Brevet US5415560 - Test clip for IC device

1 2

FIG. 4 is a side elevation view of the base of the test

TEST CLIP FOR IC DEVICE clip of FIG. 1, showing it approaching an IC device.

FIG. 5 is an enlarged sectional view of a portion of

BACKGROUND OF THE INVENTION the base of FIG. 4, showing it engaging the IC device.

„ ^ r , T„ /• ' , ■ , • -5 FIG. 6 is a bottom view of the test clip of FIG. 2.

One type of modern IC (integrated circuit) device is _T„ _. Ijj- r

, iT. .v . , , '. , ^ . FIG. 7 is an exploded isometric view of the base of

a SOP (small outlme package) which has a dielectric ^ . ,. J <• m. i_ * -4.1.

, , >, .. ./ j' .. , , the test clip of FIG. 1, and of one of the arms, but with

body with opposite sides and opposite ends, and a row . , r, ... ,

, . *1 ,„ out the headers and flexible circuit board,

of leads projected from each of its sides. There are some FIQ g is m loded ... ^ of Qne ^ of

standard lead pitches such as 0.025 inch between the w the test clip ofFIG. 7, showing the manner of its assem

centers of adjacent leads. However, there are a large bjy

number of different IC device lengths with correspond- FIG 9 is a partial plan yiew of ^ flat flexible caWe

ing numbers of leads, ranging from 8 to 64 leads per Qf pjQ j side. A different test clip is required for each of such IC

devices, and each test clip must be capable of being 15 DESCRIPTION OF THE PREFERRED

accurately aligned and locked to an IC device. EMBODIMENTS

Due to the wide range of body lengths (and even FIG. 1 illustrates a test clip 10 for connecting to the

widths) of SOP devices, it would be desirable if the leads 12 of an IC (integrated circuit) device 14. The IC

most complicated parts of the test clips, particularly device 14 is a SOP (small outline package) type wherein

those parts that position and retain the contacts, could 20 its leads are arranged in two rows 16,18 at the opposite

be used in IC devices of different lengths. Where the sides 20,22 of the insulative body 24 of the device. The

contacts lie on a pivoting arm, a low cost means would opposite ends 30, 32 of the body are free of leads,

be desirable for connecting the moving contacts to a The test clip 10 includes a frame 40 and multiple

header on the test clip. A test clip which reliably contacts 42 for engaging the leads of the IC device. The

aligned and locked to an IC device of the SOP type, 25 frame includes a base 44 and two arms 46, 48 that are

which could be changed to test IC devices of different each pivotally mounted on the base about a correspond

sizes at rninimal cost and with minimal time delay, and ing pivot axis 51,53. A band 50 surrounds the arms and

which simplified connection of the contacts to a header base to hold them together while allowing the arms to

of the test clip, would be of value. pivot on the base. The contacts 42 are arranged in two

30 rows that are each mounted on a corresponding arm.

SUMMARY OF THE INVENTION The contacts have upper ends 52 that are joined to

In accordance with one embodiment of the present conductors 54 of flexible cables 60, 62. The upper ends

invention, a test clip is described for connection to an of the cables are joined to headers 64,66, with the cable

IC device of the SOP type, that assures precise position- conductors of the cables connected to corresponding

ing of the clip with respect to the leads of the IC device, 35 terminals such as pins 70 (sockets can be used instead) of

minimizes the cost and time for constructing test clips the headers- The headers form connectors that can mate

for IC devices of different sizes, and simplifies the con- wlth corresponding connectors 68 (FIG. 2) that extend

nection of the contacts to a header on the test clip. The to test mstruments. .. - , .. .

