Aug 30, 2018|Blog

When you design and build a printed circuit board (PCB), there are many components that must come together. Missing one step could result in a malfunctioning circuit board. There are certain steps that you must complete before moving forward. Otherwise, you will not be able to go back and fix something missed. That is why it is crucial to keep track of all the steps to ensure every part of the circuit board is considered.

Here is a detailed checklist to keep on hand while designing a PCB.

Electronics and Part Placements Checks

  • Remove any unused components and check for decoupling capacitors in areas with connectors or via’s.
  • Double check the polarity of the capacitors between the pin numbers of the schematic symbol and the PCB decal.
  • Check all key signal routing.
  • Place thruhole components on the grid.
  • Orientation of the connectors checked.
  • Mating connectors checked for the same pinout.
  • Check hidden power and ground connections.
  • Outside world I/O lines filtered and protected against static discharge.
  • Minimize any component body spacing.
  • Check the voltage ratings of components.
  • All series terminators located near the source.
  • All high-speed signal traces run over their own ground or power planes.
  • There are ground turrets and test points for important signals – all labelled.
  • Check all amplifiers for stability.
  • Write up a layout of the PCB with the thickness, number of layers, power instructions, part numbers, and any special instructions.
  • Layout the PCB.
  • Mounting holes electrically isolated or not with proper clearance for hardware.
  • Check SMD pad shapes.
  • Clearance for socketed ICs.

Routing

  • Ensure only one joining point between digital and analog signal.
  • Check for traces under sensitive or noisy components.
  • Make sure parts are well insulated.
  • Look for traces that can be susceptible to solder bridging.
  • See if there are dead-end traces (unless there on purpose).
  • Ensure schematic software is still connected.
  • Check for multiple vias for high current or low impedance traces.
  • Observe the trace keepout areas and components.
  • Where possible, ground planes.

PCB Design

  • After plating, hole diameter on the drawing is finished sizes and > = 10mils larger than lead.
  • Components are > = 0.2” from the edge and test pads 100 mils from the edge of the board.
  • Thruhole drill tolerance and soldermask noted.
  • Trace width is sufficient enough.
  • High voltage traces have enough clearance.
  • Legend reads in one or two directions.
  • Company logo in silkscreen legend and in foil.
  • PCB includes the copyright notice, date code, and assembly part number.
  • Polarized components point in the same direction.
  • Silkscreen legend text weight > = 10 mils, and not over vias or holes.
  • Silkscreen serial number blank, the text is readable, and assembly revision blank on the legend.
  • All ICs are visibly marked.
  • Mounting holes matched 1:1 with mating parts.
  • Perform automated netlist check and manual netlist check.
  • Check CAD design rule.
  • Have extra connector and IC pins on hand.
  • Observe precautions for high-frequency circuitry.
  • Check hole diameters for odd components.
  • No acute inside angles in foil.
  • Note the copper weight, material, and PCB thickness.
  • Blind and buried vias allowed on multilayer PCB.
  • Layout panelized correctly.
  • High-frequency crystal cases flush to the PCB and grounded.

Assemblies

  • Assembly notes for all special operations and miscellaneous parts.
  • Special static handling precautions needed during assembly and test.
  • Wire gauge checked for compatibility. Cable ties and lacing cords shown where needed.
  • Indicate the length and colour of each wire.

Mechanical Drawings

  • Specify material, finish, units, debur, or brush and special operations.
  • File name on each sheet.
  • Check every hole diameter.
  • Note the tolerance for sheet metal feature and hole size.
  • Check the alignment of every hole with its mating holes.

Software

  • Archive each version.
  • Check the communications timeouts.
  • Test all branches.
  • Measure the interrupt response time and execution time.
  • Adhere to coding style standards.
  • Consider the power-up and power-down.
  • Load unused ROM space with trap or restart instructions.
  • Check critical timer driver code.
  • Program’s data structures contain version numbers that should detect program version upgrades.

Tests

  • Points on PCBs for critical circuits.
  • Pads for in-circuit or bed-of-nails functional testing.
  • Pads on the regular grid.
  • Each test phase has a written procedure.
  • Have special tests for arrangements and connectors.

Others

  • Fuses accessible and labelled.
  • Self-test mode.
  • Have spare parts available.
  • Vibration tolerance of entire assembly.
  • Fuse sizes marked near fuse holders with spare fuse storage.
  • There should be room to remove fuses without damaging other components.
  • Protection against liquids and foreign objects.
  • User Instructions: how to use, warranty, troubleshooting, etc.
  • Service manual included.
  • Design notes and any additional information included.

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