To reduce infiltration of foreign matters such as dust into a key pad assembly for dials or functional buttons of mobile radio communication equipment.

This assembly comprises a printed circuit board 10 provided with contact patterns 12, a first sheet 30 on which a plurality of contact means 20 are arranged so as to make contact with the contact patterns 12 and a second sheet 40 having openings for the contact means and arranged between the first sheet and the board. The second sheet 40 has at least one air ventilating means 50 formed to ventilate air in a space between the contact patterns 12 and the contact means 20 for elastic operation of the contact means 20.