Abstract:
A device is disclosed which includes a first packaged integrated circuit device, a second packaged integrated circuit device positioned above the first packaged integrated circuit device and a plurality of planar conductive members conductively coupling the first and second packaged integrated circuit devices to one another. A method is also disclosed which includes conductively coupling a plurality of extensions on a leadframe to each of a pair of stacked packaged integrated circuit devices and cutting the leadframe to singulate the extensions from one another.

Description:
BACKGROUND OF THE INVENTION 
     1. Technical Field 
     This subject matter disclosed herein is generally directed to the field of packaging integrated circuit devices, and, more particularly, to stacked packaged integrated circuit devices and various methods of making same. 
     2. Description of the Related Art 
     Integrated circuit technology uses electrical devices, e.g., transistors, resistors, capacitors, etc., to formulate vast arrays of functional circuits. The complexity of these circuits requires the use of an ever-increasing number of linked electrical devices so that the circuit may perform its intended function. As the number of transistors increases, the integrated circuitry dimensions shrink. One challenge in the semiconductor industry is to develop improved methods for electrically connecting and packaging circuit devices which are fabricated on the same and/or on different wafers or chips. In general, it is desirable in the semiconductor industry to construct transistors which occupy less surface area on the silicon chip/die. 
     In the manufacture of semiconductor device assemblies, a single semiconductor die is most commonly incorporated into each sealed package. Many different package styles are used, including dual inline packages (DIP), zig-zag inline packages (ZIP), small outline J-bends (SOJ), thin small outline packages (TSOP), plastic leaded chip carriers (PLCC), small outline integrated circuits (SOIC), plastic quad flat packs (PQFP) and interdigitated leadframe (IDF). Some semiconductor device assemblies are connected to a substrate, such as a circuit board, prior to encapsulation. Manufacturers are under constant pressure to reduce the size of the packaged integrated circuit device and to increase the packaging density in packaging integrated circuit devices. 
     In some cases, packaged integrated circuit devices have been stacked on top of one another in an effort to conserve plot space. Prior art techniques for conductively coupling the stacked packaged integrated circuit devices to one another typically involved the formation of solder balls or wire bonds to establish this connection. What is desired is a new and improved technique for conductively coupling stacked packaged devices to one another. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The present subject matter may be understood by reference to the following description taken in conjunction with the accompanying drawings, in which like reference numerals identify like elements, and in which: 
         FIGS. 1 and 2  are various views of a stacked packaged integrated circuit device in accordance with one aspect of the present disclosure; 
         FIG. 3  is a view of illustrative portions of a leadframe that may be employed as described herein; 
         FIGS. 4-7  depict one illustrative process flow for forming stacked packaged integrated circuit devices as described herein; and 
         FIG. 8  is a top view of an illustrative conductive contact for stacked packaged integrated circuit devices as disclosed herein. 
     
    
    
