Socket

A test socket 10 of the present invention includes a base member 20, a cover member 30 which is installed on base 20 to move in reciprocal straight line movement between a first position away from the base and a second position adjacent the base and a plurality of contact members 40 that are fixed in the base and are capable of making contact with terminals 2 on a semiconductor device 1 when such device 1 is mounted on base 20. A latch member 60 is supported on base 20 in a rotatable manner to move in linkage with the movement of cover member 30. A compression member 80 is pivotably attached to a tip portion 62 of latch member 60 for pressing semiconductor part 1 onto base 20 to achieve reliable contacting between terminals 2 and contacts 40 in response to movement of cover member 30. This socket design will provide for wide area engagement between the surface of semiconductor part 1 and compression member 80 to prevent damage to the semiconductor part 1 during testing.

FIELD OF THE INVENTION

This invention relates to a socket for mounting an electronic part such as a semiconductor part to external equipment.

BACKGROUND OF THE INVENTION

It has been known in the art to check for defects in semiconductor devices such as integrated circuit (IC) devices by subjecting them to a burn-in test. In connection with such a burn-in test, the semiconductor device is mounted on a socket for connecting the device to a test piece of equipment. A commonly used socket is a pop-up type which has a cover member which moves in alternating motion from a first original position away from the main base body of the socket to a second position adjacent the main base and then back again to the first position. Such a socket with straight line movement of the cover relative to the socket base is suitable for automatic mounting of a semiconductor device.

In the main base body, a plurality of contact members is mounted. One end of each contact member protrudes from the bottom of the main socket body so as to be electrically connected with a contact on a circuit substrate while the other end is positioned to electrically connect with a terminal of a semiconductor device mounted on the main base body. On the opposing sides of the semiconductor device placing surface of the main base body, a pair of latch members is installed with each latch member rotating in linkage with the straight-line movement of the cover member. At the tip of the latch member, a pressing part is provided for holding down the semiconductor device on the placing surface of the main base body.

In such a prior art device, as the cover is pushed downward toward the base body, the latch members are rotated to a retracted position away from the placing surface for the semiconductor device. In this position, the semiconductor device can be placed on the placing surface through an opening provided in the cover member. Each terminal of the semiconductor device is positioned to be electrically connected with the other end of the socket contact members. When the cover is returned to its original position away from the main base, the latch members return to their original position so as to press against the upper surface of the semiconductor and, at the same time, bring the terminals of the semiconductor device into electrical connection with the contact members of the socket.

Such a socket has been useful in practice but due to the fact that the latch member moves in a rotating arc, the area of contact between the pressing part of the respective latch members and the upper surface of the semiconductor device is small. As a consequence, a localized stress concentration is produced by the latches on the semiconductor device which can cause breakage of such semiconductor devices, especially one of a thin type.

Reliability problems can still exist even when the pressing part of the latch member is flat. This is due to the fact that the rotary movement of the latch causes its pressing part to draw an arc shaped track which makes it difficult to make a precise contact between the flat surface of the pressing part and the upper surface of the semiconductor device.

Further, due to dimensional tolerance differences in the semiconductor devices, the upper surface of such devices is not always at a fixed height making it practically impossible to cause the pressing part of the latch member to uniformly and consistently contact the semiconductor device at all times.

Still further, since the socket is exposed to elevated temperatures (approximately 135° C.) during the burn-in test, the variance of thermal expansion of different components of the socket will make it practically impossible to cause the pressing part of the latch member to accurately contact the upper surface of the semiconductor device at a height certain at all times.

SUMMARY OF INVENTION

Accordingly, it is an object of this invention to provide a socket to overcome the problems of the prior art devices.

It is yet another object of this invention to provide a socket which is capable of accurately mounting a semiconductor device, especially of the thin type without damaging it.

It is still another object of this invention to provide a socket which is suitable for automatic mounting of a semiconductor device and which has superior operability and economy.

Briefly, the present invention provides for a socket for use with a semiconductor device having a top surface and a bottom surface with a plurality of terminals on the bottom surface comprising a base, an adaptor member received on the base having a seating surface for said semiconductor device, the adaptor member having a plurality of contact member receiving holes extending through the seating surface, a cover which is arranged on the base and supported for straight line movement between a first position in which it is apart from the base and a second position in which it is adjacent the base, a plurality of contact members having tips received in each of the contact member receiving holes to be placed in contact with each terminal of the semiconductor device placed on the seating surface, and a rotary latch member having a rotational axis fixed to the base being movable in conjunction with the movement of said cover member, said latch member having a tip portion onto which a compressive part member is mounted so as to be able to pivot with regard to said tip portion, said pivoting compressive part member being positioned to be capable of pressing said semiconductor device against said seating surface when said semiconductor device is on said seating surface and said cover member is in said first position for providing reliable electric contact between said plurality of terminals and said plurality of contact members while not damaging said semiconductor device due to said compressive part number making wide area contact with said top surface of said semiconductor device.

