A method of fabricating a large area, multi-element contactor. A segmented contactor is provided for testing semiconductor devices on a wafer that comprises a plurality of contactor units mounted to a substrate. The contactor units are formed, tested, and assembled to a backing substrate. The contactor units may include leads extending laterally for connection to an external instrument such as a burn-in board. The contactor units include conductive areas such as pads that are placed into contact with conductive terminals on devices under test.

FIELD OF THE INVENTION

The present invention relates generally to a method of fabricating a large area multi-element contactor and, more particularly, to a segmented contactor fabricated by mounting multiple contactor units on a substrate.

BACKGROUND OF THE INVENTION

Semiconductor devices (such as integrated circuits) are generally fabricated on a substrate of silicon known as a wafer. A single wafer typically includes a large number of devices (such as integrated circuits) that are grouped into units called dies. A single wafer typically has a plurality of dies formed thereon. Each die is later singulated from the wafer and further processed and packaged. Modern technology typically uses 8-inch (200-mm) diameter wafers, and is moving to 12-inch (300-mm) wafers. Essentially every single device fabricated on a wafer needs to be electrically tested by probing. Probing more than one device at a time is particularly advantageous. Modern probing equipment can probe 32 or more semiconductor devices at the same time. However, this is often only a small fraction of the total number of devices on a wafer. There has been great interest in developing a probing system that can contact more, preferably all devices on a wafer at the same time.

It is generally desirable to identify which of the plurality of dies on a wafer are good prior to their packaging, and preferably prior to their being singulated from the wafer. To this end, a wafer “tester” or “prober” may be employed to make a plurality of discrete pressure connections to a like plurality of discrete connection pads (bond pads) on the dies. In this manner, the semiconductor dies can be tested, prior to singulating the dies from the wafer.

Typically, semiconductor devices are exercised (burned-in and tested) only after they have been singulated (separated) from the wafer and have gone through another long series of “back-end” process steps in which they are assembled into their final “packaged” form. The added time and expense of singulating and packaging the device goes to waste if the final “packaged” device is found to be defective after packaging. Consequently, performing testing or burn-in of semiconductor devices prior to their being singulated from the wafer has been the object of prolonged endeavor.

Modern integrated circuits include many thousands of transistor elements, for example, with many hundreds of bond pads disposed in close proximity to one another; e.g., 4 mils (about 100μ) center-to-center. One common layout of the bond pads has one or more rows of bond pads disposed close to the peripheral edges of the die. Another common layout has is called “lead on center” (LOC) with typically a single row of contacts along a center line of a die. Other layouts, some irregular, are not uncommon. The proximity and number of pads is a challenge to the technology of probing devices.

Generally, probing devices for testing semiconductor devices on a wafer have involved providing a single test substrate with a plurality of contact elements for contacting corresponding pads on the wafer being tested. To test a full wafer simultaneously generally requires extremely complex interconnection substrates, which may easily include tens of thousands of such contact elements. As an example, an 8-inch wafer may contain 500 16 Mb DRAMs, each having 60 bond pads, for a total of 30,000 connections between the wafer under test (WUT) and the test electronics. Earlier solutions included mating with some subset of these connections to support limited or specialized testing. It would be advantageous to fully connect an entire wafer.

Moreover, the fine pitch requirements of modem semiconductor devices require extremely high tolerances to be maintained when bringing the test substrate together with the wafer being tested. During testing or burn-in processes, heat is produced which causes thermal expansion of the underlying substrate materials. Thermal expansion presents a further challenge to connecting a test substrate to the WUT because of the extremely tight tolerances and close spacing of pads.

To effect reliable pressure connections between contact elements and, e.g., a semiconductor device, one must be concerned with several parameters including, but not limited to: alignment, probe force, overdrive, contact force, balanced contact force, scrub, contact resistance, and planarization. A general discussion of these parameters may be found in U.S. Pat. No. 4,837,622, entitled “High Density Probe Card,” incorporated by reference herein, which discloses a high density epoxy ring probe card including a unitary printed circuit board having a central opening adapted to receive a preformed epoxy ring array of probe elements.

