PATENT DOCUMENT

Publication Number: US-12095185-B2
Application Number: US-202117478221-A
Country: US
Kind Code: B2

Title: Built-in connector for board-to-board and flex-to-rigid board connection

Abstract:
Stacked circuit board structures and methods of assembly are described. In an embodiment, a stacked circuit board structure includes first circuit board and a second circuit board including a plurality of pins mounted thereon, and the plurality of pins are secured in a plurality of receptacles that are coupled with the first circuit board to provide electrical connection between the first circuit board and the second circuit board.

Claims:
What is claimed is: 
     
       1. A stacked circuit board structure comprising:
 a first circuit board having a first side and a second side opposite the first side; 
 a second circuit board having a first side and a second side opposite the first side, wherein the first side of the second circuit board faces the second side of the first circuit board; 
 a plurality of pins mounted onto the first side of the second circuit board; 
 wherein the plurality of pins is secured in a plurality of receptacles coupled with the first circuit board to provide electrical connection between the first circuit board and the second circuit board; and 
 wherein the plurality of receptacles includes plurality of separate board openings extending at least partially through the first circuit board, and the plurality of pins is secured in the plurality of separate board openings. 
 
     
     
       2. The stacked circuit board structure of  claim 1 , wherein each pin of the plurality of pins is separately bonded to the first side of the second circuit board. 
     
     
       3. The stacked circuit board structure of  claim 2 , wherein each pin of the plurality of pins is separately bonded to the first side of the second circuit board with a corresponding solder material. 
     
     
       4. The stacked circuit board structure of  claim 1 , wherein each receptacle is a socket including mechanical punch. 
     
     
       5. The stacked circuit board structure of  claim 1 , wherein each receptacle comprises a sleeve including a slit along a longitudinal length of the sleeve. 
     
     
       6. The stacked circuit board structure of  claim 1 , wherein each pin includes a base structure and a mesa structure protruding from the base structure, wherein the base structure is wider than the mesa structure. 
     
     
       7. The stacked circuit board structure of  claim 6 , wherein the first circuit board rests on the base structure for each pin of the plurality of pins. 
     
     
       8. The stacked circuit board structure of  claim 7 , further comprising a magnetic stiffener structure on the second side of the first circuit board, wherein the plurality of pins is attracted to a magnetic field of the magnetic stiffener structure. 
     
     
       9. The stacked circuit board structure of  claim 1 , wherein each pin is bonded to the second circuit board with a corresponding bonding layer. 
     
     
       10. The stacked circuit board structure of  claim 9 , wherein the second circuit board is in direct contact with the corresponding bonding layer for each pin. 
     
     
       11. The stacked circuit board structure of  claim 1 , further comprising a plurality of alignment pins mounted onto the first side of the second circuit board, wherein each alignment pin extends through a corresponding alignment opening in the first circuit board, and each alignment pin includes a spring portion positioned above the first side of the first circuit board. 
     
     
       12. The stacked circuit board structure of  claim 11 , wherein each spring portion presses the first circuit board toward the second circuit board. 
     
     
       13. The stacked circuit board structure of  claim 1 , further comprising:
 a plurality of contact pads on the first side of the first circuit board, each contact pad corresponding to a board opening through the first circuit board; and 
 a plurality of separate solder materials bonding the plurality of pins to the plurality of contact pads. 
 
     
     
       14. The stacked circuit board structure of  claim 13 , further comprising a first plurality of electronic components mounted on the second side of the first circuit board, and a second plurality of electronic components mounted on the first side of the second circuit board, wherein the plurality of pins extends laterally adjacent to the first plurality of electronic components and the second plurality of electronic components. 
     
     
       15. The stacked circuit board structure of  claim 1 , wherein the plurality of receptacles includes a plurality of sockets secured in the plurality of separate board openings in the first circuit board, wherein the plurality of pins is secured in the plurality of sockets. 
     
     
       16. The stacked circuit board structure of  claim 1 , wherein the plurality of pins includes a first group of pins with a first maximum width, and a second group of pins with a second maximum width that is greater than the first maximum width. 
     
     
       17. The stacked circuit board structure of  claim 1 , wherein the plurality of receptacles is a plurality of sockets including a first group of sockets with a first maximum wall width, and a second group of sockets with a second maximum wall width that is greater than the first maximum wall width. 
     
     
       18. A stacked circuit board structure comprising:
 a first circuit board having a first side and a second side opposite the first side; 
 a second circuit board having a first side and a second side opposite the first side, wherein the first side of the second circuit board faces the second side of the first circuit board; 
 an interposer between the first circuit board and the second circuit board, the interposer having a maximum thickness of 200 μm and including an array of vertical wires; 
 wherein the second side of the first circuit board is bonded to a first side of the interposer, the second side of the first circuit board including a first landing pad bonded to a plurality of vertical wires of the array of vertical wires; and 
 wherein the first side of the second circuit board is bonded to a second side of the interposer, the first side of the second circuit board including a second landing pad bonded to the plurality of vertical wires of the array of vertical wires. 
 
