Probe cards for electronic device test equipment

Abstract

The present invention provides a probe card (20) configured to be mounted in an electronic device testing apparatus, the probe card (20) including at least one probe head (21) containing a plurality of contact probes (22), each of the contact probes (22) having at least one first end (22A) configured to abut against a contact pad (23A) of a device under test (23), and the probe card (20) further includes a main substrate (27) and an intermediate substrate connected to the main substrate (27), the intermediate substrate being configured to perform spatial transformation of the distance between the contact pads formed on both surfaces thereof and functioning as a space transformer (30). Preferably, the space transformer (30) includes at least one core (30C) formed from a material having a thermal conductivity greater than 100 W / (m·K) for collecting and dissipating heat generated within the probe card (20) during testing of the electronic device (23).

Description

[Technical Field]

[0001] The present invention relates to a probe card used in an electronic device test apparatus.

[0002] The present invention particularly relates to a probe card having an intermediate substrate interposed between a plurality of contact probes and a plate for connecting to a test device and functioning as a space transformer, but is not limited thereto, and the following description will refer exclusively to this field of application for the sake of brevity. [Background technology]

[0003] As is well known, a probe card is essentially a device configured to electrically connect a plurality of contact pads of a microstructure, particularly an electronic device integrated on a wafer, to a corresponding plurality of channels of a tester that performs the test.

[0004] Testing of integrated devices is particularly useful for detecting and isolating faulty devices early in the manufacturing process, and so probe cards are typically used to electrically test devices integrated on wafers or chips before they are cut or singulated and assembled into containment packages.

[0005] The probe card includes a probe head, which essentially includes a plurality of movable contact elements or contact probes with at least one contact end or tip configured to abut a corresponding plurality of contact pads on a device under test. As used herein and hereinafter, the terms "end" or "tip" refer to the end of a probe, which is not necessarily pointed.

[0006] As is well known, the effectiveness and reliability of metrology testing depends, among other factors, on establishing a good electrical connection between the device under test and the test equipment, i.e., achieving optimal probe / pad electrical contact.

[0007] Among the types of probe heads used in the art for testing devices integrated on wafers, the so-called vertical probe heads are widespread, in which the contact probes are positioned approximately perpendicular to the plane in which the device under test is located.

[0008] In particular, a vertical probe head includes multiple contact probes held by at least one plate or guide, usually two parallel plate-like plates or guides. The guides are spaced apart at a predetermined distance from each other to leave free space or gaps for the contact probes to move and, in some cases, deform during testing, and are provided with appropriate guide holes for slidably accommodating the contact probes. More specifically, the pair of guides includes an upper guide (upper die) and a lower guide (lower die), both of which have guide holes through which the contact probes slide axially. The contact probes are made of wire made of a special alloy with excellent electrical and mechanical properties, also known in the art as needles, and the term "lower" conventionally refers to the guide closer to the device under test.

[0009] A good connection between the contact probes of the probe head and the contact pads of the device under test is ensured by pressing the probe head onto the device. During this pressing contact, the contact probes, which are movable within guide holes in the upper and lower guides, bend in the gap between the two guides and slide within the guide holes.

[0010] The bending of the contact probe within the gap can be assisted and guided by appropriate configuration of the contact probe itself or the guide, in particular by using a pre-deformed contact probe or by appropriately shifting the guide containing the contact probe laterally, the laterally being a direction approximately parallel to the plane of the device under test and the guide.

[0011] Typically, probe heads do not have probes fixedly attached, but are maintained in an electrically interfaced state with a suitable main board that is connected to the test equipment; in this case, they are called "unblocked probe heads." The main board is also called the main PCB (Printed Circuit Board) because it is usually manufactured using printed wiring board technology. While PCB technology allows the creation of large boards with active areas with contact pads, it is subject to significant limitations regarding the minimum center-to-center distance (pitch) of the contact pads, and is therefore typically only used to create the main board, since the main board is not subject to the same strict pad-to-pad distance constraints as the device under test.

[0012] Relaxation of the distance restrictions between contact pads, particularly the spacing between adjacent pads on the main substrate, is made possible by using an intermediate substrate or space transformer, which has contact pads formed on both sides with different center-to-center distances between one side and the opposite side, and which are appropriately connected by wiring, particularly metal wiring, formed inside the space transformer.

[0013] In this case, the contact probes are configured to abut against a plurality of contact pads formed on a first surface of the space transformer, in particular the surface facing the probe head and therefore the surface facing the device under test, and good electrical contact between the contact probes and the space transformer, as well as contact with the device under test, is ensured by pressing the probes against the contact pads formed on the space transformer.

