Patent Abstract:
A method and apparatus are provided to deposit conductive bonding material into cavities in a mold. A fill head is placed in substantial contact with a mold that includes cavities. The fill head includes a sealing member that substantially encompasses an entire area to be filled with conductive bonding material. The conductive bonding material is forced out of the fill head toward the mold. The conductive bonding material is provided into at least one cavity of the cavities contemporaneous with the at least one cavity being in proximity to the fill head.

Full Description:
CROSS-REFERENCE TO RELATED APPLICATION 
       [0001]    The present patent application is a divisional application of U.S. patent application Ser. No. 13/100,133, now U.S. Pat. No. ______, which was filed on May 3, 2011, which was a divisional application of U.S. patent application Ser. No. 12/018,421, now U.S. Pat. No. 7,980,445, which was filed on Jan. 23, 2008, and are all commonly assigned herewith to International Business Machines, and which their collective teachings are hereby incorporated by reference in their entirety. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention generally relates to the field of placement of conductive bonding material such as solder on electronic pads, and more particularly relates to fill techniques for injection molding of solder on integrated circuit chip pads. 
       BACKGROUND OF THE INVENTION 
       [0003]    In modern semiconductor devices, the ever increasing device density and decreasing device dimensions demand more stringent requirements in the packaging or interconnecting techniques of such devices. Conventionally, a flip-chip attachment method has been used in the packaging of IC chips. In the flip-chip attachment method, instead of attaching an IC die to a lead frame in a package, an array of solder balls is formed on the surface of the die. 
         [0004]    Controlled Collapse Chip Connection New Process (“C4NP”) is another method of depositing conducting bonding material onto molds. C4NP is a subset technology of IMS, which is further discussed in U.S. Pat. No. 5,244,143 and is commonly owned by International Business Machines Corporation, and is hereby incorporated by reference in its entirety. C4NP allows the creation of pre-patterned solder balls to be completed while a silicon wafer is still in the front-end of a manufacturing facility, potentially reducing cycle time significantly. The solder bumps can be inspected in advance and deposited onto the silicon wafer in one simple step. In this technology, a solder head with an injection aperture comprising molten solder scans over the surface of the mold. In order to fill the cavities on the mold, pressure is applied onto the reservoir of the C4NP head which comprises the molten solder as it is scanned over the cavities. The filling of the C4NP mold plate in a reliable, high speed and cost-effective manner is a challenge. Current C4NP systems use a scanning fill head which covers only a portion of the total area to be filled at any one time. This approach requires sealing elements, which must contain solder, air, and/or vacuum at significant pressure differentials while the seal is scanned across the mold plate. 
         [0005]    Therefore a need exists to overcome the problems with the prior art as discussed above. 
       SUMMARY OF THE INVENTION 
       [0006]    Briefly, in accordance with the present invention, a method for depositing conductive bonding material into a plurality of cavities in a mold is disclosed. The method includes placing a fill head in substantial contact with a mold comprising a plurality of cavities. The fill head includes a sealing member that substantially encompasses an entire area to be filled with conductive bonding material. The conductive bonding material is forced out of the fill head toward the mold. The conductive bonding material is provided into at least one cavity of the plurality of cavities contemporaneous with the at least one cavity being in proximity to the fill head. 
         [0007]    In another embodiment, another method for depositing conductive bonding material into a plurality of cavities in a mold is disclosed. The method includes placing a fill head in substantial contact with a mold comprising a plurality of cavities. The fill head comprises a sealing member that substantially encompasses an entire area to be filled with conductive bonding material. The mold is situated on top of the fill head and the fill head is situated so that the sealing member is facing in a upward direction with respect to the plurality of cavities. The fill head and mold are transitioned so that the fill head is situated on top of the mold and so that the plurality of cavities is facing in an upward direction with respect to the sealing member. The conductive bonding material is forced out of the fill head toward the mold. The conductive bonding material is provided into at least one cavity of the plurality of cavities contemporaneous with the at least one cavity being in proximity to the fill head. 