A more sophisticated probe card uses resilient spring elements to make contact with a device on a wafer. Commonly assigned U.S. Pat. No. 5,806,181, entitled “Contact Carriers for Populating Larger Substrates with Spring Contacts,” issued Sep. 15, 1998, ('181 patent), incorporated by reference herein, discloses such a probe card. The resilient spring elements of the '181 patent are pre-fabricated on individual spring contact carriers (“tiles”).

The resilient spring elements can alternatively be prefabricated on the wafer itself. This configuration is known as MOST Technology, using Microspring Contacts On Silicon. Such a wafer is conveniently manufactured using techniques described in commonly assigned, copending U.S. patent application Ser. No. 08/558,332, entitled “Method of Mounting Resilient Contact Structures to Semiconductor Devices,” filed Nov. 15, 1995, incorporated by reference herein. A contactor or testing substrate that can perform a wafer-level test or burn-in procedure on a MOST wafer must provide corresponding conductive areas that can precisely align with the thousands of microsprings disposed on the wafer.

Providing a contactor that can be precisely aligned with each of the resilient spring elements or bond pads is challenging because of tolerances and the expansion of the underlying substrate materials due to heat produced during the testing or burn-in processes. Also, providing a large size contactor that has corresponding conductive areas for each spring element on the wafer under test can be problematic because if one of the thousands of conductive areas is defective, the entire contactor will be deemed defective.

Thus, what is needed is a segmented contactor that provides separate contactor units for performing wafer-level testing or burn-in procedures and that minimizes problems related to tolerances and thermal expansion.

SUMMARY OF THE INVENTION

In one example of the present invention, a segmented contactor comprises a relatively large backing substrate and at least one relatively small contactor unit (“tile”) mounted to the backing substrate. Preferably, a plurality of contactor units is provided. The contactor units are disposed on the front (facing the WUT or other device) surface of the backing (support) substrate. It is also possible (and may be preferable) that one contactor unit is bigger than an individual device under test (DUT) and “mates” with two or more DUTs.

The contactor units can include active semiconductor devices, such as application-specific integrated circuits (ASICs). For example, the ASIC can enable the number of signals being provided to the test substrate from an outside source (e.g., a host controller) to be minimized.

In one example of the invention, resilient contact elements that provide the conductive pressure connections are preferably mounted by their bases directly to the WUT (i.e., to the DUTs on the WUT) so as to have free ends extending to a common plane above the surface of the WUT. The segmented contactor of the present invention preferably has a coefficient of thermal expansion which is well-matched with that of the WUT. Alternatively, the resilient (or spring) contact elements are mounted to the contactor units of the segmented contactor.

An example of a method of fabricating a segmented contactor is provided wherein a plurality of contactor units is mounted on a backing substrate such that resilient contact elements attached to a device on a silicon wafer can be aligned with a plurality of conductive contact areas on each contactor unit during testing.

An exemplary method includes forming a plurality of contactor units on a single contactor substrate, testing electrically each of the contactor units, separating each of the contactor units from the single contactor substrate, and assembling the contactor units which have passed the electrical testing to form the segmented contactor.

Preferably, the contactor units are tested before being separated from the single contactor substrate onto which they are formed. Alternatively, the contactor units can be tested individually after being separated.

Also, each contactor unit preferably includes a plurality of electrically conductive leads extending horizontally beyond an edge of each contactor unit. The plurality of leads is preferably in the form of a flex strip which can have a connector attached to the leads for connecting the contactor unit to an external testing device.

Assembling the contactor units to form the segmented contactor can include providing an assembly fixture for holding the contactor units during the assembly. An example of an assembly fixture is a plate that defines holding spaces. A contactor unit is placed into a corresponding holding space on the plate. Each contactor unit has a first side and a second side. An adhesive or attachment means can be provided on the second side either before or after the contactor unit is placed within its respective holding space on the plate. After the contactor units are placed into respective holding spaces, a backing substrate is pressed onto the adhesive to mount the contactor units to the backing substrate. The backing substrate is then lifted away from the plate. The contactor units are thus properly aligned and mounted to the backing substrate.

