Socket, socket base and method for operating and testing

A purpose of the invention is to provide a socket and a socket base, capable of holding the retainers outside the viewing field of the camera in spite of the size and/or shape of the retainers when measuring contact gaps, for example.

TECHNICAL FIELD

The present invention relates to a socket with a plurality of contacts corresponding to a plurality of terminals provided on a bottom surface of an integrated circuit device such as a ball grid array (BGA) device. Also, the present invention relates to a socket base for use with the socket. Further, the present invention relates to a method for using and operating the socket and the socket base and a method for testing the socket.

BACKGROUND

A patent document 1 discloses a socket for a temporal connection of a ball grid array (BGA) integrated circuit device to a test circuit. The socket includes a pattern of contacts corresponding to a pattern of terminals, e.g., solder balls provided on a bottom surface of the integrated circuit device. Each of the contacts has a pair of tips for resiliently nipping an associated one of the solder balls of the integrated circuit device. The socket also has structures for moving each pair of contact tips between an opened position in which the contact tips are spaced apart from each other to accommodate the associated solder ball therebetween and a closed position in which the contact tips resiliently hold the associated solder ball therebetween.

A patent document 2 discloses another socket including one or more pairs of retainers for forcing the integrated circuit device against the contacts to attain reliable contacts between the contacts of the socket and the associated solder balls of the integrated circuit device. Each of the retainers is supported for rotation between a protruded position in which each of the retainers is protruded above the upper surface of the integrated circuit to force the integrated circuit device against the contacts and a retracted position in which the retainer is fully retracted from above the integrated circuit device. A spring is provided for each retainer to force the retainer toward the protruded position.

The sockets have various advantages. Among other things, the retainers ensure reliable electrical contacts between the solder balls of the integrated circuit device and the associated contacts of the socket. However, when optically checking whether a sufficient opening or gap necessary for receiving the solder ball is formed between the opened contact tips and/or whether a predetermined physical condition is provided to each contact, the protruded retainers can intervene between the camera and a part of the contacts, inhibiting the measurement of the gaps of those contacts, depending upon the size and/or shape of the retainers. This requires that the retainers are retained in the retracted positions by means of exclusively designed tools before mounting the socket onto the test site. Also, a fitting and unfitting of the tool requires an extra effort and time.

In view of foregoing, a purpose of the present invention is to provide a socket, a socket base and methods for operating and testing the sockets, capable of holding the retainers outside the viewing field of the camera in spite of the size and/or shape of the retainers.

SUMMARY OF THE INVENTION

To attain this, the present invention is to provide a socket for an integrated circuit device, the socket having a plurality of contacts corresponding to a plurality of terminals mounted on a major surface of the integrated circuit device, comprising:

a base for supporting the contacts;

a plurality of retainers, each of the retainers being mounted on the base for movement between a projected position in which the retainer is projected into a region above the integrated circuit device mounted on the contacts to make a contact with an upper surface portion of the integrated circuit device and a retracted position in which the retainer is retracted out of the region above the integrated circuit device;

a plurality of springs, each of said springs being provided for biasing the retainer from the retracted position to the projected position;

wherein the base has a plurality of through-holes extending through the base, the through-holes being so positioned that, when pins are passed upwardly through the through-holes, respectively, the retainers are forced by the pins from the projected positions to the retracted positions.

Another aspect of the present invention is to provide a socket base for supporting the socket, wherein the socket base has the pins.

Another aspect of the present invention is to provide a method for operating retainers of a socket for an integrated circuit device, comprising the steps of:

(a) providing a socket including a base having through-holes extending through the base, a plurality of contacts mounted in the base, retainers mounted for movement between respective first positions in which the retainers are positioned above an integrated circuit device mounted on the contacts to retain the integrated circuit device on the contacts and respective second positions in which the retainers are retracted from above the integrated circuit device to release the integrated circuit device and springs for biasing the retainers from the respective second positions to the respective first positions;

(b) providing a socket base for supporting the socket, the socket base having pins corresponding to the through-holes;

(c) mounting the socket on the socket base so that the pins of the socket base are passed through the corresponding through-holes of the base to force the retainers from the respective first positions to the respective second positions against the springs; and

(d) removing said socket from said socket base.

