DE8313473U1 - Keypad - Google Patents

Description

SAMSON 1 BULOW PATENT LAW FIRM WIDENMAVERSTR i ΟΘ000 MUNICH 22 Applicant

Wilhelm Ruf KG Schwanthaler Strasse 18

8000 Munich 2

YOUR CHARACTER / YOUH REF OUR SIGN / OUR HEF

DATE

R 10/28-B 83 Pat / Gm
vB / dv

August 18, 1986

Keypad G 8313 473.5

The innovation relates to a keypad according to the preamble of claim 1.

Such keypads are commercially available and are characterized by their flat design and low manufacturing costs the end.

In order to prevent unintentional closing of the respective switches of the key field, is between the base plate with conductor tracks and switch contact surfaces and the flexible

le switching foil, which opposite the switching contacts has a coating of electrically conductive material (Kon- J tact area), an intermediate insulating layer in the form S

a film is provided which has openings only in the area of the switching contacts. The switch contact foil is used thus as a spacer between the switch contacts and the contact surface. To operate the respective switch mechanical pressure is exerted on the switching membrane, so that the contact surface attached to it through the said The recess of the insulating layer reaches through and touches the associated switching contacts and thus electrically with one another connects.

The disadvantage of this known keypad is the described intermediate insulation layer in the form of a film. she must namely be made with separate tools, be correctly aligned when assembling the keypad and secured by special measures against slipping during operation. 20th

The present invention is intended to eliminate these disadvantages.

The task of the innovation is therefore to improve the keypad of the type mentioned so that its Operational reliability is increased.

This task is carried out by the characterizing part of the protection claim 1 specified features solved.

Advantageous design and development of the innovation can be found in the subclaims.

The innovation makes use of the fact that in the production of keypads of the type mentioned above, certain layers are fixed on the base plate with the ——— w * s— <■ - conductor tracks by photolithography

techniques or by screen printing. In particular, these are insulation layers in the area of conductor track bridges or crossings. At the same time as the application of these insulation layers, which are necessary anyway, those insulation layers are now also applied in the innovation that are implemented in the known keypad through the film with openings.

In the following, the innovation is based on exemplary embodiments explained in more detail in connection with the drawing. It shows:

Figure 1 is a schematic sectional view of the keypad according to the innovation in the area of a switching contact (Section along line I-I of Figure 2)

FIG. 2 shows a plan view of the detail from FIG. 1;

FIG. 3 shows a modified embodiment according to FIG. 1; 20th

FIG. 4 a shows a pattern of a first insulation layer;

FIG. 4 shows a pattern of a second insulation layer which is applied to the first insulation layer of Figure 4 A; and

FIG. 4 c shows a pattern of an electrically conductive layer which is applied to the two insulation layers according to FIG Figure 4 A and Figure 4 B is applied. 30th

The same reference symbols in the individual figures denote the same parts.

In Figures 1 to 3, the section of a base plate (1) is made of electrically insulating material such as hard paper or plastic shown on which switching contacts (2 and 3), which form a switching contact pair, applied are. The switching contacts (2 and 3) exist for example

I ··· · «k · ft ι

-4-

made of an electrically conductive carbon layer that is applied by screen printing. In the top view these are Switching contacts usually semicircular, with their mutually facing edges (12) at a distance (7) from one another lie.

There is an intermediate insulation layer around a pair of switching contacts (2, 3) (4) arranged in such a way that they connect the two switching contacts (2 and 3) of a pair to the outer one Edges partially overlapped. The intermediate insulation layer (4) thus has the shape of a disk in plan view, which has a substantially circular central recess (10), whereby certain areas of the Scha.ltkontakte (2 and 3) are not covered and therefore accessible from above. Is above the structure described so far now a switching foil (5) made of electrically non-conductive and flexible material, this switching foil (5) in the In the area of the recess (10) of the intermediate insulation layer (4), an electrically conductive layer, hereinafter referred to as a contact surface (6) called, carries. This contact surface (6) can be, for example, a carbon layer on the foil is printed on.

