TECHNICAL FIELD

This invention relates in general to an apparatus for applying dome switch arrays onto substrates having switch sites, such as printed circuit boards, flex circuits or other materials, and more particularly to an apparatus for automatically and continuously taking dome switch arrays from a continuous release liner and applying them to switch sites on the substrates.

BACKGROUND ART Heretofore, it has been well known to utilize metal snap dome switches (referred generally as "domes" in the switch industry) in conjunction with printed circuit boards or flexible circuit assemblies for keyboards as disclosed in U.S. Patents Nos. 3,967,084; 4,042,439; 4,085,306, and other patents. Metal snap dome switches of the type referred to in this application take various configurations, depending on the use desired, and are made and sold by Data Entry Products, Inc. of Loveland, Colorado, the assignee of this application, under the trademark SNAP DOMES.

With respect to the manufacture of keyboards, it is also known to mount a plurality of domes on switch sites located on a printed circuit board, or other substrate having switch sites, by using a dome seal material having an adhesive surface with one or more domes prepositioned and oriented thereon so that a dome is placed and held in registry with each switch site. The domes and seal are collectively referred to herein as dome arrays. These dome arrays accordingly include a plurality of domes adhesively mounted in place on a substrate which is in the form of a thin film, sometimes called a "dome seal." The dome seal usually constitutes a sheet of die-cut polyester with

pressure-sensitive adhesive on the side contacting the domes which ultimately engages the printed circuit board or substrate having switch sites. The adhesive surface is protected against contamination by a release liner until the array is mounted on a board or substrate. Dome arrays mounted on release liners are also made and sold by Data Entry Products, Inc. under the trademark STIK-A-SWITCH. In the manufacture of keyboards, a dome array is then manually removed from the release liner and assembled with a substrate having a plurality of switch sites so that each dome aligns with a switch site and the dome seal adhesively engages the substrate. Thus, a dome array includes a plurality of domes on a dome seal that matches the pattern of switch sites on the substrate. This labor-intensive procedure of manually applying dome arrays to substrates has forced the use of less expensive domes made of plastic materials and other less labor intensive assemblies which do not produce the high-quality switching operation available with metal domes. Further, plastic domes cannot withstand the same temperatures as metal domes.

DISCLOSURE THE INVENTION The present invention overcomes the labor-intensive problems heretofore existing for the application of dome arrays to substrates having switch sites, such as printed circuit boards, flexible circuits and other materials. The present invention relates to an apparatus or machine that is capable of taking dome arrays (domes and a dome seal) from a supply of dome arrays and transferring the dome arrays from a backing or carrier, one or more at a time, onto a substrate to form a subassembly of a substrate with switch sites having domes in registry with each switch site. It will be understood that a dome array constitutes a substrate of material in the form of a film, such as a die-cut sheet of polyester, having a pressure-sensitive adhesive coating on one side, and a plurality of metal or plastic domes. It will be appreciated the film may be of an electrically

insulating material, or be of a conductive material to form an electrostatic discharge (ESD) shield, or part electrically insulating and part ESD shield. One or more domes are prepositioned in a pattern and oriented where necessary on the substrate, such that when the array is applied to a printed circuit board, the domes will correctly align and register with switch sites. In correct alignment, each dome will be operable with a switch site for manually closing a circuit by electrically connecting a pair of contacts. One acceptable film is a polyester film made by DuPont under the trademark Mylar, having a suitable thickness such as 0.002 inch with an adhesive coating of about 0.0008 inch thickness. Sometimes a thicker layer of adhesive is used. "Mylar" is a trademark of DuPont for polyester film. However, any suitable insulating film or material may be employed.

A supply of dome arrays may be in the form of a plurality of dome arrays mounted on a release liner or backing strip that is either wound on a reel or folded in a box. Preferably, the dome arrays are mounted on a release liner that is in the form of a carrier tape so that the dome arrays may be successively separated from the carrier tape or release liner at an application station of the apparatus and applied to a substrate. The apparatus also includes a conveyer for advancing substrate parts into and through the application station so that substrate sites will align with a dome array at a time when the dome array may be removed from the release liner and applied to the substrate site. A pick-and-place device is provided in the apparatus for picking and separating or peeling a dome array from the release liner and transferring it to a substrate site and thereafter laminating the array to the substrate. Suitable indexing of the substrate parts and the dome arrays will be accomplished by a controller that will ascertain the location of each at a time when the transfer and application function is to be completed.

BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a perspective view of the apparatus of the present invention in an enclosure to comply with proper safety standards and showing the inlet end of the substrate conveyer;

Fig. 2 is a perspective view similar to Fig. 1 but showing the outlet end of the substrate conveyer;

Fig. 3 is a front elevational machine with the enclosure removed to show the frame, the material feeder and the pick-and-place device;

Fig. 4 is an end elevational view of the machine with the enclosure removed to show the relationship between the pick-and-place device as it transfers dome arrays from the material feeder onto the substrates; Fig. 5 is a top plan view of the apparatus of the invention with the pick-and-place device removed for purposes of clarity and showing the heads of the pick-and- place device in phantom;

Figs. 6 to 11 are views illustrating the sequential operation of the apparatus of the invention;

Fig. 12 is a fragmentary enlarged top plan view of release liner with dome arrays mounted thereon;

Fig. 13 is a greatly enlarged cross-sectional view taken substantially along line 13-13 of Fig. 12 to illustrate the relationship between the release liner, a dome seal and a dome;

Fig. 14 is a front elevational view of a modified machine which includes only a single material feeder and a single head on the pick-and-place device for transferring a switch array from the material feeder onto a substrate and then laminating that switch array to the substrate;

Fig. 15 is an end elevational view of the machine in Figs. 14;

Fig. 16 is a top plan view of the machine in Fig. 14; Fig. 17 is an enlarged fragmentary view of the head that functions to transfer a dome array to a substrate and thereafter laminate the dome array to the substrate;

Fig. 18 is a greatly enlarged sectional view of the head taken substantially along line 18-18 of Fig. 17;

Fig. 19 is a partially fragmentary and partially diagrammatic perspective view of a further embodiment of the invention and particularly of the pick-and-place device having the end effector which removes the dome array from the carrier tape and transfers it to the substrate or printed circuit board;

Fig. 20 is an enlarged view of the top side of the end effector of the embodiment of Fig. 19 which attaches to the rotary drive motor;

Fig. 21 is a perspective view of the bottom side or array contacting side of the end effector of Fig. 19; and

Fig. 22 is a cross-sectional view taken substantially along line 22-22 of Fig. 20.

DESCRIPTION OF THE INVENTION The applicator machine or apparatus of the present invention, generally indicated by the numeral 15, includes generally a frame 16, as seen in Figs. 3 to 11, for supporting a substrate or printed circuit board conveyer 18, material feeders 20 and 21, and a pick-and-place device 23. While two feeders are illustrated, it should be appreciated the machine could be provided with only one feeder, as illustrated in Figs. 14 to 18. An enclosure 24, as seen in Figs. 1 and 2, encloses the conveyer, feeders and pick-and- place device so that an operator cannot contact the moving parts during operation of the machine and possibly sustain an injury. Once a panel is removed on the enclosure for maintenance, except for reloading a material feeder, suitable detecting switches will stop the machine if it has not already been stopped. With respect to a material feeder, it will automatically stop when the supply of dome arrays is exhausted, and can be reloaded without stopping the machine while the other feeder operates to provide arrays. The only openings in the enclosure are at opposite ends of the machine for the substrate or printed circuit

board conveyer, as seen in Figs. 1 and 2. An inlet opening 25 allows the conveyer to be suitably connected to a supply of substrates or printed circuit boards so that they may be continuously introduced into the machine. At the other end of the machine, an outlet opening 26 for the substrate or printed circuit board conveyer allows the processed substrates to be discharged from the machine.

The frame 16 may be enclosed by solid plexiglass panels in a dark gray or opaque color and which will then define the enclosure. These panels may be easily removed for servicing. Further, the plexiglass panels will protect the product from contamination as well as providing a safety barrier. The front top panel will be mounted for easier operator access to the inside of the machine for making tooling changes. For example, this front panel may be hinged and latched.

