Printed Circuit Board Designing 1

[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?

 

[BML]

One advantage is that the larger layout will take into account the variability in chip placement.  Ultimately the layout should be dependent upon the material and process capability.

 

[ldowns]

Unfortunatly your design layout is restricted by the<br>minimum manufacturing capability of the PCB manufacturer.<br>Your best bet is to contact them and find out what Design<br>For Manufacture rulings they are required to work to (each manufacturer has their own set of guidelines).&nbsp;&nbsp;You could ask for the front end engineer (there are various names for these engineers who perform this necessary task) who would apply these rules to your designs prior to the artworks being create, so that they can explain their DFM constraints.