Thermal regulation of a device under test based on a stretchable element

Abstract

The present disclosure proposes a thermal conditioning device (100) in which a process heat transfer fluid (110) is circulated in a plurality of stretchable elements (105); the pressure of the process heat transfer fluid (110) is adjusted to stretch the stretchable elements (105) so that the stretchable elements are pressed against a corresponding electronic device under test (205) to thermally condition the electronic device under test. The present disclosure also proposes a test apparatus (200) comprising such a thermal conditioning device (100). Furthermore, the present disclosure proposes a corresponding method for thermally conditioning an electronic device under test (105) and a corresponding method for testing an electronic device (205).

Description

TECHNICAL FIELD

[0001] The present invention relates to the field of electronic device testing. More specifically, the present invention relates to thermal conditioning of electronic devices under test. BACKGROUND

[0002] The following presents a discussion of background art pertinent to the present invention. However, nothing in the discussion of background art should be taken as an admission that the art is part of the common general knowledge of the field, or that the art is prior art to the present invention. Furthermore, the discussion of background art is intended only to aid in understanding the present invention, rather than to infers that any of the art discussed was known to be relevant to the present invention.

[0003] Electronic devices (e.g. each based on one or more integrated circuits) are usually tested to verify their correct operation. For each electronic device under test (also referred to as device under test or DUT), the test aims at identifying apparent (i.e. immediate) or potential (i.e. likely to occur after a short time of use of the electronic device) defects. In the latter case, the electronic device can need to be subjected to a thermal (burn-in) test. To this end, the electronic device can be tested under thermal stress conditions, by operating the electronic device at very high or very low temperatures (e.g. -50°C to +150°C), so as to simulate long time operation of the same electronic device at room temperature (e.g. 10-30°C).

[0004] In particular, the electronic devices can be tested in their final form at the package level, i.e. by encapsulating the integrated circuits in a package to protect them and provide access to their terminals. In this case, the electronic devices are temporarily housed on a test board (e.g. a burn-in board or BIB in the case of a burn-in test). The test board is used to connect the electronic devices with the test system. To this end, each test board is provided with a plurality of sockets. Each socket mechanically locks the package of an electronic device and electrically connects the terminals of the electronic device to the test system; at the same time, the socket makes it possible to dismount the electronic device at the end of the test without causing substantial damage. The sockets are usually arranged in a high-density matrix, so as to increase the parallelism of the test board and, therefore, the performance of the test.

[0005] Electronic devices generate heat during operation, resulting in heating of the electronic devices. In particular, in the case of high-power electronic devices, this heating is evident. In any case, the increasing miniaturization of electronic devices significantly increases the heating of the electronic devices. Overheating of the electronic devices reduces their performance and can cause wear, malfunction or even damage of the electronic devices. Therefore, heat sinks are usually provided to dissipate as much heat as possible from the electronic devices. In particular, in the case of electronic devices (high power and / or miniaturization) that generate a large amount of heat, cooling them by air (by natural convection or forced ventilation) can not be sufficient to ensure their normal operation. For this reason, in the last few years, complex cooling systems (such as heat pipes or liquid types) have been widely popularized, which are able to provide high cooling capacity.

[0006] However, the use of such cooling systems during testing is difficult, if not impossible.

[0007] In fact, the high density of sockets in the test board can prevent the application of cooling systems to the electronic devices housed thereon. Moreover, the cooling systems can hinder or even prevent the automatic loading of the electronic devices onto the test board / automatic unloading of the electronic devices from the test board (with a detrimental effect on the performance of the test).

[0008] In any case, the cooling systems (due to the size) are usable worldwide for all the electronic devices housed on each type of test board. However, the electronic devices (even of the same type) are subject to uneven heating (with differences of about 40-60%). This makes it difficult to accurately control the temperature of the electronic devices and, in any case, prevents the same thermal stress from being applied to the electronic devices (thus reducing the reliability of the test).

[0009] All the above cases negatively affect the effectiveness of the test of the electronic devices, thus affecting the quality of the production process of the electronic devices. SUMMARY

[0010] The simplified summary of the invention is presented herein to provide a basic understanding of the invention; however, the sole purpose of this summary is to present some concepts of the invention in a simplified form as a prelude to the more detailed description of the invention below, and it should not be interpreted as an identification of key elements of the invention or as an delineation of the scope of the invention.

[0011] In general, the present invention is based on the concept of thermally regulating the electronic devices in a separate manner by means of respective stretchable elements.

[0012] In particular, in one aspect there is provided a thermal conditioning device, wherein a process heat transfer fluid is made to circulate in a plurality of stretchable elements; the pressure of the process heat transfer fluid is regulated to stretch the stretchable elements so as to press the stretchable elements against a corresponding electronic device under test to thermally condition the electronic device under test.

[0013] In a further aspect there is provided a test apparatus comprising such a thermal conditioning device.

[0014] In a further aspect there is provided a corresponding method for thermally conditioning an electronic device under test.

[0015] In a further aspect there is provided a corresponding method for testing an electronic device.

