Patent Publication Number: US-2005117267-A1

Title: IC package substrate with over voltage protection function

Description:
FIELD OF THE INVENTION  
      The present invention relates to an IC package substrate with over voltage protection function, more particularly, to a single IC package substrate provided with a structure having multiple over voltage protection devices.  
     BACKGROUND OF THE INVENTION  
      A conventional over voltage protection device is installed on a printed circuit board to protect internal IC devices according to demands by each IC device. However, such design requires installing independent over voltage protection devices to prevent respective IC devices from damage by surge pulses.  
      Please refer to  FIG. 1   a,  which is a top view of an IC device disposed on a conventional substrate. In  FIG. 1   a,  there are a plurality of electrodes ( 11 ) and a grounding line ( 13 ) disposed on a substrate ( 12 ). Then, an IC device ( 10 ) is soldered to the plurality of electrodes and the grounding line.  FIG. 1   b  is a sectional view of an IC device disposed on a conventional substrate. In  FIG. 1   b,  we can understand the relationship among the constituent elements. Because such structure cannot provide a over voltage protection function, the IC device cannot accept the energy of surge pulses, resulting in an irrecoverable damage to the IC device.  
      In order to protect the IC device, several over voltage protection devices are subsequently proposed. However, those over voltage protection devices need to install individual protection devices on a printed circuit board according to the actual necessity after the IC device was manufactured and installed on the printed circuit board. Therefore, such design has the disadvantages of high design costs, wasting limited space, and providing incomplete protection to the IC device.  
      Therefore, there is a need to provide an IC package substrate with over voltage protection function. In this way, a plurality of over voltage protection devices are provided simultaneously to solve the problems in the prior arts that unable to provide the over voltage protection or the inconvenience in the prior arts that need to install individual protection devices on a printed circuit board. The present invention provides an IC package substrate with over voltage protection function to eliminate the inconvenience.  
     SUMMARY OF INVENTION  
      An object of the present invention is to provide an IC package substrate with over voltage protection function and thus, the IC device can be protected in the presence of surge pulses.  
      Another object of the present invention is to provide an IC package substrate with over voltage protection function and thus, the over voltage protection devices are installed on the substrate directly.  
      Still another object of the present invention is to enable the substrate to be equipped with a plurality of over voltage protection devices. Thus, the present invention can reduce design costs, save limited space and lower dozen the unit cost to install the protection device to the IC device.  
      A still further object of the present invention is to provide an IC package substrate with over voltage protection function, wherein the substrate can be designed in different IC packaging technologies, such as surface mounting technology and pin soldering technology.  
      In order to accomplish the above objects, the present invention provides an IC package substrate with over voltage protection function. The IC package substrate comprises a substrate ( 22 ); one or more lower electrodes disposed on the substrate; one or more protection material layers ( 24 ) disposed on the lower electrodes, and electrically connected with the lower electrodes; one or more upper electrodes ( 21 ) disposed on the one or more protection material layers and connected with said protection material layers, and one or more grounding lines ( 23 ).  
      In order to understand the technical contents and features of the present invention with ease, the present invention is described by referring to the accompanying drawings. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
      The present invention will be illustrated according to the following drawings, wherein:  
       FIG. 1   a  shows a top view of an IC device disposed on a conventional substrate;  
       FIG. 1   b  shows a sectional view of an IC device disposed on a conventional substrate;  
       FIGS. 2   a,    2   c,    2   e,    2   g  and  2   i  are a top view of an IC package substrate with over voltage protection function according to an embodiment of the present invention;  
       FIGS. 2   b,    2   d,    2   f,    2   h  and  2   j  are a sectional view of an IC package substrate with over voltage protection function according to an embodiment of the present invention;  
       FIG. 3   a  is schematic diagram of an assembled IC package multi-layer substrate with over voltage protection function before the multiple layers are assembled to form the substrate according to another embodiment of the present invention;  
       FIGS. 3   b,    3   c  and  3   d  are schematic diagrams of IC package multi-layer substrate with over voltage protection function according to still another embodiment of the present invention;  
       FIG. 3   e  is a sectional view of an IC package multi-layer substrate with over voltage protection function according to another embodiment of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT  
      The embodiments of the present invention are described with reference to the drawings. The same elements in the drawing have the same reference numerals.  
