Socket for testing semiconductor chip

A socket for testing a semiconductor chip includes a base cover, a conductive sheet, upper plungers, a housing, lower plungers and a support plate. The base cover has a coupling opening in the central portion thereof, and the conductive sheet is fitted into the coupling opening of the base cover and includes conductive parts and an insulation part. The upper plungers are seated onto upper ends of the conductive parts and come into contact with corresponding terminals of the semiconductor chip. The housing has insert holes at positions corresponding to the upper plungers and fastens the upper plungers to the corresponding conductive parts. The lower plungers are provided under lower ends of the conductive parts and come into contact with corresponding terminals of a PCB to electrically connect the conductive parts to the PCB. The support plate has holes at positions corresponding to the lower plungers and fastens the lower plungers to the lower ends of the corresponding conductive parts such that lower ends of the lower plungers protrude outside through the holes of the support plate.

FIELD OF THE INVENTION

The present invention relates generally to sockets for testing semiconductor chips and, more particularly, to a socket for testing semiconductor chips in which plungers are provided in the upper and lower portions of conductive parts of a conductive sheet, thus enhancing the reliability of a test.

BACKGROUND OF THE INVENTION

As is well known to those skilled in the art, semiconductor chips must be tested for whether they are normal or not. Typically, a semiconductor chip is tested in such a way that test probes which are mounted to a test socket are brought into contact with the semiconductor chip and test current is applied to a test circuit board.

Of such devices for testing semiconductor chips, there is an anisotropic conductive sheet which can reduce damage to connection terminals (solder balls) of a semiconductor chip. In the anisotropic conductive sheet, conductive silicone parts are formed by vertically arranging metal balls (powder) in a main body made of silicone. Test current is applied through the conductive silicone parts to a test circuit board disposed under the main body, thus determining whether the semiconductor chip is normal.

To detect initial failure of a semiconductor chip, when the anisotropic conductive sheet is used as an electrical connection member of a test socket which is used in a heating test, a heat-cycle test, etc., if the anisotropic conductive sheet in which a positioning hole is formed in a resin film is used, electrodes of the anisotropic conductive sheet may be misaligned with respect to electrodes of an object to be tested because of thermal expansion of the resin film. As a result, stable and correct electric contact is not ensured, so that the reliability of the test deteriorates.

In an effort to overcome these problems, an anisotropic conductive sheet assembly was proposed in Korean Patent Laid-open Publication No. 2000-45941 which was entitled ‘Anisotropic conductive sheet with positioning means’.

In this conventional technique, the anisotropic conductive sheet assembly includes a positioning means for exactly positioning electrodes of the anisotropic conductive sheet with respect to circuit components having fine electrode pitches. When the anisotropic conductive sheet assembly is used as an electric connection member between the circuit components and a circuit board in a test or measurement of the circuit components or the circuit board, stable contact and reliable electric conduction can be ensured.

In detail, as shown inFIGS. 1 and 2, the anisotropic conductive sheet assembly of No. 2000-45941 includes an anisotropic conductive sheet11and a positioning metal plate16. The anisotropic conductive sheet11includes conductive parts12which are provided in the anisotropic conductive sheet in thickness directions and are made of conductive material, and an insulation part8which is made of elastic insulation material and is formed in an area of the anisotropic conductive sheet outside of the conductive parts12. The positioning metal plate16has positioning means10which is formed at predetermined positions around the anisotropic conductive sheet11.

The anisotropic conductive sheet assembly having the above-mentioned construction is interposed between the circuit components and the circuit board and is pushed by a pressure fixing jig. Hereby, electric connection between the circuit components and the circuit board can be achieved.

Here, the positioning of the conductive parts12of the anisotropic conductive sheet11with respect both to the electrodes of the circuit components and to an electrode group of the circuit board can be realized by the positioning means10, such as positioning holes or the like, of the positioning metal plate16.

However, in the conventional technique, due to repeated tests, the upper and lower surfaces of the conductive parts12of the anisotropic conductive sheet11are damaged. Thus, the reliability of the test is reduced.

Meanwhile, another conventional technique was proposed in Korean Patent Application No. 10-2009-0017393 which was filed by the applicant of the present invention and entitled ‘Socket for testing semiconductor chips’.

