WO2004098802A1

WO2004098802A1 - Automatic semiconductor contacts cleaner

Info

Publication number: WO2004098802A1
Application number: PCT/US2004/010079
Authority: WO
Inventors: Bruce R. O'connor; Tom Toth
Original assignee: Aju Systems Usa, Inc.
Priority date: 2003-04-01
Filing date: 2004-04-01
Publication date: 2004-11-18

Abstract

An apparatus for cleaning debris and detritus from the tips of a planar array of pogo pins 4.

Description

AUTOMATIC SEMICONDUCTOR CONTACTS CLEANER

Field of the Invention

The present invention relates to semiconductor part testing and more particularly to the cleaning of the contactor in order to maintain low resistance contact with the semiconductor leads.

Background of the Invention

In the electronics industry, there is an ever increasing demand for semiconductor parts such as integrated circuit chips, semiconductor devices, transistors, diodes, hybrid circuits, and the like (hereinafter parts), to be produced less expensively and with smaller dimensions. Manufacture of these parts is not perfect electrically or mechanically. Although defects in some families of parts are quite rare, the complexity of the part and the consequence of failure usually dictate that the parts meet a high standard if quality, In other words, every part or, in some cases, at least a sample of the parts must undergo an electrical test. Ordinarily, a very large quantity of identical parts are tested, This testing step can be a significant bottleneck in electronic part manufacture. One way to increase manufacturing productivity of such electronic parts, and thereby reduce the per unit cost, is to increase the speed and accuracy of the testing of the parts.

To improve testing efficiency, an automatic part handler delivers and removes the parts from the electrical test equipment. The electrical test of the parts measures certain electrical characteristics to ascertain the quality of the part. The electrical test is accomplished via testing contactors which engage the leads of the particular part. In some cases, part testing is performed at a temperature other than ambient temperature to further measure certain operating characteristics. To improve efficiency and accuracy, parts are supplied to and removed from the testing contactor(s) by an automatic part handler that often contains a temperature conditioning means.

Significant changes in the parts being tested require higher precision testing components. Testers have become faster to be able to test parts that operate at a higher speed. Tester components have become denser and require smaller interface components to match the increasing number of leads on the parts being tested. The length of tester interface components also has become shorter in length to avoid signal delay through the interface components. The total number of parts tested with one cycle of the tester has also increased. The tester is used to evaluate part performance. The handler is used to place and remove parts automatically to an interface. The interface electrically connects the handler to the tester. The tester interface consists of a board to connect to the tester. The tester board has wires to connect to an array of boards with contactors mounted on printed circuit boards that fit an opening in the handler. The interface is a precision instrument in which all of the signal lines are exactly the same length electrically from the tester contact through the tester printed circuit board, wires, handler side printed circuit boards and contactors. There can be 5000 or more wires in each interface. The wires are high quality co-axial low loss wires for minimal signal loss and low resistance for conducting high frequency signals from the tester. The printed circuit boards are multi-player boards designed to keep signal line lengths equal and prevent cross talk between signals while keeping the line length as short as possible. The contactors are mounted on the printed circuit boards that fit the handler and are matched to the part lead design. Contactors are designed to connect each lead on a part to a wire in the interface. The wire may be for connecting static or dynamic signals to the part. Each contact in the contactor has to have some flexibility in order to maintain the proper force on the part lead without causing the part leads to be deformed.

A significant cost and efficiency consideration for all part testing is alignment between the part to be tested and the testing contactor. Precise alignment is necessary to insure proper electrical contact. As parts evolve into smaller packages with more leads, alignment between the part and the test contactor must be even more precise. The test contactor is made up of a precision body holding gold plated contacts. The contactor can be of many designs, such as 'C shaped, 'Y' shaped, or a 'pogo pin' design. The pogo pin contact usually contains a spring mechanism internally to allow the tips to compress slightly to make up for differences in part lead thickness and still ensure positive contact. The end of the pogo pin that contacts the part lead usually has several points (like a kings' crown) and is referred to as a crown tip pogo pin. The points make good contact with a device lead by virtue of the points and are shorter electrically than a same height 'C or Υ type contactor because a pogo pin is a straight line.

