Probe card for an apparatus for testing electronic devices with improved thermal control

Abstract

A probe card (20) adapted to be inserted in an apparatus for testing electronic devices is described, said probe card (20) comprising at least one probe head (11) housing a plurality of contact probes (13), each contact probe (13) having at least one first end portion (13A) adapted to abut onto contact pads (15A) of a device under test (15) and a second end portion (13B) adapted to abut onto corresponding contact pads formed on a first face (FA) of a space transformer (14) facing the device under test (15), as well as a main board (17) connected to the space transformer (14) and one or more active devices (19; 19A, 19B) housed on the first face (FA) of the space transformer (14) and in thermal contact with said space transformer (14). Suitably, the probe card (20) further comprises a microfluidic cooling system (30) including at least one manifold (31) provided with one or more microfluidic channels (32, 33) in which a cooling fluid circulates, said microfluidic channels (32, 33) being in direct or indirect thermal contact with the active devices (19; 19A, 19B) to collect and dissipate heat produced by said active devices (19; 19A, 19B) as active thermal power (PT2).

Description

[0001] Title: Probe card for an apparatus for testing electronic devices with improved thermal control

[0002] DESCRIPTION

[0003] Technical Field

[0004] The present invention relates to a probe card of an apparatus for testing electronic devices.

[0005] The invention relates particularly, but not exclusively, to a probe card comprising a space transformer interposed between a plurality of contact probes and a board for connection with a testing apparatus and the following description is made with reference to this field of application with the only purpose of simplifying the exposition thereof.

[0006] Background Art

[0007] As it is well known, a probe card is essentially a device adapted to electrically connect a plurality of pads or contact pads of a microstructure, in particular an electronic device integrated on a wafer, with corresponding channels of a testing apparatus which performs the testing thereof.

[0008] The test performed on integrated devices serves in particular to detect and isolate defective devices as early as in the production phase. Usually, the probe cards are thus used for the electrical testing of the devices integrated on wafers or chips before cutting or singulating and assembling them inside a containment package.

[0009] A probe card comprises a probe head essentially including in turn a plurality of mobile contact elements or contact probes provided with at least one end portion or contact tip adapted to abut onto a corresponding plurality of contact pads of the device under test. The terms end or tip mean here and below an end portion of said probes, being not necessarily pointed.

[0010] The contact head is interfaced to an intermediate board called space transformer which has contact pads formed on opposite faces thereof with centres at a different distance between a face and the opposite one, suitably connected with each other by means of connections, in particular metal tracks, formed inside the space transformer itself, so as to allow a relaxation between the distances between the centres of theprobes from the probe head to a mam board or mam board, also indicated as main PCB, since it is usually formed using the techniques of printed circuits or PCBs (from the English: “Printed Circuit Board”), a technology that allows to form boards with active areas, i.e. provided with contact pads, being even large-sized, although with major limitations with respect to a minimum reachable value for the distance (pitch) between the centres of the contact pads.

[0011] In vertical probe heads, the contact probes have a first end portion, or contact tip, adapted to abut onto contact pads of a device under test and a second end portion or contact head adapted to abut onto contact pads formed on a first face of said space transformer, in particular a face arranged towards the probe head and thus the device under test, having in turn corresponding contact pads formed on a second face, in particular a face facing the main board and thus the testing apparatus.

[0012] Suitable contact structures or elements are arranged in an interface layer arranged between the space transformer and the main board. Said contact elements may encompass conductive balls and pillars, i.e. usually-metal structures made in a sphere or cylinder shape and arranged so as to mechanically and electrically connect the second face of the space transformer with a first face of the main board, in particular the face facing the probe head and thus the device under test.

[0013] The assembly of the probe head, of the main plate or board, of the intermediate board or space transformer and of the interconnection layer forms a probe card, globally and schematically indicated with 10 in Figure 1.

[0014] In particular, the probe card 10 thus comprises a probe head 1, in the example in the figure comprising a containment structure 2 of a plurality of vertical probes 3; the containment structure 2 can comprise at least one guide or a pair of upper and lower guides, having respective guide holes in which the contact probes 3 slide.

[0015] Each contact probe 3 has at least one first end portion or contact tip 3A which abuts onto a contact pad 5A of a device under test 5 integrated on a semiconductor wafer 6, performing the mechanical and electrical contact between the device under test and a testing apparatus (notrepresented) which said probe head 1 forms an end element of.

[0016] Moreover, each contact probe 3 has a second end portion or contact head 3B adapted in turn to perform the contact with a plurality of contact pads formed on an intermediate board or space transformer 4, connected to a main plate or board 7 by an interface layer 8, the main board 7 being connected in turn to the real testing apparatus.

