WO2007068193A1

WO2007068193A1 - A process for recovering and recycling of waste ammoniacal alkaline copper etchant by using metallic aluminum

Info

Publication number: WO2007068193A1
Application number: PCT/CN2006/003361
Authority: WO
Inventors: Gerald A. Krulik
Original assignee: Daren Technology Limited
Priority date: 2005-12-12
Filing date: 2006-12-11
Publication date: 2007-06-21
Also published as: WO2007068193A8; CN1982505A

Abstract

A process for recovering and recycling of waste ammoniacal alkaline copper etchant by means of using metallic aluminum comprises: employing a control container for control of processing parameters and then providing one or more aluminum-containing reactors to remove copper. Said processing parameters comprise temperature, copper concentration, pH value, specific gravity, ammonia water content, chloride content and circulating rate etc. The reactors can be arranged in series, parallel or series parallel, and optionally heated to remove copper. Optionally, the reactors can have individual filtrating equipment that can reserve solid reaction product. The recycled enchant is suitable for chemical adjustment and reuse.

Description

Method for recycling and recycling waste ammonia-containing alkaline copper etchant using metal aluminum

The present invention relates to a process for recovering and reusing waste ammonia-containing alkaline copper etchants using metallic aluminum which does not substantially increase unwanted soluble by-products.

Background technique

As part of the manufacturing process, the printed circuit board industry typically removes unwanted copper from printed circuit boards using an alkaline copper etchant containing ammonia. The ammonia-containing alkaline copper etchant is a mixture of copper ammonium chloride, ammonium chloride, ammonium hydroxide, ammonium carbonate, and a small amount of other substances. When copper is in the state of divalent (+2) copper, ammonium chloride copper itself is active. Ammonium chloride copper corrodes and dissolves metallic copper to form monovalent (+1) copper ammonium chloride. As a corrosive material, the monovalent copper salt is inactive. The monovalent copper salt is reoxidized to the active etchant or divalent copper by oxygen in the atmosphere.

This etchant is widely used in the production process of printed circuit boards. This etchant is etched at a high rate and a large amount of copper can be retained in the solution after etching. After etching, the maximum copper loading under normal conditions is 105-188 grams of copper per liter (14-25 ounces of copper per gallon). The solution containing copper is not discarded. It is recycled and processed to remove excess copper to obtain new etchants and metallic copper.

In commercial recycling plants, the process of recovering ammonia-containing alkaline copper etchants is complex and expensive. One such method is to contact the waste etchant with a liquid ion exchange (LIX) material dissolved in an organic solvent that is immiscible with water, such as kerosene. This is usually a continuous processing method using a convection device. Also using a convection device, the copper-containing LIX/kerosene mixture is contacted with a sulfuric acid solution. Sulfuric acid extracts copper from the LIX/kerosene mixture to recover the ion exchange material. The copper sulfate/sulfuric acid solution can be used to produce lower priced copper sulfate crystals. Alternatively, the copper sulfate/sulfuric acid solution can be electrolyzed in an electrolysis cell to recover higher valence metal copper.

The yield of discarded gas-containing alkaline copper etchants is very large. Generally, 7 to 10 squares per process The double-sided printed circuit material of the foot produces a gallon of waste etchant. Even a medium-sized factory can produce more than 400,000 liters (100,000 gallons) of waste etchant per year. Because the amount of used ammonia-containing etchant is very large and the recovery is very complicated, the used etchant is transported to an off-site recycling facility for processing. The transport of large amounts of etchant is very expensive and dangerous, and these dangerous goods are also likely to leak.

Commercial alkaline etchant recovery equipment is large and complex. They have a plurality of countercurrent extraction flow columns containing a large amount of recycled etchant, kerosene, hazardous organic complexing agents, sulfuric acid, and copper sulfate. All of these materials are toxic and are very dangerous in the event of accidents and chemical spills. The kerosene solution is also flammable and often poses a fire hazard. If the recovery of copper is achieved by electroplating, a large rectifier with a large power consumption is required.

