KR20000035134A - Test socket - Google Patents

Abstract

PURPOSE: A test socket is provided to be easy to test a high-speed integrated circuit by joining a solid socket plunger pressed by an elastic diagram and to elongate a use span of the test socket. CONSTITUTION: A test socket comprises an upper housing(14) and a lower housing(16) fixedatan upper plane(18) and a lower plane(20) of a loading substrate(22). The upper housing(14) contains a cavity(26) receiving a ball grid array(BGA) and holes(41) so that a plurality of solid socket plungers(38) contact solder balls(32) on a BGA lower plane. The socket plungers(38) are located in plural channels(40), which are formed in rows and columns in the lower housing, and are contacted with the solder balls. An elastomeric diaphragm(46) is disposed between an upper surface(48) of the lower housing(16) and a lower surface(20) of the loading substrate. The flexible diaphragm(46) provides a spring pressed contact independently with regard to a movable socket plunger which is mounted in the lower housing. Between the plunger and a spring is located a nonconductive ball. An insulator pin is located below the socket plunger, and an insulator cap is located on the loading substrate.

Description

Test socket {TEST SOCKET}

The present invention relates to a test socket for an integrated circuit package, such as a ball grid array package, which extends through a housing, a housing located on a load board. And a plurality of angled contact pins in pressure contact with the integrated circuit package and the stacked substrate.

Testing of integrated circuits formed in ball grid array (BGA) packaging is accomplished using what is commonly referred to as test sockets in the prior art. The BGA test socket typically includes a housing mounted to a loading substrate that interfaces with the test electronics. Load boards are generally circuit boards that carry test signals from an integrated circuit in a BGA to a test electronics.

Conventional methods of attaching test sockets to a loading substrate include through hole techniques and surface mounting techniques. In the surface mount connection, the test socket includes a test pad that contacts the solder ball on the bottom of the BGA when the BGA is compressed against the test pad and transmits a test signal to the loaded substrate. Problems associated with surface mount test socket devices are that the solder balls on the bottom of the BGA can vary in height and that good electrical contact between each solder ball and the test pad is not always guaranteed. A second problem with surface mount is that once the test pad is contaminated with solder balls, the entire socket assembly must be replaced.

The through-hole method for connecting the socket to the loading board includes holes through which the spring-loaded contact pin passes through the loading board, and the contact pin contacts the solder ball on the BGA to between the test pin and the hole in the loading board. The test signal is transmitted to the loading board through the contact of. A problem with the through-hole socket arrangement is that the test pins extending upward through the loading board are easily bent or damaged, which negatively affects the test results. To avoid this problem, a receptacle can be placed between the socket and the loading board to prevent the test pin from extending through the loading board. The combined result of the receptacle requires an increase in the length of the test pins in the socket, which causes problems in testing high speed integrated circuits. In order to deal with this problem, a spring probe with a short moving length is coupled, but the short life of the spring shortens the life of the spring and requires continuous replacement. In addition, the use of spring probes in the sockets can cause impedance problems in transferring test signals from the BGA to the loading substrate.

As a result, there is a need for a new test socket for a BGA package that solves the problems associated with conventional test sockets.

Summary of the Invention The present invention provides a newly designed test socket, particularly for a ball grid array integrated circuit package, which provides a test socket that reduces the problems associated with conventional socket devices. In a preferred embodiment the test socket is designed for use with a BGA package, but the socket may also be adapted for use with other integrated circuit packages such as, for example, a QFP package.

1 is a front sectional view of a BGA test socket of the present invention in a pressurized state.

2 is a front sectional view of the test socket of FIG. 1 in a non-pressurized state.

3 is an enlarged detail view illustrating a socket plunger assembly.

4 is a perspective view of a refill cassette for a test socket.

5 is a front sectional view of the first other test socket device.

6 is a partial cross-sectional detail view of another configuration for pressing the plunger.

7 is a partial cross-sectional detail view of another socket plunger configuration.

8 is a top view of a second alternative test socket of the present invention.

9 is a side cross-sectional view of the test socket of FIG. 8.

10 is a side cross-sectional view of the first alternative embodiment of the test socket of FIG. 8.

FIG. 11 is a side cross-sectional view of a second alternative embodiment of the test socket of FIG. 8. FIG.

