Using Flowtherm to find junction temp.
Using Flowtherm to find junction temp.
(OP)
Hi guys
Has anybody used flowtherm to find junction temp. of FPGA and such?
Thanks in advance for any advice.
Has anybody used flowtherm to find junction temp. of FPGA and such?
Thanks in advance for any advice.





RE: Using Flowtherm to find junction temp.
ko (www.ecooling.biz)
RE: Using Flowtherm to find junction temp.
I am just learning flowtherm, I uasally use TAS to find junction temps, but for flowtherm how would you usally go about setting up the model. If I had to find the junction temp of a FPGA that is soldered down to a thermal pad with thermal vias...how would you do that? Off the top of my head I would use a cuboid (in PCB assembly) for the FPGA, use a collapsed cuboid for the solder, and then use cuboids for the board and thermal vias. To find the junction temp I would put a monitoring point in the FPGA. would this sound right to you?
Thank you for your time
Twoballcane
RE: Using Flowtherm to find junction temp.
TTFN
RE: Using Flowtherm to find junction temp.
Well if i know the theta junction to case already then I don't have to do that. In TAS I usally just find the case temp and then calc the junction temp from there...
RE: Using Flowtherm to find junction temp.
RE: Using Flowtherm to find junction temp.
However, I think you'd still need to get the die, e.g., the actual heat source in the right place in the package with the right thermal spreading resistance to get the correct match to the conditions used to derive or calculate the theta.jc, since I assume that you need to place a heat source somewhere inside your cuboid to make the analysis work correctly.
Depending on the manufacturer and the power dissipation, the actual geometry of the die/package can be quite different.
TTFN
RE: Using Flowtherm to find junction temp.
For your application, I suggest a detailed or general compact model. It's easiest to generate these with Flopack, but if you don't have this option you can use the "compact component" in the geometry pallette or try the method described here: http:/
Also, instead of simple blocks for the PCB, you can use "PCB" in the geometry pallette and enter the copper content and thickness at each layer. You can then superimpose any local vias over this as blocks with orthotropc conduction.
ko (www.ecooling.biz)
RE: Using Flowtherm to find junction temp.
I recommend FLOPACK for getting a detailed model of the package, or, even better, ask the component vendor to tell you the value of Theta j-b, the thermal resistance between the junction and the board. Sometimes they know that value, especially if the package is designed to have a good thermal path into the board through a solder pad.
Good luck with that. Your question is the most common in thermal analysis of electronic components, and there is no good easy answer to it yet.
RE: Using Flowtherm to find junction temp.
For example, a BGA with solder balls only around the periphery won't make contact with the pcb pad and vias under the center of the package, but a 2-resistor model does make contact here and may give misleading results.
ko (www.ecooling.biz)
RE: Using Flowtherm to find junction temp.