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Discrete Piezoelectric Stacks with Through Hole, 7.0 µm to 40.0 µm Travel
150 V Piezo Stack with Two Flat Ceramic End Plates
Central Ø2 mm
Front View of the PK4FA2H3P2
Thorlabs' Discrete Piezoelectric Stacks consist of multiple piezoelectric chips, each with a central through hole, stacked face-to-face and bonded via epoxy and glass beads. By combining many chips, a stack is able to achieve a free stroke displacement that is significantly larger than that of its single chip counterpart while maintaining sub-millisecond response times and a low drive voltage range. The central through hole makes these piezos ideal for laser tuning and micro-dispensing applications.
Flat ceramic plates with matching through holes cap the two mounting surfaces on opposite ends of the piezoelectric stack. The ceramic plates assist in both distributing the applied force of the load over the mounting surface of the stack and in directing the force along the actuator's axis of translation. When interfacing the flat surface of a load with this flat mounting surface, ensure the two surfaces are highly flat and smooth and that there is good parallelism between the two when they are mated. For more details see the Operation tab.
A ceramic layer covering the other four sides and central hole of the stack acts as a barrier against moisture. The ceramic layer offers better protection against moisture than an epoxy coating. For convenience, the stacks have pre-attached 75 mm long wires and are wrapped in Kapton® tape. Piezo chips with custom dimensions, voltage ranges, and coatings are available. Please contact Tech Support for more information.
Our piezoelectric tutorial contains more information about the design and function of piezoelectric stacks.
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Dicing the PZT Block into Individual Elements
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Chips After Binder Burnout and Sintering
Thorlabs' In-House Piezoelectric Manufacturing
Our piezoelectric chips are fabricated in our production facility in China, giving us full control over each step of the manufacturing process. This allows us to economically produce high-quality products, including custom and OEM devices. A glimpse into the fabrication of our piezoelectric chips follows. For more information about our manufacturing process and capabilities, please see our Piezoelectric Capabilities page.
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Schematic of PK4DMP2 Piezo Stack
Caution: after driving, the piezo is fully charged. Directly connecting the positive and negative electrodes has the risk of electricity discharging, spark, and even failure. We recommend using a resistor (>1 kΩ) between the wires to release the charge.
Soldering Wire Leads to the Electrodes
Interfacing a Piezoelectric Stack with a Load
Operating Under High-Frequency Dynamic Conditions
Estimating the Resonant Frequency for a Given Applied Load
Quick changes in the applied voltage result in fast dimensional changes to the piezoelectric stack. The magnitude of the applied voltage determines the nominal extension of the stack. Assuming the driving voltage signal resembles a step function, the minimum time, Tmin, required for the length of the actuator to transition between its initial and final values is approximately 1/3 the period of resonant frequency. If there is no load applied to the piezoelectric stack, its resonant frequency is ƒo and its minimum response time is:
After reaching this nominal extension, there will follow a damped oscillation in the length of the actuator around this position. Controls can be implemented to mitigate this oscillation, but doing so may slow the response of the actuator.
Applying a load to the actuator will reduce the resonant frequency of the piezoelectric stack. Given the unloaded resonant frequency of the actuator, the mass of the stack, m, and the mass of the load, M, the loaded resonant frequency (ƒo') may be estimated:
Estimating Device Lifetime for DC Drive Voltage Conditions
A ceramic moisture-barrier layer that insulates Thorlabs' piezoelectric devices on four sides is effective in minimizing the effects of humidity on device lifetime. As there is interest in estimating the lifetime of piezoelectric devices, Thorlabs conducted environmental testing on our ceramic-insulated, low-voltage, piezoelectric actuators. The resulting data were used to create a simple model that estimates the mean time to failure (MTTF), in hours, when the operating conditions of humidity, temperature, and applied voltage are known. The estimated MTTF is calculated by multiplying together three factors that correspond, respectively, to the operational temperature, relative humidity, and fractional voltage of the device. The fractional voltage is calculated by dividing the operational voltage by the maximum specified drive voltage for the device. The factors for each parameter can be read from the following plots, or they may be calculated by downloading the plotted data values and interpolating as appropriate.
In the following trio of plots, the solid-line segment of each curve represents the range of conditions over which Thorlabs performed testing. These are the conditions observed to be of most relevance to our customers. The dotted-line extensions to the solid-line segments represent extrapolated data and represent a wider range of conditions that may be encountered while operating the devices.
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For an Excel file containing these fH vs. relative humidity data, please click here.
The data used to generate these temperature, voltage, and humidity factor plots resulted from the analysis of measurements obtained from testing devices under six different operational conditions. Different dedicated sets of ten devices were tested under each condition, with each condition representing a different combination of operational voltage, device temperature, and relative humidity. After devices exhibit leakage current levels above a threshold of 100 nA, they are registered as having failed. The individual contributions of temperature, humidity, and voltage to the lifetime are determined by assuming:
where A1, A2, A3, b1, b2, and c are constants determined through analysis of the measurement data, V is the DC operational voltage, T is the device temperature, and H is the relative humidity. Because the MTTF has a different mathematical relationship with each factor, the dependence of the MTTF on each factor alone may be determined. These are the data plotted above. The regions of the above curves marked by the blue shading are derived from experimental data. The dotted regions of the curves are extrapolated.
Lifetime testing of these devices continues, and additional data will be published here as they become available. To assist in temperature control, please see our selection of thermoelectric coolers. Temperature and humidity can be monitored using our USB Temperature and Humidity Logger.