As shown inFIGS. 3 and 4, the socket for testing semiconductor chips according to this conventional technique includes a support plate, a silicone base10, a plurality of conductive silicone parts20, a plurality of plungers30and a cap80. The support plate has a planar shape. A coupling hole is vertically formed through the central portion of the support plate. The silicone base10is coupled to the coupling hole of the support plate. A boss12protrudes upwards from the silicone base10. The conductive silicone parts20are formed in the boss12by arranging metal balls in vertical directions. The plungers30are seated on the conductive silicone parts20and come into contact with corresponding solder balls of the semiconductor chip. The cap80has insert holes82at positions corresponding to the plungers30. A receiving space86is formed in the lower portion of the cap80so that the boss12is inserted into the receiving space86. The cap80is coupled to the silicone base10to fasten the plungers30to the silicone base10.

The upper ends of the plungers30come into contact with a device which is an object to be tested. A PCB (printed circuit board) is brought into contact with a lower surface of a lower piece of insulation tape which is attached to the lower surface of the support plate, so that the device is electrically connected to the PCB.

Furthermore, a lower protrusion38is provided under the lower end of a cylindrical body32of each plunger30. Depressions24having semi-conical shapes are formed in an upper surface of a conductive silicone part20. Thus, the lower protrusion38of each plunger30is seated into the corresponding depression24, such that the plunger30can be stably coupled to the conductive silicone part20, thus preventing the plunger30from being displaced from the correct position when the tests are repeated.

Furthermore, a cylindrical tip39protrudes downwards from the central portion of each lower protrusion38. The cylindrical tip39is inserted into a receiving recess26which is formed in the corresponding depression24, so that the plunger30can be disposed at the correct position.

In the technique of No. 10-2009-0017393, the contact efficiency between the socket and the device can be enhanced by installation of the plungers30. However, foreign substances may be caught between the lower surfaces of the conductive silicone parts20and the PCB, with the result that contact resistance increases because of the foreign substances, thus reducing the reliability of the test.

SUMMARY OF THE INVENTION

Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to provide a socket for testing semiconductor chips in which plungers are provided in the upper and lower portions of conductive parts of a conductive sheet, and a device and a PCB are connected to each other through the plungers, thus enhancing the reliability of a test.

In order to accomplish the above object, the present invention provides a socket for testing a semiconductor chip, including: a base cover having a planar shape, with a coupling opening formed through a central portion of the base cover in a thickness direction; a conductive sheet fitted into the coupling opening of the base cover, the conductive sheet having conductive parts provided in the conductive sheet in thickness directions, each of the conductive parts being made of conductive material, and an insulation part formed in an area of the conductive sheet other outside the conductive parts, the insulation part being made of elastic insulation material; a plurality of upper plungers seated onto upper ends of the conductive parts of the conductive sheet, the upper plungers coming into contact with corresponding terminals of the semiconductor chip; a housing having insert holes at positions corresponding to the upper plungers, the housing fastening the upper plungers to the upper ends of the corresponding conductive parts of the conductive sheet such that upper ends of the upper plungers protrude outside through the insert holes of the housing; a plurality of lower plungers provided under lower ends of the conductive parts of the conductive sheet, the lower plungers coming into contact with corresponding terminals of a PCB (printed circuit board) to electrically connect the conductive parts to the PCB; and a support plate having holes at positions corresponding to the lower plungers, the support plate fastening the lower plungers to the lower ends of the corresponding conductive parts of the conductive sheet such that lower ends of the lower plungers protrude outside through the holes of the support plate.

The housing may include: an upper housing body having the insert holes at positions corresponding to the upper plungers, the upper housing body being disposed above the conductive sheet to fasten the upper plungers to the upper ends of the corresponding conductive parts of the conductive sheet; and a lower housing body integrally extending from a periphery of the upper housing body such that the lower housing body is stepped from the upper housing body. The lower housing body surrounds the base cover. Positioning means are formed in the lower housing body.

The positioning means may comprise positioning holes formed through the lower housing body in a thickness direction.

Furthermore, each of the upper plungers may include: an upper plunger body having a cylindrical shape; a probe provided on an upper end of the upper plunger body, the probe coming into contact with the corresponding terminal of the semiconductor chip; and a contact part provided under a lower end of the upper plunger body. The contact part comes into contact with the corresponding conductive part of the conductive sheet.

Preferably, an annular protrusion may be provided around the circumferential outer surface of the lower end of the upper plunger body.

In addition, a protrusion may protrude downwards from the lower end of the contact part.

As well, through holes may be formed through the base cover in the thickness direction thereof at positions adjacent to the coupling opening.

