Contact probe for a probe head of an electronic device and corresponding probe head - Patents.com

Abstract

The present specification describes a contact probe (20), the contact probe (20) having, in addition to a first end portion (20A) terminating in a contact tip (21A) configured to abut a contact pad (51A) of a device under test (51) and a second end portion (20B) terminating in a contact head (21B) configured to abut a contact pad (61A) of a board (60) of a testing apparatus, a probe body (20C) extending between the first end portion (20A) and the second end portion (20B) along a longitudinal extension axis (HH), the first end portion (20A) comprising a first support portion (22A) interposed between the probe body (20C) and the contact tip (21A). Suitably, the first support (22A) comprises at least one contact pin (24) and one probe length (23) extending parallel to each other along a longitudinal extension axis (HH) and separated by a gap (ZA).

Description

[Technical field]

[0001] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention in its most general aspect relates to contact probes for probe heads of electronic devices and the following description is made with reference to this field of application for the sole purpose of simplifying the explanation thereof. [Background technology]

[0002] As is known, a probe head is essentially a device configured to electrically connect a number of contact pads of an electronic device integrated on a microstructure, in particular a semiconductor wafer, with corresponding channels of a test apparatus performing a functional test, in particular an electrical test, or a test in general.

[0003] The tests performed on the integrated electronic devices are particularly aimed at detecting and isolating defective devices early during the manufacturing stage. Probe heads are typically used to electrically test the electronic devices integrated on the wafer before they are subsequently cut and assembled into chip-containing packages.

[0004] The probe head comprises a number of contact elements or probes, typically formed from a special alloy having good electrical and mechanical properties, and provided with at least one contact portion that contacts one of the contact pads of the device under test.

[0005] More specifically, the vertical probe head comprises a number of contact probes accommodated in guide holes made in at least a pair of plate-like guides, parallel to each other and spaced at a certain distance apart so as to leave a free area or gap for the contact probes to move and ultimately deform, the pair of guides comprising in particular an upper guide positioned closer to the test equipment connected to the probe head and a lower guide positioned closer to the wafer comprising the devices under test, both guides being provided with respective guide holes in which the contact probes slide axially.

[0006] A good 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 against the device; the contact probes, which are movable within the guide holes in the upper and lower guides, bend within the gap between the two guides and slide within their respective guide holes during said pressure contact.

[0007] Furthermore, bending of the contact probe in the gap can be assisted by a suitable configuration of the probe and its guide, as shown diagrammatically in FIG. 1, the probe head shown being of the so-called shifted-plate type.

[0008] In such a case, the probe head 10 comprises at least a pair of upper guides or dies, in particular a first upper guide 16 and a second upper guide 17, which are plate-like and parallel to each other, and a lower guide or die 18, which are provided with respective first upper guide holes 16A, second upper guide holes 17A and lower guide holes 18A, in which the contact probes 11 slide. In other known embodiments not shown, the lower guide can also be divided into one lower guide and an intermediate guide, both of which are provided with suitable guide holes for sliding the contact probes 11.

[0009] The first upper guide 16 and the second upper guide 17 are appropriately shifted with respect to the lower guide 18, the term shifted meaning that the positions of the centers of the respective first upper guide holes 16A, second upper guide holes 17A and lower guide holes 18A are shifted with respect to each other, and instead they are not arranged along the same longitudinal direction, indicated by z in the local reference of the drawing, said longitudinal direction z being perpendicular to the reference plane π corresponding to the lateral development plane of the guides. Furthermore, the first upper guide 16 and the second upper guide 17 are shifted with respect to each other, whereby the contact probes 11 accommodated in the guide holes of the first upper guide 16, second upper guide 17 and lower guide 18 are deformed with respect to their longitudinal development axes HH of the first upper guide 16, second upper guide 17 and lower guide 18 in correspondence with the longitudinal direction z of the local reference of the drawing.

[0010] Each contact probe 11 has a probe body 11C extending substantially along a longitudinal expansion axis HH, and a plurality of contact probes 11 are arranged inside the probe head 10 with the longitudinal expansion axes HH typically oriented perpendicular to the reference plane π.

[0011] Each contact probe 11 has at least one first contact end, denoted as contact tip 11A and configured to abut against a contact pad 12A of a device under test 12 made on a semiconductor wafer 13 deployed on a reference plane π, and a second contact end, denoted as contact head 11B and configured to abut against a contact pad 14A of a board 14 for connection with a test apparatus, such as an interface PCB board or a so-called space transformer, i.e. a PCB board capable of realizing a space transformation associated with the distribution of the respective contact pads made on its opposite sides. The term end or tip is used herein and below to denote a terminal portion that is not necessarily pointed. In particular, when the probe head 10 performs testing of an integrated device, the contact tip 11A of its contact probe 11 is pressed against the contact pad 12A of the device under test 12, the probe bends and deforms, and its contact head 11B is also pressed against the contact pad 14A of the board 14, and thus the contact probe 11 performs mechanical and electrical contact between the device under test 12 and a test apparatus (not shown) of which the probe head 10 forms an end element.

[0012] Suitably, in the direction Z of the local reference of the drawing, the second upper guide 17, in the case where the first upper guide 16 is the guide closer to the board 14, and the lower guide 18 are separated by a gap 19, thereby allowing the contact probe 11 to be deformed during operation of the probe head 10.

[0013] The deformation of the contact probes 11 ensures that each contact tip 11A abuts against a contact pad 12A of the device under test 12 at an angle with respect to the longitudinal direction z, thereby ensuring the sliding of said contact tips 11A over the contact pads 12A and thus the cleaning or scrubbing of their surfaces, to ensure correct contact, not only mechanical but also electrical, between the contact probes 11 and the device under test 12.

[0014] It is equally important to ensure correct retention of the probes inside the probe head, especially when the probe head is not resting against a wafer of integrated circuits. For this purpose, mechanisms are usually provided to prevent the contact probes 11 from undesirably slipping off the probe head 10 in both directions in the longitudinal direction z, i.e. upwards and downwards, taking into account the local references of the drawing.

[0015] For this purpose, each contact head 11B of the contact probe 11 of the example of Fig. 1 is provided with an enlarged portion 11D, i.e. with a transverse diameter larger than the transverse diameter of the rest of the probe body 11C and of the first upper guide hole 16A of the first upper guide 16, the term transverse diameter meaning in this specification and below the value of the largest dimension of a cross-section, even if not circular, taken at the reference plane π. Said enlarged portion 11D ensures the abutment of the contact head 11B on the first upper guide 16 and prevents the sliding of the contact probe 11 downwards, i.e. in the direction of the wafer 13, still taking into account the local reference of the drawing, in particular without the device under test 12 on which the probe rests during normal operation of the probe head 10.

[0016] Furthermore, each contact probe 11 can be provided with a suitable protruding element, as shown in the example of FIG. 1, which is usually indicated as a stopper 15 and which protrudes starting from a wall of the probe body 11C. In particular, due to the shifting of the guides, the contact probe 11, once assembled, has a first side wall ls1 which is in contact with the wall of the corresponding first upper guide hole 16A of the first upper guide 16 and an opposing second side wall ls2 which is in contact with the wall of the second upper guide hole 17A of the second upper guide 17. The stopper 15 thus protrudes starting from the second side wall ls2 of the contact probe 11, so as to interfere with the lower surface F1 of the second upper guide 17 when the contact probe 11 moves upwards, i.e. in the direction of the test device, taking into account the local reference of the drawing, during a cleaning operation of the probe head 10, which is usually performed by a powerful air jet and which may mean a large vertical displacement of the contact probe 11, thus preventing the movement and sliding of the respective contact probe 11 outside the probe head 10.

