We live in a world where modernization in the compound semiconductor market is associated with the fine-tuning of scribing and breaking semiconductor wafers -- a process based on principles similar to the art of glass cutting. In the market as far back as three decades ago, scribe dicing semiconductor wafers yielded irregular quantities because the tools were not manufactured properly and were not accurately positioned in the system.
"To address these issues, Loomis Industries collaborated with suppliers and customers -- sharing trial and error and plenty of risk-taking -- to develop a process in scribe alignment and accuracy that is unmatched by our competitors," said Jim Cook, the company's production manager. "Some of our older equipment (the PKR-99, MKT-38LI, LCD-1, and soon the LSD-100) have been on production lines for more than a decade, with very little maintenance. By using quality, industry-proven components on our new LSD-150 (shown here), we hope to continue with this record of high reliability and productivity. I think that the compact, modular nature of Contemporary Controls' Ethernet switch and the Galil motion control components will help us with this goal."
Searching for a Better Solution
In July 2004 Loomis Industries (St. Helena, CA) made the final choice of Galil motion and I/O components as the core of their new LSD-150 scribe and break system. The Galil hardware, the DMC 2143-DC24 motion controller (a two-layer module containing the motion controller and the amplifier) and the IOC 7007 input/output board, allowed two choices for communication: serial or Ethernet.
"Ethernet was the 'cleaner' solution," explained Cook. "Many PCs sold today aren't designed with serial ports; often they come with only USB. But most PCs have Ethernet built-in."
Since the Galil products employed an Ethernet interface, Loomis Industries had to locate a manufacturer of industrial-grade, small-footprint Ethernet components. "A switch was preferred over a hub," said Cook. "Our programmers said that a switch is more efficient in this application." Further, he stated, the Galil hardware was not designed to be daisy-chained so an Ethernet switch was required to link up the Ethernet devices that occupied the limited space in the LSD-150 chassis.
"I was looking for a product aimed at giving its users compact size and versatility in power connection," Cook said. "The Contemporary Controls' BAS Switch (shown here) was a perfect fit." Why? The BAS Switch (Model EIBA5-100T/R) did not use a power transformer that had a proprietary plug on the switch housing. Loomis Industries already had a 24 Vdc switching power supply inside their LSD-150 machine. "With this Ethernet switch we were able to use up to 36 Vdc, with simple screw plugs to easily connect power from our switching power supply," explained Cook.
The size of the switch was a factor, too. "As small as possible, that's what we needed," said Cook. "When we decided to use the Galil system, we were short on space. The Galil components are much larger than what we had been using. A switch designed for home or office wasn't an option. The smallest of those are bulky in comparison to the BAS Switch."
The BAS Switch
Truly compact, the BAS switch measures only 3.3 in. H x 0.9 in. W x 3.5 in. D. The EIBA5-100T/R provides five 10/100 Mbps shielded RJ-45 ports. Each port selects the auto-negotiation protocol in order to select data rate, duplex, and flow control. All five ports are Auto-MDIX compliant, and therefore, any port can operate as an uplink port to another switch, eliminating the need for crossover cables.
The EIBA5-100T/R offers low-voltage, wide-range ac or dc power source. LEDs exist for activity/link, data rate, and power. The activity LEDs face the technician, easing troubleshooting. The unit's label can be written upon so port connections can be documented regarding location of connected equipment. Built-in broadcast storm control prevents excessive broadcasts from degrading network performance. The device provides easy DIN-rail installation, conforming to the requirements of UL 508 Listed and C-UL Listed, CSA C22.2 No. 14-M9, Industrial Control Equipment.
Benefits of Ethernet
Once Loomis Industries had connected the Galil-based system via Ethernet, the company's machine was able to do complete production runs without any interruptions.
"Ethernet is a time-tested technology that has great capability for problem diagnosis and resolution," Cook said. "Other reasons for Ethernet's popularity in this application are its speed, flexibility in expansion of generic devices, no need for special cables or connectors, and Ethernet components are not only inexpensive, but they are available worldwide."
