Abstract:
An assembly for producing partially packaged semiconductor devices is provided. In one embodiment, the assembly includes a magnetic plate; a flexible substrate disposed adjacent the magnetic plate and having two surfaces; a nonstick coating disposed on one surface of the flexible substrate thereby exposing a nonstick surface; and a tape layer having two surfaces. The tape layer is adhesively attached to the nonstick surface to expose a surface of the tape layer. A frame is disposed on the exposed surface of the tape layer, and a plurality of integrated circuit (IC) die is positioned within the frame and supported by the tape layer. A panel is formed within the frame that at least partially surrounds the plurality of IC die and that contacts the tape layer.

Description:
CROSS-REFERENCES TO RELATED APPLICATIONS 
       [0001]    This is application is a divisional of, and claims priority to, application Ser. No. 11/009,284, filed Dec. 10, 2004. 
     
    
     FIELD OF THE INVENTION 
       [0002]    The present invention generally relates to a circuit device, and more particularly, to a circuit device with at least partial packaging and a method for forming partial package circuit devices. 
       BACKGROUND OF THE INVENTION 
       [0003]    Circuit devices of all types, including but not limited to electrical, optical, active, and passive are generally packaged in a form that protects the circuit device, allows coupling external to the circuit device when desired, and is as low cost as possible while still allowing the functional use of the circuit device. It is becoming more common to transfer or sell circuit devices that have only been partially packaged. These partially packaged circuit devices can then be optionally combined with other circuit devices and packaged in a final form. This form of packaging thus allows flexibility with respect to the use of circuit devices. This manufacturing technology is also sometimes referred to as embedded packaging. Various forms of embedded packaging have been developed; however each method generally shares a common feature of embedding a die in the substrate itself. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0004]    The present invention will hereinafter be described in conjunction with the following drawing figures, wherein like numerals denote like elements: 
           [0005]      FIG. 1  is an exploded view of an assembly used in a manufacturing process according to an embodiment of the present invention; 
           [0006]      FIG. 2  is a flow chart illustrating exemplary steps in a manufacturing process according to an embodiment of the present invention; 
           [0007]      FIG. 3  is a frontal view of an assembly at one point in a manufacturing process according to an embodiment of the present invention; 
           [0008]      FIG. 4  is a frontal view of an assembly at another point in a manufacturing process according to an embodiment of the present invention; 
           [0009]      FIG. 5  is a frontal view of an assembly at still another point in a manufacturing process according to an embodiment of the present invention; 
           [0010]      FIG. 6  is a frontal view of an assembly at still another point in a manufacturing process according to an embodiment of the present invention; 
           [0011]      FIG. 7  is a frontal view showing removal of a flexible steel support from a molded panel at still another point in a manufacturing process according to an embodiment of the present invention; and 
           [0012]      FIG. 8  is a frontal view of a molded panel at the conclusion of the manufacturing process according to an embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       [0013]    The following detailed description of the invention is merely exemplary in nature and is not intended to limit the invention or the application and uses of the invention. Furthermore, there is no intention to be bound by any theory presented in the preceding background of the invention or the following detailed description of the invention. 
         [0014]    It is therefore desired to develop packaging methods and manufacturing methods that allow for the efficient and low-cost creation of partial packaged circuit devices. Various methods are presently known; however, these methods have limitations and drawbacks. Certain methods make use of a rigid backing plate on which is fabricated the chips set. In these methods it then becomes necessary to separate the backing plate from the chips set, and these separation methods have incorporated technologies such as a hot release, UV release, and solvent release. These methods add time and expense in the manufacturing process. It would also be desired to develop a method that avoids the use of solvents. Further, it would be desired to develop a method of manufacturing partial packaged circuit devices that can be easily scaled for high volume manufacturing. The present invention addresses one or more of these needs. Furthermore, other desirable features and characteristics of the present invention will become apparent from the subsequent detailed description of the invention and the appended claims, taken in conjunction with the accompanying drawings and the background of the invention. 
         [0015]    Referring to  FIG. 1 , there is shown an exploded view of a panel assembly  10  used in a manufacturing process according to an embodiment of the invention. Panel assembly  10  is generated and then disassembled during a series of manufacturing steps discussed further herein. The assembly  10  is presented here to aid in understanding the process. Assembly  10  comprises, in one embodiment, a magnetic plate  11 , a flexible steel substrate  12 , a first tape layer  13 , a second tape layer  14 , a mold frame  15 , and molded panel  16 . It will be understood by those skilled in the art that one purpose of the panel assembly  10  is to develop molded panel  16  wherein electronic components are secured within molded panel  16  at desired locations. Further an additional purpose is to develop molded panel  16  in a rapid and cost-efficient manner. 
