1111111111111111 IIIIII IIIII 11111 1111111111 1111111111 11111 1111111111 11111 1111111111 11111111
`US 20050110506Al
`
`(19) United States
`(12) Patent Application Publication
`Crippa et al.
`
`(10) Pub. No.: US 2005/0110506 Al
`May 26, 2005
`( 43) Pub. Date:
`
`(54) CONTACT PROBE FOR A TESTING HEAD
`HAVING VERTICAL PROBES FOR
`SEMICONDUCTOR INTEGRATED DEVICES
`
`(75)
`
`Inventors: Giuseppe Crippa, Merate (IT); Stefano
`Felici, Robbiate (IT)
`
`Correspondence Address:
`SEED INTELLECTUAL PROPERTY LAW
`GROUPPLLC
`701 FIFTH AVE
`SUITE 6300
`SEATTLE, WA 98104-7092 (US)
`
`(73) Assignee: Technoprobe S.p.A., Cernusco Lombar(cid:173)
`done (11)
`
`(21) Appl. No.:
`
`10/963,985
`
`(22) Filed:
`
`Oct. 12, 2004
`
`(30)
`
`Foreign Application Priority Data
`
`Oct. 13, 2003
`
`(EP) ........................................ 03425664.4
`
`Publication Classification
`
`Int. CI.7 ..................................................... G0lR 31/02
`(51)
`(52) U.S. Cl. .............................................................. 324/754
`
`(57)
`
`ABSTRACT
`
`A contact probe for a testing head is presented. The contact
`probe for a testing head has a plurality of these probes which
`are inserted in guide holes realized in respective dies, the
`probe comprising a rod-shaped body equipped at an end
`with at least a contact tip effective to ensure the mechanical
`and electrical contact with a corresponding contact pad of an
`integrated electronic device to be tested. The rod-shaped
`body has a nonuniform cross section.
`
`20
`
`21A
`
`SFl
`
`24
`
`SFl
`
`25
`
`SF2
`
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`Page 1 of 16
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`

`

`Patent Application Publication May 26, 2005 Sheet 1 of 9
`
`US 2005/0110506 Al
`
`11
`
`12
`
`8
`
`7
`
`FIG. 1
`PRIOR ART
`
`d
`
`s
`
`6
`
`FIG. 2
`PRIOR ART
`
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`Patent Application Publication May 26, 2005 Sheet 2 of 9
`
`US 2005/0110506 Al
`
`12
`
`3
`
`3
`
`1
`
`( 12
`
`3
`
`FIG. 3
`PRIOR ART
`
`/
`
`,,----12
`
`FIG. 4
`PRIOR ART
`
`FIG. 5
`PRIOR ART
`
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`Patent Application Publication May 26, 2005 Sheet 3 of 9
`
`US 2005/0110506 Al
`
`11
`
`2~
`
`8
`
`7
`
`FIG. 6
`PRIOR ART
`
`0F
`
`0F
`
`0F
`
`Gl
`
`Pl
`
`Gl
`
`Pl
`
`FIG. 7
`PRIOR ART
`
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`

`

`Patent Application Publication May 26, 2005 Sheet 4 of 9
`
`US 2005/0110506 Al
`
`L,
`
`I
`
`23
`
`20
`A/
`
`FIG. BA
`
`21
`
`22
`
`A~~:...-_· ..: : :..-=t"-"Y d-y 2
`~--·-· ·-·- ·-·-·-·-·t-
`s:i:
`: : .
`FIG. BB
`
`i
`
`I
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`I
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`I
`
`I 1
`
`I
`
`I
`
`23
`20
`A/
`
`r 21
`
`FIG. BC
`
`21A
`
`21B
`
`21A
`
`21B
`
`•
`
`I
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`I
`
`I
`
`f17(,,_,J,ccy;d-y I
`sftfr:·-· ·-·-f·-----·-·t-
`~i
`i~
`FIG. BD
`(cid:141) X
`
`I ·Xl· I
`:'ii
`
`2
`
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`Patent Application Publication May 26, 2005 Sheet 5 of 9
`
`US 2005/0110506 Al
`
`20
`V\..
