How ALS2 Recovers Gold from Lead-Tin Solder
Through-hole circuit boards contain a mixture of valuable metals, base metals, plastics and ceramics. Gold may appear as a thin surface finish on component leads, connector pins or board contacts, while lead-tin solder forms the joints that hold components in place. Recovering the gold efficiently depends on separating these materials without creating a contaminated, hazardous refining stream.
ALS2, developed by Ikoi S.p.A., addresses this challenge through acidless separation technology. The approach is designed for precious-metal recovery from electronic waste and WEEE recycling streams, using controlled processing steps to liberate valuable fractions and separate them from solder and other unwanted materials.
For Australian recyclers, the technology has relevance across printed circuit board recovery, e-waste collection and compact urban recycling plants. It can support a cleaner approach to materials handled in Sydney, Melbourne, Brisbane and regional centres, where transport costs, environmental controls and reliable downstream recovery all influence the commercial value of collected electronics.
Where gold and solder occur in through-hole boards
Through-hole components are mounted by inserting their leads through drilled holes in a printed circuit board. The leads are then soldered on the underside, traditionally with lead-tin alloys and, in newer equipment, with lead-free alternatives such as tin-silver-copper. Gold is generally present as plating or a very thin protective finish rather than as a solid component.
The valuable metal may be found on connector pins, relay contacts, sockets, component leads and selected terminal surfaces. Its quantity varies greatly between board types. Telecommunications hardware, industrial control equipment and older computer boards can have a different precious-metal profile from consumer appliances or low-grade household electronics.
Solder creates a processing complication because it bonds directly to copper tracks, plated holes and component leads. Mechanical shredding can spread solder across a mixed fraction, while excessive heat may generate fumes or alter the physical form of the material. A practical recovery process therefore begins with identification, sorting and controlled liberation rather than treating every board as an identical feedstock.
Preparing the electronic waste feed
ALS2-style processing starts with preparation that exposes the metal-bearing parts. Boards can be sorted by grade, dismantled where worthwhile, and reduced to a suitable particle size or component fraction. The objective is to release plated leads and contacts while limiting the unnecessary production of fine dust, plastic fragments and solder-rich residue.
Magnetic separation, screening, air classification and density-based methods may be used during mechanical preparation, depending on the incoming material. These steps do not extract the gold by themselves. They improve the consistency of the feed so that the subsequent separation stage can work on a more concentrated and predictable fraction.
This matters in Australia because collection streams are often mixed. A council drop-off load may contain small appliances, cables, computer peripherals and circuit boards together, while commercial dismantlers may receive more uniform industrial equipment. A compact plant benefits from a receiving protocol that records board type, estimated precious-metal content, solder composition and contamination risks before treatment.
How the acidless separation principle works
The central distinction is that ALS2 avoids conventional mineral-acid refining routes. Acidless does not mean that the process relies on physical sorting alone or that no controlled chemical reactions occur. It refers to a separation pathway designed to avoid the use of aggressive mineral acids commonly associated with traditional precious-metal recovery.
In practical terms, the prepared material is exposed to a controlled treatment that helps detach or dissolve selected metallic phases while leaving other materials available for separation. Gold-bearing surfaces, solder residues and base-metal substrates respond differently because their composition, bonding and electrochemical behaviour are not the same.
The exact chemistry, sequence and operating conditions are part of the technology’s technical development. The important process concept is selectivity: separate the precious-metal-bearing fraction from lead, tin, copper, iron and non-metallic materials in stages, rather than sending the whole board into a single corrosive bath. This can reduce unwanted reactions and make the resulting streams easier to manage.
Separating gold from lead-tin solder
Gold recovery from a soldered through-hole component depends on first breaking the physical relationship between the lead, solder fillet and board. Preparation can expose the joint and remove much of the surrounding laminate. A controlled separation stage then targets the metal mixture so that solder-rich material can be directed away from the gold-bearing fraction.
Lead and tin behave differently from gold during separation. Lead-tin solder is a relatively soft alloy that can form a dense, adherent layer around the joint. Gold is chemically resistant and often occurs in thin plated layers. The process therefore needs to avoid simply dissolving or dispersing the solder across the same stream as the precious metal.
Once the solder and base-metal portions have been separated, gold can be concentrated for recovery as a metal-bearing product. Depending on the feed and plant configuration, the output may require further refining or collection by a specialised precious-metals processor. The commercial target is a cleaner, more concentrated gold fraction with fewer lead and tin impurities.
This staged approach is useful for older Australian electronics, where leaded solder remains common in legacy equipment. It also supports separate handling of hazardous or regulated residues, which is important when recyclers are assessing worker exposure, transport requirements and downstream acceptance criteria.
Managing lead, tin and process residues
Lead is the main environmental concern in many older circuit boards. It can be present in solder, component terminations and dust generated during dismantling. Any responsible recovery plant needs enclosed handling, suitable ventilation, personal protective equipment, spill controls and testing of solid and liquid residues.
