Abstract:
Apparatus for attaching multiple metal components to integrated circuit modules reduces manufacturing time for module assemblies having metal shields and/or heat sinks that must be applied to multiple modules within a manufacturing assembly. The metal components are manufactured in an array and the array assembly is attached to the integrated circuit substrate. The metal component array is then divided along with the modules after attachment. The modules are sawed apart before or after attachment. A reduction in manufacturing time is achieved through multiple placement of the metal components rather than individual placement.

Description:
FIELD OF THE INVENTION 
     The present invention relates generally to semiconductor packaging, and more specifically, to a method and apparatus for attaching multiple metal parts to integrated circuit modules. 
     BACKGROUND OF THE INVENTION 
     Semiconductors and other electronic and opto-electronic assemblies are fabricated in groups on a wafer. Known as “dies”, the individual assemblies are cut from the wafer and are then bonded to a carrier. Typically the carrier is an insulating or conductive substrate, but in some cases the substrate is a printed wiring board (PWB), lead-frame carrier, or other structure suitable for mechanically stabilizing the die. 
     Telecommunications modules such as cellular telephone radio-frequency (RF) components typically require shielding to prevent electromagnetic interference (EMI) from disrupting or being disrupted by other components within a final assembly. Modern high-frequency semiconductors such as microprocessors and memory devices are sometimes shielded and as operating frequencies increase, the shielding requirements may also increase. Metal shields are placed over the module circuits and bonded to the module, forming an integrated assembly with an integral shield. 
     Also within telecommunications and high-frequency integrated circuit applications, modules typically require heat sinks to transfer heat away from (and sometimes prevent transfer of heat into) a module. The heat sinks transfer heat more effectively than heat conduction through a substrate alone. The heat sinks are generally metal parts and the above-mentioned M shields may serve a dual purpose as a heat sink and an EMI shield. 
     Application of the metal parts (EMI shields and/or heat sinks) is typically performed by pick-and-place robotic machines that place each shield or heat sink over circuits mounted on a substrate. The module is encapsulated after the metal parts have been placed. Individual placement is a time-consuming process that may require, for example, one second per metal part to place. With many shields to place on a manufacturing assembly, which may require for example 50 shields, the manufacturing time may be extended on the order of one minute. 
     Therefore, it would be desirable to provide a method and apparatus for attaching multiple metal parts to integrated circuit modules that does not require individual placement. 
     SUMMARY OF THE INVENTION 
     A method and apparatus for attaching multiple metal components to integrated circuit modules reduces manufacturing time for module assemblies having metal shields and/or heat sinks that must be applied to multiple modules within a manufacturing assembly. An array comprising metal components is manufactured and the array is attached to the integrated circuit substrate. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a pictorial diagram depicting a top view of a assembly of integrated circuit modules to which an embodiment of the invention may be applied; 
     FIG. 2 is a pictorial diagram depicting a top view of a metal component array in accordance with an embodiment of the invention; 
     FIG. 3A is a pictorial diagram depicting a top view of an integrated circuit module assembly in accordance with an embodiment of the invention; 
     FIG. 3B is a pictorial diagram depicting a top view of a detached integrated circuit module assembly in accordance with an embodiment of the invention; 
     FIG. 4A is a pictorial diagram depicting a side view of a detached integrated circuit module assembly in accordance with an embodiment of the invention; and 
     FIG. 4B is a pictorial diagram depicting an end view of a detached integrated circuit module assembly in accordance with an embodiment of the invention. 
    
    
     The invention, as well as a preferred mode of use and advantages thereof, will best be understood by reference to the following detailed description of illustrative embodiments when read in conjunction with the accompanying drawings, wherein like reference numerals indicate like parts throughout. 
     DETAILED DESCRIPTION 
     Referring now to the figures and in particular to FIG. 1, of a top view of an assembly of integrated circuit modules to which an embodiment of the invention may be applied is depicted. A substrate  10  comprises a mounting structure for manufacture of integrated circuit modules. A plurality of dies  12  is mounted on substrate  10  by an adhesive mechanism such as epoxy or adhesive film. Groups  14  of dies are associated together for manufacturing purposes, such as placement of the dies and for attaching the metal components of the present invention. Substrate  10  may be a printed circuit board (PCB), silicon wafer, aluminum oxide substrate or other suitable mounting structure for integrated circuit dies. Dies  12  may be discrete semiconductors, memory modules, optoelectronic components and other components known to those of ordinary skill in the art of component packaging. 
     In order to provide electronic and thermal shielding for such devices as telecommunications integrated circuit modules, metal components are attached to substrate  10  over dies  12 . The metal components may be heat sinks for conducting heat away from a die, heat shields for reflecting radiated or convected heat away from a die, or electronic shields for preventing electromagnetic interference (EMI) from disrupting operation of the die. 
     Typically in the prior art, metal components have been placed by pick-and-place machines and temporarily held in place with an epoxy or other adhesive prior to encapsulation of the integrated circuit modules. The present invention applies metal components in a group, using an array of metal components to speed the manufacturing process. Placing one shield at a time may take, for example, one second per metal component placement. Using the illustrative embodiment of FIG. 1 for example, placement may take four seconds to place nine metal components simultaneously, resulting in an assembly time of less than half of that required to place the metal components individually. As the number of metal components per array is increased, the additional assembly time increases only slightly, resulting in a greater savings in assembly time for larger arrays. 
     The limitations on the improvements provided by increased array size are array size limitations brought about by the capacity of the placement machines used and the mechanical alignment of an array with the substrate and dies. Therefore, the groups  14  of dies  12  provide an arrangement that permits proper alignment, while providing a savings in assembly time over individual placement of dies. 
