Step Stencil Ordering: Define Step Locations for Mixed-Pitch Assemblies

A step-stencil order needs a dimensioned region map, not just a request for “thicker paste at the connector.” Identify the final foil thickness in every region, the face on which the transition is made, the clearance around nearby apertures, and the printer interface. Have the stencil supplier and assembly process owner resolve those items before releasing the cutting data.

This guide is for mixed-pitch assemblies where one paste-printing arrangement must serve different deposition needs. It provides an ordering worksheet and a first-print review sequence. It does not prescribe a universal step height, keepout distance or qualified PCBSync process window.

First decide whether a step is the right solution

Mixed package sizes alone do not prove that a stepped foil is necessary. Start by identifying a specific conflict: a common foil and aperture arrangement cannot deliver acceptable deposits at both a fine-pitch field and a larger joint. Record the affected reference designators and the observed defect or design concern. A heavy component is not automatically a high-paste-volume joint, and component height is not a stencil-thickness selection rule.

ASMPT describes multi-level stencils as one approach to boards with a high component mix. That establishes an available process concept, not a guarantee that a particular layout can use it. Review aperture changes, local thickness changes and separate deposition operations with the process owner. The useful decision is which option can be built, inspected and repeated with the available printer and support arrangement. See ASMPT’s stencil technology overview for the distinctions between single-level, multi-level and other deposition approaches.

Draw the step region in the same coordinate system as the paste data

Supply the released paste file, board or panel outline and assembly reference drawing together. Mark top or bottom print, units, coordinate origin and viewing direction. A screenshot can explain intent, but the supplier needs dimensioned geometry that can be registered to the aperture data. For a bottom-side stencil, agree on the file convention instead of manually mirroring a screenshot and assuming the supplier will interpret it correctly.

Give each proposed region an ID, such as A or B, and list the components it serves. Define the region boundary as a closed shape. Include adjacent openings outside that boundary in the review: a step that clears the intended component can still interfere with printing at its neighbor. Show the nearest aperture-to-transition distances on both sides of the proposed boundary.

Specify final thickness, not an ambiguous step depth

“Reduce by 30 micrometres” has no complete meaning without a starting foil thickness, and “step up” does not identify which surface changes. Write the base thickness and the final thickness for each zone. Add a section view with the board-contact face and squeegee face labeled. If two supplier processes create the same local thickness using different surface profiles, the printing implications still need review.

Keep requested and confirmed values in separate worksheet columns. This prevents a procurement note from being mistaken for an approved process specification. Do not infer achievable tolerances or minimum distances from a generic article. They depend on the stencil construction, aperture arrangement and printing system.

Indium’s Powder Choice and Stencil Design Guidelines discusses aperture release and the role of area ratio. For a stepped stencil, assess apertures using their local foil thickness. A useful geometry screening result does not replace paste-print trials, particularly close to a transition.

A worked ordering scenario without invented production results

Consider an illustrative board with a fine-pitch IC at U1 and a connector at J1. The process engineer identifies a deposit-volume conflict. The ordering package should not merely color U1 blue and J1 red. It should answer the following questions:

1. Which U1 and J1 pads are affected, and what evidence motivates a different deposit?
2. Does U1’s proposed thin region include all its relevant openings, or only a subset?
3. What happens to R7 and C12 next to the zone boundary?
4. Can the supplier position the transition with the required clearances?
5. Will the section preserve the intended board contact and squeegee motion?
6. Which deposits will be measured during the first-print review?

If the neighboring parts leave insufficient room, record that as an unresolved layout/process issue. Options for discussion include moving the boundary, revising the layout or changing deposition strategy. Do not shrink the clearance on the drawing simply to make the order appear complete.

Copy this step-stencil handoff worksheet

Project / PCB revision:
Paste-file names and revision:
Panel drawing / print side / units / origin:
Printer / frame / usable printing area:
Base foil thickness: requested ____ confirmed ____
Zone ID / component references / boundary file:
Final local thickness: requested ____ confirmed ____
Transition face / section drawing:
Nearest openings inside and outside each boundary:
Supplier clearance requirements and exceptions:
Fiducials / squeegee direction / board support:
Approved aperture modifications:
Supplier proposal revision / approval owner / date:
First-print sample identification and review criteria:

Attach one consolidated change list. If the supplier modifies apertures while developing the step layout, record those changes against the original paste data. Keep a copy of the approved proposal with the purchase order so that a replacement stencil can be ordered from the same release, rather than an old email attachment.

Check the first print at and away from the transitions

Verify the delivered stencil identity before setup. Record the board and panel revision, paste product and lot, support arrangement and printer recipe. Inspect deposits in the fine-pitch region, the larger-pad region, and near each transition. Use the project’s agreed SPI or other measurement criteria and retain the actual inspection records. Review both insufficient and excessive deposits, plus bridging, smearing and repeatability across the selected samples.

When a trial fails, preserve the baseline and change one controllable variable at a time where practical. If several conditions change together, record them all. A successful print at one component does not qualify the full panel, and a drawing approval does not demonstrate reflowed joint acceptability. Carry the stencil revision into the PCB assembly record and evaluate downstream results separately.

Next steps for an order

Use the PCB stencil service and planning tools to organize the general scope. The stencil Gerber guide explains the paste-layer input, while 3D solder paste inspection provides the next measurement context.

For a project review, send the paste data, board/panel drawing, proposed region map and printer requirements. Identify unresolved thickness or clearance items explicitly. That makes the enquiry actionable without pretending a generic online recommendation is an approved manufacturing specification.

Editorial source check: October 11, 2026. Original explanatory diagrams and worksheets; no customer inspection results or human engineer approval are represented.