Abstract:
A semiconductor package holder includes two plates, and each plate defining a through-hole. Each of the plates has a set of first members along a periphery of the through-hole and extending into the through-hole. The first members of one of the plates are positioned to overlie the first members of the other of the plates. One of the at least two plates further has a set of second members along a periphery of the through-hole and extending into the through-hole.

Description:
BACKGROUND 
     This disclosure relates generally to packaging of integrated circuits, and more particularly to a cleaning system and a package carrier for a semiconductor package. 
     When packaging a semiconductor chip after circuitry has been formed thereon, the interconnection between the circuitry on the chip and the input/output connecting pins on a package substrate may be implemented by Flip-Chip packaging technology. A Flip-Chip assembly includes a direct electric connection of a face down (that is, “flipped”) semiconductor chip onto a package substrate, such as a ceramic substrate, a circuit board, or a carrier using conductive bumps disposed on the semiconductor chip. Flip-Chip technology is quickly replacing older wire bonding technology that uses face up semiconductor chips with the wire connected to each pad on the semiconductor chips. 
     To package a semiconductor chip using Flip-Chip packaging technology, the semiconductor chip is flipped and positioned on a package substrate. Conductive bumps are reflown to form electric connections therebetween and provide limited mechanical mounting for the semiconductor chip and the package substrate. During the reflowing process, flux is used to facilitate the joining of the conductive bumps, bond pads on the semiconductor chip, and pads on the packaging substrate. Then, excessive flux residues are removed, and an underfilling adhesive, such as epoxy, is used to fill spaces between the semiconductor chip and the package substrate in order to provide even better mechanical interconnection between the semiconductor chip and the package substrate, increase the reliability and fatigue resistance of the package interconnections, and minimize uneven stress distribution caused by thermally induced strains due to the differences in coefficients of thermal expansion (CTE) between the semiconductor chip and package substrate. 
     However, if the spaces between the semiconductor chip and the package substrate were not filled properly, more stress would be carried by the relatively thin conductive bumps. As such, even a thin film of flux residue can cause premature delamination of a bonded surface, and result in failure in one or more of the interconnections. Therefore, it is important to remove flux residues from the Flip-Chip assembly by a flux cleaning process. 
    
    
     
       DESCRIPTION OF THE DRAWINGS 
       One or more embodiments are illustrated by way of example, and not by limitation, in the figures of the accompanying drawings, wherein elements having the same reference numeral designations represent like elements throughout and wherein: 
         FIG. 1  is a view of a cleaning system for cleaning a semiconductor package; 
         FIG. 2  is a perspective view of a package carrier; 
         FIG. 3A  is a top view of a portion of a top plate of the package carrier according to a configuration of the package carrier of  FIG. 2 ; 
         FIG. 3B  is a top view of a portion of a bottom plate of the package carrier according to the configuration of  FIG. 3A ; 
         FIG. 3C  is a top view of a portion of the package carrier according to the configuration of  FIGS. 3A and 3B ; 
         FIGS. 3D-E  are cross-sectional views of the package carrier of  FIG. 3C  taken along lines A-A′ and B-B′, respectively; 
         FIG. 4A  is a top view of a portion of a top plate of the package carrier according to an embodiment; 
         FIG. 4B  is a top view of a portion of a bottom plate of the package carrier according to the embodiment of  FIG. 4A ; 
         FIG. 4C  is a top view of a portion of the package carrier according to the embodiment of  FIGS. 4A and 4B ; 
         FIGS. 4D-F  are cross-sectional views of the package carrier of  FIG. 4C  taken along lines C-C′, D-D′, and B-B′, respectively; 
         FIG. 5A  is a close-up view showing a top plate side protrusion and a bottom plate side protrusion according to an embodiment; 
         FIG. 5B  is a close-up view showing a semiconductor package placed on the bottom plate side protrusion of  FIG. 5A ; and 
         FIG. 5C  is a close-up view showing the top plate side protrusion, the semiconductor package, and the bottom plate side protrusion of  FIGS. 5A-B  in an assembled state. 
