Introduction
PCB design involves more than just schematics and layouts. Conveying your design intent to procurement, assembly, test, and manufacturing stakeholders is crucial using detailed PCBA (Printed Circuit Board Assembly) drawings.
Altium Draftsman is a powerful drawing and documentation tool integrated into the Altium ecosystem. Engineers can use Draftsman to create rich PCBA fabrication and assembly drawings that communicate all necessary design specifications.
This article explores techniques for leveraging Draftsman to convey your true PCB design intent through detailed documentation and drawings. Follow these best practices to smooth the handoff from design to production.
1. Include Clear Fabrication Drawings
PCBA fabrication drawings should provide board shop staff all required details to procure materials and fabricate your bare PCBs accurately. Here are the key elements to document:
Board Geometry - Board outline and mechanical dimensions, mounting hole locations, cutouts, thickness, and stackup.
Layer Stack - Layer material types, thicknesses, copper weights, and sequence.
Finishes - Surface finishes like HASL, immersion gold, ENIG, etc.
Soldermask - Soldermask requirements including cutout areas.
Silkscreen - Silkscreen location, text sizes, and other printing specifications.
Drill Drawings - Plated and non-plated hole sizes and locations.
Material Callouts - Details on unique substrate materials required.
Fab Notes - Other relevant notes for the fabrication house.
Table 1: Details to Include in Fabrication Drawings
| Section | Details |
|---|---|
| Board Geometry | Outline, holes, cutouts, thickness, stackup |
| Layer Stack | Materials, thicknesses, copper weights, sequence |
| Finishes | HASL, immersion tin/gold, ENIG specs |
| Soldermask | Required areas and cutouts |
| Silkscreen | Text size and location specs |
| Drill Drawings | Plated and non-plated hole tables |
| Material Callouts | Specs on any unique materials |
| Fabrication Notes | Other instructions for the board shop |
Provide fabrication drawings that thoroughly convey the physical construction of your bare PCBs.
2. Create Clear Assembly Drawings
In addition to board fabrication, assembly drawings communicate design intent regarding component selection, placement, and installation. Include:
Assembly Bill of Materials - Detailed component list with designators, descriptions, manufacturers, part numbers, and quantities.
Component Placement - Placement drawings indicating component locations and orientations.
Assembly Notes - Special assembly instructions such as pre-assembly procedures.
Solder Paste Stencil - Layer drawing showing solder paste locations and apertures.
Component Height Callouts - Notes on tall components requiring clearance in assembly.
Board Assembly Stackup - Details on conformal coating, shields, connectors, and other mounted hardware.
Table 2: Details to Include in Assembly Drawings
| Section | Details |
|---|---|
| Assembly BOM | Components, descriptions, manufacturers, part numbers, quantities |
| Component Placement | Locations and orientations |
| Assembly Notes | Special component installation instructions |
| Solder Paste Stencil | Paste layer drawing and aperture sizes |
| Component Height Callouts | Notes on tall components needing clearance |
| Assembly Stackup | Conformal coating, shields, connectors, etc. |
Thoroughly document all assembly details required for procurement and accurate PCB population.
3. Develop Test Point Drawings
PCB test requires drawings and documentation that provide:
Test Point Locations - Drawings showing locations of test points used for in-circuit testing.
Test Point Specifications - Details like minimum/maximum probe ring diameter.
Component Testability Callouts - Notes about component pins that are inaccessible for testing.
Test Fixture Requirements - Required fixtures, connectors, clamps, and other test hardware.
Test Sequence Specifications - Any required order of tests or power on/off procedures.
Test Coverage Summary - Statistics on the percentage of nets and components that will be tested.
Fault Simulation Results - Documentation of fault simulation analysis and coverage.
