Patent Publication Number: US-2021195751-A1

Title: Electronic device and method of manufacturing the same

Description:
BACKGROUND OF THE INVENTION 
     Field of the Invention 
     The present invention pertains to an electronic device. 
     The present invention further pertains to a method of manufacturing the same. 
     Related Art 
     3D printing is an additive manufacturing technology wherein a carrier material is deposited in a layer by layer process to obtain a structured stack of layers. One or more components may be embedded in the structured stack. The usual process is to print the stack so as to form a cavity therein, to embed the component in the cavity, to print conductive materials on top of the component and to continue the layer deposition process. 
     EP 1 592 588 describes a method that uses a printing system including at least one printhead for printing material to create a printed product, and an object incorporation device that incorporates components into the product being printed whilst the at least one printhead prints the product. To that end the printing process may create the cavities into which such components may be inserted. The cited document observes that “Where electrically active devices are inserted, the devices are preferably inserted with the bond pads  616  facing upwards as this makes the forming of good quality electrical connections much easier. With upward facing bond pads, electrical connections may be formed in the next few layers to be printed. In contrast, bond pads on the bottom or sides of the object will rely on correct placement of the object and good contact.” 
     Hence, it is a disadvantage of this known method that it imposes restrictions on the orientation with which the components are to be embedded 
     There is a need for an electronic device wherein a component is embedded in a structured stack of layers at an angle deviating from this imposed orientation. There is a further need for an improved process that allows for more freedom in the choice of the orientation of the components. 
     SUMMARY OF THE INVENTION 
     In accordance with a first aspect of the present invention an electronic device is provided as claimed in claim  1 . 
     In accordance with a second aspect of the present invention a method of manufacturing an electronic device is provided as claimed in claim  9 . 
     The claimed electronic device comprises 
     a stack of layers, wherein one or more of those layers carry electrical conductors, 
     a cavity which extends through the stack of layers from one of said layers to another one of said layers, 
     a component carrier being accommodated in the cavity, wherein the component carrier supports at least one electronic component and comprises electrically conductive tracks from electric contacts of the at least one electronic component to electric terminals extending from the component carrier to a wall of the cavity to form an electrical connection with a respective one of said electrical conductors. 
     The claimed method of manufacturing the electronic device, comprises the steps of: 
     depositing a stack of layers, the deposited stack of layers having a surface, and a cavity, which is accessible through an opening in said surface, wherein one or more of said layers are provided with electrical conductors; 
     inserting a component carrier supporting at least one electronic component in the cavity, wherein the component carrier comprises electrically conductive tracks from electric contacts of the at least one electronic component to electric terminals; 
     electrically connecting the electric terminals, being provided in a direction towards a wall of the cavity, with a respective ones of said electrical conductors. 
     It is noted that in addition to the electronic component specifically referred to also further components may be arranged on the component carrier. 
     The electrical connection from the electric contacts of the component to corresponding contacts with respective electrical conductors at a surface of the one of said layers, via the electrically conductive tracks of the component carrier and its electric terminals, that extend in a direction towards a wall of the cavity, allows an independent orientation of the component with respect to the layer surface having the electrical conductors. 
     In an embodiment of the electronic device the component carrier is integral with an electric terminal carrier carrying the electric terminals and that extends through the wall to in between mutually subsequent layers. In an embodiment of this embodiment the component carrier and the electric terminal carrier are of a rigid material and are interconnected by a flexible interface. 
     Due to the fact that only the interface is flexible, the component carrier can be handled relatively easily in a manufacturing process. Alternatively, the component carrier and the electric terminal carrier may be provided as a flexible foil. This allows additional tolerances in the manufacturing process. 
     In an embodiment the electric terminals are resilient elements that are arranged in tensed state to the contact points of the electrical conductors. 
     In an embodiment the electric terminals are formed by an adhesive material. It is favorable if the adhesive has an anisotropic conductivity, its conductivity in lateral directions with respect to a surface at which it is applied being lower than a conductivity in a perpendicular direction with respect to said surface. 
     According to another option the electric contacts of the electronic component are adhered to said electrically conductive tracks with a cured metal paste. 