     
    
    
     DETAILED DESCRIPTION 
     Overview 
       FIG. 1  depicts a cleaning system  100  for cleaning a semiconductor package  110 . The cleaning system  100  includes a package carrier  120 , a set of spray nozzles  130   a - 130   d , and a conveyor  140  positioned below the spray nozzles. The package carrier  120  holds the semiconductor package  110 . The set of spray nozzles  130   a - 130   d  spray cleaning fluid onto the package carrier  120  at a predetermined pressure to wash away excessive flux residue from the semiconductor package. In at least one of the embodiments, the predetermined pressure for spraying the cleaning fluid is set at a range between 800 and 1000 Kilopascals (KPa). Although there are four spray nozzles  130   a - 130   d  shown in the  FIG. 1 , in other embodiments, the number of spray nozzles may be greater or fewer than four, such as one spray nozzle or more than four spray nozzles. Further, the conveyor  140  supports the package carrier  120  and transports the package carrier past the spray nozzles. In some embodiments, the conveyor  140  is replaced by other structures that are capable of providing similar support to the package carrier  120 , such as a working table or a working platform. In some other embodiments, the spray nozzles move past the package carrier  120  during a spraying operation. 
     During operation of the cleaning system to wash away excessive flux residue from the semiconductor package, the cleaning fluid is sprayed onto the package carrier  120  at a predetermined pressure and imposes stress on the semiconductor package. At the same time, the semiconductor package is held by the package carrier  120 . As a result, the stress imposed by the pressure of the sprayed cleaning fluid and the force holding the semiconductor package together cause bending and/or vibration stresses of the semiconductor package during the flux cleaning process. In particular, when the semiconductor manufacturing process migrates to 40 nm or smaller technology with extreme-low-K (ELK) dielectric materials (such as materials having dielectric constant less than 3), the bending and/or vibration stresses during the flux cleaning process increases the possibility of damaged/cracked ELK layer and decreases the yield rate of the manufacturing process. Therefore, a carefully designed package carrier  120  helps to ease the above-mentioned effects during the flux cleaning process. 
       FIG. 2  depicts an exemplary package carrier  200  as used in an embodiment of package carrier  120  ( FIG. 1 ), connection with, for example, the cleaning system  100  ( FIG. 1 ). The package carrier  200  has a top plate  210  and a bottom plate  220 , between which semiconductor package(s) are retained. The top plate  210  defines a plurality of top plate openings (through-holes)  230 , and the bottom plate  220  defines a plurality of bottom plate openings (not shown) corresponding to the top plate openings  230 . For example, as shown in  FIG. 2 , the top plate  210  and the bottom plate  220  are both rectangular-shaped and are 200 mm in width (indicated by reference W) and 400 mm in length (indicated by reference L). For a particular semiconductor chip package having 23 mm×23 mm (Width×Length) size, the package carrier  200  is capable of holding 32 units of such semiconductor chip package, where the top plate  210  defines 32 top plate openings  230  arranged as a 4×8 array, and the bottom plate  220  defines 32 bottom plate openings arranged as a corresponding 4×8 array. In at least some embodiments, the thickness of the top plate  210  or the bottom plate  220  is set between 1 mm˜2 mm. 
     The shape of the package carrier  200  is not limited to the rectangular shape. For example, in another embodiment, the package carrier  200  is in a shape of a circle; and in yet another embodiment, the package carrier  200  is hexagonal-shaped. The number of semiconductor chip packages that package carrier  200  retains and the arrangement of the top plate openings  230  and corresponding bottom plate openings are not limited to the embodiment described above. For example, in one of the embodiments, the package carrier  200  is configured to hold only one semiconductor package, i.e., the top plate  210  defines only one top plate opening  230 , and the bottom plate  220  defines only one bottom plate opening. In another embodiment, the top plate openings  230  and the bottom plate openings are arranged as matrices of hexagonal cells. 
     In at least some embodiments, the top plate  210  and the bottom plate  220  are made of metal. For example, in a particular embodiment, the top plate  210  and the bottom plate  220  are made of stainless steel. For another example, in one embodiment, the top plate is made of Ni plated Cu, and the bottom plate is made of Ni plated Cu. Further, in another embodiment, the top plate  210  and the bottom plate  220  are made of non-metal materials, such as using plastic for the top plate  210  and plastic for the bottom plate  220 . However, in at least some embodiments, the top plate  210  and the bottom plate  220  need not be made of the same material. 
       FIGS. 3A-3E  depict a portion of a package carrier  300  according to a particular configuration of package carrier  200  ( FIG. 2 ).  FIGS. 3A and 3B  are top views of a portion of a top plate  310  and a bottom plate  320  of the package carrier  300 . 
