Contact probe for probe heads of electronic devices and related probe head

Abstract

It is herein described a contact probe (11) having a first end portion (12) which ends with a contact tip (12A) configured to abut onto a contact pad of a device under test and a second end portion (13) which ends with a contact head (13A) configured to abut onto a contact pad of an interface board for a testing apparatus, as well as a probe body (14) extended between said first end portion (12) and said second end portion (13) according to a longitudinal development axis (HH), the contact probe (11) comprising a first structural element (21) and a second structural element (22), the first structural element (21) including the first end portion (12) and a first probe body portion (23) and the second structural element (22) including the second end portion (14) and a second probe body portion (24), the first probe body portion (23) being adapted to be housed in a hollow portion (24A) of the second probe body portion (24), said contact probe (11) further comprising at least one resistive insert (20) interposed between the first probe body portion (23) and the second probe body portion (24) being adapted for passing a current between said first probe body portion (23) and said second probe body portion (24) opposing a resistance. A related probe head (30) comprising at least one of said probes is also herein described.

Description

[0001] Title: Contact probe for probe heads of electronic devices and related probe head

[0002] DESCRIPTION

[0003] Field of application

[0004] The present invention relates to a contact probe and to a related probe head adapted to perform the test of electronic devices integrated on a semiconductor wafer, in particular for the test of memory devices. The following description is made with reference to this application field with the only purpose of simplifying the exposition thereof.

[0005] Prior art

[0006] As it is well known, a probe head is basically a device adapted to electrically connect a plurality of contact pads of a microstructure, in particular an electronic device under test, or DUT, integrated on wafers, with corresponding channels of a testing apparatus that performs the functionality testing thereof, in particular electric, or generically the test.

[0007] The test, which is performed on integrated devices, is particularly useful for detecting and isolating defective devices as early as in the production phase. Normally, probe heads are therefore used for the electric test of electronic devices that are integrated on wafers before cutting and assembling them inside a chip containment package.

[0008] A probe head usually comprises a high number of contact elements or contact probes formed by special alloys with good electric and mechanical properties and provided with at least one contact portion with one of the contact pads of the device under test.

[0009] More particularly, a vertical probe head comprises a plurality of contact probes housed in guide holes made in at least one, preferably at least one pair of plate guides, parallel to each other and arranged at a certain distance, in order to leave a free area or air gap for the movement and possible deformation of the contact probes. The pair of guides in particular comprises an upper guide, arranged closer to the testing apparatus connected to the probe head, and a lower guide, arranged closer to a wafer comprising the devices under test, both guides being provided with respective guide holes within which the contact probes axially slide.

[0010] In particular, as visible in exemplifying Figure 1, each contact probe 1 comprises at least one first end portion 2 which ends with a contact end adapted to abut onto a pad or contact pad of a device under test 8 integrated on a semiconductor wafer 8’, said contact end being indicated as contact tip 2 A.

[0011] The first end portion 2 comprises a support part 2B adapted to be housed in a respective guide hole of a guide of a probe head comprising the contact probe 1, in particular a guide hole 6A of a lower guide 5, namely a guide arranged close to the device under test 8 during the testing phases of the respective device under test. The first end portion 2 also comprises, contiguous to the support part 2B, a protruding part 2C projecting from the lower guide 6A toward the device under test 8 and ends with the contact tip 2A to make the connection with the pads of the device under test 8 by means of a pressing contact thereon.

[0012] Furthermore, the contact probe 1 comprises a second end portion 3 which ends with a contact end adapted to abut onto a contact pad of an interface board 9 with a testing apparatus, said contact end being indicated as contact head 3A. The second end portion 3 also comprises a support part 3B adapted to be housed in a guide hole of a further guide of the probe head that comprises the contact probe 1, in particular a guide hole 7A of an upper guide 7, namely a guide arranged close to the interface board 9 with the testing apparatus.

[0013] The second end portion 3 further comprises, contiguous to the support part 3B, a protruding part 3C, projecting from the upper guide 6 in the direction of the interface board 9 and ends with the contact head 3A adapted to make the connection with the contact pads of said interface board, by means of a pressing contact thereon.

