Patent Publication Number: US-2016248221-A1

Title: Chip on submount carrier fixture

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This application is a divisional of U.S. patent application Ser. No. 13/797,706 filed on Mar. 12, 2013, “Chip On Submount Carrier Fixture”, the content of which is incorporated herein by reference in its entirety. 
     The present disclosure relates generally to processes and apparatuses used for laser diode testing, and more particularly, to processes and apparatuses used to reduce the cost and time for laser diode testing. 
    
    
     BACKGROUND 
     Magnetic disk drives are used to store and retrieve data in many electronic devices including computers, televisions, video recorders, servers, digital recorders, etc. A typical magnetic disk drive includes a head having a slider and a transducer with a read and write element that is in very close proximity to a surface of a rotatable magnetic disk. As the magnetic disk rotates beneath the head, a thin air bearing is formed between the surface of the magnetic disk and an air bearing surface (ABS) of the slider. The read and write elements of the head are alternatively used to read and write data while a suspension assembly positions the head along magnetic tracks on the magnetic disk. The magnetic tracks on the magnetic disks are typically concentric circular regions on the magnetic disks, onto which data can be stored by writing to it and retrieved by reading from it. 
     The slider is aerodynamically designed to fly above a rotating magnetic disk by virtue of an air bearing created between the ABS of the slider and the rotating magnetic disk. The ABS is the portion of the slider surface which is closest to the rotating magnetic disk, which is typically the head portion of the slider. The slider can also support a laser source that provides energy during writing in processes such as a heat assisted magnetic recording (HAMR) process. HAMR is a process used for recording information on magnetic medium having high coercivity. Magnetic medium having a large magnetic anisotropy constant Ku is sometimes preferred because it is thermally more stable than magnetic medium having a small Ku. Since magnetic medium with high Ku also has high coercivity, in cases where high Ku magnetic media is preferred, the preferred medium also has high coercivity. Recording information onto high Ku magnetic medium can be difficult because of the coercive forces of the magnetic recording medium. HAMR makes it easier to record onto a high Ku magnetic medium by applying heat with the use of a laser diode (LD), which is mounted onto the slider near the head. 
     HAMR uses a laser source to provide energy during the writing process. The energy source comes from an LD chip that is attached to a power source. The LD is also attached to the back of the slider and the light energy is guided to the ABS surface through a waveguide to heat the medium film for writing. 
     LD devices are often tested and screened before they are selected for use in a magnetic disk drive. The LD testing and screening processes are performed as part of a burn-in process of the LD. The burn-in process is used to screen out LD devices having “infant mortality” but often do not fail until they are used for some time. Incorporating testing and screening with the burn-in process helps reduce the number of magnetic hard drives that fail in the field as a result of having the LD devices fail. During the burn-in process, the LD is loaded into a fixture and heated at an elevated temperature for several hours with the LD energized. 
     Fixtures that are currently used to burn-in and test LD devices typically have contact probes as part of the fixture. The functions of the contact probes are to hold the LD devices in place on the fixture and to make electrical contact to the P-side and N-side of the LD. However these fixtures, which are currently used, have drawbacks. The integrated contact probes and moving shims, which are used to “lock” the components, are expensive to fabrication due to their complex design and are expensive to maintain because it is difficult to align and maintain the probes. Existing fixture designs are also limited in the number of LD devices that the fixture can support due to the probe design. Further, existing fixture designs are difficult to work with because it is difficult to load LD devices into the existing fixtures. 
     Therefore, what is needed is a system and method for LD testing and screening that is less expensive to use and maintain than existing fixtures while at the same time increases the number of devices per fixture, and provides for easy automated loading of the fixture. 
     SUMMARY 
     Several aspects of the present invention will be described more fully hereinafter with reference to various embodiments of apparatuses and methods related to LD testing and to ways of reducing the cost and time of LD testing. 
     One aspect of a system used for LD testing includes a first non-conductive layer having a plurality of through holes and a second conductive layer having a plurality of first openings. The second conductive layer is disposed over the first non-conductive layer with each of the plurality of first openings overlaying one of the plurality of through holes. The aspect of the system also includes a third non-conductive layer having a plurality of second openings that are larger than the plurality of first openings. The third non-conductive layer is disposed over the second conductive layer with each of the plurality of second openings overlaying one of the plurality of first openings. The plurality of first openings and the plurality of second openings form a plurality of pockets with a seat on the conductive layer. 
