Patent Publication Number: US-2006011926-A1

Title: Light-emitting diode device with resecurable connection

Description:
BACKGROUND OF THE INVENTION  
      An LED device generally comprises a substrate portion and a scrambler portion. The former typically includes an LED electrically connected to a printed circuit board (“PCB”) substrate, while the latter is often a plastic casing that provides structural integrity to the LED device and a light reflecting cavity in which the LED resides. These two portions have traditionally been secured to each other by a plastic “stake”. Specifically, this connection is achieved by inserting a plastic stake associated with the scrambler portion through a hole in the PCB, and then melting the tip of the plastic stake into a plastic lump to secure the scrambler portion to the substrate portion.  
       FIG. 1A  is a cross-sectional view of a prior art LED device  10  before assembly. An LED  12  is mounted on a substrate portion  14 , such as a PCB, and is connected to a substrate layer  16  with an electrical connection  18 , such as a bond wire. A scrambler portion  20  includes a reflective cavity  22 , and a plastic stake  24  with a tip  26 . A through hole  28  in the substrate portion receives the plastic stake  24  when the scrambler portion  20  is assembled to the substrate portion  14 .  
       FIG. 1B  is a cross-sectional view of the prior art LED device  10  of  FIG. 1A  with the scrambler portion  20  assembled to the substrate portion  14 . The tip  26  of the plastic stake  24  extends through the substrate portion, and the LED  12  and electrically connection  18  reside within the reflective cavity  22 .  
       FIG. 1C  is a cross-sectional view of the prior art LED device  10  shown in  FIG. 1B  with the scrambler portion secured to the substrate portion. The substrate portion  14  is secured to the scrambler portion  20  by heating the tip  26  of the plastic stake  24  to form a plastic lump  29 .  
      Unfortunately, the prior art plastic stake method is plagued with inherent challenges that render it prone to potential problems and defects. For instance, if the tip of the plastic stake is excessively heated, thermal degradation of the LED device&#39;s electronic components, open failures, intensity degradation, burning of the tip of the plastic stake, and/or contamination of the heating element employed to melt the tip may occur. Moreover, the delicate control required by the melting process often results in imperfections in the plastic lump that weaken or destroy its holding strength. Finally, once the plastic lump is broken (either intentionally or unintentionally), the substrate portion and scrambler portion cannot be re-secured by the plastic stake. Rather, a new scrambler portion having a new plastic stake must be sought, as the original scrambler portion is rendered useless.  
      In light of the above, there is a need for a device and method for securing a substrate portion of an LED device to a scrambler portion that is not fraught with such disadvantages. In addition, there is a need for a resecurable connection between a substrate portion and a scrambler portion; an adjustable securing means for creating a resecurable connection between a substrate portion and a scrambler portion; an LED device having a resecurable connection; and a method for securing a substrate portion to a scrambler portion that is resecurable. This need is met by a resecurable connection between a substrate portion and a scrambler portion; an adjustable securing means for creating a resecurable connection; an LED device having a resecurable connection; a method of constructing an LED device having a resecurable connection; and a method of forming a resecurable connection between a substrate portion and a scrambler portion according to the present invention.  
     SUMMARY OF THE INVENTION  
      According to an embodiment of the present invention, there is provided an LED device that includes a scrambler portion, a substrate portion having a light-emitting diode (“LED”), a substrate layer attached to the LED, an electrical connection between the LED and the substrate layer, and a resecurable connection between the scrambler portion and the substrate layer. 
    
    
     BRIEF DESCRIPTIONS OF THE DRAWINGS  
       FIG. 1A  is a cross-sectional view of a prior art LED device before assembly.  
       FIG. 1B  is a cross-sectional view of the prior art LED device shown in  FIG. 1A  with a scrambler portion assembled to a substrate portion.  
       FIG. 1C  is a cross-sectional view of the prior art device shown in  FIG. 1B  with the scrambler portion secured to the substrate portion.  
       FIG. 2A  is a cross-sectional view of an LED device with an unsecured resecurable connection according to an embodiment of the invention.  
