DFA Essentials a PCB Designer Should Know

Events
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Agenda:

  • Common design for assembly mistakes
  • Best practices for a flawless design file
  • Component placement strategies
  • Thermal management considerations
  • DFA tips for solder mask and silkscreen
  • DFA rules for comprehensive testing coverage
  • Panelization strategies for high-volume production
  • Sierra Circuits’ design tools:
    • BOM Compare
    • Better DFM

Date and time:

Wednesday January 24th, 2024
10:00 AM PT

Ask your questions in this thread!

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Questions:

  • Soldermask expansion;; 1:1 or pre-expanded. Pros/Cons.
  • Pastemask; 1:1 or windowed
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Thanks for your comment.
Having a 1:1 solder mask expansion and paste mask ensures an optimum soldering process. It allows sufficient room for component placement, especially in HDI designs.

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Question asked by attendee during webinar:

Components right below BGA? What about bypassing in today’s applications?

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Question asked by attendee during webinar:

What’s the benefit of including centroid data when the pick and place has coordinates?

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Question asked by attendee during webinar:

Do you prefer leaving soldermask 1:1 and letting you expand or pre-expanding it yourself?

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Question asked by attendee during webinar:

I am designing a small PCB with 54% density, can I remove the reference designators and fiducials?

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Question asked by attendee during webinar:

Any thoughts on sustainable PCB materials?

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Question asked by attendee during webinar:

What is the recommended density of a 6 layer PCB?

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Question asked by attendee during webinar:

Your BOM/DFM/DFA analysis tools seem useful. However, is there an option for how to do this with ITAR restricted designs?

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Reply by Sierra PCBA team:

Centroid data is used in automation process for placing of components.

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Reply by Sierra PCBA team:

The preference is to have mask larger than pad. A 10 mil pad would have a 16 mil clearance, 3 mils per side.

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Reply by Sierra PCBA team:

Yes, it must however be a detailed assembly. dwg will be needed for QC purposes as well as submitting an ODB++ file or possibly the schematic if possible to determine polarity pins.

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Reply by Sierra PCBA team:

Our Better DFM system sits on a server at our facility which is in compliance with NIST and ITAR.

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solder mask typically has 6 mils over the land size, a 10 mil pad would have a 16 mil mask clearance allowing 3 mils per side clearance. This will assist with
registration and ensure no mask on pads. Webbing / solder dams should be at a minimum of 3 mils, any less and a potential risk of the mask peeling or flaking. We do incorporate mask defined openings ( mask encroaches on land) but in limited applications when webbing might be an issue and we want to retain the damn all in effort to minimize bridging and controlling the amount of solder being deposited in BGA applications specifically.

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pick and place / centroid are the same, they are providing
us the coordinates / rotation details for the automated
pick and placement of parts. We are often provided data that has these details embedded in the cad files or they are provided as a separate documents that will be then be merged into the data that is provided.

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let me clarify , its ok to remove the silkscreen but
retaining the fiducials is not recommended as they
can help improve the accuracy of part placement.
if the silkscreen is removed, please ensure assembly retains a detailed assembly drawing showing pin indicators and polarity. An odb++ is always helpful in these cases.

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Providing Solder mask 1:1 with copper pads saves time at CAM Stage, the clearances can be optimized to suit the imaging process followed.