Fengfan High deposit brightness Copper Plating FI-970 Bright Acid Copper Plating Process

Product Overview

FI-970 is a high-deposit brightness acid copper process: a copper sulfate and pure sulfuric acid plating solution carrying three FI-97 addition agents, run for a bright, level copper layer that keeps its ductility and can be polished after plating.

It suits shops whose copper has to look right and still behave. That covers bright copper under nickel or nickel-chrome on steel and zinc parts, electronic plating on stamped and formed components, and hardware that is handled, bent or assembled after it leaves the tank. In metal plating, the value of a deposit like this is that it takes work out of the later stages: less polishing on the nickel, fewer rejects from a dull or streaky copper face.

Running it is a routine rather than a specialism. The bath sits in a moderate temperature band and a wide current density band, and it is kept in condition by feeding the addition agents on an ampere-hour basis and reading Hull Cell panels at intervals. An operator who already runs an acid copper tank will recognise the pattern.

We supply the FI-97 addition agents as a three-part set, with guidance on make-up concentrations, operating ranges and control so a new tank starts from a known point. If you already run a bright acid copper bath and want to compare systems, send us your current make-up and we will go through the differences with you.

Solution Composition

Operating Window

Temperature, cathode current density, anode current density and voltage each have a working range rather than a single set point, and the ranges are wide enough to cover a mixed rack.

Temperature sits between 20 °C and 35 °C. In most metal finishing shops that is close to ambient, so a small heater carries a cold shop in winter and cooling matters more in summer. Hold the band: brightness and the balance between the addition agents drift once a bath runs hot or cold for a long stretch.

Cathode current density runs from 1 A/dm² to 6 A/dm². The upper part of that band is what lets one rack carry edges, rims and small faces alongside recessed areas. High-current points take several times the current of a shielded face, and a narrow window would show it as burning at one end of the rack and dullness at the other.

Anode current density is 0.5 A/dm² to 2.5 A/dm², with rectifier voltage between 1.5 V and 6 V. Keep the anode area comfortably above the cathode area so the anodes stay inside their own range when the work sits at the top of the cathode range. A bath that suddenly demands more voltage usually has an anode problem rather than a chemistry problem.

Treat these as the envelope within which a metal plating process behaves predictably. When a part falls outside it, change the racking, the contacts or the part orientation before pushing the bath harder, and confirm the result on a Hull Cell panel first.

The three FI-97 addition agents are the organic side of the bath. Like most industrial surfactants and brighteners used in plating, they are consumed in proportion to the current that passes rather than to the litres in the tank, so their concentration follows ampere-hours.

Brightness and Leveling

• Brightness straight from the tank. The industrial surfactants in the bath keep the deposit bright across the working current range, so copper that is only an underlayer does not need a polishing step of its own before the nickel goes on.
• Leveling over fine substrate marks. Polishing lines, fine tool marks and the slight waviness left by machining are bridged by the copper instead of printing through it.
• A rack that reads evenly. Edges, rims and recessed faces sit at very different current densities on the same rack; strong leveling keeps them visually matched rather than bright at the contact points and hazy in the shadow.
• Confidence at inspection. A uniform bright face makes pits, nodules and drag-in marks obvious before the part moves on, which is the cheapest place in metal plating to catch a reject.
• A finish that carries a topcoat well. Nickel and nickel-chrome take on a flatter, deeper appearance over level copper than over a substrate that was only mechanically polished.
• What leveling cannot rescue. Deep scratches, porosity and a badly prepared substrate still show. The bath fills micro-profile, not damage.

Ductility at High Brightness

In any metal plating process, brightness and ductility pull against each other. The brightness comes from organic addition agents, and pushed too far those agents leave a hard, brittle copper that cracks the moment the part is bent. This process is built the other way round: high brightness and strong leveling with the ductility of the copper still intact.

What that means in practice depends on the part. A stamped contact that is bent after plating, a terminal that is crimped onto a cable, a shell that is riveted, a component that sees thermal cycling in service — all of them flex the copper layer. A brittle deposit cracks at the bend and the crack travels into the nickel above or down to the substrate; a ductile one moves with the part.

It matters in metal plating as well. Ductility is what lets a part be buffed with real pressure without crazing at the edges, and what keeps the layer sound when it is machined, threaded or assembled afterwards.

Ductility is not visible on the rack, so check it before a new part goes to full production: plate a panel, bend it over a mandrel or through the same bend the part will see, and look at the copper under magnification. It takes a minute and it settles the question for that part geometry.