`21A
`
`21B
`
`20
`
`21A
`
`21B
`
`FIG. 9A
`
`S2 p
`
`S1
`
`FIG. 9B
`
`21
`
`FIG. 9C
`
`S1
`
`~
`
`2
`
`FIG. 9D
`
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`Patent Application Publication May 26, 2005 Sheet 6 of 9
`
`US 2005/0110506 Al
`
`20
`
`21A
`
`21B
`
`~ s
`
`FIG. lOA
`
`FIG. 10B
`
`FIG. lOC
`
`I
`I
`
`I
`I
`
`I
`
`: :
`I X2
`:(cid:141):
`
`1:
`
`I
`I
`
`:
`
`I
`I
`
`I
`
`20
`
`21A
`
`21B {
`
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`Patent Application Publication May 26, 2005 Sheet 7 of 9
`
`US 2005/0110506 Al
`
`20
`
`21A
`
`21B
`
`SFl
`
`25
`
`20
`
`21A
`
`21B
`
`SFl
`
`FIG. 1 lA
`
`SF2
`
`SFl
`
`__ 24
`
`FIG. 11B
`
`25
`
`SF2
`
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`Patent Application Publication May 26, 2005 Sheet 8 of 9
`
`US 2005/0110506 Al
`
`( _____ J
`
`(\J
`L'.J
`
`0
`
`(\J
`Q_
`
`GAP: Gl=G2
`
`PITCH: Pl>P2
`
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`

`

`Patent Application Publication May 26, 2005 Sheet 9 of 9
`
`US 2005/0110506 Al
`
`F-----
`
`25
`
`30~
`
`26
`
`25
`
`5 30
`
`24
`_/
`
`~
`20
`
`FIG. 13A
`
`24
`_)
`
`20
`
`FIG. 13B
`
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`

`US 2005/0110506 Al
`
`May 26, 2005
`
`1
`
`CONTACT PROBE FOR A TESTING HEAD
`HAVING VERTICAL PROBES FOR
`SEMICONDUCTOR INTEGRATED DEVICES
`
`BACKGROUND OF THE INVENTION
`
`[0001] 1. Field of the Invention
`
`[0002] The present invention relates to a contact probe for
`a testing head having vertical probes effective to test a
`plurality of semiconductor integrated electronic devices
`comprising a plurality of so-called contact pads and more
`particularly to a contact probe wherein a plurality of probes
`are inserted in guide holes realized in respective plate-like
`holders, or dies, the probe comprising a rod-shaped body
`equipped at an end with at least a contact tip effective to
`ensure the mechanical and electrical contact with a corre(cid:173)
`sponding contact pad of an integrated electronic device to be
`tested.
`
`[0003] 2. Description of the Related Art
`
`[0004] As it is well known, a testing head is essentially a
`device effective to electrically connect a plurality of contact
`pads of a semiconductor integrated electronic device with
`corresponding channels of a testing machine performing the
`test thereof.
`
`[0005] The test performed on integrated electronic devices
`provides to detect and isolate defective devices already in
`the manufacturing step. Generally, testing heads are thus
`used to electrically test electronic devices integrated on
`semiconductor or silicon wafer before cutting and assem(cid:173)
`bling them inside a chip package.
`
`[0006] A testing head having vertical probes comprises at
`least a pair of parallel plates or plate-like holders located
`apart from each other in order to keep an air gap, as well as
`a plurality of suitable mobile contact elements.
`
`[0007] Each plate, called die in the relevant technical field
`and in the following description, is equipped with a respec(cid:173)
`tive plurality of through guide holes, each hole of a plate
`corresponding to a hole of the other plate wherein a respec(cid:173)
`tive contact element or contact probe, as said element will be
`called in the following description and in the subsequent
`claims, is slidingly engaged and guided. Contact probes are
`generally composed of wires made of special alloys with
`good electrical and mechanical properties.
