Additive process for producing printed circuit elements using a self-supported photosensitive sheet

A process for preparing printed circuit boards having plated through-holes from a self-supported photopolymerizable sheet having on each surface a removable cover film which comprises, in either order,

• 1. exposing a surface of the reinforced sheet imagewise to actinic radiation;
• and
• 2. introducing through-holes into the sheet;
• then
• 3. removing the removable cover film from the exposed side of the sheet without transfer thereto of exposed or underexposed areas of the photopolymerizable material;
• 4. applying to the surface of the sheet and the through-holes therein a material catalytic to electroless plating which adheres to the underexposed surface and the hole areas;
• 5. removing the second removable cover film;
• and
• 6. applying electroless plating solution to the catalyzed areas and through-holes to produce an electrically conductive circuit.

A process for the preparation of complementary printed circuits on each side of a self-supported photopolymerizable shet having on each surface a removable cover film, which comprises, in either order,

• 1. exposing both surfaces of the self-supporting sheet imagewise to actinic radiation to reduce adherence of the areas receiving radiation;
• and
• 2. introducing through-holes into the sheet;
• then
• 3. removing the removable cover films without transfer of exposed or underexposed areas of the photopolymerizable material;
• 4. applying to both surfaces of the sheet and the through-holes therein a material catalytic to electroless plating which adheres to the underexposed surfaces and the hole areas;
• 5. applying electroless plating solution to the catalyzed areas and through-holes to produce an electrically conductive circuit.

A process for the preparation of multilayered printed circuit boards with plated through-holes from a self-supported, adherent, photopolymerizable sheet having on each surface a removable cover film which comprises,

• 1. exposing the self-supported, adherent, photopolymerizable sheet through the cover film imagewise to actinic radiation;
• 2. removing the cover film;
• 3. applying finely divided catalyst material to the surface to form a catalytic image;
• 4. treating the catalytic image with an electroless plating solution to form a printed circuit substrate;
• then, using the printed circuit substrate,
• 5. laminating the surface of an adherent, photohardenable layer of a photohardenable element comprising an adherent photohardenable layer and a strippable cover film thereon, to the printed circuit substrate;
• then, in either order,
• 6. imagewise exposing the laminated element through the cover film to actinic radiation;
• and
• 7. introducing through-holes into the laminated element;
• then
• 8. removing the strippable cover film;
• 9. applying divided catalyst material to the surface and the through-holes to form a catalytic image;
• 10. treating the catalytic image and holes with an electroless plating solution to form a conductive printed circuit and holes;
• and
• 11. curing the laminated element by baking.