Three years ago, thermal pad was a significant role, predominately in thermal management of EVs battery pack.

With the advancement of EVs battery technologies, trend to shift away from thermal gap pad to thermal gap filler, providing a more closer contact between cells or cell and heat sink, and  thermally conductive structural adhesive is the best in gap filler family. GLPOLY is the first one in China to develop thermally conductive structural adhesives for “cell to pack” battery pack in a new technology—modified epoxy which differ from existing PU technology.

Consequently, we received many queries from engineers about properties of thermally conductive structural adhesives. Here I sorted out some information for your reference.

Q: What’s the linkage between bond line thickness and shear bond strength?

A: In practical application of “cell to pack” battery, there is no inevitable linkage between these two properties.

Q: Shall the bonding strength varies with Al substrates?  

A: No matter Al3003, Al6063 or Al1030, the Al content is greater than 97%. It depends on the Hydrogen bond between crosslinker and metal atom. Effect affected by other factors is less than 3% which is within the range of tolerance. GLPOLY has full set of Al3003 fixtures for validating.

Q: What factors shall affect shear bond strength?

A: 1) Bonding strength decreases a lot if the surface of aluminum is oxidized to alumina; 2) Roughness. The rougher the surface, the greater the bonding strength; 3) Modifier applied on the surface. Depending on specific conditions.  

Q: Why not mark value of butt-joint bonding strength?

A: A joint made by fastening ends together without overlapping. There is no need to test it because no butt joint happened between cell and watercooling plate.

Q: Why is it recommended to remove insulation painting?

A: Painting increases thermal resistance. And in this case, it shows bonding strength between thermally conductive structural adhesives and painting, not adhesive and watercooling plate. Furthermore, GLPOLY thermally conductive structural adhesive has electrical insulation.

Q: Are contact thermal resistance the same between different substrates? For example, PET and Al?

A: Both interface thermal resistance of PET and Al are between 0.000178~0.000679, but the contact thermal resistance is hard to test. our specification comforms to the result of nearly 300 regression tests.  The contact thermal resistance is negligible due to extremely low value. By extension, the above conclusion is true in the application of soft pads. So it is true for liquid thermally conductive structural adhesives if there is no air bubble or water film.

If you have any other question, please feel free to contact GLPOLY for detail.