         [0016]    Referring now to  FIG. 2 , there is shown a series of steps according to one embodiment of a manufacturing process that may be followed in high volume electronic fabrication packaging. The process begins in step  17  by positioning a flexible steel substrate  12  on a magnetic plate  11 . Substrate  12  (or metal plate) thus has one surface mated with magnetic plate  11  and one exposed surface. The degree of bonding between substrate  12  and magnetic plate  11  is sufficient to allow further processing to take place as described herein, and should be understood by those skilled in the art of semiconductor processing. While a magnetic plate  11  is preferred in this process, it will also be understood that other forms of gripping apparatus may be used or substituted for a magnetic plate including, by way of example only, vacuum devices and mechanical gripping devices. A flexible steel substrate approximately 1 mm thick, of spring steel, is preferred; however other thicknesses and other flexible metals may also be utilized. It is preferred to have a substrate with a thickness that ranges between approximately 0.250 mm to approximately 1.25 mm. In other embodiments, the substrate may be of a non-metal species. 
         [0017]    In step  18 , a first tape  13  (or adhesive) is adhered to the exposed surface of substrate  12 . It is noted that step  18  need not follow step  17 , so that in other embodiments first tape  13  is adhered to substrate  12  prior to positioning on magnetic plate  11 . When first tape  13  is positioned on substrate  12  there results an exposed surface on first tape  13 . 
         [0018]    In step  19 , a second tape  14  (or adhesive) is placed on the exposed surface of first tape  13 . It is noted that in other embodiments of the process, second tape  14  and first tape  13  may be positioned on substrate  12  prior to joining with magnetic plate. 
         [0019]    At this point in the process the partially packaged electrical devices may then be constructed on the second tape  14 . In one embodiment, this begins in step  20  by placing mold frame  15  on the assembly previously constructed. As shown in  FIG. 1  mold frame  15  defines a space or opening which, in one embodiment, is generally circular; alternate embodiments may use other shapes. Mold frame  15  may also have a desired thickness. The thickness may be selected to determine, for example, the thickness of mold material that is desired to be deposited in the opening. 
         [0020]    In a preferred embodiment, a die is then placed within the opening of mold frame  16  during step  21 . Circuit devices (not shown) may also be positioned within the die or otherwise placed within the mold frame opening. As is known in the art, a combined frame and die subassembly may be inserted into the mold opening by a pick-and-place tool where the dies are placed in a specific array pattern. 
         [0021]    Preferably second tape layer  14  comprises a two-sided adhesive tape. Thus, one side of second tape layer  14  adheres to first tape layer  13 . Additionally, the opposing side of second tape layer  14  also holds mold frame  15  and die in place when these components are positioned thereon. 
         [0022]    At this point, as shown in step  22 , epoxy (or other material) may be dispensed. A spout, nozzle, or similar means then directs the liquid epoxy where desired. As will be appreciated by those skilled in the art, epoxy is deposited so that it at least partially fills the area defined by the opening in mold frame  15 . Simultaneously, epoxy surrounds the dies positioned within mold frame  15 . 
         [0023]    In step  23 , the epoxy may be heated or “cured”. Preferably the epoxy is heated at its recommended cure cycle to completely solidify the material. In a preferred embodiment, the assembly is heated at approximately 150° C. for approximately ninety (90) minutes. It has been found that this degree of curing renders the epoxy sufficiently rigid to withstand the stresses of later processing. Curing typically takes place in a curing oven. If desired, the assembly may then be allowed to cool to approximately room temperature. 
         [0024]    The assembly at this stage in the operation is illustrated in a front view in  FIG. 3 . The component pieces in assembly  10  of  FIG. 3  generally correspond to the exploded view of the assembly  10  shown in  FIG. 1 . 
         [0025]    At this point, step  24 , the mold frame may be removed. This may be done by hand process, but preferably is an automated procedure. 
         [0026]    As shown in step  25 , the magnetic plate  11  may be removed. What remains of assembly  10  is now illustrated in  FIG. 4 . Heretofore the term “assembly” has been used to describe the collection of components as shown in  FIG. 1  and  FIG. 3  during the manufacturing process. Henceforth in the manufacturing process, components are removed from assembly  10  and/or assembly  10  is further processed. Thus, the term “circuit package structure” will be used to designate that remaining portion of assembly  10  as it undergoes further processing according to the manufacturing process. 
         [0027]    In step  26 , the circuit package structure may be ground if desired. The grinding step can reduce the epoxy structure to a desired thickness. In a preferred embodiment, the mold grinding apparatus includes a dedicated magnetic chuck. Thus, as shown in step  25  the circuit package structure is removed from magnetic plate  11 . It will thus be understood by those skilled in the art that other procedures may be followed for supporting the circuit package structure during an optional grinding step such as, for example, maintaining the circuit package structure on magnetic plate  11  and grinding molded panel  16  while positioned on that support.  FIG. 5  illustrates an exemplary circuit package structure after grinding step  26 . 
         [0028]    At this point, step  27 , the circuit package structure is placed on a further support such as a vacuum chuck  61 . Referring now to  FIG. 6  there is shown the circuit package structure supported on vacuum chuck  61 . It is noted that, in this embodiment, circuit package structure has been inverted. Molded panel  16  is now connected to vacuum chuck, whereas previously circuit package structure had been supported by metal plate  11  connected to support  12 . By inverting the circuit package structure and positioning it on a vacuum chuck  61 , the circuit package structure may be further manipulated as described below. 