`
`[0008] The good electrical connection between the probes
`of the testing head and the contact pads of an integrated
`electronic device to be tested is ensured by urging each
`contact probe onto the respective contact pad, mobile con(cid:173)
`tact probes elastically bending in the air gap between the two
`dies.
`
`[0009] These testing heads are generally called "vertical
`probe".
`
`[0010]
`In essence, known testing heads have an air gap
`wherein a probe bending occurs, this bending being helped
`through a convenient configuration of the probes themselves
`or of the dies thereof, as schematically shown in FIG. 1.
`
`[0012] The contact probe 6 has at least a contact end or tip
`7. In particular, the contact tip 7 is mechanically contacted
`with a contact pad 8 of an integrated electronic device to be
`tested, said integrated electronic device meanwhile electri(cid:173)
`cally contacting a testing equipment (not shown) of which
`this testing head is a terminal element.
`
`[0013] Upper 2 and lower 3 dies are spaced by an air gap
`9 allowing contact probes 6 to be deformed or sloped during
`the testing head normal operation, i.e. when this testing head
`comes into contact with the integrated electronic device to
`be tested. Moreover upper 4 and lower 5 guide holes are
`sized in order to guide the contact probe 6.
`[0014] FIG. 1 shows a testing head 1 with unblocked
`probes, i.e. being capable of sliding in respective upper 4
`and lower 5 guide holes, associated with a micro-contact
`strip or space transformer, schematically indicated with 10.
`[0015]
`In this case, contact probes 6 have a further contact
`tip towards a plurality of contact pads 11 of the space
`transformer 10, the good electrical contact between the
`probes and the space transformer 10 being ensured similarly
`to the contact with the integrated electronic device to be
`tested by urging the probes 6 onto the contact pads 11 of the
`space transformer 10.
`[0016]
`In particular, according to the technology known as
`Cobra, contact pads 6 have a pre-deformed configuration
`with an offset d between the end in contact with the contact
`pads 11 of the space transformer 10 and the contact tip 7 on
`the contact pads 8 of the integrated electronic device to be
`tested, as schematically shown in FIG. 2.
`[0017] The pre-deformed configuration, also in case the
`testing head 1 is not in contact with the integrated electronic
`device to be tested, favors the correct bending of the probe
`6 during the operation thereof, i.e. during the contact with
`the integrated electronic device to be tested.
`
`[0018] Moreover, a thin and flexible insulating material
`film 12, generally realized in polyimide, is interposed
`between the upper die 2 and the lower die 3, able to keep the
`upper end of the contact probes 6 in place during the
`assembly step.
`
`In particular, the assembly step of a testing head 1
`[0019]
`realized according to the Cobra technology is particularly
`delicate. It comprises the following steps:
`[0020] each contact probe 6 is inserted from the
`corresponding side to the contact tip 7 in a hole in the
`lower die 3, as schematically shown in FIG. 3;
`
`the other end of contact probes 6 is softly
`[0021]
`forced into the conveniently drilled flexible material
`film 12, so that it is held by this material film 12
`without risking to exit therefrom, as schematically
`shown in FIG. 4, and
`
`[0022] once all contact probes 6 are inserted in the
`flexible material film 12 as described, the upper die
`2 is applied, centering with great skill all contact
`probes 6 in the corresponding holes realized in the
`upper die 2, as schematically shown in FIG. 5.
`
`In this FIG.1 a testing head 1 comprises at least an
`[0011]
`upper die 2 and a lower die 3, having respective upper 4 and
`lower 5 through guide holes wherein a contact probe 6 is
`slidingly engaged.
`
`[0023] This assembly mode required by the probes real(cid:173)
`ized according to the Cobra technology is very long, besides
`being risky for possible probe deformations and very
`unstable up to the locking with the upper die 2.
`
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`US 2005/0110506 Al
`
`May 26, 2005
`
`2
`
`[0024] Moreover, there is the risk of mechanical interfer(cid:173)
`ence between the flexible material film 12 and contact
`probes 6 during the normal operation of the testing head 1
`since this film 12, once its task of keeping the probe 6 end
`in place during the assembly step is completed, nevertheless
`remains trapped inside the testing head 1 and it can cause
`serious problems to the sliding of the probes themselves,
`mainly for large-sized testing heads, with a high number of
`close probes.