[0016] More specifically, one or more aspects of the application are set forth in the independent claims and advantageous features thereof are set forth in the dependent claims, wherein the wording of all the claims is incorporated by reference herein word by word (where any advantageous feature is provided with reference to any particular aspect applying the necessary modifications to each other aspect). BRIEF DESCRIPTION OF DRAWINGS

[0017] The solution of the present application, as well as other features and advantages thereof, will best be understood by referring to the following detailed description, given by way of non-limiting indication only, in conjunction with the accompanying drawings in which, for the sake of simplicity, the corresponding elements are denoted with the same or similar references and their explanations are not repeated, and generally the name of each entity is used to indicate both its type and its properties, such as values, contents and representations. In this respect, it is expressly indicated that these drawings are not necessarily drawn to scale (where some details can be exaggerated and / or simplified) and, unless otherwise specified, the drawings are only used to conceptually illustrate the structures and procedures described. In particular:

[0018] Figure 1 shows an illustrative representation of a thermal conditioning device according to an embodiment of the present application, with virtual parts,

[0019] Figure 2 shows an illustrative representation of a partial cross-sectional view of a test apparatus according to an embodiment of the present application,

[0020] Figure 3 shows a cross-sectional view of a detail of a thermal conditioning device according to an embodiment of the present application, and

[0021] Figures 4A-4E shows the main steps of a test procedure according to an embodiment of the present application. DETAILED DESCRIPTION

[0022] In particular reference is made to Figure 1Fig. 1 shows an illustrative representation of a thermal conditioning device 100 according to an embodiment of the present application (with virtual parts).

[0023] The thermal conditioning device 100 is used for thermally conditioning a plurality of electronic devices under test (DUTs) housed on respective test board sockets (not shown in the figures). The thermal conditioning device 100 comprises the following components.

[0024] A plurality of stretchable elements 105 (e.g., bellows-like) are used for thermally conditioning the electronic devices in a separate manner, e.g., by cooling the electronic devices during testing thereof. Each stretchable element 105 has a variable length, so that it can be elongated and shortened. The stretchable elements 105 are arranged in a matrix (e.g., with 2-10 rows and 5-20 columns represented only partially in the figures) with a pitch of 3.0-4.0 cm (or more). For each electronic device, a respective stretchable element 105 is provided (for cooling the electronic device when in contact therewith). A process fluid 110 is circulated in the stretchable elements 105. The process fluid 110 is a liquid heat-conducting substance (e.g., a mixture of water and glycol) that accumulates and transports heat from the electronic devices (cooling the electronic devices). The circulation of the process fluid 110 in the stretchable elements 105 is achieved by a (process) circulation system 115, e.g., based on respective impellers (described in detail below). A (process) heat exchange system (e.g., a heat exchanger 120) exchanges heat with the process fluid 110 (transferring the heat absorbed from the electronic devices). A pressure regulation system (e.g., a piston 125) is used for regulating the pressure of the process fluid 110. This allows moving the stretchable elements 105 between a shortened state (low pressure) and an elongated state (high pressure). As described in detail below, the stretchable elements 105 are shortened in a resting state, while the stretchable elements 105 are elongated during testing to press against the respective electronic devices.

[0025] The above-described solution allows thermally conditioning (e.g., by cooling) the electronic devices in an efficient manner, even during testing.

[0026] In particular, it is possible to apply the thermal conditioning device 100 to the electronic devices even when the test board on which the electronic devices are housed has a high density of sockets (even with a pitch of several tens of millimeters). Moreover, the thermal conditioning device 100 does not substantially hinder the automatic loading of the electronic devices onto / from the test board (so that the thermal conditioning device does not affect the performance of the testing).

[0027] The pressure exerted by the process fluid 110 significantly improves the mechanical coupling between the stretchable elements 105 and the electronic devices 205, and therefore the heat exchange.

[0028] All the above cases have a positive impact on the effectiveness of the test of the electronic device, which leads to the quality of the production process of the electronic device.

[0029] Reference is now made to Figure 2 , showing an illustrative representation of a partial cross-sectional view of a test apparatus 200, according to an embodiment of the present application.

[0030] The test apparatus 200 is used to test electronic devices (denoted by reference sign 205) at the package level; for example, the electronic devices 205 are subjected to burn-in tests (in which the electronic devices 205 are tested under thermal stress conditions). For this purpose, the test apparatus 200 comprises a test board 210 (for temporarily housing the electronic devices 205) and the aforementioned conditioning device 100 (for thermally conditioning the electronic devices 205 housed on the test board 210). Typically, a test plant (not shown in the figures) houses several instances of the test apparatus 200, together with respective drive boards (arranged in a control area maintained at room temperature and connected to the respective test apparatus 200 to supply them with signals and exchange signals) and loaders / unloaders (for loading / unloading the electronic devices 205 from the test board 210).

[0031] In particular, the test board 210 comprises the following components.

[0032] A holder 215 of a circuited insulating material (for example, a printed circuit board or PCB) has the function of mechanical support and electrical connection for the other components of the test board 210. A plurality of sockets 220 (only partially represented in the figures) is mounted on the main (upper in the figures) surface of the holder 215. The sockets 220 are arranged with a geometry corresponding to one of the extendable elements 105 (so that, when the test board 210 and the conditioning device 100 are coaxial (with the test board 210 below the conditioning device 100 in the figures), the sockets 220 are aligned with the respective extendable elements 105. Each socket 220 is used to house the electronic devices 205 in a removable manner. In particular, the sockets 220 mechanically lock the electronic devices 205 (by acting on the package of the electronic devices) and electrically connect the electronic devices 205 to the circuits of the holder 215 (by contacting the terminals of the electronic devices); at the same time, the sockets 220 allow the electronic devices 205 to be mechanically released (to remove the electronic devices from the test board 210 without any substantial damage). For example, the sockets 220 are based on a platform for resting the electronic devices 205, with conductive pads for receiving the terminals of the electronic devices 205; a cover with a window for making the package of the electronic devices 205 accessible is hinged to the base, so that it can be closed and opened (respectively locking and releasing the electronic devices 205).

