Precision Thinning for TEM Analysis

The PELCO^® Dimpler™ is the most modern version of the Dimpler range (previously supplied by South Bay Technology) and is designed for the automated thinning of TEM samples. The PELCO^® Dimpler™ is a highly precise electro-mechanical metallographic lapping in­strument which regularly checks and feedbacks to control dimpling parameters and to stop the process at the required thickness.

The unique advanced design of the PELCO^® Dimpler™ means the dimpling process can be automated with a high level of reliable repeatability.

The PELCO^® Dimpler™ is equipped with operating functions which allow it to create dimpled samples at a high repeatability.

Z Position

The display for the Z position shows the chosen stop point and has an analog to digital dimple depth in the Non-Contact Sensor. The reading, given in microns on a digital LED screen, is updated for every revolution of the tool at the same site using the Tool Phase Detector. This minimizes errors that can occur from tool run out, this is particularly useful when padded tools are used.

Termination

The termination accuracy is improved by four factors:

• Tool Phase Sensor
• Arm damping with magnetic coupling
• Non-Contact Position Sensor
• No need for an external measurement tool

The Non-Contact Position Sensor can determine the specimen thickness by measuring the position of the fulcrum arm at an accuracy of less than one micron. The non-contact nature of the sensor means that the function of the fulcrum arm is not impacted.

The sensor has a rapid reaction time allowing for the dimpling process to be stopped as soon as the Tool Phase Sensor observes that the Z termination point has been attained.

The PELCO^® Dimpler™ directly measures the sample thickness using the tool surface as the measuring point. The incorrect translation of measurement errors is avoided by using the same reference to measure both the Z termination point and the dimple depth.

Damping

Position information, acquired using the non-contact position sensor is fed back into the arm motor, which moves up or down in response, and is used to control damping of the arm. Sensing and processing take place rapidly allowing effective damping of arm vibrations.

The damping force is coupled magnetically to the arm, which allows damping to be effective at a sub-micrometer level. Damping can be changed between stiff damping and zero damping.

Damping provides three main advantages:

• Tools remain round, with excess impacts minimized, which facilitates accurate control of the Z-position.
• The occurrence of vibrations, which can damage thin specimens, are minimized.
• When the arm is lowered contact with the specimen is gentle.

Working Interface

Research has demonstrated that the working diameter of Tools 2i and 4i is within the nap of the pad. Whilst the change in Z offset (ΔZ) between the tool surface and the sample is effectively zero the Z offset between the sample and the ‘working interface’ is affected by the tool speed, pad compliance, damping force and the dimpling force.

Following selection of the tool speed, damping force and dimpling force the working diameter is held at the pad’s working interface. Monitoring of the working interface takes place on the Z-display, and this can be used as a reference for further dimpling of the sample.

The machine operator can control the depth of the dimples produced and removal using a practically seamless padded tool. The padded tool provides a level of position control that allows the dimpling force to approach zero at increments within 1 g.

PELCO^® Dimpler™ Specifications

PELCO^® Video Alignment Microscope for PELCO^® Dimpler™