High-Power Copper Substrate Metal Core PCB
When designing high-power LED applications, customers regularly face the issue of transferring heat from the LED into a heat sink. To achieve this, customers can use metal core PCBs (MCPCB) with copper or aluminum as a base material instead of standard FR4 materials used in PCB manufacturing.
The problem with using copper or aluminum as a base material is its electrical conductivity, which makes it necessary to have an insulation layer between the signal layer and the base material. This insulation layer is called the dielectric layer.
Customers can choose from a wide range of insulated metal substrate (IMS) base materials with thermal conductivity ranging from 2.2 W/m-k to 7.0 W/m-k and dielectric thicknesses ranging from 60 µm to 150 µm. While this is often sufficient, some high-power applications may require better heat transfer from the LED, into the PCB and ultimately into a heat sink attached to the bottom-side of the PCB.
Thermoelectric separation copper substrates can help significantly by directly contacting the signal layer to the baser material, achieving zero thermal resistance and thus maximum heat dissipation into the copper substrate.
Layer Stack up Differences
The following images help illustrate the differences between a typical MCPCB with copper substrate and Thermoelectric Separation Copper MCPCBs. Pay attention to the signal layer and how a component assembled on the exposed surface finish can dissipate heat into the copper substrate.
Typical Metal Core PCB with Copper Substrate and Dielectric Layer
Thermoelectric Separation Metal Core PCB with Copper Substrate
Comparing Copper with Dielectric Layers
The thermal conductivity of copper is approximately 390 W/m-k. Comparing this to high performance dielectric materials such as 7.0 W/m-k immediately shows how much more performant a thermoelectric separation copper substrate can be, even with the thinnest dielectric materials available on the market.
Why isn't this the standard, then?
If thermoelectric separation copper substrates are so much more performant than standard copper substrate based MCPCB, why isn't this the standard then? Manufacturing of thermoelectric separation copper substrate has significantly higher requirements on the production process and technology. Like the production of flexible boards, rigid-flex PCB and multi-layer boards, many additional steps are needed while the production of "ordinary" aluminum substrates and copper substrates is much simpler and comparable to the production of single sided FR4 material.
However, this additional work can pay off and be cheaper than expensive high-performance materials that do not come close to the heat dissipation.
Additional steps during PCB manufacturing:
- Copper substrate foil is cut into the proper size for production.
- The copper foil is roughened up by brushing, micro-etching and other methods before the substrate is laminated.
- Dry film photo resist is applied with strict controls of temperature and pressure, polymerizing it by irradiating it with ultraviolet light.
- The protective film is stripped by using sodium carbonate aqueous solution before using hydrochloric acid and hydrogen peroxide to corrode and remove exposed copper.
- Finally, the dry film photo resist is removed with aqueous sodium hydroxide solution before the PCB can be finished with the solder mask layer and final surface treatment (such as gold).
Do you want to know more?
While we focus on PCB assembly at Newmatik and do not produce our own PCBs in-house, we have several PCB suppliers in Germany, Europe and China that have various PCB base materials to fit your specific application. Just contact us to discuss your requirements.