`
`It is also known to realize testing heads by using
`[0025]
`the so-called "shifted plate" technology, schematically
`shown in FIG. 6, the elements being structurally and func(cid:173)
`tionally identical to the testing head 1 of FIG. 1 having been
`indicated with the same numeral references.
`
`In this case, contact probes 6 are not pre-formed,
`[0026]
`but only realized in a straight form, with circular cross
`section being constant for the whole length thereof and
`generally pointed at the ends.
`
`[0027]
`In order to achieve the correct operation of contact
`probes 6, the upper 2 and lower 3 dies are conveniently
`shifted one another to allow probes 6 to bend preferentially
`in a same direction.
`
`[0028] The assembly of probes 6 in testing heads realized
`according to the shifted plate technology is very simple and
`fast and it does not require the use of any flexible material
`film. In particular, it is sufficient to align the upper die 2 with
`the lower die 3 in order to align also the corresponding guide
`holes 4 and 5, to insert then the contact probes 6 in the guide
`holes 4 and 5, to shift the dies therebetween by a convenient
`quantity then blocking them in position.
`
`[0029] However, also this technology has some draw(cid:173)
`backs, and in particular:
`
`it is difficult to keep contact probes 6 within
`[0030]
`their housing, i.e. inside the die guide holes. In fact,
`despite the relative shift between the upper 2 and
`lower 3 dies, causing a friction between the contact
`probes 6 and the corresponding guide holes 4 and 5,
`this friction is not always sufficient to keep probes in
`place.
`
`In particular, the risk of exit of contact probes 6 is
`[0031]
`much higher during the maintenance and cleaning opera(cid:173)
`tions of the testing head 1, operations which are generally
`performed with air blows or ultrasounds and which thus
`create mechanical stresses on contact probes 6, favoring the
`exit thereof from guide holes.
`
`[0032] The distance between two adjacent probes of the
`testing head 1 is limited because of the circular cross section
`of the wire realizing the contact probes 6.
`
`[0033]
`In particular, testing heads have intrinsic distance
`limits between two adjacent probes, and thus between the
`centers of two contact pads of the integrated electronic
`device to be tested, known in this field as "pitch". In
`particular, the minimum "pitch" value depends on the probe
`geometrical configuration and size. In order to avoid the
`
`contact between adjacent probes, the testing head 1 must
`satisfy the following relation:
`
`P>(1JF+Gl
`
`[0034] being:
`
`[0035] P the pitch value of the device to be tested, i.e. the
`distance between the centers of two adjacent contact pads;
`
`[0036] 0F the diameter of the contact probes 6; and
`
`[0037] Gl the safety distance between adjacent contact
`probes 6.
`
`[0038] The condition Gl=0, i.e. the annulment of the
`safety distance, corresponds to the probe collision.
`
`[0039]
`In the case of circular probes, the minimum pitch
`Pl is given by the probe diameter 0F corresponding to the
`diameter of the guide holes increased by the thickness Gl of
`the wall separating two adjacent holes, as schematically
`shown in FIG. 7.
`
`[0040] The need to keep a minimum distance pitch value
`between the probes is thus in contrast with the present
`market need, which pushes to design denser and denser
`devices and thus requires testing heads with a higher and
`higher number of contact probes for testing these devices.
`
`SUMMARY OF THE INVENTION
`
`[0041] Embodiments of this invention provide contact
`probes having a configuration effective to reduce the mini(cid:173)
`mum pitch required by the devices to be tested and mean(cid:173)
`while the risk for contact probes to exit from guide holes.
`
`[0042] One of the principles on which embodiments of the
`present invention stand is that of providing a non-constant
`cross section contact probe, capable of allowing probes to be
`conveniently approached and ensuring meanwhile a reduc(cid:173)
`tion of the risks for probes to exit from guide holes.
