JPS587836A - Probe assembly - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a probe for testing the electrical characteristics of integrated circuits, and more particularly to a probe for contacting terminal pads of a semiconductor chip and as an interface between these pads and test equipment. Concerning the working probe.

A VLSI board uses an array of semiconductor chips that are mounted on a multilayer stacked board. The chips are arranged in discrete areas and typically have end pads,
For example, it is surrounded by an array of EC (design change) terminal pads.

The circuitry of the chip is formed in matrices, typically 5x5 or 10x10, so that a regular pattern of pads is defined on the surface of the substrate.

When the number of FJC pads in play is large and the spacing between such pads is very small, a probe is required to act as an interface between the IC being tested and the test equipment itself. Typically, the interface consists of a probe contactor that defines the electrical interface between the board and the test equipment, as well as a space transformer that controls the electrical environment to prevent distortion of the test signal. space transformers
serves to convert the large number of electrical connectors on the tester into a dense array comparable to the pad density pattern on the board. Such space transformers are known in the art and are disclosed, for example, in US Pat. No. 5,911,561.

In addition to spatial density considerations, the mechanical properties of the substrate pose difficulties in achieving a satisfactory interface between the haspace transformer and this substrate. For example, temperatures on the order of 1500° C. are used when processing multilayer ceramic substrates. These temperatures cause the untreated green sheet to shrink, thereby changing the design dimensions of the substrate.

The location of the chip area moves and the distance between the EC pad arrays located around the periphery of the chip area changes as well.

If probes were used with preselected distances to correspond to the design distances not only between chip areas but also between pads, each probe head would be It becomes impossible to contact the respective pads in the chip area.

Furthermore, in case of high temperature processing, the height of the pad changes @ unless sufficient force is applied to the probe, it is not possible to maintain contact between this probe and the pad with the lowest height. be. However, such force applied to the end of the probe will generate force on the highest pad from the substrate. If the force is too great, the pads or the chip itself will be damaged during the testing process.

To eliminate these interface problems, probe contactors with buckled probe beams
It has been proposed in the prior art to use The probe is placed in a housing with an alignment mold, and each glove is configured to be deflected by a force over a predetermined range so that the force applied to the pad is constant. That is, when the height of the pad changes, the same force is applied to each pad by each contact probe since these probes deflect to prevent more than a predetermined force from being applied to that pad. Buckling also causes contact to rub over a larger area than the point of contact.

Such a probe configuration is disclosed in US Pat. No. 5,806,801. This patent shows a metal casting having a housing 11 and upper and lower alignment molds 10 and 12. As shown in FIG. 1 of U.S. Pat. No. 3,806,801, a plurality of probes having electrically conductive wires 16 are supported by an alignment mold. The probes have an insulating cover to prevent electrical contact if the probes accidentally touch each other during deflection. Typically, the wire is made of perylene (par) formed by vacuum evaporation.
ylene).

To control the buckling direction of the probe, US Pat.
No. 0680.1 proposes the following five techniques.

(,) Misalignment of the openings of the upper and lower alignment molds.

(b) positioning the opening in the upper alignment mold at an angle with respect to the corresponding opening in the lower alignment mold to tilt the longitudinal axis of the wire;

(c) A combination of offset and tilting at an angle.

Despite the advantages provided by the device disclosed in US Pat. No. 3,806,801, a number of deficiencies still exist. First, making alignment molds of the type disclosed in U.S. Pat. is necessary.

Second, if a VSLI structure is used and the chip areas are in an array, it is necessary to move the probe relative to the substrate to test each of these chip areas.

It is preferred that grouped probes be used rather than the single row of probes taught by the prior art to reduce the time required to test one board.

In the case of a 10.times.10 array, groups of probes, eg, 20 probes in two rows, are required for collective alignment, which is rarely possible in the prior art. Additionally, techniques for providing reliable pad-to-pad contact in a manner that biases the beam probe do not ensure uniform deflection or buckling when a predetermined axial load is applied to the probe beam. That is, the expected buckling occurs, but the direction changes and contact between the wires occurs. Because the angle of this buckling direction is unpredictable, prior art probe beams still use insulating covers.

However, such a requirement is very expensive.

Other prior art devices have proposed using integrated circuit probe assemblies for use in continuous testing processes. Devices such as that proposed in U.S. Pat. No. 5,906,565 use a contactor assembly having a plurality of metal spring fingers that frictionally contact openings in a printed circuit board. U.S. Pat. No. 5,731,191 shows a multi-probe fist assembly that uses multiple probe guide elements having probe wires movably encased and compressible in the guide elements. The probe wire is designed so that, when inserted into the probe guide element, it extends a controlled amount beyond the end of the housing, but the other end of the wire contacts against the pressure plate. Upon compression, the guide element is treated to impart spring properties to the probe wire inserted therein. This sophisticated device is equipped with probes and
Alternatives in the prior art with respect to assembly represent, but do not overcome fundamental deficiencies such as grouping and cost.