Moreover, an upper depression may be depressed downwards from the upper end of each of the conductive parts. An upper seating recess may be depressed downwards from the central portion of the bottom of the upper depression.

The base cover may be coupled to the housing by bolt coupling.

Furthermore, recess holes may be formed to predetermined depths in the upper surface of the insulation part of the conductive sheet.

In addition, the lower surface of the housing is adhered to the conductive sheet by a silicone adhesive.

Preferably, each of the upper plungers may include: an upper plunger body having a cylindrical shape; a probe provided on the upper end of the upper plunger body, the probe coming into contact with the corresponding terminal of the semiconductor chip; a contact part provided under the lower end of the upper plunger body, the contact part coming into contact with the corresponding conductive part of the conductive sheet; and a coupling hole formed through the upper plunger in an axial direction.

Furthermore, a coupling protrusion may protrude upwards from the upper end of each of the conductive parts. The coupling protrusion may be inserted into the coupling hole of the corresponding upper plunger.

In addition, a lower depression may be depressed upwards from the lower end of each of the conductive parts.

As well, a lower seating recess may be depressed upwards from the central portion of the bottom of the lower depression.

Preferably, each of the lower plungers may include: a lower plunger body having a cylindrical shape; a lower terminal contact part provided under a lower end of the lower plunger body, the lower terminal contact part coming into contact with the corresponding terminal of the PCB; and a conductive contact part provided on an upper end of the lower plunger body, the conductive contact part coming into contact with the corresponding conductive part of the conductive sheet.

Furthermore, a conductive protrusion may protrude upwards from the upper end of the conductive contact part. In addition, an annular protrusion may be provided around the circumferential outer surface of the lower plunger body.

As such, the socket uses conductive elastic material, and plungers are provided on the upper and lower portions of the socket. Thus, the reliability of a test can be enhanced.

DETAILED DESCRIPTION OF THE INVENTION

FIG. 5is a perspective view of a socket for testing semiconductor chips, according to a first embodiment of the present invention.FIG. 6is an exploded perspective view of the socket.FIG. 7is a perspective view of a base cover100of the socket.FIG. 8is a sectional view of a critical portion of the socket provided with plungers800.FIG. 9is a sectional view of the critical portion of the socket from which the plungers800have been removed.FIG. 10is a sectional view showing the coupling of a conductive sheet200to the base cover100.FIG. 11is a perspective view of an upper plunger300of the socket.FIG. 12is a perspective view of a lower plunger900of the socket.

As shown in the drawings, the socket for testing semiconductor chips according to the first embodiment of the present invention includes the base cover100, the conductive sheet200, the upper plunger300, a housing400, a support plate800and the lower plunger900.

First, the base cover100will be explained.

The base cover100is planar and is made of synthetic resin. Coupling openings110are formed through the central portion of the base cover100in vertical directions. The conductive sheet200which will be explained later is fitted into the coupling openings110. Through holes120are formed through the base cover100in vertical directions at positions adjacent to the coupling openings110. Each through hole120is smaller than the coupling opening110.

The conductive sheet200which will be explained later is formed in the coupling openings110of the base cover100by insert injection molding. Here, to increase the coupling force between the base cover100and the conductive sheet200, the through holes120are formed through the base cover100around the coupling openings110. Thus, when injection molding, an insulation part220of the conductive sheet200which is made of silicone is formed through the through holes120of the base cover100and fastened to the base cover100. Hereby, the conductive sheet200can be reliably fastened to the base cover100. This is a well known technique which was also used in the conventional socket manufacturing technique, and therefore further explanation will be omitted.

Furthermore, bolt coupling holes500are formed through the base cover100at positions adjacent to both ends of the base cover100. Thus, the base cover100is coupled to the housing400by bolts600.

The conductive sheet200includes conductive parts210and the insulation part220.

The insulation part220is formed by insert injection molding using silicone such that the insulation part220has a planar shape having a predetermined thickness and is coupled to the base cover100. The conductive parts210are vertically provided at predetermined positions in the insulation part220. Each conductive part210is formed in such a way as to pile conductive metal powder in the vertical direction.

In other words, the conductive part210is configured such that metal powder is piled up in the vertical direction, so that electricity can be transmitted from the top thereof to the bottom thereof. In addition, the upper plungers300which will be explained later respectively come into contact with the upper ends of the conductive parts210. The lower plungers900which will be explained later respectively come into contact with the lower ends of the conductive parts210.