Another known method for the recovery of ammonia-containing alkaline copper etchants is to use a dedicated electrolytic cell connected to an etching apparatus to remove copper, which is typically processed using two cells with a membrane separator. deal with. Direct electrolysis of ammonia-containing alkaline copper etchants is impractical due to the presence of chlorides, as chlorine and other by-products are produced during electrolysis. Therefore, the industry has changed the chloride system to a solubilized system. However, the use of ammonium hydroxide-reducing copper instead of ammonium chloride copper as the active agent, the etching rate of the etchant becomes very slow. In addition, because the design of such a close-range system is limited by the rate of electrolytic recovery, the etching rate is slowed down, and the actual etching speed is three times slower than that of the copper chloride-based ammonia-containing alkaline copper etchant. Many of the printed circuit manufacturers' ammonia-containing etching equipment are at or near full-load operation, and often need to use two or even three shifts a day. Therefore, the use of this processing method requires three times the expenditure on expensive equipment.

A new processing method has been developed which utilizes metal aluminum to remove copper through a simple, single-step reaction without the generation of harmful impurities and without the use of expensive membrane separators and rectifiers. This method is very effective, it is very fast, and it is very efficient, but the amount of copper recovered per unit of aluminum varies greatly, and it is difficult to control due to the large amount of heat released during the reaction (U.S. Patent No. 5,524, Another method of 780 AX on this basis has some improvements in the control of the reaction rate (U.S. Patent No. 5,556, 553 A).

The above known methods attempt to use concentration in a single can (or a single container) (US patent) US 5, 524, 780 A) or a diluted ammonia-containing copper etchant (U.S. Patent No. 5,556,553 A) to remove copper. The temperature is high and difficult to control during continuous processing, even heating or cooling is required. Therefore, it is necessary to control the processing temperature by slowing down the rate of addition of the reactants or by diluting the method of discarding the etching solution. Summary of the invention

SUMMARY OF THE INVENTION It is an object of the present invention to provide an improved process for recovering ammonia-containing ammonia-containing alkaline copper etchants which is inexpensive, less hazardous, and faster than LIX/electrolysis or direct electrolysis.

SUMMARY OF THE INVENTION The present invention provides an improved process for the copper removal reaction using metallic aluminum, allowing continuous processing of the etchant. In the improved method proposed by the present invention, a separate control tank without metal aluminum can be used to adjust the corresponding process parameters. The process parameters can include temperature, copper concentration, pH, specific gravity, ammonia capacity, chloride content, and circulation rate. Once the relevant process parameters are set, the ammonia-containing etchant solution can be transferred to one or more reaction tanks filled with metal aluminum, in which the dissolved copper becomes solid as the metal aluminum becomes solid aluminum hydroxide. copper.

By using multiple reaction tanks, better reaction control can be achieved and copper can be removed more thoroughly. The exothermic reaction of copper ions with aluminum can be more easily controlled. Even with only one reaction tank, the present invention is capable of removing copper more efficiently and faster without the risk of uncontrolled exothermic reactions. A portion of the flow is returned to the control tank through a bypass loop, allowing for higher flow rates. A large amount of liquid in the reaction tank can be used as a heat absorbing body, providing time for the heating or cooling of the reaction tank having metal aluminum.

In order to more completely remove copper in a continuous manner, multiple reaction vessels may be arranged in any known configuration. The reaction vessels can be simply arranged in series to deliver the product from one tank to the inlet of the next reactor. This configuration does not require a bypass tube loop. The initial tank has the highest concentration of copper and the fastest reaction. With the removal of dissolved copper, the reaction slows down and the used ammonia-containing etching solution can be simply heated to any desired extent to accelerate copper removal to any degree desired. The compensation heating can be an in-line heater, an immersion heater, a water jacket heater or any other means. Reaction tank can be viewed Replace with the situation, where the first row of tanks is replaced the fastest because they are the fastest filled with copper metal. Multiple reaction tanks can be arranged in parallel. All products coming out of the control tank are delivered to all reactors simultaneously. This structure does not completely remove copper from the ammonia-containing etchant because any volume of solution passes only through a single reaction tank. However, this is still useful for the processing of printed circuit boards because a certain amount of copper is required in the new etchant to ensure that the etch is acceptable. The advantage of this configuration is that all of the reactors are replaced at the same time because they are all filled with substantially the same amount of copper metal.

