PCB Material Selection: Electrical and Manufacturing Considerations

When it comes to PCB material selection, making the right choice for your design is important because materials can impact the overall performance. Knowing how the thermal and electrical properties impact your design before you get to the manufacturing stage can save you time and money while achieving the best results. 

 

In this webinar, we will be focusing on the following points:

PCB material selection: Stack-up considerations

PCB stack-up

A stack-up is the construction of a multilayer PCB in sequential order. A stack-up consists of cores, prepregs, and copper foils. Generally, stack-ups are symmetrical. The majority of the products fall under 62-mil board thickness.
What materials are used in circuit boards?

PCB materials: Foil, core and prepreg

A printed circuit board is manufactured using the following 3 items:

Prepreg: B Stage Material that is tacky and allows bonding of different laminates or foils

Copper foil: Serves as a conductor in PCBs.

Copper Clad Laminates (Core): Made of prepregs and copper foils that have been laminated and cured.

Basic properties of the dielectric materials
We know that PCB laminates are made of dielectric materials. While choosing laminates, we need to consider various properties of the dielectric material used. They are:

Thermal properties
Electrical properties

Glass transition temperature (Tg)
Dielectric constant (Dk)

Decomposition temperature (Td)
Loss tangent or dissipation factor (Tan δ or Df)

Thermal conductivity (k)

Coefficient of Thermal Expansion (CTE)

Thermal properties:
Glass transition temperature ( T g ): Glass transition temperature, or T g , is the temperature range in which a substrate transitions from a glassy, rigid state to a softened, deformable state as polymer chains become more mobile. When the material cools back down, its properties return to their original states. T g  is expressed in units of degrees Celsius (°C).
Decomposition Temperature (T d ): Decomposition temperature, or T d , is the temperature at which a PCB material chemically decomposes (the material loses at least 5% of mass). Like T g , T d is expressed in units of degrees Celsius (°C).
Thermal conductivity (K): Thermal conductivity, or k, is the property of a material to conduct heat; low thermal conductivity means low heat transfer while high conductivity means high heat transfer. The measure of the rate of heat transfer is expressed in watts per meter per degree Celsius (W/M °C).
Coefficient of Thermal Expansion (CTE): The coefficient of thermal expansion, or CTE, is the rate of expansion of a PCB material as it heats up. CTE is expressed in parts per million (ppm) expanded for every degree Celsius that it is heated. As...