Essential PCB Design Rules

In order to reduce the chances of manufacturing errors and to lower the cost of your Printed Circuit Boards, the following PCB design guidelines are set for best practice. Printed Circuit Boards that work on relatively higher power have an entirely different set of design guidelines when it comes to issues such as power isolation, track widths, track spacing and density, etc. Requirements of various PCB manufacturers differ; it is therefore important that you have read the rules provided by them before your design submission. Similar is the case with file formats and naming conventions which vary with different PCB manufacturers.

We encourage you to refer to our free Complete DFM Guideline for detailed information and design recommendations.

Printed Circuit Board Layout Guideline
1. Your board frame should be created on a grid of 0.05 inches with the lower left corner starting at the reference 0.0.

2. Different shapes such as polygons can only be used in specific cases. Normally rectangular board frame is utilized.

3. A 0.05 inch grid is to be utilized for sticking parts. This rule has to be strictly followed unless it’s absolutely necessary to be broken.

4. LEDs used on the PCB should be marked for identification. (For example: Status, Lock, D1, D2, Fault)

5. Connectors should be marked as well, such as Vin, Input Port, Vout, etc.

6. Pins on the board are to be labeled, such as, RX, Power, +5V, -5V, etc.

7. Labels for switched should be used, such as, Test, USB, Off, On, etc.

8. You should try to avoid Vias going through silkscreen when labels are being added.

9. It is advised to place components in groups. For example capacitors and resistors around an IC in the schematics should be placed near to the IC on the PCB during layout.

10. What should the minimum drill size be for my PCB design?

Drill hole sizes should be designed to be 6mils to 6mm in diameter. While micro holes of 4mils to 6mils can be accommodated, it can only be done using laser drilling which comes at additional time and cost.

11. What should the the minimum size for the annular ring be?

The minimum recommended size for annular rings is dependent on the copper weight of the board. The minimal annular ring width is 4mil for 0.5 & 1.0oz copper weight. Similarly, 6mil, and 8mil, are recommended for 2.0oz, and 3.0oz respectively. These minimal widths may be further reduced by no more than 1mil only if there are a few of them in your design.

12. What minimum trace size I should set for my design?

3.0mil minimum trace width/spacing for internal layers are recommended, and 4.0mil for external traces, at ½ or 1 oz copper weight. This required width increases with copper weight. Please refer to our free DFM guideline manual for details.

13. Power lines have to be kept comparatively thicker. For max 100mA, use 12mil; for max 500mA you can use 16mil and so on.

14. What minimum trace spacing I should use for my PCB design?

3.0mil minimum trace width/spacing for internal layers are recommended, and 4.0mil for external traces, at ½ or 1 oz copper weight. This required width increases with copper weight. Please refer to our free DFM guideline manual for details.

15. 90 degrees bends are not recommended. Instead straight lines with two 45 degrees bends are preferred.

16. If possible, ground pour can be used on first and last layers.

17. Pours can get shorted to traces; an isolation of 10mil is to be used on ground pours to avoid this from happening.

Printed Circuit Board Schematic Rules
18. For Ground connections, a symbol “GND” is to be used.

19. Power sources should be labelled accordingly, e-g: Vdd, Vc, 3.3V, 15V, etc.

20. Colour notes can be used to make smaller section of a larger complicated circuit. E-g: Power Section, Current Sense, etc.

Footprints
21. A reference designator {{reference}} is required for footprints. You should ensure all parts have this and then save your library. Pin one marker is to be set for parts that require this.

22. Silkscreen labels that show dimensions or wired aspects of a part are required by all footprints.

23. Pads or exposed metal parts shouldn’t have silkscreen over them. Silkscreen will flake off from a footprint in these cases.

24. A red cross in the center will mark the top layer.

25. Outline layers of a package are to be exactly equal to their real size.

26. All pins are to be indicated by the top courtyard layer.

27. Soldermask should be added alone with a footprint

28. Labels of new parts or footprints should be easily visually inspected or read.