IMS Aluminium PCB
Built for heat, not just current: a thin thermally-conductive dielectric sits between the copper circuit and a solid aluminium base, pulling heat away from hot components instead of trapping it in fiberglass. Here's exactly how an IMS board is built, what it's made of, how to lay it out well, and which standards apply.
Copper, thermal dielectric, aluminium
IMS stands for Insulated Metal Substrate — also called metal-core PCB (MCPCB). It's a three-layer laminate: a copper circuit layer on top, a thin thermally-conductive but electrically-insulating dielectric in the middle, and a solid aluminium base plate underneath. Standard FR4 has a thermal conductivity of roughly 0.3 W/m·K — effectively an insulator — so on a design where components genuinely generate heat, FR4 traps it right where it's made. IMS replaces that dead-end dielectric with one engineered specifically to conduct heat through it, into the aluminium base, and out to an external heatsink or chassis.
It isn't a "better" board in general — it's the right tool specifically when thermal management, not layer count or routing density, is the design's real constraint.
- LED lighting & luminaires — the dominant application
- Switch-mode power supplies
- Motor controllers & drives
- Automotive power electronics, headlamps, engine-bay modules
- Any board with real power components FR4 can't cool
The manufacturing process, step by step
IMS diverges from FR4 fabrication from the very first step — you're bonding copper foil to a thermal dielectric to a solid metal plate, not pressing fiberglass prepreg.
Stack selection
Aluminium alloy and thickness, dielectric grade and copper weight are chosen together based on the application's thermal and current requirements.
Lamination
The thermally-conductive dielectric is applied and copper foil is bonded to it under heat and pressure, then that copper-clad dielectric is bonded to the aluminium base as one laminated stack.
Imaging & etching
Photoresist is imaged with the circuit pattern and developed, then the panel is etched — with tightly controlled chemistry and timing, since the dielectric path beneath the copper is thin and the aluminium sits right below it.
Solder mask & silk screen
Applied and cured as on any board, with extra attention to adhesion given the more thermally massive, often shinier surface underneath.
Drilling
IMS boards use minimal drilling — usually just a few non-plated mechanical/mounting holes. A true plated through-hole would short straight to the conductive aluminium core, so most IMS designs are single-layer and avoid PTH entirely.
Routing / singulation
IMS panels are separated almost exclusively by mechanical routing rather than V-scoring — aluminium is ductile, so it bends instead of snapping cleanly along a scored line the way FR4's brittle glass-fibre weave does, and a router that mills away material along the profile gives a far cleaner, more controlled edge.
Electrical test
Standard continuity/isolation testing, plus — specific to IMS — a hi-pot (dielectric withstand) test confirming the dielectric layer holds its rated voltage without arcing through to the metal base.
Final QC
Optical inspection and a final visual/dimensional check against the fabrication drawing before packing.
Aluminium base, thermal dielectric, copper
The base is typically 5052-H32 aluminium (better corrosion resistance, good for humid environments) or 6061-T6 (higher strength, more machinable), commonly 1.0–2.0 mm thick. The dielectric is the layer that actually makes IMS work: kept thin — often 75–150 µm — because thermal resistance scales with thickness, but thick enough to hold its rated breakdown voltage, since it's the only electrical isolation between the live copper circuit and a metal base that's frequently grounded or chassis-mounted.
| Property | Typical range |
|---|---|
| Dielectric thermal conductivity | ~1.0 – 8.0 W/m·K (vs. ~0.3 W/m·K for FR4) |
| Dielectric breakdown voltage | ~4,000 – 11,000 V, depending on thickness |
| Aluminium thickness | 1.0 / 1.5 / 2.0 / 3.2 mm common |
| Copper weight | 1–2 oz typical, heavier for high-current power designs |
Note the distinction that matters here: that 1.0–8.0 W/m·K figure is the dielectric layer alone — some marketing material quotes higher "system-level" numbers that already include the copper and aluminium in the thermal path, which isn't the same measurement. Judge dielectric grades on the dielectric's own datasheet number.
Layout & DFM guidelines for IMS boards
On IMS, the dielectric is the thermal bottleneck — layout decisions are largely about getting heat through it efficiently.
IPC standards & testing
IPC-6012 is the standard that actually applies here — its scope explicitly covers metal-core printed boards, with or without an external heat frame, alongside standard rigid boards. It governs material, hole and electrical-test requirements the same way it does for FR4, just applied to a metal-core construction.
| Standard / method | What it covers |
|---|---|
| IPC-6012 | Qualification & performance — explicitly includes metal-core boards |
| IPC-4101 | Base material classification (laminate/dielectric properties) |
| IPC-2221 | Conductor spacing & current-carrying-capacity sizing |
| ASTM D5470 | Thermal transmission test method — how dielectric W/m·K figures are actually measured |
Our real specs for IMS Aluminium boards
Everything above is general industry practice. This is what we actually build, in-house, in Iași.
| Board thickness | 0.51 – 2.4 mm |
| Copper weight | 18 / 35 / 50 / 70 µm |
| Minimum track / isolation | 0.15 mm / 0.15 mm |
| Minimum drill | 0.3 mm (0.5 mm pad) |
| Maximum panel (1–2 layer) | 390 × 520 mm |
| Solder mask | White standard for LED work; green, black, red, blue, yellow available |
| Silkscreen | Black standard on IMS Aluminium |
| Surface finish | HASL-LF (Pb-free, RoHS compliant) |
| Testing | 100% electrical test (short circuit and open circuit, flying probe) and AOI inspection on every board |
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