WO2023227538A1

WO2023227538A1 - Probe card with improved temperature control

Info

Publication number: WO2023227538A1
Application number: PCT/EP2023/063670
Authority: WO
Inventors: Stefano Felici
Original assignee: Technoprobe S.P.A.
Priority date: 2022-05-25
Filing date: 2023-05-22
Publication date: 2023-11-30

Abstract

It is herein described a probe card (20) for the testing of devices under test (DUT), comprising a stiffener (21), an interface board (22) associated with the stiffener (21) and configured to interface the probe card (20) to a testing apparatus, an interposer (23), and a plurality of contact elements (51) adapted to electrically connect the interposer (23) with contact pads (P) of the devices under test (DUT), the contact elements (51) comprising a body (51') that extends along a longitudinal axis (H-H) between a first end (51a), which is adapted to contact the contact pads (P) of the devices under test (DUT), and a second and opposite end (51b) adapted to contact the interposer (23). Suitably, the interposer (23) comprises a plurality of modules (23m) which are separated and connected to each other by means of at least one material bridge (23mb), said at least one material bridge (23mb) being defined between adjacent modules by material removal from a starting substrate.

Description

Title: “Probe card with improved temperature control”

DESCRIPTION

Technical Field

The present invention relates to a probe card for the testing of electronic devices integrated on a semiconductor wafer, in particular a large sized probe card, for instance for the testing of memory devices (such as for instance the DRAMs). The following disclosure is made with reference to this field of application with the sole aim of simplifying the presentation thereof.

Background Art

As it is well known, a probe card is an electronic device adapted to electrically connect a plurality of contact pads of a microstructure, such as an electronic device integrated on a semiconductor wafer, with corresponding channels of a testing apparatus that performs the functionality testing thereof, in particular electric, or generically the test. The test, which is performed on integrated devices, is particularly useful for detecting and isolating defective circuits as early as in the production phase. Normally, probe cards are therefore used for the electric test of devices that are integrated on wafers before cutting and assembling them inside a containment package.

Generally, a probe card comprises a probe head which in turn comprises a plurality of contact probes held by at least one guide or by at least one pair of guides (or supports) which are substantially plate-shaped and parallel to each other. Said guides are equipped with suitable guide holes and are arranged at a certain distance from each other in order to leave a free space or air gap for the movement and possible deformation of the contact probes, which are slidingly housed in said guide holes. In particular, the pair of guides comprises an upper guide and a lower guide, both provided with guide holes within which the contact probes axially slide, usually formed by special alloys with good electric and mechanical properties.

The good connection between the contact probes and the contact pads of the device under test is ensured by the pressure of the probe head on the device itself, the contact probes undergoing, during said pressing contact, a bending inside the air gap between the two guides and a sliding inside said guide holes. Probe heads of this type are commonly called “vertical probe heads”.

Essentially, the vertical probe heads have an air gap in which a bending of the contact probes occurs, said bending can be helped through a proper configuration of the probes themselves or of the guides thereof.

By way of example, figure 1 schematically illustrates a probe card of the known type, globally indicated with reference number 15 and including a probe head 1 in turn comprising at least one upper plate-shaped support or guide 2, usually indicated as “upper die”, and a lower plateshaped support or guide 3, usually indicated as “lower die”, having respective guide holes 4 and 5, within which a plurality of contact probes 6 slides.

Each contact probe 6 ends at an end with a contact tip 7 intended to abut onto a contact pad 8 of a device under test integrated on a wafer 9, so as to form the mechanical and electrical contact between said device under test and a testing apparatus (not represented), which said probe card 15 forms an end element thereof.

As indicated in figure 1, the upper guide 2 and the lower guide 3 are suitably spaced apart by an air gap 10 which allows the deformation of the contact probes 6.

The probe head 1 is a vertical probe head in which, as previously seen, the good connection between the contact probes 6 and the contact pads 8 of the device under test is ensured by the pressure of the probe head 1 on the device itself, the contact probes 6, which are movable withing the guide holes 4 and 5 formed in the guides 2 and 3, undergoing, during said pressing contact, a bending inside the air gap 10 and a sliding inside said guide holes.