       FIG. 2B  is a cross-sectional view of the LED device f  FIG. 2A  with a first adjustable securing means (in the form of a first adjustable latch) derived from the scrambler portion and a second adjustable securing means (in the form of a second adjustable latch) derived from the scrambler portion, and showing a first resecurable sub-connection and a second resecurable sub-connection, both securing the scrambler portion to the substrate portion.  
       FIG. 3  is a cross-sectional close-up view of a portion of the LED device  30  shown in  FIG. 2B .  
       FIG. 4  is a cross-sectional close-up view of another portion of the LED device  30  shown in  FIG. 2B .  
       FIGS. 5A and 5B  illustrate the flexibility of the first adjustable securing means.  
       FIGS. 6A and 6B  illustrate the flexibility of the second adjustable securing means.  
       FIG. 7  shows an embodiment of an LED device having one adjustable securing means in the form of an adjustable latch and a second type of resecurable connection comprised of a second type of securing means to further secure the substrate portion to the scrambler portion.  
       FIG. 8A  shows another embodiment of an LED device  110  before assembly.  
       FIG. 8B  shows the LED device  110  of  FIG. 8A  after assembly. 
    
    
     DETAILED DESCRIPTION  
       FIG. 2A  is a cross-sectional view of an LED device  30  with an unsecured resecurable connection (i.e. before assembly) according to an embodiment of the invention. A substrate portion  34  includes a substrate layer  36 ; an LED  38  attached to the substrate layer  36 ; and an electrical connection  40  (of at least one of: gold, aluminium and copper) between the LED  38  and the substrate layer  36 . In this embodiment, the dimensions of the substrate layer  36  are technology dependent and can range from very small dimensions (for example a few millimetres) to relatively large sizes (for example tens of centimetres). Moreover, in alternate embodiments, the electrical connection  40  takes other forms, such as two wires, or a direct connection (e.g., via flip chip technology); and others will be readily known to those skilled in the art.  
      In addition, a protective coating  42  of silicone gel covers the LED  38  and the electrical connection  40  in order to protect them from moisture or any mishandling. Alternatively, an optical grade epoxy encapsulation (not shown) covers the LED  38  and the electrical connection  40  for the same purpose; while other protective options will be readily known to those skilled in the art. Moreover, additional embodiments do not include protection of the LED  38  and the electrical connection  40 .  
       FIG. 2A  also shows the substrate layer  36  having a first substrate layer section  44  and a second substrate layer section  46 . The first substrate layer section  44  includes a first substrate layer lower section  48  and a first substrate layer upper section  50 ; while the second substrate layer section  46  includes a second substrate layer lower section  52  and a second substrate layer upper section  54 .  
      In this embodiment, the substrate layer  36  comprises a PCB. However, it will be apparent to those skilled in the art that the substrate layer  36  alternatively comprises other substrates in alternate embodiments; such alternate substances being of at least one of: a ceramic, a molded interconnect device (“MID”), and a flexible circuit.  
      In a particular embodiment, a scrambler portion  56  comprises polycarbonate (PC) plastic. Alternatively, the scrambler portion  56  comprises one of polycarbonate, and polycarbonate and acrylonitrile/butadiene/styrene (“ABS”), and polybutylene terephthalate, liquid crystal polymer (“LCP”) or polyphtalamide (“PPA”). The dimensions of the scrambler portion are technology, design or application dependent. When the scrambler portion  56  is assembled with the substrate portion  34 , the LED  38  resides in a reflective cavity  57 .  
      Moreover, the scrambler portion  56  includes a first adjustable securing means  58  (in the form of a first adjustable latch  60  having a first adjustable latch surface  61  configured to interface with a first scrambler lower section  63 ) and a second adjustable securing means  62  (in the form of a second adjustable latch  64  having a second adjustable latch surface  65  configured to interface with a second scrambler lower section  67 ). As used herein, “adjustable” means capable of adjustment. Alternatively, “adjustable” also is meant to include at least flexible (as discussed below); and alternatively is also meant to include both flexible and resilient (as also discussed below).  
