Test adapter for packaged integrated circuits

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FIELD OF THE INVENTION

This invention generally relates to passive test adapters for connecting leads of a tester to the terminals of a packaged integrated circuit or to the bonding pads of a printed circuit board.

BACKGROUND OF THE INVENTION

There exists a wide variety of test clips, or test adapters, for packaged integrated circuits. Generally, these test clips are constructed to contact the terminals of a packaged integrated circuit which has been mounted on a circuit board. In this way, the integrated circuit may be tested while operating in its intended electrical environment.

Contact pins on the test clips are arranged to match the terminal footprint pattern of the packaged integrated circuit. The test clips must reliably contact each of the terminals of the integrated circuit and be firmly affixed to the integrated circuit during the testing.

Typically, these test clips have a separate set of connectors which are to be connected to a tester. In this way, the test clips act as an interface between the integrated circuit terminals and the tester leads.

These test clips are typically formed of plastic which is injection molded to define the body of the test clip, which includes the spacers used to separate and align the test clip contact pins.

Problems with prior art test clips include the fact that the contact pins on the test clip which contact the terminals of the integrated circuit have a limited minimum pitch due to the limited minimum pitch of the injection molded spacers. Generally, spacers having a pitch of less than 0.5 mm cannot be reliably formed using injection molding. As terminals on packaged integrated circuits are being formed to have smaller and smaller pitches, the present state of the art test clips are inadequate for these finer pitches.

Accordingly, a radical new technique for spacing the contact pins on a test clip is required to meet the needs of the industry.

Another problem with conventional test clips is that they do not securely attach to the integrated circuit package, so that the electrical contact between the test clip and the terminals of the integrated circuit is unreliable. Typically, prior art test clips rely on friction between the test clip contact pins and the terminals of the integrated circuit to maintain a grip on the integrated circuit package.

Accordingly, what is also needed is an improved means for securing a test clip to a packaged integrated circuit.

SUMMARY OF THE INVENTION

A test clip, or test adapter, is provided for connecting leads of a tester to terminals on a packaged integrated circuit. Spacers on the test clip, which act to precisely space the contact pins, are not injection molded as part of the test clip body but are formed separately using a conventional stamping process. Such spacers may be formed to any thickness, which can be accurately controlled to approximately one mil.

Each of the individual spacers is sandwiched between two contact pins to provide precise spacing of the contact pins. A bar is inserted through a hole in each of the spacers and contact pins to form a linear array of contact pins and spacers. Two or four (as appropriate) of the linear arrays of contact pins/spacers are then mounted on a test clip body sized for a specific integrated circuit package. The length of the linear arrays and the thicknesses of the spacers may be different for each size test clip body.

When the test clip is now pressed over an integrated circuit package, the contact pins will be precisely aligned with the terminals of the package.

Forming the linear arrays of contact pins and spacers separate from the test clip body simplifies the assembly process and enables fabricating test clips having customized contact pin spacings without any retooling. For non-standard contact pin spacings, a combination of two or more spacers between adjacent contact pins may be used.

Additionally, each of the spacers may include an L-shaped extension which is urged under the integrated circuit package when the test clip is fitted onto the package so as to firmly secure the test clip to the package without using excessive friction. This also enables the test clip to be removed from the package simply by releasing the spacers from the package and gently lifting off the test clip from the package.

Other features of the invention will be described in detail with respect to the preferred embodiments shown in the drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an isometric view of a standard integrated circuit package mounted on a printed circuit board and a partially cut away view of one embodiment of a test clip for interfacing the terminals of the integrated circuit package with leads of a tester.

FIG. 2 is an isometric view of the test clip of FIG. 1 now secured to the integrated circuit package of FIG. 1.

FIG. 3 is an isometric view of a single spacer used in the structure of FIG. 1.

FIGS. 4a, 4b, and 4c illustrate three configurations of contact pins which are used in the structure of FIG. 1.

FIG. 5 illustrates a portion of the structure of the test clip of FIG. 1 which secures the linear arrays of contact pins and spacers in place with respect to one another.

FIG. 6 is an isometric view of a center assembly of the test clip of FIG. 1 which is to be fitted within the opening of the structure of FIG. 5 to provide structural integrity to the test clip and maintain the relative positions of the various contact pins and spacers.

