This part is a kind of semiconductor called 2SA1870.

Function of this product has High Speed Switching Transistor.

Manufacturers : Rohm

Image and pinout :

Some of the text within the PDF file :

Transistors 2SA1870 w w a D . w S a t e e h U 4 t m o .c w 308 w w .D t a S a e h t e U 4 .c m o (96-113-A325) w w w .D a t a e h S 4 t e U m o .c [ ... ]

2SA1870 PDF Datasheet Download