[0014] The second end portion 3 may also comprise an enlarged portion 5, i.e. with increased diameter, in particular greater than the diameter of the upper guide holes 7A, said enlarged portion 5 being formed in the protruding part 3C, arranged between the support part 3B and the contact head 3 A.

[0015] Finally, the contact probe 1 comprises a probe body 4, substantially rod-shaped and extended between the first end portion 2 and the second end portion 3, according to a longitudinal development axis HH of the contact probe 1, substantially in the z direction of the local reference of Figure 1. In the following description, the term longitudinal will thus be used to indicate elements arranged according to a direction or a plane parallel to the longitudinal development axis HH, thus orthogonal to a development plane n of the device under test (and thus of the wafer in which it is integrated) and of the interface board with the testing apparatus.

[0016] As it is well known, the proper connection between the contact probes of the probe head and the contact pads of the device under test is ensured by the pressure of the probe head on the device itself, the contact probes, movable within the guide holes of the upper and lower guides, undergoing, during said pressing contact, a bending inside the air gap between the guides and a sliding inside the respective guide holes.

[0017] In Electrical Wafer Sort (EWS) testing applications, in particular of memories, a point-to-multipoint type resource sharing configuration, namely with a unique testing apparatus connected to a plurality of devices under test, is required.

[0018] In an implementation of this type in the prior art, as visible in exemplifying Figure 2, the use of a plurality of “protection” resistors 9A is provided, generally of 300-330ohm, to be set up for each device under test 8, in particular in the interface board 9.

[0019] In this way, in the event of a failure of one of said devices under test, the respective protection resistor “isolates” the failure while still allowing the proper operation of the other devices connected to the same testing apparatus.

[0020] This solution, although effective and widely used, is particularly complex from the point of view of practical implementation.

[0021] Indeed, a test in which the potential of a single testing apparatus is fully used may also include 2000-2500 devices tested simultaneously, each of which can require up to twenty resistors.

[0022] It is therefore easy to deduce that it may be necessary to install almost 50,000 resistors on a single device.

[0023] It is easy to understand how this request, as mentioned, is particularly burdensome and is also subject to multiple possibilities of error.

[0024] The technical problem of the present invention is thus to provide a configuration of a contact probe for a vertical technology probe head able to overcome the drawbacks still affecting the current prior art solutions, in particular in the parallel test of a plurality of devices.

[0025] An object of the invention is also to provide a solution that is highly effective.

[0026] A further object of the invention is to provide a solution that can be adapted according to specific testing needs.

[0027] Finally, an object of the invention is to provide a solution that is easy to maintain.

[0028] Summary of the invention

[0029] The solution idea underlying the present invention is to integrate the protection resistance function against failures of the devices under test in a contact probe. Based on this solution idea, the technical problem is solved by a contact probe having a first end portion which ends with a contact tip configured to abut onto a contact pad of a device under test and a second end portion which ends with a contact head configured to abut onto a contact pad of an interface board for a testing apparatus, as well as a probe body extended between the first end portion and the second end portion according to a longitudinal development axis, the contact probe comprising a first structural element and a second structural element, said first structural element including the first end portion and a first probe body portion and said second structural element including the second end portion and a second probe body portion, the first probe body portion being adapted to be housed in a hollow portion of the second probe body portion, the contact probe further comprising at least one resistive insert interposed between the first probe body portion and the second probe body portion being adapted for passing a current between the first probe body portion and the second probe body portion opposing a resistance.

[0030] Advantageously, the present solution allows eliminating the need to have multiple electrical protection resistors arranged on the testing apparatus and to get the resistor, now advantageously included in each probe, closer to each device under test, thus improving the overall electrical performance.

[0031] More particularly, the invention comprises the following additional and optional features, taken singularly or in combination if needed. According to an aspect of the invention, the resistive insert may at least partially surround, along the longitudinal development axis, the second probe body portion inserted in the hollow portion, said resistive insert being arranged along internal walls of the hollow portion.

[0032] Advantageously, the present solution allows distributing the presence of resistive material in the probe body, thus ensuring a proper operation thereof.

