MANUFACTURING METHOD OF A MULTI-LAYER FOR A PROBE CARD

Abstract

A method of manufacturing a multi-layer for a probe card comprises providing first contact pads on an exposed face of a first dielectric layer and second contact pads on an exposed face of a last dielectric layer. Each dielectric layer is laser ablated to realize pass-through structures and the pass-through structures are conductively filled to realize conductive structures. The dielectric layers are superimposed in a way that each conductive structure contacts a corresponding conductive structure of a contiguous dielectric layer in the multi-layer and forms conductive paths electrically connected the first and second contact pads. The second contact pads having a greater distance between its symmetry centers than the first contact pads, the multi-layer thus performing a spatial transformation between the first and second contact pads connected through the connective paths.

Claims

1. A manufacturing method of manufacturing a multi-layer for a probe card, comprising: providing a plurality of dielectric layers starting from a first dielectric layer to a last dielectric layer; providing a first plurality of contact pads realized on a first face of the multi-layer in correspondence of an exposed face of the first dielectric layer; providing a second plurality of contact pads realized on an opposite, second face of the multi-layer, in correspondence of an exposed face of the last dielectric layer; realizing, by laser ablation, in each dielectric layer of the plurality of dielectric layer a plurality of pass-through structures occurring in matching number in each dielectric layer, the matching number of pass-through structures being adapted to put into communication opposite faces of each dielectric layer; filling the plurality of pass-through structures with a conductive material to realize in each dielectric layer a plurality of conductive structures; and superimposing the plurality of dielectric layers in a way that each conductive structure of the plurality of conductive structures of each dielectric layer is in contact with a corresponding conductive structure of the plurality of conductive structures of a subsequent and contiguous dielectric layer in the multi-layer and forms a plurality of conductive paths; the conductive paths establishing an electrical connection between the first plurality of contact pads realized on the first face of the multi-layer in correspondence of an exposed face of the first dielectric layer and the second plurality of contact pads realized on the second face of the multi-layer, in correspondence of the exposed face of the last dielectric layer, the second plurality of contact pads having respective symmetry centers spaced apart by a greater distance than respective symmetry centers of the first plurality of contact pads are spaced from each other, the multi-layer thus performing a spatial transformation between the first and second pluralities of contact pads connected through the connective paths.

2. The manufacturing method of claim 1, wherein the first and second pluralities of contact pads are realized in superficial connective zones of the conductive structures in correspondence of the exposed faces of the first and last dielectric layers.

3. The manufacturing method of claim 1, wherein realizing in each dielectric layer the plurality of pass-through structures comprises realizing at least one pass-through hole, transversally extending and connecting opposite faces of the dielectric layer.

4. The manufacturing method of claim 3, wherein realizing in each dielectric layer the plurality of pass-through structures further comprises realizing at least one recess, longitudinally extending starting from the pass-through hole at one of the faces of the dielectric layer.

5. The manufacturing method of claim 4, wherein realizing the pass-through holes realizes pass-through holes having a progressively greater distance starting from the first dielectric layer gradually towards the last dielectric layer and realizing the recesses realizes corresponding recesses having longitudinal extension equal to a distance between opposed faces of corresponding pass-through holes realized in subsequent and continuous dielectric layers.

6. The manufacturing method of claim 1, wherein filling the pass-through structures comprises a selective deposition of the conductive material on each dielectric layer, in order to only fill the pass-through structures and form the conductive structures.

7. The manufacturing method of claim 6, wherein the selective deposition of the conductive material comprises a serigraphic process.

8. The manufacturing method of claim 1, wherein filling the pass-through structures comprises a non-selective deposition of the conductive material on a whole surface of each dielectric layer and in the pass-through structures, in order to form the conductive structures and a superficial conductive layer on the whole surface of each dielectric layer.

9. The manufacturing method of claim 8, further comprising removing by lapping the superficial conductive layer formed by the conductive material on the whole surface of each dielectric layer.

10. The manufacturing method of claim 1, further comprising joining the plurality of superimposed dielectric layers.

11. The manufacturing method of claim 1, wherein each dielectric layer of the plurality of dielectric layers is realized by an inorganic material.

12. The manufacturing method of claim 11, wherein the inorganic material is chosen among a ceramic material, a glass or a ceramic glass.

