Abstract:
An integrated circuit packaging structure, which can accommodate two or four memory chips in a single package. The feature rests upon a packaging structure that makes independent data buses between two memory chips, while implementing in parallel the address buses and control buses, and finally encapsulates them within one package in the expectation of doubling the memory capacity without increasing the size of the package and the number of pins.

Description:
BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to an integrated circuit packaging structure and, in particular, to a packaging structure that can double the capacity of the memory without increasing the size of the package and the number of pins. 
     2. Description of the Prior Art 
     Memory plays a very important role in the computer mechanism. Accompanying the increasing speed of the central process unit (CPU), the memory has been prosperously developed so that, in recent years, it has overwhelmed the Moore rule, which states that the capacity will increase by a factor of four every two or three years. The capacity has rapidly evolved from 16 MB, 64 MB, 128 MB to 256 MB and is still evolving toward higher capacity. 
     The memory is also modularized in accord with the need of the computer industry. A usual 64 MB SDRAM module known in the prior art is composed by eight memory integrated circuits (IC), and every memory IC with 54 pins has only one memory chip. Therefore, it is indeed a waste that there is only placed on little chip in such a big package. 
     In observation of the disadvantages in the memory packaging structure according to the prior art that awaits for improvement, the inventor then made efforts in modifying and refining and finally succeeded in the invention of this integrated circuit packaging structure after many years of research and hard-working. 
     SUMMARY OF THE INVENTION 
     The present invention provides an integrated circuit packaging structure, which has independent implementation for the data buses among chips and parallel implementation for the address buses and control buses, and then encapsulates them into one package so as to double the capacity of the memory. 
     Furthermore, the instant invention provides an integrated circuit packaging structure, by which the efficiency of a memory IC can be effectively promoted and the inner space of the package can be more effectively utilized. 
     Yet, the invention provides an integrated circuit packaging structure, via which the capacity of the memory can be rapidly doubled and modularized, and can speed up the development of the memory industry. 
     The integrated circuit packaging structure with the above mentioned merits imbeds two or four memory chips into the concave structure formed by the upper and lower circuit boards, has independent data buses for each memory chip while makes address buses and control buses work in parallel, and finally encapsulates them within a single package in the expectation of enlarging the memory capacity without increasing the size of the package and the number of pins. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     The drawings disclose an illustrative embodiment of the present invention which serves to exemplify the various advantages and objects hereof, and are as follows: 
     FIG.  1 (A) is an embodiment of packaging two memory chips into a package according to the present invention; 
     FIG.  1 (B) is an A—A cross-sectional view of FIG.  1 (A); 
     FIG. 2 is a circuit of packaging two memory chips into a package according to the present invention; 
     FIG.  3 (A) is an embodiment of packaging four memory chips into a package according to the present invention; 
     FIG.  3 (B) is an A—A cross-sectional view of FIG.  3 (A); 
     FIG. 4 is a circuit of packaging four memory chips into a package according to the present invention. 
    
    
     Main Symbols 
       1  package 
       1   a  package 
       2   a  memory chip 
       2   b  memory chip 
       2   c  memory chip 
       2   d  memory chip 
       2   e  memory chip 
       2   f  memory chip 
       21  welding pad 
       21   a  welding pad 
       21   b  welding pad 
       3  upper circuit board 
       3   a  upper circuit board 
       31  groove 
       31   a  groove 
       32  welding pad 
       4  lower circuit board 
       4   a  lower circuit board 
       41  aperture 
       41   a  aperture 
       42  welding pad 
       42   a  welding pad 
       5  colloidal protection layer 
       5   a  colloidal protection layer 
       5   b  colloidal protection layer 
       6  connecting wire 
       6   a  connecting wire 
       7  punching 
       7   a  punching 
       8  double-sided tape 
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Please refer to FIG.  1 (A), which is an embodiment of packaging two memory chips into a package according to the present invention. According to the diagram, two memory chips  2   a,    2   b  are encapsulated within a package  1 , and, by placing the memory chips  2   a,    2   b  in parallel, the memory capacity doubles without enlarging the volume of the package  1 . 
     Please refer to FIG.  1 (B), which is an A—A cross-sectional view of FIG.  1 (A). This diagram shows the embodiment structure of the instant invention, wherein the memory chip  2   a  is embedded in the groove  31  formed by the upper circuit board  3  and the lower circuit board  4 . 
     The welding pad  21  on the memory chip  2   a  and the welding pad  42  on the lower circuit board  4  can be connected by the bonding technique. Applying a colloidal protection layer (such as epoxy) may protect the inner connecting wire  6  and memory chip  2   a.  Punching  7  processes between the upper and lower circuit boards  3 ,  4  can make help connecting the circuits on the upper and lower circuit boards  3 ,  4 , which is convenient for the S.M.T. process. The invention can effectively double the memory capacity via this structure. 