Referring to Figure 1, a major problem with contactors is contamination. The majority of contamination on a contactor comes from the parts that are tested. The leads on a device can be balls of solder or flat leads that have been 'tinned' with solder. The composition and thickness of the tinning affects the gold plated contacts. After thousands of parts have been cycled through the contactors there can be a build up of solder on the contacts. This build up affects the part testing by causing no contact to be made with a part lead or an undesirable resistance which could cause a part to be cataloged as failing or down graded from its desired result. Usually the failing and downgraded parts are retested taking extra time from the tester, handler, and human operators, lowering the efficiency of the testing phase of manufacturing. Previously, when a contactor started to fail parts, the contactor was thrown away. Contactors were considered a throw-away item. They were cheap and easy to make. The contactors that are in use today are considerably more costly. The procedure for cleaning a contactor has been left up to the maintenance group for each manufacturer. Typically the contactors are manually brushed by a brass-fiber brush, but cleaning by hand does not have the precision to control motion. At times the fibers of the brush simply touch the outside of a pogo pin, never cleaning the top or inside of the pogo pin. Additionally, manual cleaning applies inconsistent force against the pogo pin sometimes damaging it. As a result, the yield loss in production may increase because common degradation such as growth of oxide films, pore corrosion can lead to increase in contact resistance and eventual failure of the pogo pin.

Other conventional methods are likewise inefficient and often destructive to the contactor. The precision contacts cannot always take the abuse they are subjected to by maintenance personnel to remove the contamination. The cleaning procedures are also time consuming and boring. This usually means the cleaning is poorly done or only contactors with a high error rate are attended to. Several large semiconductor manufacturing companies have expressed their desire to have a method of cleaning contactors that will remove all the contamination and allow the contactors to work efficiently through their expected lifetime.

From all the above it is clear that a means for cleaning a contactor efficiently, automatically and non-destructively to acquire a longer lifetime for the contactor has long been needed in the art. This invention presents just such a means.

Other advantages and attributes of this invention will be readily discerned upon a reading of the text hereinafter and a viewing of the drawings.

Summary of the Invention

The present invention favorably addresses the above described limitations. The present invention provides an automatic contactor cleaning apparatus that will quickly clean multiple contactors at a time (up to 64). The cleaning system consists of a wheeled cart and a cleaning head. The cart contains a programmable logic controller (PLC) for laterally moving wire cleaning brushes in desired cleaning patterns over an x-y plane, motor controllers responsive to the logic controller for moving the cleaning head along orthogonal axes, e.g. x-axis and y-axis, over the x-y plane, and a vacuum cleaner for removing solder, tin, etc. particles brushed from contactor tips by this invention. The cleaning head includes multiple rows of wire brushes projecting from brush holder bars configured into a brush rack. The brush rack is controlled by two motors that can cause the rack, and therefore the brushes, to move across the x-y plane. A cable connects the PLC and motor drivers to the cleaning head to move the brushes over the contactors in a preselected pattern of motion for a specified period of time to clean the debris from the contactors. The cleaning head is adaptable to different configurations of interfaces and contactor types. The cleaning head has an identification device that is recognized by the PLC and adjusts the software routine to operate the cleaning head properly for the configuration of the interface. The cart can be connected to differently configured cleaning heads without having to reconfigure the software contained on the cart. The vacuum cleaner contained in the cart is for the convenience of the maintenance personal for cleaning any debris from the interface that is left over from the cleaning.

Brief Description of the Drawings

Figure 1 is a diagram illustrating states of a conventional pogo pin which is commonly used as an electrical contactor.

Figure 2 is a diagram illustrating a preferred overlap between a wire brush according to this invention and the conventional pogo pin, for the purpose of cleaning residue from the tips of the pin.

Figure 3 A is a plan view of a wire brush holding rack which is a part of the cleaning head according to this invention.

Figure 3B is a long side view of the rack of Fig. 3 A.

Figure 3C is a detailed view of a portion of Fig. 3 A illustrating screw means for securing the brushes at a desired protrusion length.

Figure 4, is a plan view of a cleaning bed according to this invention in which the cleaning head according to this invention is superimposed upon a planar array of contactor modules for cleaning the contactors of the array, each contactor module consisting of dual spaced and parallel columns of conventional pogo pins with their tips facing the brushes of cleaning head. Certain covers of this invention are made transparent in this view for clarity of understanding.

Figures 5 A and 5B are progressively enlarged views of portions of Fig. 4 to illustrate the relationship between the cleaning head brushes and the contactor modules.

Figure 6 is a detail end view of a contactor module with a pair of cleaning head brushes respectively impinging the tips of the module's pogo pin columns.

Figure 7 is a side view of the cleaning bed of Fig. 4, according to this invention, with the cleaning head superimposed upon the planar array of contactor modules.

Figure 8 is an end view of the cleaning bed of Figs. 4 and 7, according to this invention.

Figures 9 A and 9b are side and open-top plan views of the cleaning bed according to this invention.

Figures 10 and 11 are assembly type drawings illustrating an alternative embodiment that adds another degree of adjustable movement of the test head, movement up and down vertically, to allow program controlled adjustment of the impingement of the brushes on the pogo pins being cleaned.

