Happy's Tech Talk #8: Copper Etchant Regeneration

Copper has become a valuable metal, and with the growth of EV has come higher currents needed in PCB resulting in increased weight of copper in PCBs. This creates the need for increased copper etching and consumption of copper etchants.

Alkaline ammonium chloride and acidic cupric chloride remain the most used etchants with various peroxide-sulfurics as micro-etches. Still in use, but in much smaller applications, are ferric chloride, alkaline ammonium sulfate, alkaline cupric chloride, and sodium persulfate.1,2

Any ammonium compounds in rinse water complicate water treatment as they will chelate any metals in the final effluent and make it more expensive to treat.

Etchant Regeneration Techniques
Karl Dietz wrote on this topic several times in his Tech Talk Series. No less than eight columns were devoted to etching chemistry, but only one went into details about chemical regeneration (TT#92). The etching Tech Talk columns were:

  • TT#92: Etchant Recycling (CircuiTree, May 2003)
  • TT#112: Ammoniacal Etching (Part A) (CircuiTree, January 2005)
  • TT#113: Ammoniacal Etching (Part B) (CircuiTree, January 2005)
  • TT#119: Fine Lines in High Yield (CircuiTree, August 2005)
  • TT#151: Ferric Chloride Etching of Copper (the PCB Magazine, April 2008)
  • TT#158: Fine Line Etching Revisited, Part A (the PCB Magazine November 2008)
  • TT#159: Fine Line Etching Revisited, Part B (the PCB Magazine, December 2008)
  • TT#160: Fine Line Etching Revisited, Part C (the PCB Magazine, January 2009)

Liquid-Liquid Extraction
Liquid-liquid extraction (LLE) or Liquid ion-exchange has been used for metal recovery from mining for many years. But in the early 1970s, a new organic extractant was developed out of wheat by General Mills. This new metal chelating agent is 7-ethyl-undeca-2,4-dione, trademarked by General Mills as LIX64N and LIX65N. This organic is dissolved and mixed with kerosene (~20% dissolution) and has an extremely high affinity for copper and zinc.3

The unique feature of these compounds with respect to metal chelating is that, in the extraction step, the base metal is capable of being loaded to the exclusion of ammonia or chlorides, thereby resulting in essentially a zero Happy_May_Fig1_cap.jpgcarryover of ammonia/chlorides to the stripping step. Moreover, in the stripping step the extractant does not form a salt with the acid present and hence can be recycled directly to the extraction stage without the necessity of further treatment.

The extraction and regeneration process are shown in Figure 1.4

Happy_May_Fig2_cap.jpg

Figure 2 is a diagram of a mixer-separator unit that shows the mixing and separating chamber where the organic phase is less dense and floats on the aqueous phase to extract the copper into the organic phase. Other unit operations equipment used for LLE are sieve tray and bubble-cap towers, but the mixer-separator is the simplest and easiest to maintain.

Happy_May_Fig3_cap.jpg
Figure 3 shows diagrams of an LLE system for printed circuit etching of either alkaline or acid types of etchants with copper recovery. Many of these have been installed over the years. Figure 3a is the mixer-separator unit that strips the copper out of the etchant. In Figure 3b, another mixer-separator unit can strip the copper into the acid electrolyte, whereas in Figure 3c, the copper is plated out as sheets from the copper sulphate electrolyte. Figure 3d is the final mixer-separator that removes copper from the etcher’s rinse water and returns it to the cascade etcher rinses while the organic phase is combined with the etchant extract. All streams are 100% recycled.

Figure 4 shows a typical industrial mixer-separator drawing used for etchant regeneration. Six separate mixer-separators are contained in this one unit. Many times, more than one unit is used for the extraction stage and for Happy_May_Fig4_cap.jpgthe stripping stage, as seen in Figure 1. Figure 5 shows an actual copper recovery unit installed in a printed circuit fabrication facility.5

Conclusion
When the LLE extraction and recovery unit was first designed in 1974 by Hewlett-Packard’s PCB Group for its alkaline etching system in Palo Alto, California, no others were in use. Today, more than 100 units have been installed around the world recovering copper and regenerating their PCB etchants. One of the most recent, installed at Whelen’s GreenSource Fabrication in New Hampshire, recovers over $375,000 in copper every year.

Happy_May_Fig5_cap.jpgThis puts the chemical and water recovery system into a profit generator for the facility. Their daily water use for the 100-panel per hour facility is less than what is used by their toilets.