     Another aspect of a system used for LD testing includes a plurality of LD submount assemblies and a holder that holds the plurality of LD submount assemblies. Each LD submount assembly includes an LD, which has a first contact, and a submount, which has a second contact. The LD is disposed on the submount. The holder includes a first non-conductive layer having a plurality of through holes, a second conductive layer having a plurality of first openings, and a third non-conductive layer having a plurality of second openings that are larger than the plurality of first openings. The second conductive layer is disposed over the first non-conductive layer. The third non-conductive layer is disposed over the second conductive layer with each of the plurality of second openings overlaying one of the plurality of first openings. The plurality of first openings and the plurality of second openings form a plurality of pockets with a seat on the conductive layer. The plurality of submount assemblies is disposed within the plurality of pockets with the second contact of the submount making electrical contact with the second conductive layer at the seat and each LD being disposed within one of the first openings. 
     Another aspect of a method used for LD testing includes providing a first non-conductive layer having a plurality of through holes, stacking a second conductive layer, which has a plurality of first openings, over the first non-conductive layer, and stacking a third non-conductive layer having a plurality of second openings that are larger than the plurality of first openings over the second conductive layer with each of the plurality of second openings overlaying one of the plurality of first openings. The plurality of first openings and the plurality of second openings form a plurality of pockets with a seat on the conductive layer. The aspect of the method also includes providing a plurality of LD submount assemblies, wherein each LD submount assembly includes an LD and is disposed on a submount. The LD includes a first contact and the submount includes a second contact. The aspect further includes disposing the plurality of laser diode submount assemblies in the plurality of pockets with the second contact of the submount making electrical contact with the second conductive layer at the seat and each LD being disposed within one of the first openings. 
     It will be understood that other aspects of the present invention will become readily apparent to those skilled in the art from the following disclosure, wherein it is shown and described only several embodiments of the invention by way of illustration. As will be realized by those skilled in the art, the present invention is capable of other and different embodiments and its several details are capable of modification in various other respects, all without departing from the spirit and scope of the invention. Accordingly, the drawings and detailed description are to be regarded as illustrative in nature and not as restrictive. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Various aspects of the present invention will now be presented in the detailed description by way of example, and not by way of limitation, with reference to the accompanying drawings, wherein: 
         FIG. 1  is a conceptual view an exemplary embodiment of a magnetic disk drive that incorporates a magnetic head and slider. 
         FIG. 2  is an illustration showing the main body of a Chip-On-Submount-Assembly (COSA). 
         FIG. 3A  is an illustration showing perspective view of a COSA burn-in fixture with COSA devices loaded into the fixture. 
         FIG. 3B  is an illustration showing the components of COSA burn-in fixture  300 , with COSA devices, illustrated in  FIG. 3A . 
         FIG. 4A  is an illustration showing a top view of COSA burn-in fixture  300 , with COSA devices, illustrated in  FIG. 3A . 
         FIG. 4B  is an enlarged view of region  410  identified as a circle in the top view of the COSA burn-in fixture illustrated in  FIG. 4A . 
         FIG. 4C  is an enlarged cross sectional view along cutline A-A′ illustrated in the enlarged view of the COSA burn-in fixture illustrated in  FIG. 4B . 
         FIG. 5A  is an illustration showing a top view of base plate  320  depicted in  FIG. 3A . 
         FIG. 5B  is an illustration showing a top view of plate holder  322  depicted in  FIG. 3A . 
         FIG. 5C  is an enlarged view of region  520  identified as a circle in the top view of plate holder  322 , which is illustrated in  FIG. 5B . 
         FIG. 5D  is an illustration showing a top view of conductive plate  324  depicted in  FIG. 3A . 
         FIG. 5E  is an enlarged view of region  530  identified as a circle in the top view of conductive plate  324 , which is illustrated in  FIG. 5D . 
         FIG. 5F  is an illustration showing a top view of top plate  326  depicted in  FIG. 3A . 
         FIG. 5G  is an illustration showing a side view of alignment pin  328  depicted in  FIG. 3A . 
