Probe heads for electronic devices and corresponding probe cards

Abstract

The present invention describes a probe head comprising a plurality of contact probes inserted into guide holes provided in at least one upper guide and one lower guide, each contact probe having at least one first terminal portion protruding a first length from the lower guide and terminating in a contact tip configured to abut against such a contact pad of a device under test, and a second terminal portion protruding a second length from the lower guide and terminating in a contact head configured to abut against a contact pad of a PCB for connecting or coupling to a test apparatus, the probe head comprising a bending region for the plurality of contact probes defined between the upper and lower guides, and at least one protective structure protruding from the upper guide preferably in the direction of a longitudinal extension axis of the plurality of contact probes towards the PCB, said protective structure thereby extending at the plurality of contact heads of the plurality of contact probes.

Description

[Technical field]

[0001] The present invention relates to a probe head for an electronic device test apparatus.

[0002] The present invention is particularly, although not exclusively, related to a probe head having vertical probes for testing electronic devices, in particular integrated on a semiconductor wafer, and the following disclosure makes reference to the technical field of this application solely for the purposes of simplifying the explanation thereof. [Background technology]

[0003] As is well known, a probe head is essentially a device configured to electrically connect a number of contact pads of a microstructure, in particular an electronic device integrated on a wafer, with corresponding channels of a test device verifying their functionality, in particular the electrical one.

[0004] Tests performed on integrated devices are used to detect and isolate defective devices already in the manufacturing stage. Typically, probe heads are then used for electrical testing of multiple devices integrated on a wafer before their cutting and assembly in a chip-containing package.

[0005] The probe head comprises a number of movable contact elements or contact probes held by at least one plate, usually a pair of plates or guides, generally plate-like and parallel to each other and arranged at a certain distance between them so as to leave a free or air area for the movement and possible deformation of the contact probes. The pair of guides in particular comprises an upper guide, usually denoted by the term "upper die", and a lower guide, usually denoted by the term "lower die", the adjectives "upper" and "lower" being used in the art with reference to the probe head in operation and corresponding to the illustration of the figures, said head being positioned between the (upper) test fixture and the (lower) semiconductor wafer with the devices under test, i.e. the upper guide is the one positioned closest to the test fixture and the lower guide is the one positioned closest to the wafer with the devices under test.

[0006] The guides all have guide holes through which slide axially contact probes, usually made of a special alloy wire having good electrical and mechanical properties.

[0007] The probe head is further completed by a case disposed between the upper and lower guides, typically made of ceramic and configured to house and protect the probe.

[0008] A good connection between the multiple contact probes and the respective contact pads of the device under test is ensured by the pressure of the probe head against the device itself, i.e. against the wafer carrying it; the multiple contact probes, movable within multiple guide holes made in the upper and lower guides, are subjected to bending in the air region between the multiple guides and sliding within said multiple guide holes in the event of a pressure contact.

[0009] This type of probe head is commonly referred to by the term "vertical probe head".

[0010] The multiple vertical probe heads basically have air regions within which bending of the multiple contact probes occurs, also indicated as bending regions; furthermore, bending of the multiple contact probes can be accelerated by a suitable configuration of the probes themselves and / or thanks to a suitable relative positioning or phase shift of the guides.

[0011] In some cases, the contact probes are fixedly connected to the probe head at the upper guide, for example by welding or bonding: these are called probe heads with blocked probes.

[0012] More frequently, probe heads are used with probes that are not fixedly connected but are coupled to a space transformation board, commonly called a "space transformer," which is part of a probe card that contains the probe heads and is connected to a test device; they are called probe heads with unblocked probes. Generally, a probe head is coupled to and connected to the PCB of the probe card that contains it and is coupled to the test device of which the probe card is a terminal element.

[0013] A probe card having a probe head with multiple unblocked vertical probes is shown diagrammatically in FIG. 1, which for simplicity of illustration shows only one contact probe of the multiple probes typically included in such a probe head.

[0014] In particular, the probe card 10 comprises a probe head 1 and a PCB for connecting and coupling with a test apparatus, such as a space transformer 8; the probe head in turn comprises at least upper and lower guides 3 and 4 made of a substantially flat and parallel plate-like support and having respective upper and lower guide holes 3A and 4A in which respective contact probes 2 slide. In Fig. 1 the probe card 10 is shown in an operational state with the probe head 1 resting on a wafer comprising at least one device under test 7.

[0015] The probe head 1 also comprises a case 4, which also acts as a stiffener, arranged between the upper and lower guides (3 and 4) to house and protect the contact probe 2. The case 4 extends in particular in the air or bend region 6 between said guides.

[0016] Each contact probe 2 has a generally rod-shaped body 2C and at least one contact end or tip 2A. The term end or tip is used here and below to denote an end portion, not necessarily pointed. In particular, the contact tip 2A abuts against a contact pad 7A of a device under test 7 to effect mechanical and electrical contact between said device and a test apparatus (not shown) of which the probe card 10 is a terminal element.

[0017] 1, the contact probes 2 have further contact ends, generally shown as contact heads 2B, pointing towards contact pads 8A of a space transformer 8. Good electrical contact between the probes and the space transformer as well as contact with the device under test is ensured by pressure of the ends, in particular the heads, of the contact probes against the respective contact pads.

