Physics / mechanism
Thermal interface materials fill the microscopic air gaps between a heat source (die, substrate, lid) and a heat sink or spreader. Without them, contact resistance dominates; even polished surfaces touch only at ~1–2% of nominal area. TIMs conduct heat across that interface, characterised by bulk thermal conductivity (W/m·K) and bond-line thickness (BLT, µm) — together yielding interface thermal resistance (mm²·K/W). Indium foil sits near 80 W/m·K; phase-change materials 3–10 W/m·K; filled polymer pads 3–8 W/m·K; liquid metal (Ga-In alloys) 20–40 W/m·K at <50 µm BLT. State of the art for high-performance compute is liquid metal or sintered silver (~200–250 W/m·K), deployed in HPC and AI accelerator lids where junction temps must stay below 95 °C at >300 W per die.
Competitive landscape
Incumbent categories: filled silicones/epoxies (Shin-Etsu, Momentive, Henkel), phase-change pads (Bergquist/Henkel, Laird), indium foil (Indium Corp), liquid metals (Thermal Grizzly, Indium Corp). Competing approaches include vapour chambers and embedded microfluidic cooling, which bypass the TIM problem rather than solve it. Carbon-based options — vertically aligned CNT arrays, graphene laminates — offer >400 W/m·K in lab settings but conformability and cost limit deployment. Sintered silver scales in power electronics but requires pressure/temperature cure steps incompatible with some packaging flows.
For the exhaustive material-class catalog — every TIM approach in-market and in R&D, with vendors, startups, maturity, and capture/route — see TIM Approach Map (every thermal-interface-material class, in-market + R&D) (24 commercial classes + 14 R&D approaches, swept 22 Jun 2026). This page is the physics/concept anchor; the map is the comprehensive coverage matrix.
Why it matters / where the value is
TIMs are a direct gating factor on chiplet / 2.5D / 3D packaging yield and reliability, and the binding thermal layer on >1kW AI accelerator packages — so the TIM market grows with accelerator shipments as a per-package consumable tax (the Ai Compute Toll Booths logic). The material classes do not converge: the stack stays segmented (see Thermal Stack Arms Race), which is itself the value-capture argument — a held material primitive defends one layer with a chemistry/process moat.
Companies using
Connected ideas
Sources
Frontier (open questions)
- To be added.