FIG. 7 is an isometric view of a portion of a push clamp assembly which circumscribes the pins and spacers shown in FIG. 5 and is used to urge the spacers toward the sides of the integrated circuit package to clamp onto the package.

FIG. 8 is a second portion of the push clamp assembly which enables one to manipulate the test clip.

FIG. 9 illustrates a surface mounted integrated circuit package.

FIG. 10 illustrates a second embodiment test adapter which is specifically designed for connection to a certain bonding pad pattern on a printed circuit board.

FIG. 11 is an isometric view of a spacer used in the embodiment of FIG. 10.

FIGS. 12a, 12b, and 12c are isometric views of contact pins for use with the test adapter of FIG. 10.

FIG. 13 is a partially cut away isometric view of another embodiment of a test clip for interfacing the terminals of an integrated circuit package with leads of a tester.

FIG. 14a is an isometric view of the test clip of FIG. 13 positioned over an integrated circuit package prior to the test clip being secured thereto.

FIG. 14b is a close-up side view of the cut away portion of FIG. 14a illustrating the interaction of a spacer with a side of the packaged integrated circuit.

FIG. 15a is an isometric view of the test clip of FIG. 14a now secured to the underlying integrated circuit package.

FIG. 15b is a close-up side view of the cut away portion of FIG. 15a illustrating the interaction of a spacer with a side of the integrated circuit package.

FIG. 16 is a close-up, partially cut away isometric view of a portion of the test clip of FIG. 13 illustrating the clamping mechanism used for pivoting the spacers.

FIG. 17 is an isometric view of the test clip of FIG. 13 without any cut away portions.

FIG. 18 illustrates four separate bars which are used to support the spacers and contact pins in the embodiment of FIG. 13.

FIGS. 19a, 19b, and 19c illustrate three designs of contact pins used in the embodiment of FIG. 13 and supported by the bars shown in FIG. 18.

FIG. 20 illustrates one embodiment of an insulating spacer used in the embodiment of FIG. 13 and supported by the bars in FIG. 18.

FIG. 21 is an exploded view illustrating the various pieces which are used to form the body of the test clip of FIG. 13.

FIG. 22 illustrates the three screws which are used to change the angle of the spacers to clamp onto an integrated circuit package.

FIG. 23 illustrates an insulating spacer used in a surface mounted test adapter whose contact pins are directly soldered onto a printed circuit board.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows a partially cut away embodiment of a test clip 10 which is to be used as an adapter or interface between the pins 12 of an integrated circuit package 14 and a tester (not shown). Integrated circuit package 14 is mounted on a conventional circuit board 15 so as to be connected in its intended electrical operating environment.

A standard female type connector (not shown), leading to the tester, is used to make electrical contact to pins 16 formed around the periphery of test clip 10. Typically, this standard female connector is connected to the tester using a suitable array of wires, such as a ribbon wire. Although only a few of pins 16 on test clip 10 are shown for simplicity, there would be at least the same number of pins 16 as there are pins 12 on the integrated circuit package 14.

Pins 16 are electrically connected, using conductive traces 18 or other suitable conductive means, to metal posts 20 extending from the test clip contact pins (to be described later). Traces 18 are formed on an insulating board 22, which may be made formed of plastic, resin, or any other insulating material. Posts 20 extend through holes formed in board 22.

The area within oval 24, showing spacers and contact pins, is enlarged for clarity.

The detail within oval 24 illustrates an exposed insulating spacer 26, which is preferably formed of plastic. Additional detail of a single spacer 26 is shown in FIG. 3. In one embodiment, the total height of spacer 26 is approximately 10 mm, and spacer 26 has a width at its top portion of approximately 3 mm. The thickness of spacer 26 is totally dependent upon the required separation between adjacent contact pins 30 for a particular integrated circuit package 14.

These spacers 26 are not injection molded as part of the test clip body but are formed by stamping out the spacers 26 from a flat sheet of any thickness. Water cutting may be used instead of stamping. Since the thickness of the flat sheet is easily controlled within one mil, spacers 26 may be formed to have virtually any thickness. In a preferred embodiment, the plastic sheets from which spacers 26 are stamped are manufactured by Argus Corporation and have a melting temperature exceeding approximately 250.degree. C. so that spacers 26 will not melt at soldering temperatures.

Spacer 26 within oval 24 is shown with a ghost outline to illustrate a certain degree of rotational play around axis 28.