Figures 12A through 12F are diagrammatical illustrations of both embodiments of this invention presented in level-by-level fashion.

Description of the Preferred Embodiment

As explained above, this invention presents a portable system (can be wheeled around on a cart) for cleaning from the contacts of electrical contactors any build-up of tin, solder are other materials which can accumulate on the tip of a contactor through repeated physical contact with electrical component leads. This invention is especially advantageous for cleaning planar arrays of contactors used in handlers and testers since a great plurality of tips can be cleaned automatically and simultaneously by uniform sweeps across the tips by a set of uniform wire brushes, preferably brass brushes, in any desired pattern of motion, and the degree, i.e. depth, of impingement of the brushes against the tips can be selectively adjusted for optimal cleaning and minimal abrasion.

Referring to Fig. 2, the degree of impingement, i.e., the overlapping distance between a cleaning brush 2, according to this invention, and a contact pin such as a pogo tip 4 can be tightly controlled. Preferably for many applications involving pogo pins, the overlap is 0.3 plus or minus 0.05 millimeters (mm). As can be seen the brush terminus is preferably precisely machined so that all fibers of the brush are of uniform length and uniformly flat, i.e., normal to all sweeping motions of the brush caused by the apparatus of this invention controlling the brush.

Referring to Figures 3A-3C and 6, the brushes 2 of this invention are preferably mounted in respective, and uniformly spaced, sockets 6 defined by a plurality of brush holder bars 8. The bars 8 are joined by links 10 and by cross bars (see 12 in Figure 7) into a coherent brush rack which, as further explained below, can be made to move relatively in x-y fashion with respect to an array of contactors. As shown in Fig. 3B, the brushes can be made to protrude a selected length from their respective bars and held at the selected length by locking means which are illustrated to preferably comprise screws 12, one for each brush, which engage a threaded hole 14, intersecting respectively with each of the brush sockets 6, to bear against their respective brush shanks 16.

Referring to Figure 4, the brush holder bars 8 can be seen to be superimposed on the contactor face of a planar array 18 of contactor modules 20 which are disposed in the cleaning bed of this invention. This is the operational mode of this invention. Each of the contactor modules as illustrated comprise two parallel, uniform columns 23 (Fig. 5B) of contactors. Also illustrated are worm gears, 22 and 24, driven by respective motors, 26 and 28, via respective drive belts, 30 and 32. Preferably these are under the direct control of the aforesaid PLC (not shown) for causing the brush holder bars 8 to be in x-y motion relative to the contactor array. Although not specifically described, the worm gears are directly or indirectly connected to the brush bar holders so that the turnings of the worm gears have a direct and corresponding translational effect on the brushes with respect to their respectively impinged contactor columns 23.

Referring to Figures 5 A, 5B and 6, the preferred disposition of the cleaning brushes 2 with respect to the contactor modules' pin columns 23 are illustrated in more detail. It can be seen that preferably each brush is aligned with a respective column of contactors. If the contactor module array is not as dense, e.g., thirty-two as opposed to the sixty-four illustrated in Fig. 4, this can be accommodated by arranging that some brushes are disposed in spaces between modules and do not interact with a contactor column.

Referring to Figs. 7 and 8, the former is a side view of the cleaning bed of Fig. 4, according to- this invention, is illustrated to show the cleaning head superimposed upon the planar array 18 of contactor modules 20. The latter is an end view of the cleaning bed of Figs. 4 and 7, according to this invention.

Referring to Figures 9A and 9b, illustrated are side and top views of a cart according to this invention which contains the cleaning bed and cleaning head all according to this invention. Fig. 9A illustrates a preferred operators console 34 which includes a display screen, interactive keying devices by which an operator can make the selections described above, and the PCL by which an operator can run various selected algorithms, primarily motion patterns for optimal cleaning. The electronics 39 can be as illustrated. The cart as illustrated is basically a clam shell configuration in which the cleaning head can be rotated up and away from the cleaning bed on hinge 36. Thereafter a user can then carry a planar array of contactors to be cleaned, by a tray having handles 38, and deposit it onto the cleaning bed. The cleaning head is then rotated so that the cleaning brushes are superimposed upon the array to be cleaned, as best illustrated in Fig. 9B. The interior 40 of the cart can be used for storage, and further can include a vacuum device for removing debris from the bottom of the cleaning bed. Preferably the vacuum has three layers of filtration and can filter down to one micron.

