Patent Publication Number: US-11385281-B2

Title: Heat spreaders for use in semiconductor device testing, such as burn-in testing

Description:
CROSS-REFERENCE TO RELATED APPLICATION(S) 
     This application contains subject matter related to a concurrently-filed U.S. Patent Application, titled “HEAT SPREADERS FOR USE IN SEMICONDUCTOR DEVICE TESTING, SUCH AS BURN-IN TESTING.” The related application, of which the disclosure is incorporated by reference herein, is assigned to Micron Technology, Inc., and is identified by number 010829-9410.US00. 
     TECHNICAL FIELD 
     The present technology generally relates to heat spreaders for use during semiconductor device testing, and more particularly relates to heat spreaders configured to be thermally coupled to a plurality of semiconductor devices during burn-in testing. 
     BACKGROUND 
     Packaged semiconductor dies—including memory chips, microprocessor chips, MEMs, and imager chips—typically include a semiconductor die mounted on a substrate and encased in a plastic protective covering. The die includes functional features, such as memory cells, processor circuits, and imager devices, as well as bond pads electrically connected to the functional features. The bond pads can be electrically connected to terminals outside the protective covering to allow the die to be connected to higher level circuitry. 
     Semiconductor manufacturers often test semiconductor packages after or during fabrication to verify the reliability of the packages. One such verification process is burn-in testing, in which some or all of the components of a semiconductor package are exercised prior to being placed in service (and sometimes before the package is fully assembled). In general, burn-in testing includes placing the semiconductor package under an electrical load (e.g., near the operating limits of the package) for a predetermined time and at an elevated temperature (e.g., near a maximum operating temperature of the package). Typically, during a burn-in test, a plurality of semiconductor packages are connected to the sockets of a burn-in board, which provides the electrical load, and the burn-in board is placed in a heated chamber during the test. Those packages that do not function after the burn-in test are scrapped. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Many aspects of the present technology can be better understood with reference to the following drawings. The components in the drawings are not necessarily to scale. Instead, emphasis is placed on clearly illustrating the principles of the present technology. 
         FIG. 1A  is a top view of a burn-in board configured in accordance with embodiments of the present technology;  FIG. 1B  is a side cross-sectional view of the burn-in board taken along the line  1 B- 1 B in  FIG. 1A ; and  FIG. 1C  is an enlarged view of a portion of the burn-in board shown in  FIG. 1B . 
         FIG. 2A  is a side cross-sectional view of the burn-in board of  FIGS. 1A-1C  having a heat spreader coupled thereto in accordance with embodiments of the present technology; and  FIG. 2B  is an enlarged view of a portion of the burn-in board and the heat spreader shown in  FIG. 2A . 
         FIG. 3  is a side cross-sectional view of the burn-in board of  FIGS. 1A-1C  having a heat spreader coupled thereto in accordance with another embodiment of the present technology. 
         FIG. 4  is a side cross-sectional view of the heat spreader of  FIG. 3  coupled to the burn-in board of  FIGS. 1A-1C  in accordance with another embodiment of the present technology. 
         FIG. 5  is a partially schematic, side cross-sectional view of a burn-in test system configured in accordance with embodiments of the present technology. 
         FIG. 6A  is a top view of a burn-in board illustrating a temperature distribution across a plurality of semiconductor devices during a burn-in test without a heat spreader coupled to the burn-in board; and  FIG. 6B  is a top view of the burn-in board illustrating the temperature distribution across the plurality of semiconductor devices during a burn-in test with a heat spreader coupled to the burn-in board. 
         FIG. 7  is a flow diagram of a process or method for performing a burn-in test in accordance with embodiments of the present technology. 
     
    
    
     DETAILED DESCRIPTION 
     Specific details of several embodiments of burn-in boards having heat spreaders, and associated systems and methods, are described below with reference to  FIGS. 1A-7 . In several of the embodiments, a burn-in board includes a plurality of sockets configured to receive semiconductor devices therein during a testing procedure (e.g., a burn-in test). The testing procedure can include heating the burn-in board and the semiconductor devices to a selected test temperature while electrically exercising the semiconductor devices to, for example, weed out faulty devices. A heat spreader is thermally coupled to the semiconductor devices during the testing procedure. The heat spreader can include a base portion and a plurality of protrusions extending from the base portion. The protrusions are configured to extend into corresponding ones of the sockets to thermally contact the semiconductor devices and to thereby thermally couple the semiconductor devices together. 
