Push button disposition on a circuit board.

p0001The invention relates to a push button arrangement on a circuit board. In such applications, as they are for example used in panel construction, the switch contact is produced via a snap-action disc, which is embedded in a spacer, and is protected by a cover against external attack.

p0002Several of these pushbuttons arrangements are summarized generally to keypads in PCBs. There are known pushbuttons arrangements in which the switching contact is produced via a snap disk directly to the conductor tracks of a printed circuit board. The circuit board is covered with a spacer which has recesses for embedding these domes. A cover film is pulled over the recessed domes in order to secure them in the respective recesses and to protect from contamination. The operation of the contact is done by hand, by the snap disc is depressed usually with a finger through the elastic cover therethrough. In this embodiment, the cover can be deformed as far as is consistent with the cavities under the cover sheet. Furthermore, arrangements are known in which individual pushbuttons, which are provided with protective caps, are placed as a separate switch on the circuit board, which an undesirable greater height due and additional electrical connections such as solder joints, conditionally.

p0003Compared to patch individual keys, the former arrangement is characterized by low height. The partially hollow lying cover is exposed to enormous loads, which can cause damage to the cover when the operation of the snap disk does not take place in the center or with a pointed object. Similarly, the snap disk can be plastically deformed. The body contact with the electrical potential of the snap disk is possible through the damaged cover through which a hand may result because of static charges for damage to sensitive electronic components on the other hand is not reasonable for the operator.

p0004The object underlying the invention task is to create pressure keypads in printed circuit boards, which are protected against mechanical damage and against physical contact with the electrical potential of the switching contact. According to the invention this object is achieved by the fact that the spacer of the same or similar material as the printed circuit board, and in that the snap disc is completely covered by a transparent protective cover.

p0005Thus, the invention while maintaining a low overall height allows to keep the user-related charges of cover sheets and domes so limited that no translations stresses and destruction occur. This additional contamination of the switching contacts can be prevented.

p0006For centering of the snap domes, it is advantageous when the snap disc is provided with at least two projecting tabs which engage in recesses in the printed circuit board.

p0007For an individual illumination of the pushbutton can be provided, the snap disk with recesses and / or the printed circuit board with recesses for the passage of light.

p0008The use of printed circuit boards is the possibility to increase the thickness of the spacer to greater than 1 mm and employ protection caps in spite of small overall height.

p0009The invention is illustrated below with the aid of an embodiment in conjunction with the drawings.<ul><li>FIG. 1 is a schematic sectional perspective view through an inventive push-button assembly in a printed circuit board and</li><li>FIG. 2 is a reduced scale a plan view without cover and without cover.</li></ul>

p0010In the figures, a push-button assembly is illustrated in a circuit board, which consists in its basic structure of a circuit board 1 with conductor tracks 6 and a snap disk 5, which rests on the one hand on the interconnects 6 and in the circuit board 1 and on the other hand in their movement from an overlapping protective cap 4 is limited, which is held by a cover 3 in a recess of the spacer second

p0011According to the invention, there is provided with recesses spacer 2 of a circuit board, which is connected via a tie tight to the circuit board 1 and on the opposite side with the cover. 3 The deformation of the cover 3 and the snap disc 5 is limited by the range of motion of lying in the recess of the spacer 2 cap. 4 The position of the snap-action disc 5 is secured by two protruding tabs 11, which engage in the recesses 10 of the printed circuit board first Under the circuit board 1, a light source 9 is attached, the enlightened by the Ausnehmnung 7 of the circuit board 1 and through the recess 8 on the snap disc 5 the cap 4 and the cover. 3