Accordingly, a principal object of the present invention is to provide an improved modular test probe suitable for use in multilayer VLSI structures.

Another object of the present invention is to provide an improved modular test probe having probe units mounted in clusters for use in testing a matrix of chip areas on a substrate being tested at one time. It is to be.

It is a further object of the present invention to provide a probe capable of acting as an interface between a multilayer ceramic substrate and test equipment to test for electrical shorts and opens in integrated circuits.

It is also an object of the present invention to provide a modular test probe that has a conventional guide design and can be used in all guide positions of the probe structure.

Furthermore, it is an object of the present invention to provide a probe for use in a serial test device so as to reduce the overall test time of the device by eliminating the requirement to reposition the probe in different chip areas.

These and other objects of the present invention are achieved by using test probes having a modular construction, which test probes can be assembled in groups to test MLC arrays, such as 2 x 2.6 x 5. Can be installed in any shape. The probe uses cast guide elements that have through holes for positioning the probe beam. The guide elements are identical in construction and have a projection on the bottom side and a receiving recess on the top side in order to achieve a predetermined alignment with respect to the space transformer or to pre-provide the necessary bending to the probe beam. has. By using identical cast guide elements,
Manufacturing costs of the glove configuration are substantially reduced. An offset key is used to displace a pair of guide elements relative to each other and pre-apply the necessary bending to the probe beams as they pass through the two guide elements.

The central strut and separator element is used to secure the assembly and has a height calculated to give the probe free length to buckle under a predetermined force. Grooves are cast into the body to separate these blow-boo beams and prevent electrical shorts between them.

Thus, the prior art requirement that the probe beam be coated with an insulating material is eliminated. The central strut and separator element employs a series of locating ears and recesses for positioning adjacent prop components. In addition, the ears of the strut and separator elements guide the probe beam as it buckles into the groove of an adjacent globe in the group.

In another embodiment, a mobile "Beam Seven Zeta Rator"
are used and move laterally with these beams as they buckle. The beams are arranged asymmetrically around the central strut element to provide the necessary offset or deflection to the beams and to bend them uniformly in the predetermined direction. A lug assembly is unnecessary because the beam clutter is moved laterally so that the beam can buckle and the possibility of contact between adjacent probe assemblies is eliminated.

Referring to FIG. 1, a perspective view of a first embodiment of the invention is shown exploded. The module test probe uses four guide elements 10.12.14 and 16. Each guide element is identical and made of cast insulating material. Each guide element has a central aperture 18, a boss or projection 20 on one optical surface and a corresponding recess 22 on the opposite surface. A series of through holes 24 are arranged around the outer circumference of each guide element.

The through holes are arranged to correspond to the orientation of the EC pads contacted by the globe beam.

Although FIG. 1 shows a single row circumferential array of through-holes 24, it will be appreciated that if the chip area has multiple EC frames, multiple annular arrays are equally applicable.

The through-hole 24 has a tapered guide groove for the probe beam 64 and to facilitate insertion.

As shown in FIG. 1, when the guide element 10 is positioned with respect to the upper boss 20, the alignment and tolerance of the probe relative to the space transformer is maintained.

An offset key 26 is inserted between the guide elements 10 and 120. Offset key 26 has a central opening 28 and consists of two flat elements 50 and 62. The upper flat element 50 enters the cavity or recess 22 for positioning the upper guide element 10. The lower flat element 52 is the guide element 22
The positioning is in a cavity or recess. Accordingly, as shown in FIG. 1, the guide elements 10 and 12 are positioned with respect to the use cavities 22-, which receive the flat elements or faces 5o and 52 of the offset key 26. so that they are adjacent to each other.

For the configuration shown in FIG. 1, an offset key cast from the same material as the guide element provides a positive offset of the through-hole 24 of the guide element 1o with respect to the through-hole of the guide element 12. When probe beam 54 is inserted into through-hole 24 of guide elements 10 and 12, an offset is provided and globe beam 64 is pre-bent. The tapered throughbore 24 geometry provides room for this excursion of the probe beam. This is shown partially enlarged in FIG. 2A.

That is, the use of an offset key causes the guide elements 1o and 12 to
through-holes 24 are not axially aligned with each other.

