Method and apparatus for reducing stresses applied to bonded interconnects between substrates

Abstract

A method ( 200 ) is provided for reducing stresses applied to one or more bonded interconnects ( 106 ) of a substrate ( 103 ) and a PCB (Printed Circuit Board) ( 104 ). The method comprises the steps of coupling ( 204 ) a compound ( 108 ) on a top surface of the substrate, wherein the compound has the property of expanding when a heat profile is applied thereto, coupling ( 206 ) a cover ( 102 ) to the PCB that overhangs at least a portion of the compound, and applying ( 208 ) the heat profile to the compound and optionally the cover and/or PCB. More than one apparatus implementing the method is also included.

1 . A method for reducing stresses applied to one or more bonded interconnects of a substrate and a PCB (Printed Circuit Board), comprising the steps of: 
 coupling a compound on a top surface of the substrate, wherein the compound has a property of expanding when a heat profile is applied thereto;    coupling a cover on the PCB so that it overhangs at least a portion of the compound; and    applying the heat profile to at least the compound.    
   
   
       2 . The method of  claim 1 , wherein the substrate comprises a surface mount IC (Integrated Circuit), and wherein the one or more electrically bonded interconnects comprise one or more solder bumps coupled between an electrical pad of the bottom surface of the surface mount IC and a corresponding electrical pad on a top surface of the PCB.  
   
   
       3 . The method of  claim 1 , wherein the compound comprises an epoxy resin.  
   
   
       4 . The method of  claim 1 , further comprising the step of applying a double-sided adhesive to the compound for coupling to the top surface of the substrate.  
   
   
       5 . The method of  claim 1 , further comprising the step of applying a double-sided adhesive to the top surface of the substrate for coupling to the compound.  
   
   
       6 . The method of  claim 1 , wherein the cover comprises a shield electrically coupled to the PCB for reducing EMI (Electromagnetic Interference) radiated by the substrate, and for reducing EMI entering the shield.  
   
   
       7 . The method of  claim 1 , wherein the portion of the cover overhanging the compound has rigidity sufficient to reduce stresses applied to the one or more electrically bonded interconnects.  
   
   
       8 . A substrate for coupling to a PCB in an assembly, comprising: 
 one or more bonding interconnects coupled to a bottom surface of the substrate and the PCB;    a compound having a property of expanding when a heat profile is applied thereto, wherein the compound couples on a top surface of the substrate;    a cover coupled to the PCB and arranged to overhang at least a portion of the compound and coupled to at least a portion of the compound when applying the heat profile to the compound.    
   
   
       9 . The substrate of  claim 8 , wherein the substrate comprises a surface mount Integrated Circuit (IC), and wherein the one or more bonded interconnects comprise one or more solder bumps coupled between an electrical pad of the bottom surface of the surface mount IC and a corresponding electrical pad on a top surface of the PCB.  
   
   
       10 . The substrate of  claim 8 , wherein the compound comprises an epoxy resin.  
   
   
       11 . The substrate of  claim 8 , wherein the assembly further comprises a double-sided adhesive applied between the compound and the top surface of the substrate.  
   
   
       12 . The substrate of  claim 8 , wherein the cover comprises a shield electrically coupled to the PCB for reducing EMI (Electromagnetic Interference) radiated by the substrate, and for reducing EMI entering the shield.  
   
   
       13 . The substrate of  claim 8 , wherein the portion of the cover overhanging the compound has rigidity sufficient to reduce stresses applied to the one or more electrically bonded interconnects.  
   
   
       14 . The substrate of  claim 8 , wherein a portion of the one or more bonding interconnects carry electrical signals to the PCB.  
   
   
       15 . A selective call radio (SCR), comprising: 
 a transceiver for processing signals from a communication system;    a memory for storage;    a power supply for supplying power to the components of the SCR;    an audio system for presenting audible signals to the end user of the SCR; and    a processor coupled to the foregoing components for control thereof, wherein one or more of the foregoing components of the SCR have a surface mount IC that couples to a PCB, comprising:    one or more solder bumps coupled between an electrical pad of a bottom surface of the surface mount IC and a corresponding electrical pad on the PCB;    a compound having a property of expanding when a heat profile is applied thereto;    a cover coupled to the PCB and arranged to overhang at least a portion of the compound and coupled to at least a portion of the compound when applying the heat profile to the compound; and    a double-sided adhesive applied between a surface of the compound and a top surface of the surface mount IC.    
   
   
       16 . The SCR of  claim 15 , wherein the SCR further comprises a display for presenting text and graphics to an end user of the SCR and a keypad for manipulating functions of the SCR;  
   
   
       17 . The SCR of  claim 16 , wherein the compound comprises an epoxy resin.  
   
   
       18 . The SCR of  claim 16 , wherein the cover comprises a shield electrically coupled to the PCB for reducing EMI (Electromagnetic Interference) radiated by the surface mount IC, and for reducing EMI entering the shield.  
   
   
       19 . The SCR of  claim 16 , wherein the portion of the cover overhanging the compound has rigidity sufficient to reduce stresses applied to the one or more solder bumps.  
   
   
       20 . The SCR of  claim 16 , wherein a portion of the one or more bonding interconnects carry electrical signals to the PCB.