Motion controller's CAN bus I/O simplifies wafer handling:
The combination of servo motor control axes and field-bus I/O interfaces on Baldor's NextMove motion controller is helping automation equipment manufacturer Sintech Automation (S) Pte Ltd to cut the cost and size of automation for semiconductor wafer handling. Custom-designed for one of the world's leading high-technology companies, its new PC-controlled machine sorts post-baked wafers by lot number and position, eliminating manual handling and slashing the valuable clean-room space typically required for this task. The system makes life very simple for operators thanks to a 'load and forget' principle of operation, which automatically orients, reads and sorts them as required.

Wafer handling is performed by two actuator arms driven by servo motors, which transfer the wafers from their handling 'boats', and place them into specified drawers in the machine, for subsequent removal and processing. There are 35 drawers in total, each of which is controlled and monitored by three digital input and three digital output lines.

At the outset of this design project, Sintech Automation thought that a separate PLC would be needed to provide and manage the I/O, but Baldor's Singapore distributor Servo Dynamics proposed a motion subsystem design based on a motion controller with integral CAN fieldbus ports. This approach allowed the I/O architecture of the machine to be implemented using a network, allowing an almost unlimited number of I/O channels connected directly to the motion controller. Just five of Baldor's 48-line I/O modules provide all the digital control inputs and output channels required, and these modules are also physically distributed around the machine - saving a considerable amount of cabling.

Servo Dynamics recommended Baldor's NextMove PC motion controller, as this module provided both a compact motion control solution - which plugs inside the host PC - and an easy means of interfacing to the machine's control software. The wafer sorting machine itself is controlled by a popular Windows man-machine interface package. This provides Sintech Automation with a platform to offer its customer a highly graphical user interface and control environment, with touch-screen interaction.

The man-machine interface package, and other Windows software, orients the wafers, reads the ID numbers using OCR software, and then determines which locations in the machine they will be sent to - storing the information in a database for easy integration with the overall production process management computers. It provides high-level commands to the motion and I/O control subsystem via Windows' DDE mechanism. These are then converted into real-time control signals by the motion controller's onboard processor. The motion control and I/O processing routines were written in Visual BASIC, and simply call the specific Baldor 'Mint' motion and I/O control commands as required - a simple approach which was achieved using Baldor's Mint Interface Library developer's package.