By Ron Iscoff, Editor
When it comes to ICs and dispensing of encapsulants and underfills for ICs, the old saw, "There is nothing new under the sun," is not exactly true. While accuracy, repeatability, throughput and yield, continue as the industry's mantra for assembly equipment, user demands are getting tougher-especially for dispensing systems. Today's breed of automatic, integrated dispensing systems is smarter than ever, more software intensive, and typically represents a capital investment in the six figures for a basic, vanilla machine (see Figures 1-4). Even (or especially) the dispensing equipment makers agree that accuracy is close to the Holy Grail for users. "As targets become smaller and smaller, the key challenge continues to be volume placement accuracy," says Gary Helmers, vice president of Creative Automation's Dispensing Division, Sun Valley, Calif. 'Sculpting' Helmers adds that a new challenge is the need to "sculpt" a bead by increasing and decreasing the the density of dispensed shots (pixels). As IC packaging becomes smaller and loaded with more I/O, equipment providers are facing new challenges for increasing yield and throughput, concedes Bruno Miquel, product manager for Speedline's CAMALOT Division, Haverhill, Mass. "As packages become smaller, they also become more difficult to encapsulate with standard dispensing processes," Miquel adds. Machine advances, such as vacuum-assisted injection, he says, enable higher throughput, lower equipment cost and simplify process parameters.
Next-generation CSPs are calling for dot sizes as small as 0.010 inch (0.254 mm), or volumes as small as 1 mg. As a result, an integrated engineering approach to dispenser design is needed, says Swen Wedekin, vice president/GM of GPD Global, Grand Junction, Colo. "For dispensers, accuracy in one area of the system is not enough. Instead, the entire system must accommodate the accumulating tolerances, which are attributable to pump performance, control software, platform mechanics and other factors." Improved accuracy, repeatability and UPH are needed on next generation equipment, says Jonathon Greenwood, senior director of advanced product development at Amkor Technology Inc., Chandler, Ariz. One key challenge, he emphasizes, is the need for improved volume control on smaller devices, such as flip-chips. "As flip-chip die become smaller, the need to control the amount of underfill becomes even more critical." Increased Throughput Greenwood observes that even a needle drip can have a major impact on the total amount of material dispensed, causing downstream problems and failures. On the other hand, says Greenwood, "for large die applications, increased throughput is needed. As flow times increase, the need to get more material in process is critical." Multiple pumps and lanes are ways of achieving the added throughput needed for larger die devices, he says. When Greenwood buys a dispensing system, he looks for machine capability, repeatability and throughput. After he determines that the machine can handle the application, he examines pricing, programming/ flexibility and support.
K.H. Ong of the R&D Department at Carsem in Kuala Lumpur, Malaysia, looks for such features as an auto-needle changer, auto-valve pump cleaner to improve machine downtime, multiple dispense needed to improve UPH, and a high accuracy pump (ąplusmn;0.05 mg) for low volume underfilling for small die sizes (<6 mm2). Ong says the purchase of a dispensing system is influenced by features, and service/ technical support, followed by price and flexibility. It is likely that as package sizes continue their decline into the wafer level regions, demands by users will escalate nearly proportionately. |
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