United States Patent
`Bove
`
`c191
`
`3,806,801
`[ 11 l
`[451 Apr. 23, 1974
`
`[75]
`
`[54] PROBE CONTACTOR HAVING BUCKLING
`BEAM PROBES
`Inventor: Ronald Bove, Wappingers Falls,
`N.Y.
`[ 7 3 ] Assignee: International Business Machines
`Corporation, Armonk, N.Y.
`Dec. 26, 1972
`(22] Filed:
`[21] Appl. No.: 318,156
`
`[52] U.S. CI ........ 324/72.5, 324/158 F, 339/108 TP
`Int. Cl .......................... G0lr 31/02, GO Ir 1/06
`(51]
`(58) Field of Search ............ 324/72.5, 158 P, 158 F;
`339/108 TP
`
`[ 5 6]
`
`References Cited
`UNITED ST ATES PA TENTS
`7/1972 Bauer et al. ....................... 324/72.5
`3,676,776
`I /1968 Giedd .......................... 324/158 P X
`3,361,865
`9/1966
`Shortridge ..................... 324/72.5 X
`3,274,534
`FOREIGN PA TENTS OR APPLICATIONS
`1,754,669
`10/1966
`Japan .............................. 324/158 P
`
`OTHER PUBLICATIONS
`
`M. R. Eddy, Multiprobe Testing Device, IBM Techni(cid:173)
`cal Disclosure Bulletin, Vol. 12, No. 4 September
`1969, pg. 539.
`
`Primary Examiner-Alfred E. Smith
`Assistant Examiner-Rolf Hille
`Aitorizey; Agent, or Pfi-m:....:J,rink- C .. Leach,--Jr:·;
`George 0. Saile
`
`(57)
`
`ABSTRACT
`
`A probe contactor has each of its probes formed with
`a length many times its cross sectional area so that the
`probes buckle or deflect when a predetermined axial
`load .is applied thereto. This enables the sanie force to
`be exerted on each of a plurality of pads on a semi(cid:173)
`conductor chip regardless of the deflection of the
`probes produced by variations in the heights of the
`pads.
`
`10 Claims, 10 Drawing Figures
`
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`12
`
`FF1014
`Formfactor v. Feinmetall
`Page 1 of 10
`
`

`

`?;\TENTEOAPR231874
`
`3.806,801
`
`SHEET 1 OF 3
`
`30
`
`32
`
`33
`
`11
`
`24
`
`FIG.9
`
`11
`
`FIG.10
`
`FF1014
`Formfactor v. Feinmetall
`Page 2 of 10
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`

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`FIG.2
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`21
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`FIG.
`4
`
`14
`
`18
`
`15 FIG.
`5
`
`19
`
`12
`
`15
`19
`FIG.
`6
`
`12
`
`16
`
`16
`
`16
`
`23
`
`12
`
`FF1014
`Formfactor v. Feinmetall
`Page 3 of 10
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`

`

`SHEET 3 OF 3
`
`J,806,801
`
`14
`
`FIG. 3
`
`FIG. 7
`
`FORCE
`
`DEFLECTION
`
`FIG.8
`
`FF1014
`Formfactor v. Feinmetall
`Page 4 of 10
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`

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`3,806,801
`
`50
`
`1
`PROBE CONT ACTOR HAVING BUCKLING BEAM
`PROBES
`In testing the electrical characteristics of integrated
`circuits connected to pads on a semiconductor chip, for
`example, by probes of a probe contactor engaging the
`pads so as to connect the pads to a tester, it is necessary
`to be able to have each of the pads contacted by a
`probe with a controlled force to prevent damage to the
`pad or to the chip. If the force of the probe engaging
`the pad exceeds that for which the pad or chip has been
`designed, then the pad and/or the chip can be damaged
`whereby a deflective chip is produced.
