PCB Designing Tips

Checklist for Mechanical design considerations:

1. Board size should be compatible with the manufacturing equipment.

2. The board should have correct mechanical dimensions.

3. The assembled board should have sufficient clearance when mounted in the equipment.

4. The input, output connectors and on-board controls should be located at properly accessible place with respect to the enclosure.

5. The components leads should cover spans of multiples of 2.5 mm and not bent too close to the component body.

6. Leads of components of same type should be bent to the same span.

7. The components should be accessible for replacement.

8. It should be possible to clip logic probe over the IC packages.

9. The packaging density should be fairly homogeneous across the board.

10. Temperature sensitive components should be placed at a distance with respect to heat developing components.

11. Heat-sinks should be mounted at properly ventilated place.

12. The overall cooling conditions should be considered.

13. Heavy components should be mechanically fastened with enclosure.

14. The assembled board should be withstand with operating environment parameters like, vibrations, humidity, ambient temperature etc.

15. Proper contact pads should be provided for test probe for in-circuit testing.

16. The board’s base material should have proper value of mechanical strength for intended application.

Checklist for Electrical design considerations:

1. The component locations should give a logical signal flow.

2. Undesirable couplings from out to input should be avoided.

3. The grounding system should be divided into separate ground conductors.

4. Inductive loops should be avoided or reduced.

5. Conductors with critical resistance, current capacity, inductance or insulation properties should be considered.

6. The temperature conditions of current carrying conductors should be examined.

7. The power supply conductors should be designed with desirable width to withstand a possible short circuit in the system.

8. Safety precautions should be taken where mains voltage is on the board.

9. Slotting should be provided to isolate high voltage and low voltage levels.

10. The unused inputs and outputs of digital ICs should be connected to ground.

11. The number of jumpers should be kept as low as possible.

12. Precautions should be taken to ensure that compatible components can be used as if required.

13. It should be possible to isolate the individual parts of the circuitry in order to perform the testing process.

14. It should be easy to connect the board to the test instruments.

15. It should be specified the right type of copper clad laminate, like type of base material and its thickness, copper foil thickness and type, solder masking, legend printing etc.

Checklist for drawing considerations:

1. Any special machining of the board, like cutouts, slots or V-groove cutting should be indicated.

2. All the necessary mechanical dimensions should be stated.

3. Mounting factors should be taken into consideration when determining the size of the board.

4. All the conductors should be minimum 0.5 mm away from the edge of the board.

5. Solder pads should not be too close to interfere with mounting structure.

6. The determination of conductor width should be as their current carrying capacity.

7. It should be in regular design practice of placing ground connected copper pouring.

8. The solder pads should be in standard sizes.

9. The size of the solder holes need to in compatible with the terminal leads.

10. All the solder pads should be located at the intersection of grid lines.