      The first adjustable securing means  58  and the second adjustable securing means  62  are essentially derived from the scrambler portion  56  through a plastic injection molding process. The plastic injection molding process forms a first hollow slot  66  and a second hollow slot  68 . The formation of the first adjustable securing means  58 , second adjustable securing means  62 , and hollow slots  66 ,  68  will be readily known to those skilled in the art.  
      The scrambler portion  56  also includes a first protective stake  70  and a second protective stake  72  to protect the first and second adjustable securing means  58 ,  62  from being unintentionally moved and/or damaged (e.g. as the LED device  30  is typically connected to a circuit (not shown) via connecting conductive pins (also not shown). The formation of, and rationale behind, the first and second protective stakes  70 ,  72 —which are also derived from the scrambler portion  56 —will be readily apparent to those skilled in the art. Alternate embodiments do not include the first and second protective stakes  70 ,  72 . The formation of the protective stakes will also be readily apparent to those skilled in the art.  
       FIG. 2B  is a cross-sectional view of the LED device  30  of  FIG. 2A  with a first adjustable securing means  58  (in the form of a first adjustable latch  60 ) derived from the scrambler portion  56  and a second adjustable securing means  62  (in the form of a second adjustable latch  64 ) derived from the scrambler portion  56 , and showing a first resecurable sub-connection  74  and a second resecurable sub-connection  76 , both securing the scrambler portion  56  to the substrate portion  34 . A resecurable connection  78  secures the substrate portion  34  to the scrambler portion  56 . The term “resecurable,” as used herein, means capable of being secured, unsecured, and re-secured.  
      As described below, alternate embodiments use other adjustable securing means that are distinct from, but attached to, an alternate scrambler portion. Moreover, it will be readily apparent to those skilled in the art that there are numerous other ways, using molding technology, to form the first and second adjustable securing means  58 ,  62 . In addition, other forms of the two adjustable securing means will be readily known to those skilled in the art.  
       FIG. 2B  shows the LED  38  and the electrical connection  40  residing in the reflective cavity  57  of the scrambler portion  56 . A portion of the light from the LED  38  reflects off the reflective cavity  57 . The reflective cavity  57  includes a light reflecting coating of at least one of: silver, aluminium, and nickel. Also, it will be readily understood that other embodiments have a plurality, and even tens or hundreds of light-reflecting cavities.  
      The first adjustable latch  60  is located at a substantial mid-point on the side of the scrambler portion  56  on which it is located, and the second adjustable latch  64  is located at a substantial mid-point of its respective side of the scrambler portion as well, which supports the substrate portion  34  most effectively. In alternate embodiments, first and second adjustable latches are placed in other locations that will be readily known to those skilled in the art.  
      Resecurable connection  78  comprises a first resecurable sub-connection  74  and a second resecurable sub-connection  76 . However, alternative embodiments have only one resecurable sub-connection, and other alternative embodiments have more than two resecurable sub-connections. In light of strength and costs considerations, some embodiments have four resecurable sub-connections. That said, it will be readily apparent to those skilled in the art than more than four resecurable sub-connections. In fact, alternate embodiments have tens, and even hundreds, of resecurable sub-connections.  
       FIG. 3  is a cross-sectional close-up view of a portion of the LED device  30  shown in  FIG. 2B . The first resecurable sub-connection  74  is secured. The first resecurable sub-connection  74  includes a first adjacency  80  between the first substrate layer lower section  48  and a first adjustable securing means surface  82 , the first adjustable securing means surface  82  being a first adjustable latch surface (see  FIG. 2A , ref. num.  61 ); and a second adjacency  84  between the first substrate layer upper section (see  FIG. 2A , ref. num.  50 ) and the first scrambler lower section (see  FIG. 2A , ref. num.  63 )). The first resecurable sub-connection  74  includes the first substrate layer section of the substrate layer (see  FIG. 2A , ref. nums.  44 ,  36 ) sandwiched between the scrambler portion  56  and the first adjustable securing means  58 .  
