It's time to ask ourselves, "Where is the future of electronic circuits?"

The chips are getting smaller and thinner, and the traditional PCB is being replaced by ever smaller, finer lines and more complicated circuits. Then along comes a new breakthrough. Some of you will see the future of the technology and many will not.

The new technology is paper circuits.

Yep, you read that right. Conductive circuits on paper and cardboard. The new circuits - printed on standard photocopier paper - can be as complicated as fine-line 6-layer circuits. And they're less costly than PCBs.

Figure 1. Photo of the first layer of a 4 layer PEC circuit on cardboard.

You're probably saying, "Tarzwell, you've finally lost it." But remember that the name of this column is "The Bleeding Edge," not "The Same Old, Same Old." It's my job to push the envelope, and recently I did just that.  

One of my clients wanted to place a video game on the back of a cardboard cereal box. He wanted to print 4-layer circuits with 7/7 lines and spaces, flip-chip die mounting, using HDI technology with blind and buried microvias, and through-holes to connect to key pads printed in text on the box.

To top it off, he said it had to be very inexpensive.

After a bit of R&D, I was printing multilayers on just about anything: Paper, cardboard stock, cloth and plastic film. These circuits use UV-cured silver ink and a UV-cured dielectric material. Microvias of 7 mils including pads were used between silver layers, and the resulting silver conductors were soldered to components with very low temperature solder in an IR oven. 

The paper circuit is possible in large part because the ongoing reduction of chip size has led to increased capacity. The thinned down die, mounted flip-chip style to the ink, is encapsulated with more circuit layers.