[0017] In such a case, the upper guide holes 16A and 17A are dimensioned to ensure the passage of the stopper 15 during assembly of the probe head 10, as described below, and the shift between the upper guides 16 and 17 ensures, in any case, the positioning of the contact probe 11, whose second side wall ls2 rests on the second upper guide hole 17A above the stopper 15, and therefore ensures the contrast of the stopper 15 with the second upper guide 17 thereon and the correct retention of the contact probe 11 inside the probe head 10.

[0018] This efficient method of holding the contact probe 11 by the expansion of its head portion 11B and the interference between the stop 15 and one of the upper guides which is shifted to bend and deform the probe as required, involves that the contact probe 11 is assembled inside the probe head 10 starting from above, i.e. starting from the side of the board 14 which connects with the test device. (The assembly direction from above is shown as the test machine side (arrow TS in FIG. 1).)

[0019] Currently, the assembly of contact probes in a probe head using vertical technology is mainly done manually, in particular by an operator positioning the contact probes so that they are centered in the guide hole of the first guide, i.e. the upper guide, which is closer to the board that interfaces with the test equipment, and then lowering them by gravity to the last guide, i.e. the lower guide, which is closer to the device under test integrated on the wafer, until they are centered in the other guide hole of the other guide, the movement of each contact probe being stopped by an enlarged head portion that does not allow it to slide beyond the guide hole of the first guide, i.e. the upper guide.

[0020] The above-mentioned assembly of contact probes in the probe head is closely dependent on the geometry of the probe and the relative alignment of the guide holes in the guides of the probe head; these characteristics are uncontrollable and critically limit the efficiency of the assembly process preventing the process from being efficiently automated.

[0021] Also, manual assembly, when performed by a specialized operator, possibly assisted by a camera and lighting system, requires time and costs associated with the operator's own skills, does not allow for large production scales or to meet peaks in demand, and the period required to train a specialized operator is often longer than the period of the production peak requiring such a specialized operator. In some cases, when the probe has a particularly irregular profile and / or the position of the associated guide hole of the guide is significantly misaligned, the assembly cannot be successful (i.e. the probe cannot be inserted into the guide hole), which may even cause the breakage of said probe, further wasting time as well as resources, making the whole machine-side type assembly mode inefficient.

[0022] The problems associated with assembling the contact probes in the probe holes of the probe head guide are also not limited to when assembling the probe head: indeed, once assembled, the probe head may be subject to wear or failure, particularly with respect to the contact probes contained therein.

[0023] If by performing the necessary tests a problem is found with the contact probe such that it should be replaced, the contact head, still with the problematic mechanism already described for extracting and inserting from above, should be disassembled from the test fixture and partially disassembled so that the defective probe can be removed and replaced with a new probe, and after replacing the defective probe the probe head should be reassembled and reconnected to the test fixture.

[0024] The test / disassembly / replacement / reassembly operations should be repeated several times since the various contact probes contained in the probe head are tested, and the number of probes can be several thousand. In case of a fault, e.g. a breakage of a contact probe during the useful life of the probe head, the same operation sequence should be repeated during the useful life of the probe head.

[0025] The technical problem of the present invention is to provide a configuration of contact probes for a probe head with vertical technology which not only simplifies the assembly operation of the probe head, but also allows its operation and regular testing and replacement of potentially defective contact probes, while still ensuring correct retention of the contact probes inside the probe head in any circumstances and overcoming the limitations and drawbacks that still affect contact probes and probe heads manufactured according to the prior art. Summary of the Invention

[0026] The idea underlying the present invention is to provide each contact probe with an additional connection pin with said lower guide that can hold the probe inside the probe head to interfere with said lower guide without the need to provide an additional holding mechanism such as an enlargement of the head part of each contact probe or the presence of a stopper protruding from its side, thereby allowing the assembly of the contact probe starting from the bottom, i.e. from the side of the device under test, generally indicated as the probe side.

[0027] Based on the above solution, the technical problem is solved by a contact probe having a first end part terminating in a contact tip configured to abut against a contact pad of a device under test, a second end part terminating in a contact head configured to abut against a contact pad of a board of a testing apparatus, and a probe body extending between the first and second end parts along a longitudinal expansion axis, wherein the first end part comprises a first support interposed between the probe body and the contact tip, the first support comprising at least one contact pin and a probe length extending parallel to each other along the longitudinal expansion axis and separated by an air gap.

[0028] More particularly, the invention includes the following additional and optional features taken alone or in any combination as appropriate:

[0029] According to one aspect of the invention, the first support may further comprise at least one material bridge configured to connect the contact pin and the probe length along a lateral direction perpendicular to the longitudinal axis of deployment, the probe length, the contact pin and the material bridge collectively configuring the first support as a U-shape.

[0030] In accordance with another aspect of the invention, the contact tip may be aligned with the contact pin along an additional longitudinal axis that is separate from and parallel to the longitudinal axis of deployment of the contact probe.

[0031] Furthermore, according to an embodiment of the invention, the contact pin can be provided with at least one retaining portion at its free end opposite the end connected to the material bridge, said retaining portion having a transverse diameter larger than the transverse diameter of the contact pin outside the retaining portion, the transverse diameter meaning the maximum dimension of the cross section perpendicular to the longitudinal development axis even in the case of a non-circular cross section.

[0032] The enlarged portion may further comprise a majority portion, the enlarged portion configured to define at least one undercut wall of the retention portion.

[0033] Additionally, the retaining portion may also include at least one longitudinal opening extending along the further longitudinal axis and configured to define at least a pair of portions of the retaining portion that can move toward and away from each other when subjected to a lateral compressive force, i.e., a force perpendicular to the further longitudinal axis.

[0034] According to another aspect of the invention, the second end portion can include at least one retention feature configured to generate friction with a wall of the guide hole when the guide hole receives the second end portion, the retention feature preferably comprising a corrugated surface.

[0035] The second end portion may further comprise at least one opening arranged longitudinally along the longitudinal expansion axis in a second support portion of the second end portion adjacent the contact head, the at least one longitudinally arranged opening being configured to define two opposing portions of the second support portion that can move toward and away from each other when subjected to a lateral compressive force, i.e., a force perpendicular to the longitudinal expansion axis.

[0036] According to aspects of the invention, the contact probe may also include at least one longitudinal slot extending along the probe body and configured to define at least a pair of arms therein that are generally parallel to one another and separated by the longitudinal slot.

[0037] The probe body may have a pre-deformed shape in a curvilinear configuration at rest, including at least one bend, and preferably two bends.

[0038] According to another aspect of the invention, the contact probe may further comprise at least one reduced cross-sectional area portion forming a bent neck positioned in the probe body corresponding to one of the first end portion and the second end portion.

[0039] The technical problem is also solved by a probe head for testing the functionality of a device under test, comprising a single upper guide provided with upper guide holes for accommodating a plurality of contact probes and a single lower guide provided with lower guide holes, said contact probes being made as indicated above, said lower guide holes comprising a first lower guide hole configured to accommodate a probe length of the contact probe and a second lower guide hole configured to accommodate a contact pin of the contact probe.