     
     
       19. The stacked circuit board structure of  claim 18 , wherein the array of vertical wires embedded in a thermoset polymer layer that adheres to the first landing pad and the second landing pad. 
     
     
       20. A stacked circuit board structure comprising:
 a first circuit board having a first side and a second side opposite the first side; 
 a second circuit board having a first side and a second side opposite the first side, wherein the first side of the second circuit board faces the second side of the first circuit board; 
 a plurality of magnets mounted separately mounted onto the second side of the first circuit board; and 
 a plurality of pins mounted onto the first side of the second circuit board; 
 wherein the plurality of pins rests on the plurality of magnets and each pin is attracted to a magnetic field of a corresponding magnet.

Description:
BACKGROUND 
     Field 
     Embodiments described herein relate to electronic packaging, and more particularly to printed circuit board assembly. 
     Background Information 
     Printed circuit boards (PCBs) may commonly be connected using PCB connectors. In a basic multi-pin connection system, a pair of boards including a corresponding mating pair of PCB connectors are fit together, with one PCB connector including an array of header pins, and the mated PCB connector including a corresponding housed array of sockets to receive the array of header pins. Each corresponding PCB connector can be hard soldered to a corresponding board. The housing can function to align and position the header pins accurately, as well as to insulate the header pins and socket contacts from each other. 
     SUMMARY 
     Stacked circuit board structures and methods of assembly are described. In some embodiments, the stacked circuit board structures may allow for local strain relief. Furthermore, some embodiments may facilitate the ability for re-work, and overall volume reduction relative to traditional stacked circuit board structures including housed PCB connectors. 
     In an embodiment, a stacked circuit board structure includes a first circuit board having a first side and a second side opposite the first side, and a second circuit board having a first side and a second side opposite the first side, wherein the first side of the second circuit board faces the second side of the first circuit board. A plurality of pins may be mounted onto the first side of the second circuit board. When brought together the plurality of pins is secured in a plurality of receptacles coupled with the second circuit board. For example, the receptacles may include sockets or board openings, or combinations thereof. The circuit boards may be clamped together with physical or magnetic techniques, or combinations thereof. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG.  1 A- 1 C  are perspective view illustrations of a sequence of assembling a stacked circuit board structure with a perpendicular pin array in accordance with an embodiment. 
         FIG.  2    is a schematic top layout view of circuit board electronic components and a perpendicular pin array on a circuit board in accordance with embodiments. 
         FIG.  3 A  is a perspective view illustration of a pin and socket receptacle in accordance with an embodiment. 
         FIG.  3 B  is a perspective view illustration of a compliant pin and socket receptacle in accordance with an embodiment. 
         FIG.  4    is a perspective view illustration of a metallic split sleeve socket receptacle in accordance with an embodiment. 
         FIGS.  5 A- 5 B  are schematic cross-sectional side view illustration of mechanical locking pin socket receptacles with different dimensions in accordance with embodiments. 
         FIGS.  6 A- 6 B  are schematic cross-sectional side view illustrations of a sequence of assembling a stacked circuit board structure with a surface mounted perpendicular pin array and surface mounted socket receptacles in accordance with an embodiment. 
         FIGS.  7 A- 7 B  are schematic cross-sectional side view illustrations of a sequence of assembling a stacked circuit board structure with a surface mounted perpendicular pin array and board openings in a receiving circuit board in accordance with an embodiment. 
         FIGS.  8 A- 8 B  are schematic cross-sectional side view illustrations of a sequence of assembling a stacked circuit board structure with a surface mounted perpendicular pin array and socket receptacles mounted in corresponding board openings in a receiving circuit board in accordance with an embodiment. 
         FIG.  9    is a schematic cross-sectional side view illustration of a stacked circuit board structure with a magnetic perpendicular pin array in accordance with an embodiment. 
         FIG.  10    is a schematic cross-sectional side view illustration of a stacked circuit board structure with a surface mounted perpendicular pin array, board openings in a receiving circuit board, and magnetic stiffener clamp in accordance with an embodiment. 
         FIG.  11    is a close-up schematic cross-sectional side view illustration of circuit board resting on a base structure of a pin in accordance with an embodiment. 
         FIG.  12    is a schematic cross-sectional side view illustration of a stacked circuit board structure with a surface mounted perpendicular pin array, board openings in a receiving circuit board, and magnetic stiffener clamp in accordance with an embodiment. 
         FIG.  13    is a close-up schematic cross-sectional side view illustration of circuit board resting on a bonding layer for a pin in accordance with an embodiment. 
         FIG.  14    is a schematic cross-sectional side view illustration of a stacked circuit board structure with a plurality of alignment pins in accordance with an embodiment. 
         FIG.  15    is a schematic top view illustration of a perpendicular pin array and alignment pins in accordance with an embodiment. 
         FIGS.  16 - 17    are schematic cross-sectional side view illustrations of stacked circuit board structures including an intermediate interposer with a plurality of vertical wires in accordance with embodiments. 
     
