Patent Description:
As well knows, a probe head is essentially a device adapted to electrically connect a plurality of contact pads of a microstructure, in particular an electronic device integrated on a semiconductor wafer, with corresponding channels of a testing apparatus which carries out the functionality check thereof, in particular electric, or generically the test.

The test carried out on integrated circuits in particular serves to detect and isolate defected circuits already in the production step. Normally, the probe heads are then used for electrically testing the circuits integrated on wafer before cutting and mounting thereof inside a chip containment package.

A probe head usually comprises a plurality of movable contact probes held by at least one pair of supports or guides which are substantially plate-shaped and parallel to each other. Said plate-shaped supports being provided with specific holes and are placed at a certain distance between each other so as to leave a free zone or an air zone for moving and possibly deforming the contact probes, which are normally formed by special alloy wires 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 same device, the contact probes, which are movable within the guide holes and formed in the guides, being subjected, during said pressing contact, to a flexion inside the air zone and a sliding inside said guide holes. Probe heads of this type are commonly called vertical probe heads.

In some cases, the contact probes are secured to the same head at the upper plate-shaped support in a fixed manner: in this case, they are called probe heads with blocked probes. However, more often, probe heads are used having probes which are not blocked in a fixed manner but are kept interfaced with a so-called board, possibly by a microcontacter: they are called probe heads with non-blocked probes. The microcontacter is usually called "space transformer" since, in addition to the contact with the probes, it allows also to spatially redistribute the contact pads formed thereon, with respect to the contact pads on the device under test, in particular with a loosening of the distance constraints between the centres of the same pads.

In the last years, there has been a considerable development of the so-called integrated photonic circuits (PIC, from "Photonic Integrated Circuits"), where it is possible to obtain extremely high (in the order of THz) data transmission speeds with dissipated power lower with respect to the electronic traditional technology. The development of this technology is particularly driven by the need of integrating fast transmission lines between electronic devices, as well as between elements inside the same devices.

In order to integrate the optical transmission means in electronic chips, the confinement of the light and the transmission thereof occur by taking advantage of the silicon combined with substrates formed starting from materials such as oxides or other dielectrics having lower refraction indices, thus forming integrated waveguides. The waveguides on silicon can have dimensions smaller than micron and are thus easily integrable in a chip, such that it is possible to integrate optical and electric components inside a CMOS component, creating faster devices, with much higher computing powers and with higher performances from an energetic point of view.

A problem of these devices is due to the coupling of the light in the waveguide of the chip, which can be observed also in the test step thereof.

In particular, in order to test devices comprising electronic components and at the same time integrated optical components, it is necessary to at the same time obtain the optical coupling between the light signal coming from testing apparatus and the waveguides of the device under test on one side, and the traditional electric and mechanical contact by the contact probes on the other side.

In fact, in accordance with the known solutions, the contact probes contact the contact pads of the device under test and feed it via power and ground probes in order to check the electric operation of said device via signal probes. Furthermore, in the systems comprising integrated photonic circuits, the chips have input/output optical interfaces and, for testing said components, it is necessary to couple the light in the waveguides via said optical interfaces and detect the outgoing light, as schematically indicated in <FIG>. In particular, in <FIG>, a probe head <NUM> is able to send electronic signals 2a (via traditional contact probes which are not illustrated) and optical signals 2b (via optical elements- in general waveguides - which are also not illustrated) to a device under test <NUM>, which comprises traditional contact pads 4a for electrically coupling and optical interfaces 4b for optically coupling the light signal coming from the probe head <NUM>.

In general, the test of the device under test begins with an optical alignment routine wherein some circular movements (indicated in the sector as "spiral" movements) of the waveguides of the probe head are carried out, while the quality of the optical coupling is continuously checked, in particular the value of the coupled optical power in the device. When the signal power reaches a target value, the test may begin. The accuracy requested for this type of procedure is of about ± <NUM>.

In accordance with some known solutions, probe heads can be coupled to external mechanical systems, such as movable mechanical arms on which an array of waveguides (for example optical fibres) intended for the optical test of the device. These probe heads are usually provided with contact probes of the cantilever type. Said probe heads must then provide a free space for moving the arm carrying the waveguides, thus increasing the bulks.