The assembly fixture provided for the assembly of the segmented contactor is preferably a flat plate that includes grooves into which guide blocks are placed to define the holding spaces between the guide blocks. The guide blocks provide the proper relative alignment of each contactor unit.

The method and apparatus of an example of the present invention also provide that the first sides of the contactor units are substantially coplanar when mounted onto the backing substrate.

The contactor units can be removably mounted to the backing substrate, such that each contactor unit can be removed and replaced upon failure or discovery of a defect in any one particular contactor unit, for example.

An example of the device of the present invention can be readily used for partial to full wafer-level testing of devices which have spring contact elements mounted thereto. In use, the segmented contactor including the backing substrate with plurality of contactor units mounted thereto and having conductive leads extending therefrom (the leads being connected to external testing equipment) is urged toward the wafer under test so that the resilient contact elements extending from the devices on the wafer make contact with corresponding conductive areas or pads on corresponding contactor units of the segmented contactor. The ability of all the resilient contacts to make contact with the plurality of contactor units, all at once, can facilitate such processes as wafer-level burn-in or testing. However, it is not necessary that every die on the wafer contact a corresponding contactor unit on the segmented contactor at once.

An alternative example of the present invention includes a segmented contactor which includes spring contact elements mounted to the contactor units of the segmented contactor.

It will also be appreciated that a segmented contactor of the invention may be used, after assembly, to test devices other than a semiconductor wafer, such as another contactor or a printed circuit board.

DETAILED DESCRIPTION

An improved large area multi-element contactor and method of fabricating the contactor is described. In the following description numerous specific details are set forth, such as specific equipment and materials, etc., in order to provide a thorough understanding of the present invention. It will be obvious, however, to one skilled in the art that the present invention may be practiced without these specific details. In other instances, well-known machines and methods for making such machines have not been described in particular detail in order to avoid unnecessarily obscuring the present invention.

FIG. 1illustrates a method of fabricating a segmented contactor comprising forming a contactor unit (110), testing electrically the contactor unit (112), and assembling the contactor unit which has passed the electrical testing with a substrate to form the segmented contactor (114). The method shown inFIG. 1can include forming a plurality of contactor units and assembling the plurality of tested contactor units with a substrate to form the segmented contactor. When a plurality of contactor units is formed, each of the contactor units is preferably tested before assembling to the substrate to form the segmented contactor. Alternatively, the testing can be performed after assembling. In another example of the method of fabricating a segmented contactor, the contactor unit (or units) can be retested after assembling the contactor unit with a substrate.

The method ofFIG. 1can include, as a precursor, forming the contactor unit from a single contactor substrate. For example, a tile can be formed on the single contactor substrate. The tile is the body of the contactor unit and may include conductive areas on at least one side. The tile may also include runners or conductive pathways within the tile. The tile can be made from a layered substrate, for example, with the runners disposed within or through selected layers.

The tile can be tested electrically either before or after being separated from the contactor substrate. Preferably, the testing is performed before the tile is used in a testing assembly such as a segmented contactor.

The method shown inFIG. 1can further include testing a device on a wafer with the segmented contactor. For example, a wafer can include a plurality of semiconductor devices, such as integrated circuits. The segmented contactor can be used to test some or all of the devices on the wafer. Techniques for performing wafer-level burn-in and test of semiconductor devices are described in commonly assigned, copending, U.S. patent application Ser. No. 08/784,862, entitled “Wafer-Level Burn-In and Test,” filed Jan. 15, 1997, incorporated by reference herein.

FIG. 2illustrates another method of fabricating a segmented contactor. An example of the method shown inFIG. 2comprises forming a plurality of contactor units on a single contactor substrate (120), testing electrically each of the contactor units (122), separating each of the contactor units from the single contactor substrate (124), and assembling the contactor units which have passed the testing to form the segmented contactor (126). Forming the plurality of the contactor units (120), however, need not be accomplished on a single contactor substrate. For example, the contactor units can be formed individually.

