User Manual

Page 9
Figure 4.
displaced or off-set lead-attach tabs. The top and bottom tabs are off-set with respect to each
other (when viewed through the film thickness). This allows a precisely defined active area
(overlapped electrodes) with non-piezo conductors (off-set tabs) leading to remote bonding sites,
a technique most frequently employed for "small" devices.
! Mechanical Strength — very often the greatest strain experienced by a polymer transducer is
around the connection, whether by accident (tripping over the cable) or by design. In general,
those methods which involve the interconnection penetrating through the film at the off-set tab
locations with crimps, eyelets or rivets yield the best ultimate strain resistance. Often the lead
attach area is reinforced with polyester to improve the strength of the penetrative
interconnection.
! Long-term Stability — including all the usual environmental parameters. Most interconnections
have unlimited life (crimps, eyelets, conductive rubber connectors). Others have a more limited
shelf life (conductive tapes)
! Speed and Ease of application — of particular importance when high volume production is
planned. Many interconnection techniques are supported by semi-automatic equipment for
volume production (crimps, eyelets) while others are labor intensive (conductive adhesives).
! Electrical strength — an issue associated mainly with electrically driven (high voltage) elements
such as loudspeakers and actuators.
The Design Considerations
Two major issues control the selection of lead-attach methods:
! Is anchorage of the film allowed at the site of lead-attach? This can be a major advantage, for
example, direct connection or capacitive coupling to the conductive traces of a printed-circuit
board.
! Is special patterning of the film available, which would allow penetrative techniques? (with MSI
Sensors custom patterning service, the answer is almost always "yes.") Simple experimental
methods allow the same result.
This concludes the "questions" section—now, hopefully, are the "answers."
The Methods
Penetrative - Here the
techniques involve piercing the
film (and possibly additional
reinforcing laminates to give
sufficient thickness and
strength), and thus the film
should be patterned with a
displaced or off-set lead-out
arrangement to prevent
shorting of upper and lower
electrodes by the inserted
connector.
! Rivets or eyelets can be
affixed to the off-set
conductive traces on the
piezo film. Included
between the eyelet or rivet
can be a ring tongue lug terminal with wire attached. The eyelet or rivet mechanically presses the
conductive ring against the off-set patterned electrode to make reliable interconnection.