It is in general difficult to ensure in a simple way the alignment of the waveguides with the optical interfaces of the device under test, which, in the known solutions, can be obtained with complicated dynamics.

The relative alignment between the optical components and the electric contact probes inside the probe head should also be ensured, for example the relative alignment in a plane parallel to the plane in which the device under test lays (for example the plane x-y of the reference system of the figures), in which an accuracy of at least <NUM> is required.

It is finally important to also ensure the precise vertical positioning (that is along the axis z of the reference system of the figures) of the optical elements of the probe head.

US patent applications n. <CIT>, <CIT>, and <CIT> disclose test devices comprising optical detection means.

The technical problem of the present invention is to devise a probe head having functional and structural features so as to allow to overcome the limitations and drawbacks which still affect the probe heads made according to the prior art, in particular which is able to allow a simple and stable alignment of the optical components integrated therein, without complicating the structure of the head and at the same time maintaining high performances. In particular, a simple integration of the optical and electric part is desired to be obtained in order to avoid coupling the probe head with external mechanical systems and to allow the electric/optical test of more devices in parallel.

The invention is defined by the probe head according to claim <NUM>. Further aspects are defined in the dependent claims.

With reference to such figures, a probe head made according to the present invention is globally and schematically indicated with <NUM>.

It should be noted that the figures represent schematic views and are not drawn to scale, but they are instead drawn so as to emphasize the important characteristics of the invention. Furthermore, in the figures, different elements are represented in a schematic way, their form can vary according to the desired application. It should furthermore be noted that identical reference numbers in the figures refer to identical elements in form or function. Finally, particular improvements described in relation to an embodiment illustrated in a figure can be used also for other embodiments illustrated in the other figures.

As will be described in the following, in the more general form thereof, the probe head <NUM> is adapted to connect with a testing apparatus (not shown in the figures) for carrying out the test of integrated electronic devices on a semiconductor wafer, said electronic devices comprising also integrated optical elements such as photonic chips, and it is therefore provided with optical components designated for said test. A probe head of this type is also called optoelectronic probe head.

As illustrated in <FIG> and <FIG>, the probe head <NUM> comprises a plurality of contact probes <NUM> adapted to electrically and mechanically contact contact pads 12a of a device under test <NUM>. The contact probes <NUM> are then the elements designated to carry out the electric test of the device under test <NUM> and, as known in the sector, they can be divided in ground probes, power probes and probes designated to transport operational signals I/O towards/from said device under test <NUM>.

In particular, the contact probes <NUM> comprise a body <NUM>' vertically extending along a longitudinal axis H-H between a first end 11a and a second and opposite end 11b. The first end 11a can be adapted to contact an interface board (not illustrated in the figures) interfaced with the probe head <NUM>, such as for example a interposer or a printed circuit board (PCB), while the second end 11b is adapted to contact the contact pads 12a of the device under test <NUM>.

In other words, according to the present invention, the contact probes <NUM> are vertical probes, having for example a substantially vertical body <NUM>' which is able to flex when in contact with the device under test <NUM>, the probe head <NUM> being therefore a vertical probe head.

The probe head <NUM> thus comprises at least one guide <NUM> provided with a plurality of guide holes <NUM> for slidingly housing the contact probes <NUM>. By way of example, the guide <NUM> can be made of a ceramic material, as known in the field.

In an embodiment of the present invention, the guide <NUM> is a lower guide and the probe head <NUM> further comprises an upper guide <NUM>, also provided with guide holes <NUM> corresponding to guide holes <NUM> for slidingly housing the vertical contact probes <NUM>.

In order to carry out the optical test of the optical components integrated in the device under test <NUM>, the probe head <NUM> comprises at least one test optical signal distribution element <NUM> configured to transmit a test optical signal to said device under test <NUM>. As will be specified in the following, in an embodiment of the present invention, the test optical signal distribution element <NUM> is connected to the lower guide <NUM>.

It can be immediately observed that the particular form of the test optical signal distribution element <NUM> is not a limiting factor in the protection scope of the present invention and that said optical signal distribution element <NUM> can be associated with the lower guide <NUM> in different ways.