Another aspect of the present invention is to provide a method for testing a socket for an integrated circuit device, comprising the steps of:

(a) providing a socket having a base having through-holes extending through the base, a plurality of contacts mounted in the base, retainers mounted for movement between respective first positions in which the retainers are positioned above an integrated circuit device mounted on the contacts to retain the integrated circuit device on the contacts and respective second positions in which the retainers are retracted from above the integrated circuit device to release the integrated circuit device and springs for biasing the retainers from the respective second positions to the respective first positions;

(b) providing a socket base for supporting the socket, the socket base having pins corresponding to the through-holes;

(c) mounting the socket on the socket base while the pins of the socket base are passed through the corresponding through-holes of the base to force the retainers from the respective first positions to the respective second positions against the springs; and

(d) removing the socket from the socket base.

According to the socket, socket base and the combination thereof, when the socket is mounted on the socket base, the pins of the socket base are passed through the corresponding through-holes of the base to force the corresponding retainers from the projected positions to the retracted positions. This allows that, when measuring the gaps of the contacts and/or the physical conditions of the contacts such as heights of the contact tips relative to the base, the optical device such as camera are capable of viewing and measuring the gaps and/or physical conditions of all contacts.

DETAILED DESCRIPTION

With reference to the accompanying drawings, several embodiments of the socket will be described below in connection with a specific operation for measuring contact gaps. Referring toFIGS. 1-3, in particularFIG. 3, a socket generally indicated by reference numeral10has an alignment plate100, a base200, retainers300, a nest assembly400, a guide frame500, a lever assembly600and a top cover700.

The alignment plate100, which is in the form of substantially rectangular plate of electrically non-conductive material, has a rectangular, contact alignment region102. The region102has a number of contact alignment holes104arranged in a grid, at regular intervals in the orthogonal X- and Y-directions. The plate100also has through-holes106each extending vertically between top and bottom surfaces of the alignment plate100and provided adjacent and outside the central portion of the opposite edges of the rectangular region102(one of the through-holes is omitted from the drawing.)

As indicated inFIG. 4, the base200, which is made of electrically non-conductive material, has a rectangular bottom portion202and peripheral walls204surrounding the bottom portion202. The bottom portion202has a rectangular contact alignment region206corresponding to the contact alignment region102of the alignment plate100. Similar to the contact alignment region102of the alignment plate100, the contact alignment region206has a number of contact alignment holes208arranged in a grid, at the regular intervals in the orthogonal X- and Y-directions.

FIG. 5shows an embodiment of the contact800. The illustrated contact800, which is made of electrically conductive material, has a central portion802in the form of “U” when viewed from above. The opposite ends of the central portion802are extended upward to form a pair of cantilever arms804each of which terminate at tip portions806. A part of the central portion802is extended downward to form a leg808. Each contact800is securely held by the base200with the central portion802fitted within the contact alignment hole208, so that the cantilever arms804and the tips806are projected from the top surface of the base and the legs808are projected from the bottom surface of the base.

As indicated inFIGS. 3 and 4, the base200further has a pair of retainer supports210positioned outside the contact alignment region206to oppose to each other across the region206. Each retainer support210has a pair of vertical walls212positioned in line and parallel to the adjacent peripheral edge of the region206, defining a vertical slot212therebetween. Each of the walls212has on its back an upper engagement portion216and a lower engagement portion218, both projected rearward therefrom. In addition, provided below the vertical slot214and outside the contact alignment region206is a through-hole220extending vertically through the bottom portion202of the base.

As shown inFIG. 3, the alignment plate100and the base200are assembled with each other. In this assembling, the legs808of the contacts projected from the bottom surface of the base are each passed through the associated contact alignment holes104of the alignment plate100to protrude downward. When assembled, the through-holes220of the bottom portion202of the base are properly aligned in line with the associated through-holes106of the alignment plate100. This in turn means that the through-holes106of the alignment plate100and the through-holes220are so positioned that they oppose to each other in the assembled condition.

Preferably, the assembling of the alignment plate100and the base200is attained by means of a snap-fit mechanism made of, for example, four vertical legs108of the alignment plate100and the corresponding four recesses or through-holes222of the base200into each of which the legs108are inserted for engagement.

As shown inFIG. 4, the retainer300has a main portion302in the form of substantially inversed “J” or “L” with a distal end304projected forwardly from its top portion. The main portion302has a proximal end portion306with a pair of bearing shafts308projecting from its left and right edges. The proximal end306further has a front projection310which projects from a central, front surface portion thereof and a rear projection312which projects from a central, rear surface portion thereof.