In another embodiment of the present invention, the socket includes rotatable holding members to work in conjunction with latch members to provide wide area contact by the holding member with the semiconductor device being tested with socket.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

As shown inFIGS. 1-3, a socket10of the present invention is provided for testing a semiconductor device1of the Land Grid Array (LGA) type. Such LGA device1contains a plurality of terminals2that are two-dimensionally arranged at a pitch, by way of example, of 0.75 millimeters on the lower surface with each terminal having a contact region at a concave location slightly inside of its lower surface.

Socket10has a base member20and a cover member30in which cover member30is capable of moving in an alternating motion between a position away from base member20and a position generally adjacent base member20. Base member20is formed of electrically insulating material preferably by injection molding a high heat resistant ether sulfone or the like. Approximately, at the center of base member20there are provided a plurality of slots21for receiving and enclosing a plurality of contact members40in rows parallel with the Y—Y line. Each slot21is separated by a partition wall in the direction of line X—X. The partition wall extends from the lower of base member20to an adaptor installation surface22.

A stopper member23is installed at the bottom part of base member20for the prevention of the possible withdrawal of contacts40. A plurality of through-holes24are provided in conformity with the arrangement of contacts40. A hook member25is arranged on the sides of stopper member23and is positioned to contact engaging part26of base member20.

Contacts40are typically formed by punching them out of a strip of metal material. The contacts have a base portion41secured in stopper member23which is wider than an upper upwardly extending intermediate curved part42. Extending downward from base portion41of contact40and protruding from the bottom of socket10is a leg portion43which is provided for making electrical contact with a circuit substrate (not shown). Extending up from intermediate curved part42of contact40is a contacting portion44which protrudes from adaptor installation surface22to make electrical contact with a selected terminal2of LGA device1. In this embodiment, the distal end of contacting portion44has a rounded shape so as to not damage terminal2when contact is made between contacting portion44and terminal2. Curved portion42of contact40provides an elastic force that opposes the application of a compressive load in the axial direction against contacting portion44.

Prior to the installation of stopper member23on base member20, each contact40is inserted in its respective slot21from the under side of base20. As the base portion41of each contact40engages the partition wall of slot21, the further insertion of the contact is prohibited. Next, stopper member23is affixed on base2with each leg portion43of contact40passing through a respective through-hole24of stopper member23so as to fix contacts40in base member20.

An adaptor member50is installed on adaptor installation surface22so as to move up and down thereby providing a placing surface51for the receipt of LGA device1. A pair of hooks52is provided on both sides of adaptor50and positioned so as to be able to engage an engagement part27of base member20. A coil spring53is wound around each hook52of adaptor50to thereby bias the adaptor50in an axial direction away from base20. When a force greater than that of coil springs53is applied, adaptor50will move in opposition to coil spring53.

On placing surface51of adaptor50, a plurality of apertures54are formed at positions that correspond to each contact40or slot21of base member20with contacting portion44of each contact extending through apertures54. At the time when adaptor50is at its at rest uppermost position due to the force of coil springs53, the contacting position44of each contact40remains inside aperture54without protruding from placing surface51; its position being slightly below the placing surface51.

In accordance with this embodiment, a guide55including an inclined surface is formed around placing surface51of adaptor50so that the LGA device1can be easily and accurately positioned on placing surface51.

At each corner of cover member30, there is provided a post31which extends downward to be received into an aperture (not shown in the drawings) that is formed at each corner of base member20. a coil spring32is wound around each post31between cover member30and base member20to bias cover member30to a position away from base member20. Additionally, cover member30has opposing side walls33with each having a pair of slots34formed therein. These slots work with a rotary shaft61of latch member60which will be discussed in detail below.

Slots34guide the movement of cover member30in the upward and downward direction. At the time rotary shaft61touches the lowest point of slot34, cover member30is at a position which it is farthest away from base member20. At the time when rotary shaft61touches the highest part of slot34, cover member30is at a position which is closest to the base member20.

A rectangular opening35is formed generally at the center of cover member30so as to provide for the insertion of LGA device1along guide member55of adaptor50onto placing surface51.