         [0008]    An advantage of the foregoing embodiments of the present invention is that conductive bonding material such as solder can be precisely dispensed into the mold plate using a full-field solder fill head that can cover the entire region to be filled. The present invention allows the seal(s) of the fill head to be stationary during the solder fill process steps where the highest pressure differentials occur. The fill head seals only slide over the mold surface during the solder fill process steps where relatively low pressure differentials are required. Stated differently, the present invention does not require a sealing member to withstand large pressure differentials while sliding across a mold plate. Another advantage of various embodiments of the present invention is that air can be evacuated from all cavities so that the cavities can be reliably filled with pressurized solder. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0009]    The accompanying figures where like reference numerals refer to identical or functionally similar elements throughout the separate views, and which together with the detailed description below are incorporated in and form part of the specification, serve to further illustrate various embodiments and to explain various principles and advantages all in accordance with the present invention. 
           [0010]      FIG. 1  is a block diagram showing a top view of a conventional C4NP mold fill process; 
           [0011]      FIG. 2  is a block diagram showing a cross-sectional view of the conventional C4NP mold fill process of  FIG. 1 ; 
           [0012]      FIG. 3  is a block diagram showing a cross-sectional view of an example of a full-field fill head according to one embodiment of the present invention; 
           [0013]      FIG. 4  is a block diagram showing a top view of the full-field fill head of  FIG. 3 ; 
           [0014]      FIG. 5  is a block diagram showing a cross-sectional view of another example of a full-field fill head according to one embodiment of the present invention; 
           [0015]      FIG. 6  is block diagram showing a top view of the full-field fill head of  FIG. 5 ; 
           [0016]      FIG. 7  is a block diagram showing a cross-sectional view of a full-field coverage system according to one embodiment of the present invention; 
           [0017]      FIG. 8  is a block diagram showing a top view of the full-field coverage system of  FIG. 7 ; 
           [0018]      FIG. 9  is a block diagram showing a cross-sectional view of another full-field coverage system according to one embodiment of the present invention; 
           [0019]      FIG. 10  is a block diagram showing a top view of the full-field coverage system of  FIG. 9 ; 
           [0020]      FIG. 11  is a block diagram showing a cross-sectional view of yet another full-field coverage system according to one embodiment of the present invention; 
           [0021]      FIG. 12  is a block diagram showing a top view of the full-field coverage system of  FIG. 11 ; 
           [0022]      FIG. 13  is a block diagram illustrating a sequence of steps for depositing conductive bonding material into cavities on a mold according to one embodiment of the present invention; 
           [0023]      FIG. 14  is an operational flow diagram illustrating an example of a process of filling molds using a full-field coverage system according to one embodiment of the present invention; 
           [0024]      FIG. 15  is an operational flow diagram illustrating another example of a process of filling molds using a full-field coverage system according to one embodiment of the present invention; 
           [0025]      FIG. 16  is an operational flow diagram illustrating yet another example of a process of filling molds using a full-field coverage system according to one embodiment of the present invention; and 
           [0026]      FIG. 17  is an operational flow diagram continuing the process of  FIG. 16 . 
       
    
    
     DETAILED DESCRIPTION 
       [0027]    As required, detailed embodiments of the present invention are disclosed herein; however, it is to be understood that the disclosed embodiments are merely exemplary of the invention, which can be embodied in various forms. Therefore, specific structural and functional details disclosed herein are not to be interpreted as limiting, but merely as a basis for the claims and as a representative basis for teaching one skilled in the art to variously employ the present invention in virtually any appropriately detailed structure. Further, the terms and phrases used herein are not intended to be limiting; but rather, to provide an understandable description of the invention. 
         [0028]    The terms “a” or “an”, as used herein, are defined as one or more than one. The term plurality, as used herein, is defined as two or more than two. The term another, as used herein, is defined as at least a second or more. The terms including and/or having, as used herein, are defined as comprising (i.e., open language). The term coupled, as used herein, is defined as connected, although not necessarily directly, and not necessarily mechanically. 