Specifically, the test optical signal distribution element <NUM> is a waveguide, in particular comprises a plurality of waveguides configured to transmit the test light signal from the testing apparatus (not illustrated in the figures) to the device under test <NUM>.

For example, as illustrated in <FIG>, the test optical signal distribution element <NUM> may comprise an array of optical fibres 50f aligned and ending with the end of the same fibres at the face of said test optical signal distribution element <NUM> facing the device under test <NUM>. In this case, the test optical signal distribution element <NUM> can vertically extend inside the probe head, that is along a vertical axis substantially parallel to the axis z of the reference system of the figures, thereby following the extension of the optical fibres 50f.

In the embodiment of <FIG>, the test optical signal distribution element <NUM> instead has a substantially horizontal extension and can comprise a body made of a plastic or glass material, having channels thereinside with index of refraction modified with respect to the same material, thus forming paths designated for trasmitting light (which also ensures an excellent positioning accuracy), as will be also detailed in the following. Also many other suitable configurations are however possible, what matters is that the test optical signal distribution element <NUM> is configured to transmit the light signal from the probe head <NUM> towards the device under test <NUM>, in particular towards optical interfaces 12b thereof.

Referring now to <FIG> and <FIG>, the probe head <NUM> comprises a containment element or housing <NUM> adapted to support the lower guide <NUM> and the upper guide <NUM>. In particular, the containment element <NUM> is arranged between the lower guide <NUM> and the upper guide <NUM>. As can be seen in <FIG>, <FIG> and <FIG>, the containment element <NUM> houses at least one portion of the contact probes <NUM>, and provides a rigid support structure of the probe head <NUM> as a whole.

The containment element <NUM> thus acts as support element of the probe head <NUM>, and the lower guide <NUM>, as well as the upper guide <NUM>, is associated thereto.

According to the present invention, the containment element <NUM> comprises a first portion 40a and a second portion 40b, which can be moved with respect to the first portion 40a.

In an embodiment of the present invention, as for example illustrated in <FIG>, the containment element <NUM> comprises at least one deformable arm <NUM> which connects the first portion 40a and the second portion 40b to each other. For example, in a non-limiting embodiment of the present invention, deformable arms <NUM> can be provided at four vertices of the containment element <NUM> and configured to connect the first portion 40a to the second portion 40b. For example, eight arms <NUM> can be provided, two for each vertex, said arms extending in pairs from the vertices and being separated by an empty space. The arms <NUM> are shaped to be flexible, wherein the form of said arms <NUM> allows to carry out the desired movements of the second portion 40b of the containment element <NUM> with respect to the first portion 40a, as will be described in the following.

In an embodiment of the present invention, the containment element <NUM> has an overall substantially rectangular form and the first portion 40a is the fixed external frame thereof (that is it is a fixed peripheral portion) and the second portion 40b is the movable central part thereof.

As mentioned above, in an embodiment of the present invention represented in <FIG>, the test optical signal distribution element <NUM> comprises a body <NUM>', for example made of a glass material or plastic material, and a plurality of waveguides <NUM> which are formed in said body <NUM>' and are configured to guide light from a light source towards the device under test <NUM>. The waveguides <NUM> end in terminals <NUM>' from which a suitable light beam is emitted towards the optical interfaces 12b of the device under test <NUM>. The test optical signal distribution element <NUM> has a design configured to facilitate the integration and alignment thereof inside the probe head <NUM>, in particular its connection to the guide <NUM>.

By way of example, the thickness of the test optical signal distribution element <NUM> can vary from <NUM>,<NUM> to <NUM>, said thickness not being however limited to a particular value. As mentioned above, also the form of the test optical signal distribution element <NUM> can vary according to the needs and/or circumstances, for example based on the position of the optical interfaces 12b and/or of the electric contact pads 12a of the device under test <NUM>, so that the form represented in the figures is purely indicative and non-limiting of the scope of the present invention.

Furthermore, means configured to transmit the light signal from the testing apparatus to the test optical signal distribution element <NUM> are provided, such as for example a cable <NUM> which connects said testing apparatus to said test optical signal distribution element <NUM>, said cable <NUM> comprising optical fibres therein and possibly also cables adapted to transport electric signals. In an embodiment, the test optical signal distribution element <NUM> is connected to a component <NUM>, which comprises means for connecting to the optical fibres of the cable <NUM>, as well as electronic means (such as a PCB board) for connecting and managing the electric cables coming from said cable <NUM>.

