WO1998047162A1

WO1998047162A1 - Subassembly and method for making devices such as keyboards

Info

Publication number: WO1998047162A1
Application number: PCT/FR1998/000711
Authority: WO
Inventors: Eugène Lecourtois
Original assignee: Nicomatic
Priority date: 1997-04-11
Filing date: 1998-04-08
Publication date: 1998-10-22
Also published as: FR2762134B1; FR2762134A1

Abstract

The invention concerns the manufacture of electrical devices, in particular a method for manufacturing devices comprising a circuit card (10) and a panel (24) between which are arranged components (16) and a spacer (12) which maintains the card (10) distant from the panel (24) and having openings (14) at the locations of the components. The method includes making a subassembly comprising the spacer (12), the components (16) and a device for maintaining the components, such as an adhesive film (18), consisting of steps for making a spacer (12) and fixing each component (16) into an opening (14), then in setting the subassembly on the card (10). The invention is applicable to the manufacture of keyboards.

Description

Sub-assembly and method for manufacturing devices such as keyboards

The present invention relates to a method of manufacturing electrical devices comprising a number of stacked elements, and in particular of keyboards of various types, and sub-assemblies useful for simplifying this manufacture.

The invention is described below with reference to a keyboard of the type in which flat but slightly domed metal springs, sometimes called "domes", are intended to make electrical contacts with a printed circuit board. However, the invention is not limited to these electrical devices alone, and it can be applied to the manufacture of other electrical devices in which components of one or more types are positioned relative to a circuit board. printed circuit board.

The domes keyboards have, as main elements, a printed circuit board on which is placed a spacer which delimits openings intended for the housing of the domes constituting the contacts of the keyboard. These domes are metallic while the spacer is insulating. A closure panel covers one spacer, on the side opposite the card, and comprises either separate operating members, such as keys, movable in translation in the closure panel and intended to exert pressure on the domes, or a flexible element by means of which a finger can exert a force on a dome placed below. A specific conductive part of the printed circuit board, the dome placed above in an opening of the spacer and an operating part guided by the closure panel are aligned in a direction perpendicular to the entire stack formed.

During the manufacture of these keyboards, one begins by positioning, on the printed circuit board, the spacer which thus ensures proper positioning of the openings relative to the conductive paths of the printed circuit board. The components are then placed, manually or by special machines, in the form of domes in the necessary openings, then the panel is applied exterior closure to maintain the domes in the openings. The outer closure panel is also positioned with respect to the stack so that the operating members which it positions (for example separate keys or which are part of a flexible element whose operating members carry alphanumeric characters) are aligned with the domes.

The above method has a drawback in that, when the domes have been placed in the openings of the spacer, they are not maintained and the slightest shock can cause them to exit, partially or completely, from the openings.

To remedy the aforementioned drawback and reduce the labor required, the domes have already been placed on an adhesive sheet so that all the domes of a keyboard, previously positioned on an adhesive film, are simultaneously housed in the openings 1 spacer already placed on the printed circuit board. The adhesive film is then used practically over its entire surface, on the one hand locally for retaining the components and on the other hand, between the components, for fixing the film to the spacer. Consequently, the domes must be placed on the adhesive film when it is completely uncovered. The handling of these adhesive films is then delicate. Indeed, the adhesive side can easily stick anywhere. In addition, given the flexibility of the film, the positioning of the adhesive film carrying the domes just above the openings of the spacer is not convenient. It sometimes happens that a movement in a direction parallel to the plane of the spacer for positioning the adhesive film carrying the domes causes a dome to be torn off from the adhesive film, so that the assembly becomes unusable. This delicate operation therefore requires two precise positions, on the one hand the positioning of the domes on the adhesive film at the locations provided for the openings of the spacer, and on the other hand, the overall positioning of the adhesive film carrying the domes on 1 ' spacer. In the case of the first aforementioned process, the industrialist who assembles the keyboards, if he wants to eliminate the manpower for positioning the domes, must be equipped with special machines for positioning the domes in the openings of the spacers. The aforementioned variant of the process in which the domes are glued to an adhesive film allows it to overcome this constraint and therefore not to use these laying machines. However, he must then use a special material for the installation of the flexible adhesive film carrying the domes in a well-defined position relative to the spacer.

