Abstract:
A system and method are disclosed for remelting solder balls in the forming of electrical connections between an electrical component being mounted on a printed circuit board (PCB). Vias are formed in the PCB. Underneath the PCB, a laser is directed through the via to remelt the solder ball to make the connection. In one version, the laser is included on a positioning device. The positioning device translates the laser to a location from which it is aimed through the aperture at the solder mass. In other versions, a camera on the positioning device helps position the laser by making reference to a fiducial mark on the PCB. Further, a detector can be used to determine laser intensity by measuring the output after it passes through the via.

Description:
BACKGROUND 
       [0001]    A recent trend in reducing size and cost of electronic systems is the increased use of surface mount components, which mount to one side of a printed circuit board (“PCB”). Such components may require less space on a PCB, and alleviate PCB routing constraints, as compared to components having pins that mount through holes of the PCB. However, reliability of an electronic system is often determined, at least in part, by the reliability of soldered connections among devices and PCBs of the system, and it can be problematic to ensure reliable connections of surface mounted components to a PCB. 
         [0002]    One example of a surface mount component is a Ball Grid Array (“BGA”) package that includes solder balls laid out in a grid. BGA packages may be installed by using hot, forced air or infrared heat applied to a substantial area of a PCB, or the entire PCB, to melt (or “reflow”) the solder balls. The amount of heat required to insure that all of the solder balls of a BGA are properly reflowed can create collateral damage to other adjacent components on the PCB, or damage connections between the components and the PCB. 
       SUMMARY 
       [0003]    Some embodiments disclosed include systems and methods for melting one or more solder masses. The mass, in some embodiments, is used to form an electrical connection between an electrical component and a PCB where the PCB includes an aperture (e.g., a via). The system, in one embodiment, includes a laser which is able to be directed at the solder mass through the aperture. In one embodiment the laser is attached to a translatable positioning device for the purpose of translating said laser to a location from which a beam emitted from said laser is aimed through the aperture at the solder mass. 
         [0004]    In other embodiments a detector is used for calibration. The detector can be used to receive the beam and determine its intensity after passing through the aperture. (This is done before the component has been positioned for installation). 
         [0005]    In other embodiments a camera is associated with said laser. The camera makes reference to a fiducial mark such that laser position is determinable when a control system receives information from said camera regarding said fiducial mark. 
         [0006]    Embodiments of the system also include the use of an optical device. The optical device receives the laser beam and changes a characteristic of the beam. In one embodiment, the characteristic is focus. 
         [0007]    In other embodiments, the laser is located remotely from a translatable laser positioning device. In these embodiments one or more fiber optic cables are used to deliver the laser beam emitted into one or more optical devices on the positioning device. The optical devices aim and focus the laser light for transmission at the solder. In other embodiments, a fiber optic splitter arrangement might be used to divide a single beam into many. 
     
    
     
       BRIEF DESCRIPTION OF DRAWINGS 
         [0008]      FIG. 1  shows a cross-sectional schematic view of one through-via laser reflow system that mounts a surface mount component to a PCB, in accord with an embodiment. 
           [0009]      FIG. 2  shows the through-via laser reflow system, PCB and surface mount component of  FIG. 1  after reflow of a solder ball. 
           [0010]      FIG. 3  shows a cross-sectional schematic view of one through-via laser reflow system that mounts a surface mount component to a PCB, in accord with an embodiment. 
           [0011]      FIG. 4  shows a cross-sectional schematic view of one through-via laser reflow system that mounts a surface mount component to a PCB, in accord with an embodiment. 
           [0012]      FIG. 5  shows a cross-sectional schematic view of one through-via laser reflow system that mounts a surface mount component to a PCB, in accord with an embodiment. 
           [0013]      FIG. 6  shows a cross-sectional schematic view of one portion of another through-via laser reflow system that mounts surface mount component  20 ( 2 ) to a PCB, in accord with an embodiment. 
           [0014]      FIG. 7  shows a cross-sectional schematic view of one portion of another through-via laser reflow system that mounts surface mount component  20 ( 2 ) to a PCB, in accord with an embodiment. 
           [0015]      FIG. 8  shows a block diagram of components of a through-via laser reflow system, in accord with an embodiment. 
           [0016]      FIG. 9  shows a flowchart illustrating steps of a process for calibration and setup of a through-via laser reflow system, in accord with an embodiment. 
           [0017]      FIG. 10  shows a flowchart illustrating steps of a process for installing a component to a PCB by utilizing a through-via laser reflow system to reflow solder balls, in accord with an embodiment. 
