| Bottom Electrode Package MOSFETs Realize High Current and Miniaturization
| Features low ON resistance and reduced heat generation, smaller than SBD
Formation of stable solder fillets using wettable flank technology

Automotive cameras, which are essential for ADAS, face limitations in installation space, leading to a growing demand for miniaturization of onboard components. To meet these market demands, bottom-electrode package MOSFETs are attracting attention for their ability to achieve miniaturization while maintaining high current.

ROHM announced on the 23rd that it has developed the 'RV4xxx series', a 1.6mm × 1.6mm size MOSFET that ensures reliability after component mounting.

Schottky barrier diodes (SBDs) were the mainstream in the reverse connection protection circuits of existing ADAS camera modules. However, in the automotive electronics market, where cameras increasingly pursue higher resolution and high current is required, a transition to MOSFETs—which are smaller than SBDs—is being promoted due to their ability to reduce heat generation through low ON resistance.

For example, with a current of 2.0A and a power consumption of 0.6W, replacing it with a MOSFET in a terminal type package, which is widely used in the automotive electronics market, can reduce the mounting area by 30% compared to an SBD.

In the case of a MOSFET with a bottom electrode package, the bottom surface is an electrode, so heat dissipation is excellent, allowing for a small size and high current. Accordingly, the mounting area can be reduced by 78% compared to conventional SBDs and by 68% compared to conventional MOSFETs.

The RV4xxx series also has advantages in visual inspection. Visual inspection is also known as automated optical inspection and AOI (Automated Optical Inspection). It scans the board with a camera to inspect for missing components, quality defects, soldering status, etc.

In automotive components, visual inspection is performed after component mounting to ensure reliability. However, bottom electrode packages do not form sufficient solder fillets on the sides, making it impossible to secure the solder height required by automotive electronics. Consequently, there has been a challenge in that visual inspection of the soldering state after mounting is difficult.

The RV4xxx series is manufactured in accordance with the automotive electronics reliability standard AEC-Q101. In addition, by introducing ROHM's proprietary Wettable Flank forming technology, stable solder fillet formation is possible even with bottom electrode packages.

The wettable flank forming technology cuts the lead frame portion on the side of the package and performs plating processing. However, when cutting the lead frame, unnecessary parts in the form of metal protrusions occur more as the height of the cut surface increases.

To suppress unnecessary protrusions, ROHM developed a proprietary method of forming a barrier layer on the front of the lead frame. As a result, it is possible to prevent the product from tilting or soldering defects during component mounting, thereby guaranteeing a height of 130μm for the electrode portion on the side of the package with the DFN1616 package (1.6mm × 1.6mm). Consequently, the soldering condition can be reliably verified during visual inspection after component mounting.

"We will continue to develop small packages by utilizing wettable flank formation technology," said a ROHM official. "We will expand our product lineup to pursue high reliability in small sizes by expanding into bipolar transistors and diodes as well as MOSFETs."

Sample shipments of the RV4xxx series began in May, and mass production is scheduled to commence this September with a production capacity of 100,000 units per month.