Preferably, the plurality of reaction vessels can be arranged in a manner to mix the flow channels. A good arrangement is to use a high flow rate in series from the control tank to enter the multi-head conduit and then to the reactor tanks arranged in parallel. The products in the tanks arranged in parallel are brought together and pumped in series into a second multi-headed conduit and then split again to the second parallel-arranged reaction tank. After three repetitions, the copper-containing ammonia-containing etchant blend can be filtered and transferred to a storage device or reused. A pump can be used to direct the flow, or multiple smaller pumps can be used.

The hybrid structure provides maximum flexibility in removing copper, which allows for maximum flow and greater copper removal capacity before the reactor tank needs to be refilled and refurbished. In general, the first parallel reaction tanks require frequent replacement because new waste ammonia-containing etchants are first reacted in these tanks. The dissolved copper received in the reaction tanks in the rear row is gradually reduced, so the number of replacements is less.

Another invention is that a filter unit can be optionally used in each reaction tank. The filter unit can be simply a sealed filter bag containing metal aluminum. The copper and aluminum hydroxide reaction products are all solid materials. The input waste ammonia-containing etchant can be simply pumped directly into the bag to react with the metal aluminum. The filter bag retains all of the solid reaction product. This allows the particle-free treated etchant to be discharged from the reaction tank. By using a filter unit in each reaction tank, pump wear and blockage are substantially reduced or eliminated, which provides greater economic benefits.

The use of a filter bag in each reaction tank provides an added benefit. After the metal aluminum is consumed, the filter bag is filled with metallic copper and solid aluminum hydroxide. The reaction tank can be opened and the filter bag assembly can be removed and replaced with a new filter bag assembly. After removing the copper and aluminum hydroxide, the filter bag assembly can be washed and reused, and new aluminum is added. A more efficient method is to remove the entire reaction tank from the row after the aluminum metal is consumed. The new mobile reactor can be simply placed in place, and the recovery of the ammonia-containing etchant can be quickly restored. Used reaction tanks can be refurbished and can be replaced at any convenient time and place. The most economical option is to ship all used reaction vessels to a centralized recycling facility for disposal.

In summary, the method can be improved by simultaneously using one control tank and one or more reaction tanks. Control slots allow for the setting of important process parameters, but are not actually used to remove copper ions. The reaction tank is filled with metallic aluminum, and copper removal occurs in it. A plurality of reaction tanks are simply used in the process, with optional filter structures or temperature adjustment devices inside or outside the reaction tank. detailed description

Although the disclosure herein is specific and detailed, the method is merely illustrative of the invention. Anybody skilled in the art can use these concepts to develop a number of processing methods based on the examples shown.

The test solution is a waste ammonia-containing copper etchant obtained from commercial printed circuit manufacturers. This material

(Ultra traetch50, MacDermid) is usually a commercially available waste ammonia etchant. The original etchant has a pH of 8. 2-8. 8 with about 120-188 g/l of copper. The waste etchant contains different ratios of (1+) copper and (2+) copper, depending on the parameters of the process, and subsequent storage, exposure to the atmosphere, such as different total time, temperature, and cooling time. The etchant starting solution is essentially the same as the used ammonia-containing etchant, and the copper concentration can be as low as 100-120 grams per liter, depending on the manufacturer and process. The etchant uses ammonium chloride copper as the active etchant, so the etchant starting solution must contain copper. The etchant supplement is substantially free of copper. Etchant Supplement Material Safety Data Sheet (MSDS) List: ammonium chloride 10-25 weight percent, ammonium hydroxide 20-40 weight percent, pH 9-10. A new printed circuit manufacturer can start the copper etching step with an etchant starting solution. Thereafter, the used etchant is mixed in the extender to maintain a given pH, specific gravity, and copper content to facilitate etching. For UUraetch50 this For a product, the recommended pH range is 8. 2- 8. 8, the working specific gravity is 1.20- 1. 202, and the copper content of the waste etchant is between about 120 and 188 g/l.