     While the subject matter disclosed herein is susceptible to various modifications and alternative forms, specific embodiments thereof have been shown by way of example in the drawings and are herein described in detail. It should be understood, however, that the description herein of specific embodiments is not intended to limit the invention to the particular forms disclosed, but on the contrary, the intention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention as defined by the appended claims. 
     DETAILED DESCRIPTION OF THE INVENTION 
     Illustrative embodiments of the present subject matter are described below. In the interest of clarity, not all features of an actual implementation are described in this specification. It will of course be appreciated that in the development of any such actual embodiment, numerous implementation-specific decisions must be made to achieve the developers&#39; specific goals, such as compliance with system-related and business-related constraints, which will vary from one implementation to another. Moreover, it will be appreciated that such a development effort might be complex and time-consuming, but would nevertheless be a routine undertaking for those of ordinary skill in the art having the benefit of this disclosure. 
     Although various regions and structures shown in the drawings are depicted as having very precise, sharp configurations and profiles, those skilled in the art recognize that, in reality, these regions and structures are not as precise as indicated in the drawings. Additionally, the relative sizes of the various features and doped regions depicted in the drawings may be exaggerated or reduced as compared to the size of those features or regions on fabricated devices. Nevertheless, the attached drawings are included to describe and explain illustrative examples of the subject matter disclosed herein. 
       FIG. 1  depicts an illustrative stacked die package  10  in accordance with one aspect of the present disclosure. A first packaged integrated circuit device  12 A is positioned beneath a second packaged circuit device  12 B. A plurality of solder balls  32  or other known techniques may be employed to conductively couple the first packaged integrated circuit device  12 A to an illustrative printed circuit board  40 . As will be recognized by those skilled in the art after a complete reading of the present application, the first packaged integrated circuit device  12 A and second packaged circuit device  12 B may be the same type of integrated circuit device or they may be different from one another. For example, the first packaged integrated circuit device  12 A may be a packaged DRAM device while the second packaged circuit device  12 B may be a NAND device. Additionally, the first packaged integrated circuit device  12 A and second packaged circuit device  12 B may be in packages having different physical package sizes. In the illustrative example discussed herein, the first packaged integrated circuit device  12 A and second packaged circuit device  12 B have the same approximate package size. Additionally, using the methodologies disclosed herein, the stacked die package  10  may comprise more than the two illustrative packaged devices  12 A,  12 B depicted in  FIG. 1 . For example, 3-5 packaged integrated circuit devices may be positioned in a single stack  10  using the structures and methods disclosed herein. 
     In the disclosed example, each of the first packaged integrated circuit device  12 A and the second packaged circuit device  12 B comprise a printed circuit board  14  with a cavity  16  formed therein. An integrated circuit die  18  is secured within the cavity  16  in accordance with traditional techniques, e.g., an adhesive material. Illustrative wire bonds  20  are used to conductively couple the bond pads  24  on the die  18  and the bond pads  26  on the printed circuit board  14 . Traditional mold compound material  22  may be used to fill the cavity  16 . 
     A plurality of conductive terminals  28  may be formed on the top surface  30 T and the bottom surface  30 B of the first packaged integrated circuit device  12 A and the second packaged circuit device  12 B.  FIG. 2  is a top view of the second packaged integrated circuit device  12 B (without the mold compound material  22 ), wherein an illustrative layout of the conductive terminals  28  is depicted. Of course, the particular layout or arrangement of the conductive terminals  28  may vary depending upon the particular application. 
       FIGS. 3-7  depict one illustrative method of forming the stacked packaged die  10  disclosed herein.  FIG. 3  depicts a portion of an illustrative leadframe  50  that may be employed in packaging integrated circuit devices. The leadframe  50  comprises a plurality of tie bars  52 , each of which have a plurality of leadframe extensions  54  that physically extend from the bar  52 . The size, number and spacing of the leadframe extensions  54  may vary depending upon the particular application. In one example, the extensions  54  are planar plate structures that have a thickness ranging from approximately 50-150 μm. The other physical dimensions, e.g., length, width, as well as the general configuration of the extension, may vary. As will be recognized by those skilled in the art after a complete reading of the present application, the size and pitch of the extensions  54  will be coordinated to match the size and pitch of the conductive terminals  28  to which the extensions  54  will, ultimately, be conductively coupled. The extensions  54  may be comprised of a variety of conductive materials, e.g., copper, alloy  42 , etc. Depending upon the material of the extensions  54 , a surface protectant may be applied to the extensions  54  for a variety of reasons, e.g., to prevent oxidation. In some applications, the extensions  54  may be coated with a material such that a wettable surface is created, e.g., a coating of silver, tin, gold/nickel, etc. Such a coating may have a thickness of approximately 0.25-4.0 μm. Additionally, in some applications, gold or copper stud bumps could be employed on the extensions  54  to make the connection from the extensions  54  to the packaged integrated circuit devices  12 A,  12 B. 
     As shown in  FIG. 4 , the leadframe  50  is conductively coupled to the conductive terminals  28  on the top surface  30 T of the first packaged integrated circuit device  12 A. In one specific example, a solder flux is applied to the extensions  54  and/or to the conductive terminals  28  on the top surface  30 T of the first packaged integrated circuit device  12 A. The leadframe  50  is aligned and positioned such that the extensions  54  contact the conductive terminals  28 . A first heat treatment process is then performed to reflow the solder to thereby conductively couple the extensions  54  and the conductive terminals  28  to one another. 
     Next, as shown in  FIG. 5 , the second packaged circuit device  12 B is positioned above and aligned with the leadframe  50 . During this process, the conductive terminals  28  on the bottom surface  30 B of the second packaged circuit device  12 B are aligned so as to be conductively coupled to the extensions  54 . A solder flux may be applied to the conductive terminals  28  and/or extensions  54  during this process. A second heat treatment process is then performed to reflow the connection between the extensions  54  and the conductive terminals  28  on the bottom surface  30 B of the second packaged circuit device  12 B. 
     Thereafter, as shown in  FIG. 6 , a plurality of solder balls  32  are formed on conductive terminals  28  on the bottom surface  30 B of the first packaged integrated circuit device  12 A using traditional techniques. Then, the tie bar portions  52  of the leadframe  50  are trimmed to result in the structure depicted in  FIG. 7 . This trimming process may be performed using any of a variety of known techniques, e.g., a punch.  FIG. 3  depicts an illustrative cut line  56  for the leadframe  50 . The trimming process results in the singulation of the extensions  54  such that they are not conductively coupled to one another. Also note that an outer edge  54   e  of the extension  54  is approximately aligned with an edge  12   e  of the first and second packaged integrated circuit devices  12 A,  12 B. In some applications, if the first and second packaged integrated circuit devices  12 A,  12 B are of different physical sizes, then the edge  54   e  of the extension  54  may only align with the edge of one of the stacked packaged integrated circuit devices.  FIG. 8  is a top view of an individual extension  54  and the contact  28  on the bottom of the second packaged integrated circuit device  12 A. The extension  54  acts as a generally rectangular, planar conductive member between the stacked packaged integrated circuit devices  12 A,  12 B.