The Wafers
Loomis Industries had reached a unique ranking in the industry with its process for dicing wafers made of Gallium Arsenide, Indium Phosphide, and other semiconductor compounds less than 300 microns thick. Wafers are covered with thousands of copies of a device that the manufacturer desires to assemble. For example, the devices (or chips) might be integrated circuit components for use in cellular telephones. These copies of the chip are separated from each other via Loomis Industries' scribe and break system. The devices are laid out on the wafer in a grid. The space between the devices is referred to as a "street." Streets are typically 50 microns wide and act as the pathway for the scribing process.
The LSD-150 System
From an implementation perspective, much time and effort was exercised in making certain the network and infrastructure were correct for the scribe and break process. The system is comprised of a PC and the LSD-150 unit, a tabletop machine measuring approximately 3 x 2 ft. The LSD-150 is used inside environmentally controlled clean rooms. (Shown here, the EIBA-100T/R inside the LSD-150 machine.)
The PC is positioned near the LSD-150 since interaction is required, at times, from the operator via mouse and keyboard. A two-meter unshielded (UTP) typical CAT5 Ethernet cable connects the PC to the LSD-150. The PC functions as the supervisory controller. All the motors, digital I/O, and analog I/O are controlled and monitored by the Galil components to do the real-time servoing. The Galil components interface with the PC through the EIBA5-100T/R switch.
The Galil DMC 2143-DC24 motion controller is described as a 4-axis Ethernet, RS232 controller card with a 96-pin DIN connector. This device measures only 4.25 x 7.0 in. to satisfy the area-sensitive needs of this application. The IOC 7007 eliminates the need for an external PLC. It includes a 32-bit microcomputer with memory and multitasking for programming various I/O events.
Considering an open architecture in order to build in modularity for future expansion was an obvious choice by Loomis Industries. "Occasionally, we will customize the machinery to meet our customers' requirements," Cook said. "We can install extra modular controllers under the supervisory PC controller if we chose to add more motors or other devices."
Through the user interface, the PC communicates to the LSD-150 how to process the wafer once it is loaded on the scriber. The PC and the corresponding recipe file dictate scribing air pressure, breaking air pressure (both analog controls), scribing and break speeds, and focus positions.
"Ethernet communications are not time-critical, but there's a strong likelihood that any delay over 1 ms per message will begin to affect throughput," says Cook's programmer.
Cook explained that throughput depends on numerous factors such as the die size, the material being scribed, scribe speed, break speed, the size of the wafer (the machine can handle substrates from 2 to 6 in.), the shape of the wafer (round or rectangular), and the process. The "process" means to scribe and break the wafer on the LSD-150 machine, or scribe (without breaking) the entire wafer on the LSD-150, then break (the now scribed wafer) with the Loomis Roller Break Machine. If the latter process is used, a 4-in. wafer with a die size of 750 micrometers square can take as little as 20 minutes to process.
Regarding the physical arrangement of the devices in the system, Cook says, "It is very straightforward." The EIBA5-100T/R switch is DIN-rail mounted inside the LSD-150, fastened to the base plate of the machine. A two-meter CAT5 cable runs from the PC's Network Interface Card (NIC) to a bulkhead connector on the back of the LSD-150. One 1ft CAT5 cable connects the bulkhead connector to the EIBA5-100T/R switch inside the machine. Two separate 2 ft CAT5 cables run from the switch to the Galil motion control components, connecting the DC servomotors and 3-phase servos, the valves, pressure regulators, and the sensors. A camera interface board ("frame grabber") in the PC takes video input from the LSD-150's video microscope.
By linking the motors and other components to the Galil controller via Ethernet, Loomis Industries was able to reduce and simplify much of the cabling and in turn improve the level of diagnostic capability. "We can observe the input of each motor and drive and realize precisely what's happening at each machine position," Cook explained.
Conclusion
Commenting on his experience with Contemporary Controls, Cook said the company's Ethernet switch was a good fit due to it size, construction, and performance. "In addition, these switches are inexpensive; so I can stock several at a time, and I don't have to wait weeks to get them shipped to me," he explained.
"A reliable supplier benefits not only our company, but also our customers," Cook explained. "It helps our company to provide quality products and services for our customers, on time."
