(12) INTERNATIONAL APPLICATION PUBLISHED UNDER THE PATENT COOPERATION TREATY (PCT)
`
`(19) World Intellectual Property Organization
`International Bureau
`
`11111111111111111111111111111111111111111111111111111111111111111111111111111111
`
`(43) International Publication Date
`17 January 2002 (17.01.2002)
`
`PCT
`
`(10) International Publication Number
`WO 02/04966 A2
`
`(51) International Patent Classification7:
`
`G01R 31/04
`
`(21) International Application Number: PCT/US01/20099
`
`(22) International Filing Date:
`
`22 June 2001 (22.06.2001)
`
`(25) Filing Language:
`
`(26) Publication Language:
`
`(30) Priority Data:
`09/610,873
`
`English
`
`English
`
`6 July 2000 (06.07.2000) US
`
`(71) Applicant: ADVANCED MICRO DEVICES, INC.
`[US/US]; One AMD Place, Mail Stop 68, Sunnyvale, CA
`94088-3453 (US).
`
`(72) Inventor: HUSSAIN, Rafiqul; 43667 Skye Road, Fre(cid:173)
`mont, CA (US).
`
`(81) Designated States (national): AE, AG, AL, AM, AT, AU,
`AZ, BA, BB, BG, BR, BY, BZ, CA, CH, CN, CO, CR, CU,
`CZ, DE, DK, DM, DZ, EE, ES, FI, GB, GD, GE, GH, GM,
`HR, HU, ID, IL, IN, IS, JP, KE, KG, KP, KR, KZ, LC, LK,
`LR, LS, LT, LU, LV, MA, MD, MG, MK, MN, MW, MX,
`MZ, NO, NZ, PL, PT, RO, RU, SD, SE, SG, SI, SK, SL,
`TJ, TM, TR, TT, TZ, UA, UG, UZ, VN, YU, ZA, ZW.
`
`(84) Designated States (regional): ARIPO patent (GH, GM,
`KE, LS, MW, MZ, SD, SL, SZ, TZ, UG, ZW), Eurasian
`patent (AM, AZ, BY, KG, KZ, MD, RU, TJ, TM), European
`patent (AT, BE, CH, CY, DE, DK, ES, FI, FR, GB, GR, IE,
`IT, LU, MC, NL, PT, SE, TR), OAPI patent (BF, BJ, CF,
`CG, CI, CM, GA, GN, GW, ML, MR, NE, SN, TD, TG).
`
`Published:
`without international search report and to be republished
`upon receipt of that report
`
`(74) Agent: RODDY, Richard, J.; Advanced Micro Devices,
`Inc., One AMD Place, Mail Stop 68, Sunnyvale, CA 94088-
`3453 (US).
`
`For two-letter codes and other abbreviations, refer to the "Guid(cid:173)
`ance Notes on Codes and Abbreviations" appearing at the begin(cid:173)
`ning of each regular issue of the PCT Gazette.
`
`iiiiiiii
`
`iiiiiiii
`!!!!!!!!
`iiiiiiii
`
`----iiiiiiii
`!!!!!!!! --
`- --------------------------------------------------------------------------------------
`
`(54) Title: AN APPARATUS AND METHOD FOR TESTING A SOCKET ON A BURN-IN BOARD USING A FLEX STRIP
`PROBE
`
`!!!!!!!! -iiiiiiii
`iiiiiiii ----
`
`12
`
`SOCKET
`BURN-IN BOARD
`
`18
`
`\0
`\0
`0\
`~
`0 ..........
`~ (57) Abstract: An apparatus and method for testing a socket (16) on a burn-in board (18) using a flex strip probe (12). The flex
`strip probe (12) is a flex strip having wires (24) with leads (22) on one and connected to a tester (14) at the other end. The leads (22)
`0 are inserted into a socket (16) and the tester (14) provides signals to and from the socket (16) through the flex strip probe (12). The
`> signal simulates the signals to a semiconductor package which will be inserted into the socket (16) and tested. If necessary, a second
`~ flex strip probe (12) can be used in conjunction wiht a first flex strip.