In the exemplary embodiment in FIG. 1, the diameter dj> r Contact surface (6) smaller than the diameter of the recess (10). Thus, only the switching foil (5) is on the Edges of the intermediate insulation layer (4), while the contact surface (6) completely into the recess (10) protrudes. It can be seen that the intermediate insulation layer (4) acts as a spacer, in the technical argon also a spacer called, serves and thus prevents unintentional closing of the switch.

In the embodiment of Figure 3, however, is the diameter the contact surface (6) larger than the diameter of the recess (10), so that the outer edges of the contact surface (6) rests on the edge of the intermediate insulation layer (4) surrounding the recess (10). This is

-δ- the distance between the contact surface (6) and the switching contacts (2 and 3) is slightly larger than in the embodiment of FIG.

The switching contacts (2 and 3) of a switching contact pair are each electrically connected to a conductor track (8) or (9), as is generally known in the prior art. The switching contacts are also beveled in the transition area between the straight edges (12) and their circular outer contour, as can be seen from FIG. 2 with reference number (11).

The actuation of the respective switch takes place in that in the area of a switching contact pair a mechanical Force is exerted on the switching foil (5). This wire the contact surface (6) is pushed so far downwards with sufficient force that both switch contact surfaces (2nd and 3) touches so that an electrical connection is made, which ultimately leads to the conductor tracks (8 and 9) are electrically connected to each other. The contact surface (6) is also here to a certain extent flexible, so that there is no risk of cracks or breaks. :

In Figures 1 and 3 is in the transition area between the outer circumference of the switching contacts (2 and 3) and the intermediate insulation layer (4) a small cavity is shown. In practice this cavity does not exist. Rather, it will be filled with the intermediate insulation layer.

Furthermore, FIGS. 1 to 3 each show that the intermediate insulation layer (4) is the switching contacts (2 and 3) partially covered. According to a variant of the innovation, the recess (10) of the intermediate insulation layer (4) also be so large that no such overlap takes place. Of course, the layer thickness must be the 7, we can see that 1 at ion layer (4) will be larger in this case

than the layer thickness of the switching contacts (2 and 3), so that the intermediate insulation layer (4) can fulfill its task as a spacer.

j The manufacture of the keypad will now be described. The intermediate insulation layer (4) is applied from insulating varnish, for example printed on by means of screen printing. In the figures 4 a to 4 c print samples of a specific embodiment are shown. FIG. 4 a shows the printing pattern for a first intermediate insulation layer (13) which is printed onto a base plate provided with conductor tracks. This pattern has different recesses for switching contacts and for bridges. As an example, two essentially circular recesses (14 and 15) are designated for switching contacts and rectangular recesses (16 and 17) for conductor track crossings or bridges, the two recesses (16 and 17) lying exactly over sections of two conductor tracks that later through a bridge should be connected to each other. Furthermore, a recess (19) is provided which leaves solder connection points free. Finally, an alignment mark (18) is also shown, which enables the further layers to be aligned during subsequent printing processes. Otherwise, the first intermediate insulation layer (13) completely covers the base plate and the conductor tracks applied to it. After this first intermediate insulation layer (13) has been applied, a second intermediate insulation layer is applied in accordance with FIG. 4b. This intermediate insulation layer forms, on the one hand, further spacers (24 and 25) around the recesses (14 and 15) of FIG. The section of the second insulation layer denoted by the reference numeral 26 then covers the area of the first insulation layer (13) lying between the openings (L6 and 17). Correspondingly, the section labeled 27 of the second insulation layer covers the section of the first insulation layer (13) which is between

the recess (17) and the recess located to the right of it with FIG. 4 a .

In a third printing process, the pattern of FIG. 4c is then printed on from electrically conductive material, for example in the form of a carbon layer. The two pairs of switching contacts (34 and 35) are then pressed into the openings formed by the spacers (24 and 25) and the recess (14 and 15), while the section 36, the recesses (16, 17 and 20) and thus the connecting bare conductor tracks underneath.

