Brush Plating Repair: 6 Rules for Selective Plating

Brush plating repair deposits metal on a local area of a finished board using a hand held anode wrapped in an absorbent sleeve soaked in plating solution. It restores a damaged track, a worn edge connector or a pad that has lost its finish, without immersing the whole assembly in a plating tank.

The technique is genuinely useful and genuinely difficult. The deposit forms only where the wand touches, so the operator controls the area, the thickness and, to a large extent, the quality of the bond. A repair that looks right and adheres badly will fail at the first thermal cycle, so it is a repair tool rather than a production process.

<img src="https://www.gopcba.com/wp-content/uploads/2026/08/iStock-1307839840-jpg.webp" alt="Brush plating repair with an anode wand on a PCB pad” />

What Brush Plating Is Used For

The usual applications are repair rather than production: a track damaged during handling, a worn gold edge after repeated insertion, a pad that has lost plating, and test coupons that need a finish before an evaluation. In each case the board is too far through the process to return to the tank.

Brush plating is also used where a small area needs a different finish from the rest of the board. The bath is the sleeve rather than a tank, so the chemistry is applied only where it is wanted, which is what makes the process selective plating in the literal sense. The same equipment is used in the laboratory to plate a coupon where a full bath is impractical.

Cleaning and Surface Preparation

The deposit bonds only to what it can reach, so cleaning is the step that decides the result. Oxide, residue and the remains of a previous finish all sit in the interface and become the failure plane later, whatever the deposit looks like at the time.

Preparation is mechanical and chemical: abrade lightly, clean with a compatible solvent, and activate the surface immediately before plating. The window between activation and plating is short and should be treated as a process limit. The preparation practice used for a pad repair, as described in rework site preparation, applies directly to brush plating.

The Anode Wand and Its Movement

The wand has to be in contact with the surface through the sleeve, and it has to keep moving. A stationary wand burns the solution, deposits a spongy layer and can etch the area it is meant to build up. The sleeve also has to stay wet, because a dry sleeve stops conducting and starts scratching the surface.

Movement speed and pressure are the operator variables that decide the deposit structure. Slow, even strokes with light pressure produce a dense deposit, while fast strokes with heavy pressure give a thin deposit that looks bright and measures short of the target thickness.

Solution Selection and Deposit Purity

Solutions are supplied for copper, nickel, gold and other metals, and each has its own current density and rate. Using the right solution for the surface underneath is what makes the repair compatible with the rest of the board, since a gold deposit on a nickel barrier behaves differently from gold directly on copper.

Contamination of the sleeve is a real risk, because the same wand is used repeatedly and the solution picks up whatever the last board carried. The test methods used in ionic contamination testing show what a repair can leave behind if the area is not rinsed, and a dedicated wand for each solution is the simplest way to avoid cross contamination.

Deposit Adhesion and Thickness

Adhesion is verified by a tape test or by a bend test on a coupon plated with the same setup, and it is a better predictor of service life than appearance. A coupon plated with the same parameters is the evidence that the setup is capable. Where the deposit lifts with tape, the preparation was insufficient and the repair must be redone from cleaning.

Thickness is controlled by time and current rather than by appearance, and it should be measured. The measurement methods used in copper thickness measurement work apply to a plated repair area as they do to a plated panel.

Masking and Keeping the Repair Local

The repair has to stay where it is wanted. Masking tape, lacquer and a defined wand path keep the solution off neighbouring pads, vias and components, and the masking has to be removed cleanly afterwards without leaving adhesive behind, so the tape chosen has to survive the solution and still come away clean.

Solution that creeps under a mask leaves a thin, poorly bonded film that is harder to find than an obvious splash. The area around the repair should be inspected under magnification after cleaning, not simply wiped.

Rework Rules and Acceptance

A plated repair is still a repair, and it has to fit the rework rules that the product carries. Some customers prohibit it on certain features, and some products are classed so that a plated repair is not permitted at all.

The decision framework used in site preparation and the general practice in PCB rework and repair work should be applied before the wand is picked up, so that the repair is allowed as well as possible, and the rule should state how many times an area may be repaired before the board is scrapped.

Testing the Repaired Area

The repair should be tested electrically and mechanically. Continuity and resistance confirm that the connection exists, and a solderability check on a plated pad confirms that the surface will accept solder in the next assembly step, using the methods in solderability testing, and the check should be made at the repair rather than on the board as a whole.

Where the repair is on a functional feature, the test should include a thermal exposure, because the interface is what fails first. A repair that passes a resistance check and fails after a reflow cycle has not been verified.

Records, Limits and Training

The record should carry the board serial, the location, the solution, the current, the time, the thickness, the adhesion result and the operator. Without those fields, a repair can be repeated on the same board without anyone noticing that the limit has been reached.

Brush plating is a skill, and it should be limited to trained operators working to a written procedure. Where the process follows a published standard, such as the repair documents from IPC, the permitted repairs and their acceptance criteria should be quoted in the procedure rather than left to judgement, and operators should be recertified on a schedule so that the skill does not drift.

FAQ

Is brush plating as strong as tank plating? A well prepared and correctly applied deposit can be sound, but the interface depends entirely on the operator. That variability is why repaired areas need their own inspection and, where the feature is critical, are often not permitted.

Why does the deposit lift after a thermal cycle? Preparation is the usual cause: oxide, residue or an incomplete activation step leaves an interface that survives at room temperature and fails when the joint expands. Redoing the repair from cleaning is the correction.

Can brush plating be used on gold edge connectors? It is commonly used there, but the deposit has to match the original finish and the thickness requirement. Where the specification calls for a nickel barrier, plating gold directly onto copper is not an equivalent repair.