[0033] According to another aspect of the invention, the resistive insert may be made according to a mode selected from: the resistive insert fully fills in a space of the hollow portion left free by the first probe body portion, the resistive insert fully surrounding the first probe body portion; the resistive insert only partially fills in the space of the hollow portion left free by the first probe body portion; the resistive insert is arranged along a single wall of the hollow portion; or the resistive insert comprises a portion of the first probe body portion inserted in the hollow portion.

[0034] Still according to another aspect of the invention, the hollow portion may comprise a transversal closing portion adjacent to the resistive insert and to an end of the first probe body portion opposite the first end portion, so as to ensure an insulation between the first structural element and the second structural element of the contact probe.

[0035] In particular, the transversal closing portion may be filled in with air or made of a resistive material, preferably of a same resistive material which forms the resistive insert, integral therewith. Advantageously, said configuration allows having a homogeneous behaviour of the entire probe, maximizing the resistive function thereof. Moreover, the integral variant is easier from the point of view of the manufacturing and assembly of the contact probe.

[0036] According to another aspect of the invention, the hollow portion may have a longitudinal development dimension comprised between 200 and 3000 pm and a transversal dimension, orthogonal to the longitudinal development axis, comprised between 20 pm and 100 pm.

[0037] Furthermore, the closing portion may have a height along the longitudinal development axis comprised between 10 pm and 50 pm.

[0038] The modulation of these values modifies the overall dimensions of the resistive insert and therefore allows to advantageously adapt the resistivity of each portion of the contact probe and of the probe as a whole to the operational needs.

[0039] According to another aspect of the invention, the resistive insert may have a resistance comprised between 250 O and 400 O, preferably between 280 > and 350 Q, more preferably between 300 £1 and 330 Q, so as to adapt to the several usage scenarios of the contact probe that includes it.

[0040] Furthermore, the resistive insert may be made of plastic materials.

[0041] Advantageously, said class of materials are very effective but meanwhile easy to find and therefore low cost. More preferably, the at least one resistive insert comprises partially electrically conductive composite materials or carbon materials or high resistivity metal materials.

[0042] Advantageously, these specific materials ensure optimal resistivity features, but also mechanical resistance ones, the latter feature being always required given the stresses to which the probes are subjected during the implementation of the various connections.

[0043] According to a further aspect of the invention, the resistive insert may be made by means of a multilayer, which allows optimizing the resistivity values inside the probe body and using consolidated production processes of the contact probes.

[0044] Furthermore, the probe body may have a pre-deformed shape with a curvilinear configuration in rest conditions, comprising at least one bend, preferably two bends.

[0045] Advantageously, this configuration is optimal in particular in the case of short probes, such as those used in high frequency solutions.

[0046] According to a further aspect of the present invention, a probe head is provided for verifying the functionality of an integrated device under test including at least one guide provided with a plurality of guide holes adapted to house respective contact probes, each contact probe being provided with at least one end portion adapted to abut onto contact pads of said device under test, at least one of said contact probes being advantageously made as above described.

[0047] In this way, the probe head may be used for the Electrical Wafer Sort (EWS) testing, in particular of memories, where a point-to-multipoint type resource sharing configuration is required, without having to set up specific protection resistors for the devices under test, each contact probe made as described above also integrating this resistive function.

[0048] The features and advantages of the contact probe and of the probe head according to the invention will be apparent from the description, made hereinafter, of embodiments thereof, given by way of indicative and non-limiting example, with reference to the appended drawings.

[0049] Brief description of the drawings

[0050] In these drawings:

[0051] Figure 1 schematically shows a frontal view of a probe head made according to the prior art;

[0052] Figure 2 schematically shows a memory EWS Testing Application with a sharing configuration of the point-to-multipoint type resources according to the prior art;

[0053] Figures 3A-3D show respective longitudinal and cross- sectional views of a first schematic embodiment of a contact probe according to the present invention;

[0054] Figures 4A-4D, 5A-5D, 6A-6B, 7A-7B show respective cross-sectional or longitudinal views of embodiment variants of a contact probe according to the present invention; and

[0055] Figure 8 schematically shows a frontal view of a probe head made according to the present invention.