It will be appreciated that the drawings are generally diagrammatic. Many of the parts are of a standard type, such as used to make the conveyer and the pick-and- place device. It will be appreciated that the conveyer will receive substrates at the inlet end 25 from a stacker or any suitable pre-processing area.

The conveyer 18 is preferably an edge-belt conveyer system that engages the opposite edges of a substrate or circuit board 32 to leave the substrate upper face free for application of a dome array. The conveyer includes opposed movable belts 29 and 30 for engaging the opposite edges of substrates 32 and conveying the substrates from the inlet to the outlet end of the machine and through an applicator station 34. A suitable drive mechanism will be provided for the conveyer to produce intermittent movement and indexing as required to properly place a substrate part and substrate or printed circuit board site in a designated location. With respect to the substrate parts illustrated, each substrate part 32 includes a plurality of substrate sites

36a, 36b, 36c, 36d, 36e and 36f. Within each site there are a plurality of switch sites, each of which would ultimately

coact with a dome for operating the switch site. Thus, each substrate part 32 includes a plurality of substrate sites. Where the substrate sites are printed circuit board or flexible circuit sites, in the subsequent processing the sites would be separated from each other whereby each substrate and dome array mounted thereon would become part of a keyboard assembly. The conveyer 18 will move a substrate part into the applicator station and then index that part within the station as needed in order to place it in position for receiving a dome array.

As seen in Figs. 12 and 13, the dome arrays are provided on a release liner or carrier tape 38. The dome arrays are indicated by the numeral 40, and each includes a dome seal 41 having at least one dome switch and generally a plurality of dome switches or domes 42 mounted thereon. The domes may be made of metal or plastic. The dome seal 41 is provided with a pressure-sensitive adhesive coating 43 on the side to which the domes are mounted and which releasably attaches to the release liner or carrier tape 38. The substrate film or dome seal is of a suitable polyester, usually transparent. One form of acceptable substrate film is Mylar film made by DuPont. It may be appreciated that any number of domes may be provided on a precut substrate constituting the dome array 40. This will depend upon the design of the keyboard for which the dome array is to be used and also in connection with the substrate upon which the dome array is applied. Further, the domes will be arranged in a predetermined pattern and oriented, if necessary. It will now be understood that the substrate conveyer will move the substrate parts through the machine from the pre-processing area, as indicated by the part 32a, to the processing area at the. applicator station 34, as indicated by the part 32b, to the post-processing area, as indicated by the board part 32c. Depending on board or substrate size, there may not be a pre-processing area. The board or substrate would be input and moved directly to the processing area. Inasmuch as each substrate part includes a

plurality of substrate sites, the conveyer will suitably index the substrate part in the processing area until dome arrays are applied to each of the substrate sites.

Accordingly, the substrate part at the processing area is precisely positioned and held for placement of a dome array. During the placement of a dome array, a substrate support tool 44 is brought up against the bottom side of the substrate part to support the substrate during laminating of the dome array to the board. This support tool may be pneumatically powered into position at the time that the laminating process is being accomplished or also when the dome array is being placed on the substrate site.

Dual material feeders 46 and 48 are provided in this embodiment to feed dome arrays into position on a carrier tape release liner for application to the substrate parts. These feeders will handle material that is fan-folded in a box as well as rolled or wound on a reel. One feeder is operated at a time and when the supply of arrays is exhausted in that feeder, the other feeder is placed into operation. As previously mentioned, when the supply of arrays in a feeder is exhausted, it will automatically stop. Further, the other feeder will automatically be placed into operation. A signal will be given to the operator, who can replenish the supply of arrays in the empty feeder while the machine continues to operate. Inasmuch as the material comprises spaced-apart dome arrays on a release liner carrier tape, once a dome array is removed from the carrier tape, the carrier tape is advanced to bring the next dome array into position and the carrier tape is then rolled onto a take-up reel. Each feeder is mounted for reciprocal movement to properly position an array in position to be transferred to a circuit board. Suitable drive mechanisms move the feeder into position and advance the carrier tape release liner to properly position an array in place for transfer to a board.