     One challenge with burn-in testing is maintaining each of the semiconductor packages connected to the burn-in board at the selected test temperature. Semiconductor packages that are below the selected test temperature (i.e., under-stressed) can prematurely fail in the field, while semiconductor packages that are above the selected test temperature may exceed their maximum operating temperature, resulting in false failures and destruction of otherwise marketable devices. In one aspect of the present technology, the heat spreader distributes heat among the semiconductor devices during the testing procedure to maintain the semiconductor devices at or near the selected test temperature. In contrast, conventional testing procedures do not include the use of such a heat spreader. Without the heat spreader, the semiconductor devices may be unevenly heated above or below the selected test temperature—increasing the number of false positives (e.g., detected, non-faulty devices) and false negatives (e.g. undetected faulty devices) of the testing procedure. 
     Numerous specific details of heat spreaders for use in semiconductor device testing, and associated systems and methods, are disclosed herein to provide a thorough and enabling description of embodiments of the present technology. A person skilled in the art, however, will understand that the technology may have additional embodiments and that the technology may be practiced without several of the details of the embodiments described below with reference to  FIGS. 1A-7 . For example, some details of semiconductor devices and burn-in testing components well known in the art have been omitted so as not to obscure the present technology. In general, various other devices and systems in addition to those specific embodiments disclosed herein may be within the scope of the present technology. 
     The term “semiconductor device” can refer to an assembly of one or more semiconductor devices, semiconductor device packages, and/or substrates, which may include interposers, supports, and/or other suitable substrates. The semiconductor device assembly may be manufactured as, but not limited to, discrete package form, strip or matrix form, and/or wafer panel form. The term “semiconductor device” generally refers to a solid-state device that includes a semiconductor material. A semiconductor device can include, for example, a semiconductor substrate, wafer, panel, or a single die from a wafer or substrate. A semiconductor device may refer herein to a semiconductor wafer, but semiconductor devices are not limited to semiconductor wafers. 
     As used herein, the terms “vertical,” “lateral,” “upper,” “lower,” “above,” and “below” can refer to relative directions or positions of features in the semiconductor devices in view of the orientation shown in the Figures. For example, “upper” or “uppermost” can refer to a feature positioned closer to the top of a page than another feature. These terms, however, should be construed broadly to include semiconductor devices having other orientations, such as inverted or inclined orientations where top/bottom, over/under, above/below, up/down, and left/right can be interchanged depending on the orientation. 
       FIG. 1A  is a top view of a burn-in board  100  configured in accordance with embodiments of the present technology.  FIG. 1B  is a side cross-sectional view of the burn-in board  100  taken along the line  1 B- 1 B in  FIG. 1A , and  FIG. 1C  is an enlarged view of a portion of the burn-in board  100  shown in  FIG. 1B . Referring to  FIGS. 1A-1C  together, the burn-in board  100  includes an electrical substrate  102  and plurality of sockets  110  coupled to the electrical substrate  102 . In some embodiments, the electrical substrate  102  can include an electrically-insulating material (e.g., glass, plastic, glass-filled plastic, and/or ceramic) having conductive contacts, traces, etc., disposed in and/or on the electrically-insulating material. For example, in some embodiments the electrical substrate  102  can be a printed circuit board. 
     Each of the sockets  110  is configured to receive a semiconductor device  120  therein and to electrically couple the semiconductor device  120  to the electrical substrate  102 . The semiconductor devices  120  can be semiconductor packages, silicon dies, etc., and can include various memory circuits (e.g., dynamic random memory (DRAM) or other type of memory circuits), controller circuits (e.g., DRAM controller circuits), logic circuits, and/or other circuits. In the illustrated embodiment, the burn-in board  100  includes twenty sockets  110  aligned in rows and columns. In other embodiments, the burn-in board  100  can include any number of sockets  110  (e.g., more or fewer than twenty) that can be arranged in rows and columns, or in another suitable arrangement. Individual ones of the sockets  110  can be spaced apart from and/or abut adjacent ones of the sockets  110 . For example, in the illustrated embodiment the sockets  110  are spaced laterally apart from one another in columns and rows (e.g., a grid arrangement) across the electrical substrate  102 . Moreover, in the illustrated embodiment each of the sockets  110  and the semiconductor devices  120  are substantially identical. In other embodiments, the configurations of the sockets  110  and semiconductor devices  120  can differ. 
