Tough competition between makers of electronic circuit chips for use on pc-boards has driven many dicing and packaging operations offshore. As a result, finished wafers are frequently stacked for shipment into containers, called jars, with interleafs placed between each wafer to protect the circuitry.
Today, removing wafers from cassettes and loading them into shipping jars is done either by hand, or with automated equipment. Manual operations are prone to circuit damage because only a narrow 2-3-mm deadzone at the wafer's edge is suitable for grasping. With wafer values ranging anywhere from a few hundred to thousands of dollars, one slip can be costly. Such damage, and counting errors, are driving the replacement of manual operations with automated systems. Though automated systems achieve greater throughputs and better counting accuracy, many cost $150,000 or more, and may require special jars and more expensive, non-porous interleaf materials, which increase the cost of operation.
A new, automated wafer-jar loader from Speedline Manufacturing Co. is bound to raise a few eyebrows in the semiconductor manufacturing technology arena with its innovative, non-vacuum interleaf feed mechanism, and an inverted cassette registration feature. Unlike some automated jar loaders that handle only newer shipping containers and interleaf materials, Speedline's unit supports all popular container and interleaf types. It also eliminates the need to rotate wafers during the jar loading operation. "Placing the wafer-holding cassette upside down eliminates the need for a robotic wafer-flipping mechanism," says Speedline President and Chief Designer Frank Linker. "The result is a simpler, smaller, and lower cost machine."
Thinking upside down: Registering the cassette with the H-bar facing up orients the wafers properly for loading into the shipping jar.
In some instances, according to Linker, suppliers of automated jar loading systems require users to buy their containers. "Buying one of these machines is similar to buying a copier that operates only with the copier manufacturer's paper," he explains. In contrast, Linker designed Speedline's wafer jar loader, Model 325-6000, to support newer containers and interleafs, as well as the older and lower cost ones. "Shipping containers and interleafs should be selected based on merit," Linker says, "not the automation equipment used."
Thanks to a patent-pending, non-vacuum, interleaf feed that operates like a copier paper supply mechanism designed to strip off a single round leaf at a time, Linker's design handles both porous (Tyvek«) or nonporous, carbon-based interleafs. "Either style runs equally well," Linker says, "which means users are not locked into using one type of interleaf over another."
Linear guide bearings from THK America (Schaumburg, IL) support the vacuum pick-and-place arm on the horizontal x-axis and the z-axis that moves the wafer cassette platform up and down. Leadscrews from BSA (San Jose, CA) drive the loads, and motion chipsets from Performance Motion Devices (Lincoln, MA) coordinate the motion of Alpha-step motors from Oriental Motor USA Corp. (Torrance, CA). An embedded controller board from Tern Inc. (Davis, CA) controls overall machine operation. The machine has a built-in vacuum generator powered by a miniature scroll compressor from Air Squared (Hamilton, OH).
Before starting the machine, the operator fills the interleaf chamber, and places any common container up to 3-1/8-inches deep on a special pull-out shelf. After loading any popular style wafer cassette onto the cassette platform, the operator hits the start button next to the control panel from Maple Systems (Everett, WA) to set the machine in action.
Prior to unloading a wafer from the cassette, dc motors from Maxon Precision Motors (Burlingame, CA) kick in to drive the interleaf feed mechanism, feeding a leaf into the chute that accurately and gently inserts it into the bottom of the shipping jar. Another leaf is then fed into the top of the chute, where it is held until a wafer is inserted into the jar.
Meanwhile, the vacuum cup moves into position over the wafer cassette. The cassette platform raises up until the cup contacts the top wafer. Once the wafer contacts the cup and the vacuum takes hold, the cassette platform moves down just enough to center the wafer between its supporting rungs. After the pick-and-place arm moves over the top of the jar, the vacuum switches off, and the wafer gently drops into the jar. The interleaf at the top of the chute is released on top of the wafer, and the whole sequence starts again. The process continues until the wafer cassette is empty, or the jar is full.
While the unit is being beta tested, Linker has been busy increasing its size slightly to support 200-mm wafers. The size increase, approximately 13 inches in length and 2 inches in height, according to Linker, will also open up some real estate and allow for an optional integrated OCR (Optical Character Recognition) vision system that will provide customers with 100% traceability by recording each wafer as it is loaded.
|Contact Frank Linker, Speedline Manufacturing Co., 1820 Springvalley Dr., Springfield, PA 19064; Tel: (610) 604-9932; Fax: (610) 328-6357; E-mail: firstname.lastname@example.org; or Enter 501.