       
    
    
     DETAILED DESCRIPTION 
       [0018]      FIG. 1  shows a cross-sectional schematic view of a through-via laser reflow system  100 ( 1 ) that mounts a surface mount component  20 ( 1 ) to a PCB  10 ( 1 ).  FIG. 1  may not be drawn to scale. Component  20 ( 1 ) is, for example, a Ball Grid Array (“BGA”) package that includes an arrangement of solder balls  30 ( 1 )- 30 ( 4 ). PCB  10 ( 1 ) forms apertures  15 ( 1 )- 15 ( 4 ) in an arrangement that matches the arrangement of solder balls  30 ( 1 )- 30 ( 4 ) at electrical connection points  40 ( 1 )- 40 ( 4 ) of component  20 ( 1 ). In the disclosed embodiment, apertures  15 ( 1 )- 15 ( 4 ) are vias. PCB  10 ( 1 ) includes metallization  12 ( 1 )- 12 ( 4 ) that surrounds each of vias  15 ( 1 )- 15 ( 4 ), respectively, as shown. It is understood that the depiction of solder balls is illustrative and that other configurations of solder are within the scope of the present disclosure. Furthermore, the number of vias  15  and solder balls  30  depicted in the appended drawings are illustrative only; another, typically higher number and arrangement of vias  15  and solder balls  30  is within the scope of the present disclosure. 
         [0019]    A laser  120 ( 1 ) of through-via laser reflow system  100 ( 1 ) emits a beam  110 ( 1 ) of electromagnetic energy that reflows one of solder balls  30 ( 1 )- 30 ( 4 ) of component  20 ( 1 ) to PCB  10 ( 1 ). For example,  FIG. 1  shows beam  110 ( 1 ) aimed through via  15 ( 2 ) so that it impinges on solder ball  30 ( 2 ). Heat generated when solder ball  30 ( 2 ) absorbs beam  110 ( 1 ) melts solder ball  30 ( 2 ), forming an electrical connection between connection point  40 ( 2 ) of component  20 ( 1 ) and metallization  12 ( 2 ) of PCB  10 ( 1 ). Via  15 ( 2 ) allows direct access of beam  110 ( 1 ) to solder ball  30 ( 2 ) so that the heat is concentrated where it is required, thus minimizing transfer of heat to PCB  10 ( 1 ) and adjacent components thereon. 
         [0020]    Through-via laser reflow system  100 ( 1 ) includes an optional mechanical positioning subsystem  140 ( 1 ) that moves at least beam  110 ( 1 ) in one or both of the directions of arrows  145 ,  145 ′ so that beam  110 ( 1 ) aims accurately into a specific via  15  (e.g., any of vias  15 ( 1 )- 15 ( 4 ), or other vias  15  not shown in  FIG. 1 ). Mechanical positioning subsystem  140 ( 1 ) may include, for example, a linear stepper motor, an air bearing slider, a leadscrew system, or some other known arrangement capable of executing the desired positioning. It is understood that additional mechanical positioning subsystems (not shown) may also be utilized to position laser  120 ( 1 ) in directions besides those depicted by arrows  145 ,  145 ′. For example, positioning subsystem  140 ( 1 ) may move in one of the directions of arrows  145 ,  145 ′ while other such positioning subsystems move in and out of the cross-sectional plane illustrated in  FIG. 1 , and focusing subsystems may move laser  120 ( 1 ) vertically (that is, along the direction of beam  110 ( 1 )) to adjust focus of beam  110 ( 1 ) on PCB  10 ( 1 ). Still other positioning subsystems may align coordinate axes of the laser (e.g., the directions of arrows  145 ) with coordinate axes of PCB  10 ( 1 ). In another embodiment, laser could be moved in a two dimensional coordinate plane (with one dimension coming into and out of the page with respect to  FIG. 1 ) instead of the linear movement embodiment of  FIG. 1 . Alternatively, mechanical positioning subsystems may move PCB  10 ( 1 ) relative to system  100 ( 1 ), instead of moving laser  120 ( 1 ) relative to system  100 ( 1 ). Also, system  100 ( 1 ) may include an optical positioning subsystem (not shown) that aims beam  110 ( 1 ) while leaving laser  120 ( 1 ) stationary within system  100 ( 1 ). 
         [0021]    Through-via laser reflow system  100 ( 1 ) may include an optical alignment subsystem (not shown) having an illumination source, a processor, and a camera for capturing an image of a PCB  10  (e.g., PCB  10 ( 1 )) and/or alignment marks thereon. The processor may perform pattern recognition on the image to determine a position of PCB  10  relative to system  100 ( 1 ), in order to position subsystem  140 ( 1 ) so that beam  110 ( 1 ) aims at a specific via  15 . 
         [0022]    System  100 ( 1 ) may include apparatus that adjusts parameters of beam  100 ( 1 ) for optimum performance in various ways. For example, optics  130 ( 1 ) may include a focusing subsystem that adjusts a spot size and shape of beam  110 ( 1 ) and thereby compensates for (a) variations in distance between system  100 ( 1 ) and PCB  10 ( 1 ) and/or component  20 ( 1 ), (b) variations in size and shape among vias  15 , and/or (c) other manufacturing variables (e.g., composition of solder balls  30 ). Beam  110 ( 1 ) may be a form of electromagnetic energy that performs its intended purpose, such as ultraviolet light, visible light, infrared light or microwaves. System  100 ( 1 ) may include circuitry (not shown) for turning laser  120 ( 1 ) on or off. Laser  120 ( 1 ) may be a continuous wave laser, or may be a pulse laser. Laser  120 ( 1 ) may be operable to adjust wavelength and/or power of beam  110 ( 1 ). System  100 ( 1 ) may include mechanical and/or optical apparatus (not shown) for diverting or absorbing beam  110 ( 1 ) when beam  110 ( 1 ) is not in use. 