[0018] More generally, as described above, multiple contact pads with multiple contact heads of multiple probes are fabricated on a PCB for connection or coupling with a test apparatus used to connect with a probe card having the probe heads, and the above considerations may also be valid for such a PCB.

[0019] The upper guide 3 and the lower guide 4 are preferably spaced apart with an air or bending area 6 allowing deformation of the contact probes 2, the upper guide holes 3A and the lower guides 4A being dimensioned as required to allow sliding of such contact probes therein. A further area 9 called floating area is defined between the upper guide 3 and the space transformer 8; said floating area 9 is established in such a way that a movement of the contact heads 2B in case of a pressing contact of the probe head 1 and thus of the contact probes 2 on the device under test 7, i.e. of the contact tips 2A on the associated contact pads 7A, is guaranteed and in any case the contact of the contact heads 2B with the contact pads 8A of the space transformer 8 is ensured.

[0020] In the case of probe heads made according to the so-called "shifted plate" technique, the upper guide 3 and the lower guide 4 are displaced or moved in a direction Dshift which is parallel to their development plane, indicated in the figure by π, and the contact probes 2, also called "buckling beams", therefore have a probe body which is suitably deformed in an approximately central position as shown in Figure 1 so as to enable correct holding of the probe in the guide holes of the upper and lower guides and to impose its privileged bending direction which corresponds approximately to the direction Dshift.

[0021] It should not be forgotten that the correct operation of the probe head and therefore of the probe card comprising it is fundamentally associated with two parameters, namely the vertical movement or overtravel of the contact probes and the horizontal movement or scrubbing of the respective contact tips, in particular the contact tips 2A, on the contact pads 7A of the device under test 7, which allows to achieve surface "cleaning" of said pads and thus improve the contact made by the probe head 1, i.e. by the contact probes 2, during its entire useful life.

[0022] It is also important to ensure that the floating area 9 of the multiple contact heads 2B of the multiple contact probes 2 is sized as required to ensure correct accommodation of the multiple contact heads 2B within the probe head and their mechanical and electrical contact on the multiple contact pads 8A of the space transformer 8.

[0023] All these features must be evaluated and calibrated during the realization of the probe head, and good electrical connections between the probes, the device under test, and the test equipment must be guaranteed at all times.

[0024] The ends of contact probes, particularly the tips which contact the pads of devices under test, are subject to a build-up of material commonly referred to as dirt during use, which degrades their performance and runs the risk of impairing proper contact of the probes with the device under test, in which case scrubbing the tips however cannot ensure electrical contact with the pads.

[0025] It is therefore known to perform periodic cleaning operations of the probe heads, and in particular of the contact tips of the probes, with an abrasive cloth.

[0026] The cleaning action, however, involves the consumption of a portion of the ends of the probes, in particular the contact tips, and is therefore limited in number precisely by the length of the tips, which is shortened with each cleaning. Any subsequent wear of the ends of the contact tips must be limited in particular to the portion of the tapered probe protruding from the lower guide, which comprises the contact tips precisely.

[0027] The number of cleaning operations of a probe head actually determines its useful life, and hence the useful life of the probe card which houses it.

[0028] The use of a spacer element removably inserted between a storage element and one of the upper and lower guides so as to adjust the length of the ends of a plurality of contact probes, in particular at the contact points, is known from international application WO 2014 / 167410, published on 16 October 2014 (PCT), in the name of the same applicant.

[0029] While the probe head is advantageous in many respects, the change in length of the ends caused by removing the spacer or a layer thereof inevitably also changes the air or bending region of the contact probes, thus modifying the contact mechanics and causing problems with respect to the forces exerted by the probes on the contact pads and also the scrubs that may be applied thereto, as well as having drawbacks associated with modifying the deformations undergone by the probes in the air region, with the risk of permanent deformation or engagement of the probes in their respective guide holes.

[0030] It is also readily apparent how measures aimed at modifying the length of the contact probes protruding from the probe head, particularly at their tip ends, towards the device under test, often also involve unnecessary changes in the floating areas at the head ends of the probes, compromising their connection with the PCB towards the test equipment and resulting in incorrect operation of the probe head as a whole. Furthermore, US Patent Application Publication US2019 / 113539A1 by Crippa et al. (TECHNOPROBE) is known a probe card with a suitable spacer element inserted between a space transformer and its upper guide, the spacer element comprising a plurality of overlapping layers that are individually removable and have a gradually increasing or decreasing length between each other, with respective protruding portions from the probe head allowing easy removal of the corresponding layers. Furthermore, US Patent US6,150,830 by Schmid et al. (FEINMETALL GMBH) and European Patent EP2645113 in the name of Nihon Micronics KK relate to a probe head with a plurality of contact probes, the probe head having a covering layer or portion suitable for abutting one of the guides and preventing any of the plurality of probes from sliding. Furthermore, UK Patent Application Publication No. GB2086670 in the name of Everett Charles Inc., JP 2015-025749 in the name of Micronics Japan Co. Ltd., and US Patent Application Publication No. US2008 / 238408 by McQuade (DSL LABS INC) disclose probe heads with an additional frame or layer that acts as a stopper. Summary of the Invention [Problem to be solved by the invention]