`In one previously available probe contactor, the de(cid:173)
`flection of the probe has been directly proportional to
`the force applied to the end of the probe by the engage(cid:173)
`ment of the probe with the pad. That is, as the force on
`the probe increases, the probe deflects further.
`Thus, to insure sufficient space between the probes
`to compensate for varying deflections due to varying
`forces thereon, it has been necessary to space the
`probes sufficiently from each other to enable the
`probes to deflect without contacting each other. This
`has significantly decreased the density of the probes.
`Furthermore, to insure contact between the probes
`of the previously available probe contactor and the 25
`pads on a semiconductor chip, a relatively large force
`has been required to insure the desired contact since
`the pads on a semiconductor chip may be of varying
`heights. This has sometimes resulted in the force on the
`pad of greatest height having a force exerted thereon
`greater than that for which the pad or chip has been de(cid:173)
`signed so that the pad and/or the chip has been dam(cid:173)
`aged. Therefore, failure of the height of the pads to fall
`within a relatively tight range has resulted in damage to
`the pads and/or the chip when testing with the previ(cid:173)
`ously available probe contactor.
`The present invention satisfactorily solves the forego(cid:173)
`ing problems by providing a probe contactor in which
`each of the probes will exert a substantially constant
`force on each of the pads on the chip irrespective of the
`relative heights of the pads on the chip as long as the
`pads on the chip have their heights within the predeter(cid:173)
`mined range in which the probes can engage the pads.
`The present invention accomplishes this by forming
`each of the probes with a length many times its cross
`sectional area so that each of the probes may be
`deemed to be a beam. Each of the probes is designed
`so that it will deflect over a range when a predeter(cid:173)
`mined force is applied at its ends engaging the pad to
`axially load the probe so as to prevent any additional
`force, beyond the predetermined force, being applied
`to the pad due to engagement of the pad with the
`probe.
`With this arrangement, each of the probes will con(cid:173)
`tinue to deflect when the predetermined force is axially
`applied thereto through engagement of the end of the
`probe with the pad. Thus, with the heights of the pads
`varying, the same force is applied to each of the pads
`by its contacting probe or probes because each probe
`will continue to deflect and not apply a further reactive
`force to the pad so that all of the pads are contacted
`· with a substantially constant force if their heights are
`within a predetermined range.
`Additionally, by allowing the probes to deflect over
`a range for a predetermined force, variations in the
`manufacture of the probes can be obtained without any
`damage to the pads or the chip. Accordingly, the probe
`
`2
`contactor of the present invention enables a controlled
`force to be applied to each of the pads of a semicon(cid:173)
`ductor chip.
`In addition to being capable of having the probe con-
`s tinue to deflect so that it does not exert an increased
`force on the pad which the probe is engaging, it is nec(cid:173)
`essary for each of the probes tci have its deflection con(cid:173)
`trolled. That is, to be able to increase the density of the
`probes, all of the probes must deflect or buckle in a
`10 predetermined direction. The present invention satis(cid:173)
`factorily meets this requirement by providing means to
`control the deflection or buckling of each of the probes
`so that all of the probes buckle or deflect in a predeter(cid:173)
`mined direction whereby they cannot normally engage
`15 each other.
`It also has been previously suggested to utilize a
`probe contactor for the pads on a semiconductor chip
`in which the probes engage the pads at an acute angle
`rather than a right angle but with a substantially con-
`20 stant force through the use of a leaf spring acting on the
`probe. However, this previously suggested probe con(cid:173)
`tactor has had a very low density of probes because of
`the deflection required and the angle at which the
`probes engage the pads on the chip.
`The present invention satisfactorily overcomes the
`density problem since the probes are disposed to be
`substantially perpendicular to the surface of the pad
`that the probe engages. Thus, the probe contactor of
`the present invention may have a much higher pro be
`30 density than the previously suggested mechanical con(cid:173)
`tactor while still obtaining a substantially constant
`force on each of the pads.