         [0023]      FIG. 2  shows through-via laser reflow system  100 ( 1 ), PCB  10 ( 1 ) and surface mount component  20 ( 1 ) after reflow of solder ball  30 ( 2 ).  FIG. 2  may not be drawn to scale. Solder that originally formed solder ball  30 ( 2 ) forms electronic connection  35 ( 1 ) between connection point  40 ( 2 ) of component  20 ( 1 ) and metallization  12 ( 2 ) of PCB  10 ( 1 ). 
         [0024]      FIG. 3  shows a cross-sectional schematic view of a through-via laser reflow system  100 ( 2 ) that mounts a surface mount component  20 ( 2 ) to a PCB  10 ( 2 ).  FIG. 3  may not be drawn to scale. Component  20 ( 2 ) is, for example, a BGA package that includes an arrangement of solder balls  30 ( 5 )- 30 ( 8 ), that matches an arrangement of vias  15 ( 5 )- 15 ( 8 ) in PCB  10 ( 2 ). A laser  120 ( 2 ) of through-via laser reflow system  100 ( 2 ) emits electromagnetic energy that is focused by optics  130 ( 2 ) into a fiber optic line  132 ( 1 ). Optics  160 ( 1 ) focuses the electromagnetic energy into beam  110 ( 2 ). System  100 ( 2 ) includes an optional mechanical positioning subsystem  140 ( 2 ) that moves a mechanical support element  165 ( 1 ) holding optics  160 ( 1 ). Subsystem  140 ( 2 ) moves in one of the directions of arrows  145 ,  145 ′ so that beam  110 ( 1 ) aims accurately into a specific via  15  (e.g., any of vias  15 ( 5 )- 15 ( 8 ), or other vias  15  not shown in  FIG. 3 ). Beam  110 ( 2 ) aims through one of respective vias  15 ( 5 )- 15 ( 8 ) so that it impinges on one of solder balls  30 ( 5 )- 30 ( 8 ), generating heat that melts the solder ball to form an electrical connection between component  20 ( 2 ) and PCB  10 ( 2 ). System  100 ( 2 ) may provide more rapid and/or precise positioning of beam  110 ( 2 ) as compared to system  100 ( 1 ) because fiber optic line  132 ( 1 ) and optics  160 ( 1 ) may present a lower mass to be moved than laser  120 ( 1 ). Reliability and/or longevity of laser  120 ( 2 ) may also be improved over that of laser  120 ( 1 ) since laser  120 ( 2 ) is not subjected to the mechanical stresses of movement. 
         [0025]    It is understood that additional mechanical positioning subsystems (not shown) may also be utilized to position beam  110 ( 2 ) in directions besides those depicted by arrows  145 ,  145 ′. For example, such positioning subsystems may move beam  110 ( 2 ) in and out of the cross-sectional plane illustrated in  FIG. 3 , and/or may align coordinate axes of the laser (e.g., the directions of arrows  145 ) with coordinate axes of PCB  10 ( 2 ). Alternatively, mechanical positioning subsystems may move PCB  10 ( 2 ) relative to system  100 ( 2 ), instead of moving laser  120 ( 2 ) relative to system  100 ( 2 ). Also, system  100 ( 2 ) may include an optical positioning subsystem (not shown) that aims beam  110 ( 2 ) while leaving laser  120 ( 2 ) stationary within system  100 ( 2 ). PCB  10 ( 2 ) includes a fiducial mark  17  that system  100 ( 2 ) can utilize to determine a relative position of positioning subsystem  140 ( 2 ) (and/or other positioning subsystems, not shown) with respect to PCB  10 ( 2 ); use of fiducial mark  17  is explained in connection with  FIG. 6 , below. 