`
`[0043] Presented is a contact probe for a testing head
`having a plurality of probes which are inserted in guide holes
`realized in respective plate-like holders, or dies, the probe
`comprising: a rod-shaped body equipped at an end with a
`contact tip effective to ensure mechanical and electrical
`contact with a corresponding contact pad of an integrated
`electronic device to be tested, wherein the rod-shaped body
`has a non-uniform cross section.
`
`[0044] Additionally presented is a testing head including:
`an upper die having a plurality of guide holes; a lower die
`having a plurality of guide holes; and a plurality of contact
`probes inserted in the guide holes of the upper and lower
`dies, wherein the contact probes comprise a rod-shaped
`body equipped at an end with a contact tip effective to ensure
`mechanical and electrical contact with a corresponding
`contact pad of an integrated electronic device to be tested,
`the rod-shaped body having a non-uniform cross section.
`
`[0045] Also presented is a method for obtaining a contact
`probe with a non-uniform cross section. The method
`includes the steps of:
`
`[0046] providing a wire having a predetermined profile
`cross section effective to realize a rod-shaped body of the
`contact probe; and
`
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`US 2005/0110506 Al
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`May 26, 2005
`
`3
`
`[0047] deforming the wire in correspondence with at least
`a portion of the rod-shaped body, obtaining a cross section
`with different profile with respect to the predetermined
`profile of the wire.
`[0048] The features and advantages of the contact probe
`and testing head according to the invention will be apparent
`from the following description of embodiments thereof
`given by way of non-limiting example with reference to the
`attached drawings.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`[0049] FIG. 1 is a cross-sectional view of a testing head
`according to an embodiment of the prior art;
`[0050] FIG. 2 is a schematic view of a testing head
`according to the embodiment of FIG. 1;
`[0051] FIGS. 3 to 5 are schematic views of a testing head
`according to the embodiment of FIG. 1 during different
`assembly operations;
`[0052] FIG. 6 is a cross-sectional view of a testing head
`according to another embodiments of the prior art;
`[0053] FIG. 7 is a top plan view of a testing head
`according to the embodiment of FIG. 6, showing significant
`dimensions;
`[0054] FIGS. SA to SD are cross-sectional and top plan
`views of a contact probe according to an embodiment of the
`invention;
`[0055] FIGS. 9A to 9D are cross-sectional and top plan
`views of a contact probe according to another embodiment
`of the invention;
`[0056] FIGS. lOA to lOD are cross-sectional and top plan
`views of a contact probe according to a further embodiment
`of the invention;
`[0057] FIGS. llA and 11B are perspective views of a
`testing head according to an embodiment of the invention;
`[0058] FIGS. 12A and 12B are top plan views of different
`arrangements of a testing head according to other embodi(cid:173)
`ments of the invention;
`[0059] FIGS. 13A and 13B are cross-sectional views of a
`testing head according to an embodiment of the invention in
`different assembly steps.
`
`DETAILED DESCRIPTION OF THE
`INVENTION
`
`[0060] With reference to FIGS. SA to SD, a contact probe
`according to an embodiment of the invention is indicated
`with 20.
`[0061] The contact probe 20 has a rod-shaped body 21
`equipped with at least a contact end or tip 22. In particular,
`as seen with reference to the prior art, the contact tip 22 is
`in mechanical contact with a contact pad of an integrated
`electronic device to be tested, said integrated electronic
`device meanwhile being electrically contacted with a testing
`equipment (not shown) of which this testing head is a
`terminal element.
`[0062] Moreover, for example in the case of probes for a
`testing head having unblocked probes, associated with a
`micro-contact strip or space transformer, the contact probe
`
`20 has a second contact tip 23 towards a plurality of contact
`pads of this space transformer. This is given by way of
`non-limiting example of a testing head according to an
`embodiment of the invention.
`
`[0063] Advantageously according to an embodiment of
`the invention, the rod-shaped body 21 of the contact probe
`20 has a non-uniform cross section with respect to a main
`development line LL thereof.
`
`In particular, the rod-shaped body 21 of the contact
`[0064]
`probe 20 has at least a first portion 21A and a second portion
`21B having cross sections Sl and S2 of different profile, as
`shown in enlarged scale in FIG. 8B.
