>Which reminds me of another possibility for making boards. Have a pen with
>insulating ink and another with conductive ink. Draw traces with the
>conductive ink. Where they need to cross, put down a layer of insulating
>ink. No limit to the number of layers!
>
>Harold

This is the standard method for hybrid circuits on alumina substrate
except you need to use different solvents for the alternating layers, and
this makes the process complex. Inks like this exist, and you can even
print resistors and make capacitors between layers etc. The number of
layers is limited by mechanical resistance. 6 layers per side is commonly
maximum. I don't think that you can buy the inks in small quantities and
they need baking between layers afaik. You CAN do it with the proper tools
however. The technology predates integrated circuits slightly.

Peter

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