[0017] The main board 7 is also kept in place by means of a stiffener (not illustrated), which is configured to make the whole assembly more rigid and resistant and allows the flatness defects to be reduced, in particular in connection with the space transformer 4, which has generally very reduced thicknesses and which has thus considerable flatness problems.

[0018] The spatial transformation performed by the space transformer 4 concerns in particular the distances between the centres of the contact pads formed on the opposite faces thereof, in particular a first face FA facing the probe head 1 at the contact heads 3B of the contact probes 2 and connected by means of suitable metallizations to a second plurality of contact pads formed on a second opposite face FB thereof facing the main board 7, said second plurality of contact pads having a different spatial distribution, in particular with centres of the pads at a greater distance, namely greater pitches compared to the pitch of the first plurality of contact pads, which are instead distributed in a manner substantially corresponding to the contact pads 5A of the device under test 5 so that the space transformer 4 can perform the desired spatial transformation, by moving away the contact pads formed on the second face FB thereof with respect to the contact pads formed on the first face FA thereof. They are commonly referred to as probe side pad or fine pitch and as PCB side pad or large pitch to indicate the contact pads on the first face FA and on the second face FB, respectively.

[0019] In the vertical probe technology, it is important to ensure the good connection of the contact probes with the device under test, particularly at the contact tips thereof, and with the testing apparatus, particularly at the contact heads thereof and thus at the space transformer, which plays a very important role especially in the testing operations of integrated circuits formed according to the most recent integrationtechnologies which provide for contact pads on the devices under test which are extremely close and very small in size, constraints which are poorly compatible with the PCB technology through which the main board of the probe card is formed.

[0020] The mutual positioning of the elements composing the probe card turns out to be an extremely important parameter for a correct operation of the card itself and the different technologies used to make said elements introduce flatness problems which complicate the configuration of the card as a whole and especially in connection with the mutual positioning of the space transformer and main board. Even the presence of the stiffener, which makes the whole assembly more rigid and resistant, generally does not allow the flatness defects of the space transformer to be eliminated in a sufficient way and the correct and complete contact thereof with the main board to be ensured.

[0021] The whole thing is further complicated by the operating temperature of the card itself, in particular in case of testing operations at extreme temperatures. In that case, in fact, the thermal expansions of the elements composing the probe card can affect the correct behaviour thereof, in particular due to the different thermal expansion coefficients of the different materials which said elements are made of. It is in fact usual to bind together the elements composing a probe card by means of screws, which, in particular during temperature testing operations, apply to the different boards a constraint which tends to cause a warpage thereof, resulting in a malfunction of the probe card as a whole, to the limit even in the lack of contact of the contact probes of the probe head with the contact pads of the device under test.

[0022] This problem is particularly felt in the case of large-sized probe cards, such as for example the probe cards for the testing operations of storage devices such as DRAMs. For this type of probe cards, the lack of control of the thermal expansion of the components involves considerable problems in the testing phase.

[0023] Moreover, during the testing operations, the contact probes heat up due to the passage of the several signals, increasing the heat that is present inside the probe head, in particular in case of a probe headprovided with a very high number of contact probes.

[0024] Similarly, the abutment of said contact probes onto the pads of the space transformer and the transport of the signals therein from the probe side pads to the PCB side pads produce an undesirable heat that accumulates in the probe card, in particular in the space transformer through which the thermal power generated by the probes, indicated as passive thermal power, passes.

[0025] However, most of said passive thermal power is conveyed and dispersed at the device under test, although a part remains confined in the space transformer. The passive thermal power that must be dissipated by the space transformer is limited to overall values of approximately 30W of equivalent electrical power and is usually transported outside the space transformer toward the main board simply by the system of welds and metal tracks that are already present in the space transformer, in the interface layer and in the main board.

[0026] However, the most recent probe cards also comprise active components or dies, which can be positioned in mechanical and thermal contact with the space transformer. Said active components generate an active thermal power which is completely discharged in the space transformer. Unfortunately, said active thermal power has values that are equal to 30-35W of equivalent electrical power for each of the active components. Considering the use of even only a limited number of active components, for example four components arranged in contact with the space transformer, this results in an active thermal power that is higher than 100W of equivalent electrical power, that cannot be dissipated simply by the transport through the welds.