     Referring to  FIG. 3A , the top plate  310  defines a top plate opening  312  therethrough corresponding to the opening  230  depicted in  FIG. 2  for retaining the semiconductor package. The top plate  310  has a set of top plate corner protrusions  314  extending inward to the top plate opening  312 , and each of the top plate corner protrusions  314  is disposed to align with at least a portion of a corresponding bottom plate corner protrusion  324  ( FIG. 3B ) defined by the bottom plate. The set of top plate corner protrusions  314  includes four top plate corner protrusions  314 . Referring to  FIG. 3B , the bottom plate  320  defines at least a bottom plate opening  322  therethrough. The bottom plate  320  has a set of bottom plate corner protrusions  324  extending inward to the bottom plate opening  322 , and each of the bottom plate corner protrusions  324  is configured to support at least a portion of a corner of the semiconductor package. The set of bottom plate corner protrusions  324  includes four bottom plate corner protrusions  324 , and, in at least some embodiments, each bottom plate corner protrusions  324  supports a different corner of the semiconductor package  350  ( FIG. 3C ). 
     Each of the bottom plate corner protrusions  324  has a pair of guide pins  326  extending perpendicularly from the face of the bottom plate, and each of the top plate corner protrusions  314  has a pair of guide pin holes  316  for receiving the guide pins  326  of corresponding bottom plate corner protrusions  324 . In at least some embodiments, package carrier  300  comprises greater or fewer numbers of guide pins  326  and guide pin holes  316 . In at least one embodiment, there is one guide pin  326  disposed on each bottom plate corner protrusion  324  and one guide pin hole  316  disposed on each top plate corner protrusion  314 . Guide pins  326  and their corresponding guide pin holes  316  help to better align top plate opening  312  and bottom plate opening  322  while the top plate  310  and the bottom plate  320  are in an assembled state. 
       FIG. 3C  is a top view of a portion of the package carrier  300  according to the embodiment of  FIGS. 3A and 3B , which comprises the top plate  310  and the bottom plate  320  in an assembled state and retaining a semiconductor package  350 . The top plate  310  and the bottom plate  320  together hold the semiconductor package  350 . The semiconductor package  350  includes a semiconductor chip  354 , a package substrate  352 , and a set of solder bumps  356  ( FIG. 3E ) connecting the chip  354  and the package substrate  352 . Other than the portions with corner protrusions  314  and  324 , the top plate opening  312  and the bottom plate opening  322  are larger in the length and width dimensions than the size of the semiconductor package  350 . Thus, during the flux cleaning process, cleaning fluid sprayed onto the semiconductor package  350  is drained by allowing the cleaning fluid to flow through gaps defined by the top plate opening  312 , the bottom plate opening  322 , and the semiconductor package  350 , i.e., between chip  354  and the top and bottom plate openings  312 ,  322 . 
       FIG. 3D  is a cross-sectional view showing a cross section of the package carrier  300  and the semiconductor package  350  in an assembled state along the A-A′ line ( FIG. 3C ); and  FIG. 3E  is a cross-sectional view showing the cross section of the package carrier  300  and the semiconductor package  350  in an assembled state along the B-B′ line ( FIG. 3C ). When the package carrier  300  is in an assembled state, each of the bottom plate corner protrusions  324  is aligned with a corresponding top plate corner protrusion  314 . The top plate  310  and the bottom plate  320  hold portions of four corners of the semiconductor package  350  by forming a sandwich-like arrangement between the top plate corner protrusions  314 , the semiconductor package  350 , and the bottom plate corner protrusions  324 . 
     Further, the weight of the top plate  310  provides a force to push the semiconductor package  350  against the bottom plate  320 . The top plate opening  312 , the bottom plate opening  322 , and gaps between the semiconductor package  350 , the top plate  310 , and the bottom plate  320  together define a path  330  ( FIG. 3E ) through which the cleaning fluid drains. However, by merely holding portions of four corners of the semiconductor package  350 , the semiconductor package  350  may still suffer from certain undesirable level of bending and/or vibration when cleaning fluid is sprayed at the predetermined pressure during the flux cleaning process. 
     Particular Embodiments 
       FIGS. 4A-4F  depict a portion of a package carrier  400  according to a particular embodiment of package carrier  200  ( FIG. 2 ).  FIGS. 4A and 4B  are top views of a portion of a top plate  410  ( FIG. 4A ) and a bottom plate  420  ( FIG. 4B ) of the package carrier  400 . 
