DE19815288A1 - Process for the energy-saving and wastewater-free treatment of ammoniacal metal solution from the etching process for the production of printed circuit boards - Google Patents

Abstract

The invention relates to a method for preparing alkaline etching solutions containing metal, whereby a liquid-liquid extraction is carried out, the etching solution forms a heavy phase, an organic solution forms a light phase and the metal ions are removed from the etching solution. Mixing and separation of the heavy and light phases are coalesced at each stage of extraction. The extract phase is washed and the alkaline component and metal component are recovered from the extract phase. The alkaline component is removed from the washing liquid, which is loaded with said component by means of stripping.

Description

Alkaline etching solution is used for special PCB manufacturing processes used. It is primarily used for circuit boards where the Copper conductor tracks with metals such as tin, tin / lead, nickel / tin or gold were protected against etching. These metals are like acidic etchants Copper chloride or iron chloride attacked. The alkaline etching medium will used in all etch-resistant layers and all photoresists that are do not dissolve in the alkaline range.

Alkaline caustic solution contains free ammonia and one or more Ammonium salts such as ammonium chloride, ammonium carbonate, ammonium bicarbonate, ammonium sulfate. The copper rises during the etching concentration in the etching solution and the etching speed decreases to to standstill at approx. 170 g / l. The used ammoniacal caustic solution can after a liquid-liquid extraction process through which the copper is extracted from the etchant after restoring the had Setpoint parameters can be used again.

The following process steps were mentioned in European Patent 0 638 662 A1:

• 1) Extraction of the metal ions from the used etching solution using the liquid ion exchanger;
• 2) Washing out the ammonia from the liquid ion exchanger with Wash water containing a small amount of hydrochloric acid;
• 3) evaporation of the wash water;
• 4) crystallization of the salt after evaporation;
• 5) filtration of the regenerated etching solution;
• 6) Add the missing amounts of chemicals to the regenerated Caustic solution;
• 7) Re-extraction of the copper ions from the one loaded with copper ions liquid ion exchanger with dilute sulfuric acid;
• 8) washing out the liquid ion exchanger with washing water;
• 9) Wash water neutralization using lime milk;
• 10) filtering the gypsum-containing washing water;
• 11) Electrolytic copper recovery.

Although this process is state of the art in facto recycling technology On the other hand, it is so energy-intensive that an economy use is significantly restricted and has problems, which practically prevent a trouble-free process flow.  

Energy-intensive due to steps 3) and 4),
the evaporation of the wash water and the corresponding subsequent crystallization of the concentrate.

These steps, used to avoid contaminated wastewater, are beneficial socially unacceptable.

The use of a crystallizer causes the overall price to become more expensive location and also of the procedure.

Also uneconomical because of step 2),
the unnecessary conversion of ammonia to ammonium salt.

Ammonia is a necessary component of the basic etching solution. Through the Converting the ammonia to ammonium salt must replace the ammonia become.

The excess ammonium chloride that forms from the process (Crystallization) must be disposed of: hazardous waste.

Problematic due to step 9),
the practiced reuse in the process of the sulfate-containing washing water neutralized with lime milk. The circulation of the treated water carried out at this point is inevitably followed by gypsum precipitation in the system according to the Solubility Products Act.

The precipitation of calcium sulfate (gypsum) in the process complicates the desired phase separation of the mixed solutions (liquid ions from exchanger in the diluent and aqueous mixed solution phase) due to Ver Soiling and soaping of the phase separation area considerable.

The process-related chemical and possibly copper ions gypsum with plaster attracts another not inconsiderable special waste disposal compulsory obligation.

The invention has for its object to provide a method for liquid-liquid To develop extraction that is energy-saving, wastewater-free, inexpensive, does not have the problems described above and is not environmentally expires.