     In an embodiment of the electronic device the cavity has a wedge shape cross-section, tapering outward to the opening. This embodiment allows for a relatively easy placement of the component carrier with the component inside the cavity, while providing for a good fixation once the placement is completed. 
     In an application, of the electronic device the electronic component is a light emitting device, and the stack of layers is translucent. In this application, the component carrier may have arranged thereon for example in addition component(s) to control the light emitting device and/or sensor components, e.g. to sense an intensity of impinging light. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       These and other aspects are described in more detail with reference to the drawing. Therein: 
         FIG. 1  shows a perspective view of an embodiment of the electronic device according to the first aspect. 
         FIG. 2  shows a cross-sectional view of that embodiment. 
         FIG. 3  shows according to the same cross-sectional view a portion of that embodiment in more detail. 
         FIG. 4  shows a top-view according to IV in  FIG. 3 . 
         FIG. 5A to 5C  show different views of a component carrier provided with a component. 
         FIG. 6A-6E  show subsequent steps in an embodiment of a method of manufacturing according to the second aspect of the invention. 
         FIG. 7A, 7B  shows additional steps of in an embodiment of a method of manufacturing according to the second aspect of the invention. 
         FIG. 8A-8F  show a first set of further embodiments. 
         FIG. 9A-9F  show a second set of further embodiments. 
         FIG. 10A, 10B  show a still further embodiment of the electronic device. 
         FIG. 11A, 11B, 11C  show another embodiment of a method of manufacturing resulting in the intermediate product shown in  FIG. 11C . 
         FIG. 12A, 12B  show an additional embodiment of the electronic device. 
     
    
    
     DETAILED DESCRIPTION OF EMBODIMENTS 
     Like reference symbols in the various drawings indicate like elements unless otherwise indicated. 
       FIG. 1 . shows an electronic device  1  that comprises a stack  10  of layers. The stack  10  has a cavity  14  wherein a component carrier  23 , which is part of a carrier module  20  and provided with an electronic component  30  is arranged. The electronic product in this example comprises a further electronic component  30   a  which is arranged on a further component carrier  23   a  within a further cavity  14   b  in the stack  10 . 
       FIG. 2  shows a cross-sectional view of the product of  FIG. 1 . As shown therein, the cavity  14  extends through the stack of layers from one of the layers, denoted as  12   n  to another one of said layers  12   x  in a direction d 14 . The direction is d 14  is in between a direction aligned with a plane of the one  12   n  of the layers and a direction perpendicular to that plane. In the example shown the direction of the cavity  14  is at an angle of approximately 45 degrees. Alternatively another angle may be selected that deviates from one aligned with or perpendicular to the plane of  12   n , for example in a range between 5 and 85 degrees or a range between 95 and 175 degrees. However alternatively the direction of the cavity may be even selected as perpendicular to the plane of  12   n  or close to perpendicular. In the embodiment shown, the further cavity  14   a  extends from the layer  12   n  to another  12   y , at a different level than the layer  12   x . The extension direction d 14a  of the further cavity  14   a  is approximately the same as that of the cavity  14 , but that is not necessary. It is also not necessary that the cavities  14 ,  14   a  end in the same layer  12   n , as is the case here.  FIG. 2  shows that the stack  10  of layers  12  of the electronic device  1  comprises further layers until a top layer  12   nn  on the layer  12   n . In such further layers still further cavities accommodating respective further component carriers with electronic components may be provided, but this is not necessary, also additional layers above layer  12   n  may be absent in other embodiments. 
     In the embodiment shown the stack  10  is provided on a substrate  5 . The substrate  5  is optional and may serve during a manufacturing stage as a surface on which to deposit the layers  12   a  to  12   nn . In the embodiment shown, a release layer  6  is provided between the substrate  5  and the stack  10 , so that the substrate  5  (and the release layer  6 ) can be released from the stack  10  if desired. 
     As shown in more detail in  FIG. 3, 4  in the embodiment of  FIG. 1 , the component carrier  23  is integral with an electric terminal carrier  21  that carries the electric terminals. The component carrier  23  and the electric terminal carrier  21  form a carrier module  20 . The electric terminal carrier  21  extends through the wall  141  to in between mutually subsequent layers, where the electric terminals are electrically connected with the electrical conductors carried by one of those mutually subsequent layers  12   n . The component carrier  23  that supports the electronic component  30  is accommodated in the cavity  14 . 
