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Metal core / IMS

At Multi-CB you can get aluminium core PCBs with a thermal conductivity of 1.0 W/mK to 8 W/mK. The aluminium core helps to distribute the selective heat of heat-intensive components and to make the heat development on the printed circuit board more homogenous. The rule of thumb for many high-power LEDs is: A 10° C lower junction temperature increases the lifetime by 10.000h.

For one-sided metal core PCBs, a heat sink and/or fan (active cooling) can be mounted directly on the aluminum (passive cooling).

Design parameters

NPTH-drills - Metal core

PCB thicknessMin. drill diameter
0.5mm Metal core0.7mm (o.r. 0.5mm)
0.8mm Metal core0.7mm
1.0mm Metal core0.8mm
1.5mm Metal core0.9mm
2.0mm Metal core1.0mm

1 layer Metal core

35µm Cu70µm Cu
Min. conductor width150µm200µm
Min conductor spacing150µm200µm
Min. annular ring125µm200µm
Min. drill (NPTH)0.7mm0.7mm
Min. drill spacing250µm250µm

2 layers Metal core (plated-through)

35µm Cu70µm Cu
Min. conductor width150µm200µm
Min conductor spacing150µm200µm
Min. annular ring125µm200µm
Min. drill(NPTH)0.7mm0.7mm
Min. via (PTH)0.3mm0.3mm
Min. drill spacing250µm250µm
Min. via spacing300µm300µm
Aspect ratio10:110:1

Z-axis milling

To bond components directly to the aluminium with thermal compound, Z-axis milling (depth milling) can be used. The isolation / prepreg is removed in this area.

 

Thermal conductivity

The given thermal conductivity W/mK always refers to the insulation layer (prepreg) between copper and aluminium.

Typical Thermal conductivity figures

MaterialThermal conductivity
Copper380 W/mK
Aluminium140 – 220 W/mK
Prepreg1 – 8 W/mK

Isolation / Prepreg

The thinner the insulation layer is chosen, the lower the thermal resistance (= better overall thermal resistance). However, it also reduces the breakdown voltage.

Exemplary breakdown voltage – Material Ventec VT-4A1

Prepreg thicknessDielectric breakdown (AC)
75µm6.0kV
100µm7.5kV
125µm9.0kV
150µm10kV

Heat development - example

The following is a comparison of the heat development on different PCB types. Conducted by OSRAM using an OSLON © SSL high-power LED (1W, 3.2V, 350mA), ambient temperature: 25° C.

FR4 1LayerFR4 max. padsFR4 Thermal ViasMetal core 1Layer
Heat development FR4 PCBHeat development FR4 PCB with max. PadsHeat development FR4 PCB with Thermal ViasHeat development Metal core IMS PCB
ConstructionFR4 0.8mm, 35µm CuFR 0.8mm, 35µm Cu, max. pad sizeFR4 0.8mm, 70µm Cu, w. Thermal ViasAluminium core 1.5mm, 2.2 W/mK, Isolation 75µm
Heat conduction Cu
Heat development FR4 PCB  scale
Heat development FR4 PCB thermicHeat development FR4 PCB with max. pads thermicHeat development FR4 PCB with Thermal Vias thermicHeat development Metal core IMS PCB thermic
Thermic resistance Rth45 K/W28 K/W8 K/W3 K/W
Junction temperature rise53°C35°C15°C10°

Optional

You can get UL Certified Metal core Printed Circuit Boards from Multi-CB.

In addition, we also offer flexible Metal core PCBs. The prepreg is in this case filled with ceramics (instead of glass). Material e.g. Ventec VT-4B1.