Circuit board pad layout.

[mosfit]

What are the possible manufacturing issues and drawbacks involved in using a pad layout that is exactly the same dimensions as the maximum tolerance of the footprint of the device being installed?  Can I get away with having a 7% overhang of the interior "heel" of the surface mount part relative to the pad?  Why should I follow an IPC recomended pad layout that takes up so much of my board space when the device will fit snug on a smaller layout?

 

[ronhotchkiss]

Keep in mind that IPC dictates standard practices. This is not to say that you will not have situations that will not meet this standard to the letter. The only caution is that you are confident that the board can be manufactured (in other words, the manufacturing facility can make it and make it consistently). Also, be sure that completed board meets your design intent. Keep in mind that during most training on the IPC, the IPC standard is presented as the last restriction imposed behind the engineer's design (intent) and the purchase order.

Another caution is to be sure that whatever manufacturing facility you are using is willing to build a board that does not meet IPC and that they understand that this is the case. Document it!

Hope this gives you some confidence in your decision.
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