[0014] Additionally, the main substrate is typically held in place by a stiffener. This assembly of the probe head, main substrate, intermediate substrate or space transformer, and stiffener forms a probe card, shown generally at 10 in FIG.

[0015] In particular, the probe card 10 in the illustrated example includes a probe head 1 having a plurality of vertical probes 2 and at least one upper guide 4 and at least one lower guide 5, each having an upper guide hole and a lower guide hole within which the contact probes 2 slide.

[0016] Each contact probe 2 has at least one first end or contact tip 2A that abuts against a contact pad 3A of a device under test 3 integrated on a semiconductor wafer 3', thereby realizing a mechanical and electrical connection between the device under test and a test apparatus (not shown), and the above-mentioned probe head 1 is the end element.

[0017] Furthermore, each contact probe 2 has a second end, referred to in the art as a contact head 2B, and a probe body portion 2C extending along the longitudinal extension axis of the contact probe 2 between the contact tip 2A and the contact head 2B, the longitudinal extension axis being approximately perpendicular to the face of the device under test and therefore to the guide.

[0018] On the other hand, the contact head 2B is configured to abut against a plurality of contact pads 6A formed on an intermediate substrate that functions as a space transformer 6, and the intermediate substrate is connected to a main substrate 7, which is further connected to a testing device.

[0019] The spatial transformation achieved by the space transformer 6 is particularly related to the center-to-center distance of the contact pads formed on its opposite surface. The space transformer 6 has a plurality of first contact pads 6A formed on its first surface FA facing the probe head 1 and arranged at the positions of the contact heads 2B of the contact pads 2. The contact pads 6A are connected by appropriate metal wiring 6C to a plurality of second contact pads 6B formed on its opposite second surface FB facing the main substrate 7. The second contact pads 6B have a different spatial distribution, particularly a larger center-to-center distance, i.e., a larger pitch, than the first contact pads 6A, which are arranged to substantially correspond to the distribution of the contact pads 3A of the device under test 3. In this way, the space transformer 6 performs spatial transformation by using the spacing of the contact pads 6B formed on its second surface FB relative to the contact pads 6A formed on its first surface FA. These are generally referred to as probe-side pads or fine pitch to refer to the plurality of first contact pads 6A, and as PCB-side pads or large pitch to refer to the plurality of second contact pads 6B.

[0020] Good electrical contact between the contact probes 2 and the space transformer 6, as well as contact with the device under test 3, is ensured by pressing the probes against contact pads 6A formed on the first face FA of the space transformer 6.

[0021] As already mentioned, the main substrate 7 is also held in place by stiffeners 8, which make the whole assembly a more rigid and durable structure, making it possible to reduce flatness defects, especially with respect to the space transformer 6, which is often made very thin and therefore has significant flatness issues.

[0022] 1, the probe head 1 further includes an intermediate guide 5′ (medium guide), which is plate-shaped and disposed parallel to the upper guide 4 and the lower guide 5, and is disposed between them, preferably close to the lower guide 5. The intermediate guide 5′ is also provided with a plurality of intermediate guide holes 5′A in which the contact probes 2 are slidably housed.

[0023] Suitably, the upper guide 4, lower guide 5 and intermediate guide 5' are offset from one another in a lateral direction corresponding to the x-axis in the local coordinate system of Figure 1 so as to give them a preferential deflection direction in addition to properly retaining the contact probes 2 within the probe head 1, which is completed by a housing 9 that integrates the guides and surrounds the contact probes 2.

[0024] Therefore, in vertical probe technology, it is important to ensure good connection between the contact probe and the device under test, particularly at its contact tip, as well as good connection with the test equipment, particularly at its contact head, i.e., space transformer, which plays a very important role, especially in the testing operation of integrated circuits manufactured according to recent integration technology, where the contact pads on the device under test are arranged very closely and are extremely small in size, and which are not compatible with the PCB technology from which the main substrate of the probe card is formed.

[0025] It has also been found that the relative positioning of the elements that make up the probe card is a crucial parameter for the correct operation of the probe card itself, and the different technologies used to manufacture these components create flatness issues that complicate the overall probe card configuration, particularly with respect to the positioning of the intermediate substrate or space transformer relative to the main substrate. Even if stiffeners are provided to make the overall assembly more rigid and durable, they generally cannot sufficiently eliminate flatness defects in the space transformer to ensure accurate and complete contact between the space transformer and the main substrate.

[0026] Additionally, the operating temperature of the probe card itself, especially during testing under extreme temperature conditions, can further complicate the above-mentioned issues. In such cases, the thermal expansion of each component of the probe card can affect the correct behavior of the probe card, especially since these components are made of different materials with different thermal expansion coefficients. Typically, the components of the probe card are connected to each other with screws. During temperature testing, these screws exert a restraining force on each plate, which can easily cause the plates to warp. This can lead to failure of the entire probe card, or in extreme cases, the contact probes of the probe head may no longer make contact with the contact pads of the device under test.