[0056] Detailed description

[0057] With reference to these figures, a contact probe made according to the present invention and globally indicated with reference number 11 is described.

[0058] It should be noted that the figures represent schematic views and are not drawn to scale, but instead they are drawn so as to enhance the important features of the invention.

[0059] Furthermore, in the figures, the different pieces are shown schematically, since their shape may vary according to the desired application. Moreover, particular expedients illustrated in a figure in relation to an embodiment may also be used in one or more of the embodiments illustrated in the other figures.

[0060] Furthermore, structurally and functionally equal elements in the several figures, and in particular analogous to the prior art solutions as above described are indicated hereinafter with the same alphanumeric references.

[0061] In the following description, relative terms such as “above”, “below”, “upwards”, “downwards” will be used with reference to the illustrations of the probes and of the probe heads given in the figures with the only purpose of simplifying the exposition thereof.

[0062] 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 relation to physical elements and not to geometrically abstract ones, and therefore must always take into account the tolerances introduced by the passage from a pure mathematical / geometric world to the real world.

[0063] The contact probe 11 according to the present invention is made to be implemented inside a probe head which, in an EWS testing application, in particular of memories, unlike the prior art, does not need to be punctually connected to a related so-called protection resistor.

[0064] Despite the fact that, for simplicity of exposition, the contact probe 11 is represented in the figures with a rectilinear conformation, it is emphasized that it generally provides a probe body 14 with a predeformed shape, in particular having a curvilinear configuration in the rest condition, comprising at least one S-shaped bend, preferably two S- shaped bends, analogously to the probe body of the probes made according to the prior art illustrated in Figure 1.

[0065] Said S-shaped pre-deformed shape is particularly suitable to ensure the proper operation of the contact probe 11 even when its overall dimensions are reduced, for instance in high frequency applications or RF applications.

[0066] As seen in connection to the known solutions, the contact probe 11 comprises the probe body 14 extended between a first end portion 12, which ends with a contact tip 12A adapted to abut onto a contact pad of a device under test (not illustrated) and a second end portion 13 which ends with a contact head 13A adapted to abut onto a further contact pad of an interface board with a testing apparatus (also not illustrated), as explained in connection with the prior art. The second end portion 13 may also comprise an enlarged portion 15, i.e. a portion having a transversal diameter Db greater than a transversal diameter De of the probe body 14, transversal diameter herein and hereinafter indicating a maximum dimension of a cross-section, namely perpendicular to a longitudinal development axis HH of the probe, in particular along the z axis of the local reference of the figure, said section can be of any shape, even non-circular.

[0067] More particularly, the diameter De of the probe body 14 has values comprised between 20 and 100 pm and the diameter Db of the enlarged portion 15 has values comprised between 40 and 100 pm.

[0068] Furthermore, according to the present invention, the contact probe 11 comprises a first structural element 21 and a second structural element 22, the first structural element 21 including the first end portion 12 and a first probe body portion 23 and the second structural element 22 including the second end portion 14 and a second probe body portion 24.

[0069] The first probe body portion 23 is adapted to be inserted into the second probe body portion 24, with at least one resistive insert 20 interposed between the first probe body portion 23 and the second probe body portion 24 adapted for passing a current between the first probe body portion 23 and said second probe body portion 24 opposing a resistance.

[0070] In the embodiment shown in Figures 3A-3D, a contact probe 11 is shown, in which the second structural element 22 is provided with at least one hollow portion 24A formed in the second probe body portion 24 and adapted to house the second probe body portion 23 of the first structural element 21. Suitably, as visible in Figure 3A which shows a longitudinal section of the contact probe 11 according to the present invention, the resistive insert 20 surrounds the second probe body portion 23 inserted in the hollow portion 24A at least partially along the longitudinal development axis HH, the resistive insert 20 being in particular arranged substantially along internal walls of the hollow portion 24A, interposed between the first probe body portion 23 and the second probe body portion 24, as shown in Figure 3B, which shows a cross section of the contact probe 11 at a first transversal plane n 1 of Figure 3A, positioned in particular in a median section of the probe body 14.