Process steps according to the invention

• a) extraction of the metal ions from the used etching solution using the liquid ion exchanger, a 30 vol% solution from Extrak tion agent of the aldoxime and / or the ketoxime complexing agents in kerosene-like liquid agent;
• b) removing the traces of the organic phase from the regenerated Etching solution using a coalescence separator and activated carbon adsorber;
• c) Washing out the ammonia and removing the traces of etching solution from the liquid ion exchanger using water;  
• d) recovering the ammonia from the wash water using a vacuum stripper;
• e) metering in the necessary consume during the etching process chemicals in the regenerated caustic solution (recovery the setpoint parameters);
• f) filtration of the finished etching solution;
• g) re-extraction phase as regeneration of the complexing agents organic Light phase mixed solution using dilute acid (electrolyte solution);
• h) removing the traces of the organic phase from the electrolyte solution using a coalescence separator and activated carbon adsorber;
• i) washing out the liquid ion exchanger to remove the electro traces of lytic solution using wash water from the 1st wash Ammonia stripping process, but not completely free of ammonia;
• k) electrolytic copper recovery;
• l) removal of the ammonium sulfate from the wash water of the second Wash before reuse.

A device for Liquid-liquid extraction used, in which the solvent phase is easy phase solution and the raffinate phase as the secondary phase is difficult is phase solution, whereby a multi-stage tower mixture room, separator, Integrated coalescer, conveyor, mixing and feeding device includes and the solution phase mixing takes place by means of a static mixer.

The integrated coalescer allows considerable volume reduction and Shortening the separation time.

The use of static mixers allows everyone to be eliminated Stirrer organs and thus their storage, sealing and ent speaking maintenance.

This allows the procedure to be carried out in a proportionate manner limited phase separation time to a volume-limiting, piping restrictive, space saving and very low maintenance way, therefore also economical in facto device.

Example: Treatment in the extraction process of ammonium copper Chloride, loaded with up to 160 g / l copper (called used etching solution) the ammonium chloride etching process of the electronics and printed circuit board industry.

Process for preparing ammoniacal metal solution from the conductor plate etching process that involves the extraction and re-extraction processes in stages counterflow and reuse of the washing water.

The embodiment of the description on which the following description is based Invention, which is intended to have exemplary and non-limiting character shown in figure. The two illustrated in the drawing Tower batteries are identical. The lower and intermediate parts of the Towers are intended for extraction or re-extraction, the upper tower parts are there for the respective washing processes. With arrows shown in bold the transport of the aqueous heavy phase solutions is shown, while the thin arrows transport the organic light phase solution Show. The small, thin arrows indicate the continuation of the stripped ammonia.

(Tu-Tz-To) Separation rooms, filled with packing material, contain the respective stacked mixed-state holding rooms (Gu-Gz-Go)
(Gu-Gz) Under and intermediate mixed state hold spaces are there for the two times mixed preservation of spent etching solution and organic light phase solution
(Go) Upper mixture state holding space is there for the time mixture preservation of the mixture of organic light phase solution with water
(E) Multi-stage (Eu-Ez-Eo) pump feed tower, connected to the respective overflow pipe of the organic light phase solution (2-4-6)
(SM) Conveying, Mixing, Introducing and Mixture Storage Device (uSM-zSM-oSM)
(Kp) Coalescence pack for the coalization of the mixed phase dispersions and possible unstable emulsions
(Wt) heat exchanger for preheating the ammonia-containing wash water from the 1st wash
(As) ammonia vacuum stripper
(KKÄ) Candle-tipped coalescer of the etching solution
(KKS) Candle-tipped coalescer of the electrolyte solution
(AkÄ) activated carbon adsorber of the etching solution
(AkS) activated carbon adsorber of the electrolyte solution
(F) Filter for low-copper electrolyte
(El) electrolyte bath
(Se) sulfate precipitation bath
(fWw) feed pipe for make-up water.