[0033] Reference is now made to Figure 3Figure 3, showing a cross-sectional view illustrating details of the thermal conditioning device 100 according to an embodiment of the present application.

[0034] The heat exchanger 120 enables heat exchange between the process fluid 110 and a service fluid 303 (a similar liquid heat-conductive substance, for example, still a mixture of water and glycol). The heat exchange occurs indirectly through surfaces separating different compartments in which the process fluid 110 and the service fluid 303 circulate (so that they do not come into contact with each other). In particular, the (service) chamber 306 contains the service fluid 303 and the (process) chamber 309 contains the process fluid 110. The service chamber 306 and the process chamber 309 have a common (heat exchange) wall 312. For this purpose, the wall 312 is made of a heat-conductive material (for example, copper); in addition, the wall 312 is equipped with fins 315 facing the process chamber 309 to further facilitate heat exchange with the process fluid 110. A delivery pipe 318 (or more) and a suction pipe 321 (or more) connect the service chamber 306 to a (service) heat exchange system, for example, a cooler 324 common to all the test equipment in the test plant (not shown in the figure), which is in heat exchange with the service fluid 303 (transfers the heat absorbed by the process fluid 110).

[0035] A pair of (equal and coaxial) holes 327 and 330 are formed in the wall 312 and in the (working) wall 333 of the service chamber 306 opposite said wall, respectively. A sleeve 336, having a section matching that of the holes 327, 330, passes through the service chamber 306 between said holes; the edge of the sleeve 336 is sealed to the edge of the hole 327, and the other edge of the sleeve 336 protrudes beyond the wall 333 (the lateral surface of the sleeve 336 is sealed to said wall at the hole 330). In this way, the sleeve 336 delimits a through hole 339 through the service chamber 306 between the walls 312 and 333. A bellows 342 has an edge attached to the edge of the sleeve 336 protruding from the wall 333. The bellows 342 is flexible (e.g. foldable like an accordion) so that it can be elongated and shortened. A cup 345 has an edge attached to the other edge of the bellows 342. The sleeve 336, the bellows 342 and the cup 345 delimit the stretchable element 105. In this way, the stretchable element 105 stretches from the process chamber 309 through the through hole 339 of the service chamber 306, with the base of the cup 345 protruding beyond the wall 333 to delimit a contact face 348 with a respective electronic device (not shown in the figures). A heating element 351 is arranged at the contact face 348 to heat the electronic device (e.g. made by a coil of electrically conductive material, such as constantan, embedded in the base of the cup 345). A temperature sensor 354 is associated with the contact face 348 (e.g. arranged on the outside of the cup 345 immediately next to the cup) to detect the temperature of the electronic device. The heating element 351 and the (temperature) sensor 354 are electrically connected to the control board, e.g. via a hole made in the screw for the mechanical coupling between the process chamber 309 and the service chamber 306 (not shown in the figures). A delivery pipe 357 stretches along the stretchable element 105, having an (upper) inlet protruding above the wall 312 and a (lower) outlet close to the base of the cup 345. In this way, a delivery duct 360 is delimited between the suction pipe 357 and the lateral wall of the stretchable element 105. For each stretchable element 105, the circulation system 115 comprises an impeller 363 and an electromagnet crown 366. The impeller 363 (e.g. of tangential type) is arranged in a suction chamber (not shown in the figures) for sucking the process fluid 110 from the process chamber 309 and delivering it into the delivery pipe 357 (in a direction perpendicular to its longitudinal axis). The electromagnet crown 366 is arranged coaxially with the impeller 363 outside the process chamber 309 to operate (without mechanical coupling) the impeller 363, which in turn is equipped with permanent magnets (not shown in the figures). A blocking valve is arranged at the (upper) inlet of the delivery pipe 357 (to block the flow of process fluid 110 into the suction pipe 357 when the impeller 363 is stopped). The blocking valve is formed by a valve cap or pin 369 (having a flared profile) and an electromagnet 372.A valve cap 369 is positioned above the inlet of the suction pipe 357 in the processing chamber 309 (mounted on a corresponding vertical guide rail, not shown in the figures); the valve cap 369 has a specific weight higher than that of the process fluid 110, so as to keep it lowered by gravity onto the inlet of the suction pipe 357. An electromagnet 372 is placed above the valve cap 369 outside the processing chamber 309 to lift the valve cap 369 by acting on a permanent magnet embedded in the valve cap (not shown in the figures). A blocking valve 375 is arranged at the (upper) outlet of the suction pipe 360 (to block the process fluid 110 from flowing out of the suction pipe 360 due to natural convection when the impeller 363 is stopped). The blocking valve 375 is formed by a ring (with a flared profile) fitted on the suction pipe 357; the blocking valve 375 has a specific weight higher than that of the process fluid 110, so as to keep it lowered by gravity at the outlet of the suction pipe 360 when it is not pushed upwards by the hydraulic head of the flow of process fluid 110 generated by the rotation of the impeller 363.

[0036] Reference is now made to Figures 4A-4E , showing the main steps of the testing process according to an embodiment of the present application.