The testing (122) of the contactor units can be performed either before or after separating (124) each contactor unit from the single contactor substrate. Another example of the method includes testing (122) the contactor units after they are assembled (126) to the substrate to form the segmented contactor. The method can also include retesting of the contactor units once they are assembled after having been previously tested before assembly to form the segmented contactor.

The method of fabricating a segmented contactor for testing multiple devices on a wafer can also include connecting at least one of the contactor units that have been assembled on the substrate with another one of the contactor units on the substrate. This electrical connection can be accomplished with discrete wires or through flexible strips which include a plurality of conductive leads, for example. The wires or flexible strips can be soldered or otherwise suitably connected between two or more contactor units. The electrical connection between contactor units can also be accomplished with connectors on corresponding edges of adjacent contactor units. Alternatively, contactor units can be electrically connected to each other through conductive pathways formed in the backing substrate, which conductive pathways terminate at conductive pads or vias on the surface of the substrate. The conductive paths or vias can be aligned with corresponding conductive areas on separate contactor units that are to be electrically connected. The contactor units and the conductive pathways of the backing substrate can thus be electrically connected with a suitable means of connecting, such as wiring or solder.

Connecting multiple contactor units together on a segmented contactor can be advantageous when the segmented contactor is designed for testing a plurality of semiconductor devices on a single wafer. For example, although there can be a one to one correspondence between contactor units of the segmented contactor and devices on the wafer, each separate contactor unit can be sized and designed to test a plurality of devices on the wafer. For example, to test a wafer having 400 devices (DUTs), a segmented contactor can be provided that has 8 contactor units, each of which can accommodate 50 DUTs.

Another example of the method shown inFIG. 2can further include attaching a plurality of electrically conductive leads to at least one of the plurality of contactor units. Preferably, the leads extend beyond the edge of a corresponding contactor unit, and a connector is provided on the leads for connecting the leads to an external testing device, for example to a burn-in board, which in turn may be connected to other test equipment.

FIG. 3shows a method of assembling a segmented contactor comprising providing an assembly fixture including a plate that defines a contactor position (130), placing a contactor unit into the contactor position (132), and placing a backing substrate over the contactor unit in order to mount the contactor unit to the backing substrate (134).

An example of the plate preferably defines a plurality of contactor positions that are holding spaces into which can be placed corresponding ones of a plurality of contactor units. The holding spaces are defined in the plate such that boundaries are defined for the individual contactor units which are placed into the holding spaces. The assembly fixture of the example of the method ofFIG. 3can provide a selected configuration of contactor positions so that the contactor units can be arranged to match corresponding dies or devices as they are laid out on a semiconductor wafer. The assembly fixture preferably holds the contactor units in near final position as accurately as possible.

In one preferred implementation following the method ofFIG. 3, a plate is provided in which grooves are defined. The method can further comprise inserting guide blocks into the grooves to define the holding spaces or boundaries between the guide blocks. The contactor unit has a first side and a second side. The first side preferably faces the plate when the contactor unit is placed into the holding space.

The method can also further include providing a securing mechanism such as an adhesive on the second side of the contactor unit for securing or mounting the contactor unit to the backing substrate. The method can include affixing the adhesive to the contactor unit before the contactor unit is placed into the assembly fixture. Alternatively, the adhesive can be affixed to the backing substrate before the backing substrate is placed over the contactor unit that has been inserted into the holding space of the assembly fixture. Another alternative is to place the adhesive onto the contactor unit after the contactor unit has been placed into the holding space of the assembly fixture.

The method shown inFIG. 3can further include testing of the contactor unit. The testing can be performed before or after placing the contactor unit into the holding space of the assembly fixture. The method can further include retesting the contactor unit after placing the backing substrate onto the contactor unit.

