Abstract:
According an embodiment, a package-on-package heatsink interposer for use between a top package and a bottom package of a package-on-package device, may include a top heatsink below the top package; an interposer substrate below the top heatsink; a bottom heatsink below the interposer substrate; a first interposer substrate metal layer between the interposer substrate and the top heatsink; a second interposer substrate metal layer between the interposer substrate and the bottom heatsink; and interposer solder balls between the second interposer substrate metal layer and the bottom package.

Description:
BACKGROUND 
       [0001]    Package-on-package (POP) structures are designed for products with package area imitations but with few vertical size limitations. Devices, such as mobile phones, digital cameras, and other portable devices that have horizontal size limitations, can include POP structures. POP structures can save horizontal space in a device by vertically stacking packages on top of one another rather than placing packages horizontally adjacent to one another. 
         [0002]    A POP configuration can include two or more ball grid arrays (BGA) stacked on top of one another. In a two-piece assembly, the bottom package can include a logic device, and the top package can include a memory device. 
         [0003]    In order to affix the top package to the bottom package, a mold compound can be used. The mold compound can be applied to a center portion of the bottom package and can cover the die of the bottom package. 
         [0004]    A problem associated with POP structures includes heat and warping. Heat can cause warping by causing one portion of the POP structure to expand faster and larger than other portions of the POP structure. For example, mismatches in thermal expansion of the die, the molding compound, and/or the substrate can cause warping. Bottom substrates of bottom packages can be especially prone to warping, for example, because the molding compound on the die has a different coefficient of thermal expansion compared to the die of the bottom package. For this reason, die sizes are often limited to reduce warping effects on the dies, especially the dies located on the bottom package. 
       SUMMARY OF EMBODIMENTS 
       [0005]    According to one embodiment, a device may include a package-on-package structure including a top package and a bottom package; and a heatsink interposer located between the top package and the bottom package, where the heatsink interposer includes: a heatsink; an interposer substrate; and interposer solder balls. 
         [0006]    According to another embodiment, a package-on-package structure may include a top package; a heatsink interposer, where the heatsink interposer is under the top package and the heatsink interposer, including: an interposer substrate; a top heatsink between the top package and the interposer substrate; a bottom heatsink between the bottom package and the interposer substrate; and interposer solder balls between the bottom package and the interposer substrate; and a bottom package under the heatsink interposer. 
         [0007]    According to still another embodiment, a package-on-package heatsink interposer for use between a top package and a bottom package of a package-on-package device, may include a top heatsink below the top package; an interposer substrate below the top heatsink; a bottom heatsink below the interposer substrate; a first interposer substrate metal layer between the interposer substrate and the top heatsink; a second interposer substrate metal layer between the interposer substrate and the bottom heatsink; and interposer solder balls between the second interposer substrate metal layer and the bottom package. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0008]    The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate one or more embodiments described herein and, together with the description, explain these embodiments. In the drawings: 
           [0009]      FIG. 1A  is a diagram of an example package-on-package structure according to an embodiment described herein; 
           [0010]      FIG. 1B  is a diagram of an example package-on-package structure according to an embodiment described herein; 
           [0011]      FIG. 2  is a diagram of an example heatsink interposer according to an embodiment described herein; 
           [0012]      FIG. 3A  is a diagram of an example package-on-package structure with capillary underfill; 
           [0013]      FIG. 3B  is a diagram of an example package-on-package structure with capillary underfill and a heatsink interposer according to an embodiment described herein; 
           [0014]      FIG. 4A  is a diagram of an example package-on-package structure with mold underfill; 
           [0015]      FIG. 4B  is a diagram of an example package-on-package structure with mold underfill and a heatsink interposer according to an embodiment described herein; 
           [0016]      FIG. 5A  is a diagram of an example package-on-package structure with capillary underfill; 
           [0017]      FIG. 5B  is a diagram of an example package-on-package structure with capillary underfill and an increased die size; 
           [0018]      FIG. 5C  is a diagram of an example package-on-package structure with capillary underfill, an increased die size, and a heatsink interposer according to an embodiment described herein; 
           [0019]      FIG. 6A  is a diagram of an example package-on-package structure with capillary underfill; 
           [0020]      FIG. 6B  is a diagram of an example side-by-side structure with capillary and a heatsink; and 
           [0021]      FIG. 6C  is a diagram of an example package-on-package structure with capillary underfill, an increased die size, increased thermal dissipation requirement, and a heatsink interposer according to an embodiment described herein. 
