little design effort if you attach partition walls on the inlet side and expediently also on the outlet side in the electrolysis tank.

You can also adapt with this device, depending on whether you want to load the container from above or below with the liquid electrolyte.

One possibility is that the feed into the liquid buffer container takes place from below under liquid pressure, i.e. that, as it were, a very even distribution takes place under hydraulic pressure.

If you want to load the container from above, it is essential that the feed into the liquid buffer container takes place via a further upstream buffer container which is loaded from above.

The design of the buffer container or the partition walls can be different. One possibility is that the upper edge of the intermediate wall projects above the liquid level of the electrolysis container and inlet openings are arranged in the intermediate wall below the liquid level.

Depending on the size of the electrolysis container and the type of liquid electrolyte, it is also possible for the inlet openings, arranged approximately in the middle of the liquid level, to conduct the liquid flow evenly between the electrodes.

Again, it is possible that instead of many inlet openings, these are combined into a slot. Another possibility is that there are several partition walls forming a siphon-like template.

The use of several partition walls means that the liquid flow will be distributed more and more differently even in a large electrolysis container with as many electrodes.

It is important that the outlet side also has one or more intermediate walls and that the discharge below the liquid level takes place through individual openings and / or slits comparable to that at the inlet.

According to this version, a wide variety of designs can be combined on the inlet side with the outlet side. For example, two partitions could be used on the inlet side and only one partition on the outlet side, or the same distribution devices for the liquid flow could be used on the inlet and outlet sides. Depending on the requirements, one can e.g. B. in the partitions or partitions on the inlet side of the inlet openings above, but still below the liquid level, while they are further down on the outlet side. It is always essential that the liquid enters or exits the electrolysis container, always through openings, slots, overflow edges and the like, which lie below the liquid level.

• Figur 1 zeigt schematisch den Strömungsverlauf in einem Elektrolysebehälter,
• Figur 2 zeigt schematisch einen im Rahmen der Erfindung eingesetzten Elektrolysebehälter,
• Figur 3 zeigt eine andere Ausbildung einer Zwischenwand wie in Figur 2,
• Figur 4 zeigt eine weitere mögliche Ausbildung einer Zwischenwand,
• Figur 5 zeigt schematisch ein Ausführungsbeispiel einer erfindungsgemäßen Vorrichtung mit Ätzbehälter, Elektrolysezelle und Sensor, wobei ein bestimmter Kupfergehalt in der Ätzflüssigkeit einstellbar ist.
• Figur 6 zeigt ganz allgemein die laufende Kontrolle einer Ätzflüssigkeit durch eine Meßanordnung nach der Erfindung, wobei entsprechend Zusätze der Ätzflüssigkeit zugesetzt werden.

Embodiments of the invention are shown in the drawings. Further features of the invention emerge from the drawings and the description for this.

• FIG. 1 schematically shows the flow pattern in an electrolysis container,
• FIG. 2 schematically shows an electrolysis container used in the context of the invention,
• FIG. 3 shows another embodiment of an intermediate wall as in FIG. 2,
• FIG. 4 shows a further possible embodiment of an intermediate wall,
• FIG. 5 schematically shows an exemplary embodiment of a device according to the invention with an etching container, electrolysis cell and sensor, a specific copper content in the etching liquid being adjustable.
• FIG. 6 shows in general the ongoing control of an etching liquid by means of a measuring arrangement according to the invention, additives being added to the etching liquid accordingly.

In FIG. 1, the direction of the arrow 1 schematically shows the liquid flow of the liquid electrolyte through the electrolysis container 3. The liquid flow enters on the inlet side 6 and leaves the container on the outlet side 18. Electrodes 16 are connected in series as anodes or cathodes. The uniform supply or flow through the individual cells is of the utmost importance.

