Patent Publication Number: US-9841461-B2

Title: Transport apparatus for moving carriers of test parts

Description:
This patent application is a continuation of a patent application entitled “Transport Apparatus for Moving Carriers of Test Parts” having Ser. No. 12/890,530 which was filed on Sep. 24, 2010 Now U.S. Pat. No. 8,970,244 and which is incorporated herein in its entirety, and which patent application is a nonprovisional patent application of U.S. Provisional Application No. 61/246,124 filed Sep. 26, 2009, U.S. Provisional Application No. 61/279,121 filed Oct. 17, 2009 and U.S. Provisional Application No. 61/279,358 filed Oct. 19, 2009 from which U.S. provisional applications priority is claimed under 35 USC §119(e), and which provisional applications are incorporated herein in their entirety. 
    
    
     TECHNICAL FIELD OF THE INVENTION 
     One or more embodiments of the present invention relate to transporting carriers of test parts such as, for example and without limitation, microelectronic devices, to enable one or more procedures such as, for example and without limitation, test and/or burn-in, and more specifically to method and apparatus for transporting an array of microelectronic devices in a movable tray adapted for making electrical contact to an electronic test equipment. 
     BACKGROUND 
     Semiconductor processing is an increasingly complex and mature technology for which the cost of test and burn-in consumes an ever larger share of production costs. However, continuous progress is being made in semiconductor technology and wafer fabrication efficiency where such progress can be characterized by Moore&#39;s law which has successfully predicted a doubling of the number of devices on a semiconductor chip every two years. Productivity gains from advances in semiconductor technology and wafer fabrication efficiency underlie the modern economy, making possible mobile electronics, Internet communications and much of modern life. However, semiconductor packaging and testing have not maintained the same pace of technological progress. 
     Methods commonly used for contacting individual, separated semiconductor chips during testing have remained largely the same for decades. For example, after wafer probe testing, a wafer is sawn apart into individual chips. Then, additional packaging steps may be used to protect the chip and facilitate its attachment to an electronic system. After packaging, each chip is inserted into a first socket to test for opens and shorts. Each chip is then released from the first socket and transported in a tray. In an optional next step, the chip is inserted into a second (burn-in) socket and burned-in for eight hours at an elevated temperature of about 125° C. After burn-in, the chip is removed from the burn-in socket and transported in a tray to final test where it is inserted into a third socket. A comprehensive set of tests is done in final test, which tests are typically done at several speeds, voltages and temperatures. The socketing, sockets, fixtures, test boards and handling involved with the process of testing individual chips and other microelectronic devices present increasing problems in streamlining the production of semiconductor devices. 
     Attempts have been made to eliminate the need for individual sockets in test and burn-in, with limited success, in certain segments of the industry. For example, wafer probe testing using full wafer contactors has been used to test and burn-in all chips on a wafer in parallel, simultaneously. In DRAM and FLASH memory production, wafer probe testing is now being done in parallel for each chip on a wafer. However, at present, cost and performance limitations prevent the practical use of full wafer contactors to burn-in and performance test all chips on a wafer. In particular, for more complex chips, such as microprocessors, signal processors, ASICS and communications chips, the high I/O count, power and performance associated with these complex chips prevent use of full wafer contactors for anything other than simple wafer probe testing at best. Although considerable resources, including work in university, U.S. government and industrial laboratories, have been devoted to full wafer burn-in and speed testing, the problem of finding a practical solution remains unsolved. 
     Other attempts to test and burn-in devices have been made which entail contacting a strip of partially packaged chips. In the process of packaging semiconductor chips as chip scale packages (CSPs) or ball grid arrays (BGAs), an array of chips is held together in a strip format. An array contactor is then used to test and burn-in arrays of chips in the strip format by having the array contactor contact terminals on each partially packaged chip without using an individual chip socket. After testing, the process of packaging the chips is completed, and the strip is sawn into individual finished devices. While testing in a strip format eliminates the need for individual costly sockets for some electrical tests, strip testing is only applicable to packages that are processed in strip format. Dimensional stability limits the application of testing in a strip format to relatively small array sizes and low densities due to problems with alignment of terminals on devices to corresponding contactors. A further limitation results from a complication of the process flow wherein devices leave a packaging area to be tested in a test facility, and then return to packaging for finishing and singulation into individual devices. 
     Another approach involves placing chips, whether packaged or not, in an accurately positioned array on a carrier. The carrier is moved automatically through the process on tracks or belts. In order to test devices in the carrier, the carrier is physically picked up and placed accurately on the contactor. After testing, the carrier is extracted from the contactor and physically placed back on a track for automatic transport to a next operation. A complex, slow and expensive mechanical apparatus is required to place the carrier accurately on a mating contactor. 
     SUMMARY 
     One or more embodiments of the present invention solve one or more of the above-identified problems by providing a transport mechanism that moves a first tray of devices onto a test position while simultaneously moving a second tray of devices off the test position. The devices, for example and without limitation, microelectronic devices, are disposed in an array of apertures in each tray. In accordance with one or more embodiments of the present invention, a tray is resiliently supported by flexural springs to a planar frame wherein the tray is movable in a direction perpendicular to the tray. In a test procedure the tray is moved into a test position between a test head and a juxtaposed contactor, wherein the test head moves toward the tray, thereby urging the devices into electrical contact with corresponding contacts of the contactor. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a perspective view of a transport mechanism for moving carriers for holding microelectronic devices onto and off a test site, which transport mechanism is fabricated in accordance with one or more embodiments of the present invention. 
         FIGS. 2A and 2B  are perspective views of a carrier for holding microelectronic devices, which carrier is fabricated in accordance with one or more embodiments of the present invention, the carrier being shown in a retracted configuration in  FIG. 2A  and in an extended configuration in  FIG. 2B . 
         FIGS. 3A and 3B  are top views of carriers for holding an array of microelectronic devices, which carriers are fabricated in accordance with one or more embodiments of the present invention. 
         FIGS. 4A-4B  are top cutaway views of a portion of a carrier for holding an array of microelectronic devices in conjunction with a mechanism for loading and unloading devices from the carrier, which carrier and mechanism are fabricated in accordance with one or more embodiments of the present invention. 
         FIG. 4C  is a top cutaway view of the mechanism for loading and unloading devices shown in  FIGS. 4A and 4B . 
         FIG. 5A  is a top view of a transport mechanism with a carrier in an input position, which transport mechanism and carrier are fabricated in accordance with one or more embodiments of the present invention. 
         FIGS. 5B-5F  are simplified side views of the transport mechanism and the carrier shown in  FIG. 5A  which help illustrate a sequence of steps for moving the carrier from an input position to a test position. 