`It also has previously been suggested to utilize a sub(cid:173)
`stantially constant force on each of the contacts of a
`35 printed circuit board through using spring loaded
`probes. In this type of probe contactor, a coil spring has
`been disposed around the probe with one end of the
`spring engaging an enlarged head on the end of the
`probe to exert a substantially constant force on each of
`40 the contacts of the printed circuit board. However, this
`relatively large head and the use of the coil spring has
`significantly reduced the density of the probes. Thus,
`this type of probe contactor could not be satisfactorily
`used with pads on a semiconductor chip since the en-
`45 Iarged heads and the coil springs have required a rela(cid:173)
`tively large area for each probe. Accordingly, this type
`of probe contactor would not solve the problem as has
`the probe contactor of the present invention.
`In the previously available probe contactor in which
`the amount of deflection of the probe i.s directly pro(cid:173)
`portional to the force applied thereto, the required
`movement of the chip towards the probe contactor to
`obtain the necessary force between the probes and the
`55 pads to insure contact therebetween has resulted in the
`probe engaging the metallurgy on the surface of the
`chip if a pad was missing. Similarly, this movement of
`the chip for a sufficient distance relative to the probes
`to obtain the desired force contact between the probes
`60 and the pads has resulted in a pad, which would not
`have sufficient height to be structurally connected to
`the substance on which the chip is to be mounted,
`being engaged by the probe.
`Accordingly, the determination of whether a pad was
`65 missing from a chip or not of the requisite height for
`connection to the substrate to which the chip is joined
`after testing could not be made with the previously
`available probe contactor. Thus, the chip would pass
`
`FF1014
`Formfactor v. Feinmetall
`Page 5 of 10
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`

`

`3,806,801
`
`3
`the functionality test prior to being joined to the sub(cid:173)
`strate and the absence of the pad or the failure of the
`pad to have the requisite height would be determined
`only after the chip was joined to the substrate when fur(cid:173)
`ther tests were made to show that there was no contact
`between one of the pads on the chip and the cooperat(cid:173)
`ing conductive element on the substrate. As a result,
`the cost of manufacture was increased since the defec(cid:173)
`tive chip was not recognized as such until after being
`joined to the substrate.
`Since the probe contactor of the present invention
`does not have to be moved for as great a distance to in(cid:173)
`sure that there is the necessary contact with each of the
`pads because of the absence of any additional force be(cid:173)
`tween the pad and the probe after a predetermined
`force is applied, determination of the presence ofa pad
`at each of the locations with the pad having the re(cid:173)
`quired height is readily ascertained with the probe con(cid:173)
`tactor of the present invention. With the reduced
`movement of the chip toward the probe contactor, any
`pad lacking the required height for bonding to the sub(cid:173)
`strate on which the chip is to be mounted will not be
`engaged. Similarly, the surface metallurgy will not be
`contacted by one of the probes of the present inven(cid:173)
`tion. Therefore, determination that a chip is defective
`because of the absence of a pad or the pad not having
`the required height is made prior to joining the chip to
`the substrate so that the cost of manufacture is de(cid:173)
`creased.
`An object of this invention is to provide a unique
`probe contactor.
`Another object of this invention is to provide a high
`density constant force probe contactor.
`A further object of this invention is to provide a
`probe contactor having probes axially loaded when en(cid:173)
`gaging pads of a semiconductor chip, for example.
`The foregoing and other objects, features, and advan(cid:173)
`tages of the invention will be more apparent from the
`following more particular description of the preferred
`embodiments of the invention, as illustrated in the ac(cid:173)
`companying drawings.
`In the drawings:
`FIG. 1 is a schematic exploded elevational view,
`partly in section, showing the probe contactor of the
`present invention.
`FIG. 2 is a fragmentary sectional view showing one
`end of a plurality of the probes being fixed to a support.
`
`4
`FIG. 8 is a diagram for showing the relationship be(cid:173)
`tween force and deflection of an axially loaded probe
`of the probe contactor of the present invention.
