Ammonium Persulfate

Product Overview

Ammonium Persulfate ((NH4)2S2O8) is the finishing and electronics industry's controlled copper etchant and micro-etchant. Where a plated or printed-copper surface must be cleaned, roughened or stripped to a precise depth - before electroplating, electroless copper, or soldermask - persulfate solutions dissolve copper smoothly and stop when the bath is spent, unlike peroxide systems that decompose on their own. In QLQ's finishing plants ammonium persulfate does the light copper micro-etch that keys subsequent plating layers on hardware and electronic parts. The market sells it as a white crystalline salt at 98%+ assay; the two specifications that matter for etching are assay (it is sold on active oxidizer content) and chloride, because chloride ions shift etch geometry toward pitting and undercut. Ammonium persulfate is a strong oxidizer - a fact that governs everything from storage to waste handling - and it is chosen over sodium persulfate where the higher solubility of the ammonium salt is wanted at high etch rates.

Product Identity (Encyclopaedia Card)

What it is and what it does. Ammonium persulfate is the standard oxidising etchant used to remove copper oxide and to micro-etch copper and nickel surfaces before plating, and to activate copper after polishing.

• White crystals, dissolves readily; when dissolved it slowly releases oxygen, so solutions are made up on the same shift they are used.
• Used as a 10-25% solution, often activated with a little sulfuric acid or with a proprietary activator, at room temperature.
• It is a strong oxidiser and must be kept away from reducing agents, solvents and combustible material.

Typical Use in a Plating / Finishing Line

Safety, Handling & Storage

Quality Documents Shipped With Every Batch

Buyer Questions We Answer Every Week

How It Works in the Etch Station (Chemistry and Control)

In acid solution the persulfate ion is a powerful oxidizer that converts metallic copper to soluble copper sulfate: the etch is controlled entirely by concentration, temperature and time, and it stops when the oxidizer is consumed. For a micro-etch - the 1-3 micron bite that keys a new plating layer onto an existing copper surface - the working bath is roughly 100-200 g/L ammonium persulfate with sulfuric acid in the tens of g/L, run at 25-40°C for 30 seconds to a few minutes. The same chemistry at higher concentration and temperature becomes a full etchant for stripping and pattern work. Two control habits keep the process honest: etch rate is measured by weight loss on a test coupon, never by clock alone, because the bath slows as persulfate is consumed and ammonium sulfate accumulates; and the bath is dumped on a schedule set by analysis, because an exhausted bath etches unevenly and leaves a rainbow oxide film that ruins adhesion.

Rinsing after the etch is a process step, not a formality: persulfate carried into a plating bath oxidizes organic brighteners, so a double rinse with good dwell is standard before the part sees a plating solution.

How to Check Quality Before Loading a Batch

How QLQ controls it: persulfate lots are checked for assay and chloride on arrival, and the etch rate of every new lot is measured against the retained standard before the bags reach the line. Because an etch bath is only as good as its oxidizer, lot records sit beside the etch-rate log so an adhesion failure can be traced to chemical, time or temperature in minutes.

Common Problems & Fixes (Workshop Table)

Handling & Safety for the Plating Line

• Oxidizer: ammonium persulfate is a Class 5.1 oxidizer. Store away from acids, reducing agents, organics, metals dust and flammables; a contaminated oxidizer can self-heat and start a fire.
• Cyanide rule: never let persulfate contact cyanide solutions or waste - oxidizers and cyanide react violently and can liberate toxic gas. Segregate the etch station completely from cyanide lines.
• Health: persulfate salts are respiratory and skin sensitizers - allergy can develop after months of trouble-free handling. Wear gloves, goggles and a dust mask; ventilate the make-up area.
• Dissolving: add crystals to water with stirring; dissolution is endothermic (solution cools). Do not add water to the salt and do not heat solutions above about 50°C - decomposition accelerates.
• Storage: keep cool, dry and sealed; damp or warm storage decomposes the salt and can cause caking and container stress. Store below 30°C and use oldest stock first.
• Waste: spent etch is copper-bearing acid waste - collect for metal recovery or treatment; check residual oxidizer before discharge.

What It Does on Iron, Zinc Alloy, Copper and Stainless Steel Parts

FAQ

Etching uneven or plating adhesion failing? QLQ supplies ammonium persulfate with COA and engineers who help customers in 10+ countries set etch rates and diagnose adhesion faults. Contact us with your coupon weights.