In some cases, the contact probes are fixedly fastened to the probe head itself at the upper plate-shaped support in a fixed manner: such probe heads are referred to as “blocked probe heads”. However, more frequently, probe heads with not fixedly blocked probes, but held interfaced to a so- called board, possibly by means of a micro contact board, are used: such probe heads are referred to as “unblocked probe heads”. The microcontact board is usually called “space transformer” since, in addition to the contact with the probes, also allows spatially redistributing the contact pads formed thereon, with respect to the contact pads present on the device under test, in particular loosening the distance constraints between the centres of the pads themselves.

In this case, still referring to figure 1, each contact probe 6 has a further end area or region which ends with a so-called contact head 11 toward a contact pad 12 of a plurality of contact pads of a space transformer 13 of the probe card 15 comprising the probe head 1. The good electrical connection between contact probes 6 and space transformer 13 is ensured by the pressure abutment of the probe heads 11 of the contact probes 6 onto the contact pads 12 of said space transformer 13 analogously to the contact between the contact tips 7 with the contact pads 8 of the device under test integrated on the wafer 9.

Furthermore, the probe card 15 comprises a support plate 14, generally a printed circuit board (PCB), connected to the space transformer 13, through which the probe card 15 interfaces with the testing apparatus (not illustrated).

The proper operation of a probe head is basically linked to two parameters: the vertical movement, or overtravel, of the contact probes and the horizontal movement, or scrub, of the contact tips of such contact probes on the contact pads. All these features should be evaluated and calibrated in the manufacturing phase of a probe card, since the proper electric connection between probes and device under test should always be ensured.

Furthermore, according to the known solutions, the support plate 14 is kept in position by a stiffener 16.

It is also worth noting that that the space transformer 13 has thicknesses which are generally very reduced and therefore has significant flatness issues. For this reason, it is also generally associated with a stiffener (not illustrated in figure 1), which is configured to make the whole more rigid and resistant and allows reducing the flatness defects, which often result in invalidating the proper operation of the cards made using the aforementioned technology.

Generally, test methodologies require the probe card to withstand extreme temperatures, as well as to work correctly at different temperatures (both very low and very high temperatures). In this case, however, the thermal expansions of the elements making up the probe card can invalidate its correct behaviour. Indeed, the elements that make up the probe cards of the known type (like the aforementioned stiffener, PCB, and interposer) are usually fastened through screws and have different thermal expansion coefficients, as well as they are subjected to different temperatures during the test, with the formation of a temperature gradient in the probe card. During a temperature test, due to the different thermal expansion coefficients of the materials that make these elements and the bonds between them, the elements themselves tend to arch, resulting in malfunctions of the probe card as a whole, at least its lack of contact with the contact pads of the device under test.

This problem is particularly felt in case of large sized probe cards, such as for instance the probe cards for the test of memory devices such as the DRAMs. For this kind of probe cards, indeed, failure to control the thermal expansion of the components leads to considerable problems in the testing phase. The technical problem of the present invention is to provide a probe card for the test of electronic devices having functional and structural features such as to allow overcoming the limitations and drawbacks still affecting the known solutions, in particular a probe card that allows ensuring the correct performance of tests even at extreme temperatures and to withstand considerable temperature variations, while having a simple structure and being easy to assemble.

Disclosure of Invention

The solution idea underlying the present invention is to provide a probe card having an interposer structured in a plurality of semi-independent modules that allow an improved control of the thermal expansion during the test, each module being connected to the adjacent module through at least one material bridge which is formed by removing material from a starting substrate or monobloc. Particularly, from said starting monobloc, the single modules are defined (for instance by laser cutting), which however are not completely separated but remain connected to each other through the above material bridges, thus ensuring their mutual connection and meanwhile the thermal expansion thereof thanks to the gaps between a module and the other, thus solving the problem of the mechanical stresses caused by mismatched CTEs among various components.

Based on this solution idea, the above technical problem is solved by a probe card for the testing of devices under test, comprising a stiffener, an interface board associated with the stiffener and configured to interface the probe card to a testing apparatus, an interposer, and a plurality of contact elements adapted to electrically connect the interposer with contact pads of the devices under test, the contact elements comprising a body that extends along a longitudinal axis between a first end, which is adapted to contact the contact pads of the devices under test, and a second and opposite end adapted to contact the interposer, characterized in that the interposer comprises a plurality of modules which are separated and connected to each other just by means of at least one material bridge, said at least one material bridge being defined by material removal from a starting substrate.