13. The manufacturing method of claim 11, wherein the inorganic material is silicon nitride.

14. A multi-layer realized by a manufacturing method comprising: providing a plurality of dielectric layers starting from a first dielectric layer to a last dielectric layer; providing a first plurality of contact pads realized on a first face of the multi-layer in correspondence of an exposed face of the first dielectric layer; providing a second plurality of contact pads realized on an opposite, second face of the multi-layer, in correspondence of an exposed face of the last dielectric layer; realizing, by laser ablation, in each dielectric layer of the plurality of dielectric layer a plurality of pass-through structures occurring in matching number in each dielectric layer, the matching number of pass-through structures being adapted to put into communication opposite faces of each dielectric layer; filling the plurality of pass-through structures with a conductive material to realize in each dielectric layer a plurality of conductive structures; and superimposing the plurality of dielectric layers in a way that each conductive structure of the plurality of conductive structures of each dielectric layer is in contact with a corresponding conductive structure of the plurality of conductive structures of a subsequent and contiguous dielectric layer in the multi-layer and forms a plurality of conductive paths; the conductive paths establishing an electrical connection between the first plurality of contact pads realized on the first face of the multi-layer in correspondence of an exposed face of the first dielectric layer and the second plurality of contact pads realized on the second face of the multi-layer, in correspondence of the exposed face of the last dielectric layer, the second plurality of contact pads having respective symmetry centers spaced apart by a greater distance than respective symmetry centers of the first plurality of contact pads, the multi-layer thus performing a spatial transformation between the first and second pluralities of contact pads connected through the connective paths.

15. The multi-layer of claim 14, wherein the first and second plurality of contact pads are realized in superficial connective zones of the conductive structures in correspondence of the exposed faces of the first and last dielectric layers.

16. The multi-layer of claim 14, wherein each pass-through structure comprises at least one pass-through hole, transversally extending and connecting opposite faces of the dielectric layer.

17. The multi-layer of claim 14, wherein each pass-through structure further comprises at least one recess, longitudinally extending starting from the pass-through hole at the surface of the dielectric layer.

18. The multi-layer of claim 17, wherein the pass-through holes have a progressively greater distance starting from the first dielectric layer gradually towards the last dielectric layer and the recesses have longitudinal extension equal to a distance between opposed faces of corresponding pass-through holes realized in subsequent and continuous dielectric layers.

19. The multi-layer of claim 14, wherein the pass-through structures comprise the conductive material forming the conductive structures.

20. The multi-layer of claim 19, wherein the plurality of dielectric layers are realized by an inorganic material.

21. The multi-layer of claim 20, wherein the inorganic material is chosen among a ceramic material, a glass or a ceramic glass.

22. The multi-layer of claim 20, wherein the inorganic material is silicon nitride.

23. The multi-layer of claim 14, adapted to realize a structure chosen between a noble zone of an interposer of a probe card, a core zone of an interposer of a probe card, an interposer of a probe card or a structure comprising a fine central core sandwiched between two noble zones to a finest step.

24. The multi-layer of claim 23, wherein the noble zone or zones have pitches from 60 m to 200 m, and the core zone has pitches from 200 m to 400 m.

25. A manufacturing method of a multi-layer for a probe card for a testing apparatus for electronic devices, comprising: providing a plurality of dielectric layers starting from a first dielectric layer to a last dielectric layer; providing a first plurality of contact pads realized on a first face of the multi-layer in correspondence of an exposed face of the first dielectric layer; providing a second plurality of contact pads realized on an opposite, second face of the multi-layer, in correspondence of an exposed face of the last dielectric layer; realizing, by laser ablation, in each dielectric layer of the plurality of dielectric layer a plurality of pass-through structures occurring in matching number in each dielectric layer, the matching number of pass-through structures being adapted to put into communication opposite faces of each dielectric layer; filling the plurality of pass-through structures with a conductive material to realize in each dielectric layer a plurality of conductive structures; and superimposing the plurality of dielectric layers in a way that each conductive structure of the plurality of conductive structures of each dielectric layer is in contact with a corresponding conductive structure of the plurality of conductive structures of a subsequent and contiguous dielectric layer in the multi-layer and forms a plurality of conductive paths; the conductive paths establishing an electrical connection between the first plurality of contact pads realized on the first face of the multi-layer in correspondence of the exposed face of the first dielectric layer and the second plurality of contact pads realized on the second and opposite face of the multi-layer, in correspondence of the exposed face of the last dielectric layer, the second plurality of contact pads having respective symmetry centers spaced apart by a greater distance than respective symmetry centers of the first plurality of contact pads, the multi-layer thus performing a spatial transformation between the first and second pluralities of contact pads connected through the connective paths, wherein realizing in each dielectric layer the plurality of pass-through structures comprises: realizing at least one pass-through hole, transversally extending and connecting opposite faces of a corresponding dielectric layer, and realizing at least one recess, longitudinally extending starting from the pass-through hole at the surface of the dielectric layer.

