One sentence apart: one removes material, one grows it
Laser cutting is subtractive. It starts from an already-rolled stainless-steel foil. The beam ablates material along the aperture outline from the top down. The hole is carved out of intact foil.
Electroforming is additive. It starts from a patterned mandrel. Nickel deposits and grows layer by layer from the exposed areas of that mandrel; aperture locations are masked so nickel never grows there. The finished nickel foil is then stripped off the mandrel. The hole is *left*, not removed — no material ever had to be taken away.
This isn't terminology. It directly sets two things:
- What determines wall condition. A laser wall is a product of ablation: energy distribution, expulsion of molten metal, and cooling all leave marks. An electroformed wall is a replica of the nickel-to-mask interface: whatever the mandrel pattern is, that's what the wall is.
- What a revision costs. Changing apertures on the laser route means changing a data file. On the electroformed route it means changing the mandrel.
The laser route: where taper and dross come from
A laser-cut wall has two inherent traits, both consequences of top-down ablation.
Taper. The beam is not a column of constant width — it has a focus and an energy distribution. Combined with material being ablated from the entry side and molten metal being expelled downward, more material typically comes off the entry side than the exit side. The aperture is not a perfect straight wall through thickness but slightly converging. Stencil orientation therefore matters: with the larger side away from the board, paste leaves through a widening opening and is more likely to stay on the pad rather than in the aperture.
Dross and recast layer. Not all molten metal is expelled cleanly. Some re-solidifies at the aperture mouth and on the wall, leaving burrs, adherent particles, and a thin layer whose structure has been altered. This is a direct enemy of printing: it raises wall friction, and paste snags on it during release.
Which is why post-processing on laser-cut stencils is a requirement, not an upgrade. The two options on the service page map to two distinct levels:
- Grinding polish — the standard step. It addresses burrs and adherent material at the aperture mouth and on the surface, so the squeegee travels smoothly and the stencil seats against the board.
- Electrolytic polish — an option, and the service page states plainly that it improves paste release. It works inside the aperture wall: electrochemical dissolution preferentially removes microscopic peaks and levels the wall overall. This is the closest a laser route gets to a smooth wall.
One boundary to be precise about: electrolytic polish improves wall roughness but does not change where taper comes from. Taper is a result of ablation geometry; polishing is subtractive refinement on top of that geometry. Expecting polish to turn an unsuitable taper into a straight wall misreads the process chain.
The electroformed route: the wall is replicated, not machined
An electroformed wall carries no dross, because nothing was ever melted, and no machined surface layer, because nothing was cut. Nickel grows layer by layer against the mask, and the final wall is a replica of the mask flank — inherently smooth, and close to a straight wall.
Three practical consequences:
- Lower release friction. At the same aperture size and the same area ratio, a smoother wall lets the paste brick release more completely. That is the core reason electroformed stencils get specified for ultra-fine-pitch work.
- Aperture consistency comes from the mandrel, not from per-aperture machining. Every wall on the sheet is the product of one forming condition, so aperture-to-aperture variation is smaller than with sequential ablation.
- Revisions are expensive. Change the apertures and you change the mandrel. A revision on the laser route is a data change; on the electroformed route it is retooling. This is the most commonly overlooked selection criterion, and the one most likely to bite mid-project.
Material follows the route. The service page states stainless-steel foil as the standard stencil material and nickel for electroformed stencils. These are not interchangeable material choices — they're consequences of the route. Rolled foil is what makes stainless steel available; electrodeposition grows nickel.
Translating wall condition into print results: back to area ratio
Any discussion of aperture walls has to land on a computable criterion, or it stays qualitative. That criterion is area ratio.
Area ratio = aperture area ÷ aperture wall area. It compares the force pushing paste out against the friction holding paste in. The IPC rule of thumb keeps it at 0.66 or above; below that, paste tends to stay in the aperture and you get insufficient deposits or open joints. The derivation and the common component/aperture combinations are covered on the service page's aperture design reference and in stencil aperture area ratio and paste release; no need to repeat them here.
What this article adds is the assumption inside that formula: aperture wall area is an ideal geometric value. It contains no variable for wall condition.
That explains a familiar floor puzzle — two stencils compute to the same area ratio and print differently. The formula counts *how much wall there is*; what actually acts is *how rough that wall is and how much it grips*. So:
- Area ratio ≥ 0.66 is a necessary condition, not a sufficient one. If the wall condition is poor, a good number won't release paste.
- The closer the ratio sits to the limit, the more weight wall condition carries. Around 0.66, the gap between laser-plus-electrolytic-polish and electroforming widens into visible print defects.
- When the computed value itself is borderline, the right move is to change the route or the thickness, not to keep nudging apertures toward a prettier number. Thickness changes have to respect what the board can hold too — see manufacturing capabilities and tolerance standards.
Thickness and size ranges: what the route constrains
Published foil thicknesses are 0.08 / 0.10 / 0.12 / 0.15 / 0.20 mm, with common framed sizes from 370×470 mm to 584×584 mm. Those are the day-to-day ranges; anything beyond — custom frames, oversized foils, specialty coatings — is reviewed case by case.
What matters is that thickness freedom has a different nature on each route:
- On the laser route, thickness comes from foil selection. Foil is an off-the-shelf specification; changing thickness means changing sheets and recomputing aperture data for the new thickness.
