PCB Cleaning

A board carries components that a static discharge too small to feel can damage. An ordinary nylon brush rubbed across a board builds charge, and that charge goes into the nearest pin. So every brush that touches a populated board is static-dissipative or conductive, with a path to ground through the handle and the operator.

The cleaning itself is three different jobs. Flux left after soldering or rework sits around and under the joints, and has to be worked out with solvent, not spread. Solder paste stays in stencil apertures and on the underside of the foil. Dust and fiber cling to the board by static and come off only when the charge goes.

On production lines, brushes go into the machines: rollers and discs in board-cleaning lines, ring brushes on drilling pressure feet, and sponge rollers in etching and wet-process lines.

Sizes from the PCB brushes we make:

The bench brush is a flat conductive head, about 25 × 100 mm with 20 mm trim, on a static-dissipative carbon-fiber handle. Narrow heads of 3–10 mm reach between connector rows and around through-holes after rework.

In machines, conductive roller brushes on carbon-fiber cores run at up to 500 rpm, at line speeds up to about 20 m/min. Pressure-foot ring brushes on drilling and routing machines are matched to the foot’s inner diameter, from 5 mm up to 620 mm.

A conductive brush works only when it is grounded: through the handle to a grounded operator, a mat or a ground lead, or through the machine frame. Its resistance rises as the fill wears, so check it on a schedule.

• Work at an ESD-safe station, grounded through a wrist strap and mat.
• Apply flux remover to the joint area, then work the brush in short strokes between the leads.
• Wick or rinse the dissolved flux off the board so it does not dry back as a film.
• Clean stencils from the underside, with the brush moving across the apertures, not into them.
• Let the board dry fully before power is applied.

• Bench brushes, or brushes for a cleaning line, drilling machine or wet line.
• For machine brushes: the drawing, shaft or hub, diameter and face length.
• The resistance range your ESD program requires.
• Solvents and process temperatures.
• Quantity: 500 pieces for small hand brushes, 100 for medium and large machine brushes.

No-clean flux is designed to stay on the board; brushing it with solvent can leave a partly dissolved film that is worse than the original. Follow the flux maker’s guidance. Boards that need validated cleanliness are cleaned in a defluxing machine, with brushing only for local rework.

• An ordinary nylon brush on a populated board, which charges and can damage components.
• Brushing dissolved flux around the board instead of removing it.
• A conductive brush with no ground path.
• Scrubbing into stencil apertures, which deforms the foil.
• Powering a board before the solvent has dried.