Best Practices

Design Layout

Use Your Silkscreen

Label reference designators on your silkscreen to help with component orientation, reduce the probability for errors or rework, and save time in your assembly process.

Provide helpful notes for debugging and giving the device operator direction. For example, adding directions for polarizing caps or the positive orientation of inserting a battery.

Verify your silkscreen isn’t drawn over your solder pads. This makes it more difficult to solder components.

Component Selection

For prototypes under a strict deadline: Validate that all your parts are available, in stock, and orderable before placing your PCB order.

Double check the footprints of your components are the right size and large enough to make the connection to your part during assembly.

Be aware that some components will be more difficult to assemble than others due to their size and pinouts. For example: SOIC, DIP, and standard 0603 packages are manageable while BGAs can’t be done without proper assembly machines.

Reduce Board Noise

Crosstalk occurs when an unwanted signal from one trace generates noise onto another trace through the coupling of electromagnetic fields.

Crosstalk can be reduced by how you route your traces:

  • Avoid routing traces in parallel right next to each other that have any fast-changing signals.
  • When two different traces need to cross over each other, try to cut over at a perpendicular angle.
  • Isolate noisy areas of your board—e.g., switching voltage regulators from your power section—from your analog signals.
  • Keep your ground planes separated; for example: analog, high frequency digital, and RF.
  • If you have traces routed horizontally on one layer of your board, route the next layer in the opposite direction vertically.

High Frequency Considerations

Ensure your traces are not too long, especially for high frequency signals.

Copper inherently has capacitance, inductance, and resistance which can distort the integrity of the signal in longer lengths.

In general, it’s better to route traces as short and direct as possible. Refer to your part’s datasheet; many ICs today have impedance-controlled signals, and you should follow suggested termination and trace width to achieve the needed impedance with your board specifications.

Trace Widths

Consider your minimum trace width for connections requiring higher currents. Digi-Key has a free online Trace Width Calculator to make sure your trace is large enough for your design.

Thermal Considerations

Determine which components dissipate the most heat or are most sensitive to heat. Next, be sure to review application notes within the datasheet for your specific component. Thermal Relief pads can be added to help thermal dissipation for some components.

Design for Manufacturing (DFM) Checks

Before your board is manufactured, it goes through a DFM check at the board house.

DFM checks vary slightly from board house to board house. DFM is a common way board houses validate that your layout design will be built properly.

For example, checks are done to ensure your trace widths are not too small, your drill holes are large enough, or the space between two pins is large enough so it does not create a solder bridge.

Order Preparation

When should I use stencils?

A stencil is used to efficiently transfer solder paste to the circuit board during the assembly process for surface mount components. To save time, use a stencil if you are assembling multiple copies of the same PCB board.

Versioning for each build

It’s good to label a new version of your PCB build each time you make a change to your PCB design. This is helpful if you are working in teams, tracking history, or determining root cause when debugging.

Accounting for fabrication time, communication time, and ship time

Several factors affect the interval from when you order your board to when you receive it. Be sure you factor in the following:

  1. Order Placement Time - Each board house starts the day at different times. Therefore, if an order is placed after that specific time in the day, your order will be processed with orders of the next day, not the current day.
  2. Fabrication Time - This is the time PCB houses need to manufacture your PCB.
  3. Communication Time - If a board house notices a minor issue, they may contact you before they begin building your board. The time it takes to communicate back and forth between the board house is not factored into the fabrication time and could cause delays in your order.
  4. Ship Time

Factors that increase overall cost:

  1. Hole quantity per board area
  2. Adding blind and buried vias
  3. Adding layers
  4. Requiring faster turnaround times
  5. Increasing board size
  6. Using expensive materials