[0027] This problem is particularly pronounced in the case of large probe cards, such as those used for testing memory devices such as DRAMs, where the inability to control the thermal expansion of components in such probe cards poses significant challenges during the testing process.

[0028] Furthermore, during testing operations, the contact probes heat up as different signals pass through them, which increases the heat inside the probe head, especially in probe heads with a large number of contact probes.

[0029] Similarly, the application of the contact probes to the pads of the space transformer and the process of transmitting signals from the probe pads to the PCB pads within the space transformer also generates undesirable heat that builds up within the probe card.

[0030] The technical problem of the present invention is to provide a probe card with structural and functional features that can facilitate the removal of heat generated during test operations and suppress the increase in the operating temperature of the probe card and the probe head contained therein, while overcoming the limitations and drawbacks still present in probe cards manufactured using conventional technology. Summary of the Invention

[0031] The basic idea of ​​the solution underlying the present invention is to provide a space transformer for a probe card that starts from a core made of a material with high thermal conductivity, capable of collecting and dissipating heat generated inside it and inside the connected probe heads, said core preferably being selected to be sufficiently rigid to form the mechanical support of the entire space transformer.

[0032] Based on this solution concept, the technical problem is solved by a probe card configured to be attached to an electronic device test apparatus. The probe card includes at least one probe head containing a plurality of contact probes, each of the contact probes having at least one first end configured to abut against a plurality of contact pads on a device under test. The probe card further includes a main substrate and an intermediate substrate connected to the main substrate. The intermediate substrate is configured to realize a spatial transformation of the distance between the contact pads formed on both sides of the intermediate substrate and functions as a space transformer. Preferably, the space transformer includes at least one core formed of a material having a thermal conductivity greater than 100 W / (m·K) for collecting and dissipating heat generated by the probe card during an electronic device test operation.

[0033] More specifically, the present invention includes the following additional and optional features which may be taken individually or in combination as appropriate:

[0034] According to one aspect of the present invention, the core may be formed from a material having a thermal conductivity greater than 500 W / (m·K).

[0035] In accordance with another aspect of the present invention, the core may be formed from a non-conductive material.

[0036] More specifically, the core may be formed from a material selected from silicon nitride, silicon carbide, CVD-D (chemical vapor deposition diamond) and aluminum nitride.

[0037] The core may also be formed from a material having a Young's modulus greater than 30,000 MPa, preferably greater than 1,200,000 MPa.

[0038] According to another aspect of the invention, the core may include a plurality of through holes arranged to connect the first surface and the opposing second surface.

[0039] According to yet another aspect, the core may be formed by multiple layers of different materials.

[0040] According to yet another aspect, the space transformer may comprise a plurality of additional layers formed on at least one surface of the core, the number of which may be any number greater than or equal to two, and which may be arranged symmetrically or asymmetrically with respect to the core.

[0041] According to yet another aspect, the space transformer may include the additional layer only on a first surface of the core, with an opposite second surface of the core being in direct thermal contact with the main substrate.

[0042] In particular, the other layer may be formed from an organic material, with the space transformer being a multi-layer organic MLO structure, or may be formed from a metallic or ceramic material, with the space transformer being a ceramic multi-layer MLC structure.

[0043] According to yet another aspect, the further layer and the core may have lateral dimensions along the plane of extension of the device under test that are equal to one another.

[0044] Alternatively, the core may have at least one lateral dimension larger than the space transformer and include at least one peripheral edge exposed to the space transformer.

[0045] According to yet another aspect, the probe card may further include a conductive layer covering the core and extending to the periphery.

[0046] According to yet another aspect, the probe card may further comprise a heat sink thermally associated with the core at the periphery.

[0047] The probe card may also further comprise a heat exchange structure configured to thermally connect the core to the main substrate.

[0048] In particular, the heat exchange structure may be selected from active or passive screws or thermal pipes and may be press-contacted, welded, glued with a thermally conductive adhesive or crimped to the core, preferably at the periphery.

[0049] According to yet another aspect, the core may further include microchannels through which a cooling fluid passes.

[0050] In particular, the microchannel may include a plurality of microchannel channels through which a cooling fluid passes between a fluid inlet region and a fluid outlet region, the fluid inlet region and the fluid outlet region being formed at the periphery of the core.

[0051] Furthermore, the plurality of microchannels may include a first group of microchannels formed in the fluid inlet region and a second group of microchannels formed in the fluid outlet region.