Buffable Copper Surface

• A deposit that responds to a wheel. Light haze, fine handling marks and the faint striping left by a rack contact can be cut back and brought to a uniform shine.
• Correction without stripping. Buffing is quicker and cheaper than stripping and re-plating a part that only needs a cosmetic correction.
• Where buffing sits in the route. Between copper and nickel on decorative work, or as the final operation on parts that are plated in copper only.
• Pressure tolerance. The layer is ductile enough to take normal buffing pressure without crazing or lifting at the edges, which is the usual failure of a hard, over-brightened copper deposit.
• Compound hygiene. Buffing compound left in recesses or blind holes has to be washed out before the next plating step; trapped compound is a common source of adhesion faults later in the metal plating process.
• When to leave it out. If the tank is running correctly, most decorative work goes straight from copper to nickel. Buffing is a correction step, not a mandatory one.

Bath Control Routine

1. Fit an ampere-hour meter and log it every shift. Dosing follows the current that has passed through the tank, not the clock and not the tank volume, so the meter reading is the number the whole routine is built on.
2. Feed the three agents separately. MU, A and B each have their own concentration band and are topped up in proportion to the ampere-hours run. Never blend them into one dose; the ratio between them is part of the process.
3. Pull a Hull Cell panel on a fixed routine. Same current, same time, same panel every run, so panels from different weeks can be laid side by side and compared honestly.
4. Read the panel for balance, not only shine. A dull high-current end and a dull low-current end point to different corrections. Send us the panel and we will tell you which way to move rather than guessing at the tank.
5. Keep the inorganic side steady. Copper sulfate and pure sulfuric acid by routine analysis; hold the chloride at its target, because a chloride shift shows up first as a change in brightness.
6. Stay inside the temperature and current density bands. Chemistry work will not compensate for a bath running outside its window; correct the tank conditions first, then the addition.
7. Write it down. What was added, when, the panel result and what changed afterwards. A plating solution that is documented is a plating solution that can be corrected instead of replaced.

Copper in the Coating Stack

Copper rarely goes on for its own sake in industrial metal plating. On steel and on zinc parts it is the leveling layer between the substrate and the nickel or nickel-chrome that provides the final colour, and its job is to make everything above it look flatter and brighter than the base metal ever was.

A bright acid copper layer takes over part of the work that would otherwise be done by mechanical polishing before plating: the bath fills fine tool marks, and the buffer only has to deal with what is left. On parts with recesses and internal corners, that is work a mop cannot do evenly at all.

Copper is a cathodic layer over steel and zinc, so it protects nothing on its own. The corrosion protection comes from the nickel and chrome above it, and from the copper being sound, well bonded and free of nodules underneath.

For electronic work the layer is doing a different job: it builds a conductive, solderable base under nickel or gold, and its brightness makes visual inspection of the plated surface practical before the next layer goes on.

Where the layer sits decides how much copper a part needs and how bright it has to be, so agree the stack — substrate, copper thickness, nickel, top coat — with us before the tank is made up.

Electronic Component Plating

• Stamped contacts and terminals. Copper under nickel or gold, plated bright and level, then formed or bent; the ductility is what lets the part survive the bend without a crack running through the copper.
• Connector shells and shielding. Large visible faces that would otherwise need mechanical polishing before the nickel goes on.
• Current-carrying parts. Copper builds the conductive layer on the part. How much thickness a part needs depends on the current it carries, so agree thickness and plating time against your own sample.
• Inspection before the next layer. In electronic plating the copper is followed by nickel, gold or silver, and a bright uniform copper face is the cheapest place to catch a problem in the stack.
• Small and awkward parts. The wide cathode window covers the current spread between a contact tip and a shielded body sitting on the same rack.
• Where it is not the answer. Parts that need a matte or satin copper surface, or work where copper is only a thin conductive seed layer, are better served by a different process.

Precision Metal Finishing

Precision metal finishing is where the copper is judged on its own face rather than under a topcoat: instrument bodies, machined and turned components, decorative hardware, fittings that are handled in service.

What this bath gives that shop is flatness and shine in the same operation. The leveling effect does work that a polishing mop would otherwise do, and it does it inside the recesses and around the edges where a mop cannot reach evenly.

Complex geometry is where the wide cathode current density window pays for itself. A machined part with deep grooves and sharp external corners pulls very different current densities at each feature, and a bath that holds its brightness across that spread avoids the usual compromise of racking the same part three times at different angles.