       
    
    
     DETAILED DESCRIPTION 
       [0022]    The following detailed description refers to the accompanying drawings. The same reference numbers in different drawings may identify the same or similar elements. 
       Overview 
       [0023]    Systems and/or methods described herein may utilize a heatsink interposer to provide temperature regulation, accommodation of die sizes for varying sized top and bottom packages, and provide increased stiffness. Systems and/or methods described herein may also utilize a heatsink interposer to enable higher power and larger dies in a POP structure with smaller footprints. 
       Example Arrangement 
       [0024]      FIG. 1A  is a diagram of an example POP structure  100  according to an embodiment described herein. As shown, POP structure  100  may include a top package  110 , a bottom package  120 , and a heatsink interposer  130 . 
         [0025]    Top package  110  may include any mechanically mating device. In one implementation, top package  110  can include a memory device that can work with a logic device bottom package  120 . Top package  110  can be any size capable of fitting on heatsink interposer  110 . In one implementation, top package  110 , bottom package  120 , and heatsink interposer  130  can be approximately the same length and width. For example, top package  110 , bottom package  120 , and heatsink interposer  130  can be 10-17 mm in length and width, (e.g., top package  110 , bottom package  120 , and heatsink interposer  130  can be 12 mm×12 mm). 
         [0026]    In one implementation, top package  110 , bottom package  120 , and heatsink interposer  130  can be approximately the same height. For example, top package  110 , bottom package  120 , and heatsink interposer  130  can have a height of 500-1500 microns (e.g., 1000 microns). In another implementation, the height of the heatsink interposer  130  can be different from the top package  110  and/or the bottom package  120 . For example, top package  110  can have a height of 1000 microns, bottom package  120  can have a height of 800 microns, and heatsink interposer  130  can have a height of 500 microns. 
         [0027]    Bottom package  120  may include any mechanically mating device. In one implementation, bottom package  120  can include a logic device with a die on a top portion of the bottom package  120 . In one implementation, the die can be any size smaller than bottom package  120 . For example, the die can be 5-15 mm in length and width, and 150-250 microns in height (e.g., bottom package  120  can be 15 mm×15 mm×1000 microns and the die can be 10 mm×10 mm×200 microns). 
         [0028]    Heatsink interposer  130  may include a structure that can provide heat dispersal, heat dissipation, and structural support for POP structure  100 . In one implementation, heatsink interposer  130  can include a bottom ball footprint to accommodate a die size of bottom package  120 , while having the space on a top portion of heatsink interposer  130  to accommodate the ball footprint of top package  110 . For example, heatsink interposer  130  can include a bottom ball footprint that includes a space of 10 mm×10 mm to accommodate a die of 8 mm×8 mm, and can include space around a top portion of heatsink interposer  130  to accommodate solder balls on top package  110 . 
         [0029]    In another implementation, as illustrated in  FIG. 1B , POP structure  100  can be provided with a bottom package  120  that is larger than a top package  110  and heatsink interposer  130  between bottom package  120  and top package  110 . Bottom package  120  may be larger than top package  110  for any number of reasons. For example, bottom package  120  may be larger than top package  110  to accommodate a larger die size, a smaller top package  110  may be desirable for cost reasons, etc. 
         [0030]    As illustrated in  FIG. 1B , heatsink interposer  130  can be manufactured to accommodate the size of die  125  and bottom package  120  and also accommodate top package solder balls  115  and top package  110 . For example, heatsink interposer  130  can include solder balls on a bottom surface with an area between interposer solder balls  135  that can accommodate the die  125  in bottom package  120  and a top surface with an area to accommodate solder balls  115  of top package  110 . As further illustrated in  FIG. 1B , die  125  can be larger than an area  140  between solder balls  115  and die  125  can be smaller than an area  150  between solder balls  135  on a bottom surface of heatsink interposer  130 . 
         [0031]    In another implementation, higher power than a standard power for POP structure  100  can be used on the bottom package while the heat produced by the higher power can be dissipated using heatsink interposer  130 . 
         [0032]    In another implementation, heatsink interposer  130  can be used as a stiffener to reduce warpage of bottom package  120  and help on the mounting of bottom package  120  to POP structure  100 . 
         [0033]    Although  FIGS. 1A and 1B  show example components of POP structure  100 , in other embodiments, POP structure  100  may include fewer components, different components, differently arranged components, or additional components than depicted in  FIGS. 1A and 1B . 