The carrier tape with the dome arrays is advanced into the processing area for the applicator station and to a

position in alignment with the pick-and-place device 23. The pick-and-place device 23 includes a transfer head 50 and a laminating head 52. The transfer head includes a suitably driven shaft or rod 54 having a suction head 55 for engagement with a dome array. Preferably, the rod is driven by a servomotor, but other drive devices may be used. The transfer head 50 includes a suitable servomotor to vertically reciprocate the shaft 54 with the suction head 55 to pick up a dome array and move it to a substrate part. The suction head would be live or active during the transfer operation. Thus, the suction would be turned on when the head first engages a dome array mounted on the release liner, and turned off after placing the array on the substrate site. Both the transfer head 50 and the laminating head 52 are transversely slidable along a track 56 in order to move to the proper location for applying and laminating a dome array.

The laminating head 52 similarly includes a servomotor for vertically driving the rod 58. A laminating member 60 is mounted on the end of the rod or shaft 58. The laminating member is preferably of soft material to softly but firmly press the dome array against the substrate so that the exposed areas of the substrate having pressure- sensitive adhesive will contact and grip the substrate site and effectively laminate the dome array to the substrate. The laminating head, like the transfer head, is driven transverse the direction of the conveyer and when it is aligned with a particular substrate site having just received a dome array, the laminating member 60 will then be vertically driven downwardly to engage and laminate the array to the site. Suitable drive mechanisms will be provided to drive the transfer head and the laminating head. Preferably, these drive mechanisms will be electric servomotors to provide the precision movements for placing the elements in proper registry. The laminating member 60 may be made of a suitable resilient material, such as foamed latex and shaped he ispherically to first engage the dome

seal of the array in the central area and then spread to the outer areas to remove any air bubbles.

In operation, a substrate part is precisely positioned at the application station 34 and held for proper placement of the dome arrays. The first two substrate sites 36a and 36b are aligned with the pick-and-place device 23 so that both the transfer head 50 and the laminating head 52 will be able to process the substrate sites. At this point, the laminating head is in its home position as shown in Figs. 5 and 8, while the transfer head 50 is in alignment directly overhead of a dome array on the release liner carrier tape 38. The suction head 55 or the end effector is lowered to make contact with the dome array at this position. The vacuum is turned on in the end effector to cause the suction head to connect to the dome array. The material feeder or a peeler plate moves the release liner carrier tape in the direction opposite the movement of the conveyer so that where the carrier tape takes a sharp downward turn over a release liner roller, the liner will be effectively peeled or separated from the dome array which includes the domes and the dome seal or barrier. Where a peeler plate is employed, once the dome array is moved upwardly and away from the plate by the end effector, the peeler plate is moved back to its home position. When the dome array is free from the release liner, the transfer head raises the suction head to the correct position and then is driven transverse of the conveyer until the suction head is in the presentation position to one of the substrate sites. The head will be lowered to place the array on the site, and the vacuum will be turned off to release the grip of the head on the array. Normally, a dome array will be placed on the site farthest from the home position of the transfer head before it is returned for picking up a further dome array to apply to the substrate site closest to the home position of the transfer head. The home position of the transfer head is also shown in Fig. 5. Thus, a dome array may first be placed on the site 36b and thereafter on the

site 36a. It will be appreciated that the carrier tape is synchronized with the feeder and the carrier tape would be advanced following the separation of the dome array from the tape until it is in the correct position for the succeeding dome array to be engaged by the suction head of the transfer head and removed from the carrier tape.

Immediately following the deposit of the dome array onto the substrate site, laminating head 52 is driven into position over that site so that the laminating member 60 can be moved down into position to effect the lamination of the substrate to the substrate face and to assure the removal of any bubbles from between the substrate and the dome array. Following the laminating operation, the laminating head or plate 60 is raised and then returned to its home position. During the laminating function the substrate support tool 44 is raised into position beneath the substrate part to support the substrate during lamination.