       Conventional C4NP Mold Fill Process 
       [0029]      FIGS. 1-2  illustrate a conventional C4NP mold fill process. In particular  FIG. 1  shows an overhead view of a conventional fill head  102  dispensing solder into cavities  104  on a mold plate  106 .  FIG. 2  shows a cross-sectional view of  FIG. 1 . The conventional fill head  102  of  FIGS. 1-2  dispenses molten solder into the mold plate  106  utilizing a round O-ring seal. In conventional C4NP systems the fill head  102  is heated above the melting point of the solder, for the case of Tin/Copper solder above 230 C. The liquid solder is held in a reservoir  208  inside the fill head  102  and covered by a lid (not shown). The fill head  102  rests on the mold plate  106  and O-ring seal  210  prevents the solder from leaking out the bottom of the fill head  102 . The fill process begins by first applying a nominal load or down force on the O-ring seal  210 , typically on the order of 2.5 lbs/linear inch. The fill head reservoir  208  is then pressurized, usually to 20 psi, to ensure the solder enters the mold plate cavities  104  during the fill process. 
         [0030]    Next, the fill head  102  is moved across the mold plate surface, typically at a speed of between 0.1 to 10 mm/sec. As the fill head moves over the mold plate  106  the air in the cavities  104  is expelled and replaced by liquid solder from the fill head  102 . The mold plate  106  with the solder filled cavities  104  is then removed and passed to the next tool for transfer of the solder to a silicon wafer. 
         [0031]    A key difficulty of this conventional approach is that the O-ring  210  is sealing against significant solder pressure at the same time that it is being dragged across the mold surface. This requires that a seal material be selected that can withstand high temperatures and solder contact and seal against substantial pressure differential, while also not experiencing mechanical failure or excessive wear as a result of contact with the cavity-filled mold plate  106 . Given that the mold plate  106  is often made of glass and the cavities often have relatively sharp edges, it can be quite difficult to find a material that can withstand the “filing action” of the mold-plate under the high compression forces needed to seal against solder leakage. 
       Full-Field Solder Coverage 
       [0032]    According to an embodiment of the present invention,  FIGS. 3-13  illustrate a systems and methods for C4NP full-field solder coverage according to various embodiments of the present invention. In particular  FIG. 3  shows a cross-sectional view of an example of a full-field fill head  302 .  FIG. 4  is a top-view of the fill head  302  of  FIG. 3 . The fill head  302 , according to the present example, comprises an O-ring  310  that substantially surrounds an area of a mold  306  to be filled. The mold in one embodiment can be rectangular, non-rectangular, or any combination of shapes. In one embodiment, the conductive bonding material such as solder is forced out of the reservoir  308  and into the cavities  304  using high pressure. The high pressure is applied while the mold  306  is stationary with respect to the fill head  306 . This is advantageous because the large normal forces needed to seal against solder leakage are only needed when the seal  310  is stationary and when the seal is located above smooth parts of the mold plate  306 . After the solder is forced into the cavities  304  at high pressure, the pressure can be reduced while the mold  306  is translated out from underneath the fill head  302 . Since the sliding occurs only when the solder pressure is low, the normal force applied to the seal  310  can be low thereby reducing friction and wear occurring at the seal  310 . 
         [0033]      FIG. 5  shows a cross-sectional view of another example of a full-field fill head  502 .  FIG. 6  illustrates a top-view of the fill head  502  shown in  FIG. 5 . The fill head  502  includes a rotating and/or agitating blade  512  inside the molten solder pool  514 . This blade  512  can be rotated and/or agitated vigorously during various steps of the solder filling process to improve the fill performance, which is discussed in greater detail below. 
         [0034]      FIGS. 7-8  illustrate one embodiment of depositing a conductive bonding material into cavities in a mold using a full-field coverage process.  FIG. 7  shows a cross-sectional view of a full-field coverage system  700  where a fill head  702  deposits solder into cavities  704  on a mold  706 .  FIG. 8  shows a top-view of the full-field coverage system  700  of  FIG. 7 .  FIGS. 7-8  show a succession of the mold  706  during the solder filling process. For example,  FIGS. 7-8  show the mold  706  as empty, being filled with solder, and filled with solder. As discussed above the full-field fill head  702  includes an O-ring seal  710  that substantially covers an area on the mold  706  that is to be filled with solder. 
         [0035]    In one embodiment, unfilled mold  706  is placed in position next to the full-field solder fill head  702 . The unfilled mold  706  is slid underneath the fill head  702  while the solder is being held near ambient pressure. The seal  710  is held in contact with the mold  706  with just enough force to prevent/minimize any solder leakage during the motion. A region above the solder is filled with high-pressure gas such as nitrogen to force the solder into the mold cavities  704 . 