FIG. 4shows a method of repairing a segmented contactor assembly comprising removing a selected mounted contactor unit from a backing substrate of the segmented contactor assembly (140), testing electrically a replacement contactor unit (142), and mounting the replacement contactor unit of the backing substrate (144). The exemplary method ofFIG. 4can be implemented in a variety of sequences. For example, the mounted contactor unit can be tested (142) to determine whether it is defective, for example, prior to being removed (140) from the backing substrate. Alternatively, a known “bad” contactor unit can be removed from the backing substrate and replaced with a new contactor unit without testing the bad contactor unit. The new contactor unit can be tested (142) either before or after being mounted (144) to the backing substrate. Yet another alternative scenario can include repair of the contactor unit which has been removed (140) from the backing substrate. In this case, the bad contactor unit can be removed (140) from the backing substrate, tested (142), repaired if necessary, and then replaced (144) onto the backing substrate. The method illustrated inFIG. 4can also be implemented when it is desired to change a contactor unit that may not necessarily be defective. For example, it may be desirable to change a particular configuration of contactor units to accommodate a change in the semiconductor dies or devices being tested on the wafer.

FIG. 5shows a method of testing a plurality of devices on a wafer comprising providing a segmented contactor (150) as previously described. The segmented contactor provided in the example ofFIG. 5preferably includes a tile having a first side and a second side wherein the tile has electrically conductive areas on the first side for contacting corresponding electrically conductive terminals on the device or devices of the wafer under test. The tile further preferably has a plurality of electrically conductive leads extending beyond edge of the tile. The method further comprises connecting the plurality of leads extending from the tile to an external testing instrument or device, bringing the terminals on the devices under test into contact with corresponding conductive areas on the tiles, energizing the contactor units, and performing a test on the devices.

An electrical testing assembly200such as a segmented contactor for testing a device on a semiconductor wafer, is shown in FIG.6. The electrical testing assembly includes a substrate210, a plurality of contactor units220assembled with the substrate210, and a plurality of electrically conductive areas222arranged on each of the contactor units220. For simplicity of illustration, only a few of the plurality of conductive areas222on the contactor units220are shown in FIG.6.

The contactor units220preferably have each been tested electrically prior to being assembled with the substrate210to form the segmented contactor200. Also, the conductive areas222on each of the contactor units220are configured to be electrically connected to the device under test (not shown).

As shown inFIG. 6, the substrate210is a rectangular piece on which is mounted a plurality of generally rectangular contactor units220that are arranged in two columns224and multiple rows226. The arrangement or configuration of the contactor units220on the substrate210can, however, be any desired shape, size, or arrangement as may be required for the particular devices and wafer being tested by the segmented contactor200.

The electrically conductive areas222on each contactor unit220can also be arranged or configured in any desired arrangement as necessary to match corresponding electrically conductive terminals on the wafer that will be tested with the segmented contactor200. The electrically conductive areas222of the contactor units220are preferably conductive pads, but alternatively can include other contact elements such as solder balls, points, and the like. Particularly preferred are extended freestanding resilient contact elements.

As further shown inFIG. 6, the contactor units220can be electrically connected to each other by wire bond connections228or by a flexible strip230that includes a plurality of conductive leads232.

The segmented contactor200shown inFIG. 6can also include a plurality of electrically conductive leads240extending from at least one (shown inFIG. 6) and preferably from each of the contactor units220. The electrically conductive leads240are preferably configured for connection to an external instrument (not shown). For example, a connector242can be provided on the free ends of the leads240. The leads240are preferably attached to the contactor unit220and correspond to selected ones of the plurality of electrically conductive areas222on the contactor unit220. The leads240are preferably carried in a flexible strip244. A plurality of flexible strips244can be provided and attached to one contactor unit220. The flexible strip244can be secured to the contactor unit220on either the first side221or the second side (not shown) of the contactor unit230.

FIG. 7shows the contactor units220extending partially over the edge212of the backing substrate210. The extending portion234of the contactor units220provides an area that is available to secure a flexible strip244or a plurality of flexible strips244to either the first221or second sides223or both sides of the contactor unit220.