         FIG. 6A  is an illustration showing a cross sectional view of a COSA burn-in fixture. 
         FIG. 6B  is an illustration showing a cross sectional view of COSA devices loaded into pockets of a COSA burn-in fixture  600 , which is illustrated in  FIG. 6A . 
         FIG. 6C  is an illustration showing a cross sectional view of a COSA burn-in fixture, with loaded COSA devices, which is illustrated in  FIG. 6B  with a base plate  320  in place. 
         FIG. 7A  is an illustration showing a cross sectional view of a COSA mounted in a COSA burn-in fixture with one electrical contact being made using a pogo pin on a printed circuit board (PCB). 
         FIG. 7B  is an illustration showing a cross sectional view of a COSA mounted in a COSA burn-in fixture with one electrical contact being made using a dimple on a PCB. 
         FIG. 8  is an illustration showing two rows of COSA devices mounted in a COSA burn-in fixture orientated to allow measurement of COSA laser power output during burn-in. 
         FIG. 9  is a flowchart illustrating an embodiment of a method used to test and screen COSA devices during the COSA fabrication process. 
     
    
    
     DETAILED DESCRIPTION 
     The detailed description is intended to provide a description of various exemplary embodiments of the present invention and is not intended to represent the only embodiments in which the invention may be practiced. The term “exemplary” used throughout this disclosure means “serving as an example, instance, or illustration,” and should not necessarily be construed as preferred or advantageous over other embodiments. The detailed description includes specific details for the purpose of providing a thorough and complete disclosure that fully conveys the scope of the invention to those skilled in the art. However, the invention may be practiced without these specific details. In some instances, well-known structures and components may be shown in block diagram form, or omitted entirely, in order to avoid obscuring the various concepts presented throughout this disclosure. 
     Various aspects of the present invention may be described with reference to certain shapes and geometries. Any reference to a component having a particular shape or geometry, however, should not be construed as limited to the precise shape illustrated or described, but shall include deviations that result, for example, from manufacturing techniques and/or tolerances. By way of example, a component, or any part of a component, may be illustrated or described as rectangular, but in practice may have rounded or curved features due to manufacturing techniques and/or tolerances. Accordingly, the components illustrated in the drawings are schematic in nature and their shapes are not intended to illustrate the precise shape of the component, and therefore, not intended to limit the scope of the present invention. 
     In the following detailed description, various aspects of the present invention will be presented in the context of lapping row bars during the fabrication of magnetic heads used in magnetic disk drives. While these inventive aspects may be well suited for this application, those skilled in the art will realize that such aspects may be extended to other applications. Accordingly, any reference to apparatuses and methods related to lapping row bars during magnetic head fabrication processes, which are used in magnetic disk drives, is intended only to illustrate the various aspects of the present invention, with the understanding that such aspects may have a wide range of applications. 
       FIG. 1  is a conceptual view of an exemplary magnetic disk drive. The magnetic disk drive  100  is shown with a rotatable magnetic disk  102 . The magnetic disk  102  may be rotated on a spindle  103  by a disk drive motor (not shown) located under the magnetic disk  102 . A head  104 , which can be a perpendicular magnetic recording (PMR) head or lateral magnetic recording (LMR) head, may be used to read and write information by detecting and modifying the magnetic polarization of the recording layer on the disk&#39;s surface. The head  104  is generally integrally formed with a carrier or slider (not shown). The function of the slider is to support the head  104  and any electrical connections between the head  104  and the rest of the magnetic disk drive  100 . The slider is mounted to a positioner arm  106  which may be used to move the head  104  on an arc across the rotating magnetic disk  102 , thereby allowing the head  104  to access the entire surface of the magnetic disk  102 . The positioner arm  106  comprises a head gimbal assembly (HGA), which includes a load beam and a gimbal disposed on the end of the load beam, and an actuator unit  108 . The positioner arm  106  may be moved using a voice coil actuator, which is part of the actuator  108 , or by some other suitable means. 