         FIG. 6A  is a top view of a transport mechanism with a first carrier in a test position under a test head and a second carrier in an input position, which transport mechanism and carriers are fabricated in accordance with one or more embodiments of the present invention. 
         FIGS. 6B-6F  are simplified side views of the transport mechanism and the first and second carriers shown in  FIG. 6A  which help illustrate a sequence of steps for moving the first carrier from the test position to an output position while simultaneously moving the second carrier from the input position to the test position. 
         FIG. 7A  is a top view of a transport mechanism with a first carrier in an output position, a second carrier in a test position under a test head, and a third carrier in an input position, which transport mechanism and carriers are fabricated in accordance with one or more embodiments of the present invention. 
         FIGS. 7B-7F  are simplified side views of the transport mechanism and the first, second and third carriers shown in  FIG. 7A  which help illustrate a sequence of steps for moving the first carrier from the output position, and subsequently for moving the second carrier from the test position to the output position while simultaneously moving the third carrier from the input position to the test position. 
         FIG. 8A  is a top view of a test position wherein a test head is positioned over a tray carried by a frame, which test position is fabricated in accordance with one or more embodiments of the present invention. 
         FIGS. 8B-8D  are cross sectional views of the test position shown in  FIG. 8A  for testing arrays of microelectronic devices held in a tray supported on a frame of a carrier that is fabricated in accordance with one or more embodiments of the present invention, where: (a)  FIG. 8B  shows the tray in a retracted configuration; (b)  FIG. 8C  shows a test head urging the tray to an extended configuration; and (c)  FIG. 8D  shows the tray in the extended configuration while a thermal plate is urged into contact with an array of devices under test. 
         FIG. 9A  is a cross sectional view of concatenated transport mechanisms moving devices in carriers through a sequence of thermal soaking and testing operations. 
         FIG. 9B  is a cross sectional view of an array of test pods fed by an automatic loader that is fabricated in accordance with one or more embodiments of the present invention. 
     
    
    
     DETAILED DESCRIPTION 
     In accordance with one or more embodiments of the present invention, a transport mechanism is used to move carriers to positions to carry out test and burn-in operations. A carrier is provided for holding devices, for example and without limitation, microelectronic devices, in place in an array so the devices may be: (a) moved to a test position that includes, for example and without limitation, a contactor block (the term “contactor block” refers to an array of connectors or contactors, and the term “contactor” refers to a connector such as, for example and without limitation, a spring pin such as a Pogo® spring pin) such as, for example and without limitation, a test socket; and (b) aligned with mating contactors, for example and without limitation, test contactors (for example, an electrode terminal of a socket), in the contactor block, for example and without limitation, the test socket. 
     As used herein, the term device is used in the broadest sense and includes, without limitation, an electronic device and a microelectronic device including a semiconductor chip, a flip chip, a packaged electronic circuit, a hybrid circuit, a daughter card, a multi-chip module, and the like. As further non-limiting examples of the types of microelectronic devices which may be held in a carrier fabricated in accordance with one or more embodiments of the present invention are BGAs (as used herein the term BGA, or ball grid array, is a two dimensional array of solder bump terminals on a microelectronic device), CSPs (as used herein, the term CSP is a chip scale package), flip-chips, wafer level packages (WLPs), TSVs (as used herein, the term TSV is a through silicon via device), bare semiconductor dice, MEMS, and multi-chip modules. 
     As used herein, the terms up, down, top and bottom generally refer to an orientation with respect to figures showing aspects of embodiments of the present invention. These terms are not intended to describe orientation with respect to a gravitational field, but rather are used to facilitate description of aspects of embodiments of the present invention as illustrated in the figures. As used herein, the expression “respectively” means that a first item in a first list relates to a first item in a second list; a second item in the first list relates to a second item in the second list; and so forth. 
     In accordance with one or more embodiments of the present invention, a carrier comprises a frame that is resiliently coupled to a tray, which frame includes two or more flexible links, for example and without limitation, springs that are disposed so the tray may be resiliently moved relative to the frame (for example and without limitation, moved perpendicular to a plane associated with the frame such as an aperture in which the tray may be disposed). In accordance with one or more such embodiments, the tray includes a plurality of apertures disposed in an array of sites, wherein each site is a location within the tray that is adapted to hold a unitary module, (typically a unitary module is one device; however, the unitary module may be comprised of multiple devices). The each aperture may extend completely through the tray, or alternatively, extend partially through the tray. In accordance with one or more embodiments of the present invention, a carrier comprises a tray that is separable from, and is attachable to, a frame, for example and without limitation, by attachment to springs or to a structure that is coupled to the springs—for example and without limitation, the tray may be a molded plastic tray with apertures therethrough. Alternatively, in accordance with one or more further embodiments of the present invention, a carrier comprises a frame that includes a tray and flexible links that are disposed so the tray may be resiliently moved relative to the frame (for example and without limitation, moved perpendicular to a plane associated with the frame such as an aperture in which the tray may be disposed), wherein the tray is an integral part of the frame. 
       FIG. 1  is a perspective view of transport mechanism  100  for moving a plurality of devices on carriers of various types through a sequence of test locations to carry out a sequence of test operations. Carriers  151 - 153  are slidably supported on rails  110  for use in testing and/or burn-in testing in accordance with one or more embodiments of the present invention. As shown in  FIG. 1 , rails  110  support carriers  151 - 153 , each of which carriers  151 - 153  includes a mesh of serpentine flat springs (springs  121   1  and  121   2 ; springs  122   1  and  122   2 ; and springs  123   1  and  123   2 , respectively) that form spring beds for trays  101 - 103 , respectively. In operation, serpentine flat springs  122   1  and  122   2  provide resiliency that enables devices held in tray  102  to be urged by a test head (not shown) mounted above tray  102  downwardly into contact with socket  116  mounted below tray  102 . As further shown in  FIG. 1 , trays  101 - 103  are held in place on frames  191 - 193  of carriers  151 - 153 , respectively, by four (4) fasteners (for example, PEM nuts  181   1 - 181   4  affixed to tray  101 ). As further shown in  FIG. 1 , pin carrier  134  on mobile trolley  130  mounted to pneumatic drive  132  transports carriers  151 - 153  along a track having rails  110  (as used herein, the term “track” is a guide having with two or more rails for holding carriers slidably). Pins (not visible in  FIG. 1 ) on pin carrier  134  engage with transport apertures  162   2  and  163   1  on frames  192  and  193 , respectively, thereby enabling mobile trolley  130  to move carriers  152  and  153  into position simultaneously. In  FIG. 1 , carrier  151  is in an input position, carrier  152  is in a test position, and carrier  153  is in an output position. Each end of frames  191 ,  192  and  193  has one or more transport apertures (transport apertures  161   1  and  161   2 ; transport apertures  162   1  and  162   2 ; and transport apertures  163   1  and  163   2 , respectively) that enable engagement for transport from either end of the frames. As further shown in  FIG. 1 , apertures in the trays (for example, apertures  173   1 - 173   4  disposed in tray  102 ) may be used to align the trays with registration pins on test sockets. In accordance with one or more further embodiments of the present invention, the carriers may be transported by robots, slides, belts, magnetic levitation tracks, a pin carrier moved by a linear motor, a lead screw, a ball screw, a belt drive, a stepper motor (with cable and pulleys) and the like, or manually, all of which embodiments may be fabricated routinely and without undue experimentation by one of ordinary skill in the art in light of the description herein. Further, in accordance with one or more embodiments of the present invention, various identification marks, alignment features, tracking labels and the like may be added to a carrier in accordance with any one of a number of methods that are well known to one of ordinary skill in the art of conventional semiconductor packaging and testing. 