References

  1. “Improved Inner Layer Etching by Simultaneous Cupric Regeneration and Copper Recovery System,” by Paul Watson, ILS Conference, Leeds, UK, 1999.
  2. CEMCO Etchant Regeneration Brochure for Cupric Chloride, 2 Relay Rd. Waterlooville, Hampshire UK, 1999.
  3. Liquid Ion Exchange in Metal Recovery and Recycling, by Lawrence V. Gallacher.
  4. “New Horizons in Metal Removal And Recovery,” by W. Daniel Ernt, P.E., American Institute of Chemical Engineers Annual Technical Meeting, April 17, 1990.
  5. The MecerTM System Brochure for PCB etchant recycling and copper recovery, Sigmametallextrakton AB, Datavagen 51, Sweden.

This column originally appeared in the May 2022 issue of PCB007 Magazine.

Happy Holden has worked in printed circuit technology since 1970 with Hewlett-Packard, NanYa Westwood, Merix, Foxconn, and Gentex. He is currently a contributing technical editor with I-Connect007, and the author of Automation and Advanced Procedures in PCB Fabrication, and 24 Essential Skills for Engineers.

Back

2022

Happy's Tech Talk #8: Copper Etchant Regeneration

05-31-2022

Copper has become a valuable metal, and with the growth of EV has come higher currents needed in PCB with increasing weight of copper in PCBs. This creates the need for increased copper etching and consumption of copper etchants. Today, in an effort to recoup some of that cost, increasingly more extraction and recovery units are being installed in PCB facilities around the world. Annual profit generation from recovering copper and regenerating PCB etchants has the potential to reach six figures.

View Story

Happy's Tech Talk #7: Next Generation Application Specific Modules

05-02-2022

In 1965, Gordon Moore predicted that the number of transistors that could be packaged into a square inch of space would double every year for the near future. Although his projection was later revised to every 18 months, Moore’s Law has withstood the test of time for five decades. Today, we are beginning to see obstacles to this type of exponential growth due to the inherent limits associated with silicon lithography, packaging of the devices, and component placement on PCBs.

View Story

Happy's Tech Talk #6: Looking at the Process of Repanelization

03-28-2022

I have spent many years in printed circuit fabrication, including nearly 20% of my career in Asia. One problem that concerns all fabricators is the issue of “How many ‘X-outs’ are allowed per assembly sub-panel array? Here are a couple of solutions I have used and encountered in my travels.

View Story

Happy's Tech Talk #5: Advanced Boards for Heterogeneous Integration

03-07-2022

The expansion of IC functionality usually progresses with the shrinking of IC geometries, called “Moore's Law” after Gordon Moore who first coined the phrase. But now that geometries are below 5 nm, the costs and difficulties are creating a barrier to much further advances. So, the solution seems to be to mix IC die on the same substrate as a system-in-package (SiP) that is now called heterogeneous integration (HI).

View Story

Happy's Tech Talk #4: Semi-Additive Processes and Heterogeneous Integration

01-31-2022

The semi-additive processes (SAP) are not new. I first used them with a novel process back in 1978. MacDermid had a novel SAP process called PLADD II (PLAted Additive). It was an anodized aluminum foil applied to laminates that we could easily etch off after drilling and continue with a special electroless copper for thin metallization.

View Story
Back

2021

Happy's Tech Talk #3: Photonic Soldering

12-20-2021

Printed Electronics (PE) continues to be a growing technology. But one of the advantages, as well as a drawback is using low-cost substrates, like paper, that cannot take the temperature of solder paste reflow. Also, the inks need to be cured. One current way to cure the printed inks is with ultraviolet radiation curing, such as used with solder mask or legend inks.

View Story

Happy's Tech Talk #2: Induction Lamination

11-23-2021

Multilayers have been around about as long as the printed circuit. The industry has always used heated hydraulic lamination presses to produce these multilayers, with the introduction of vacuum assist in the 1980s. But recently, with the encouragement of GreenSource Fabrication, induction lamination has been perfected by Chemplate Materials of Spain. Chemplate had introduced the use of induction-pinning by optical alignment of innerlayers for multilayer stackup in the early 2000s. This was to go with another innovative way to laminate innerlayers together—the Italian CEDAL resistance-foil vacuum-press, which had some early adopters.

View Story

Happy’s Tech Talk #1: Vertical Conductive Structures (VeCS)

10-22-2021

The industry has not had many new structures in the last 60 years. Multilayers have continued to evolve with thinner materials, smaller traces / spaces as well as drilled vias. It’s been nearly 40 years since Hewlett-Packard put their first laser-drilled microvia boards into production for their innovative Finstrate process.