As shown inFIG. 7, the contactor units220are secured to the backing substrate210with a securing mechanism such as an adhesive250, for example. Any suitable securing means can be used to accomplish the mounting of the contactor units220to the backing substrate210; however, an adhesive that is relatively thin, durable and that can withstand high temperatures is preferable. The adhesive250can be such that the contactor units220are either relatively securely or removably mounted to the substrate210. Alternatively, the contactor units220can be mounted to the backing substrate210with a conductive material in place of the adhesive250. The conductive material can be electrically conductive and/or thermally conductive.

FIG. 7also shows that the first sides221of the contactor units220are preferably coplanar with each other when mounted onto the backing substrate210. The coplanarity of the contactor units220of the segmented contactor200is desirable to provide a better electrical connection between the resilient contact elements or conductive terminals of the wafer under test over the entire surface of the segmented contactor200.

FIG. 8shows a segmented contactor200that includes a backing substrate210and contactor units220mounted to the backing substrate210. Also, an alignment mechanism260such as a rail or block can be provided between contactor units220. Preferably, the alignment mechanism does not extend significantly higher than the surface of the contactor units220.

Preferably, the backing substrate210and the contactor units220or tiles are made of silicon. It is preferable that the backing substrate210and contactor units220have a similar coefficient of thermal expansion relative to each other and to the wafer under test. Providing materials having similar coefficient of thermal expansion among all the pieces of the segmented contactor and the wafer under test is advantageous because the heat generated during testing procedures can cause thermal expansion of the parts. Due to the enormous number of connections and extremely tight tolerances that must be maintained between conductive areas and between each terminal on the wafer, any amount of expansion due to heat can potentially cause misalignment of the conductive areas222on the contactor units220and the conductive terminals of the wafer under test. Therefore, if all the materials have a substantially similar coefficient of thermal expansion, the effect of thermal expansion on the dimensions of the parts can be minimized. Also, because the segmented contactor200is preferably comprised of a plurality of contactor units220rather than a single contactor unit substrate, the effect of thermal expansion on each contactor unit220is not as great as the same amount of expansion over a longer span of material. Thus, the effect of thermal expansion on the tolerance stack-up is minimized.

An example of a material that can be used to construct the substrate of the contactor unit is silicon. An alternative material that can be used is glass or a material including silicon dioxide (SiO2). It is contemplated that the contactor units220can be made of a flexible material such as UPILEX™ material. Also, the contactor units220can potentially be made of an organic material such as that which is commonly used as the base material of printed circuit boards.

FIGS. 9 and 10show examples of segmented contactors used for testing wafers that include semiconductor devices such as integrated circuits. Referring toFIG. 9, a segmented contactor200is shown attached to an external instrument270such as a testing device or a burn-in board. The contactor units220ofFIG. 9include electrically conductive areas222on their top or first sides221. The electrically conductive areas222in the example ofFIG. 9are configured as electrically conductive pads. Backing substrate210is shown below the contactor units220in the exemplary configuration of FIG.9. Leads240are shown extending from the contactor units220and connected to the external instrument270. As shown inFIG. 9, the leads240can extend from either the first side221or the second side223of the contactor units220. Also, the leads240can be configured in groups such as those carried in flexible strips244. Such grouped leads240or flexible strips244can extend from one side of the contactor units220but can be attached in a staggered fashion or an overlapping fashion as shown in FIG.9.

The wafer under test180in the example ofFIG. 9, includes electrically conductive terminals182that are resilient contact elements184, for example. The wafer180is positioned above the segmented contactor200such that the resilient contact elements184face the first side221of the contactor units220and are aligned with the electrically conductive areas222on the contactor units220. The wafer180is securely held and accurately positioned by any of a variety of techniques. See, for example, U.S. patent application Ser. No. 08/784,862 (generally). To accomplish the test, the wafer180and the segmented contactor200are urged toward each other so that the resilient contact elements184come into physical contact with the electrically conductive areas222on the segmented contactor220. Preferably, the resilient contact elements184are configured such that when a force is applied perpendicularly to the wafer180, the resilient contact elements184exhibit slight movement laterally such that a scrubbing action can occur on the electrically conductive areas222. The scrubbing (or siping) action serves to provide a better electrical contact by scraping away oxidation or contamination that may be accumulated on the electrically conductive areas222.