    
    
     DETAILED DESCRIPTION 
     Embodiments describe stacked circuit board structures in which opposing circuit boards are stacked on top of one another and interconnected with vertical pin arrays. For example, the vertical pin arrays may be for signal and power transmission between the circuit boards. 
     In an embodiment, a stacked circuit board structure includes a first circuit board having a first side and a second side opposite the first side, and a second circuit board having a first side and a second side opposite the first side, where the first side of the second circuit board faces the second side of the first circuit board. A plurality of pins may be mounted onto the first side of the second circuit board. When brought together the plurality of pins is secured in a plurality of receptacles coupled with the second circuit board. In this manner, a connector is built into the stacked board assembly rather than as a separate component. In accordance with embodiments, the pins and receptacles can be brought together with magnetic or physical force to provide electrical connection between the first circuit board and the second circuit board. 
     In one aspect, it has been observed that a common reliability failure point for stacked PCB connector assemblies is the solder connection of the PCB connector assemblies to the circuit boards. In accordance with embodiments, the pin connections can be integrated directly onto the circuit boards, and housing-less. This may distribute stresses across the circuit boards, improving reliability. In addition, mechanical contact with the receptacles (e.g. sockets) and pins can allow for local strain relief during drop and temperature cycling. For example, the pins and sockets may be free-standing, and not encased within a housing, between the circuit boards. 
     In another aspect, embodiments describe stacked circuit board structures in which the in-situ integration of connector assemblies facilitates the ability for re-work, which can allow for repairability and speed matching between electronic components, improving overall production yield and performance. 
     In yet another aspect, the housing-less aspect of in-situ integration of the connector assemblies onto the circuit boards can result in a volume reduction, reducing overall assembly size and z-height. In some embodiments, the pins and receptacles such as sockets, are free-standing between opposing circuit boards such that they are not encapsulated with a molding compound, or encased within a housing between the opposing circuit boards. This may facilitate the ability to freely re-work the circuit boards or replace one circuit board without replacing both circuit boards. 
     In various embodiments, description is made with reference to figures. However, certain embodiments may be practiced without one or more of these specific details, or in combination with other known methods and configurations. In the following description, numerous specific details are set forth, such as specific configurations, dimensions and processes, etc., in order to provide a thorough understanding of the embodiments. In other instances, well-known semiconductor processes and manufacturing techniques have not been described in particular detail in order to not unnecessarily obscure the embodiments. Reference throughout this specification to “one embodiment” means that a particular feature, structure, configuration, or characteristic described in connection with the embodiment is included in at least one embodiment. Thus, the appearances of the phrase “in one embodiment” in various places throughout this specification are not necessarily referring to the same embodiment. Furthermore, the particular features, structures, configurations, or characteristics may be combined in any suitable manner in one or more embodiments. 
     The terms “above”, “over”, “to”, “between”, and “on” as used herein may refer to a relative position of one layer with respect to other layers. One layer “above”, “over”, or “on” another layer or bonded “to” or in “contact” with another layer may be directly in contact with the other layer or may have one or more intervening layers. One layer “between” layers may be directly in contact with the layers or may have one or more intervening layers. 
     Referring now to  FIGS.  1 A- 1 C  isometric view illustrations are provided of a sequence of assembling a stacked circuit board structure  150  with a perpendicular pin array in accordance with an embodiment. As illustrated in  FIG.  1 A , the sequence may begin with a plurality of electronic components  110  mounted on a first circuit board  102 . For example, the electronic components  110  can be mounted on a first side  104  of the first circuit board  102  and/or on a second side  106  of the first circuit board  102 . 
     The first circuit board  102  in accordance with embodiments may be rigid or flexible, and may be formed of a variety of suitable printed circuit board (PCB) materials including FR4, prepreg, polyimide, etc. In an embodiment, a flexible first circuit board  102  (also commonly referred to as a flex circuit, or flex board) includes flexible dielectric layers (e.g. polymer such as polyimide, polyester, polyethylene naphthalate, etc.) with laminated circuit patterns (e.g. metal foil pattern such as copper) on one or both sides of the flexible dielectric layers. The electronic components  110  in accordance with embodiments can be dies ranging from system-on-chip (SOC) to memory, passive components (resistors, capacitors, inductors, etc.), micro-electromechanical systems (MEMS), sensors, etc. A variety of configurations of different electronic components is understood. 
