22 August 2014

SemiLEDs launches Enhanced FlipChip LED series to maximize lumen density and simplify integration

LED chip and component maker SemiLEDs Corp of Hsinchu, Taiwan has announced sampling and volume availability of the first in its new Enhanced FlipChip (EF) LED series.

The series launches with the EF-B40, a blue 40-mil flip chip that simplifies the packaging and integration process by eliminating wire bonding while increasing both lumen density and decreasing the lumen-per-dollar value proposition, the firm claims, while enabling packagers to use standard surface-mount assembly techniques.

“SemiLEDs' unique flip chip approach combines a sapphire front surface and proprietary back side architecture that provides the electrical contacts exclusively on the bottom of the chip, making it fully compatible with chip-on-board (COB) surface-mount processes,” says Mark Tuttle, general manager for SemiLEDs Optoelectronics Co Ltd. “Eliminating wire bonds also lowers the profile of the chips, and allows them to be placed more closely together, which results in higher lumen density and reduces the complexity of the optics,” he adds. “The EF series is an ideal platform for COB assemblies, or really for any approach that calls for either secondary optic design or high-density mounting.”

Flip-chip construction presents what was originally the bottom sapphire layer in a horizontal LED structure as the top surface of the chip. By flipping the chip in this way, the electrical pads become part of the bottom of the device rather than running bonding wires from the top surface of the chip down to the package or board. Not only are delicate areas of the chip protected by the clear sapphire layer but, by eliminating wire bonds (arguably the most failure-prone part of any LED assembly), both reliability and overall design flexibility of the packaged device are increased. In addition, individual chips may be more closely mounted, opening the door to more densely packed arrays of LED chips. The nearly continuous light-emitting surface - unbroken by gaps, bonding wires, or top electrodes - can greatly simplify the mounting and mixing requirements of the optics, producing smooth lighting effects. In addition, in a flip-chip structure, the heat-generating junction is positioned adjacent to the substrate, increasing thermal conductivity and allowing improved device performance at high currents.

The EF-B40 is available in wavelengths of 445-460nm, with outputs of up to 300 lumens at 1A as a packaged emitter. The SAC-compatible chips are offered with standard Au bonding pads, or are available with an AuSn option to further reduce thermal resistance and add to system reliability. A 140-degree viewing angle makes the EF suitable for general and commercial lighting, while the lowered profile addresses the needs of LED backlight, smartphone flash or LED projector applications. The EF series of LED chips are RoHS compliant, with production quantities available now.

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