„i;„: I„jm „ u„„~ „,;*t, „ A~„, ,~-au, As shown m FIG. 3, the base 44 of the test chp frame

test cup mcludes a base with a downwardly-opening ,„ . , TM ^_ ^ J- ,

.. K ■ ■, j j ... 11 r , , 40 has a lower end that forms a cavity 80 that faces downcavity havmg side and end cavity walls for closely ,, . ,. .. _ TM / , .,

.j ■ ... \ . , , e .,J wardly, in the direction D. The frame has cavity side

positioning the test clip with respect to the body of the „ >' g. , .. ,. om,Qsite sjde, 2fl 22 of

IC device^ Opposite cavity side walls he adjacent to the ^ &^ M ^ a at ^ Qne

upper parts of the body sides while opposite end cavity side ^ ^ a fe he ... of

walls he m interference fit with the opposite body ends, 45 ^ body each haye ^ lower ^ S6 ^ witfa

at least dunng installation the leads 16 projecting from near the intersection of the

Each test clip frame includes a base that forms the ^ ,ower ^ md lowef m

cavity and a pair of arms pivotally mounted on the base each te d in ite directionS; as a result of the

with each arm holding a row of contacts. To accommo- body moldmg process During molding of the body ^

date IC devices of different lengths, different base are 50 upper ^ lower mold parts respectively form the upper

used, but the same arms are used with some contacts or ^ lower body partS; with a draft (^peT^ being re.

contact positions not being used. A flat flexible cable quired in each mold part to enable release of the body

has a lower end connected to the tops of the contacts, from the moid Tne cavity sjde waus 82j 84 lie adjacent

with the upper end of the cable connected to the termi- t0 the upper parts 86 of the sjde waus to provide moder

nals of a header that is mounted on the base. 55 ateiy accurate alignment in a lateral or sideward direc

BRIEF DESCRIPTION OF THE DRAWINGS tio* ^ wi* resPe<* ^the IC devfe

When the arms 46,48 are pivoted to move the contact

FIG. 1 is an isometric view of a test clip of the present iower ends 90 against the leads 16, the test clip will be

invention, with the lower ends of the arms pivoted located precisely enough to assure that all contact

together towards an IC-engaging position, and showing 60 lower ends engage corresponding leads. Applicant pre

the test clip approaching an IC device. fers to use spring 92 (FIG.2) that urges the arms to pivot

FIG. 2 is a front view of the test clip of FIG. 1, with so their lower ends move toward the IC device. The

the arms pivoted partially towards an IC-engaging posi- opposite ends of each arm have body-engaging surfaces

tion, with the left half of the figure being a sectional 94, 96 that engage the body to limit arm pivoting,

view and the right half being an elevation view. 65 FIG. 4 shows that the cavity has a pair of opposite

FIG. 3 is a sectional view of a portion of the test clip cavity end walls 100, 102 that are designed to engage

of FIG. 2, showing the arms in their lead-engaging opposite ends 30, 32 of the IC device body. Each body

position. end has upper and lower portions 104,106 that are each

tapered as shown, for the same reasons that the opposite sides are tapered. When a person moves the test clip towards the IC device 14, the test clip is positioned so the cavity side and end walls are approximately aligned with the sides and ends of the body of the IC device. 5 The test clip can be moved horizontally in the lateral directions X and in longitudinal directions Y until the person senses that the test clip is vertically aligned with the IC device body. The person then presses down the IC device to approximately its final position. Prior to 10 installing the test clip, the person presses against name plates 110, 112 (FIG. 2) on the opposite arms to pivot them against the force of the spring 92 to keep the lower ends of the contacts out of the way during installation of the clip. After the clip has been fully lowered, the name 15 plates on the arms are released to allow the spring force to pivot the arms so that the contact lower arms engage the leads of the IC device.

FIG. 5 shows the manner in which each cavity end wall such as 100 engages a corresponding end such as 30 20 of the IC device body 24. The cavity end wall 100 tends to assume the position 100A prior to encountering the body 24. As the end wall encounters the body, the end wall is longitudinally deflected as it slides downwardly along the upper portion 104 of the body end, until it 25 reaches the intersection of the upper and lower parts 104,106. In its lowermost position, shown in solid lines in FIG. 5, a lower body end-engaging surface 120 of the cavity end wall engages the lower part 106 of the body end in an interference fit, so that the opposite cavity end 30 walls press against the lower parts of the body ends. Such interference results in the test clip being securely held or locked on the IC device, so the test clip does not fall off and can be removed only by applying a moderate upward force to it. 35

