Guides / Assembly
Solder paste stencils: framed, frameless, and printing basics
How paste gets onto the board before placement — which stencil to order and how to print a clean deposit.
Before a single part is placed, solder paste has to land on the pads — and it gets there through a stencil. Get the print right and reflow mostly takes care of itself; get it wrong and you chase bridges and tombstones all day.
Framed vs frameless
A framed stencil is foil tensioned in a permanent frame — rigid and fast for production. A frameless (foil) stencil is just the foil in a reusable jig — cheaper and compact, ideal for prototypes. See all the stencil types.
Thickness and apertures
Foil thickness sets paste volume — 0.12–0.15 mm is a common all-round choice, thinner (0.10 mm) for fine-pitch QFN and 0.4 mm-pitch parts. Apertures are often shrunk slightly from the pad to avoid too much paste on fine features.
Printing a clean deposit
- ·Align the stencil to the pads and clamp or tape it down
- ·Lay a bead of paste and pull one firm squeegee stroke at about 45°
- ·Lift straight up — a clean release leaves crisp, brick-shaped deposits
- ·Wipe the underside between prints so paste doesn't smear
Once paste is down and parts are placed — the converter prepares that placement step — the board goes to reflow.
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