In FIG. 2, which shows an electrolysis container 3 used in the device according to the invention, the liquid flow in the direction of the arrow 1 is fed from above by a feed 14. In this case, in addition to the usual buffer container 5, there must be an upstream buffer container 13 through which the liquid flow flows in the direction of the arrow 24. He then enters the additional intermediate wall 17 flowing around the bottom into the liquid buffer container 5. The liquid buffer container 5 is formed in a manner known per se from an intermediate wall 7, the side edges 10, 11, such as. B. Fig. 3 shows, and the lower edge 9 are liquid-tightly connected to the container 3 so that they form a partition. In this intermediate wall 7 inlet openings 4 are then arranged. These inlet openings can either be arranged above, in the middle or in some way distributed. If necessary, tests will determine how the most uniform loading of the individual plates is achieved during the deposition. It is only essential that the inlet openings are below the liquid level 2. The electrolyte is then passed through the individual cells in the direction of arrow 25 such that the individual electrodes 16 experience an even distribution of the liquid flow. 2, the upper edge 15 of the intermediate wall 7 is above the liquid level 2, so that the inlet openings or slots 4 are below the liquid level 2. It is also possible, as shown in Fig. 3, that the upper edge 8 of the intermediate wall 7 is below the liquid level 2 and the intermediate wall then has no inlet openings. The liquid flow supplied will then flow below the liquid level 2 in the direction of arrow 26 over this edge 8.

It is indicated schematically in FIG. 2 that a lower inlet 12 can also be provided instead of the upper inlet or the upper feed 14. In this case, the upstream buffer container 13 would then be omitted.

In Fig. 4 is shown again in perspective, such as. B. inlet openings 4 can be arranged below the liquid level 2 in the upper region within the intermediate wall 7.

2 also schematically indicates that the outlet side 18 can also be designed accordingly, it being possible to combine individual elements on the inlet side with other elements on the outlet side, but these elements are in themselves the same. In the exemplary embodiment, in order to achieve regulation of the liquid level 2, 20 processes 21 are arranged in an intermediate wall. These processes can in turn be circular, slit-shaped or otherwise adapted to the flow. In the exemplary embodiment, the liquid flow arriving in the direction of the arrow 25 then enters in the direction of the arrow 27 into the buffer container 28 on the outlet side, which can be designed analogously to the buffer container 5 on the inlet side. Another partition 19, which is arranged at a distance 29 from the bottom of the container 3, then allows the outflowing liquid to enter the downstream container 23 in the direction of the arrow 30. An overflow 22 is provided there, that is to say the liquid which now flows out is released in free fall. This overflow automatically ensures that the liquid level 2 remains constant. Although the exemplary embodiment described below can also be applied to an arrangement according to FIGS. 1 to 4, the structure of the measuring device is described using a modified exemplary embodiment for better understanding.

FIG. 5, which shows an exemplary embodiment of the entire device of the invention, schematically shows printed circuit boards 31, which are immersed in the etching container 32 by dipping in the direction of the arrow 43 in a manner known per se for producing electrical circuits. The etching container 32 is connected to an electrolysis cell 33 which, according to the above statements, has a buffer container (not shown). A sensor 34, which in the exemplary embodiment (FIG. 6) has a float 35, is arranged in the bypass 36 of a circulation line 37. As can be seen from FIG. 6, the valve 38, which controls the inflow to an overflow vessel 40 in which the float 35 is located, can be actuated by a program control 42. In the exemplary embodiment, the float has a known inductive tap 39, i.e. the measurement order switches on or off via their contact connections 44 when the contact 39 attached to the float 35, e.g. B. a reed contact from the magnetic field of the excitation coils 45 in the fixed part.