     The slider is aerodynamically designed to fly above the magnetic disk  102  by virtue of an air bearing created between the surface of the slider and the rotating magnetic disk  102 . This surface of the slider is referred to as an air bearing surface (ABS). The ABS is the portion of the slider surface which is closest to the rotating magnetic disk  102 , which is typically the head  104 . In order to maximize the efficiency of the head  104 , the sensing elements (i.e., the read and write heads) are designed to have precise dimensional relationships to each other. In addition, the distance between the ABS and the rotating magnetic disk  102  is tightly controlled. The dimension that relates to the write function is known as the throat height and the dimension that relates to the read function is known as the stripe height. Both the stripe height and the throat height are controlled by a lapping process. 
     The slider can also support a laser source that provides energy during a writing process, such as in a heat assisted magnetic recording (HAMR) process. HAMR is a process used for recording information on magnetic medium having high coercivity. Magnetic medium having a large magnetic anisotropy constant Ku is sometimes preferred because it is thermally more stable than magnetic medium having a small Ku. Since magnetic medium with high Ku also has high coercivity, in cases where high Ku magnetic media is preferred, the preferred medium also has high coercivity. Recording information onto high Ku magnetic medium can be difficult because of the coercive forces of the magnetic recording medium. HAMR makes it easier to record onto high Ku magnetic medium by applying heat with a laser diode (LD), along with a magnetic field, at the time of recording so that coercive forces are reduced. The energy source comes from a laser diode (LD) chip bonded on a submount chip which is referred to as the Chip-On-Submount-Assembly (COSA). The COSA is attached to the back of the slider and the light energy is guided to the ABS surface through a waveguide to heat the medium film for writing. 
       FIG. 2  is an illustration showing the main body of a COSA  200 , which includes a submount  210  and a laser diode (LD)  212 . LD  212  can be an edge type emitting LD with a first electrode underneath (not shown) and a second electrode  214  disposed on top of LD  212 . In one embodiment the first electrode is an n-electrode that is electrically coupled to an n-electrode of LD  212  and the second electrode is a p-electrode that is electrically coupled to a p-electrode of LD  212 . In another embodiment the first electrode is a p-electrode that is electrically coupled to a p-electrode of LD  212  and the second electrode is an n-electrode that is electrically coupled to an n-electrode of LD  212 . 
     Submount  210  is made from a substrate, such as silicon, and has a first electrical pad  218  disposed on top of a mounting surface  216  of submount  210 . Mounting surface  216  can be covered with an insulation layer. The insulating layer separates the top of the substrate from the first electrical pad  218  and is used to electrically isolate the first electrical pad  218  from the substrate as well as provide electrical isolation to LD  212 . LD  212  is mounted on a mounting surface  216  of submount  210  so that a first electrode of LD  212  is electrically coupled and firmly attached to the first electrical pad  218 , by soldering or other means. Second electrode  214  can include a second electrical pad formed directly or indirectly on the second electrode  214  to fan out the electrical contact area for the second electrode  214 . 
     The first electrical pad  218 , which is electrically connected to the first electrode, can be electrically connected with a connection wiring disposed at a head gimbal assembly (HGA) supporting the magnetic head  104  by an appropriate method such as wire bonding, etc. Similarly, the second electrode  214  can be connected with the wiring of the HGA by an appropriate method such as wire bonding. During operation of the magnetic disk device  100 , current is supplied to LD  212  from a power source of the magnetic disk device  100  through the first electrical pad  218 , which is electrically connected to the first electrode, and the second electrode  214 . 
     During fabrication of the magnetic disk drive  100 , COSA  200  undergoes a burn-in process along with testing of LD  212 . The burn-in process is used to screen out laser diodes with “infant mortality” and to perform a characteristic assessment of LD  212 . During the burn-in process, COSA  200  is loaded into a COSA burn-in fixture and heated at an elevated temperature for a predetermined time (i.e. several hours) with the laser diode energized. The burn-in process includes a test that measures and assesses variation over time of LD  212  light output at high temperatures while a current passes through LD  212 . 
       FIG. 3A  is an illustration showing perspective view of a COSA burn-in fixture  300  with COSA  200  devices loaded into the fixture. COSA burn-in fixture  300  is used to perform burn-in and test of LD  212 . COSA burn-in fixture  300  is made of shims with pre-fabricated pockets or openings having layers of interleaving conducting and non-conducting material, as explained with reference to  FIG. 3B . 