[0027] The technical problem underlying the present invention is to devise a probe card, having such structural and functional features as to allow the limitations and drawbacks still affecting the probe cards formed with known technologies to be overcome, promoting the removal of the heat being produced during the testing operations by active devices housed therein and limiting the increase in the operating temperature of the probe card and the probe head contained therein.Disclosure of Invention

[0028] The solution idea underlying the present invention is to provide the probe card with an active thermal exchange mechanism, in particular using a cooling (cooling) fluid circulating in microfluidic channels arranged in a thermal dissipation system at active devices housed on the space transformer and in direct or indirect thermal contact with said active devices to draw heat and transport it outside the probe card.

[0029] Based on said solution idea the technical problem is solved by a probe card adapted to be inserted in an apparatus for testing electronic devices, said probe card comprising at least one probe head housing a plurality of contact probes, each contact probe having at least one first end portion adapted to abut onto contact pads of a device under test and a second end portion adapted to abut onto corresponding contact pads formed on a first face of a space transformer facing the device under test, as well as a main board connected to the space transformer and one or more active devices housed on the first face of the space transformer, characterized in that it further comprises a thermal dissipation system including at least one manifold provided with one or more microfluidic channels in which a cooling fluid circulates, said microfluidic channels being in direct or indirect thermal contact with one or more of the active devices to collect and dissipate heat produced by said active devices as active thermal power.

[0030] More particularly, the invention comprises the following additional and optional features, taken individually or in combination if necessary.

[0031] According to an aspect of the invention, the microfluidic cooling system can be formed inside a mounting ring of the probe head on the main board and can comprise portions passing through the main board at an opening thereof.

[0032] According to another aspect of the invention, the manifold can have a first end in contact with at least one of the active devices and a second end at the opening of the main board and the microfluidic channels can comprise at least one inlet fluid passageway and one outlet fluid passageway extending between the first and second ends of the manifold.

[0033] In particular, the inlet fluid passageway can receive and distributean inlet cooling fluid flow and the outlet fluid passageway can collect an outlet cooling fluid flow.

[0034] According to another aspect of the invention, the manifold and the microfluidic channels can have a cross-section according to a plane that is orthogonal to a development plane of the space transformer having a shape selected from an L- shape, a broken line shape, a mixed line shape, said shape being adapted to connect the first and second ends of the manifold.

[0035] Still according to another aspect of the invention, the manifold can be in direct thermal contact with at least one of the active devices at the first end of the manifold (31).

[0036] The microfluidic cooling system can further comprise a thermal interface thermally connecting the manifold and the microfluidic channels with one or more of the active devices.

[0037] According to this aspect of the invention, said thermal interface can be positioned on the probe head contained in the probe card.

[0038] The microfluidic cooling system can further comprise insulating material positioned between said thermal interface and the probe head.

[0039] In particular, the thermal interface can be made of a material having a thermal conductivity X that is greater than 500 W / (m*K), preferably greater than 1000 W / (m*K), said material being selected from a graphene-based composite material, diamond and CVD-D (Chemical Vapor Deposition-Diamond), preferably a graphene-based composite material.

[0040] According to another aspect of the invention, the manifold can be in direct thermal contact with the space transformer at the first end of the manifold.

[0041] Still according to another aspect of the invention, the manifold can be in direct thermal contact with a peripheral portion of the space transformer in which the active devices are housed.

[0042] According to this aspect of the invention, the microfluidic cooling system can further comprise a thermal interface thermally connecting the manifold and the microfluidic channels with the peripheral portion of the space transformer.Said thermal interface can be formed positioned on the probe head contained in the probe card.

[0043] Furthermore, the microfluidic cooling system can further comprise insulating material positioned between the thermal interface and the probe head.

[0044] Finally, the thermal interface can be made of a material having a thermal conductivity X that is greater than 500 W / (m*K), preferably greater than 1000 W / (m*K), said material being selected from a graphene-based composite material, diamond and CVD-D (Chemical Vapor Deposition-Diamond), preferably a graphene-based composite material.

[0045] The features and advantages of the probe card according to the invention will be apparent from the following description of exemplary embodiments thereof given by way of non-limiting examples with reference to the attached drawings.

[0046] Brief description of the drawings

[0047] In the drawings:

[0048] - Figure 1 shows a schematic sectional view of a probe card formed according to the prior art;

[0049] - Figure 2 shows a schematic sectional view of a probe card according to an embodiment of the invention; and

[0050] - Figures 3A-3C and 4A-4B show respective schematic sectional views of alternative embodiments of the probe card of Figure 2.

[0051] Detailed description

[0052] With reference to the figures, and particularly to Figure 2, a probe card comprising at least one probe head provided with a plurality of contact probes for testing electronic devices, in particular integrated on wafers, formed according to the present invention, is globally indicated with 20.

