ASME K-16 / ITherm 2026–27 · Assembly.stp

Cold Plate Geometry

This is the test assembly from the competition files, shown as built. Rotate the 3D model, then use the drawings below. They show where the water goes and what "between the fins" means.

Follow the water

Each dot is a drop of water. Step through the journey, or press All steps to watch the whole loop. The drops are blue while cold. They turn orange as they pick up heat from the chips.

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Steps

The assembly in 3D

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Y = up (stack direction)

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Parts

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Section cut

plane at 0 mm

1 · Across the fins: what "between the fins" means

Between the fins = the water channels. The fin plate is a comb of 271 thin copper walls standing on the baseplate. Each fin is 0.1 mm thick, with a 0.1 mm gap to the next one. The water flows through those gaps, the narrow slots between neighbouring fins, so the baseline has 270 tiny channels side by side, each 0.1 mm wide and 2 mm tall. The gasket presses on the fin tips from above and closes the top of each channel.

A slice across the fins, looking along the flow. Only 22 of the 271 fins are drawn, and the horizontal scale is stretched so the 0.1 mm features are visible. The water (light blue) fills every gap. Heat goes up from the chip, through the TIM and baseplate, into the fin walls, and out into the water sliding past them.

2 · Along the flow: where the water goes

A slice down the middle, along the fin direction (to scale in Z, layers stretched in Y). The water enters at the two outer ends, drops into the fin channels where the gaskets stop, runs inward under the gaskets for about 13.6 mm, meets in the 3 mm center slot, and leaves straight up through the center port. The two halves flow toward each other, so each channel carries half the flow over half the length.

3 · Top view: fins over the chips

Looking down through the manifold. The fins run top-to-bottom, the same way the water flows. The dark bands are the two gaskets. Water can only drop into the fins in the strips outside them, over the HBM chips. It then has to squeeze along the channels under the gaskets, over the GPUs, to the center slot.

So the memory chips sit right where cold water arrives, and the GPUs sit under the long, gasket-covered part of the path. That matters for design, because the score weights the HBM temperature at 0.7.

fins: 271 · 0.1 mm thick · 0.1 mm gaps
fin height: 2 mm
fin length: 52.15 mm (along flow)
channels: 270 · 0.1 × 2 mm each
gasket strips: 13.6 mm long, 3 mm slot between
inlet / outlet: Ø 10.3 mm ports · side in, center out
flow: 2.25 L/min · 45 °C · splits in two
in a channel: ≈ 0.35 m/s · Re ≈ 110 (laminar)