Once the wafer under test180and the segmented contactor200are in contact, electrical power and signals can be provided from the burn-in board or external instrument270through the leads240to test or exercise the devices such as the integrated circuits on the wafer180. This testing procedure can be accomplished within a testing chamber (not shown) so that the atmosphere and temperature can be controlled, for example.

FIG. 10illustrates an alternative embodiment of the segmented contactor300wherein resilient contact elements384are mounted to the first side321of the contactor units320. The wafer under test190in the example ofFIG. 10includes conductive terminals192such as pads194that are aligned with the resilient contact elements384of the contactor units320. The wafer190and the segmented contactor300are urged toward each other, similarly to the configuration ofFIG. 9, to accomplish testing or wafer exercise procedures.

It will be appreciated that a segmented contactor of the invention may be used to test devices other than a semiconductor wafer, such as another contactor or a printed circuit board.

FIGS. 11 through 15show an example of a contactor unit220. As shown inFIG. 11, a contactor substrate215can be provided on which a plurality of contactor units220can be formed. The contactor substrate215can be monolithic. The contactor units220preferably comprise tiles225that are defined or formed on the larger contactor substrate215. It is not necessary, however, to form a plurality of contactor units220on a large contactor substrate215. Alternatively, contactor units220can be formed individually. The contactor substrate215can preferably be a semiconductor wafer or similar substrate.

FIG. 12shows an example of a contactor unit220that comprises a tile225having electrically conductive areas222on its first side221. For simplicity of illustration, electrically conductive areas222are only partially shown on FIG.12. The electrically conductive areas222are preferably disposed over most of the first side221, but can be arranged in any desirable configuration for a particular contactor unit220.

FIG. 13shows the contactor unit220including leads240attached to electrically conductive areas222on the first side221and the second side223of the tile225. The leads240are shown overlapping and including connectors242on the free ends of the leads240. As previously described, leads240can be carried in flexible strips244or can be discrete wires. Alternatively, an edge connector (not shown) can be provided in place of leads240. The edge connector can be configured to accept a jumper wire or cable for connection to the external instrument, or the edge connector can be directly connected to an external instrument.

FIG. 14shows a contactor unit220having electrically conducive areas222on its second side223. It is not necessary, however, to provide electrically conductive areas222on the second side223of the contactor unit220.

FIG. 15shows an example of a contactor unit220that has electrically conductive areas222on both the first side221and the second side223of the tile225.

An example of a contactor unit220having conductive areas222on both sides can be an interposer. The electrically conductive areas222on both sides of the tile225can be connected by conductive pathways227through the tile225. The conductive pathways227need not be formed vertically or directly through the tile225, but can extend laterally along the length of the tile225so as to connect electrically conductive areas222on both sides or on the same side of the tile225that are not directly opposed from each other.

FIG. 15also shows the backing substrate210mounted to the contactor unit220with an example of conductive material252. As shown inFIG. 15, the conductive material252can comprise individual pieces that are associated with corresponding electrically conductive areas222on the surface of the contactor unit220. For example, the conductive material252can be discrete amounts of solder.

Also shown inFIG. 15is the backing substrate210having electrically conductive runners217such as those found in a multi-layer printed circuit board (PCB). The conductive material252provides a connection between the conductive pathways227and the electrically conductive areas222on the contactor unit220to electrically conductive areas or pathways217on the backing substrate210.

FIG. 16shows an example of a backing substrate210on which a plurality of contactor units can be mounted. The backing substrate210is preferably made of the same material as the tiles of the contactor units, however, it can alternatively made of PCB material or glass. The example of the backing substrate shown inFIG. 16is generally a square shaped piece, but any suitable shape or size can be provided for a particular application. For example, the backing substrate can be a rectangle 8 inches wide by 8.25 inches long.