         [0026]      FIG. 4  shows a cross-sectional schematic view of a through-via laser reflow system  100 ( 3 ) that, like system  100 ( 2 ), mounts surface mount component  20 ( 2 ) to PCB  10 ( 2 ).  FIG. 4  may not be drawn to scale. A laser  120 ( 3 ) of through-via laser reflow system  100 ( 3 ) emits electromagnetic energy that is focused by optics  130 ( 3 ) into a fiber optic line  132 ( 2 ), which couples with a fiber splitter  150 . Fiber splitter  150  mounts on a positioning subsystem  140 ( 2 ); line  132 ( 2 ) is long enough to allow positioning subsystem  140 ( 2 ) to move as necessary in the direction of arrows  145 ,  145 ′ (and in other directions, such as in and out of the cross-sectional plane illustrated in  FIG. 4 ). Fiber splitter  150  transmits portions of the electromagnetic energy transmitted through line  132 ( 2 ) into fiber optic lines  132 ( 3 )- 132 ( 6 ). Each of fiber optic lines  132 ( 3 )- 132 ( 6 ) emits a respective portion of electromagnetic energy as one of beams  110 ( 3 )- 110 ( 6 ) that may be shaped by optional optics  160 ( 2 )- 160 ( 5 ). Each of beams  110 ( 3 )- 110 ( 6 ) aims through one of respective vias  15 ( 5 )- 15 ( 8 ) so that they impinge on solder balls  30 ( 5 )- 30 ( 8 ), generating heat that melts solder balls  30 ( 5 )- 30 ( 8 ) to form electrical connections between component  20 ( 2 ) and PCB  10 ( 2 ). 
         [0027]    Use of fiber splitter  150 , fiber optic lines  132 ( 3 )- 132 ( 6 ) and optional optics  160 ( 1 )- 160 ( 4 ) to facilitate reflow of solder balls  30 ( 5 )- 30 ( 8 ) improves manufacturing throughput of system  100 ( 3 ) relative to system  100 ( 1 ). Again, the depiction of four beams  110  reflowing four solder balls  30  is illustrative only, it should be apparent that modifications may be made to generate any number of beams  110  to melt a corresponding number of solder balls  30 . Characteristics of fiber splitter  150 , of fiber optic lines  132 ( 3 )- 132 ( 6 ) and of optional optics  160 ( 1 )- 160 ( 4 ) may be individually configured to optimize reflow for solder balls and/or vias that are not identical in shape, size or solder ball composition. 
         [0028]    Optics  160 ( 1 )- 160 ( 4 ), fiber optic lines  132 ( 3 )- 132 ( 6 ) and/or fiber splitter  150  may couple with a mechanical support element  165 ( 2 ) so that they maintain alignment relative to each other while positioning subsystem  140 ( 2 ) moves. Collectively, optics  160 ( 1 )- 160 ( 4 ), fiber optic lines  132 ( 3 )- 132 ( 6 ), fiber splitter  150  and support element  165 ( 2 ) may form an optical subsystem (“OSS”)  167 ( 1 ) that is tailored to the arrangement of vias on board  10 ( 2 ). OSS  167 ( 1 ) may be removable as a unit from system  100 ( 2 ) by removing support element  165 ( 2 ) from positioning subsystem  140 ( 2 ) and disconnecting fiber splitter  150  from fiber optic line  132 ( 2 ) (or by disconnecting line  132 ( 2 ) from optics  130 ( 3 ). OSS  167 ( 1 ) and other OSSs (not shown) may install interchangeably on system  100 ( 3 ) as manufacturing demands may require, for reflowing solder balls of components having different via arrangements. 
         [0029]      FIG. 5  shows a cross-sectional schematic view of a through-via laser reflow system  100 ( 4 ) that, like systems  100 ( 2 ) and  100 ( 3 ), mounts surface mount component  20 ( 2 ) to PCB  10 ( 2 ).  FIG. 5  may not be drawn to scale. A laser  120 ( 4 ) of through-via laser reflow system  100 ( 4 ) emits electromagnetic energy that is split by beam splitters  170 ( 1 )- 170 ( 4 ) into separate beams  110 ( 8 )- 110 ( 11 ), which may be focused by optional optics  175 ( 1 )- 175 ( 4 ). System  100 ( 4 ) includes an optional mechanical positioning subsystem  140 ( 4 ) that moves a mechanical support element  165 ( 3 ) holding beam splitters  170 ( 1 )- 170 ( 4 ) and optional optics  175 ( 1 )- 175 ( 4 ). Subsystem  140 ( 2 ) moves in one of the directions of arrows  145 ,  145 ′ so that each of beams  110 ( 8 )- 110 ( 11 ) aims accurately into a specific via  15  (e.g., one of vias  15 ( 5 )- 15 ( 8 ), or other vias  15  not shown in  FIG. 5 ). Each of beams  110 ( 8 )- 110 ( 11 ) generates heat that melts solder balls  30 ( 5 )- 30 ( 8 ) to form electrical connections between component  20 ( 2 ) and PCB  10 ( 2 ). Again, the depiction of four beams  110  reflowing four solder balls  30  is illustrative only, it should be apparent that modifications may be made to generate any number of beams  110  to melt a corresponding number of solder balls  30 . 