[0053] It should be noted that the figures represent schematic views of the card according to the invention and are not drawn to scale, but instead they are drawn so as to emphasize the important features of the invention.

[0054] Moreover, the several aspects of the invention represented by way ofexample in the figures are obviously combinable with each other and interchangeable from one embodiment to another.

[0055] In the following description, relative terms such as “above”, “below”, “upward”, “downward”, “upper”, “lower” will be used referring to the illustrations of the different elements given in the figures only to simplify the exposition thereof.

[0056] Finally, indications of particular geometries (circular, rectangular) or of the arrangement of the elements (parallel, orthogonal, contiguous) as well as the term “substantially” are always to be intended in connection with physical and not geometrically abstract elements, and thus they must always take into consideration the tolerances introduced by the transition from a pure mathematical / geometric world to the real world.

[0057] In particular, as illustrated in Figure 2, the probe card 20 comprises a probe head 11 including a containment element or housing 12 housing a plurality of contact probes 13, eight in the example, only for simplicity of illustration, a probe head 11 actually comprising a much higher number of contact probes 13. Considering the case of a probe head 11 of the unblocked probe vertical type, the containment element 12 comprises at least one upper plate or guide and a lower plate or guide, having respective guide holes through which the contact probes 13 slide and made integral by an appropriate housing.

[0058] Each of the contact probes 13 comprises at least one first end portion or contact tip 13A adapted to abut onto a corresponding contact pads 15A of a device under test 15, in particular integrated on a semiconductor wafer 16, so as to establish the desired contact, in particular an electrical contact, between the contact probes 13 of the probe head 11 and the contact pads 15A of the device under test 15.

[0059] Each contact probe 13 further comprises a second end portion or contact head 13B adapted to establish the contact with a main board 17 or main PCB for connection with a testing apparatus (not illustrated). A rod-shaped probe body is arranged between the contact head 13B and the contact tip 13A and substantially arranged along a longitudinal development direction of the contact probe 13, that is in particularorthogonal to a plane on which the semiconductor wafer 16 is arranged, where the device under test 15 is integrated, that is along the Z axis of the local reference of Figure 2.

[0060] The probe head 11 is associated with the main board 17 by means of a mounting ring 21 passing through the main board 17 at an opening 17A formed therein, in particular a substantially circular opening 17A. The term “circular” means here and below a closed element non necessarily having a circle-shaped section, although the circular section is the preferred section, always taking into consideration the tolerances and the local variations of a physical world compared to a pure mathematical world.

[0061] The probe card 20 further comprises an intermediate board arranged between the probe head 11 and the main board 17 and adapted to perform a spatial transformation, in particular in connection with the distribution of contact pads on the opposite faces thereof and for this reason indicated as space transformer 14.

[0062] The space transformer 14 has a first face FA facing the probe head 11 (in the operating conditions, i.e. when the space transformer 14 is inserted into a probe card 20 comprising the probe head 11 and inserted as an end element of a testing apparatus), a first plurality of contact pads being formed on said first face FA, onto which the contact heads 13B of the contact probes 13 abut. Said first face FA is also indicated as probe side face.

[0063] The space transformer 14 further has a second face FB, opposite the first face FA, facing the main board 17 in the operating conditions and connected thereto at an interface layer 18. Said second face FB is thus also indicated as tester side face.

[0064] Similarly, the main board 17 has a first face FC facing the space transformer 14 at the interface layer 18 and a second face FD, opposite the first face FC and facing the testing apparatus (not illustrated).

[0065] The interface layer 18 comprises a plurality of connection elements 18A, such as for example spherical elements or mechanical and electrical connection balls between the space transformer 14 and the main board 17.The space transformer 14 is usually formed as an organic multilayer or MLO (acronym for “MultiLayer Organic”) associated with a rigid support, for example glued thereto, said MLO including a plurality of layers of organic material that form a plurality of non-conductive layers, one or more conductive layers being arranged on said non-conductive layers in a suitable configuration, adapted to make the internal conductive paths to connect the contact pads arranged on the faces thereof. The rigid support is preferably a ceramic support.

[0066] Alternatively, in place of an organic multilayer MLO, it is also possible to use a ceramic-based multilayer or MLC (acronym for “MultiLayer Ceramic”), that comprises a plurality of layers of rigid ceramic material with a high degree of flatness, interspersed with conductive layers that connect contact pads made on the opposite faces of the space transformer 14.

[0067] Furthermore, the space transformer 14 can be formed as a silicon multilayer in which suitable connection metal tracks are formed, also indicated as SI (acronym for “Silicon Interposer”) .