26. The manufacturing method of claim 25, wherein the first and second pluralities of contact pads are realized in superficial connective zones of the conductive structures in correspondence of the exposed faces of the first and last dielectric layers.

27. The manufacturing method of claim 25, wherein realizing the pass-through holes realizes pass-through holes having a progressively greater distance starting from the first dielectric layer gradually towards the last dielectric layer and the step of realizing the recesses realizes corresponding recesses having longitudinal extension equal to a distance between opposed faces of corresponding pass-through holes realized in subsequent and continuous dielectric layers.

28. The manufacturing method of claim 25, wherein filling the pass-through structures comprises a selective deposition of the conductive material on each dielectric layer, in order to only fill the pass-through structures and form the conductive structures.

29. The manufacturing method of claim 28, wherein the selective deposition of the conductive material comprises a serigraphic process.

30. The manufacturing method of claim 25, wherein filling the pass-through structures comprises a non-selective deposition of the conductive material on a whole surface of each dielectric layer and in the pass-through structures, in order to form the conductive structures and a superficial conductive layer on the whole surface of each dielectric layer.

31. The manufacturing method of claim 30, further comprising removing by lapping the superficial conductive layer formed by the conductive material on the whole surface of each dielectric layer.

Description

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

[0058] FIG. 1 schematically shows a probe card for a testing apparatus of electronic devices manufactured according to the prior art, wherein a probe head, an interposer and a PCB board are comprised.

[0059] FIG. 2 schematically shows the interposer of FIG. 1, wherein a noble zone and a core zone are comprised, which can be manufactured by the method according to the present disclosure;

[0060] FIG. 3 schematically shows a multi-layer, which can be used as the interposer of FIG. 2, with particular reference to the noble zone, which can be manufactured by the method according to the present disclosure;

[0061] FIG. 4A schematically shows a section view of a portion of the multi-layer of FIG. 3 in a first step of the method according to the present disclosure;

[0062] FIG. 4B schematically shows a section view of a portion of the multi-layer of FIG. 3 in a second step of the method according to the present disclosure;

[0063] FIG. 4C schematically shows a section view of a portion of the multi-layer of FIG. 3 in a third step of the method according to the present disclosure;

[0064] FIG. 4D schematically shows a section view of a portion of the multi-layer of FIG. 3 in a fourth step of the method according to the present disclosure;

[0065] FIG. 5 shows a schematic top view of a single dielectric layer of the multi-layer of FIG. 3 formed by the method described in FIGS. 4A-4D; and

[0066] FIGS. 6A-6D schematically show the steps of a method for producing the multi-layer of FIG. 3 according to a second embodiment of the present disclosure.

DETAILED DESCRIPTION

[0067] With reference to these Figures, a method for producing a multi-layer is described, which can be used as interposer of a probe card for a testing apparatus of electronic devices, of the type globally indicated by 20 in FIG. 1.

[0068] 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 disclosure. Furthermore, in the Figures the different elements are schematically shown, since their shape can vary according to the desired application.

[0069] As shown in FIG. 2, an interposer of a probe card, still globally indicated by 20, generally comprises a plurality of layers 21a-21n, 22a-22n, superimposed on each other to perform the desired spatial transformation of the distances between pluralities of contact pads arranged on opposed faces Fa and Fb thereof, as described in connection with the prior art.

[0070] In particular, the interposer 20 comprises a first plurality of contact pads 20A arranged on a first face Fa thereof, facing a probe head (not shown in FIG. 2), and having a distance equal to that between contact pads of a device under test (also not shown in FIG. 2), as well as a second plurality of contact pads 20B arranged on a second and opposite face Fb thereof, having a greater distance than the first plurality of contact pads 20A and in particular analogous to the distance between contact pads being on a PCB board for the connection with a testing apparatus, as explained in connection with the prior art.

[0071] As previously indicated, distance between contact pads means a distance between respective centres of symmetry of such contact pads, commonly referred to as pitch.

[0072] Within the interposer 20 suitable conductive paths 24 are also provided to perform the routing between the first plurality of contact pads 20A and the second plurality of contact pads 20B.

[0073] In particular, the contact pads of the first plurality of contact pads 20A usually have a distance of 60-80 m, that is to say equal to the usual pitch values for contact pads of the devices under test integrated on a wafer, while the contact pads of the second plurality of contact pads 20B usually have a distance of about 400 m, that is to say equal to the usual pitch values for contact pads of PCB boards interfacing with testing apparatus.