         [0030]    Beam splitters  170 ( 1 )- 170 ( 4 ) and optics  175 ( 1 )- 175 ( 4 ) may couple with a mechanical support element  165 ( 3 ) so that the beam splitters and optics maintain alignment relative to each other while positioning subsystem  140 ( 4 ) moves. Collectively, beam splitters  170 ( 1 )- 170 ( 4 ), optics  175 ( 1 )- 175 ( 4 ) and support element  165 ( 3 ) may form an OSS  167 ( 2 ) that is tailored to the arrangement of vias on board  10 ( 2 ). OSS  167 ( 2 ) and other OSSs (not shown) may install interchangeably on system  100 ( 4 ) as manufacturing demands may require, for reflowing solder balls of components having different via arrangements. 
         [0031]    It should be apparent that system  100 ( 4 ) uses free space optics (e.g., beam splitters  170 ( 1 )- 170 ( 4 ) and optional optics  175 ( 1 )- 175 ( 4 )) analogously to system  100 ( 3 )&#39;s use of corresponding fiber coupled optics. Use of beam splitters  170 ( 1 )- 170 ( 4 ) to generate beams  110 ( 8 )- 110 ( 11 ) to reflow solder balls  30 ( 5 )- 30 ( 8 ) improves manufacturing throughput of system  100 ( 4 ) relative to system  100 ( 1 ). Characteristics of beam splitters  170 ( 1 )- 170 ( 4 ) and of optional optics  175 ( 1 )- 175 ( 4 ) may be individually configured to optimize reflow for solder balls and/or vias that are not identical in shape, size or solder ball composition. It is appreciated that other combinations of free space optics and fiber optics may be utilized in various embodiments, and that all such combinations are contemplated by the present disclosure. 
         [0032]      FIG. 6  shows a cross-sectional schematic view of one portion of a through-via laser reflow system  100 ( 5 ) that, like systems  100 ( 2 )- 100 ( 4 ), mounts surface mount component  20 ( 2 ) to PCB  10 ( 2 ).  FIG. 6  may not be drawn to scale. System  100 ( 4 ) includes a mechanical positioning subsystem  140 ( 5 ) that aims one or more laser beams (not shown) through respective vias  15 ( 5 )- 15 ( 8 ) (and/or other vias  15 ); each of the laser beams impinges on and melts a corresponding solder ball to form electrical connections between component  20 ( 2 ) and PCB  10 ( 2 ). The laser beams may be aimed by a laser alone, by fiber coupled optics, or by free space optics or by combinations thereof, as described in connection with  FIG. 1  through  FIG. 5 ; these elements are not shown in  FIG. 6  for clarity of illustration. 
         [0033]    A camera  180  mounts with positioning subsystem  140 ( 5 ); camera  180  forms images of a field of view  185 . Light emanates from one or more illuminators  190 ; camera  180  captures light that reflects from features of PCB  10 ( 2 ), including fiducial mark  17 . Camera  180  transmits image data of PCB  10 ( 2 ) to a processor (not shown) that utilizes pattern recognition processing to determine a location of camera  180 , and thus a location of positioning subsystem  140 ( 5 ), with respect to fiducial mark  17 . System  100 ( 5 ) may utilize location information of vias  15 ( 5 )- 15 ( 8 ) and other vias  15  (not shown) with respect to fiducial mark  17  (e.g., information from a design database utilized to generate PCB  10 ( 2 )), along with the location of positioning subsystem  140 ( 5 ) with respect to fiducial mark  17  to determine positioning information for aiming laser beams through any of vias  15 . 
         [0034]    Extensions of the technique described above will be apparent to those skilled in the art of registering positioning systems to workpieces; for example, a PCB  10  may include multiple registration marks  17  so that whose location of a positioning subsystem  140  may be determined relative to each of marks  17  in order to calculate scaling factors and correct for rotational misalignment. 
         [0035]      FIG. 7  shows a cross-sectional schematic view of a through-via laser reflow system  100 ( 5 ) that, like systems  100 ( 2 ),  100 ( 3 ) and  100 ( 4 ), mounts a surface mount component (not shown) to PCB  10 ( 2 ).  FIG. 7  may not be drawn to scale. Like system  100 ( 4 ), system  100 ( 5 ) includes laser  120 ( 4 ), optional mechanical positioning subsystem  140 ( 4 ) and mechanical support element  165 ( 3 ) holding beam splitters  170 ( 1 )- 170 ( 4 ) and optional optics  175 ( 1 )- 175 ( 4 ) to form OSS  167 ( 2 ). System  100 ( 5 ) also includes a second, optional mechanical positioning subsystem  210  that moves in directions  220 ,  220 ′. A detector  200  that is capable of detecting electromagnetic energy from laser  120 ( 4 ) mounts with positioning subsystem  210 . Detector  200  is capable of detecting at least an intensity of electromagnetic energy from laser  120 ( 4 ); detector  200  may also be capable of forming an image thereof. Output of detector  200  transmits to a processor (not shown) that utilizes such output to determine data of OSS  167 ( 2 ) and/or PCB  10 ( 2 ) that may be useful in calibration, troubleshooting, and/or to abort assembly of a compromised PCB. 