     Modalities of the operation of one or more embodiments of the present invention may be understood better by reference to carriers shown in  FIGS. 2A and 2B  and in  FIGS. 3A and 3B .  FIGS. 2A and 2B  are perspective views of carrier  200  for holding microelectronic devices, which carrier  200  is fabricated in accordance with one or more embodiments of the present invention.  FIG. 2A  shows carrier  200  with tray  220  in a retracted configuration, while  FIG. 2B  shows carrier  200  with tray  220  in an extended configuration. In use, microelectronic devices (not shown) are held in a plurality of apertures  212   n  at sites  210   n  of tray  220 , thereby enabling the devices to be transported, in alignment as a group, by carrier  200  to and from contactors for making temporary test connections to the devices so transported. For clarity of exposition and ease of understanding, numerical labeling of repeated elements, for example sites  210   n , are omitted as having been defined for a typical element. Each of an array of devices resides in an aperture  212   n  at site  210   n  of tray  220 . A device at site  210   n  is prevented from falling through aperture  212   n  by retaining feature  216   n  which is, by way of example and without limitation, a ledge. As further shown in  FIGS. 2A and 2B , tray  220  is resiliently coupled to frame  230  of carrier  200  by attachment to flexural springs  232 , thereby enabling tray  220  to be moved resiliently relative to frame  230  (for example, in a direction perpendicular to a plane of an opening in frame  230 ) by flexing flexural springs  232 . Flexural springs  232  of  FIG. 2A  are sheets of resilient metal cut to form two legs of substantially equal length whereby tray  220  moves in a direction perpendicular to the plane of carrier  200  when moving from a retracted position shown in  FIG. 2A  to an extended position shown in  FIG. 2B . As further shown in  FIGS. 2A and 2B , tray  220  includes alignment features  266   n  that may be used to position tray  220  accurately with respect to a mating element such as, for example and without limitation, a contactor block, test socket, a burn-in socket, or a processing head. As further shown in  FIGS. 2A and 2B , frame  230  includes slots  261   1  and  262   2  disposed at each end thereof which are useful in engaging transport mechanisms for moving carrier  200  from one station to another. As further shown in  FIGS. 2A and 2B , frame  230  includes: (a) side sections  270  having surfaces adapted to be slidably supported on rails (not shown in  FIGS. 2A and 2B ); and (b) notches  268   1  and  268   2  disposed along a side section of frame  230  to enable alignment, for example and without limitation, by means of shot pins (not shown) that engage the notches laterally in response to a force being applied thereto in the plane of frame  230 . 
     In accordance with one or more embodiments of the present invention, apertures  212   n  may extend through the body of tray  220  to enable access to top surfaces of devices (not shown), for example and without limitation, for direct chip cooling, while enabling access to bottom surfaces of the devices, for example and without limitation, for connection to contactor probes of a test socket. Alternatively, apertures  212   n  may have a bottom structure  216   n  (for example, refer to  FIG. 2A ) so that devices held therein are prevented from falling downward and out of aperture  212   n . In accordance with one or more such alternative embodiments of the present invention, the bottom structure may comprise one or more tabs, one or more ledges, one or more protrusions, a thin sheet with a grid of holes therethrough, a sheet of material with or without apertures therein, and so forth. In accordance with one or more such embodiments, the bottom structure comprises a thin sheet of copper, copper alloy, steel, polyimide, or other suitable material. In accordance with one or more further embodiments, the bottom structure comprises a thin sheet with embedded contactors disposed through the sheet whereby electrical connections may be made between terminals on bottom surfaces of devices and corresponding terminals of a mating socket. Embedded contactors may include, without limitation, terminals with roughened surfaces, spring probes, resilient metal vias, cantilever probes, buckling beam probes, flat spring probes, and the like. 
     While tray  220  (which is fabricated to have a multiplicity of sites like site  210   n  shown in  FIG. 2A ), as shown in  FIGS. 2A and 2B , is substantially planar, it will be understood by one of ordinary skill in the art that trays fabricated in accordance with one or more embodiments of the present invention may include additional features that facilitate loading and unloading of various types of microelectronic devices. For example and without limitation, beveled “picture frames” may be added to each site  210   n  to guide devices into apertures like aperture  212   n . In accordance with one or more such embodiments of the present invention, beveled picture frames may be formed individually, i.e., with one picture frame per site, or beveled picture frames may be formed in an array that is attached to a planar tray  220 . As used herein, a picture frame, typically fabricated from molded plastic material, is a frame that is used to guide a device into an aperture in the tray. As one of ordinary skill in the art can readily appreciate, many embodiments of tray  220  may be fabricated that include variations from the beveled picture frames described above. For example and without limitation, a portion of a picture frame need not surround each site (for example, a picture frame portion associated with a site need not include four (4) sides), or even be present at each site. In addition, the tray may include prongs activated by cams that open the prongs and allow a device to be inserted into the site. 
     In accordance with one or more embodiments of the present invention, tray  220  may be fabricated using any one of a number of conventionally practiced methods of plastic molding. For example and without limitation, suitable plastics for fabricating trays include: FR-4 epoxy, liquid crystal polymer, polyether ether ketone (PEEK), polyether sulfone (PES), and polyamide-imide (Torlon® available from Quadrant Engineering Plastics, Reading, Pa.) and Semitron 410C Ultem® plastic material available from Boedeker Plastics of Shiner, Tex. (Ultem is a trademark of GE Plastics). Tray  220  may also be fabricated of an insulative material or a metal with an insulative coating. For example and without limitation, a dielectric material of a high performance tray may be selected from a group of dimensionally stable polymer materials including, for example and without limitation: glass reinforced Torlon 5530 available from Quadrant Engineering Plastics, of Reading Pa.; Vespel; Ultem 2000 available from GE Inc.; carbon filled PEEK; liquid crystal polymer; aramid fiber reinforced polyimide sheet; and others. A high degree of dimensional stability may be achieved with trays of metals such as, for example and without limitation, brass, stainless steel, titanium alloy 6al-4v, or aluminum 7075, the metal body being provided with an insulative conformal coating of one or more dielectric materials that are well known in the electronic circuit board industry. 