     Please refer to FIG. 2, which is a circuit of packaging two memory chips into a package according to the present invention. The diagram shows that the memory chip  2   a  and memory chip  2   b  are encapsulated within the package  1 , wherein the data bus (DQ 0 ˜DQ 7 ) on the package  1  is composed by the data bus (DQ 0 ˜DQ 3 ) on the memory chip  2   a  and the data bus (DQ 0 ˜DQ 3 ) on the memory chip  2   b  independently; while the address bus (A 0 ˜A 11 , BA 0 , BA 1 ) and control bus ({overscore (CS)}, {overscore (WE)}, {overscore (CAS)}, {overscore (RAS)}, CLK, CKE, DQM) on the package  1  are implemented by combining the address bus (A 0 ˜A 11 , BA 0 , BA 1 ) and control bus ({overscore (CS)}, {overscore (WE)}, {overscore (CAS)}, {overscore (RAS)}, CLK, CKE, DQM) in parallel. Applying this circuit to the packaging structure described in FIG.  1 (B) can make a memory IC with doubled memory capacity. 
     Please refer to FIG.  3 (A), which is an embodiment of packaging four memory chips into a package according to the present invention. The most difference between this diagram and FIG.  1 (A) is to encapsulate four memory chips  2   a ,  2   b ,  2   c , and  2   d  into a package  1   a , and, by putting the memory chips  2   a ,  2   b ,  2   c , and  2   d  in parallel and in stack, the memory capacity can be increased by a factor of four without enlarging the volume of the package  1   a.    
     Please refer to FIG.  3 (B), which is an A—A cross-sectional view of FIG.  3 (A). According to the diagram, the backs of the upper and lower memory chips  2   e ,  2   c  are glued together by the double-sided tape  8 , and are, stacked as double layers, embedded into the groove  31   a  formed by the upper circuit board  3   a  and the lower circuit board  4   a . The welding pad  21   a  on the upper memory chip  2   e  and the welding pad  32  on the upper circuit board  3   a  are connected via the bonding technique, while the welding pad  21   b  on the lower memory chip  2   c  may be exposed in the aperture  41   a  on the lower circuit board  4   a , and the welding pad  21   b  on the lower memory chip  2   c  and the welding pad  42   a  on the lower circuit board  4   a  may be connected via the bonding technique too. Applying colloidal protection layers  5   a,    5   b  (such as epoxy) on both ends of the bonded elements can protect the inner connecting wire  6   a  and the memory chips  2   e ,  2   c . Punching  7   a  processes between the upper and lower circuit boards  4   a ,  4   b  help connecting the circuits on the upper and lower circuit boards  4   a ,  4   b , which in turn is convenient for the S.M.T. process. This invention can effectively increase the memory capacity by a factor of four with the help of this structure. 
     Please refer to FIG. 4, which is a circuit of packaging four memory chips into a package according to the present invention. The diagram demonstrates that the memory chips  2   c ,  2   d ,  2   e , and  2   f  are encapsulated into a package  1   a  with 54 pins, wherein the data bus (DQ 0 ˜DQ 15 ) on the package  1   a  are composed by the data bus (DQ)˜DQ 3 ) on each of the memory chips  2   a ,  2   b ,  2   c , and  2   d  independently, while the address bus (A 0 ˜A 11 , BA 0 , BA 1 ) and control bus ({overscore (CS)}, {overscore (WE)}, {overscore (CAS)}, {overscore (RAS)}, CLK, CKE, LDQM, UDQM) on the package  1   a  are implemented by putting the address bus (A 0 ˜A 11 , BA 0 , BA 1 ) and control bus ({overscore (CS)}, {overscore (WE)}, {overscore (CAS)}, {overscore (RAS)}, CLK, CKE, DQM) on each of the memory chips  2   a ,  2   b ,  2   c , and  2   d  in parallel. Applying this circuit feature to the packaging structure described in FIG.  3 (B) can produce a memory IC with four times of memory capacity. 
     The integrated circuit packaging structure provided by the instant invention, when compared with the prior art, has the following merits: 
     1. the integrated circuit packaging structure according to the invention can encapsulate two memory chips into a single package and thus enlarges the memory capacity by a factor of two or four without increasing the size of the package and the number of pins; 
     2. the integrated circuit packaging structure according to the invention can effectively promote the efficiency of a memory IC, and can make good use of the inner space of the package; and 
     3. the integrated circuit packaging structure according to the invention can effectively double and modularize the memory, which can stimulate rapid development in memory industry. 
     Many changes and modifications in the above described embodiment of the invention can, of course, be carried out without departing from the scope thereof. Accordingly, to promote the progress in science and the useful arts, the invention is disclosed and is intended to be limited only by the scope of the appended claims.