The waste ammonia-containing copper etchant test solution used herein did not directly analyze the ratio of (1+) copper to (2+) copper, and instead compares the amount of aluminum consumed per gram of copper content. For example, if all of the dissolved copper in the waste etchant is in the form of (2+) ammonium chloride, the theoretical consumption of aluminum is 1 gram of aluminum per cubic gram of copper recovered. For example, if all of the dissolved copper in the waste etchant is in the form of (1+) ammonium chloride, theoretically, the consumption of aluminum is 7 grams of copper per gram of copper consumed per gram of recovery. Since (2+) copper ammonium chloride is an active etchant material, it can re-dissolve the copper formed during the reaction with aluminum, thereby reducing the efficiency to under the theoretical value of 3.5 grams of copper per gram of aluminum. . Therefore, the economic recovery method will depend decisively on the value of (2+) ammonium chloride copper and (1+) ammonium chloride.

Economics also depend on the system's feed rate and resistance to shutdown. For example, if the temperature is too high, the solution will boil and spill and stop production. Therefore, it is critical that the recovery system be designed so that the waste etchant is preferably processed continuously. Proper design will optimize copper removal speed while reducing control and minimizing manpower.

Example 1

This is the original design used in the aforementioned patents, which is related to the copper recovery of the process and the recovery of ammonia-containing etchants.

In this test, a single can was used as the reaction vessel. This is a polypropylene slant bottom can. The tank is filled with a fluorocarbon coated stainless steel heater and a fluorocarbon serpentine water cooler. Approximately 24 x 24 x 0. 32 cm, 2,874 grams of 14 pieces of aluminum were placed on the grid in the tank. The tank contained 66 liters of an almost pure ammonia-containing etchant containing 0.1 g/l of copper. The solution is heated to 70 ° C to reach an initial reaction temperature.

The copper-containing copper etchant containing 130 g/L of copper was slowly pumped into the tank at a rate of 2.4 liters per minute to increase the copper concentration at a rate of 4.7 g/min. . While monitoring the temperature, the speed of copper addition is controlled by turning the pump on or off. Cooling was used to keep the temperature below about 75 degrees Celsius. Electrical heating is used only to adjust the initial temperature, and further heating comes from An exothermic reaction between copper ions and aluminum.

The total reaction time was 27 minutes before heating and boiling were uncontrollable. A total of 68. 2 g / liter of copper was pumped in 14. 5 minutes.

After the reaction was completed, copper, remaining aluminum fragments, and aluminum hydroxide precipitate were separated from the solution by filtration.

This is an overall design that uses a single tank for simultaneous control and reaction.

Example 2

This is an example of an improved design. Unlike the previous examples, two types of canisters are used to increase control of the reaction process.

Two types of cans are used in this example, one of which is the control slot. The control tank is not filled with metal aluminum. It is only used to dilute the concentrated etchant and heat it to the operating temperature. If necessary, it is allowed to adjust the corresponding process parameters, including temperature, copper concentration, H value, specific gravity, ammonia capacity, chlorine. Compound content and circulation speed, etc. The second type is the reaction tank. Once the relevant process parameters are set in the control tank, the spent etchant after the adjustment process is output from the control tank and enters the reaction tank to remove copper. The reaction tank is filled with metallic aluminum for reversing the copper ions dissolved in the waste etchant. Alternatively, the metallic aluminum can be placed in a filter bag in a reaction tank or other solid support as long as the solution is free to flow relative to the metallic aluminum. In the present example, the control tank can be the same as the tank structure in the foregoing example, and the reaction tank can be selectively used to be smaller, which makes it easier to control the reaction, and can be cooled by, for example, immersing it in a water bath.

The reactor tanks can be arranged in a simple series to allow the product in one reactor to be transported to the inlet of the next reactor to increase the efficiency of copper removal.

As the dissolved copper is removed, the concentration of copper in the reaction vessel gradually decreases, the reaction rate decreases, and the amount of heat released is also reduced, so that the solution temperature is lowered to such an extent that it is disadvantageous for further removal of copper. If necessary, additional compensation heating can be provided to the reaction vessel to allow the reaction solution to be simply heated to any desired extent to force copper removal to any degree desired. The compensation heating can be an in-line heater, an immersion heater, a water jacket heater or any other means.

Example 3 This example is an example of an improved design proposed on the basis of an example suitable for large-scale continuous copper removal. In this example, the reaction tanks are arranged in a mixed manner to increase control and efficiency.