         [0034]    For example, although  FIGS. 1A and 1B  show POP structure  100  as a two-stacked structure with heatsink interposer  130 , in other embodiments, POP structure  100  may be implemented to include more stacks in the POP structure  100 . 
         [0035]      FIG. 2  is a diagram of example components of a heatsink interposer  130  that may be included in POP structure  100 . Heatsink interposer  130  may include a top heatsink  210 , an interposer substrate  220  with interposer substrate vias  230 , interposer substrate metal layers  240 , interposer solder balls  135 , and a bottom heatsink  260 . In one implementation, heatsink interposer  130  may range from 10-17 mm in length and width, and may have a thickness of 500-1000 microns. For example, a heatsink interposer  130  can be 12 mm×12 mm with a thickness of 500 microns. 
         [0036]    Top heatsink  210  and bottom heatsink  260  may be provided in heatsink interposer  130  to provide thermal conduction between heatsink interposer  130  and top package  110  and bottom package  120 , as well as to provide thermal dissipation and structural integrity. In one embodiment top heatsink  210  may or may not be in thermal communication with top package  110  and bottom heatsink  220  can be in thermal communication with bottom package  120 . 
         [0037]    Top heatsink  210 , material filling interposer substrate vias  230 , interposer substrate metal layers  240 , and bottom heatsink  260  may include any conductive material, such as a metal (e.g., copper, aluminum, metal alloy) or a non-metal (e.g., diamond, copper-tungsten pseudoalloy, AlSiC (silicon carbide in aluminum matrix)) material. In one implementation, top heatsink  210 , material filling interposer substrate vias  230 , interposer substrate metal layers  240 , and bottom heatsink  260  may be the same or different materials. For example, top heatsink  210 , material filling interposer substrate vias  230 , interposer substrate metal layers  240 , and bottom heatsink  260  may be formed of copper. 
         [0038]    Top heatsink  210  and bottom heatsink  260  may be any size in width, length, or height. In one implementation, top heatsink  210  and bottom heatsink  260  and can be 10-17 mm in length and width, top heatsink  210  can be 100-300 microns, and bottom heatsink can be 50-150 microns. For example, top heatsink  210  and bottom heatsink  260  can be 12 mm×12 mm×200 microns. Additionally, or alternatively, as illustrated in  FIG. 2 , top heatsink  210  can be different in height, width, and/or length from bottom heatsink  260 . For example, top heatsink  210  can be 12 mm×12 mm×200 microns and bottom heatsink  260  can be 10 mm×10 mm×100 microns. 
         [0039]    Additionally, or alternatively, top heatsink  210  can be customized in size to accommodate solder balls from top package  110 . For example, top heatsink  210  can be 10 mm×10 mm for a 15 mm×15 mm top package  110  with an area between solder balls of 11 mm×11 mm, so that top heatsink  210  can fit within the area between the solder balls of top package  110 . 
         [0040]    Additionally, or alternatively, bottom heatsink  260  can be customized in size and shape to accommodate any portion of bottom package  110 , including a die  125 . In one implementation, bottom heatsink  260  can be sized larger than a die  125  from bottom package  110 . For example, for a bottom package with a die  125  of 10 mm×10 mm×100 microns, bottom heatsink  260  can be 12 mm×12 mm×200 microns. 
         [0041]    Interposer substrate  220  can provide insulating and stiffening properties to interposer heatsink  130 . Interposer substrate  220  may include any insulating material including a rigid material such as glass-reinforced epoxy laminate sheets (e.g., FR-4), Bismaleimide-Triazine (BT-Epoxy), Ajinomoto Build-Up Film (ABF), or any available industry substrate dielectric material. In one implementation, interposer substrate  220  may be 400-750 micron in height and may be the same length and width as heatsink interposer  130 . For example, interposer substrate  220  may be 12 mm×12 mm×500 microns. 
         [0042]    Interposer substrate vias  230  can be found in interposer substrate  220  to provide heat dissipation and/or electrical connection ability between top and bottom interposer substrate metal layers  240  and the heatsink interposer  130 . In one implementation, interposer substrate vias  230  may be cylindrical or rectangular in shape and can be through holes in interposer substrate  220 . Interposer substrate vias  230  can range in diameter or width from 200-400 microns. For example, interposer substrate vias  230  can be 300 microns in diameter. 
         [0043]    Material can be used to completely or partially fill interposer substrate vias  230  to improve thermal conduction. In one implementation, interposer substrate vias  230  can be filled with the same material as the top heatsink  210 , interposer substrate metal layers  240 , and bottom heatsink  260 , as mentioned above. For example, interposer substrate vias  230  may be filled with copper. 