[0071] Likewise, Figures 3C and 3D show respective cross-sections of the contact probe 11 at a second transversal plane n2, positioned at the enlarged portion 15 of the second end portion 13 and at a third transversal plane n3, positioned at a non-tapered section of the first end portion 12 having diameter D2.

[0072] The hollow portion 24A develops in the probe body 14 starting from the first end portion 12 along the longitudinal development direction, namely according to the z axis, so as to allow the coupling of the first probe body portion 23 into the second probe body portion 24, the resistive insert 20 remaining suitably interposed between them and the first end portion 12 projecting from the probe body 14, in particular from the second probe body portion 24.

[0073] In the present embodiment, the hollow portion 24A of the second probe body portion 24 further comprises a transversal closing portion 25 adjacent to the resistive insert 20 and to an upper end 23A of the first probe body portion 23, opposite the first end portion 12. Said closing portion 25 extends by a height H l according to the longitudinal development direction of the contact probe 11 , namely according to the z axis, which varies from 10 to 50 pm.

[0074] In the example illustrated in Figure 3A, the closing portion 25 is made of an empty cavity, in particular filled in with air.

[0075] Advantageously, the closing portion 25 thus made allows for a correct separation between the electrodes made by the first structural element 21 and the second structural element 22 of the contact probe 11. Alternatively, the closing portion 25 may be made by means of a dielectric material which also ensures the electrical separation between said structural elements 21 and 22.

[0076] The hollow portion 24A, in the present embodiment, extends longitudinally by a length LI equal to or less than the length LC of the probe body 14, for instance comprised between 200 and 3000 pm. Moreover, the hollow portion 24A has a transversal dimension DI, perpendicularly to the longitudinal development direction HH of the contact probe 11 , namely according to an x axis of the local reference of the figure, having a value comprised between 20 and 50 pm.

[0077] The first probe body portion 23 is inserted into the hollow portion 24A, said first probe body portion 23 having diameter D2 substantially constant and with a value comprised between 200 and 3000 pm up to the first end portion 12, where said diameter D2 narrows until it forms the contact tip 12A, said first end portion 12 ending with a tapered section having length LAI with a value comprised between 100 and 500 pm.

[0078] In the embodiment illustrated in Figure 3A, the hollow portion 24A is positioned centrally in the second probe body portion 24 with respect to the transversal extension of the probe body 14. It is of course possible to make the hollow portion 24A in the second probe body portion 24 in a non-central position.

[0079] Although in the figures the contact tip 12A and the contact head 13A are illustrated as having a tapered shape to form a substantially point-like contact area on the respective contact pads of the device under test and of the interface board, it is obviously possible to make such contact areas not necessarily pointed and / or positioned centrally with respect to the corresponding end portion.

[0080] The resistive insert 20, in the present embodiment, is suitably made with a resistance comprised between 250 £1 and 400 £ , preferably between 280 £1 and 350 £1, more preferably between 300 £1 and 330 £1. An extended range 20-1000 ohm would not be excluded, so as to effectively implement the failure protection function of a device under test connected to the contact probe 11 , as explained in relation to the prior art.

[0081] More specifically, the at least one resistive insert 20 is made of plastic materials, more preferably comprising partially electrically conductive composite materials or carbon materials or high-resistivity metallic materials, materials with a higher resistivity than that which the contact probe 11 is made of. It is emphasized that these materials are particularly suitable for memory EWS testing.

[0082] The resistive insert 20 may also be made by means of a multilayer made of highly resistant materials, or by means of a charged dielectric material so as to make it at least partially conductive.

[0083] Suitably, it is also possible to use composite materials, such as carbon fiber materials or nanotubes to make such resistive insert 20.

[0084] The overall value of resistance of such a resistive insert 20 may be determined not only by the materials used but also by its dimensions, both the extension LI in the hollow portion 24A of the second probe body portion 24, and the thickness of its walls and the height Hl of the closing portion 25.

[0085] It is possible to make the resistive insert 20 so as to completely fill in the space of the hollow portion 24A left free from the first probe body portion 23, such resistive insert 20 therefore completely surrounding the first probe body portion 23.

