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IPC-7351 Land Patterns: Scope, Revision Status and Practical Review
IPC-7351 is associated with generic surface-mount design and land-pattern principles. It does not eliminate the need to review the exact component drawing, assembly process and product constraints. A footprint named after a standard is not automatically correct for every package or manufacturing route.
The official IPC document revision table currently lists IPC-7351 as no longer maintained, with Revision B shown from June 2010, and separately lists IPC-7352 as a generic guideline. This status should prompt a controlled document review, not an unsupported claim that an existing contract or library is automatically invalid.
Establish the applicable document basis
Identify which document and revision govern the project. A customer contract, component recommendation and internal library rule may refer to different sources. Resolve their relationship explicitly instead of silently choosing whichever produces the smallest footprint.
Public contents and scope pages help identify a document but are not the full normative text. This page does not reproduce paid standard tables or claim to implement the IPC-7351 algorithm. Consult the controlled document for requirements and definitions that affect acceptance.
Land-pattern review envelope
Land-pattern review envelope
Use the current inputs and keep the assumptions
Choose the question you want to resolve before entering numbers. The fields start blank. Load example deliberately if you want to understand the calculation, and keep that example separate from your project record. The example label remains visible after editing; reset the tool before preparing a record from your own data.
Use the displayed units and identify the source of each input. A dimension should refer to the same layer, reference plane and design revision as the other dimensions in the model. An entered limit is your review requirement, not an IPC value supplied by this website. Where a value is unknown, obtain it or preserve the question as open instead of guessing a familiar number.
Read the assumptions with the result. A negative margin is retained so a conflict remains visible. A positive margin only answers the stated mathematical question. It does not establish process capability, compliance, electrical performance or production yield. Checklist statuses are self-reported and do not imply that the underlying evidence has been inspected.
Changing a field invalidates the result and disables its download until you calculate again. The text download contains the current inputs, result and limitations. No CAD file is read, no project data is uploaded and nothing is automatically inserted into Contact. Attach the record manually if useful. You can request a review directly without using the worksheet.
| Input | What to establish before using it |
|---|---|
| Review reference | Connect this worksheet to a nonconfidential design/revision reference. |
| Maximum body width 繚 mm | Use the actual released drawing and one dimensional reference. |
| Maximum body length 繚 mm | Use the actual released drawing and one dimensional reference. |
| Total land extent width 繚 mm | Use the actual released drawing and one dimensional reference. |
| Total land extent length 繚 mm | Use the actual released drawing and one dimensional reference. |
| Additional courtyard allowance per side 繚 mm | Entered project rule; this is not the IPC-7351 calculation algorithm or a normative density level. |
Separate the footprint's responsibilities
Copper lands support the electrical and solder attachment interface. Mask openings control the exposed board surface. Paste apertures support printing. Assembly outlines, component bodies and courtyards support different mechanical and manufacturing checks.
A courtyard should not be mistaken for a copper clearance or electrical creepage boundary. A library tool can display all these layers together, so naming and visibility conventions matter. The SMT footprint review helps audit the exported geometry and package match.
| Review item | What to establish |
|---|---|
| Status | Check the official revision table and contractual basis. |
| Scope | Public contents are not the full standard. |
| Tool | Rectangle envelope is not the IPC land-pattern algorithm. |
| Library | Tie changes to the exact drawing and exported board instance. |
Start from the actual component dimensions
Use the exact package drawing with its dimensional tolerances and terminal form. Body dimensions alone do not establish lead span or terminal location. For QFP and QFN, the package comparison highlights why apparently similar pin counts can require different land and inspection discussions.
Review manufacturer recommendations and any approved project-specific deviation. Preserve the source and rationale in the library record. An unexplained manual pad edit can persist through several projects while losing the reason it was introduced.
Use the envelope worksheet for a limited check
The tool takes the larger of the entered body and total land extents in each axis, then adds a user-defined allowance on both sides. It assumes centered rectangular extents. This can help visualize a simple review envelope, but it is not a standards-based land-pattern generator.
For a 5 by 6 mm body, 6 by 7 mm total land extent and 0.25 mm allowance per side, the resulting rectangle is 6.5 by 7.5 mm. It does not calculate solder fillets, statistical tolerances or a normative density level. Irregular or offset geometry requires a different construction.
Review the footprint in the assembled product
Neighboring components, placement access, inspection, rework and enclosure constraints can require additional space. A library courtyard is an input to that review, not a guarantee that every operation is accessible. Use component placement review to bring the relevant disciplines together.
For hidden-joint packages, verify copper, mask and paste relationships with the package-specific guidance. For polarized components, confirm that the origin and pin-one convention remain consistent through the placement export and assembly drawing.
Keep changes and validation traceable
Record library revision, source drawing, checks performed and accepted exceptions. Recheck the actual exported files after a footprint correction; updating the library alone may not update an existing board instance. A repeated design should identify which library state it uses.
For an enquiry, provide the part drawing, relevant footprint layers and the question to resolve. 勛圖tv can review the assembly and manufacturing interface with that context. A claim of IPC compliance should rest on the applicable controlled requirements and evidence, not on this page, its calculator or a filename containing IPC-7351.
Audit a footprint from supplier drawing to released output
Open the exact package drawing and the board instance side by side. Establish the part number, package suffix and reference orientation before comparing dimensions. A library name can be helpful, but it is not evidence that the installed footprint corresponds to the ordered component. Variants with similar names can differ in lead span, exposed pad or terminal numbering.
Compare the copper geometry first, then the mask and paste layers. Check that each layer performs its intended function and that a local override has not silently replaced the library rule. Include a trace connection or nearby via where it affects the attachment interface. Review the origin and rotation convention separately from the visible pin-one marker.
Keep dimensional tolerances on a consistent basis. Diameter variation, radial allowance, center offset and lead-position tolerance should not be combined as though they were the same quantity. A conservative review can be useful, but double counting the same process variation can also lead to an unnecessary redesign. Record the source and meaning of each allowance.
Inspect the footprint in its actual neighborhood. Adjacent bodies, inspection access, enclosure constraints and rework needs may require additional space beyond the land pattern. A good standalone footprint can still be placed in a poor manufacturing arrangement. The footprint and placement reviews should exchange their findings without merging all responsibilities into one unexplained clearance number.
When a correction is accepted, update the controlled source and determine which existing board instances are affected. Re-export the manufacturing data and inspect a representative changed feature. A corrected library does not prove that the current board was refreshed or that an older paste file was replaced.
For a review request, include the component drawing, relevant exported layers and a marked question. State whether copper, mask, paste or placement may change. This limits the review to an actionable decision and preserves the product requirements that a general footprint optimization might otherwise overlook.
Standards, source context and limits
The references below support the stated package, design or process context. Apply a component manufacturer's guidance to its named device or family and confirm the exact drawing revision. A supplier application note is not a universal manufacturing rule, and a public standards scope is not the complete controlled standard.
Agree the governing documents, revision basis, acceptance requirements and exceptions with the responsible engineering and quality teams. The official IPC revision table is useful for checking document status; it does not by itself resolve a project's contractual requirements. This page does not reproduce paid normative tables or claim certification.
Archive photographs illustrate relevant boards, components or assembly activity. They are not proof of the current equipment inventory or a completed qualification for your project. The explanatory drawings and worked examples are original teaching aids. Confirm actual process availability and the proposed inspection scope during the project review.