A pair of latch members60is installed freely rotatably on rotary shaft61anchored in base member20as shown in FIG.2. Latch members60, as shown inFIG. 4, have a tip or pressing part62for pressing LGA device1onto placing surface51. A link member70is arranged on both sides of the pair of latch members60. A second shaft is provided at the lower end71of link member70which is received in an elongated slot63of latch member60. A top end72of link70is rotatably supported by a shaft73mounted in cover30. Lower end71of link70has an arc shaped outer peripheral surface74which is provided for sliding on a cam surface28that is formed in base member20.

When cover member30is moved from its at rest position toward base member20, with the arc-shaped outer peripheral surface74of link70riding on cam surface28, link70begins its rotation with shaft73as its center and shaft75of link70moves within elongated slot63. This action causes latch member60to rotate around shaft61as it center thereby moving the tip62of each latch member60in an outward arc from a first position which is adjacent or in touch with adaptor50to second position away from adaptor50as shown in FIG.2.

FIG. 4shows in detail the construction of the latch member andFIG. 5shows the construction of a pivoting contacting member80which is installed on the latch member. In this embodiment, latch member60has a through hole64for accommodating a rotary shaft61mounted in base member20. In addition, a through hole65is provided in the tip portion62of latch60for receiving a shaft84for installing contacting member80on tip portion62of latch60. Contacting member80has a pressing face81with a flat surface in its longitudinal direction and an installation part82extending from both sides of pressing surface81in which an installation hole83is formed.

A shaft84is passes through hole65of latch60and installation holes83of contacting member80in a manner such that contacting member80is attached to tip portion62of latch60so as to be freely rotatable. It is desirable that installation holes83have a diameter which is larger than that of shaft84, thereby making it possible for contacting member80to have “play” in the axial direction and the perpendicular direction of shaft84, in addition to the rotary movement of contacting member80.

On both sides (in the vertical direction toward the surface of the sheet inFIG. 2) of latch member60, the respective links70are arranged with shaft75being installed at one end71running through the elongated hole63of latch member60.

With regard to the installation of contacting member80on latch member60, the above described method is by way of example and other methods could be used. For example, it is possible to form a shaft integrally at tip62of latch member60with contacting member80being installed on this shaft without forming the through hole65on latch member60. In this construction, at least one of the installation parts82of contacting member80is made to be removable from the contacting member itself for the insertion of the shaft. Once again, it is desirable that the size of installation hole82is made larger than the diameter of the shaft, thereby providing for multi axial movement of contacting member80.

Separately from what has been described above, a shaft may be formed integrally on the axial installation part82of contacting member80with latch member60being provide thereon. Also, in this case, it is desirable that at least one of the installation parts82be constructed to be able to be removed from contacting member and that for the same reason, the hole of the latch member be made larger than the diameter of the shaft.

The operation of loading a semiconductor device1will be explained below:

At the time when cover member30is in the state of being apart from base member20by the force of springs32, the pressing surface81of contacting member80attached to latch member60is in contact or directly adjacent placing surface51. If the cover member is pushed down for the purpose of mounting a LGA device on the socket, the downward movement of link70and correspondingly the movement of arc shaped outer peripheral part74along cam surface28caused latch member60to rotate around rotary shaft61to position tip62of latch member60in a retracted position. This allows for the insertion of the LGA device1through the opening35of the cover.

LGA device1is positioned on placing surface51of adaptor50using guide55to help with the accurate positioning (the state as shown in the half portion of FIGS.2and3). Subsequent to the placement of LGA device1on adaptor50and the removal of the downward force on cover member30, cover member moves away from base member20due to the force of springs32with the result that lower end71of link70moves outwardly from the socket center and latch60starts rotating to the position where tip62is adjacent LGA device1on adaptor50.

At near the end of the rotation of latch60, a part of pressing surface81of contacting member80attached to tip62touches the top surface of LGA device1. Since contacting member80in a free state is capable of pivoting with relation to tip62of latch member, the pressing surface81sways/pivots so as to align with the upper surface of the LGA device1, with the consequence that pressing surface81as a whole makes contact with the device surface.

As the cover member finishes its upward movement, latch member60rotates to its final position with the result that LGA device1is pressed down by the pressing surface of contact member80. This results in moving adaptor50downward due to the downward force of latch member60being greater than the upward biasing force of springs53.

Almost simultaneously with the above actions, terminals2on the lower surface of LGA device1move into contact with contacting portion44of contacts40as they protrude out of through holes54. With the cover at its upper most position, a balance is reached between the pressing force exerted against LGA device1and the spring force of contacts40. This balanced position is set so that there is proper contacting force for all terminals2with respective contacts40(refer to state shown in the left half in FIGS.2and3).

