Originally Posted by
gabe
sorry for not being able to get back to you faster, but I am in China right now, and facing very hectic schedule.
You are essentially correct: the key here is standoff height. So please make sure that all standoffs are completly fastened tight, particularly in the VRM's area. One or two more turns of fastening the standoff will make the difference between poor contact and good contact. We are indeed dealing with very small distances here, of the order of 0.1 to 0.2mm. anmd since we do not want to warp the PCB in excess, tolerances are tight indeed.
I officially implemented the "no pad" tweak after successfully testing it myself with 5850, 5870 and 5970, so I felt very comfortable recommending it.
BUT making sure that all standoffs are fastened tight is something that I do automatically without even thinking twice about it, and in hindsight I should have added this in the instructions. Using pads gave us sufficient margin to allow for larger tolerance gaps, but not using pads is obviously reducing the margin of tolerance that we have, and therefore absolute repect of the specified standoff height relative to PCB becomes obviously critical.
The conendrum we find ourselves into is this: using standoffs to prevent excessive warpage of the PCB, in other words user safety, and the desire to provide a perfect TIM between VRM's and copper plate. In theory, these two goals are mutually incompatible. In practice, they are possible, but reserved to advanced users who have a solid understanding of the underlying difficulties associated with this kind of mechanical challenge. This is the very reason why I included the tweak in an "advanced users" section of the installation guide.
Other vendors (who do not use standoffs) do provide a better TIM, but this is at the cost of safety. The users of these competing solutions typically qualify themselves as advanced, and so they do not really mind taking the risk. We on the other hand, want to provide safety as well as performance, and it would appear that we still have either some tweaking or better maybe explaining to do in order to accomplish this.
Doing a hard mount (without pads) is quite possible with the Komodo's, I have done it, and I'll stick to my guns about it. Performance is exceptional, and pcb warpage was minimal. Should I revise my standoff heights and therefore reduce the tolerance gap without pads is something I now need to consider carefully.