[0074] More particularly, the interposer 20 is divided into a noble zone 21 and a core zone 22. The noble zone 21 comprises a first plurality of dielectric layers 21a-21n, usually of equal thickness, superimposed and in contact with each other, which performs a first spatial transformation having fine pitch, with distances between contact pads ranging for example from 60-80 m for a first dielectric layer 21a up to about 200 m for a last dielectric layer 21n. The core zone 22 likewise comprises a second plurality of dielectric layers 22a-22n, having greater thickness (usually equal to each other) and whose amount is greater with respect to the layers of the noble zone; the layers of such second plurality of dielectric layers 22a-22n are superimposed and in contact with each other, so as to perform, similarly to the noble zone 21, a second spatial transformation having less fine pitch, with pitches between contact pads ranging for example from about 200 m for a first dielectric layer 22a up to about 400 m for a last dielectric layer 22n.

[0075] The plurality of contact pads 20A and 20B are electrically connected thanks to conductive paths 23 formed in the noble zone 21 and to conductive paths 24 formed in the core zone 22, as will be explained more in detail below.

[0076] A method will be described in detail below, for manufacturing a multi-layer, which can form both the noble zone 21 and the core zone 22 of the interposer 20 of FIG. 2. This method according to the disclosure will be described with reference to a generic multi-layer, globally indicated by 30 in FIG. 3.

[0077] With reference to such Figure, the multi-layer 30 is divided into a plurality of dielectric layers 30a-30n, starting from a first dielectric layer 30a up to a last dielectric layer 30n, which perform a spatial transformation between a first plurality of contact pads 30A being on a first face F1 thereof, at the first dielectric layer 30a, and a second plurality of contact pads 30B being on a second and opposite face F2 thereof, at the last dielectric layer 30n. In particular, the contact pads of the second plurality of contact pads 30B have a distance between the centres thereof, namely the so-called pitch, greater than the distance between the centres of the contact pads of the first plurality of contact pads 30A. Within the multi-layer 30 suitable conductive paths 36 are also provided to perform the routing between the first plurality of contact pads 30A and the second plurality of contact pads 30B.

[0078] Substantially, the face F1 and the face F2 correspond to respective opposite faces of the multi-layer 30 and such multi-layer performs a spatial transformation between the plurality of contact pads 30A and 30B arranged thereon, suitably connected by the conductive paths 36.

[0079] The amount and the thickness of the dielectric layers of the plurality of dielectric layers 30a-30n can vary depending on the desired spatial transformation. For example, if the multi-layer 30 is adapted to form the noble zone 21, the dielectric layers can be selected so as to have a reduced thickness and in a smaller amount than if the multi-layer 30 is adapted to form the core zone 22.

[0080] It is underlined that the thickness of the dielectric layers of the multi-layer 30 may possibly vary also within the noble zone 21 or the core zone 22 according to the need and/or circumstances.

[0081] With particular reference to FIGS. 4A to 4D, it is now described the manufacturing method of the multi-layer 30 which comprises, suitably according to the disclosure, the steps of: [0082] providing a plurality of dielectric layers 30a-30n starting from a first dielectric layer 30a to a last dielectric layer 30n; [0083] forming, by means of laser ablation, in each dielectric layer of this plurality of dielectric layers 30a-30n a plurality of pass-through structures whose amount is the same in each dielectric layer 30a-30n, such plurality of pass-through structures being adapted to connect opposite faces of each dielectric layer to each other; [0084] filling such plurality of pass-through structures by means of a conductive material to form a plurality of conductive structures in each dielectric layer; and [0085] superimposing such plurality of dielectric layers 30a-30n so that each conductive structure of the plurality of conductive structures of each dielectric layer contacts a corresponding conductive structure of the plurality of conductive structures of a subsequent and contiguous dielectric layer in such multi-layer 30 and thus forms a plurality of conductive paths 36.

[0086] In this way, the conductive paths 36 establish an electrical connection between a first plurality of contact pads 30A arranged on a first face F1 of the multi-layer 30, at an exposed face of the first dielectric layer 30a, and a second plurality of contact pads 30B arranged on a second and opposite face F2 of the multi-layer 30, at an exposed face of the last dielectric layer 30n.

[0087] The expression exposed face refers hereinafter to that face of a dielectric layer of the multi-layer 30 which does not contact any other dielectric layer of the plurality of dielectric layers 30a-30n of the multi-layer 30.

[0088] Suitably, the second plurality of contact pads 30B has a different distance, in particular a greater distance, of its centres of symmetry with respect to the first plurality of contact pads 30A, the multi-layer 30 thus performing a spatial transformation between the pluralities of contact pads 30A and 30B connected by the conductive paths 36.

[0089] As previously stated, hereinafter, for the sake of simplicity of exposure, we will talk about the distance between contact pads, meaning the distance between the respective centres of symmetry, that is to say the so-called pitch.

