Types and selection of laminates

PCB Designer should choose the type of laminate suitable for the purpose of the finished device.

The most important laminate parameters:

  • thickness of base laminate – the thickness of the laminate on which no production processes were carried out,
  • thickness of finished PCB –  include : thickness of :copper foil, dielectric (FR4/ prepreg etc.), metallization, soldermask, surface finish, and tolerances of these thicknesses,
  • glass transition temperature Tg – is the temeprature in which the laminate  will begin to change from a solid to a liquid state – it can cause deformation or delamination. It is recommended to choose a laminate, that have Tg  above 25°C of maximum operating temperature of designing divice.The number of soldering cycles and the choice of its method is also depends on the Tg parameter,
  • thermal conductivity TC means the efficiency of heat transfer to enviroment and reduction of heat retention within the material,
  • Comparative Tracking Index CTI (V) – breakdown strength between the circuit paths.There are 6 PLC (Performance Level Categories) classes - a higher class means, for example: PLC0 means a higher level of user safety,
  • Coefficient of Thermal Expansion CTE –  is the coefficient of thermal expansion of laminates that is projected along the XY plane and the Z axis.  When the temperature rises above Tg, the CTE rises simultaneous,
  • Dielectric constant permittivity Dk – Dielectric constant defines the relative permittivity of materials to vacuum,
  • Df  paramater – determines signal losses converted into heat due to material absorption.


Type of laminateProperties
FR4, FR4 with high Tg and FR4 halogen-free The most popular laminate, used to PCB production - made of fiberglass and epoxy resin. It has a high dielectric constant, strongly dependent on frequency.
PTFE PTFE is polytetrafluoroethylene, which has excellent dielectric properties on microwave and radio frequencies. It has low Dk and Df parameters.
MCPCB Metal Core PCB) High thermal conductivity TC, high dimensional stability and hardness. Used in applications where efficient heat dissipation is important.
Poliymide (Pi) Polyimide is a very durable laminate that is very resistant to chemical and environmental influences, with low CTE. Used in the production of Flex and Rigid-Flex circuits.

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