MCPCB (Metal Core PCB) — composition, benefits and manufacturing
What is a MCPCB (Metal Core PCB)?
A metal core PCB (MCPCB) also known as IMS PCB (insulated metal substrate PCB) or Thermal PCB is a type of printed circuit board that incorporates a thick metal layer as the base substrate or core material. The most common Metal Core PCB materials are aluminum, copper or alloy materials.
The metal core of MCPCB acts as a thermal conductor and heat spreader. It provides superior heat dissipation capabilities compared to standard PCB substrates like FR4 glass epoxy. This enables effective cooling of high–power electronics and devices that generate substantial heat like LEDs, power modules, laser diodes, and RF amplifiers.
The metal substrate is first coated with a thin dielectric layer, typically a polymer film, which electrically insulates the metal plate. On top of this a thin layer of copper is laminated, before being photolithographically processed to produce the circuit traces, pads, vias, and other conductive features required for the metal core printed circuit.
The dielectric layer electrically isolates the bottom metal plate from the top conductive copper traces, while at the same time facilitating efficient thermal conduction between the two layers of the MCPCB. This allows the metal core to act as an internal heat sink, rapidly conducting heat laterally across the PCB and away from hot spots.
Key properties and benefits of metal core PCBs
Metal core PCB offer several significant advantages over conventional FR4 PCB substrates:
Thermal management
The high thermal conductivity of the metal substrate allows for rapid lateral conduction and dissipation of heat across the MCPCB. This prevents localized hot spots under critical board components. Aluminum, for example, which is used as metal core for Aluminium PCB has a thermal conductivity around 200 W/mK, compared to just 0.25 W/mK for standard FR4. Copper which is used as metal core for Copper PCB is even better at around 400 W/mK. This enables superior cooling capacity, making it ideal for LEDs, power devices, laser diodes, RF modules and other heat generating electronics.
Reliability of MCPCB
The coefficient of thermal expansion (CTE) of the metal core of MCPCB is much lower than FR4. This reduces mechanical stresses from thermal cycling. This makes MCPCB less prone to warping and fracturing over time under repeated heating/cooling. It also reduces solder joint fatigue and failures.
Current capacity
The high electrical conductivity of the thick metal core produces very low impedance. Excellent power distribution minimizes voltage drops across the MCPCB at high currents. This allows higher continuous current flow without overheating, which makes MCPCB ideal for power electronics.
Other properties of MCPCB
- Good physical strength and ruggedness.
- Metal cores can shield and contain electromagnetic interference (EMI).
- Wide range of dielectric materials available, including ceramic, flexible and high temperature variants.
In summary, the metal core gives MCPCB superior thermal management, reliability and current capacity compared to standard PCB materials. This makes them ideal for cooling LED lighting, power devices, RF amplifiers and other demanding electronic applications. The tradeoff is higher cost.
Typical metal core PCB materials and construction
While specific designs vary, MCPCB generally consist of:
Metal Core — Forms the substrate with thicknesses ranging from 0.8mm to 6mm. Copper and aluminum are the most common materials used. Copper provides excellent conductivity while aluminum is lightweight and cost-effective.
Dielectric Layer — Thin insulation layer applied to the metal core, typically 50 to 150μm thick. The thickness and type of dielectric layer used are two of the most important aspects when it comes to MCPCBs because these factors have a direct influence on the heat dissipation level, which is measured in W/mK. The dielectric layer is mainly built by epoxy-/polyimide-reinforced with woven glass and conductive filler. It acts as bonding glue between the copper layer and metal base and also has an isolation function.
Copper Foil — An 18 to 70μm thick layer of copper laminated to the dielectric layer and etched to form the circuit traces based on the PCB design.
Protective Coating — Immersion gold, ENIG, OSP or another surface finish protects the copper traces of MCPCB from oxidation and enhances soldering.
Solder Mask — An epoxy layer that coats the PCB surface providing electrical insulation and mechanical protection.
SMD Components — Surface mount devices like resistors, capacitors, LEDs and ICs are mounted by being soldered to the circuit traces.
Steps in manufacturing metal core PCBs
Manufacturing custom MCPCB involves precision processes including:
Materials Bonding — The dielectric (polymer) layer and copper foil are bonded to the metal substrate through processes like spraying, electrophoretic deposition, anodization, and lamination.
Photolithography — A photoimageable solder mask is applied to the copper layer of a MCPCB. Ultraviolet light exposes the desired circuit patterns.
Etching — Chemical etching removes unwanted copper, leaving only the intended circuit traces protected by the mask.
Drilling — High accuracy CNC mechanical drilling forms all the holes for the component pins and vias.
Plating — MCPCB surfaces are plated with nickel, gold, tin or other metals to facilitate soldering and prevent oxidation.
Testing and QC — 100% electrical testing and visual inspection ensures quality and reliability.
Get your custom MCPCB from copperdot
When you need precision engineered MCPCB, choose copperdot as your procurement partner. As MCPCB specialists, we offer affordable and durable printed circuit boards with 1 to 2 layer circuits built on metal cores made of copper or aluminum.
Our automated sourcing and rigorous quality control ensures your finished boards are delivered on time and to your exact specifications. Contact us today for a fast quote for your MCPCB or to discuss your next project!
FAQ
Metal core PCBs are characterised above all by significantly better heat dissipation. The metal core acts as a large cooling surface. In addition, MCPCB are less susceptible to thermal expansion and mechanical stress. They are therefore suitable for heat-intensive applications.
MCPCB are used wherever reliable heat dissipation is crucial. Typical examples include LED lighting, power electronics, telecommunications, automotive applications and medical technology.
Since metals have a higher thermal expansion than FR4, larger components and assemblies must be placed with more clearance to the edge. Hole spacing also differs. In general, the PCB manufacturer's design guidelines should be followed.
Yes, there are also flexible MCPCBs, so-called “IMS-Flex” PCBs. However, the bending radius is limited by the thickness of the metal core. Ultra-thin flex MCPCBs are therefore not feasible.