[0040] According to an embodiment of the present invention, the second lower guide hole may have a lateral diameter equal to or smaller than the lateral diameter of the holding portion of the contact pin, these lateral diameters preferably differing by 0-10%.

[0041] According to another aspect of the invention, the probe head may comprise a first contact probe and a second contact probe, the respective contact pins of which are spaced apart from the respective probe lengths by a first distance and a second distance, the first distance and the second distance being different from one another so as to spatially redistribute contact pads of an interface board against which the respective contact heads of the first contact probe and the second contact probe abut relative to contact pads of a device under test against which the respective contact tips of the first contact probe and the second contact probe abut.

[0042] According to yet another aspect of the invention, the probe head may further comprise at least one upper frame coupled to the single upper guide and provided with respective upper openings configured to accommodate the contact probes, and at least one lower frame associated with the single lower guide and provided with respective lower openings for accommodating the contact probes.

[0043] Finally, the contact probe may include a lateral material bridge configured to connect the probe length and the contact pin, in a resting state, positioned at a distance from the lower guide greater than a maximum overtravel value of the contact probe, the overtravel being the displacement of the contact tip of the contact probe along the longitudinal axis of deployment when the contact probe is pressed against a contact pad of the device under test.

[0044] BRIEF DESCRIPTION OF THE DRAWINGS Features and advantages of the contact probe and probe head according to the invention result from the description given hereinafter, by way of indicative and non-limiting example, with reference to the accompanying drawings, in which: FIG.

[0045] The disclosure described herein will be more fully understood from the detailed description given herein below and the accompanying drawings, which should not be construed as limiting the disclosure described in the appended claims. The drawings show: [Brief description of the drawings]

[0046] [Figure 1] 1 shows a schematic front view of a probe head made according to the prior art; [Figure 2A] 1 shows a front view of an embodiment of a contact probe according to the present invention. [Figure 2B] 1 shows a front view of an embodiment of a contact probe according to the present invention. [Figure 3A] 13 shows a front view of an alternative embodiment of a contact probe according to the present invention. [Figure 3B] 13 shows a front view of an alternative embodiment of a contact probe according to the present invention. [Figure 4] 1 shows a front view of a preferred embodiment of a contact probe according to the present invention; [Figure 5A] 5 shows an enlarged view of a detail of the embodiment of FIG. 4. [Figure 5B] 5 shows an enlarged view of a detail of the embodiment of FIG. 4. [Figure 6] 5 shows a front view of a probe head according to the invention, comprising a contact probe according to the embodiment of FIG. 4; [Figure 7A] 1 shows a front view of a probe head according to the invention in its different operating states; [Figure 7B] 1 shows a front view of a probe head according to the invention in its different operating states; [Figure 8A] 5A-5C show top views of possible configurations of contact probes made in accordance with the embodiment of FIG. 4. [Figure 8B] 5A-5C show front views of possible configurations of contact probes made in accordance with the embodiment of FIG. 4. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0047] Referring now to the drawings, and in particular to FIGS. 2A and 2B, a contact probe, generally designated 20, made in accordance with the present invention is illustrated.

[0048] It should be noted that the drawings represent schematic views and are not drawn to scale, but are instead drawn to highlight important features of the invention. Also, in the drawings, various parts are shown diagrammatically and their shapes may vary depending on the desired application. Also, certain features shown in one drawing in relation to an embodiment may be used in one or more of the embodiments shown in the other drawings.

[0049] Furthermore, structurally and functionally equivalent elements in the various embodiments illustrated in the various figures and described below are designated with the same alphanumeric designations.

[0050] In the following description, relative terms such as "top", "bottom", "upper" and "lower" are used solely for ease of description with reference to the drawings of the probes and probe heads shown in the drawings.

[0051] Finally, the representation of a particular geometric shape (circular, rectangular) or arrangement of elements (parallel, orthogonal, adjacent) as well as the term "substantially" should be understood to always relate to physical elements rather than to geometrically abstract elements, always taking into account the tolerances introduced by the transition from the world of pure mathematics / geometry to the real world.

[0052] The contact probe 20 comprises at least one first end portion 20A configured to abut against a contact pad of a device under test and terminating in a contact end, denoted as contact tip 21A, the first end portion 20A comprising a first support 22A adjacent to said contact tip 21A and configured to be accommodated in a respective guide hole of a guide of a probe head comprising the contact probe 20, in particular a guide hole of the lower guide, i.e. the guide positioned closer to the device under test. In other words, the first end portion 20A comprises a first section and a second section, the first section being accommodated at least partially in a guide hole of a guide of the probe head into which the probe is inserted during the testing process of the respective device under test, in particular the lower guide, said first section substantially comprising the first support 22A, and the second section being configured to protrude from said guide towards the device under test and to realize a connection with the pad of the device under test via pressure contact, said second section substantially comprising the contact tip 21A.

[0053] Furthermore, the contact probe 20 comprises a second end portion 20B arranged to abut against a contact pad of an interface board of the test apparatus and terminating in a contact end, indicated as contact head 21B, the second end portion 20B comprising a second support 22B adjacent to the contact head 21B and arranged to be accommodated in a guide hole of a guide of a probe head comprising the contact probe 20, in particular the upper guide, i.e. a guide hole of a guide located close to the interface board of the test apparatus. In other words, the second end portion 20B in turn comprises a first section and a second section, the first section being accommodated at least partially in a guide hole of a guide of the probe head, in particular the upper guide, into which the probe is inserted during the testing process of the respective device under test, the second section substantially comprising the second support 22B, the second section being arranged to protrude from said guide towards the interface board of the test apparatus and to realize a connection with its pad via pressure contact, said second section substantially comprising the contact head 21B.

[0054] Finally, the contact probe 20 comprises a probe body 20C that is substantially rod-shaped and extends between a first end portion 20A and a second end portion 20B substantially in the direction z of local reference in the drawing, according to a longitudinal extension axis HH of the contact probe 20. Thus, in the following description, the term longitudinal is used to denote elements arranged according to a direction or plane parallel to the longitudinal extension axis HH.

[0055] Suitably, according to the invention, the first end portion 20A further comprises a contact pin 24 extending parallel to a probe length 23 comprised in the first support part 22A of the contact probe 20, said probe length 23 being separated from the contact pin 24 by an air gap ZA, in particular the contact pin 24 extending along a further longitudinal axis of extension H'H' which is distinct from and parallel to the longitudinal axis of extension HH of the contact probe 20 and thus of the probe length 23, and which is spaced apart by a distance S. The first support part 22A thereby comprises a probe length 23 and a contact pin 24 which are parallel to each other and separated by an air gap ZA.

[0056] Suitably, the probe length 23 and the contact pin 24 are connected to each other and to the contact tip 21A by a material bridge 25 extending across the gap ZA, the probe length 23, the contact pin 24 and the material bridge 25 thus defining a first part 22A of the contact probe 20 according to a U-shape. The contact probe 20 thereby extends along a longitudinal extension axis HH between the contact head 21B and the contact tip 21A and comprises a first support part 22A therebetween comprising the probe length 23, the contact pin 24 and the material bridge 25 according to a U-shape.