Description of the procedural steps and procedures Procedural step

• a) Extraction of the metal ions from the used etching solution using the liquid ion exchanger.
  Two-stage extraction of the metal ions from the aqueous spent etchant ammonium-copper-chloride (aqueous heavy phase), by mixing using a static mixer with a 30 vol% solution of extractant of the aldoxime and / or the ketoxime complexing agent in kerosene-like liquid (organic light phase solution ).
  • a1.) In each case pre-coalization of the aqueous heavy phase / organic light phase solution in a correspondingly integrated coalescer, equipped with a suitable wire-knitted or fiber-knitted coalescence pack. Elimination of possible unstable emulsions.
  • a2.) Separation of the two mixture phases in the corresponding separation space filled with packing.

Process flow

Aqueous heavy metal phase is fed through a pipe connection ( 1 ) into the static mixer (zSM) of the intermediate tower (Tz). There it is mixed together with the corresponding amount of partially loaded organic light phase solution from the intermediate stage (Ez) of the pump feed tower and part of the phase mixture from the lowest point of the mixture state holding space (Gz). The resulting phase mixture is conveyed further and remains in the mixture state holding space (Gz) for the prescribed time and is kept in the mixture state by means of a corresponding hydraulic stirrer device. The overflow takes place through pipe ( 9 ). After the phase coalization in a coalescence packing (Kp) and as far as possible a complete phase separation in the intermediate separation space (Tz), the aqueous heavy phase solution, which is now partially metal-laden, passes through the drain pipe ( 3 ) into the static mixing and conveying device (uSM) of the intermediate tower (Tu). The organic metal phase solution, which is now fully loaded with metal, passes through the overflow pipe ( 6 ) into the upper stage (Eo) of the pump feed tower (E). From there it is transported to the washing process c).

The partially metal-contaminated aqueous heavy phase solution from ( 3 ) is mixed in the static mixing and conveying device (uSM) with metal-free organic light phase solution from the lower part (Eu) of the pump feed tower (E) and with part of the mixture from the lowest point of the mixture state holding space ( Gu) mixed together. The resulting phase mixture is conveyed onward and kept in the mixed state in the mixed state holding space (Gu) by means of a corresponding hydraulic stirrer device. The overflow takes place through pipe ( 8 ). After the phase coalization in a coalescence packing (Kp) and as far as possible a complete phase separation in the intermediate separation area (Tu), the partially loaded organic light phase solution passes through the overflow pipe ( 4 ) into the intermediate stage (Ez) of the pump feed tower (E).

The now metal-free aqueous heavy phase solution flows through tube ( 11 ) to process step b).

Process step / process sequence

• b) Removal of traces of the organic light phase from the regenerated etching solution (metal-free aqueous heavy phase solution).
  • b1.) Coalization in coalescence candle (KKA) and removal of the possibly still contained organic particles from the demetallized etching solution.
    The organic light phase solution accumulated in the upper part of the coalescer is passed through pipe ( 15 ) for further use.
  • b2.) Activated carbon adsorption of traces of the organic light phase. Demetallized etching solution is passed through activated carbon adsorber (AkA) before the chemical content target parameter is reset, because otherwise possible even the smallest organic light solution particles contained in the etching system would make the etching process extremely difficult and would reduce the quality of the etched boards.

After the further treatment phases e) have been carried out, the necessary chemicals consumed during the etching process (Restoration of the setpoint parameters) and process step f) (Filtration of the finished etching solution). Then the recycled etching solution is ready for Reuse.

Procedural step

• c) Washing process of the heavily metal-laden, ammonia-laden organic light phase solution with traces of etching solution.
  • c1.) Pre-coalization of the wash water loaded with ammonia and the copper-loaded light phase solution in a correspondingly integrated coalescer, equipped with a suitable coalescence pack. Elimination of possible unstable emulsions.
  • c2.) Separation of the two phases in the corresponding separation room.