[0086] Alternatively, the resistive insert 20 is made so as to at least partially fill in the space of the hollow portion 24A left free by the first probe body portion 23, so as to develop along a wall of the hollow portion 24A, arranged according to the y axis of the local reference of the figures and only partially along walls arranged according to the x axis (Figure 4 A) , or along a wall arranged according the x axis and only partially along walls arranged according to the y axis (Figure 4B), or still along a single wall of the hollow portion 24A, a wall arranged according to the y axis (Figure 4C) or according to the x axis (Figure 4D).

[0087] Suitably, the resistive insert 20 may be arranged in a bending plane of the contact probe 11 , namely the plane defined by the x and z axes indicated in Figure 3A, corresponding to the plane of the sheet of the figure.

[0088] According to an embodiment variant of Figure 5A, the space of the hollow portion 24A left free by the first probe body portion 23 passes through said first probe body portion, as also visible from the sectional view according to plane nl of Figure 5B.

[0089] In other words, the space of the hollow portion 24A left free by the first probe body portion 23 is a gap in the first probe body portion 23 having thickness along the X axis analogous to that of the second probe body portion 24 and thickness along the Y axis coinciding with that of the first probe body portion 23.

[0090] The second probe body portion clearly has a shape complementary with said gap and two resistive inserts 20 are provided, which are interposed respectively on the two internal facing walls 27 of said gap.

[0091] Even in the present exemplifying and non-limiting embodiment a closing portion 25 is provided, which is transversal adjacent to the resistive inserts 20 and to an upper end 23A of the first probe body portion 23, opposite the first end portion 12, the closing portion 25 being constituted by an empty cavity, in particular filled in with air.

[0092] According to an embodiment variant of Figure 6A, the contact probe 11 comprises a head portion 25 made of the same material as the at least one resistive insert 20, so as to optimize and maximise the resistive function of the contact probe 11 as a whole. It is also possible to make the closing portion 25 of a resistive material different from that which the rest of the resistive insert 20 is made of, for instance to achieve a shock-absorbing function for the first probe body portion 23 or to strengthen the probe body 14 of the contact probe 11.

[0093] According to a further embodiment variant, shown in Figure 6B, the contact probe 11 comprises a first end portion 12 provided with an enlarged-section area 26, arranged at the second probe body portion 24, so as to strengthen the part of the first structural element 21 in contact with the resistive insert 20. The enlarged-section area 26 has a transversal diameter D3 with values comprised between 40 and 100 pm.

[0094] In the present embodiment, the section variation in the first end portion 12 is step-shaped, but nothing prevents from providing a gradually decreasing section up to the contact tip 12A.

[0095] It is also possible to make the contact probe 11 with a hollow portion 24A which extends not only in the second probe body portion 24, but also in the second end portion 13, as schematically shown in Figure 7A. In this way, the second probe body portion 24 could have a length LI’ with values comprised between 300 and 3000 pm.

[0096] In this way, a homogeneous resistivity distribution is obtained along the longitudinal development HH of the contact probe 11.

[0097] Suitably, the hollow portion 24A may end at an enlarged portion 15 of the second end portion 13, namely in a more robust and less subject to bending area of the contact probe 11 , which reduces the probability of cracking of the probe itself at a terminal area 24C of the hollow portion 24A, which notoriously introduces critical points in the contact probe 11.

[0098] Furthermore, the contact probe 11 may be made with a first probe body portion 23 made at least partially of a resistive material, so as to form the resistive insert 20, the hollow portion 24A having dimensions corresponding to the first probe body portion 23 therein inserted, as shown in Figure 7B.

[0099] Alternatively, the first probe body portion 23 made of a resistive material may be made integral with the resistive insert 20 which extends along the walls of the hollow portion 24A having dimensions greater than said first probe body portion 23.

[0100] Suitably, the first probe body portion 23 made of a resistive material is made so as to extend beyond an edge portion 24B of the second probe body portion 24, so as to ensure the isolation between the electrodes made by the first structural element 21 and by the second structural element 22.