[0031] The technical problem of the present invention is to provide a probe head for electronic devices integrated on a wafer, which has structural and functional properties that ensure correct accommodation of multiple contact probes therein and further follow cleaning operations of the multiple contact probes without functional loss, eliminating the limitations and drawbacks that still adversely affect multiple probe heads made by the prior art, and in particular ensuring sufficient protection and correct holding of the multiple contact heads of the multiple probes in the floating area, correct sliding of the multiple probes in their respective guide holes, and an essential scrubbing mechanism for correct contact between the multiple probes, the contact pads of the device under test, and the PCB connected to the test apparatus over the lifetime of the probe head and the probe card comprising it, even after multiple cleaning operations. [Means for solving the problem]

[0032] The solution idea underlying the present invention is to provide a suitable protective structure within the probe head for the multiple contact head parts of the multiple probes, which protective structure is further positioned so as not to interfere with the normal operation of the probe head and is preferably removable and, in some cases, provided by individually removable layers to modify the length of the floating region and thus the length of the probes protruding from the probe head towards the device under test after a cleaning operation, which, however, reduces its length at the contact tips without changing the length of the bending region of the multiple probes.

[0033] Based on the idea of ​​the solution, the technical problem is solved by providing a plurality of contact probes inserted into guide holes provided in at least one upper guide and one lower guide, each of the plurality of contact probes having at least one first terminal portion protruding from the lower guide by a first length and terminating in a contact tip configured to abut a respective contact pad of a device under test, and a second terminal portion protruding from the upper guide by a second length and terminating in a contact head configured to abut a contact pad of a PCB for connecting or coupling with a test apparatus, comprising a bending area for the plurality of contact probes defined between the upper and lower guides, and at least one protective structure protruding from the upper guide towards the PCB in the direction of a longitudinal development axis of the plurality of contact probes, the protective structure comprising: Towards the PCB, Multiple contact probes The protective structure is provided by a protruding portion of the upper guide in the direction of the longitudinal deployment axis, the protective structure being made integral with the upper guide. , is resolved by the probe head.

[0034] In particular, the invention comprises the following further and optional features taken individually or, where appropriate, in combination:

[0035] According to another aspect of the invention, the protective structure comprises: It may comprise at least a fixed part made integral with the upper guide, having a height equal to or greater than the height of the contact heads of the contact probes, and a further part having a number of individually removable layers. .

[0038] According to yet another aspect of the present invention, a protective structure Further parts ofmay comprise multiple individually removable layers stacked alternately between the PCB and the upper guide.

[0039] In particular, the protective structure Further parts of may comprise an adhesive material, preferably a glue with a weak seal, or a removable joining means configured to unite the layers together.

[0040] According to another aspect of the invention, the protective structure may have a shape selected from a frame, a pair of half frames, a single protruding element such as a post, etc.

[0042] The protective structure, and possibly its layers, may be made of a transparent or translucent plastic material, a ceramic material, or a metallic material, an organic material, or a silicone, preferably Kapton®.

[0043] According to another aspect of the invention, a probe head includes pairs of primary supports and may include upper and / or lower guides with spacer structures positioned between the primary supports.

[0044] According to the above aspects of the invention, the spacer structure may be fixed, possibly removably, to one of a number of base supports or may be provided by a protruding portion thereof or may comprise a number of overlapping and individually removable layers.

[0047] The technical problem is also solved by a probe card for a testing apparatus for electronic devices, comprising at least one probe head and at least one PCB for connecting and coupling with the testing apparatus, the probe head being provided with a plurality of contact probes configured to abut against a plurality of contact pads of a space transformer, the probe head being provided as described above. Effect of the Invention

[0049] The characteristics and advantages of a probe head according to the invention will become apparent from the following description of examples of its embodiments, given as non-limiting examples, with reference to the accompanying drawings, in which: [Brief description of the drawings]

[0050] [Figure 1] 1 shows a schematic representation of a probe card for electronic devices, in particular integrated on a wafer, provided according to the prior art; [Diagram 2] 2A and 2B show schematic cross-sectional views of a provided probe head according to an embodiment of the present invention; [Figure 3A] 2A-2C show schematic diagrams of probe cards with alternative embodiments of a probe head provided in accordance with the present invention, in respective cross-sectional views; [Figure 3B] 1A-1C show schematic diagrams of probe cards with alternative embodiments of probe heads provided in accordance with the present invention, in respective cross-sectional views; [Figure 3C] 1A-1D show, in respective cross-sectional views, schematic diagrams of a probe card with alternative embodiments of a probe head provided in accordance with the present invention; [Figure 4A] 1A-1C show schematic diagrams of probe cards with alternative embodiments of probe heads provided in accordance with the present invention, in respective cross-sectional views; [Figure 4B] 1A-1D show, in respective cross-sectional views, schematic diagrams of a probe card with alternative embodiments of a probe head provided in accordance with the present invention; [Figure 4C] 1A-1C show schematic diagrams of probe cards with alternative embodiments of probe heads provided in accordance with the present invention, in respective cross-sectional views; [Figure 5A] 1A-1D show, in respective cross-sectional views, schematic diagrams of a probe card with alternative embodiments of a probe head provided in accordance with the present invention; [Figure 5B] 1A-1C show schematic diagrams of probe cards with alternative embodiments of probe heads provided in accordance with the present invention, in respective cross-sectional views; [Figure 5C]1A-1C show schematic diagrams of probe cards with alternative embodiments of probe heads provided in accordance with the present invention, in respective cross-sectional views; [Figure 5D] 1A-1C show schematic diagrams of probe cards with alternative embodiments of probe heads provided in accordance with the present invention, in respective cross-sectional views; [Figure 6] 1A-1C show schematic diagrams of probe cards with alternative embodiments of probe heads provided in accordance with the present invention, in respective cross-sectional views; [Figure 7] 1A-1C show schematic diagrams of probe cards with alternative embodiments of probe heads provided in accordance with the present invention, in respective cross-sectional views; DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0051] With reference to these figures, and in particular to FIG. 2, a probe head according to the present invention is indicated generally at 21 .

