# The best way to attach a heatsink to a SMD component?

There's a SoC I want to throw a heatsink on. What's the best way to do this for maximum heat transfer and longevity?

I know of thermal pads, thermal adhesive, and thermal paste -- but when it comes to the standard black plastic packages, I have no clue which of the options would be best.

• Standard black plastic packages are not designed for applications with excessive power dissipation, they should be well cooled by PCB they are attached to. If a IC has the power dissipation that exceeds standard plastic package, the package usually has a corresponding thermal bottom slug, which is meant to be soldered down, and multi-layer PCB must be used with massive internal copper layers. If you need extra cooling, it means that either the PCB is wrongly designed, or you are using some overclocking. Throwing a heat sink is up to you, any method will work, depending on mechanical/vibration – Ale..chenski Sep 5 '18 at 0:19
• which SoC package? and throw how by what W/'C spec? – Tony Stewart Sunnyskyguy EE75 Sep 5 '18 at 0:21
• No decent design can be done without specs – Tony Stewart Sunnyskyguy EE75 Sep 5 '18 at 0:25
• Exynos5422 is a serious octacore prcessor, and likely requires a serious approach to extra cooling. – Ale..chenski Sep 5 '18 at 1:10
• @Saustin you claim this to be "generic catch-all passive cooling question", but missing the point of several comments above that SoC is not generic IC. You need to study datasheet for thermal characteristics and recommended PCB design just to make it work in standard operating range. Then you can make a guess what would be the best way to improve heat dissipation. Most likely it won't be a heatsink on top of the chip but rather beefed-up copper on PCB – Maple Sep 5 '18 at 8:42

I don't know about maximum efficiency but there are little stick-on heatsinks that can reduce the junction temperature of BGA and LQFP packages.

I got like 90 of them (2 sizes) from Aliexpress for about $7 US shipped, but you can also find them at distributors. Chances are good the adhesive might be better in terms of longevity and thermal conductivity from the disties, but$\$.

There are other options such as using a high tech thermal pad between the chip and a finned case, but there isn't so much advantage in that for the relatively low power levels and home/office environment. Chances are your SoC will be obsolete before it fails if you keep the junction temperature reasonable.

As others have said, most of the heat is typically conducted out through a thermal pad (with copious thermal vias on your board) to planes on the board. Keeping the board cool can be done with a fan, or perhaps something attached to the opposite side of the board (insulation is really important or something could be damaged).

I think this processor calls for more than a little stick on heatsink.

The Exynos5422 has
Mali™-T628 MP6 GPU +
Video VP8 Codec +
WQXGA

This is an image of two Exynos5422 boards.
This is the way to go, one active, one passive.

And for those with the idea of cooling from the bottom side,
this is why that may be problematic.

Anything thermally conductive on the top of an IC can decrease thermal heating (with some thickness, aluminum foil probably won't work).

In the past I have taped on pieces of aluminum for prototyping with a dab of thermal compound, even a 1cm^2 bit of aluminum with no fins can decrease the temp of an SOIC by 20-30C (and keep it from burning up), because the surface area to air goes up substantially.