Furthermore, an upper depression211is formed in the upper end of each conductive part210in a shape in which it is depressed downwards from the upper end of the conductive part210. An upper seating recess212is further depressed downwards from the central portion of the bottom of the upper depression211. Each upper plunger300is coupled into the upper depression211and the upper seating recess212of the corresponding conductive part210. Here, a contact part of the upper plunger300is seated into the upper depression211, and a protrusion of the upper plunger300is seated into the upper seating recess212. Hereby, the upper plunger300is electrically connected to the conductive part210.

A lower depression215is formed in the lower end of each conductive part210in a shape in which it is depressed upwards from the lower end of the conductive part210. A lower seating recess216is further depressed upwards from the central portion of the top of the lower depression215. Each lower plunger900is coupled into the lower depression215and the lower seating recess216of the corresponding conductive part210. Here, a conductive contact part of the lower plunger900is seated into the lower depression215, and a conductive protrusion of the lower plunger900is seated into the lower seating recess216. Hereby, the lower plunger900is electrically connected to the conductive part210.

In addition, recess holes221are depressed downwards from the upper surface of the insulation part220to predetermined depths. Hence, even though pressure is transmitted to the conductive parts210by pushing force of the upper plungers300and the conductive parts210are thus expanded, the recess holes221can absorb the expansion pressure of the conductive parts210.

Each upper plunger300which is coupled to the corresponding conductive part210is made of conductive material and includes an upper plunger body310, a probe320and a contact part330. The upper plungers300electrically connect the conductive parts210of the conductive sheet200to a device to be tested.

The upper plunger body310has a cylindrical shape having a predetermined length and forms the central portion of the upper plunger300. The upper portion of the upper plunger body310protrudes upwards through an upper end of a corresponding insert hole410of the housing400which will be explained later.

The probe320has a crown shape and is integrally provided on the upper end of the upper plunger body310. The probe320is electrically connected to a corresponding terminal of the device to be tested. Furthermore, the probe320protrudes upwards from the upper end of the insert hole410of the housing400.

An annular protrusion311is provided around the circumferential outer surface of the lower end of the upper plunger body310. The upper surface of the annular protrusion311is stopped by the lower surface of the housing400around the lower end of the insert hole410, so that the upper plunger300can correctly come into contact with the corresponding conductive part210and be prevented from being undesirably removed from the housing400.

The contact part330has a reverse-conical shape and is integrally provided under the annular protrusion311. The contact part330is seated and coupled into the upper depression211of the conductive part210. The protrusion331integrally protrudes downwards from the lower end of the contact part330. The protrusion331is seated and coupled into the upper seating recess212formed in the conductive part210. As such, because the contact part330and the protrusion331are provided on the upper plunger300and the upper depression211and the upper seating recess212are formed in the conductive part210, the upper plunger300can be reliably electrically connected to the conductive part210by the coupling of the contact part330and the protrusion331into the upper depression211and the upper seating recess212.

The housing400defines a space in the lower surface thereof. The conductive sheet200and the base cover100are contained in the space of the housing400in a shape in which the housing400covers the upper surface of the conductive sheet200and surrounds the periphery of the base cover100. The housing400is coupled to the base cover100by bolts.

The housing400comprises an upper housing body450and a lower housing body460.

The upper housing body450has a planar shape and is made of synthetic resin. The insert holes410are formed through the upper housing body450at positions corresponding to the upper plungers300. The upper housing body450is disposed above the conductive sheet200and connects the upper plungers300to the upper ends of the corresponding conductive parts210.

Here, the upper portions of the main bodies310of the upper plungers300protrude upwards from the upper ends of the corresponding insert holes410of the upper housing body450. The contact parts330of the upper plungers300are disposed below the insert holes410. The upper surfaces of the annular protrusions311of the main bodies310come into close contact with the lower surface of the upper housing body450around the lower ends of the insert holes410. Hereby, the upper plungers300can be stably coupled to the upper housing body450and prevented from being undesirably removed from the upper housing body450. Furthermore, bolt coupling holes700are formed through the upper housing body450at positions which are adjacent to both ends of the upper housing body450and correspond to the bolt coupling holes500formed through the base cover100. Thus, the base cover100and the housing400are coupled to each other by bolts600.