`FIG. 9 is a fragmentary sectional view showing a con-
`5 nection between elements of the probe contactor.
`FIG. 10 is a fragmentary sectional view showing an
`arrangement for aligning elements of the probe contac(cid:173)
`tor.
`Referring to the drawings and particularly FIG. 1,
`10 there is shown a probe contactor 10 of the present in(cid:173)
`vention. The probe contactor 10 includes a housing 11,
`which is preferably a metallic casting. The housing 11
`supports a lower alignment die 12 at one end and an
`upper alignment die 14 at the other end. The dies 12
`15 and 14 may be secured to the housing 11 by suitable
`means. An adhesive such as epoxy or screws, for exam(cid:173)
`ple, could be employed.
`The probe contactor 10 has a plurality of probes 15,
`which include electrically conductive wires 16, sup-
`20 ported in the upper alignment die 14 and extending
`therefrom through the hollow housing 11 and through
`openings 17 in the lower alignment die 12. Each of the
`openings 17 is larger than the wire 16 of the cooperat(cid:173)
`ing probe 15 as shown in FIGS. 4-6 to allow the wire
`25 to slide relative to the die 12 when an axial load is ap(cid:173)
`plied to the end of the wire 16.
`The alignment dies 12 and 14 are formed of a suit(cid:173)
`able electrically insulating material so that there is no
`short between any of the wires 16 of the probes 15 and
`30 either of the dies 12 or 14. The probe 15 has a tight fit
`with the upper alignment die 14 as it passes through an
`opening 18 therein. A suitable example of the material
`of the dies 12 and 14 is a plastic or an epoxy.
`To prevent shorting of the wires 16 of the probes 15
`35 if they should accidentally engage each other during
`deflection, each of the probes 15 has an electrical insu(cid:173)
`lating material surrounding the wire 16. As shown in
`FIG. 2, a sleeve 19 of electrically insulating material is
`secured to the wire 16 of the probe 15 but does not ex-
`4o tend to the upper surface of the lower alignment die 12
`as shown in FIGS. 4-6.
`The sleeve 19 of electrically insulating material may
`extend through the opening 18 in the upper alignment
`die 14 or end near the lower surface of the upper align-
`45 ment die 14. When the sleeve 19 of electrically insulat(cid:173)
`ing material extends through the opening 18 in the
`upper alignment die 14, the opening 18 in the upper
`alignment die 14 must have sufficient cross section to
`include the thickness of the sleeve 19.
`The sleeve 19 of electrically insulating material may
`be a coating on the wire 16 with the coating being
`stripped from the portion of the wire 16 just above the
`upper surface of the lower alignment die 12 to the
`lower end of the wire 16. The sleeve 19 of electrically
`insulating material may be deposited on the wire 16 by
`electrophoretic or vacuum deposition, for example.
`One suitable means of forming the sleeve 19 on the
`wire 16 is to coat the wire 16 with parylene by vacuum
`60 deposition.
`As shown in FIGS. 4-6, there is no electrically insu(cid:173)
`lating material on the portion of the wire 16 of the
`probe 15 adjacent the lower alignment die 12. This in(cid:173)
`sures that there is good electrical contact of the wire 16
`65 of the probe 15 with the pad of the semiconductor chip
`with which it is to engage.
`It should be understood that the probe 15 is secured
`to the upper alignment die 14 in any suitable manner.
`
`50
`
`55
`
`FIG. 3 is a fragmentary sectional view, partly in ele(cid:173)
`vation, showing another arrangement for mounting the
`end of the probe to prevent axial movement thereof
`and to provide interconnection when an axial load is
`applied thereto.
`FIG. 4 is a fragmentary sectional view, partly in ele(cid:173)
`vation, showing one arrangement for controlling the
`direction of buckling or deflection of each of the
`probes.
`FIG. 5 is a fragmentary sectional view, partly in ele(cid:173)
`vation, showing another arrangement for controlling
`the direction of buckling of each of the probes.
