- The most common layout
error is reversed diodes and polarized capacitors. Double and triple check
the polarity of these parts. Check the pin numbers between the schematic
symbol and the PCB decal
- Write up layout
instructions before going to layout. Include board thickness, number of
layers, layer stack up, power and ground instructions, a list of critical
nets, trace thickness and spacing, instructions for autoroute or no
autoroute, logos and part numbers, mechanical constraint drawings, bypass
capacitor instructions, any special instructions and a hard copy of the
- Check the PCB decals very
carefully. Use the NetEDA Decal Report Generator to speed up decal
checking. Visually inspect the decals, place a part on a 1-to-1 plot if
- Check all mechanical
constraints. It is very expensive to rework an board to move a connector a
few millimeters after it has been routed.
- Run the NetEDA Netlist
Compare Utility between the PCB netlist and schematic netlist. Pay
attention to the decal name and resolve all differences.
- Check all pin 1 orientation
on all IC's and connectors. Try to have the CAD designer limit the
orientation of IC's to two axis. This will speed up manufacturing and
reduce the chance of errors. Verify proper silkscreen annotation.
- Check all bypass capacitor
placement and power/ground connections.
- Check for mechanical
conflicts with components, especially connectors. Verify that the mating
half of the connector will clear surrounding components.
- Check for any component
height limitations, especially heat sinks.
- Check the power layers and
- Check all polarized capacitors,
Verify proper silkscreen annotation.
- Check all transistors,
capacitors, diode routing. Often the PCB designer has to interpret netlist
as to gate source, drain, emitter, cathode and anode.
- Check all key signal
routing. Verify high speed signals are short. Verify signal pairs and
busses have matched lengths.
- Check for sloppy routing,
excessive vias, etc.
- Check for proper via
selection. You don't want a microvia connecting two large power traces.
- Check hole drawing. Verify
all connector holes are proper size. Remember a 0.025 square pin requires
a 1.414 x 0.025 or 0.035 hole (0.040 when tolerances are considered).
- Check silkscreen. Verify
all reference designators are visible and not under components.
- Check part numbers, logos,
- Check for clearance
problems with screws and mounting hardware.
- Check for nets routed too
close to mounting holes. These may become shorted when the mounting
hardware is installed.
- Hold placement reviews and
- Run the NetEDA Netlist
Compare Utility against the new and old PCB netlist when making changes to
the layout. Turn on the Check Component Placement and verify that only the
changes you want were made.
- Complete all of the items
above. Be VERY careful, skipping these double checks is often incredibly
expensive. Always try to get an independent party to triple check your
design. Use all tools available.