In an embodiment of the present invention, the test optical signal distribution element <NUM> is configured to couple light via a grating coupler of the device under test <NUM>. In this case, the optical interface 12b of the device under test <NUM> comprises a grating 12r configured to channel the incident light in a waveguide of the device under test <NUM>. During the test, the waveguides of the test optical signal distribution element <NUM> surmount said grating 12r, as schematically illustrated in <FIG> and <FIG>, to which reference is now again made. This optical coupling configuration is advantageous since it allows a test directly on wafer without the need of singulating the single devices integrated on said wafer.

It can be however observed that the present invention is not limited by the structure and the specific operation of the test optical signal distribution element <NUM>, which can be any structure of waveguide adapted to couple light in the device under test according to any suitable configuration, according to the needs and/or circumstances. Similarly, the present invention is not limited by a particular optical coupling mode with the device under test.

Advantageously, according to the present invention, in order to obtain the desired optical alignment, the test optical signal distribution element <NUM> is associated to the second portion 40b of the containment element <NUM> and is arranged to be moved integrally therewith.

It can be observed that, in the context of the present invention, the term "associated" means that the test optical signal distribution element <NUM> is physically put into relation with the containment element <NUM>, for example connected according to any suitable mode, and not necessarily directly connected thereto, but for example indirectly connected via further components of the probe head <NUM>.

Even more particularly, suitably, in order to allow the optical coupling of the light emitted by the test optical signal distribution element <NUM> associated with the second portion 40b of the containment element <NUM>, the probe head <NUM> comprises movement means <NUM> adapted to move said second portion 40b with respect to the first portion 40a thereof.

In this way, the movement means <NUM> are configured to move the test optical signal distribution element <NUM> (via the movement of the second portion 40b) and thus to allow the alignment of said test optical signal distribution element <NUM> with respect to the optical interfaces 12b of the device under test <NUM>, in particular an alignment at least in the plane x-y according to the reference of the figures, that is in a plane parallel to the plane in which said device under test <NUM> lays.

Referring again to <FIG>, in an embodiment of the present invention, the movement means <NUM> are arranged in specific housing seats <NUM> formed in the first portion 40a of the containment element <NUM>.

Thank to this architecture, it is possible to obtain, in a simple way, a stable alignment of the light emitted by the test optical signal distribution element <NUM> with regards to the optical interface 12b of the device under test <NUM>.

In a preferred embodiment of the present invention, the test optical signal distribution element <NUM> is connected to the lower guide <NUM>, and it is then associated with the containment element <NUM> via said lower guide <NUM>.

As illustrated in <FIG> and as detailed in <FIG>, in an embodiment of the present invention, the lower guide <NUM> is not made of a single piece but is at least structured as a first guide portion 20a, which is connected to the first portion 40a of the containment element <NUM>, and a second guide portion 20b, which is connected to the second portion 40b of the containment element <NUM> and is configured to move together with said second portion 40b, in particular for the effect of the actuation of the movement means <NUM>. In this way, also the lower guide <NUM> is provided with a fixed part, that is the first guide portion 20a connected to the fixed portion of the containment element <NUM> (for example via screws <NUM> passing through holes <NUM> formed in said first guide portion 20a), and with a movable part, that is the second guide portion 20b connected to the movable part of said containment element <NUM> (still via suitable fixing screws).

In an embodiment of the present invention, the second movable guide portion 20b in turn comprises a first guide portion 20b', which includes the guide holes <NUM> for housing the contact probes <NUM>, and a second guide structure 20b" adapted to house the test optical signal distribution element <NUM>, said second guide structure 20b" being structurally independent from the first guide structure 20b'.

It can be observed that, in the context of the present invention, the term "structurally independent" means that the two guide structure 20b' and 20b" are not initially secured to each other in a fixed way but they maintain an own structural independence, that is they are initially made of two pieces, for example two separated ceramics. The term "structurally independent" thus means that the two guide structures 20b' and 20b" are initially made as separate components.