Each of the retainer300is assembled to the retainer support210of the base200with the main portion302positioned behind the vertical walls212and each of the left and right bearing shafts308engaged between the upper and lower engagements216and218, so that the retainer300is supported for rotation between a first position or projected position in which the distal end304projects above the contact alignment region208of the base200(seeFIG. 2) and a second position or retracted position the distal end304stays outside the contact alignment region208(seeFIG. 7). In the assembled state, the forward projection310stays within the vertical slot214and above the through-hole220when the retainer300takes the projected position. A biasing means or spring314is provided for each retainer and positioned between the base200and the rear projection310of the retainer so that the retainer300is biased and retained in the projected position while the main portion302is forced against the vertical walls212.

As indicated inFIG. 3, the nest assembly400has a pair of comb structures402as described in U.S. Pat. No. 5,498,970. Each of the comb structures402, which is made of electrically non-conductive material, has an end frame portion404and a plurality of parallel cantilever racks406extending orthogonally therefrom. A gap defined between the neighboring racks406is slightly larger than the width of the cantilever rack so that the comb structures402can be assembled to each other with each of the cantilever racks of one comb structure402positioned between the neighboring cantilever racks of the other comb structure402.

The nest structures402are oriented in opposite directions and then assembled with each of the cantilever arms406of one nest structure402positioned between the each neighboring cantilever arms406of the other nest structure402to form the nest assembly400. The nest assembly400so assembled is placed on the base200with the cantilever arms406oriented in the X-direction. As indicated inFIG. 6A, ones of the contact tips806are located between the neighboring projections408of the racks406of one comb structure402and the other ones of the tips806are located between the neighboring projections408of the racks406of the other comb structure402. As indicated inFIGS. 6A-6D, this allows that, by forcing the comb structures402close to each other in the X-direction against the resiliency of the cantilever arms804, each pair of contact tips806is forced from a free state (seeFIG. 6A) to an open state (seeFIG. 6B), creating a larger space therebetween having a size sufficient for receiving a terminal or solder ball902provided on the major surface (e.g., bottom surface) of the integrated circuit device900.

To ensure the relative movement of the comb structures402, the nest assembly400is connected to the base200so that at least one of the comb structures402can move to and from the other. For example, as shown inFIG. 3, each of the comb structures402has engagement legs410at opposite ends of the end frame portion40. The base200, on the other hand, has four engagement holes222to each of which the engagement legs410are inserted. The size of the engagement holes222in the X-direction is larger than that of the legs41so that the legs410can move in that direction within the associated engagement holes222. This allows the relative movement of the comb structures402between two positions corresponding to the free and open states.

The package guide500, which is made of electrically non-conductive material and is used for guiding the BGA integrated circuit device into a proper position of the nest assembly400, has a rectangular frame502defining a rectangular opening region504which corresponds to the external configuration of the integrated circuit device. The package guide500is assembled to the base200to which the nest assembly400has been mounted. In this assembled state, the tips806of the contacts held by the nest assembly400are exposed within the opening region504, allowing the contacts800to hold the corresponding solder balls902on the bottom surface of the integrated circuit device900placed within the opening504(FIGS. 6A to 6D). Preferably, four inner edges of the rectangular frame502have respective surface portions506each inclined downwardly and inwardly to ease the insertion of the integrated circuit device into the opening504. Also preferably, the frame portions508running in the X-direction have downwardly extended cutouts510to ensure rearward rotations of the retainers300. Further preferably, the package guide500has restrictions512which restrict the rearward movements of the bearing shafts308retained by the retainer supports210of the base200. Furthermore, the package guide500is preferably secured to the nest assembly400using the legs514of the package guide500(only two of which are illustrated inFIG. 3) and the recesses224of the base200into which the legs514are engaged.

Referring toFIG. 3, the lever assembly600has a pair of substantially U-shaped brackets602. Each bracket602has a transverse member604in the form of place extending in the Y-direction and sides arms606each extending substantially perpendicularly from either end of the transverse member602. The brackets602are so assembled with each other that the arms604of one bracket intersect obliquely with those of the other. The assembled lever assembly600is then mounted on the base200so that each of the transverse members604is positioned between the end frame404of the nest assembly400on the base200and the opposed side wall of the base200, with the arms606oriented obliquely and upwardly. This ensures that, when the distal ends of the arms606are depressed downward, the transverse members604rotate about their longitudinal axes to force the end frames404of the nest assembly400toward each other, which results in that the tips806of each contact800are changed from the free state to the open state. When, on the other hand, the depressing force is eliminated, the tips806of each contact800are moved from the open state to the free state due to the resiliency of the contacts.