More particularly, the invention comprises the following additional and optional features, taken singularly or in combination if needed.

According to an aspect of the present invention, the modules of the interposer may be formed (obtained) by cutting the starting substrate by means of a laser, which is initially in the form of a monobloc of material.

According to an aspect of the present invention, the interposer may be connected to the stiffener.

According to an aspect of the present invention, the stiffener may comprise a first stiffener portion and a second stiffener portion, the interface board being arranged between the first stiffener portion and the second stiffener portion.

According to an aspect of the present invention, the interposer may be connected to the second stiffener portion.

According to an aspect of the present invention, the second stiffener portion may comprise a plurality of housing seats, wherein at each of said housing seats there is a corresponding module of the plurality of modules of the interposer.

According to an aspect of the present invention, the probe card may comprise a plurality of electrical connection elements housed in the housing seats and configured to electrically connect the interposer and the interface board to each other.

According to an aspect of the present invention, the interposer may be made of an organic multilayer material (MLO).

According to an aspect of the present invention, the second end of the contact elements may be adapted to contact the interposer in a non-fixed manner. According to an aspect of the present invention, the interface board may be a printed circuit board (PCB) .

According to an aspect of the present invention, the interposer may comprise a number of modules from 50 to 150.

According to an aspect of the present invention, the stiffener may be made of at least one of Invar, Kovar, Alloy 42 or FeNi alloys, Titanium or alloys thereof, Aluminum or alloys thereof, Steel, Brass, Macor.

According to an aspect of the present invention, a module of the interposer may be connected to an adjacent module by means of a plurality of material bridges (namely at least two material bridges), for instance one at the centre of a side and one at the vertex of a same module.

According to an aspect of the present invention, the modules of the interposer may have a shape selected from a squared shape, a rectangular shape, or any suitable polygonal shape.

According to an aspect of the present invention, the material bridge may be arranged at a vertex of the modules, or at the centre of a side of the modules, or at any position between the two aforementioned different placements.

According to an aspect of the present invention, the material bridge may have a thickness that is lower than a thickness of the modules of the interposer, so as to favour the thermal expansion of the latter.

The features and advantages of the probe card according to the invention will become apparent from the following description of an embodiment thereof, given by way of indicative and non-limiting example, with reference to the attached drawings.

Brief Description of Drawings

In these drawings: Figure 1 schematically shows a probe card according to the prior art;

Figure 2 schematically shows a probe card according to the present invention;

Figure 3 schematically shows a probe card according to an embodiment of the present invention; and

Figure 4 is a schematic top view of a portion of an interposer of the probe card according to an embodiment of the present invention.

Modes for Carrying Out the Invention

With reference to these figures, reference number 20 globally and schematically indicates a probe card for the testing of electronic devices integrated on a semi-conductor wafer made according to the present invention.

It should be noted that the figures represent schematic views and are not drawn to scale, but instead they are drawn so as to enhance the important features of the invention. Furthermore, in the figures, the different pieces are shown schematically since their shape may vary according to the desired application. It should also be noted that, in the figures, identical reference numbers refer to elements that are identical in shape or function. Finally, particular features disclosed in relation to an embodiment illustrated in one figure may also be used in one or more of the embodiments illustrated in the other figures.

It is also noted that, unless expressly indicated, the process phases may also be inverted if necessary.

As it will be illustrated hereinafter, the probe card 20 of the present invention is particularly suitable for the test of memory devices, such as for instance the DRAMs, due to its large size. Indeed, it is noted right away that, as a whole, the area under test may reach 300 mm (in this case we are talking of 12 -inch size cards), so that as a whole the probe card 20 may also reach dimensions up to 520 mm, even if obviously said probe card is not limited by a specific dimension. For instance, in embodiments in which the probe card 20 is circular-shaped as a whole (and thus comprises circular- shaped guides), its maximum diameter may be around 520 mm.

