Layer 5 — Liquid cooling (IT-side: chip to CDU)

Position in the die→grid hierarchy: the rack.

Liquid cooling on the IT side, from the chip to the coolant distribution unit: cold plates, manifolds, quick disconnects, hoses, CDUs, the pumps and plate heat exchangers inside them, the fluids in the loop, and the sensors watching for leaks.

Parts in this layer

• 5.01 Direct-to-chip cold plates · 21 companies
  A metal plate with internal microchannels, bonded or clamped directly onto a GPU, CPU, or switch package, that carries coolant across the die to remove heat by conduction rather than airflow.
• 5.02 Rack manifolds (CDMs) · 11 companies
  The manifold (sometimes called a CDM) that distributes coolant from the CDU supply line to each cold plate in a rack and collects the return flow, usually mounted vertically at the rear or side of the rack.
• 5.03 Quick disconnects (UQD / UQDB) · 7 companies
  Blind-mate connectors (UQD or UQDB) that let a compute tray or cold plate be connected to or disconnected from the coolant manifold without draining or spilling the loop.
• 5.04 Hoses, tubing, fittings, valves · 9 companies
  The flexible hoses, rigid tubing, compression and push-fit fittings, and shutoff or balancing valves that carry coolant between manifolds, quick disconnects, and the CDU.
• 5.05 Coolant distribution units (in-rack, in-row, 1–2.5 MW+ facility units) · 24 companies
  The unit that separates the IT-side (technology) coolant loop from the facility water loop, exchanging heat between them and pumping and filtering the technology-side flow — sized from in-rack and in-row units up to multi-megawatt facility-class units.
• 5.06 CDU internals: plate heat exchangers, pumps, filters · 13 companies
  The internal components of a CDU — plate heat exchangers, pumps, and filters — that do the actual heat exchange, circulation, and particulate control inside the unit.
• 5.07 Rear-door heat exchangers · 8 companies
  A heat exchanger mounted on the rear door of a server rack that cools exhaust air with chilled water or refrigerant before it leaves the rack, without cooling the chips directly.
• 5.08 Immersion cooling systems · 9 companies
  Systems that submerge servers or trays directly in a dielectric fluid, either in open tanks (single-phase) or sealed chambers where the fluid boils and recondenses (two-phase), to cool the whole tray rather than individual dies.
• 5.09 Fluids & coolant treatment · 16 companies
  The coolant fluids that circulate through direct-to-chip and immersion loops, plus the chemical treatment (inhibitors, biocides) that keeps them stable over the life of the loop.
• 5.10 Leak detection, flow & pressure sensing · 10 companies
  Sensors and systems that detect coolant leaks and monitor flow rate and pressure throughout the liquid-cooling loop, feeding alerts to rack and row controls.
• 5.11 Rack/row cooling controls & software · 5 companies
  Software and controllers that manage coolant setpoints, pump speed, and valve positions at the rack and row level, and that tie into facility-wide data center infrastructure management (DCIM) systems.

Public plays in this layer

Listed companies with the most part placements in layer 5. Placement count is breadth, not revenue exposure.