- On the electroformed route, thickness comes from deposition time — nickel is as thick as it grew. Electroforming is therefore continuously controllable in thickness, but the cost still lands on the mandrel: a new thickness means a full growth-and-strip cycle.
Step stencils are a third dimension stacked on top of the route. Different thickness zones on one sheet let you accommodate widely different components at once. Their design constraints — transition zones, squeegee travel, local aperture correction — are an independent topic from route selection; see multilevel step stencil aperture design.
Nano-coating is not a substitute for a route
The service page lists nano-coating as an option and describes it precisely: it cuts wipe frequency and extends service life. Not one word in there says it changes how the aperture wall was formed. That's the point.
What nano-coating does is lower surface energy: paste and board contamination adhere less readily to the stencil surface and aperture mouth, so wipe intervals stretch and continuous printing holds steadier. It is a layer added to an already-formed surface.
What it does not do:
- change the direction or magnitude of laser-cut taper;
- compensate for wall roughness itself (that belongs to polishing and to route choice);
- change the computed area ratio.
So "the area ratio is a bit low, let's try nano-coating" is a remedy pointed the wrong way. Coating improves the maintenance interval, not the geometric and frictional basis for release. The order is always: fix the route and thickness so the area ratio stands up, then polish the wall properly, and only then consider coating for wipe frequency.
Decision table: when to switch routes
| Condition | Favors laser cutting | Favors nickel electroforming |
|---|---|---|
| Component pitch | Standard to fine pitch | Ultra-fine pitch, miniature chip parts, dense BGA |
| Area ratio margin | Computed value comfortably above 0.66 | Computed value near the 0.66 limit |
| Revision rate | Data still iterating, multiple trial builds | Design frozen, sustained production |
| Print frequency | Short term, small batch, prototype | High frequency on the printer, long production runs |
| Thickness needs | Falls within standard foil specifications | Needs a thickness between standard foils |
| Lead time and cost | Shorter cycle, lower cost | Requires additional mandrel investment |
Two cautions when reading this. First, neither route wins on every axis — electroforming's wall advantage and its revision cost are two faces of the same mechanism (the mandrel defines aperture form). Second, most projects aren't a one-time either/or: validating the process window on laser during data iteration, then moving to electroformed for volume once the design freezes, is a legitimate and common path.
Engineering release: what to confirm from data to shipment
The two ends of the flow are identical regardless of route.
Input side. The service page states accepted inputs: Gerber RS-274X (paste, solder mask and outline layers), ODB++, DXF. The usual failure here isn't format but layer completeness — with only a paste layer, engineering cannot confirm aperture position relative to pads and outline. Quantity and quotation, per the service page, are confirmed after review of Gerber data, quantity and process requirements, not quoted before the data is seen.
Release side. Three things to align: aperture data governed by the engineering-reviewed release version; foil thickness and frame size confirmed within published ranges or already sent through case-by-case review; polishing and coating options confirmed in the order above rather than treated as universal fixes. Once built, a stencil is only truly tested on the printer — the print station in SMT assembly and PCBA services reproduces exactly the quality of the formed wall. Overall inspection and release criteria are on quality assurance.
To have the stencil and the board process window evaluated together, submit your data for a quote. If you're still deciding at the material and frame level, start with stencil material and frame tension selection.
FAQ
Can laser-cut and electroformed stencils use the same aperture data?
The data can share a source, but it should not be copied across directly. Wall condition and taper differ between routes, so the same aperture size releases differently on each. Hand the aperture data to engineering for review against the intended route, and treat the reviewed release version as governing.
Can electrolytic polish or nano-coating replace electroforming?
No — they solve different layers of the problem. Electrolytic polish improves the wall roughness left by laser cutting. Nano-coating improves wipe frequency and service life in use. Electroforming changes the wall-forming mechanism itself, giving an inherently smooth, near-straight wall. The first two optimize an existing geometry; the third replaces where that geometry comes from.
Why do stencils have an orientation, and what happens if it's reversed?
Laser-cut apertures are tapered through thickness, with the entry side typically slightly larger. Mounted correctly, paste exits through the widening side, which aids release. Reversed, paste has to release through the converging side and release resistance rises. Orientation is a fixed confirmation item at installation.
Area ratio is already above 0.66 but printing is still unstable. Where else to look?
Area ratio describes geometry only. It excludes wall condition, paste characteristics, tension and handling. A rough wall, a reversed orientation, decayed tension or inadequate cleaning will all produce defects while the geometry stays compliant. Confirm wall condition and orientation first, then tension and handling, and only then return to the apertures.
Can stencil thickness be outside the published specifications?
The published 0.08 / 0.10 / 0.12 / 0.15 / 0.20 mm are the foil thicknesses built day to day. Requirements beyond that range — including custom frames, oversized foils and specialty coatings — are reviewed case by case per the service page, and need board thickness, component mix and aperture requirements submitted together for assessment.
Can an order proceed with only the paste layer in Gerber?
Not advisable. The service page asks for paste, solder mask and outline layers in Gerber RS-274X. Without solder mask and outline, engineering cannot verify aperture-to-pad registration or board outline, so aperture release has no basis. Quantity and quotation likewise require data review first.
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