     Referring now to  FIG.  1 B , a second circuit board  202  is illustrated including a plurality of electronic components  210  mounted on a first side  204  of the second circuit board. Additional electronic components  210  may also be optionally mounted on a second side  206  of the second circuit board  202 . Similar to the first circuit board  102 , the second circuit board  202  may be rigid or flexible, and formed of the same materials described with regard to the first circuit board  102 . Similarly, electronic components  210  may be selected from the same electronic components  210  in accordance with embodiments can be dies ranging from system-on-chip (SOC) to memory, passive components (resistors, capacitors, inductors, etc.), micro-electromechanical systems (MEMS), sensors, etc. In a specific implementation the second circuit board  202  is a rigid wireless access point (AP) board, while the first circuit board  102  is a rigid or flexible radio frequency (RF) board. 
     Still referring to the embodiment illustrated in  FIG.  1 B , a plurality of pins  220  is mounted onto the first side  204  of the second circuit board  202  laterally adjacent to the plurality of electronic components  210 . As shown, the pins  220  may be taller than the plurality of electronic components  210 . The first circuit board  102  may then be mounted onto the pins  220  as illustrated in  FIG.  1 C . Alternatively, the second circuit board  202  including the pins  220  may be stacked onto the first circuit board  102 . In the resulting structure, the first circuit board  102  and the second circuit board  202  are separated by the pins  220  as opposed to an interposer, or housed PCB connector. 
       FIG.  2    is a schematic top layout view of circuit board components and a perpendicular pin array on a circuit board in accordance with embodiments. In interest of clarity, the schematic top layout view of  FIG.  2    is made with regard to the electronic components  210  and pins  220  relative to the second circuit board  202  within the circuit board stack. As illustrated, the pins  220  can be placed at any open place, including between electronic components, along the perimeter of the second circuit board  202 , or around the perimeter of one or more electronic components  210 . 
     In accordance with embodiments, the first circuit board  102  is configured with a plurality of receptacles to mate with and receive the plurality of pins  220 . For example, the receptacles can include sockets of various shapes or board openings within the first circuit board  102 . Furthermore, the receptacles can include sockets mounted within board openings in the first circuit board  102 . Mechanical contact between the receptacles and pins  220  can help secure the first circuit board  102  to the second circuit board  202 , while allowing for strain relief during drop and temperature cycling. Furthermore, integration directly onto or within the circuit boards can reduce overall dimensions, including area and z-height while additionally providing flexibility for electrical vertical interconnects with different dimensions. In some embodiments, magnets can be utilized to attract the circuit boards together and maintain electrical contact between the circuit boards. Furthermore, alignment pins can be included to facilitate contact and gross alignment. 
       FIG.  3 A  is a perspective view illustration of a pin  220  and socket  130  receptacle in accordance with an embodiment. As shown, the socket  130  receptacle may be in the shape of a clip in which mechanical punches  44  are designed to provide a compressive clamping force onto sidewalls  221  of pin  220 . In an embodiment, the pin  220  is pillar shaped, and extends from a base  225  which can be bonded to the first circuit board  102 . For example, the pin  220  can be tubular, rod-like, include multiple sides as shown, obelisk, etc. In accordance with embodiments, the pins  220  can be characterized by a maximum width (Wp). Furthermore, the stacked circuit board structures may include groups of pins having different maximum widths. 
       FIG.  3 B  is a perspective view illustration of a compliant pin  220  and socket  130  receptacle in accordance with an embodiment. In such a configuration, the compliant pin  220  may include a wire  222  shape extending from the base  225  to provide possible x-y bending motion. In the particular embodiment illustrated, the wire  222  can be folded to increase the pin thickness within the socket  130  receptacle. 
       FIG.  4    is a perspective view illustration of a metallic split sleeve socket  130  receptacle in accordance with an embodiment. As shown, the split sleeve socket  130  receptacle can include a tubular sleeve structure with slit  134  through the sidewalls  140  of the tubular sleeve structure running at least a portion of the longitudinal length (L) of the socket  130  receptacle. In an embodiment, the slit  134  is formed at least in the terminal end  137  that accepts the pin  220 , and may optionally extend to the base end  138  that can be bonded to the first circuit board  102 . In accordance with embodiments, the longitudinal length (L) of the split sleeve socket  130  receptacle can be designed to eliminate wasted space (height) after receiving a pin  220  to reduce total height of the stacked circuit board structure. 