[0052] The characteristics and advantages of the probe card according to the invention will become apparent from the following description of embodiments given as non-limiting examples with reference to the accompanying drawings, in which: FIG. [Brief explanation of the drawings]

[0053] [Figure 1] FIG. 1 shows a schematic cross-sectional view of a probe card manufactured by a conventional technique. [Figure 2] FIG. 2 shows a schematic cross-sectional view of a probe card according to one embodiment of the present invention. [Figure 3A] 3A shows schematic cross-sectional views of a probe card according to another embodiment of the present invention. [Figure 3B] FIG. 3B shows schematic cross-sectional views of a probe card according to another embodiment of the present invention. [Figure 3C] FIG. 3C shows schematic cross-sectional views of a probe card according to another embodiment of the present invention. [Figure 3D] 3D shows schematic cross-sectional views of a probe card according to another embodiment of the present invention. [Figure 4A] FIG. 4A shows a side cross-sectional view of a space transformer included in a probe card according to yet another embodiment of the present invention. [Figure 4B] FIG. 4B shows a plan cross-sectional view of a space transformer included in a probe card according to yet another embodiment of the present invention. [Figure 5A] FIG. 5A shows a side cross-sectional view of a space transformer included in a probe card according to yet another embodiment of the present invention. [Figure 5B] FIG. 5B shows a plan cross-sectional view of a space transformer included in a probe card according to yet another embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0054] Referring to the drawings, and particularly to FIG. 2, a probe card constructed in accordance with the present invention and including at least one probe head with a plurality of contact probes for testing electronic devices integrated on a wafer is generally designated 20.

[0055] It should be noted that the figures are schematic representations of probe cards according to the present invention, are not drawn to scale, and are drawn to highlight important features of the invention.

[0056] Furthermore, the multiple aspects of the present invention illustrated in the drawings can of course be combined with one another and can be interchanged from one embodiment to another.

[0057] In the following description, relative terms such as "above," "below," "upward," and "downward" are used based on the illustration of different elements shown in the figures and are for ease of description only.

[0058] Finally, statements about specific shapes (circular, rectangular) or arrangements of components (parallel, orthogonal, tangent) and the term "substantially" always relate to physical components and not to geometric abstractions, and therefore always take into account the tolerances introduced by the transition from the mathematical / geometric ideal world to the real world.

[0059] 2, the probe card 20 includes a probe head 21 that houses a plurality of contact probes 22. The illustrated probe head 21 is an unblocked vertical type and includes at least one upper plate or guide 24 and one lower plate or guide 25, each formed with an upper guide hole 24A and a lower guide hole 25A through which the contact probes 22 slide.

[0060] As is common in the technical field of the present invention, the term "lower guide" means a guide positioned closer to the device under test, and the term "upper guide" means a guide positioned closer to the test equipment connected to the probe card 20 when the probe card 20, and therefore the probe head 21, is mounted as an end element of the test equipment and is in an operational state.

[0061] The probe head 21 also includes a receiving element or housing 29 that integrates the upper guide 24 and the lower guide 25 and is configured to enclose the contact probe 22 .

[0062] 2, the probe head 21 further comprises an intermediate plate or guide 25', which is arranged parallel to and between the upper guide 24 and the lower guide 25, particularly close to the lower guide 25, and which also comprises an intermediate guide hole 25'A through which the contact probe 22 slides. This three-guide embodiment is merely exemplary, and the probe head 21 may optionally include one guide or two or more guides.

[0063] Each contact probe 22 has at least a first end, i.e., a contact tip 22A, configured to abut against a contact pad 23A integrated on the device under test 23, in particular a semiconductor wafer 23', so as to establish the desired contact, in particular electrical contact, between the contact probe 22 of the probe head 21 and the contact pad 23A of the device under test 23.

[0064] Each contact probe 22 further includes a second end, i.e., a contact head 22B, configured to establish contact with a main substrate 27 or main PCB that is connected to a test apparatus (not shown). A rod-shaped probe body 22C is disposed between the contact head 22B and the contact tip 22A, and extends substantially along the longitudinal extension direction of the contact probe 22, particularly perpendicular to the plane π on which the semiconductor wafer 23′ on which the device under test 23 is integrated is disposed, i.e., along the z-axis of the local coordinate system of FIG. 2.

[0065] The upper guide 24, the lower guide 25, and the middle guide 25' are plate-like elements arranged parallel to one another and parallel to the plane π of the semiconductor wafer 23', and therefore the device under test 23. Suitably, as in the prior art, the upper guide 24, the lower guide 25, and the middle guide 25' are shifted relative to one another in a direction tangent to the plane π of the semiconductor wafer 23', i.e., the x-axis direction in the local coordinate system of FIG. 2, so as to impart a preferential bending direction to the contact probe 22. Due to this shifting of the guides, the guide holes formed therein and accommodating identical contact probes are no longer aligned relative to one another in a direction perpendicular to the plane π of the semiconductor wafer 23', i.e., the z-axis direction in the local coordinate system of FIG. 2, which forces the probe body 22C of the contact probe 22 to bend and determines the preferential bending direction mentioned above.