Analogously to the adjustment point (18), the layers in FIG. 4 b and FIG. 4 c also have corresponding adjustment points (28 or 38).

Instead of the two layers of FIGS. 4 a and 4 b, a single layer with either the shape of the Figure 4a or the shape of Figure 4b can be printed.

However, this must then be thicker than the two layers described in FIG. 4 a and FIG. 4 b. However, it is it is nevertheless advantageous to apply the two intermediate insulation layers of FIG. 4 a and FIG. 4 b, since in particular Small imperfections in the area of the conductor track bridges when only one intermediate insulation layer is applied, for example, dust particles can occur, which then destroy the insulation, which is the case with subsequent Formation of the conductor track bridges can lead to short circuits.

Although it is preferred to apply the individual layers by screen printing, other known application methods can also be used are used, preferably photolithographic processes, in which first the entire surface with a photosensitive, electrically insulating lacquer is coated, then covered with a mask and is exposed and then developed, so that during the development process the unexposed or the exposed, d. H. those covered or not covered by the mask

covered areas are removed, so that then ultimately the pattern of FIG. 4a is produced.

Instead of being printed on, the intermediate insulation layers can also be glued on, for example by means of self-adhesive insulating layers which have the configuration of FIG. 4a or that of FIG. 4b.

In practice, the thickness of the intermediate insulation layer is approx. 30It. In the exemplary embodiment in the figure, the first intermediate insulation layer (13) also serves as a “solder stop”. During the later soldering process, it is thus prevented in a manner known per se that the solder penetrates into areas which are covered by the intermediate insulation layer.

Claims (6)

SAMSON ^: & BÜLOW *. F.awnSAMSON-HMMELSTJERNA IMOOO MUNICH l ^ ^T PATENT LAW FIRM AT CKPL-NQ., DiPL-WWTSCH-NG TELEX: 521 4940 egu d TELEFAX: OMOS »4 BS Applicant: Wilhelm Ruf KG
Schwanthal er Strasse 18 8000 Munich 2 R 10/28-B 83 Gm July 25, 1986 vB / dv File number: G 83 13 473.5 Keypad ;; Protection claims ^ 1. Keypad with eiru.r base plate, with switch- [contacts that are arranged in pairs at a distance from one another and are each electrically connected to a conductor track, with a ;. Intermediate insulation layer, which is at least in the area of the has clock recesses, and with a switching foil, the opposite the switching contacts have a coating of electrically conductive material (contact surface), characterized in that that the intermediate insulation layer (4) is firmly applied to the base plate (1). 2. Keypad according to claim 1, characterized in that the intermediate insulation layer (4) is arranged in a ring around the switching contact pairs (2, 3). Il III · · · · · · · IJ · ■ · ι ) 1 1 I ■ · · 1 I · · t ■ Il I · · ■ i <111 * I -Z- 3. Keypad according to claim 2, characterized in that the intermediate insulation layer (4) the switching contact pairs (2, 3) overlaps their outer edges in the area. f 5 4. Keypad according to one of claims 1 to 3, characterized in that the recesses (10) of the intermediate insulation layer (4) for the switching contacts have a smaller opening width than the outer diameter of the contact surface (6). 5. Keypad according to one of claims 1 to 4, characterized in that the intermediate insulation layer (4) made of zv /.- i Layers (13, 24- ^ 6), the second layer being arranged in a ring around the switching contact pairs (2, 3) and as a spacer between the attached to the switching foil (5) brought contact surface (6) and the associated switching contact pair (2, 3) serves. 6. Keypad according to claim 5, characterized in that the first layer (13) of the intermediate insulation layer (4) the Baseplate with conductor tracks essentially covered over the whole area with the exception of recesses (14, 15, 16, 17, 19) for switching contacts, connections "for soldering points and connections" for conductor track bridges, and that the second layer (24-26) only annular areas (24, 25) around the switching contacts and Areas (26, 27) covers that are to be insulated for the formation of conductor track bridges. 30th 35