     In accordance with one or more embodiments of the invention, and as shown in  FIG. 2A , tray  220  includes seal band  224  which encircles sites  210   n  to provide a top sealing surface  204  for tray  220  when carrier  200  is used in the manner described below. In accordance with one or more such embodiments of the present invention, and as shown in  FIG. 2A , seal band  224  is a solid band of material around a periphery of tray  220  that encircles device receiving sites  210   n . In accordance with one or more such embodiments, top surface  204  of seal band  224  provides a top sealing surface for tray  220 , and a portion of a bottom surface of tray  220 , for example, a flat portion, provides a bottom sealing surface for tray  220 . In accordance with one or more such embodiments, seal band  224  is a solid band of material disposed on, or formed as a portion of, tray  220  (refer to  FIG. 2A ). 
     As shown in  FIGS. 2A and 2B , flexural springs  232  are serpentine folded flat springs wherein ends  234  and  236  of springs  232  are in close proximity to reduce movement of tray  220  that is not in a direction perpendicular to a plane of frame  230 . A force F (refer to  FIG. 2B ) acting upon tray  220  in a direction perpendicular to the plane of frame  230  displaces tray  220  to an extended configuration shown in  FIG. 2B . Upon release of force F, tray  220  returns to a retracted configuration shown in  FIG. 2A . The term “retracted configuration” refers a configuration of tray  220 , and hence springs  232 , for example and without limitation, where no external forces other than gravity act upon tray  220 . 
     In accordance with one or more embodiments of the present invention, frame  230  may be fabricated from a sheet of full hardness, tempered 304 stainless steel having, for example and without limitation, a thickness of about 0.50 mm. In accordance with one or more such embodiments, the features of frame  230  shown in  FIGS. 2A and 2B  and described above may be laser cut in the full hardness, tempered 304 stainless steel sheet to an accuracy of ±5 micrometers. In accordance with one or more alternative embodiments, frame  230  may be fabricated from a material including, without limitation, stainless steel, tempered steel, Monel 500, glass fiber reinforced polyimide, aramid fiber reinforced polyimide (available from Arlon Materials for Electronics, a Division of WHX Corporation, of Rancho Cucamonga, Calif.), NiTi shape memory alloy (available from National Electronic Alloys, Inc. of Santa Ana, Calif.), carbon fiber reinforced polymer, or a resilient plastic material. 
     As shown in  FIGS. 2A and 2B , and in accordance with one or more embodiments of the present invention, tray  220  is resiliently coupled to frame  230  by attachment to springs  232 . In accordance with one or more such embodiments, tray  220  is attached to springs  232  by fastening means  252  which, for example and without limitation, may be PEM® nuts available from PEM Fastening Systems of Danboro, Pa. 
       FIGS. 3A and 3B  are top views of carriers  200  and  300 , respectively, for holding an array of microelectronic devices, which carriers are fabricated in accordance with one or more embodiments of the present invention. As shown in  FIG. 3A , data matrix serialization mark  244  is positioned near one end of frame  230  and is provided for use in automatic machine reading an identity of carrier  200  by, for example and without limitation, an optional sensor on a transport apparatus. Mark  244  is fabricated in accordance with any one of a number of methods that are well known to those of ordinary skill in the art, and it enables tracking devices in tray  220  for forward and backward traceability from, for example and without limitation, picking a device from a sawn semiconductor wafer to, for example and without limitation, packing the device for final shipment. For example and without limitation, data specifying the location of devices in sites of a carrier may be collected by factory mechanization computers in accordance with any one of a number of methods that are well known to those of ordinary skill in the art. This data may be correlated, for example and without limitation, by such factory mechanization computers or by other computers, with data relating to the various process steps entailed in fabricating and testing devices to enable forward and reverse traceability of the devices at any subsequent process or testing step and so forth performed while the devices are held in the carrier. 
       FIG. 3B  shows carrier  300  which is fabricated in accordance with one or more embodiments of the present invention wherein frame  330  and tray  320  are fabricated from a unitary sheet of material. In accordance with one or more such embodiments, the thickness of carrier  300  may range from (for example and without limitation, using a thin sheet of 304 stainless steel) about 0.1 mm in thickness for use, for example and without limitation, in flip chip applications to (for example and without limitation, using a molded plastic sheet) about 5.0 mm in thickness for use, for example and without limitation, with a MEMS pressure sensor device. As further shown in  FIG. 3B , tray  320  is depended on flexural springs  332  from frame  330 , thereby allowing tray  320  to move relative to support rails  370  of frame  330 . As further shown in  FIG. 3B , flexural springs  332  are attached at proximal ends  336  to tray  320 , and at distal ends  334  to frame  330 . In accordance with one or more embodiments of the present invention, stiffness of a body of a frame such as frame  300  may be increased by embossments, flanges, j-flanges, folds, and other stiffeners known in the art. As further shown in  FIG. 3B , alignment features  366   1 - 366   4  are disposed in tray  320 , which alignment features are provided to enable engagement with alignment elements on a mating contactor block during a process of urging tray  320  downwardly onto the contactor block as will be described below. As further shown in  FIG. 3B , slots  361   1  and  361   2  are disposed in frame  330 , which slots are adapted for engagement with transport mechanisms for slidably moving carrier  300  along the rails of a track. As further shown in  FIG. 3B , notches such as  368   1  and  368   2  are provided along a side section of frame  330  to enable engagement, for example and without limitation, with shot pins (as will be described below) that hold frame  330  in a predetermined position along rails of a track. 
     As further shown in  FIG. 3B , tray  320  includes an array of sites  310   n  having apertures  312   n  for receiving microelectronic devices (not shown). As further shown in  FIG. 3B , each site  310   n  includes a pair of resilient prongs  316   n  and  318   n  that are adapted for holding a device in position in tray  320 . Seal band  324  encircles sites  310   n  with solid material which provides a top sealing surface for tray  320 , and a bottom surface of tray  320  provides a bottom sealing surface for tray  320 . Optionally, carrier  300  is provided with a machine readable mark  344  for identification and machine control. For example, and without limitation, mark  344  is a data matrix used to uniquely identify carrier  300  for process and transport control. Mark  344  allows tracking of devices in tray  320  for forward and backward traceability from picking a device from a sawn semiconductor wafer to packing the device for final shipment. 
