Methods And Apparatus For Identifying Nonmagnetic Articles

Abstract

Selected nonmagnetic semiconductor devices in an array of such devices are identified for subsequent processing by coating them with a material containing magnetizable particles. The devices are then tested to select those having the desired electrical characteristics. The selected devices in the array are contacted by the tip of a tubular marking stylus. A magnetic flux is concentrated at the tip and ink flows through stylus so that contact between the tip and article simultaneously magnetically and visibly marks the devices. Magnetic identification permits automatic sorting and removal of the selected devices from the array and the visible marking permits original set up of the array and subsequent verification of the sorting operation.

Description

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to methods and apparatus for identifying nonmagnetic articles. More particularly, it relates to identifying both magnetically and visibly selected semiconductor devices in an array.

2. Description of the Prior Art

In the manufacture of semiconductor devices, such as diodes, transistors, integrated circuits and the like, the devices are formed, including their beam leads, in and on one side of a wafer or slice of semiconductor material. The slice is subsequently adhered with wax to a ceramic or similar support, its active side containing the leads being against the wax. The slice is divided into an array of individual devices or chips by etching the slice from the exposed side to remove the semiconductor material along grid lines directly above the leads. The width of the grid lines is such that a portion of each lead is exposed and a portion remains covered and attached to the semiconductor material. The beam leads provide the connection from the device elements, e.g., transistor base, emitter or collector to the circuit conductors. The exposed portion of the leads may be contacted to measure the electrical characteristics of the devices. For further information concerning the manufacture of these devices refer to S. S. Hause and R. A. Whitner "Manufacturing Beam-Lead, Sealed-Junction Monolithic Integrated Circuits," The Western Electric Engineer, Vol. XI, No. 4 (Dec. 1967) pp. 3-15

It has been found that a certain percentage of the devices will not meet one or more of the requirements for which they are designed. Accordingly, the device leads are contacted by a test probe and the characteristics measured to determine whether or not they fall within design requirements, i.e., specifications. Where characteristics do fall within the specification, such devices are identified for later removal from among the devices in the array. The original orientation of the good devices is maintained while they are removed and positioned to form a new array of all good devices.

Where the devices are not to be positioned in another array of all good devices and, therefore, the orientation need not be maintained, the devices failing specifications (or those passing specifications) may be marked with magnetic ink in accordance with the test results, removed from the support, and the good separated from the bad magnetically. Methods and apparatus for such marking and sorting of devices are disclosed in U.S. Pat. Nos. 3,474,904; 3,507,389; 3,572,400; and 3,623,603 which issued to B. G. Casner et al. Oct. 28, 1969; Apr. 21, 1970; Mar. 23, 1971 and Nov. 30, 1971, respectively, and are assigned to the same assignee as the present application.

In general, these methods separate the magnetically marked devices from the others by passing all of them adjacent to a magnet which attracts the magnetically marked devices to it. However, where device orientation must be maintained, such methods cannot be used.

In other cases, e.g., the canning art, cans are magnetized in bands (which may be of varying magnetic fields) to identify known contents for subsequent labeling. But the cans are cylindrical and must be revolved to magnetize the cans around their entire circumference, or if marked in one spot they must be revolved to find the spot, in order to facilitate detection and sorting for labeling. Such a system is not suitable for identifying individual semiconductor devices both because of the disparity in size between cans and semiconductor devices (a semiconductor device may be only 0.020 by 0.020 by 0.002 inches in each dimension), and because semiconductors must remain oriented for testing and positioning in a new array.

Still other art, e.g., magnetic parts sorting, in which parts must be capable of becoming magnetized are carried passed a magnetizing head, magnetized, and then the degree of magnetization measured. The parts are then sorted on the basis of sufficient magnetization. Such methods or apparatus do not provide for magnetically marking selected parts nor maintaining their orientation. Again, the disparity in size between semiconductor devices and the parts found in the magnetic sorting art renders the methods and apparatus thereof unadaptable to the semiconductor devices.