`
`TESTER
`
`

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`AN APPARATUS AND METHOD FOR TESTING A SOCKET
`ON A BURN-IN BOARD USING A FLEX STRIP PROBE
`
`TECHNICAL FIELD
`
`The present invention relates to an apparatus and method for testing a socket on a burn-in board. The
`
`5
`
`present invention has particular applicability in testing a clam shell socket on a burn-in board.
`
`BACKGROUND ART
`
`Burn-in boards are used to test semiconductor packages, such as integrated circuit (IC) chips, to
`
`ensure that the semiconductor packages are operating in a proper manner. Typically, the semiconductor
`
`packages are inserted into sockets mounted on a burn-in board. For example, an IC chip is inserted into an IC
`
`10
`
`socket on a burn-in board The burn-in board is then placed in a testing chamber and power, ground and test
`
`signals are coupled to the burn-in board. The semiconductor packages are tested for a period of time under
`
`stress conditions to ensure that the semiconductor packages are performing according to set standards or
`
`specifications.
`
`In order to accurately test if a semiconductor package is working in a proper manner, the burn-in
`
`15
`
`board and the components on the burn-in board must also be working properly. For example, if a socket on the
`
`burn-in board contains a short or an open, then the semiconductor package inserted into the socket can be
`
`damaged. Although many semiconductor packages are less expensive than in the past, it is more cost efficient
`
`to replace a defective burn-in board than risk damaging one or more semiconductor packages due to a
`
`defective burn-in board. Therefore, the burn-in board should be tested first, prior to inserting the
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`20
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`semiconductor packages into the sockets on the burn-in board.
`
`Presently, a test probe is used to test a socket on a burn-in board. The test probes are expensive,
`
`inefficient, intrusive, and limited in their capabilities. For example, using a conventional test probe to test a
`
`burn-in board having 24 sockets takes approximately 15-20 minutes. Not only are conventional test probes
`
`inefficient for testing, but the test probes also can damage a socket and wear the connections on a socket,
`
`25
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`thereby reducing the life of the socket. In addition, if the test probe damages a socket when it is being removed
`
`from the socket, the semiconductor package which is inserted into the socket will be damaged. Furthermore,
`
`the test probe only performs continuity tests and cannot simulate a semiconductor package that would be
`
`placed into the socket, such as a semiconductor package having a land grid array or ball grid array package.
`
`There exists a need for a methodology and test probe for testing a socket on a burn-in board in an
`
`30
`
`efficient manner, thereby reducing manufacturing costs and increasing production throughput. There also
`
`exists a need for a methodology and test probe for testing a socket on a burn-in board in a non-intrusive
`
`manner, thereby not damaging a socket during testing. There also exists a need for a methodology and test
`
`probe for testing a socket on a burn-in board which simulates the semiconductor package to be tested in the
`
`socket.
`
`35
`
`DISCLOSURE OF THE INVENTION
`
`These and other needs are met by embodiments of the present invention which provide a method of
`
`using a flex strip probe for testing a socket on a burn-in board. A socket is tested by inserting a flex strip
`1
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`probe into a socket and connecting the other end of the flex strip probe to a tester. Signals are provided to the
`
`socket through leads, e.g., solder balls, on the end of the flex strip probe. The signals simulate a
`
`semiconductor package that would be placed into the socket.
`
`The flex strip probe of the present invention is for testing a socket on a circuit board. The flex strip
`
`5
`
`probe includes a flex strip comprising a plurality of wires with each wire having a connector end and a lead
`
`end, a connector connected to the connector end of the wires, and a lead, e.g., a solder ball, configured to fit
`
`into the socket connected to the lead end of at least one wire. The flex strip probe allows the socket to be
`
`tested without risking damage to an actual semiconductor package. The leads allow for a non-intrusive and
`
`efficient manner of testing the socket.