     Each of the sockets  110  is configured to receive, hold, and facilitate testing of the semiconductor device  120  positioned therein. More particularly, each of the sockets  110  can include a base portion  112  and a sidewall  114  extending from the base portion  112  that together define a recess configured (e.g., sized and shaped) to receive the semiconductor device  120 . Each of the sockets  110  can include a mounting seat  116  (shown schematically in  FIGS. 1B and 1C ) on/in the base portion  112  and having electrical contacts that are configured to contact and electrically couple to corresponding contacts (e.g., leads) of the semiconductor device  120  positioned therein. The mounting seats  116  are configured to electrically couple the semiconductor devices  120  to testing circuitry (not shown) configured to provide power and electrical test signals to the semiconductor devices  120  during a testing procedure, such as a burn-in test. In some embodiments, the electrical contacts of the mounting seats  116  can have moveable contact portions configured to move into and out of electrical engagement with the respective leads of the semiconductor devices  120 . For example, the electrical contacts can include electrical clips, conductive traces, and/or double-ended electrical pogo-pins. In other embodiments, the burn-in board  100  can be a socketless burn-in board in which the mounting seats  116  (and/or other components that include the electrical connections necessary to power and communicate with the semiconductor devices  120 ) are positioned on a surface of the electrical substrate  102 . 
     The burn-in board  100  is configured to be placed within a heating chamber (e.g., a burn-in heating chamber  576  shown in  FIG. 5 ) during a procedure for testing the semiconductor devices  120  to, for example, identify failed or failing ones of the semiconductor devices  120  (e.g., those including manufacturing defects). The heating chamber is configured to heat the semiconductor devices  120  to a selected test temperature, such as a temperature at or near a maximum operating temperature of the semiconductor devices  120 . The semiconductor devices  120  can be powered/operated during the test procedure via the testing circuitry. In some embodiments, the heating chamber can be part of a burn-in convection oven having temperature cycling capabilities. In some embodiments, the heating chamber is configured to heat the semiconductor devices  120  via convective heat transfer. In the illustrated embodiment, heated air generated within the heating chamber is passed over the burn-in board  100 , as indicated by arrows  130 , and circulates around the semiconductor devices  120  to heat the semiconductor devices  120 . 
     However, heat may be irregularly distributed to the semiconductor devices  120  during the testing procedure depending on, for example, the position of the semiconductor devices  120  along the burn-in board  100 . For example, air pockets (e.g., an air pocket  132  shown in  FIG. 1C ) may form within one or more of the sockets  110 . Such air pockets can impose a significant thermal resistance by inhibiting the circulation of the heated air around the semiconductor devices  120 , thereby causing the semiconductor devices  120  to be below/above the selected test temperature during all or a portion of the testing procedure. Furthermore, heat generated by the semiconductor devices  120  during the testing procedure can propagate to other ones of the semiconductor devices  120 . For example, the circulating air can carry the heat from upstream ones of the semiconductor devices  120  to downstream ones of the semiconductor devices  120  (e.g., in the direction of arrows  130 ). This additional heat transfer can increase the temperature of the downstream semiconductor devices  120  above the selected test temperature, which can affect the performance of the semiconductor devices  120  and potentially cause premature failures and degradation. Premature failures caused by excessive heating of the semiconductor devices  120  above the selected test temperature are false positives identified by the testing procedure. 
       FIG. 2A  is a side cross-sectional view of the burn-in board  100  of  FIGS. 1A-1C  having a heat spreader  240  (which can also be referred to as a heat disperser, a heat sink, plate, etc.) coupled thereto in accordance with embodiments of the present technology.  FIG. 2B  is an enlarged view of a portion of the heat spreader  240  and the burn-in board  100  shown in  FIG. 2A . Referring to  FIGS. 2A and 2B  together, in general, the heat spreader  240  is configured to evenly distribute heat across the burn-in board  100  to the semiconductor devices  120  during a testing procedure using the burn-in board  100  to maintain the semiconductor devices at or near a selected test temperature. 
