A set-top box is a tough thermal case: no fan, a plastic housing, vents easily blocked in a TV cabinet, all-day runtime, a tight BOM and lifetime silence. Those constraints shape the material choice long before any conductivity number does.
So the real question isn't the highest W/(m·K) — it's which grade each position needs, and where a higher one stops paying for itself. This guide maps FEHONDA's grades position by position, explains what changes between them, and why teams specify us.
FEHONDA | Thermal Solution by Grade
Thermal Materials for TV Set-Top Boxes
A fanless plastic box that runs for years: match the conductivity grade to the load, not to the highest number on the list
ABS and polycarbonate conduct only about 0.17 to 0.20 W/(m·K), roughly a thousandth of aluminium, and a sealed plastic box carrying a several-watt load can show 9 to 12 K/W of effective resistance. Heat leaves through chip, interface, spreader, inside air, plastic wall, room air — and the last three dominate. Raising every pad from 3.0 to 6.0 W/(m·K) may therefore move the hotspot by only a degree or two. Enlarging the contact area or adding a metal spreader plate usually buys more.
Figure 1. The plastic wall and the surface-to-air step dominate the resistance chain.
| Grade | Where it belongs in a set-top box | Move up a grade only when |
| 1.5 W/(m·K) | Memory, tuner, interface ICs, Wi-Fi module, board-to-housing gaps | That part measures close to its temperature limit |
| 2.0 W/(m·K) | General-purpose default: power stage, wide-area gap filling | The same gap must carry more heat, or contact area has shrunk |
| 3.0 W/(m·K) | Mainstream 4K SoC to a small heatsink or shield can | The SoC is the limiting hotspot and spreading is already adequate |
| 4.5 W/(m·K) | High-clock SoCs, 8K or AI upscaling, multi-tuner designs | Thermal imaging confirms the interface itself is the bottleneck |
| 6.0 W/(m·K) | The single hottest die in a premium, densely packed box | Rarely — and only after ruling out the plastic wall |
Use thermally conductive gel instead of a pad wherever component heights vary under one shield. FEHONDA carbon fibre pads at 25.0 and 35.0 W/(m·K) through-plane suit concentrated hotspots with no spreading path, but we would not normally recommend them here — a plastic enclosure rarely lets that much heat out.
Figure 2. Four product tiers, four different material budgets.
| Product tier | Sustained load | Recommended grades |
| Entry HD / basic IPTV | 1–3 W | SoC 1.5; memory, tuner and Wi-Fi 1.5 or none; board-to-case 1.5–2.0 |
| Mainstream 4K / Android TV | 2–5 W, higher peaks | SoC 3.0; power stage 2.0; memory, Wi-Fi and board-to-case 1.5–2.0 |
| Premium 4K / 8K, AI upscaling, multi-tuner | Above 5 W | SoC 4.5–6.0; power stage 3.0; elsewhere 2.0; gel for uneven stacks |
| Operator / 24·7 IPTV and hospitality | Continuous | Same grades, but specify long-life behaviour at every position |
The last row deliberately does not say use the highest grade. A 24·7 box usually fails from an interface that dried or pumped out, or from a capacitor whose life was halved by a 10 °C rise — not from insufficient conductivity on day one.
Figure 3. Heat sources and material positions inside a typical fanless box.
| Position | Material and grade |
| SoC to heatsink or shield can | Pad 3.0–6.0 by tier, or gel if the gap varies |
| DDR / eMMC memory, tuner | Pad 1.5; keep memory out of the SoC's thermal shadow |
| PMIC and DC-DC stage | Pad or gel 2.0–3.0; route this heat away from the SoC |
| Wi-Fi / Bluetooth module | Pad 1.5; keep conductive fillers out of the antenna keep-out zone |
| Board to housing wall | Soft pad or gel 1.5–2.0 — often the most valuable thermal change in the box |
Two free checks before any material change: put vents low and high so buoyancy works, and validate in a closed cabinet at the highest expected ambient rather than on an open bench.
Send the board layout, the gap and assembly pressure at each position, the housing material and the sustained workload. We will return a grade map, samples and a lead time — including where a lower grade is the right answer. Please submit your request via our custom service form to ensure a faster response.
FEHONDA's new materials are used in a variety of applications around the world, providing effective solutions for thermal conductivity, shielding and more for products. Our sales and engineering support teams are ready to help you with any questions you may have, including quotations, product application support and product customization. Please submit your request via our custom service form to ensure a faster response.
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