SANTA CLARA, Calif. ( ChipWire/EET) -- National Semiconductor Corp. has developed a chip-scale package for analog circuits, called the micro SMD, that the company is touting as the preferred means for delivering standard linear components, such as op amps, comparators, data converters and voltage regulators.
Meanwhile, the Santa Clara-based Siliconix division of Vishay Intertechnology today announced that it is sampling power MOSFETsin a leadless, 1206 surface-mount package. The new ChipFET package occupies approximately half the board area ordinarily used by a leaded TSOP-6. This allows designers to shrink power-management circuitry for cell phones and notebook computers, according to Vishay Siliconix.
Like National's micro SMD, the Siliconix ChipFET package depends on thermal conduction between pc-board traces and solder dots to draw heat from a die when it is powered up on a board. Unlike the National approach, which uses a bumped die, Siliconix employs a lead frame in which the leads are folded under the encapsulated MOSFET die.
National's strategic marketing manager, Seamus Coyle, said the company was among the first to put op amps and data converters in SOT23 plastic packages. It also initiated the move to a smaller SC70 package, which wasn't much bigger than a pepper flake. But both of those packages put a semiconductor die on a metal lead frame encapsulated in plastic. "With the micro SMD, the die is the package," Coyle said.
The packaging requires die with solder bumps on a 0.5-mm pitch. It is essentially a "dumped die" surrounded with plastic, Coyle said. But by eliminating the Kovar lead frame, it can reduce the printed-circuit-board area occupied by an IC by as much as seven times. The five-lead SOT23 package, for example, is 10 times larger than the die it holds. The micro SMD will offer more package conformance with the actual die size.
In addition, because the bumps are more thermally conductive than Kovar lead frames, National will package some of its miniature power devices -- in particular some of its "Boomer" series of audio power amplifiers -- in the micro-SMD package. The popular LP2980 LDO, used by many portable phone makers, will be available in this package, Coyle said.
While the new package initially will cost a little more than larger ones, its increasing popularity in space-constrained applications like new-generation cellular handsets and PDAs will drive down the price. Ultimately, the selling price of the miniaturized package will compete with the costs of other plastic packages, Coyle said.
Mark Levi, who directs the analog marketing effort at National, said builders of large custom circuits, such as cell phone makers, will be among the best customers for analog in micro SMD. "It is difficult to put good analog elements on a digital ASIC chip," he said. "As geometries shrink, a certain amount of 'disintegration' makes sense. You can do 2.5-V analog, but maybe not on the same chip with 60 million noisy transistors clicking away," Levi said.
Though not on the same chip, the miniaturized packaging allows analog line drivers, receivers and other sensitive components to reside on the printed-circuit board right next to the ASIC -- without picking up their noise or absorbing additional space, Levi said.
Already, miniature packages like SOT23-5 and SC-70-5 account for 50% of the number of analog components shipped from National -- roughly 2 billion units a year, Levi said. Shipments of semiconductor "pick-and-place" machinery are good indicators of SMD use, Levi explained, adding that he foresees National shipping a billion micro-SMD units within the next five years.
Some of National's largest customers are interested in the package, Levi said. "We're in discussion with anyone who builds small, portable handheld devices." Cell phone makers like Ericsson, Motorola and Nokia are examining it, and Japanese manufacturers also have expressed interest in National's micro SMD-packaged audio devices, according to Coyle.
The new package will also affect manufacturing costs and delivery schedules, according to National. The semiconductor industry generally fabricates its devices in one location and ships wafers to other locations for devices to be assembled, packaged and tested. Since the lead-frame and wire-bonding processes are eliminated, the micro-SMD package can encourage one-plant manufacturing for analog semiconductors. At the very least, two weeks are cut from themanufacturing cycle time, Coyle said.