Hi I have not monitored the detail of the posts about heat sinks, but two cents worth based on the XDM receiver built a few years ago at HartRAO.
I learned a great deal about thermal control from Ian Robertson at Tellumat. The most important thing is that aluminium is actually a very poor conductor. The first, obvious, issue is to transfer heat from the device to the heatsink. There is always going to be a real issue with the thermal resistance of the package and the matching pad to the heatsink. However, heat will just not flow any distance through aluminium. If you work through the sums with a simple diffusion equation, you will see why. We settled on a block (copper would be best) attached to the device, and a heat pipe taking the heat to the outside of our system. The design of these blocks, and choice of material is important. The heat pipes needed will be quite basic, and are made to order in terms of length. This system worked very well compared to a heatsink block conducting to the outside. We used an outside contractor who has a Russian sourced thermal design and simulation software, and this allowed us to try a large number of combinations, to find the best. Then there is the issue of the terminal heatsink and structures that encourage convection, which is the only way the heat is going to be removed. A chimney structure at the back of racks, with fans is best. Sun actually has a radiator in the door of their racks, with chilled water, and air is drawn in with fans and exhausted to the room. It can then be drawn in again: this save 40% in the size of chiller and fans, apparently. You will notice that most laptops have moved to heat pipe technology, which, in turn, comes from the Space industry. Regards Mike On 16 April 2013 17:44, David Hawkins <[email protected]> wrote: > Hey Jason, > > I don't know of anyone who's actually done this, but we do also have >> a passive-cooled concept for our new digitiser board (loosely based >> on ROACH2). We've been thinking about a prototype that'd essentially >> be turning a ROACH2 board upside-down and bolting it onto a giant >> metal plate that's been appropriately milled out of a solid chunk of >> alu. The FPGA, PPC, QDR and other hot bits would make contact with >> the plate and use it as heatsink. The other high-profile parts (RAM >> DIMM, for example) needs holes or cavities milled out the alu. >> > > Talk to Brent Carlson at DRAO (Canada). The EVLA correlator > boards have a massive heatsink with a 3D profile machined > on the PCB-side to accommodate the various heights of the > devices on the board. > > Verification of the installation of the heatsink involved > using an IR camera to view the rear side of the board to > look for "hot spots". > > The EVLA boards are huge. Installation of a heatsink on > your digitizer board should not have to be as complicated :) > > Cheers, > Dave > > > -- Michael Inggs Department of Electrical Engineering, University of Cape Town, Private Bag, Rondebosch 7701, South Africa. Tel: +27 21 650 2799 Fax: +27 21 650 3465 Skype: mikings "Ex Africa semper aliquid novi"