     Referring now to FIG. 2, a top view of an array of metal components  20  in accordance with an embodiment of the present invention is depicted. A carrier frame  26  holds metal components  22  via tabs  24  that are disposed between metal components  22  and carrier frame  26 , forming a rigid mechanical assembly that may be applied over the groups  14  of dies  12  of FIG.  1 . Tabs  24  are cut, dividing the metal component array  20  into individual metal components when substrate  10  is sawed to separate the individual dies  12 . Encapsulation of the metal components  22 , dies  12  and the substrate  10  may be performed to create a mechanically durable assembly. Encapsulation may be performed before or after sawing. It should be understood that the present invention applies to assemblies such as chip-on-board assemblies wherein dies are encapsulated on the PCB, but the metal component is attached subsequently as part of an array. Such assemblies may be desirable to manufacture with the metal component unfilled with encapsulant. 
     An alternative to sawing all of the tabs may be desirable for thermal or electrical conductivity of the individual metal components. If a multi-die module is being manufactured, it may be desirable to leave the tabs that connect metal components that will be left on a single final assembly. The tabs may provide a thermal and/or electrical coupling between the metal components, improving the performance of the overall shield or heat sink. 
     Referring now to FIG. 3A, a top view of an integrated M circuit assembly  30  is depicted. Metal component  22  is attached to substrate area  31  over an integrated circuit die (or multiple dies). While the substrate extends beyond the assembly of FIG. 3A, a dashed line shows the saw channel for cutting the integrated circuit assembly  30  from a larger substrate that includes the other assemblies associated with other metal components in the metal component array. 
     Metal component  22  as depicted is a dual-use component for providing both heat sink and electronic shielding. A dimpled area  38  is produced by indenting the top surface of metal component. The bottom surface of the metal component dimpled area  38  may contact the die, so that heat may be conducted from the die to metal component  22 . Apertures  36  are formed in metal component  22 , generally by stamping although they may be drilled. Apertures  36  provide a mechanism for introducing encapsulant and permitting the outflow of air or other gas during the encapsulation process. Apertures  36  may alternatively be used in a non-encapsulated assembly permit convection of heat. For both types of assemblies, apertures  36  reduce the weight of the metal shielding. Reduced weight is critical in assemblies for use in portable devices such as cellular telephones or pocket computing devices. 
     Metal tabs  24  are shown as extending past assembly  30 , as the depiction of FIG. 3A shows assembly  30  prior to division by sawing, laser cutting or other separation technique. Metal tabs  24  provide a means for securing metal component  22  within an array of metal components during assembly. 
     Referring now to FIG. 3B, a detached integrated circuit assembly  40  in accordance with a preferred embodiment of the invention is depicted. Assembly  40  includes metal component  22  mounted to a cut substrate  31 A. Metal component  22  has a dimpled area  38  in contact with the top of a die  12  (not visible) underneath metal component  22 . Portions of tabs  24 A extend from integrated circuit assembly  40  and may be attached to electrical or thermal connections for enhancing the thermal and electromagnetic shielding performance of metal component  22 . An integrated circuit assembly manufactured by the methods of the present invention may be identified by the presence of metal tab portions  24 A, whether or not they are used for thermal and electrical connection. 
     Referring now to FIG. 4A, a side view of detached integrated circuit assembly  40  is shown. Die  12  mounted on substrate  31 A is visible under metal component  22 , with a dashed line depicting dimpled area  38  contacting the top of die  12  to provide thermal conduction. Die  12  is coupled to solder ball contacts  41 A by wires  42  in a wire-bond attach as is well known in the art of integrated circuit manufacturing. A portion of metal tab  24 A is shown protruding from the end of metal component  22 , in which the side panel has been removed for illustrative purposes. The portion of metal tab  24 A will be visible in a circuit that has been encapsulated and then sawn in accordance with an embodiment of the present invention. The tab may have a different cross section appearance that the illustrative depiction shown in FIG. 4, for example, a cylindrical tab will have a circular cross section. Tab  24 A may be attached to a thermal conductive or electrical conductive path for enhancing the thermal or electrical effectiveness of the heatsink or shield. 
     Electrical connection to integrated circuit assembly  40  is made by a plurality of electrical contacts  41  disposed on the bottom side of substrate  31 A. A “flip chip” connection is provided by inserting electrical contacts  41  into mating holes in the system in which integrated circuit assembly  40  is used. Alternatively, wire bonding pads may be disposed on the bottom side of substrate  41  so that wires may be attached after the integrated circuit assembly is complete. 
     Referring now to FIG. 4B, an end view of a detached and encapsulated integrated circuit assembly  50  is shown. Die  12  is coupled to solder ball/flip-chip post contacts  41 B in a flip-chip attach as is well known in the art of integrated circuit manufacturing. Encapsulant  51  has been applied to the assembly and portions have been removed in order to depict die  12  and metal component  22 . A portion of metal tab  24 A is shown protruding from the end of metal component  22 , in which the side panel has been removed for illustrative purposes. The portion of metal tab  24 A internal to the encapsulant (the reentrant portion) will be visible in a circuit that has been encapsulated and then sawn in accordance with an embodiment of the present invention. FIG. 4B further illustrates an uncut tab  24 B, that may be used for connection to a thermal conductive or electrical conductive path for enhancing the thermal or electrical effectiveness of metal component  22 . 
     The above description of embodiments of the invention is intended to be illustrative and not limiting. Other embodiments of this invention will be obvious to those skilled in the art in view of the above disclosure and fall within the scope of the present invention.