[0066] The probe card 20 further comprises an intermediate substrate arranged between the probe head 21 and the main substrate 27 and configured to achieve a spatial transformation, particularly relating to the distribution of contact pads on both sides thereof, and for the reasons mentioned above is denoted as a space transformer 30.

[0067] The space transformer 30 has a first surface FA facing the probe head 21 (in the operating state, i.e., when the space transformer 30 is inserted into the probe card 20 equipped with the probe head 21 and attached as an end element of the test apparatus), and a plurality of first contact pads, i.e., probe-side pads 26A, are formed on this first surface FA, against which the contact heads 22B of the contact probes 22 abut. Furthermore, the space transformer 30 has a second surface FB' facing the main board 27 in the operating state.

[0068] Finally, the probe card 20 includes a stiffener 28 associated with the main substrate 27 and configured to improve the flatness of the main substrate 27 and prevent bending of the substrate, particularly when the temperature rises during operation of the probe card 20, i.e., during testing operations.

[0069] Preferably, according to the present invention, the space transformer 30 comprises a core 30C formed from a material having a high thermal conductivity λ of greater than 100 W / (m·K), preferably greater than 500 W / (m·K). This high thermal conductivity λ allows optimal collection and subsequent dissipation of heat generated within the space transformer 30 during testing operations of the probe card 20, and also assists in the collection and dissipation of heat generated within the probe head 21 via the contact probes 22 connected to the space transformer 30.

[0070] In a preferred embodiment, core 30C is formed from a non-conductive material so as not to interfere with the electrical operation of space transformer 30.

[0071] Preferably, the core 30C is made of a highly rigid material, i.e., a material having a high tensile modulus of elasticity or Young's modulus E of greater than 30,000 MPa, preferably greater than 1,200,000 MPa, so as to serve as a mechanical support for the space transformer 30, which comprises a plurality of layers superimposed on one another and the core 30C.

[0072] The core 30C may be formed in particular from silicon nitride, silicon carbide or CVD-D (chemical vapor deposition diamond), all of which are substantially dielectric and have a high thermal conductivity λ and are rigid enough to support the layers of the space transformer 30, in particular the organic layers configured to form a multi-layer organic (MLO).

[0073] In a preferred embodiment, the space transformer 30 is formed symmetrically around the core 30C and includes a first portion or lower portion 30L formed on a first face F1 of the core 30C, specifically, on the lower surface of the core 30C based on the local coordinate system of FIG. 2, and a second portion or upper portion 30U formed on the opposite side of the core 30C, specifically, on the upper surface of the core 30C based on the local coordinate system of FIG. 2. When the probe card 20 is in an operational state, i.e., when the probe card 20 is attached as a terminal element of a test apparatus (not shown) and the contact probes 22 of the probe head 21 are positioned between the space transformer 30 and the device under test 23, the first face F1 of the core 30C faces the device under test 23. When the probe card 20 is in an operational state, the second face F2 of the core 30C faces the main board 27.

[0074] More specifically, when the probe card 20 is in an operational state, the upper portion 30U is disposed between the core 30C and the main substrate 27, and is in contact with a plurality of pads 27B formed on the surface FB of the main substrate 27, which faces the device under test 23. On the other hand, the lower portion 30L is disposed between the core 30C and the probe head 21, and includes a plurality of pads 26A formed on the first surface FA of the space transformer 30, which faces the device under test 23, when the probe card 20 is in an operational state, and the plurality of pads 26A are in contact with the contact probes 22 of the probe head 21, particularly the contact heads 22B of the probes.

[0075] In the example shown in FIG. 2, the upper portion 30U and the lower portion 30L of the space transformer 30 each have a pair of layers 30U1, 30U2 and 30L1, 30L2, but it is of course possible to consider one or more different numbers of layers for each portion, and it is also possible for the upper and lower portions to have different numbers of layers. Preferably, layers 30U1, 30U2 and 30L1, 30L2 are formed of an organic material such as epoxy or polyimide, thus making space transformer 30 a multi-layer organic or MLO (multi-layer ceramic) structure. Alternatively, space transformer 30 may be formed as a ceramic-based multi-layer or MLC (multi-layer ceramic) structure. The layers 30U1, 30U2, 30L1, 30L2 of the upper 30U and lower 30L have lateral dimensions along the extension plane π of the device under test 23 and the extension plane of the guide that are equal to each other and to the core 30C, specifically, their length along the x-axis and their depth along the y-axis in Figure 2. References to "equal" dimensions and terms such as "plane," "parallel," and "orthogonal" always refer to physical elements rather than purely geometric abstractions, and therefore must necessarily take into account tolerances that arise when moving from the mathematical-geometric world to the real world.

