Feature: Displays
Motion control solutions for micro- LED chip testing
By Bill Hennessey, President, ALIO T
here is a growing adoption of micro-LEDs in modern displays. However, testing those chips is full of challenges. ALIO recognises those challenges
and maintains that precision stages can be a crucial tool in the testing process, since they provide the precise positioning and motion control necessary to achieve accuracy and repeatability.
Micro-LEDs A micro-LED is a light-emitting diode that is a lot smaller than a traditional LED, suitable for a whole host of applications in addition to displays and lighting, including sensing. One of the main advantages of micro-
LEDs is their high brightness and efficiency. Tey can emit a lot of light using a relatively small amount of power, which makes them energy efficient and long lasting. Additionally, micro-LEDs can be used to create highly customisable displays with excellent colour accuracy and contrast. However, micro-LED technology is
still relatively new and can be expensive to produce. Moreover, the testing and manufacturing of micro-LEDs require highly-precise equipment and processes
due to their small size, which can be a challenge for manufacturers. And, as the micro-LED market gears up for mass production, the focus is shiſting to the two major stumbling blocks that slow down commercialisation – low yield and high cost. Since the chip size of micro-LEDs can
be as small as a single micron, existing inspection equipment is oſten inadequate. Many standard tools simply don’t provide high enough resolution. Moreover, with the smaller pixel sizes, there is also a dramatic rise in the number of pixels that need to be processed during inspection. Test technologies are therefore emerging such as electroluminescence (EL), which easily identifies many defects.
EL testing EL testing is a non-destructive method of testing micro-LEDs and other semiconductor devices. It involves passing a small electrical current through the device, which causes it to emit light. Te emitted light can then be measured and analysed, to determine the quality and performance of the device. EL testing is particularly useful for
micro-LEDs because it detects defects and performance problems that may not be detectible with other testing methods.
48 September 2023
www.electronicsworld.co.uk
For example, EL testing can find small defects in the micro-LED structure such as dislocations or disclinations that may otherwise be invisible to the naked eye. Additionally, EL testing can provide information about the uniformity of the device’s emission and the distribution of current within it. Te EL testing process requires physical
probing of the electrical contacts on the micro-LED chips, which must be done with extremely high precision to avoid device damage. Te smaller pixel sizes of micro-LEDs
mean that there is a significant increase in the number of pixels that need to be processed during inspection, which makes high-throughput inspection a major challenge. Precision motion control solutions can
help to optimise the speed and efficiency of the testing process, enabling rapid and accurate movement of the testing equipment, and reducing the time and cost associated with testing large numbers of micro-LED chips.
Test technology experience ALIO’s experience in this field has helped it develop different motion control technologies that are suitable for testing micro-LEDs. Our Hybrid Hexapod, for example, is a parallel kinematic motion control system that provides six degrees of freedom with sub-micron precision and repeatability. Tis technology is ideal for micro-LED testing requiring high precision, accuracy and speed. Te Hybrid Hexapod combines rotary
and linear motion to provide a large range of movements and high load capacity, allowing it to test large numbers of micro- LEDs simultaneously. Ten, there are the Air Bearing Stages,
linear motion control systems that provide frictionless motion with high precision and accuracy. Tis technology is suitable for micro-LED testing that requires high speed and accurate motion control. Air bearing stages are capable of achieving nanometre-level positioning accuracy and repeatability, making them ideal for testing micro-LEDs with high resolution and high accuracy.
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