Obviously, the above-illustrated application is just indicative and the probe card 20 of the present invention may be used for the test of many other electronic devices. For instance, another one of the many possible applications is in the automotive filed, as well as many other different applications. The measures and shapes indicated are also purely indicative and the probe card 20 may have any suitable measure or shape.

It is also noted that herein the term “associate” means connect, both directly and indirectly, an element to another, not necessarily in a rigid way.

As illustrated in the embodiment of figure 2, the probe card 20 comprises a stiffener 21, which has the purpose of keeping the components of the probe card 20 in position and to solve the flatness problems.

In a particular and non-limiting embodiment of the present invention, illustrated in figure 3, the stiffener 21 in turn includes a first stiffener portion 21’ and a second stiffener portion 21”. Particularly, the first stiffener portion 21’ and the second stiffener portion 21” are initially structurally independent from each other, namely the stiffener 21 is substantially structured into two separated stiffeners. As known in the field, the first stiffener portion 21’ is also called upper stiffener and the second stiffener portion 21” is also called lower stiffener. The first stiffener portion 21’, during the test, is closer to the testing apparatus (not illustrated in the figures), whereas the second stiffener portion 21”, during the test, is closer to the wafer W including the devices under test (indicated herein with reference “DUT”, acronym from “Device Under Test”). The probe card 20 further comprises an interface board 22 associated with the stiffener 21 and configured to interface the probe card 20 to the testing apparatus. Particularly, the interface board 22 is a printed circuit board (PCB).

The PCB 22 comprises at least one lower face Fa which, during the test, faces toward the wafer W including the devices under test DUT, and an upper face Fb opposite the lower face Fa.

As illustrated in figure 3, in a non-limiting embodiment, the PCB 22 is arranged between the first stiffener portion 21 ’ and the second stiffener portion 21”, thus substantially forming a sandwich configuration.

For instance, the PCB 22 has a thermal expansion coefficient (CTE) of around 16 ppm/ °C (IO ⁶/ °C). In order to limit the effects of the thermal expansion of the PCB 22 during the test, in an embodiment of the present invention, said PCB 22 is associated with the stiffener 21 in a floating manner.

More particularly, connection elements with clearance 22c for the connection of the PCB 22 to the stiffener 21 (particularly to the first stiffener portion 21’) are provided, said connection elements with clearance 22c (such as for instance suitable screws) being housed in a plurality of respective seats 22s (such as for instance suitable slotted holes) formed in the PCB 22, so as to allow associating said PCB 22 with the stiffener 21 in a floating manner.

The connection between the first stiffener portion 21’ and the second stiffener portion 21 ” is also such as to allow the relative movement of the PCB 22 arranged therebetween, at least in the x-y plane (namely the plane in which the wafer W lies, and possibly slightly also along the z vertical axis), namely, to avoid fixedly fastening said PCB 22.

As illustrated in figure 3, the first stiffener portion 21’ and the second stiffener portion 21” are fastened to each other by means of a plurality of screws 21c. Bushings 21b to favour the above mentioned floating of the PCB 22 may further be provided.

In an embodiment, the first stiffener portion 21 ’ and the second stiffener portion 21” are rigidly thus connected to each other, for instance through screws as above illustrated.

Obviously, many other connection modes may also be provided, the figures being only provided by way of indicative and non-limiting example of the scope of the present invention.

In an embodiment of the present invention, the stiffener 21 is made of a material selected from suitable FeNi alloys (for instance Invar, Kovar, Alloy 42, and others), Titanium or alloys thereof, Aluminum or alloys thereof, Steel, Brass, Macor, however, without limiting to these materials. In general, the CTE of the stiffeners is optimized depending on the temperature range which the probe card 20 must operate at, which is controllable thanks to the materials used.

In a non-limiting embodiment of the present invention, the first stiffener portion 21’ and the second stiffener portion 21” are made of materials having different CTEs, respectively, since during the test a temperature gradient is created and the first stiffener portion 21 ’ (which is the farthest from the device under test) preferably has a CTE that is greater than the second stiffener portion 21”. The balancing between said stiffener portions is carried out, as mentioned above, according to the testing platform and the operating temperature range. Obviously, it is possible to use a same material (for instance just Kovar) for these components, but with a differently controlled CTE so as to compensate for the above gradients, as well as to also use different materials (for instance selected among the above-mentioned ones or chose particular alloys) .