[0076] Preferably, the layers 30U1, 30U2 and 30L1, 30L2 constituting the upper and lower parts 30U, 30L of the space transformer 30 are provided with conductive vias 32U, 32L, respectively, which are in contact with each other to form conductive paths from the pad 26A to the core 30C and from the core 30C to the pad 27B.

[0077] More specifically, the conductive via 32L on the first layer 30L1 of the lower part 30L contacts the conductive via 32L on the second layer 30L2 of the lower part 30L, and also contacts the pad 26A arranged on the first face FA of the space transformer 30. Similarly, the conductive via 32U on the first layer 30U1 of the upper part 30U contacts the conductive via 32U on the second layer 30U2 of the upper part 30U, and also contacts the pad 27B on the second face FB' of the space transformer 30.

[0078] The conductive vias 32U, 32L are formed to be spaced apart from each other starting from the pad 26A to the pad 27B, thereby realizing the desired space transformation, and the center-to-center distance (pitch) of the pads 26A is smaller than the center-to-center distance of the pads 27B. Furthermore, a conductive connection structure 33, in particular a conductive bump, is formed on the second face FB' of the space transformer 30 to form an electrical connection between the conductive vias 32U in the upper layer 30U of the space transformer 30 and the pads 27B of the main substrate 27.

[0079] Advantageously, according to the present invention, the core 30C further comprises a plurality of through holes 31 that communicate the first face F1 with the second face F2. The through holes 31 are configured to transport heat generated in the lower portion 30L and the upper portion 30U of the space transformer 30 into the core 30C, and the core 30C redistributes the heat among all the through holes 31 present, thereby improving the heat transport efficiency in a direction perpendicular to the core 30C, i.e., in a vertical direction along the z-axis in FIG. 2. Furthermore, the heat is discharged in a tangential direction contacting the core 30C, i.e., in a horizontal direction along the x-axis in FIG. 2, and reaches the outer edge of the core 30C, where it is promoted to dissipate into the air.

[0080] In the variant shown in Figure 3A, the core 30C comprises several layers (two in the example shown) of different materials bonded together so as to improve the mechanical performance of said core 30C while maintaining a good level of heat exchange. Among the materials used to form the different layers of the core 30C, silicon nitride, silicon carbide, CVD-D (chemical vapor deposition diamond) and aluminum nitride, to name a few, come into consideration.

[0081] Preferably, as will be described later, by using two layers made of different materials, it is possible to form microchannels along the x-axis in the figure, i.e., the horizontal direction, to obtain the desired cooling, and also to reduce the amount of coating with a high thermal conductivity material, such as CVD-D, which provides substantial advantages not only from an economical point of view considering the cost of the material, but also from a technical point of view related to the maximum thickness that can be achieved in manufacturing.

[0082] In the embodiment shown in FIG. 3A, the core 30C includes a first layer 30C1 of a first material and a second layer 30C2 of a second material, which are overlapping and bonded to form the core 30C, and the first layer 30C1 and the second layer 30C2 have respective lateral dimensions that are equal to each other, in particular equal to each other and equal to the core 30C, i.e., have the same length along the x-axis and the same depth along the y-axis of FIG. 3A.

[0083] It is also possible to form the space transformer 30 in a structure that is not symmetrical with respect to its core 30C. In this case, the space transformer 30 may, for example, only include a lower portion 30L associated with the core 30C at a first face F1, and the core 30C may directly include a conductive connection structure 33 for contacting the pad 27B of the main board 27 on a second face F2, i.e., the face that coincides with the second face FB′ of the space transformer 30, as shown schematically in FIG. 3B. Even in this case, the core 30C may be formed of multiple layers of different materials, such as two layers of silicon nitride, silicon carbide, CVD-D (chemical vapor deposition diamond), and aluminum nitride, as described above.

[0084] In the example shown in FIG. 3B, layers 30L1 and 30L2 of lower portion 30L have equal lateral dimensions to each other and to core 30C, in particular, the same length along the x-axis and the same depth along the y-axis of the local coordinate system of FIG. 3B.

[0085] Preferably, according to this alternative embodiment, the space transformer 30 is configured such that the core 30C, which is a layer having high thermal conductivity, is in direct thermal contact with the main substrate 27, thereby maximizing heat exchange through the main substrate 27.

