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Archive for September 6th, 2019

Raspberry Pi “Moster” Heatsink Retaping

A pair of colorful laser-cut stacked acrylic Raspberry Pi cases with “Moster” (*) heatsinks arrived, with the intent of dressing up the HP 7475A plotters for their next Show-n-Tell:

Moster RPi Heatsink - assembled case
Moster RPi Heatsink – assembled case

Unfortunately, the thermal tape on one of the CPU heatsinks was sufficiently wrinkled to prevent good contact with the CPU:

RPi taped heatsinks - as received
RPi taped heatsinks – as received

The seller sent a replacement copper slug with tape on one side. Presumably, they glue it to the heatsink with thermal silicone:

Moster RPi Heatsink - silicone adhesive
Moster RPi Heatsink – silicone adhesive

Of which, I have none on hand.

So I did what I should have done originally, which was to drop a few bucks on a lifetime supply of thermally conductive heatsink tape, apply it to the bare side of the slug and stick the slug to the heatsink with their tape:

Moster RPi Heatsink - replacement adhesive tape
Moster RPi Heatsink – replacement adhesive tape

The blue stuff is the separation film, with the tape being white. It doesn’t match the black tape on the other side, but seems gooey enough to work.

Done!

Despite the heatsink hype, ball grid array chips dissipate most of their heat through their pads (and perhaps a central thermal pad) into the PCB, so sticking a heatsink atop the package is largely decorative, along the lines of hotrod ornamentation.

The epoxy packages used in previous Raspberry Pi iterations had better thermal conductivity to their top surface:

RPi 3 B - epoxy CPU
RPi 3 B – epoxy CPU

Than the more recent metal-top packages, which surely have inert-gas fill under the lid:

RPi 3 B - metal CPU
RPi 3 B – metal CPU

Pix cropped after being pilfered from the Official Raspberry Pi site.

Yes, the heatsink does conduct some heat into the air, even if not nearly as much as you might want.

(*) I’m pretty sure “Moster” was a typo in the original eBay listing which took on a life of its own to become something of an unofficial trademark. All of the search results ship from Duluth, Georgia (USA), regardless of the nominal seller; feel free to draw your own conclusions.

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