How ALS2 lifts precious metals from solder mask and coatings
Australia generates more than twenty kilograms of electronic waste per person each year, putting it near the top of OECD rankings for per-capita discarded electronics. With old laptops stacking up in Melbourne offices, mobile phones discarded across Sydney, and televisions piling in Brisbane depots, the volume of e-waste handled by recyclers is climbing steadily. The National Television and Computer Recycling Scheme has shaped a baseline infrastructure, yet much of the country's printed circuit board material still ends up being exported, downcycled, or sent to landfill because the metals inside are locked behind protective layers.
Precious metals in electronics are concentrated on printed circuit boards. Gold sits on connector fingers and bond pads, silver appears in conductive traces and internal vias, and palladium turns up in multilayer ceramic capacitors and certain surface finishes. When a board reaches a refinery, the goal is simple in principle: liberate the metallic fraction so it can be sorted, smelted, or chemically extracted. In practice, two thin polymer layers routinely stand in the way. Solder mask covers almost every modern board, sealing copper traces beneath a UV-cured epoxy or acrylate film. Conformal coatings add a second barrier — silicone, urethane, or parylene — applied to protect assemblies from humidity and contamination.
Ikoi S.p.A.'s ALS2 project was set up under the European Union's Horizon 2020 programme to confront exactly this kind of obstacle. The acronym stands for acidless separation, and the technology is positioned as a safer, cleaner alternative to the aqua regia and cyanide routes that dominate traditional precious-metal refining. ALS2 is aimed squarely at the recovery of gold, silver, palladium and related metals from WEEE streams, with a focus on compact plants that can be installed close to where electronics are collected.
The remainder of this article walks through what solder mask and conformal coatings actually do on a board, why they frustrate conventional leaching, how ALS2 liberates metals without aggressive chemicals, and what the approach could mean for processors in Australia looking to capture more value from every tonne of incoming scrap.
The hidden barrier inside every circuit board
Solder mask is not optional. It is printed onto nearly every commercial PCB to keep solder from bridging between adjacent pads during assembly. Without it, modern surface-mount production lines would fail reliability tests within days. The cured mask is chemically resistant by design: it survives reflow temperatures above 260 °C and shrugs off the fluxes used during soldering. Those same properties make it stubbornly inert when a recycler tries to attack the underlying copper or the gold plating on top.
Conformal coatings go a step further. They are brushed, dipped, or vapor-deposited over finished assemblies to guard against moisture, dust, and salt spray. Parylene variants can be less than a micron thick, while acrylic and urethane coatings may reach fifty or sixty microns. Once a board has been deployed in the field, these coatings age, harden, and bond more tightly to the underlying surfaces. A recycler looking at a smartphone mainboard or a server backplane sees a sealed sandwich of polymers, glass fibre, copper, and trace quantities of precious metals — and the polymers are on the outside.
Why solder mask and conformal coatings confound conventional refining
Acid-based refining relies on direct contact between the metal surface and a reagent such as nitric acid, aqua regia, or sodium cyanide. A continuous polymer film stops that contact almost completely. In practice, refiners have responded in three ways, each with drawbacks. Some pre-roast boards in furnaces to burn off coatings, which loses energy and vents volatiles into off-gas systems. Others shred boards and rely on prolonged leaching times, accepting lower yields because reagent penetration is uneven. A third group dissolves the entire board, then separates metals downstream — a route that consumes enormous amounts of acid and produces wastewater laden with copper, tin, and dissolved organics.
The Australian context sharpens these concerns. Processors in New South Wales and Victoria operate under strict environmental licensing through the state Environment Protection Authorities, and any expansion of acid leaching capacity triggers scrutiny over effluent, occupational exposure, and stack emissions. Avoiding the acid bath altogether therefore carries immediate operational advantages, particularly for smaller regional facilities that cannot afford complex wastewater treatment trains.
The ALS2 approach without acids or strong oxidants
ALS2 is built around a physical-chemical route that separates metallic and non-metallic fractions of a board without dissolving anything in aggressive reagents. The core idea is to weaken the bond between the metallic layer and the polymer substrate so that the two can be lifted apart mechanically. Instead of attacking the metal, the process targets the interface itself.
The technology relies on controlled thermal-mechanical action combined with a proprietary conditioning step that softens and fractures the cured polymer films. Because the mask and conformal coatings are designed to survive short thermal spikes, the ALS2 cycle uses a slower, more uniform energy input that penetrates the coating rather than scorching it. The result is a brittle, friable coating layer that releases its grip on the metal beneath, allowing fine separation downstream through density and conductivity sorting.
