Fabrication method for printed circuit board

A method for making a rigid printed circuit board with a comparatively flexible dielectric material, said board including component signal lead holes, comprising the steps of:

• forming first holes defining an axis through a blank board at locations at which component signal lead holes are desired, said blank board including a plate of said flexible dielectric material defining first and second broad sides, a thin conductive layer affixed to said first broad side and a conductive plate affixed to said second broad side, said conductive plate providing a major portion of the rigidity of the printed circuit board drilling at said locations from the accessible side of said conductive plate, coaxial with said axes of said first holes, to form second holes having a larger diameter than said first holes, each of said second holes extending partially through said conductive plate and having a generally conical bottom surface inclined at an acute angle relative to said axis;
• covering at least the interior surfaces of said second holes with etch resist;
• drilling at said locations from said accessible side of said conductive plate, centered on said axes of said first holes to enlarge said second holes into third holes, each of said third holes extending almost through said conductive plate, and having a conical bottom surface inclined at an obtuse angle relative to said axis to thereby remove at least an annular portion of said etch resist from said bottom of said third hole;
• and
• applying etching material to at least the interiors of said third holes so as to etch through that portion of said conductive plate overlying said second broad side of said dielectric plate and underlying said annular portion.