[0037] Starting from Figure 4A , at the beginning of the test (not shown in the figures), the electronic devices 205 are conveyed in a tray close to a loader / unloader, which is positioned laterally in front of the testing board 210, away from the thermal conditioning device 100. The loader / unloader collects the electronic devices 205 from the tray and places them sequentially onto the (open) sockets 220. Once the testing board 210 has been (partially or totally) filled, the sockets 220 are closed and the testing board 210 is moved back under the thermal conditioning device 100, as shown in the figures, so that each electronic device 205 is aligned with a corresponding extendable element 105.

[0038] Moving to Figure 4B , the thermal conditioning device 100 and the testing board 210 are brought close (e.g. by lowering the thermal conditioning device 100). The bringing close causes each extendable element 105 to move close to the electronic device 205, with the contact face 348 of the extendable element at a corresponding close distance (e.g. 0-1 mm), in case a corresponding electronic device 205 is present in the socket 220 (as shown on the left side of the figures). Therefore, if no electronic device 205 is present in a corresponding socket 220 (as shown on the right side of the figures), each extendable element 105 remains spaced apart from the bottom of the (empty) socket 220, with the contact face 348 of the extendable element at a distance equal to the close distance plus the thickness of the electronic device 205 (e.g. 1-2 cm in total).

[0039] Moving to Figure 4C, the operating piston 125 is operated to increase the pressure of the process fluid 110. Therefore, when a respective electronic device 205 is present in the socket 220 (as shown on the left side of the figure), each extendable element 105 is elongated (e.g. by 1-2 mm) until it abuts against the electronic device 205, so as to press the contact surface 348 against the electronic device (directly or through an elastic insert, made of a thermally conductive material, not shown in the figure). In particular, the bellows 342 are able to adapt even in the case where the contact surface 348 and the electronic device 205 are not perfectly parallel; this ensures that they have a good mechanical coupling in any case, further improving the heat exchange.

[0040] On the other hand, if no electronic device 205 is present in the respective socket 220 (as shown on the right side of the figure), each extendable element 105 will be elongated without any abutment, at least until the contact surface 348 reaches the bottom of the (empty) socket 220. Therefore, in the embodiment of the application, a stop system is provided to limit the elongation of the extendable element 105, for example comprising a respective stop element 405 for each extendable element 105. The stop element 405 is formed by a container that surrounds the extendable element 105, fixed below the wall 312. When the extendable element 105 is in the shortened state, the stop element 405 is slightly elongated beyond the length of the bellows 342 by the above-mentioned approach distance (e.g. 1.2-2.0 times if not zero and in any case at least equal to 1-2 mm). In the bottom of the stop element 405 a hole is formed. Said hole has a diameter matching that of the cup 345 to allow the passage of the cup (so that the contact surface 348 protrudes beyond the stop element 405); on the contrary, the hole is narrower than the bellows 342 (wider than the cup 345), so that the remaining part of the bottom of the stop element 405 (the outer edge) delimits a seat for the bellows 342.

[0041] Therefore, when a respective electronic device 205 is present in the socket 220, each extendable element 105 is elongated as above (where the cup 345 slides in the hole of the stop element 405 so that the stop element does not interfere in any way with the operation of the extendable element 105). On the contrary, in the case where no electronic device 205 is present in the respective socket 220, each extendable element 105 is elongated but only until the bellows 342 abut against the seat of the stop element 405. This avoids or at least significantly reduces the risk of damage to the bellows 342.

[0042] Moving to Figure 4DAt the start, all heating elements 351 are off, all electromagnet crowns 366 are off to stop all impellers 363, and all electromagnets 372 are off to let all valve caps 369 drop by gravity on the suction pipes 357 (suction valves 369, 372 closed) and all delivery valves 375 drop by gravity on the delivery pipes 360 (closed). The lower threshold temperature and the upper threshold temperature define a regulation range (e.g. ±5-10°C) around a target temperature to be maintained by the electronic device 205 during the test.

[0043] For each electronic device 205, a driving board (not shown) monitors the (actual) temperature of the electronic device as detected by the sensor 354. If the actual temperature is lower than the lower threshold temperature, then the driving board activates the heating elements 351 (with a power increasing with the difference between the actual temperature and the lower threshold temperature, e.g. by applying a voltage of 12-24V to generate 0.1-10kJ of heat by Joule effect). The heating elements 351 increase the temperature of the contact face 348 and thus of the electronic device 205. Once the actual temperature exceeds the lower threshold temperature, the driving board deactivates the heating elements 351.

[0044] Moving to Figure 4E If the actual temperature (as detected by the sensor 354) is higher than the upper threshold temperature, then the driving board (not shown) activates the electromagnets 372 to lift the valve caps 369 against gravity (delivery valves 369, 372 open), thus clearing the inlet of the delivery pipes 357. The driving board then activates the electromagnet crowns 366 to rotate the impellers 363 (at an angular speed increasing with the difference between the actual temperature and the upper threshold temperature, e.g. 5-20rpm). In this way, the impellers 363 suck the process fluid 110 from the process chamber 309 and deliver it into the delivery pipes 357 to the contact face 348. The process fluid 110 decreases the temperature of the contact face 348, and then of the electronic device 205; in particular, the cooling of the electronic device 205 depends on the flow rate of the process fluid 110, which in turn depends on the angular speed of the impellers 363 (with the cooling increasing with the angular speed). The (heated) process fluid 110 flows back in the suction pipes 360; the flow of the process fluid 110 lifts the suction valves 375 (opening the suction valves) against gravity, thus clearing the outlet of the suction pipes 360. The process fluid 110 can thus return from the suction pipes 360 into the process chamber 309. The process fluid 110 hits the wall 312 (and in particular the fins 315 of the wall) to cool (at the expense of the service fluid 303, which gets hot and is then cooled by the cooler 324, which in turn disperses heat into the external environment).

