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What Do Know About Soldermask?

John T

Should PCB designers supply exact soldermask information in the artwork files when ordering boards? And should this be 1:1 with pad-size?


After some time at Cadence, a vast difference is very apparent between various designers. Some PCB designs exhibit strict rules regarding soldermask openings, gaps and sizes.

However, many other designers simply export soldermask artworks with an exact 1:1 replica of each components’ copper pad sizes. What are the pros and cons; and what about paste mask artworks?

Please let us know what you expect or do? Should designers: 
A. Supply 1:1 soldermask. Let the PCB Fabricator decide.
B. Supply exact custom soldermask. The Fabricator must follow the artwork precisely. 
C. Supply exact custom soldermask AND solder-paste information should also be supplied.  

Example of SM gap control affecting copper exposure

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  • DG202504226528

    I used to do B, but the last few years, I've been doing the A since my fab prefers it.

  • John T
    in reply to DG202504226528

    Hi DG, yes this is what I can see on many user designs. This seems quite common for specific design types such as bga laden designs. An example concern I have is that some things the pcb fabricator might prefer to do which the pcb assemblers ( or designer) might not want. Examples: how does this affect via openings, via in pads or adjacent to pad. I also have concerns for DFN type components with diepads and what happens underneath. 

    Do you find any other advantages or disadvantages to ordering boards this way?  

Reply
  • John T
    in reply to DG202504226528

    Hi DG, yes this is what I can see on many user designs. This seems quite common for specific design types such as bga laden designs. An example concern I have is that some things the pcb fabricator might prefer to do which the pcb assemblers ( or designer) might not want. Examples: how does this affect via openings, via in pads or adjacent to pad. I also have concerns for DFN type components with diepads and what happens underneath. 

    Do you find any other advantages or disadvantages to ordering boards this way?  

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