Small transistors reduce footprint in smartphones, wearables

March 13, 2014 // By Jean-Pierre Joosting
The VML0604 from ROHM Semiconductor claims to be the smallest transistor in the industry ans is available in a 0.6 mm x 0.4 mm x 0.36 mm package.

The transistor reduces board space by 50% compared with alternative offerings, making it ideal for smartphones and other devices requiring smaller, thinner form factors.

For transistors in particular, in addition to technical challenges such as bonding stability and package processing accuracy, it has been especially difficult to decrease transistor size, resulting in higher ON resistances and maximum voltages in the 20 V range. ROHM, however, was able to successfully reduce package size and ON resistance while improving voltage resistance up to 60 V, providing breakthrough performance and reliability.

New high precision package and transistor processes, combined with internal structure optimization, have allowed ROHM to successfully develop the smallest transistor package in the industry. This new package will be expanded to small-signal MOSFETs, contributing to increased space-savings in a variety of offerings.

As devices become smaller substrate mounting becomes increasingly difficult. In response, ROHM has maintained a 0.2 mm terminal gap that facilitates mounting using existing equipment.

Decreasing package dimensions places a limit on element size. As the transistor size decreases, ON resistance increases dramatically, making it difficult to maintain the performance of conventional small-signal transistors.
However, adopting a new process makes it possible to develop ultra-compact transistors featuring a maximum voltage of 30 V along with industry-leading 0.25 ohm ON resistance (VGS of 4.5 V).