Where the articles are nonmagnetic, they may be made magnetic as disclosed in U.S. Pat. No. 3,692,168 which issued to H. E. Hughes et al. Sept. 19, 1972. However, the magnetic coating disclosed herein is preferred for use with the instant invention.

In contradistinction to the prior art, the instant invention relates to methods and apparatus for identifying semiconductor devices, having unknown characteristics, according to test results while the devices are in close array and in a manner which will not disturb their orientation.

SUMMARY OF THE INVENTION

Accordingly, an object of the invention resides in providing new and improved methods and apparatus for identifying nonmagnetic articles.

With this and other objects in view, the present invention contemplates new and improved methods of identifying nonmagnetic articles which includes coating the articles with a material which will retain a magnetic flux when magnetized and testing the articles individually to determine which articles are to be identified. Then, the individual articles to be identified are contacted with a tip of a marking member, having magnetic flux concentrated at the tip thereof, to magnetize the material and identify the articles in accordance with the test.

The present invention also contemplates new and improved appartus for identifying nonmagnetic articles having coatings of a material which will retain a magnetic flux when magnetized. The apparatus includes facilitates for testing the articles while in the array to determine the characteristics thereof and also includes provisions for both inducing a magnetic field in the coating and for visibly marking the articles to insure the identification thereof.

The invention contemplates, among other things, coating the inactive surfaces of semiconductor device while the devices are still in array and adhered to a wafer support, with a magnetizable material such as a phenolic base containing iron oxide or the like. The devices are tested to determined which ones have desired electrical characteristics so that they may be identified.

Identification is made by concentrating a magnetic flux at the tip of a magnetizing member, which is small enough to fall within the perimeter of the device, and contacting the iron oxide coating to magnetize it. Further, the magnetizing member is tubular and conducts a marking fluid to the coating so that the devices are simultaneously magnetically and visibly marked to distinguish the devices having desired characteristics from those which do not.

The wafer support with the devices is removed from the test set and the array transferred undisturbed to a new support from which the devices may be removed with a vacuum pickup. The new support is positioned in a sorting apparatus having a magnetic sensor which detects the magnetic-field of those marked or identified devices those coating has been magnetized. The apparatus automatically removes the identified devices and positions them in a new array which can be instantaneously verified visually for completeness of devices having the desired characteristics. This verification is important where the devices are automatically assembled because a missing device, or an unmarked device transferred erroneously to the array, will produce a defective assembly.

Since the devices have a magnetic coating, they may be arrayed on a magnetic carrier and will remain as placed while being transferred.

BRIEF DESCRIPTION OF DRAWINGS

Other objects and features of the invention will be more readily understood from the following detailed description of the specific embodiments thereof, when read in conjunction with the accompanying drawings in which:

FIG. 1 is a plan view of an interdigitated array of semiconductor devices;

FIG. 2 is an isometric view of one of the devices of the array of FIG. 1;

FIG. 3 is an enlarged plan view of a portion of FIG. 1 enclosed by dashed lines showing interdigitation;

FIG. 4 is a partial cross section along line 4--4 of FIG. 1 with magnetic material applied to the devices;

FIG. 5 is an enlarged plan view of a semiconductor device with test probes contacting its leads;

FIG. 6 is a plan view of test table and probes arranged to contact a device;

FIG. 7 is a front elevation of the apparatus of FIG. 6 with some of the probes removed;

FIG. 8 is an isometric view of a stylus for marking devices in accordance with the present invention;

FIG. 9 is a isometric view of a silicon resin coated carrier having part of an array of devices thereon;

FIG. 10 is a plan view of sorting apparatus;

FIG. 11 is a front elevation of the apparatus of FIG. 10; and

FIG. 12 is a schematic electrical diagram of a circuit for sensing identified devices.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring now to FIG. 1, an array 20 of interdigitated beam-lead semiconductor devices 22 are contained in a slice of semiconductor material and are shown adhered to a support 24. The devices 22 are very small, refer to FIG. 2, the body 26 being about 0.020 of an inch on a side and 0.002 of an inch thick in this example. The beam leads 28 are about 0.004 of an inch wide, 0.008 of an inch long and 0.007 of an inch thick and interdigitated as shown in the enlarged view, FIG. 3.