       FIGS.  5 A- 5 B  are schematic cross-sectional side view illustration of mechanical locking pin socket  130  receptacles with different dimensions in accordance with embodiments. As shown, the locking pin socket  130  receptacles can have a tubular sidewalls  140  of maximum width (w) and a pedestal  141  extending from the base end  138  a depth (D). The tubular sidewalls  140  may have an inner width (I). Mechanical punches  144  can protrude from the sidewalls  140  to press onto the pins  220  when inserted. For example, mechanical punches  144  can be dome-shaped mesa structures extending from the sidewalls  140 , or compliant members that can be pushed into the sidewalls  140  by insertion of the pin  220  while still providing a locking function to retain the pin  220 . Multiple mechanical punches  144  can be distributed around a perimeter of the sidewalls  140 , or a continuous mechanical punch  144  can be formed along the sidewalls  140 . As shown in  FIGS.  5 A- 5 B , dimensions of the locking pin socket  130  receptacles can be varied. For example, maximum width (w) of the sidewalls  140  can be adjusted to provide a specific conductivity or pressure. Likewise depth (D) of the pedestal  141  and longitudinal length (L) can be adjusted. In some embodiments, locking pin socket  130  receptacles with different dimensions are provided to accommodate pins  220  of different sizes (e.g. maximum widths). For example, different pin sizes can be used to transfer power or ground signals compared to RF signals. Alternatively, the same pin sizes can be used, while adjusting dimensions of the locking pin socket  130  receptacles. For example, inner width (I) can be maintained, while maximum width (w) of the sidewalls  140  is adjusted for signals. In an embodiment, a pin  220  carrying an RF signal is retained by a locking pin socket  130  receptacle with thicker maximum width (w) of the sidewalls  140  to mitigate insertion loss, while a pin  220  carrying a power or ground signal can be retained by a locking pin socket  130  receptacle with thinner maximum width (w) of the sidewalls  140 . 
     It is to be appreciated that the particular examples illustrated in  FIGS.  3 A- 5 B  are illustrative of possible pin and socket  130  receptacle configurations, and embodiments are not necessarily limited to the specific structures illustrated. The clip structures of  FIGS.  3 A- 3 B  may resemble a more traditional-type socket design, while  FIGS.  4 - 5 B  represent alternative designs that may potentially reduce space. 
     Referring now to  FIGS.  6 A- 6 B  schematic cross-sectional side view illustrations are provided for a sequence of assembling a stacked circuit board structure  150  with a surface mounted perpendicular pin array and surface mounted socket receptacles in accordance with an embodiment. In particular,  FIG.  6 A  illustrates a first circuit board  102  with a plurality of socket  130  receptacles aligned over a second circuit board  202  with a plurality of pins  220 , while  FIG.  6 B  illustrates a stacked circuit board structure  150  with the plurality of pins  220  secured in the plurality of socket  130  receptacles. As illustrated, the stacked circuit board structure  150  may include a first circuit board  102  having a first side  104  and a second side  106  opposite the first side, and a second circuit board  202  having a first side  204  and a second side  206  opposite the first side, where the first side  204  of the second circuit board  202  faces the second side  106  of the first circuit board  102 . A plurality of pins  220  may be mounted onto the first side  204  of the second circuit board  202 . For example, the pins  220  can be bonded with a solder material  240 . When brought together, the plurality pins  220  is secured in the corresponding plurality of socket  130  receptacles that are coupled with the first circuit board  102 , which provide an electrical connection between the first circuit board  102  and the second circuit board  202 . 
     In the particular embodiment illustrated the plurality of socket  130  receptacles is mounted onto the second side  106  of the first circuit board  102 . For example, each socket  130  receptacle can be separately mounted, for example with a separate solder material  143 . Similarly, each pin  220  of the plurality of pins can be separately bonded to the first side  204  of the second circuit board  202  with a separate solder material  240 . 
     In accordance with embodiments, the socket  130  receptacles can be bonded to corresponding landing pads  142  of the first circuit board  102  to provide electrical connection to wiring within the first circuit board  102  as well as electronic components  110  mounted on the first and/or second sides of the first circuit board  102 . Likewise, electronic components  110  can also be mounted onto and in electrical connection with corresponding landing pads  142 . Similarly, pins  220  and electronic components  210  can be bonded to landing pads  242  of the second circuit board  202  to provide electrical connection to wiring within the second circuit board  202  as wells as between the electronic components  210  and pins  220 . 
     In accordance with embodiments, the pins  220  and sockets  130  are free-standing between the first circuit board  102  and the second circuit board  202  such that they are not encapsulated with a molding compound or encased within a housing between the opposing circuit boards. For example, adjacent pins  220  and sockets  130  may be separated by air. This may facilitate the ability to freely re-work the circuit boards or replace one circuit board without replacing both circuit boards 