Probe beam 54 is formed from a suitable material to permit deflection within a predetermined range when a predetermined force is actually applied to the beam. After reaching the predetermined force, this force remains approximately constant and deflection of the probe beam occurs. With this technique, the mismatch in forces exerted on the globe beam produced by different heights of the pads manifests itself in beam deflection, which can be seen on the pads of semiconductor chips touching the ends of the beam. This is in contrast to what appears in the form of an increase in power.

Various materials can be used to form probe beam 64. For example, B'eNi, BeCu.

Tungsten, PALINE'Y (trade name, J, M, N
Electrical contact materials such as those manufactured by EW Corporation can be used.

The length of the probe beam is determined by methods known in the art. The probe beam is designed according to the following formula.

F=(3π)2E I/L2 Now, F is the axial load acting on the end of the probe beam 54, which causes the probe beam to buckle. -E is the elastic modulus of the probe beam material.

■ is the moment of inertia of the probe beam.

L is the length of the probe beam.

If the probe beam 54 is a solid rond of circular cross section, the moment of inertia is equal to πD4/64.

Now, D is the diameter of the probe beam.

However, although a circular cross-section is shown, it is clear that any other shape of the probe beam can be used, such as rectangular or square.

It is immediately clear from the above formula that the required length of the probe beam can be ascertained since E is a function of the material, D is known, and 2 is derived as a function of the cross section. Therefore, by controlling the length of the probe beam, a predetermined and selected force is applied to the EC pad and the probe beam is easily deflected by bending or buckling when high levels of force are applied. Because of this, no great force is applied.

As shown in FIG. 1, each of the probe beams 34 is
This probe beam and space transformer
It has a conductive ball end formed of solder or the like to engage between the ends. Other ball end configurations can be used.

In the embodiment of FIG. 1, the central strut and separator element 66 serves to secure the assembly and allows the probe beam 54 a free length to buckle under a predetermined force.
have a height calculated to give each of them. Groove 68
are cast into the body to separate the probe beams 54 and prevent electrical shorts between the probes. The central strut and separator element has a recessed portion 40 which receives the projection 20 for positioning the guide element 12. The through hole 42 is also provided for receiving a fixing screw, as described below. The bottom of the strut and separator element has a boss or protrusion 44 which engages a recess or positioning recess 22 in the guide element 14.

The guide elements 14 and 16 overlap each other by placing the protrusion 20 in the recess 22 of the guide element 16.

In this position, the through holes of each guide element are aligned and the protrusion on the guide element 16 provides a positive stop and prevents excessive buckling of the probe beam.

The entire assembly is secured together by hollow screws 46. It will be apparent that other coupling members can be used to secure the probe parts together.

The lug portions 48 serve to guide the probe beams as they buckle into the grooves of the adjacent globes. The second function is the central pillar/separator element 5
The upper ear portion 48 and recess portion 50 of 6 are coincident. When the probes are mounted in a collective configuration to test multiple chip areas in a single contact operation, the probes in each row are aligned with each other using their matchable elements. Optical alignment may be performed on each chip area to align the probes with respect to the area being tested. The primary function of the lug portions 48 is to prevent the probes from moving out of planar deflection when the probes buckle.

Referring to FIG. 2, a completed probe assembly is shown. The probe assembly is mounted on a movable arm that attaches probes to respective pads arranged in the chip area. A space transformer such as that shown in U.S. Pat.
It could be used in conjunction with beam play. When the probe beam is placed over the chip area, a uniform rubbing contact force on each pad occurs, which ensures uniform electrical contact. Changes in pad height are reflected by changes in the deflection angle of the individual probe beams. Although contact is guaranteed for each pad,
Excessive forces that are potentially harmful to the substrate are not transmitted.

The glove assembly containing the specific area is moved to a different chip area on the substrate and then testing is initiated.

Referring to FIG. 5, a second preferred embodiment of the invention is shown. In this embodiment, two pairs of guide elements are used in a superimposed and coincident configuration. That is, the first significant difference between this embodiment and the embodiment of FIG. 1 is that the offset key of the first embodiment is not used. As shown in FIG. 5, guide element 10 overlaps guide element 12, while guide element 14 overlaps guide element 16. Therefore, two pairs of guide elements are used to provide initial alignment of the probe beam. As shown in FIG. 6, the through-holes 24 are tapered to allow deflection of the probe beams as they pass therethrough.

As in the embodiment of FIG.
is formed from a suitable material that allows a predetermined range of deflection when the predetermined force is actually applied to the beam. After reaching this chapel; this force remains approximately constant and deflection of the beam occurs. The same selected materials as defined for the embodiment of FIG. 1 can be used to form the probe beam 34 of the embodiment of FIG.