12 is a front sectional view of a third alternative and most preferred embodiment of the test socket of the present invention;

In summary, the test socket of the most preferred embodiment of the present invention includes a housing located on the loading substrate. The housing has a plurality of inclined holes drilled through the housing. The spring probe is positioned in the hole to form a pressure contact between the test site and the load substrate. Another embodiment of the present invention includes an upper housing and a lower housing respectively fixed to the upper and lower surfaces of the stacked substrate. The stacked substrate is a small circuit board that electrically interfaces with the test electronics of the tester. The upper housing includes a cavity for receiving the BGA and a hole in the lower surface to allow a plurality of solid socket plungers to contact the solder ball on the bottom of the BGA. The socket plunger is located in a plurality of channels formed in rows and columns in the lower housing, and extends through the mounting substrate through a plurality of holes, which also constitute rows and columns, to contact the solder balls. An elastic diaphragm is located between the upper surface of the lower housing and the lower surface of the loading substrate, which presses upwards in the BGA direction by providing spring force by extending upward into the channel in the lower housing below the plunger. do. The flexible diaphragm provides independently spring-pressed contact to a movable socket plunger mounted in the lower housing. Alternatively and more preferably, the spring is located in the lower housing below the plunger to pressurize the plunger. Nonconductive balls are located between the plunger and the spring to prevent interference in high frequency applications. In addition, an insulator pin may be located under the socket plunger, and an insulator cap may be located on the loading substrate for high frequency application. An electrically conductive cylindrical eyelet is disposed in the hole of the loading substrate to guide the movement of the socket plunger and transmit a test signal from the socket plunger to the loading substrate. As an alternative, the through hole in the stacked substrate is plated to carry the test signal.

The socket plunger of the present invention solves the problems associated with the conventional BGA test socket device by combining the solid socket plunger pressurized by the elastic diaphragm to solve the problem of long lead length and spring inductance. The device also compensates for the lack of coplanar solder balls on the BGA for long travels for the plunger. The use of elastic diaphragms also increases the service life of the test socket when compared to mechanical springs.

At closely spaced test sites, the test sockets of the present invention may be provided with holes in the stacking substrate, with very thin daughter boards soldered, by shielded probes, or with brackets and It includes a configuration that is coupled to one of the connected substrates by a flexible printed circuit board (flexible printed circuit board). Since the housing is connected to the sub-board, the socket plungers can be accommodated in the desired closely spaced arrangement. These and other advantages of the present invention will be more clearly understood with reference to the following detailed description.

A test socket 10 for a ball grid array (BGA) integrated circuit package 12 is shown in FIGS. 1 and 2. Although the present invention is described and illustrated for use with a BGA package, the novel design of test sockets is equally applicable for testing other integrated circuit packages. For clarity, most of the details will be limited to the BGA package. The test socket 10 of the present invention includes an upper housing 14 and a lower housing 16 fixed to the upper surface 18 and the lower surface 20 of the stacked substrate 22, respectively. The upper housing 14 and the lower housing 16 are preferably made of plastic, and are firmly fixed to the loading substrate 22 by screws 24 passing through the housing and into the loading substrate. The stacked board is a circuit board that electrically interfaces with test electronics of an external tester (not shown).

The upper housing defines a cavity 26 inside the upper housing that houses the ball grid array package 12. The ball grid array package includes an integrated circuit 28 located on a substrate 30, which is located on a lower surface of the substrate opposite the integrated circuit and in electrical communication with the integrated circuit through the substrate 30. A plurality of solder balls 32 are provided. The solder ball 32 serves as a test pad for testing an integrated circuit. The substrate 30 is mounted on a flange 34 at the base of the cavity 26, and the solder ball 32 is mounted on the flange 18 on the upper surface 18 of the loading substrate 22. It extends through the hole 36 defined by 34.

The hole 36 at the bottom of the upper housing also provides an opening that allows a plurality of solid socket plungers 38 to contact the solder ball 32. As shown in FIG. 3, the socket plunger is located in a plurality of channels 40 formed in rows and columns in the lower housing 16 and extends through a plurality of holes 41 penetrating the stacked substrate. ). The holes 41 are also arranged in rows and columns similar to the pattern of the solder balls 32 on the BGA package. The solid socket plunger 38 consists of an enlarged head portion 42 and a small and long arm portion 44. The arm portion extends through the hole 41 of the loading substrate 22, while the enlarged head portion 42 remains in the channel 40 of the lower housing 16.

An elastic diaphragm 46 is located between the upper surface 48 of the lower housing 16 and the lower surface 20 of the loading substrate, and upwards into the channel 40 in the lower housing below the head 42 of the socket plunger. By extending and providing a spring force, the socket plunger is pressed in the BGA direction so that the inclined top surface 50 of the plunger arm 44 is in good electrical contact with the solder ball 32. The inclined surface 50 at the distal end of the plunger arm is machined to provide a pressing contact to the solder ball. The flexible diaphragm 46 provides independent spring press contact with a movable socket plunger mounted in the lower housing. An electrically conductive cylindrical eyelet 52 is positioned through each hole 41 of the loading substrate 22 to guide the movement of the socket plunger arm and transmit a test signal generated from the solder ball to the loading substrate through the socket plunger. The eyelet is preferably made of a conductive material such as cooper beryllium or nickel silver. The through hole 41 of the loading substrate is generally plated, and the eyelet includes a solder preform ring 53 for firmly fixing the eyelet to the loading substrate by soldering the eyelet through the plated through hole.

