Abstract:
A method of fabricating packaging for a product comprises forming a plurality of conductive tracks on a sheet of material and forming a physical barrier, such as a hole, for impeding fluid flow between adjacent conductive tracks. The method may further comprise depositing first and second regions conductive fluid onto adjacent first and second conductive tracks either side of the physical barrier and mounting an electronic device having first and second terminals such that the electronic device forms a bridge over the physical barrier and the first ands second terminals contact the first and second conductive adjacent tracks.

Description:
FIELD OF THE INVENTION 
     The present invention relates to product packaging and/or printed matter. 
     SUMMARY 
     According to the present invention there is provided a method of fabricating packaging for a product and/or printed mater, the method comprising forming a plurality of conductive tracks on a sheet of material and forming a physical barrier for impeding fluid flow between adjacent conductive tracks. 
     Thus, the physical barrier can help to prevent, during a subsequent step, conductive fluid from forming a short between the conductive tracks for example by preventing the two regions from being smudged into each other or being drawn together by capillary action. 
     Forming the physical barrier may comprise removing a portion of the substrate. 
     Removing the portion of the substrate may comprise forming a hole through the sheet, for example punching the hole. Forming the physical barrier may comprise forming a trench in the sheet, for instance by impressing a stamp into a surface of the sheet supporting the conducting tracks. Forming the physical barrier may comprise forming a wall upstanding from the sheet, for example by impressing a stamp into a surface which is reverse to a surface supporting the conducting tracks. 
     The barrier may be elongate having a longitudinal axis which is transverse to a shortest line between adjacent tracks. 
     Forming the plurality of conductive tracks on a sheet of material may include forming at least one conductive track and breaking at least one conductive track into more conductive tracks. Forming the physical barrier may break the at least one conductive track into the more conductive tracks. 
     The method may comprise printing ink onto the sheet of material to form text and/or image(s) and may comprise printing multiple inks to form colour text and/or image(s). 
     The method may comprise cutting the sheet into smaller sections and may comprise folding the sheet or a section of the sheet to form an enclosure. 
     The method may comprise depositing first and second regions conductive fluid onto first and second conductive adjacent tracks either side of the physical barrier; and mounting an electronic device having first and second terminals such that the electronic device forms a bridge over the physical barrier and the first and second terminals contact the first and second conductive adjacent tracks. 
     According to a second aspect of the present invention there is provided a method of fabricating packaging for a product and/or printed mater, the method comprising providing a printed sheet comprising a plurality of conductive tracks disposed on a sheet of material and having a physical barrier for impeding fluid flow between adjacent conductive tracks, depositing first and second regions conductive fluid onto first and second conductive adjacent tracks either side of the physical barrier; and mounting an electronic device having first and second terminals such that the electronic device forms a bridge over the physical barrier and the first and second terminals contact the first and second conductive adjacent tracks. 
     According to a third aspect of the present invention there is provided a printed sheet for packaging a product and/or for use as printed mater comprising a sheet of material, a plurality of conductive tracks supported on sheet of material and a physical barrier for impeding fluid flow arranged between adjacent conductive tracks. 
     The barrier may comprise a trench in the sheet, a hole through the sheet and/or a wall upstanding from the sheet. The barrier may be elongate and has longitudinal axis which is transverse to a shortest line between adjacent tracks. 
     The sheet material may comprise a packaging material or print medium and may comprise cardboard or a plastic. 
     According to a fourth aspect of the present invention there is provided an assembly comprising a printed sheet, first and second regions of conductive glue arranged on first and second conductive adjacent tracks either side of the physical barrier and an electronic device having first and second terminals such that the electronic device forms a bridge over the physical barrier and the first ands second terminals contact the first and second conductive adjacent tracks. 
     The conductive glue may be fluid. The electronic device may be a light emitting diode or a circuit board assembly. 
     The assembly may be configured as packaging for a product and/or as printed matter. 
     According to a fifth aspect of the present invention there is provided apparatus for fabricating packaging for a product and/or printed mater comprising means for forming a plurality of conductive tracks on a sheet of material and means for forming a physical barrier for impeding fluid flow, said means configured to form said physical barrier between adjacent conductive tracks. 
     According to a sixth aspect of the present invention there is provided apparatus comprising a printer configured to form conductive tracks on a sheet of material; and a press configured to form a physical barrier for impeding fluid flow, said press configured to form said physical barrier between adjacent conductive tracks. 
     The press may be configured to punch a hole in the sheet to form the physical barrier. 