`FIG. 6 is a fragmentary sectional view, partly in ele(cid:173)
`vation, showing a further arrangement for controlling
`the direction of buckling of each of the probes.
`FIG. 7 is a fragmentary sectional view showing a
`modified probe utilized for AC testing.
`
`FF1014
`Formfactor v. Feinmetall
`Page 6 of 10
`
`

`

`3,806,801
`
`5
`6
`40 connected thereto as the number of the contacts 29
`Thus, an adhesive may be employed. Furthermore, a
`on the printed circuit board 30 and the number of the
`layer of epoxy may be disposed on the upper surface of
`probes 15.
`the upper alignment die 14 to secure the probes 15 to
`the upper alignment die 14.
`Accordingly, electrical power can be supplied from
`As shown in FIG. 2, each of the wires 16 of the 5 a tester through each of the conductors 40 to the con-
`probes 15 has a ball 21 of reflowed solder connected
`nected contact 29 of the printed circuit board 30 and
`to its end. The ball 21 of solder must be connected
`then through the element 22 of the substrate 23 to the
`wire 16 of the probe 15. Thus, each of the probes 15
`through a space transformer or the like to a tester.
`Accordingly, each of the balls 21 of solder is shown
`can be selectively powered as desired.
`in FIG. 2 as being connected to an electrically conduc- IO The wire 16 of each of the probes 15 is formed of a
`tive element 22 of metal in a multilayered ceramic sub-
`suitable material, which will continue to deflect over a
`strate 23, which is supported on a support flange 24 of
`predetermined range when a predetermined force is ax-
`the housing 11. The substrate 23 may be secured to the
`ially applied thereto. As shown in FIG. 8, the predeter-
`flange 24 by suitable means such as an adhesive, for ex-
`mined force, after a minimum predetermined force has
`15 been reached, is substantially the same irrespective of
`ample.
`The electrically conductive elements 22 in the sub-
`the deflection of the wire 16 of the probe 15. Thus, a
`strate 23 are aligned with the balls 21 of solder through
`substantial deflection of the probe 15 can occur with-
`utilizing dowel pins 25 to orient the substrate 23 with
`out any increase in the force applied against the pad
`respect to the housing 11. The dowel pins 25 are dis-
`of the semiconductor chip which is being engaged by
`posed in machined openings in the adjacent surfaces of 20 the probe 15. Suitable examples of the material of the
`the housing 11 and the substrate 23.
`wire 16 of the probe 15 include BeNi, BeCu, tungsten,
`The balls 21 of solder are disposed at the desired Io-
`an electrical contact alloy sold under the trademark Pa-
`cation with respect to the housing 11 through the use
`liney by J. M. New Company, Bloomfield, Corin. and
`of dowel pins 26 ( see FIG. 1) to align the upper align-
`an electrical contact alloy sold under the trademark
`ment die 14 with respect to the housing Ii so that the 25 Niborium "B" by Niborium Industries, Inc., Provi-
`dence, R.I.
`openings 18 are set at the desired locations. Similarly,
`the openings 17 in the lower alignment die 12 are
`The wire 16 of the probe 15 is designed in accor-
`aligned with respect to the housing 11 by dowel pins
`dance with the formula, F= (31r) 2 E l/L2 where Fis an
`27, which cooperate with the lower alignment die 12
`axial load on the end of the wire 16 which will cause
`and the housing 11 through being disposed in machined 30 buckling of the wire 16, E is the modulus of elasticity
`openings in the adjacent surfaces of the housing 11 and
`of the material of the wire 16 of the probe 15, / is the
`the lower alignment die 12.
`least moment of inertia of the wire 16 of the probe 15,
`Each of the elements 22 is a layer of metal extending
`and L is the length of the wire 16. If the wire 16 is a
`through the substrate 23 to engage a metallic pad 28 on
`solid rod having a circular cross section, I = 1T D 4/64
`the upper surface of the substrate 23. The pads 28 are 35 where D is the diameter of the wire 16.