[0045] Returning to Figure 4DOnce the actual temperature drops below the upper threshold temperature, the drive plate deactivates the electromagnet crown 366, causing the impeller 363 to stop. Furthermore, the drive plate deactivates the electromagnet 372, causing the valve cap 369 to fall onto the delivery pipe 357 due to gravity (closing the blocking valves 369 and 372), thus blocking the inlet of the delivery pipe. Therefore, the flow of process fluid 110 in the suction pipe 357 and then in the delivery pipe 360 ​​is insufficient, causing the delivery valve 375 to fall onto the suction pipe 360 ​​due to gravity (closing), thus blocking the outlet of the suction pipe. The blocking valves 369 and 372 and the suction valve 375 block any convective movement of process fluid 110 within the extendable element 105, thus preventing further cooling of the electronics 205.

[0046] In this way, the temperature of each electronic device 205 can be precisely controlled individually (using hysteresis control); specifically, even when the electronic device 205 is subjected to uneven heating, the same thermal stress can be applied to the electronic device (whereby the result increases the reliability of the test).

[0047] This result is achieved in a simple and efficient manner by using a single service fluid 303 for all extendable elements 105. Specifically, the service fluid 303 can be regulated (depending on the power dissipated by the electronics 205) to a certain temperature so that the temperature control range is focused around the target temperature by the action of the impeller 363 and the heating element 351 (in order to limit their interference as much as possible).

[0048] In this way, the electronic device 205 can be tested via the driver board (sending stimulation signals and receiving corresponding result signals) while maintaining the temperature of the electronic device at the desired value.

[0049] At the end of the test (not shown), the above operations are repeated in reverse order. Specifically, the test plate 210 is placed in front of the loader / unloader (so that the test plate is moved laterally away from the thermal conditioning device 100) and the socket 220 is opened. The loader / unloader collects the electronic devices 205 from the test plate 210 and places the electronic devices sequentially on the tray.

[0050] Modifications

[0051] Naturally, in order to satisfy local and specific requirements, a person skilled in the art can apply to the application many logical and / or physical modifications and alterations. More specifically, although the application has been described in relation to one or more embodiments thereof, it is understood that many other embodiments can be obtained using the concepts described, which are intended to be covered by the scope of the application. Specifically, different embodiments of the application can be practiced even without the specific details (such as numerical values) set forth in the preceding description, in order to provide a more thorough understanding of the application; conversely, well-known features can have been omitted or simplified in order not to obscure the description with unnecessary particulars. Furthermore, it is expressly intended that the specific elements and / or method steps described in connection with any embodiment of the application can be incorporated in any other embodiment as a general design choice. Furthermore, items presented in the same group or in different embodiments, examples or alternatives can not be mutually exclusive; they are independently and separately useful. In any case, each numerical value should be read either as modified in absolute value by the term "about" or "approximately" or in relative value, i.e. 10% or less than the given value. Moreover, each numerical range should be intended as independently established along the continuum between the extreme values of that range, irrespective of the independence of the ranges each other; moreover, the ordinal or other qualifiers are used merely as labels to distinguish between elements of the same name, but do not imply any priority, precedence or order, unless otherwise indicated. Furthermore, the terms comprising, including, having, involving, containing, characterised by, based on, dependent from, according to, etc. shall be intended as non-exclusive, i.e. in the sense of "including, but not limited to"; the term a / an shall be intended as one or more than one; the term means for shall be intended as any structure adapted to, or configured to, perform the relevant function; and the term comprising, including also any tautology thereof, shall be intended as an open ended reference that can be altered by subsequent formulation to be treated as a restriction instead of an open ended reference.

[0052] For example, embodiments provide a thermal conditioning device. However, the thermal conditioning device can be used for applying any type of thermal conditioning (e.g. cooling, heating, cooling / heating to any temperature, etc.).

[0053] In embodiments, the thermal conditioning device can be used for thermally conditioning a plurality of electronic devices under test. However, the electronic devices can be of any number and of any type (e.g. based on integrated circuits and / or discrete elements, provided in any type of packaging, having any number and type of terminals, etc.) and they can be subjected to any type of test (e.g. reliability, functionality, parameters, performing under any thermal stress condition or even simply keeping their temperature within a predetermined range, etc.).

[0054] In embodiments, the thermal regulation device comprises a plurality of stretchable elements having variable lengths, each one being used to thermally regulate a respective one of the electronic devices in a separate manner. However, the stretchable elements can be of any number (to thermally regulate a respective maximum number of electronic devices) and of any type (e.g. bellows-like, telescopic, elastic, etc.).

[0055] In embodiments, the thermal regulation device comprises a process circulation system for circulating a process heat transfer fluid in the stretchable elements. However, the process circulation system can be of any type (e.g. for separately or globally controlling the circulation of the process heat transfer fluid in each stretchable element, for pushing and / or sucking the process fluid in the stretchable elements, etc.) and use any process heat transfer fluid (e.g. liquid, gas, etc.).

[0056] In embodiments, the thermal regulation device comprises a process heat exchange system for exchanging heat with the process heat transfer fluid. However, the process heat exchange system can be of any type (e.g. global for all stretchable elements, having different components, each one for a group of one or more stretchable elements, liquid-based, oil-based, air-based, etc.).