[0090] Suitably, the method according to the present disclosure can be used interchangeably both for manufacturing the noble zone 21 and for manufacturing the core zone 22, as described with reference to the interposer 20 illustrated in FIG. 2. Alternatively, such method can be used only for the manufacture of the noble zone 21, while the core zone 22, wherein the distance constraints between the contact pads are looser, can be manufactured by known methods and subsequently solidarized to the noble zone 21.

[0091] Furthermore, the method comprises a final step wherein all the dielectric layers that form the multi-layer 30 are provided with conductive structures and superimposed so as to form conductive paths 36 between the plurality of contact pads 30A of the first dielectric layer 30a and the plurality of contact pads 30B of the last dielectric layer 30n, such dielectric layers being finally solidarized (namely physically connected).

[0092] Each dielectric layer of the multi-layer 30 is preferably made of an inorganic material, the laser processing of the surface thereof being easier. In particular, such inorganic material is selected among a ceramic material, such as Si.sub.3N.sub.4 silicon nitride, a glass or a ceramic glass.

[0093] For the sake of simplicity and not to overload the following description, in FIGS. 4A-4D only a portion of the multi-layer 30 is shown, comprising a first dielectric layer 30a and a second dielectric layer 30b, subsequent and contiguous to the first dielectric layer 30a, of the plurality of dielectric layers 30a-30n which realise the multi-layer 30, the subsequent dielectric layers can be formed using the described steps, even all parallel to each other, these Figures being provided only by way of non-limiting example.

[0094] As shown in FIG. 4A, the manufacturing method of the multi-layer 30 starts with the step of arranging the dielectric layers 30a, 30b for the following processing.

[0095] Subsequently, as shown in FIG. 4B, the method comprises the step of forming, in each dielectric layer of such plurality of dielectric layers 30a, 30b, a plurality of pass-through structures, respectively indicated by 31a for the first dielectric layer 30a and by 31b for the second dielectric layer 30b, such pass-through structures being in the same amount in each dielectric layer.

[0096] Suitably, these pluralities of pass-through structures 31a, 31b are obtained by laser ablation, that is by selective removal of portions of the relative dielectric layer by means of a suitably focused laser beam.

[0097] It should be noted that, although the method described in FIGS. 4A-4D forms on each dielectric layer only two pass-through structures, such configuration does not in any way limit the scope of the disclosure, but is provided only by way of example, since any number of pass-through structures can be provided on each dielectric layer. It is also underlined that the positioning of such pass-through structures 31a, 31b in the respective dielectric layers 30a, 30b is free and tied only to the relative positioning of such pass-through structures and to possible further components to be placed in the dielectric layers 30a, 30b.

[0098] In particular, suitably according to the disclosure, the step of forming in each dielectric layer the plurality of pass-through structures 31a, 31b by laser ablation comprises a step of forming at least one pass-through hole or via, such pass-through hole connecting the opposite faces of each dielectric layer.

[0099] Furthermore, the step of forming in each dielectric layer the plurality of pass-through structures 31a, 31b by laser ablation comprises a step of forming at least one cavity or recess, such recess extending lengthwise on the surface of the dielectric layer starting from a pass-through hole formed therein. Obviously in certain configurations the pass-through structures 31a, 31b can comprise only a pass-through hole adapted to connect the opposite faces of a corresponding dielectric layer, without providing also a respective recess.

[0100] More particularly, as illustrated in FIG. 4B, each pass-through structure of the plurality of pass-through structures 31a of the first dielectric layer 30a comprises pass-through holes 32a and recesses 33a, while each pass-through structure of the plurality of pass-through structures 31b of the second dielectric layer 30b comprises pass-through holes 32b and recesses 33b.

[0101] Suitably, the pass-through holes 32a, 32b have a transverse extension in the respective dielectric layer 30a, 30b, namely in a vertical direction considered the local reference of the Figures, greater than that of the recesses 33a, 33b, crossing the whole thickness of the dielectric layer and allowing the connection between the opposite faces of each dielectric layer. Alternatively, the recesses 33a, 33b have a lengthwise extension in the respective dielectric layer 30a, 30b, namely in a horizontal direction considered the local reference of the Figures, greater than that of the pass-through holes 32a, 32b, allowing the formation of conductive tracks on the surface of each dielectric layer, as clear in FIG. 5 which shows, by way of example, a schematic top view of the first dielectric layer 30a following the formation process of the pass-through structures 31a, 31b by laser ablation.

[0102] The reversed-L shape of the pass-through structures 31a, 31b of the dielectric layers 30a, 30b illustrated in FIG. 4B also allows to form the pass-through holes 32b of the second dielectric layer 30b at a greater distance with respect to the pass-through holes 32a of the first dielectric layer 30a, which will be suitably arranged closer to a probe head than the second dielectric layer 30b, in case the multi-layer 30 comprising it forms an interposer, as will be further clarified in the following description.