       FIGS. 4A-4B  are top cutaway views of a portion of carrier  300  (refer to  FIG. 3B ) for holding an array of microelectronic devices  394   n  in conjunction with mechanism  390  for loading and unloading devices from carrier  300 -carrier  300  and mechanism  390  are fabricated in accordance with one or more embodiments of the present invention. In accordance with one or more embodiments of the present invention, microelectronic devices  394   n  are inserted into and extracted from apertures at sites  310   n  utilizing mechanism  390  (for example and without limitation, cam apparatus  390 ) shown in  FIGS. 4A-4C . For ease of understanding, it may be understood that each of devices  394   1 - 394   n  is equivalent and that the labels are interchangeable. 
     In accordance with one or more embodiments of the present invention, tray  320  of carrier  300  is aligned to cam apparatus  390  by mating alignment features  366   1 - 366   4  (refer to  FIG. 3B ) with alignment pins, for example, pin  367   3  on support plate  392  of cam apparatus  390 . In a process of aligning and mounting carrier  300  to cam apparatus  390  in accordance with one or more embodiments of the present invention, each of cams  380   1 - 380   n  is inserted between corresponding pairs of prongs  316   1  and  318   1  to  316   n  and  318   n  of tray  320  (refer to  FIGS. 3B, 4A and 4B ). Next, cams  380   1 - 380   n  are rotated, for example and without limitation, by about 90°, thereby urging each cam  380   n  against resilient prongs  316   n  and  318   n  so that prongs  316   n  and  318   n  are spread apart to release force on device  394   n  to enable its removal from aperture  312   n  in site  310   n . Correspondingly, cams  380   1 - 380   n  may be rotated so as to urge against prongs  316   n  and  318   n  and open aperture  312   n  so that device  394   n  may be inserted into aperture  312   n , and then rotated back to enable prongs  316   n  and  318   n  to hold device  394   n . 
       FIG. 4C  is a top cutaway view of cam apparatus  390  where elements behind mounting plate  392  are shown in phantom. In accordance with one or more such embodiments, mounting plate  392  has a coefficient of thermal expansion (CTE) that is matched to a CTE of carrier  300 , and in particular, of tray  320 . In accordance with one or more such embodiments, cam apparatus  390  moves cams  380   n  in concert so that each cam is rotated through about 90° by mechanical linkages. In accordance with one or more such embodiments of the present invention, the mechanical linkages comprise gears  396  mounted to shafts of motors  398 ; cams  380   1 - 380   n  mounted to cam gears  382   1 - 382   n ; and spur gears  384   1 - 384   n . In accordance with one or more such embodiments, motor  398  rotates gear  396  clockwise, which gear  396  rotates spur gear  384   1  counterclockwise, which spur gear  384   1 , in turn, rotates cam gear  382   1  clockwise, which cam gear  382   1 , in turn, rotates spur gear  384   2  counterclockwise, which spur gear  384   2  rotates cam gear  382   2  clockwise, and so forth. In the manner described above, all of cams  380   1 - 380   n  are rotated through a set angle so that a pair of prongs at a site is urged apart by a cam interposed therebetween. As one of ordinary skill in the art will understand, mechanical linkages of cam apparatus  390  may be fabricated, for example and without limitation, to be comprised of: (a) belts and pulleys; (b) cranks and linkages; (c) cables and pulleys; (d) electromechanical actuators; (e) pneumatic actuators; or (f) wedges linked to actuators. In addition, one of ordinary skill in the art will also understand that mounting plate  392  may include vacuum channels for holding devices  394   n  against mounting plate  392  during the process of inserting devices into apertures in a carrier fabricated in accordance with one or more embodiments of the present invention. In further addition, and in accordance with one or more such embodiments, a temperature of mounting plate  392  may be set to a fixed temperature using any one of a number of methods that are well known to those of ordinary skill in the art to facilitate opening or closing the pair of prongs around each aperture. In still further addition, and in accordance with one or more such embodiments, mechanical vibration may be used to seat properly the devices in their respective apertures, which mechanical vibration may be generated using any one of a number of methods that are well known to those of ordinary skill in the art such as, for example and without limitation, applying ultrasonic, sonic, or subsonic vibrations. 
     In accordance with one or more embodiments of the present invention, cam apparatus  390  is incorporated into automatic device handling equipment known in the art as a “handler.” In accordance with one or more such embodiments of the present invention, cam apparatus  390  is incorporated into a wafer picker to enable devices picked from a wafer to be mounted in a carrier using a pick and place robot. In addition, in accordance with one or more embodiments of the present invention, cam apparatus  390  is incorporated into a taping machine to enable devices to be picked from a carrier by a pick and place robot and placed into pockets in a shipping tape, for example and without limitation, a tape of the type commonly used to ship microelectronic devices. In further addition, in accordance with one or more embodiments of the present invention, cam apparatus  390  is used in conjunction with a second cam apparatus  390  to enable devices to be picked from one carrier by a pick and place robot and to be placed in a second carrier. In yet further addition, in accordance with one or more embodiments of the present invention, a combination of several such cam apparati may be used to pick devices from one carrier and to place them in appropriate other carriers as determined, for example and without limitation, by results of tests on the devices. 
     According to one or more embodiments of the invention, carriers are transported onto and off a test position by a transport mechanism. At the test position, electrical contact is made to devices held in a tray of the carrier by moving the tray in a direction substantially perpendicular to, for example and without limitation, a plane of a frame of the carrier to bring the devices held in the tray into contact with a contactor block.  FIGS. 5A to 5F  help illustrate steps in transporting and testing microelectronic devices  614   n  held in tray  620  of carrier  600 .  FIG. 5A  shows a top view of transport mechanism  400  with carrier  600  positioned on rails  444  and  446  in an input position of transport mechanism  400 . As shown in  FIG. 5A , test head  490  is juxtaposed over contactor  470  at a test position. 
     In operation, transport mechanism  400  brings carrier  600  under test head  490 . Then, test head  490  clamps down onto carrier  600 , thereby urging devices  614   n  into contact with contactor block  470 . As shown in  FIG. 5A , alignment holes  666   1 - 666   4  in tray  620  and notches  668   1  and  668   2  in frame  630  are used for positioning devices  614   n  held in carrier  600  in the manner to be described below. 