[0057] In embodiments, the thermal regulation device comprises a pressure regulation system for regulating the pressure of the process heat transfer fluid. However, the pressure regulation system can be of any type for regulating the pressure of the process heat transfer fluid in any manner (e.g. mechanical, hydraulic, etc.) (e.g. by simply activating / deactivating said pressure regulation system, setting the pressure to any value selected in a continuous / discrete manner, etc.).

[0058] In embodiments, the stretchable elements are moved between a shortened state and an elongated state using regulation of the pressure. However, the shortened state and the elongated state can be defined in any manner (e.g. wherein the stretchable elements in the shortened state are mutually separated from the electronic devices by any distance or have been brought into contact with the electronic devices, wherein the elongated state is defined by any elongation with respect to the shortened condition, etc.).

[0059] In embodiments, each one of the stretchable elements in the elongated state is pressed against the respective electronic device. However, the stretchable elements can be pressed against the electronic devices with any force (e.g. fixed, adjustable, etc.).

[0060] Further embodiments provide additional advantageous features, however said additional advantageous features can be completely omitted in the basic implementation.

[0061] In particular, in an embodiment, the process circulation system comprises a plurality of process circulation elements, each one for circulating the process heat transfer fluid in a respective one of the stretchable elements. However, the process circulation elements can be of any type (e.g. tangential, circumferential or axial impellers, suction pumps, etc., driven by respective electromagnet crowns, solenoid coil crowns directly integrated into a multilayer printed circuit board, etc.).

[0062] In an embodiment, the process circulation elements are individually controllable to independently regulate the flow rate of the process heat transfer fluid in the respective stretchable elements. However, the process circulation elements can be individually controlled in any way (e.g. on / off, with the flow rate regulated according to any law, such as any linear or non-linear function based on the difference from or proximity to a target temperature, etc.) by any control system (e.g. a respective control board, a central computer of the whole test plant, etc.).

[0063] In an embodiment, the thermal regulation device comprises a plurality of blocking devices, each one for blocking the convective movement of the process heat transfer fluid in a respective one of the stretchable elements when the respective process circulation element is in the deactivated state. However, the blocking devices can be of any type (e.g. input and / or output, active, passive, etc.) or they can be completely omitted.

[0064] In an embodiment, the thermal regulation device comprises a plurality of heating elements, each one arranged in a respective one of the stretchable elements for heating the respective electronic device. However, the heating elements can be of any type (e.g. based on the Joule effect, magnetic induction, etc.) or they can be completely omitted.

[0065] In an embodiment, the heating elements are individually controllable to independently heat the respective electronic devices. However, the heating elements can be individually controlled in any way (e.g. on / off, with the power controlled according to any law, such as any linear or non-linear function based on the difference from or proximity to a target temperature, etc.) by any control system (the same as or different from the above); in any case, the possibility of globally controlling the heating elements is not excluded.

[0066] In an embodiment, the thermal regulation device comprises a plurality of temperature sensors, each one for detecting the temperature of a respective one of the electronic devices. However, the temperature sensors can be of any type and arranged in any position; in any case, the possibility of having fewer temperature sensors, each one associated with a plurality of electronic devices (as few as one temperature sensor for all the electronic devices), or even completely omitting the temperature sensors, is not excluded.

[0067] In embodiments, the process circulation elements and / or the heating elements can be controlled as a function of the temperature of the respective electronic devices. However, it is possible to control only the process circulation elements, only the heating elements or both in any way as a function of the temperature of the respective electronic devices (e.g. based on their value or their variation over time, with any linear or non-linear law, etc.).

[0068] In embodiments, the thermal conditioning device comprises thermal coupling elements for exchanging heat between the process thermally conductive fluid and the service thermally conductive fluid. However, the thermal coupling elements can be of any type (e.g. based on plates or tubes, with the fluids in parallel, counter-current or cross-flow, etc.) to exchange heat with any service thermally conductive fluid (equal to or different from the process thermally conductive fluid).

[0069] In embodiments, the thermal conditioning device comprises a service heat exchange system for exchanging heat with the service thermally conductive fluid. However, the service heat exchange system can be of any type (e.g. a chiller, a heat pump, etc.).

[0070] In embodiments, the thermal conditioning device comprises a process chamber for containing the process thermally conductive fluid and a service chamber for containing the service thermally conductive fluid. However, the process chamber and the service chamber can be of any material, shape and size (the same as or different from each other).

[0071] In embodiments, the process chamber and the service chamber are separated by a heat exchange wall. However, the heat exchange wall can be of any material, shape and size (e.g. with any number and type of fins, without fins, etc.).

[0072] In embodiments, the service chamber is crossed by a plurality of through holes which extend from the heat exchange wall to an operating wall opposite the heat exchange wall. However, the through holes can be of any shape, size and type (e.g. delimited by stretchable elements, integrated in the service chamber independently of the stretchable elements, etc.).

[0073] In embodiments, the stretchable elements extend from the process chamber, each one of the stretchable elements passing through a respective one of the through holes from the heat exchange wall to the operating wall, wherein the contact faces of the stretchable elements protrude from the operating wall to contact the respective electronic devices. However, the stretchable elements can protrude from the operating wall with any of their contact faces (e.g. flat, convex, rigid, elastic, for direct / indirect contact, etc.) at any distance.

