As an example:

The SOT23 reflow footprint takes up 3.3x3 mm while the wave takes up 4.5x4.6mm.

The IPC standard has a 8x8!! placement courtyard. Like, yeah right. Someone 
tell me this is a typo - at that size I may as well us a TO-92.

Taking the distance of the outer edge of a pad on one side of the SOT-23 to 
the outer edge of the other pad (the IPC Z dimension):

Philips Reflow: 2.7mm
My footprint: 2.95 mm
IPC: 3.6mm
Philips Wave: 4mm

In high density layouts what are you going to use?  (Actually, I am a bit 
timid going as low as the Philips reflow footprint as it feels mighty small 
when you see it -it is not easy to hand solder.  But the point about reflow 
footprints being able to be made very small is clear.  My footprint has 
been in use for many years, on many boards, assembled by many manufacturers 
without any issues.)

Also, if you have a look at the Philips wave footprint
http://www.semiconductors.philips.com/acrobat/packages/footprint/FOOTPRINT-SOT23.pdf

You can see that the single pad is very wide.  This is different from the 
old data I have from the early to mid 90's so they have updated it.  Also, 
I think they have changed the preferred wave direction - I think it used to 
be in the other direction.  I am not sure I like the new wave footprint but 
maybe it heats the device more evenly or something.

Ian


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