WSON-10 3×3 mm Footprint: DFM, Layout, and Assembly Guide

WSON-10 3×3 mm is a no lead package used for surface mount assembly, also seen labeled 10-WSON, SON-10 exposed-pad, 0.5 mm-pitch WSON. A dependable footprint follows the exact orderable-device drawing rather than the family name: nominal body 3.0 × 3.0 mm nominal, overall span 3.0 × 3.0 mm body, seated height Often 0.7–0.9 mm, pitch 0.5 mm, pin count 10 perimeter terminals plus exposed pad, and exposed pad Common and often functional.

Use the exact package code and center-pad tolerances; WSON-10 is not a single cross-vendor footprint.

Typical uses include battery monitors, power management, analog switches. WSON-10 3 × 3 mm at 0.5 mm pitch remains package-code-specific in both perimeter and exposed-pad geometry.

• Five 0.5 mm-pitch terminals run along each side of a 3 mm body, tightening the exposed-pad clearance compared with WSON-8.
• A no-lead package is defined by its complete manufacturer drawing: nominal body and pitch do not fix terminal length, pullback, exposed-pad size, or corner geometry.

Separate force and sense nets where used, keep power loops broad and short, and place thermal vias only within an approved paste and fill plan.

• Escape outer terminals without narrowing below the fab profile, keep copper out from under the package unless intended, and connect any exposed pad to its documented net.

Hand assembly is rated expert-only. Controlled stencil and reflow with hidden-joint inspection. Watch for narrow center-to-terminal gap and a wrong exposed-pad assumption.

• Analyze mask and copper tolerances at the inner terminal ends, then segment center paste to hold package height and voiding within process limits.
• Use a windowed or otherwise reduced paste pattern on a large exposed pad so the body is not floated above its perimeter joints.
• Agree mask-defined versus non-mask-defined geometry, via fill, and inspection method with the assembler before release.

Inspection focus:

• Use X-ray for center-pad and row alignment, then verify measurement accuracy or switching behavior across the intended current range.
• Perimeter wetting may be only partly visible and the center pad is hidden. Use X-ray or validated process evidence when voiding and opens matter.

Common mistakes:

• A footprint that visually centers the body can still overlap the exposed pad with all ten terminal heels if terminal pullback differs.
• Do not copy a generic QFN, DFN, or SON footprint with the right pin count but a different exposed pad or terminal pullback.

1. Before approving WSON-10 3×3 mm, compare the exact orderable-device drawing with the library item: body range (3.0 × 3.0 mm nominal), terminal or lead span (3.0 × 3.0 mm body), pitch (0.5 mm), pin count (10 perimeter terminals plus exposed pad), height (Often 0.7–0.9 mm), and exposed-pad definition (Common and often functional). Record the source drawing revision and every intentional courtyard, toe, heel, side, mask, or paste adjustment.
2. Treat the expert-only hand-solder rating as a prototype-planning input, not proof of production yield. Review narrow center-to-terminal gap and a wrong exposed-pad assumption with the assembler, confirm that controlled stencil and reflow with hidden-joint inspection is compatible with the build, and require the S1 connectivity gate plus relevant S2 geometry checks to pass against the released footprint and selected fabrication profile.

Manufacturing gate checks:

1. S1Pad count, numbering, and schematic parity. Center-pad clearance and net, ten terminal assignments, force/sense separation, and via construction need explicit evidence.
2. S1Exposed-pad connectivity and paste segmentation. A missing or wrongly netted center pad can break electrical, thermal, and mechanical performance while remaining visually hidden.
3. S2Courtyard and body clearance. The body, leads, placement tolerance, rework access, and nearby height limits all belong in the manufacturing review.