Printed wiring board having a cover lay laminated on a polyimide resin base film containing conductive circuits

#1. Field of the Invention

#The present invention relates to a printed wiring board, and in particular, to improvement of a cover lay which is laminated on a surface of a polyimide resin basefilm on which conductive circuits made from copper foil are formed.

#2. Description of the Related Art

#The present invention will be better understood from the description of the preferred embodiments of the invention set forth below, together with the accompanying drawings, in which:

#FIG. 1 is an exploded perspective view showing a first embodiment according to the present invention;

#FIG. 2 is a sectional view showing a structure of laminated layers of the printed wiring board described in FIG. 1; and

#Note that in this specification, the polyimide-containing resin material may not be pure polyimide resin, but may include other materials, such as epoxy resin, for example.

#The present invention will be now described with reference to the accompanying drawings wherein, FIG. 1 is an exploded perspective view of the printed wiring board according to the first embodiment, and FIG. 2 is a sectional view which shows the structure of laminated layers.

#A basefilm 10 is made by laminating copper foil sheets 12, 13 onto both sides of a sheet 11 made from polyimide-containing resin material. Conductive circuits are made by etching the copper foil sheets 12, 13. First prepregs 14, 15 are made by saturating a glass fiber sheet with epoxy resin. The first prepreg 14 is laminated onto the upper side of the basefilm 10, and the first prepreg 15 is laminated onto the lower side of the basefilm 10. The prepreg 14 has an opening portion 16 and the prepreg 15 has an opening portion 17. The opening portions 16, 17 overlap each other.