The elastic diaphragm 46 is supported by screws 24 between the lower housing and the mounting substrate. The elastic diaphragm is preferably an expandable thin flexible latex rubber sheet that is in direct contact with the socket plunger head 42. While the elastic diaphragm is preferably made of latex rubber, other materials are contemplated that allow the diaphragm to provide a spring force to press against the socket plunger. The diaphragm in the normal position is stretched to fit the shape of each plunger head, and the axial force applied to each plunger in the diaphragm direction during use increases the diaphragm and complies with the plunger end in a manner similar to a normal return spring. to provide. In response to the axial movement of the plunger, the thin flexible diaphragm is freely expandable into the channel 40 in the lower housing and can be freely extended or stretched into the empty space of each channel. The axial force is, in one embodiment shown in FIG. 1, a housing lid hinged to the upper housing 14 and fixed to the upper housing in a closed position by a clasp (not shown). 54) to the socket plunger. The cover 54 includes an extended center section 56 sized to stretch the elastic diaphragm by pressing the BGA package down against the socket plunger. Alternatively, the axial force may be exerted on the BGA package by a robotic arm 58 positioned above the BGA package and extending through the cavity 26 into the upper housing, as shown in FIG. 2. In this structure, the housing cover is not required or will be kept in the open position. The use of robotic arms will be applied to automated test structures. In Figure 2 the elastic diaphragm is shown in its normal position before axial force is applied to the BGA package.

The test socket device of the present invention makes it possible to easily replace the socket plunger when the socket plunger is contaminated with the solder ball 32, so that the test socket can be retrofitted easily and at low cost. Through repeated use, the inclined surface 50 of the socket plunger may be contaminated with tin or lead deposits from the solder balls. Retrofitting can be easily accomplished through the use of the refill cassette 60 shown in FIG. The refill cassette 60 preferably has a plurality of recesses 62 made of plastic blocks and formed in rows and columns extending into the refill cassette containing the replacement socket plunger 64. 4 illustrates six replacement socket plungers extending upward from recess 62 for illustrative purposes. It will be appreciated that individual socket plungers 64 are located within each recess 62 and are flush with the upper surface 66 of the refill cassette. The refill cassette also includes a positioning hole 68 for aligning the refill cassette during the retrofit process.

To retrofit the test socket, the contaminated socket plunger is simply replaced by removing the lower housing and elastic diaphragm to free the contaminated plunger from the test socket. The refill cassette is then placed on the bottom surface of the loading board and the test socket replaced with a new plunger. The resilient diaphragm and lower housing are then remounted on the loading substrate for further testing.

5, a first alternative test socket device is shown. The test socket 70 of FIG. 5 is similar to the test socket of FIGS. 1 and 2 except that the compliant means is a spring 72 located in the channel 40 of the lower housing 16. In this embodiment, the upper surface 48 of the lower housing is adjacent to the lower surface 20 of the stacked substrate 22. The channel 40 in the lower housing is a blind hole that is blocked at the bottom 74 without extending through the lower housing. While such test sockets may be used to test a BGA package, other integrated circuit packages with different types of test sites 76, which may be, for example, test pads or test leads, may also be tested. Yes is illustrated.

A second alternative test socket structure 80 is shown in FIG. 6. The test socket 80 is generally similar to the sockets of FIGS. 1, 2 and 5 and includes different devices for pressing the plunger 82. Each plunger is pressurized by a spring 84 located in the hole 86 and extending through the lower housing 80. The spring 84 is held inside the hole 86 by a retention cap 90 secured to the lower surface of the lower housing by screws (not shown). The retention cap 90 covers the rows and columns of the holes 86 in the lower housing.

A ball 94 is located between the plunger head 96 and the spring 84. The ball contacts the inclined surface 102 at the bottom of the plunger head 96 to urge the plunger against the plated through hole or eyelet 98 of the stacked substrate 100. The ball may be metal or may be a non-conductive material such as ceramic to prevent interference to the test signal in high frequency applications. The plunger may also have an inclined distal end 104 that contacts the solder ball 106 of the integrated circuit 108. The inclined distal end 104 ensures good contact with the test site.

The test signal is sent into the plunger from either the top of the loading board or the bottom of the loading board before moving to the solder balls of the BGA package. For high frequency test signal applications, alternative plunger arrangements are provided as shown in FIG. In such a device, a non-conductive pushrod 110 is located below the plunger 112 and a non-conductive cap 114 is located above the plunger. The push rod 110 has an enlarged base 116 held above the spring 84 in a hole 86 in the lower housing. The smaller diameter arm 118 extends into the plated through hole 98. Arm 118 has a circular distal surface 120 in pressure contact with the inclined distal end 122 of the plunger 112.