[0057] 2A and 2B, the contact tip 21A is aligned with the probe length 23 along the longitudinal extension axis HH, while the contact pin 24 is shifted with respect to the probe length 23 and the probe body 20C by a distance equal to the length of the material bridge 25. It is possible to realise the contact tip 21A with a tapered shape, i.e. with a cross section perpendicular to the longitudinal extension axis HH, which tapers towards the pad of the device under test with which the contact tip 21A is intended to abut, thereby reducing the area actually abutting said pad and making the contact probe 20 particularly suitable for applications with pads of reduced size.

[0058] Furthermore, the contact pin 24 is configured to be at least partially accommodated in an additional guide hole of a guide of a probe head comprising the contact probe 20, in particular in an additional guide hole of the lower guide, the lower guide hole at least partially accommodating the probe length 23.

[0059] Suitably, the contact pin 24 also comprises at least one retaining portion 24B, which, as will be made clear below, extends substantially longitudinally and is configured to retain the contact probe 20 in a corresponding probe head, preventing movement of the contact pin 24 outside an additional guide hole that accommodates the contact pin 24 in a guide of said probe head, in particular towards the device under test when the probe head is moved away from the wafer comprising said device under test, for example at the end of a test operation or during a cleaning operation by air jet, the retaining portion 24B protruding from the guide in the opposite direction to the device under test. Suitably, the retaining portion 24B is made corresponding to the free end of the contact pin 24, i.e. the end opposite to the end that is joined to the material bridge 25, said free end being the end closer to the interface board with the test apparatus, while the joined end is the end closer to the device under test.

[0060] The contact probe 20 thus configured is thereby configured to be assembled in a probe head starting from the side corresponding to the device under test, i.e. the so-called probe side, in which its second end portion 20B is not provided with any enlargements or protruding parts, e.g. in the form of a head enlargement or along the probe body 20C, e.g. in the form of a stopper, the retention of the contact probe 20 in the corresponding probe head being ensured by the retaining parts 24B of its contact pins 24. In other words, the assembly of the contact probe 20 made in this way is performed in an opposite manner to the known solution, i.e. according to the arrow shown in Fig. 1, from the probe side PS and not from the tester side TS, said assembly being possible due to the absence of protruding parts such as enlargements at the head portion and / or stops located along the probe body.

[0061] In an alternative embodiment shown in FIG. 2B, the contact probe 20 also includes at least one longitudinal slot 26 defining at least a pair of arms 26a, 26b extending along the probe body 20C and separated by the slot 26, which can increase the overall resiliency of the contact probe 20, allowing for reduced longitudinal extension when the overall length of the contact probe 20 needs to be reduced for applications involving non-RF signals, making the contact probe 20 suitable for high frequency or RF applications as well.

[0062] In the embodiment shown in FIG. 2B, arms 26a and 26b have equal diameters or lateral dimensions, although it is clearly possible to make arms having different lateral dimensions, for example, obtained by a slot 26 that is not centrally positioned with respect to the lateral extension of the probe body 20C.

[0063] It is also possible to define multiple arms within the probe body 20C by creating corresponding multiple longitudinal slots therein that are sized and spaced apart according to the application needs of the contact probe 20 that is desired to be obtained.

[0064] According to a preferred embodiment shown in Figures 3A and 3B, the contact tip 21A is aligned adjacent to the contact pin 24, i.e. said contact tip 21A and said contact pin 24 are arranged one after the other along a further longitudinal axis H'H'. This allows the material bridge 25 arranged to connect the probe length 23 and the contact pin 24 to realize an eccentricity of the protruding contact tip 21A with respect to the probe length 23 and thus with respect to the probe body 20C and the contact head 21B, thus increasing the distance between the contact tip 21A and the contact head 21B with respect to the longitudinal extension axis HH of the contact probe 20.

[0065] The value of the eccentricity or misalignment between the contact head 21B and the contact tip 21A is therefore determined by the length S of the material bridge 25, which also corresponds to the distance between the longitudinal expansion axis HH of the probe length 23, and thus of the contact head 21B, and the longitudinal expansion axis H'H' of the contact pin 24, and thus of the contact tip 21A.

[0066] Additionally, in the embodiment of FIG. 3B, the contact probe 20 includes a slot 26 configured to define at least a pair of arms 26a, 26b within the probe body 20C, suitable for RF applications.

[0067] The contact probe 20 with the contact tip 21A misaligned with respect to the contact head 21B, as shown in Figures 3A and 3B, is advantageously self-centered with respect to the pad of the device under test, the contact tip 21A being automatically aligned thanks to the contact pin 24 accommodated in an additional guide hole. More specifically, it is possible to realize an additional guide hole for accommodating the contact pin 24 so that it is centered with respect to the contact pad of the device under test. It is thus possible to avoid the known centering process, which is a time-consuming process, especially in the case of probe heads with a large number of probes, and which is used in particular for known cantilever probe heads.

[0068] More specifically, according to a preferred alternative embodiment shown in Fig. 4, when the contact probe 20 is not pressed against the contact pad of the device under test, the probe body 20C has a pre-deformed shape, i.e. a curved configuration that is already in a rest state. In the example shown in Fig. 4, the probe body 20C has a curved shape with one bend, i.e. a circular arc shape. Thus, suitably, the shape with one bend of the contact probe 20, and in particular of its probe body 20C, is also present in the non-operated state of the probe, i.e. before the probe is bent and deformed during testing, and the pre-deformation of the one bend of the probe body 20C ensures that the contact probe 20 bends in the same desired direction during testing.

[0069] Although not shown, it is also possible to realize the probe body 20C with a pre-deformed shape with two bends, which are arranged substantially in an S-shape and opposite to the longitudinal deployment direction z. The pre-deformed S-shape is especially configured to ensure correct operation of the contact probe 20 even when the overall dimensions of the contact probe 20 are reduced, e.g. in RF applications.

[0070] Suitably, the retaining portion 24B of the contact pin 24 of the contact probe 20 comprises a longitudinal opening 27 extending along a further longitudinal axis H'H' and configured to define two opposing portions 27a, 27b in the retaining portion 24B that can move towards and away from each other when subjected to a lateral compression force, i.e. a force orthogonal to the further longitudinal axis of extension H'H' along which the contact pin 24 extends, said lateral compression force therefore being applied according to the local reference direction x of Fig. 4. In the following description, the term lateral is used to denote elements arranged according to a direction or plane orthogonal to the longitudinal axis of extension HH and thus to the further longitudinal axis H'H'.

[0071] More specifically, as shown in the enlarged view of FIG. 5A, the longitudinal opening 27 extends over a length LI that varies between 100 μm and 300 μm inside the contact pin 24 so as to prevent or at least hinder movement of the contact probe 20 downwards along the direction z of local reference in the drawing, i.e. towards the device under test, when the probe head comprising said contact probe 20 is subjected to testing and removed from the device under test, in particular in the case of undesired adhesion of the contact tip 21A on the corresponding contact pad of the device under test, which adhesion would cause the contact probe 20 to slide downwards, i.e. towards the device under test, when the corresponding probe head is moved away from the device under test after testing, and is laterally dimensioned to enlarge the retaining portion 24B to similar and slightly higher lateral dimensions of the corresponding further guide hole made in the guides of the probe head that accommodate the contact probe 20, in particular the lower guide.

[0072] Thereby, the contact pins 24 provided on the holding part 24B act as holding elements for the contact probes 20 in the corresponding probe head. Due to the presence of the longitudinal openings 27, the holding part 24B is configured as a resilient holding means.