`
`10
`
`The flex strip probe can also be used in a method for testing a socket on a circuit board. The method
`
`comprises the steps of connecting a tester to at least one flex strip probe, connecting the at least one flex strip
`
`probe to a socket on a circuit board and sending test signals to the socket through the at least one test probe.
`
`The method allows for efficient testing of a socket without damaging the socket.
`
`Additional advantages of the present invention will become readily apparent to those skilled in this
`
`15
`
`art from the following detailed description, wherein only the preferred embodiment of the present invention is
`
`shown and described, simply by way of illustration of the best mode contemplated for carrying out the present
`
`invention. As will be realized, the present invention is capable of other and different embodiments, and its
`
`several details are capable of modifications in various obvious respects, all without departing from the
`
`invention. Accordingly, the drawings and description are to be regarded as illustrative in nature, and not as
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`20
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`restrictive.
`
`BRIEF DESCRIPTION OF THE DRAWINGS
`
`Reference is made to the attached drawings, wherein elements having the same reference numeral
`
`designations represent like elements throughout, and wherein:
`
`Figures 1 is an overview of a testing system in accordance with an embodiment of the present
`
`25
`
`invention.
`
`Figure 2a is a frontal view of an exemplary flex strip probe in accordance with an embodiment of the
`
`present invention.
`
`Figure 2b is a side view of an exemplary flex strip probe in accordance with an embodiment of the
`
`present invention.
`
`30
`
`Figure 3a is a side view of an exemplary ball grid array package.
`
`Figure 3b is a side view of an exemplary land grid array package.
`
`Figure 4 is a top view of an exemplary socket in accordance with an embodiment of the present
`
`invention.
`
`Figure 5 is a top view of two flex strip probes attached to a socket in accordance with an embodiment
`
`35
`
`of the present invention.
`
`Figure 6 is side view of an exemplary flex strip probe having two rows of solder balls in accordance
`
`with an embodiment of the present invention.
`
`Figure 7 is a side view of an exemplary flex strip attached to a clam shell socket in accordance with
`
`an embodiment of the present invention.
`
`2
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`Figure 8 is a flow diagram illustrating the steps of testing a burn-in board in accordance with an
`
`embodiment of the present invention.
`
`MODES OF CARRYING OUT THE INVENTION
`
`Conventional methodologies for testing a socket on a bum-in board are expensive,
`
`inefficient,
`
`5
`
`intrusive, and limited in their capabilities. Test probes that have been used are expensive, inefficient and
`
`damage the sockets. The present invention addresses and solves these problems, among others, stemming
`
`from conventional testing of a socket on a burn-in board.
`
`According to the methodology of the present invention, the conventional test probe is replaced with a
`
`flex strip probe having leads, such as solder balls, on the end of the flex strip probe. The flex tape probe
`
`10
`
`provides a more forgiving test probe and can simulate a semiconductor package, such as a semiconductor
`
`package having a land grid array or a ball grid an·ay. The flex tape probe ensures that the socket and burn-in
`
`board are working properly. Once all of the sockets on a burn-in board are tested, the actual semiconductor
`
`packages can be inserted into the sockets for testing.
`
`Referring to Figure 1, an overview of a testing system in accordance with an embodiment o~ the
`
`15
`
`present invention is illustrated. As shown, the test system 10 has a flex tape probe 12 connecting a tester 14 to
`
`a socket 16 mounted on a burn-in board 18. The tester 14 sends and receives signals to and from the socket 16
`
`through the flex tape probe 12 for testing the socket 16 and the burn-in board 18 and ensuring that both the
`
`socket 16 and burn-in board 18 are working properly. Power, ground and test signals are supplied to the
`
`socket 16 to test both the socket 16 and burn-in board 18. Typically, power and ground are supplied to the
`
`20
`
`burn-in board 18 through edge connections (not shown). The test signals are supplied to the socket 16 through
`
`the flex tape probe 12. In the preferred embodiment, the test signals simulate signals that would be sent to a
`
`semiconductor package inserted into the socket 16. In the preferred embodiment, the tester 14 is a computer.
`
`In an alternate embodiment, the socket 16 is on a circuit board.