     More in particular,  FIG. 3  depicts a portion of the stack  10 , excluding the layers above layer  12   n .  FIG. 4  is a top-view according to IV in  FIG. 3  of this portion. An exemplary carrier module  20  and the component  30  supported by its component carrier are shown in more detail in  FIGS. 5A, 5B and 5C . 
       FIG. 3,4  show that the component carrier  23  is accommodated in the cavity. The carrier module  20 , which supports the electronic component  30  at its component carrier  23  within the cavity  14  comprises electrically conductive tracks  24  from electric contacts  31  of the electronic component to electric terminals  25  at the electric terminal carrier  21  that extends over layer  12   n . The electric terminals  25  are electrically connected with respective electrical conductors  15  at a surface  122   n  of the layer  12   n.    
     In this exemplary embodiment of the electronic device according the electronic component  30  is a light emitting device and the stack  10  of layers is translucent. Alternatively or in addition other electronic components may be provided for example on a same component carrier  23  or on another component carrier in another cavity. 
     In the embodiment shown, the carrier module  20  is a printed circuit board having the electric terminal carrier  21  as a first rigid portion  21 , and the component carrier  23  as a second rigid portion and further a flexible portion  22  that forms the flexible interconnecting interface between the electric terminal carrier  21  and the component carrier  23 . The flexible portion  22  provides for a blunt angle of about 135 degrees between the first rigid portion  21  and the second rigid portion  23 . By way of example, the further component carrier  23   a  that carries the further electronic component  30   a  is a portion of a flexible foil. Further, in this example the flexible foil  20   a  is folded over a part of the surface  122   n  above the cavity and that portion forms a electric terminal carrier. To avoid an unduly high curvature in the flexible foil  20   a , an edge portion  124   n  at that part of the surface  122   n  is curved, for example with a radius of curvature of a few mm. 
       FIG. 4  further shows the electrically conductive tracks  24   a  extending from electric contacts of the further electronic component  30   a  to further electric terminals  25   a  that are electrically connected with further electrical conductors  15   a  at the surface  122   n  of the layer  12   n . As can be seen in  FIG. 3 , in this case, where the flexible foil  20   a  is folded over a part of the surface  122   n  above the cavity  14   a  the combination of the component carrier  23   a  with the component  30   a  and the electric terminal carrier formed by the folded portion only requires a modest surface area. In order to be able to reuse the surface area defined by the opening of the cavity, the cavity may be filled, for example with the same material as used for the layers of the stack. 
     A method of manufacturing the electronic device is now illustrated with reference to  FIG. 6A-6E . Therein  FIG. 6A  schematically show how a stack  10  of layers is deposited. 
       FIG. 6A  shows a first intermediate product obtained after deposition of layers  12   a  to  12   a ′ in steps S 1   a -S 1   a ′. The layers  12   a  to  12   a ′ are deposited on a substrate  5 . A release layer  6  may be provided, so that the stack  10 , optionally including the release layer  6  can be released from the substrate  5 . Alternatively the substrate  5  may remain with the product. 
     Further layers including layer  12   a ″ are deposited in subsequent steps S 1   a ′-S 1   a ″ as shown in  FIG. 6B . The material of the subsequent layers is deposited in a patterned manner, so that cavities  14 ″ and  14   a ″ start to form, respectively from layer  12   x ,  12   y  onwards. 
     As shown in  FIG. 6C , the formation of the cavities  14 ,  14   a  is completed after deposition of layer  12   n  and the cavities are accessible through an opening  128   n ,  126   n  in the surface  122   n  of the layer  12   n.    
     As shown in  FIG. 6D , upon completion of the cavities  14 ,  14   a , step S 2  follows, wherein component carriers supporting electronic components  30 ,  30   a  and being part of carrier modules  20 ,  20   a  are inserted. In a step S 3 , as also schematically shown in  FIG. 6D , electric terminals  25  (See  FIG. 4 ) arranged at a terminal carrier  21  of carrier module  20 , are electrically connected with respective electrical conductors  15  at the surface  12   n  of the stack of layers  10 . A curable metal paste or an electrically conductive adhesive, for example an anisotropically conductive adhesive may be used for this purpose. 