       FIG. 3B  is an illustration showing the components of COSA burn-in fixture  300  with COSA  200  devices illustrated in  FIG. 3A . COSA burn-in fixture  300  is made of shims with pre-fabricated pockets or openings having three layers of interleaving conducting and non-conducting material. COSA burn-in fixture  300  includes a base plate  320 , a plate holder  322 , a conductive plate  324 , a top plate  326 , and an alignment pin  328 . Base plate  320  is a metallic layer which serves as the base or foundation for the subsequent COSA burn-in fixture  300  layers. The plate holder  322  is a non-conducting layer with an opening bigger than the width of COSA  200 . The thickness of this plate holder  322  is less than the thickness of the submount  210 . 
     Conductive layer  324 , which is the middle layer and is made of a conductive material, has an opening bigger than the width of LD  212  of COSA  200  device. The thickness of conductive layer  324  is greater than the thickness of LD  212 , as described in more detail with reference to  FIGS. 6A-6C . Conductive layer  324  is used to make electrical contact to the first electrical pad  218 , which is electrically connected to the first electrode. In the embodiment where the first electrode is an n-electrode, conductive layer  324  is used to make electrical contact to the N-side on LD  212  and COSA  200 . Alternatively, in the embodiment where the first electrode is a p-electrode, conductive layer  324  is used to make electrical contact to the p-side on LD  212  and COSA  200 . 
     Top plate  326  is a non-conductive layer with a through hole. The through hole forms an opening that is bigger or smaller than the width of LD  212 . The thickness of top plate  326  can be less than or greater than the thickness of LD  212 . Plate holder  322 , conductive plate  324  and top plate  326  are stacked such that they form pockets for holding COSA  200  devices. COSA  200  devices are disposed in the pockets. Plate holder  322 , conductive plate  324 , top plate  326 , and COSA  200  devices are all pressed together and secured to the base plate  320  using alignment pin  328 . Electrical contact to the second electrode of LD  212  is made through the opening on top plate  326 . In the embodiment where the second electrode is a p-electrode, electrical contact to the p-side on LD  212  is made through the opening on top plate  326 . Alternatively, in the embodiment where the second electrode is an n-electrode, electrical contact to the n-side on LD  212  is made through the opening on top plate  326 . 
       FIG. 4A  is an illustration showing a top view of COSA burn-in fixture  300  with COSA  200  devices, illustrated in  FIG. 3A . The top view of COSA burn-in fixture  300  shows top plate  326  with openings  402  ( 20  shown) and the top of alignment pins  328 . The openings  402  provide a path to access the second electrode of LD  212 .  FIG. 4B  is an enlarged view of region  410  identified as a circle in the top view of COSA burn-in fixture  300 , which is illustrated in  FIG. 4A . The enlarged region  410  illustrates openings  402  in top plate  326  with the second electrode  214 , which is located on the top portion of LD  212 , being exposed. 
       FIG. 4C  is an enlarged cross sectional view along cutline A-A′ illustrated in the enlarged view of COSA burn-in fixture  300  shown in  FIG. 4B . The cross sectional view along cutline A-A′ shows base plate  320 , plate holder  322 , conductive plate  324 , top plate  326  with openings  402 , and COSA  200  device disposed in COSA burn-in fixture  300 . 
       FIG. 5A  is an illustration showing a top view of base plate  320  with holes for alignment pins  328 , as depicted in  FIG. 3A . Base plate  320  can be made of a metallic material such as aluminum, stainless steel, etc. Base plate  320  can also be rectangular in shape. In one embodiment, base plate  320  is fabricated using etching methods. 
       FIG. 5B  is an illustration showing a top view of plate holder  322  depicted in  FIG. 3A . Plate holder  322  is a non-conducting layer having a shape similar to base plate  320  and having an opening bigger than the width of COSA  200  device. Plate holder  322  can be made of a non-conductive material such as a polymer, plastic, ceramic, etc.  FIG. 5C  is an enlarged view of region  520  identified as a circle in the top view of plate holder  322 , which is illustrated in  FIG. 5B . Region  520  shows that plate holder openings  522  have a shape that is either square or rectangular with circular corners. In one embodiment, plate holder  322  is fabricated using etching methods. 