       FIGS. 5B-5F  are simplified side views of transport mechanism  400  (also referred to as transporter  400 ) and carrier  600  which help illustrate a sequence of steps in transporting and contacting devices  614   n  for electrical test on contactor block  470  that is electrically connected to test interconnection means  472  (for example, a printed wiring substrate). As shown in  FIGS. 5B-5F , test head  490  is juxtaposed to contactor block  470  and printed wiring substrate  472  at a test position (for clarity of exposition and ease of understanding, rails  444  and  446 , actuator  440 , and trolley  442  are not shown in  FIGS. 5B-5F ). In a first step in a test procedure, and as shown in  FIG. 5B , carrier  600  is mounted on transporter  400  in an input position. As shown in  FIG. 5B , a gap between a bottom of test head  490  and a top of contactor block  470  enables lateral translation of carrier  600  to a test position interposed between test head  490  and contactor block  470 . Next, in a second step, and as shown in  FIG. 5C , pin carrier  476  (for example, a fixture for holding pins used to transport carriers) is raised, for example and without limitation, by a pneumatic actuator, an electromagnetic actuator, a mechanical cam or other actuator in a manner that is well known to those of ordinary skill in the art), thereby urging engagement pin  478   1  into an engagement feature of carrier  600 , for example and without limitation, slot  661   2  in frame  630  of carrier  600  (refer to  FIG. 5A  wherein slot  661   2  is partially obscured by pin  478   1  engaged therein). Next, in a third step, and as shown in  FIG. 5D , pneumatic actuator  440  of transporter  400  is activated to move trolley  442  and attached pin carrier  476 , thereby slidably moving carrier  600  along rails  444  and  446  by action of pin  478   1  acting upon slot  661   2 . As carrier  600  moves into the test position between test head  490  and contactor block  470 , its presence is sensed by reflective optical detector  447  which is actuated when carrier  600  reaches a set position along rails  444  and  446  (in accordance with one or more further embodiments of the present invention, other types of detectors that are well known to those of ordinary skill in the art may be used in place of optical detectors such as, for example and without limitation, proximity detectors). When carrier  600  reaches the set position and detector  447  is actuated, the carrier is locked in position, for example and without limitation, by engagement of shot pins (not shown) with notches  668   1  and  668   2  in frame  630 . Next, in a fourth step, and as shown in  FIG. 5E , test head  490  is moved downwardly toward contactor block  470 , thereby urging tray  620  and devices  614   n  contained therein into contact with contactor block  470 . As tray  620  is moved downwardly, alignment pins  474   1  and  474   4  of contactor block  470  engage alignment features  666   1  and  666   4  of tray  620 , respectively, thereby bringing tray  620  and devices  614   n  into registration with contactor block  470  (in particular, registration refers to alignment of terminal pads on microelectronic device devices  614   n  to contactors of a mating socket of contactor block  470 ). In accordance with one or more embodiments of the present invention, flexure of flexural springs  632  enables tray  620  to move in a direction perpendicular to frame  630  while frame  630  remains stationary on rails  444  and  446 . Next, pin carrier  476  is dropped, whereby pin  478   1  is disengaged from alignment feature hole  661   2 . Next, in a fifth step, as shown in  FIG. 5F , pin carrier  476  is returned to its initial position, i.e., as seen in  FIG. 5B , in readiness for engagement with a next carrier that moves into the input position. 
       FIG. 6A  is a top view of transport mechanism  400  with carrier  600  in a test position under test head  490  and carrier  700  in an input position, which transport mechanism  400  and carriers  600  and  700  are fabricated in accordance with one or more embodiments of the present invention.  FIGS. 6B-6F  are simplified side views of transport mechanism  400  and carriers  600  and  700  which help illustrate a sequence of steps for moving carrier  600  from the test position to an output position while simultaneously moving carrier  700  from the input position to the test position. In a step in a test procedure, and as shown in  FIG. 6B , carrier  700  is mounted on transporter  400  in an input position. In a next step, and as shown in  FIG. 6C , pin carrier  476  is raised, thereby urging engagement pin  478   1  into an engagement feature of carrier  700 , for example and without limitation, slot  761   2  of frame  730  of carrier  700  (refer to  FIG. 6A  wherein slot  761   2  is partially obscured by pin  478   1  engaged therein) while also urging engagement pin  478   2  into an engagement feature of carrier  600 , for example and without limitation, slot  661   1  of frame  630  of carrier  600 . In a next step, as shown in  FIG. 6D : (a) test head  490  is raised to enable flexural springs  632  to resiliently return tray  620  to a retracted configuration and extract devices  614   n  from contactor block  470  (the term “retracted configuration” refers to a configuration of carrier  600 , and hence springs  632  of frame  630 , for example and without limitation, where no external forces other than gravity act upon tray  620 ); (b) shot pins are retracted; and (c) carrier  600  is removed from the test position and carrier  700  is moved to the test position simultaneously, by the action of pneumatic actuator  440  moving trolley  442  and attached pin carrier  476 . As a result, pins  478   1  and  478   2  slidably move carriers  700  and  600 , respectively, along rails  444  and  446 . As carrier  700  moves into juxtaposition with contactor block  470 , detector  447  is actuated and shot pins (not shown) in rail  446  are fired, and they engage notches  768   1  and  768   2 , thereby stopping motion of carrier  700  along the rails and locking carrier  700  in position. In a next step, a shown in  FIG. 6E , test head  490  is moved downwardly toward juxtaposed contactor block  470 , thereby urging tray  720  and devices  714   n  held therein against contactor block  470 -flexural springs  732  flex to enable tray  720  to be deflected downwardly while frame  730  of carrier  700  remains on rails  444  and  446 . Pin carrier  476  is retracted, thereby disengaging pins  478   1  and  478   2  from slots  761   2  and  661   1  respectively. In a next step, as shown in  FIG. 6F , pin carrier  476  is returned to its initial position, i.e., as seen in  FIG. 6B , by actuation of pneumatic actuator  440 , thereby moving trolley  442  and pin carrier  476  mounted thereto. 
