Abstract:
An improved method of testing and sorting electronic devices uses two or more test stations and two or more sorting stations applied to a single track to improve system throughput. Applying two or more test stations and two or more sorting stations to a single track accomplishes improved system throughput while increasing system cost less than would be expected if a duplicate track was installed for each test station.

Description:
TECHNICAL FIELD 
       [0001]    The present invention regards improved systems and methods for testing and sorting electronic devices. In particular it regards systems and methods for testing electrical and/or optical properties of miniature electronic devices. In more particular it regards a system and method for testing at least two miniature device properties at high speed in parallel and sorting them into categories according to those properties using two separate testing stations and one test track. 
       BACKGROUND OF THE INVENTION 
       [0002]    Many electronic devices are tested for electrical and/or optical properties during manufacturing by automated test systems. Typical automated test systems use precision electrical and/or optical test equipment to find values associated with electrical and optical properties of a device and either accept, reject or sort it into an output category depending upon the measured values. For miniature devices, automated test systems are often designed to handle bulk loads, where the manufacturing process creates a volume of devices which have substantially identical mechanical characteristics such as size and shape but differ in electrical and/or optical characteristics. It is common practice to build a volume of devices with electrical and optical properties which generally fall within a range and rely on testing to sort the devices into commercially useful groups with similar characteristics. Typical electronic devices tested and sorted in this fashion include passive components such as resistors, capacitors and inductors and active electronic devices such as digital or analog integrated circuits or light emitting diodes. 
         [0003]    These devices are often supplied to the automated test system as containers filled with devices. Typically the automated test system must extract a single device from the bulk load of devices in a process called singulation, orient the device and fixture it so the test equipment can perform the desired tests. Testing often requires probing the device, wherein electrical leads are brought into contact with the device to permit signals and power to be applied to the device and to monitor responses to the inputs. The task of the automated test system is to determine the electrical characteristics of devices and sort the devices into groups depending upon those characteristics. The automated test system typically singulates devices onto a track where the devices are indexed past one or more test stations where various electrical and/or optical properties of the device are tested and the results stored. As the devices are subsequently indexed past the sorting stations, the devices are removed from the track and deposited in one of a number of bins depending upon the results of the preceding tests. A typical prior art automated test system is shown in  FIG. 1 , where a track  2  with locations  3 ,  4  spaced “p”=pitch distance apart are indexed by the track  2  in the direction of the arrow to the loader  5  where bulk parts  6  are loaded  7  onto the track. The device  7  is indexed by the track  2  to location  10  where it is tested by test station  9  and the results stored on a controller (not shown). The device  7  is subsequently indexed by track  2  to location  11  where the sort tube  12  removes the device  13  from the track  2  for sorting. 
         [0004]    U.S. Pat. No. 5,842,579 ELECTRICAL CRICUIT COMPONENT HANDLER, inventors Douglas J. Garcia, Steven D. Swendrowski, Mitsuaki Tani, Hsang Wang, Martin J. Twite, III, Malcolm Hawkes, Evart David Shealey, Martin S. Voshell, Jeffrey L. Fish and Vernon P. Cooke, Dec. 1, 1998, assigned to the assignee of this invention, discloses a rotary disk test machine with multiple tracks able to test multiple parts at once. Another exemplary system that uses duplicate tracks to test devices in parallel is the MT20 LED tester manufactured by Mirae Corporation, Chungcheongnam-Do 331-220, Korea. The track holding the devices does not have to be rotary. U.S. Pat. No. 4,747,479 DEVICE FOR THE TESTING AND/OR PROCESSING OF SMALL COMPONENT PARTS, inventor Jakob Herrman, May 31, 1988 discloses a linear belt to hold parts under test. What these disclosures do not consider is the possibility of testing more than one device in parallel without having to duplicate the tracks that feed parts to the test stations whether they are rotary or linear. 
         [0005]    What is needed, then, is an automated test system for testing and sorting miniature electronic devices that can test at least two devices in parallel and sort them at high speed using a single track to deliver devices to the test stations. 
       SUMMARY OF THE INVENTION 
       [0006]    Aspects of the instant invention provide an improved method of testing and sorting electronic devices based on electrical and/or optical properties using an automated test system which carries parts to be tested on a track. The improvements include providing the test system with first and second test stations adjacent to the track and testing a portion of the devices on the first test station and testing another portion of the devices on the second test station. The devices are then sorted based on the test with a sorting mechanism according to the test results. The system tests and sorts said electronic devices with two test stations on one track. The instant invention performs these tests in parallel, thereby increasing the throughput over systems which test devices serially, and at less expense than systems which test parts in parallel by duplicating the track mechanism. 
         [0007]    Aspects of this invention index the track and the devices in order to process the devices. Indexing refers to stop/start type motion where the track is moved to a position, stopped for a period of time and then moved to a next position. In the case of automated test systems, the track is typically indexed from load position, where the devices are put in the track, to test position where the device is tested, to sort position where the devices are removed from the track and sorted into bins and then back to load position in a series of steps. The instant invention is able to process devices in parallel on a single track by offsetting the positions of the test stations so that when the track is indexed by a predetermined amount greater than the pitch between adjacent devices, one device will be presented to the first test station, while another device will be presented to the second test station. Since the track is indexing twice as far per unit time, the system throughput will be nearly doubled. 
         [0008]    To achieve the foregoing and other objects in accordance with the purposes of the present invention, as embodied and broadly described herein, a method and apparatus is disclosed. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]      FIG. 1 . Prior art automated test system. 
           [0010]      FIG. 2 . Automated test system showing duplex device arrangement. 
       