The non-conductive cap 114 is located on the upper surface of the stacked substrate 100 and has an enlarged head portion 124 for holding the plunger 112. The reduced diameter portion 126 of the plunger 112 extends through a hole in the head portion 124 such that the larger portion 128 of the plunger 112 is not pressurized 130. Allow it to stop against the cap. A state 132, in which pressure is applied to the plunger, is also shown in FIG. 7. In high frequency applications, a test signal is sent through the plunger to the solder balls from the bottom of the stacked substrate. In this way, the signal is not moved to the spring 84, thereby preventing the loss of the signal.

The test socket of the present invention uses an auxiliary substrate 134 as shown in FIGS. 8 and 9 to accommodate closely spaced test sites. Typically, the loading substrate 136 to which the test socket is connected has a thickness of 0.125 inch, so that for closely spaced test sites, it is necessary to drill the desired holes to accommodate the test plunger for such a test site pattern. it's difficult. Thus, auxiliary substrates, typically .030 inches thick, can be used to easily drill holes through the secondary substrate to accommodate the needs of closely spaced test sites (which can be as close as 0.020 inches). . Since the hole 138 is drilled at the center of the loading substrate 136 to accommodate the auxiliary substrate, the auxiliary substrate may be soldered to the upper surface of the loading substrate by overlapping the hole drilled in the loading substrate. The upper housing 140 includes a flange 142 for other structural preservation and connection of the auxiliary substrate and the loading substrate. The lower housing 144 and the end cap 146 are connected to the auxiliary substrate by screws 148.

Another method of mounting the auxiliary substrate 134 to the stacked substrate 136 is shown in FIGS. 10 and 11. In FIG. 10, a shield probe 150 is firmly mounted to the loading substrate 136, and then the auxiliary substrate 134 is located on the opposite end of the shielding probe. In FIG. 11, the auxiliary substrate 134 is electrically connected to the stacked substrate 136 by the flexible printed circuit board 152. In this embodiment the upper housing 140 does not require a flange 142. In order to preserve the structure, the frame member 154 is firmly fixed to the lower portion of the loading substrate so that the lower housing 144 and the end cap 146 can be mounted.

Referring to FIG. 12, a test socket 160 of a third alternative and preferred embodiment is shown. The test socket 160 includes a housing 162 secured to the loading substrate 164 by screws (not shown) or other preferred fasteners. The housing 162 has a plurality of holes 166 formed in rows and columns that are perforated to slope through the housing. Hole 166 houses a spring probe 168 for pressure contact between test site 170 and loading substrate 164 on device 172 under test. Although the test socket 160 is shown as only having an upper housing, the novel concept of having a test pin inclined in the housing can equally apply to the other socket structures illustrated above.

While the invention has been described and illustrated with respect to various embodiments, it will be understood that modifications and variations are possible that fall within the intended full scope of the invention as hereinafter claimed, and are not so limited.

The present invention combines a solid socket plunger pressurized by an elastic diaphragm to solve the test pin length problem, making it easier to test high-speed integrated circuits and eliminate spring inductance. The use of elastic diaphragms also extends the service life of the test socket compared to mechanical springs.

Claims (8)

In a test socket for an integrated circuit package having a plurality of test sites, A housing disposed on the circuit board, the housing having a plurality of inclined holes; A plurality of test pins located in the inclined hole; And Compliant means for pressing the test pin to make electrical contact with a test site on the integrated circuit package and the circuit board Test socket comprising a. The method of claim 1, A test socket in which the compliant means is a spring located within the test pin. In a test socket for an integrated circuit package having a plurality of test sites, An upper housing positioned on a circuit board having a plurality of inclined holes, the upper housing having a cavity for receiving the integrated circuit package; A lower housing positioned below the circuit board and having a plurality of sloped channels for receiving a solid test pin; And Compliant means located below the circuit board and pressurized to make electrical contact with a test site on the integrated circuit package through the circuit board. Test socket comprising a. The method of claim 3, And the compliant means is a spring located in each channel of the lower housing below the test pin. The method of claim 3, And the compliant means is an elastomeric diaphragm extending into the lower housing channel below the test pin between the circuit board and the lower housing. The method of claim 3, The test socket of the elastic diaphragm is a thin latex sheet. The method of claim 3, An inclined hole in the circuit board guides the movement of the test pin through the circuit board and includes a test eyelet for conducting the test signal from a test site of the integrated circuit package to the circuit board . The method of claim 3, And a housing lid positioned above the upper housing, the housing lid compressing the integrated circuit package with respect to the test pin.