     Referring to  FIG. 4A , the top plate  410  defines a top plate opening  412  therethrough corresponding to the opening  230  depicted in  FIG. 2 . The top plate  420  has a set of top plate side protrusions  414  extending inward to the top plate opening  412 , and each of the top plate side protrusions  414  is disposed to align with at least a portion of a corresponding bottom plate side protrusion  424  ( FIG. 4B ). The top plate opening  412  is rectangular-shaped, and the set of top plate side protrusions  414  includes one top plate side protrusions  414  for each side of the top plate opening  412 . In at least some embodiments, the shape of the top plate side opening  412  is not limited to rectangles, and the set of top plate side protrusions  414  includes greater or fewer numbers of top plate side protrusions  414 . For example, in one embodiment, the top plate opening  412  is square-shaped, and there are two top plate side protrusions  414  for each side of the top plate side opening  412 . 
     Referring to  FIG. 4B , the bottom plate  420  defines at least a bottom plate opening  422  therethrough. The bottom plate  420  has a set of bottom plate side protrusions  424  extending inward to the bottom plate opening  422  along a periphery of the bottom plate  424  opening and a set of bottom plate corner protrusions  428  extending inward to the bottom plate opening  422 . Each of the bottom plate side protrusions  424  supports at least a portion of an edge of the semiconductor package  450  ( FIG. 4C ), and each of the bottom plate corner protrusions  428  supports at least a portion of a corner of the semiconductor package  450 . Similar to the description for the top plate  412 , the bottom plate opening  422  is rectangular, and the set of bottom plate side protrusions  424  includes one bottom plate side protrusions  424  for each side of the bottom plate opening  422 . In at least some embodiments, the shape of the bottom plate opening  422  is not limited to rectangles, and the set of bottom plate side protrusions  424  includes greater or fewer numbers of bottom plate side protrusions  424 . For example, in one embodiment, the bottom plate opening  422  is square-shaped, and there are two bottom plate side protrusions  424  for each side of the bottom plate side opening  422 . 
     Each of the bottom plate side protrusions  424  has a pair of guide pins  426  extending perpendicularly from the face of the bottom plate, and each of the top plate side protrusions  414  has a pair of guide pin holes  416  for receiving the guide pins  426  of corresponding bottom plate side protrusions  424 . In at least some embodiments, package carrier  400  comprises greater or fewer numbers of guide pins  426  and guide pin holes  416 . In at least one embodiment, there is one guide pin  426  disposed on each bottom plate side protrusion  424  and one guide pin hole  416  disposed on each top plate side protrusion  414 . Guide pins  426  and their corresponding guide pin holes  416  help to better align top plate opening  412  and bottom plate opening  422  while the top plate  410  and the bottom plate  420  are in an assembled state 
       FIG. 4C  is a top view of a portion of the package carrier  400  according to the embodiment depicted in  FIGS. 4A and 4B , which comprises the top plate  410  and the bottom plate  420  in an assembled state. The top plate  410  and the bottom plate  420  together retain a semiconductor package  450  therebetween. The semiconductor package  450  includes a chip  454 , a package substrate  452 , and a set of solder bumps  456  ( FIG. 4E ) connecting the chip  454  and the package substrate  452 . Other than the portions with side protrusions  414  and  424 , and the corner protrusions  428 , the top plate opening  412  and the bottom plate opening  422  are larger in the length and width dimensions than corresponding dimensions of the semiconductor package  450 . Thus, during the flux cleaning process, cleaning fluid sprayed onto the semiconductor package  450  drains through gaps defined by the top plate opening  412 , the bottom plate opening  422 , and the semiconductor package  450 . 
     Refer to  FIGS. 4D ,  4 E, and  4 F,  FIG. 4D  is a cross-sectional view showing the cross section of the package carrier  400  and the semiconductor package  450  in an assembled state along the C-C′ line ( FIG. 4C );  FIG. 4E  is a cross-sectional view showing the cross section of the package carrier  400  and semiconductor package  450  in an assembled state along the D-D′ line ( FIG. 4C ); and  FIG. 4F  is a cross-sectional view showing the cross section of the package carrier  400  and the semiconductor package  450  in an assembled state along the E-E′ line ( FIG. 4C ). 
     When the package carrier  400  is in an assembled state, each of the bottom plate side protrusions  424  align with a corresponding top plate side protrusion  414  and are positional on opposite faces of a respective edge of the semiconductor package  450 . The top plate  410  and the bottom plate  420  hold portions of four edges of the semiconductor package  450  by forming a sandwich-like arrangement between the top plate side protrusions  414 , the semiconductor package  450 , and the bottom plate side protrusions  424 . 