       FIG. 5D  is an illustration showing a top view of conductive plate  324  depicted in  FIG. 3A . Conductive plate  324  can be made of a metallic material such as copper, aluminum, stainless steel, etc. Conductive plate  324  is a conducting layer having a shape similar to base plate  320  and/or plate holder  322  and has an opening bigger than the width of LD  212 , which is part of COSA  200  device. The thickness of conductive layer  324  is also greater than the thickness of LD  212 .  FIG. 5E  is an enlarged view of region  530  identified as a circle in the top view of conductive plate  324 , which is illustrated in  FIG. 5D . Region  530  shows that conductive plate  324  has light channels  532  that extend from where LD  212  is disposed to the outer edge of conductive plate  324 . The light channels  532  in conductive plate  324  are openings that allow light, which is emitted from LD  212 , to escape COSA burn-in fixture  300  for testing. In one embodiment, conductive plate  324  is fabricated using etching methods. 
       FIG. 5F  is an illustration showing a top view of top plate  326  depicted in  FIG. 3A . Top plate  326  can have a thickness that is less than the thickness of LD  212  and is made of a non-conductive layer material such as a polymer, plastic, ceramic, etc. Top plate  326  also has a through hole that forms a top plate opening  542  that can be bigger or smaller than the width of submount  210  or the width of LD  212 . In one embodiment, top plate  326  is fabricated using etching methods. 
       FIG. 5G  is an illustration showing a side view of alignment pin  328  depicted in  FIG. 3A . Alignment pin  328  can be any shape such as a rod shape, cylindrical shape, rectangular shape, etc. Alignment pin  328  fits into the alignment holes of base plate  320 , plate holder  322 , conductive layer  324  and top plate  326  and is used to align them all together and secure all of them together along with COSA  200  devices. 
       FIG. 6A  is an illustration showing a cross sectional view of plate holder  322 , conductive layer  324  and top plate  326  arranged as part of COSA burn-in fixture  300 . Plate holder  322 , conductive layer  324  and top plate  326  are stacked such that they form a pocket  610  for a COSA  200  device. In one embodiment, plate holder  322 , conductive layer  324  and top plate  326  are stack directly on each other so that plate holder  322  makes direct contact with conductive layer  324  and conductive layer  324  makes direct contact with top plate  326 . Plate holder  322  includes through holes  602  that extend completely through plate holder  322 . 
       FIG. 6B  is an illustration showing a cross sectional view of COSA devices  200  loaded into pockets  610  of a COSA burn-in fixture  600  illustrated in  FIG. 6A . Pocket  610  is configured to have COSA  200  devices sit inside the pockets and to have the COSA  200  devices make contact with conductive layer  324 . Specifically, the first electrical pad  218  disposed on the submount  210  makes electrical contact with conductive layer  324 . Since the first electrical pad  218  is electrically coupled to the first electrode of LD  212 , the conductive layer  324  is electrically connected to the first electrode of LD  212 . When LD  212  is disposed within pocket  610 , LD  212  is aligned with through holes  602  and LD  212  does not contact top plate  326 . In one embodiment, all COSA  200  devices are in contact with the same conductive layer  324  and therefore all COSA  200  devices share the same electrical contact to the first electrode of their LD  212 . In an embodiment where the first electrical contact is an n-contact, all COSA  200  devices share a common n-contact. 
       FIG. 6C  is an illustration showing a cross sectional view of a COSA burn-in fixture with loaded COSA  200  devices illustrated in  FIG. 6B  with base plate  320  in place. Once all COSA  200  devices are loaded into pockets  610  of COSA burn-in fixture  300 , base plate  320  is put in place to hold and keep COSA  200  devices in position inside their respective pockets  610 . Base plate  320 , plate holder  322 , conductive layer  324 , top plate  326  and all COSA  200  devices are aligned and secured together using alignment pin  328 . This configuration puts a force on COSA  200  devices so that the first electrical pad  218  of COSA  200  device presses against conductive layer  324  to provide secure electrical contact. 
