Semiconductor package structure with a heat-dissipation stiffener and method of fabricating the same

Abstract

A semiconductor package structure with a heat-dissipation stiffener and a method of fabricating the same are proposed. The proposed packaging technology includes a substrate; a thermally-conductive stiffener mounted over the front surface of the substrate, the stiffener being formed with a centrally-hollowed portion and an outward-extending passage; a semi-conductor chip mounted on the front surface of the substrate and within the centrally-hollowed portion of the stiffener; an underfill layer filled and cured in a gap between the semiconductor chip and the substrate; and a plurality of solder balls mounted on the back surface of the substrate. Alternatively, the passage can be formed in the front surface of the substrate. During fabrication process, the passage is used for the injection of a cleaning solvent into the gap between the semiconductor chip and the substrate so as to clean away remnant solder flux. The proposed packaging technology allows the cleaning solvent used in the solder flux cleaning process to be unobstructed by the stiffener so that the cleaning solvent can be more smoothly injected into the gap between the semiconductor chip and the substrate. This benefit allows the subsequently formed underfill layer to be substantially free of voids, allowing the finished package product to be more assured in quality and reliability.

What is claimed is:  
     
         1 . A semiconductor package structure, which comprises: 
 a substrate having a front surface and a back surface;    a thermally-conductive stiffener mounted over the front surface of the substrate, the stiffener being formed with a centrally-hollowed portion and an outward-extending passage;    a semiconductor chip mounted on the front surface of the substrate and within the centrally-hollowed portion of the stiffener;    an underfill layer filled and cured in a gap between the semiconductor chip and the substrate; and    a plurality of solder balls mounted on the back surface of the substrate.    
     
     
         2 . The semiconductor package structure of  claim 1 , wherein the centrally-hollowed portion of the stiffener is greater in dimension than the semiconductor chip to allow the semiconductor chip to be accommodated therein.  
     
     
         3 . The semiconductor package structure of  claim 1  or  2 , wherein the semiconductor chip is bonded to the substrate by means of solder balls.  
     
     
         4 . The semiconductor package structure of  claim 1  or  2 , further comprising: 
 a lid mounted over the centrally-hollowed portion of the stiffener for sealing the semiconductor chip therein.  
 
     
     
         5 . The semiconductor package structure of  claim 4 , wherein the lid is integrally formed with the stiffener.  
     
     
         6 . A thermally-conductive stiffener for use on a semiconductor package, which is formed with a centrally-hollowed portion and a passage extending outwards from the centrally-hollowed portion to the edge thereof.  
     
     
         7 . A semiconductor package structure, which comprises: 
 a substrate having a front surface and a back surface, with the front surface being formed with a passage extending from edge to center of the substrate;    a thermally-conductive stiffener mounted over the front surface of the substrate, the stiffener being formed with a centrally-hollowed portion;    a semiconductor chip mounted on the front surface of the substrate and within the centrally-hollowed portion of the stiffener;    an underfill layer filled and cured in a gap between the semiconductor chip and the substrate; and    a plurality of solder balls mounted on the back surface of the substrate.    
     
     
         8 . A substrate for use on a semiconductor package, which has a front surface and a back surface, with the front surface being formed with a passage extending from edge to center of the substrate.  
     
     
         9 . A method for fabricating a semiconductor package, comprising the steps of: 
 preparing a substrate having a front surface and a back surface;    mounting a thermally-conductive stiffener over the front surface of the substrate, the stiffener being formed with a centrally-hollowed portion and an outward-extending passage;    mounting a semiconductor chip through the centrally-hollowed portion of the stiffener onto the front surface of the substrate;    injecting a cleaning solvent through the passage in the stiffener into the gap between the semiconductor chip and the substrate;    performing a flip-chip underfill process to form an underfill layer in the gap between the semiconductor chip and the substrate;    implanting a plurality of solder balls on the back surface of the substrate; and    performing a singulation process to cut apart each package unit.    
     
     
         10 . A method for fabricating a semiconductor package, comprising the steps of: 
 preparing a substrate having a front surface and a back surface, with the front surface being formed with a passage extending from edge to center of the substrate;    mounting a thermally-conductive stiffener over the front surface of the substrate, the stiffener being formed with a centrally-hollowed portion;    mounting a semiconductor chip through the centrally-hollowed portion of the stiffener onto the front surface of the substrate;    injecting a cleaning solvent through the passage into the gap between the semiconductor chip and the substrate;    performing a flip-chip underfill process to form an underfill layer in the gap between the semiconductor chip and the substrate;    implanting a plurality of solder balls on the back surface of the substrate; and    performing a singulation process to cut apart each package unit.    
     
     
         11 . The method of  claim 9  or  10 , further comprising the step of: 
 accelerating the flow speed of the cleaning solvent.  
 
     
     
         12 . The method of  claim 11 , wherein the cleaning solvent is accelerated through centrifugal type of flow accelerating means.  
     
     
         13 . The method of  claim 11 , wherein the cleaning solvent is accelerated through rotating type of flow accelerating means.  
     
     
         14 . The method of  claim 11 , wherein the cleaning solvent is accelerated through disturbance type of flow accelerating means.  
     
     
         15 . The method of  claim 9  or  10 , wherein the semiconductor chip is bonded to the substrate by means of solder balls.  
     
     
         16 . The method of  claim 9  or  10 , further comprising the step of: 
 mounting a lid over the centrally-hollowed portion of the stiffener to seal the semiconductor chip therein.