A dielectric film for a printed wiring board that has excellent heat
resistance, moisture resistance, insulation properties, adhesiveness, ease
of handling, ease of processing, and the like, and possesses low
elasticity and high elongation as stress relief functions. The dielectric
film has drawn porous polytetrafluoroethylene used as the base material;
this is impregnated with an adhesive or fusible resin; the
post-solidification tensile modulus of elasticity is 0.1 to 1.8 GPa; and
the tensile elongation at break (at 25.degree. C.) is at least 4.0%. A
semiconductor device, comprising a multilayer printed board having a
plurality of circuit layers, and a semiconductor element mounted on the
multilayer printed board, this semiconductor device having an
insulating/adhesive layer with a stress relief function between the
outermost circuit layer of the multilayer board on the side of the
semiconductor element, and the circuit layer adjacent thereto; and the
insulating/adhesive layer is formed from the dielectric film. Also, a
printed wiring board therefor.