[0073] More specifically, in the embodiment shown in Fig. 4 and in the enlarged view of Fig. 5A, the longitudinal opening 27 is centrally positioned with respect to the holding portion 24B so as to define two substantially equal and opposing portions 27a, 27b. The holding portion 24B thus configured essentially acts as an elastic stopper which controls the passage of the contact pin 24 through the further guide hole without its passage during the assembly operation of the contact probe 20 in the probe head or its withdrawal by an operator during possible maintenance operations which require, for example, the contact probe 20 to be removed and replaced, and the correct holding is still ensured even when the probe head containing the contact probe 20 is not pressed against the device under test, said holding portion 24B being able to efficiently control the movement of the contact probe 20 due to gravity or other lateral forces, such as during cleaning operations which are usually performed by air jets.

[0074] Suitably, the holding portion 24B of the contact pin 24 also comprises an enlarged portion 27c, i.e. with a transverse diameter Dc which is greater than the transverse diameter of the corresponding additional guide hole accommodating the contact pin 24, transverse diameter here and below meaning also in the case of a non-circular cross section the maximum dimension of the transverse section of the holding portion 24B, i.e. perpendicular to the further longitudinal axis H'H'. Preferably, the transverse diameter Dc of the enlarged portion 27c is equal to 102-110% of the transverse diameter of the corresponding additional guide hole accommodating the contact pin 24.

[0075] Thereby, the enlarged portion 27c defines at least one undercut wall Sq of the retaining portion 24B configured to abut against a guide having an additional guide hole that accommodates the contact pin 24, thereby further ensuring retention of the contact pin 24 within said additional guide hole.

[0076] In particular, the enlarged portion 27c projects relative to the lateral dimension of the additional guide hole by an amount equal or comparable to the lateral dimension of the longitudinal opening 27, where comparable means here and below that the lateral dimension differs by ±1-5%, thereby enabling, in any case, during the assembly operation, the holding portion 24B, and in particular its enlarged portion 27c, to pass through the additional guide hole which accommodates the contact pin 24 and approach the opposing portions 27a, 27b, thereby eliminating the space defined by the longitudinal opening 27 in the holding portion 24B.

[0077] Furthermore, in the embodiment shown in FIG. 4 and in the enlarged view of FIG. 5A, the material bridge 25 is made with rounded, preferably arc-shaped, sides 25s connecting the contact tip 21A and the probe length 23, made to face the device under test, said arc-shaped connection reducing the stress generated in the material bridge 25 during operation of the contact probe 20 when the contact tip 21A is pressed against a pad of the device under test.

[0078] Suitably, the second end portion 20B of the contact probe 20 may also be provided with a retention mechanism 28, shown in more detail in FIG. 5B, configured to create friction against the walls of a guide hole in which the contact probe 20, in particular the second end portion 20B, is accommodated. In the embodiment shown in FIGS. 4 and 5B, said retention mechanism 28 comprises at least one corrugated surface that can create friction by contrasting with the walls of a guide hole of a corresponding guide of the probe head that accommodates the contact probe 20, in particular the guide hole of the upper guide of said probe head. The retention mechanism 28 further contributes to maintaining the contact probe 20 in the probe head thanks to the additional friction obtained in correspondence with the upper guide, which is combined with the retention provided in correspondence with the lower guide thanks to the retention portion 24B of the contact pin 24.

[0079] Obviously, the retaining mechanism 28 should be configured so as not to completely prevent movement of the contact probe 20, i.e., the engagement of the contact probe 20 in the guide hole of the upper guide, so as not to interfere with the proper operation of the contact probe 20, which is intended to bend and slide within the guide hole that accommodates it according to the well-known so-called bulking action.

[0080] In other words, the retaining mechanism 28 of the contact probe 20 which corresponds to the guide hole of the upper guide should not be so strong as to prevent the contact 21B of the contact probe 20 from being displaced and abutting against the corresponding contact pad of the interface board with the test equipment connected to the probe head including said probe, i.e., should not hinder the operation of the contact probe 20 during a test operation performed by the probe head including the contact probe 20.

[0081] Moreover, the second end portion 20B also comprises at least one opening 29 arranged longitudinally in its second part 22B, thereby defining two opposing portions 29a, 29b of said second part 22B and endowing said second part 22B with an elasticity that allows realizing that said second part 22B comprises a transverse diameter equivalent to that of the corresponding guide hole accommodating the contact probe 20, in particular the second part 22B of the second end portion 20B, facilitating the generation of friction thanks to a retaining mechanism 28 in sliding contact with the wall of said guide hole in which the contact probe 20 is accommodated substantially without clearance. In particular, the opposing portions 29a, 29b of said second part 22B can also move towards and away from each other when subjected to a transverse compressive force.

[0082] Suitably, as shown diagrammatically in Figures 4 and 5A, the contact probe 20 further comprises at least one bent neck 30A positioned at an end of the probe body 20C corresponding to the first end portion 20A, preferably corresponding to one of the ends of the probe body 20C as in the illustrated example. More specifically, the bent neck 30A comprises a cross-sectional reduced portion of the probe body 20C, preferably having a cross-sectional diameter Da reduced by 30-60% relative to the cross-sectional diameter D1 of the probe body 20C, more preferably by an amount equal to 50% of the cross-sectional diameter D1.

[0083] In the embodiment shown in FIG. 4 and in the enlarged view of FIG. 5B, the contact probe 20 comprises a further bent neck 30B positioned at the end of the probe body 20C corresponding to the second end portion 20B, corresponding to the other end of the probe body 20C, said further bent neck 30B being preferably made by a cross-sectional reduced portion having a diameter Db reduced by 30-60% relative to the cross-sectional diameter D1 of the probe body 20C, more preferably by an amount equal to 50% of said diameter D1.

[0084] In the embodiment shown in Fig. 4, the bent necks 30A and 30B are preferably arranged in the center of the contact probe 20, concentrically with respect to the probe body 20C along the longitudinal deployment direction z, and are obtained by removing material symmetrically from the probe body 20C, in particular starting from opposite side walls of said probe body 20C or annularly along the entire contour of the probe body 20C. Moreover, in the embodiment shown in Figs. 4, 5A, 5B, the bent necks 30A, 30B are substantially equal to each other and both arranged concentrically with respect to the probe body 20C. It is obviously possible for the contact probe 20 to comprise bent necks 30A and 30B that are different from each other, one or both of which are arranged non-concentrically with respect to the probe body 20C and are made, for example, by asymmetrically removing material from the probe body 20C.

[0085] It is immediately apparent that the presence of the bent necks 30A and 30B, particularly corresponding to the ends of the arms 26a, 26b and therefore the slots 26 realized in the body 20C, which are known to be areas more susceptible to damage, makes it possible to reduce the stresses experienced by the arms 26a, 26b, particularly during the testing operation, i.e. when the contact probe 20 is bent and deformed by abutting against the contact pads of the device under test.

[0086] Furthermore, the bent necks 30A and 30B, by virtue of their central location, do not adversely affect the bending mechanism of the contact probe 20 and the scrubbing of its contact tip 21A.

[0087] Preferably, contact pin 24 of first end portion 20A has a transverse diameter D2 that is equal to or less than transverse diameter D1 of the cross section of probe body 20C.

