Aluminum PCBs exist to move heat. Calling them "FR-4 with a metal back" misses the point: the stack is a thermal path, and every layer in that path has resistance that shows up as hotter LED junctions, derated MOSFETs, and shorter field life.
Metal-core boards (MCPCBs) are common in LED lighting, drivers, electronic ballasts, automotive lamps, and compact power stages. Overseas buyers usually hit them when FR-4 pours and external heatsinks can no longer keep temperatures inside the lifetime budget.
The thermal sandwich
A typical single-sided aluminum PCB has three functional layers:
- Copper circuit layer for pads, routing, and lateral heat spreading
- Thin dielectric that is electrically insulating but thermally conductive
- Aluminum base that spreads heat and provides mechanical stiffness
Heat generally flows chip to solder to copper to dielectric to aluminum to TIM to housing or heatsink. The dielectric is usually the bottleneck. Conductivity in the rough range of 1 to 3 W/mK and thickness often around 75 to 150 um set the tradeoff: thinner, higher-conductivity dielectrics move heat better but reduce breakdown voltage margin. Design from voltage and temperature together, not from a marketing conductivity number alone.
Aluminum itself is a strong spreader compared with FR-4 laminates, which is why LED arrays and switching power parts live happier on MCPCB when the rest of the path is designed honestly.
Structures you will actually buy
Single-sided MCPCB remains the workhorse for LED plates and simple power circuits. Double-sided aluminum constructions exist but cost more and complicate vias. Hybrid builds combine FR-4 control sections with an aluminum LED or power plate when routing density and thermal load refuse to share one stack.
Copper-base or steel-base metal cores appear in niche cases. Aluminum usually wins the commercial balance of weight, cost, and thermal performance for lighting and ballast-class products.
Design practices that survive production
Use wider copper and heavier weights (often 2 oz or more) on high-current paths. Place hot devices near mounting points that couple into the heatsink. Maintain creepage between mains and SELV regions. On hybrids, thermal vias under power ICs only help if the via strategy and dielectric stack are intentional. Specify TIM between aluminum and enclosure; dry or poorly chosen interface materials erase expensive dielectric upgrades.
Reflow behavior differs from FR-4. Aluminum's thermal mass wants more careful preheat and a profile that respects LED and connector limits. Thicker stencils on large pads, board preheat for rework, and controlled screw torque into heatsinks all belong in assembly notes. Over-tightening can stress the dielectric; under-supporting tall parts invites solder fatigue under thermal cycling.
Failure modes buyers should name in the RFQ
Thermal fatigue cracks solder when copper and mechanical constraints fight expansion. Sharp copper geometry can stress thin dielectrics. Moisture at unsealed edges invites corrosion. Interface aging raises thermal resistance after months in the field.
For quoting, "aluminum PCB" without dielectric conductivity/thickness, copper weight, base thickness, and isolation voltage is not a comparable RFQ. Prototype with more than one dielectric option when the thermal margin is tight, and verify with measurement rather than brochure watts.
XFPCB builds aluminum PCBs and related metal core PCB constructions for LED and power products. When assembly is included, LED PCB assembly notes should carry the same thermal stack assumptions used in fab so profiling and mounting instructions match the board you actually ordered.