Abstract:
A bar coded magnetic recording pattern uniquely identifying the disk of a disk drive is disposed, at the time the disk is single disk tested and accepted, in a reserved area that is not used for data recording by the disk drive assembly. The identifying recording is disposed in a reserved region that is accessible by the magnetic transducer of the disk drive. The identifying recording may be read to determine the orientation of the disk in the disk drive and may be read to positively identify the disk to permit repair, recall or data transfer from specifically identified disks without shut down and/or disassembly of the disk drives incorporating the designated disks.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS 
     This application is a continuation of application Ser. No. 08/796,988 filed Feb. 7, 1997, now abandoned. 
    
    
     FIELD OF THE INVENTION 
     This invention relates to a method of manufacturing magnetic disk drives and, specifically, to the unique identification of magnetic disks before, during, and after the assembly of the disk drive. 
     BACKGROUND OF THE INVENTION 
     A system to avoid accessing of defects or defective regions on a storage media is disclosed in U.S. Pat. No. 4,498,146 to Maria N. Martinez. The locations of defects on the disk, provided by the disk manufacturer are used to construct a list or table of addresses of defects on the storage media and is recorded on the disk data recording surface. Through conversion, the defect address list is used to produce real addresses of the defects on the disk recording surface. The resulting defect address table is loaded into the disk file controller and the addresses are used to prevent accessing the defective regions during disk drive operations. New defects may be added to the defect address table as detected. 
     A system for detection of contamination errors for optical disks is disclosed in U.S. Pat. No. 5,513,160 to Isao Satoh et al. The system first detects the defect errors on the disk and, at a later time, detects the total defect errors. The difference represents the contamination errors on an optical disk. 
     U.S. Pat. No. 5,075,804 issued to Deyring discloses a method for managing recording media defects. The identity and location of good or usable sectors of the recording tracks are maintained in an operating list stored in memory so that the disk drive microprocessor can avoid the use of bad sectors. 
     Presently, disk drives are comprised of disks that are not or have not been clearly individually identifiable. The disks have been individually tested and, if the disks pass the single disk test criteria, each single disk so tested and accepted is made available for assembly. Once assembled into the disk drive, these disks are retested for defects, and the locations of the defects are determined relative to the rotational datums of the disk drive. Thereafter, a defect table is assembled from the defect locations for each disk and stored on the media or in the memory of the disk controller. The duplicative testing of the disk is necessary both to prevent the use of a grossly defective disk and further to assemble the defect table of locations of the disk relative to disk drive established datums. 
     Currently, due to cost and inability to access and physically identify a unique disk surface once the disk drive is assembled, the surfaces of magnetic storage disks during the manufacturing process are not serially numbered or marked with any unique identification for later use in the assembled disk drive. Therefore, in the disk drive following assembly, the identity of a particular disk surface is not discernable. 
     Disk surfaces sometimes have laser scribed serialization; however, reading of the laser scribing requires a microprocessor and microprocessor associated image reading circuitry not found in a magnetic disk drive. Once assembled, however, the laser scribing is not readable in a magnetic disk drive. 
     As the current trend in magnetic disk drives of higher speed access rates continues, disk drives continue both to be reduced in size and also refined to store larger and larger amounts of data. Due to the very narrow width and close spacing of the data tracks on the disk, the affect of a surface defect in the recording media can render unusable, varying numbers of data tracks on a disk. A few surface defects affecting a nominal number of tracks may be tolerated; but, as the number of defects increases, the affected tracks and sectors soon start to severely limit the storage capacity of the disk. 
     The ability to identify and accurately account for or keep track of disk surfaces in assembled disk drives, particularly those drives in customer installations, is limited to identifying the disks by manufacturing lot or batch number. The manufacturing data for the disk drive may indicate the lot or batch numbers of the disks incorporated therein, but there is no certainty that the disk identity is reliable, particularly if there has been an overlap or changeover from lot to lot of disks incorporated into the disk drive assembly. Experience has shown that the lot or batch number associated in records with a particular disk drive is not accurate in many instances due to more than one lot or batch of disks being available on the manufacturing line at the same time, particularly whenever such lot or batch changeover occurs. Additionally, when more than one lot or batch number is used in a drive, presently there is no way to know which disk is from the lot being considered. Thus, in the event of a need to recall a lot or batch of disks due to a lot-wide defect, such as low coercivity of the magnetic coating or some other widespread type problem, a large number of disk drives may be needlessly recalled to insure that all the affected disks are identified. 