Shown abutting spacer 26 within oval 24 is a test clip contact pin 30, which is a unitary piece of conductive metal, such as beryllium copper or phosphor bronze. The beryllium copper may be plated with a layer of nickel and an outer layer of gold to prevent oxidation and to add any selected thickness to the beryllium copper base. In one embodiment, the contact pins 30 are formed by a conventional chemical etch. Each contact pin 30 has a resilient, lower contact portion 30a and an upper body portion 30b which includes post 20.

Within oval 24 is shown three types of contact pins: 30, 30' and 30", which are shown in greater detail in FIGS. 4a, 4b and 4c, respectively. Between each of the contact pins 30, 30' and 30" is an insulating spacer 26 identical to that shown in FIG. 3.

The only difference between the three contact pins 30, 30' and 30" is the position of the top post 20. These different positions of post 20 enable posts 20 to be staggered when they protrude through insulating board 22 in FIG. 1 to provide greater spaces between adjacent posts 20. If crowding of the contact pins 30 were not a problem, each contact pin 30 in the test clip 10 of FIG. 1 may be identical.

Spacers 26 and the various contact pins 30 are retained in position by a dowel 38. Additional details of the internal structure of the test clip 10 will be described later with respect to FIGS. 5 and 6.

A center assembly 42 of test clip 10 provides additional mechanical integrity to the test clip 10 and prevents contact pins 30 from rotating about dowel 38. Center assembly 42 will be described in detail later with respect to FIG. 6. The center assembly 42 is held together in the preferred embodiment using a screw 44.

To now position test clip 10 on integrated circuit package 14, a handle 48 of the test clip 10 is grasped manually, and the test clip 10 is centered over package 14. It is also foreseeable that a machine may manipulate test clip 10 in position by grasping handle 48 or its equivalent.

In the embodiment of FIG. 1, a clamping bar 56 is connected to handle 48 via upper clamping assembly 58. Lifting of handle 48 also lifts clamping bar 56 so that clamping bar 56 does not ride over rounded projections 60 extending from each spacer 26. In one embodiment, similar projections 60 are formed on each of the contact pins 30 as shown in FIGS. 4a-4c. When handle 48 and clamping bar 56 are lifted, as shown in FIG. 1, spacers 26 are rotate away from the center portion of the test clip 10 in the direction of arrow 62. This will allow the spacers 26 to clear the sides of the integrated circuit package 14.

The test clip 10 is then placed over integrated circuit package 14, using an index marker 64 on integrated circuit package 14 to insure that the orientation of the test clip 10 is proper.

Shown in FIG. 2 is the test clip 10 after being positioned on top of integrated circuit package 14 and after upper clamping assembly 58 has been pressed down to cause clamping bar 56 to ride over projections 60 on spacers 26 so as to cause an L-shaped portion 65 of spacers 26 to be inserted underneath the integrated circuit package 14.

Typically, plastic packages are formed to have a top half 66 and a bottom half 67 which are then sandwiched together to encapsulate the silicon chip and wire leads. For ease of manufacturing, the two halves are formed to have bevelled sides such that the completed package has sides which angle inward below where the pins 12 extend from the package. The L-shaped portions 65 of spacers 26 which are urged against these inwardly angled sides of integrated circuit package 14 cause test clip 10 to be firmly clamped to the package 14.

The pressing down of handle 48 and upper clamping assembly 58 also causes clamping bar 56 to ride over projections 60 on contact pins 30 so as to urge the contact pins 30 against the associated integrated circuit package pins 12. This increases the electrical contact between pins 30 and pins 12 as well as more firmly secures test clip 10 to package 14.

When test clip 10 is to be removed from integrated circuit package 14, handle 48 is simply pulled up to disengage clamping bar 56 from the projections 60 on the spacers 26 and contact pins 30 so as to allow test clip 10 to be easily lifted off package 14. In this way, little mechanical stress is imparted to the integrated circuit package 14 when either securing test clip 10 to package 14 or removing test clip 10 from package 14.

The construction of the test clip 10 will be discussed in more detail with respect to FIGS. 5-8.

FIG. 5 illustrates how contact pins 30 and spacers 26 are arranged on dowels 38 and how the three forms of contact pins 30, 30', and 30", shown in greater detail in FIGS. 4a-4c, are arranged so as to stagger the posts 20 to achieve a high density of posts 20 exposed through board 22 (shown in FIG. 1).