[0101] According to a further variant not illustrated, the first probe body portion 23 made of a resistive material may be arranged in a hollow portion 24A which also extends outside the probe body 14, in particular up to the second end portion 13.

[0102] In all of the embodiments above illustrated, it is possible to modify the behaviour of the contact probe 11 by modifying the dimensions LI and Hl of the hollow portion 24A and those of the related resistive insert 20. Moreover, though not illustrated in the figures, it is possible to make said resistive insert 20 so as to only extend in the hollow portion 24A and to leave an end portion thereof free at the edge portion 24B, the air inside the hollow portion 24A may anyway ensure the isolation between the electrodes made between the first structural element 21 and the second structural element 22 of the contact probe 11.

[0103] Suitably, one or more resistive contact probes 11 of the type above illustrated may be inserted into a probe head 30 for verifying the functionality of a device under test 18, in particular integrated in a semiconductor wafer 18’, as schematically illustrated in Figure 8, the probe head 30 being part of a probe card 40 provided with an interface board 19 for a testing apparatus (not illustrated).

[0104] In the example of Figure 8, the probe head 30 comprises a plurality of contact probes 11 , in particular according to the embodiment of Figures 3A-3D, each contact probe 11 being provided with at least one end portion 12 which ends with a contact tip 12A adapted to abut onto contact pads 18A of the device under test 18 integrated on wafers 18’ and with a second end portion 13 which ends with a contact head 13A adapted to abut onto corresponding contact pads 19A of the interface board 19. The second end portion 13 may also comprise an enlarged portion 15.

[0105] The probe head 30 also comprises at least one plate-shaped support or guide, preferably a pair of supports, namely a lower guide 16 and an upper guide 17 provided with respective pluralities of lower guide holes 16A and of upper guide holes 17A adapted to slidingly house the contact probes 11.

[0106] It is also possible to provide that the probe head 30 comprises resistive contact probes 11 and traditional contact probes, namely not comprising a hollow portion 24A or a resistive insert 20, associated or not with an external protection resistor.

[0107] It is emphasized that a contact probe made according to the present invention allows overcoming the drawbacks of the known solutions, primarily by eliminating the need for individual protection resistors to be assembled for each device under test in the probe card, in particular in its interface board with the testing apparatus.

[0108] Moreover, advantageously, it is possible to get the resistive portion of the contact probes, which acts as a protective resistor, closer to the device under test, thus improving the overall electrical performance. Furthermore advantageously, it is possible to select the best solution for each specific need both from the point of view of required resistance and from a mechanical point of view, thus minimizing any problems of malfunction and damage of the contact probes against any failures of the devices under test.

[0109] Furthermore, advantageously according to the present invention, it is possible to vary the resistivity features of each contact probe by varying the size of its resistive insert and the overall features of a probe head, simply by using contact probes with different resistive features.

[0110] It is also possible to maintain the probe head more easily in case of problems with some contact probes, with a usual replacement operation thereof.

[0111] Obviously, a person skilled in the art, in order to satisfy contingent and specific requirements, may make to the contact probe and to the probe head above described numerous modifications and variations, all included in the scope of protection of the invention as defined by the following claims.

[0112] In particular, it is possible to consider any shape of the contact probe as a whole and / or of the resistive portion therein contained.

[0113] Finally, it is possible to provide the contact probe of the present invention with further features, such as particular geometric configurations of the tip and contact head portions, such as contact tips of smaller dimensions with respect to the probe body or provide the probe with suitable retaining means such as stoppers.

Claims

CLAIMS1. A contact probe (11) having a first end portion (12) which ends with a contact tip (12A) configured to abut onto a contact pad of a device under test and a second end portion ( 13) which ends with a contact head (13A) configured to abut onto a contact pad of an interface board for a testing apparatus, as well as a probe body (14) extended between said first end portion (12) and said second end portion (13) according to a longitudinal development axis (HH), said contact probe (11) comprising a first structural element (21) and a second structural element (22), said first structural element (21) including said first end portion (12) and a first probe body portion (23) and said second structural element (22) including said second end portion (14) and a second probe body portion (24), said first probe body portion (23) being adapted to be housed in a hollow portion (24A) of said second probe body portion (24), said contact probe (11) further comprising at least one resistive insert (20) interposed between said first probe body portion (23) and said second probe body portion (24) being adapted for passing a current between said first probe body portion (23) and said second probe body portion (24) opposing a resistance.