The mode of operation can be seen from FIGS. 5 and 6 as follows:

The etching liquid 46 is drawn in by the pump 48 in the direction of the arrow 47 and thus reaches the circulation line 37. In the exemplary embodiments shown, there is also a water jet pump 49 in the circulation line, which draws in partial quantities of regenerated etching liquid from the electrolysis cell 33 in the direction of the arrow 50. The pump then conveys the partially regenerated etching liquid back into the etching tank 32 in the direction of the arrow 51. The feed to the electrolysis cell 33 takes place via a branch 52 when the valve 53 is open. At intervals, e.g. B. by a program control 42, the valve 38 is opened. As a result, a sample amount is taken from the etching liquid located in the circulation line 37 and is fed into an overflow vessel 40 in the direction of arrow 54 (cf. FIG. 6). The overflow 55 in this vessel ensures that the amount to be measured in the measuring container 56 remains the same. If this measuring container 56 is filled, the excess sample quantity runs again in the direction of arrow 57 into the etching container 32.

Depending on the measurement result, the float 35 now moves in the direction of arrow 58, so that the contacts 45 z. B. switch off the power supply of the electrolytic cell 33, not shown, if the copper content in the etching liquid becomes too high, or switch it on again if it becomes too low.

In addition or also alone, further valves 59, 60 can be switched, which feed additives into the etching container 32 via lines 61, 62 into the etching container 32. Depending on the type of etching liquid and / or the materials used for the printed circuit boards, there are known additives for this in order to bring the etching speed to an optimal level.

Claims (9)

1. Working process for the deposition of copper from a liquid electrolyte serving as an etchant by metered guiding of the stream of liquid through an inlet into a multicell electrolysis vessel (3), from which, after deposition of the copper, it exits through an outlet, the stream of liquid (1) passing through a reservoir of liquid formed by the stream of liquid in a liquid buffer tank (5) upstream of an inlet lying below the level of liquid (2) in the electrolysis vessel (3), in order to flow through the individual cells of the electrolysis vessel (3) with uniform distribution, characterised in that a sensor (34) for regulating the etchant is located in a bypass (36) to a circulation line (37) of the etchant between an etching tank (32) and the electrolysis cell (33) and is connected to the circulation line (37) in adjustable intervals of time via a valve (38), a switching phase of the sensor (34) taking place with the valve (38) closed, i.e. with the etchant at rest.

2. Device for the deposition of copper from a liquid electrolyte serving as an etchant using a multicell electrolysis vessel (3) with, lying below the level of liquid to be obtained in the electrolysis vessel, an inlet for entry of the liquid electrolyte, and an outlet for removal of the electrolyte, as well as a buffer tank (5), upstream of the inlet, formed by a partition (7) located parallel to the inlet side (6) of the electrolysis vessel (3), the lower edge (9) and side edges (10, 11) of the partition forming a liquid-tight connection with the electrolysis vessel (3) in the manner of a dividing wall and the partition (7) being provided with inlet openings (4) if appropriate, characterised in that to regulate the etchant a sensor (34) is located in a bypass (36) to a circulation line (37) of the etchant between an etching tank (32) and the electrolysis cell (33) and can be connected to the circulation line (37) at adjustable intervals of time via a valve (38).

3. Device according to claim 2, characterised in that the top edge (8) of the partition (7) of the electrolysis vessel (3) lies below the level of liquid to be obtained therein.

4. Device according to claim 2 or 3, characterised in that the feed (12) into the liquid buffer tank (5) takes place from the bottom under liquid pressure.

5. Device according to claims 2 to 4, characterised in that the feed into the liquid buffer tank (5) takes place via another buffer tank (13) upstream, which is charged from the top.

6. Device according to claims 2 to 5, characterised in that the sensor (34) is a float with an inductive or capacitive tap (39).

7. Device according to claims 2 to 6, characterised in that the sensor (34) is in an overflow vessel (40) located in the bypass line (36).

8. Device according to claims 2 to 7, characterised in that the valve (38) is located in a feed (41) to the overflow vessel (40).

8. Device according to claim 8, characterised in that the valve (38) is an electromagnetic valve, the opening and closing position of which is programme-controlled (42).

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