     It is very important that any disk drive placed in service not be displaced, removed from service, or disturbed imprudently because the affect can be extremely serious in terms of system down time. Being able to precisely identify individual disks already incorporated into an installed disk drive would permit avoiding use of a potentially defective disk in a drive, reduce the chance of data failure and an associated system crash and permit either the preservation of data or more orderly replacement of the disk drive at a time to minimize system disruption. 
     Serializing of a disk heretofore has been impractical at the single disk stage of manufacture inasmuch as the recording surface of the disk is not formatted at the single disk stage. Any widespread magnetic recording of readable data patterns thereon later interferes with reading and writing of data on the disk. Accordingly, the magnetic storing of a disk serial number and defect data on the disk has heretofore proved to be futile since the information either would not be reliably retrievable or the defect data would be effectively destroyed whenever the disk was formatted for servo control of the actuator following disk drive assembly and drive level testing. 
     Data storage disks typically have storage capacity on both sides of a disk. The disk surface includes a data storage region, an annular region near the periphery of the disk in which data is not stored, and an annular ring of substantial width which surrounds the central hole of the disk. As no effort is made to limit coating to only the data recordable portion of the surface, on each side of the disk, the magnetically coated and recordable surface of the annular storage portion of the disk extends between the central hole and the disk edge. 
     Part of the inner annular ring not used for data recording is used as a clamping region for engagement with inter-disk spacer rings resident on the disk drive hub. The balance of the inner annular ring and an outer ring adjacent the periphery of the disk may be used as a parking or landing zone or load/unload zone for the disk drive magnetic head whenever the drive is stopped, thereby preventing the head from contacting the recordable surface in the data storage zone of the disk surface which may result in disk surface and/or head damage. 
     The exposed portion of the inner ring and the outer ring are referred to as reserved areas. The manufacturing processes create recordable but otherwise unused surfaces in these reserved areas. 
     Heads for disk drives may be parked or loaded and unloaded either near the inner limits or the outer limits of the disk depending on the disk drive design. Thus, the magnetic read/write head is capable of being positioned at proper flying height over at least one of the reserved regions of a disk drive. 
     OBJECTS OF THE INVENTION 
     It is an object of the invention to readably serialize or otherwise readably uniquely identify each disk surface of a data storage disk drive at an individual disk level for identification in an assembled magnetic disk drive. 
     It is another object of the invention to serialize or otherwise uniquely identify the disk surfaces of a data storage drive in a manner that is readable in the assembled disk drive while not interfering with formatting, reading from or writing to such a disk surface. 
     It is a further object of the invention to improve the manufacturing and testing process of a disk drive and thereby enhance the reliability of the disk drive. 
     It is an additional object of the invention to enhance the accountability of the magnetic recording disks manufactured and tested for purposes of being able to identify specific disks in assembled disk drives and in customer systems. 
     It is a still further object of the invention to provide a method of manufacture for a data storage disk in such a manner as to permit the circumvention of a defective disk and the avoidance of a potentially disastrous incident and a possible loss of significant amounts of data. 
     It is yet another object to provide a disk drive with the ability to identify the disks incorporated therein by reading unique disk identifications from said disks. 
     SUMMARY OF THE INVENTION 
     A recordable magnetic disk for use in a magnetic disk drive is prepared using conventional disk fabrication, coating and curing techniques. 
     Thereafter, the disk is tested to determine defects in the magnetic disk recordable surface coating and/or ascertain the acceptability of the quality of the disk. If the defect level of the disk is excessive, the disk is scrapped and no record of the scrapped disk created or retained. Once a disk is determined to be acceptable, the disk is uniquely identified and a serial number or Disk Identification Number (DINUM) is recorded in one of the reserved areas of one side of the disk. The recording is made in a non-track specific manner, i.e., a magnetic pattern extending over a wide path in the selected reserved area. One example of such a recording pattern is a bar code type pattern which would extend across what might represent as many as 100 recording track widths. The recorded pattern not only provides uniquely identifying data but also a rotational orientation datum from which recording surface defects may be located. 
     Thereafter, the disk is selected and assembled with other parts and disks from varied lots or batches into a disk drive. The disk drive further is tested as a complete unit, and the defect location data previously determined in disk drive testing is retrieved from a computer data base using the DINUM or Disk Identification Number. 