[0052] It should be noted that the figures represent schematic diagrams and are not drawn to scale, but are instead drawn to highlight important features of the present invention. Furthermore, it is pointed out that measures shown with reference to a particular embodiment can obviously be used in combination with other embodiments. Finally, the same reference numerals are used in different figures to indicate structurally and functionally corresponding elements.

[0053] The probe head 21 is plate-like and comprises a number of contact probes 22 housed in suitable guide holes in respective parallel supports or upper and lower guides 23 and 24. The probe head 21 also comprises a storage element or case 25 extending between the upper and lower guides 23 and 24 in an air or bending area 26 having a height indicated by L in which the number of contact probes 22 can be further deformed in case of a pressing contact of the probes on a device under test, typically contained in a semiconductor wafer, against which the probe head 21 abuts in a first plane indicated by π1 in the figure.

[0054] In particular, the probe head 21 shown in Fig. 2 is of the unblocked vertical probe type, and the contact probes 22 each have a respective terminal portion 21A and 21B configured to make mechanical and electrical contact with a respective contact pad; in particular, the first terminal portion 21A terminates in a contact tip 22A configured to abut a contact pad of a device under test in a first plane π1, while the second terminal portion 21B terminates in a contact head 22B configured to abut a further contact pad of a connection element towards a test device, such as a space transformation or space transformer layer or a generic connection or interface PCB, in a second plane, indicated in the figure by π2. In this way, the contact probe 22 provides for mechanical and electrical contact between the device under test and a test device (not shown) of which the probe head 21 is a terminal element. The contact probe 22 also has a generally rod-shaped probe body 22C extending between said first and second ends (21A and 21B).

[0055] The term "terminal" refers to the part of the contact probe 22 that projects into the guide and thus into the case 25, in particular towards the PCB of the device under test or of the probe card comprising the probe head 21, respectively. Moreover, as mentioned above, the term tip denotes an end that is not necessarily pointed.

[0056] In particular, a first terminal portion 21A of the contact probe 22 at the contact tip 22A extends below the lower guide 24 of the probe head 21 in the opposite direction to the longitudinal axis of development of the probe, indicated by z in the local reference of the figure. Similarly, a second terminal portion 21B of the contact probe 22 at the contact head 22A extends above the upper guide 23 of the probe head 21 in the direction of the longitudinal axis of development z.

[0057] As mentioned above, the contact probe 22 has a first terminal part 21A with a contact tip 22A having a tapered shape so as to make a substantially point-like contact on a contact pad of the device under test. Furthermore, the contact probe 22 has a second terminal part 21B with at least one enlarged portion, i.e. a contact head 22B with a transverse diameter D2 that is a dimension larger than the transverse diameter D1 of the second terminal part 21B and of the remaining part of the probe body 22C in general, the diameter representing the maximum transverse diameter of a cross section of said part perpendicular to the longitudinal extension axis z of the contact probe 22; the contact head 22B has a further tapering so as to make a substantially point-like contact on a pad of the PCB of the probe card comprising the probe head 21. The contact head 22B also has a respective undercut wall that, thanks to its enlarged portion, rests on the upper guide 23 and is configured to achieve the desired retention of the contact probe 22 in the probe head 21 even in the absence of contact of said probe head 21 with the device under test.

[0058] Precisely, the presence of such enlarged portions in the contact heads 22B of the contact probes 22 increases the problems associated with the correct storage and freedom of movement of the contact probes 22 in the probe head 21. As already explained, during operation of said probe head 21, i.e. in case of testing operation of devices integrated on a semiconductor wafer, the contact probes 22 undergo bending and deformation when their contact tips 22A abut against the pads of the device under test and their contact heads 22B abut against corresponding contact pads of the PCB or of the space transformer of the probe card comprising said probe head 21; during said contact, the contact probes 22, but also the entire probe head 21, i.e. according to the direction of the longitudinal expansion axis z in the figure, are substantially pushed up towards the test device.

[0059] Advantageously, the probe head 21 according to the invention comprises at least one protective structure 27 which projects from the upper guide 23 in the direction of the test device, i.e. in the direction of the longitudinal extension axis z shown in the figures. The protective structure 27 therefore extends precisely in a number of contact heads 22B which project from the upper guide 23 according to the direction of the longitudinal extension axis z.