     According to a seventh aspect of the present invention there is provided apparatus for fabricating packaging for a product and/or printed mater comprising means for providing a printed sheet comprising a plurality of conductive tracks disposed on a sheet of material and having a physical barrier for impeding fluid flow between adjacent conductive tracks, means for depositing first and second regions conductive fluid onto first and second conductive adjacent tracks either side of the physical barrier and means for mounting an electronic device having first and second terminals such that the electronic device forms a bridge over the physical barrier and the first ands second terminals contact the first and second conductive adjacent tracks. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Embodiments of the present invention will now be described by way of example, with reference to the accompanying drawings in which: 
         FIGS. 1   a - 1   c  illustrate how two regions of conductive glue can be drawn together when mounting a device to a substrate; 
         FIGS. 2   a - 2   c  illustrate a side view, corresponding to  FIGS. 1   a - 1   c  of how two regions of conductive glue can be drawn together when mounting a device to a substrate; 
         FIG. 3  is a perspective view of packaging providing a printed circuit board on which is mounted a device and which uses a slot in accordance with the present invention; 
         FIG. 4  is a cross-sectional view through the printed circuit board and the device taken along a line A-A′ in  FIG. 3 ; 
         FIG. 5  is a cross-sectional view of packaging in which a trench is used instead of a slot; 
         FIG. 6  is a cross-sectional view of packaging in which a wall is used instead of a slot; 
         FIG. 7  is a schematic diagram of production line; 
         FIG. 7   a  illustrates components of a gravure printing process; 
         FIGS. 8   a - 8   e  illustrate a method of fabricating packaging in accordance with the present invention; and 
         FIG. 9  is a plan view of a different type of device. 
     
    
    
     DETAILED DESCRIPTION 
     A problem can arise when conductive glue, for example in the form of metallic particles suspended in a carrier, is used to attach electronic devices, such as light emitting diodes, to conductive tracks. 
     Referring to  FIGS. 1   a  and  2   a , first and second separate regions  1   a ,  1   b  of conductive glue are deposited on respective conductive tracks  2   a ,  2   b  running on an upper surface  3  of a substrate  4 . The conductive glue regions  1   a ,  1   b  are closely separated by a gap  5  (e.g. about 1 mm) and contain, between them, sufficient excess glue for the glue to bridge the gap  5 . 
     Referring to  FIGS. 1   b  and  2   b , an electronic device  6 , such as a light emitting diode, having at least first and second terminals  7   a ,  7   b  is positioned over the conductive tracks  3   a ,  3   b  such that the device terminals  7   a ,  7   b  are aligned with the first and second regions  1   a ,  1   b  respectively and is lowered onto the conductive tracks  3   a ,  3   b.    
     As the device  6  is lowered, it touches the top (i.e. the meniscus) of one or both of the conductive glue regions  1   a ,  1   b . By capillary action, the regions  1   a ,  1   b  run together in a shallow space formed between the bottom of the device  6  and the top of the conductive tracks  2   a ,  2   b  and substrate  4 . 
     As shown in  FIGS. 1   c  and  2   c , a joined region  1   c  is formed which electrically shorts the terminals  7   a ,  7   b  of the device  6 . 
     It is noted that this problem does not tend affect conventional printed circuit boards because solder tends to adhere to copper tracks and does not flow onto the substrate. 
     The problem may be addressed by increasing the size of the gap  5 , minimising the amount of the glue and/or using glue which is sufficiently viscous or reduces capillary action in some other way. 
     The present invention seeks to provide another solution this problem. 
     Referring to  FIG. 3 , packaging  9 , in the form of a printed sheet of cardboard folded into the shape of a box, provides a printed circuit board  10  on which are mounted electrical devices  11  to provide circuitry  12  which can be used for entertaining a user, for providing information to the user or effecting some other user-directed function. For clarity, only part of the circuitry  12  is shown. 
     The packaging  9  may be a primary, secondary or tertiary form of packaging and may be used to package diverse forms of product such as foods (e.g. a cereal box), medicines (e.g. a box containing a blister pack of tablets or a tube of cream), household or office supplies, games and so on. 
     Electrical devices  11  may include discreet and integrated components and typically include a battery or other power source, such as a solar cell or inductive loop, and one or more other devices such as light emitting diodes, displays, speakers, buzzers, switches, sensors, transducers, integrated circuits and memory. 
     Referring also to  FIG. 4 , the packaging  9  includes a sheet of cardboard (herein also referred to as a “substrate”) supporting conductive tracks  14   1 ,  14   2  (herein the tracks  14   1 ,  14   2  collectively are sometimes referred to as the “circuit”), patterned layers of ink  15 ,  16 ,  17 ,  18  (herein also referred to as a “text and images”) and, optionally, a top layer of a clear varnish  19 . 