As in the previous example, the control tank is not filled with metallic aluminum, only used to dilute the concentrated etchant and heat it to the operating temperature, allowing adjustment of the corresponding process parameters, including temperature, copper concentration, pH, specific gravity, if required. , ammonia water capacity, chloride content and circulation speed.

Once the relevant process parameters are set in the control tank, the spent etchant after the adjustment process is output from the control tank and pumped through the first multi-head conduit to a plurality of parallel reaction tanks of the first row, for example 5 In a parallel reaction tank. Thus each reactor in this row has essentially the same amount of waste etchant. The products coming out of each of the reaction tanks of the first row are collected into the first sump or the collection tank.

This example uses a bypass loop. The purpose of the bypass loop is to allow control of the concentration of copper in the control tank. The bypass circulation circuit is disposed at the outlet of the first sump, allowing a portion of the flow to flow back to the control tank, and the remaining flow to the second plurality of conduits of the second row of reaction vessels. If the concentration of copper in the control bath is required to be 20% of the concentration of copper in the waste etchant, then the product coming out of the first row of reactors is only 20°/. The system can be drained and other concentrations of copper will continuously accumulate in the control tank. Alternatively, two pumps can be used to simultaneously add new etchant and waste etchant to the control tank at a fixed ratio, but this is not economical relative to the use of a bypass loop.

The sump can be provided with a cooler; a cooler or radiator can be added to the loop of the bypass loop back to the control tank; or other cooling devices can be used if needed. The most efficient heating is the use of an in-line heater that is mounted to the lower end of the branch circuit leading to the bypass loop of the second multi-head conduit.

To demonstrate the process, it is assumed that a 5 liter/minute waste etchant is pumped into the control tank. It is assumed that the concentration of the copper in the control tank is desirably 20% of the concentration in the waste etchant. The diluted solution was pumped from the control tank and entered the first row of reaction tanks at a rate of 25 liters per minute. If five reactors were used in the first row, each reactor received 5 liters per minute of diluted etchant for reaction with the metal aluminum. The first collection tank collects a mixed stream of products discharged from the five reaction tanks of the first row at a flow rate of 25 liters/min. It is then pumped into the 5 reaction tanks of the second row. The bypass loop is adjusted to flow 20 liters/minute of flow in the first sump back to the control tank. A flow rate of 5 liters per minute was allowed to flow to the 5 reaction tanks of the second row. This keeps the concentration of copper in the control tank constant. The cooler can be selected to be placed in the control tank or bypass loop.

If desired, a flow rate of 5 liters/minute to the second row of 5 reactors can be pumped through an in-line heater to increase the temperature. The flow of solution through the second row of reactors will be only 1 liter per minute per tank, which results in a residence time five times that of the first row of tanks. The concentration of copper entering the second row of tanks is much lower, so the overall residence time for the reaction with the metal aluminum is longer and, optionally, the reaction temperature is higher, which will cause most of the remaining copper to precipitate.

The process is repeated again, except that no additional bypass loops are required. The temperature can be further raised in the third or even rear reaction tank to obtain any desired final copper concentration.

Example 4

The reaction products of copper ions and aluminum metal are copper metal and aluminum hydroxide. Copper metal has a high specific gravity and is not moved by the flow rate. Although aluminum can be placed on any bracket to allow the solution to come into contact with it freely, this may also cause problems because the metal aluminum is loaded in a block, sheet, sphere or other shape and is fixed by the bracket. Make it not carried away by the flow described. However, its product, aluminum hydroxide, is light and fluffy, and is limited by special methods, which can be carried by flow to different reaction tanks.

A large amount of aluminum hydroxide is a drawback for any large-scale continuous production process unless it is limited in some way. If free flow is allowed, the flow of aluminum hydroxide between the can and the can gradually increases with the removal of copper. It will accumulate in low flow areas, which will increase pump wear, reduce flow and increase pressure.

Another example of an improved design is suitable for large scale continuous copper removal, which is related to the structure of the reaction tank.

