Abstract:
The present invention provides an improved connection for circuit substrates. The circuit substrates are connected at concave and convex portions at their ends. The concave portion is formed such that the inside width is larger than the entrance width. The convex portion fits into the concave portion. Thereby, a connected portion of the circuit substrates has increased tensile strength. Furthermore, abnormality of the connected portion of the circuit substrates may be easily perceived.

Description:
CROSS REFERENCE TO RELATED APPLICATIONS  
       [0001]     This U.S. non-provisional application claims priority from Korean Patent Application No. 2003-50203 filed Jul. 22, 2003, the contents of which are incorporated by reference in their entirety.  
       BACKGROUND OF THE INVENTION  
       [0002]     1. Field of the Invention  
         [0003]     The present invention relates to semiconductor packages and, more particularly, to a connection structure for connecting circuit substrates.  
         [0004]     2. Description of the Related Art  
         [0005]     Integrated circuits (IC) have specific needs. Functionally, they require signal and power supplies. ICs can operate at high temperature and require heat dissipation. Furthermore, ICs damage easily by humidity, shock or thermal stress. Proper packaging satisfies these requirements.  
         [0006]     In semiconductor package fabrication, circuit substrates or package substrates may use lead frames, printed circuit boards, ceramic substrates or tape wiring substrates. Strip-type circuit substrates may be used for simultaneous fabrication of a plurality of semiconductor packages. Single-type circuit substrates may be used for a single semiconductor package.  
         [0007]     Tape wiring substrates and printed circuit boards may be flexible and thin, for example 150 μm to 200 μm thick, allowing the semiconductor packages to be fabricated with a reel-to-reel process. In a reel-to-reel process, the strip-type circuit substrates are wound on two reels and spaced at predetermined intervals and move from one reel to the other reel. The semiconductor package fabricating method using the reel-to-reel process allows mass production of packages, thereby increasing productivity. In conventional reel-to-reel processing, when a circuit substrate  10  (“a first circuit substrate”) reaches its end, a new circuit substrate  20  (“a second circuit substrate”) should be connected to the first circuit substrate  10 ). In general, the ends of the first and second circuit substrates  10 ,  20  are cut and connected to each other using an adhesive tape  30  to form a connected portion  40 .  
         [0008]     Currently, the connection between the circuit substrates  10  and  20  depends on the adhesive tape  30 . The tensile strength of the connected portion  40  decreases considerably compared with an intact circuit substrate.  
         [0009]     The reel-to-reel process occasionally deforms or otherwise damages the connected portion  40 . Thus, a poorly connected portion may tear off at a tape feeder (not shown) or cause ajam.  
         [0010]     Further, if the adhesive tape  30  expands, a gap between the first circuit substrate  10  and the second circuit substrate  20  occurs, causing a transfer fault. Specifically, the tape feeder utilizes guide holes formed on the circuit substrate at predetermined intervals and feeds the circuit substrate. If the adhesive tape  30  connecting the circuit substrates  10  and  20  expands abnormally, the guide holes in the connected portion  40  have irregular pitches, consequently generating the transfer fault. Evading detection with the naked eye, this expansion range of the adhesive tape  30  generally resides between 120 μm and 130 μm, as shown in  FIG. 5 .  
       SUMMARY OF THE INVENTION  
       [0011]     The present invention is directed to an improved connection structure for a circuit substrate, improving the tensile strength of the connected substrates, thus preventing deformation or damage at the connected portion.  
         [0012]     The present invention further allows easy detectability of abnormality in a connection structure of a circuit substrate.  
         [0013]     In one embodiment, circuit substrates manufactured with complementary geometries may interlock with improved structural integrity. For instance, a first circuit substrate having at least one concave portion may interlock with a second circuit substrate having at least one convex portion. The concave portion may be formed with a larger inside width than the entrance width, therefore providing structural integrity against forces with components perpendicular to the substrate junction and planar with the substrates. The convex portion fits into the concave portion.  
         [0014]     Numerous geometries can utilize the present invention so long as they are complementary in structure, thus strengthening the substrate connection based on their geometry. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0015]     These and other objects, features and advantages of the present invention will be readily understood with reference to the following detailed description in conjunction with the accompanying drawings, wherein like reference numerals correspond to structural elements, and in which:  
         [0016]      FIG. 1  is a perspective view illustrating a conventional connection for connecting circuit substrates;  
         [0017]      FIG. 2  is a plan view of the connection structure shown in  FIG. 1 ;  
         [0018]      FIG. 3  is an exploded perspective view of one embodiment, illustrating a circuit substrate connection;  
         [0019]      FIG. 4  is a plan view of a connection structure of  FIG. 3 ;  
         [0020]      FIG. 5  is a table showing the results of tension testing for the connection structures of the prior art and the present invention;  
         [0021]      FIG. 6  is a plan view of a connection structure in accordance with another embodiment of the present invention; and  
         [0022]      FIG. 7  is a plan view of a connection structure in accordance with yet another embodiment of the present invention. 
