Epoxy sealant on peltier module

I am interested in a product that exists in two versions on DigiKey, 387004989 and 387004989. The difference between these two versions is an epoxy sealant on 387004727. The note on the technical drawing says: Allow 0.5 mm around perimeter of the thermoelectric cooler and lead wire attachement to accommodate sealant.
My questions are the following: is the expoy sealant already applied or do I have to apply it myself? What is the advantage of the sealant version over the sealant-free version?
Thank you in advance for your consideration and support.

Hello, chilmas.

Welcome to the DigiKey forum.

Yes, the sealing is one difference between 387004989 and 387004727 with the 727 part including “Low density syntactic foam epoxy encapsulant.”

You may be interested in this paragraph concerning the thermoelectric coolers:

It is also important to protect laser electronics against condensation. Even for applications where the set point temperature is at 20⁰C, the cold side of the thermoelectric cooler can be at 10⁰C or colder to maintain that set point temperature. This will most likely be below the due point temperature and cause moisture in the air to condense. Sealing the perimeter of the thermoelectric cooler with epoxy or RTV is not sufficient and it is therefore recommended to have a second insulation barrier to protect the thermoelectric cooler cavity. All surfaces that go below dew point will require some type of insulation to keep moisture from condensing. This is usually a close cell foam or other type of insulation that does not absorb moisture and has good thermal insulating properties.

Based on this statement, it appears that sealant is mandatory for long life. Not just one, but two barriers against moisture.

Best Wishes,



Hi APDahlen,

Thank you for your quick reply and information.
I understand that the epoxy sealant is already applied to the 727. Do you supply close cell foam or other types of insulation for 40x40 mm peltier modules on Digikey?

Best wishes,

The sealant would come pre-applied.

Epoxy and Silicone materials are often used, Silicone being more forgiving with thermal expansion and contraction.

The advantage of these sealants is they create a vapor barrier that keeps condensation away from the interior semiconductors.


Thank you for the information Kristof_2649.