         [0036]    Once the solder has been forced into the cavities  704  and contacts the cavity walls, the gas pressure above the solder can generally be reduced without affecting the solder-filled cavities  704 . The mold  706  is moved out from under the fill head  702  while the solder is held at a relatively low positive pressure with respect to the ambient environment. The wiping action of the seal  710  during this motion acts to squeegee the solder off of the mold surface, leaving only the solder which is in the mold cavities  704 . 
         [0037]      FIGS. 9-10  illustrate another embodiment of depositing a conductive bonding material into cavities in a mold using a full-field coverage process.  FIG. 9  shows a cross-sectional view of a full-field coverage system  900  where a fill head  702  deposits solder into cavities  704  on a mold  706  under a vacuum. The system  900  of  FIG. 9  removes substantially all of the air from the cavities  904  of the mold  906  by drawing a vacuum above the molten solder before the space above the solder is pressurized to force the solder into the cavities  904 .  FIG. 10  shows a top-view of the full-field coverage system  900  of  FIG. 9 .  FIGS. 9-10  show a succession of the mold  906  during the solder filling process. For example,  FIGS. 9-10  show the mold  906  as empty, being filled with solder, and filled with solder. An unfilled mold  906  is placed in position next to the full-field solder fill head  902 . 
         [0038]    In one embodiment, an unfilled mold  906  is slid underneath the fill head  902  while the solder is being held near ambient pressure. The seal  910  is held in contact with the mold  906  with just enough force to prevent/minimize any solder leakage during the motion. The region above the solder is evacuated, thereby causing most of the gas trapped in the cavities  904  to bubble up through the solder where it is carried away by the vacuum source  916 . The region above the solder is then filled with high-pressure gas such as nitrogen to force the solder into the mold cavities  904 . Since most of the gas in the cavities  904  was removed in the previous step, the pressurized solder is more likely to completely fill the cavities as desired. 
         [0039]    Once the solder has been forced into the cavities  904  and it makes contact with the cavity walls, the gas pressure above the solder can generally be reduced without affecting the solder-filled cavities. The mold  906  is moved out from under the fill head  902  while the solder is held at a relatively low positive pressure with respect to the ambient environment. The wiping action of the seal  910  during this motion acts to squeegee the solder off of the mold surface, thereby leaving only the solder which is in the mold cavities  904 . 
         [0040]      FIGS. 11-12  illustrate another embodiment of depositing a conductive bonding material into cavities in a mold using a full-field coverage process.  FIG. 11  shows a cross-sectional view of a full-field coverage system  900  where a fill head  1102  deposits solder into cavities  1104  on a mold  1106  utilizing an agitator bar  1112 .  FIG. 12  shows a top-view of the full-field coverage system  1100  of  FIG. 11 .  FIGS. 11-12  show a succession of the mold  1106  during the solder filling process. The agitator bar  1112  is used to help dislodge gas bubbles during (and after) the evacuation process stage discussed above. Without agitation, some of the gas trapped in the cavities  1104  can adhere to the mold as small bubbles, even when a vacuum is drawn above the solder, as discussed above. By vigorously stirring the molten solder during this phase, the heavy liquid solder can be used to dislodge such gas bubbles adhering to the mold  1106 . Thus, the combination of vacuum above the solder plus vigorous mechanical agitation can substantially improve the probability that essentially all gas is removed from all cavities  1104  in the mold  1106 . 