In this way, the lower guide is divided in three guides: the first guide portion 20a, which is fixed (that is fixed to the external frame 40a of the containment element <NUM>), the first guide structure 20b' and the second guide structure 20b", which are movable, that is they are fixed to the movable core 40b of the containment element <NUM>.

In this embodiment, both said guide structures 20b' and 20b" are then secured to the second portion 40b of the containment element <NUM> and move integrally together. In an embodiment, the first guide structure 20b' is suitably shaped to leave space to house the second guide structure 20b", that is said second guide structure 20b" can be housed at the shaping of the first guide structure 20b'.

In other words, referring in particular to <FIG>, <FIG> and to <FIG> (which represents a simplified view of <FIG> where only the lower guides are displayed), in an embodiment of the present invention the lower guide <NUM> comprises a static portion (that is the first portion 20a) and a dynamic portion. The dynamic portion is represented by the portion 20b, which comprises the guide structure 20b' which houses the guide holes <NUM> for the contact probes <NUM> and the guide structure 20b" which houses the test optical signal distribution element <NUM>, said guide structures thus forming together the second guide portion 20b. In this embodiment, the test optical signal distribution element <NUM> is thus associated to the second guide structure 20b" of the second guide portion 20b, so as to be connected to an independent support of the lower guide <NUM>, while the contact probes <NUM> are associated to the first guide structure 20b' which houses the guide holes <NUM>. In other words, the test optical signal distribution element <NUM> is connected to its own support ceramic, which facilitates the alignment thereof with respect to the contact probes <NUM>, as will be described in the following.

In this embodiment, the movement elements <NUM> are adapted to move the second portion 40b and thus also the second guide portion 20b. In this embodiment, both the first guide structure 20b' and the second guide structure 20b" are moved by the movement means <NUM>, so that the contact probes <NUM> and the test optical signal distribution element <NUM> are moved integrally to each other, that is they are subjected to a same displacement. In this way, the optical alignment movement of the test optical signal distribution element <NUM> causes an analogous movement of the contact probes <NUM>, which does not affect in any way the electric and mechanical contact made by the latter maintaining unaltered the electric and mechanical performances of the probe head <NUM>. The contact probes <NUM> are thus also associated with the second movable portion 40b of the containment element <NUM> and are arranged to move integrally with said second portion 40b and with the test optical signal distribution element <NUM>.

In this embodiment, the first guide portion 20a, which is stationary, instead substantially acts as lower covering element of the probe head <NUM>.

In an alternative embodiment of the present invention, illustrated in <FIG>, only the test optical signal distribution element <NUM> is made to be movable, while the contact probes <NUM> are always stationary. For example, in the embodiment of <FIG> (wherein for the sake of simplicity, only the lower guides are represented), the contact probes <NUM> are housed in the first guide portion 20a (which is secured to the first portion 40a of the containment element <NUM> and comprises the guide holes <NUM>) and the test optical signal distribution element <NUM> is housed (connected, for example glued) in the second guide portion 20b (which is connected to the second portion 40b, for example via fixing screws) without further divisions of the lower guide <NUM>. In this case, it can be said that it does no longer exist the first guide structure 20b' which houses the contact probes <NUM>, while the second movable guide portion 20b corresponds to the second guide structure 20b", therefore, in this embodiment, reference is made only to first and second guide portions 20a and 20b. As before, the first guide portion 20a is suitably shaped to allow housing the second guide portion 20b.

In this embodiment, the contact probes <NUM> are thus associated with the first portion 40a of the containment element <NUM> and are configured to be stationary during the movement of the second portion 40b of said containment element <NUM>. In particular, the contact probes <NUM> are associated with the first portion 40a of the containment element <NUM> through the first guide portion 20a, and the test optical signal distribution element <NUM> is connected to the second portion 40b of said containment element <NUM> through the second guide portion 20b.

The containment element <NUM> comprises an empty space G at the zone of the guide portion 20a where the guide holes <NUM> are present (usually in a central zone), so as to allow suitably housing the contact probes <NUM>.

Other configurations are also possible in which the probe head <NUM> is configured such that the movement means <NUM> are adapted to move only the second guide structure 20b", as well as it is possible to also provide cases where the test optical signal distribution element <NUM> is not associated with a guide but is directly connected to the containment element <NUM>, in particular to the movable portion thereof.