[0074] In embodiments, the process circulation system is configured for circulating the process thermally conductive fluid in each one of the stretchable elements from the process chamber to the contact face and from the contact face to the heat exchange wall. However, the process fluid can be circulated in the stretchable elements in any way (e.g. along any predetermined path, indistinctly, etc.).

[0075] In an embodiment, the heat regulation device comprises a plurality of suction pipes of process heat transfer fluid, each suction pipe extending in a respective one of the stretchable elements from the treatment chamber to a position proximate to the contact surface. However, each suction pipe can be of any shape and size and it can extend in the respective stretchable element in any way (e.g. protruding beyond the heat exchange wall by any distance (even zero distance), stopping at any distance (even zero distance) from the contact surface in case of being provided with one or more lateral windows corresponding thereto, etc.).

[0076] In an embodiment, the suction pipes are mutually separated from the lateral surface of the stretchable elements to define a delivery pipe of process heat transfer fluid. However, the suction pipes can be mutually separated from the lateral wall in any way (e.g. symmetrically or asymmetrically, by any distance, etc.).

[0077] In an embodiment, each of the blocking devices comprises a suction valve for blocking the flow of process heat transfer fluid from the treatment chamber into the suction pipe when the corresponding process circulation element is in the inactive state. However, the suction valve can be of any type (e.g. with opening and / or closing control, bonnet type, butterfly type, ball type, etc.).

[0078] In an embodiment, each of the blocking devices comprises a delivery valve for blocking the flow of process heat transfer fluid from the delivery pipe into the treatment chamber when the corresponding process circulation element is in the inactive state. However, the delivery valve can be of any type (same as or different from the suction valve).

[0079] In an embodiment, the suction valve is normally closed by gravity. However, the suction valve can have any specific weight (higher than that of the process fluid) for closing the suction pipe with any force.

[0080] In an embodiment, the suction valve is opened in response to an external command opposite to gravity. However, the external command can be of any type (e.g. magnetic, such as via an electromagnet or solenoid coil directly integrated in a multilayer printed circuit, mechanical, etc.).

[0081] In an embodiment, the delivery valve is normally closed by gravity. However, the delivery valve can have any specific weight (higher than that of the process fluid) for closing the delivery pipe with any force.

[0082] In an embodiment, the delivery valve is opened in response to said circulation of process heat transfer fluid opposite to gravity. However, the flow valve can be opened in response to any pressure exerted by the flow of process heat transfer fluid.

[0083] In embodiments, the thermal conditioning device comprises a limiting system for limiting the length of each of the stretchable elements when moving towards the elongated state in the absence of the corresponding electronic device. However, the limiting system can be of any type (e.g. with a limiting element for each stretchable element or group of stretchable elements, unique for all stretchable elements, passive, active, etc.) or it can be omitted altogether.

[0084] Embodiments provide a test apparatus comprising the above-described thermal conditioning device and one or more test boards. However, the test apparatus can comprise any number of any type of test boards.

[0085] In embodiments, each test board has a plurality of sockets, each socket for detachably housing one of the electronic devices. However, each test board can have any number (equal to or less than the number of stretchable elements of the thermal conditioning device) of any type (e.g. pads / holes for receiving terminals of the electronic devices, covers / clasps for locking the package of the electronic devices, etc.) of sockets.

[0086] In general, similar considerations apply if the thermal conditioning device and the test apparatus have different structures or comprise equivalent components (e.g. of different materials) or have other operational characteristics. In any case, where each component can be divided into more elements, or two or more components can be combined together into a single element; moreover, each component can be replicated to support the parallel execution of the corresponding operations. Moreover, unless otherwise specified, any interaction between different components does not need to be continuous and it can be direct or indirect through one or more intermediaries.

[0087] Embodiments provide a method for thermally conditioning a plurality of electronic devices under test. The method comprises circulating a process thermally conductive fluid in a plurality of stretchable elements having a variable length. The method comprises exchanging heat with the process thermally conductive fluid. The method comprises adjusting the pressure of the process thermally conductive fluid to move the stretchable elements between a shortened state and an elongated state. Each of the stretchable elements in the elongated state is pressed against a corresponding electronic device to thermally condition the electronic device.

[0088] Embodiments provide a method for testing a plurality of electronic devices. The method comprises detachably housing the electronic devices on corresponding sockets of one or more test boards. The method comprises thermally conditioning the electronic devices as above. The method comprises testing the thermally conditioned electronic devices.

[0089] In general, similar considerations apply, if a similar method is used to implement the same solution by using similar steps having the same functionality with more steps or parts thereof, removing some non-essential steps or adding more optional steps; furthermore, these steps can be executed in a different order, simultaneously or in an interleaved way (at least in part).

Claims

1. A thermal conditioning device (100) for thermally conditioning a plurality of electronic devices under test (205), characterized in that said electronic devices (205) are housed in one or more test boards (210), each of said test boards (210) having a plurality of sockets (220), each of said sockets (220) being configured to removably house a respective one of said electronic devices (205); said thermal conditioning device (100) comprises: a plurality of stretchable elements (105) having variable lengths corresponding to said sockets (220), each of said stretchable elements being configured to individually thermally condition a respective one of said electronic devices (205) housed in a respective one of said sockets (220), a process circulation system (115) configured to circulate a process thermally conductive fluid (110) in said stretchable elements (105), a process heat exchange system (120) configured to exchange heat with said process thermally conductive fluid (110), and a pressure regulation system (125) configured to regulate the pressure of said process thermally conductive fluid (110) to move said stretchable elements (105) between a shortened condition and an elongated condition, each of said stretchable elements (105) in said elongated condition being pressed against a respective one of said electronic devices (205).