     In some embodiments, the plurality of pins  220  includes a first group of pins with a first maximum width (Wp), and a second group of pins with a second maximum width (Wp) that is greater than the first maximum width. In some embodiments, the plurality of socket receptacles includes a first group of sockets with a first maximum wall width (w), and a second group of sockets with a second maximum wall width (w) that is greater than the first maximum wall width. 
     It is to be appreciated that while the embodiment illustrated in  FIGS.  6 A- 6 B  is made with regard to the socket receptacles illustrated in  FIGS.  5 A- 5 B , this is merely exemplary and a variety of different socket receptacles and pin configurations can be used including, but not limited to, those illustrated and described with regard to  FIGS.  3 A- 3 B  and  FIG.  4   . 
     Referring now to  FIGS.  7 A- 7 B , schematic cross-sectional side view illustrations are provided for a sequence of assembling a stacked circuit board structure  150  with a surface mounted perpendicular pin array and board openings in a receiving circuit board in accordance with an embodiment. In particular,  FIG.  7 A  illustrates a first circuit board  102  with a plurality of receptacles aligned under a second circuit board  202  with a plurality of pins  220 , while  FIG.  7 B  illustrates a stacked circuit board structure  150  with the plurality of pins  220  secured in the plurality of receptacles. 
     As illustrated, the stacked circuit board structure  150  may include a first circuit board  102  having a first side  104  and a second side  106  opposite the first side, and a second circuit board  202  having a first side  204  and a second side  206  opposite the first side, where the first side  204  of the second circuit board  202  faces the second side  106  of the first circuit board  102 . A plurality of pins  220  may be mounted onto the first side  204  of the second circuit board  202 . For example, the pins  220  can be bonded with a solder material  240 . When brought together, the plurality pins  220  is secured in the corresponding plurality of receptacles that are coupled with the first circuit board  102 , which provide an electrical connection between the first circuit board  102  and the second circuit board  202 . 
     Specifically, the plurality of receptacles can include a plurality of separate board openings  160  extending at least partially through the first circuit board  102 , where the plurality of pins  220  is secured in the plurality of board openings  160 . As shown, solder material  143  may be used to bond the pins  220  to contact pads  146  on the first side  104  of the first circuit board  102 . For example, the contact pads  146  can be formed only on the first side  104  of the first circuit board  102  or as barrel contacts that also line sidewalls  161  of board openings  160 , and optionally the second side  106  of the first circuit board  102 . In an embodiment, a first plurality of electronic components  110  is mounted on the second side  106  of the first circuit board  102 , a second plurality electronic components  210  is mounted on the first side  204  of the second circuit board, and the plurality of pins  220  extends laterally adjacent to the first plurality of electronic components  110  and the second plurality of electronic components  210 . 
     The sockets  130  and board openings  160  in accordance with embodiments are not necessarily mutually exclusive. In some embodiments, the receptacles include both sockets  130  receptacles and board openings  160 .  FIGS.  8 A- 8 B  are schematic cross-sectional side view illustrations of a sequence of assembling a stacked circuit board structure  150  with a surface mounted perpendicular pin array and sockets  130  mounted in corresponding board openings  160  in a receiving circuit board in accordance with an embodiment. In such an embodiment, each receptacle of the plurality of receptacles includes a socket  130  secured in a corresponding board opening  160  in the first circuit board  102 , and a corresponding pin  220  is secured in the socket  130 . In such a configuration, the pin  220  can also extend into the board opening  160 . In such a configuration, orientation of the socket  130  within the first circuit board  102  can potentially lead to a further reduction in z-height for the stacked circuit board structure  150 . 
     Up until this point, stacked circuit board structures have been described as including pin-to-receptacle connections made with physical force. In some embodiments, magnets may be used to retain the stacked circuit board configuration. 
       FIG.  9    is a schematic cross-sectional side view illustration of a stacked circuit board structure  150  with a magnetic perpendicular pin array in accordance with an embodiment. In the particular embodiment illustrated, the stacked circuit board structure  150  includes a first circuit board  102  having a first side  104  and a second side  106  opposite the first side, a second circuit board  202  having a first side  204  and a second side  206  opposite the first side, where the first side  204  of the second circuit board  202  faces the second side  106  of the first circuit board  102 . As shown a plurality of magnets  164  can be separately mounted onto the second side  106  of the first circuit board  102 . For example, this may be accomplished with a conductive epoxy or low temperature solder material  162 . A plurality of pins  220  can be mounted onto the first side  204  of the second circuit board  202 , for example using a plurality of solder materials  240 . The second circuit board  202  and the first circuit board  102  can be brought together, with the plurality of pins  220  rest on the plurality of magnets  164 , and each pin  220  is attracted to a magnetic field of a corresponding magnet. For example, the pins  220  may be formed of a material that can be magnetized, such as some stainless steels. 