[0068] The probe card 20 can also comprise a stiffener (not illustrated) associated with the main board 17 and adapted to improve the flatness thereof and to avoid the curvature thereof, in particular in case of an increase in temperature during the operation of the probe card 20, i.e. during the testing operations.

[0069] In accordance with the most recent embodiments, one or more active devices or dies 19 are further arranged on the space transformer 14, in particular at the first face FA thereof facing the probe head 11 (probe side face). These active devices 19 can be mounted on the space transformer 14 by welding or other bonding system. In the example of the figure, only two active devices 19A and 19B are shown for simplicity of illustration.

[0070] As it is well known, the active devices 19A, 19B have a high-power consumption, which can reach 30-35W for each single device. Considering to house on the space transformer 14 four active devices, arranged in particular outside an active area of the space transformer 14, i.e. the area where the contact pads are formed, onto which the contact heads 13B of the contact probes 13 abut, this results in an additionalpower of 120- OW that is fed into the space transformer 14 and that results in an active thermal power PT2 having a much higher value than a passive thermal power PT 1 that passes through the space transformer 14 due to the signals, in particular the currents, that pass through the contact probes 13 during the normal testing operations of the device under test 15 based on the well-known Joule effect. As already explained in connection with the prior art, said passive thermal power PT 1 is in fact only linked to a residue of the power due to the current that passes through the contact probes 13, most of which is instead discharged just on the device under test 15.

[0071] Advantageously according to the present invention, the probe card 20 comprises a heat dissipation system shaped as a microfluidic cooling system 30, adapted to draw thermal power, i.e. heat from inside the probe card 20 and to transport it outside it, so as to be able to disperse it and consequently cool the elements of said probe card 20, in particular the active devices 19A, 19B, but also the space transformer 14 which are the elements of the probe card 20 heating up the most. In particular, the microfluidic cooling system 30 according to the present invention is able to collect and disperse the active thermal power PT2 generated by the active devices 19A, 19B in a very effective manner, using a cooling fluid flowing in suitable microfluidic channels formed in said microfluidic cooling system 30 in direct or indirect thermal contact with the active devices 19A, 19B, as explained in more detail below.

[0072] In a first embodiment, schematically illustrated in Figure 2, the microfluidic cooling system 30 is formed inside the mounting ring 21 of the contact head 11 in the probe card 20, portions of said micro fluidic cooling system 30 passing through the main board 17 of the probe card 20 at the circular opening 17A arranged therein. More particularly, the microfluidic cooling system 30 comprises a manifold 31 with a substantially toroidal pattern which develops around the space transformer 14 and passes through the main board 17 at the circular opening 17A. In particular, the manifold 31 has a first end 31A positioned in contact with the active devices 19A, 19B housed on the space transformer 14 and a second end 3 IB positioned at the second face FDof the mam board 17 facing the testing apparatus at the opening 17A. Said manifold 31 has a cross-section, according to a plane that is orthogonal to a development plane n of the semiconductor wafer 16 and of the space transformer 14 in the direction of the Z axis of the local reference of the figures, having an L-shaped pattern between the first end 31A and the second end 3 IB.

[0073] Furthermore, the manifold 31 has a longitudinal section, according to said development plane n in the direction of the Y axis of the local reference of the figures, with a substantially circular pattern like the opening 17A.

[0074] Suitably, the microfluidic cooling system 30 is in direct or indirect thermal contact with the active devices 19A, 19B housed on the space transformer 14 at the first end 31A of the manifold 31, so as to be able to collect and disperse the heat, i.e. the active thermal power PT2 produced by said devices, in particular using a cooling fluid flowing in suitable microfluidic channels 32, 33 formed in the manifold 31 itself. Here and below, two elements are indicated as in direct thermal contact when they are able to exchange heat, i.e. thermal power with each other and in indirect thermal contact when the heat, i.e. thermal power, exchange occurs through intermediate elements.

[0075] More particularly, as schematically illustrated in Figure 3A, the microfluidic cooling system 30 comprises the manifold 31 provided with one or more microfluidic channels or conduits 32, 33, for a suitable fluidic material to pass through, in particular a cooling fluid adapted to collect and transport heat, in the example of the figure two by simple way of example. In particular, the manifold 31 comprises a fluid inlet conduit or inlet fluid passageway 32 that receives an inlet flow Fin of fluidic material, that is then distributed in the manifold 31 and collected as an outlet flow Font by a fluid outlet conduit or outlet fluid passageway 33. Obviously, it is possible to use any number of inlet and outlet fluid passageways, depending on the specific requirements of the probe card 20.