To adhere the devices 22 to the support 24, refer to FIG. 4, a cement is used, such as wax 30, which may be of the type sold by the Biwax Corporation under the trade designation B-7050 wax. The wax 30 is filtered to remove all particles over 0.2 of a mil in diameter. The support 24 may be a material such as ceramic, glass or sapphire.

The slice, sometimes called a wafer, of semiconductor material containing all the devices 22 is adhered to the support 24 with the leads 28 against the support. The slice is etched into the array 20 of separate devices 22, while still on the support 24, by photolithographic and etching processes well known in the art. These processes expose a portion of the beam leads 28, as shown in FIG. 3 and 4, which may be contacted by suitable probes to measure the electrical characteristics of the devices 22 while they are still adhered to the support 24 with the wax 30.

Coating The Article

The bodies 26 of the devices 22 are coated with a magnetically hard material 32, i.e., one which will retain a magnetic flux after the magnetizing field is removed. It is desirable that the material 32 not stress the devices 22 mechanically and for this reason an organic material containing iron oxide particles is preferred.

The material 32 may be that sold by the Markem Corporation under the trade designation 7252-H-6A. This is a phenolic base with a fast solvent system to retard vehicle separation. Total solids range from 70 to 85 percent by weight solvents from 15 to 30 percent, the iron oxide particles from 35 to 50 percent, and viscosity from (0.2 to 5) .times.10.sup.6 centipoises

The material 32 may be "silk" screened on the bodies 26 using stainless steel mesh-emulsion, stainless steel-nickel or a molybdenum sheet screen. The latter is necessary where the devices 22 are smaller than 30 mils square. For additional mask information refer to R. W. Berry, P. M. Hall, and M. T. Harris Thin Film Technology, Princeton, New Jersey: D. VanNostrand Company, Inc., pages 462-466.

A screen having a pattern which exposes the bodies 26 of the devices 22 is aligned and placed in contact with the bodies. Magnetic coating material 32 is then squeegeed through the screen onto the bodies 26 of the devices 22 but not the leads 28. The screen is then removed and the material 32 cured to provide a magnetically hard coating. Typically, the curing is carried out in two steps: first, at 75.degree.C for one hour before testing to dry the material without disturbing the wax and, second, at 110.degree.C for one hour before sorting.

Testing the Articles

The support 24 containing the coated devices 22 is mounted on the indexing table 33 of a probe tester, designated generally by the numeral 34. The probe tester 34 may be that disclosed in the article, J. J. Egan, M. E. Kimmel and W. R. Wanesky, "Probe Tester for Beam Lead Devices" technical digest, No. 21, Western Electric Co. Inc. (Jan. 1971) pages 9 and 10, or that sold by Electroglas, Inc., Menlo Park, California under the trade designations Model 901, 902 or 910.

Leads 28, refer to FIG. 5, are contacted by probes 36 which are connected to a test set (not shown) for measuring the characteristics of the devices 22. The probes 36, refer to FIGS. 6 and 7, are supported by probe heads 38 which may be positioned anywhere around a support ring 40 and adjusted so that the points of the probes 36 just make good electrical contact with the leads 28. As many probe heads 38 with probes 36, as are required to provide a contact for each lead 28 involved in the test, are positioned at appropriate places on the ring 40.

The support 24 is held on the table 33 by a vacuum supplied through a valve 42 and manifold 44 and the rows of devices 22 are aligned with the X and Y directions of movement of the table 33. The probes 36 are lifted clear of the devices 22 to permit indexing the devices 22 into position beneath the probes by actuating an air cylinder 46 to raise the support ring 40 which pivots about pins 47. The indexing of the devices 22 and raising of the support ring are controlled by the test set (not shown) and are done automatically when the test has been completed on each device 22.