     In the illustrated embodiment, the heat spreader  240  includes a base portion  242  and a plurality of protrusions  244  (e.g., contact portions, projections, etc.) projecting from the base portion  242 . Each of the protrusions  244  is configured to contact a corresponding one of the semiconductor devices  120 . More specifically, the protrusions  244  can project into the sockets  110  such that a lower surface of each protrusion  244  contacts an upper surface of the semiconductor device  120  in the socket  110 . That is, the protrusions  244  can be arranged in a pattern (e.g., a grid) corresponding to the placement of the semiconductor devices  120  on the burn-in board  100 . 
     The heat spreader  240  can be a single (e.g., continuous, integral, etc.) structure/piece of heat-conducting material such as, aluminum, copper, etc. In other embodiments, the heat spreader  240  can comprise multiple heat-conducting materials and/or discrete portions/components. For example, each of the protrusions  244  can be a separate thermally-conductive component that is permanently or releasably coupled to the base portion  242 . Accordingly, the heat spreader  240  can thermally couple the semiconductor devices  120  together to, for example, promote the even distribution of heat amongst the semiconductor devices  120 . In some embodiments, the heat spreader  240  can be formed by milling a single piece of thermally conductive material such as aluminum or copper. 
     The heat spreader  240  can be configured (e.g., sized and shaped) to cover each of the sockets  110 . Accordingly, the heat spreader  240  can have a shape generally corresponding to the dimensions (e.g., width and length) of the burn-in board  100  and/or the arrangement of the sockets  110  positioned thereon. In other embodiments, the heat spreader  240  can cover only a subset of the semiconductor devices  120  on the burn-in board  110  such that the protrusions  244  thermally contact only a subset (e.g., a fixed number of rows or columns) of the semiconductor devices  120 , or the illustrated heat spreader  240  can include fewer of the protrusions  244 . For example, in some embodiments the heat spreader  240  is configured to cover and/or thermally contact only a subset of the semiconductor devices  120  positioned downstream of the flow of heated air—which are more likely to overheat as described in detail above. In some embodiments, the heat spreader  240  can be sized and shaped based on the dimensions of the heating chamber in which the burn-in board  100  is configured to be placed during a testing procedure. For example, the heat spreader  240  can be sized to abut or contact a portion of the heating chamber. In some embodiments, the heat spreader  240  has the same planform shape as the burn-in board  100  such that the sides of the heat spreader  240  are generally flush with the sides of the burn-in board  100 . 
     In the illustrated embodiment, the base portion  242  of the heat spreader  240  includes an upper surface  246  and a lower surface  248  opposite the upper surface  246 . The protrusions  244  generally project downward away from the lower surface  248  of the base portion  242  to contact the semiconductor devices  120 . The heat spreader  240  can be supported by the semiconductor devices  120  and/or the sidewalls  114  of the sockets  110 . For example, the dimensions of the protrusions  244  and/or the dimensions of the sidewalls  114  of the sockets  110  can be selected such that the weight of the heat spreader  240  is supported by one or some combination of the sockets  110  and the semiconductor devices  120 . More particularly, with reference to  FIG. 2B , a height H 1  (e.g., a thickness, depth, etc.) of each protrusion  244  can be selected based on (i) a height H 2  of the sidewall  114  of the corresponding one of the sockets  110  and/or (ii) a height H 3  of the semiconductor device  120  therein. 
     In some embodiments, the height H 1  is equal to or about equal to the difference between the heights H 2  and H 3  such that (i) a lower surface  249  of the protrusion  244  thermally contacts an upper surface  247  of the semiconductor device  120  and (ii) most of or substantially all the weight of the heat spreader  240  is supported by the socket  110 . In other embodiments, the height H 1  is greater than the difference between the heights H 2  and H 3  such that (i) the lower surface  249  of the protrusion  244  thermally contacts the upper surface  247  of the semiconductor device  120  and (ii) substantially all the weight of the heat spreader  240  is supported by the semiconductor device  120 . In some such embodiments, the heat spreader  240  is instead supported by a spring or other support coupled to the burn-in board  100  (e.g., to the electrical substrate  102  as shown in  FIGS. 3 and 4 ) or another attachment point in the heating chamber. In yet other embodiments, the height H 1  is less than the difference between the heights H 2  and H 3  such that (i) the lower surface  249  of the protrusion  244  does not contact the upper surface  247  of the semiconductor device  120  and (ii) substantially all the weight of the heat spreader  240  is supported by the socket  110 . In some such embodiments, a thermal interface material, thermal grease, thermally-conductive pad, etc., can be positioned between the semiconductor device  120  and the protrusion  244  and can thermally couple the semiconductor device  120  to the heat spreader  240 . In other embodiments, the heat spreader  240  can alternatively or additionally be supported by a clamp, a holder, a shelving of the heating chamber, or another portion of the heating chamber. 