`[0065] Advantageously according to an embodiment of
`the invention, the first cross section Sl has at least a higher
`dimension than a corresponding dimension of the second
`cross section S2, to prevent the contact probe 20 from
`exiting from the guide holes realized in the dies, as it will be
`better seen hereafter.
`
`In particular, as it can be noted in FIG. 8B, the first
`[0066]
`section Sl of the portion 21A has a longitudinal dimension
`Xl being higher than a corresponding longitudinal dimen(cid:173)
`sion X2 of the second section Sl (Xl>X2). Moreover, the
`first section Sl has a longitudinal dimension Yl being lower
`than a corresponding longitudinal section Y2 of the second
`section S2 (Yl<Y2).
`
`It is also possible to consider a contact probe 20 as
`[0067]
`shown in FIGS. SC and 8D for which the portion 21B near
`the contact tip has, dually to the probe shown in FIGS. SA
`and 8B, the first section Sl with a longitudinal dimension
`Xl being lower than the corresponding longitudinal dimen(cid:173)
`sion X2 of the second section S2 (Xl<X2) and the longi(cid:173)
`tudinal dimension Yl being higher than the corresponding
`longitudinal dimension Y2 of the second section S2
`(Yl>Y2).
`
`[0068] Advantageously according to an embodiment of
`the invention, it is possible to obtain a contact probe 20 with
`non-uniform cross section starting from a probe realized in
`a traditional way by means of a circular cross section wire.
`This circular cross section wire is flattened at two different
`thicknesses in correspondence with the portions 21A and
`21B of the rod-shaped body 21 of the contact probe 20 thus
`obtaining a contact probe 20 having a first Sl and a second
`S2 substantially rectangular cross section with rounded
`edges.
`
`[0069]
`It is also possible, according to another embodi(cid:173)
`ment of the invention, to flatten the wire only in correspon(cid:173)
`dence with one of the portions 21Aor 21B of the rod-shaped
`body 21, for example in correspondence with the first
`portion 21A thus obtaining a first rectangular cross section
`Sl with rounded edges and a second circular cross section
`S2, as schematically shown in FIGS. 9A and 9B. Similarly
`it is possible to flatten the wire only in correspondence with
`the portion 21B, thus obtaining a first circular cross section
`Sl and a second rectangular cross section S2 with rounded
`edges, as schematically shown in FIGS. 9C and 9D.
`
`[0070] Similarly it is possible to obtain a non-uniform
`cross section contact probe 20 according to a further
`embodiment of the invention starting from a probe having a
`rectangular cross section and flattening a portion thereof,
`thus obtaining a contact probe 20 having a first Sl and a
`
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`

`US 2005/0110506 Al
`
`May 26, 2005
`
`4
`
`second S2 rectangular cross section, as schematically shown
`in FIGS. lOA and 10B and in FIGS. lOC and 10D.
`
`In particular, the section of the contact probe 20 in
`[0071]
`correspondence with the contact tip 23 towards the space
`transformer has however a profile having at least a dimen(cid:173)
`sion being higher than a corresponding dimension of the
`profile of the contact probe 20 section in correspondence
`with the contact tip 22 towards the device to be tested.
`
`In fact, as shown in FIG. 10B, the cross dimension
`[0072]
`Xl of the first section Sl is higher than the cross dimension
`X2 of the second section S2 and, as shown in FIG. 10D, the
`longitudinal dimension Yl of the first section Sl is higher
`than the longitudinal dimension Y2 of the second section S2.
`
`[0073] More generally, the contact probe 20 according to
`some other embodiments of the invention has two or more
`cross sections of any shape, but different from each other,
`obtained with the several presently available technologies.
`
`[0074]
`In a preferred embodiment of the invention, the
`contact probe 20 is obtained with a method comprising the
`following steps:
`
`[0075] providing a wire effective to realize the rod(cid:173)
`shaped body 21 of the contact probe 20; and
`
`[0076] deforming, for example by flattening, this
`wire in correspondence with at least a portion 21Aor
`21B in order to obtain in this portion a cross section
`with different profile with respect to the profile of the
`wire cross section and thus a non uniform cross
`section contact probe 20.
