Waterproof keyboard

A waterproof keyboard, comprising:

• a lower housing;
• a circuit membrane disposed on the lower housing;
• a pressure plate disposed on the circuit membrane, the pressure plate having a main body and a plurality of ridges protruded therefrom upwardly in a grid-like pattern, the main body having a plurality of openings, wherein the openings are surrounded independently and separated by the ridges;
• an elastomer member including a plurality of switch domes disposed in the respective openings, a base layer extending from the periphery of the switch domes at a predetermined distance from a bottom edge thereof, and a plurality of raised portions protruded upwardly from the base layer in grid-like pattern, wherein the base layer is disposed on the main body of the pressure plate, and the raised portions are disposed on the respective ridges;
• an upper housing having a plurality of guiding tubes disposed on the elastomer member;
• and
• a plurality of key caps, each key cap having a key stem formed on a bottom surface thereof, with each key stem passing through the respective guiding tube and abutting the respective switch dome;
• wherein the raised portions of the elastomer member and the ridges of the pressure plate are orderly arranged and fixed to a bottom surface of the upper housing, and the ridges are abutted against the underside of respective raised portions, wherein the elastomer member is disposed between the pressure plate and the upper housing.