Then I ran across an article on the web where the writer was discussing this very topic and his conclusion was what I had decided from my experiment. I was trying to find that article tonight but before I did I ran across a related discussion about automobile radiators Aluminum vs Copper. https://www.researchgate.net/p..._aluminium_or_copper Read about 1/3 down the page and look for the name Ammar Eqbal, Indian Institute of Technology Patna where he says the best heatsinks are a composite with a copper base and aluminum fins. I am glad I did the test but to my way of thinking it was a draw. j
My experience was the exact opposite. The application was high power IR diode lasers for a medical product. My choices for heat sinks were: copper base with graphite fins, all aluminum heat sink, and aluminum base with copper fins. The aluminum base with copper fins was the best choice [for this application]. Please note that the heat sink grease was silver filled and a high speed ducted fan cooled the fins. Lasers have the nasty habit of thermal runaway when they reach 80~85C. At a grand a copy I had to get it right.
If you have an interest in copper heat sinks just Google: Cool Innovations Thermal Systems.
To circle back to the original intent of the question: yes small heat sinks will help and they can be attached using at least two different ways mentioned in this thread.