     Similarly a further carrier module  20   a  is provided having a first end which forms an electric terminal carrier extending outside the cavity  14   a  and a second end inside the cavity  14   a  forming a component carrier for component  30   a . The electric terminals  25   a  (See  FIG. 4 ) are electrically connected with respective electrical conductors  15   a  at the surface  12   n  of the stack of layers  10   
       FIG. 6E  shows optional further steps S 4   n -S 4   nn , wherein further layers up to  12   nn  are deposited. After deposition of the further layers the terminal carrier  21  of carrier module  20  provides for electric terminals that extend from the component carrier of that carrier module  20  to a wall  141  of the cavity  14  to form an electrical connection with the electrical conductors  15  arranged between layer  12   n  and the subsequent layer. 
     Similarly, the end portion of the flexible foil  20   a  is a further electric terminal carrier that provides for electric terminals  25   a  that extend from the component carrier to a wall  141  of the cavity to form an electrical connection with the electrical conductors  15   a  arranged between layer  12   n  and the subsequent layer. 
     As shown in the right portion of  FIG. 6D , insertion of the component carrier of the carrier module  20   a  with its component  30   a  is facilitated as the cavity  14   a  has a wedge shaped cross-section that tapers outward to the opening  14   a.    
       FIG. 7A  shows a step SOA, wherein the electrical component  30  is assembled with the component carrier  23  of a carrier module  20  before the step S 2  of inserting. 
     As schematically shown in  FIG. 7B , the step of assembling may comprise the step of adhering SOB the electric contacts  31  of the electronic component  30  to the electrically conductive tracks  24  with an electrically conductive adhesive  32 . The adhesive  32  may have an anisotropic conductivity. That is to say that its conductivity in lateral directions with respect to a surface at which it is applied is lower than a conductivity in a perpendicular direction with respect to said surface. Instead of using an adhesive, the electric contacts  31  of the electronic component  30  may be connected to the electrically conductive tracks  24  with a metal paste, e.g. a silver paste, which subsequently cured. 
       FIG. 8A to 8D  show further examples of a carrier module  20  with one or more components  30 ,  30 A,  30 B, which may be used in embodiments of the claimed electronic device. In the example of  FIG. 8A , the carrier module  20  is a single layer flexible PCB. As shown in  FIG. 8D , the carrier module  20  has a first end portion  21  that serves as an electric terminal carrier, a second end portion  23  that serves as a component carrier and an intermediate portion  22 , that allows the end portions to hinge with respect to one another. 
     In the example of  FIG. 8B , end portions of the carrier module that define the terminal carrier and the component carrier are provided at their backside with a respective stiffening layer  26 ,  27 . In the example of  FIG. 8C , the end portion  23  to be inserted in the cavity is provided with an additional component  30 B, opposite the component  30 A. In the example of  FIG. 8D , end portion  23  carrying the component  30  to be inserted in the cavity is in an orientation parallel to the end portion  21  having the electric contacts. As shown in  FIG. 8E , this is achieved in that an angle α between the end portion  21  and an intermediate portion  22  is complimentary to an angle β (180-α) between the intermediary portion  22  and the end portion  23 . Therewith the component  30  can be arranged aligned with a layer  12   x  at a lower level, than the level (layer  12   n ) where the electric contacts for that component  30  are provided.  FIG. 8F  shows a perspective view of this application. 