    
    
     DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS 
       [0011]    Embodiments of this invention are improved systems and methods for testing and sorting of miniature electronic devices. Embodiments of the instant invention provide an improved method of testing and sorting electronic devices based on electrical and/or optical properties using an automated test system which carries parts to be tested on a track. The improvements include providing the test system with first and second test stations adjacent to the track and testing a portion of the devices on the first test station and testing another portion of the devices on the second test station. The devices are then sorted based on the test with a sorting mechanism according to the test results. The system tests and sorts said electronic devices with two test stations on one track. The instant invention performs these tests in parallel, thereby increasing the throughput over systems which test devices serially, and at less expense than systems which test parts in parallel by duplicating the track mechanism. 
         [0012]    Embodiments of this invention employ tracks having locations which fixture or hold securely electronic devices for testing. Embodiments of this invention index the track and the fixtured devices in order to process the devices. Indexing refers to stop/start type motion where the track and the fixtured devices are moved to a position, stopped for a period of time and then moved to a next position. 
         [0013]    For example,  FIG. 2  shows an embodiment of this invention, comprising a single track automated test system  50  with a track  14 , which indexes in the direction of the arrow, arranged according to an embodiment of this invention. The track  14  has locations  15 - 27  operative to fixture electronic devices  34 ,  36 .  FIG. 2  shows two adjacent locations  15 , 16  which are a distance “p” =pitch apart. Note that locations  15  and  17  are a distance 2 p apart, or twice the pitch. Bulk electronic devices  32  are loaded into a feeder  30  which loads parts  34 ,  36  into locations  18 ,  19  on the track  14 . Note that the loader must load at least two parts since the track  14  will next index a distance of 2 p thereby bringing two new empty locations  16 ,  17  to the loader  30  and indexing electronic devices  34 ,  36  to locations  20 ,  21 . Two loaders could also be employed. With the next 2 p index of the track  14  the electronic devices are brought to locations  22 ,  23  where they are tested by test stations  38 ,  40  in parallel. Following testing and storing of test results in the controller (not shown), the track  14  indexes the electronic devices in steps of size 2 p to locations  26 ,  27  where the electronic devices  46 ,  48  are removed from the track  14  by sorting tubes  42 ,  44 . 
         [0014]    Since the track  14  is indexed by 2 p rather than p, it makes half as many stops and therefore dwells, accelerates and decelerates half as many times, thereby speeding up system throughput by nearly a factor of two. In addition, the concept can be extended to more than two sets of load, test and sort stations. For example, with three sets of load, test and sort stations, the stations would be arranged so that the system could index three times the pitch or 3 p with each index in order to test and sort all of the devices in a single pass. Embodiments of this invention use rotary tracks, where a disk-like assembly rotates with one or more tracks on or in its surface or linear tracks which may be flexible belts or other arrangements that permit the track to recirculate locations past stations. 
         [0015]    Bulk devices can be singulated and loaded into the track using rotary feeders, vibratory bowl feeders, gravity, special mechanisms or a combination of these. The track may comprise a series of specially shaped recesses or holes arranged in a circular pattern on a rotary plate or more complex mechanisms including load fences and fluid ports, the common property being that they fixture devices so that the device can be indexed into position, probed, tested, and then ejected into one of a number of bins while the track indexes. The track is indexed from load position, where the devices are put in the track, through possible intermediate positions, then to test positions where the device is tested, through more possible intermediate positions and finally to sort position where the devices are removed from the track and sorted into bins. The track is then indexed back to load position in a series of steps. The instant invention is able to process devices in parallel on a single track by offsetting the positions of the test stations so that when the track is indexed by a predetermined amount greater than the offset, one portion of the devices will be presented to the first test station, while another portion of the devices will be presented to the second test station. Since the track is indexing twice as far per unit time, the system throughput will be nearly doubled. This arrangement of indexing at greater than the device pitch and placing two or more sets of loaders, test heads and sort bins at appropriate positions adjacent to the track permits the automated test system to process nearly twice as many parts per unit time with less hardware and less space than would be required if the track mechanisms were duplicated to provide the same throughput. 
         [0016]    It will be apparent to those of ordinary skill in the art that many changes may be made to the details of the above-described embodiments of this invention without departing from the underlying principles thereof. The scope of the present invention should, therefore, be determined only by the following claims.