[0103] It should be pointed out that the method illustrated in the present detailed description allows to form in each dielectric layer of the multi-layer 30 pass-through structures wherein the pass-through holes and the recesses are both formed by laser ablation, without the need to deposit a resist film on the surface of each dielectric layer, as instead required in the known methods.

[0104] With reference to FIG. 4C, the manufacturing method of the multi-layer 30 further comprises the step of filling such plurality of pass-through structures 31a, 31b, formed in each dielectric layer 30a, 30b, with a conductive material, preferably copper, thus obtaining a plurality of conductive structures, indicated respectively by 34a for the first dielectric layer 30a and by 34b for the second dielectric layer 30b.

[0105] Such plurality of conductive structures 34a, 34b have respective pluralities of surface conductive zones 35a and 35b, at exposed horizontal faces (considered the local reference of FIG. 4C) of the first dielectric layer 30a and the second dielectric layer 30b, respectively, and respective pluralities of surface conductive zones 35a and 35b, at contacting horizontal faces (again considered the local reference of FIG. 4C) of the first dielectric layer 30a and the second dielectric layer 30b, respectively; in this way, the conductive structures 34a, 34b can ensure the effective electrical contact between two subsequent and contiguous dielectric layers, such as the dielectric layers 30a and 30b of FIGS. 4A-4D, suitably superimposed so that the surface conductive zones 35a and 35b of the pluralities of conductive structures 31a, 31b formed in the dielectric layers 30a, 30b are in contact with each other at respective faces of such dielectric layers, also in contact with each other.

[0106] As clear in FIG. 4C, such conductive structures 34a, 34b, thanks to the reversed-L shape given by the combination of pass-through holes and recesses, form a distance between the surface conductive zones, respectively 35a and 35a, 35b and 35b, formed in each layer as well as a distance between the surface conductive zones 35a and 35b formed at exposed faces of the dielectric layers 30a, 30b, in particular an increase in the distance of the symmetry centres thereof.

[0107] This progressive distance is in particular obtained by forming in each dielectric layer pass-through holes 32a and 32b having progressively greater distance starting from the first dielectric layer 30a gradually towards the last dielectric layer 30n and recesses 33a, 33b having a lengthwise extension equal to a distance DF between opposite walls of respective pass-through holes 32a, 32b formed in the first and second dielectric layers 30a, 30b, as indicated in FIG. 4C.

[0108] More particularly, as indicated in FIG. 4C, the first dielectric layer 30a has a distance D1 between the centres of the surface conductive zones 35a arranged on the exposed face thereof, namely the upper face using the local reference of the Figure, and a distance D2 between the surface conductive zones 35a arranged on the lower face thereof (again using the local reference of the Figure), greater than the distance D1 (D2>D1); the first dielectric layer 30a is then put into contact to the second subsequent and contiguous dielectric layer 30b, which has a distance D3 between the surface conductive zones 35b arranged on the exposed face thereof, namely the lower face, always using the local reference of the Figure, greater than the distance D1 and the distance D2 (D3>D2>D1). The position and sizing of the conductive structures 34a, 34b of the first and second dielectric layer 30a, 30b is such that when such dielectric layers contact each other, even at least one portion of the respective conductive structures is in contact.

[0109] Taking into account a multi-layer comprising only the first dielectric layer 30a and the second dielectric layer 30b, it is possible to form a first plurality of contact pads 36A at the surface conductive zones 35a defined at the exposed face of the first dielectric layer 30a and a second plurality of contact pads 36B at the surface conductive zones 35b defined at the exposed face of the second dielectric layer 30b, the multi-layer so formed performing a spatial transformation between such respective pluralities of contact pads 36A and 36B, in particular with an increase in the distance between their centres of symmetry or pitches starting from the first dielectric layer 30a towards the second dielectric layer 30b.

[0110] Finally, as shown in FIG. 4D, the manufacturing process of the multi-layer 30 ends with the step of superimposing the dielectric layers 30a and 30b such that the plurality of conductive structures 34a of the first dielectric layer 30a contacts the corresponding plurality of conductive structures 34b of the second dielectric layer 30b, subsequent and contiguous, forming conductive paths 36.

[0111] The step of superimposing the dielectric layers 30a-30n further comprises a step of solidarization (namely of physical connection or union) of the single dielectric layers.