       FIG.  10    is a schematic cross-sectional side view illustration of a stacked circuit board structure  150  with a surface mounted perpendicular pin array, board openings  160  in a receiving circuit board, and magnetic stiffener structure  170  in accordance with an embodiment.  FIG.  11    is a close-up schematic cross-sectional side view illustration of a pin  220  secured in a board opening  160  in accordance with an embodiment. 
     As illustrated, the stacked circuit board structure  150  may include a first circuit board  102  having a first side  104  and a second side  106  opposite the first side, and a second circuit board  202  having a first side  204  and a second side  206  opposite the first side, where the first side  204  of the second circuit board  202  faces the second side  106  of the first circuit board  102 . A plurality of pins  220  may be mounted onto the first side  204  of the second circuit board  202 . For example, the pins  220  can be bonded with a solder material  240 . When brought together, the plurality pins  220  is secured in the corresponding plurality of receptacles that are coupled with the first circuit board  102 , which provide an electrical connection between the first circuit board  102  and the second circuit board  202 . Clamping force may be provided by a magnetic stiffener structure  170  to attract the array of pins  220  and/or second circuit board  202 . The magnetic stiffener structure  170  can be secured to the first side  104  of the first circuit board  102  with any suitable adhesive material  172  (e.g. epoxy, solder, etc.). 
     The plurality of receptacles can include a plurality of separate board openings  160  extending at least partially through the first circuit board  102 , where the plurality of pins  220  is secured in the plurality of board openings  160 . In the embodiment illustrated, landing pads  142  may be in the form of barrel contacts. For example, the barrel contacts can be through-hole plated (e.g. copper) along sidewalls  161  of the board openings, as well as along the second side  106  and optionally first side  104  of the first circuit board  102 . As shown, each pin  220  can include a base structure  224  and mesa structure  226  protruding from the base structure  224 . The base structure  224  can be wider than the mesa structure  226  so that the first circuit board  102  rests on a ledge  227  of the base structure  224  for each pin  220  of the plurality of pins. Each mesa structure  226  may also include tapers  228  along a top surface to facilitate guiding of the pins  220  into the board openings  160 . Electrical contact may be made by contacting the landing pads  142  with the pins  220 , where pressure is applied by attracting the pins  220  and/or second circuit board to the magnetic field supplied by the magnetic stiffener structure  170 . For example, pins  220  may be formed of a magnetizable material. 
     In one aspect, the stacked circuit board structure of  FIGS.  10 - 11    can be used to connect multiple circuit boards with a thin form factor. In a particular embodiment, the second circuit board  202  is a rigid circuit board, while the first circuit board  102  is a flexible circuit board. Pin size can be at least partially determined by first circuit board  102  thickness. Where electronic components are not mounted on the facing circuit board sides, the vertical interconnection thickness can be largely attributed to only solder material  240  thickness, adhesive layer  172  thickness, and base structure  224  thickness. The form factor can be even further reduced by removal of the base structure  224 . 
       FIG.  12    is a schematic cross-sectional side view illustration of a stacked circuit board structure  150  with a surface mounted perpendicular pin array, board openings  160  in a receiving circuit board, and magnetic stiffener structure  170  in accordance with an embodiment.  FIG.  13    is a close-up schematic cross-sectional side view illustration of circuit board resting on a solder material  240  for a pin  220  in accordance with an embodiment.  FIGS.  12 - 13    are substantially similar to those of  FIGS.  10 - 11   , with the elimination of base structure  224 . As such, each pin  220  can be I-shaped, rather than T-shaped. Upon bringing the first circuit board  102  and second circuit board  202  together, the first circuit board  102  may rest on the solder material  240  used to mount the pins  220  onto the landing pads  242 . Alternatively, the first circuit board  102  may rest directly on the landing pads  242 . In both cases, electrical contact can be made directly with the landing pads  142  of the first circuit board. 
     The stacked circuit board structures  150  described thus far have utilized clipping force from sockets or magnets to maintain contact between the circuit boards. In accordance with embodiments, these mechanisms can be further supported by alignment pins, to aid with rough alignment as well as to provide clamping force. Alternatively, alignment pins can be utilized to provide clamping force without the presence of sockets or magnets. 