     Further, the weight of the top plate  410  provides a force to push the semiconductor package  450  against the bottom plate  420 . The top plate opening  412 , the bottom plate opening  422 , and gaps between the semiconductor package  450 , the top plate  410 , and the bottom plate  420  together define a path  430  through which the cleaning fluid drains. Therefore, by holding portions of four edges of the semiconductor package  450 , the bending and/or vibration when cleaning fluid is sprayed at the predetermined pressure during the flux cleaning process are minimized because the semiconductor package  450  is more rigidly held at its four edges than at its four corners. 
       FIGS. 5A-5C  are perspective views of a package carrier  500  according to another particular embodiment of package carrier  400  ( FIG. 4 ) illustrating relationships between a top plate side protrusion  514 , a semiconductor package  550 , and a bottom plate side protrusion  524 , corresponding to the top plate side protrusions, the semiconductor packages, and the bottom plate side protrusions depicted in  FIGS. 4A-4F . 
       FIG. 5A  is a close-up view of an interfitting relationship between a top plate side protrusion  514 , a pair of guide pin holes  516 ,  516 ′, a bottom plate side protrusion  524 , and a pair of guide pins  526  and  526 ′. The package carrier  500  includes a top plate  510  and a bottom plate  520 . The top plate  510  has at least one top plate side protrusion  514 , and the bottom plate  520  has at least one bottom plate side protrusion  524 . The top plate side protrusion  514  further has two guide pin holes  516  and  516 ′, and the bottom plate side protrusion  524  further has two guide pins  526  and  526 ′ extending perpendicular to the face of bottom plate  520  and corresponding to the guide pin  516  and  516 ′. 
     The guide pins  526  and  526 ′ are cylindrical. In at least some embodiments, at least one of the guide pins  526  or  526 ′ is formed in a shape other than a cylinder. For example, in one embodiment, the guide pin  526  is formed in a shape of an N-sided prism. The guide pins  526  and  526 ′ are formed on the bottom plate side protrusion  524  as an integrated part of the bottom plate  520 . In other embodiments, the guide pins  526  and  526 ′ are formed as separate members and fastened to the bottom plate side protrusion  524  by a fastening means such as a screw, an adhesive material, or a threaded portion formed on the guide pins  526  or  526 ′. In at least one of the embodiments, the bottom plate side protrusion  524  has only one guide pin  526  or  526 ′. Further, according to  FIG. 5A , the sizes and shapes of guide pins  526  and  526 ′ are identical. However, in at least some embodiments, the sizes and shapes of guide pins  526  and  526 ′ are different. For example, in one of the embodiments, the guide pins  526  and  526 ′ are circular cylinders, where the guide pin  526  has a larger diameter than the diameter of the guide pin  526 ′. 
     The guide pin holes  516  and  516 ′ are configured to receive the guide pins  526  and  526 ′ of the corresponding bottom plate side protrusion  524 . The guide pin holes  516  and  516 ′ are configured in a way that when the package carrier  500  in the assembled state, each of the pin holes  516  and  516 ′ is aligned to receive the corresponding pins  526  or  526 ′. The sizes and shapes of the cross sections of guide pin holes  516  and  516 ′ are the same as their corresponding guide pins  526  and  526 ′. 
       FIG. 5B  is a close-up view illustrates a semiconductor package  550  placed on the bottom plate side protrusion  524  of  FIG. 5A . When the semiconductor package  550  is placed on the bottom plate  520 , a portion of the edge of the semiconductor package  550  is placed on and supported by the bottom plate side protrusion  524 . In at least one embodiment, the edge of the semiconductor package  550  abuts the guide pins  526  and  526 ′. 
       FIG. 5C  is a close-up view showing the top plate side protrusion, the semiconductor package, and the bottom plate side protrusion of  FIGS. 5A-B  in an assembled state. The top side protrusion  514  is aligned with the corresponding bottom plate side protrusion  524 . The weight of the top plate  510  provides a force to push the semiconductor package  550  against the bottom plate  520 . In at least some embodiments, the top plate  510  and the bottom plate  520  are made of metal. For example, in a particular embodiment, the top plate  510  and the bottom plate  520  are made of stainless steel. However, the top plate  510  and the bottom plate  520  are not limited to comprising the same material. 
     It will be readily seen by one of ordinary skill in the art that the disclosed embodiments fulfill one or more of the advantages set forth above. After reading the foregoing specification, one of ordinary skill will be able to affect various changes, substitutions of equivalents and various other embodiments as broadly disclosed herein. It is therefore intended that the protection granted hereon be limited only by the definition contained in the appended claims and equivalents thereof.