`
`Referring to Figure 2a, a front view of an exemplary flex strip probe 12 is illustrated. The flex strip
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`25
`
`probe 12 includes a flex strip 20 and a plurality of leads 22a-x at an end of the flex strip 20. The flex strip or
`
`tape 20 includes a plurality of conductive wires 24a-x which correspond to the leads 22a-x at the end of each
`
`wire 24a-x .. The leads 24a-x are configured to fit into the socket being tested. A connector (not shown) for
`
`connecting the flex strip probe 12 to a tester 14 is at the other end of the flex strip 20.
`
`In alternate
`
`embodiments, not every wire 24 has a lead 22 at the end of the wire. Referring to Figure 2b, a side view of the
`
`30
`
`exemplary flex strip probe 12 having a row of leads balls 24 at one end of the flex strip 20 is illustrated.
`
`The leads 22 on the end of the flex strip probe 12 are configured to be similar in shape and size as the
`
`connections on a semiconductor package, such as the solder balls 34a-34f of a ball grid array (BGA) package
`
`32 as illustrated in Figure 3a or the lands 38a-38f of a land grid array (LGA) package 36 as illustrated in
`
`Figure 3b. Although different leads can be used in alternate embodiments, the solder balls 22 are used in the
`
`35
`
`preferred embodiment since they are more forgiving than conventional leads. Moreover, if needed, one or
`
`more leads 22 can be replaced by soldering a new lead 22 on the end of the flex strip 20.
`
`Referring to Figure 4, a top view of an exemplary socket is illustrated. As shown, the exemplary
`
`socket 16 includes two rows of bonding pads 40 with each row having five bonding pads 40. The leads 22 are
`
`positioned on the flex strip probe 12 such that each lead 22 aligns with a corresponding bond pad 40. For the
`3
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`exemplary socket 16, two flex strip probes 12 are needed to test the socket 16 as shown in Figure 5. As
`
`shown, a first flex strip probe 12a is positioned on one side of the socket 16 and a second flex strip probe 12b
`
`is positioned on the other side of the socket 16.
`
`The exemplary socket 16 in Figure 4 is shown having only two rows of bond pads 40. However, for
`
`5
`
`sockets having two or more rows of bond pads, the flex strip probe 12 can have a plurality of rows of leads 62,
`
`64 as illustrated in Figure 6. In this embodiment, each row of leads is connected to a set of wires having a set
`
`length. Therefore, each row of leads is connected to a set of wires having different lengths than other sets of
`
`wires.
`
`Once the leads 22 on a flex strip probe 12 are aligned with the corresponding bond pads 40, the flex
`
`10
`
`strip probe 12 or probes 12a, 12b are fastened to the socket 16 in the same manner as the semiconductor
`
`package would be fastened to the socket 16. For example, in Figure 7, the flex tape probe 12 is fastened to a
`
`clam socket 72 using the cover 74 of the clam shell socket 72. The cover 74, when closed in the direction of
`
`the arrow, presses the flex strip probe 12 towards the socket 72 thereby ensuring solid connections between
`
`the socket balls 22 and corresponding bonding pads 40.
`
`In other embodiments, other fasteners, such as
`
`15
`
`clamps, can be used to fasten the flex strip probe 12 to the socket 16.
`
`Using a fastener to press the sockets balls 22 and corresponding bonding pads 40 together ensures
`
`solid connections between them. In addition, the physical configuration of the flex tape probe 12 can be
`
`designed accordingly. For example, for the clam shell socket 72, the flex tape probe 12 is designed to be the
`
`same size as the semiconductor package that will be tested in the socket 72. By adjusting the size and/or shape
`
`20
`
`of the leads 22, the flex tape probe 12 not only provides the signals for the semiconductor package but also has
`
`similar dimensions to the semiconductor package.