       FIG. 4  is cross-sectional close-up view of another portion of the LED device  30  shown in  FIG. 2B . The second resecurable sub-connection  76  includes a third adjacency  86  between the second substrate layer lower section (see  FIG. 2A , ref. num.  52 ) and a second adjustable securing means surface  88  (the second adjustable securing means surface  88  being a second adjustable latch surface (see  FIG. 2A , ref. num.  65 ); and a fourth adjacency  90  between the second substrate layer upper section and the second scrambler lower section (see  FIG. 2A , ref. nums.  54 ,  67 ). However, it will be readily apparent that the first and second resecurable sub-connections  74 ,  76  in alternative embodiments do not include some, or any, of these adjacencies  80 ,  84 ,  86 ,  90 . The second resecurable sub-connection  76  includes the second substrate layer section of the substrate layer (see  FIG. 2A , ref. nums.  46 ,  36 ) sandwiched between the scrambler portion  39  and the second adjustable securing means  63 . In this regard, only the former applies in embodiments having only one resecurable sub-connection.  
      In the embodiment shown in  FIG. 2B , the first and second adjustable securing means surfaces  82 ,  88  each respectively have dimensions that are technology, design or application dependent. Generally, the size of the first and second adjustable securing means surfaces  82 ,  88  depend on the size of the LED device  38  and the number of adjustable latches (e.g. first and second adjustable latches  60 ,  64 ) employed (as it will be readily apparent that one, or more than two adjustable latches—even tens and hundreds—are employed in alternate embodiments). On a similar note, increasing the area of the first and second adjustable securing means surfaces  82 ,  88  (i.e. adjustable latch surface length times adjustable latch surface width) will enhance their respective contact forces and their strength; and, therefore, the overall strength of the first and second resecurable sub-connections  74 ,  76 .  
      It will be readily apparent to those skilled in the art that there are innumerable shapes of adjustable latches in alternate embodiments. Moreover, it will be readily apparent that the lengths of the first and second adjustable securing means surfaces  82 ,  88  are technology, design or application dependent. As mentioned above, the first and second securing means  58 ,  62  (i.e. the first and second adjustable latches  60 ,  64  in this embodiment) comprise plastic and are, therefore, flexible. “Flexible” meaning that the substrate portion  34  may be placed adjacent to the scrambler portion  56  without causing any undesirable permanent deformations to either the substrate portion  34  and/or the scrambler portion  56  (including the adjustable first and second adjustable latches  60 ,  64 ).  
       FIGS. 5A and 5B  illustrate the flexibility of the first adjustable securing means  58 . The first adjustable securing means  58  of the scrambler portion  56  is movable from a first position  92  (shown in  FIG. 5A )—its “home position”—to a second position  94  (shown in  FIG. 5B ). The second position  94  permits the first substrate layer section (see  FIG. 2A , ref. num.  44 ) to be positioned above the first adjustable securing means  58 , and the first position  92  allows the first resecurable sub-connection (see  FIG. 2B , ref. num.  74 ) to be secured.  
       FIGS. 6A and 6B  illustrate the flexibility of the second adjustable securing means  62 . The second adjustable securing means  62  of the scrambler portion  56  is movable from a third position  96 —its “home position”—(shown in  FIG. 6A ) to a fourth position  98  (shown in  FIG. 6B ). The fourth position  98  permits the second substrate layer section (see  FIG. 2A , ref. num.  46 ) to be positioned above the second adjustable securing means  62 , and the third position  96  allows the second resecurable sub-connection (see  FIG. 2B , ref. num.  76 ) to be secured. In alternate embodiments, only the first adjustable securing means  58  is flexible or only the second adjustable securing means  62  is flexible—but, importantly, such embodiments still allow the substrate portion to be placed adjacent to the scrambler portion without causing any permanent deformations to either.  
      The first and second adjustable securing means  58 ,  62  (i.e. the first and second adjustable latches (see  FIG. 2B , ref. nums.  60 ,  64  in this embodiment) are also resilient. “Resilient” meaning that the first adjustable securing means  58  naturally—i.e. without manual assistance—returns to at least substantially the first position  92  from the second position  94 , and the second adjustable securing means  62  naturally—i.e. without manual assistance—returns to at least substantially the third position  96  from the fourth position  98 .  