Marking Stylus and Identifying the Articles

Further, after the test has been completed but before the devices 22 is indexed, the test set actuates a marking head 48, such as that sold by Electroglas, Inc., under the trade designation Model 395 Automatic Inker. A marking member or marking stylus 50 is inserted into a spring holding member 52 fastened to the head 48 at the bottom by screws 54. Upon a signal from the test set, the member 52 is moved outward at the top by a solenoid in the head 48. This movement rotates the spring member 52 clockwise and, as a result, moves a tip 56 of the stylus 50 downward into contact with a device 22.

Referring now to FIG. 8, a tubular member 58 extends from a base 60 of the marking stylus 50. The base 60 contains a reservoir 62 for nonmagnetic marking fluid, such as white, water-soluble ink sold by the Carter Corporation under the trade designation No. 443. The tubular member 58 may be stainless steel tubing, preferably nonmagnetic, and is joined by a transition member 64, which curves from the horizontal to the vertical. The transition member 64, may be magnetic stainless steel tubing having an inside diameter or bore of 0.010 of an inch and an outside diameter of 0.020 of an inch. However, an opening 65 at the tip 56 is smaller than the bore of the transition member 64 and may be about 0.007 of an inch in diameter. This constriction prevents excess marking fluid from flowing from the end of the stylus 50 and, thus, controls the flow of marking fluid.

The stylus 50 not only marks with a visible fluid but also induces a magnetic field in the permanently magnetizable material 32 on the devices 22 by virtue of a permanent magnet 66 which bridges the curve of transition member 64. Although a permanent magnet is preferred for reasons of convenience and small size, a more bulky electromagnet could be wound around the vertical portion of the transition member 64 when space permits, and the same signal which actuates the solenoid in the head 48 could be passed through the electromagnet to magnetize the devices 22. In either case, permanent or electromagnet, the devices 22 are selected by the test set in accordance with predetermined desired characteristics and the coating of magnetic material 32 of each selected device is simultaneously, visibly and magnetically marked to identify the devices.

The simultaneous dual marking of devices having desired characteristics provides decided advantages. The magnetic marking permits electronic sensing of any marked device in an array. This, in thurn, permits the selection and sorting to be done without human guidance and the automatic formation of a new array of devices all of which have the desired characteristics. The visible marking speeds setup and sorting of the array of mixed devices and permits a quick and easy inspection of the new array to make sure it is complete and consists of nothing but desired-characteristic devices.

The setup and sorting of the array of mixed devices are speeded because the edge rows, which may contain no devices having the desired characteristics, may be skipped. That is, the sorting apparatus may be started on the first row containing a device having the desired characteristic. Thus, the apparatus will traverse fewer rows to sort the devices.

If there is no interruption in the pattern of visible marks in the new array, it has been completed satisfactorily and all devices have the desired characteristics. However, if there is an interruption, i.e., one mark missing from the pattern of marks, it is immediately noticeable and it is known that a device is missing or an unmarked device has been inadvertently transferred to the array. In either case the fault may be corrected.

Sensing and Sorting Out the Identified Devices

The support 24 with its array 20 of identified devices 22 is treated in accordance with U.S. Pat. No. 3,690,984 issued to W. R. Wanesky, Sept. 12, 1972, the subject matter of which is incorporated herein by reference. In this regard, the steps which are of interest, refer to FIG. 9, relate to the transfer of the array 20 of devices 22 (Wanesky's devices 10) from a support 24 (Wanesky's mounting disc 14) to a silicone resin coated carrier 68 (Wanesky's disc 36). These steps transfer the devices 22 in an oriented array to a support from which devices may be removed with a vacuum pickup and without the use of heat or a solvent. This, in turn, permits the devices having desired characteristics to be placed on still another support which will then have an ordered array of nothing but the desired devices. Accordingly, the entire array 20 of devices 22 is transferred to the carrier 68, which is coated with a pressure-sensitive holding material 70 such as the silicone resin sold by the Dow Corning Corporation under the trade designation "Sylgard 182, " for subsequent removal of those devices 22 which have been identified as having the desired characteristics.

