A Few Essential Things About Metal Core PCB

 A metal core printed circuit board or MCPCB is a printed circuit board that has a metallic core. This is a type of PCB that has a thicker copper layer than traditional PCBs. This makes it more resistant to corrosion and also allows for greater current flow in the traces of the circuit board. A metal core PCB is used primarily in high-voltage circuits such as power supplies.

MCPCBs are often used in power supplies because they can handle more current than standard PCBs without overheating or burning out components. They are also able to dissipate heat much more efficiently than traditional PCBs, meaning they can be used at higher voltages without damaging them.

Manufacturing Process

The manufacturing process for metal core printed circuit boards involves several key steps:

Etching - The copper foil on the substrate is coated with a photoresist material and then exposed to ultraviolet light through a mask. The photoresist that was exposed to UV light becomes soluble while the unexposed photoresist remains on the copper foil. The board is then washed with a chemical solution to dissolve away the exposed photoresist and etch away the copper that is no longer protected by the photoresist. This leaves behind the desired copper circuit pattern.

Plating - The etched board then goes through an electroplating process to build up a desired thickness of copper on the traces. This plating process also allows other metallic surfaces to be added, like nickel, gold, or tin. Plating helps protect the copper from corrosion and improves solderability.

Lamination - Prepreg bonding sheets are layered between the core substrate and outer copper layers. This full stack is laminated together under heat and pressure, and bonds the layers into a single board. The lamination process also serves to cure the resin in the prepreg layers.

Drilling - Once laminated, the board undergoes drilling to create holes that allow connections between layers. High-speed numerical control drill bits are used to precisely drill these holes to facilitate component assembly later on. The holes are then typically plated to form a conductive path between layers.

Quality Control

Quality control is a critical part of the metal core PCB manufacturing process. Rigorous testing procedures are implemented to catch any defects and ensure the boards function properly.

Testing for Shorts and Opens

One of the main tests conducted is testing for electrical shorts and opens. Shorts occur when an undesired connection exists between two points in a circuit. This results in excessive current flow and can cause circuit failure. Opens describe breaks in the intended conductive paths on the PCB. Both shorts and opens prevent the proper flow of electricity and impair circuit operation.

To check for shorts and opens, manufacturers employ flying probe testing. Probes are programmed to check each trace on the boards for continuity and isolation from other nets. Any shorts or opens detected are flagged and addressed before the board moves to the next step. This verifies all conductive paths function as designed without any unintended connections.

Impedance Testing

Impedance testing is also important for MCPCBs. A controlled impedance is critical for maintaining signal integrity and preventing signal reflection in high-speed designs. Manufacturers use impedance testers to validate the designed impedance values match the actual fabricated boards.

Any sections falling outside the acceptable impedance tolerance are identified. The PCB layout may then be adjusted and reviewed to correct the issue on subsequent board revisions. Tight impedance control ensures reliable functionality for high-frequency and sensitive circuit designs with metal core boards.

Other Tests

Additional testing steps may include AOI (Automated Optical Inspection) to check for physical defects and electrical testing to confirm proper functionality using test points on the board. Comprehensive testing provides full confidence in the quality and reliability of the completed metal core PCBs.

Applications

Metal core printed circuit boards are used in a variety of applications where their thermal management abilities are advantageous. Some of the major uses include:

·         LED Lighting - MCPCBs help dissipate heat in high-power LED lighting fixtures. The metal substrate acts as a heat spreader to take heat away from the LEDs to improve performance and longevity.

·         Automotive - In automotive electronics, metal core PCBs are used in control units, infotainment systems, ADAS, and lighting. The high current densities required make thermal management essential.

·         Aerospace - Avionics, power systems, and controls in the aerospace industry utilize metal core PCBs to handle demanding environmental conditions.

·         Industrial - For industrial equipment with high power demands, like servo motor controls and power conversion, metal core PCBs manage heat properly.

The thermal conductivity of a MCPCB allows them to spread heat over the surface, rather than building up in components. This helps sensitive electronics operate reliably for longer durations before failure. The applications that benefit from metal core PCBs tend to have high power densities, size constraints, and challenging operating environments.