The object of the invention is to remedy the drawbacks of the abovementioned methods and to allow an increase in the production rates and a reduction in the cost of the electrical devices in question, for example keyboards, by improving the manufacturing process. This improvement includes the production of a sub-assembly which does not only comprise a flexible adhesive film and domes, but which also comprises the spacer, in the openings of which the components are positioned, and possibly an electromagnetic screen and / or a flexible element carrying operating members. Alternatively, in place of the adhesive film, the components are mechanically retained in the openings. In the embodiment in which the components are retained in the openings of the spacer by an adhesive film, the problems of positioning the adhesive film carrying domes with respect to a spacer are solved because the domes are not placed on the adhesive film only after gluing the adhesive film to the spacer. The precise positioning of the adhesive film with respect to the spacer is therefore entirely superfluous, and it is not possible for domes to be moved from the openings since they are placed directly one by one in the openings of the spacer and are then retained directly.

More specifically, the invention relates to a method for manufacturing electrical devices of the type which comprises a circuit board carrying electrically conductive paths and a closure panel, between which are arranged components which cooperate with conductive paths of the card and which can be controlled by operating members guided by the closure panel, and a spacer having openings at the locations of the components; according to the invention, the method comprises the following stages: the selection of the spacer so that it keeps the card and the panel at a distance, the manufacture of a sub-assembly comprising the spacer, a part at the least of the components and a device for retaining these components at least in cooperation with the spacer, then the fitting of the sub-assembly on the card, with relative positioning of the spacer and of the card. Preferably, the manufacture of the sub-assembly comprises the following stages: the manufacture of a spacer having openings for all the components, and the fixing of at least part of the components in an opening each. In an advantageous embodiment, the step of manufacturing the sub-assembly includes the selection of a spacer having a thickness which corresponds to the thickness of the components, the cutting of the openings in the spacer, the bonding of a film. adhesive to one side of the spacer, and the introduction of components into at least some openings which lead to the other side so that the components introduced are held by bonding to the adhesive film.

In another embodiment, the fixing comprises the selection of a spacer having a thickness at least equal to the thickness of the thickest of the components to be introduced, the cutting of the openings in the spacer, the introduction of a part components at least in the spacer so that at least some components are retained by wedging in the openings, and the introduction of the components so that their face of cooperation with the card is at the surface of the spacer . The invention also relates to a sub-assembly of an electrical device intended for the implementation of a method according to one of the preceding paragraphs, and which comprises a spacer having openings, and components housed in at least part of the openings and practically not protruding from either side of the spacer.

In an advantageous embodiment, the thickness of the spacer is substantially equal to the height of the components, and the subassembly further comprises an adhesive film bonded to one face of the spacer and retaining a component by bonding to the film. in the openings.

Preferably, the film has a perforation in the center of the part which is opposite an opening. It is also advantageous that the film has at least one linear cut in the part which is opposite an opening.

In an advantageous embodiment, the subassembly further comprises an electromagnetic screen. This screen can be formed by an additional metallized film adjacent to the adhesive film, or by metallization of the adhesive film itself.

In a very advantageous embodiment, at least some components are elastic keyboard domes. In this embodiment, the sub-assembly preferably comprises a flexible element incorporated in the sub-assembly on the side opposite to the side of the spacer, the flexible element having at least one operating member disposed opposite an opening containing an elastic keyboard dome. Preferably, the flexible element comprises all of the keyboard operating members to be produced.

It is advantageous that the openings have a cylindrical shape of section corresponding to the configuration of the component. In a variant, the openings of the spacer have a shape of variable section along their length so that they wedge the components in only one part. It is also advantageous for the spacer to have channels connecting the openings.

Preferably, the spacer comprises a positioning device intended to cooperate with an additional positioning device for a circuit board carrying electrically conductive paths.

Other characteristics and advantages of the invention will emerge more clearly from the description which follows of an exemplary embodiment, made with reference to the appended drawings in which: FIG. 1 represents a section of an electrical device such as a keyboard domes; Figure 2 shows a section through a sub-assembly according to the invention; FIG. 3 represents a section of another sub-assembly according to the invention, comprising an additional element; FIG. 4 represents a section of another sub-assembly according to the invention, comprising one more element than the sub-assembly of FIG. 2; FIG. 5 represents a section of another sub-assembly according to the invention, comprising one more element than the sub-assembly of FIG. 3; and FIG. 6 is a plan view of an example of a spacer useful for implementing the invention.

