Temperature

Hi just a quick question. I know most people recommend having a hot side temperature of around ninety degrees, but does that mean ninety degrees on the substrate or ninety degrees as an ambient temperature?

90F surface temp. So if you are using a UTH you'd want to take the temp under the substrate where your UTH is. If you are using a RHP you'd want it on the substrate or where ever your hot spot it. In both cases you'd need a temp gun.