         [0044]    Additionally, or alternatively, material can be used to completely fill interposer substrate vias  230 . For example, interposer substrate vias  230  can be at least partially filled by a conductive material to disperse heat from bottom heatsink  260 . 
         [0045]    Interposer substrate metal layers  240  may be located between top heatsink  210  and interposer substrate  220  and may be located between bottom heatsink  260  and interposer substrate  220 . Interposer substrate metal layers  240  may also be located between interposer substrate  220  and interposer solder balls  135 . In one implementation, interposer metal layers  240  may be 25-75 microns. For example, interposer metal layers may be 50 microns. Interposer substrate metal layers  240  can be patterned to provide electrical connections between top and bottom interposer substrate metal layers  240  and to accommodate the electrical connections to top package  110  and bottom package  120 . 
         [0046]    Interposer solder balls  135  may include any number of solder balls in any size that assists in heat transfer from the bottom package  120  to the heatsink interposer  130 . Interposer solder balls  135  may also provide electrical connections between the bottom package  120  and the heatsink interposer  130 . Interposer solder balls  135  can be customized in size and pattern to accommodate any portion of bottom package  110 , including a die  125 . In one implementation, interposer solder balls  135  can have a diameter of 200-400 microns and can be sized to be the same or different in material and diameter compared to solder balls of top package  110  and bottom package  120 . For example, interposer solder balls can be 300 microns. Interposer solder balls  135  may be made of any soldering material, such as SAC305 (Sn, Ag, Cu, such as 96.5% Sn, 3% Ag, 0.5% Cu). 
         [0047]    As illustrated in  FIGS. 3A and 3B , heat interposer  130  can be used with a POP structure including capillary underfill (CUF). 
         [0048]    As illustrated in  FIG. 3A , POP structure  300  can include a top package  110 , a bottom package  120 , die  125  placed on top of bottom package  120 , CUF  320  to package interconnections  330 , and top package solder balls  115  to separate and electrically connect top package  110  and bottom package  120 . 
         [0049]    As illustrated in  FIG. 3B , heatsink interposer  130  can be used with POP structure  350  including CUF. Heatsink interposer  130  can be placed between top package  110  and bottom package  120  and on top of die  125 . Interposer solder balls  135  can be placed between heatsink interposer  130  and bottom package  120 . Top package solder balls  115  can be placed between top package  110  and heatsink interposer  130 . 
         [0050]    In one implementation, heatsink interposer  130  can have a bottom heatsink  260  with a larger horizontal area than die  125  to provide uniform heat transfer from die  125  to heatsink interposer  130 . In one implementation, CUF  320  can cover any portion of die  125  and interposer solder balls  135  can be placed on heatsink interposer  130  with sufficient space for CUF  320  to not contact with interposer solder balls  135 . 
         [0051]    As illustrated in  FIGS. 4A and 4B , heat interposer  130  can be used with a POP structure including mold underfill (MUF). 
         [0052]    As illustrated  4 A, POP structure  400  can include a top package  110 , a bottom package  120 , die  125  can be placed below top package  110 , MUF  420  can cover package interconnections  430 , and top package solder balls  115  can separate and electrically connect top package  110  and bottom package  120 . 
         [0053]    As illustrated in  FIG. 4B , heatsink interposer  130  can be used with POP structure  450  including MUF. In  FIG. 4B , heatsink interposer  130  can be placed on top of die  125 , interposer solder balls  135  can be placed between heatsink interposer  130  and bottom package  120 , and top package solder balls  115  can be placed between top package  110  and heatsink interposer  130 . In one implementation, heatsink interposer  130  can have a bottom heatsink  260  with a larger horizontal area  460  (outlined) than die  125  to provide heat transfer from die  410  to heatsink interposer  130 . 
         [0054]    Additionally, or alternatively, MUF  420  can be in contact with bottom heatsink  260  and interposer solder balls  135 . In one implementation, as illustrated in  FIG. 4B , MUF  420  can cover die  125  and package interconnections  430 , and be in contact with bottom heatsink  260  and interposer solder balls  135 . Additionally, or alternatively, MUF  420  can partially or completely package interposer solder balls  135 . For example, can be provided for packaging die  125  and package interconnections  430  after interposer solder balls  135  are placed on bottom package  120 . 