     In some embodiments, the lower surface  249  of the protrusion  244  is configured (e.g., sized and shaped) to contact all or substantially all the upper surface  247  of the semiconductor device  120 . For example, in the illustrated embodiment the lower surface  249  of the protrusion  244  is larger than (e.g., over-sized compared to) the upper surface  247  of the semiconductor device  120 . In other embodiments, the lower surface  249  of the protrusion  244  and the upper surface  247  of the semiconductor device  120  can have the same shape and area. In other embodiments, the lower surface  249  of the protrusion  244  can be smaller in at least one dimension than the upper surface  247  of the semiconductor device  120 . Moreover, in the illustrated embodiment the lower surface  249  of the protrusion  244  has a generally planar shape. In other embodiments, the lower surface  249  can be contoured (e.g., including one or more recesses, curves, etc.), can include one or more bumps or projections, etc. Additionally, in the illustrated embodiment a height H 1  of the protrusion  244  is greater than a height H 4  of the base portion  242 . In other embodiments, the height H 4  can be equal to or greater than the height H 1 . 
     Referring again to  FIGS. 2A and 2B  together, in the illustrated embodiment the protrusions  244  are identical (e.g., all having the same height H 1 ). In other embodiments, the protrusions  244  can have different heights to, for example, accommodate testing of different semiconductor devices  120  and/or the use different sockets  110 . In some embodiments, the heat spreader  240  can be heavy enough to provide a robust thermal coupling (e.g., suitable contact) between the protrusions  244  and the semiconductor devices  120  in the sockets  110  without the need for a thermal interface material therebetween. In some embodiments, an additional weight/force (not shown) can be applied to the heat spreader  240  to improve the contact and thermal coupling between the protrusions  244  and the semiconductor devices  120 . In some embodiments, the heat spreader  240  is configured to include different portions having different thermal conductivities to, for example, compensate for irregularities of temperature distribution across the burn-in board  100 . For example, a downstream portion of the heat spreader  240  can be relatively more thermally conductive than an upstream portion or vis versa. In some embodiments, to achieve the different thermal conductivities, the heat spreader  240  can have varying thicknesses or other dimensions and/or can comprise two or more different thermally conductive materials. 
     The heat spreader  240  is configured to be installed onto the burn-in board  100  (e.g., before the burn-in board  100  is placed within the heating chamber) for testing the semiconductor devices  120 . For example, heat spreader  240  can be lifted and placed onto the burn-in board  100 . In some embodiments, the heat spreader  240  is passively secured to the burn-in board  100  while, in other embodiments, the heat spreader  240  is clamped, fastened, or otherwise secured to the burn-in board  100 . During a testing procedure, when the heat spreader  240  and the burn-in board  100  are placed within the heating chamber, the heat spreader  240  absorbs/transmits heat to/from the heated air flowing in the direction of arrows  130  and the semiconductor devices  120 . For example, the heat spreader  240  can absorb heat from the air and distribute it to the semiconductor devices  120  via the thermal coupling between the protrusions  244  and the semiconductor devices  120  to heat the semiconductor devices  120  to a selected test temperature. At the same time, the heat spreader  240  can absorb, redistribute, and/or dissipate heat from any of the semiconductor devices  120  that are above the selected test temperature. Moreover, because the protrusions  244  extend into the sockets  110  to contact the semiconductor devices  120 , the heat spreader  240  can inhibit or even prevent air pockets (e.g., the air pocket  132  shown in  FIG. 1B ) from forming in the sockets  110 . Accordingly, in one aspect of the present technology the heat spreader  240  operates to evenly distribute heat across the burn-in board  100  and the semiconductor devices  120 . The heat spreader  240  can therefore help ensure that all of the semiconductor devices  120  are at or near the selected test temperature during the testing procedure, which can reduce the number of false positives (i.e., the identification of semiconductor devices that failed the testing procedure only because they were above the selected test temperature during the testing procedure) and/or false negatives (i.e., the failure to identify faulty semiconductor devices that passed the testing procedure only because they were below the selected test temperature during the testing procedure). 