As shown in FIG. 5, four separate linear arrays of contact pins 30/spacers 26 are arranged on four dowels 38. A portion of a dowel 38 extends from the ends of each of the arrays. The ends of the dowels 38 are secured within a groove of a plastic retainer 68. Plastic retainer 68 is formed so that two grooves intersect at a 90.degree. angle. In this way, four retainers 68 are required to retain the four sets of linear arrays of contact pins 30/spacers 26 in a rectangle or square shape. Preferably, the grooves in the retainer 68 are such that the round dowels 38 may simply be snapped into place within the grooves and held in place by the resiliency of the plastic retainer 68. Retainer 68 also acts to press contact pins 30 and spacers 26 together so that the separation between adjacent contact pins 30 equals the thickness of the spacer 26 sandwiched therebetween.

The assembly of FIG. 5 can be easily formed to any dimensions, by selecting the appropriate length dowels 38, and with any desired spacing of contact pins 30. Therefore, custom test clip sizes may be easily and quickly assembled.

FIG. 6 is a center assembly 42 of the test clip 10 which coacts with the assembly of FIG. 5 to secure the contact pins 30 in place and to increase the overall mechanical integrity of the test clip 10. The center assembly 42 of FIG. 6 is formed of three separate plastic pieces comprising a base 70, a middle portion 72, and a top plate 74, each of which may be injection molded using conventional means.

Base 70 is positioned inside of the assembly shown in FIG. 5 so that a top surface of the base 70 abuts the shelf portion 75 of the contact pins 30 shown in FIGS. 4a-4c.

Middle portion 72 is then placed within the square opening in the assembly of FIG. 5 so that the perimeter walls of middle portion 72 substantially abut the opposing edges 76 of the contact pins 30 and spacers 26.

Top plate 74 is then positioned on top of middle portion 72 so as to abut against the upper shelf portions 82 of contact pins 30.

The three layer center assembly 42 is then tightly secured together, using a center screw 44 to clamp the top plate 74 and base 70 together onto the opposing shelf portions 82 and 75 of the contact pins 30, so as to prevent contact pins 30 from rotating about dowel 38.

In the embodiment shown in FIG. 6, the middle portion 72 is formed to have grooves 86 for providing a rough alignment and spacing of contact pins 30. The edges 76 of the contact pins 30 are inserted into an associated narrow groove 86. These grooves 86 are not necessary, however, due to the use of spacers 26. Additionally, if the pitches between contact pins 30 are small (e.g., less than 0.5 mm), then injection molding of the narrow grooves 86 would be unduly difficult. Thus, in an alternative embodiment, grooves 86 are not incorporated into the middle portion 72.

In an alternative embodiment, base 70 and middle portion 72 are formed as a unitary member in an injection molding process. This would reduce the cost of the resulting test clip 10 and ease the assembly of the test clip 10. In another embodiment, the middle portion 72 may be deleted altogether.

After the center assembly 42 of FIG. 6 is secured to the contact pin assembly of FIG. 5, a suitable printed circuit board 22, shown in FIG. 1, is then positioned over the posts 20 so that posts 20 extend through holes in board 22. Posts 20 may then be soldered or otherwise electrically connected to traces or other conductors on board 22 which lead to another set of pins 16 for connection to a tester. Board 22 may be any suitable structure, as would be known to one of ordinary skill in the art, which would enable posts 20 to be electrically connected to leads of a tester. It can be easily envisioned how board 22 may be eliminated altogether and a suitable connector may be directly connected to posts 20.

FIG. 7 illustrates clamping bar 56, which connects to upper clamping assembly 58, shown in FIG. 8, by means of a suitable threaded connector 90. As shown in FIG. 1, threaded connector 90 is inserted through four relatively large holes in board 22 so that upper clamping assembly 58 and clamping bar 56 may move up and down relative to board 22 and pins 30. As would be understood, there are many other suitable configurations which would provide a means to raise and lower clamping bar 56 with respect to the projections 60 on the spacers 26 and contact pins 30.

If package 14 were not formed with inwardly angled sides but with flat sides, such as in the case with ceramic packages, then L-shaped portions 65 of spacers 26 would be urged against the flat sides of the package and a secure frictional grip would result.