       FIG. 7A  is an illustration showing a cross sectional view of a COSA  200  device mounted in a COSA burn-in fixture  300  with one electrical contact being made using a pogo pin  710  on a PCB  720 . COSA  200  devices are disposed in pockets  610 , which are formed by stacking plate holder  322 , conductive layer  324  and top plate  326  together. COSA  200  devices also have their first electrical pads  218 , which are disposed on their submounts  210 , making electrical contact with conductive layer  324 . Further, since the first electrical pads  218  is electrically coupled to the first electrode of each LD  212 , conductive layer  324  is electrically connected to the first electrode of each LD  212 . Electrical contact is made to the second electrode of LD  212  using a pogo pin  710  on PCB  720 . 
     PCB  720  is aligned with top plate  326  so that pogo pins  710  align with the top plate openings of top plate  326 . Pogo pins  710 , which are inserted into the top plate openings, extend through the openings making contact with the second electrode  214  disposed on top of LD  212 . A power source  730  is then connected to pogo pins  710  and conductive layer  324 . Since conductive layer  324  is electrically connected to the first electrode of LD  212 , a complete circuit is formed between the power source  730 , pogo pins  710  disposed on PCB  720 , LD  212 , and conductive layer  324 . With this configuration LD  212  can be powered to produce light. In the embodiment where the first electrode is an n-electrode and the second electrode is a p-electrode, pogo pins  710  are connected to the p-electrode of LD  212  and conductive layer  324  is connected to the n-electrode of LD  212 . 
       FIG. 7B  is an illustration showing a cross sectional view of a COSA  200  device mounted in a COSA burn-in fixture  300  with one electrical contact being made using a dimple  740  on a PCB  720 . COSA  200  devices are disposed in pockets  610 , which are formed by stacking plate holder  322 , conductive layer  324  and top plate  326  together. COSA  200  devices also have their first electrical pads  218 , which are disposed on their submounts  210 , making electrical contact with conductive layer  324 . Further, since the first electrical pads  218  is electrically coupled to the first electrode of each LD  212 , conductive layer  324  is electrically connected to the first electrode of each LD  212 . Electrical contact is made to the second electrode of LD  212  using a dimple  740  on PCB  720 . 
     PCB  720  is aligned with top plate  326  so that dimples  740  align with the top plate openings of top plate  326 . Dimples  740 , which are inserted into the top plate openings, extend through the openings making contact with the second electrode  214  disposed on top of LD  212 . A power source  730  is then connected to dimples  740  and conductive layer  324 . Since conductive layer  324  is electrically connected to the first electrode of LD  212 , a complete circuit is formed between the power source  730 , dimples  740  disposed on PCB  720 , LD  212 , and conductive layer  324 . With this configuration, LD  212  can be powered to produce light. In the embodiment where the first electrode is an n-electrode and the second electrode is a p-electrode, dimples  740  are connected to the p-electrode of LD  212  and conductive layer  324  is connected to the n-electrode of LD  212 . 
       FIG. 8  is an illustration showing two rows of COSA  200  devices mounted in a COSA burn-in fixture  300  orientated to allow measurement of laser power output during burn-in. COSA burn-in fixture  300  is used to identify defective COSA  200  devices by mounting COSA  200  devices in COSA burn-in fixture  300  and measuring pre and post burn-in by independently energizing each LD  212 , which is disposed in COSA burn-in fixture  300 , in a testing system having an array of detectors  810 . Alternatively, COSA burn-in fixture  300  can be mounted into a testing system that has only one detector/tester on each side of COSA burn-in fixture  300 . In this alternative tester, LD  212  can be moved in front of a detector/tester by indexing COSA burn-in fixture  300  with mounted COSA  212  devices so that one LD  212  is moved in front of the detector/tester at a time. 
     COSA burn-in fixture  300  is aligned with a plurality of detectors/testers  810  ( 28  shown with  14  on each side) so that light  820  generated by each of LD  212 , which comes out of the COSA burn-in fixture  300  through the light channels  532 , is captured by the detectors/testers  810 . The light generated by LD  212  is extracted from the COSA burn-in fixture through the light channels  532  formed in conductive layer  324 . The different layers which make up COSA burn-in fixture  300  are aligned with alignment pin  328 . 
