MPS in one line
MPS is the trade name for sodium 3-mercaptopropanesulphonate, an organic sulphur salt used as the brightener component of acid copper systems. We supply it as a white powder at 95% assay for printed circuit boards, for decorative copper, and for functional copper where the plating process is judged on what the layer has to survive rather than on how it looks on the rack.
What the molecule does
The sodium sulphonate end carries the salt into water; the mercapto sulphur is the part that reaches the cathode and refines the copper grain as it grows. Brightness and ductility come out of that same action, which is why they tend to move together — a fine, even grain reflects light cleanly and still bends without cracking. In electronic plating shops the same behaviour is what keeps a plated through-hole continuous instead of nodular.
| Chemical name | Sodium 3-mercaptopropanesulphonate |
| Trade name | MPS |
| CAS No. | 17636-10-1 |
| EINECS No. | 241-620-3 |
| Molecular formula | C3H7NaO3S2 |
| Molecular weight | 178.2 |
| Melting point | ~220 °C (dec.)(lit.) |
| Assay | 95% |
| Appearance | White powder |
| Chemical family | Organic sulphur salt |
| Functional groups | Mercapto (thiol) and sodium sulphonate |
| Ionic character | Anionic |
| Solubility | Water-soluble |
With a polyether and a non-ionic surfactant
Run MPS alongside a polyether and a non-ionic surface active agent and the pair does more than either alone: the polyether moderates how copper reaches the surface while the sulphur compound sets the grain, so brightness and ductility improve at the same time. This is the combination most acid copper packages are built on, and it is the first thing to get right before trimming anything else.
With a polyamine, a dye or another sulphur compound
Adding a polyamine, a dye or a further sulphur compound to the same package pushes the response further — the effect is noted to improve rather than to plateau. In practice MPS is almost never used alone: it is one member of a multi-component system, and its level is set against the other members rather than in isolation.
Matching a package you already run
Tell us the bath type — sulphate or mixed acid copper — the substrate, and the other plating chemicals already in your brightener, and we will say whether this 95% powder is the right grade for that make-up. Formulators building something new usually start from the same three questions: what brightness does the part need, how much ductility can be traded for it, and what does the rest of the package already contain.
In the plant
Treat MPS as a fine powder rather than a liquid. Weigh it in a dry, draught-free area, wear a dust mask and eye protection, and keep the scoop and balance clear of acid or oxidiser residues from the next drum along — in a metal plating process, a scoop that has been in the wrong container is a contamination event, not a rounding error. Most lines dissolve the weighed powder in a small volume of demineralised water with stirring before it joins the make-up, which stops undissolved particles from settling on the work.
In the store
Keep the container closed and the store dry. Moisture is the practical enemy of a sulphonate powder: it takes up water, cakes, and then weighs heavy, so a scoop from a damp drum is not the same dose as a scoop from a dry one. Store away from acids, oxidisers and direct sunlight, and rotate stock so the oldest lot goes first.
Before it ships
The safety data sheet for the current lot is available from your sales contact, together with the transport information a freight forwarder will ask for. Classification and labelling differ between markets, so check the rules that apply where you operate before the consignment leaves.
On the line
Label the brightener container clearly and keep it apart from the wetter. In a busy plating process, mis-pouring two pale powders is a common and expensive mistake, and it usually shows up as a batch of parts that will not pass inspection.
Reading the assay
95% is the figure to build dosing on. It is not a purity claim in the absolute sense — it tells you how much of the weighed powder is the active sodium salt, so a formulation written for 95% material stays reproducible through a plating process that runs for months, provided every lot is checked against the same number.
Checking identity
Three values do most of the work when a delivery is queried: CAS 17636-10-1 confirms the molecule, EINECS 241-620-3 is the inventory reference, and a molecular weight of 178.2 matches the formula C3H7NaO3S2. A product sold under the same three trade letters from a different CAS is a different brightener and will not behave the same in a tuned bath.
What the powder looks like
White, with a fine granular texture. In the container it can settle into soft clumps; those break up under a spatula and are not a sign of degradation, but a lot that has taken up enough water to feel damp should be queried before it goes into a make-up.
Lot to lot
In the process of electroplating copper, the additive is usually the first thing to move when a deposit starts to drift. Holding the same grade and the same assay from lot to lot takes one variable off the troubleshooting list, and it is the reason we treat the assay as a specification rather than as a typical value.
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.
No. They are different molecules that happen to be sold under similar three-letter names in acid copper work, and those letters are not standardised between suppliers. MPS is sodium 3-mercaptopropanesulphonate, CAS 17636-10-1 — a single sulphur compound, not a disulphide and not a benzothiazole derivative. When you are matching a formulation, order by CAS number and assay: in the process of electroplating copper, swapping a supplier on a trade name alone is how a stable bath suddenly starts drifting.
The grade we supply is built for acid copper baths driven by rectifier current. Electroless copper plating deposits chemically and runs a different additive package, so the powder should not be substituted into one on the assumption that it behaves the same. Send us the bath type and the operating conditions and we will say whether MPS is the right component for your case.
A raw material — one component of a brightener package. Buying plating chemicals at this level means you dissolve the powder and build your own concentrate, or add it to an existing one under your own formulation. If you want a single product that fixes a dull copper bath, a complete acid copper process is the better purchase than an intermediate.
No. MPS works as the brightener component and is dosed as a minor part of the package. Wetting and surface-tension control come from the non-ionic surface active agent, and levelling from the polyether or polyamine side of the formulation. Taking one of those out to make room for more MPS usually gives a brighter but more brittle deposit, which is the opposite of what the combination is for.
Yes. The chemistry is the same; what changes is what the deposit has to survive. On a decorative part the copper is judged on colour and brightness under nickel or chrome. On a board it is judged on continuity through the hole and on how the layer behaves in the etch and resist steps that follow, which is why electronic plating lines build their brightener package around a sulphur component rather than around a wetter alone.