[0060] In particular, the protective structure 27 has a height H1 (H1≧HB) equal to or preferably greater than the corresponding heights HB of the contact heads 22B starting from their enlarged portions to the substantially point-like ends of the actual contact. More specifically, the height HB of each individual contact head 22B is measured from the undercut wall Sq, i.e., from the maximum diameter cross section, to the tapered end forming the actual contact area, i.e., the substantially point-like minimum diameter cross section. Furthermore, the height H1 of the protective structure 27 is selected to be equal to or preferably greater than the maximum of all heights of the contact heads 22B of the contact probes 22; in this way, the protective structure 27 can properly protect all the contact heads 22B of the contact probes 22 of the probe head 21.

[0061] Although not shown in the figure, it is noted that the probe head 21 may also comprise a plurality of contact probes 22 having a second terminal portion 21B provided with a plurality of non-magnified contact heads 22B. In this case, the protective structure 27 is used to avoid excessive approach of the plurality of contact heads 22B, in particular of the actual area of ​​contact, with the upper guide 23, which approach may result in engagement of the plurality of contact heads 22B in such a plurality of upper guide holes 23H with the resultant malfunction of the probe head 21 as a whole, in particular due to lack of contact with a PCB for connecting and coupling with a test device. In this case, the height H1 of the protective structure 27 is selected to be larger than the tapered portion of the second terminal portion 21B forming the contact head 22B, or in any case to avoid engagement of the contact head 22B in the corresponding upper guide hole 23H that accommodates it in the upper guide 23; furthermore, in this case, the height H1 of the protective structure 27 is determined to be equal to or preferably larger than the maximum one of all the heights of the multiple tapered portions of the multiple contact heads 22B of the multiple contact probes 22.

[0062] The protective structure 27 is substantially removably fixed to the upper guide 23, for example by an adhesive glue layer, by welding or by fastening means such as screws or clips that at least partially intersect the protective surface 27 and the upper guide 23.

[0063] Such a protective structure 27 may be substantially shaped as a frame or may have one or more parts in the area of ​​the upper guide 23 that is not intersected by a plurality of guide holes and therefore by a plurality of contact probes 22 all protruding from the upper guide 23 in the direction of the longitudinal development axis z.

[0064] 3A shows a probe head 21 mounted on a probe card 20, which also comprises a space transformer or, in general, a PCB 28 for connecting and coupling with a test device (not shown). In particular, the PCB 28 comprises a plurality of contact pads 28A against which the plurality of contact heads 22B of the plurality of contact probes 22 abut. The probe card 20 is configured to abut by its probe head 21 against a device under test 30, which is in particular integrated on a semiconductor wafer 30′ and which is provided with a corresponding plurality of pads 30A against which the plurality of contact tips 22A of the plurality of contact probes 22 abut.

[0065] As already shown, during a test operation performed by the probe card 20, i.e. when the probe head 21 is in pressing contact with the device under test 30 and with the PCB 28, the contact probes 22 extend between the upper guide 23 and the lower guide 24 and bend in a bending region 26 having a length L corresponding to the height of the case 25.

[0066] The first terminals 21A of the contact probes 22 at the contact tips 22A extend in a first area ZA between the lower guide 24 and the device under test 30; in particular, the contact tips 22A protrude with a preferred first length LA relative to the lower guide 24 of the probe head 21, relative to a plane π1 defined by the wafer 20' of the device under test 30 in pressing contact with said probe head 21, corresponding to the length of the first area ZA. The first area ZA allows movement of the contact tips 22A of the contact probes 22 over the contact pads 30A of the device under test 30 during operation of the probe head 21 and of the probe card 20 comprising it, and is therefore denoted as a scrub area ZA.

[0067] Similarly, the second terminals 21B of the contact probes 22 in the contact head 22B extend in a second region ZB between the upper guide 23 of the probe head 21 and the PCB 28; in particular, the contact head 21B projects a preferred second length LB relative to said upper guide 23, relative to the plane π2 of the PCB 28, which is in pressing contact with the probe head 21 as well as the device under test 30, corresponding to the length of the second region ZB. The second region ZB allows movement of the contact tips 22B of the contact probes 22 during operation of the probe head 21 and of the probe card 20 comprising it, and is therefore denoted as a floating region ZB.

[0068] Essentially, Figure 3A shows the probe head 21 in an operational state, i.e. during the testing phase of a device under test 30 integrated in a wafer 30', where each of the multiple contact probes 22 contained therein has a contact tip 22A in pressing contact with a contact pad 30A of the device under test 30, and a contact head 22B in pressing contact with a contact pad 28A of a PCB 28; in the example shown, the protective structure 27 is in contact with the PCB 28.

[0069] It is thus pointed out that the protective structure 27 of the probe head 21 essentially acts as a spacer element between the contact heads 22B of the contact probes 22 and the PCB 28, ensuring a constant and correct contact with said PCB 28 and therefore with the test elements of the test device of which the probe card 20 constitutes the terminal elements, precisely by the contact heads 22B abutting against the contact pads 28A of the PCB 28, allowing the length LB of the floating area ZB to remain constant. The protective structure 27 also prevents the contact probes 22, even without the enlarged contact heads 22B, from meshing in the upper guide holes 23H provided in the upper guide 23 and arranged to accommodate them. A corresponding number of lower guide holes 24H are provided in the lower guide 24 to accommodate the contact probes 22.

