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I have never gotten a good answer from board houses, but once you require a via in pad process (IPC 4761 Type V) you might as well do as many as you want right?

Effectively 1 vs 100 vias is going to be the same amount of work, and thus a similar price? I find I typically try to user them as little as possible, but in reality if I need an IC that requires it for route out, I might as well use them all over and maximize board density (if desired)?

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It all depends on scale. When you start making tens of thousands of boards per month, the vendor will calculate very carefully the actual cost, in terms of time on each machine, operator time, machine depreciation, consumable supplies, etc., required to make your board, and this will inform the lowest price you'll be able to negotiate down to. Yield will also become critical to determining cost, and each low-yield feature on the board will therefore increase the yielded cost of the board.

So at this scale, yes, 100 in-pad vias might cost a (noticeable) few cents more than 10 in-pad vias. The cost difference between 100 in-pad vias and 10 in-pad vias plus 90 other vias is probably still "pretty small" compared to the total cost of the board, but will eventually be calculated and will affect your cost.

If you're only making 10 or even 100 boards, then the set up and NRE costs will dominate, the yield will be unknown, and the marginal cost per via (whether through, filled, or filled and planarized) will be miniscule. But the number of processes that need to be set up will be important. So in this scenario, the cost difference between 1 in-pad via and 100 is likely insignificant.

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  • \$\begingroup\$ Thanks, That is what I assumed. They are small runs of 100 pieces typically, so yep NRE and setup is a larger part of the cost. \$\endgroup\$
    – MadHatter
    Commented Sep 19, 2020 at 22:43

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