[0076] Like the manifold 31 , the microfluidic channels or fluid passageways 32, 33 also have L-shaped cross-section between the first end 31A andthe second end 3 IB of the manifold 31.

[0077] It is possible to envisage different geometries for the cross-sections of the manifold 31 and of the microfluidic channels 32, 33 housed therein, in particular comprising more straight and non-straight segments, for example broken or mixed line shaped, always adapted to connect the first end 31A and the second end 3 IB of the manifold 31.

[0078] Suitably, the manifold 31 is in direct thermal contact with at least one of the active devices 19, at the first end 31A. In particular, the inlet fluid passageway 32 and the fluid outlet passageway 33 of the manifold 3 1 are in direct thermal contact with one or more of the active devices 19 at the first end 31A of the manifold 31. Thereby, an inlet cooling fluid flow Fin, which is received by the inlet fluid passageway 32, is brough into contact with one or more of the active devices 19 and is then collected as an outlet cooling fluid flow Font by the outlet fluid passageway 33, so as to collect and remove heat, in particular the active thermal power PT2 generated by the active devices 19, transporting it outside the probe card 20 so as to disperse it.

[0079] In the example of Figure 3A, the inlet fluid passageway 32 and the outlet fluid passageway 33 are in lateral direct thermal contact with a first active device 19A and a second active device 19B, by simple way of example, since the probe card 20 may comprise more than two active devices in thermal contact with the fluid passageways 32, 33 of the manifold 31.

[0080] In a further embodiment schematically illustrated in Figure 3B, the inlet fluid passageway 32 and the outlet fluid passageway 33 are in direct thermal contact with the first active device 19A and with the second active device 19B extending along a whole surface thereof arranged toward the device under test 15.

[0081] In an alternative embodiment schematically illustrated in Figure 3C, the microfluidic cooling system 30 further comprises a thermal interface 34 thermally connecting the manifold 31, and thus the fluid passageways 32, 33 contained therein, with one or more of the active devices 19. In that case too, the microfluidic cooling system 30 is in direct thermal contact with one or more of the active devices 19.Suitably, said thermal interface 34 is formed at the probe head 11 contained in the probe card 20, in particular at the housing 12 thereof. Furthermore, an insulating material 35 can be positioned between the thermal interface 34 and the housing 12, used to decrease or avoid heat dispersions toward the probe head 11 and thus inside the probe card 20. In fact, the overall dimensions of the contact head 11 make it completely exposed to the temperature of the chuck supporting the device under test 15, in particular at the active devices 19A and 19B and also at the thermal interface 34. The insulating material 35 thus prevents the heat of the chuck, which can even reach values of 125°C in the so-called “hot” tests, from reaching the thermal interface 34, decreasing the overall cooling effect of the microfluidic cooling system 30.

[0082] The thermal interface 34 can be made of a material having a high thermal conductivity X, i.e. greater than 500 W / (m*K), preferably greater than 1000 W / (m*K), so as to maximize the collection of the heat, i.e. of the active thermal power PT2 produced by the active devices 19.

[0083] Preferably, the thermal interface 34 is made of a material selected from a graphene-based composite material, diamond and CVD-D (Chemical Vapor Deposition-Diamond), more preferably a graphenebased composite material, which is less delicate than diamond. It is noted that said materials, for example diamond, can reach values of thermal conductivity X that are equal to 2000-2500 W / (m*K).

[0084] In the example of Figure 3C, the probe card 20 comprises a first active device 19A and a second active device 19B, in contact with respective portions 34A, 34B of the thermal interface 34, provided in turn with respective portions 35A, 35B of the insulating material 35.

[0085] The microfluidic cooling system 30 provided with the manifold 31 and with the fluid passageways 32, 33, and possibly with the thermal interface 34 in direct thermal contact with the active devices 19 forms an effective mechanism for removing the heat, i.e. the active thermal power PT2, produced by said active devices 19.

[0086] In an alternative embodiment, as shown in Figure 4A, it is possible to form the manifold 31 and the fluid passageways 32, 33 thereof in direct thermal contact with the space transformer 14 and in indirect thermalcontact with the active devices 19. In that case, the microfluidic cooling system 30 is able to collect and disperse the active thermal power PT2 generated by the active devices 19 by cooling the space transformer 14 housing said active devices 19.