       FIG. 7A  is a top view of transport mechanism  400  with carrier  600  in an output position, carrier  700  in a test position under test head  490 , and carrier  600  in an input position, which transport mechanism  400  and carriers  600 ,  700  and  800  are fabricated in accordance with one or more embodiments of the present invention.  FIGS. 7B-7F  are simplified side views of transport mechanism  490  and carriers  600 ,  700  and  800  which help illustrate a sequence of steps for moving carrier  600  from the output position, and subsequently for moving second carrier  700  from the test position to the output position while simultaneously moving carrier  800  from the input position to the test position. For clarity of exposition and ease of understanding, enumeration of repeated labeled elements is omitted. In operating transport mechanism  400  in accordance with one or more embodiments of the present invention, carriers are moved in sequence through input, test, and output positions repetitively. In a step in a test procedure, and as shown in  FIG. 7B , carrier  800  is moved into the input position of transport mechanism  400 . To do this, for example, starting from the configuration shown  FIG. 6F , test head  490  is retracted from tray  720 , thereby enabling tray  720  to relax resiliently to a retracted configuration in which carrier  700  is unencumbered by engagement with either test head  490  or contactor block  470  or with associated alignment pins  474   1  and  474   4 . Then, in accordance with one or more embodiments of the present invention, transport mechanism  400  awaits removal of carrier  600  from the output position before proceeding to the next step. In a next step, and as shown in  FIG. 7C , pin carrier  476  is raised, thereby urging engagement pins  478   1  and  478   2  into engagement features of carriers  800  and  700 , for example and without limitation, slot  861   2  of frame  830  of carrier  800  and slot  761   1  of frame  730  of carrier  700 , respectively. Then shot pins (not shown are disengaged from notches  768   1  and  768   2 , freeing carrier  700  to move along rails  444  and  446 . In a next step, as shown in  FIG. 7D , carriers  700  and  800  are slidably moved simultaneously along rails  444  and  446  by traction of pins  478   1  and  478   2  of pin carrier  476  mounted to trolley  442 , which trolley  442  is moved by pneumatic actuator  440 . As carrier  800  moves into juxtaposition with contactor block  470 , as sensed by detector  447 , shot pins (not shown) in rail  446  are fired and they engage notches  868   1  and  868   2 , thereby locking carrier  800  in position. In a next step, as shown in  FIG. 7E , test head  490  is moved downwardly toward juxtaposed contactor block  470 , thereby urging tray  820  and devices  814   n  held therein against contactor block  470  to establish contact between contactor block  470  and devices  814   n  held in tray  820 . Next, pin carrier  476  is retracted, thereby disengaging pins  478   1  and  478   2  from slots  861   2  and  761   2 , respectively. In a next step, as shown in  FIG. 7F , pin carrier  476  is returned to its initial position, i.e., as seen in  FIG. 7B , by actuation of pneumatic actuator  440 , thereby moving trolley  442  and pin carrier  476  mounted thereto. 
     One of ordinary skill in the art will understand that steps of the test sequence may be executed in other combinations in which an important part is the simultaneous movement of two carriers by motion of a trolley temporarily engaged with each of the two carriers. 
     Operation of test head  490  with a carrier at a test position in accordance with one or more embodiments of the present invention is described in conjunction with  FIGS. 8A-8D .  FIG. 8A  is a top view of a test position wherein test head  490  is positioned over tray  200  which is coupled to frame  230  of carrier  200 . As shown in  FIG. 8A , shot pins  452  and  454  of rail  446  engage notches  261   3  and  261   4 , respectively, of frame  230 , thereby stopping motion of carrier  200  along rails  444  and  446  and holding carrier  200  against a reference surface of rail  444 . After moving carrier  200  into the test position, pin carrier  476  (with pins  478   1  and  478   2 ) is returned to an initial position by activating actuator  440 , thereby moving trolley  442  into a position shown in  FIG. 8A . In the test position, alignment pins  474   1  and  474   4  of contactor  470  underlie alignment holes  266   1  and  266   4 , respectively, of tray  220 . 
       FIGS. 8B-8D  are cross sectional views of the test position shown in  FIG. 8A  that help illustrate successive stages of its operation. In a first step, as shown in  FIG. 8B , carrier  200  is transported on rails  444  and  446  to the test position where tray  220  is interposed between test head  490  and contactor block  470 . During transport, devices  214   n  in tray  220  move above contactor block  470  without mechanical interference therebetween because tray  220  is in a retracted configuration wherein tray  220  is supported on a plane above a top surface of contactor block  470 . As shown in  FIG. 8B , tray  220  is coupled by flexural springs  232  to frame  230  in the retracted configuration wherein flexural springs  232  are relaxed (relaxed is understood herein to mean that no significant external forces cause flexural springs  232  to be deformed from an unloaded state). 
     In a next step, as shown in  FIG. 8C , test head  490  urges tray  220  to an extended configuration wherein tray  220  is displaced in a direction perpendicular to a plane of frame  230  to an extent sufficient to bring tray  220  into contact with contactor block  470 . In accordance with one or more embodiments of the present invention, flexural springs  232  enable tray  220  to move relative to frame  230 , and enable backing plate  488  to urge devices  214   n  into contact with mating connectors (not shown) of contactor block  470 . In accordance with one or more such embodiments, and as shown in  FIG. 8B : (a) seal ring  493  of test head  490  (for example and without limitation, an O-ring such as a silicone or elastomeric O-ring, or other sealing surface such as, for example and without limitation, a flat surface) is juxtaposed with top sealing surface  202  of seal band  224  of tray  220  (which seal band  224  and top sealing surface  202  encircle test devices  214   n ); and (b) seal ring  494  of contactor block  470  (for example and without limitation, an O-ring such as a silicone or elastomeric O-ring, or other sealing surface such as, for example and without limitation, a flat surface) is juxtaposed with bottom sealing surface  204  of tray  220  (which bottom sealing surface  204  encircle test devices  214   n ). In accordance with one or more such embodiments, and as shown in  FIG. 8C , when test head  490  is moved downward: (a) test head  490  is brought into contact with tray  220 , seal ring  493  is brought into contact with top sealing surface  202 ; and (b) as test head  490  is moved further downward, bottom sealing surface  204  is brought into contact with seal ring  494  of contactor block  470 . In addition, as shown in  FIGS. 8B-8D , contactor block  470  is sealed to printed wiring substrate  472  by seal ring  495  (for example and without limitation, an O-ring such as a silicone or elastomeric O-ring, or other sealing surface such as, for example and without limitation, a flat surface). After moving and urging as described above in conjunction with  FIG. 8C , devices  214   n  are enclosed within a sealed chamber (also referred to as a “test cell”) comprising cavity  491  of test head  490 , tray  220 , contactor block  470 , and printed wiring substrate  472 . 
     In a next step, as shown in  FIG. 8D , tray  220  is in the extended configuration while backing plate  488  (as used herein, the term “backing plate refers to a plate that clamps the devices to the contactor block such as, for example and without limitation, a thermal transfer or exchange plate, a cold plate or a heat sink) is urged into contact with the array of devices  214   n  under test. In accordance with one or more such embodiments, backing plate  488  is moved downward into thermal and mechanical contact with devices  214   n , and as such, it urges terminals (not shown) on devices  214   n  into contact with contacts (not visible) on contactor block  470 . In accordance with one or more such embodiments, pneumatic cylinder actuator  486  moves backing plate  488  in an upward or downward direction relative to test head  490 , thereby providing a controlled force on devices  214   n  to establish good thermal contact between backing plate  488  and devices  214   n  as well as to establish good electrical contact between terminals (not shown) on devices  214   n  and corresponding contacts (not shown) on contactor block  470 . In the test step described in conjunction with  FIG. 8D , a gas (for example and without limitation, nitrogen, forming gas, hydrogen, helium, dry air and mixtures thereof) may be introduced through port  499  of test head  490  into sealed cavity  491  to reduce moisture condensation and to increase thermal efficiency. In accordance with one or more embodiments, channels  482  of backing plate provide a path for thermal transfer fluid to flow through backing plate  488  to regulate temperature of backing plate  488 . 