FIG. 1 represents a diagrammatic section of a keyboard comprising contact domes. In FIG. 1, the reference 10 designates a printed circuit board having, on its upper face in FIG. 1, a drawing of conductive paths intended to be connected for example to a connector placed at the edge of the card 10. This card 10 is formed of any conventional material, for example an epoxy resin substrate loaded with glass fibers, although any other printed circuit board, of single-sided or double-sided type for example, can be used.

A spacer 12 is disposed flat on the upper face of the card 10. This spacer 12 has openings 14 corresponding to the components to be placed, that is to say domes in the example considered. This spacer 12 must simply determine a thickness which corresponds to the thickness of the domes 16. It is electrically insulating and preferably practically rigid, to ensure the spacing of the printed circuit and the operating members, but it can however have some flexibility. Preferably, it is a waterproof cardboard and treated so that it is rot-proof, but it can also be made of any suitable plastic material.

FIG. 6 represents an advantageous example of spacer 12, described below.

Domes 16 are placed in the openings 14. These are advantageously domes of the type described in international patent application No. WO-96/20799. These domes are particularly advantageous insofar as they cannot stick. They may be circular domes, with several branches, etc., having a hole or a projection in the central position, or any other embodiment. A film 18 has been shown glued to the spacer 12 and at the top of the domes 16 in FIG. 1, although this film is not essential. This has been indicated because it is representative of the process in which the domes 16 are glued to the adhesive film 18 before the domes are introduced into the spacer 12, according to the above-mentioned process which poses the problem indicated in the introduction.

The assembly then comprises a closure panel 24, which guides the operating members 22 of a flexible element 20 which bear inscriptions, for example figures, corresponding to the function of the dome 16 placed below. Flexible parts placed above the domes thus form "operating devices".

The film 18 is advantageously a known adhesive film, for example with a polyester or polyethylene terephthalate support, and the flexible element 20 is for example formed of an elastomer. The flexible element 20, the operating members 22 of which have a printing layer carrying the indications, such as alphanumeric characters, is retained on the inner face of a simple closure panel 24. The panel 24 is preferably formed from a hard impact-resistant plastic. Such a panel and flexible element are already used in the art and one skilled in the art knows the materials used for their production.

The features just described are known for the most part, and there are many variations. In the conventional manufacturing process, the spacer 12 is placed on the card 10, and the domes 16 are introduced by hand or by a laying machine. Then, the flexible element 20 and the panel 24 are put in place. In a variant of the process, the spacer 12 is positioned on the card 10, and a sub-assembly formed of the adhesive film 18 and of the domes 16, previously produced, is applied to the spacer 12, before positioning the flexible element 20 and panel 24. The disadvantages of each of these methods have been indicated in the introduction.

According to the invention, the problems posed by these known methods are resolved by making a sub-assembly as shown in one of FIGS. 2 to 5. It is noted that the sub-assembly shown in FIG. 2 includes the spacer 12, the adhesive film 18 and the domes 16 housed in the openings 14 of the spacer 12. The method of manufacturing this sub-assembly does not correspond to the steps used for the manufacture of the assembly shown in FIG. 1. In fact, during the manufacture of the sub-assembly of FIG. 2, the spacer, optionally cut beforehand so that it has the openings 14, is provided with the adhesive film 18. In an advantageous embodiment, the film 18 and 1 spacer 12 are already associated before the formation of the openings 14 which are simply cut by blade punches, according to a well known technique. Then, the method includes the positioning, manual or by laying machines, of the domes 16 in the openings 14, the sub-assembly obviously having at this moment a position opposite to that which is shown in FIG. 2. In this way, the domes are glued by their top with adhesive film 18 and are held in position.

It is advantageous for the adhesive film to have, at the center of each opening, a hole which allows the film to be bonded to the domes over the entire periphery of the hole, so that the total bonding surface of the domes is increased. In addition, slits can be formed in the film, in the part exposed by the openings, so that the film allows more movement of the domes glued to the film.

FIG. 3 represents another sub-assembly according to the invention. This sub-assembly comprises, in addition to that of FIG. 2, an additional film 26 forming an electromagnetic screen. This film can advantageously be formed from aluminized polyethylene terephthalate. In a variant not shown, such an electromagnetic screen is formed by aluminizing one face of the film constituting the adhesive film 18, preferably before it is made adhesive.