In general, the first guide portion 20a thus remains static while the second guide portion 20b is made to be dynamic and moved by the movement means <NUM>. In an embodiment, said second guide portion 20b, together with the second portion 40b of the containment element <NUM>, is the movable central core of the probe head <NUM> to which the test optical signal distribution element <NUM> is also fixed. In this way, it is possible to move with accuracy said test optical signal distribution element <NUM>, for example based on a standard spiral routine, in order to obtain the desired optical alignment.

As previously indicated, it is furthermore possible to associate the test optical signal distribution element <NUM> directly with the containment element <NUM>, so that the guide <NUM> comprises only the first fixed guide portion 20a, even if it is preferable to provide said test optical signal distribution element <NUM> with an own guide (such as precisely the second guide structure 20b" or more in general the second guide portion 20b) so as to facilitate the association thereof and the alignment thereof in the probe head <NUM>.

In an embodiment of the present invention, the upper guide <NUM> is instead made of a single piece, said single piece comprising the guide holes <NUM> and alignment holes as will be described in the following.

The probe head <NUM> of the present invention thus comprises a monolithic housing provided with an external frame (that is the first portion 40a thereof) for statically fixing to the mechanics of the probe head <NUM>, and with a central movable portion or movable central core (that is the second portion 40b thereof) connected to the external frame by flexible and elastically deformable elements, such as the arms <NUM>, which can be in any number and have any form. The second movable portion 40b is controlled by the movement means <NUM> arranged in the housing seats <NUM> formed in the first portion 40a.

In an embodiment of the present invention, the movement means <NUM> comprise at least two piezoelectric transducers, each of said piezoelectric transducers being configured to cause a linear movement in a direction (in particular one of the directions x and y according to the reference system of the figures) of the second portion 40b of the containment element <NUM>.

Obviously, also other suitable movement means are comprised in the scope of the present invention, which is not only limited to the piezoelectric transducers, although such an embodiment is considered as being preferred since the piezoelectric transducers allow obtaining a fine adjustment of the movement in a simple way. In an embodiment, the piezoelectric transducers can cause movements of <NUM> with an accuracy of <NUM>.

As illustrated in the attached figures, in an embodiment, the test optical signal distribution element <NUM> is connected to a face Fa of the lower guide <NUM>, said face Fa facing the device under test <NUM>.

In a preferred embodiment of the present invention, the test optical signal distribution element <NUM> is glued to the lower guide <NUM>, in particular glued to the face Fa thereof. For this reason, with reference to <FIG>, the second guide structure 20b" designated to house the test optical signal distribution element <NUM> comprises a plurality of grooves <NUM>, the area of the guide occupied by said grooves forming the glueing substrate. The grooves <NUM> are then filled with resin or other suitable glue <NUM> to allow fixing the test optical signal distribution element <NUM> to the lower guide <NUM>, in particular to said second guide structure 20b".

As previously mentioned, the containment element <NUM> is not limited by a particular form, and various forms different from each other fall within the scope of the present invention. What matters is that said containment element <NUM> is such as to ensure the mobility of a portion thereof by the movement elements <NUM> housed therein, for example by a suitable combination of used forms and materials, in particular for the connection arms <NUM> between the first portion 40a thereof and the second portion 40b thereof. In this aim, the embodiments of <FIG> and <FIG> can be compared, which are given only by way of example, which differ from each other because of a different form of the arms <NUM>, which in any case ensure the desired elasticity of the connection between fixed portion and movable portion.

In order to align the test optical signal distribution element <NUM> with respect to the contact probes <NUM>, and thus in order to precisely adapt the probe head <NUM> to the layout of the device under test, an efficient alignment system is provided which can be easily used in a assembly step of said probe head <NUM>.

In particular, referring now to <FIG> and <FIG>, the test optical signal distribution element <NUM> suitably comprises first alignment holes 50al, the second guide structure 20b", which is structurally independent from the first guide structure 20b', comprises second alignment holes 20al, and the upper guide <NUM> comprises corresponding third alignment holes 30al.

