For young Designers and for mature Designers, this is a word to the wise. Talk to your board house before you start on the new design. We spend a lot of time helping Designers after the fact to bring their pride and joy to a state of manufacturability. If only we had spoken before….
There are 2 groups I am speaking to here. For the young Designer, it is more about understanding the board manufacturing process and limitations, for the mature Designer it is more about adjusting to shrinking parts and expanding complexity. Either group, same comments apply even if for different reasons.
Here are the 4 steps to improving your Design-to-Completion process…and saving money –
1. Pre-select a board fabricator based, not just on cost and competence, but on their willingness and ability to communicate with you about your design needs. Pick someone who will answer your phone call or respond quickly to your messaging. Lay your questions out in a logical way that will allow you to set, or re-set your CAD design rules. The times are a changing and what was good enough last time, can, … maybe, be improved. Don’t be afraid to get into cost trade offs. (For more information on cost analysis, see our Blog on the subject). We will usually respond with our own questions to help narrow down the best solution. Most of the questions we get have more than one possible answer and usually that will drive cost.
2. Teach yourself enough about how modern PCBs are constructed so that you can visualize the solutions we are proposing. We have a tutorial walk through on our web site called “PCB Explained” under the banner “Helpful Design Stuff” (www.precisionpcbs.com/pcb-manufacturing). The better Fab houses will have similar information available on line to bring you into the fabricator’s processes. When we are talking stack ups and process limitations, this will greatly help you communicate with a fabricator.
3. Make that phone call as you are developing your plan for the layout. Think of it as an early design review. Walk us through your plan and concerns. The first question to us should be – what are your line and space rules and what are your smallest via and ring dimensions. Answers to these questions will drive the rest of the discussion. Other helpful bits of information are what the chip architecture is and the package options, what your heat concerns are, what size passives you prefer ( tip: always use the largest parts you can squeeze in; smallest is not necessarily better). Ask for a standard stack-up for the layer count you anticipate. Another big topic to discuss is via fill or not fill and why. Talk about total tool count for efficiency. Most designs should not go over 10 different tool sizes.
4. Fabrication drawing. Just getting ODB++ or Gerbers to us is not enough. We need instructions on board material, soldermask, thickness, stackup if a default stackup will not work, surface finish, any unique needs like press fit connector tolerances. All of this should be in your Fab drawing. Panelization instructions are another important item to include if possible. Our web site has templates you can use for the Fab drawing. It can be either in Gerber format as part of the file package, or a separate pdf.
Follow these steps and you will avoid days lost and money wasted on re-dos. For more information go to www.precisionpcbs.com.