     
    
     DETAILED DESCRIPTION OF THE INVENTION  
       [0023]     Exemplary embodiments of the present invention will be described below with reference to the accompanying drawings.  
         [0024]      FIG. 3  is an exploded perspective view illustrating a connection for circuit substrates in accordance with an embodiment of the present invention.  FIG. 4  is a plan view of a connection structure shown in  FIG. 3 .  
         [0025]     Referring to  FIGS. 3 and 4 , circuit substrates are connected in accordance with a T shaped embodiment of the present invention. The rear end  68  of a first circuit substrate  60  may be connected to the front end  76  of a second circuit substrate  70 . An adhesive tape  80  may attach the connected ends of the first and second circuit substrates  60  and  70 , thus securing the connected portion  90 . Therefore, the connection structure geometry provides bonding strength for the connection structure in addition to the adhesive tape  80 . This connection structure of circuit substrates improves bonding strength in comparison to conventional connection structures.  
         [0026]     The first circuit substrate  60  preferably has a plurality of guide holes  62  at each side thereof, spaced at specified intervals. The first circuit substrate  60  may have package areas  64  spaced at specified intervals. In one embodiment, the first circuit substrate  60  preferably has at least one concave portion  68  at its end  66 . The concave portion  68  may be formed with the inside width larger than the entrance width. In this embodiment, two concave portions are substantially of “T” shape and are spaced at predetermined intervals at the rear end of the first circuit substrate  60 .  
         [0027]     The second circuit substrate  70  may have a similar structure to the first circuit substrate  60 . The second circuit substrate  70  preferably has at least one convex portion  78  at end  76 . The convex portion  78  is substantially of “T” shape, corresponding to the concave portion  68  of the first circuit substrate  60  so that the convex portion  78  complements the concave portion  68 .  
         [0028]     The convex portion  78  of the second circuit substrate  70  interlocks with the concave portion  68  of the first circuit substrate  60 , connecting the first circuit substrate  60  to the second circuit substrate  70 . An adhesive tape  80  may attach to the rear end  66  of the first circuit substrate  60  and the front end  76  of the second circuit substrate  70 , securing the connected portion. One embodiment provides dummy guide holes  82  at the adhesive tape area in conformity of intervals between the guide holes  62  and  72  of the first and second circuit substrates  60  and  70 . Preferably, the length of the rear portion of the first circuit substrate  60  and the front portion of the second circuit substrate  70  may maintain the intervals of the guide holes  62  and  72 . Alternatively, the dummy guide holes may not be formed.  
         [0029]     Although this embodiment of the present invention shows the concave portion  68  formed at the rear end of the first circuit substrate  60  and the convex portion  78  formed at the front end of the second circuit substrate  70 , the concave portion may be formed at the front end of the second circuit substrate  70  and the convex portion may be formed at the rear end of the first circuit substrate  60 .  
         [0030]      FIG. 5  is a table showing the results of tension testing for the connection structures of the conventional art and the present invention.  
         [0031]     Referring to  FIG. 5 , the tensile strength of the connection structure of circuit substrates of the present invention increases, in one case by approximately 20%, compared to that of the conventional connection structure.  
         [0032]     Conventionally, the expansion of the adhesive tape may result in a gap between the circuit substrates, generating a transfer fault. Further, it is not easy to perceive such a gap with the naked eye. In accordance with the present invention, however, the connected portion may not expand, but may be destroyed at the yield strength. This allows an operator to perceive abnormality of the connected portion of the circuit substrates with the naked eye. In other words, the connection structure may maintain its original structure within the yield strength, reducing the generation of transfer faults during a reel-to-reel process.  
         [0033]     Although this embodiment shows the concave and convex portions formed in the shape substantially of a “T”, the concave and convex portions may be formed of various shapes. For example, as shown in  FIG. 6 , the concave and convex portions  168  and  178  may be formed in the shape substantially of an oval. The concave portion  178  is preferably formed such that the inside width is larger than the entrance width and the center of the oval is located in the concave area.  
         [0034]     Referring to  FIG. 7 , the concave and convex portions  268  and  278  may also be formed in the shape substantially of a trapezoid. The concave portion  268  is preferably formed such that the inside width is larger than the entrance width.  
         [0035]     Accordingly, the convex portion  68 ,  168 ,  268  of the second circuit substrate  70 ,  170 ,  270  fits into the concave portion  78 ,  178 ,  278  of the first circuit substrate  60 ,  160 ,  260 . The bonding strength of the connection structure may be provided by the connection structure itself as well as by the adhesive strength of the adhesive tape, improving the tensile strength of the connected portion of the circuit substrates.  
         [0036]     Although the exemplary embodiments of the present invention have been described in detail hereinabove, it should be understood that many variations and/or modifications of the basic inventive concepts taught herein, which may appear to those skilled in the art, will still fall within the spirit and scope of the present invention as defined in the appended claims.