A tiny vacuum encoder is playing a big role in improving the throughput, quality and packing density of wire bonding machines, as used by manufacturers of micro-electronic devices. The MicroE Mercury II encoder by Celera Motion — available in the UK from INMOCO — is one-third the size of other encoders, yet is easy to install and set up.
As performance expectations for microelectronic equipment continues to grow, manufacturers need to achieve denser wire bonding yet greater reliability — whilst also increasing throughput and reducing overall cost of ownership of the production machinery.
Microelectronics is essentially electronics on a micrometre-scale or smaller and includes transistors, capacitors, inductors, resistors, diodes etc. As the technology continues to develop components constantly decrease in size. But at reduced scales, imperfect bonding can lead to efficiency losses and adverse parasitic effects. Thus wire bonding quality needs to be constantly improved, whilst production equipment has to become faster, more compact and increasingly reliable.
In practical operational terms this means wire bonds need to be placed closer together and with a more consistent and predictable three-dimensional wire path. Higher placement accuracy is also required due to smaller bond pad size and increased pad density.
In order to achieve these ends, a wire bonder’s motion control system needs to have the best possible control of velocity, acceleration and the third order derivative of position (which is often called 'jerk'), with high-speed positioning, excellent repeatability and high resolution. The motion feedback encoders need to perform in a high electromagnetic interference (EMI) environment with good thermal stability, have long cable flex life and high reliability.
MicroE Mercury II encoders provide cost-effective solutions to system designers seeking either an analogue or digital incremental encoder for their next generation wire bonders. The Mercury II MII6000 digital encoders offer excellent options for those wire bonder designs requiring encoder interpolation external to the motion controller. These user-programmable encoders offer high speed, robust noise immunity, 1.2nm resolution and long cable life. They boast a ±20nm cyclical error on glass scales for excellent velocity stability.
A programmable input filter helps to eliminate the effects of high frequency noise in the encoders as well. The sensor heads are compatible with both linear scales and rotary gratings, while for partial-rotation requirements MicroE can supply arc segments of the rotary gratings so that the system footprint is minimised.
Gerard Bush, one of INMOCO’s application engineers, says the MicroE vacuum encoders are smaller, higher performance, faster to install, and easier to set up and align than any other encoder. He says: “They fit into very tight spaces and work in both linear and rotary applications. Vented and constructed with vacuum compatible materials they are designed for a 48-hour bake out at 150degC, while simple things like colour coded leads aid rapid installation.”
Technically the MicroE encoders have advanced electronics built into a shielded D-sub connector, and they are fitted with an LED alignment indictor. The output is A-quad-B with programmable interpolation in integer steps for resolutions to 0.005μm (linear); 67.1M CPR (rotary). Other technical specifications include external dimensions of 22.6mm x 12.7mm x 8.1mm and a weight of 3gms and a 20µm grating period.
“A bi-directional index signal and best-in-class noise immunity make them robust and easy to use,” says Bush. “People marvel at how much electronics has developed over their lifetime. But most don’t realise that this has only been possible because of equal advances in manufacturing techniques — and that this has spun out many, many related technologies such as tiny yet precise encoders and other motion control equipment.”