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Single source servo system for specialist machine

Edited by the Engineeringtalk editorial team Sep 25, 2000

Chess Systems' PAT 3500 is able to feed and sort semiconductors at a rate of 1500 units/hour; the servo and controller package for the machine is supplied by Heason Technologies Group

Specialist semiconductor handling machines for component test systems required for short run and product development applications is a niche market currently served by just one UK manufacturer, Chess Systems of Horsham.

Key to the company's success in this field is its ability to design and build machines that can both perform at the high levels of speed and accuracy demanded by the electronics industry and be adapted to satisfy different customer requirements.

Chess' current machine, the PAT 3500, is able to feed and sort semiconductors according to sixteen different test performance classifications at a rate of 1500 units/hour.

To achieve this, Chess employs linear and rotary brushless servo systems with all motion controlled by a central controller card.

The total servo and controller package was supplied by Heason Technologies Group, Chichester, and comprises Etel linear motors and drives, Kollmorgen servo motors and drives and an Harmonic Drive gearhead.

Control of the servo systems is achieved via a Baldor NextMove PC based multi-axis controller.

In addition to the hardware Heason also wrote the control software governing the motion routines.

According to Graham Beall of Chess, the advantages of single sourcing the servo components and technical backup include proven component compatibility demonstrated in the field by Heason, plus the benefits of a single centre of responsibility for trouble shooting.

In operation, trays of semiconductors are loaded into the PAT 3500 using a conventional JEDEC system.

From these input trays the semiconductors are individually lifted and placed in a holding station from where it is picked up, inverted and located in a retaining socket in a 1m dia.

rotating carousel that indexes them through to the testing station.

At the testing station the semiconductors are lifted to undergo testing and then lowered again back to the carousel to complete a 180deg travel to be returned to its original orientation and sorted into output trays according to the test gradings.

The transporting of the semiconductors to the holding station is performed by a pneumatic pick-and-place device mounted upon one the two Etel linear motors.

The second linear motor carries a similar pneumatic attachment which places the tested semiconductors in appropriate trays.

Both motors are mounted on a single track and a single integral linear encoder is employed for positioning both motors.

Travel speeds are up to 3m/sec and accuracy is to 4 microns.

Carousel motion and positioning is performed by a Kollmorgen ServoStar motor/drive package with a 100:1 Harmonic Drive gearhead.

Rapid response and zero backlash are essential to synchronise with the 1.8sec index cycles, and ensure correct alignment with load/unload points and test station.

A second Kollmorgen servo motor drives a ball screw arrangement to lift and accurately position the semiconductors into a testing socket, then return them to the carousel.

The 1500 units/hour PAT 3500 is a second generation machine and Chess is already working on a third generation which will handle 6000 units/hour.

The company's markets are world-wide and 80% of its business goes for export.