These series of contacting movements by latch member60, and more particularly tip62, with respect to LGA device1are arc-shaped movements. The free pivoting rotation of contacting part80attached to tip62allows for the pressing surface81to make wide area contact as if in a straight line movement with the top surface of LGA device1.

In accordance with this invention, both the pressing force from the latch members60and the counter force from contacts40work on the LGA device1. As the lower surface of LGA device1is supported by the placing surface of adaptor50, while its upper surface is pressed by pressing surface81of contacting members80, any concentration of stress totally at specific points on the LGA device, or the application of twisting or shearing force, is at an absolute minimum with the consequence that possible damage to the semiconductor device is prevented.

Next, alternative embodiments of the present invention will be explained below which use different examples of latch members and contacting members for uniformly holding LGA device1.

As is shown inFIG. 6, there is shown a latch member60′ to be used in place of the latch member60described above. In this second embodiment the contact member80is biased away from latch member60′ by an elastic member such as a spring member85interposed between latch member60′ and contacting member80. With this construction, it becomes possible for contacting member80to make stable contact in a fixed direction at all times when it contacts the upper surface of LGA device1.

FIG. 7shows a third embodiment of the present invention with a modified latch member60″ to be used with two or more pressing plates90mounted in a tip portion62″ of latch member60″. More specifically, notches are provided in tip portion62″ to house spring members91. At the end of each spring member91, the pressing plates90are attached so as to be able to pivotally move around the axis of the spring member. Thus, upon the cover member returning to its upper most position, each individual pressing plate member90will contact the upper surface of LGA device1on a wide area due to the pivoting movement of the pressing plates.

FIG. 8shows a fourth embodiment of the present invention with yet still another design of a contacting member mounted to a latch member at its tip portion. In this case, a spherical member100is attached to tip portion62′″ of latch member60′″. A contacting member101having a circular cavity102is in turn rotatably mounted on spherical member100. There is a clearance area provided between contacting member101and tip62′″ of latch member60′″, thereby making it possible for the pivoting movement of contacting member101around spherical member100. With this construction, there is an advantage in that the contacting member101is installed on latch member60′″ using a minimum number of parts. It would also be possible to make the spherical member as part of the contacting member and the circular cavity as part of latch member60′″ or use an elastic rubber joint, etc.

FIG. 9shows a fifth embodiment of the present invention using a pair of separate holding members110instead of using a pivoting/rotating member at the tip of latch member60. The holding members110are installed on base20close to the inner side of latch member60on the side that faces adapter50. An elongated hole is formed at one end of holding plate110for receiving a rotary shaft111to thereby make it possible for holding plate110to be able to rotate to contact adapter50or LGA device1when placed on adapter50in response to movement of latch member60. Even if the thickness of device1may change, the holding plate110moves in a generally perpendicular direction to shaft111in conformity therewith, making it possible to effect contact with the upper surface of LGA device1in a wide area.

In operation, after the placement of LGA device1on placing surface51of adaptor50(in the state shown in the right-side half in FIG.9), cover member30is elevated and latch member60is rotated. In this situation, the holding plates110come into contact with the upper surface of LGA device1as they are moved by latch members60. Accordingly, latch member60presses holding plate110and in the turn upper surface of device1(in the state shown in the left-side half in FIG.9). By using holding plates110, the area of contact can be increased and, at the same time, a latch member of conventional construction can be used as it is. Holding plates110may also be used in conjunction with spring members to bias them away from the surface of adaptor50.

Some desirable embodiments of this invention have been described above in detail. It is pointed out, however, that this invention is not to be restricted by the forms of the specific embodiments mentioned, but that it can be modified in various ways within the range of the essence of this invention that has been described in the scope of claims below.

For example, a pair of latch members at opposing locations with reference to the adaptor has been used in the various embodiments described above. However, the latch member with contacting member may be arranged on only one side, by way of example, or on all four sides. Additionally, the invention has been described with reference to a semiconductor device of LGA type, but other conductor device types such as ball grid array devices can also be used. Even the general shape of the contact members may be varied and not be limited to the one shown.

This invention has been described for sockets of the so-called “pop-up” type. The movement means from the cover member to the latch member has been a link mechanism, but it could also be other mechanisms such as a cam means as are known in the art. This invention is applicable to any type of socket where the semiconductor device is pushed down by a latch member which is connected to the straight line movement of the cover member.