Suitably, the alignment holes 20al, 30al and 50al are arranged and configured to allow, when the centres of the alignment holes of respective components are aligned along a same predetermined axis, in particular along a vertical axis parallel to the axis H-H, the passage of alignment pins or pin <NUM> to ensure the reciprocal alignment between the contact probes <NUM> housed in the first guide structure 20b' and the test optical signal distribution element <NUM> connected to the second guide structure 20b" of the lower guide <NUM>.

In other words, when the respective alignment holes of the lower guide <NUM> (in particular of the second guide structure 20b"), of the test optical signal distribution element <NUM> and of the upper guide <NUM> are aligned to each other along a determined axis (and said alignment is obtained by inserting the alignment pins <NUM>), the precise alignment and positioning (in particular in the plane x-y) of the test optical signal distribution element <NUM> in the probe head <NUM> is obtained, which can be thus fixed to the containment element, for example via suitable fixing screws.

As previously mentioned, the upper guide <NUM> is made of a single piece. In this way, the upper guide <NUM> houses, in a single piece, both the guide holes <NUM> designated to house the contact probes <NUM> and the alignment holes 30al.

In this way it is possible to obtain in a simple way a precise reciprocal alignment between the test optical signal distribution element <NUM> and the guide holes <NUM> which houses the contact probes <NUM>, passing from a routine of spatial search of <NUM>-<NUM> to a search with maximum amplitude of <NUM> or even less.

In other words, the alignment holes 20al, 30al, and 50al are arranged and configured to allow, when the centres of the alignment holes 50al of the test optical signal distribution element <NUM> are aligned along a respective predetermined axis (for example vertical) with centres of corresponding alignment holes 20al of the second guide portion 20b and with centres of corresponding alignment holes 30al of the upper guide <NUM>, the passage of the alignment pins <NUM> to ensure reciprocal alignment between the contact probes <NUM> and the distribution element of the test optical signal <NUM>. The alignment holes in which a single pin <NUM> passes thus form a group of corresponding aligned alignment holes.

In an embodiment of the present invention, the alignment holes are obtained by laser drilling with accuracy less than <NUM>, so that the alignment accuracy is also very high.

Once the alignment pins <NUM> are inserted in all the specific alignment holes, the test optical signal distribution element <NUM> is thus perfectly aligned with respect to all the other components of the probe head <NUM>. Once aligned, the test optical signal distribution element <NUM>, in particular the support to which it is glued, is fixed to the containment element <NUM> via tightening screws passing through respective tightening holes <NUM> formed in the lower guide. As mentioned above, the potential alignment error between these components of the probe head <NUM> is equal to the accuracy of the forming process of alignment holes, for example via laser, generally lower than <NUM>, and thus very low, thus minimizing the subsequent optical alignment routine of the test optical signal distribution element <NUM>.

Furthermore, in order to ensure the precise positioning along the vertical axis, that is along the axis z according to the reference system of the figures, in an embodiment of the present invention, at least one spacer element <NUM> arranged between the containment element <NUM> and the second guide structure 20b" is provided, said spacer element <NUM> being removable to allow the adjustment of the distance between the test optical signal distribution element <NUM>, e thus the outlets of the waveguides, and the device under test <NUM>. <FIG> shows the probe head <NUM> including a single spacer element <NUM>, even if any suitable number of spacer elements <NUM>, of any suitable form, can be obviously used.

By way of example, the spacer element <NUM> can be made of steel or a polyamide material, even if other materials are obviously possible.

The spacer elements <NUM> thus represent calibrated thicknesses (for example from <NUM> or <NUM>) arranged between the containment element <NUM> and the lower guide <NUM>, which can be removed if needed to ensure the adjustment of the distance along the axis z as indicated above.

It is furthermore possible to carry out a further vertical fine calibration by calibrated lapping of the contact probes <NUM>.

Thanks to the vertical calibration above illustrated, the distance between the outlet of the waveguides is substantially equal to the positioning requirement of the test optical signal distribution element <NUM> plus the working overdrive.