`arranged in a circle so that each of the pads 28 will en-
`Because the sleeve 19 has a thickness of only about
`gage a contact 29 on an annular shaped printed circuit
`one-fortieth of the diameter of the wire 16 and the
`board 30 when the substrate 23 is disposed between the
`modulus of elasticity of the material of the sleeve 19 is
`housing 11 and the printed circuit board 30.
`very low in comparison with the elasticity of the mate-
`The housing 11 is secured to the printed circuit board 40 rial of the wire 16, the effect of the sleeve 19 of insulat~
`30 by threaded dowel pins 31 (see FIG. 9), which are
`ing material on the bending or buckling of the probe 15
`diametrically disposed, on downwardly extending pro-
`can be ignored. This is why it need not be considered
`trilsions 32 of the printed circuit board 30 passing
`in the formula.
`through openings 33 in the flange 24 of the housing 11.
`By selecting the desired force which is to be applied
`Nuts 34 are secured to the threaded dowel pins 31 to 45 to the pad and will cause buckling of the wire 16 and
`connect the housing 11 to the printed circuit board 30.
`with E known because of the selection of the material
`of the wire 16 of the probe 15 and D known because
`of the area of the wire 16, only L is unknown in the for(cid:173)
`mula. As a result, the required length of the wire 16 of
`50 the probe 15 can be readily ascertained. Thus, by con(cid:173)
`trolling the length of the wire 16 relative to its area, a
`predetermined and selected force is applied to the pad
`of the semiconductor chip and no greater force is ex-
`55 erted on the pad because of the deflection of the wire
`16 of the probe 15 due to the bending or buckling
`thereof because of the axially applied force.
`As an example, if the wire 16 is formed of Paliney so
`as to have a modulus of elasticity of 17 X l 0 6 pounds
`60 per square inch, the diameter of the wire is 4 mils, and
`the predetermined load to be applied axially on the end
`of the wire 16 is 7 grams, then the length of the wire is
`600 mils.
`While the wire 16 of the probe 15 has been described
`65 as having a circular cross section, it should be under(cid:173)
`stood that the cross sectional area of the wire 16 of the
`probe 15 may have any other shape. Thus, it could be
`rectangular or square, for example.
`
`Diametrically disposed dowel pins 35 (see FIG. 10),
`which are spaced 90° from each of the diametrically
`disposed threaded dowel pins 31, extend from protru(cid:173)
`sions 36 of the printed circuit board 30 for disposition
`in machined openings 37 in the support flange 24 of
`the housing 11. This aligns the housing 11 and the sub(cid:173)
`strate 23 relative to the contacts 29 on the printed cir(cid:173)
`cuit board 30 prior to the housing 11 being secured to
`the printed circuit board 30 by the threaded dowel pins
`31 and the nuts 34.
`The printed circuit board 30 is bonded to an annular
`shaped aluminum plate 38. Each of the contacts 29 is
`a radial finger extending from the edge of the inner sur(cid:173)
`face of the printed circuit board 30 to the outer surface
`of the printed circuit board 30.
`Each of the contacts 29 on the printed circuit board
`30 makes contact by means of solder 39, for example,
`with an electrical conductor ·40, which is connected to
`the aluminum plate 38. Accordingly, the aluminum
`plate 38 has the same number of electrical conductors
`
`FF1014
`Formfactor v. Feinmetall
`Page 7 of 10
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`3,806,801
`
`7
`8
`While the wire 16 of the probe 15 has been shown
`example, through forming the opening 18 at an angle
`to the vertical as shown in FIG. 5.