       FIG. 3  is a side cross-sectional view of the burn-in board  100  of  FIGS. 1A-1C  having a heat spreader  340  coupled thereto in accordance with another embodiment of the present technology. The heat spreader  340  can include features generally similar or identical to the features of the heat spreader  240  described in detail with reference to  FIGS. 2A and 2B . For example, the heat spreader  340  includes a base portion  342  having an upper surface  346  and a lower surface  348 , and a plurality of protrusions  344  projecting from the lower surface  348  into the sockets  110  to thermally contact the semiconductor devices  120 . 
     However, in the illustrated embodiment the heat spreader  340  is supported by a stand  350  (e.g., a support, support member, frame, platform, base, etc.). More particularly, the stand  350  can extend between the lower surface  348  of the base portion  342  and the electrical substrate  102  of the burn-in board  100 . In general, the stand  350  can be positioned anywhere between the burn-in board  100  and the heat spreader  340  to fully or partially support the heat spreader  340 . In the illustrated embodiment, the stand  350  is positioned around and between an outer periphery of the burn-in board  100  and an outer periphery of the heat spreader  340 . The stand  350  can extend around the entire outer peripheries of the burn-in board  100  and the heat spreader  340 , or only a portion or portions of the outer peripheries. In some embodiments, the stand  350  can additionally or alternatively be positioned between the sockets  110  and the corresponding protrusions  344  across all or a portion of the burn-in board  100 . The stand  350  can comprise any suitably strong material (e.g., metal, plastic, etc.) and can be permanently or releasably attached to the burn-in board  100  and/or the heat spreader  340 . In some embodiments, the stand  350  can comprise a portion of the heat spreader  340 . In other embodiments, the stand  350  can extend between the heat spreader  340  and a portion of the heating chamber. For example, the heat spreader  340  could be supported by a sidewall of the heating chamber, a rack disposed within the heating chamber, etc. 
     In the illustrated embodiment, the stand  350  supports the heat spreader  340  above the sockets  110  such that the heat spreader  340  does not rest on the sockets  110  (e.g., such that the heat spreader  340  is spaced apart from the sidewalls  114  of the sockets  110 ). Accordingly, the protrusions  344  can have a relatively greater height than the protrusions  244  of the heat spreader  240  shown in  FIGS. 2A and 2B  to facilitate thermal contact between the protrusions  344  and the semiconductor devices  120 . In one aspect of the present technology, this arrangement can prevent or relieve pressure on the sockets  110  while still permitting the heat spreader  340  to thermally contact the semiconductor devices  120 . In some embodiments, a soft material (e.g., foam) can be positioned between the sockets  110  and the heat spreader  340  to inhibit the heat spreader  340  from damaging or putting excessive pressure on the sockets  110 . In some embodiments, a height H 5  of the stand  350  can be adjusted to vary a position of the protrusions  344  within the sockets  110  such that, for example, the protrusions  344  thermally contact the semiconductor devices  120 . In some embodiments, the stand  350  can be swapped with a different stand (not shown) having a height different than the height H 5  to facilitate adjustment based on, for example, the configuration (e.g., height, shape, etc.) of the semiconductor devices  120  to be tested. 
       FIG. 4  is a side cross-sectional view of the heat spreader  340  of  FIG. 3  coupled to the burn-in board  100  of  FIGS. 1A-1C  in accordance with another embodiment of the present technology. In the illustrated embodiment, the heat spreader  340  is supported by a plurality of springs  460  rather than a stand. More particularly, the springs  460  can extend between the lower surface  348  of the base portion  342  and the electrical substrate  102 . The springs  460  can be positioned anywhere between the burn-in board  100  and the heat spreader  340  to fully or partially support the heat spreader  340 . For example, in the illustrated embodiment the springs  460  are positioned at and between an outer periphery of the burn-in board  100  and an outer periphery of the heat spreader  340 . In some embodiments, the springs  460  can additionally or alternatively be positioned between the sockets  110  and the corresponding protrusions  344  across all or a portion of the burn-in board  100 . In other embodiments, the springs  460  can extend between the heat spreader  340  and a portion of the heating chamber. For example, the springs  460  could be coupled between the heat spreader  340  and a sidewall of the heating chamber, a rack disposed within the heating chamber, etc. 