`
`[0077] Moreover,
`to another
`the method according
`embodiment of the invention can comprise a flattening step
`of further portions of the rod-shaped body 21 of the contact
`probe 20.
`
`[0078] Advantageously according to a further embodi(cid:173)
`ment of the invention, the non uniform cross section contact
`probe 20 allows the problem linked to the probe exit,
`affecting the known shifted plate vertical technologies, to be
`solved.
`
`[0079]
`In fact, as seen with reference to the prior art,
`according to this shifted plate technology, contact probes
`with circular guide holes realized in the upper and lower dies
`are generally provided. Therefore, these guide holes do not
`ensure that contact probes are retained inside a testing head.
`Probes tend to slide out of the respective guide holes, in
`particular during cleaning operations, usually performed by
`means of air blows or cleaning in liquid solutions with
`ultrasounds.
`
`[0080] Advantageously according to an embodiment of
`the invention, the nonuniform cross section contact probe 20
`is associated with a convenient hole with different profile
`between an upper die 24 and a lower die 25 of the testing
`head, as schematically shown in FIGS. llA and 11B. In
`particular, the lower die 25 has holes having a cross section
`SF2 whose profile substantially corresponds to the profile of
`the second cross section S2 of the second portion 21B of the
`contact probe 20, while the upper die 24 has holes having a
`cross section SFl whose profile corresponds to the union of
`the profiles of cross sections Sl and S2 of portions 21A and
`21B of the contact probe 20.
`
`In this way, it is ensured that contact probes 20 are
`[0081]
`retained inside the dies of a testing head comprising these
`dies and a plurality of contact probes 20. In fact, each
`contact probe 20 cannot move because of the holes of the
`lower die 25, having a cross section with at least a dimension
`being lower than the corresponding dimension of the cross
`section of at least one portion 21A of the contact probe 20.
`
`[0082]
`In other words, the so-obtained testing head has a
`preferred exit direction of contact probes 20, particularly
`from the lower die 25 towards the upper die 24, any
`movement in the opposite direction being prevented by the
`guide holes of the lower die 24 being conveniently shaped
`and having at least a dimension being lower than a corre(cid:173)
`sponding dimension of the section profile of the probe
`portion 21A.
`
`[0083] A more reliable testing head is thus obtained,
`allowing washings and cleanings while preventing contact
`probes 20 from exiting from the testing head itself. To this
`purpose it is sufficient to use a gas blow pushing the contact
`probes 20 towards the lower die 25, wherefrom they cannot
`exit, or by blocking the probe exit from the upper die by
`means of a convenient cap it is possible to perform any
`washing and cleaning without any risk of probe exit in any
`of the two directions.
`
`[0084] Advantageously, the non-uniform cross section
`contact probe 20 also allows the problem linked to the
`assembly of the testing head comprising them to be solved.
`
`In particular, it is sufficient to overlap the upper 24
`[0085]
`and lower 24 dies and the corresponding guide holes and to
`insert contact probes 20 in the overlapped guide holes
`simply by starting from the upper die 24 towards the lower
`die 25.
`
`[0086]
`It is thus sufficient to space the upper and lower
`dies, contact probes 20 being allowed to slide in the guide
`holes of the upper die 24.
`
`[0087] The testing head assembly according to an embodi(cid:173)
`ment of the invention is completed by blocking the upper 24
`and lower 25 dies in the spaced position, providing in case
`the shift thereof one another or the insertion of a spacer 26
`between the dies before blocking them.
`
`[0088]
`It can be immediately noticed that this assembly
`technique is faster and safer than the assembly technique
`used in the known technique, for example in Cobra tech(cid:173)
`nologies.
`
`[0089]
`In practice, the described assembly of a testing
`head comprising a plurality of non-uniform cross section
`contact probes 20 has a considerably reduced execution
`time, besides being simpler and more reliable.
`
`[0090] Finally, advantageously, the non-uniform cross
`section contact probe 20 allows the problem linked to the
`minimum pitch required by the device to be tested to be
`solved.