Obviously, the provided examples are just indicative and non-limiting of the scope of the present invention, which is not limited by the materials used and many other solutions may be implemented.

Furthermore, the probe card 20 comprises an interposer 23, for instance connected to the stiffener 21, in particular connected to the second stiffener portion 21 ”.

As known in the field, the interposer 23 is adapted to make a spatial transformation of the distances between contact pads made on its opposite faces, reason why this component is also called “space transformer”.

Advantageously according to the present invention, the interposer 23 comprises a plurality of modules 23m separated and connected to each other through at least one material bridge 23 mb, which is defined among adjacent modules by material removal from a starting substrate.

In a non-limiting embodiment, the modules 23m of the interposer 23 are formed by laser cutting of the starting substrate, even if other processing modes of said interposer 23 are possible and the present invention is not limited to a particular manufacturing process.

In this way, once the single modules 23m, which are connected to each other just through the material bridge 23 mb, have been formed, said interposer 23 is associated with the remaining components of the probe card 20 as a single component (for instance a single board), but with the modules 23m already suitably formed.

In this way, initially at least one single monobloc of material is provided, namely a single structural element in which elements separated from each other are not present, element which is suitably shaped as above described prior to the connection with the remaining components of the probe card 20, with the formation of the modules 23m.

As above noted, the modules 23m are not completely separated but are semi-independent, each module being connected to the adjacent module through at least one material bridge 23mb which is formed by removing material from the starting substrate or monobloc, which allows an improved control of the thermal expansion during the test. The material bridges 23mb thus ensure the mutual connection between the modules 23m and meanwhile the thermal expansion thereof thanks to the gaps between a module and the other (indicated in the figures with reference G, said gaps being formed by the aforementioned material removal from the substrate), thus solving the problem of the mechanical stresses caused by mismatched CTEs among various components. The structural independence of the modules 23m thus ensures a greater control of the thermal expansion of the components during the test, in particular at extreme temperatures, as it will be specified hereinafter.

All of this also greatly simplifies the assembling process and setting up the probe card 20, since it is no longer necessary to align the single modules (which would however be requested should these modules be associated with the other components of the probe card already completely singularized) .

In an alternative embodiment, it is also possible to use more than one starting monobloc (for instance two or three, in any case in a limited number), said monoblocs being however always subsequently divided into many modules 23m connected through the material bridges 23mb, and then joined to the other components of the probe card 20.

As illustrated in the figures, the probe card 20 further comprises a probe head 50, which includes a plurality of contact elements 51 (for instance contact probes) adapted to electrically connect the interposer 23 with contact pads P of the devices under test DUT integrated in the semiconductor wafer W.

As mentioned above, the interposer 23 has the function of redistributing the signals carried by the contact elements 51 and of allowing a redistribution of the contact pads on the PCB. Generally, the space transformers are made of an MLC (acronym for the term “Multi-Layer Ceramic”). Well, advantageously according to the present invention, the interposer 23 is instead made of a multilayer organic material (MLO, acronym from the English term “Multi-Layer Organic”) The use of an MLO ensures a greater flexibility than a ceramic material, as well as greater ease of processing (making for instance the laser cutting easier, resulting in savings in processing costs) .

The contact elements 51 comprise a body 51’ that extends along a longitudinal axis H-H between a first end 51a and a second and opposite end 51b. The first end 51a is adapted to contact the contact pads P of the devices under test DUT, whereas the second end 51b is adapted to contact the interposer 23, preferably in a non-fixedly manner. In this way, the contact elements are not fixedly fastened to the interposer 23.

Suitably, in a preferred embodiment, the contact elements 51 are thus vertical contact probes, as well as it is possible to exploit all of the advantages of this vertical technology.

Still referring to figure 3, the second stiffener portion 21” comprises a plurality of housing seats 24, at each of which a corresponding module of the plurality of modules 23m of the interposer 23di is arranged. The housing seats 24 may be in the form of through-holes made in the second stiffener portion 21” and are in an identical number to that of the modules 23m of the interposer 23, which are arranged at respective housing seats 24.