[0070] It is also possible to make the protective structure 27 by a suitable configuration of the upper guide 23, in particular by providing it with a protruding portion 23' in the direction of the PCB 28, said protruding portion 23' for example extending outside the area of ​​said upper guide 23 provided with the upper guide holes 23H and thus having the form of a frame or edge of the upper guide 23 configured to accommodate the contact probes 22 so as to ensure a correct operation of the probe head 21 and of the probe card 20 comprising it, as shown diagrammatically in Fig. 3B. In this case, the protective structure 27 is made integral with the upper guide 23.

[0071] 3C, the protective structure 27 may also be made of multiple layers 27a, 27b, 27c, 27d that are individually removable or peelable, preferably stacked alternately between the PCB 28 and the upper guide 23, to provide a protective structure 27 with a height H1 that may be modified. The multiple layers 27a, 27b, 27c, 27d may be integrated with each other by an adhesive material, such as glue with a weak seal, to easily allow them to be separated from each other.

[0072] The protective structure 27 shown in FIG. 3C comprises four layers, by way of non-limiting example only, although the structure may comprise any number, even just one, of layers having equal or different thicknesses.

[0073] Such an embodiment has been found to be particularly advantageous. Indeed, it is well known that as the probe head 21 is used, the first terminal portion 21A reduces its length LA due to the passage of its contact tip 22A over the polishing cloth, as described above. Essentially, the first terminal portion 21A wears during each cleaning action of the corresponding contact tip 22A, reducing the length LA of the scrub area ZA until the probe head 21 is no longer able to function properly.

[0074] Preferably, according to this embodiment, the protective structure 27 is reduced in height by removing one or more layers 27a, 27b, 27c, 27d, which reduces the length LB of the floating area ZB and thus allows the upper guide 23-lower guide 24-case 25 assembly, i.e., the probe head 21, to move to the other side and allows the contact probe 22 housed therein to protrude more from the lower guide 24, thereby increasing the length LA of the scrub area ZA.

[0075] The protective structure 27, and in particular the number or height of its multiple layers 27a, 27b, 27c, 27d, are dimensioned as required to have a height H1 sufficiently greater than the height HB of the contact head 22B so as to ensure correct storage of the contact head 22B and, in particular, a sufficient length LB of the floating region ZB even after removal of one or more of the multiple layers 27a, 27b, 27c, 27d of the protective structure 27.

[0076] According to an alternative embodiment not shown in the figures, the protective structure 27 comprises at least a fixed part, the height of which is equal to or greater than the height HB of the contact head 22B, and a further part with individually removable layers. In this way, it is ensured that the height H1 of the protective structure 27 is always equal to or greater than the height HB of the contact head 22B, even after removal of all the removable layers.

[0077] The protective structure 27 and, if present, its layers 27a-27d are made of transparent or translucent plastic, ceramic or metallic, organic or silicone materials, preferably Kapton®. Furthermore, said layers may be integrated with one another, for example by a layer of adhesive material, preferably with weak adhesion, or by further removable fastening means such as screws or clips.

[0078] 3C, by way of example, the protective structure 27 and its individual layers 27a-27d are made in the form of a frame. It is also possible to make the protective structure 27 in the form of a half-frame pair extending along substantially both parallel sides of the probe head 21 and the upper guide 23.

[0079] Although not shown in the figures, it is noted that the protective structure 27 and, if present, its layers 27a-27d may be made to protrude relative to the upper guide 23 and / or the PCB .

[0080] The protective structure 27 may also assume a completely different shape, such as, for example, one or more individual posts positioned on the upper guide 23 in the housing area of ​​the contact probes 22 in an area without a corresponding plurality of upper guide holes 23H, as shown diagrammatically in Fig. 4A. In the illustrated example, the protective structure 27 comprises a pair of posts extending between the upper guide 23 and the PCB 28 in the area not occupied by the contact probes 22.

[0081] Moreover, in this case, the protective structure 27 protrudes from the upper guide 23 in the direction of the test device and is substantially removably fixed to said guide, for example by an adhesive glue layer, by welding or by fastening means such as screws or clips that at least partially cross the protective structure 27 and the upper guide 23. Moreover, as mentioned above, the protective structure 27 always has a height H1 (H1≧HB) that is equal to or preferably greater than the corresponding height HB of the contact heads 22B, intended as the maximum of the heights of the individual contact heads 22B of the contact probes 22 housed in the probe head 21 and corresponding to the total volume of the contact heads 22B with their enlarged portions. Alternatively, the height H1 of the protective structure 27 is established to avoid engagement of the contact heads 22B in the corresponding upper guide holes 23H of the upper guide 23, especially in the absence of enlarged portions.

[0082] As mentioned above, it is also possible to make the protective structure 27 by a suitable configuration of the upper guide 23, in particular by providing it with a portion 23' protruding in the direction of the PCB 28, as shown diagrammatically in FIG. 4B, or by a protective structure 27 comprising a single pillar formed by a plurality of individually detachable or peelable layers 27a, 27b, 27c, preferably by a plurality of layers 27a, 27b, 27c, alternately stacked between the PCB 28 and the upper guide 23, as shown diagrammatically in FIG. 4C, by way of example only, three layers.