`
`[0091] As previously seen for the existing technologies,
`the minimum pitch value of a device to be tested is limited
`by the fact that the cross section of the wire realizing contact
`probes is circular. In fact, the minimum pitch value is given
`by the diameter of guide holes increased by the thickness Gl
`of the separation wall between two adjacent holes, as
`
`FF1010
`Formfactor v. Feinmetall
`Page 14 of 16
`
`

`

`US 2005/0110506 Al
`
`May 26, 2005
`
`5
`
`schematically shown in FIG. 12A in the case of contact
`probes realized according to the prior art.
`[0092] Advantageously, the non-uniform cross section
`contact probe 20 allows the minimum pitch to be reduced by
`a quantity being equal to the reduction of the cross section
`between the cross sections Sl and S2 of the rod-shaped body
`21 of the contact probe 20, as schematically shown in FIG.
`12B.
`[0093] FIGS. 13A and 13B show, by way of example, a
`testing head 30 realized in the shifted plate technology and
`comprising a plurality of contact probes 20 according to an
`embodiment of the invention.
`[0094]
`In particular, after assembling the contact probes
`20 between the upper die 24 and the lower die 25, a shift of
`these dies is applied to allow probes to bend, as schemati(cid:173)
`cally indicated in FIG. 13A by means of an arrow F. In this
`way, contact probes 20 have a preferred bending direction.
`[0095] Moreover, it is possible to provide a spacer 26,
`sometimes indicated as housing or spacer, of variable height,
`in order to allow the forces in the bending step to be
`correctly adjusted, as schematically shown in FIG. 13B.
`[0096]
`In a preferred embodiment of the invention, the
`dies of the testing head, and particularly at least the lower die
`25, comprise very long guide holes. These guide holes can
`be obtained by increasing the thickness of the die itself or,
`in a simpler way, by using two or more thin dies overlapped
`to each other or also by using two very thin dies ( and thus
`very easy to be drilled) located apart. It is thus possible to
`obtain long guide holes substantially aligned with each
`other.
`[0097]
`In the case of the shifted plate technology, to help
`contact probes 20 to bend in a preferred direction, it is also
`possible to use guide holes obtained with offset drillings.
`Also in this case, the guide holes can be obtained by using
`two or more dies overlapped to each other or located apart,
`wherein holes are drilled slightly offset with each other.
`[0098]
`to
`In conclusion, advantageously according
`embodiments of the invention, the nonuniform cross section
`contact probe 20 allows the following problems to be
`solved:
`[0099] probe exit, as seen with reference to known
`shifted plate vertical technologies;
`[0100] assembly, as seen with reference to known
`"Cobra" technologies;
`
`[0101] allowed minimum pitch and good electrical
`contact.
`[0102] Changes can be made to the invention in light of
`the above detailed description. In general, in the following
`claims, the terms used should not be construed to limit the
`invention to the specific embodiments disclosed in the
`specification and the claims, but should be construed to
`include all methods and devices that are in accordance with
`the claims. Accordingly, the invention is not limited by the
`disclosure, but instead its scope is to be determined by the
`following claims.
`
`1. A contact probe for a testing head having a plurality of
`probes which are inserted in guide holes realized in respec(cid:173)
`tive plate-like holders, or dies, the probe comprising: a
`
`rod-shaped body equipped at an end with a contact tip
`effective to ensure mechanical and electrical contact with a
`corresponding contact pad of an integrated electronic device
`to be tested, wherein the rod-shaped body has a non-uniform
`cross section.
`2. The contact probe of claim 1, wherein the rod-shaped
`body has a first portion and a second portion having respec(cid:173)
`tive first and second cross sections of different profile.
`3. The contact probe of claim 2, wherein the first cross
`section has a dimension higher than a corresponding dimen(cid:173)
`sion of the second cross section.
`4. The contact probe of claim 2, wherein the first and
`second cross sections are rectangular with rounded edges.
`5. The contact probe of claim 2, wherein the first cross
`section is circular and said second cross sectio