Table 3: Details to Include in PCB Test Documentation
| Section | Details |
|---|---|
| Test Point Locations | Drawings showing test point locations |
| Test Point Specifications | Probe ring diameter, access |
| Component Testability | Callouts on hard to probe pins |
| Test Fixture Requirements | Needed fixtures, connectors, clamps, etc. |
| Test Sequence Specs | Required power on/off procedures |
| Test Coverage Summary | Statistics on coverage of nets and components |
| Fault Simulation Results | Analysis of fault simulation and coverage |
Provide documentation to enable thorough validation testing that completely covers your design.
4. Generate Fabrication and Assembly Drawings
Altium Designer integration with Draftsman streamlines generating fabrication and assembly production drawings. Here is a summary workflow:
Fabrication Drawings
- Import PCB file into Draftsman
- Add fabrication drawing template
- Publish board geometry, layer stack, drill table, notes, etc.
Assembly Drawings
- Import PCB file into Draftsman
- Add assembly drawing template
- Publish BOM, placement drawing, assembly notes, etc.
- Update with test point drawing and details
Table 4: Overview of Draftsman Drawing Generation Workflow
| Task | Details |
|---|---|
| Import PCB | Open target PCB file in Draftsman |
| Apply Template | Select fabrication or assembly template |
| Publish Content | Bring in required drawings, tables, notes, etc. |
| Place and Edit | Arrange elements and edit as needed |
| Output PDF | Generate final PDF drawings for production |
Leverage the linked workflow between Altium Designer and Draftsman to efficiently create fabrication and assembly drawings.
5. Use Layer Colors and Text to Clarify Intent
Certain drafting techniques in Drawman help communicate design intent clearly:
Color Coding - Use standard color coding for fabrication layers like red for copper, green for soldermask, etc.
Text Legibility - Ensure text is large enough to read easily when printed. Avoid overlaps.
Annotation Leaders - Use leader lines to clearly connect notes and callouts to specific PCB features.
Highlighting - Spot colors, shading, dotted lines, and other highlights draw attention to important details.
Consistent Symbols - Use standard symbols consistently for common features like fiducials, tooling holes, etc.
Page Frames - Include title block info like name, date, revision number clearly on each page.
Table 5: Drafting Techniques for Clear Documentation
| Technique | Purpose |
|---|---|
| Color Coding | Clarify fabrication layer materials and sequences |
| Text Legibility | Ensure notes are readable when printed |
| Annotation Leaders | Connect notes to specific PCB features |
| Highlighting | Use colors and lines to highlight key details |
| Standard Symbols | Use consistent standard symbols throughout |
| Page Frames | Title block on each page with key info |
Leverage basic drafting best practices to create professional, easy to understand production drawings.
FAQ
Here are some frequently asked questions about using Draftsman to convey PCB design intent through fabrication and assembly drawings:
Q: What are the most critical fabrication details to convey?
A: The layer stack, board outline geometry, hole sizes/locations, and finishes require meticulous documentation for fabrication.
Q: How do I indicate special assembly instructions or sequences?
A: Use assembly notes and callouts on the drawings. A separate assembly sequence document can be provided also.
Q: What is the best way to call out hard-to-test component pins?
A: Create a short table listing the limited components pins and brief explanation, then reference in assembly docs.
Q: How can I make board geometry drawings easiest to understand?
A: Use color coding for layers. Add dimensions for location reference. Include annotation leaders to call out key features.
Q: What drawing elements are most prone to errors?
A: Incorrect hole sizes, outdated bill of materials, and layer stack misrepresentations are common pitfalls.
Conclusion
Draftsman's drawing creation capabilities integrated with Altium Designer enable detailed documentation to convey PCB design intent to your fabrication and assembly partners. By thoroughly capturing board geometry, layer stack, BOM, component placement, test points, and assembly sequences, your production handoff will go smoothly.
Dedicate time up front to learn best practices for PCBA drawings. Well-crafted documentation demonstrates professionalism, reduces ambiguities, and ensures your boards are produced true to your design vision. With the techniques explored in this guide, Draftsman can help you efficiently generate outstanding fabrication and assembly drawings.
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