     Formatting of the disk surfaces of the disk drive for servo control of the disk drive actuator is accomplished and supervised by a computerized routine which typically is not part of the control capability of the disk drive controller but rather the disk drive assembly testing controller. Thus, the formatting is accomplished after the single disk test. 
     During formatting of the disks, a pattern of recorded signals is recorded in each recording track of the typically 6,000 tracks on a 3½ inch diameter disk. The signals are referred to as servo patterns. These servo pattern signals are used to insure that tracking or following of the data track by the disk drive read/write head is controlled and accurate. Without accurate tracking, data cannot be reliably recorded or read. 
     The formatting of the disk and recording of the servo patterns on the disk may be rotationally positioned to maximize usable recording sectors. By judiciously positioning the servo patterns relative to previously detected surface defects, the number of sectors affected by the defects may be minimized and the recording capacity of the disk maximized. 
     The defect data base for a particular disk thereafter is stored in a defect table on the disk&#39;s surface within the data storage area. The designations of areas identified by tracks and sectors which are usable also may be included in the defect table, as desired. 
     A greater understanding of the invention may be had from the drawings and the Detailed Description of the Invention to follow. 
    
    
     DRAWINGS 
     FIG. 1 is a depiction of a surface of a data disk incorporating the invention and an associated tester read/write head and arm. 
     FIG. 2 is an illustration of a segment of the disk surface of FIG.  1 . 
     FIG. 3 is an illustration of the disk and the read/write head and actuator arm of a disk drive, shown in a variety of positions. 
     FIG. 4 is an illustration of a portion of a disk drive having a disk and an actuator. 
     FIG. 5 is a flow diagram of the manufacturing process for the disk and disk drive. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     The following is a detailed description of the best mode of the preferred embodiment of the invention as contemplated by the inventors. Referring now to FIGS. 1-4, the central opening  12  of disk  10  is sized to accept a hub  13  or rotor  13  of a disk drive  26 , such as that disclosed in FIG.  4 . The central opening  12  is surrounded by a relatively wide zone  18  which, like the remainder of the disk surface  14 , data recording area  16  and outer zone  20  or outer reserved area  20 , is coated with a magnetic recording media capable of receiving a series of recording signals and forming a magnetic pattern which may be read by the head  24  of a recording/reading apparatus such as a single disk tester. To test and format the disk  10  during assembly and disk drive testing, the read/write head  24  of the disk drive tester (not shown) used is sufficiently wide to record a magnetic pattern across a wide band so that the magnetic head  34  of disk drive  26 , such as that in FIG. 4, can read the pattern without precise placement of the head  34  on a precise recording track  28  whenever the head  34  is disposed in the wide zone  18 . Zone  18  may be used as a load/unload or landing zone for the magnetic head  34  whenever the disk drive  26  is stopped. Whenever flown over the DINUM  30 , the magnetic head  34  may respond to the magnetic pattern. 
     The recorded servo pattern  32  on disk  10  is a pattern of servo signals recorded in arcs  31  about the pivot axis  23  of actuator  21  with uniform arcuate spacing, such as shown in 
     FIG.  2 . FIG. 2 shows a very limited portion of disk  10  embodying the invention. The Disk Identification Number (DINUM)  30  is shown recorded in a bar code pattern  30 . The nature of the bar coding of DINUM  30  is not critical so long as the disk drive  26  is capable of reading and decoding the bar code pattern  30 . The bar code pattern  30  or other suitable recording pattern is preferably written on the wide landing zone  18  during the single disk testing of the disk  10 , prior to disk drive assembly. Whenever the disk  10  is individually tested and determined to have a sufficiently small number and size of surface defects to meet the testing criteria, the disk  10  is accepted and the recording head  24  is positioned over the landing zone  18  or wide zone  18  and the DINUM  30  is recorded as described above. 
     The DINUM  30  then is correlated with the single disk test data which defines the location and size of the recording surface defects. This data is stored in a computer memory for use during servo formatting of the disks  10  and subsequently forming the defect table. Thereafter, the accepted disk  10  together with other disks which were accepted after individual disk testing are assembled into disk drives, such as disk drive  26  of FIG. 4, using conventional assembly techniques. 