FIG. 17shows an example of an assembly fixture400that can be used to assemble a segmented contactor of the present invention. Assembly fixture400includes a plate410that is a generally flat piece of material having moderate thickness. The plate410can be any suitable shape that will accommodate the desired or selected configuration of contactor units220. One example of a plate410defines grooves420that preferably have been cut into plate410using a wafer saw, for example. The grooves420are of a selected depth and width such that they accommodate guide blocks430. The grooves420are cut into the plate410in a configuration such that when the guide blocks430are placed into the grooves420, contactor positions440are defined within the boundaries defined by the guide blocks430. In the example shown inFIG. 17, contactor positions440are the areas or spaces within the boundaries defined by guide blocks430. Contactor positions440can also be referred to as holding spaces.

WhileFIG. 17shows one example of a plate that defines contactor positions, other examples can be contemplated. For example, the plate can define holes or sockets into which a key or protrusion on the tile or contactor unit can fit.

As further shown inFIG. 17, during assembly of the segmented contactor, a contactor unit220is placed within a corresponding contactor position440defined on the plate410of the assembly fixture400. The contactor unit220may already include an adhesive250or other securing mechanism on the second side223of the contactor unit220. The contactor unit220is placed into the contactor position440with the adhesive250, if applied, facing up. The backing substrate210can then be pressed or placed onto the adhesive250in order to mount the contactor unit220to the backing substrate210.

Preferably, the adhesive is cured after the backing substrate210is pressed onto the adhesive250of the contactor unit220. One way to accomplish curing is to expose the parts to relatively higher temperatures. Also, pressure can be applied to the backing substrate210in order to effect curing and proper adhesion. An example of an adhesive is a thermal set epoxy such as, for example, TORRAY™ T-61 epoxy. For example, the assembled parts can be baked at approximately 150° C. for approximately 45 minutes while the backing substrate210is applied to the contactor unit220under pressure of approximately 15 psi. The pressure is then released, and the flatness of the contactor units can be measured. This laminating assembly procedure results in a high degree of coplanarity among the contactor units220; preferably less than about 0.3-0.4 mm

FIG. 18shows an example of a plate410that can be used for an assembly fixture400including grooves420defined therein. Grooves420are preferably about 4 to 5 mils wide, for example.

FIG. 19shows an example of the grooves420that have been cut into the plate410.

FIGS. 20 and 21show an example of a guide block430that can be inserted into the grooves of the plate ofFIGS. 18 and 19. The guide blocks430are preferably dimensioned for a snug fit within the grooves of the plate. The guide block430is preferably made of a polyamide material such as, for example, KAPTON™ or UPILEX™ materials.

FIG. 22shows a guide block430inserted into a groove420of a plate410and extending upwardly beyond the surface412of the plate410.

FIG. 23shows a cross section of a plate410having guide blocks430inserted into grooves420that have been cut into the plate410. The guide blocks430define contactor positions440between adjacent guide blocks430. The guide blocks and the contactor positions are preferably dimensioned to take into account tolerances and to allow a release of the contactor units from the assembly fixture. A plurality of contactor units220is shown placed between the guide blocks430and in the contactor positions440. An adhesive250is shown placed on top of the contactor units220. A backing substrate210is shown placed on top of the adhesive250.

FIG. 24also illustrates the plate410including a groove420into which a guide block430has been inserted. The guide block430extends above the surface412of the plate410so that contactor units220can be placed between adjacent guide blocks430. An adhesive250is shown placed on top of contactor units220. Preferably the adhesive250is placed on the second side223of the contactor unit220. The first side221of the contactor unit220is preferably placed into the assembly fixture400facing the plate410. A backing substrate210is shown on top of the adhesive250.

FIG. 25shows an alternate embodiment plate of an assembly fixture500including a plate510that defines contactor positions540. In the example of the assembly fixture500ofFIG. 25, the contactor positions540can be defined by removing material from the plate510and leaving upwardly extending walls530. In this case, pockets532are formed into the plate510in which the contactor units210are then placed. The first side221of the contactor unit220is similarly placed facing downwardly toward the plate510, while the second side223of the contactor unit220faces up. An adhesive250can be applied to the contactor unit220, and a backing substrate210can then be pressed onto the adhesive250using the techniques previously described.