         [0036]    For example, in a first example, system  100 ( 5 ) may align to a fiducial mark  17  of PCB  10 ( 2 ), then aim a laser beam through a via of PCB  10 ( 2 ) (e.g., may aim laser beam  110 ( 11 ) through via  15 ( 8 ), as shown). Intensity and/or image data formed by detector  210  may indicate that the via is blocked (e.g., optically opaque) or not blocked. If a via is blocked, the processor may abort assembly of PCB  10 ( 2 ) since the via may be entirely missing, or blocked by foreign matter; aborting assembly in such a case may preclude costly rework or scrap. 
         [0037]    In a second example, system  100 ( 5 ) may align to a fiducial mark  17  of PCB  10 ( 2 ), then may move a laser beam in increments, thus “stepping” it across one or more selected vias. Intensity and/or image data formed by detector  210  at each of the “steps” may be utilized to calculate fine alignment corrections to improve a coarse alignment provided by aligning to fiducial mark  17 . This procedure may be repeated, for example, at multiple vias across a PCB so that scaling, translational and rotational factors of the PCB may be determined. 
         [0038]    In a third example, system  100 ( 5 ) may align one or more laser beams at a time with detector  210  without PCB  10 ( 2 ) loaded in place. Intensity and/or image data formed by detector  210  may be utilized to determine a power output of laser  120 ( 4 ), and/or information of beam splitters  170 ( 1 )- 170 ( 4 ) or optics  175 ( 1 )- 175 ( 4 ) (e.g., data that may help to determine whether any of the beamsplitters or optics are degraded or misaligned, or whether any optical path thereamong is blocked). 
         [0039]    It is also contemplated that rather than mounting on a mechanical positioning subsystem, a detector  200  may be fixedly mounted on a through-via laser reflow system, and may be mounted in a location such that lasers, optics or OSSs may be positioned so as to receive laser beams from various sources (e.g., different instances of a laser  120 , optics  160  or optics  175 ). 
         [0040]      FIG. 8  shows a block diagram of components of a through-via laser reflow system  100  (e.g., any of through-via laser reflow systems  100 ( 1 )- 100 ( 5 ), numbers without parentheses serving to identify any of the specific examples with parentheses previously disclosed) and electrical connections there between. A processor  300  acts as a data processing and control unit for system  100 . Memory  305  stores information of system  100 , such as software  310 , positioning subsystem data  315 , image data  320 , fiducial location data  325 , PCB layout data  330  and detector data  335 . Processor  300  may receive data from camera  180  and/or detector  200 . Processor  300  may send commands to any of positioning subsystems  140  and  200 , laser  120 , illuminator  190  and camera  180 . External I/O capability  350  may also send instructions or data to processor  300 , and/or receive information therefrom. External I/O capability  350  may include a user interface for humans to exchange information with system  100  (such as a keyboard, a mouse, a joystick, image displays, alphanumeric displays, indicator lights and/or audible devices); I/O  350  may also include interfaces to other electronic devices such as, for example, Internet or other network connections. 
         [0041]      FIG. 9  shows a flowchart illustrating steps of a process  400  for calibration and setup of a through-via laser reflow system (e.g., any of through-via laser reflow systems  100 ( 1 )- 100 ( 5 )). The steps of process  400  may be implemented by components of a through-via laser reflow system under control of a processor (e.g., processor  300 ,  FIG. 8 ). The steps of process  400  may be performed individually or may be aggregated into automated sequences, may be executed in the order shown in  FIG. 9  or in a different order, and certain steps of method  400  may be omitted, in certain embodiments. 
         [0042]    In a step  402 , the process accepts user input. User input may, for example, specify a type of PCB and/or component to be mounted thereon, start or stop single steps or automated sequences of calibration and/or processing, manually control positioning subsystems, lasers, illumination and/or cameras, or request output of information. It is appreciated that step  402  may occur many times in the execution of process  400  (as often as a user of a through-via laser reflow system feels it necessary to assert control, or request information, from such a system). An example of step  402  is processor  300  accepting user input through external I/O  350 ,  FIG. 8 . Step  405  moves subsystems of a through-via laser reflow system to home positions, such as positions that such subsystems may assume upon startup of such systems. An example of step  405  is one or more of mechanical positioning subsystems  140 ( 1 )- 140 ( 4 ) or  210  moving to a home position under the control of processor  300 . 
         [0043]    Steps  410  through  435  perform calibration of system  100 . Step  410  positions a laser, optics, or an OSS such that a laser beam is in a predetermined position for calibration, and a detector will be in a predetermined position so as to receive the laser beam. An example of step  410  is one of mechanical positioning subsystems  140 ( 1 )- 140 ( 4 ) moving so that a laser beam  110  is in a predetermined position, and a mechanical positioning subsystem  210  moving so that detector  200  receives laser beam  110 . Step  415  emits a laser beam, and receives the laser beam in a detector, so that attributes of a laser and/or optics can be measured. An example of step  415  is one of lasers  120 ( 1 )- 120 ( 4 ) emitting electromagnetic energy that is transmitted and/or directed by one or more of optics  130 ( 1 )- 130 ( 4 ), fiber optic line  132 ( 1 )- 132 ( 6 ), fiber splitter  150 , beam splitters  170 ( 1 )- 170 ( 4 ) and optics  160 ( 1 )- 160 ( 5 ) or  175 ( 1 )- 175 ( 4 ) as one or more of laser beams  110 ( 1 )- 110 ( 15 ), and then detector  200  receiving the laser beam. 
