I searched and most of the info online was from the computer
guys managing heat and their preferrence is compound. it seems that the terms are kind of used interchangeably but I want to make sure I use the correct product for mounting the led/pcb on the pill. it seemed like the compound was more of a contact/filler material for heat dissipation rather than an adhesive. which is the preferred product you guys are using?
this:
or this:
http://www.mtnelectronics.com/opencart/index.php?route=product/product&path=25_74&product_id=114
I prefer to use compound on the led stars with screw mount or lense pressure centering mount [ea4] works well. I just use unick compound, but arctic silver 5 is top shelf. Adhesive would be good for stars without centering mount or screws but it nails those stars down for good.
Both have their uses.
Adhesive is a lot more permanent, so you need to be completely sure before you glue anything down or it's going to be extremely hard or expensive to rectify any problem you come across.
But it's also useful for holding LED MCPCBs down and in place.
Most of us just use FUJIK adhesive unless we're really pushing the LED beyond limits.
It depends on the application! In a perfect world, we would use very little or no thermal compound and rely only on two highly polished and lapped surfaces to give optimal contact. In any application, you want enough pressure exerted to maximize metal-to-metal contact and minimize air pockets and thick layers of thermal compound or adhesive. In lights where a lot of positive pressure is maintained on the MCPCB (such as the S2, S3, S6, M1, etc.), I prefer thermal compounds because they are easier to work with and easily removed. In lights where there isn't as much contact pressure (like in my C12 MT-G2 build) I like the adhesive because it allows me to set the LED with a lot of pressure then not worry as much about the reflector/etc. being as tight. In either case, adequate pressure is important either continuously (compound) or until cured (adhesive).
The better the metal-to-metal contact the less you rely on the quality of the thermal compound/adhesive. This isn't to say that I spend hours lapping and polishing all of my lights, because I don't, but if you are looking for optimal heat transmission that's where it's at.
It's good to have them both in your bag and a little bit goes a long way!