KEY BENEFITS OF CARBON FIBERS IN A PRINTED CIRCUIT BOARD (PCB) AND INTEGRATED CIRCUIT(IC) SUBSTRATE

摘要

Printed Circuit Board (PCB) is one of the key building blocks of any electronics today. A migration towards compactness of an electronics have pushed envelop of the existing material options. Today’s PCB needs material that can handle high heat flux, allow reducing CTE, maintaining rigidity at an elevated temperature without adding weight. PAN and PITCH Carbon Fiber has several properties such as Negative to low Co-efficient of Thermal Expansion (CTE), good Thermal Conductivity, High Tensile Modulus and low Density. Unique techniques can be used to utilize these fiber properties in an Electronics Applications. Thin Carbon Composite Laminate is used in the integral structure of Printed Circuit Boards (PCB) today to spread the heat from the Chips, tailor the CTE of a printed circuit board to match with the IC Components, increase tensile modulus, and reduces the weight of the PCB [compared to boards using other thermal solutions like Heavy Copper, CIC (Copper Invar Copper), CMC (Copper-Moly-Copper)]. Thermally Conductive carbon will reduce the junction temperature of the components, while the negative CTE of the carbon allows the engineer to tailor the surface expansion of the PCB to more closely match with the ceramic components (6-8ppm/oC) or silicon die (2.5ppm/oC). Higher tensile modulus of the carbon increases rigidity of the PCB and Substrate, allows reducing or eliminating need for mechanical reinforcements such as Aluminum. The composite layer can be used as a ground or power layer into PCB structure. Carbon composite also acts as an internal heat spreader thus, concentrated heat from the high power Ics can be spread out to entire plane area. A series of tests have been performed on carbon composite PCB and have shown 8-12oC temperature reduction compared to Glass Epoxy material. A series of CTE tests have been performed at finished PCB level and shown values ranging from 2-12ppm/oC versus standards material CTE of 17-20ppm/oC. Carbon composite PCB has shown 75% to 450% improvement in rigidity compare to Typical glass PCB.