Test clip 10 may be modified, if desired, to eliminate projections 60 on spacers 26 and on pins 30, and eliminate clamping bar 56. With these modifications to test clip 10, test clip 10 may then be directly pressed onto the top of package 14 so that the contact pins 12 contact the various pins 102. In this embodiment, spacers 26 remain substantially stationary. The resiliency of the metal contact pins 30 enables pins 30 to adapt to relatively large variations in the shape of pins 12.

Accordingly, the structure of test clip 10 and its method of operation have been completely described with respect to FIGS. 1-8. The size of the test clip 10 and the contact pin 30 configuration would, of course, depend on the specific integrated circuit package 14 to be tested.

FIG. 9 illustrates a conventional surface mounted package 100 which is generally designed to lay flat against a surface of a printed circuit board and whose terminals 102 are soldered to flat pads formed on the circuit board. An index marker 110 on package 100 enables the user to properly orient the package 100 on a printed circuit board.

A second embodiment of a test adapter is shown in FIG. 10 as contact pin/spacer assembly 120. Assembly 120 has a contact pin 130 arrangement which corresponds to a bonding pad arrangement on a conventional printed circuit board. The bonding pad arrangement would correspond to a terminal footprint pattern of an integrated circuit package, such as the surface mounted package 100 in FIG. 9, intended to be mounted on the printed circuit board.

The contact pins 130 are soldered (or equivalently connected) to the corresponding bonding pads on the printed circuit board so that the assembly 120 acts as an adapter between the bonding pads and a tester.

A suitable female connector leading to a tester may directly connect to the various posts 110 or, alternatively, a board, such as board 22 in FIG. 1, may be used to interface posts 110 with another type of connector.

The center assembly 126 of assembly 120 may be identical to center assembly 42 described with respect to FIG. 6. This center assembly 126 is designed to simply retain the four linear arrays of contact pins 130 and spacers 132 in their relative positions and to provide mechanical integrity to the resulting structure. A screw 134 is used in the embodiment of FIG. 10 to secure a base 136 to a top plate 138 so as to sandwich an extending portion 140 (see FIGS. 12a-12c) of each contact pin 130 therebetween. This prevents contact pins 130 from rotating and provides additional mechanical integrity to the resulting structure.

In the embodiment shown in FIG. 10, there is no middle portion between base 136 and top plate 138, and both the base 136 and top plate 38 are supported solely by the extending portions 140 of contact pins 130. In an alternative embodiment, a middle portion, similar to middle portion 72 in FIG. 6, may also be used.

Since spacers 132 are not required to latch on to an integrated circuit package, spacers 132 may be formed to have virtually any shape, such as the trapezoidal shape shown in FIG. 11. These spacers 132 may be formed using methods identical to that previously described, where spacers 132 are simply stamped out of a sheet of insulating material, such as plastic. The thickness of spacers 132 may be virtually any thickness and can be reliably controlled down to approximately one mil tolerance. The prior art spacers which are injection molded could not be formed to this tolerance and could not be formed thin enough for many of the high density terminal configurations of state of the art integrated circuits.

FIGS. 12a, 12b, and 12c illustrate three shapes of contact pins 130, which are identified as 130, 130' and 130", respectively.

The portion of pins 130 which is sandwiched between base 136 and top plate 138 is identified in FIG. 12a as portion 140.

As in FIG. 1, a dowel 144 is inserted through the hole formed in the spacers 132 and contact pins 130. The ends of these dowels 144 are secured in a groove formed in a plastic retainer 148, similar to retainer 68 in FIG. 5. The grooves are provided at 90.degree. angles, so that four linear arrays of contact pins 130 and spacers 132 may be secured together in a rectangle or square configuration.

FIG. 13 illustrates a third embodiment of a test clip 200. The primary difference between test clip 200 of FIG. 13 and test clip 10 of FIG. 1 is that test clip 200 uses a clamping screw 204 to raise and lower an inner clamping structure 206a/206b to control the pivoting of spacers 202 about bar 208, while test clip 10 of FIG. 1 uses a handle 48 to raise and lower an outer clamping bar 56 to control the pivoting of spacers 26 about dowel 38. Otherwise, the overall operation of the test clips 10 and 200 are similar in that a movable clamping means is used to control the angle of the spacers, where the spacers are individually formed and supported by a bar.

The embodiment of test clip 200 shown in FIG. 13 has an advantage over test clip 10 shown in FIG. 1 in that a printed circuit board, such as ci