Securing a Stripe Actuator; Connecting Electrical Leads

In order to accomplish its task, a Stripe actuator must be secured to a solid surface. Of the three approaches -- gluing, soldering, and clamping -- the overall best approach usually is gluing. An epoxy or acrylate glue will provide a strong, flexible, non-conducting bond. The flexible nature of a glue bond usually eliminates the possibility of vibration-induced fatigue during long-term operation. When needed, glues are available that can be used at temperatures exceeding 150°C. Such temperatures will encompass the recommended operating limit for almost any piezoelectric ceramic material. Be aware, however, that high temperature programs needed to set some glues could affect the piezoelectric characteristics of the actuator. Compare the Curie point and recommended maximum operating temperature of the ceramic with the curing temperature of the glue; if there is overlap, contact the glue manufacturer about the feasibility of prolonging the curing time at a lower temperature -- or use another glue.

Soldering is a less reliable means of securing a ceramic element because, over time, vibrations in the ceramic can cause the bond to fail. Also, the high temperatures associated with soldering must be applied carefully to a ceramic element -- the Curie point of a polarized ceramic can be well below the temperature of hot solder. On the other hand, a soldered connection is electrically conductive and, in some situations, this characteristic might be needed.

The following general soldering procedure can be adapted for securing a Stripe actuator into place. To minimize the effects of heat on the piezoelectric properties of the ceramic, always keep the soldering time as short as possible (3 seconds or less is ideal). This procedure also is appropriate for making electrical connections -- when soldering electrical connections to a Stripe actuator, or any other APCI piezoelectric ceramic element, follow these recommendations (type of solder and flux to be used, etc.).

Remember that piezoelectric ceramic elements have substantial pyroelectric coefficients. The thermal energy introduced by soldering an element into place, or by soldering an electrode to an element, will generate an electrical charge in the element. To avoid the unpleasant (but generally harmless) consequences associated with discharging a piezoelectric ceramic element, apply solder to the element with the element in short-circuit conditions.

General Soldering Procedure
Equipment and Materials
     Soldering iron (15 W / 275°C - 300°C)
     Solder (SN 62: 62% tin / 36% lead / 2% silver, 0.032" diameter)
     Flux (active rosin) (Kestor 1544 or equivalent - no ZnCl or other corrosive agents)
     Leads (common sizes 28AWG-32AWG)
     Small, sharp blade (X-acto® knife or equivalent)
     Solvent (for removing excess flux)
     Cotton swabs

Procedure

1. Turn on soldering iron and allow to stabilize at 275°C - 300°C.
   
2. If necessary, use knife blade to remove conductive coating from areas where leads are to be attached.
   For a Stripe actuator, this will expose the silver electrode. DO NOT remove the electrode.
   
3. Wipe prepared surface with solvent and allow to dry.
   
4. Flux and tin wire with solder.
   
5. Place small amount of flux on wire and solder area.
   
6. Melt small amount of solder onto soldering iron tip.
   
7. Place wire on surface in desired position.
   
8. Place iron with solder on wire and surface. Hold for 1 - 2 seconds, then remove iron. Solder should flow from iron to wire and surface. Allow solder joint to cool before moving wire.
   
9. Repeat steps 2 - 8 for each connection.
   
10. Clean solder joint(s) with solvent.

More Technical Notes:

     Performance of Stripe Actuators
     Blocking Forces and Half-Deflections for Stripe Actuators
     Dimension Specifications for Stripe Actuators

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