The coated carrier 68 with the array 20 is placed on a table 71 of an input positioning fixture 72, refer to FIGS. 10 and 11, of a sorting apparatus designated generally by the numeral 74. The input positioning fixture 72 and an output positioning fixture 76, having a table 77, are mounted on a base 78. The X-Y movement of these fixtures is provided by means of stepping motors (not shown) which drive the shafts 80 of the fixtures. The positioning fixtures 72 and 76 are commercial items, such as may be obtained from Automation Gages, Inc., and are under control of the apparatus 74. A microscope 82, only the objective of which is shown in FIG. 11, permits the operator to view the devices 22 for aligning the array 20 with the X-Y movement of the fixture 72, setting the starting point and checking the operation of the apparatus 74.

A transfer mechanism 84 is located between the positioning fixtures 72 and 74. Two identical arms 86, one having a pickup tip 87 and the other a magnetic field detector 100 at the extremity, are pivoted in a yoke 88 of the transfer mechanism 84. The arms 86 are raised or lowered by lobes 90 and 91 on cams 92 and 93, respectively. The cam 93 is rotated by a pickup motor 94 and the cam 92 is rotated by a detector motor 95. The motors 94 and 95 are stepping motors supported by the yoke 88. The motors rotate by stepping in small increments and may be stopped at any point desired in their rotation. A flexible vacuum connection (not shown) is made to a tube 96 which leads to the vacuum tip 87.

The detector 100 may be of the type sold by Western Magnetics, Inc., of Glendale, California under the trade designation Magnistor, or it may be a tape recorder pickup. However, the Magnistor is preferred because no relative motion is required between the pickup and magnetic field. The field can be detected while the device 22 is stationary. The tip of the detector 100 is positioned about 0.002 of an inch above the surface of the coating of magnetic material 32 on the devices 22 for detection but is lifted about 0.015 of an inch during index.

The yoke 88 is fixed to a vertical shaft 102 which is mounted in bearings 104. The shaft 102 is rotated 180.degree. clockwise or counterclockwise by means of a rack 106 and pinion 108. Friction material 110 is fixed to a friction disc 112 which, in turn, is fastened to the shaft 102. The pinion 108 is urged against the friction disc 112 by a spring 114. The rack 106 is connected, by a link 116, to a crank disc 118 which is rotated 180.degree. for each revolution of a single revolutionary clutch and motor (not shown). Thus, the rack 106 is driven forward by one revolution of the clutch and pulled back by the next revolution.

The stroke of the rack 106 is slightly greater than that which is needed to rotate the pinion 108 through 180.degree.. An ear 120 is provided on the yoke 88 while stop screws 122 are provided on the transfer mechanism 84. The stop screws 122 and the ear 120 permit stopping the yoke 88 at precisely the same point each time at the end of 180.degree. of rotation, while the friction drive permits a slight amount of overtravel of the rack 106 to insure that at least 180.degree. of rotation of the pinion 108 and yoke 88 will occur.

In operation, the coated carrier 68 (FIGS. 10 and 11) with the array 20 of devices 22 is placed on the table 71, rotated and aligned using the microscope 82, and moved in the X-Y directions to set the starting point such that indexing will carry the first row (having a marked device such as 22a) of devices 22 beneath the detector 100. Another coated carrier 68, or uncoated, magnetized equivalent thereof, is placed on the table 77 and also adjusted to a suitable starting point. The array 20 on the table 71 is then indexed automatically along the X-axis so that each device 22 in the first row is brought beneath the detector 100.

When a magnetic field is sensed by the detector 100, because the coating material 32 of the device 22a is magnetized, the detector generates a signal. This signal actuates the motors 94 and 95 to raise the arms 86, and causes a motor (not shown) to rotate the yoke 180.degree. clockwise to position the vacuum pickup tip 87 over the magnetized device 22. Next, in order to pickup the device 22a and transfer it to the coated carrier 68 on the table 77, the motor 94 is rotated once to lower and raise the tip 87. A vacuum is applied when the tip 87 is in its lowermost position. This vacuum is maintained until the yoke 88 is revolved 180.degree. counterclockwise and the motor 94 revolved once again to lower and raise the tip 87 while it is over the table 77. The vacuum is removed when the tip 87 is in its lowermost position; thus, depositing the device 22a on the carrier 68 on table 77.