Because no aqua regia, cyanide, or nitric acid is consumed in the liberation step, the plant footprint is smaller and the permitting pathway simpler. Operators report that workplace air monitoring becomes a routine dust and noise exercise rather than a programme of acid vapour sampling.
From coated board to clean metal fraction
The process flow inside an ALS2 module is deliberately compact. Incoming boards — already depopulated of capacitors and batteries at a pre-processing stage — enter a controlled chamber where the conditioning cycle is applied. Timing and energy levels are tuned to the board type: a multilayer server board with heavy conformal coating requires a longer cycle than a consumer router with a thin acrylic layer.
After conditioning, the material passes through a mechanical separation stage. Eddy current separators, vibrating tables, or air classifiers pull the now-fragile metallic fraction away from the fibreglass and polymer fines. The metallic stream is rich in copper, tin, gold, silver, and palladium, ready for downstream refining that can be far smaller and simpler than a full acid leach train. The non-metallic fraction is dry, low-odour, and suitable for further processing as a plastic or composite output rather than hazardous waste.
Throughout the cycle, water use is limited to cooling and dust suppression. There is no spent acid to neutralise, no cyanide tailings pond, and no NOx scrubbing train. For a country like Australia where water is a recurring operational concern across New South Wales, Queensland, and Western Australia, the closed-loop water design is a quiet but real advantage.
Where ALS2 fits inside a modern WEEE plant
ALS2 has been promoted as a front-end module that sits between dismantling and final refining. It does not replace smelting or hydrometallurgical polishing steps; it replaces the messy preparation stage where coatings, components, and substrates are still entangled. In a typical line, depopulated boards are shredded, the ALS2 conditioning step is applied, and the resulting fractions are sorted automatically.
The modular nature of the technology matters for Australian operators. Several regional recyclers — including facilities around Perth and Adelaide — have expressed interest in compact, containerised units that can be deployed next to existing collection points rather than requiring a greenfield acid plant. CSIRO and various state programmes have published work on urban mining, and ALS2 fits neatly into that narrative by keeping metal-rich fractions in forms that downstream Australian smelters can accept.
Comparing ALS2 with conventional acid-based refining
| Parameter | Acid-based refining | ALS2 acidless separation |
|---|---|---|
| Primary reagents | Aqua regia, nitric acid, cyanide | No strong acids or cyanides |
| Coating handling | Burn-off, shredding, or full dissolution | Conditioned mechanical release |
| Worker exposure risk | Acid vapours, cyanide | Dust and noise only |
| Wastewater volume | High, requires neutralisation | Low, mostly cooling water |
| Air emissions | NOx, SOx, acid mist | Particulates, controlled dust |
| Suitability for coated PCBs | Limited, low penetration | Designed for masked boards |
| Recovery yield for Au/Ag/Pd | Variable, often below 70% | Higher on coated substrates |
| Permit complexity in Australia | High (EPA-NSW, EPA-Vic) | Lower, simplified approvals |
| Plant footprint | Large, fixed infrastructure | Compact, modular |
This comparison is not a replacement for site-specific feasibility work, but it captures the broad contrasts that matter most to operators weighing capital and compliance risk.
What this means for Australian WEEE operators
Australia's recycling industry has matured around collection and dismantling rather than primary refining. The country ships a significant share of its circuit board scrap overseas for processing, which exposes local operators to commodity price swings and shipping logistics. A compact, acidless separation stage changes that calculus by letting domestic plants produce a clean, high-grade concentrate that can be sold into Australian and Asian refining markets directly.
There is also a circular economy angle. Gold recovered from a board decommissioned in a Sydney data centre can be reintroduced into local jewellery and electronics manufacturing. Silver can feed into Perth's industrial silver users, and palladium can return to catalytic and electronics supply chains. Closing these loops domestically aligns with the sustainability targets set by state governments and with the broader push for resource security that has featured in recent federal discussions on critical minerals.
For Australian processors weighing their next investment, ALS2 offers a way to add value without taking on the regulatory load of a traditional precious-metal refinery. It is a front-end technology designed to deal with the messy reality of coated, aged, mixed boards arriving at the gate — the kind of boards that today too often leave the country in shipping containers rather than being processed locally.
To learn more about pilot results, deployment options, and the wider ALS2 project under Horizon 2020, visit the project website or contact the Ikoi S.p.A. team directly through the partners page. Early-adopter discussions are open to Australian operators interested in integrating acidless separation into their WEEE and electronic scrap lines, and demonstration data from European reference sites is available on request.