The lower housing body460integrally extends from the periphery of the upper housing body450such that the lower housing body460is stepped from the upper housing body450. The lower housing body460surrounds the periphery of the base cover100. A positioning means is formed in the lower housing body460at positions adjacent to both ends thereof. In the embodiment, positioning holes461which are formed through the lower housing body460serve as the positioning means. Thus, the lower housing body460is positioned with respect to a device to be tested or a jig for the device in such a way as to insert positioning pins into the positioning holes461.

Here, the upper housing body450of the housing400contains the base cover100provided with the conductive sheet200in a shape in which the upper housing body450covers the upper surface of the base cover100. The lower housing body460surrounds the periphery of the base cover100. As such, the base cover100is contained in the receiving space formed in the lower surface of the housing400and coupled to the housing400. Hereby, the upper plungers300which are coupled to the conductive sheet200can be stably connected to the conductive parts210of the conductive sheet200.

Meanwhile, the lower plungers900are connected to the lower ends of the corresponding conductive parts210. Each lower plunger900is made of conductive material and includes a lower plunger body910, a lower terminal contact part920and a conductive contact part930. The lower plungers900connect terminals of a PCB (printed circuit board) to be tested to the corresponding conductive parts210of the conductive sheet200.

The lower plunger body910has a cylindrical shape having a predetermined length and forms the central portion of the lower plunger900. The lower portion of the lower plunger body910protrudes downwards through a corresponding hole810of the support plate800which will be explained later.

The lower terminal contact part920is integrally provided under the lower end of the lower plunger body910. The lower terminal contact part920electrically comes into contact with a corresponding terminal of a PCB to be tested. Here, the lower terminal contact part920protrudes downwards from the corresponding hole810of the support plate800.

An annular protrusion911is provided around the circumferential outer surface of the upper end of the lower plunger body910. The lower surface of the annular protrusion911is stopped by the upper surface of the support plate800around the upper end of the hole810, so that the lower plunger900can correctly come into contact with the lower end of the corresponding conductive part210and be prevented from being undesirably removed from the support plate800.

The conductive contact part930has a conical shape and is integrally provided on the annular protrusion911. The conductive contact part930is seated and coupled into the lower depression215of the conductive part210. A conductive protrusion931integrally protrudes upwards from the upper end of the conductive contact part930. The conductive protrusion931is seated and coupled into the lower seating recess216formed in the lower end of the conductive part210.

As such, because the conductive contact part930and the conductive protrusion931are provided on the lower plunger900and the lower depression215and the lower seating recess216are formed in the conductive part210, the lower plunger900can be reliably electrically connected to the conductive part210by the coupling of the conductive contact part930and the conductive protrusion931into the lower depression215and the lower seating recess216.

The support plate800is made of synthetic resin and has a planar shape. The holes801are formed through the support plate800at positions corresponding to the lower plungers900. The support plate800couples the lower plungers900to the corresponding conductive parts210such that the lower portions of the lower plungers900protrude downwards through the holes810.

The operation and effect of the present invention having the above-mentioned construction will be explained below.

When a user desires to test a device, the device is disposed on the socket, and a PCB is disposed under the socket. Here, the device and the PCB can be easily positioned with respect to the device in such a manner as to insert the positioning pins into the positioning holes461of the housing400.

Then, electrodes of the device come into contact with the upper portions of the probes320of the corresponding upper plunger300. Terminals of the PCB come into contact with the lower portions of the corresponding lower plungers900.

In this state, the test is conducted. Here, because downward pressure is applied to the device to be tested, the electrodes of the device, the upper plungers300, the conductive parts210, the lower plungers900and the terminals of the PCB are electrically connected to each other. Hereby, the test for the device can be conducted.

In the present invention, when the test is processed, the upper plungers300can be stably disposed in the housing400which supports the upper surface and the periphery of the base cover100. Furthermore, the upper plungers300and the lower plungers900are stably coupled to the conductive parts210of the conductive sheet200at correct positions. Therefore, the reliability of the test can be enhanced.

As described above, the present invention is configured such that the upper and lower plungers300and900are coupled to the conductive sheet200by the housing400and the support plate800. Those skilled in the art will appreciate that various modifications, additions and substitutions are possible within the above-mentioned basic scope and spirit of the invention.

FIG. 13is a sectional view showing a critical portion of a socket for testing semiconductor chips, according to a second embodiment of the present invention.FIG. 14is an exploded perspective view of the socket according to the second embodiment of the present invention.

As shown in these drawings, the socket according to the second embodiment of the present invention has almost the same construction as that of the first embodiment, other than only the partial structures of the housing and the upper plunger. Hereinafter the socket according to the second embodiment will be described in detail.

