Advanced Print Circuit Board Materials

A silica/epoxy resin nanocomposite exhibiting high thermal stability and low thermal expansion based on the uniform dispersion of hydrophilic colloidal silica nanospheres

“…Unfortunately, many electrical/electronic materials have CTEs that are particularly low, or at least lower than those of the epoxy resins commonly used to encapsulate circuits. [1][2][3] Hence, drastically reducing the CTE of epoxy resins by adding inorganic nanoparticles could represent one approach to lowering CTE mismatches. The addition of inorganic fillers to epoxy resins has the added advantage of increasing the glass transition temperature (T g ) of the resin such that the resin's thermal stability is improved.…”

“…Silica is preferred as a filler as a consequence of its low CTE and because silica provides superior electrical insulation and mechanical properties at a reasonable cost. [1][2][3][4][5] Even so, obtaining suitable thermo-mechanical characteristics, including an effective CTE of from 20 to 30 ppm°C -1 below the T g of the polymer, requires the incorporation of 55-70 vol% silica particles having dimensions on the micron scale. 6,7 Elevated filler levels such as these can both increase the viscosity of the molten polymer and promote delamination of the electronic device.…”