`
`Referring to Figure 8, a flowchart of the steps for a method for testing a socket on a burn-in board in
`
`accordance with an embodiment of the present invention is illustrated. The method starts with connecting one
`
`or more flex strip probes to a tester at step 80. Inserting one or more flex strip probes into a socket on a burn-
`
`25
`
`in board is preferred at step 82. The leads of the flex strip probe are pressed against the bonding pads of the
`
`socket at step 84. Typically, a fastener is used to press the flex strip probe against the socket. In some
`
`embodiments, the flex strip probe does not need to be pressed to the socket as long as there are solid
`
`connections that provide adequate electrical connectivity between the leads of the flex strip probe and the
`
`bonding pads of the socket. Signals from a tester are supplied to the socket through the flex strip probe at step
`
`30
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`86. In the preferred embodiment, the test signals simulate signals that would be sent to a semiconductor
`
`package in the socket. It is then indicated whether the socket and burn-in board are working in a proper
`
`manner at step 88. An audio and/or a visual audio indication can be provided by the tester. If all of the sockets
`
`on the burn-in board pass the tests, then the semiconductor packages can inserted into the sockets and tested.
`
`If a socket or the burn-in board fails a test, then appropriate action can be taken to correct the problem. For
`
`35
`
`example, the defective socket can be replaced, the burn-in board can be discarded, or the defective socket is
`
`not used.
`
`Testing the sockets on a burn-in board as described above, provides an indication of whether the
`
`sockets, components on the burn-in board and the burn-in board are all working properly.
`
`The present invention can be practiced by employing conventional materials, methodology and
`
`40
`
`equipment. Accordingly, the details of such materials, equipment and methodology are not set forth herein in
`4
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`detail.
`
`In the previous descriptions, numerous specific details are set forth, such as specific materials,
`
`structures, chemicals, processes, etc., in order to provide a thorough understanding of the present invention.
`
`However, it should be recognized that the present invention can be practiced without resorting to the details
`
`specifically set forth. In other instances, well known processing structures have not been described in detail,
`
`5
`
`in order not to unnecessarily obscure the present invention.
`
`Only the preferred embodiment of the present invention and but a few examples of its versatility are
`
`shown and described in the present disclosure. It is to be understood that the present invention is capable of
`
`use in various other combinations and environments and is capable of changes or modifications within the
`
`scope of the inventive concept as expressed herein.
`
`10
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`5
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`WHAT IS CLAIMED IS:
`
`PCT/USOl/20099
`
`1.
`
`A flex strip probe (12) for testing a socket (16) on a circuit board (18), comprising:
`
`a flex strip (20) comprising a plurality of wires (24) with each wire (24) having a connector end and a
`
`lead end;
`
`5
`
`a connector connected to the connector end of the wires (24); and
`
`a lead (22) configured to fit into the socket (16) connected to the lead end of at least one wire (24).
`
`2.
`
`The flex strip probe (12) of claim 1, wherein the at least one lead (22) is a solder ball (22).
`
`3.
`
`The flex strip probe of claim 1, wherein the wires (24) further comprise at least two sets of
`
`10
`
`wires (24) with each set of wires (24) having a set length and at least one wire (24) in each set has a lead (22)
`
`connected to the lead end of at least one wire (24) in each set.
`
`4.
`
`A testing system for testing a socket (16) on a circuit board (18), comprising:
`
`a socket ( 16) on the circuit board;
`
`a flex strip probe (12) further comprising:
`
`15
`
`a flex strip (20) comprising a plurality of wires (24) with each wire (24) having a connector
`
`end and a lead end;
`
`a connector connected to the connector end of the wires (24); and
`
`a lead (22) configured to fit into the socket (16) connected to the lead end of at least one
`
`wire (24); and
`
`20
`
`a tester (14) connected to the flex strip probe (12) through the connector, the tester (14) configured
`
`for supplying test signals to and from the socket (16) through the flex strip probe (12) and indicating if the
`
`socket (16) passes a test.
`
`5.
`
`The test system of claim 4, wherein the circuit board (18) is a burn-in board (18).
`
`25
`
`6.