         [0055]    As illustrated in  FIGS. 5A-5C , increasing die size from a smaller die  125  in  FIG. 5A  to a larger die  520  in  FIG. 5B  could conventionally lead to a larger package size  530 , as illustrated in  FIG. 5B , compared to the original package size  500  in  FIG. 5A . However, using heatsink interposer  130 , as illustrated in  FIG. 5C , increasing the die size to larger die  520  can be done without changing the width or length of the original package  500  by providing an interposer structure to accommodate the larger die  520  in  FIG. 5B  and the area between top solder balls  115 . 
         [0056]    In one implementation, as illustrated in  FIG. 5C , interposer solder balls  135  can be placed on heatsink interposer  120  to accommodate a larger die  520  by moving interposer solder balls  135  to create an area for larger die  520  to fit. For example, interposer solder balls  135  can be placed to provide a larger area  150  between interposer solder balls  135  than an area  140  between top package solder balls  115 , and larger die  520  can be accommodated by area  150  but not area  140 . 
         [0057]    Additionally, or alternatively, the size and shape of top heatsink  210  can be customized to allow for top package solder balls  115  to remain the same or be changed. In one implementation, top package solder balls  115  can be positioned in their same locations with the same area  140  between top package solder balls  115 . For example, as illustrated in  FIGS. 5A and 5C , area  140  can be the same width and length even though die  125  is increased in width and length to larger die  520 . 
         [0058]    By allowing the size of original package  500  to be maintained, the size of top package  110  can also be maintained. By maintaining the size of top package  110 , new and/or different top packages  110  do not have to be provided in order to compensate for the larger die  520  size if a larger die is used. 
         [0059]    As illustrated in  FIGS. 6A-6C , increasing die size from a smaller die  610  in  FIG. 6A  to a larger die  620  in  FIG. 6B  and/or increasing power from the power used for the original POP structure in  6 A can increase the heat in bottom package  120 . In order to dissipate the increased heat, heatsink  630 , as illustrated in  FIG. 6B  can be provided. The addition of heatsink  630  to a structure has conventionally led to a side-by-side structure  600 , as illustrated in  FIG. 6B . Side-by-side structures can be less than ideal because they tend to have larger horizontal footprints than vertically-stacked POP structures. 
         [0060]    As illustrated in  FIG. 6C , heat sink interposer  130  can be provided to dissipate heat similar to heatsink  630 , and allow for POP structure  600  to be vertically-stacked. 
         [0061]    In one implementation, POP structure  640  can be provided with substantially identically sized top package  110 , bottom package  120 , and heatsink interposer  130 . For example, each of the top package  110 , bottom package  120 , and heatsink interposer  130  can be 15 mm×15 mm×1000 microns. In another implementation, POP structure  100  can be provided with three different sized top package  110 , bottom package  120 , and heatsink interposer  130 . For example, each of the top package  110  can be a 10 mm×10 mm×800 microns, bottom package  120  can be a 12 mm×12 mm×500 microns, and heatsink interposer  130  can be a 12 mm×12 mm×1000 microns. 
         [0062]    Systems and/or methods described herein may utilize a heatsink interposer in a POP structure to provide temperature regulation, accommodation of die sizes for varying sized top and bottom packages, and provide increased stiffness. The heatsink interposer may be used with POP structures that utilize CUF or MUF. The heatsink interposer may be used to accommodate larger die sizes and/or increased power, while maintaining package size overall, as well as top package size. The heatsink interposer can also be used as a stiffener to reduce warpage of the bottom package and help with the mounting of the top package to the POP structure. The heatsink interposer can also be used to lower the temperature of the POP structure, especially the bottom package when higher power is used on the bottom package. 
         [0063]    The foregoing description of embodiments provides illustration and description, but is not intended to be exhaustive or to limit the claims to the precise form disclosed. Modifications and variations are possible in light of the above disclosure or may be acquired from practice of implementations described herein. 
         [0064]    Even though particular combinations of features are recited in the claims and/or disclosed in the specification, these combinations are not intended to limit the disclosure of the possible implementations. In fact, many of these features may be combined in ways not specifically recited in the claims and/or disclosed in the specification. Although each dependent claim listed below may directly depend on only one other claim, the disclosure of the possible implementations includes each dependent claim in combination with every other claim in the claim set. 
         [0065]    No element used in the present application should be construed as critical or essential to an implementation unless explicitly described as such. Also, as used herein, the article “a” is intended to include one or more items. Where only one item is intended, the term “one” or similar language is used. Further, the phrase “based on” is intended to mean “based, at least in part, on” unless explicitly stated otherwise.