[0088] Although the embodiment shown in FIG. 4 and in the enlarged views of FIGS. 5A and 5B shows the contact probe 20 provided with the retention mechanism 28 and the two bent necks 30A, 30B, it is also possible for the contact probe 20 to have only the two bent necks 30A and 30B, or only one bent neck 30A or 30B, or only the retention mechanism 28, or still only the retention mechanism 28 and one bent neck 30A or 30B. Furthermore, although not shown, the contact probe 20 can have the retention mechanism 28 and / or one or two bent necks 30A, 30B without the slot 26. In other words, although not shown, the characteristics related to the presence of the slot 26, the retention mechanism 28, and the bent necks 30A and / or 30B can be used separately in the contact probe 20 according to the present invention. Furthermore, the characteristics related to the pre-deformation of the probe body 20C and the presence of the slot 26 can also be used separately.

[0089] The invention may also refer to a type of probe head with vertical probes, which may advantageously have only a pair of guides provided with guide holes for a number of contact probes, made as previously described.

[0090] More specifically, with reference to Figure 6, a probe head 40 is described comprising a number of probes made according to the embodiment shown in Figure 4, i.e. provided with contact pins 24 aligned with contact tips 21A. In the embodiment of Figure 6, the contact probes 20 comprise a probe body 20C pre-deformed and provided with a slot 26 and a retaining portion 24B of the contact pins 24 provided with a longitudinal opening 27, the second end portion 20B also being provided with bent necks 30A and 30B as well as a frictional retaining mechanism 28 and a further opening 29, although it is obviously also possible to make a probe head 40 using contact probes 20 that do not comprise one or more of the above features.

[0091] The probe head 40 comprises a first plate-like guide or upper guide 41, generally denoted as an upper die, provided with suitable upper guide holes 41A for accommodating the contact probes 20, as well as a second plate-like guide or lower guide 42, generally denoted as a lower die, also provided with suitable first lower guide holes 42A for accommodating the contact probes 20 corresponding to the probe length 23. Suitably, the lower guide 42 also comprises second lower guide holes 42B for accommodating the contact probes 20 corresponding to the contact pins 24.

[0092] Suitably, the second lower guide hole 42B has a transverse diameter equal to or smaller than the transverse diameter Dc of the enlarged portion 27c of the contact pin 24, said diameters preferably differing by 0-10%.

[0093] As can be seen in connection with the prior art, the upper guide 41 and the lower guide 42 are spaced apart from each other so as to define a gap therebetween, in which the contact probe 20 is free to bend during pressing of its contact tip 21A against a contact pad 51A of a device under test 51 integrated on a semiconductor wafer 50, with the corresponding contact head 21B abutting against a contact pad of an interface board with a testing device (not shown) of which the probe head 30 forms an end element. As can be seen in connection with the prior art, said interface board can be a so-called space transformer.

[0094] Suitably, the probe head 40 also comprises an upper frame 43 associated with the upper guide 41 and provided with respective upper openings 43H configured to accommodate the contact probes 20, and a lower frame 44 associated with the lower guide 42 and equally provided with lower openings 44H for accommodating the contact probes 20. Preferably, the upper frame 43 and the lower frame 44 are ceramic or metallic elements.

[0095] More specifically, the upper frame 43 is fixedly connected to the upper guide 41 by using connecting elements such as screws, pins or adhesive films, and similarly the lower frame 44 is fixedly connected to the lower guide 42 by connecting elements such as screws, pins or adhesive films. The upper and lower frames 43 and 44 are thereby integral with the upper and lower guides 41 and 42, respectively, and act as structural reinforcement elements thereof, as well as aligning means for the contact probes 20 during assembly of the probe head 40. This allows the use of reduced thickness, preferably ceramic, guides that facilitate the sliding of the contact probes 20 in their guide holes. Suitably, the presence of, and in particular the arrangement of, the second lower guide holes 42B for receiving the contact pins 24 also ensures centering of the contact tips 21A with respect to the contact pads 51A of the device under test 51.

[0096] Besides the upper guide 41 and the lower guide 42, the upper frame 43 and the lower frame 44 are also parallel to each other and extend along the reference plane π, just as the interface board of the test equipment (not shown) also extends along the reference plane π, besides the semiconductor wafer 50 and the device under test 51. Here and elsewhere in the context, references to elements that are planar or extend on a plane should not be intended in an abstract geometrical sense but as in the material world, and it is therefore emphasized to take into account the imperfections of real objects versus the perfection of purely geometrical objects.

[0097] More specifically, the lower guide 42 and the upper guide 41 have respective thicknesses Hlw, Hup along the longitudinal development direction z varying from 0.200 mm to 0.450 mm, preferably having values ​​equal to 0.250 mm for the lower guide 42 and equal to 0.320 mm for the upper guide 41, while the upper frame 43 and the lower frame 44 have respective thicknesses Hfup, Hflw varying from 0.150 mm to 0.200 mm, preferably equal to each other and equal to 0.180 mm.

[0098] It is also possible to configure the guides and frames so that the upper guide 41 and upper frame 43 assembly has a similar, preferably equal, thickness to the lower guide 42 and lower frame 44 assembly, thereby ensuring symmetry in the overall dynamic and elastic performance of the contact probe 20 and probe head 40, where equal means there is a ±20% difference between the two overall thickness values.

[0099] In a preferred embodiment, the upper guide 41 and the lower frame 44 are arranged at a distance Hs along the axis z comprised between 2.000 mm and 3.000 mm, preferably equal to 2.750 mm, thereby keeping limited the overall thickness of the probe head 40. Furthermore, it is emphasized that the contact probes 20 comprised in the probe head 40 suitably have reduced dimensions, in particular an overall length Ls of less than 5 mm, preferably less than 4 mm, thus making them suitable for high frequency or RF applications.

[0100] As explained above, the contact probe 20 can advantageously be assembled in the probe head 40 from the bottom, i.e. from the probe side, as indicated by the arrow PS in Fig. 6. Therefore, expediently, in case of a problem found during the operation of the probe head 40 related to a failure of the contact probe 20, for example in case said probe is broken, it is not necessary to disassemble and reassemble the holding mechanism of the contact probe 20 in order to access the contact probe 20, which operation may imply a force for disassembly of more than 50 screws and subsequent reflattening operations, and the operator can extract said failed contact probe 20 from the bottom by simply applying a force capable of overcoming the retention made by the holding part 24B of the corresponding contact pin 24, in particular a force sufficient to reduce the overall diameter of said holding part 24B and to deform the longitudinal opening 27 so as to allow the passage of the contact pin 24 into the respective second lower guide hole 42B housed in the lower guide 42.

[0101] The probe head 40 may also comprise contact probes having different configurations. In particular, as shown in Fig. 6, by way of example only, the probe head 40 comprises a first contact probe 20 having a contact pin 24 aligned with the contact tip 21A and spaced apart from the probe length 23 by a first distance S1 corresponding to the length of the material bridge 25 connecting the probe length 23 and the contact pin 24. Said first distance S1 is more specifically calculated as the distance between the longitudinal extension axes HH and H'H' of the probe length 23 and the contact pin 24, respectively, and corresponds to the distance between the first lower guide hole 42A and the second lower guide hole 42B realized in the lower guide 42 and accommodating the above elements of the first contact probe 20.

[0102] The probe head 40 also comprises a second contact probe 20' with a contact pin 24' aligned with the contact tip 21A' and spaced from the probe length 23' by a second distance S2 corresponding to the length of the material bridge 25' connecting the probe length 23' and the contact pin 24'. Said second distance S2 is more specifically calculated as the distance between the longitudinal development axes of the probe length 23' and the contact pin 24', respectively, and corresponds to the distance between the second lower guide holes 42A' and 42B' realized in the lower guide 42 and accommodating said elements of the second contact probe 20'. Suitably, the second distance S2 is different from the first distance S1, for example being longer than the first distance S1.