         [0044]    Step  420  processes detector data generated in step  415  for calibration purposes. An example of step  420  is processor  300  comparing actual laser power against a desired laser power and calculating a power correction that is subsequently used to adjust laser power so that a correct amount of power is received at a solder ball to be reflowed. Another example of step  420  is processor  300  processing image data to determine whether a laser beam is forming a desired spot size, and calculating position information for focusing subsystems to adjust focus. Step  425  determines whether data (e.g., raw detector data from step  415 , or such data after processing in step  420 ) is within defined tolerances. If the data is not within tolerances, process  400  may terminate at step  430 , with an indication that the system requires adjustment or repair before processing can continue. An example of step  425  is processor  300  comparing laser intensity data with defined tolerances. If the data is within tolerances, step  435  decides whether more calibration steps need to be performed. An example of step  435  is processor  300  determining whether all calibration steps of a predetermined set of calibration steps have been performed. If so, process  400  returns to step  410 ; if not, process  400  continues with step  440 . 
         [0045]    Steps  440  through  480  perform setup and PCB validation utilizing system  100 . Step  440  moves subsystems of a through-via laser reflow system  100  to PCB load positions, and loading a PCB  10 . An example of step  440  is positioning subsystems  140  moving to a predetermined load position, and a user of system  100  (or a loading machine) loading one of PCBs  10 ( 1 )- 10 ( 2 ) into system  100 . Step  445  performs an alignment. An example of step  445  is processor  300  (a) controlling positioning subsystems  140  so that camera  180  images fiducial mark  17  on one of PCBs  10 ( 1 )- 10 ( 2 ); (b) controlling illuminators  190  to generate suitable lighting of fiducial mark  17 ; (c) controlling camera  180  to generate image information of fiducial mark  17 ; (d) processing image information of fiducial mark  17  to determine location and/or rotational corrections; and, optionally, (e) controlling positioning subsystems  140  to implement the location and/or rotational corrections. 
         [0046]    In step  450 , processor  300  controls a positioning subsystem to position one or more of a laser  120 , optics  130 ( 1 )- 130 ( 4 ), beam splitters  170 ( 1 )- 170 ( 4 ) and optics  160 ( 1 )- 160 ( 5 ) or  175 ( 1 )- 175 ( 4 ) (or collectively, an OSS  167  incorporating such elements) to align a laser beam  110  to a via of PCB  10 , and positions detector  200  to receive the laser beam. An example of step  450  is processor  300  (not shown in  FIG. 7 ) of system  100 ( 4 ) controlling positioning subsystem  140 ( 4 ) to position OSS  167 ( 2 ) (including beam splitter  170 ( 4 ) and optics  175 ( 4 )) such that beam  110 ( 15 ) aligns to via  15 ( 8 ) of PCB  10 ( 2 ), with detector  200  receiving beam  110 ( 15 ), as shown in  FIG. 7 . Another example of step  450  is moving components to align a laser beam sequentially among positions defined by expected edges of a via, for example in concert with repetitions of steps  455  and  460  as explained below, to perform fine alignment of the laser beam to via locations. Step  455  emits a laser beam, and receives the laser beam in a detector, so that attributes of a via can be measured. An example of step  455  is laser  120 ( 4 ) emitting electromagnetic energy that is directed by beam splitter  170 ( 4 ) and optics  175 ( 4 ) as laser beam  110 ( 15 ), and detector  200  receiving laser beam  110 ( 15 ), as shown in  FIG. 7 . 
         [0047]    Step  460  processes detector data generated in step  455  for PCB validation purposes. An example of step  460  is processor  300  comparing actual laser power received in step  455  against a desired laser power (which may depend, for example, on a via size determined from a PCB design database, and may depend on a type and/or quantity of solder to be reflowed). Another example of step  460  is processor  300  processing image data to determine intensity at each of a sequence of positions, to complete a fine alignment of the laser beam to via locations, as discussed above. Step  465  determines whether data (e.g., raw detector data from step  455 , or such data after processing in step  460 ) is within defined tolerances. If the data is not within tolerances, process  400  may terminate at step  470 , with an indication that one or more vias of PCB are blocked or missing, so that continued processing may result in scrap product. An example of step  425  is processor  300  determining that laser intensity data obtained in step  455  is below a defined tolerance. If the data is within tolerances, step  475  decides whether more vias need to be checked. An example of step  475  is processor  300  determining whether any vias to be checked on a PCB  10  remain to be checked. If so, process  400  returns to step  450 ; if not, process  400  ends with step  480 , with an aligned PCB  10  having been checked and found ready to have a component installed thereto. 
