Design Constraints for the NI 9695 sbRIO Heat Spreader

Updated Apr 9, 2018

Reported In

Hardware

  • sbRIO-9695

Issue Details

I have an sbRIO-9605/06/23/26/33/36 and I want to design my own heat spreader and thermal solution. What thermal gap pad does NI use in the NI 9695's design and what height considerations are needed when designing a thermal spreader solution?

Solution

To properly design a heat spreader solution similar to the NI 9695, you must know the height from the heat spreader solution with respect to the PCB (height X in the Figure 1). It is not recommended to use the component height as a reference as process variation and assembly variation leads to larger tolerances.

The NI 9695 Dimensional Drawings lists the heat spreader dimensions needed to calculate height X. It also states the 16 mm stand-off height. With this information, we can infer height X. One height that is not known is the uncompressed thickness of the gap pad, which is 0.06".

National Instruments recommends researching gap pads in the ultra soft category that also have a good thermal conductivity. For example, National Instruments selected the following gap pad from Bergquist:

BERGQUIST GPVOUS - 0.060 - AC - 0816

Please refer to the external link shown below for more information regarding the gap pad.

Note that the five areas that connect the heat spreader to the components dimensions are listed in the dimensional drawings.


FIGURE 1
 
For your reference, Figure 2 illustrates an alternate view of the heat spreader. Please note the farthest two areas of the heat spreader are identical; thus, the 'x2' notation for the 2.17 mm height.


FIGURE 2
 

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