`and described as having the ball 21 of reflowed solder
`provide the connection between the end of the wire 16
`Another arrangement for controlling the direction of
`of the probe 15 and the metal conductive element 22
`buckling or deflection of the wire 16 of the probe 15
`is to employ the offset of FIG. 4 in combination with
`in the substrate 23 so that the end of the wire 16 of the 5
`the slanted opening of FIG. 5 . . This arrangement is
`probe 15 is rigid against axial movement, it should be
`shown in FIG. 6 wherein the opening 17 in the lower
`understood that other suitable connections may be em(cid:173)
`alignment die 12 is offset with respect to the opening
`ployed. For example, a bead of conductive epoxy may
`18 in the upper alignmerit die 14 and the axis of the
`be used to join the wire 16 of the probe 15 to the metal
`conductive element 22 in the substrate 23 to prevent 10 opening 18 in the upper alignment die 14 is at an angle
`to the axis of the opening 17 in the lower alignment die
`axial movement of the end of the wire 16.
`12. It should be understood that the offset of the open(cid:173)
`Furthermore, instead of forming a structural connec(cid:173)
`ing 17 could be in the opposite direction to that shown
`tion between the metal conductive element 22 in the
`in FIG. 6 so that the opening 17 would be away from
`substrate 23 and the "Vire 16 of.the probe 15, the ball
`21 of solder could be replaced by enlarging the end of 15
`the direction in which the opening 18 slants.
`The offset of the opening 17 in the lower alignment
`the wire 16 of the probe 15 so that it is a ball 41 and
`die 12 with respect to the opening 18 in the upper
`forming the opening 18 in the upper alignment die with
`alignment die 14 is about 10 mils. The clearance be(cid:173)
`a clearance as shown in FIG. 3. This arrangement,
`tween the opening 17 in the lower alignment die 12 and
`which has the sleeve 19 end prior to the lower surface
`of the upper alignment die 14, would result in electrical 20
`the wire 16 is between 0.03 and 0.7 mil. The thickness
`of each of the lower alignment die 12 and the upper
`contact between the wire 16 and the conductive ele-
`ment 22 in the substrate 23, but there would not be a
`alignment die 14 is between 20 and 40 miis.
`The wire 16 protrudes about 12 mils beyond the
`solid connection of the conductive element 22 to the
`enlarged end of the wire 16. As a result, the end of the
`lower surface of the lower alignment die 12. The sleeve
`wire 16 of the probe 15 would be forced against the ele- 25 19 of the electrically insulating material terminates
`ment 22 making an electrical connection and the probe
`about 10 mils above the upper surface of the lower
`alignment die 12·
`15 would continue to buckle when an axial load is ap-
`plied thereto, but this would enable easy replacement
`While the probe contactor of the present invention
`may be utilized for both DC and AC testing, there may
`of any of the wires 16 if they were to break acciden- 30 be some instances in which it would be desired to have
`tally. That is, it would only be necessary to disconnect
`the substrate 23 from the housing l l.
`AC testing of devices in which a high density of the
`probes 15 is not required but a very tightly matched im-
`It should be understood that the opening 18 in the
`pedance between the probes is needed. Accordingly,
`upper alignment die 14 is slightly larger than the wire
`there is shown a modification of the invention in FIG.
`16 for the probe l5 to provide a clearance therebe- 35 7 in which the probe 15 is replaced by a probe 42.
`tween to insure that the enlarged end of the wire 16 al-
`Each of the probes 42 includes a center conductor
`ways engages the electrically conductive element 22 in
`43, which is a first conductive wire, surrounded by a di-
`the substrate 23 when an axial load is applied to the
`electric material 44. A metallic shield 45, which is a
`other end of the wire 16 by its engagement with a pad
`second conductive wire, is disposed around the dielec-
`on a semiconductor chip, for example. Without this 40 tric material 44.
