Keyswitch and keyboard thereof

A keyboard comprising:

• a board;
• and
• a plurality of keyswitches disposed on the board, at least one of the plurality of keyswitches comprising:
• a cap located above the board;
• a membrane circuit board disposed on the board, the board having a first engaging structure, a second engaging structure, a third engaging structure, and a fourth engaging structure corresponding to the at least one of the plurality of keyswitches, and the membrane circuit board having a first hole and a second hole formed corresponding to the first engaging structure and the second engaging structure respectively, to make the first engaging structure and the second engaging structure protrude from the first hole and the second hole respectively, wherein the membrane circuit board forms a third hole and a fourth hole respectively corresponding to the third engaging structure and the fourth engaging structure to make the third engaging structure and the fourth engaging structure protrude from the third hole and the fourth hole respectively, the third hole is separated from the first hole by a first interval portion along a sliding axis of the third engaging structure, and the fourth hole is separated from the second hole by a second interval portion along the sliding axis;
• and
• a lifting device connected to the cap and the board to make the cap movable relative to the board via the lifting device, the lifting device comprising:
• a first support member movably connected to the cap and having a pivot end portion, the pivot end portion being movably connected to the first engaging structure and the second engaging structure and having at least one first abutting portion extending toward at least one first edge of the first hole and at least one second edge of the second hole along a pivot axis of the first engaging structure, and the at least one first abutting portion abutting on the membrane circuit board to make the pivot end portion partially abut on the membrane circuit board for reducing an impact noise between the first support member and the board;
• and
• a second support member movably connected to the cap and the board, the second support member rotatably intersecting with the first support member, the second support member having a sliding end portion movably connected to the third engaging structure and the fourth engaging structure, the sliding end portion having a second abutting portion extending toward a third edge of the third hole and a fourth edge of the fourth hole along the pivot axis, and the second abutting portion abutting on the membrane circuit board for reducing an impact noise between the second support member and the board;
• wherein the membrane circuit board forms a first intermediate bridge portion and a second intermediate bridge portion along the pivot axis and adjacent to the first hole and the second hole respectively;
• wherein a sum of a first projection length of the at least one first abutting portion on the membrane circuit board along the pivot axis, a second projection length of the second abutting portion on the membrane circuit board along the pivot axis, and a third projection length of the first support member on the first interval portion, the second interval portion, the first intermediate bridge portion, and the second intermediate bridge portion along the sliding axis has a ratio greater than 0.4 compared to a projection perimeter of the lifting device on the membrane circuit board.