[0087] Suitably, in an advantageous embodiment, the active devices 19 are arranged on the space transformer 14 at a peripheral portion 14A thereof which is in contact with the first end 31A of the manifold 31 and thus in contact with the passageways 32, 33 formed therein. The peripheral portion 14A has a substantially toroidal pattern with a longitudinal section on the plane n with a substantially circular pattern, in particular ring-shaped. Different shapes may be taken into consideration for the longitudinal section of said peripheral portion 14A, for example rectangular, square or broken or mixed line-shaped, said shape substantially depending on the longitudinal section of the space transformer 14.

[0088] It should be noted that the positioning of the active devices 19 at the peripheral portion 14A of the space transformer 14 is also suitable to avoid the active area of the space transformer 14, i.e. the area in which the contact pads are formed, onto which the contact heads 13B of the contact probes 13 abut.

[0089] According to a further alternative embodiment shown in Figure 4B, the microfluidic cooling system 30 comprises a thermal interface 34 thermally connecting the manifold 31, and thus the fluid passageways 32, 33 contained therein, with the space transformer 14 at the peripheral portion 14A thereof in which the active devices 19 are positioned.

[0090] In that case too, the thermal interface 34 can be suitably formed at the probe head 11 contained in the probe card 20, in particular at the housing 12 thereof, and an insulating material 35 can be positioned between the thermal interface 34 and said housing 12, to decrease or avoid heat dispersions toward the probe head 11 and thus inside the probe card 20, in particular avoiding heat infiltrations from the chuck, as explained above.

[0091] In this case too, the thermal interface 34 can be made of a material having a high thermal conductivity X, i.e. greater than 500 W / (m*K),preferably greater than 1000 W / (m*K), so as to maximize the heat collection from the space transformer 14, mainly due to the active thermal power PT2 of the active devices 19 housed thereon.

[0092] As already indicated, said thermal interface 34 can be made of a material selected from a graphene-based composite material, diamond and CVD-D (Chemical Vapor Deposition-Diamond), preferably a graphene-based composite material.

[0093] In the example of Figure 4B, the probe card 20 comprises a first active device 19A and a second active device 19B, in contact with respective portions 34A, 34B of the thermal interface 34, provided in turn with respective portions 35A, 35B of the insulating material 35.

[0094] The cooling fluid flowing in the fluid passageways 32 and 33 in thermal contact with the space transformer 14 allows the micro fluidic cooling system 30 of Figures 4A and 4B to perform an effective thermal exchange, although being smaller than that performed by the microfluidic cooling system 30 of Figures 3A and 3B, where the fluid passageways 32, 33 are in direct thermal contact with the active devices 19. The microfluidic cooling system 30 of Figures 4A and 4B is however simpler to manufacture and position, with no risk of touching and damaging the active devices 19A, 19B

[0095] In conclusion, advantageously according to the invention, the probe card provided with a microfluidic cooling system is able to effectively disperse heat produced by active devices housed on the space transformer thereof, by direct cooling of said active devices or by cooling of the space transformer housing them.

[0096] It is noted that the active thermal power generated by the active devices is located in particular on the face of the space transformer facing the probe head and thus toward the device under test, in extremely reduced spaces, where the dissipation thereof turns out to be extremely important for a correct operation of the space transformer itself and of the probe card as a whole, more so in applications in which said probe card has to operate at high temperatures (so-called “hot conditions”).

[0097] Suitably, the microfluidic cooling system according to the present invention is able to effectively dissipate the heat produced by activedevices housed on the space transformer and thermally connected thereto, indicated as active thermal power.

[0098] Thereby, the probe card turns out to be suitable for applications in which the testing operations considerably heat the card as a whole, ensuring a correct operation thereof and avoiding any deformation of the elements composing it, deformation which could affect the good outcome of the testing operations, in particular in the case in which a plurality of active devices are housed on the space transformer of said probe card.

[0099] The heat dispersion turns out to be further improved due to the use of a thermal interface thermally connecting the cooling fluid passageways with one or more of the active devices or with the portion of the space transformer in which they are housed, said thermal interface being suitably made of a material having a high thermal conductivity X.

[0100] Furthermore, it is noted that the manufacture of the microfluidic cooling system at the mounting ring of the probe card, as well as the manufacture of the circular opening in the main board, are particularly simple and thus do not bring critical issues in the manufacturing process of the card itself.

[0101] Obviously, in order to meet contingent and specific requirements, a person skilled in the art will be allowed to bring several modifications and alternatives to the above-described probe card, all falling within the scope of protection of the invention as defined by the following claims.