Following the placement and lamination of dome arrays on sites 36a and 36b, the conveyer indexes to place into position the next succeeding substrate sites 36c and 36d. Similarly, the transfer head will successively place dome arrays on sites 36d and 36c, after which the laminating head will laminate the dome arrays to the sites. For purposes of illustrating the position of the transfer head 50 during the placement of a dome array onto a substrate site, reference is made to Figs. 6, 7 and 8. For purposes of illustrating the operation of the laminating head and illustrating its position for the laminating function, reference is made to Figs. 9, 10 and 11. Following the application of dome arrays on sites 36c and 36d of the substrate part 36, the conveyer indexes the part to align sites 36e and 36f with the pick-and-place device 23 so that the transfer head 50 can apply an array to one of the sites followed by the laminating function and thereafter to the other of the sites again followed by the laminating function. After the substrate part at the application station 34 has been properly processed so that a

dome array is in position on each of the substrate sites on the substrate part, the substrate part is driven by the substrate conveyer out of the application station and a further substrate part is driven into the application for successive application of dome arrays. Thus, the conveyer aligns the substrate sites of a substrate part with the pick-and-place device at the application station, while the material feeders align dome arrays successively with the transfer head. The operation of the material feeders, the substrate conveyer, and the pick-and-place device is synchronized and controlled by a computerized controller suitably programmed to handle the processing of the substrate parts and the dome arrays. Suitable sensors are provided to obtain precise positioning of the material feeder, the substrate conveyer, and the pick-and-place device so as to precisely place a dome array in position on a substrate site. It will be appreciated that the end effector or suction head on the transfer device will be sized in accordance with the dimensions of the dome array. Similarly, the laminating head will be sized to provide proper lamination of the dome array to a substrate. It will further be appreciated that the speed of operation of the machine may be varied in order to provide the most efficient speed of applying the dome arrays to the substrate parts.

A further embodiment of the invention is shown in Figs. 14 to 18 which differs from the embodiment of Figs. 1 to 11 in that only a single material feeder is provided and only a single head is provided for transferring dome arrays from the material feeder onto a substrate and then laminating the dome arrays to the substrate. The machine of Figs. 14 to 18 is generally designated by the numeral 15A and includes a single material feeder 66 with a pick-and- place device 23a having a single head 70 for transferring a dome array from the material feeder to a substrate carried by the substrate conveyer 18a and thereafter laminating that dome array to the substrate.

The feeder 66 is constructed like the feeders in the first embodiment in that the feeder includes upper and lower spools or reels 72 and 73. The upper reel 72 would have the supply of dome arrays carried on the carrier tape 74 and the lower reel 73 would be the takeup reel that would rewind the carrier tape after the dome arrays have been removed at the upper end of the feeder. Similar to the feeders 20 and 21 of the earlier embodiment, the feeder 66 will be driven to place the dome array in proper relation to the head 70 which removes the dome array for transfer to the substrate. Also, the carrier tape 74 would be driven to continuously place a dome array in position for removal by the pickup and laminating head 70. Once the supply of arrays is exhausted, the machine will automatically stop. The pickup and laminating head 70 includes a rod 82 that is suitably driven up and down and preferably by a servomotor, and will not only transfer a dome array from the carrier tape to a switch site, but also laminate the dome array to the board. The head is mounted on a carriage 76 and which is slidably supported on track 77 to move between the material feeder location and a desired substrate site on the substrate part 32 and also preferably driven by a servomotor. The illustrated substrate part 32 includes a plurality of substrate sites 32a and movement of the pick- and-place head 70 is coordinated with the movement of the substrate part 32 as it moves into and out of the processing area for receiving a dome array.