[0083] It is also well known that in "buckling beam" type vertical probe heads, such as those shown in the figures, the contact probes 22 exhibit significant problems of friction within their respective guide holes which can make it difficult or even prevent the probes from sliding therein.

[0084] The shortening of the first terminal portions 21A of the contact probes 22 due to the cleaning operation increases the likelihood of the probes interlocking within the corresponding lower guide holes; similarly, the closer the upper guide 23 is to the PCB 28, and therefore the reduction in the length LB of the floating region ZB, increases the risk of the contact probes 22 interlocking within the upper guide holes 23H, particularly in the absence of the enlarged contact heads 22B.

[0085] Advantageously, the above-mentioned reduction in sliding friction of multiple probes can be achieved thanks to the use of multiple, preferably two, parallel basic supports for forming at least one of the upper and / or lower guides of the probe head, as diagrammatically shown in Figures 5A to 5D.

[0086] For example, as in the embodiment shown in Figure 5A, the probe head 21 may have an upper guide 23 formed by a pair of plate-like, parallel basic supports, namely an upper basic support 23A and a lower basic support 23B, separated by at least one upper air region ZU having a length LU.

[0087] The probe head 21 in this case also comprises a protective structure 27 protruding from the upper guide 23, in particular from its upper basic support 23A in the direction of the PCB 28, while a bending area 26 in which the multiple contact probes 22 can further deform in case of pressure contact of the multiple probes with the device under test 30 is defined between the lower basic support 23B and the lower guide 24.

[0088] Preferably, the probe head 21 also comprises an upper spacer structure 27u having a height H2 positioned between the multiple base supports of the upper guide 23 and ensuring that the distance therebetween, and therefore the length LU of the upper air region ZU, as shown diagrammatically in FIG. 5A, is maintained.

[0089] By a suitable configuration of the lower basic support 23B of the upper guide 23, in particular by providing it with a protruding portion 23B' in the direction of the upper basic support 23A and thus of the PCB 28, as shown diagrammatically in FIG. 5B, or by a plurality of individually detachable or peelable layers, preferably alternately stacked between the upper basic support 23A and the lower basic support 23B, as shown diagrammatically in FIG. 5C, it is also possible to provide an upper spacer structure 27u, which, by way of example only, comprises three layers and has a height such as to ensure the desired length LU for the upper air region ZU.

[0090] Preferably, an upper spacer structure 27u made of multiple individually peelable layers can be used to adjust the length of the floating area ZB and the scrub area ZA without modifying the length L of the bending area 26 defined between the lower base support 23B of the upper guide 23 and the lower guide 24, as described above for the laminated protective structure 27.

[0091] In a preferred embodiment, shown diagrammatically in FIG. 5D, the probe head 21 may comprise both a protective structure 27 and an upper spacer structure 27u made up of a number of individually and independently removable or peelable layers.

[0092] The considerations just made may also apply when the lower guide 24 is formed by a pair of basic supports (24A and 24B) separated by a lower spacer structure 27l having a height H3, defining a lower air region ZL having a length LL, as shown diagrammatically in Figure 6, and when both guides are similar, the probe head therefore comprises, in addition to a protective structure 27 for the multiple contact heads 22B of the multiple contact probes 22, as shown diagrammatically in Figure 7, two pairs of basic supports (23A, 23B and 24A, 24B) and two spacer structures 27u and 27l having respective heights H2 and H3.

[0093] Furthermore, in the above alternative embodiments, it is possible to combine solutions with each other depending on the application needs of the probe head 21 and the probe card 20 comprising it, to include one or more of the structures as described above.

[0094] It is pointed out that the different layers of the protective structure 27 and of the spacer structures 27u and / or 27l can be made to have parts protruding from the probe head 21, preferably with different lengths to facilitate their correct removal. Preferably, the protruding parts have equal lengths for corresponding layers of the different structures, for example the protruding part of the layer closest to the PCB 28 having the same short length as one of the subsequent layers, which is progressively closer to the guide or support located under the structure, taking into account the local reference of the figure. It is also possible to provide for the numbering of the layers, for example by gradually increasing numbering, which is visible and is applied on the protruding parts of the layers in such a way that it is possible to verify that all the structures comprise the desired number of layers, simply by reading the numbering on all the protruding parts of the layers.

[0095] The asymmetric removal of the layers makes it possible to modify the relative distance between the supports and / or guides, and in particular may result in a tilt thereof to compensate for manufacturing or assembly errors of either the supports or the guides.

[0096] The probe card 20 also comprises such a retaining means (not shown) adapted to integrate the various components of said board, in particular the element guides and / or supports, as well as the protective structure 27 and the spacer structures (27u and 27l) provided for said purpose with suitable receiving seats for the retaining means. Said retaining means may also be used to make the PCB 28, i.e. the space transformer, and the case 25 integrated with each other.

[0097] It is noted that the illustrated embodiments of the probe head and probe card according to the present invention are all equipped with a contact tip and therefore allow the adjustment of the length of the terminal part of the contact probe, which is consumed without modifying the length of the bending region of the probe itself and therefore its dynamics, particularly with respect to scrubbing, and ensure constant maintenance of a floating region for the contact head of the contact probe so as to ensure constant and correct contact with the PCB or space transformer and therefore the test equipment, said floating region being maintained at a constant and unaltered length when the length of the contact tip of the contact probe is adjusted.

