At the same time that Bosch Sensortec announced its orientation sensor, they also announced their BMA355 accelerometer, which is distinguished by its size. Prior to this, the smallest footprint available for an accelerometer was 2×2 mm2. This guy is 1.2×1.5 mm2.
This was done via a die shrink. The MEMS is placed over the ASIC; the ASIC is more or less bonded straight down to its leads; it’s essentially chip-scale packaging.
In fact, they could have made the ASIC even smaller, but they were limited by a couple things:
– The pad pitch is limited to 0.4 mm, which is standard at this point (smaller pitches are possible, but they’re considered specialized). So they’re now officially pad-limited.
– They need to be able to put the MEMS chip on top of the ASIC and bond it down; that also sets a size constraint.
Size notwithstanding, they still include the standard interrupts, including motion on/off, double-tap, tilt, and shock. You can find more info in their release.