     The springs  460  can support the heat spreader  340  above the sockets  110  such that (i) the heat spreader  340  does not rest on the sockets  110  (e.g., the sidewalls  114  of the sockets  110 ) and (ii) the protrusions  344  still thermally contact the semiconductor devices  120 . In one aspect of the present technology, the springs  460  are configured to dampen external forces—for example, forces arising when the burn-in board  100  is moved into or from the heating chamber—to inhibit or even prevent the heat spreader  340  from damaging the semiconductor devices  120  while still permitting the heat spreader  340  to thermally contact the semiconductor devices  120 . In another aspect of the present technology, the springs  460  can facilitate thermal contact between the heat spreader  340  and the semiconductor devices  120  even where the burn-in board  100  (e.g., the electrical substrate  102 ) is warped. 
       FIG. 5  is a partially schematic, side cross-sectional view of a burn-in test system  570  (“system  570 ”) configured in accordance with embodiments of the present technology. In the illustrated embodiment, the system  570  is a convection-heating system including a heater  572 , a blower or fan  574 , an inflow duct  575 , a heating chamber  576 , and an outflow duct  577 . A plurality of the burn-in boards  100  ( FIGS. 1A-1C ) are positioned within the heating chamber  576  and coupled to corresponding heat spreaders (e.g., the heat spreader  240  shown in  FIGS. 2A and 2B ). In the illustrated embodiment, the burn-in boards  100  are arranged in a stack and spaced apart from one another. The height H 4  of the base portion  242  ( FIGS. 2A and 2B ) of each of the heat spreaders  240  can be selected such that there is a gap or channel between each of the burn-in boards  100  in the stack. The burn-in boards  100  and coupled heat spreaders  240  can be selectively inserted and removed from the heating chamber  576  to facilitate loading/unloading of the semiconductor devices  120 . In some embodiments, the burn-in boards  100  can be inserted into racks in the heating chamber  576  and plugged into corresponding edge connectors (not shown) configured to electrically couple the burn-in boards  100  and the semiconductor devices  120  to external testing circuitry (not shown). 
     Referring to  FIGS. 2A, 2B, and 5  together, in operation during a testing procedure, the system  570  is configured to circulate heated air or other inert gases (e.g., represented by arrows in  FIG. 5 ) past the burn-in boards  100  to heat the semiconductor devices  120  to a selected test temperature. More particularly, the heater  572  is configured to heat the air (e.g., via a resistive heating element, electrical heating element, etc.) and the blower  574  is configured to direct the heated air into the inflow duct  575 . In some embodiments, the inflow duct  575  includes a plate  578  (e.g., a kicker plate) configured to guide the heated air from the inflow duct  575  into the heating chamber  576  and past the burn-in boards  100 . The plate  578  can be angled relative to the heating chamber  576  to provide a substantially equal rate of air flow across/past the different burn-in boards  100 . The heated air then flows through the spaces between the burn-in boards  100  (e.g., over/under/around the burn-in boards  100 ) to the outflow duct  577 , where the air is recirculated to the heater  572 . As described in detail above, the heat spreaders  240  thermally couple the semiconductor devices  120  on each of the burn-in boards  100  and operate to evenly distribute heat amongst the semiconductor devices  120  such that the semiconductor devices  120  are maintained at or near the selected test temperature during the duration of the testing procedure. 
       FIG. 6A  is a top view of a burn-in board  600  illustrating a temperature distribution across a plurality of semiconductor devices  620  during a burn-in test without a heat spreader coupled to the burn-in board  600 .  FIG. 6B  is a top view of the burn-in board  600  illustrating the temperature distribution across the plurality of semiconductor devices  620  during a burn-in test with a heat spreader (e.g., one the heat spreaders  240 ,  340 , or  440 ) coupled to the burn-in board  600 . Referring to  FIGS. 6A and 6B  together, heated air passes over the burn-in board  600  in the direction indicated by arrows  630  (e.g., as the air travels through the heating chamber  576  from the inflow duct  575  to the outflow duct  577  shown in  FIG. 5 ). 