Process flow

Organic light phase solution heavily contaminated with ammonia and containing traces of caustic solution, conveyed from (Eo) accordingly, is fed into (oSM) with water through pipe ( 7 ) and mixed together with a mixture of parts from the lowest point of the mixture state holding space (Go). The resulting phase mixture is conveyed further and kept in the mixture state in the mixture state holding space (Go) by means of a corresponding hydraulic stirrer device. The overflow takes place through pipe ( 10 ), thus it is freed from absorbed ammonia and adhering alkaline traces. After Phasenkoalisierung in Koaleszenzpackung (Kp) and as far as possible complete phase separation in the upper separation space (To), the organic light-phase solution passes through the overflow pipe (2/2 R) to the lower stage (EUR) of the pump feeding tower (ER) of the method Trittes g) (Reextraktionsphase as Regeneration of the organic light phase solution using dilute acid (electrolyte solution).

The wash water now loaded with ammonium / ammonia passes through ( 5 ) to process step d).

Procedural step

• d) Recovering the ammonia from the wash water using a vacuum stripper.
  Stripping the ammonia from the washing water loaded with ammonia and ammonium chloride traces from the first washing process and supplying the stripped ammonia into the converted etching solution before the setpoint parameter restoration.

Process flow

Washing water loaded with ammonia from the drain pipe ( 5 ) through the heat exchanger (Wt) reaches the ammonia vacuum stripper (As). After the ammonia stripping process, this is piped ( 12 ) through heat exchangers (Wt) to the sulfate wash of the reextraction tower. Abge cooled ammonia is mixed through tube ( 14 ) in tube ( 13 ) with etchant. Pipe ( 13 ) leads to the setpoint adjustment.

Procedural step

• e) Dosing the necessary to consume during the etching process the chemicals in the regenerated caustic solution (restoration of the ge have setpoint parameters).
• f) Filtration of the finished etching solution.

Procedural step

• g) Two-stage re-extraction phase as regeneration of the complexing agent organic light phase mixed solution by means of dilute acid (electrolyte solution).
  • g1.) In each case precoalization of the copper-containing electrolyte solution / light phase solution in a correspondingly integrated coalescer, equipped with a suitable coalescence pack. This eliminates possible unstable emulsions.
  • g2.) Separation of the two mixture phases in the corresponding separation room.

Process flow

The structure of the re-extraction tower (R) is identical to that of the extraction tower (E). The parts correspond to those of the extraction tower, also have the same numbers and are marked with an added letter "R". As far as the parts and functions are the same, they will not be described again. Instead of the used metal-containing etching agent, an aqueous sulfate-containing electrolyte solution is fed through the feed pipe ( 1 R). The drain pipe ( 11 R) is intended for the discharge of copper sulfate through an additional candle coalescer (KKS) and activated carbon adsorber (AkS) into an electrolyte bath (EI), from which a low-copper electrolyte solution reaches the feed pipe ( 1 R) via a filter (F) .

Process step / process sequence

• h) Removing the traces of the organic phase from the electrolyte solution using a coalescence separator and activated carbon adsorber.
  • h1.) Coalization by means of a corresponding coalescence candle (KKS) and removal of the organic copper-free light phase solution traces from the copper-containing electrolyte solution.
    Light phase solution is passed through tube ( 15 R) for further use.
  • h2.) Adsorption of the organic light phase from the copper sulfate (electrolyte) upstream of the electrolyte bath feed using activated carbon adsorber (AKS) to prevent accumulation in the electrolyte bath causing a reduction in the electrolyte bath efficiency and, in extreme cases, floating on the electrolyte surface with possible anodes / cathodes -Short circuit can lead to surface ignition.

Procedural step

• i) Washing out the stripped low-metal organic light phase solution by means of washing water from the 1st washing process after ammonia stripping, but not completely free of ammonia.
  • i1.) In each case precoalization of the copper-containing electrolyte solution / copper-free light-phase solution in a correspondingly integrated coalescer, equipped with a coalescence packing. Elimination of possible unstable emulsion.
  • i2.) Separation of the two mixture phases in the corresponding separation room.
  • i3.) Wash water treatment before reuse to remove traces of chemicals.