The system design is further improved to prevent the movement of the aluminum hydroxide reaction product if the metal aluminum is placed in a porous container. One suitable container is a porous filter bag, such as 25 to 100 micron polypropylene. This can be tightly closed after the metal is added and has an inlet for the copper-containing etchant. The etchant that reacts will flow freely through the bag while copper metal, aluminum metal and aluminum hydroxide remain in the filter bag. This prevents excessive pump wear and pump reversal Pressure, and eliminates pipe blockage and deposits in the tank. Therefore, in the end, it is only necessary to use the end filter structure to filter out the particles that have been leaked from the main filter structure, and the etchant that needs to be finally recovered is obtained.

Example 5

The reaction products of copper ions and aluminum metal are copper metal and aluminum hydroxide. The metal aluminum in the reaction tank is finally substantially depleted and filled with copper metal and aluminum hydroxide. If the filter bag is not used, the entire reaction tank must be removed for maintenance and cleaning.

Another benefit of using a filter bag is related to the repair of the reaction tank. The filter bag can be easily removed from the reaction tank and replaced with a new bag containing metal aluminum. Old filter bags can be disposed of in situ or processed on a centralized reprocessing equipment to recover unused aluminum, copper, and aluminum hydroxide.

The filter bag is porous and difficult to drain and dry. The remaining ammonia vapor will cause trouble after vaporization. An alternative improvement to this process is the use of a transportable, replaceable reaction tank.

A more efficient method is to remove the entire reaction tank from the row after the aluminum metal is consumed. The new mobile reactor can be placed in place simply, and the recovery of the ammonia-containing etchant can be recovered very quickly. Used reaction tanks can be refurbished and can be replaced at any convenient time and place. The most economical option is to ship all used reaction tanks to a centralized recycling facility for disposal. Another example of such an improved design is particularly suitable for large scale continuous copper removal.

The reaction tank used in this example is designed to be mobile, easy to transport, easy to remove from the production line, emptied and rinsed, and can be transported or moved to any desired processing location. If the used reaction tank is essentially dry and sealed, it will not pose any environmental hazard. The lost production time is reduced because the cans can be easily disassembled and replaced.

Of course, the reaction tank can also be designed to be non-mobile for replenishing aluminum locally and removing reaction products.

Claims

Claim

A method of recovering and reusing waste ammonia-containing alkaline copper etchant using metal aluminum, comprising controlling a process parameter using a control cell, and then using one or more separate reaction vessels containing aluminum to remove copper.

The method according to claim 1, wherein the control tank is used to control process parameters affecting the etchant, including: temperature, copper concentration, pH value, specific gravity, ammonia water capacity, chloride content, and circulation speed. .

3. The method of claim 1 wherein the control tank uses heating or cooling to maintain an effective reaction temperature for treating the etchant.

The method of claim 1 wherein the control tank maintains an effective copper concentration by controlling the amount of input of the single agent and the circulating flow rate.

The method of claim 1 wherein the control tank feeds at least one reaction tank carrying aluminum for removing copper from the etchant.

The method according to claim 1, wherein the control tank is fed to a plurality of reaction tanks for carrying aluminum for removing copper from the etchant.

7. The method of claim 6 wherein the control tank feeds a plurality of reaction tanks carrying aluminum for copper removal, the reaction tanks being accelerated using one or more auxiliary temperature control devices The rate at which copper is removed from the etchant.

8. A method according to claim 6 wherein the reaction tank is designed to be portable for replenishing aluminum at different locations and removing reaction products.

9. A method according to claim 6 wherein the reaction tank is designed to be non-mobile for replenishing aluminum locally and removing reaction products.

10. The method of claim 6 wherein the control tank is fed to a plurality of reactor tanks arranged in series.

11. The method of claim 6 wherein the control tank is fed to a plurality of reaction vessels arranged in parallel.

12. The method of claim 6 wherein the control tank is fed to a plurality of mixing tanks.

13. A method according to claim 5 wherein the reaction vessel uses a separate filtration structure to remove solid matter from the etchant.

14. The method of claim 13 wherein a filter bag is used in the reaction tank.

15. The method of claim 13 wherein the reaction tank uses a cross flow filtration structure.

16. The method of claim 5 wherein the reaction tank removes solid matter from the etchant using a terminal filtration structure.

17. The method of claim 5 wherein the reaction vessel removes solid matter from the etchant using a deposition process.