Claims

CLAIMS1. A probe card (20) adapted to be inserted in an apparatus for testing electronic devices, said probe card (20) comprising at least one probe head (11) housing a plurality of contact probes (13), each contact probe (13) having at least one first end portion (13A) adapted to abut onto contact pads (15A) of a device under test (15) and a second end portion (13B) adapted to abut onto corresponding contact pads formed on a first face (FA) of a space transformer (14) facing said device under test (15), as well as a main board (17) connected to said space transformer (14) and one or more active devices (19; 19A, 19B) housed on said first face (FA) of said space transformer (14) and in thermal contact with said space transformer (14), characterized in that it further comprises a micro fluidic cooling system (30, 40) including at least one manifold (31) provided with one or more microfluidic channels (32, 33) in which a cooling fluid circulates, said microfluidic channels (32, 33) being in direct or indirect thermal contact with one or more of said active devices (19; 19A, 19B) to collect and dissipate heat produced by said active devices (19; 19A, 19B) as active thermal power (PT2).

2. The probe card (20) according to claim 1, characterized in that said microfluidic cooling system (30) is formed inside a mounting ring (21) of said probe head (11) on said main board (17) and comprises portions passing through said main board (17) at an opening (17A) thereof.3 The probe card (20) according to claim 2, characterized in that said manifold (31) has a first end (31 A) in contact with at least one of said active devices (19; 19A, 19B) and a second end (3 IB) at said opening (17A) of said main board (17) and in that said microfluidic channels (32, 33) comprise at least one inlet fluid passageway (32) and one outlet fluid passageway (33) extending between said first and second ends (31A, 3 IB) of said manifold (31).4 The probe card (20) according to claim 3, characterized in that said inlet fluid passageway (32) receives and distributes an inlet cooling fluid flow (Fin) and in that said outlet fluid passageway (32B) collects an outlet cooling fluid flow (Font).5 The probe card (20) according to claim 3, characterized in that said manifold (31) and said microfluidic channels (32, 33) have a cross-section according to a plane that is orthogonal to a development plane of said space transformer (14) having a shape selected from an L-shape, a broken line shape, a mixed line shape, said shape being adapted to connect said first and second ends (31A, 3 IB) of said manifold (31).

6. The probe card (20) according to claim 4, characterized in that said manifold (31) is in direct thermal contact with at least one of said active devices (19; 19A, 19B) at said first end (31A) of said manifold (31).

7. The probe card (20) according to claim 6, characterized in that said microfluidic cooling system (30) further comprises a thermal interface (34; 34A, 34B) thermally connecting said manifold (31) and said microfluidic channels (32, 33) with one or more of said active devices (19; 19A, 19B).

8. The probe card (20) according to claim 7, characterized in that said thermal interface (34; 34A, 34B) is positioned on said probe head (11) contained in said probe card (20).

9. The probe card (20) according to claim 8, characterized in that said microfluidic cooling system (30) further comprises insulating material (35; 35A, 35B) positioned between said thermal interface (34; 34A, 34B) and said probe head (11).

10. The probe card (20) according to claim 8, characterized in that said thermal interface (34; 34A, 34B) is made of a material having a thermal conductivity X that is greater than 500 W / (m*K), preferably greater than 1000 W / (m*K), said material being selected from a graphene-based composite material, diamond and CVD-D (Chemical Vapor Deposition-Diamond), preferably a graphene-based composite material.

11. The probe card (20) according to claim 4, characterized in that said manifold (31) is in direct thermal contact with said space transformer (14) at said first end (31A) of said manifold (31).

12. The probe card (20) according to claim 11, characterized in that said manifold (31) is in direct thermal contact with a peripheralportion (14A) of said space transformer (14) in which said active devices (19; 19A, 19B) are housed.

13. The probe card (20) according to claim 12, characterized in that said microfluidic cooling system (30) further comprises a thermal interface (34; 34A, 34B) thermally connecting said manifold (31) and said microfluidic channels (32, 33) with said peripheral portion (14A) of said space transformer (14).

14. The probe card (20) according to claim 13, characterized in that said thermal interface (34; 34A, 34B) is formed positioned on said probe head (11) contained in said probe card (20).

15. The probe card (20) according to claim 13, characterized in that said microfluidic cooling system (30) further comprises insulating material (35; 35A, 35B) positioned between said thermal interface (34; 34A, 34B) and said probe head (11).

16. The probe card (20) according to claim 13, characterized in that said thermal interface (34; 34A, 34B) is made of a material having a thermal conductivity X that is greater than 500 W / (m*K), preferably greater than 1000 W / (m*K), said material being selected from a graphene-based composite material, diamond and CVD-D (Chemical Vapor Deposition-Diamond), preferably a graphene-based composite material.

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