     The conductive tracks  14   1 ,  14   2  comprise a conductive ink, for example based on graphite, and typically have a thickness of the order of 1, 10 or 100 μm (usually dependent on the type of printing process used), a width of the order of 100 μm or 1 mm and a length of the orders of 1 mm to 1 m. The conductive tracks  14   1 ,  14   2  typically have a line spacing (e.g. minimum spacing between two lines running parallel to one another) of the order of 10 μm, 100 μm or 1 mm. The layers of ink  15 ,  16 ,  17 ,  18  comprise layers of cyan, yellow, magenta, black ink. 
     The printed circuit  14   1 ,  14   2  is formed under the text and images  15 ,  16 ,  17 ,  18 . However, the printed circuit  14   1 ,  14   2  can be located between and/or on top of the layers of ink  15 ,  16 ,  17 ,  18  and varnish  19 . 
     Packaging material other than cardboard may be used such card, a flexible plastic, such as polyethylene terephthalate (“PET”) and polyimide, a flexible metallised plastic or a laminate of materials, e.g. card or paper between plastic. 
     As shown in  FIG. 4 , the printed circuit  14   1 ,  14   2  and the text and images  15 ,  16 ,  17 ,  18  are formed on a first side  20  (herein also referred to as a “face” or “surface”) of the substrate  13 . However, both sides of the substrate may be used. 
     An electronic device  11 , in this example a light emitting diode, has terminals  21   1 ,  21   2  connected to respective conductive tracks  14   1 ,  14   2  through windows (or “vias”)  22   1 ,  22   2  through the layers  15 ,  16 ,  17 ,  18 ,  19 . The terminals  21   1 ,  21   2  are connected to the tracks  14   1 ,  14   2  using regions  23   1 ,  23   2  of conductive glue, for example comprising graphite or silver particles. The conductive glue  23  may also help to secure the device  11 . The glue regions  23   1 ,  23   2  may be referred to as “spots”, “blobs” or “patches”. 
     A rectangular hole or slot  24  is provided between sections  25   1 ,  25   2 , (in this case the ends) of the conductive tracks  14   1 ,  14   2  to which the terminals  21   1 ,  21   2  are connected. The slot  24  need not be rectangular, but may be elliptical or irregularly shaped. Furthermore, the slot  24  may trace a path, for example having one or more turns and which may include straight or curved sections. 
     As will be explained in more detail later, the slot  24  is used to provide a physical barrier to prevent the conductive glue  23 , when liquid or when more fluid, from spreading, particularly due to capillary action. In this and some other embodiments of the invention, the slot  24  also serves to define one or more edges of the conductive tracks  14   1 ,  14   2 . Thus, a single line  14  ( FIG. 8   a ) can be printed or formed and broken into two or more lines  14   1 ,  14   2  ( FIG. 8   c ) using one or more slots  24 . 
     Slots are positioned relative to the conductive tracks such that when glue is placed on the tracks ready for a device to be connected, the glue is located to one side of a slot and the slot separates the glue from another part of the circuit where a short should be avoided. Glue may be located immediately next to a slot or spaced some way away. Thus, the slots prevent glue from spreading over the surface of the substrate and/or over layers lying on the substrate  13  towards another track and/or another spot of glue. 
     Other forms of physical barrier can be used. 
     Referring to  FIGS. 5 and 6 , the physical barrier may be a trench or trough  25  or a wall  26  used to separate tracks  14  on a substrate  13 . The physical barrier may comprise a combination of trench(es) and wall(s). The trench  25  or wall  26  can be formed by stamping or scoring. It will be appreciated that a similar tool can be used for stamping and that the difference between punching a hole and simply deforming the substrate may lie in the sharpness of the tool and/or the force or range of movement of the tool. 
     The profile (in cross section) of the trench  25  or wall  26  may be vertical and/or in some way discontinuous so as to inhibit the spread of ink or to break up a spreading film of ink. 
     Additionally or alternatively, the depth (d) of the trench  25  or height (h) of the wall  26  is chosen such there is sufficient clearance to inhibit capillary action and/or such that a typical volume of ink (typically of the order of picolitres) cannot bridge trench  25  or wall  26 . Values of depth and height can be found by routine experiment and typically exceed 100 μm. 
     Typically the physical barrier need only have a width of order of 100 μm, 1 mm or 10 mm, usually about 1 mm, and need only be effective while the glue is liquid or semi-liquid, typically for periods of the order of 0.1, 1 or 10 seconds. 
