20CM length of Smart Tape, 25mm wide.
Smart tape is a remarkable double-sided adhesive tape. It looks like conventional double-sided tape but conducts electric current through its thickness – i.e., in the ‘Z’ axis. It does not, however, conduct sideways along the ‘X’ and ‘Y’ axes. It can therefore be used in a single piece, for example, to bond a multi-conductor ribbon cable to a row of correspondingly spaced circuit board pads. The ribbon conductors connect to their respective pads, but there is no conductivity sideways between them.
The explanation for this puzzling behaviour turns out to be very simple. If the tape is viewed under a microscope (200 x magnification), a fine matrix of black spots can be seen. These are metal particles passing through the thickness of the tape to facilitate conduction. Because they are not in touch across the tape, there is no ‘X’ /‘Y’ conductivity.
The tape is used extensively in well know brands of smart phone to make electrical connections and brings a WOW factor into any discussion or demonstration of joint making in electronics. It can also be extremely useful for prototype printed circuit board work where components and leads need bonding to tracks or pads other than by soldering or other mechanical means.