PCB Substrate During the early stages of the printed circuit boards, the circuit boards were made from Bakelite. It was the cheap dielectric material available at that time with good electrical and physical properties. After the evolution of radios, the circuit was shifted to the classic glass fiber PCB substrate. With the advancement in technology, it was cheaper. And more suited than most of the other materials due to its unique properties.
1.Requirements of PCB Substrate
A mass-produced commercial PCB must comply with various standards. The PCB substrate material must have a few of the basic requirements for making a quality PCB. The selection should include the analysis of chemical, electrical, thermal, and mechanical properties.
The PCB substrate must be chemically stable to use in the circuit board. The material should be fireproof. Underwriters Laboratories and various other institutes determine the fire safety levels of the material. In simple terms, the substrate must resist high temperatures and should stop burning immediately if it does catch on fire. PCB substrate must also be resistive to moisture and chemical reactions.
The must-have high electrical resistance to prevent current leakage. The dielectric material must not change its conductance with exposure to various environments.
The substrate is analyzed for surface and volume resistance to ensure the board’s conductive nature stays below the requirements. The material must be stable in case of a power surge and high voltage sparks.
4.PCB Substrate—Thermal properties
The critical property of the substrate is its thermal conductivity.
The material must conduct thermal energy produced by the components on board.
The material must also be resistive to thermal shocks and overheating of the components.
The thermal coefficient must remain constant with the exposure to various environments.
The must-have sufficient mechanical strength and vibration resistance to avoid damage to the circuitry. The material must also be reasonably flexible to compensate for the stress and thermal expansions.
6.PCB Substrate—Glass epoxy
Glass epoxy laminate is the most used PCBs substrate. It is made by compression of multiple glass fiber sheets together with a temperature-activated epoxy-based adhesive in-between them.
Present so of glass makes the substrate harder and offers the maximum resistivity. The glass epoxy is available in various thicknesses for a varity of applications.
Power electronics and high-power dissipation applications use aluminum as a substrate to heavy house components and have excellent thermal conductivity. High power LED circuits mostly use aluminum to have good thermal conductivity as they are susceptible to temperature changes. Having bare aluminum also avoids the need for heatsink in various applications.