ROHM Semiconductor of Kyoto, Japan has launched what it claims is the industry’s smallest class (1608 size) of two-color chip LEDs. The SML-D22MUW also features a special design that is said to improve reliability along with a backside electrode configuration that supports high-resolution displays.
In recent years, chip LEDs have increasingly been used for numerical displays in industrial equipment and consumer devices. Conventional numerical displays use a single color to indicate numbers, but there is a growing need to change the color to make it easier to recognize abnormalities. However, this typically entails using two separate LEDs (doubling the mounting area, along with development costs) or opting for a standard two-color LED (which also increases board size).
In contrast, ROHM says that, in addition to chip miniaturization, the SML-D22MUW leverages proprietary PicoLED mounting and wire bonding technologies and processes to integrate the two chips (red and green) in a compact 1.6mm x 0.8mm package – the same size as conventional single-color LEDs. This makes it possible to emit multiple colors in a smaller footprint. Board space is reduced by 35% over standard 1.5mm x 1.3mm two-color LEDs, contributing to thinner displays.
In addition, the extremely close configuration of color elements results in color mixing properties that make it possible to produce not only red and green colors but a number of intermediate colors as well.
Also, after taking into consideration usage conditions during reflow, countermeasures were adopted. Incorporating a stopper resist before the gold plating process blocks the gold pattern (that features good wettability). This prevents solder penetration into the resin, eliminating failures due to short circuits and contributing to greater reliability.
Finally, adopting a backside electrode design allows mounting in narrow spaces, enabling high-definition display in dot matrix and other applications.
The SML-D22MUW is priced at $0.136 each in 3000-unit quantities.