     COSA burn-in fixture  300  provides a simple, low cost, easy to manufacture, and easy to load fixture design as compared to other systems available to test laser diodes. COSA burn-in fixture  300  has no moving components which has a distinct maintenance cost advantage, enables a high device loading/fixture area for high throughput and space utilization in the burn-in system, and allows for fast and low cost conversion for new laser and submount configurations, sizes and designs. COSA burn-in fixture  300  also increases the number of COSA  200  devices that can be loaded onto the fixture, facilitates easy insertion of COSA  200  devices into COSA burn-in fixture  300 , eliminates delicate complicated wire probes that hold and power LD  212  devices, and allows the ability to quickly disassemble COSA burn-in fixture  300  to allow for cleaning of the individual layers, which do not have any deep pockets and cavities which would make cleaning difficult. COSA burn-in fixture  300  can also hold at least 50 COSA  200  devices per fixture. COSA burn-in fixture  300  is also much less expensive to build and maintain than other commercially available fixtures. 
       FIG. 9  is a flowchart illustrating an embodiment of a method used to test and screen out COSA devices during the fabrication process of the magnetic disk drive  100 . The process starts in operation  902  when process equipment, including detectors/testers, is initialized. In operation  904 , a plate holder  322 , which is first non-conductive layer, having a plurality of through holes is provided. Next in operation  906 , a conductive layer  324  is stacked over plate holder  322 . Conductive layer has a plurality of first openings. In operation  908 , a top plate  326 , which is a non-conductive layer, having a plurality of second openings that are larger than the plurality of first openings, is stacked over conductive layer  324 . Top plate  326  is stacked over conductive layer  324  so that each of the plurality of second openings overlays one of the plurality of first openings. The plurality of first openings and the plurality of second openings form a plurality of pockets with a seat on the conductive layer for disposing COSA  200  devices. 
     In operation  910 , a plurality of COSA  200  devices are provided. COSA  200  devices include a submount  210  and an LD  212 , where a first electrode of LD  212  is coupled to a first electrical pad  218  on the submount and a second electrode  214  of LD  212  is on LD  212 . Next in operation  912 , the plurality of COSA  200  devices are disposed in the plurality of pockets with the first electrical pad  218  of the submount  210  making electrical contact with the second conductive layer  324  at the seat. Each LD  212  is disposed within one of the first openings. In operation  914 , a base plate  320  is provided and aligned with plate holder  322 . In operation  916 , base plate  320 , plate holder  322 , conductive plate  324 , and top plate  326 , are all aligned and held together with alignment pin  328 . In operation  918 , the plurality of the first electrical pad  218  on the plurality of submounts  210  are pressed together with conductive layer  324  at the seat by putting a force on base plate  320 , plate holder  322 , conductive plate  324  and top plate  326 , which are all aligned and held together with alignment pin  328 . 
     In operation  920 , a PCB  720  having pogo pins  710 , or dimples  740 , or other connectors is aligned with top plate  326  so that pogo pins  710 , or dimples  740 , or other connectors extend into the openings of top plate  326  and make electrical contact with the second electrode  214  of LD  212 . In operation  922  the circuit is completed by connecting a power source  730  to conductive layer  324  and pogo pins  710 , or dimples  740 , or other connectors. In operation  922 , COSA  200  devices are also tested and screened by placing the attached COSA burn-in fixture in a detector/tester. The process ends in operation  924  when COSA  200  devices are disposed after testing. 
     The various aspects of this disclosure are provided to enable one of ordinary skill in the art to practice the present invention. Various modifications to exemplary embodiments presented throughout this disclosure will be readily apparent to those skilled in the art, and the concepts disclosed herein may be extended to other devices. Thus, the claims are not intended to be limited to the various aspects of this disclosure, but are to be accorded the full scope consistent with the language of the claims. All structural and functional equivalents to the various components of the exemplary embodiments described throughout this disclosure that are known or later come to be known to those of ordinary skill in the art are expressly incorporated herein by reference and are intended to be encompassed by the claims. Moreover, nothing disclosed herein is intended to be dedicated to the public regardless of whether such disclosure is explicitly recited in the claims. No claim element is to be construed under the provisions of 35 U.S.C. §112, sixth paragraph, unless the element is expressly recited using the phrase “means for” or, in the case of a method claim, the element is recited using the phrase “step for.”