In an embodiment of the present invention, the probe card 20 comprises a plurality of electrical connection elements 25 housed in the housing seats 24 and configured to electrically connect the interposer 23 and the PCB 22 to each other. In this way, during the creation of the probe card 20, the electrical connection elements 25 are inserted into the respective housing seats 24 prior to connecting the interposer 23 to the second stiffener portion 21”. By way of example, the electrical connection elements 25 may be in the form of conductive elastomers, pogo pin or conductive clips.

In a non-limiting embodiment, the interposer 23 may be connected to the stiffener 21 through screws, as well as it is possible to adopt different attachment modes of the interposer 23. For instance, in an alternative embodiment, the interposer 23 may be glued to the stiffener. Furthermore, in an embodiment, the interposer 23 may not be connected to the stiffener 21, but for instance to the PCB 22.

The interposer 23 may comprise a high number of modules 23m, for instance a number of modules varying from 50 to 150. Each module is moreover configured for the testing of a plurality of devices, for instance a number of devices ranging from 1 to 30. It is thus clear that, with a single testing operation, the probe card 20 of the present invention manages to perform, thanks to its large size and the large number of modules 23m associated therewith, the test of a high number of devices, being at the same time easy to assemble and ensuring an excellent control of the thermal expansion of the components thereof.

Suitably, as above illustrated, the probe card allows using a vertical probe head, thus exploiting all of the potential of the vertical technology as described above.

Furthermore, in an embodiment, a module of the interposer 23 may be connected to an adjacent module by means of a plurality of material bridges 23mb, and thus not only of a single material bridge but also of two or more material bridges, for instance one at the centre and one at the vertex of a same module.

The modules 23m are not limited by a particular embodiment. For instance, said modules 23m may have a shape selected from a squared shape, a rectangular shape, or in general any suitable polygonal shape.

Even the arrangement of the material bridges is not limited by one in particular, the optimal arrangement being selected based on the needs and/or circumstances. For instance, the material bridge 23mb may be arranged at a vertex of the modules 23m, or (as schematized in figure 4) at the centre of a side of said modules 23m, or at any position between said two different placements.

Finally, it is noted that the material bridge 23m may have a thickness that is lower than the thickness of the modules 23m, so as to favour the thermal expansion of the latter.

In conclusion, the present invention provides a probe card having an interposer structured in a plurality of semi-independent modules that allow an improved control of the thermal expansion during the test, each module being connected to the adjacent module through at least one material bridge that is formed by removing material from a starting substrate or monobloc. Particularly, starting from said starting monobloc, the single modules are defined (for instance through laser cutting), which, however, are not completely separated but remain connected to each other through the so-called material bridges, thus ensuring their mutual connection and meanwhile the thermal expansion thereof thanks to the gaps between a module and the other, thus solving the problem of mechanical stresses caused by mismatched CTEs among various components.

Advantageously according to the present invention, it is thus possible to control the thermal expansion of the components of the probe card during the tests at extreme temperatures in an extremely easy manner, significantly reducing, if not completely eliminating, the harmful effects of said thermal expansion. The proposed probe card can withstand significant temperature variations (for instance from -40 °C to + 125 °C) without suffering warping of its components, thus solving the technical problem of the present invention.

More particularly, thanks to the presence of the various modules of the interposer separated from each other, said interposer is independent from the thermal expansion coefficient of the stiffener (namely it is not affected by the expansion of the latter) and of the other components of the probe card, so that the expansion of said components does not cause mechanical stresses of the interposer thanks to the gaps between a module and the other, which allow a relative movement thereof.

The thermal expansion of the probe card as a whole is thus mainly due to the stiffener’s contribution, whose thermal expansion coefficient may be calibrated in such a way that the components can expand without creating warping, thus ensuring the flatness of the probe head over the entire test temperature range (which, as noted above, can vary between extreme values that are distant from each other). In other words, the relative independence of the modules of the interposer makes the global coefficient of the thermal expansion of the probe card be substantially managed by the stiffener, so that it is easier to compensate for the temperature gradients and the different expansions within said card.

Suitably according to the present invention, this configuration is obtained in an extremely easy manner, simply by making the above interposer, whose modules are connected to each other by the material bridges, which are made by material removal from a starting substrate.