[0112] In a first embodiment of the present disclosure, as schematically indicated in FIG. 4C, the step of filling the pluralities of pass-through structures 31a, 31b comprises a step of selectively depositing the conductive material on each dielectric layer 30a, 30b so as to fill only the pass-through structures 31a, 31b and form the conductive structures 34a, 34b, in particular by a serigraphic process, namely distributing the conductive material through the openings of metal stencil applied onto each dielectric layer 30a, 30b so as to form the conductive structures 34a, 34b. The serigraphic process can employ for example a conductive paste.

[0113] Alternatively, according to another embodiment of the present disclosure represented in FIGS. 6A to 6D, the method comprises the initial step of providing the dielectric layers 30a, 30b per the subsequent processing.

[0114] Subsequently, as schematically illustrated in FIG. 6A, the method comprises the step of forming in each dielectric layer of such plurality of dielectric layers 30a, 30b, a plurality of pass-through structures 31a, 31b, in the same amount in each dielectric layer 30a, 30b.

[0115] Furthermore, once the step of forming the pluralities of pass-through structures 31a, 31b has been completed, the step of filling such pluralities of pass-through structures 31a, 31b comprises a step of non-selective deposition of the conductive material over the entire surface of each dielectric layer 30a, 30b and in the pass-through structures 31a, 31b, and not only in the pass-through holes 32a, 32b and in the recesses 33a, 33b, as illustrated in particular in FIG. 6B. In that way, the conductive material forms the conductive structures 34a, 34b within the respective dielectric layers 30a, 30b as well as respective surface conductive layers, indicated by 37a and 37b, on a surface of each dielectric layer 30a, 30b.

[0116] Subsequently, the method according to this second embodiment further comprises the step of removing by lapping the surface conductive layers 37a, 37b formed by the conductive material on the surface of each dielectric layer, as schematically illustrated in FIG. 6C, for example by means of a lapping machine 38 which reduces the roughness of each dielectric layer 30a, 30b after removing the surface conductive layers 37a, 37b.

[0117] More generally, with reference to FIG. 3 for example, the conductive paths 3 establish an electrical connection between the first plurality of contact pads 30A, arranged on the first face F1 of the multi-layer 30 at an exposed face of the first dielectric layer 30a, and the second plurality of contact pads 30B, arranged on the second and opposite face F2 of the multi-layer 30 at an exposed face of the last dielectric layer 30n, this second plurality of contact pads 30B having a greater pitch than the first plurality of contact pads 30A, such multi-layer thus performing a spatial transformation between said pluralities of contact pads 30A, 30B.

[0118] It should be noted that the pluralities of contact pads 30A, 30B of the multi-layer 30 of FIG. 3 can be formed by surface conductive zones of the conductive structures 34a, 34b formed in each dielectric layer, in particular at the surface conductive zones arranged on the exposed faces of the first and the last dielectric layers 30a, 30n, namely at the faces F1 and F2 of the multi-layer 30 itself. More particularly, according to an embodiment of the disclosure, the contact pads 30A and 30B are formed by a portion of such surface conductive zones 35a, 35b of the conductive structures 31a, 31b formed in each dielectric layer; alternatively, the entire surface conductive zones 35a, 35b of the conductive structures 31a, 31b may form such contact pads 30A, 30B.

[0119] In this way it is possible to use the multi-layer 30 as an interposer, namely a structure capable of providing a desired spatial transformation between contact pads arranged on opposite faces thereof. More in particular, such an interposer has the first dielectric layer 30a in proximity to a contact head, with contact pads 30A formed at the surface conductive zones 35a and having a distance D1 substantially corresponding to a distance or pitch between the contact pads of the device under test integrated on a wafer, as well as the second dielectric layer 30b superimposed on such first dielectric layer 30a in the direction of a PCB board. If the second dielectric layer 30b were a last dielectric layer of such an interposer, it would also comprise contact pads 30B formed at the surface conductive zones 35b and having a distance D3 greater than the distance D1 and in particular substantially corresponding to a distance or pitch between contact pads of the PCB board.

[0120] In conclusion, the method according to the disclosure replaces the photolithographic and LDI techniques and allows the manufacture of the multi-layer 30 of a probe card 1 for a testing apparatus of electronic devices, performing by suitable conductive paths 36 the spatial transformation between a first plurality of contact pads 30A on a first face F1, facing the probe head of the card and a second plurality of contact pads 30B on a second and opposite face F2 thereof, facing the PCB board and having a distance greater than the first plurality of contact pads 30A.

[0121] Suitably according to the disclosure, the described method allows to manufacture, by using a same technique, both the noble zone 21 and the core zone 22, with the advantage of having a great precision in the formation of the conductive paths in both zones.