     Referring to  FIG. 6A , without the heat spreader, the temperature of the semiconductor devices  620  has as a significant gradient that generally increases in the direction of air flow such that the temperature of downstream ones of the semiconductor devices  620  is significantly hotter than the temperature of upstream ones of the semiconductor devices  620 . That is, the temperature of the semiconductor devices  620  proximate a downstream side  621  of the burn-in board  600  can be significantly hotter than a temperature of the semiconductor devices  620  proximate an opposing upstream side  623  of the burn-in board  600 . Referring to  FIG. 6B , with the heat spreader thermally coupled to the semiconductor devices  620 , the temperature gradient across the burn-in board  600  (e.g., between the sides  621 ,  623 ) can be generally uniform, or at least significantly less than the temperature gradient without the heat spreader ( FIG. 6A ). Accordingly, the heat spreaders of the present technology can significantly improve the temperature uniformity across the burn-in board  600  and can maintain the semiconductor devices  620  at or near a selected test temperature. 
       FIG. 7  is a flow diagram of a process or method  780  for performing a burn-in test in accordance with embodiments of the present technology. The method  780  can be implemented, for example, using the burn-in board  100 , the heat spreader  240  (or the heat spreader  340 , the heat spreader  440 , etc.), and/or the system  570  described in detail above with reference to  FIGS. 1A-5 . Accordingly, for the sake of illustration, some features of the method  780  will be described in the context of the embodiments shown in  FIGS. 1A-5 . 
     Beginning at block  782 , the method  780  includes loading the semiconductor devices  120  onto the burn-in board  100 . For example, the semiconductor devices  120  can be electrically coupled to the mounting seats  116  in the sockets  110 . At block  784 , the method  780  includes thermally contacting at least a portion (e.g., a subset) of the semiconductor devices  120  with the heat spreader  240 . For example, the heat spreader  240  can be placed over the burn-in board  100  such that the protrusions  244  of the heat spreader  240  project into the sockets  110  to thermally contact the semiconductor devices  120 . In some embodiments, the heat spreader can be positioned on a spring or stand (e.g., the stand  350  and/or the springs  460  illustrated in  FIGS. 3 and 4 , respectively). In some embodiments, each of the semiconductor devices  120  loaded on the burn-in board  100  at least partially contacts a respective protrusion  244  of the heat spreader  240 . 
     At block  786 , the method includes positioning the burn-in board  100  and the heat spreader  240  in a heating chamber (e.g., the heating chamber  576  of the system  570 ). For example, the burn-in board  100  can be positioned on a rack or other support within the heating chamber  576  and electrically coupled to testing circuitry. At block  788 , the method includes performing a burn-in test. For example, the heating chamber  576  can be heated to a selected test temperature for a predetermined amount of time while the semiconductor devices  120  are electrically activated, exercised, cycled, biased, etc. More specifically, the heater  572  of the system  570  can heat the air and the blower  574  can direct the heated air into the inflow duct  575  and to the plate  578 , which guides the heated air from the inflow duct  575  into the heating chamber  576  to heat the semiconductor devices  120  on the burn-in board  100 . 
     The above detailed descriptions of embodiments of the technology are not intended to be exhaustive or to limit the technology to the precise form disclosed above. Although specific embodiments of, and examples for, the technology are described above for illustrative purposes, various equivalent modifications are possible within the scope of the technology, as those skilled in the relevant art will recognize. For example, while steps are presented in a given order, alternative embodiments may perform steps in a different order. Moreover, the various embodiments described herein may also be combined to provide further embodiments. Reference herein to “one embodiment,” “an embodiment,” or similar formulations means that a particular feature, structure, operation, or characteristic described in connection with the embodiment can be included in at least one embodiment of the present technology. Thus, the appearances of such phrases or formulations herein are not necessarily all referring to the same embodiment. 
     Moreover, unless the word “or” is expressly limited to mean only a single item exclusive from the other items in reference to a list of two or more items, then the use of “or” in such a list is to be interpreted as including (a) any single item in the list, (b) all of the items in the list, or (c) any combination of the items in the list. Where the context permits, singular or plural terms may also include the plural or singular term, respectively. Additionally, the term “comprising” is used throughout to mean including at least the recited feature(s) such that any greater number of the same feature and/or additional types of other features are not precluded. Directional terms, such as “upper,” “lower,” “front,” “back,” “vertical,” and “horizontal,” may be used herein to express and clarify the relationship between various elements. It should be understood that such terms do not denote absolute orientation. Further, while advantages associated with certain embodiments of the technology have been described in the context of those embodiments, other embodiments may also exhibit such advantages, and not all embodiments need necessarily exhibit such advantages to fall within the scope of the technology. Accordingly, the disclosure and associated technology can encompass other embodiments not expressly shown or described herein.