What is the purpose of high clamp pressures on peltiers?

[Muggy]

I'm just about ready to fire up my new peltier cooled p3 system. I've had an aweful time trying to put the right amount of pressure on pelt/coldplate to the heatsink. I'm beginning to wonder if I'm understanding this right. Is the pressure just pre-install to make sure there is no residual grease left over, or is that pressure supposed to be there constantly? I fashioned a nice little brass clamp for the copper coldplate but I found out the straps I used were just a bit thicker than the CPU die. Not a good thing! If anyone has some suggestions, I'd love to hear 'em. I'm going to try going strapless and see if I get decent cooling.

[Random Nonsense]

it is supposed to be constant pressure. to understand it, picture the surface of the pelt and heatsink on a microscopic level, it will be rough, when both are placed togeather there will be tiny gaps. the pressure makes these gaps smaller, therefore you have more surface area in contact and get a more efficient joint for conducting heat