How to choose PCB components

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The design of a printed circuit board can be a difficult and challenging undertaking.  Of course here at Hi5 we are more than happy to consult on the design of PCBs.  However, if you are keen on Hi5 manufacturing to your own design, here is a 10-point plan of some things you should be thinking about:

1.  BOM

A Bill of Materials (BOM) will help you create a list of virtual parts you’ll need, and allow you to review those parts in the design.  Virtual parts might include ground signals and power and as these are virtual, these parts will be specifically included in the schematic environment, won’t be transferred to the layout, and will not carry a footprint.

2. Reference designators

As part of the Bill of Materials, make sure you number the reference designators, which will further help with the review of the BOM.

3. BOM Data

In terms of that review, make sure it is complete.  Look over the Bill of Materials report and make sure nothing is missing and that all parts are included before you move on to the design.

sketching an outline4. Basic outline

Before launching into any expensive prototype designs, why not digitally sketch out your design, and render in 3D, to give you an early heads up on how the design will pan out?  This will give a basic sense of the positioning of the components, the required height, and whether the whole design will work – holistically, as well as electronically.

5. Grounding practices

Depending on the final application of the PCB, you will need appropriately capacitors, in terms of size and frequencies involved.  Your design should include appropriate ground planes and bypass capacitors.

6. Footprint

Moving on to the drawing, think about landpattern and also footprint.  Again, early good practice here will help when it comes to layout.

7. Landpatterns

Landpatterns detail the hole shapes on board, to which the part will be soldered.  These landpatterns therefore should be precisely sized, to make sure soldering is exact, confirming thermal integrity for the components that will connect.

8. Selecting components

An important one.  Some components have height restrictions so think about the housing of the PCB on both its top and bottom sides, and make sure component choices are appropriate.

9. SMT or PTH?

Again, as early as is possible, think about the ultimate design of your PCB.  Which components will be Surface Mount Technology and which will be Plated Through Hole?  When considering component choices, there will be issues in terms of costs, density… even availability, that will impact your design.

10. Spare gates

Review any spare gates.  Any unwired inputs can “float”, affecting the final functioning of the PCB, so connect the inputs for any spare gates to a signal.

Always remember, a little time spent planning at the early stages – especially when it comes to choosing components – can help hugely when it comes to manufacture and the end use for the PCB.  Your choice of components can (and often will) change through these processes, so be open and receptive to where your design is taking you.  Again, the process can be organic, as well as electronic.

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