Particularly, thanks to the material bridges, it is very simple to manage the interposer in the assembly phase, since there is only a single element to manage and associate with the remaining components of the probe card, but with the modules already formed (and not completely separated, which would make the alignment difficult), and meanwhile the expansion and relative movement of said modules are ensured even at extreme temperatures.

Advantageously, the solution adopted thus allows not having to align the various modules with each other, since they are already perfectly aligned once the interposer has been shaped (initially in the shape of a single piece of material, which may be formed separately), thus considerably simplifying the manufacturing and use of the probe card of the present invention. All this leads to a considerable saving in production times and costs, without renouncing the advantages of said probe card but rather obtaining a much more reliable solution, since there are no relative alignment errors between the various components.

Furthermore, the use of an MLO for the space transformer makes the above process simpler and more economical. This is particularly advantageous in case of large sized probe heads, such as for instance those used in the test of memory devices such as the DRAMs, for which the relative alignment of the various components is even more delicate precisely because of the large dimensions, and for which the thermal expansion of the various components is even more critical.

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

Claims

1. A probe card (20) for the testing of devices under test (DUT), comprising: a stiffener (21); an interface board (22) associated with the stiffener (21) and configured to interface the probe card (20) to a testing apparatus; an interposer (23); and a plurality of contact elements (51) adapted to electrically connect the interposer (23) with contact pads (P) of the devices under test (DUT), said contact elements (51) comprising a body (51’) that extends along a longitudinal axis (H-H) between a first end (51a), which is adapted to contact the contact pads (P) of the devices under test (DUT), and a second and opposite end (51b), which is adapted to contact the interposer (23), characterized in that the interposer (23) comprises a plurality of separate modules (23m) which are connected to each other by means of at least one material bridge (23mb), said at least one material bridge (23mb) being defined between adjacent modules by material removal from a starting substrate.

2. The probe card (20) according to claim 1, wherein the modules (23m) of the interposer (23) are obtained by cutting the starting substrate by means of a laser.

3. The probe card (20) according to claim 1, wherein the interposer (23) is connected to the stiffener (21).

4. The probe card (20) according to claim 1, wherein the stiffener (21) comprises a first stiffener portion (21j and a second stiffener portion (21”), the interface board (22) being arranged between the first stiffener portion (21j and the second stiffener portion (21”), and wherein the interposer (23) is connected to the second stiffener portion (21”).

5. The probe card (20) according to claim 4, wherein the second stiffener portion (21”) comprises a plurality of housing seats (24), and wherein at each of said housing seats (24) there is a corresponding module of the plurality of modules (23m) of the interposer (23).

6. The probe card (20) according to claim 5, comprising a plurality of electrical connection elements (25) housed in the housing seats (24) and configured to electrically connect the interposer (23) and the interface board (22) to each other.

7. The probe card (20) according to claim 1, wherein the interposer (23) is made of an organic multilayer material (MLO).

8. The probe card (20) according to claim 1, wherein the second end (51b) of the contact elements (51) is adapted to contact the interposer (23) in a non-fixed manner.

9. The probe card (20) according to claim 1, wherein the interface board (22) is a printed circuit board (PCB).

10. The probe card (20) according to claim 1, wherein the interposer (23) comprises a number of modules ranging from 50 to 150.

11. The probe card (20) according to claim 1, wherein the stiffener (21) is made of at least one of Invar, Kovar, Alloy 42 or FeNi alloys, Titanium or alloys thereof, Aluminum or alloys thereof, Steel, Brass, Macor.

12. The probe card (20) according to claim 1, wherein a module of the interposer (23) is connected to an adjacent module by means of a plurality of material bridges (23mb).

13. The probe card (20) according to claiml, wherein: the modules (23m) of the interposer (23) have a shape selected from a squared shape, a rectangular shape, or any polygonal shape, and the material bridge (23mb) is arranged at a vertex of said modules (23m), or at the centre of a side of said modules (23m), or at any position between said two placements.

14. The probe card (20) according to claim 1, wherein the material bridge (23mb) has a thickness that is lower than a thickness of the modules (23m) of the interposer (23).