As shown in FIG. 3, a central post 60 is used which has a protrusion 62 at each "end, which protrusion is dimensioned to fit into the recessed portion 22 of the respective guide element. , are superimposed on the ends of the strut 60 as shown in FIG. 5. These parts are secured together in a compression manner by bushings 64 and 66 I/c. It is clear that a compressive fit is thus achieved between the projection 62 on the central post and the bushing assembly, and the four guiding elements shown in FIG. It will be fixed in the fixed position.

Embodiment L1 in FIG. 6 differs from the embodiment in FIG. 1 in that the pillar member 60 of the middle man is not used as a separator. Instead, floating beam separator elements 68 are used. The floating beam separator element pre-bends and separates the probe beam 64. The separator element 68 has an array of holes 70 which are symmetrical with respect to their alignment with respect to the through holes 24 of the guide element.

However, the floating beam separator elements 68 are arranged in an asymmetric configuration with respect to the central column 60. This offset is shown in FIG. 5 and is constructed by providing an asymmetric central hole 72 in the floating beam separator element. Thus, when separator element 68 is mounted on column 60, this separator element is moved asymmetrically with respect to the positioning of probe beam 54 with respect to guide elements 10, 12, 14 and 16. As shown in FIG. 5, the holes 70 in the floating beam separator elements are larger than the through holes 24 in the guide elements.

The through-hole is enlarged to allow beam clearance and biaxial displacement as the deflected probe beam is passed through the separator element.

A series of standoff members 74-76 are placed over the probe beam located adjacent to the probe to prevent vertical movement of the floating beam separator element 70 as the probe beam is deflected. There is.

The bottom surface of the guide element 16 may be coated to provide a positive stop and prevent bonding and damage to the surface of the IC during testing. Alternatively, some variation of the embodiment of FIG. 5 may be used. For example, a floating guide element
They may be arranged below the guide element 16 to reduce the protrusion length of the respective probe beams. The floating guide element reduces the susceptibility of the assembly to damage in bending, but still moves with the probe. The floating guide element may be held by attaching it to the probe beam with epoxy or other adhesive, or it may be mechanically integrated into the bottom guide element 16. The floating guide element therefore consists of a generally flat plate with an array of through holes corresponding to the through holes 24 of the guide element and the probe beam 54 projects from the plate with a reduced protrusion length. Located at the bottom end of the assembly. Another variation is to use guide bins, which are placed through the guide elements 14 and 16 so as to contact the floating guide element at a particular angular orientation. For example, if a 6 degree offset is used, the bottom tip of the probe beam will be deflected in a uniform angular relationship to produce the desired scraping action of the probe beam at the point of contact. Such guide bins are inserted into guide bin holes machined in the lower two guide elements 14 and 16 as well as in the floating guide plate. The guide bin is pushed into the bottom of the floating guide plate,
This floating guide plate is slidably mated to the upper guide element. Therefore, in this embodiment, in addition to pre-bending the probe beam by using floating separator elements 68, the probe beam 54
is deflected in a desired angular relationship so that the desired rubbing action of the bottom bald lobe beam occurs on the contact surface.

For example, other biasing techniques can be used, such as using the offset arrangement of FIG. 1 with the embodiment of FIG.

In this modified structure, a floating separator bias is used.

[Brief explanation of drawings]

FIG. 1 is an exploded perspective view showing the parts forming the probe assembly of the present invention; FIG. 2 is a perspective view showing the assembled globe assembly; and FIG. 2A is an enlarged view showing the through holes of the globe assembly. Figure 5 is a cross-sectional view showing the second embodiment of the present invention. 54... Probe beam, 24... Through hole,
10.12.14.16...Guide element, 26...
・Offset key, 66... Support and separator element, 46... Screw. Applicant I × outside → -ya Naru Business Machines
Kozutsu en 13

Claims (1)

[Scope of Claim] (A probe assembly for arranging a plurality of deflectable beam elements in an arrangement corresponding to the surface terminal arrangement of an integrated circuit to be retested, the probe assembly having an aperture and receiving the beam elements; first guiding means having a plurality of through holes around the aperture for receiving and aligning the beam elements in a predetermined orientation; a second guiding means having a plurality of through holes around said opening for aligning the beam elements in a predetermined orientation; said first and second guiding means being attached at opposite ends; comprising a central post for establishing a predetermined distance between the means; and fixing means positioned in the aperture to configure the central post and the first and second guide means into a single assembly; characterized in that when the beam end contacts the surface of the integrated circuit to be tested, the applied load causes the beam elements to buckle in the same direction at different rates, thereby establishing a uniform predetermined beam contact force. (2) The probe assembly according to claim (1), wherein the first and second guide means are a pair of identical guide elements. (3) A probe assembly according to claim 1, wherein said first guide means has staggered through holes for deflecting said beam element in a predetermined bending orientation.