`
`The test system of claim 4, wherein the socket (16) is a clam socket (72) having a cover (74)
`
`and bonding pads (40), wherein the cover (74) presses the flex strip probe (12) to the socket (72), thereby
`
`providing a connection betWeen the at least one lead to a corresponding bond pad (40) in the socket (72).
`
`7.
`
`The test system of claim 4, further comprises a fastener (74) for pressing the flex strip probe
`
`(12) to the socket (72), thereby providing a connection between the at least one lead to a corresponding bond
`
`30
`
`pad (40) in the socket (72).
`
`6
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`

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`8.
`
`The test system of claim 4, wherein the socket (72) is designed to receive a semiconductor
`
`package and the leads (22) of the flex strip probe (12) are shaped similar to the leads of the semiconductor
`
`package.
`
`5
`
`9.
`
`The test system of claim 8, wherein the leads (22) of the flex strip probe (12) are configured
`
`as solder balls (22) of a ball grid array package (32).
`
`10.
`
`The test system of claim 8, wherein the leads (22) of the flex strip probe (12) are configured
`
`10
`
`as lands of a land grid array package (36).
`
`11.
`
`The test system of claim 4, wherein the tester (14) provides test signals to the socket (16)
`
`through the flex tape probe (12) simulating signals to a semiconductor package.
`
`12.
`
`The test system of claim 4, further comprising a second flex tape probe (12), wherein both
`
`15
`
`flex tape probes are connected to the tester (14) and the socket (16).
`
`13.
`
`A method for testing a socket (16) on a circuit board (18), comprising the step of:
`
`connecting a tester (14) to at least one flex strip probe (12);
`
`connecting the at least one flex strip probe (12) to a socket (16) on a circuit board (18); and
`
`sending test signals to the socket (16) through the at least one test probe (12).
`
`20
`
`14.
`
`The method of claim 13, wherein the test signals simulate signals to a semiconductor
`
`package.
`
`15.
`
`The method of claim 13, further comprising providing a visual indication by the tester (14)
`
`indicating whether the socket (16) is operating properly.
`
`16.
`
`The method of claim 13, further comprising providing an audio indication by the tester (14)
`
`25
`
`indicating whether the socket (16) is operating properly.
`
`17.
`
`The method of claim 13, further comprising pressing the flex strip probe (12) to the socket
`
`(16) using a fastener (74).
`
`7
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`BURN-IN BOARD
`
`18
`
`TESTER
`
`FIG. 1
`
`12
`
`24x
`
`24a
`
`22a
`
`~ tJCr , UCHT' MI(Jr2o
`FIG. 2a
`
`oo ooou~ooo
`
`22x
`
`y
`
`24
`
`12.
`
`["'20
`
`i (
`
`FIG. 2b
`
`

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`I LGA Package r36
`l 0 0 00 \
`
`38a
`
`38f
`
`flGA Package r
`
`32
`
`0000~
`34f
`
`34a
`
`FIG. 3a
`
`FIG. 3b
`
`FIG. 4
`
`12a
`
`16
`
`FIG. 5
`
`

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`PCT/USOl/20099
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`3/4
`
`£::16
`
`~
`
`6 0
`t t
`
`62 64
`
`FIG. 6
`
`12
`
`72
`
`18
`
`SOCKET
`
`BURN-IN BOARD
`
`FIG. 7
`
`

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`CONNECTING THE FLEX
`STRIP PROBE TO A TESTER
`
`r- 80
`
`INSERTING THE FLEX
`STRIP PROBE INTO A
`SOCKET
`
`r--
`
`82
`
`COMPRESSING THE'LEADS
`ON THE FLEX STRIP PROBE
`TO THE BONDING PADS
`OF THE SOCKET
`
`·r---.. 84
`
`SENDING SIGNALS
`SIMULATING A
`SEMICONDUCTOR PACKAGE
`TO THE SOCKET
`
`·r-- 86
`
`INDICATING WHETHER
`THE SOCKET & BURN-IN
`BOARD ARE OPERATING
`ACCORDING TO SPECIFICATIONS
`
`I' 88
`
`FIG. 8
`
`