Process flow

This takes place in exactly the same way as the washing processes in the extraction phase, with the exception of the washing water, which arrives in the feed pipe ( 7 R) after ammonia stripping from the heat exchanger (Wt) to the washing process, prior to coalition and corresponding separation and through pipe ( 5 R) to the (Se ) Sulphate precipitation bath, process step 1).

Process step / process sequence

• k) Electrolytic copper recovery in electrolytic bath (EI), (F) filter of low-copper electrolysis, through tube ( 1 R) for reuse in (zSMR).

Process step / process sequence

• l) removal of the ammonium sulfate from the wash water of the second wash before reuse by means of a precipitation bath (Se).
  There it is merged with barium chloride. This creates barium sulfate and sulfate-free, reusable wash water for the purpose. Barium sulfate is a commercially available chemical product.

Claims (15)

1. A process for preparing alkaline, metal-containing etching solution, in which a liquid-liquid extraction is carried out,
the etching solution forming the heavy phase and an organic solution the light phase
and the metal ions are removed from the etching solution,
wherein the heavy and light phase solution is coalesced in each extraction stage,
the extraction phase is washed and the alkaline load and the metal component are recovered from the extraction phase and the alkaline load of the washing liquid is removed by stripping. 2. The method according to claim 1, characterized in that the alkaline loading of the washing liquid by vacuum stripping Will get removed. 3. The method according to claim 1 and 2, characterized in that the removed alkaline load cooled and the regenerated Etching solution is supplied. 4. The method according to any one of claims 1 to 3, characterized in that the washing liquid after removing the alkaline load recovery of the metal component is used. 5. The method according to any one of claims 1 to 4, characterized in that in the recovery of the metal component the sulfate load by precipitation reaction from that used for the extraction phase Washing liquid is removed. 6. The method according to any one of claims 1 to 5, characterized in that the washing liquid after removing the sulfate load by the Precipitation reaction is used to wash the extraction phase. 7. The method according to any one of claims 1 to 6, characterized in that water is used as the washing liquid. 8. The method according to any one of claims 1 to 7, characterized in that the metal component from the metal-containing extraction phase in a liquid-liquid re-extraction using diluted Acid electrolyte solution is removed. 9. The method according to claim 8, characterized in that the extraction phase after removal of the metal component liquid-liquid re-extraction as a light phase solution for liquid Liquid extraction is used again.   10. The method according to any one of claims 8 or 9, characterized in that by means of the metal-containing electrolyte solution of the metal component Electrolysis is removed and recovered. 11. The method according to claim 10, characterized in that the electrolyte solution after removal of the metal component for the Liquid-liquid re-extraction is used again. 12. The method according to any one of claims 1 to 11, characterized in that the electrolyte solution after re-extraction through coalescers and activated carbon adsorbers from traces of organic Light phase solution is freed. 13. The method according to any one of claims 1 to 12, characterized in that in each re-extraction stage Coalescence separation of the heavy and light phase solution carried out becomes. 14. The method according to any one of claims 1 to 6, characterized in that the etching solution after extraction by Coalescers and activated carbon adsorbers from traces of organic Light phase solution is freed. 15. Device for processing alkaline metal-containing etching solutions, in which a liquid-liquid extraction is carried out,
an organic light solution being conducted in countercurrent to the etching solution
and the metal ions are removed from the etching solution, in particular for carrying out the method according to one of claims 1 to 14, comprising a coalescence separation device for the light and heavy phase in each extraction and washing stage,
a hydraulic stirrer device,
a washing stage or countercurrent washing stage for the extraction and re-extraction phase,
a device for recovering the alkaline load and the metal component from the extraction phase and
a stripping device for the removal of the alkaline load of the washing liquid.