:: DIP / SOIC package surface reistance

Bob pease' video about femtoampere things gives us a very interesting look into package inter pin insulation resistance.

What's All This Femtoampere Stuff, Anyhow?

from various ic specifications

we can draw up inter pin dimensions to estimate further, we could estimate what kind of insulation tolerances the packages have, by counting the number of squares between the pins. as surface resistivity is characterized by "ohm.square" and using the thickness of the pin as a way to visualize the number (as seen in the below estimation by drawing diagonal lines)

DIP inter pin overview

due to manufacturing tolerances, the pin maybe 10mils thick or 15mils thick. 30 or 40 mils between pin. this seem to suggest the plastic DIP worse case insulation tolerance needs to go as high as 500Tohm.square

best case tolerance 240Tohm.square

SOIC inter pin overview

at worse tolerance, 290Tohm.square

at best tolerance, 150Tohm.square

MSOP inter pin overview

MSOP worse tolerance 560Tohm.square

if the tolerances are to be expected, the SOIC is a good replacement for DIP. but not for anything smaller. and it also looks like SOIC may have better error limits due to the small package tolerance. but soldering heat may cause more severe deformation/stress problems for SOIC than DIP.