View Story
Back

2017

Happy’s Essential Skills: Tip of the Month—The NIST/SEMATECH e-Handbook of Statistical Methods

07-05-2017

In the 1990s, the National Bureau of Standards was distributing a popular statistical document, the Handbook 91, written by Mary Natrella of the NBS Statistical Engineering Laboratory. A request by Patrick Spagon of the Statistical Methods Group of SEMATECH to update the NBS Handbook 91, Experimental Statistics, led to the creation of a project team from NIST and SEMATECH to create a new web-based statistical handbook including statistical software.

View Story
Back

2016

Happy's Essential Skills: Understanding Predictive Engineering

12-16-2016

New product realization and design for manufacturing and assembly (DFM/A) have now started to become more visible as programs that can improve a company’s time-to-market and lower product costs. Many programs are underway by many companies and what is now needed is a framework to coordinate the application of these programs. This column will cover the interactions of DFM/A and the need for development of a new framework to coordinate the trade-offs.

View Story

Happy’s Essential Skills: Technology Awareness and Change

11-22-2016

From Happy Holden: A long-time printed circuit-industry friend of mine, Martin Tarr, an instructor at University of Bolton, UK, is a leading expert on change. He wrote an excellent tutorial for his university course on electronics manufacturing. With permission from Tarr, I am including a portion of it here as the basis of this column, starting after the graph in Figure 2. But first, a few thoughts of my own.

View Story

Happy's Essential Skills: 10-Step Business Plan Process

11-03-2016

It takes more than just a good idea to exploit that brainstorm of yours. Hewlett Packard’s “10-Step Business Plan Process” is the format to present an idea or product in a fashion that will answer most questions that management may have about a product or idea.

View Story

Happy's Essential Skills: Lean Manufacturing

10-19-2016

Lean doesn’t have to exist in manufacturing alone. Lean is a fairly recent principle that can apply to all of our goods and services. For those of you not familiar with Lean, I recommend the free E-book "Survival Is Not Mandatory: 10 Things Every CEO Should Know about Lean" by Steve Williams, a regular columnist for I-Connect007.

View Story

Happy's Essential Skills: Metrics and Dimensional Analysis

10-05-2016

After 20 of my columns, readers probably realize that I am an analytical person. Thus, I dedicate this column to metrics—the method of measuring something. I mentioned the four levels of metrics in my June column "Producibility and Other Figures of Merit." I also introduced the five stages of metrics in the second part of the column "Design for Manufacturing and Assembly, Part 2." This column completes the discussion with a look at dimensionless quantities.

View Story

Happy’s Essential Skills: Recruiting and Interviewing

09-29-2016

Hopefully, your career has progressed to the point that you are empowered to recruit your own team or a key person for your team. There are always technical people looking for better jobs, but many times, the most talented are busy doing their work and not looking for a new opportunity.

View Story

Happy’s Essential Skills: Computer-Aided Manufacturing, Part 2 - Automation Examples

09-22-2016

Semiconductor fabs like to avoid writing custom software to fit all of the idiosyncrasies of individual processing systems. So HP developed PC-10 to handle IC process equipment by separating it into general classes. SECS II was a mandatory prerequisite of the equipment before an interface to PC-10 could be developed.

View Story

Producibility and Other Figures of Merit

06-10-2016

Metrics are data and statistically backed measures. It is always expedient to base decisions on data and metrics, for example, in PCB design. These measures can be density, first-pass yield connectivity or in this context, producibility. These measures are the basis for predicting and planning a printed circuit design. But what if a metric doesn’t exist? Then you can create the next best measure, the Figure of Merit

View Story

Learning Theory/Learning Curves

06-01-2016

Learning is not instantaneous! Nor is progress made in a steady manner, but at a rate that is typified by one of two basic patterns. In some cases, plateaus will be seen in learning curves. These are caused by factors such as fatigue, poor motivation, loss of interest, or needing time to absorb all the material before progressing to new. This column will not go into details of how learning is achieved, but will summarize some of these theories.

View Story

Happy’s Essential Skills: Project/Product Life Cycle

05-18-2016

The product, and or project (process) life cycle (PLC) is fundamental to a corporation intent on developing new products or processes. It sometimes is called the new product introduction (NPI) process but that is only half of the life cycle. There is product support, enhancement and eventually, obsolescence.

View Story
Copyright © 2022 I-Connect007. All rights reserved.