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Blackadder March 27, 2003 11:10

Temperature Distribution on a circuit board
Hi there!

I have been given the task to simulate a reflow-soldering process. As I have never used CFD before, I hope that somebody here in this forum can help me with that. A link to some helpful resources on the net would also be very much appreciated.

The most interesting part to me is to simulate the temperature distribution on the circuit board while it goes through a convection-soldering oven. If possible, I would also like to simulate the temperature distribution in a condensation-soldering oven in a later stage of the project.

The convection oven has a length of about 4m and consists of 5 different temperature zones ranging from about 450K to 550K. The circuit board is transported through the oven with the help of a chain. The software should be capable of simulating the movement of the circuit board, as the board passes several air guide plates. While the board is transported through the oven, hot air is blown at it through a number of nozzles. In the first stage of the project, the board will be "naked". Later, the model should be extended and components like ICs will be placed on the board.

Maybe somebody here also knows how to model the process in a condensation-soldering oven. Again, what interests me is the temperature distribution in the circuit board. The difference is, that this time there is no air blowing at the circuit board. Instead, the board moves through saturated steam, which leads to film condensation on the board and the components located on it.

My first problem now is to find the best software for the given task. My predecessor, who already built a model, was using CFDesign 4.1. The software I have considered so far is FLOTHERM, ICEPAK, CFDesign 5.0 and StarCD.

Thx a lot,


Harry Fulmer March 27, 2003 12:32

Re: Temperature Distribution on a circuit board
The choice will depend on the modelling methodology adopted. If you want to explicitly include the effects of steam, moving conveyor etc then you'd be better off with a general purpose tool (StarCD).

If it's justified to make assumptions like the conveyor is static (w.r.t. the velocity scales in the ovens so the full model can be broken down into a series of steady state models with the board in different locations), that the steam effects can be included via modification of the fluid properties and phase change heat transfer is insiginificant compared to more standard convection, conduction and radiation then you'd get an answer much more quickly using tools such as FLOTHERM or ICEPAK.

If you're wanting to get a feel of thermomechanical stresses in the board then FLOTHERM has the advantage of FLOSTRESS, a fully embedded stress solver with direct links to the CFD generated T field. This module I believe has been created specifically for board level and solder joint stress prediction.

Good luck!

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