Friday, July 17, 2015

Printed Circuit

An electrically conductive circuit was finally able to be achieved. This was done using the "Fingerprint Method". I smudged my fingers on the transparency (cellulose acetate) where my circuit would be printed. Then I ran it through the printer. The initial resistance of the trace (right after printing) is about 250 - 300 Ω for a current traveling 1 cm. This drops down to about 25 - 50 Ω after a few hours.

A few different methods were experimented with when it came to attaching the components to the circuit. At first, electrical tape was used to adhere the components to the substrate. This worked, but if it was not placed tight enough then the component had a change to "hover" over the trace and not complete the connection. I drop of solder was then used to try to help stick the components to the circuit. This proved difficult as there was a high change that the heat radiated from the iron would melt away the circuit and substrate (Fig 1). It was finally settled on to use copper tape. This provides good adhesion for the components as well as being conductive itself (Fig 2).

Fig 1. Combination of Electrical Tape and Solder Connections
Fig 2. Copper Tape Connections 
A blank piece of paper was placed under the substrate to allow for less glare during imaging. Fig 3 shows that the trace is complete and the LED is lit up. Some of the components were bent to allow for easier taping.

Fig 3. Working Circuit
Future work will involve more precise placement of the tape using tweezers and the design/measurement of printed capacitors. 

* The LED and Resistor are connected directly to each other as the trace between them was accidentally melted away with the soldering iron.

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