The positioning fixture 72 indexes the next device 22 on the table 71 into position and the detector 100 is lowered to within 0.002 of an inch of the device by the motor 95 and corresponding cam 92. Also, the positioning fixture 76 indexes the table 77 so that the carrier 68 thereon is indexed one position in preparation for receiving the next device 22. If the next device 22 is magnetized, the sequence previously described is repeated. If not magnetized, the fixture 72 indexes again until a magnetized device 22 is encountered. Thus, the input table 71 is indexed continuously along the rows of the array while the output table 77 is indexed only to receive a device 22 which has been picked up. A row is transversed in the X direction in this manner and at the end of the row the fixture 72 shifts in the Y direction to the next row. This continues until all marked devices 22 are transferred to the carrier 68 on the table 77. Then, another carrier 68 of tested and marked devices 22 is placed on the table 71 and the process repeated. The result is a new array of devices 22 all of which have been selected by test to have the same characteristics.

Since the output table 77 is moved independently of the input table 71, table 77 may be moved the same increment as that of the original array 20, or what is often the case, much larger increment to expand the array.

Referring now to FIG. 12, there is shown a schematic electrical circuit diagram for detecting the devices 22 which have been magnetized. The detector 100 is a Magnistor which is essentially a transistor having two collectors 124. Originarily the current is divided equally between them. However, when the unit is subjected to a magnetic field, the current is diverted as it leaves the emitter so that more current is directed to one collector than the other. The detector 100 is adjusted when no magnetic field is present for equal current in each collector 124 by eans of a potentiometer 126, a meter 125, and a switch 127 set in the "read" position. When the currents are equal, the output of a probe amplifier 128 at a point A is zero volts. As a result, a lamp 130 and relay 132 in an output driver circuit 134 are unenergized.

When the detector 100 is brought within the magnetic field of a magnetized device 22, the difference in currents through the collector circuits generates a voltage which is amplified to about 30 millivolts at point A by the amplifier 128. This voltage is applied through a resistor 135 to point B which is at the input of a trip circuit 136 whose amplifier 137 is adjusted to conduct at a certain voltage level such as +15 millivolts or greater. This causes transistors 138 and 140 to conduct and the current through the collector circuit of transistor 140 to energize the lamp 130 and relay 132.

In order to eliminate the effect of drift, a "sample and hold" circuit 142 is included. The output voltage of the circuit 142 is equal to its input voltage but opposite in sign. A relay 141 is energized to place the circuit 142 in the "sample" mode during index from one position to another. The relay 141 is left unenergized to place the circuit 142 in the "hold" mode, while in position above one of the devices 22. For example, if the output of the probe amplifier 128 at point A during index is +10 millivolts, the input to circuit 142 is +10 millivolts just prior to detecting a device 22. With the switch 127 in the "test" position and the relay 141 energized, i.e., in the sample position, the output of the circuit 142 at point B is -10 millivolts. The relay 141 is then de-energized so that the -10 millivolts is held. When the detector 100 is positioned above a magnetized device 22, the voltage applied to point B by the amplifier 128 through the resistor 135, may be +30 millivolts. Accordingly, the net voltage at point B available for tripping the circuit amplifier 137 will be the difference between the output of the probe amplifier 128 at A and the -10 millivolt output of the sample and hold circuit 141, i.e., +20 millivolts. In this way the voltage due to any drift, up to the time immediately prior to detection, plus the magnetic field voltage is applied to point B where the negative of any voltage due to drift is also applied. Consequently, the trip circuit 136 "sees" the +20 millivolt difference which is the voltage due to the affect on detector 100 of the magnetic field of the magnetized device 22.

While there has been described and illustrated herein practical embodiments of the present invention, it is to be understood that various modifications and refinements which may depart from the disclosed embodiment may be adopted without departing from the spirit and scope of the present invention.