[0098] Furthermore, the presence of the protective structure makes it possible to maintain a suitable distance between the upper guide and the PCB associated with the probe head so as to ensure protection and correct retention of multiple contact probes, particularly their contact heads which may be provided with enlarged portions.

[0099] In summary, the probe head according to the invention has a long duration, since by subsequent adjustment of the length of the terminal parts of the contact probes, which protrude relative to the lower guide so as to be equal to or greater than the length corresponding to the correct operation of the probe head, it is always possible to ensure the correct storage of the further terminal parts with the contact head for multiple cleaning operations of the corresponding tips. In this way, the useful life of a probe card equipped with such a head is further extended.

[0100] Advantageously, the protective structures of the contact heads are made to extend over a limited area, even if they are severely limited with respect to the length of the guide, and thus can be arbitrarily positionable both in number and in position.

[0101] Furthermore, it is possible to make further adjustments to the length of the terminal portions of the contact probes at different points in the life of the probe head that contains them, in particular whenever the terminal portions with their contact tips have been shortened due to use and cleaning and have a length that is smaller than that corresponding to correct operation of the probe head, and furthermore, to allow the length of the terminal portions to be corrected in different ways for different contact probes in the event of misalignment of the respective contact tips due to tolerances in the process for making the probes themselves.

[0102] Obviously, those skilled in the art may make numerous modifications and variations to the above-described probe head in order to meet non-specific and specific needs, all of which fall within the scope of protection of the present invention, as defined by the following claims.

[0103] In particular, it is clearly possible to consider other geometric shapes than those illustrated by way of example in the figures.

[0104] Furthermore, further measures such as specific formation of the tip, such as a recess or an enlarged portion, and of the body, such as a stopper protruding therefrom, may be provided in the contact probe of the probe head according to the invention.

[0105] Finally, the contact probe may be made by the combination of multiple layers of conducting, semiconducting or insulating materials in planar overlap or concentric or coaxial; multi-layer solutions are also possible due to the inclusion of guides and / or supports in the probe head according to the invention.

Claims

1. A probe head (21), At least one upper guide (23) and one lower guide (24), each having a guide hole; A plurality of contact probes (22) inserted into the guide holes; a bending region (26) for the plurality of contact probes (22) defined between the upper and lower guides (23, 24); At least one protective structure (27); Equipped with Each of the plurality of contact probes (22) has at least one first terminal portion (21A) protruding from the lower guide (24) by a first length (LA) and terminating in a contact tip (22A) configured to abut a respective contact pad (30A) of a device under test (30), and a second terminal portion (21B) protruding from the upper guide (23) by a second length (LB) and terminating in a contact head (22B) configured to abut a contact pad (28A) of a PCB (28) for connecting or coupling with a test apparatus, the second terminal portion (21B) extending within a floating region (ZB) between the upper guide (23) and the PCB (28); said at least one protective structure (27) protruding from said upper guide (23) in the direction of a longitudinal extension axis (z) of said plurality of contact probes (22) towards said PCB (28); the protective structure (27) comprises a protruding portion (23') of the upper guide (23) in the direction of the longitudinal extension axis (z) of the plurality of contact probes (22) towards the PCB (28), which is made integral with the upper guide (23) and forms a fixed part of the protective structure (27), and a number of individually removable layers (27a, 27b, 27c, 27d) stacked alternately between the PCB (28) and the protruding portion (23') of the upper guide (23), which form a further part of the protective structure (27), The protective structure (27) is a spacer element between the contact heads (22B) of the multiple contact probes (22) and the PCB (28) and is configured to keep the length (LB) of the floating area (ZB) constant and to avoid excessive approach of the contact heads (22B) of the multiple contact probes (22).

2. The probe head (21) of claim 1, wherein the fixed portion of the protective structure (27) has a height equal to or greater than a height (HB) of the contact heads (22B) of the contact probes (22).

3. 2. The probe head (21) of claim 1, wherein the further portion of the protective structure (27) comprises an adhesive material or removable joining means configured to integrate the individually removable layers (27a, 27b, 27c, 27d) with one another.

4. The probe head (21) of claim 3, wherein the further portion of the protective structure (27) comprises glue as the adhesive material.

5. The probe head (21) of claim 1, wherein the protective structure (27) has a shape selected from a frame, a single protruding element.

6. The probe head (21) of claim 1, wherein the individually removable layers (27a-27d) of the protective structure (27) are made of a transparent or translucent plastic material, a ceramic material, or a metallic material, an organic material, or a silicone.

7. 2. The probe head (21) of claim 1, comprising a pair of elementary supports (23A, 23B; 24A, 24B) and comprising the upper guide (23) and / or the lower guide (24) with spacer structures (27u, 27l) positioned between a plurality of the elementary supports (23A, 23B; 24A, 24B).

8. A probe card (20) for an electronic device testing apparatus, comprising at least one probe head (21) according to any one of claims 1 to 7, and at least one PCB (28) for connecting and coupling with the testing apparatus, the probe head (21) being provided with a plurality of contact probes (22) configured to abut against a plurality of contact pads (28A) of a space transformer (28).

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