The pickup and laminating head 70 includes a rod or shaft 80 having the pickup and laminating head member 82 mounted at its very end. The head member 82 includes a suction head 83 for engaging the dome arrays and lifting them from the carrier tape 74 for transfer to a substrate site. The suction head 83 is resiliently mounted within the rod 80 by a spring 84 and arranged within a bore 86 extending through a compressible laminating head 87. The compressible laminating head is made of a suitable compressible material such as foam rubber or foam plastic

that will serve to apply a force to the dome array and spread over the dome array to cause a lamination of the dome array to the substrate site by substantially removing all air bubbles. Thus, the relatively soft laminating head will compress and flatten over the upper surface of the dome array as it is lowered against the dome array when it is in engagement with the substrate. During downward movement of the head and compression of the laminating head, the suction head 60 can retract into the rod 80 against the bias of the spring 84 and will be forced to retract as the suction head bottoms on the substrate. Thus, the pickup and laminating head member 82 will function not only to allow pickup and transfer of the dome array from the carrier tape on the material feeder but also to laminate the dome array onto the substrate.

Thus, the embodiment of Figs. 14 to 18 includes only a single material feeder and a combination pickup and laminating pick-and-place device having a combination pickup and laminating head member. A further embodiment of the pick-and-place device is illustrated in Figs. 19 to 22, and generally designated as 90. This embodiment is the preferred embodiment and includes an end effector 91 suitably mounted on the end of a drive shaft of a stepper motor 92. The stepper motor is suitably mounted on a bracket 95 secured to a vertically driven head 96. The head 96 is mounted on a carrier 99 that is horizontally driven along a track 102. A suitable servo motor 105 vertically drives the head 96 on the carrier 99. The carrier 99 is horizontally driven by a suitable servo motor 107. The stepper motor 92 merely rotates the end effector 91 after picking up an array to properly align the array with a switch site on the substrate.

The end effector 91 includes an aluminum block 110, a rubber plate or pad 111, and a steel mounting plate 112. The steel mounting plate is secured by suitable fasteners to the aluminum block, and is in turn suitably connected to the stepper motor 92 so that the end effector may be easily

removed and replaced with another end effector. While the end effector is essentially shown to have a relatively square configuration, it could have any suitable geometric shape to provide the proper operation as desired. The top side 114 of the aluminum block 110 includes a recessed area 115 communicating with a plurality of suction holes 117 extending through the block which are arranged in the same pattern as the domes in the dome array being handled so that each suction hole essentially provides suction to the center of a dome area thereby providing a strong grip on the array. It will be appreciated the end effector actually contacts the dome seal of the array, which overlies the domes.

Each of the suction holes 117 has an inlet end that communicates with to the recessed area 115. The outlet ends of the suction holes are coextensive with and connect to holes 127 formed in the rubber plate 111. The rubber plate 111 is suitably secured to the aluminum plate by adhesive or other means. Thus, the holes 127 in the rubber plate constitute an extension of the holes 117 in the aluminum block. The bottom side or underside 116 of the aluminum block is the side to which the rubber pad or plate 111 is attached. Preferably, the rubber plate 111 is electrically conductive so as to define an electrical path between the dome array and the end effector which, of course, would be electrically connected to ground so as to remove the effect of any static electricity. Preferably, the rubber pad is made of an electrically conductive silicone rubber, and the air holes or suction holes formed therein are in the pattern that will place a suction hole at every dome in the dome array to provide an effective suction connection between a dome array and the end effector. The approximate thickness of the rubber pad is 0.075 inch (2 mm), but it may be of any suitable thickness. Any suitable connection to a suction source will be made to the end effector so as to provide suction in the recessed area and at the inlet ends of the suction holes 117.

It will be appreciated that the end effector 91 may easily be changed on the stepper motor so as to provide a different end effector for another pattern of domes in a dome array. Once a dome array is deposited onto a substrate or printed circuit board, application of a laminating force through the rubber plate 111 will cause proper lamination of the dome array to the printed circuit board.

It will be appreciated that when the dome array is first removed from the carrier tape by the end effector, it may need to be rotated 90 degrees in order to bring it into proper orientation for application to a printed circuit board. The stepper motor 92 will provide the necessary rotation of the end effector and dome array being transferred by the end effector and most likely in the amount of a 45-degree rotation so that the dome array can be properly applied to the circuit board.

It will be understood that modifications and variations may be effected without departing from the scope of the novel concepts of the present invention, but it is understood that this application is to be limited only by the scope of the appended claims.