[0086] In another preferred embodiment, as schematically shown in Fig. 3C, the core 30C is formed to have a dimension larger than that of the space transformer 30, particularly a length larger in the x-axis direction. In the example shown in Fig. 3C, the core 30C is formed to have a dimension larger than that of the upper portion 30U and the lower portion 30L included in the space transformer 30.

[0087] In particular, the core 30C includes at least one peripheral edge 34 that is not in contact with, and in particular not covered by, the layers of the space transformer 30, more particularly the upper 30U and lower 30L layers of the space transformer 30, and is therefore exposed to air.

[0088] 3C clearly improves the heat dissipation efficiency, particularly to the air, achieved by the space transformer 30 due to the presence of the peripheral edge 34. According to another embodiment (not shown), conductive layers can be deposited on both exposed surfaces of the core 30C and extend to the peripheral edge 34, thereby further facilitating heat dissipation. Furthermore, the peripheral edge 34 may be provided with through-holes, which allow the conductive layers on both surfaces to communicate with each other.

[0089] Advantageously, according to an alternative embodiment shown in FIG. 3C, the probe card 20 may also include a heat sink 35 thermally coupled to the core 30C, particularly to the periphery 34 thereof.

[0090] 3D, a heat exchange structure 36 in the form of a screw or a thermal pipe may be provided, which penetrates the main substrate 27 to reach the core 30C, particularly its peripheral edge 34, and transports the heat collected by the core 30C to the outside of the probe card 20. In other words, the heat exchange structure 36 may thermally connect the core 30C with the main substrate 27, particularly by pressure contact, or may be joined to the core 30C, preferably its peripheral edge 34, by welding, gluing with a thermally conductive adhesive, or crimping.

[0091] The heat exchange structure 36 may be a passive thermal pipe in the form of a rod of substantially solid material, preferably a material selected from metallic or inorganic materials having a high thermal conductivity λ, in particular a thermal conductivity λ greater than 100 W / (m·K), preferably greater than 500 W / (m·K). Preferably, the heat exchange structure 36 may be made of a material selected from copper, aluminum, aluminum nitride, silicon nitride, silicon carbide and CVD-D (chemical vapor deposition diamond).

[0092] The heat exchange structure 36 may also be constituted by active thermal pipes, which essentially comprise an evaporation chamber through which a liquid flows, is transformed into vapor by heat generated in the probe card 20, and is transported along each thermal pipe to a condensation chamber where the vapor transforms back into a liquid and releases heat to a suitable radiator, whereupon the liquid returns to the evaporation chamber to begin the process again.

[0093] Finally, as shown in the example of Figure 3D, the heat exchange structure 36 may be formed to include a reduced diameter portion, particularly along the core 30C.

[0094] Furthermore, according to another improved embodiment shown schematically in Figures 4A and 4B, the core 30C is provided with a microchannel 37, which includes a plurality of microchannel channels 38, which are arranged between the through-holes 31 and which communicate with a fluid inlet region 37A and a fluid outlet region 37B provided at the peripheral portion 34 of the core 30C.

[0095] Preferably, the microchannel channels 38 can be formed by laser drilling. More specifically, the microchannel channels 38 are preferably formed in via-free regions of the upper and lower portions 30U and 30L of the space transformer 30, thereby providing a preferential path for a suitable cooling fluid FR through the microchannel 37 from the fluid inlet region 37A to the fluid outlet region 37B.

[0096] Alternatively, the microchannel channels 38 may be formed only in the peripheral portion 34, and in particular, a first group of microchannel channels 38A may be provided in the fluid inlet region 37A and a second group of microchannel channels 38B may be provided in the fluid outlet region 37B, as shown schematically in Figures 5A and 5B.

[0097] The presence of the microchannels 37 makes it possible to realize liquid cooling, acting either on the entire space transformer 30 (embodiment of Figures 4A and 4B) or only on its peripheral edge 34 (embodiment of Figures 5A and 5B), which in either case can significantly improve the efficiency of the heat exchange performed by the space transformer 30, and in particular its core 30C.

[0098] In conclusion, according to the present invention, a probe card having a space transformer with a core made of a material with high thermal conductivity can effectively dissipate heat generated during testing of an integrated device, particularly during power signals. Preferably, the core can dissipate not only the heat generated therein but also the heat transferred to it from the contact probes of the probe head during operation.

[0099] The probe card is therefore found to be suitable for applications in which the entire probe card is significantly heated by the test operation, ensuring correct operation of the probe card and avoiding deformation of components that may affect the successful outcome of the test operation.

[0100] Furthermore, it is found that the heat dissipation performance can be further improved when the heat dissipation structure is combined with an additional heat sink or with a micro-channel through which a cooling fluid circulates.

[0101] Furthermore, the core is suitably formed of a material that is rigid enough to mechanically support the other layers that make up the space transformer, particularly the organic layers.

