CPU recovery walkthrough

Reference · Recovery walkthrough

From “OSCAR identified a CPU” to a weighed, photographed batch on /boards. This guide covers PPE, tools, mechanical pin-stripping (the safe and legal route), chemical aqua regia leaching (where your jurisdiction and environmental permit allow), and verification at the yard. Always cross-check your local environment agency’s guidance before handling acids.

Step 1

Before you start

Make sure you have what you need before the first cut. Trying to back-track mid-process with hot tools or open acid is what causes most accidents.

Pre-flight checklist
  • Identified the part as a CPU via /guide and confirmed pin plating
  • Photographed the part, top and bottom, in good light
  • Weighed the intact part on a 0.01 g scale and logged the reading
  • Verified the part is not connected to mains or any live circuit
  • Work area is clear, ventilated, and has an eyewash within reach

Step 2

PPE & safety

Step 3

Tools

Three groups. Mechanical tools are needed for every batch; chemical tools only if your jurisdiction and permit allow leaching; verification tools always, so your yard quote has a clean paper trail.

Mechanical
  • Heat gun (capable of ~80 °C sustained)
  • Fine-tip pliers and tweezers
  • Fine-tip snips or jeweller's cutters
  • Fine saw / Dremel with a thin kerf disc
  • Fine sandpaper or Scotch-Brite for cleaning pins
  • Jeweller's loupe (10×) for inspection
Chemical (if leaching)
  • Borosilicate glass beakers only — never metal or unknown plastic
  • Graduated cylinders, glass stirring rod
  • Filter paper + glass funnel
  • pH strips
  • Dedicated acid storage (labelled, locked)
Verification
  • Jeweller's loupe (10× or stereo microscope)
  • Digital scale, 0.01 g resolution
  • XRF if you have access — invaluable for confirmation
  • Sample vials for retained pin samples

Step 4

Mechanical pin-stripping

This is the route a home operator should default to. It is legal everywhere PPE is used, requires no acid, and produces a clean pin batch that any yard will assay.

  1. Pre-heat the package

    Warm the CPU to roughly 80 °C with a heat gun for 30–60 seconds. The ceramic substrate softens the bond between the die and the pins so the package opens without shattering into dust.

  2. Slit the seam

    With a Dremel or a fine saw, cut along one of the ceramic package seams — the cut is shallow, just enough to break the seal. Stop if you feel resistance; the gold-plated pins are directly under.

  3. Lever the die out

    Use a flat-blade screwdriver or a tough plastic wedge to gently lever the die and substrate out of the carrier. The gold-plated pins will start to release as the package flexes.

  4. Tap the pins loose

    Hold the carrier over a glass dish and tap the underside. Most pins will drop out cleanly. Stragglers come free with tweezers — never with bare fingers, both for ESD and pin-prick reasons.

  5. Sweep, never spill

    Sweep loose pins into the glass dish with a soft brush. Do not let pins touch metal surfaces — a single ferrous shaving will contaminate the whole lot and a yard assay can reject it.

  6. Weigh and photograph

    Weigh the batch on a 0.01 g scale, photograph the dish and the weighed reading, and keep a small retained sample in a labelled vial. These three artefacts are what yards ask for when they quote.

Step 5 — optional

Chemical leaching (aqua regia) — legal only where permitted

  1. Mix the aqua regia

    3 parts hydrochloric acid (HCl) to 1 part nitric acid (HNO₃), mixed in a borosilicate beaker. Always add acid to acid, never water. Do this under a fume cupboard with the FFP3 respirator on.

  2. Submerge the pins

    Lower the pins into the acid in a glass cradle — never drop them in; small splash risk. The acid will fume a deep orange as it dissolved the gold.

  3. Apply low heat

    Heat from a hot plate at ~50–60 °C. Never use an open flame — aqua regia releases NO₂ and chlorine on heating; both are acutely toxic.

  4. Stir and observe

    Stir gently with a glass rod. The pins will be fully dissolved within an hour if the bath is hot enough. The solution turns deep yellow / orange.

  5. Dilute and precipitate

    Slowly dilute the solution 3:1 with distilled water, then add sodium metabisulphite (Na₂S₂O₅) a little at a time. A fine brown / gold powder precipitates out — that is your gold.

  6. Wash and dry

    Decant the supernatant through a filter paper in a glass funnel, wash the precipitate repeatedly with distilled water until the wash water runs neutral, then dry the powder on a warm hot plate.

Step 6

Verification at the yard

Weigh your pin batch on a 0.01 g digital scale, photograph the dish and the reading, and take a small retained sample in a labelled vial. These three artefacts are what you bring to the yard.

Compare the per-board yield against the /boards typical band for the matching board class — a CPU-rich desktop board typically sits in the 0.2–0.3 g Au / kg range. Anything wildly above that band warrants a second look (an assay, or a recount of pins).

List the batch on /boards to get assayed yard quotes before you commit to anything irreversible. Yard quotes are a price floor; you stay in control as long as the pins are still pins.

Frequently asked

FAQ

What yield should I expect?

Indicatively roughly 0.2–0.3 g of gold per kilogram of pin-rich scrap, but this is a wide band — actual recovery depends on pin density, plating thickness, substrate, and how clean your pins are. Public references include the Boardsort community averages, USGS platinum-group-metals refining literature, and the UNEP / PMC critical-metals Stocks & Flows reports. Use /analyze to estimate against today’s £/g spot, or list your pin batch on /boards to get yard quotes.

Do I need PPE if I am only doing mechanical stripping?

Yes. Mechanical stripping still risks sharp pin edges, ceramic substrate dust, and flux residue. At minimum: cut-resistant gloves, safety glasses, and a dust mask. FFP3 becomes mandatory the moment you move to chemical leaching.

Is chemical leaching legal at home?

In most jurisdictions, no — acid leaching of e-waste is regulated. Confirm with your local environment agency before purchasing acids. Unlicensed leaching can attract fines. The safer route for non-permitted operators is mechanical stripping followed by listing your lot on /boards, where licensed yards quote assayed weights. We do not provide legal advice.

Next step

List your pins on the marketplace

Your batch is weighed, photographed, and a sample is vialed. Drop it into /boards and let yards quote your lot against the same live Au / Ag / Pt / Pd snapshot /prices uses.

List your pins on the marketplace

Methodology & references

Where the indicative yield comes from

The 0.2–0.3 g Au / kg figure quoted above is an indicative range, not a buyer’s quote. Three public references back it:

  • Boardsort— per-class Au/Ag gram ranges for desktop, laptop, server, GPU, phone, RAM, NIC, and miscellaneous PCB populations.
  • USGS Platinum-Group Metals — annual statistics & information on Pt / Pd supply, refining yields, and end-use demand.
  • UNEP / PMC Critical Metals — reporting on PGM Stocks & Flows, secondary recovery rates, and e-waste refining pathways.

Real per-lot recovery depends on board age, plating thickness, component density, lot purity, and your yard. Always sample-test before committing. See the /boards methodology for the broader yield derivation.