Key-press and backlight module unit thereof

The invention discloses a button and a backlight module thereof. The button comprises a printed circuit board, a contact part, a contact, an elastic plate switch, a light guide membrane and a light source, wherein the contact part is separately arranged with the printed circuit board; the contact is positioned on the side of the contact part facing to the printed circuit board; the elastic plate switch is positioned on the side of the printed circuit board facing to the contact and aligned with the contact; the light guide membrane is positioned between the printed circuit board and the contact, and the materials of the light guide membrane comprise transparent silica gel; and the light source is positioned on the lateral side of the light guide membrane. The invention also discloses a backlight module. The button is provided with the light source and the light guide membrane, so as to illuminate marks on the button and be more practical.