Take a Blank Epoxy Card. No Copper, just the glass epoxy card. It will not be copper clad. I am trying to explain the concept. The Glass Epoxy card as you know is Epoxy (Like Ciba Araldite) with glass fiber as filler. Maybe new technologies have come now. The fiber is for Reinforcement and Epoxy you know is a Marvel of an Engineering Material.
EE Design Library - Electronic Product Design Resource.
PCB belongs to AVR JTAG adapter - MadWizard.org
In those days some people told me that these epoxy with glass fiber and iron flakes as powder are used to repair aircraft/spacecraft. It could be cast into a shape and even turned on lathe for making custom replacement components.
This nudged an idea, If we Screenprint a Mixture of Epoxy + Fine Iron Dust + ? over the blank Glass Epoxy card. The positive is used not the negative. That means Pads and Tracks on Positive create an Image of Pads and Tracks of this Epoxy/Iron paste on Glass Epoxy surface. Now Screenprinting done, let it dry. We can also be print a thin layer of epoxy pcb pattern and blow iron dust on it.
Dip this Printed Epoxy card with this iron/epoxy pattern; into a Copper Sulfate CuSO4 + ? + ? Solution. The ? has to figured by chemical engineers. I used to be good at Organic and Inorganic Chemistry, when i was young. The copper replaces/plates the iron powder and with some electrostatic and electrochemical methods the copper layer grows over the entire tracks and pads quickly. Now the card is Tin Sn plated to complete.
A single Prototype PCB is ready and no extra copper wasted. Copper and Tin was deposited.
2004 - delabs Notes