Thermal Interface Material for Mounting High Power Laser Diodes

[Alan]

Can anyone recommend a good thermal interface material for mounting CS package high power laser diodes?

[Larry Johnson]

Low thermal resistance is generally critical to ensure that the temperature of the part under test is kept as close as possible to the cold plate temperature. Tests at ILX Lightwave yielded the following results for thermal resistance when mounting CS packaged laser diodes onto a bare aluminum cold plate:

Bare part 0.70 C/W
Thermal Grease 0.33 C/W
Pyrolytic Graphite 0.04 C/W

In all three cases we used 35 pounds of clamping pressure to hold the laser down. Pyrolytic graphite sheet (PGS) is a flexible, high thermal conductivity material designed for heat sink applications. The PGS material used in these tests was electrically conductive. PGS laminated with a thin insulating layer is also available. Pyrolytic graphic sheet is manufactured by Panasonic and a few other vendors. Information on the Panasonic material can be found at, http://www.panasonic.com/industrial/...al/thm_hsm.htm. A convenient distributor of this material is www.digikey.com.

[Larry Johnson]

PANASONIC PYROLYTIC GRAPHITE - Apparently Panasonic pyrolytic graphite material is not recommended for clean room use. Following is an exerpt from an email received from one of their engineers:

"Unfortunately, we don’t have data for Class 1000 clean room. Basically, PGS has carbon powder happen very easily, if you rub the PGS’s naked surface. We think that it isn’t applicable for clean room, if their control level can’t bring paper in clean room. But, we have covered both surfaces with PET or Double sided adhesive tape type. We suppose these type are powder occur less than naked type."

GRAFTECH EGRAF - We are also experimenting with another material manufactured by GrafTech International (www.graftechaet.com) that is clean room qualified. Following is a comment from an email received from one of their engineers:

"eGraf materials can be used in clean room applications. We offer our "edge-Seal" technology and different surface coatings to insure that flaking or dusting of the base flexible graphite material does not occur."