2. The thermal conditioning device (100) of claim 1, wherein said process circulation system (115) comprises: a plurality of process circulation elements (363-366) corresponding to said stretchable elements (105), each of said process circulation elements being configured to circulate said process thermally conductive fluid (110) in a respective one of said stretchable elements (105), said process circulation elements (363-366) being individually controllable to independently regulate the flow rate of said process thermally conductive fluid (110) in a respective one of said stretchable elements (105).

3. The thermal conditioning device (100) of claim 2, wherein said thermal conditioning device (100) comprises: a plurality of blocking devices (369-375), each of said blocking devices being configured to block the convective movement of said process thermally conductive fluid (110) in a respective one of said stretchable elements (105) when a respective one of said process circulation elements (363-366) is in an inactive condition.

4. The thermal conditioning device (100) of claim 2, wherein said thermal conditioning device (100) comprises: a plurality of heating elements (351), each of said heating elements being arranged in a respective one of said stretchable elements (105) to heat a respective one of said electronic devices (205), said heating elements (351) being individually controllable to independently heat a respective one of said electronic devices (205).

5. The thermal conditioning device (100) of claim 4, wherein said thermal conditioning device (100) comprises: a plurality of temperature sensors (354), each of said temperature sensors being configured to detect a temperature of a respective one of said electronic devices (205), said process circulation elements (363-366) and / or said heating elements (351) being controllable as a function of the temperature of the respective one of said electronic devices (205).

6. The thermal conditioning device (100) of claim 3, wherein said thermal conditioning device (100) comprises: a thermal coupling element configured to exchange heat between said process thermally conductive fluid (110) and a service thermally conductive fluid (303), and a service heat exchange system (318-324) configured to exchange heat with said service thermally conductive fluid (303).

7. The thermal conditioning device (100) of claim 6, wherein said thermal conditioning device (100) comprises a process chamber (309) configured to contain said process thermally conductive fluid (110) and a service chamber (306) configured to contain said service thermally conductive fluid (303), said process chamber (309) and said service chamber (306) being separated by a heat exchange wall (312), wherein said service chamber (306) is traversed by a plurality of through holes (339) extending from said heat exchange wall (312) to an operating wall (333) opposite said heat exchange wall (312), said extendable elements (105) extending from said process chamber (309), each of said extendable elements traversing a respective one of said through holes (339) from said heat exchange wall (312) to said operating wall (333), wherein a contact face (348) of said extendable elements (105) protrudes from said operating wall (333) to contact a respective one of said electronic devices (205), and wherein said process circulation system is configured to circulate said process thermally conductive fluid (110) in each of said extendable elements (105) from said process chamber (309) to said contact face (348) and from said contact face (348) to said heat exchange wall (312).

8. The thermal conditioning device (100) of claim 7, wherein said thermal conditioning device (100) comprises: a plurality of suction pipes (357) of said process thermally conductive fluid (110), each of said suction pipes (357) extending from said process chamber (309) to a position proximate to said contact face (348) within a respective one of said extendable elements (105), said suction pipes (357) being mutually separated from lateral surfaces of said extendable elements (105) to define a delivery pipe (360) of said process thermally conductive fluid (110).

9. The thermal conditioning device (100) of claim 8, wherein each of said blocking devices (369-375) comprises: suction valves (369-372) for blocking the flow of the process thermally conductive fluid (110) from the processing chamber (309) to the suction duct (357) when the corresponding process circulation element (363-366) is in the inactive state, and / or delivery valves (375) for blocking the flow of the process thermally conductive fluid (110) from the delivery duct (360) to the processing chamber (309) when the corresponding process circulation element (363-366) is in the inactive state.

10. The thermal conditioning device (100) of claim 9, wherein the suction valves (369-372) are normally closed by gravity, the suction valves (369-372) opening in response to an external command opposite to gravity.

11. The thermal conditioning device (100) of claim 9, wherein the delivery valves (375) are normally closed by gravity, the delivery valves (375) opening in response to a process thermally conductive fluid circulation opposite to gravity.

12. The thermal conditioning device (100) of claim 1, wherein the thermal conditioning device (100) comprises a limiting system (405) for limiting the length of each of the stretchable elements (105) when moving towards the elongated state in the absence of the corresponding electronic device (205).

13. A testing apparatus (200) comprising the thermal conditioning device (100) of any one of claims 1 to 12 and one or more test boards (210), each having a plurality of sockets (220), each socket for detachably housing a corresponding one of the electronic devices (205).

14. A method for thermally conditioning a plurality of electronic devices under test (205), wherein the method comprises: housing the electronic devices (205) in one or more test boards (210), each test board (210) having a plurality of sockets (220), each electronic device (205) being detachably housed in a corresponding socket (220), circulating a process thermally conductive fluid (110) in a plurality of stretchable elements (105) having variable lengths corresponding to the sockets (220), exchanging heat with the process thermally conductive fluid (110), adjusting the pressure of the process thermally conductive fluid (110) to move the stretchable elements (105) between a shortened state and an elongated state, each of the stretchable elements (105) in the elongated state pressing against a corresponding one of the electronic devices (205) housed in a corresponding socket (220) to thermally condition the electronic devices (205).

15. A method for testing a plurality of electronic devices (205), wherein the method comprises: thermally conditioning the electronic devices (205) according to claim 14, and testing the thermally conditioned electronic devices (205).

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