Can i use GREY 999 Silicone to glue Leds to Heatsink ?

gamezawy · 2018-11-26T01:17:59.000Z

Hello every one

I am making an outdoor light with big heatsink and some XHP50.2 ON 12 Volt MCPCB with 1.5A AC constant current Driver

i dont want to use normal thermal paste and screws to fasten the leds to the heatsink, too much work for me

so can i use GREY 999 RTV Silicone instead of fujick ?

BlueSwordM · 2018-11-26T01:21:21.000Z

You can use RTV silicone, although it will have lower performance than thermal paste, but will be slightly better than thermal glue/thermal pads.

gamezawy · 2018-11-26T01:36:59.000Z

Thank you for your fast answer , but How much lower performance than thermal paste ?

BlueSwordM · 2018-11-26T01:39:12.000Z

Since you are pushing only 18W to an XHP50.2 with a big heatsink outside, it shouldn’t make a noticeable difference at all.

Barkuti · 2018-11-26T03:34:21.000Z

Given the question here entails, what about this thermal glue compound from the far east? :

https://www.ebay.com/itm/Silicone-Thermal-Conductive-Adhesive-Glue-Sticky-Compound-Curing-Heat-Sink-Paste/263353438319
https://www.aliexpress.com/item/-/32871038694.html

Its price is fair.

Cheers ^:)

gamezawy · 2018-11-26T14:24:16.000Z

its just i have the GREY 999 RTV Silicone and buying fujick will take time

hank · 2018-11-26T14:32:38.000Z

Remember the goal is not to goop the stuff in between heat source and heat sink.
You want to put a tiny amount on and spread it thoroughly with something like the edge of a credit card so you have metal to metal contact wherever possible, and the goop is only filling the tiny gaps between the surfaces where they are not sufficiently ‘lapped’ to match up exactly.

https://www.overclockersclub.com/guides/lapping/

Due to the machining process, just about every heat sink will have a rough surface. To the naked eye it may look flat or even feel smooth, but there are microscopic groves in the surface. These groves will trap air between the heat sink and the CPU, and cause a poor transfer of heat.

Thermal compound (Artic Silver, Nanotherm, etc.) is used to fill these groves and help transfer the heat from the CPU to the heat sink. Just like air, thermal compound is something else that the heat has to pass through to get from the CPU to the heat sink.

We lap the heat sink to make it smooth, allowing us to get the best possible contact between the CPU and heat sink. Even after lapping, there will still be grooves for the air to be trapped in, but the grooves will be much smaller, and cause less of a problem.