In this tutorial, we are going to learn about pre layout checklist.
- Previous Review-
- Schematic design review conducted. All action items taken care of.
- Net list review conducted.
- BOM review conducted.
- Design function-
- JTAG circuit has reviewed and simulated.
- System level simulation and component level simulation reviewed.
- Bypass capacitance reviewed.
- Design meets test requirement on all power supplies analyzed.
- Deviations from specification area understood/approved by management /marketing /software
- If subsequent revision, compare netlist against previous netlist and explain changes made.
- If subsequent revision, changes have been modeled in real hardware.
- Conformance to mechanical requirements reviewed, including stiffing, component height clearance, and card edge clearance.
- Design data integrity-
- Symbols in golden library.
- Connector pin outs verified against pin outs of daughter/mother card.
- Device pin outs have been verified against spec sheet.
- Power /ground connection verified.
- No package errors, package warning, over sights explained.
- All single-node nets checked and explained.
- Archive checked in and verified.
- Layout guidelines-
- Mechanical layout constraints (e.g. outline, maintaining hole locations, keep outs, height restrictions, stiffener, etc.) established.
- Preliminary stack-up (layer assignment) established.
- Preliminary fabrication design rules established (e.g. trace width, trace spacing, ZO)
- Fabrication design rules sanity-checked and pre-quoted with PCB vendor to assess manufacturability, cost.
- Preliminary floor- plan defined.
- Critical nets and corresponding layout rules defined.
- No critical nets have unknown signal names.
- Analog power supply and signal names.
- If application, board size efficiently uses available panel size.
- Specify ICT requirements for layout (e.g. via-per-net accessibility.
- DFM ( DESIGN FOR MANUFACTURING)-
- Distinct pull-ups/pull-downs for multiple pins on the same part, if possible.
- Disable un-used inputs on large parts, e.g.FPGA’s, custom chips.
- Boundary scans on complex parts, e.g.FPGA, custom chips.
- Single –ended and differential clocks are controllable.
- Test points in design for all power supplies.
- DESIGN FOR EMI(ELECTROMAGNETIC INTERFERENCE)-
- Heat sinks grounded, as appropriate.
- Requirements for gasket assessed and designed in if needed.
- Card guide grounding provision is designed in if needed.
- Mechanical-
- Mechanical drawing developed for board outline.
- Layout symbol for board developed from mechanical drawing, including mounting holes, interface connector locations, hardware keep outs, guide keep outs, mezzanine board provision, and tooling holes.
- Thermal Design-
- Board thermally modeled per predicted air flow conditions.
- Heat sink has adequate clearance.
- Heat sink mounting details fully hashed out.
- Heat sink, mounting hardware, and thermal interface materials have PNR’s (part number request) and are on order.