Component Placement Guidelines
Place each component for the circuit it serves—and for the way the finished board will be assembled, inspected and used.
- Circuit intent
Short paths, return paths and thermal needs
- Physical fit
Bodies, mating parts and tolerance
- Assembly access
Placement, soldering, inspection and rework
The best location is not always the neatest row.
Electrical-critical placement must follow the actual device and circuit requirements. Power-conversion guidance, for example, treats current paths and sensitive feedback connections as functional design decisions—not cosmetic alignment choices.
Use the mechanical constraints and electrical priorities to establish the layout, then review the process access around each part. A generic spacing rule cannot capture component height, nozzle geometry, connector access or the planned soldering method.
- Land pattern
- The copper, mask and paste features that connect the package.
- Component envelope
- The occupied space, including body and terminal tolerances.
- Process envelope
- The additional space needed for tools, inspection and handling.
What to resolve before release
Use these review prompts with the actual design, component documentation and agreed manufacturing process.
Anchor the mechanical interfaces first
Locate connectors, mounting hardware, controls and enclosure interfaces against controlled mechanical data. Include the mating connector, latch motion, screwdriver path and cable exit—not just the footprint outline.
Protect circuit-critical positions
Keep decoupling, switching loops, sensitive feedback and other critical placement consistent with the device guidance and electrical design. Resolve any conflict with assembly access jointly rather than moving parts only to make the layout uniform.
Check the complete occupied volume
Use package dimensions and tolerances to check both sides of the board. Model tall components, shields, heatsinks and items installed later. A two-dimensional body outline cannot reveal every assembly collision.
Make orientation intentional
Use clear pin-1, diode, LED and polarized-capacitor references. Verify how the export expresses bottom-side rotation. Assembly-checking tools illustrate why footprint orientation and placement data must be reconciled.
Reserve access for the chosen process
Review component pickup, selective soldering, board support and depanelization before releasing the layout. Keep fiducials visible and confirm edge handling requirements with the assembler; do not assume a universal edge clearance.
Keep inspection and repair practical
Check whether tall parts hide neighboring joints or obstruct a rework nozzle. Put useful reference markings where they remain legible, without printing in areas that interfere with assembly.
Review clearances by purpose—not by one universal number
Populate your CAD rules with values agreed for the actual components, equipment and board construction.
On a small screen, scroll the table horizontally to see every column.
| Area to review | What needs space | Requirement owner / evidence |
|---|---|---|
| Board edge and tabs | Conveyor support, handling, routing or depanelization tools. | Assembler and panel drawing; include stress-sensitive components. |
| Neighboring components | Worst-case body/lead dimensions plus the required process access. | Package drawings and an agreed assembly rule set. |
| Connectors and controls | Mating parts, latches, cable bends and service access. | Mechanical assembly and enclosure model. |
| Tall or heavy parts | Nozzle path, fixture support, thermal influence and retention. | Assembly process and mechanical review. |
| Dense and hidden-joint packages | Inspection approach and any local rework envelope. | Package guidance and approved inspection/rework plan. |
| Test and programming points | Probe approach, connector engagement and support below the board. | Test engineer and fixture design. |
Keep the approved project requirements in control. Record uncertainties, agreed exceptions and the supporting evidence before the affected operation is released.
Placement data needs a shared coordinate convention.
Document the board origin, measurement units, component center definition, fitted side and rotation convention. Validate the exported placement against the assembly drawing using asymmetric packages on both sides of the board. Resolve differences in the source data instead of relying on an operator to guess.
- Pin 1 is a cross-check
- Compare the package drawing, footprint, placement output and assembly view.
- The bottom side needs attention
- A mirrored view and a machine rotation convention are not interchangeable.
- DNP is configuration data
- Keep unused locations visible in the review but unambiguously excluded from fitting.
Move from open questions to controlled decisions.
These steps organize a project review. They do not replace your formal release or acceptance process.
Constrain
Set enclosure interfaces and board mechanics.
Prioritize
Place circuit-critical components and paths.
Validate
Check tolerances, access and orientation.
Release
Export and reconcile the placement data.
Record the review.
Keep the evidence.
12 checks for this topic. Record status and notes, then export a text copy for your project discussion. A completed checklist is not certification or production approval.
Session only. Nothing is saved automatically or transmitted. Export before closing or reloading. “Reviewed” records evaluation—not a pass verdict. Explain blocked and not-applicable items in the notes.
Showing 12 of 12 checks. Export always includes all checks.
Connectors align with the mating assembly.
Include plugs, latches and cable access.
Height limits and installation sequence are checked.
Inspect both sides and later-installed parts.
Mounting hardware and tools have adequate access.
Use the actual screw head, spacer and tool.
Critical placement follows the circuit requirements.
Record exceptions to device guidance.
Thermal and airflow constraints are reviewed.
Include heatsinks and nearby temperature-sensitive items.
Package envelopes and tolerance are represented.
Do not use nominal body size alone.
Board handling and depanelization areas are agreed.
Check support and stress-sensitive locations.
Placement and soldering tools can reach the sites.
Review tall neighbors and both-side interactions.
Fiducials and assembly markings are unobstructed.
Avoid legend that interferes with solderable areas.
Pin-1 and polarity indications are consistent.
Cross-check CAD, drawing and package.
Bottom-side rotation has been validated.
Use an asymmetric reference component.
Probe and rework access have been reviewed.
Record inaccessible sites and the agreed alternative.
No checks match these filters. Change a filter to view other items.
Export your checklist and resolve outstanding items with your engineering team before production. Confirm any changes through your normal approval process.
Practical answers
before release.
Use these answers to frame the discussion. The approved project requirements remain the authority for the build.
What is the minimum spacing between components?
There is no single value suitable for all packages and processes. Derive the limit from dimensional tolerance, electrical rules and the agreed assembly, inspection and rework access. Put the resulting values into the project CAD rules.
Should all similar components face the same direction?
Consistent orientation can simplify review, but it is not a reason to compromise critical electrical paths or connector mechanics. Document intentional exceptions and ensure the placement export is correct.
Can silkscreen go underneath a component?
Check the actual package and assembly rules. Legend can interfere with very small parts or solderable features, and hidden markings may not help inspection. The cited design-rule guidance explains clipping and readability concerns rather than a universal clearance.
Why can a bottom-side component appear reversed?
CAD views and placement exports use conventions that need to be understood explicitly. Confirm side, rotation and pin-1 identity against a known asymmetric component instead of inferring orientation from a screenshot.
Should rework clearance be reserved on every prototype?
Decide this in the project review. Critical or high-risk components may need planned removal and replacement access. BGA rework, for example, involves local thermal and mechanical constraints that should not be discovered after assembly.
Technical references & scope
- Analog Devices — AN-117, power-module PCB layout
An example of component-specific electrical and thermal placement priorities.
- KiCad — PCB Editor: Manufacturing Outputs and Design Rules
Typical placement review issues: pin 1, outlines, footprints and rotation.
- Analog Devices — AN-1448, PBGA rework
Rework planning, thermal characterization and post-rework verification.
- KiCad — PCB Editor: Manufacturing Outputs and Design Rules
KiCad design-rule guidance on silkscreen readability and solder-mask clipping; project-specific assembly clearances still require review.
- Texas Instruments — SMT and packaging application notes
Starting point for the application note appropriate to the actual package.
Use these engineering references alongside your component documentation and the standards specified for your order. Share your completed checklist with us to confirm assembly, testing and material requirements.