     In accordance with one or more embodiments of the present invention, after the test operation is carried out, backing plate  488  is raised, thereby releasing pressure on devices  214   n  and enabling tray  220  to return to the retracted configuration shown in  FIG. 2B  wherein carrier  200  and devices  214   n  held therein may be moved on rails  444  and  446  without mechanical interference between devices  214   n  and test head  490 , backing plate  488  or contactor block  470 . 
     A carrier that is fabricated in accordance with one or more embodiments of the present invention may have a variety of uses in testing of microelectronic devices such as, for example and without limitation, wafer picking, burn-in, functional test, stress test, laser trim, marking, reflow of solder balls, and dynamic programming.  FIGS. 9A and 9B  illustrate several applications for one or more embodiments of the carrier. In particular,  FIG. 9A  is a cross sectional view of concatenated transport mechanisms that move devices in carriers through a sequence of thermal soaking and testing operations. As shown in  FIG. 9A , trays  912 ,  922 ,  932  and  942  of carriers  916 ,  926 ,  936  and  946 , respectively, are transported on rails  900  through a sequence of, for example and without limitation, thermal conditioning pods  910  and  930  and test pods  920  and  940 . Arrays of devices (not visible in  FIG. 9A ) held in trays  912 ,  922 ,  932  and  942  may be shuttled from one process location to another by means of automated transport that is effected by the chain of transporters  950  and  960  where the operation of each of transporters  950  and  960  has been described above in conjunction with  FIGS. 5A-7F . By way of example, carrier  926  is transported from pod  920  to pod  930  by activating actuator  954  which causes trolley  952 , and carrier  926  attached temporarily thereto by pin  958  of pin carrier  956 , to move to the right (as seen in  FIG. 9A ). In a subsequent step, carrier  926  is transported from pod  930  to pod  940  by activating actuator  964  which causes trolley  962 , and carrier  926  attached thereto by pin  968  of pin carrier  966 , to move to the right (again as seen in  FIG. 9A ). By way of example, and without limitation: (a) pod  910  is a thermal soak station with heater  914  set to establish a temperature of T 1  on devices enclosed therein; (b) pod  920  is a test station for testing electrically at a temperature T 1  devices in tray  922  in contact with contactor block  924 ; (c) pod  930  is a pre-heat station with heater  934  set to establish a temperature T 2  on devices enclosed therein; and (d) pod  940  is a test station for testing devices in tray  942  in contact with contactor block  944  at temperature T 2 . In accordance with one or more embodiments of the present invention, arrays of devices held in trays may be moved through a sequence of tests performed at different temperatures by concatenating pre-heat and test locations along rails or other suitable transport means. As one of ordinary skill in the art can readily appreciate, the carrier may be used to transport arrays of devices into position automatically for a wide range of process and test operations. 
     A tray transport apparatus fabricated in accordance with one or more embodiments of the present invention may be used to move devices automatically through a burn-in process. In particular,  FIG. 9B  is a cross sectional view of an array of test pods fed by an automatic loader that is fabricated in accordance with one or more embodiments of the present invention. As shown in  FIG. 9B , one of burn-in pods  901 - 908 , shown as pod  905 , is open and ready to receive tray  999 . 
     As further shown in  FIG. 9B , pusher  974  on actuator  976  moves carrier  985  out of magazine  978  (as used herein, a magazine is, for example and without limitation, a cassette for holding a plurality of trays) to a position where, for example, pin  998  on pin carrier  996  of transport apparatus  997  (which is fabricated in accordance with one or more embodiments of the present invention) may engage carrier  985  near a right end thereof. After engagement, transport apparatus  997  moves carrier  985  on rails  990  by activating actuator  994 , thereby moving trolley  992 , and carrier  985  temporarily attached thereto by pin  998  on pin carrier  996 , to the right (as seen in  FIG. 9B ). As a next step, trolley  992  is returned to its initial position (as shown in  FIG. 9B ) by actuator  994 . As a next step, elevators  972  and  973  of automatic loader  970  (which elevators are well known to those of ordinary skill in the art) raise transport apparatus  997  (and hence, carrier  985 ) in a vertical direction so that rails  990  are aligned with available burn-in pod  905 . As a further next step, pin  991  on pin carrier  996  engages carrier  985  near the left end thereof, thereby enabling actuator  994  to transport carrier  985  into position in burn-in pod  905  by moving trolley  992  and attached pin  991  on pin carrier  996  to the right (as seen in  FIG. 9B ). Carrier  985  is transported from rails  990  to rails  905   5  which straddle burn-in pod  905 . 
     After burn-in, testing during burn-in, run-in, or other stress testing, transport apparatus  997  removes carrier  985 , with devices therein, from burn-in pod  905 , and transports it, for example and without limitation, in conjunction with automatic loader  970 , to a next process step, or alternatively, to magazine  978 . 
     Burn-in pods  901 - 908  may be provided with thermal transfer plates, clamping mechanisms, air circulation means, vibration mechanisms, mechanical shock mechanisms, sealed chambers, and drive electronics to facilitate a range of stress tests on the devices in carriers  981 - 988 , respectively. Connections are made to an array of devices under test in burn-in pods  901 - 908  by means of burn-in boards, flexible circuits, rigid flex, high speed cables or other high performance interconnects that allow location of test electronics in close proximity to the devices under test in order to perform testing at high speeds without the encumbrance of long interconnect cables. 
     As one of ordinary skill in the art will readily appreciate, the steps described above in conjunction with  FIGS. 5A-9B  may be carried out in response to commands provided by a controller (not shown for ease of understanding) such as, for example, a processor, microprocessor, computer and the like. In addition, one of ordinary skill in the art will be able to program such a controller routinely and without undue experimentation in light of the description presented herein. For example and without limitation, the steps may be presented to the controller in the form of a “recipe” or a data structure comprised of a collection of data pertaining to various process steps to be carried out for test and/or burn-in operations. 
     Embodiments of the present invention described above are exemplary. As such, many changes and modifications may be made to the description set forth above by those of ordinary skill in the art while remaining within the scope of the invention. In addition, materials, methods, and mechanisms suitable for fabricating embodiments of the present invention have been described above by providing specific, non-limiting examples and/or by relying on the knowledge of one of ordinary skill in the art. Materials, methods, and mechanisms suitable for fabricating various embodiments or portions of various embodiments of the present invention described above have not been repeated, for sake of brevity, wherever it should be well understood by those of ordinary skill in the art that the various embodiments or portions of the various embodiments could be fabricated utilizing the same or similar previously described materials, methods or mechanisms. As such, the scope of the invention should be determined with reference to the appended claims along with their full scope of equivalents.