         [0041]    In one embodiment, an unfilled mold  1106  is placed in position next to the full-field solder fill head  1102 . The unfilled mold  1106  is slid underneath the fill head  1102  while the solder is being held near ambient pressure. The seal  1110  is held in contact with the mold  1106  with just enough force to prevent/minimize any solder leakage during the motion. The region above the solder is evacuated, thereby causing most of the gas trapped in the cavities  1104  to bubble up through the solder, where it is carried away by the vacuum source  1116   
         [0042]    The molten solder is vigorously stirred and/or agitated by the agitator bar  1112  to dislodge any gas bubbles which remain adhered to the mold surface. Any dislodged bubbles then rise to the surface of the solder where they are removed by the vacuum source  1116 . The region above the solder is then filled with high-pressure gas such as nitrogen to force the solder into the mold cavities  1114 . Since most of the gas in the cavities  1114  was removed in the previous step, the pressurized solder is more likely to completely fill the cavities as desired. Once the solder has been forced into the cavities  1114  and makes contact with the cavity walls, the gas pressure above the solder can generally be reduced without affecting the solder-filled cavities  1114 . The mold  1106  is moved out from under the fill head  1102  while the solder is held at a relatively low positive pressure with respect to the ambient environment. The wiping action of the seal  1110  during this motion acts to squeegee the solder off of the mold surface, leaving only the solder which is in the mold cavities  1104   
         [0043]      FIG. 13  is a block diagram illustrating a sequence of steps for ensuring that substantially all gas is removed from cavities  1304  in a mold  1306  being filled with solder  1318 . In this embodiment, substantially the entire fill head  1302  plus the mold plate  1306  is mounted as one assembly in such a way that it can be rotated between a first position and second position. A rotational mounting arrangement is mechanically coupled with the fill head for rotating the fill head and the mold as one mounted assembly. The rotational mounting arrangement can include one or more mechanical and electrical components that can hold the fill head and the mold as one assembly and can rotate the fill head and the mold between the first and second positions. When the fill head and the mold are together as one assembly, a volume is defined in the fill head between an inner surface of the fill head and a surface area of the mold including a plurality of cavities to be filled. In the first position the mold  1306  is below the fill head  1302  and gravity forces the solder  1318  in contact with the mold  1306  (as discussed above). A second position is utilized where the mold  1306  is substantially at a top portion of the volume and above the fill head  1302  so that gravity holds the solder away from the mold plate  1306 . By providing a system  1300  whereby gravity holds the liquid solder away from the mold surface it is possible to evacuate (e.g., via a gas exchange port in the fill head) the cavities  1304  directly without requiring any gases to bubble up through the solder  1318 . 
         [0044]    In this embodiment, the cavities  1304  can be fully and completely evacuated while the solder is below the mold  1306 . After the cavities  1304  (and the rest of the free volume inside the fill head  1302 ) have been evacuated substantially the entire assembly is slowly flipped over so that the solder flows across the mold surface and pools above the mold  1306 . At this point, the solder  1318  might not perfectly wet the entire cavity surface (because of surface tension effects, etc.), and any gas trapped in the cavities  1304  can cause defects. Therefore, application (e.g., via a gas exchange port in the fill head) of pressurized gas above the molten solder can now reliably force the solder completely into all cavities  1304 . 
         [0045]    In one embodiment, an unfilled mold  1306 , at times T 0  and T 1 , is transitioned from a face-up position to a face-down position next to the full-field solder fill head  1302 . The full-field solder fill head  1302  is orientated so that the seal  1310  is upward and the solder  1318  is pooled at the bottom of the head  1302 , away from the seal  1310 . At time T 2 , the unfilled mold  1306  is slid across (above) the fill head  1302  while gravity holds the solder  1318  away from the seal  1310  and mold plate  1306 . The gas above the solder  1318  such as nitrogen is held near the ambient pressure. The seal  1310  is held in contact with the mold  1306  with just enough force to prevent/minimize any solder leakage during the motion. The region  1320  above the solder, at time T 3 , is evacuated, thereby directly removing any gas that was in the mold cavities  1306  as well as any gas above the solder  1318  or mixed into the solder  1318 . All gas in the cavities is directly carried away by the vacuum source. 
         [0046]    The entire assembly comprising the fill head  1302 , seal  1310 , and mold plate  1306  are then slowly rotated 180 degrees at time T 4  (i.e., flipped over). This brings the mold plate  1306  underneath (substantially below) the fill head  1302 , thereby allowing gravity to force the liquid solder to pool over the entire surface of the mold  1306  as compared to the inside of the seal  1310 . The region  1320  above the solder  1318 , at time T 5 , is then filled with high-pressure gas such as nitrogen to force the solder  1318  into the previously evacuated cavities  1304 . Since essentially all of the gas in the cavities  1304  was removed in the previous step, the pressurized solder is virtually guaranteed to completely fill all of the cavities  1304  as desired. 