     After disk drive assembly, the disk drive  26  further is tested as a functional unit; and, if found acceptable, the disks  10  in the disk pack (not visible) are formatted for servo control of actuator  21 . Servo formatting of the disks  10  involves writing a servo pattern  32  of magnetic flux changes onto the magnetic disk surface  14 . The servo pattern  32  recordings provide the signals necessary for the servo system of disk drive  26  and serve to define the annular recording tracks  28  around the disk surface  14 , as shown in FIG.  2 . The recording of the servo pattern  32  comprises creating a plurality of short bursts or flux changes on the surface  14  of disk  10  in a defined pattern. The servo patterns  32  are spaced about every four (4) degrees around the disk  10  in or intersecting each recording track  28 . The servo signals in an individual track  28  provide signals to the read/write head  34  of the disk drive  26  that physically define the recording track  28  and provide a control signal for compensating and moving the head  34  to eliminate any alignment error of the recording head  34  relative to the track  28 . The servo pattern  32  signals and the servo control circuit in the disk drive  26  function to keep the recording head  34  centered over the recording track  28  to insure reliability of recording and reading of data. 
     Referring to FIG. 3, the recorded servo patterns  32  form arcs  31  extending across the recording tracks  28  in the path of the read/write head  34  as it is swept across the recording surface  16  of the magnetic disk  10 . This assures that all sectors  29  registered at a particular rotational angle on the disk  10  begin and end at the same rotational displacement of the disk  10  relative to the disk drive  26  read write head  34 . The pattern of arcs  31  of servo patterns  32 , spaced at about four (4) degree intervals, are located relative to the magnetic recording of the DINUM  30 , which forms a datum for the disk  10 . 
     The formatting of servo patterns  32  may be shifted rotationally relative to the DINUM datum (the beginning of the recorded pattern  36 ) to some degree to optimize the recordable portion of the disk surface  14 . With reference to FIG. 2, the existence of a surface defect within the data recording area  16  of the disk  10 , even if affecting a small portion of a sector  29  in which it resides, renders the entire sector  29  unusable. Thus, if a defect would extend into adjacent sectors  29  but have a size such that it may be contained within fewer sectors  29 , the number of affected and thus unusable sectors  29  may be reduced by shifting the servo patterns  32 , maximizing the recordable capacity of the disk  10 . Utilizing the test data defining the defect locations and the sizes of the defects stored after single disk  10  testing, the servo format pattern  32  can be shifted rotationally about the disk central opening  12  to minimize the number of sectors  29  affected by the defect. 
     As an example, if the size of a known defect is such that it will affect six (6) degrees of arc on the disk surface  14 , one will understand that the defect could render as many as three sectors  29  unusable by spanning a complete four (4) degree sector  29  plus a portion of the preceding and a portion of the trailing sectors  29 . By shifting the position of the servo patterns  32  slightly at servo formatting, the defect can be confined to only two sectors  29 . Because the defects may be such as to affect a plurality of tracks  28 , the saving of the single sector  29  on a single track  28  can easily translate to saving a much larger number of sectors  29 . 
     All of the defects on both surfaces  14 A,  14 B of the disk  10  must be considered and the placement of the formatting servo patterns  32  optimized to be effective for the entire disk surface  14  inasmuch as the servo patterns  32  are defined for the entire disk  10 , with only its rotational placement being variable. 
     The disks  10  and particularly the DINUM  30  on each disk  10  need not be aligned with each other in the disk drive  26 , and each of the formatting servo patterns  32  of a disk surface  14  need not precisely align with the patterns on the other disks of the same disk drive  26 . In fact, it may prove advantageous to relate a progressive misalignment of the formatting pattern  32 , with due regard to sector  29  availability, to reduce lost access time whenever accessing sequential disks  10  in a disk drive  26 . 
     The defect table, i.e., the data on the location and dimensions of the surface defects on the disk surface  14 , may be recorded on the data recording surface  16  of the disk  10  after formatting of disk  10 . The defect data may be expressed in terms of radial location, rotational position from a datum, such as the DINUM  30 , and rotational and radial extent of the defect, and a list of tracks  28  and sectors  29  that are unusable. Other notational schemes also may be used. 
