Printed circuit boards are essential to professionally design any electronic system. It is often happens that a circuit which functions well over a breadboard may not work properly when implemented on a PCB. This leads to complexity over circuit and system engineers need to be spend at least 2-3 days to rectify the problems.
The causes for this failures are numerous, PCB design and fabricating is one of them.If the pCB is not designed properly, it often need a high level of rework. PCB design tips listed here is intended to help you to improve the reliability of PCB design.
Checklist For PCB Design
1. First of all verify that the schematic you designed is compatible with your schematic circuit diagram.
Checklist For PCB Design
1. First of all verify that the schematic you designed is compatible with your schematic circuit diagram.
2. Make sure that the flow of the signal is maintained over the designed layout.
3. Distribute the circuit components over the entire PCB and observe the weight distribution in all area.
4. Try to keep the components of same family in same direction which will reduce the errors and complexity of the design
5. Mark PCB body outline or physical size of all the components and ensure that all components on the PCB can well placed and avoid chances of overlapping.
6. Check that the components reference text are not placed direct under the components which will be head ache to service engineer.
7. Make sure that the connectors are well arranged and the person assembling the circuit can connect external peripherals without tightening each other.
8. The component references should be of readable font and size
9. Check the placement of fixed components with their respective origin of placement
10. Label all the layer of PCB properly
11. Make sure that test points are there in the circuit
12. Avoid placements of components near the edge of the PCB as it may create problems during machine placement of components (SMD) or during wave/re flow soldering.
13. Design the components according to the component packages from different manufactures. The body size of the components may vary from manufacture to manufacture although the pitch of the components remains same.
14. Make sure that the position of mounting holes is as per the mechanical placement of the PCB and the placement of PCB in the cabinet. Mounting holes are designed as non-electric unless that are connected to graoung or any other nets
15. Dont make too many holes near the edges of the PCB. This may lead to break the entire board.
16. Provide the sufficien number of mounting holes as long PCBs tnd to warp if not supported normally.
17. Check the ratio between pad size and drill size. There should be sufficient area for soldering the component leads properly. Generally the pad size must be 2-3 times larger than drill size.
18. Check the drill size specified in the design. MArk it is furnished or non furnished in case of multilayer PCB.
19. At least 0.2mm extra drill diameter to fill the component lead as well as solder properly to top layer in a plate through hole (PTH) PCB.
20. Define the global spacing such as track to track, pad to pad,track to pad etc to overcome manufactures limitations.
21. Ensure that the minimum number of drill tools in the PCB to reduce the machine cycle time.
22. Different nets or connections should have minimum and maximum trace width.
23. Avoid routing traces at the edge of the PCB
24. Avoid rout traces at 90 degree corner. You can route trace on 135 degree instead of 90
25. Placing via holes under metal components are not appreciated as it leads the solder to flow through vias and short circuit the components.
26. Check the trace width depending upon the current requirement of the circuit elements.
27. When designing SMD's dont forget to place fidcials. These should be placed over the tree edges of the PCB
28. Never place via hole adjacent to an SMD lan area in the case of an SMD design.
29. The components reference text should not be placed on a land or pad as it will not allow good soldering
30. For reference, don't forget to place the part number, company logo and revision code in the design.
31. Write PCB notes properly to give necessary information about copper thickness requirement,tolerance etc.
32. Make sure that the component spacing satisfies the requirement of the developing automatic equipment.
33. It is appreciable to add machine readable labels such as bar code in the design.
34. PCB's are often required to be stepped and repeated onto an array for assembly. So you must provide a correct assemble array data to assembler.
35. After all, make sure that your design is optimized for maximum material utilization.
These routine tips in PCB designing should help you to make better PCB and improving the reliability of the assembly.
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3 comments:
thanks for the tips! very useful for my project!
Thanks for sharing these tips in designing a reliable PCB. These will certainly be helpful to people like me who are very much interested in PCB design layouting. I think that big companies that make circuit boards for large production run would greatly benefit from the list that you've provided.
I definitely learned a lot. Thanks.
PCBs are inexpensive, and can be highly reliable. For this they require much more layout effort and higher initial cost than either wire wrap or point-to-point construction. Thanks for sharing these necessary tips for constructing PCB.
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