[0102] Of course, those skilled in the art can make numerous modifications and substitutions to the above probe card to meet fortuitous and specific requirements, all of which fall within the protection scope of the present invention as defined in the following claims.

Claims

1. 1. A probe card (20) configured to be mounted in an electronic device testing apparatus, the probe card (20) comprising: at least one probe head (21) accommodating a plurality of contact probes (22); each of the contact probes (22) having at least one first end (22A) configured to abut against a plurality of contact pads (23A) of a device under test (23); the probe card (20) further comprising: a main substrate (27) and an intermediate substrate connected to the main substrate (27); the intermediate substrate is configured to realize spatial transformation of the distance between the contact pads formed on both sides of the intermediate substrate and functions as a space transformer (30); and the space transformer (30) includes at least one core (30C) formed from a material having a thermal conductivity greater than 100 W / (m·K) for collecting and dissipating heat generated within the probe card (20) during a test operation of the electronic device (23).

2. 2. The probe card (20) of claim 1, wherein the core (30C) is formed from a material having a thermal conductivity greater than 500 W / (m·K).

3. The probe card (20) of claim 1, wherein the core (30C) is formed from a non-conductive material.

4. The probe card (20) of claim 1, wherein the core (30C) is formed from a material selected from silicon nitride, silicon carbide, CVD-D (chemical vapor deposition diamond), and aluminum nitride.

5. The probe card (20) of claim 1, wherein the core (30C) is formed from a material having a Young's modulus greater than 30,000 MPa.

6. The probe card (20) of claim 1, wherein the core (30C) is formed from a material having a Young's modulus greater than 1,200,000 MPa.

7. The probe card (20) of claim 1, characterized in that the core (30C) includes a plurality of through holes (31) configured to connect a first surface (F1) of the core (30C) to an opposite second surface (F2).

8. The probe card (20) of claim 1, wherein the core (30C) is constructed from multiple layers of different materials.

9. The probe card (20) of claim 1, characterized in that the space transformer (30) comprises a plurality of separate layers (30L1, 30L2, 30U1, 30U2) formed on at least one surface (F1, F2) of the core (30C), in any number of two or more, and arranged symmetrically or asymmetrically with respect to the core (30C).

10. The probe card (20) of claim 9, characterized in that the space transformer (30) has the additional layers (30L1, 30L2) only on a first surface (F1) of the core (30C), and a second surface (F2) opposite the core (30C) is in direct thermal contact with the main substrate (27).

11. 10. The probe card (20) of claim 9, wherein the further layers (30L1, 30L2, 30U1, 30U2) are made of organic materials and the space transformer (30) is a multi-layer organic MLO structure.

12. 10. The probe card (20) of claim 9, wherein the further layers (30L1, 30L2, 30U1, 30U2) are made of a metallic or ceramic material, and the space transformer (30) is a multi-layer ceramic (MLC) structure.

13. 10. The probe card (20) of claim 9, wherein the other layers (30L1, 30L2, 30U1, 30U2) and the core (30C) have equal lateral dimensions along the extension plane of the device under test (23).

14. The probe card (20) of claim 1, wherein the core (30C) has at least one lateral dimension larger than the space transformer (30) and includes at least one peripheral edge (34) exposed to the space transformer (30).

15. The probe card (20) of claim 14, further comprising a conductive layer covering the core (30C) and extending to the periphery (34).

16. The probe card (20) of claim 14, further comprising a heat sink (35) thermally associated with the core (30C) at the periphery (34).

17. The probe card (20) of claim 14, further comprising a heat exchange structure (36) configured to thermally connect the core (30C) to the main substrate (27).

18. The probe card (20) of claim 17, wherein the heat exchange structure (36) is selected from an active or passive screw or thermal pipe and is pressure-contacted, welded, bonded with a thermally conductive adhesive, or crimped to the core (30C).

19. The probe card (20) of claim 1, wherein the core (30C) further comprises microchannels (37) through which a cooling fluid (FR) passes.

20. 20. The probe card (20) of claim 19, wherein the microchannel (37) includes a plurality of microchannel channels (38) through which the cooling fluid (FR) passes between a fluid inlet region (37A) and a fluid outlet region (37B), the core (30C) has at least one lateral dimension larger than the space transformer (30) and includes at least one peripheral edge (34) exposed to the space transformer (30), and the fluid inlet region (37A) and the fluid outlet region (37B) are formed in the peripheral edge (34) of the core (30C).

21. 21. The probe card (20) of claim 20, wherein the plurality of microchannel channels (38) includes a first group of microchannel channels (38A) formed in the fluid inlet region (37A) and a second group of microchannel channels (38B) formed in the fluid outlet region (37B).

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