NEW YORK — Chip-scale packages (CSPs) could be in short supply next year if its Direct Rambus DRAMs (D-RDRAMs) are quickly adopted, warned Rambus Inc. chief executive officer Geoff Tate. Rambus said it hopes that its 10 RDRAM licensees will ship between 100 million and 200 million D-RDRAMs next year. For density and electrical reasons, Rambus designed its D-RDRAM with chip-scale packaging, but few of Rambus' 14 DRAM partners have installed volume CSP production capability, Tate said.

Concern about a possible shortage in CSPs was shared by Paul Hoffman, vice president of advanced development at Amkor Electronics Inc. (Chandler, Ariz.). "We're producing 300,000 to 400,000 CSPs per week, probably second in the Tessera-style parts," he said. "We're meeting demand, but we're doing SRAMs and flash memory, not DRAM. When demand for Rambus chips kicks in, there could be a situation where there are shortages for a while."

Chip-scale usage is growing sharply because the technology provides significant decreases in size, yet is still easy to handle. CSPs are only 1.2 times the size of ICs or smaller, and consume far less space than any alternative other than flip chip. They come lightly coated in protective material, which makes them somewhat larger but easy to handle. Smaller flip chips require special handling equipment because the dice are unpackaged.

Tate said the CSP approach is currently about 50 percent more expensive than a TSOP (thin small-outline package). Packaging accounts for about 10 percent of the cost of the finished chip, so the CSP premium is about 5 percent. That should disappear in several years, he said, arguing that the tiny BGA package is "fundamentally no more expensive than a TSOP."

Samsung Electronics uses CSPs for its flash production in Korea, and Fujitsu Ltd. also uses the microBGA-type CSPs for flash chips used in cellular phones and small systems.

Hyundai Electronics' packaging subsidiary, ChipPac Inc. (Santa Clara, Calif.), is installing volume CSP capability. ChipPac has announced plans to drop costs from around 2 to 3 cents per I/O to 1 to 1.5 cents by the second half of 1999. Though ChipPac is reportedly being spun off as the Korean company struggles for cash, it highlights the fevered pace in CSP. It was set up as an independent company last September when it became clear there was too much activity to leave it as part of another Hyundai operation.

"For the DRAM companies that don't also have flash production capability, CSPs present more of a learning curve," said Tate. During a round of meetings with investors and the media here, he said Rambus is characterizing the D-RDRAMs from four early producers: LG Semicon, NEC, Samsung and Toshiba. The initial goal is to get the Rambus modules, or RIMMs, ready for the early adopters that seek their faster performance. Intel expects system companies to begin shipping desktops with the Rambus architecture sometime in 1999.

However, Tate said price is as important as performance. The RDRAMs have 72 pins, or BGA-type I/Os, and the number of pins on the memory controller can be far less. Using wide buses to get equivalent performance with SDRAMs increases the controller package to more than 500 pins, Tate said.

For a year analysts have been saying that manufacturing capabilities might lag behind demand, and the quick takeoff of yet another major program will only increase the potential gap.

"Capacity is the big issue for chip-scale packages," said Jan Vardaman, president of TechSearch International (Austin, Texas), a consulting company. "The biggest problem with the microBGA from Tessera has been capacity. Fortunately, a lot more has come on line lately. Still, Intel and Rambus could dominate the entire microBGA capacity."

Even without the new thrust in this type of memory, CSP use is skyrocketing. Intel and AMD have been packaging their flash chips in CSP for a year or so, and the number of system makers who have adopted that package is rising quickly. AMD uses technology developed by Fujitsu, and that's helped push Fujitsu's volumes up quickly.

"I would guess our production has gone up five times from 18 months ago," said Dennis Stephenson, director of advanced packaging technology at Fujitsu Microelectronics Inc. (San Jose, Calif.). "The big driver is wireless mobile communications. Every cell phone made in the last year has several CSPs, and there are lots of little CSPs in convergence products like the Pilot."

Intel's flash chips, like Rambus memories, are packaged in the microBGA developed by Tessera (San Jose). Though that package has been around for years and is licensed by several manufacturers, volumes are still emerging. Of Tessera's 29 licensees, so far only those who provide Intel with the packages for its flash products have gone to volume production.

Fujitsu makes 12 CSPs for different applications. Companies like Fujitsu and Sharp that make both chips and packages appear to have taken the volume lead, with help from licensees.

"The volumes today are in non-Tessera packages," Vardaman said. "There are tons of things other than memories. There are TI's DSP chips, lots of ASICs, some controllers. Plus, there are memories from several companies like Sharp that aren't in Tessera microBGAs."

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