It should be noted that instead of an array of contactor modules, a dead-flat calibration plate, with several inherent height adjustments, can be placed in the cleaning bed to calibrate the brushes of all the holder bars to an optimal projection length. During calibration, the brushes are released to freely float and find their respective settling points on the calibration plate. Preferably the calibration plate height adjustments are accomplished by a series of stepped counter-bores within the plate itself which raise or lower the calibration plate as desired.

Preferably each brush 2 is moved in a pattern which optimally cleans its respective column of contactors 23. Also preferably the cleaning head gets its power from the cart so that it need only contain, electronically- wise, the motors and screws for x-y motion in response to the PLC. Also, the preferable motion pattern is a multi-pointed star pattern, like the shape of an "asterisk," which sweeps the tips symmetrically. Also preferably the motion patterns make use of the full area of the brushes' tips to avoid asymmetrical wearing of the brashes.

It should be understood that the PLC can be implemented by means of a microprocessor or micro-controller executing pre-programmed instructions.

This invention in the enhanced, i.e., alternative embodiment, has the added capability of automatically finding the pogo pin height to insure proper pogo pin tip impingement. This is advantageous to the cleaning process since there is a slight variation of pogo pin height with interfaces of the same type. This difference is due to differences in the thicknesses of the multilayered PC boards. Because the cleamng brush/pogo pin impingement is affected by this small difference, there was a need to correct for this difference. In the alternative embodiment, the pre-brushing adjustment of the degree of impingement of the brushes upon the pogo pins is preferably done automatically by the PLC according to rules pre-programmed therein. As soon as the test head is mounted to, i.e., placed over the contact array and a start button is pressed, the pre-operation of the system is to look for the proper brush height to obtain the best cleaning result without damaging the pin. This can be done by means of the PLC consulting one or more pre-installed look-up tables. The automatic calibration is performed with a logic sensor and an AC servo motor.

Referring to Figs. 12A through 12F, this invention has three degrees of brush movement: movement horizontally along mutually orthogonal axes, e.g. an "x axis" and a "y axis," movement that is under the control of the pre-programmed algorithms executed by the PLC during the brushing operation, and a third degree of adjustable movement along a "z axis" that is orthogonal to the other two axes in the vertical. In the first embodiment of this invention, vertical adjustment is done manually by shims 12, but because the spectrum of planar arrays of pogo pins that can be cleaned by this invention project vertically at varying heights, the need to automatically adjust the z-stack height of the brushes is both desirable and preferred. The degrees of movement are achieved by stacking multiple levels, one for each degree. In Fig. 12A a level one planar base plate 70 has affixed to it is motor 28 belt coupled to lead screw 24, and two bearing rods, 72 A and 72B. In the first embodiment, this level one plate is in fixed relation to the pogo pin array under test, except for pre-brushing adjustment. In the level one base plate 74 of the enhanced embodiment it is expanded, as shown in Figs. 10, 11 and 12F to include vertical lead screws 50 powered by motor 54 via belts 56 and 58. In both embodiments the level one plate does not move co-planarly with the pogo pin array.

A level two base plate 76 is shown in Fig. 12B. It is slidingly affixed atop the level one plate and can slide in either direction along an axis of the pogo pin array which is arbitrarily referred to herein as a "y-axis." The level two plate has a centralized rectangular opening 78 to allow the brush bars 8 or 60 access to the pins being cleaned. The level two plate has sufficient clearance along the y-axis to allow to avoid interfering with the cleaning operation. Affixed to it is the motor 26 belt coupled to lead screw 22, and bearing rods, 80A. 80B and 82.

A level three base plate 84 is shown in Fig. 12C. It is slidingly affixed atop the level two plate and can slide in either direction along an axis of the pogo pin array which is arbitrarily referred to herein as a "x-axis." The level three plate has a centralized rectangular opening 86 to allow the brash bars 8 or 60 access to the pins being cleaned. The level three plate has sufficient clearance along both the y-axis and the x-axis to allow to avoid interfering with the cleaning operation. Affixed to it are the brush bars 8 or 60 for the enhanced embodiment.

Fig. 12D shows the assembly of the levels one and two plates, and the bearings 88 by which the level two plate slides in relation to the level one plate. Fig. 12E shows the assembly of the levels one, two and three plates, and the bearings 88 by which the level two plate slides in relation to the level one plate, and by which the level three plate slides in relation to the level two plate.

Claims

1. 1. An apparatus for cleaning debris and detritus from the tips of a planar array of pogo pins comprising:

(a) a planar array of brass brashes for impinging the pogo pin array sufficiently to brashing clean the pin tips;

(b) a mechanism having three degrees of movement:

(1) one for adjusting the degree of impingement, and

(2) two mutually orthogonal degrees for motion parallel to the pin array; and

(c) a processor operatively coupled to the mechanism for automatically cleaning the pins.