In recent years, there has been great popularity in the use of LED products. This is why mcpcbs – metal core printed circuit boards have also gained popularity. The lighting and automobile sectors have already accepted the technology, same way consumers have. This is because an LED light can prove to be five times less expensive compared to the incandescent unit. Also, compact fluorescents seem to have a little higher cost for operating and when we talk about using space efficiently, they don’t have what it takes to compete with very small LEDs.
Due to these, as well as other factors, many other devices have started incorporating LEDs as one very important design feature. However, there is a very important aspect of operation of LEDs, which has to be accounted for when handling product designs; that is heat.
What is a Metal Core PCB (MCPCB)?
MCPCB, which is also referred to as a metal backed PCB or thermal PCB is a PCB having its base material as metal for the board’s portion that spreads heat. This thick metal, which is always copper or aluminum in most cases, is covering one of the PCBs’ sides. This metal core has to do with the position of the metal, whether it is in the center or middle or on the mcpcb board’s back.
The main task of the MCPCB’s core is to help in redirecting heat from board components that are critical in nature as well as areas that are less crucial like the metallic core. MCPCB’s base metals usually serve as an option to CEM3 or FR4 boards.
Thickness and Materials of Metal Core PCB (MCPCB)
The thermal PCB’s metal core could be aluminum, copper, or a combination of different special alloys. For the aluminum type, it is called aluminum core PCB, which is the most commonly used. While for the copper type, it is called either heavy copper PCB or copper core PCB.
Some other materials, such as steel or brass, are requested sometimes, however, they are usually not recommended. The materials of the metal PCB are usually very hard. This is why cutting these PCBs to get smaller pieces could pose some problems. There are other things to consider when choosing materials for a metal PCB. These include the chemicals used during manufacturing and if there will be a reaction of the metal to them.
The metal cores’ thickness, which is found in the plates of the PCB base usually falls between 30 mil to 125 mil. However, it is possible to have thinner and thicker plates. The thickness of the copper foil of MCPCB can fall between 1 to 10 oz.
Benefits of MCPCB
In so many scenarios, LEDs are similar to all other components that can be mounted on or attached to a circuit board. The fact is that if just a few LEDs are available like red and green indicators, then whenever you are laying out the PCB, the reason to do something unusual will be little. However, lighting solutions which integrate either arrays or rows of MCPCB LEDs are available. This stays on for a long time period.
Ensuring that these devices are kept cool to prevent them from failing prematurely, as well as creating a safety hazard could become a major problem. Cooling it efficiently is also necessary to ensure that there is a consistent light output. Converting your PCB to a MCPCB from the standard type (FR4)is also a good alternative to consider.
Some benefits of metal core PCBs is its use of unique substrate materials that are formulated specifically to help in improving the designs’ reliability, which run at temperatures that are above normal
Rather than serve as just a surface for mounting for these components, these substrates help in drawing heat actively from areas where the components are hot-running via the mcpcb board’s opposite layer, where dissipation can be done safely and efficiently.
MCPCB has proved to be a great solution to problems concerning the cooling of PCBs using a large number of LEDs.
Applications of Metal Core PCBs
Applications generating much heat frequently cannot be cooled adequately making use of traditional fans only. Cooling done conductively via MCPCBs are a great option for production.
Most times, MCPCBs are seen in LED technologies. This is because they require less LEDs to give a desired illumination. Diodes that emit light release heat in great amounts in applications like:
- Back light units
- Street safety such as lighting, streetlights, etc.
- System automotive
- Electric/hybrid motor control
- General lighting
- Photovoltaic
- Power converters such as power supplies, regulator of high voltage, industrial, telecom
Some other applications, which are great for integrating MCPCBs include motion control and solar panel applications.
Differences Between MCPCBs and Standard Epoxy Glass Boards
One great difference to comprehend between MCPCB and standard PCB is the working of the materials together to help achieve the result desired. In a MCPCB LED, we have one circuitry copper foil layer that is bonded and linked to a dielectric material that is thermally conductive.
The measurement of the thermal conductivity of a dielectric material is in W/mK – watts per meter, Kelvin. A rating of 2.0W is usually common; this type of material is usually approximately six to seven times thermally conductive like FR4.
The best practice here is keeping this dielectric layer very thin. By doing so, this builds the shortest path possible from the source of heat to the backing plate of the metal which is far more thermally conductive compared to dielectric materials. Majority of materials usually come in different thicknesses. This usually falls between 0.003 inches and 0.006 inches. You will not have too many opportunities or chances to specify a thicker material, which could reduce the material’s effectiveness to perform its function of thermal transfer.
The backing plate, which is utilized on the bottom, is seen as the structure’s thickest element. This can be found in different thicknesses. However, it is advisable that you use any of the three common types (3.2mm, 1.5mm, and 1.0mm). This is because these types are very easy to buy; there’s no delay. Also, its metal layer ensures the circuit is kept flat, adds rigidity, and makes sure that enough thickness is added. This is to ensure that the MCPCB will be able to utilize the mounting hardware used for other circuit board with standard thickness. The board’s metal plate area does not accept soldermask or surface finishes.
Metal Core PCB Surface Mounted Components
One important factor to integrate into any design of MCPCB is using just surface-mounted components rather than use plated through holes. Majority of LED PCBs that are built on FR4 substrates with more than two layers must utilize a plated pattern that is closely-spaced through vias. During assembly, solder can find its way or migrate through the vias, if they are not properly filled. This will lead to an imperfect solder joint.
Using MCPCB, the function of vias is achieved by the materials. The whole section of the bottom is made up of metal having an efficient and higher thermal conductivity. This enhances the cooling and there’s no need for vias to get thermal relief. Majority of MCPCBs only need minimal drilling, a few mounting holes that are large.
Removing via drilling coupled with the ability of stacking more than one panel for drilling large holes simultaneously, makes it possible for the fabricator to quickly move your boards via a bottleneck operation. After a drill cycle, your MCPCB (1-layer) avoids the deposition of graphite or electroless copper deposition hole wall step, which would be necessary for the PTH processing. It then progresses to circuit imaging. Then, from this point, your MCPCB works with fewer or more process steps, which standard FR4 designs should follow.
Comparing the MCPCB with the FR4 PCB
Conductivity: The thermal conductivity of FR4 is low. It stands at around 0.3W. For MCPCBs, their thermal conductivity is higher. This ranges from 1.0W to 4.0W. Most times, this value stands at about 2.0W.
Plated Through Holes: Usually, FR4 PCBs make use of plated through holes. However, In MCPCB, you cannot have plated through holes for a 1-layer PCB. This is because all its components are usually surface-mounted.
Thermal Relief: For FR4 PCB, the thermal relief involves vias to ensure heat transfer. With a longer drill cycle, many processes are added. MCPCB materials give their own thermal relief. The processes of via drilling, plating, and deposition are eliminated.
Solder Mask: The solder masks of FR4 PCB are usually dark colors (black, blue, red, green). They are usually applied at the bottom and top. For MCPCB, their solder masks are usually white. They are only applied to the top.
Thickness: The FR4 PCB features different thicknesses, which are available with the use of different layer counts and material combinations. The thickness variation of the MCPCB is limited by the thickness of the dielectric sheet and the available thicknesses of the backing plate.
Conclusion
MCPCB, is a PCB having its base material as metal for the board’s area that spreads heat. MCPCBs use unique substrate materials that are formulated specifically to help in improving the designs’ reliability. MCPCB has proved to be a great solution to problems concerning the cooling of PCBs using a large number of LEDs.
