PCB Thermal Analysis

[rickman]

I have a very small board that I would like to model for thermal
analysis. I am pretty confident that I can get by with a first order
analysis since I only want to know if I have a prayer of a chance of
dissipating the heat from this board, rather than a detailed analysis
of the range of temperatures across the board. I was thinking about
drawing a simple spice circuit with current to represent heat,
resistors to represent thermal resistance and voltage to represent
temperature.

Sounds pretty simple, right? But even after doing some web searching,
I have no idea where to find details on the thermal conductivity of
PCB material and the values to use for transmitting heat from the
board to the air. I am surprised that this is not commonly used, but
it appears that most IC data just *assumes* that your board is large
enough that it is a good heatsink. I did not find a single reference
with info on the PCB.

Am I not looking hard enough? Can anyone point me to the raw data on
PCB thermal characteristics I need for this analysis?

 

[Leon]

On 31 Jan, 17:27, rickman <gnu...@gmail.com> wrote:

I have a very small board that I would like to model for thermal
analysis. I am pretty confident that I can get by with a first order
analysis since I only want to know if I have a prayer of a chance of
dissipating the heat from this board, rather than a detailed analysis
of the range of temperatures across the board. I was thinking about
drawing a simple spice circuit with current to represent heat,
resistors to represent thermal resistance and voltage to represent
temperature.

Sounds pretty simple, right? But even after doing some web searching,
I have no idea where to find details on the thermal conductivity of
PCB material and the values to use for transmitting heat from the
board to the air. I am surprised that this is not commonly used, but
it appears that most IC data just *assumes* that your board is large
enough that it is a good heatsink. I did not find a single reference
with info on the PCB.

Am I not looking hard enough? Can anyone point me to the raw data on
PCB thermal characteristics I need for this analysis?

You could try asking a manufacturer of PCB laminate, I'd have thought
that it would be a fairly common request and they should have the
figures.

The PCB software I use (Pulsonix) has an interface for the Betasoft
thermal analysis program, which presumably includes modeling for the
PCB material. You might be able to find something relevant on the
Betasoft web site.

Leon

 

[EE123]

On Jan 31, 12:27 pm, rickman <gnu...@gmail.com> wrote:

I have a very small board that I would like to model for thermal
analysis.  I am pretty confident that I can get by with a first order
analysis since I only want to know if I have a prayer of a chance of
dissipating the heat from this board, rather than a detailed analysis
of the range of temperatures across the board.  I was thinking about
drawing a simple spice circuit with current to represent heat,
resistors to represent thermal resistance and voltage to represent
temperature.

Sounds pretty simple, right?  But even after doing some web searching,
I have no idea where to find details on the thermal conductivity of
PCB material and the values to use for transmitting heat from the
board to the air.  I am surprised that this is not commonly used, but
it appears that most IC data just *assumes* that your board is large
enough that it is a good heatsink.  I did not find a single reference
with info on the PCB.

Am I not looking hard enough?  Can anyone point me to the raw data on
PCB thermal characteristics I need for this analysis?

There is a book:
"The Electronics of Radio" by David Rutledge of Caltech.

There is a section in there deaking with thermal analysis.

Dave