      In  FIGS. 2   a  and  2   b,  a lower electrode ( 25 ) is disposed on a substrate ( 22 ), wherein a grounding line ( 23 ) and the lower electrode ( 25 ) are connected. In another embodiment, the grounding line and the lower electrode can be separated.  
      In  FIGS. 2   c  and  2   d,  protection material layers ( 24 ) are disposed on the lower electrodes ( 25 ). In  FIGS. 2   e  and  2   f,  one or more upper electrodes ( 21 ) are disposed on the protection material layers ( 24 ), wherein the protection material layers are variable resistance material layers.  
      In  FIGS. 2   g  and  2   h,  an IC chip ( 20 ) is installed on the substrate. The IC chip is a flip chip, and is connected with the upper electrodes ( 21 ) and the grounding line ( 23 ) by soldering. In another embodiment of the present invention, the chip ( 20 ) is connected with the upper electrodes ( 21 ) and the grounding line ( 23 ) by wire bonding.  
       FIGS. 2   i  and  2   j  are schematic diagrams of the IC chip installed on the substrate. An overcoat ( 26 ) protects the IC chip ( 20 ) and helps the heat dissipation.  
      Another embodiment of the present invention provides an IC package substrate with over voltage protection function by a multiplayer structure. With reference  FIG. 3   a,  an IC package substrate with over voltage protection function has a four-layer structure, wherein a first layer is provided with a plurality of upper electrodes ( 311 ) and a grounding line ( 313 ) on a protection material layer ( 314 ). The protection material layer ( 314 ) is a variable resistance material layer. A third layer has the same structure as the first layer. Namely, a plurality of upper electrodes ( 331 ) and a grounding line ( 333 ) are disposed on a protection material layer ( 334 ). A second layer is provided with a lower electrode ( 325 ) and a grounding line ( 323 ) on a protection material layer ( 324 ). The protection material layer ( 324 ) is a variable resistance material layer. A fourth layer has the same structure as the second layer. Namely, a lower electrode ( 345 ) and a grounding line ( 343 ) are disposed on a protection material layer ( 344 ).  
       FIG. 3   b  is a schematic diagram showing an assembly of the first layer to the fourth layer. In  FIG. 3   b,  physical relationships among the associated layers in the multi-layer structure are clearly shown. In  FIG. 3   c,  a plurality of terminations ( 37 ) are electrically connected to the groundings lines ( 313 ,  323 ,  333 ,  343 ) in each layer. By the way, the upper electrodes ( 311 ,  331 ) on the first and third layers are also electrically connected by the terminnations ( 37 ).  FIG. 3   d  shows a flip chip ( 30 ) disposed on the top layer of the multi-layer structure, wherein the flip chip is electrically connected with the terminations. The electrical connection can be accomplished by soldering. In  FIG. 3   e,  the connection relationships between the flip chip and the multi-layer protection material device are clearly shown. In another embodiment of the present invention, the chip can be electrically connected with the terminations by wire bonding.  
      When a surge pulse occurs, the energy of the surge pulse will enter into the electrodes via terminations and transmit to the grounding line through the multi-layer structure protection material layers. Because the features of the variable resistance materials and the multi-layer structure, the energy of the surge pulse will be released evenly to the grounding lines of each layer and thus, the IC device will not be damaged and the object to protect the IC device is achieved.  
      Although the invention has been disclosed in terms of preferred embodiments, the disclosure is not intended to limit the invention. The invention still can be modified or varied by persons skilled in the art without departing from the scope and spirit of the invention which is determined by the claims below.