[0103] Thereby, thanks to the use of contact probes 20, 20', which are provided with contact pins 24, 24' and their aligned contact tips 21A, 21A', displaced relative to the probe length 23, 23' and thus the probe body, the probe head 40 realizes a spatial transformation in the lower guide 42, which therefore also functions as a space transformer.

[0104] The first and second contact probes 20, 20' further have respective second end portions 20B, 20B' received in corresponding upper guide holes 41A, 41A' formed in the upper guide 41.

[0105] More specifically, the contact heads 21B, 21B' of the first contact probe 20 and the second contact probe 20' emerge from the upper guide 41 in the direction of a test device (not shown) within an upper opening 43H made in the upper frame 43, and similarly, the holding portions 24B, 24B' of the contact pins 24, 24' of the first contact probe 20 and the second contact probe 20' emerge from the lower guide 42 in the direction of the upper guide 41 within a lower opening 44H of the lower frame 44, i.e., in the direction of the test device.

[0106] Suitably, as seen before, the contact probe 20, 20' may also comprise, corresponding to its second end portion 20B, 20B', at least one retaining mechanism 28, 28', e.g. in the form of a corrugated surface or provided with reliefs or bumps, capable of generating friction with the respective upper guide hole 41A, 41A' so as to hinder movement of the contact probe 20, 20' towards the device under test 51. Each second end portion 20B, 20B' may further comprise an opening so as to configure a resilient retaining mechanism for the respective contact probe 20, 20'.

[0107] Although not shown, the probe head 40 may also include a contact probe 20 provided with contact pins 24 as described above, as well as a vertical contact probe made in accordance with the prior art.

[0108] As a further advantage, the contact probes 20, 20' comprised in the probe head 40 are configured such that their material bridges 25, 25' are positioned at a distance H of the lower guide 42 in the resting state, i.e. by bringing the respective contact tips 21A, 21A' into contact with the contact pads 51A of the device under test 51. The distance H is therefore selected to be greater than the maximum value of the so-called overtravel, i.e. the movement performed by the contact probes 20, 20' upwards, i.e. in the direction of the test apparatus, taking into account the local reference of the drawing, during the test operation, so as not to affect the correct operation of the entire probe head 40.

[0109] More specifically, as shown in FIG. 7A, in which only one contact probe 20 is shown for simplicity of illustration, the contact probe 20 is in a stationary state, with the contact tip 21A abutting against a contact pad 51A of the device under test 51 and the contact head 21B abutting against a corresponding contact pad 61A of an interface board 60 with the testing apparatus, and the contact probe 20 has a material bridge 25 arranged at a distance H according to the axis z of the drawing, i.e. obtained in the direction of the longitudinal extension axis HH, having a first value H1. In operation, as shown in FIG. 7B, when the contact tip 21A is pressed against the contact pad 51A of the device under test 50, the contact tip 21A is pushed upwards, i.e. towards the testing apparatus, and its probe body 20C deforms within the gap defined between the upper guide 41 and the lower guide 42 of the probe head 40; in these conditions, the distance H between the material bridge 25 and the lower guide 42 is reduced to a value H2, which in any case makes it possible to avoid contact between the probe 20 and the lower guide 42.

[0110] Typical values ​​of the distance H in the rest state (H1) are 250 μm to 450 μm, preferably 350 μm, with an overtravel value less than 100 μm, preferably equal to 80 μm, thereby ensuring a value of the distance H in the operating state (H2) that is in any case greater than 150 μm and thus avoiding possible contact risks between the material bridges 25 of the contact probes 20 and the lower guides 42 of the probe head 40 that accommodate them.

[0111] Thanks to the use of contact pins 24, which are separated by material bridges 25 over the probe length 23, it is thus possible to redistribute the contact pads 61A of the interface board 60 with the test equipment relative to the contact pads 51A of the device under test 51, as is shown diagrammatically in top and front views in Figures 8A and 8B, respectively. In particular, using contact probes 20 with material bridges 25 of different lengths S1, S2, it is possible to further increase the spacing of the contact pads 61A on the interface board 60, where there are no limitations associated with the ever-decreasing dimensions of the chip and thus the contact pads 51A of the device under test 50.

[0112] In the example shown in Figures 8A and 8B, as an advantage, the linear configuration of the contact pads 51A on the device under test 50 is converted into a matrix configuration with four rows of contact pads 61A on the interface board 60 thanks to the use of the contact probe 20 provided with the contact pins 24, and as a further advantage, the contact pads 61A have larger dimensions than the contact pads 51A of the device under test 50.

[0113] In conclusion, a contact probe provided with at least one contact pin can be accommodated in the probe head by an assembly process from the probe side, where the contact probe first traverses the lower guide to reach the upper guide, and the presence of the contact pin eliminates the need for a post-assembly centering process.

[0114] The presence of contact pins has the advantage that the contact probes can achieve a real spatial transformation at the level of the lower guide and also allow the probes to be distributed at different levels, thus providing a suitable spacing for direct contact on the interface board towards the test equipment, which is achieved in a method known as Direct Attach.

[0115] Suitably, the probe head can be made using only two guides, an upper guide and a lower guide, which may be associated with a reinforcing frame, and the contact probe can be pre-deformed and provided with a holding portion with an enlarged diameter corresponding to the contact pin and a holding mechanism with a corrugated surface corresponding to the contact head so as to eliminate the need for a shifted double guide used in known solutions, thus ensuring current retention of the probe in the corresponding probe head.

[0116] The pre-deformation of the contact probes can also facilitate uniform bending of the contact probes when accommodated in the corresponding probe head, particularly during pressure application to the device under test during a test operation performed by the probe head, thereby minimizing the risk of contact between adjacent probes even in the absence of a pair of shifted guides as in known solutions.

[0117] The contact probe according to the invention also makes it possible to overcome the drawbacks of known solutions with double guides for realizing probe offset, which can subject the device under test to lateral forces that can cause undesirable displacements, especially when a large number of contact probes are present.

[0118] A further advantage of the present invention is that the elasticity of the holding parts not only ensures that the contact pins of the contact probes are threaded through the respective guide holes during assembly operations, but also that the probes are withdrawn by the operator during possible maintenance operations which require, for example, the removal or replacement of the probes; yet, thanks to the contrast created by said holding parts corresponding to the contact pins in conjunction with the possible holding mechanisms corresponding to the contact heads, correct holding is guaranteed even when the probe heads which house the probes are not pressed against the device under test or in contact with the board of the test apparatus, and that movement of the probes under the influence of gravity can also be prevented when the probe heads are separated from the device under test or pulled away from the test apparatus, as well as when other lateral forces are present, such as during cleaning operations which are usually carried out by air jets.

[0119] Suitably, the retaining portion corresponding to the contact pin and the retaining mechanism corresponding to the contact head can be made elastic in a very simple manner by means of openings configured to define parts of at least a pair of said elements which can move towards or away from each other.

[0120] Additionally, the probe may have openings formed in its probe body to form multiple longitudinal arms and / or flexure necks to improve the overall resiliency of the probe.