Tin can complicate separation because it may form oxides, sludges or mixed residues during processing. Keeping the feed consistent helps operators understand how solder composition affects the process. Lead-free boards should not automatically be treated as equivalent to leaded boards, since their solder may contain silver, copper or other alloying elements that change recovery behaviour.
An acidless route can reduce the risks associated with strong-acid storage, corrosion and acidic wastewater, but it does not remove the need for environmental management. Operators still need documented procedures for residue classification, water management, equipment cleaning and safe storage of recovered metals. Australian state and territory requirements can differ, so a plant in New South Wales may face different approvals and reporting expectations from one in Victoria or Queensland.
Digital traceability is also useful when several suppliers, carriers and processing partners are involved. If staff rely on online messaging accounts for collection schedules or compliance documents, a documented recovery procedure can sit alongside account appeal guidance, while formal records remain the authoritative source.
Why compact recovery plants suit local recycling
A compact precious-metals recovery plant can be placed closer to collection, dismantling or aggregation activities than a large central refinery. This may reduce the distance that low-volume, high-value board fractions travel. For Australian operators, that is significant because material collected in Perth, Adelaide or regional New South Wales may otherwise move across long freight routes before processing.
Local processing can also improve sorting discipline. Staff can separate high-grade telecommunications boards, connector-rich assemblies and industrial control cards from lower-value mixed electronics before treatment. This helps preserve value and reduces the chance that gold-bearing components are diluted into general shredder residue.
The model fits Australia’s growing emphasis on resource recovery and product stewardship. E-waste is generated by households, offices, schools, mines, hospitals and manufacturing sites, yet the composition of each stream is different. A flexible plant can serve dismantlers and specialist recyclers without requiring every supplier to build a full refining operation.
There are practical limits. Throughput, feed variability, transport economics and approvals must be assessed before installation. The strongest business case usually combines precious-metal recovery with responsible management of copper, aluminium, steel, plastics and solder-bearing residues rather than relying on gold alone.
Comparing conventional and acidless recovery routes
The following comparison describes broad process characteristics rather than fixed performance figures. Actual outcomes depend on board grade, component mix, solder alloy, preparation equipment and the specific ALS2 configuration.
| Consideration | Conventional acid-based refining | ALS2 acidless separation approach |
|---|---|---|
| Primary process environment | Strong mineral-acid chemistry | Controlled acidless separation chemistry |
| Gold-bearing feed | Often mixed after aggressive treatment | Prepared and sorted before selective treatment |
| Lead and tin management | Can enter acidic liquors and create complex residues | Targeted separation into distinct residue streams |
| Equipment considerations | Corrosion-resistant tanks, ventilation and wastewater controls | Controlled reactors or separation equipment with reduced acid-handling demands |
| Operator priorities | Acid safety, fumes, neutralisation and effluent treatment | Feed preparation, selectivity, residue control and process monitoring |
| Suitability for compact plants | Can be demanding for small operators | Designed to support compact precious-metal recovery applications |
| Environmental focus | Managing acidic solutions and dissolved contaminants | Reducing reliance on aggressive acids while maintaining full residue controls |
For a recycler evaluating the technology, the relevant question is not simply how much gold a board contains. The assessment should include recovery yield, labour, energy, chemical inputs, residue disposal, plant footprint and the value of secondary metals. A process that produces a slightly lower-grade input but cleaner, more manageable streams may be more useful commercially.
Building a responsible Australian recovery workflow
A workable facility begins with feed acceptance rules. Suppliers should declare the origin and general type of electronics, while operators inspect incoming loads for batteries, mercury-containing parts, pressurised items and other materials that require separate handling. Through-hole boards can then be graded according to component density, plating, solder type and likely precious-metal content.
The next stage combines mechanical liberation with controlled ALS2 separation. Gold-bearing fractions are collected for recovery, while lead-tin solder and other base-metal streams are isolated for appropriate treatment. Sampling at each stage helps verify mass balance and identifies where gold or contaminants may be accumulating.
For Australian customers, clear chain-of-custody records can support contracts with councils, commercial collectors and manufacturers. A facility serving Melbourne’s industrial areas may need a different logistics model from one supplying remote communities in Western Australia, but both benefit from documented weights, batch references and verified downstream destinations.
ALS2 presents a pathway for turning complex electronic waste into a more manageable set of material streams. By combining careful dismantling, selective separation and responsible residue handling, recyclers can recover gold from soldered through-hole components while reducing dependence on conventional acid-intensive refining.
Explore the ALS2 Project to understand how acidless precious-metal recovery can fit into a cleaner e-waste strategy. For Australian recyclers, technology providers, councils and equipment investors, the next practical step is to assess representative local feedstock and determine how a compact recovery plant could integrate with existing collection and dismantling operations.