         [0048]      FIG. 10  shows a flowchart illustrating steps of a process  500  for installing a component  20  to a PCB  10  by utilizing a through-via laser reflow system  100  (e.g., any of through-via laser reflow systems  100 ( 1 )- 100 ( 5 )) to reflow solder balls. The steps of process  500  may be implemented by components of a through-via laser reflow system under control of a processor (e.g., processor  300 ,  FIG. 8 ). The steps of process  500  may be performed individually or may be aggregated into automated sequences, may be executed in the order shown in  FIG. 10  or in a different order, and certain steps of method  500  may be omitted, in certain embodiments. 
         [0049]    Process  500  can begin in one of two ways. One way is for a system  100  to first execute process  400  described above, ending at step  480 ; thus step  480  is shown in dashed outline in process  500 . Another way of beginning process  500  is to load and optionally align a PCB utilizing steps  505  and  510 ; these steps are the same as steps  440  and  445 , respectively, of process  400 . Process  500  may also include a step  502  of accepting user input that may, for example, specify a type of PCB and/or component to be mounted thereon, start or stop single steps or automated sequences of calibration and/or processing, manually control positioning subsystems, lasers, illumination and/or cameras, or request output of information. It is appreciated that step  502  may occur many times in the execution of process  500  (as often as a user of a through-via laser reflow system feels it necessary to assert control, or request information, from such a system). An example of step  502  is processor  300  accepting user input through external I/O  350 ,  FIG. 8 . 
         [0050]    Once a PCB is loaded, process  500  continues with step  515 , which loads a component  20  to be reflowed onto a PCB  10  (e.g., loads component  20 ( 1 ) onto PCB  10 ( 1 ) or component  20 ( 2 ) onto PCB  10 ( 2 )). An example of step  515  a user of system  100  (or a loading machine) loading a component  20  onto PCB  10 . In step  520 , processor  300  controls a positioning subsystem to position one or more of a laser  120 , optics  130 ( 1 )- 130 ( 4 ), beam splitters  170 ( 1 )- 170 ( 4 ) and optics  160 ( 1 )- 160 ( 5 ) or  175 ( 1 )- 175 ( 4 ) (or collectively, an OSS  167  incorporating such elements) to align one or more laser beams  110  to one or more vias of PCB  10 . An example of step  520  is processor  300  controlling positioning subsystem  140 ( 3 ) to position OSS  167 ( 1 ) to align laser beams  110 ( 3 )- 110 ( 6 ) to vias  15 ( 5 )- 15 ( 8 ), as shown in  FIG. 4 . Step  525  emits one or more laser beams into corresponding vias of a PCB to reflow solder balls of a component to the PCB. An example of step  525  is laser  120 ( 3 ) emitting electromagnetic energy that is transmitted through fiber optic line  132 ( 2 ), directed by fiber splitter  150  through fiber optic lines  132 ( 3 )- 132 ( 6 ) and formed by optics  160 ( 2 )- 160 ( 5 ) into laser beams  110 ( 3 )- 110 ( 6 ) which travel through vias  30 ( 5 )- 30 ( 8 ) and reflow solder balls  30 ( 5 )- 30 ( 8 ) of component  20 ( 2 ), as shown in  FIG. 4 . Step  530  decides whether more reflows need to be performed. An example of step  530  is processor  300  checking to see whether more reflows are required to complete assembly of a PCB. If so, process  500  returns to step  520 ; if not, process  500  ends with step  535 . 
         [0051]    The execution of the above processes using the disclosed systems is significantly superior to the conventional methods of installing BGA packages which use hot, forced air or infrared heat. These conventional techniques involve exposing a substantial area of the PCB, or sometimes the entire PCB, to melt (or “reflow”) the solder balls. The processes disclosed here, however, do not expose the PCB to heat in remelting the BGA solder balls. Thus, there is no collateral damage done to the PCB, collateral components, or connections between the components on the PCB. 
         [0052]    This also eliminates verification processes necessary with the prior art methods. Because the prior art processes involve heat exposure to the PCB, post-processing inspections are normally required for BGA installations. These inspections are necessary to insure that the board and related components have not been not damaged by the heat administered. The inspection process typically requires testing, X-ray observations, and other time consuming procedures necessary to ensure that the board is still fully operational. With the processes and systems here, however, only the mounted components need to be tested, since the integrity of the PC board and its already existing components are not compromised during the reflow process. 
         [0053]    The changes described above, and others, may be made in the through-via laser reflow system described herein without departing from the scope hereof. It should thus be noted that the matter contained in the above description or shown in the accompanying drawings should be interpreted as illustrative and not in a limiting sense. The following claims are intended to cover all generic and specific features described herein, as well as all statements of the scope of the present method and system, which, as a matter of language, might be said to fall there between.