The top cover700, which is made of electrically non-conductive material, has a rectangular frame702defining therein an opening704which is so sized and shaped that the integrated circuit device900can pass therethrough and is assembled on the base200on which the nest assembly400, the guide frame500and the lever assembly have been already assembled thereto. To allow the top cover700to move vertically between an elevated position (seeFIG. 1) and a lowered position (not shown), relative to the base200, the top cover700has a plurality of downwardly extending legs706and the base200has in its outer peripheral surfaces a plurality of vertical grooves226in each of which the legs706of the top cover700are slidably engaged. The inner surface of each leg706has an engagement portion712and the associated base groove226has in its top portion a projection228to which the engagement portion712will be engaged to inhibit the top cover700from elevating beyond its elevated position. A plurality of biasing springs708are provided between the top cover700and the base200, so that the top cover700is normally forced in the elevated position. The top cover700further has a pair of downwardly extending actuators710capable of engaging with the rearward projections312of the retainers300to move the retainer300from the projected position back to the retracted position due to the downward movement of the top cover700from the elevated position to the lowered position.

When testing the BGA integrated circuit device900using the socket10, as shown inFIGS. 6A to 6D, the legs808of the contacts800extending from the bottom surface of the alignment plate100are electrically connected to the testing circuit not shown. In this state, the top cover700is depressed to force the distal ends of the arms606of the lever assembly600downwardly, which rotates the transverse portions604of the lever assembly600rotate about respective longitudinal axes to force end frame portions404of the nest assembly400to each other. This results in that the actuators710of the top cover700depress the rearward projections312of the retainers300, which rotates the retainers300from the projected positions to the retracted positions. Also, each gap defined by the opposed tips806of each contact800is enlarged, in which each of the solder balls902mounted on the bottom surface of the integrated circuit device900is accommodated (seeFIG. 6A-6D).

When the depressing force is removed, the top cover700returns to the elevated position due to the biasing force from the springs708. As a result, the comb structures402are moved back to a closed state due to the resiliency of the cantilever arms804of the contacts800, in which each solder ball902is nipped by the obliquely opposed tips806of the contacts and thereby the integrated circuit device900is electrically connected to the test circuit not shown. Also, the retainers300rotate from the retracted positions to the projected positions where the tips304of the retainers make forcing contacts with the respective portions of the integrated circuit device900. Preferably, the retainers300, in particular the tips304are so shaped and sized that the tips304are brought into contact with the upper surface portions where the tips304oppose the solder balls902, which prevents an unwanted upward warpage of the central portion of the integrated circuit device which would otherwise be caused if the tips304of the retainer300depress a region outside the solder balls and prevents the resultant unreliable connections between the contact tips806and the solder balls902of the contacts in its central region.

After the completion of the test for the integrated circuit device900, the top cover700is again depressed to lower the distal ends of the arms of the lever assembly600, which causes the contact tips806to move from the closed state to the open state. At this moment, the retainers300rotate from the projected positions to the retracted positions. This allows the integrated circuit device900to be removed from the socket10to lose contacts with the associated contacts.

When testing whether each pair of opposed contact tips806defines a predetermined size of gap or opening therebetween, the socket10is mounted on a socket base1000indicated inFIG. 7. The socket base1000, which is made of electrically non-conductive material, has, for example, four positioning portions1002provided according to the outer configuration of the base200. The socket base1000also includes two actuation rods or pins1004extending upwardly from the socket base1000within a region surrounded by the four positioning portions1002. The actuation pins1004are positioned at respective places where both the through-holes106of the alignment plate and the associated through-holes220of the base aligned therewith oppose when the socket10is positioned on the socket base1000by means of the positioning portions1002.

At measuring gaps of the contact tips, the socket10is mounted on the socket base1000. At this moment, the socket10is properly positioned by the four positioning portions1002. As shown inFIGS. 8 and 9, this causes that the actuation pins1004are passed through the through-holes106of the alignment plate and also the through-holes220of the base and then projected therefrom above the bottom portion202of the base, forcing the retainers300on the through-holes220of the base upward against the biasing forces derived from the springs314. This results in that the retainers300rotate from the projected positions back to the retracted positions and the distal end portions304of the retainers are moved away from the region positioned above the contacts800, which ensures that all the gaps of the contact tips to be reliably measured by means of an image pickup device such as camera (not shown). After the completion of the gap measurement, the socket10is removed from the socket base, which returns the retainers300into the projected positions due to the biasing forces from the springs314.

In view of the foregoing, the socket according to the present invention causes the retainers300to be moved from the projected positions to the retracted positions simply by mounting the socket10onto the socket base1000, without using any purpose-built specific tools designed for moving and then keeping the retainers300at the retracted positions, before mounting the socket onto the socket base. Also, the measurement of the gaps is significantly simplified.