A base cover100is planar and is made of stainless steel. A coupling opening is formed through the central portion of the base cover100. A conductive sheet200is fitted into the coupling opening of the base cover100. Furthermore, through holes which are smaller than the coupling opening are formed through the base cover100at positions adjacent to the coupling opening. This structure of the second embodiment is almost the same as that of the first embodiment. In addition, the coupling of the conductive sheet200to the base cover100according to the second embodiment is also similar to that of the first embodiment.

However, in the second embodiment of the present invention, the shape of an upper end of each conductive part210of the conductive sheet200differs from that of the first embodiment.

In detail, an upper depression211is formed in the upper end of the conductive part210in a manner similar to that of the first embodiment, but a coupling protrusion213protrudes upwards from the central portion of the upper depression211, unlike in the first embodiment. Thus, the conductive part210is coupled to the corresponding upper plunger300in such a way that the coupling protrusion213is inserted into a coupling hole340of the upper plunger300.

Furthermore, in the same manner as in the first embodiment, each upper plunger300which is coupled to the upper end of the conductive part210includes an upper plunger body310, a probe320and a contact part330. The upper plunger300electrically connects a device to be tested to the corresponding conductive part210of the conductive sheet200.

The upper plunger body310has a cylindrical shape having a predetermined length. The upper portion of the upper plunger body310protrudes upwards through an upper end of a corresponding insert hole410of the housing400which will be explained later.

The probe320has a crown shape and is integrally provided on the upper end of the upper plunger body310. The probe320is electrically connected to a corresponding terminal of the device to be tested.

An annular protrusion311is provided around the circumferential outer surface of the lower end of the upper plunger body310. The upper surface of the annular protrusion311is stopped by the lower surface of the housing400around the lower end of the insert hole410, so that the upper plunger300correctly comes into contact with the corresponding conductive part210and is prevented from being undesirably removed from the housing400.

The contact part330has a reverse-conical shape and is integrally provided under the annular protrusion311. The contact part330is seated and coupled into the upper depression211of the conductive part210. The coupling hole340is vertically formed through the contact part330, so that the coupling protrusion213of the conductive part210is inserted into the coupling hole340.

As such, because the contact part330and the coupling hole340are provided in the upper plunger300, and the upper depression211and the coupling protrusion213are provided in the conductive part210, the upper plunger300can form a reliable electrical connection to the conductive part210because of the coupling of the contact part330and the coupling protrusion213into the upper depression211and the coupling hole340.

The housing400covers the upper portion of the conductive sheet200. In other words, the housing400contains the conductive sheet200in a space defined in the lower surface thereof.

In detail, the housing400is adhered at the lower surface thereof to the upper surface of the conductive sheet200by silicone adhesive201. The housing400is made of engineering plastic, more preferably, Ultem formed by extruding polyetherimide.

The insert holes410are formed through the housing400at positions corresponding to the upper plungers300in vertical directions. The housing400is disposed above the conductive sheet200and couples the upper plungers300to the upper ends of the corresponding conductive parts210.

Meanwhile, a support plate800has a synthetic resin tape shape. Holes810are formed through the support plate800at positions corresponding to lower plungers900. In the same manner as in the first embodiment, the lower plungers900are coupled to lower ends of the corresponding conductive parts210such that the lower portions of the lower plungers900protrude downwards through the holes810of the support plate800.

Each lower plunger900includes a lower plunger body910, a lower terminal contact part920and a conductive contact part930. The lower plungers900connect terminals of a PCB (printed circuit board) to be tested to the corresponding conductive parts210of the conductive sheet200. The lower plunger900has an annular protrusion911having the same structure as that of the first embodiment, and the structure of the conductive contact part930is also the same as that of the first embodiment.

As such, the socket according to the second embodiment of the present invention is configured such that the upper and lower plungers300and900are coupled to the conductive sheet200. Those skilled in the art will appreciate that various modifications, additions and substitutions are possible within the above-mentioned basic scope and spirit of the invention.

As described above, in the present invention, a socket is made of conductive elastic material, and plungers are provided in upper and lower portions of the socket made of conductive material. Thus, the present invention can enhance the reliability of a test.

While the present invention has been described with reference to the particular illustrative embodiment, it is not to be restricted by the embodiment but only by the appended claims. It is to be appreciated that those skilled in the art can change or modify the embodiment without departing from the scope and spirit of the present invention.