         [0029]    In step  28 , the molded panel  16  can be separated from the substrate  12 . This is illustrated in  FIG. 7 . Here it is seen that by holding molded panel  16  against vacuum chuck  61 , the molded panel  16  remains after substrate  12  is removed. 
         [0030]    Still referring to the steps in  FIG. 2 , molded panel  16  may be further processed. In step  29 , second tape layer  14  is separated from molded panel  16 . Thus, according to an embodiment, first tape layer  13  and second tape layer  14  are designed so that a separation occurs between these layers when, in step  28 , flexible steel support  12  is removed. In step  28 , first tape layer  13  is remains with steel support  12  as it is removed. Second tape layer  14  remains with molded panel  16 . Thus, in step  29  second tape layer  14  is removed from molded panel  16 . What remains is illustrated in  FIG. 8 , a molded panel  16  which may have circuit devices positioned therein. 
         [0031]    Next, in step  30 , molded panel  16  is removed from the vacuum chuck  61  or sent on for further processing, as is known in the art. 
         [0032]    While the preferred embodiment has been described as utilizing two tape layers, a first tape  12  and a second tape  13 , it will be understood that other embodiments may employ a single tape layer. It has been found, however, that a double tape layer of the preferred embodiment is advantageous. The advantage is the easier separation that takes place when molded panel  16  is removed from the circuit package structure. It is often the case that molded panel  16  includes tight specifications regarding the placement and positioning of electronic devices thereon. Thus, it is desired to avoid any severe jostling or deformation of the molded panel  16  during processing lest this positioning be disturbed. Hence, it has been found that the use of two tape layers allows for the separation of molded panel  16  with little mechanical stress to the panel. A single layer of tape has been found to be less satisfactory in that regard. 
         [0033]    In a further embodiment, a layer of non-stick coating such as PTFE is substituted for first tape layer  13 . In this embodiment the surface of substrate  12  that would receive the first tape layer  13  is instead coated with a non-stick material. PTFE (polytetrafluoroethylene), also sometimes referred to by the trademark “TEFLON”, is a preferred non-stick material. A layer of PTFE may be deposited onto the substrate  12  through known means. A PTFE layer can achieve the same functionality as described with respect to first tape layer  13 . That is, the PTFE layer allows second tape layer  14  to adhere to the PTFE surface. However, when it comes time to separate substrate  12  from molded panel (step  28 ) the non-stick PTFE surface allows a ready separation from second tape layer  14 . 
         [0034]    First tape layer  13  is preferably a tape having two surfaces with one surface having adhesive and the opposite surface having a non-stick (PTFE) material. First tape layer  13  is applied to substrate  12  so that the adhesive portion bonds first tape layer  13  to substrate. In this manner the non-stick surface of first tape layer  13  is exposed. When second tape layer  14  is applied, it will be applied onto the non-stick surface of first tape layer  13 . By thus exposing a non-stick surface on first tape layer  13 , it allows a separation between first tape layer  13  and second tape layer  14 . 
         [0035]    Second tape layer  14  is also a tape with two surfaces. This tape is designed so that it sticks somewhat, but not too much, to the taped (or coated) steel substrate  12 . A degree of stickiness is needed in order to hold the assembly  10  in position during processing. However, the tape layers must also allow for separation without doing too much violence to molded panel  16 , and thus it is desired not to have too much stickiness in second tape layer  14 . In one embodiment second tape layer  14  has one surface of acrylic material and a second surface of a filled silicone material. The surface of acrylic material is the surface to be put in contact with first tape layer  13 , or the lower surface. The filled silicone surface, or upper surface, is the surface to be put in contact with mold frame  15  and molded panel  16 . Acrylic material is chosen to be placed in contact with first tape layer  13  because it has been found to display an easy and clean peel away behavior from the PTFE surface of first tape layer  13 . 
         [0036]    The filled silicone layer includes a material of inorganic filler. In one embodiment, this inorganic filler is calcium carbonate. It has been found that a filled silicone material improves the separation between the second tape layer  14  and molded panel  16 . It is desired that the separation leave a molded panel  16  that is relatively free of contamination or tape residue. A filled silicone thus provides a clean separation with molded panel  16  so that molded panel  16  does not have a degree of organic material or tape residue that would impede further processing or usage. 
         [0037]    In a preferred embodiment, second tape layer is up to approximately 200 microns thick. The filled silicone layer is up to approximately 100 microns thick, and the acrylic layer is up to approximately 100 microns thick. 
         [0038]    The manufacturing process described above has referred to various pieces of manufacturing machinery such as a magnetic plate, vacuum chuck, and a pick and place tool. It is intended that these items be utilized and selected as is understood in the semiconductor manufacturing industry. 
         [0039]    While at least one exemplary embodiment has been presented in the foregoing detailed description of the invention, it should be appreciated that a vast number of variations exist. It should also be appreciated that the exemplary embodiment or exemplary embodiments are only examples, and are not intended to limit the scope, applicability, or configuration of the invention in any way. Rather, the foregoing detailed description will provide those skilled in the art with a convenient road map for implementing an exemplary embodiment of the invention; it should be understood that various changes may be made in the function and arrangement of elements described in an exemplary embodiment without departing from the scope of the invention as set forth in the appended claims.