[0122] Alternatively, such method can be used only to manufacture the noble zone 21, which performs a spatial transformation having fine pitch and wherein the thickness of each dielectric layer and the distance between the contact pads involve the use of fine manufacturing techniques; the core zone 22 can instead be manufactured by known processes and subsequently solidarized to the noble zone 21, thus obtaining the desired interposer 20. Suitably, this also allows to select a material constituting the layers of the core zone 22 different from the material constituting the layers of the noble zone 21. It is in fact known that inorganic materials formed using MLC ceramic-based technology have a coefficient of thermal expansion (CTE) around 3-810.sup.6 C..sup.1, while organic materials formed using MLO organic-based technology have CTE up to 13-1410.sup.6 C..sup.1, therefore very close to the typical CTE of the most common PCB boards, generally higher than 1010.sup.6 C..sup.1.

[0123] In a particularly preferred embodiment, the method described above is used to manufacture the noble zone 21. The core zone 22 is instead manufactured by known processes, for example by means of a MLO organic-based technology, and subsequently solidarized to the noble zone 21, thus selecting for the core zone 22 a material with CTE comparable to that of the PCB board, so as to have an overall CTE of the interposer 20 capable of limiting the most the dimensional variations of the elements constituting the probe card during the test phase, thus making it usable even at high temperatures and also facilitating the welding between the multi-layer and the PCB board of the probe card.

[0124] In an alternative embodiment not shown in the Figures, the method according to the present disclosure can be used to form a multi-layer comprising a central core zone sandwiched between two noble zones having a finer pitch.

[0125] Suitably, the method according to the disclosure allows the parallel formation of the plurality of dielectric layers constituting the multi-layer, without the need of a manufacturing process of the sequential type, wherein each layer, once it has been processed and completed, forms the base for a subsequent layer to be processed.

[0126] In particular, the multi-layer thus formed and subdivided into a plurality of dielectric layers, can suitably perform a spatial transformation between a first plurality of contact pads on a first face thereof, at a first dielectric layer, and a second plurality of contact pads on a second and opposite face thereof, at a last dielectric layer, the pads of the second plurality of contact pads having a distance between their centres, namely the so-called pitch, greater than the distance between the centres of the pads of the first plurality of contact pads and being connected by suitable conductive paths which perform the routing thereof.

[0127] In particular, the multi-layer can form an interposer of a probe card, the first plurality of contact pads being in this case arranged on a first face, facing a probe head, and having a distance equal to that between the contact pads of a device under test, while the second plurality of contact pads is arranged on a second and opposite face and it has a greater distance with respect to the first plurality of contact pads and in particular analogous to the distance between contact pads on a PCB board for the connection with a testing apparatus.

[0128] It is also possible to form the conductive paths 36 in the multi-layer 30 such that two or more contact pads of the plurality of contact pads 30A arranged on the first face F1 of the multi-layer 30 contact a same contact pad of the plurality of contact pads 30B arranged on the second and opposite face F2 of the multi-layer 30, at an exposed face of the last dielectric layer 30n, thus connecting one to many pads. In this way it is possible to reduce the total amount of pads of the plurality of contact pads 30B arranged on the face F2.

[0129] Suitably according to the disclosure, the plurality of dielectric layers is superimposed such that each conductive structure of the plurality of conductive structures of each dielectric layer contacts a corresponding conductive structure of the plurality of conductive structures of a subsequent and contiguous dielectric layer in such multi-layer so as to form a plurality of conductive paths which establish an electrical connection between the pluralities of contact pads arranged on the opposed faces of the multi-layer.

[0130] Suitably, the amount and the thickness of the layers of the plurality of dielectric layers of the multi-layer can vary based upon the desired spatial transformation.

[0131] Suitably, the method according to the present disclosure can be employed for manufacturing the entire interposer or even only a portion thereof, for example the noble zone thereof where the distance constraints between the pads are more complicated.

[0132] Finally, suitably according to the disclosure, the described method allows to form on each dielectric layer of pass-through structures wherein the pass-through holes and the recesses are both formed by laser ablation, without the need to deposit a resist film on the surface of each dielectric layer, thus avoiding the use of masks, with a significant saving in terms of production costs.

[0133] From the foregoing it will be appreciated that, although specific embodiments of the disclosure have been described herein for purposes of illustration, various modifications may be made without deviating from the spirit and scope of the disclosure.

[0134] The various embodiments described above can be combined to provide further embodiments. These and other changes can be made to the embodiments in light of the above-detailed description. In general, in the following claims, the terms used should not be construed to limit the claims to the specific embodiments disclosed in the specification and the claims, but should be construed to include all possible embodiments along with the full scope of equivalents to which such claims are entitled. Accordingly, the claims are not limited by the disclosure.