      In further embodiments, the first and second adjustable securing means  58 ,  62  are one of the following: both flexible but not resilient; both flexible and only one resilient; both flexible and resilient; and, one flexible only and the other resilient only. In embodiments where one or more of the first and second adjustable securing means  58 ,  62  are not resilient, manual assistance will be needed to position each non-resilient adjustable securing means to its respective “home position”.  
      More generally, the flexibility and resilience of the first and second adjustable securing means  58 ,  62  will depend on their design and size. For instance, ones having greater dimensions—and most importantly larger lengths of adjustable latch surfaces, e.g. first and second adjustable latch surfaces  61 ,  65  shown in  FIG. 2A —require greater flexibility vis a vis adjustable latches having smaller latch surface lengths (assuming they are made of similar material).  
      As shown in  FIG. 5B  and  FIG. 6B , first and second adjustable latches  60 ,  64  (i.e. the first and second adjustable securing means  58 ,  62 ) are respectively moved to their second and fourth positions  94 ,  98  to unsecure the resecurable connection (see  FIG. 2B , ref. num.  78 ); thereby allowing the separation of the substrate portion (not shown in  FIGS. 5B and 6B ) from the scrambler portion  56 . In alternate embodiments, it is sufficient that either adjustable latch, e.g. the first adjustable latch  60 , is positioned in the second position  94  or the second adjustable latch  64  is positioned in the fourth position  98  to unsecure the resecurable connection.  
      The resecurable connection is also resecurable. The resecuring process is the same as discussed generally above with regard to the first and second adjustable securing means  58 ,  62  (i.e. the first and second adjustable latches  60 ,  64 ). As mentioned above, other embodiments have one adjustable latch, and alternate embodiments have more than two adjustable latches.  
       FIG. 7  shows an embodiment of an LED device  100  having one adjustable securing means  102  in the form of an adjustable latch  104  and a second type of resecurable connection  106  comprised of a second type of securing means  108  (such as an adhesive or glue) to further secure the substrate portion  34  to the scrambler portion  56 ′. Generally, more adjustable latches provide a stronger connection between the substrate portion  34  and the scrambler portion  56 ′. That said, in light of cost considerations, four adjustable latches often provide a strong and cost-effective connection in many instances.  
       FIG. 8A  shows another embodiment of an LED device  110  before assembly. The LED device  110  has first and second adjustable securing means  112 ,  114 , a scrambler portion  116 , and a substrate portion  34  with an LED  38  and an electrical connection  40 .  
       FIG. 8B  shows the LED device  110  of  FIG. 8A  after assembly. The first and second adjustable securing means  112 ,  114  attach the substrate portion  34  to the scrambler portion  116 . Comparing  FIG. 8B  to  FIG. 2B , the two embodiments are similar except that the first and second adjustable securing means  112 ,  114  in the embodiment of  FIG. 8B  are distinct from, and attached to, the scrambler portion  116 .  
      Molded hollow slots  118 ,  120  in the embodiment  110  shown in  FIG. 8B  have a slightly different shape than the first and second hollow slots  66 ,  68  in the embodiment shown in  FIG. 2B  to accommodate the shape of the first and second adjustable securing means  112 ,  114 . The molded hollow slots  118 ,  120  are shaped in this way to allow the first and second adjustable securing means  112 ,  114  to be inserted into the scrambler portion  116  between the substrate portion  34  and the protective stakes  122 ,  124  to form a connection between the scrambler portion  116  and a substrate layer  126 . The formation of these adjustable securing means will be readily known to those skilled in the art.  
      The attachment of the first and second adjustable securing means  112 ,  114  to the scrambler portion  116  is accomplished by manual insertion or mechanically pressed by jigs, fixtures or machines.  
      Although the invention has been described with reference to specific examples, it will be appreciated by those skilled in the art that it may be embodied in many other forms.