Ceramic Thermal Substrates & Metal Core PCB

Ceramic thermal substrates claim a higher thermal conductivity than other components in metal core circuits.

Many mainstream applications have begun to use ceramics including solar equipment, LED televisions, smart mobile phones and automotive components.

These ceramic substrates are one of either thick or thin film. Thick is mostly used in the automotive and military fields for high heat generating equipment, while the latter is used mostly for powerful LEDs.

The main materials of these 2 kinds of ceramic thermal substrates are AlN, Alumina and Al₂O₃.

Low CTE Boards

CTE is the Coefficient of Thermal Expansion.

Understanding CTE in metal core PCB fabrication is critical. Every material expands or contracts when its temperature changes.

CTE is very important in board design since multiple materials are often used in the final assembly, causing situations of different levels expansion/contraction. This, in turn, can cause stress on the overall board or the solder joints.

LED Prices & Effect on Metal Core PCB Fabrication

Many sources are discussing LED pricing in the next 5-15 years, with all sources pointing to a huge decrease in pricing for a number of reasons.

The most particular and promising other than the natural lowering of pricing from increased competition comes from the components and materials used.

The newer use of larger silicon carbide wafers will bring prices down eventually as well as the promising technology of GaN-on-Silicon wafers.

Pricing for assembled LED applications are predicted to drop by up to 100% from industry sources.

LEDs are up to 40 times more efficient and longer lasting than regular incandescent light bulbs. With the more affordable pricing, they will surely take over more of the new and replace old lighting applications.

This will also increase the effect of demand for metal core pcb designers, fabricators and assembly firms.

Nanotechnology Circuits in Wireless Devices

IBM researches released information that they designed nanotechnology circuits for use in wireless devices.

They are graphene-based making them the most thin electronic material available.

IPC PCB Industry Reports

Off the topic of metal core boards and onto rigid and flex boards:

The IPC releases some information on the PCB industry for April 2011 compared to April 2010:

- Rigid PCB shipments are up just 0.8% (for the YTD, up ~5%)
- Flex PCB shipments are up a whopping 7.2%

This data just goes to show the huge increases in use for high technology boards over standard (soon to be called old technology) boards. Flex boards, rigid flex and metal core boards are becoming more and more commonplace in applications.

Source: IPC

Back to Basics: What is a Printed Circuit Board?

Let's discuss some basics of PCBs and their components.



Printed Circuit Board Uses
We use PCBs everyday, whether you realize it or not. They're used in medical devices, automobiles, flashlights, mobile phones, defense systems, computers and so much more. Literally, everything that is "electronically alive" probably has a PCB in it.

What is a PCB?
It is a board of non-conductive material, either glass or plastic, that has electrically conductive patterns printed onto it, using either copper metal or India ink. In the case of metal core boards, this pattern uses an aluminum core, copper core or a combination of substrates. India ink, in comparison, is low in conductivity.

The electrically conductive portion of the board supplies an electrical current to various components on the circuit board that are attached during the PCB assembly process. The electrical components of the board control the rate of flow and the behavior of the electrical current.

Printing Methods: Etching & Silkscreen Printing
A substrate is a material that does not conduct electricity. A PCB is a substrate that has a electrically conductive pattern printed on it. The pattern dictates the flow of electrons and is etched onto the bare circuit board.

The etching process begins with cutting copper sheet metal to the same size as the substrate. Epoxy is used on the board to bind the conductive portion to the board then an etching machine cuts the desired pattern in the copper sheet, leaving a pattern on the substrate.

Silkscreen Printing can also be used to print on the boards. With this method a silkscreen printer prints onto the board with an electrically conductive ink.

Components & PCB Assembly
PCB Assembly or PCBA is the process of attaching or embedding components onto the printed board. Common components are diodes, resistors, heat syncs (for high heat applications; common with metal core boards) and magnets.

Leads are common and important on assembled PCBs as they act as the connection between the board and another electronic device.

Metal Core PCB Demand on the Rise

The demand for LED products and LED applications has been steadily on the rise, in reports from Taiwan.

Taiwan manufacturers have reported that LED applications, primarily LED panels, are in greater demand and steadily increasing.

This will surely increase the demands and technology for metal core printed circuit boards and interconnects for the boards.

LED Circuit Boards

LED lights are primarily connected through the circuit board for display in many applications.

These boards can be custom done flex PCBs or standard FR4 rigid boards. Flex boards are often used to get the lights in the correct positioning as they can be adjusted during the bending and flexing process to fit virtually any design shape.

Modern LEDs, in general, are assembled to the board using surface mount technology, or SMT. The LEDs as well as all other SMT components are bonded directly to the pads so no holes are required in the circuit board.

Metal Core Boards - Thermal Conductivity

Thermal conductivity is the ability materials or a material that reports its ability to conduct heat. In terms of MCPCB, heat conductivity refers to how the metal core reacts to heat and which levels of heat.

Thermal conductivity is calculated by the amount of heat transmitted over a certain period of time through thickness in a direction along the surface of an area as a result of temperature differences. Controlled conditions are maintained for the calculation and the heat transfer depends only on the temperature gradient/change.

The thermal conductivity of the metal core has been represented as the symbol K. A more common and modern symbol for it is the Greek lambda, used extensively in Fourier's Law.

Metal Core Basics

Metal Core Boards use a base metal material to spread heat across the circuit board.

Metal core is used in high-heat creating environments, including LED, power and motion based applications.

The core used is usually an aluminum core or copper core.
It can also be composed of special alloys.

Plate thickness generally ranges from 30 to 125 mil, while the copper foil thickness can be 1-10 mil.

MCPCBs can transfer and dissipate heat many times faster than regular FR4 boards. This improved thermal management helps to extend the life and quality of use of many products.