Review of 8-mm Piezoelectric Motor Connection Methods Page: 14 of 31
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Figure 8. Woven Wire Connections
Recent Work
Late in 1997, new ideas and materials were used in tackling the piezo motor connection problem. A
printed circuit ceramic collar was designed to interface between a fixed cable and the moving PZT
elements. Suspended under (and free from) the moving web and stator, the collar offered a solid base for
bonding Kapton flexcables, gold wires, or ribbons. Several flexible conductive adhesives were obtained
which yielded crack-resistant, vibration-tolerant bonds for moving electrical connections. Soldering was
investigated to attach copper leads to PZT elements. New concentrically slit flexcables were designed to
incorporate shape-conformance and flexibility, thus reducing stresses on conductors and bond points.
Cables were designed in-house and purchased commercially to obtain small features like slits, short-radii
curves, and Kapton ablation over copper paths. Ablating a small area of Kapton over a copper trace
allows soldering the copper to the metal below for an improved bond. It was decided that small, thin,
symmetric Kapton cables with minimal mass offered the best solution for electrical connections.
Following are discussions of the work performed.
Fixed Ceramic Collar
The fixed ceramic collar design was intended to reduce contact with the moving web of the stator. Figure
9 shows a thin round ceramic collar, supported in the middle by a metal spacer and washer, providing
centering and standoff of the collar, below the web. In Figure 10, Kapton cable connections and wire or
ribbon bonding to the PZT elements were to be made to the printed circuit trace pads on the collar. To
determine whether resonances at the motor driving frequencies were likely to break the ceramic collar or
the gold wire or ribbon, finite element analyses were done of the collar and various gold wire and ribbon
geometries. The analysis of the ceramic collar eliminated the resonance concern for it. Based on the
analysis results of the ceramic collar, the first vibration mode occurs at 116.7 kHz and the three-wave
mode occurs at 204.2 kHz. The three-wave mode used to drive the stator (occurring at about 50 kHz for
phosphor bronze material and about 69 kHz for a stainless steel material) is far too low to be expected to
excite the three-wave mode of the collar. The driving frequency of the motor is also different from, and
far away from, the first mode of vibration of the collar. The analyses of the gold wire and ribbon showed
that (as confirmed by the previous failures in the gold ribbon and wire connected to motors) the14 of 31
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Barben, C. L. & Yerganian, S. S. Review of 8-mm Piezoelectric Motor Connection Methods, report, June 8, 2000; Kansas City, Missouri. (https://digital.library.unt.edu/ark:/67531/metadc707989/m1/14/: accessed April 24, 2024), University of North Texas Libraries, UNT Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.