     The manufacturing and testing process for a disk  10  and a disk drive  26  is described below. A coated magnetic storage disk  10  is selected at operation  100  of FIG.  5  and both surfaces  14 A,  14 B of the disk  10  are tested on an individual disk basis for surface defects affecting each disk&#39;s ability to accept recordings and to be reliably read by conventional testing techniques. Both surfaces  14 A,  14 B of the disk  10  are tested in operation  102  to a specific disk test criteria previously established. If sufficient recordable space or area  16  is found to be available on the disk  10  to meet the test criteria and any other test standards met, then the disk  10  is accepted in operation  104 . 
     If the single disk test criteria is not met, the disk  10  is rejected and discarded in operation  106 ; however, it may be found acceptable for use in a disk drive requiring lesser recording capacity. In operation  108 , the accepted disk  10  is magnetically encoded using head  24  in landing zone  18  or in some other non-data recording surface (reserved area) with a unique Disk Identification Number (DINUM)  30 . The test data, number of defects, and data relating to each defect as to location and size on both surfaces  14 A,  14 B are stored in the tester computer memory or other suitable memory for future use in operation  110 . Thereafter, disk  10  is assembled into a disk drive  26  in operation  112 . After assembly, the disk drive  26  then is drive level tested in operation  114  to assure the operability of the disk drive  26 . 
     Upon a successful completion of the drive level test in operation  114 , the DINUM  30 , a unique identifier, is read from the reserved space  18  by the read/write head  34  of the disk drive  26  in operation  116 . The test software uses the DINUM  30  to access the tester or host computer memory to retrieve the surface defect data stored therein during the single disk test in operation  118 . The defect data is analyzed to optimize the positioning of the servo patterns  32  in operation  120  in order to minimize the number of sectors affected by the defects. Optimization involves shifting the servo patterns  32  relative to the datum established on the disk  10  by the DINUM  30  location and the positioning of the servo patterns  32  to minimize the number of sectors  29  rendered unusable by the recording surface defects. 
     The optimization process may be as simple as electronically shifting the servo patterns  32  by small increments and determining the number of unusable sectors  29 . The displacement yielding the minimum number of unusable sectors  29  is the preferred location. 
     After the optimization of the servo patterns  32  positioning in operation  120 , the servo patterns  32  are recorded onto the disk  10  during the formatting of the disk in operation  122 . 
     Thereafter, in operation  124 , the defect table is magnetically written to the recordable portion  16  of the disk  10  so that the defect data is available in the disk drive  26  when installed and operated. The format of and contents of the defect table is a matter of choice. 
     The recording of the unique DINUM  30  on a reserved but accessible portion of a disk  10  provides many advantages. One such advantage is the ability to identify a disk  10  in the field while the disk  10  remains within its host disk drive  26 . The unique DINUM  30  carried by each disk  10  and readable in the disk drive  26  provides the capability of identifying the disks  10  within a particular disk drive  26 . It becomes possible to detect and report disk failures specific to a given surface of a particular disk  10  rather than relative to a large number of drives having disks  10  from a targeted lot or batch. Additionally, if a lot or batch of disks  10  subsequently are found to be substandard, a list of DINUMs  30  that require action, attention, adjustment or maintenance can be distributed. This permits targeting of specific drives  26  for recall or service without disrupting customers or users with a less precisely targeted recall involving a number of disks  10  which need not be subject to recall. By specifically identifying a possibly faulty disk  10 , the data stored thereon may be transferred to another disk  10  prior to failure, and the disk drive  26  fixed or replaced at a time of low usage, resulting in minimal disruption. 
     An additional advantage provided by the invention is that the disk drive  26  can be operated to determine whether the disk  10  is assembled properly in disk drives  26  where only one side of the disk  10  is used for recording data. A failure to detect the DINUM  30  on the read/write head  34  associated with supposed reserved surface  18  would indicate the disk  10  is improperly oriented in the drive  26 . 
     While disks  10  can have serial numbers laser engraved on the disks  10  without special equipment, such a serial number is not readable in and by the disk drive  26  once the disk  10  is assembled into a disk drive  26  without disassembly of the drive  26 . Accordingly, a laser engraved disk is not practically, directly identifiable in the disk drive  26 . 
     It should be understood by those skilled in the art that the described approach of recording the DINUM  30  into the reserved space  18  could include types of recording patterns of magnetic recording other than bar coding so long as the recording may be read by the head  34  of the disk drive  26  and the DINUM  30  recording does not affect the servo formatting and the read/write operations on the data region of the disk  10 . One skilled in the art will further recognize that other changes may be made to various aspects of the disclosed invention while remaining within the scope of the appended claims.