         [0047]    Once the solder  1318  has been forced into the cavities  1304  and it makes contact with the cavity walls, the gas pressure above the solder  1318 , at time T 6 , can generally be reduced without affecting the solder-filled cavities. The mold  1306 , at time T 7 , is moved out from under the fill head  1302  while the solder  1318  is held at a relatively low positive pressure with respect to the ambient environment. The wiping action of the seal  1310  during this motion acts to squeegee the solder  1318  off of the mold surface, thereby leaving only the solder  1318  which is in the mold cavities  1304 . 
         [0048]    As can be seen from the above discussion the various examples of the present invention are advantageous in that they improve the reliability of the mold plate fill process by using a fill head and related processes that do not require a sealing member to withstand large pressure differentials while sliding across the mold plate. The sealing element, according to various embodiments of the present invention, only has to withstand high pressure differential while stationary, and only has to withstand sliding motion while sealing against small pressure differentials. The solder fill head, according to certain examples, can be at least as large as the full mold pattern to be filled. The fill head is scanned onto a mold plate while the solder is kept near ambient pressure. A vacuum is then drawn above the pooled solder (which covers the entire mold area) in order to draw any trapped air away from the mold surface. After the air has been evacuated, the space above the pooled solder is highly pressurized with inert gas to force the solder into the cavities. 
         [0049]    The fill head is scanned off of the mold plate while the solder pressure is held at a relatively low pressure differential with respect to ambient. Note that in this process, the seal was stationary during high-pressure-differential operations such as vacuum evacuation and pressurized solder fill, and the seal was only sliding during low-pressure-differential operations such as mold loading and final solder wiping. This approach thus allows the use of high seal loading forces during high-pressure operations which occur while stationary, and low seal loading forces during sliding motion, thereby greatly reducing seal wear and increasing the range of seal materials which can be used. 
         [0050]    Various embodiments of the present invention, as discussed above, also utilize a rotating or oscillating agitator blade to improve the vacuum evacuation of the cavities by aggressively stirring the molten solder so as to dislodge any gas bubbles adhering to the mold cavities. Another advantage is that the entire mold plate plus solder fill head assembly can be flipped over during the process, thereby allowing some process steps (especially vacuum evacuation) to occur with the liquid solder supply below and not in contact with the mold surface. Other process steps (especially pressurized solder filling of the cavities) can occur with the liquid solder above and in contact with the mold surface. 
       Process Of Filling A Non-Rectangular Mold With Solder 
       [0051]      FIG. 14  is an operational flow diagram illustrating an example of a process of filling molds using a full-field coverage system. The operational flow diagram of  FIG. 14  begins at step  1402  and flows directly to step  1404 . An unfilled mold  906 , at step  1404 , is placed in position next to the full-field solder fill head  902 . The unfilled mold  906 , at step  1406 , is transitioned underneath the fill head  902 . This occurs while the solder within the fill head  902  is being held near ambient pressure. The seal  910 , at step  1408 , is held in contact with the mold  906  with just enough force to prevent/minimize any solder leakage during the motion. 
         [0052]    A region above the solder, at step  1410 , is evacuated, causing most of the gas trapped in the cavities to bubble up through the solder, where it is carried away by the vacuum source  916 . The region above the solder, at step  1412 , is then filled with high-pressure gas such as nitrogen. The solder, at step  1414 , is then forced into the mold cavities  904 . Since most of the gas in the cavities  904  was removed in the previous step, the pressurized solder is more likely to completely fill the cavities  904  as desired. The gas pressure, at step  1416 , above the solder is reduced without affecting the solder-filled cavities  904 . The mold  906 , at step  1418 , is transitioned from under the fill head  902  while the solder is held at a relatively low positive pressure with respect to the ambient environment. The wiping action of the seal during this motion acts to squeegee the solder off of the mold surface, leaving only the solder which is in the mold cavities  904 . The control flow then exits at step  1420 . 
       Another Process Of Filling A Non-Rectangular Mold With Solder 
       [0053]      FIG. 15  is an operational flow diagram illustrating another example of a process of filling molds using a full-field coverage system. The operational flow diagram of  FIG. 15  begins at step  1502  and flows directly to step  1504 . An unfilled mold  1106 , at step  1504 , is placed in position next to the full-field solder fill head  1102 . The unfilled mold  1106 , at step  1506 , is transitioned underneath the fill head  1102 . This occurs while the solder within the fill head  1102  is being held near ambient pressure. The seal  1110 , at step  1508 , is held in contact with the mold  1106  with just enough force to prevent/minimize any solder leakage during the motion. 