2. The contact probe according to claim 1, wherein said resistive insert (20) at least partially surrounds, along said longitudinal development axis (HH), said second probe body portion (23) inserted in said hollow portion (24A), said resistive insert (20) being arranged alonginternal walls of said hollow portion (24A).

3. The contact probe according to claim 2, wherein said resistive insert (20) is made according a mode selected from: said resistive insert (20) fully fills in a space of said hollow portion (24A) left free by said first probe body portion (23), said resistive insert (20) fully surrounding said first probe body portion (23); said resistive insert (20) only partially fills in said space of said hollow portion (24A) left free by said first probe body portion (23); said resistive insert (20) is arranged along a single wall of said hollow portion (24A); or said resistive insert (20) comprises a portion of said first probe body portion (23) inserted in said hollow portion (24A).

4. The contact probe according to claim 1, wherein said hollow portion (24A) comprises a transversal closing portion (25) adjacent to said resistive insert (20) and to an end (23A) of said first probe body portion (23) opposite said first end portion (12).

5. The contact probe according to claim 4, wherein said transversal closing portion (25) is filled in with air.

6. The contact probe according to claim 4, wherein said transversal closing portion (25) is made of a resistive material.

7. The contact probe according to claim 4, wherein said transversal closing portion (25) is made of a same resistive material that forms said resistive insert (20), integral with said resistive insert (20).

8. The contact probe (11) according to claim 1, wherein said hollow portion (24A) has a longitudinal development dimension (LI)comprised between 200 and 3000 pm and a transversal dimension (DI), orthogonal to said longitudinal development axis (HH), comprised between 20 pm and 100 pm.

9. The contact probe (11) according to claim 4, wherein said closing portion (25) has a height (Hl) along said longitudinal development axis (HH) comprised between 10 pm and 50 pm.

10. The contact probe according to claim 1, wherein said hollow portion (24A) develops in said second probe body portion (24) starting from an end (24B) thereof placed at said first end portion (12) along said longitudinal development axis (HH) to allow a coupling of said first probe body portion (23) in said second probe body portion (24).

11. The contact probe according to claim 10, wherein said hollow portion (24A) extends along said longitudinal development axis (HH) up to said second end portion (13).

12. The contact probe according to claim 11, wherein said second end portion (13) comprises an enlarged portion (15) having a transversal diameter (Db) with values comprised between 40 and 100 pm.

13. The contact probe according to claim 1, wherein said first end portion (12) comprises an enlarged-section region (26), arranged at said second probe body portion (24) .

14. The contact probe according to claim 13, wherein said enlarged-section region (26) has a transversal diameter (D3) with values comprised between 40 and 100 pm.

15. The contact probe (11) according to any one of thepreceding claims, wherein said at least one resistive insert (20) has a resistance comprised between 250 > and 400 Q, preferably between 280 £ and 350 £2, more preferably between 300 £2 and 330 £2.

16. The contact probe (11) according to any one of the preceding claims, wherein said at least one resistive insert (20) is made of plastic materials.

17. The contact probe (11) according to claim 16, wherein said at least one resistive insert (20) comprises partially electrically conductive composite materials or carbon materials or high resistivity metal materials.

18. The contact probe (11) according to any one of the preceding claims, wherein said at least one resistive insert (20) is made by means of a multilayer.

19. The contact probe (11) according to any one of the preceding claims, wherein a probe body (14) has a pre-deformed shape with a curvilinear configuration in the rest conditions, comprising at least one bend, preferably two beds.

20. A probe head (30) for verifying the functionality of a device under test including at least one guide (16, 17) provided with a plurality of guide holes (16A, 17A) adapted to house respective contact probes (11), each contact probe (11) being provided with at least one end portion (12) adapted to abut onto contact pads (18A) of said device under test (18), characterized in that at least one of said contact probes (11) is made according to any one of the preceding claims.

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