Repeatability is the other half of the value. A process like this is judged on how it behaves over a month, not on the first panel, which is why the addition agents and the operating ranges are all written down and can be adjusted deliberately rather than by feel.

For a shop moving from a generic brightener to a defined system, that is the practical difference: every parameter has a starting point, and a deviation can be traced back to a specific change instead of to the weather.

Production Lines with Routine Bath Control

1. Check the hardware before the chemistry. An ampere-hour meter on the rectifier and a rectifier that holds its voltage under load at your normal current are the two things the control routine depends on.
2. Set up a Hull Cell bench. A cell, a small supply and a fixed routine are enough; what matters is that the panel is run the same way every time so results can be compared.
3. Fix the make-up against your tank. Send the tank volume and we will confirm the make-up quantities and the addition plan for your line rather than leaving you to scale it by hand.
4. Put the addition rule into the shift sheet. Who adds, at what ampere-hour reading, and how the dose is split between the three agents — written down, not carried in someone's head.
5. Keep a panel file. Date, panel, reading, action. Over a few months this file is what turns a plating process from something the line hopes will hold into something it can steer.
6. Re-check when the work changes. A new substrate, a new rack or a much larger part changes the current distribution and deserves a fresh panel before the production run.
7. Watch the line, not only the tank. Pre-treatment and rinse quality show up in the copper; a bright bath will not cover a badly cleaned part.

Ordering and Delivery

• Payment. 100% T/T in advance.
• Order quantity. Varies by chemical; confirmed with our sales team per order.
• Lead time. 2 weeks.
• Packing. 10 kg/box; 25 kg or 50 kg/bag; 20 kg/25 kg/30 kg/200 kg/drum; 1000 kg/IBC drum.
• Shipping. Per the terms agreed in the current contract.
• Warranty. An inspection certificate is issued after delivery, stating the batch number and warranty period.
• Technical questions. Bath make-up, operating and addition-control questions go to your Fengfan sales contact, who can also confirm packing and availability for your order.

Tank Conversion Checklist

1. Start with the tank itself. Confirm the lining, wetted parts, filtration and fume extraction are in acid copper service and that nothing is due for repair; a conversion is the moment to fix a weeping liner or a weak filter, not to find it on the first production rack.
2. Plan a full drain, clean and rinse before make-up. Residual brightener, chloride or drag-in from the old bath will distort the first Hull Cell panel, so the tank should go into the new chemistry clean. If you intend to retain any of the old solution, confirm it with us first.
3. Check the make-up quantities against your working volume. The bath calls for copper sulfate at 200-220 g/L, pure sulfuric acid at 55-70 g/L, chloride at 100 ppm, FI-97 MU at 4-8 ml/L, FI-97 A at 0.4-0.6 ml/L and FI-97 B at 0.4-0.6 ml/L. Send us the tank volume and we will go through the arithmetic with you before the drums are opened.
4. Confirm the rectifier and current spread on your parts. The process runs at 1.5-6 V, 1-6 A/dm² cathode current density and 0.5-2.5 A/dm² anode current density. Put a representative rack or barrel in the tank and check the rectifier can hold voltage at your normal load; if it cannot, the current density band is not actually available to you.
5. Confirm temperature control across the year. This is a 20-35 °C bath. In a cold room that means a heater sized for the tank; in a hot room it means cooling or a reduced load. Check both before you commit, not after the first summer.
6. Set up the control bench before make-up. An ampere-hour meter on the rectifier, a Hull Cell and a fixed panel routine are what the addition plan depends on. If the meter is not fitted, fit it first; if the Hull Cell bench is new, run a baseline panel on the old bath so you have something to compare against.
7. Plate a sample of your own part before the full switch. Make up a pilot volume, plate the geometry you run most, and check brightness across the rack, leveling over the substrate, ductility by bending the sample, and how the surface responds to a buff. Agree the acceptance criteria with us before the production tank is converted.
8. Agree the first-week support plan. Tell us the conversion date and who will read the panels. A new bath is judged over its first weeks of addition, so the person adding the agents and the person reading the Hull Cell should work from the same written rule.

Use Scenarios

Use scenarios vary from shop to shop, so the practical way to judge a fit is to match the product to your own line rather than to a general description. Share the base material you plate, the bath type and volume, the operating temperature and current density you run, and how you currently top up addition agents, and the supplier can confirm whether FI-970 suits your process or recommend the right starting point for a trial.

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.

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