[0121] This makes it possible to particularly shorten the overall length of the probe, making it suitable for state-of-the-art applications, such as very high frequency applications using only a single pair of guides, while still ensuring correct retention of the probe inside and without the risk of said probe being plastically, i.e. permanently, deformed.

[0122] Contact probes and corresponding probe heads made in this way with limited longitudinal dimensions are also suitable for applications for large devices, such as modern 12" memories, which require the use of corresponding large-area probe heads, whose movements are critical and risk damage, especially during the inspection process. Suitably, a probe head made with contact probes as described above does not have to be subjected to long and delicate operations of assembling and reassembling the mechanism, for example when one or more contact probes need to be replaced, thus reducing the risk of damage thereto.

[0123] Obviously, those skilled in the art can make numerous modifications and variations to the above contact probe and probe head to meet their unspecified and specific needs, all of which fall within the scope of protection of the present invention as defined by the following claims.

[0124] In particular, in addition to the possible use of flexible materials for filling the openings, it is possible to consider any shape for any number of longitudinal openings for forming any number of arms in the probe body, in addition to the openings made in the retaining portions of the contact pins and the retaining mechanisms of the contact heads.

[0125] Finally, it is possible to provide the contact probe of the present invention with further features, such as a particular geometric configuration of the contact tip and head portion, e.g. a contact tip of reduced dimensions relative to the probe body, or the presence of a coating film.

Claims

1. a contact probe (20), the contact probe (20) having a first end portion (20A) terminating in a contact tip (21A) configured to abut a contact pad of a device under test; a second end portion (20B) terminating in a contact head (21B) adapted to abut against a contact pad of a test apparatus board; a probe body (20C) extending between said first end portion (20A) and said second end portion (20B) along a longitudinal axis of deployment (HH); the first end portion (20A) comprises a first support portion (22A) interposed between the probe body (20C) and the contact tip (21A); The contact probe (20), characterized in that the first support part (22A) comprises at least one contact pin (24) and one probe length (23) extending parallel to each other along the longitudinal axis of expansion (HH) and separated by a gap (ZA).

2. 2. The contact probe (20) of claim 1, wherein the first support portion (22A) further comprises at least one material bridge (25) configured to connect the contact pin (24) and the probe length (23) along a lateral direction perpendicular to the longitudinal expansion axis (HH), and the probe length (23), the contact pin (24) and the material bridge (25) together configure the first support portion (22A) as a U-shape.

3. 2. The contact probe (20) of claim 1, characterized in that the contact tip (21A) is aligned with the contact pin (24) along a further longitudinal axis (H'H') that is separate and parallel to the longitudinal extension axis (HH) of the contact probe (20).

4. 2. A contact probe (20) according to claim 1, characterized in that the contact pin (24) comprises at least one retaining portion (24B) corresponding to its free end opposite the end connected to the material bridge (25), the retaining portion (24B) having a transverse diameter (Dc) greater than the transverse diameter (D2) of the contact pin (24) outside the retaining portion (24B), the transverse diameter meaning the maximum dimension of a cross section perpendicular to the longitudinal development axis (HH) even in the case of a non-circular cross section.

5. The contact probe (20) of claim 4, wherein the retaining portion (24B) further comprises at least one enlarged portion (27c) having the transverse diameter (Dc) greater than the transverse diameter (D2) of the contact pin (24), the enlarged portion (27c) being configured to define at least one undercut wall (Sq) of the retaining portion (24B).

6. The contact probe (20) according to claim 4, characterized in that the holding portion (24B) also comprises at least one longitudinal opening (27) extending along a further longitudinal axis (H'H') and is configured to define at least a pair of portions (27a, 27b) of the holding portion (24B) which can move towards and away from each other when subjected to a lateral compressive force, i.e. a force perpendicular to the further longitudinal axis (H'H').

7. 2. The contact probe (20) of claim 1, wherein the second end portion (20B) comprises at least one retention feature (28) configured to generate friction with a wall of the guide hole when the guide hole receives the second end portion (20B), the retention feature (28) preferably comprising a corrugated surface.

8. 2. The contact probe (20) of claim 1, characterized in that the second end portion (20B) further comprises at least one opening (29) arranged longitudinally along the longitudinal axis of expansion (HH) in a second support portion (22B) of the second end portion (20B) adjacent to the contact head (21B), the at least one longitudinally arranged opening (29) being configured to define two opposing portions (29a, 29b) of the second support portion (22B) that can move towards and away from each other when subjected to a lateral compressive force, i.e. a force perpendicular to the longitudinal axis of expansion (HH).

9. 2. The contact probe (20) of claim 1, characterized in that the contact probe (20) comprises at least one longitudinal slot (26) extending along the probe body (20C) and is configured to define at least a pair of arms (26a, 26b) therein that are generally parallel to one another and separated by the longitudinal slot (26).

10. The contact probe (20) of claim 1, characterized in that the probe body (20C) has a pre-deformed shape with a curvilinear configuration in a rest state, including at least one bend, preferably two bends.

11. 2. The contact probe (20) of claim 1, wherein the probe body (20C) further comprises at least one reduced cross-sectional area portion forming a bent neck positioned in the probe body (20C) corresponding to one of the first end portion (20A) and the second end portion (20B).

12. A probe head (40) for testing the functionality of a device under test, the probe head (40) comprising a single upper guide (41) provided with upper guide holes (41) for accommodating a plurality of contact probes (20) and a single lower guide (42) provided with lower guide holes (42A, 42B); Characterised in that the contact probe (20) is realised according to any one of claims 1 to 11, The probe head (40), characterized in that the lower guide holes (42A, 42B) include a first lower guide hole (42A) configured to accommodate a probe length (23) of the contact probe (20) and a second lower guide hole (42B) configured to accommodate a contact pin (24) of the contact probe (20).

13. The probe head (40) of claim 12, characterized in that the second lower guide hole (42B) has a transverse diameter equal to or smaller than the transverse diameter (Dc) of the retaining portion (24B) of the contact pin (24), said transverse diameters preferably differing by 0 to 10%.

14. 13. The probe head (40) according to claim 12, characterized in that the probe head (40) comprises a first contact probe (20) and a second contact probe (20'), each of whose contact pins (24, 24') are spaced from its respective probe length (23, 23') by a first distance (S1) and a second distance (S2), the first distance (S1) and the second distance (S2) being different from each other so as to spatially redistribute contact pads (61A) of an interface board (61) against which contact heads (21B, 21B') of the first contact probe (20) and the second contact probe (20') abut relative to contact pads (51A) of a device under test (50) against which contact tips (21A, 21A') of the first contact probe (20) and the second contact probe (20') abut.

15. The probe head (40) of claim 12, further comprising at least one upper frame (43) associated with the single upper guide (41) and provided with respective upper openings (43H) configured to accommodate the contact probes (20), and at least one lower frame (44) associated with the lower guide (42) and provided with respective lower openings (44H) for accommodating the contact probes (20).

16. 13. The probe head (40) of claim 12, characterized in that the contact probe (20) comprises a lateral material bridge (25) configured to connect the probe length (23) and the contact pin (24) positioned at a distance (H) from the lower guide (42) that is greater than a maximum overtravel value of the contact probe (20) in a resting state, the overtravel being the displacement of a contact tip (21A) of the contact probe (20) along a longitudinal extension axis (HH) when the contact probe (20) is in pressure contact with a contact pad (51A) of a device under test (51).

Images