To conclude, the present invention provides a probe head with vertical probes comprising a pair of guides between which is arranged a containment element (also called housing) of the vertical probes, wherein the vertical probes head technology is combined with the presence of optical elements, in particular waveguides, inside the probe head, in particular associated to the lower guide, to carry out the test of devices including integrated photonic circuits, wherein the optical elements are integrated inside the probe head forming a simple and compact structure. In particular, the containment element is provided with a fixed portion (for example an external frame) and a movable portion (for example the central core) to which at least the waveguides for the optical test are connected via a designated ceramic support and simple movement means are present, such as for example piezoelectric transducers, to move said movable portion and obtain a fine and precise alignment of the optical elements with respect to the optical interfaces of the device under test. In this way, both the contact probes and the waveguides are associated with a same containment element of the probe head, wherein the movement of the movable portion of the containment element is only required to obtain the optical alignment, obtaining a structure which is compact and allows the use of vertical probes housed in the guides and in the containment element. The designed architecture further allows a simple relative alignment between contact probes and optical elements, by simply moving the ceramic support of the waveguides, as well as a simple adjustment of the distance in the vertical direction.

It is thus possible to test optoelectronic devices via vertical probes, without the aid of complicated and expensive precision mechanics.

Advantageously according to the present invention, an optoelectronic probe head is obtained which includes optical components for the optical testing of a device and which allows an extremely simplified alignment of said optical components, wherein all the components are integrated in a compact structure which allows to use vertical probes.

In particular, suitably, the optical elements integrated in the probe head are associated with the containment element of the same, obtaining an extremely compact structure, without needing to introduce specific mechanical support arms to hold and move said optical elements, thus simplifying the mechanical structure of the probe head and optimizing the spaces.

The alignment of the waveguides with respect to the optical interfaces of the device under test is really simple and requires only the movement of the movable portion of the housing for example by means of a pair of piezoelectric transducers, without having to resort to expensive mechanics and without renouncing to the simplicity and compactness of the overall structure.

Suitably, as mentioned above, the probe head of the present invention houses vertical contact probes, that is contact probes having a substantially vertically extended body, which slide in guide holes of at least one guide and adapted to flex while in contact with the device under test, usually having both ends free. It is thus possible for example to use very short contact probes to limit the self-inductance phenomenon and thus to carry out tests of high-frequency devices (for example carry out an electric test up to GHz of frequency), as well as there is more freedom in choosing the layout, obtaining highly improved performances.

Also the relative alignment between contact probes and optical components is very precise and simple, thanks to the possibility to move the support of such optical components before fixing the same having as reference the alignment holes.

The excellent reciprocal alignment between probes and waveguides implies a short optical coupling routine, which gives a considerable advantage on the testing time.

Also the possibility of precisely calibrating the vertical distance between the optical element and the device under test is added to all the above.

The probe head of the present invention puts thus together a compact structure and the ease and stability of the alignment in all the space directions, both of the optical components with respect to the device under test, and of said optical components with respect to the contact probes designated for the electric test.

The described probe head thus resolves the technical problem of the present invention and achieves all the various above-mentioned advantages.

An important application of the probe head of the present invention is in the field of data centres, which require a fast data transmission and reduced energy consumption.

Claim 1:
A probe head (<NUM>) for a testing apparatus of electronic devices, comprising:
- a plurality of contact probes (<NUM>) adapted to electrically and mechanically contact contact pads (12a) of a device under test (<NUM>), wherein said contact probes (<NUM>) are vertical contact probes comprising a body extended along a longitudinal axis (H-H) between a first end (11a) and a second end (11b);
- at least one guide (<NUM>) provided with a plurality of guide holes (<NUM>) for slidingly housing the contact probes (<NUM>);
- a containment element (<NUM>) which is adapted to support the guide (<NUM>) and houses at least one portion of the contact probes (<NUM>), wherein said containment element (<NUM>) comprises a first portion (40a) and a second portion (40b) which is movable with respect to said first portion (40a);
- movement means (<NUM>) configured to move the second portion (40b) of the containment element (<NUM>) with respect to the first portion (40a); and
- at least one test optical signal distribution element (<NUM>) configured to transmit a test optical signal to the device under test (<NUM>),
wherein the test optical signal distribution element (<NUM>) is associated with the second portion (40b) of the containment element (<NUM>) and is arranged to be moved integrally therewith by means of the movement means (<NUM>), said movement means (<NUM>) being configured to allow the alignment of said test optical signal distribution element (<NUM>).