         [0054]    A region above the solder, at step  1510 , is evacuated, causing most of the gas trapped in the cavities to bubble up through the solder, where it is carried away by the vacuum source  1116 . The solder within the fill head  1102 , at step  1512 , is vigorously stirred and/or agitated to dislodge any gas bubbles which remain adhered to the mold surface. Any dislodged bubbles then rise to the surface of the solder where they are removed by the vacuum source  1116 . The region above the solder, at step  1514 , is then filled with high-pressure gas such as nitrogen. The solder, at step  1516 , is then forced into the mold cavities  1104 . Since most of the gas in the cavities  1104  was removed in the previous step, the pressurized solder is more likely to completely fill the cavities  1104  as desired. The gas pressure, at step  1518 , above the solder is reduced without affecting the solder-filled cavities  1104 . The mold  1106 , at step  1520 , is transitioned from under the fill head  1102  while the solder is held at a relatively low positive pressure with respect to the ambient environment. The wiping action of the seal during this motion acts to squeegee the solder off of the mold surface, leaving only the solder which is in the mold cavities  1104 . The control flow then exits at step  1522 . 
       Another Process Of Filling A Non-Rectangular Mold With Solder 
       [0055]      FIGS. 16-17  are operational flow diagrams illustrating another example of a process of filling molds using a full-field coverage system. The operational flow diagram of  FIG. 16  begins at step  1602  and flows directly to step  1604 . A full-field fill head  1302 , at step  1604 , is positioned so that the seal  1310  is upward and the solder  1318  is pooled at the bottom of the fill head  1302  away from the seal. An unfilled mold  1306 , at step  1606 , is placed in position next to the full-field solder fill head  1302 . The unfilled mold  1306 , at step  1608 , is transitioned across the fill head  1302 . Gravity holds the solder  1318  away from the seal and mold  1306 . The gas above the solder  1318  in the fill head  1302 , at step  1610 , is held substantially near ambient pressure. The seal  1310 , at step  1612 , is held in contact with the mold  1306  with just enough force to prevent/minimize any solder  1318  leakage during the motion. 
         [0056]    A region above the solder  1318 , at step  1614 , is evacuated, causing most of the gas trapped in the cavities to bubble up through the solder  1318 , where it is carried away by the vacuum source  1316 . The fill head  1302  and mold  1306 , at step  1616 , are transitioned  180  degrees so that the mold  1306  is underneath the fill head, thereby allowing gravity to force the liquid solder  1318  to pool over the entire surface of the mold  1306  (inside the seal  1310 ). The control flows to entry point A of  FIG. 17 . The region above the solder  1318 , at step  1704 , is then filled with high-pressure gas such as nitrogen. The solder  1318 , at step  1706 , is then forced into the mold cavities  1304 . Since most of the gas in the cavities  1304  was removed in the previous step, the pressurized solder  1318  is more likely to completely fill the cavities  1304  as desired. The gas pressure, at step  1708 , above the solder  1318  is reduced without affecting the solder-filled cavities  1304 . The mold  1306 , at step  1710 , is transitioned from under the fill head  1302  while the solder  1318  is held at a relatively low positive pressure with respect to the ambient environment. The wiping action of the seal during this motion acts to squeegee the solder  1318  off of the mold surface, leaving only the solder  1318 , which is in the mold cavities  1304 . The control flow then exits at step  1712 . 
       Non-Limiting Examples 
       [0057]    The foregoing embodiments of the present invention are advantageous because they provide a technique for filling non-rectangular molds or substrates with a conductive bonding material using an IMS system. The discussed examples of the present invention allow for molds that more closely resemble their associated non-rectangular silicon wafer to be used. Furthermore, the fill heads provide a means for heating throughout the heads that melt material to be deposited into cavities of a mold and cooling gasses that solidify the material within the cavities. 
         [0058]    Although specific embodiments of the invention have been disclosed, those having ordinary skill in the art will understand that changes can be made to the specific embodiments without departing from the spirit and scope of the invention. The scope of the invention is not to be restricted, therefore, to the specific embodiments, and it is intended that the appended claims cover any and all such applications, modifications, and embodiments within the scope of the present invention.

Technology Classification (CPC): 7