can I use a tec without a coldplate?
 

like this:

block
tec
northbridge

or do you "HAVE" to 100% use a cold plate?? assuming that the right pressue is apllyed..

100%, you have to.

The cold plate, aka spacer, also acts as a heat spreader. Also, I really don't think that you would want to subject your mobo/NB to the kind of clamping pressures that are required. As a guide, nylon bolts can barely handle the pressure themselves!

IMHO you don't have to use a cold plate - it won't be very efficient, but it won't hurt anything. The purpose of the cold plate is to act as a heat spreader (as Ben said) which couples the relatively large surface area of the TEC cold side to the much smaller surface (NB???) you are trying to cool. Any of the TEC cold side that is not in direct contact won't be able to transfer heat. It will have to be well insulated because it's exposed and will get cold = condensation.

The cold plate also acts as a thermal buffer - to help moderate temperature changes.

On the other hand, the hot side of the TEC "HAS" to 100% be in contact with a heatsink or it can overheat the couples and burn out.

(I won't ask why... :) ) Good luck

It's hard to get the optimal clamping pressure of 100PSI+ if you don't...