Our thermal management team is back from a fun, education-filled week at Electric & Hybrid Vehicle Technology Expo where we exhibited and showcased our latest products and innovations. In case you missed out, we’re recapping our Principal Scientist, Tim Fornes’ presentation, “Comparison of Thermal Pads and Gap Fillers for Thermal Management of EVs.”
Tim’s presentation outlined gap fillers and their comparison to thermal pads. He also explained how gap fillers help reduce thermal impedance in battery packs. The top three questions he received at EV Tech Expo are:
Question: How does the surface roughness of the substrate affect thermal impedance results between liquid-dispense gap fillers and thermal pads?
Answer: We’ve seen that by machining metal to different practical levels of roughness, which are on the micron scale, gap fillers still greatly outperform thermal pads.
Question: What advantages (or disadvantages) do liquid-dispense gap fillers have over thermal pads during the manufacturing of battery packs?
Answer: Gap fillers have a distinct advantage over thermal pads when it comes to dealing with finite tolerances in bondline thickness. The quantity of gap fillers can be varied locally using meter-mixed equipment (link to video) to account for differences in bondline thickness or simply filling in large interstitial spaces between individual prismatic or pouch cells. Moreover, the gap fillers can be dispensed in unique patterns to direct heat into or out of certain areas. Thermal pads, on the other hand, lack this feature as they are supplied at constant thickness.
Question: What role does open time of the cureable gap filler play in final thermal impedance of the cured assembly?
Answer: It’s important to first define open time. Open time is the time after an adhesive is applied during which a serviceable bond can be made. Thermal impedance of the bondline should not be affected as long as one mates the parts together in the correct amount of time. Failing to do this will cause the material to become too solid-like and in turn lead to higher impedance values.