Polymer Base
High-frequency circuit boards require laminate materials with exceptional dielectric properties to minimize signal losses in microwave and millimeter-wave applications. The ptfe substrate represents the industry standard for low-loss applications due to its high chemical inertness and stable dielectric constant. This fluoropolymer material is combined with glass or ceramic fillers to enhance its mechanical stability.
Material Advantage
The low dissipation factor of this material ensures that high-speed signals propagate with minimal thermal dissipation or attenuation. Because of its symmetric polymer structure, this fluoropolymer has a very low dielectric constant of approximately two point one, which remains stable across a wide temperature range. This stability is necessary for high-frequency circuits like automotive radar and satellite communications where signals must not distort.
However, the soft nature of the material makes it susceptible to deformation under heat and pressure during multilamination. Specialty ceramic and glass fiber reinforcements are added to mitigate this deformation and match the coefficient of thermal expansion of copper.
Processing Modification
Special chemical or plasma treatment must be applied to the hole walls after drilling to ensure reliable copper plating. Due to the high surface energy of the untreated fluoropolymer, electroless copper cannot adhere directly to the hole surface. Sputtering or sodium naphthalene etching modifies the polymer interface to promote mechanical adhesion of the plated copper.
This treatment ensures that the plated vias survive thermal shock testing without delamination.