As mentioned above, the lower part 106 of the body ends are tapered to enable them to be removed from an injection mold. A common mold taper angle is about 7 degrees. Applicant prefers to taper the lower surface 120 of the cavity end wall 100 at an angle A of about 7 40 degrees. A moderate interference fit is desirable so that it requires a vertical force of about 3 pounds (1.5 kg.) to install or remove the test clip from the IC device. With a coefficient of friction of the cavity wall surface 120 against the body end of about 0.3, this results in the need 45 for sufficient interference fit that the cavity end wall surface 120 presses with a force of about 9 pounds (4 kg.) against the body end. This is achieved with an interference B at each end of about 0.1 mm and a total interference of about 0.2 mm (0.1 mm to 0.4 mm) where 50 the base is formed of an engineering plastic having a Young's modulus of elasticity of about 300,000 psi. It is desirable that the body end-engaging surfaces 120 resiliently separate by about 0.2 mm when a separating force of about 4 kg. (between 1 kg. and 8 kg.) is applied. 55 Suitable material for the base is polyetherimid (ULTEM), or a liquid crystal polymer material (VECTRA). Applicant forms the cavity end wall 100 with a thinned location 124 at its upper end to facilitate bending of the cavity end wall. It can be seen that the length 60 of the end wall below the location 124 is at least 4 times as great as the thickness at 124.

The cavity side and end walls are fixed to each other and to the rest of the stationary portion of the frame. As a result, no pivoting or sliding elements are used to 65 move the cavity end walls 100, 102 against and away from the body ends. This not only simplifies construction and use of the test clip, but results in more precise

locating of the cavity end walls. It is noted that the end walls do not "hook" under the bottom 126 of the IC device body. Such hooking could damage the IC device when the test clip was removed. Instead, the cavity walls are moved to their final position, and later removed, merely by pressing down, and later lifting up the test clip (with the arms preferably pivoted apart before moving down the test clip).

FIG. 8 shows some details of the arm 46 and of the contacts 42. The arm includes a main housing part 130 which has a row of closely space barriers 132, with each contact 42 received between a pair of barriers. A cover 134 covers the upper portions of the contacts to protect them and keep them in place, while leaving the lower ends 90 of the contacts exposed on one side. The cover has tabs 136 that lock it in place on the main housing part, with the upper ends 140 of the contacts projecting above the main housing part and cover. The main housing part 130 and cover 134 are relatively complex devices which are difficult to machine or to fabricate injection mold dies to make them. The base 44 shown in FIG. 7 is less expensive to machine or to make a die for injection molding. As discussed below, applicant is able to use the same arms for different size test clips.

FIG. 7 shows the manner in which the arm 46 is pivotally mounted on one side of the base 44. The base 44 has a pivot bar 150 formed thereon, which receives a pivot recess 152 formed by four sets of projections 154, 155. The arm also has a pair of tabs 156, 158 that are designed to abut opposite ends 160,162 of the pivot bar.

As discussed earlier, SOP types of IC devices are available in a wide range of lengths with corresponding different numbers of leads, although there are only a limited number of commonly used lead pitches or spacings. FIG. 4 indicates, in phantom lines, another IC device 14A with an additional lead on each side. Although FIG. 7 shows one base 44 with a cavity 80 of predetermined width and length (as measured respectively between the side and end walls), applicant can make a different base indicated at 44A which has a longer cavity 80A. However, the second base 44A has a pivot bar 150 of the same dimensions and length as the pivot bar for the first base 44. As a result, the same arms such as 46 can be mounted on the second base 44A.

The arm 46 is made so the number of contacts 42 is equal to the number of leads on a side of that IC device having the largest number of leads. For IC devices having fewer leads, those contacts 42 near one or both ends of the arm are not utilized. In FIG. 1, three header terminals 70 are missing in each row (two at one end and one at the other end) and six contacts will not be present or used in each header. As a result, the same arms 46 (FIG. 7) can be used for test clips constructed to test IC devices having a range of leads, so long as the leads of all of the IC devices of the group have the same lead pitch (center-to-center spacing). Even the width of the cavity 80 can be varied from one base 44 to another. It is noted that only the lower portions of the different bases 44 vary from one another. The use of the same arms but different bases, enables applicant to more rapidly provide a limited number of new test clips for a new IC device that differs from previous ones. The new IC device may differ by having a different number of leads, or by having a different spacing between each endmost lead and an end of the body, or by having a different width. Such new test clip only requires machining of another base such as 44.

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Brevets

Test clip for IC device