Author Topic: Do you layout to reduce stencil size or spread out parts?  (Read 1903 times)

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Offline alank2Topic starter

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Do you layout to reduce stencil size or spread out parts?
« on: June 25, 2015, 11:59:28 am »
I'm working on my second SMT pcb and the pcb because of a few parts that need to be in specific places is quite a bit larger than the parts going onto it, roughly 100 mm x 90 mm.  My question is, is it easier from a stencil perspective to try to fit all the stenciled parts in a smaller area, or spread them out over the larger area of the pcb?  Any thoughts?
 

Offline m98

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Re: Do you layout to reduce stencil size or spread out parts?
« Reply #1 on: June 25, 2015, 10:00:48 pm »
That depends on your design requirements. But why should it make a difference for the stencil how you place the parts?
 

Offline H.O

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Re: Do you layout to reduce stencil size or spread out parts?
« Reply #2 on: June 26, 2015, 05:18:16 am »
Theoretically, a rotational misallignment of the stencil of x degrees makes the problem worse on a big board compared to a small. Of course, in practice you just tweak it untill it's "spot on". I wouldn't let that aspect "drive" the part placement.
 

Offline zapta

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Re: Do you layout to reduce stencil size or spread out parts?
« Reply #3 on: June 26, 2015, 05:31:53 am »
If the stencil costs you by area (e.g. oshstencil.com) then smaller = less expensive.
 

Offline Muxr

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Re: Do you layout to reduce stencil size or spread out parts?
« Reply #4 on: June 26, 2015, 06:37:04 am »
There are so many other factors that i find more important when placing parts than to worry about the stencil size. I spend so much time worrying about not painting myself into a corner leaving room for modification on a working design, efficient manufacturability, mechanical design, interferences, stray capacitance, the length of traces and also the board size as the cost cutting measure that the stencil size doesn't even enter the list of concerns.

Considering that it's usually a one time fee, I wouldn't worry too much about it.
« Last Edit: June 26, 2015, 01:36:53 pm by Muxr »
 


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