Figures 4 and 5 show other sub-assemblies according to the invention. They correspond respectively to the sub-assemblies of FIGS. 2 and 3, with an additional element which is the flexible element 20 provided with the operating members 22. This flexible element 20 is preferably glued to the adjacent film 18 or 26.

FIG. 6 represents an advantageous characteristic of the spacer 12 used in the sub-assembly of FIG. 2. It is noted, on this spacer 12, that the openings 14 intended to contain the domes are connected to each other by channels 22. From this manner, when a dome is inserted, the air contained in the corresponding opening 14, instead of resisting the depression of the dome, escapes towards the spaces of the adjacent openings 14 so that the overpressure is extremely reduced. It can even be canceled when, according to another variant, a channel 24 connects the interior space of the openings 14 to the exterior of the spacer.

With reference to FIGS. 2 to 5, sub-assemblies have been described in which the domes 16 have a height corresponding to the thickness of the spacer 12 and are held by an adhesive film 18. In another embodiment of embodiment, the means for fixing the domes 16 are not constituted by an adhesive film, such as the film 18, but on the contrary are formed by wedging the domes or components 16 in the openings 12 of cylindrical shape of any cross section. This jamming can be ensured at the normal edges of the components 16 or on the contrary on specially provided parts on these components.

In another variant, the components have a height less than the thickness of the spacer 12, and they are also wedged in the openings 14, which are not cylindrical, because they have appendages (arms or claws) formed especially for retaining the components on the spacer 12. The only condition is that the components are integral with the spacer 12 and have their working face practically at the face of the spacer 12 intended to come into contact of the printed circuit board 10, or slightly projecting.

Thus, the invention relates to a new method of manufacturing electrical devices, in particular of keyboards, and a sub-assembly intended for the implementation of this method. This sub-assembly has the advantage of being easily packaged and of avoiding delicate positioning steps during the manufacture of the electrical devices.

It is understood that the invention has only been described and shown as a preferential example and that any technical equivalence may be made in its constituent elements without going beyond its ambit.

Claims

1. A method of manufacturing electrical devices of the type which comprises a circuit board (10) carrying electrically conductive paths and a closure panel (24), between which are arranged components (16) which cooperate with paths card conductors which can be controlled by actuators guided by the closure panel, and a spacer (12) having openings (14) at the locations of the components, the method being characterized in that it comprises the steps following:

- selecting the spacer (12) so that it keeps the card (10) and the panel (24) at a distance,

the manufacture of a sub-assembly comprising the spacer (12), at least part of the components (16) and a device for retaining these components at least in cooperation with the spacer, then

- the installation of the sub-assembly on the card (10), with relative positioning of the spacer and the card.

2. Method according to claim 1, characterized in that the manufacturing step of the sub-assembly comprises the selection of a spacer (12) having a thickness which corresponds to the thickness of the components (16), the cutting of the openings (14) in the spacer (12) and gluing an adhesive film (18) to one face of the spacer (12), then the introduction of components (16) in at least some openings (14) which open on the other side so that the components introduced (16) are held by bonding to the adhesive film (18).

3. Sub-assembly of an electrical device intended for the implementation of a method according to one of claims 1 and 2, characterized in that it comprises:

- a spacer (12) having openings (14), and

- components (16) housed in at least part of the openings (14) and practically not projecting from either side of the spacer (12).

4. Sub-assembly according to claim 3, characterized in that the thickness of the spacer (12) is substantially equal to the height of the components (16), and the sub-assembly further comprises an adhesive film (18) glued to one face of the spacer (12) and retaining a component (16) by gluing to the film (18) in the openings (12).

5. Sub-assembly according to one of claims 3 and 4, characterized in that it further comprises an electromagnetic screen.

6. Sub-assembly according to claim 5, characterized in that the electromagnetic screen is formed of an additional metallized film adjacent to the adhesive film.

7. Sub-assembly according to claim 5, characterized in that the electromagnetic screen is formed from a metallization of the adhesive film.

8. Subassembly according to any one of claims 3 to 7, characterized in that certain components (16) at least are elastic keyboard domes.

9. Sub-assembly according to claim 8, characterized in that it further comprises a flexible element incorporated in the sub-assembly on the side opposite to the side of the spacer, the flexible element having at least one operating member disposed in face of an opening containing an elastic keyboard dome.

10. Sub-assembly according to any one of claims 4 to 7, characterized in that the spacer (12) comprises a positioning device intended to cooperate with an additional device for positioning a card (10) of the carrying circuit conductive paths of electricity.