     Referring to  FIG. 7 , apparatus  27  (or a “press”) for manufacturing the packaging  9  ( FIG. 3 ) generally comprises two parts  27   1 ,  27   2 . A first part  27   1  is used to take a sheet  28  of material, such as cardboard, and produce a printed sheet  29 . A second part  27   2  takes the printed sheet  29  and mounts devices  11  ( FIG. 4 ) on the printed sheet  29  to form an assembled printed sheet  30 . 
     The first and second parts  27   1 ,  27   2 , may form parts of the same production line. However, they may form different lines and be located at different sites or plants. 
     Referring also to  FIG. 7   a , the apparatus is based on a gravure printing process having several stages, each having a gravure cylinder  31 , a doctor blade  32  and ink reservoir  33  and an opposing impression cylinder  34 . However, other printing process can be used, such as offset, flexography, screen and inkjet printing processes and a mixture of different printing processes can be used in the same line. 
     In the first part  27   1  of the apparatus, the (unprinted) sheet  28  of material is paid out from a roller  35  and passes through a printing stage  36  used to print conductive tracks on the sheet  29 , through printing stages  37 ,  38 ,  39 ,  40  used to print cyan, yellow, magenta, black graphic layers and, optionally, through a stage  41  for printing a varnish layer. Fewer graphic printing stages  37 ,  38 ,  39 ,  40  may be used if, for example, a black-and-white or monochrome image is required. 
     A resulting sheet  29 ′ passes through a cutting and creasing stage  42  used to crease the sheet  29 ′ for allowing the sheet to be easily folded in the shape of a box and to cut the sheet  29 ′ to form a web or matrix, ready to be divided into smaller parts, if necessary to form windows. The cutting and creasing stage  42  also forms the physical barriers, for example by stamping out holes in and/or between tracks, and/or by forming creases (troughs and/or wall) between tracks. 
     The printed sheet  29  is wound onto a take up roller  42  or fed directly into the second part  27   2  of the apparatus. 
     In the second part  27   2  of the apparatus, the printed sheet  29  passes through a gravure printing stage  44  used to print conductive glue on the sheet  29  and then passed through a device mounting stage  45  after which the assembled printed sheet  30  can be wound onto a take up roller  46 . 
     The devices are provided on a web  47  and stamped out onto the sheet  29  using a patterned cylinder  48  and an impression roller  49 . However, other processes can be used such as “pick-and-place” robots. 
     The whole press  27  or the second part of the press  27   2  need not be a web press, but can be a sheet-fed press. For example, rather than using cylinders  48 ,  49  to cut and crease the sheet, boards can be used instead. 
     Referring to  FIGS. 7 and 8 , a method of fabricating the device will now be described. 
     Referring in particular to  FIG. 8   a , a conductive track layer  14  and ink layers  15 ,  16 ,  17 ,  18  and varnish  19  are deposited on the sheet  13 . The ink layers  15 ,  16 ,  17 ,  18  and/or varnish  19  may be printed with windows  22   1 ,  22   2  onto the conductive track layer  14 . 
     Referring in particular to  FIG. 8   b , a stamping tool  50  stamps out a portion  51  of the sheet  13  and the overlying layers  14 ,  15 ,  16 ,  17 ,  18 ,  19 . 
     Referring in particular to  FIG. 8   c , stamping leaves a hole  24  which, in some embodiments, serves in part, to define, first and second conductive tracks  14   1 ,  14   2 . However, holes need not be used to break a conductive track. 
     Referring in particular to  FIG. 8   d , spots of glue  23   1 ,  23   2  are applied into the windows  22   1 ,  22   2 , which open onto the tracks  14   1 ,  14   2 . 
     Referring to  FIG. 8   e , the device  11  is mounted during which the terminals  21   1 ,  21   2  are pressed into the windows  22   1 ,  22   2 . 
     The slot  24  prevents a shallow channel  52  formed between an upper surface  53  of the top-most layer  19  and an under surface  54  of the device  11  extending between the terminals  21   1 ,  21   2 . 
     The use of physical barriers, particularly slots, can be used with more complex devices having more than two terminals. 
     Referring to  FIG. 9 , a printed circuit board assembly  55  having more than two tracks  56  can be mounted onto corresponding tracks  57  of a printed sheet  58  using conductive glue  59 . The printed sheet  58  has slots  60  punched out in regions between locations where glue is applied. 
     It will be appreciated that many modifications may be made to the embodiments hereinbefore described. 
     The use of physical barriers can be used printed sheets which are used to provide printed mater which need not necessarily be used as packaging. For example, the printed matter, for example in form of playing or trading card, can be used as a game or for information. 
     Instead of conductive ink, foil can be used to form the conductive tracks formed by (hot or cold) stamping or by masked etching of a metallised sheet. 
     A liquid, such as an ink, or semi-liquid, such as a paste may be used instead of glue.