Claims

What is claimed is:

1. A method of identifying nonmagnetic articles which comprises the steps of:

coating the article with a material which is capable of retaining a magnetic flux when magnetized;

testing the articles individually to determine which articles are to be identified;

and contacting the individual articles to be identified in accordance with the testing, with a tip of a marking member having a magnetic flux concentrated at the tip thereof to magnetize the material and identify the articles.

2. The method of claim 1 wherein only one article is tested to determined whether it should be identified.

3. The method of claim 1 wherein a portion of the marking member is tubular and marking fluid flows through the tubular portion so that the step of contacting both visibly and magnetically identifies the articles.

4. The method of claim 3, wherein the visible and magnetic identification are accomplished simultaneously.

5. A method of identifying magnetizable article which comprises the steps of;

testing the articles to determine whether they have a certain characteristic;

concentrating a magnetic flux at the tip of a marking member;

flowing a marking fluid through the member; and

placing the tip of the marking member adjacent the article to simultaneously deposit fluid on and magnetize the article having the characteristic determined in accordance with the testing, to both visibly and magnetically identify the article.

6. A method of identifying semiconductor devices in an array which comprises the steps of:

coating all the devices in the array with a material which will retain a magnetic flux when magnetized;

testing the devices in the array;

concentrating the flux of a permanent magnet at the tip of a marking member;

flowing a marking ink through the marking member; and

contacting certain devices in the array, in accordance with the testing, with the tip of the member to deposit marking fluid and simultaneously magnetize the coating material so that the selected devices are visibly and magnetically identified and identification is insured.

7. A method of identifying and sorting articles form an array of the articles which comprises the steps of:

coating all the articles with a material which will retain a magnetic flux;

testing the articles individually to determine which articles are to be identified;

concentrating a magnetic flux at the tip of a marking member;

contacting the individual articles to be identified, as determined by the test, with the tip of the marking member to induce a magnetic field in the material and identify the articles;

sensing the magnetic field induced in the magnetic material of the identified articles; and

sorting the identified articles from the array in accordance with the magnetic field.

8. The method of claim 7 wherein the articles are beam-lead semiconductor devices in an interdigitated array.

9. The method of claim 8 wherein a portion of the marking member is tubular and marking fluid flows through the member to both visibly and magnetically identify the semiconductor devices to insure identification.

10. The method of claim 9 wherein a magnetically sensitive transistor is used to sense the induced magnetic field.

11. Apparatus for identifying nonmagnetic article having a magnetizable coating in an array such devices, which comprises:

means for testing the articles while in an array to determine the characteristics thereof; and

means for both inducing a magnetic field in the magnetizable coating and visibly marking the articles to insure the identification of said articles.

12. The apparatus of claim 11 wherein the articles are beam-lead semiconductor devices and the means for simultaneously inducing a magnetic field in the magnetizable coating material and visibly marking the device, comprises:

a reservoir for marking fluid;

a tubular portion extending from the reservoir, said portion being ferromagnetic and having a fluid dispensing tip smaller than then article to be identified; and

magnet means adjacent the tubular portion at the tip for magnetizing the article whereby the article is simultaneously visibly and magnetically identified to insure identification.

13. A marking stylus, for identifying semiconductor devices coated with a magnetizable material, which comprises:

a reservoir for marking fluid;

means for conducting marking fluid from the reservoir and magnetic flux to the devices to be identified; and

a magnet means for providing magnetic flux to the conducting means whereby the devices may be both visibly and magnetically marked upon contact with the conducting means to insure identification.

14. A marking stylus according to claim 13, wherein the means for conducting marking fluid and magnetic flux, comprises:

a tubular member joined at one end to the reservoir and extending horizontally therefrom to an exit end; and

a ferromagnetic tubular transition member, smaller in area at the tip than the devices to be identified, which curves from a horizontal plane at the exit end of the tubular member to a vertical plane, and the bore of which is constricted at the tip of form an opening smaller than the bore to control the flow of marking fluid.

15. A marking stylus according to claim 14, wherein the magnet means is a permanent magnet which bridges the curve of the transition member and provides magnetic flux concentrated at the tip of said member.