Fengfan FI-7885 Chemical Gilding PCB chemical nickel gold and decorative immersion gold

Product Overview

This immersion gold bath lays a 24-carat gold layer onto nickel and nickel alloys by chemical displacement: gold ions in the solution swap places with nickel atoms at the surface, and the reaction stops on its own once that surface is covered. In a PCB shop the nickel gold plating step is the last wet stage before test and pack, and it is what gives each pad its flat, oxidation-resistant, readily solderable finish. The same bath finishes decorative work too — a hardware fitting, a jewellery component or a connector shell that already carries a nickel layer.

Because the deposit grows by displacement rather than by current, it reaches every isolated pad, pin and recess on the rack without bus bars or contacts. That is what makes it a practical metal plating process for high-density boards and for parts with deep internal geometry: coverage depends on the solution reaching the surface, not on where current can flow.

Working deposits are a fraction of a micron thick, and the reaction stops by itself once the nickel is covered — leaving parts in longer will not grow a heavy gold layer. That ceiling is deliberate. It keeps gold consumption predictable for a gold plating business running several customers on one line, and it is what protects the solder joint from gold embrittlement.

Process Specifications

Performance Advantages

• Cyanide-free chemistry. The bath dissolves its gold with an organic ligand system instead of cyanide, so the line avoids cyanide handling and the effluent side has no cyanide destruction stage to run.
• Self-limiting plating thickness. The displacement reaction slows and stops as the nickel is covered, so the layer cannot run away on a long dwell and the pad stays flat.
• A dense, non-porous barrier. Porosity is what lets the nickel underneath corrode and what turns into black pad failures later; a continuous gold layer closes that route.
• A wide gold window. You can run at the lower end of the gold concentration range without losing deposition speed, which lowers the metal a gold plating business ties up in the tank.
• Built around the electroless nickel plating step. The chemistry is designed to sit on mid- or high-phosphorus nickel without attacking the barrier layer, which is what keeps colour and solderability stable.
• Even colour on awkward geometry. Recessed and isolated areas take the same 24-carat tone as the flat faces because the reaction is chemical rather than field-driven.

Bath Make-Up & Control

1. Load the rack so solution can reach every face. Parts that touch each other shield the nickel from the gold and leave contact marks that no amount of extra dwell will plate over.
2. Dissolve the gold salt completely before anything else. Add it to hot deionised water and stir until the solution is clear; undissolved salt settles on the bottom and produces local over-plating and colour streaks.
3. Add the additive and set the pH before the first rack goes in. Measure pH again after every top-up, because it drifts as work passes through the tank.
4. Hold the working temperature steady. A bath that cools mid-shift deposits more slowly and gives a thinner, redder layer, so watch the heaters and the level through the day.
5. Analyse and replenish in ratio. Titrate the gold content on a fixed schedule and top up the gold salt together with the plating chemicals so the two stay in balance rather than chasing each other.
6. Keep a slow filter loop running and watch the level. A hot metal plating process loses volume to evaporation all shift; replace it with deionised water, not with raw water that brings hardness and chloride into the bath.
7. Book the dwell against the customer specification. Time in the tank is what the required thickness is recorded against, so log it per rack instead of running the line on feel.

Use Scenarios

Decorative hardware and connector shells

A finishing shop running gold plating brass fittings for telecommunications racks starts with an electroless nickel layer on the brass, then transfers the parts into the gold tank. The brass never meets the gold solution directly — the nickel is what the gold displaces — so the quality of the nickel layer decides the final result.

Automotive sensor boards

A process engineer finishing multi-layer boards for under-bonnet sensors uses this tank as the final finish after the electroless nickel plating step. The flat pad surface matters more than the colour here: fine-pitch components need a pad that sits level with the solder mask and wets instantly in reflow.

A shop running nickel gold plating for several customers

A job plater taking boards from more than one customer runs a single bath of plating chemicals and books the dwell against each customer's specified thickness. Because the reaction is self-limiting, a rack left in a few minutes longer does not come out visibly over-plated.

Incoming inspection

A quality technician cross-sections a finished board to confirm that the gold sits on the nickel as a continuous, non-porous layer with no nickel corrosion underneath. A clean cross-section and a good wetting balance result are what release the batch to assembly.

Decorative Gold Finishing

1. Confirm the finish on a sample first. Chemical gilding gives a 24-carat yellow tone over nickel; check it against the customer's approved sample before the run, since tone shifts with the nickel phosphorus level and with dwell time.
2. Build the nickel underlayer before anything else. Decorative parts need a sound mid- or high-phosphorus nickel layer; a thin or porous layer shows through the gold as patches and dull spots.
3. Rinse and transfer wet. Dry nickel passivates in air within minutes, so keep the parts under water between the nickel tank and the gold tank.
4. Rack for drainage rather than packing parts tightly. Watch the recesses when your gold plating business works with brass shells and jewellery findings: that is where the nickel layer thins out, and the gold will faithfully follow that weakness.
5. Rinse, dry and inspect under proper light. Check colour against the approved sample and look at the recesses and edges rather than the flat faces, where defects hide.
6. Decide on a topcoat if the part will be handled. A decorative gold layer is thin by nature; if the item will be touched, packed loose or worn against skin and clothing, ask our team about a protective topcoat before you commit the specification.

Ordering & Delivery

Technical Support & Model Matching

Choosing the right match is where most sourcing decisions stall. As a trading supplier, we keep one point of contact from first enquiry to after-sales: tell us what you are making and the conditions you work under, and we shortlist the closest matches from our supplier network, compare specifications and arrange samples before you commit to a bulk order. If something does not behave as expected, we work with the supplying partner on the cause and a practical fix, and stay with the case until it is settled. Email, WeChat or WhatsApp enquiries get a reply within 24 hours.

FAQ