       FIG.  14    is a schematic cross-sectional side view illustration of a stacked circuit board structure  150  with a plurality of alignment pins  250  in accordance with an embodiment.  FIG.  15    is a schematic top view illustration of a perpendicular pin array and alignment pins  250  in accordance with an embodiment. For illustrative purposes,  FIG.  14    is similar to the structure illustrated and described with regard to  FIG.  10   . It is to be appreciated however that this is exemplary, and the alignment pins  250  are not limited to the particular pin  220  configuration. Several distinctions are present in  FIG.  14    relative to  FIG.  10   . Foremost, the stiffener structure  180  may or may not be magnetic. Secondly, the stiffener structure  180  is optional, and may or may not be used. In some embodiments, the alignment pins  250  provide requisite clamping force. The optional stiffener structure  180  includes a first side  184  and a second side  186  and a plurality of alignment openings  182  extending therebetween. The second side  186  of the stiffener structure  180  may optionally be adhered to the first circuit board using a suitable adhesive layer  172 . As shown, a plurality of alignment pins  250  are mounted onto the first side  204  of the second circuit board  202 . Suitable bonding material  251  may be used such as epoxy, solder, etc. Each alignment pin  250  may further include a spring portion  254 , illustrated as an O-ring spring. Once brought together, the spring portions  254  may be positioned above the first side of the first circuit board  102  and press the first circuit board  102  toward the second circuit board  202 . Thus, where the first circuit board  102  is rigid enough, a stiffener structure  180  may be optional. Alternatively, the spring portions  254  can press directly against the first side  184  of the stiffener structure  180  which in turn transfers the pressure. 
     Referring now to  FIGS.  16 - 17    schematic cross-sectional side view illustrations are provided for stacked circuit board structures  150  including an interposer  300  with a plurality of vertical wires  320  in accordance with embodiments. In an embodiment, nano or micro wires can be vertically embedded in a polymer layer  310  or flex board to provide anisotropic conductive properties and fine pitch capability. The vertical wires  320  may have a diameter of 100 nm to 5 μm, and be formed of materials such as Cu, Ni, Ag, Au metals or alloys. In an embodiment, the vertical wires  320  may be electroplated or electroless plated. In an embodiment, the interposer  300  has a maximum thickness of 200 μm. 
     In the particular embodiment illustrated in  FIG.  16   , the interposer  300  can be directly applied between landing pads  142 ,  242  to form contact with the vertical wires by polymer curing. For example, heat can be applied to flow and cure a thermosetting polymer (e.g. epoxy, acryl, etc.) including the vertical wires  320  directly onto the first circuit board  102  and the second circuit board  202 . In such a configuration, the cured polymer layer  310  may adhere to the landing pads  142 ,  242  to provide mechanical support and the vertical wires  320  may contact landing pads  142 ,  242  to provide electrical connection. Such a technique can additional increase alignment tolerances when arranging the circuit boards. Alternatively, in the embodiment illustrated in  FIG.  17   , a solder material  143 ,  240  (or conductive adhesive) can be used to bond to the interposer  300  to the landing pads  142 ,  242 . In either configuration, the polymer layer  310  may absorb mechanical and thermal stress, and provide some compliance for the stacked assembly. 
     In utilizing the various aspects of the embodiments, it would become apparent to one skilled in the art that combinations or variations of the above embodiments are possible for forming a stacked circuit board structure. Although the embodiments have been described in language specific to structural features and/or methodological acts, it is to be understood that the appended claims are not necessarily limited to the specific features or acts described. The specific features and acts disclosed are instead to be understood as embodiments of the claims useful for illustration.

Metadata:
Filing Date: 20210917
Publication Date: 20240917
Grant Date: 20240917
Priority Date: 20210917
Inventors: HOANG, LAN H.
KATAHIRA, TAKAYOSHI
KANI, BILAL MOHAMED IBRAHIM
RENJAN, KISHORE N.
VADEENTAVIDA, MANOJ
TAO, JING
Assignee: APPLE INC
CPC Classifications: [{"code": "H01R13/6205", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01R12/79", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01R13/631", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01R12/57", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01R12/62", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01R12/58", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01R12/52", "inventive": true, "first": false, "tree": "[]"}, {"code": "H05K7/1438", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01R12/73", "inventive": false, "first": false, "tree": "[]"}, {"code": "H01R12/718", "inventive": true, "first": true, "tree": "[]"}, {"code": "H05K7/142", "inventive": true, "first": true, "tree": "[]"}, {"code": "H01R13/631", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01R13/6205", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01R12/79", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01R12/62", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01R12/58", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01R12/57", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01R12/52", "inventive": true, "first": false, "tree": "[]"}, {"code": "H01R12/718", "inventive": true, "first": true, "tree": "[]"}]
Family ID: 85572378