`sliding capability of the wire 16 relative to the upper
`The central conductor 43 could be formed of tung-
`alignment die 14, the possibility could exist that manu-
`sten, for example, with the dielectric material 44 being
`Teflon and the metallic shield 45 being copper. Since
`facturing tolerances would cause the enlarged end of
`the wire 16 to be slightly spaced from the electrically
`the conductor 43 would have a diameter of 4 mils, the
`conductive element 22 in the substrate 23. Thus, this 45 dielectric material 44 would be an annular member
`having a diameter of 40 mils, and the shield 45 would
`possibility is eliminated while still preventing axial
`movement of the wire 16 when an axial load is applied
`be a ring having a thickness of 1 mil, the dielectric ma-
`thereto by engagement of the wire 16 with the pad on
`terial 44 and the shield 45 cannot be ignored in deter-
`mining the length of the probe 42 to have the desired
`the semiconductor chip.
`The direction of buckling of each of the wires 16 of 50 force applied to the electrical contact with which the
`the probes 15 must be controlled to have the high den-
`conductor 43 would engage. Both the shield 45 and the
`sity of the probes 15. One means for controlling the di-
`dielectric material 44 would terminate prior to the
`rection of buckling is to offset the opening 17 in the
`upper surface of the lower alignment die 12, which is
`lower alignment die 12 relative to the corresponding
`formed of an insulating material, in the same manner
`opening 18 in the upper alignment die 14 for the wire 55 as the sleeve 19 of the probe 15 terminates.
`16 of the probe 15. As shown in FIG. 4, this offset
`The upper alignment die 14 would be formed of a
`causes each of the probes 15 to buckle in a desired lo-
`suitable electrically conductive material so that the
`shield 45 of each of the probes 42 would be grounded
`cation so that there is no interference between the
`probes 15.
`60 thereon. This would provide a matched impedance be-
`tween the probes 42 to enable more stringent AC re-
`Another arrangement for controlling the direction of
`buckling of the wire 16 of the probes 15 is shown in
`quirements to be met. A single wire would extend from
`FIG. 5. In this arrangement, the opening 18 in the
`the upper alignment die 14 to the tester,
`upper alignment die 14 is disposed at an angle to the
`While the present invention has shown and described
`axis of the corresponding opening 17 in the lower align- 65 the probes 15 making contact to a tester through the
`ment die 12 so as to slant the longitudinal axis of the
`substrate 23 and the printed circuit board 30, it should
`wire 16 adjacent the upper alignment die 14. This slant-
`be understood that any other suitable means for fan-
`ing of the end of the wire 16 can be accomplished, for
`ning out the connections to the probes 15 could be em~
`
`FF1014
`Formfactor v. Feinmetall
`Page 8 of 10
`
`

`

`3,806,801
`
`15
`
`35
`
`10
`and means to supply electrical power to each of said
`wires.
`2. The contactor according to claim 1 including elec(cid:173)
`trical insulating means to prevent each of said wires
`5 from engaging any of the other of said wires in the area
`in which said probes buckle.
`3. The contactor according to claim 2 in which said
`electrical insulating means includes electrical insulat(cid:173)
`ing means on each of said wires.
`4. An electrical contactor including:
`a plurality of probes;
`each of said probes including a first electrically con(cid:173)
`ductive wire formed of a flexible material and hav(cid:173)
`ing a length many times its cross sectional area;
`each of said wires extending substantially axially for
`its entire length when not subjected to an axial
`load;
`means to prevent one end of each of said wires from
`moving axially beyond a predetermined position
`when an axial load is applied to its other end;
`means to slidably support said probe adjacent its
`other end to allow said probe to flex and slide when
`its other end has an axial load applied thereto so as
`to buckle between its ends;
`each of said wires having its other end extend beyond
`said slidably support means to have the axial load
`applied thereto;
`each of said wires buckling throughout a predeter(cid:173)
`mined range when a predetermined axial load is ap(cid:173)
`plied thereto;
`means to control the direction of buckling of each of
`said wires so that each of said wires buckles in a
`predetermined direction;
`means to supply electrical power to each of said
`wires;
`a housing surrounding said probes;
`said slidably support means including a first member
`supported by said housing and having a plurality of
`openings, each of sa