       FIG. 9A to 9D  show still further examples of a carrier module  20  with one or more components  30 ,  30 A,  30 B, suitable for use in embodiments of the claimed electronic device. In these examples the carrier module  20  has a plurality of component carriers  23   a ,  23   b . Component carrier  23   a , carrying component  30 A, is coupled via flexible portion  22   a  with the terminal carrier  21  carrying the electric terminals. Component carrier  23   b , carrying component  30 B, is coupled via flexible portion  22   b  with component carrier  23   a . As illustrated in  FIG. 9E , the components  30 A,  30 B can therewith be arranged in a single cavity at mutually different angles. This is shown for example in  FIG. 9E  in a cross-section for example 9A, and in  FIG. 9F  in a perspective view for example 9C. It is further noted that in the example of  FIG. 9B , the terminal carrier  21  and the component carriers  23   a ,  23   b  are provided at their backside with a respective stiffening layer  26 ,  27   a ,  27   b . In the example of  FIG. 9C , the component carriers  23   a ,  23   b  each are provided at their backside with a proper additional component  30 C,  30 D. In the example of  FIG. 9D , component carrier  23   a  carries a first component  30 A at its front side and component carrier  23   b  carries a second component  30 B at its back side. 
       FIG. 10B  shows another embodiment of the electronic device  1 . Therein  FIG. 10A  shows the component carrier  23  provided with the component  30  in more detail. In the embodiment shown, the electric terminals  25   a ,  25   b ,  25   c  are resilient elements that are arranged in a tensed state to the contact points, e.g.  15   a   1  of the electrical conductors  15   a ,  15   b ,  15   c . The contact points, such as  15   a   1  may be formed by depositing an electrically conductive material on an end of the corresponding electrical conductor, e.g.  15  at the boundary where a layer carrying that electrical conductor faces the wall  141  of the cavity  14 . The electrically conductive material is for example an adhesive or solder. In a manufacturing process, the component carrier  23  can be inserted into the cavity  14  and when insertion is completed, the resilient elements  25   a ,  25   b ,  25   c  are arranged in a tensed state to the contact points at the wall  141 , so that they form an electrical connection therewith. 
       FIGS. 11A, 11B and 11C  show an alternative method of manufacturing an electronic device  1  according to the invention. As shown in  FIG. 11A , therein the electric terminals  25   a ,  25   b ,  25   c  are provided (S 0 C) as adhesive electric contacts. 
     As further shown in  FIG. 11B , the step of inserting (S 2 A) comprises keeping the adhesive electric contacts  25   a ,  25   b ,  25   c  away from the wall  141  of the cavity  14  until the adhesive electric contacts  25   a ,  25   b ,  25   c  face respective contacts, e.g.  15   a   1  of the electrical conductors  15   a ,  15   b ,  15   c  exposed at the wall. Subsequently an electric connection is provided as shown in  FIG. 11C  by moving (S 3 A) the component carrier  23  with the adhesive electric contacts  25   a ,  25   b ,  25   c  towards the wall in a direction aligned with the surface normal of the wall  141 . The adhesive may for example be cured by UV-radiation, or as result of the exerted pressure. Alternatively the adhesive may be provided as a self-curing two-component material. 
     In alternative embodiment the adhesive electric contacts have an anisotropic conductivity, such that its conductivity in the lateral directions with respect to the surface of the wall is lower than a conductivity in a perpendicular direction with respect to the wall. In that case it is not necessary to keep the adhesive electric contacts  25   a ,  25   b ,  25   c  away from the wall  141  during insertion. Upon completion of the insertion, the adhesive electric contacts  25   a ,  25   b ,  25   c  already form an electrical connection with the electrical conductors  15   a ,  15   b ,  15   c . The adhesive may for example be cured by UV-radiation, or as result of the exerted pressure. Alternatively the adhesive may be provided as a self-curing two-component material. 
     A still further embodiment is disclosed with reference to  FIG. 12A, 12B . In the embodiment shown therein the electric terminals  25   a ,  25   b ,  25   c  are formed by an elastic interlayer  29  of an anisotropically electrically conductive material. The material is anisotropically electrically conductive in the sense that its conductivity in the lateral directions with respect to the surface of the wall  141  is lower than a conductivity in a perpendicular direction with respect to the wall. It will be appreciated by the person skilled in the art that the carrier may be provided with a larger number of component carrier portions that are coupled between flexible intermediary portions. 
     In the appended claims the word “comprising” does not exclude other elements or steps, and the indefinite article “a” or “an” does not exclude a plurality. A single component or other unit may fulfill the functions of several items recited in the claims. The mere fact that certain measures are recited in mutually different claims does not indicate that a combination of these measures cannot be used to advantage. Any reference signs in the claims should not be construed as limiting the scope.