SMT stencil thickness: mm, mils, and how to choose
The foil thickness decides how much solder paste lands on each pad. Here is how to pick it — and when one thickness is not enough.
Most SMT stencils are 0.10–0.15 mm thick, and 0.12 mm is the usual starting point for boards that mix standard SMD parts. The rule is to let the finest-pitch component decide: parts at 0.4 mm pitch and below usually want 0.10 mm or thinner. When one board needs both thin and thick deposits, the answer is a step stencil rather than a compromise foil.
The eight thicknesses we stock
We keep eight foil thicknesses in stock, from 0.08 to 0.30 mm. These are the same options the quote engine offers, with the typical use for each. Mils are included because a lot of component datasheets and design guides still use them: one mil is one thousandth of an inch, or 0.0254 mm.
| Thickness | mils | Typical use |
|---|---|---|
| 0.08 mm | 3.1 | Thinnest foil — fine-pitch work and 01005 parts |
| 0.10 mm | 3.9 | Fine pitch — around 0.4 mm pitch and below |
| 0.12 mm | 4.7 | The usual starting point for mixed boards |
| 0.15 mm | 5.9 | Mixed boards with larger through-hole parts |
| 0.18 mm | 7.1 | More paste for through-hole and larger pads |
| 0.20 mm | 7.9 | Heavy paste deposit — connectors and power pads |
| 0.25 mm | 9.8 | Power components and large-area joints |
| 0.30 mm | 11.8 | Thickest foil — IGBT modules and heavy components |
Why thickness decides the printing
A stencil is a one-to-one tool: the aperture in the foil is the deposit on the pad. Thicker foil makes a deeper aperture and leaves more paste; thinner foil leaves less. More paste helps big joints and heavy components fill properly, but too much paste on a fine-pitch part bridges two pads together. Less paste is safer for fine pitch, but too little starves large through-hole joints. The limit on how fine a given thickness can print is the area ratio — the opening area compared with the aperture wall area.
Matching thickness to the board
A practical way to read a board:
- Boards of 0402/0603/0805 passives and standard SOICs print happily at 0.12 mm — the everyday starting point.
- QFN, QFP and BGA parts at 0.4 mm pitch and below generally want 0.10 mm, and the finest work goes down to 0.08 mm.
- Boards with large through-hole joints, connectors or power pads need more paste — 0.15 mm and up, or a local thickening.
- When both extremes live on one board, no single thickness serves both well — that is the step stencil case.
When to step instead of choosing
If your finest pitch calls for 0.10 mm but a connector needs the paste volume of 0.20 mm, a step stencil carries both: the fine-pitch area stays thin, the connector area is thickened, and the board prints in one pass. Send us the Gerber and we will quote the step from the actual layout — it is priced from the file, not from a list.
If you are not sure
Tell us the smallest part on the board and its pitch — that single number usually settles the thickness. Send the Gerber file and we will check it ourselves and confirm the choice, usually within the same working day.
Common questions
Should I choose 0.12 mm or 0.15 mm?
Both are general-purpose choices. 0.12 mm is the safer start for boards with 0402–0805 parts and any fine pitch at or below 0.5 mm. 0.15 mm suits boards whose smallest parts are 1206 and larger, or that carry heavy through-hole joints — it deposits more paste, which those joints need. If the board mixes both worlds, ask for a step stencil.
What is a mil in mm?
One mil is one thousandth of an inch, exactly 0.0254 mm. In stencil terms: 4 mil ≈ 0.10 mm, 5 mil ≈ 0.12 mm, 6 mil ≈ 0.15 mm. Older datasheets and US process guides often quote mils; the table above converts each of our stock thicknesses.
Can I order a thickness that is not on the list?
Our stock covers 0.08–0.30 mm in eight steps, which is the working range for most SMT boards. If your process calls for something outside it, tell us the requirement and we will look at it together — some requests are better solved by a different material or a step, and we will say so.
How does this connect to the area ratio?
The area ratio is the geometry check that decides whether a given aperture can release paste from a given foil thickness. Our area-ratio guide walks through the 0.66 rule with formulas and worked examples — it is the calculation behind most of the thickness advice above.
Related guides
Stencil cost
What a stencil costs, and what changes the price.
Step stencils
When one board needs two foil thicknesses in one stencil.
Framed vs frameless
Which mounting suits your production.
Area ratio
The 0.66 rule that decides whether paste releases cleanly.
Buying from China
Ordering direct from a Chinese factory, step by step.
See full specifications
Covers almost every PCB assembly process.
Need a price today?
Pick your specifications and see the price immediately, or send us a message and we will get back to you.
English / 中文 / Español / 日本語 / 한국어 / Tiếng Việt