Method and apparatus for underfilling semiconductor devices

Abstract

A method and apparatus for underfilling a gap between a multi-sided die and a substrate with an encapsulant material. The die and/or the substrate is heated non-uniformly by a heat source to generate a temperature gradient therein. The heated one of the die and the substrate transfers heat energy in proportion to the temperature gradient to the encapsulant material moving in the gap. The differential heat transfer steers, guides or otherwise directs the movement of the encapsulant material in the gap. The temperature gradient may be established with heat transferred from the heat source to the die and/or the substrate by conduction, convection, or radiation. The temperature gradient may be dynamically varied as the encapsulant material moves into the gap.

1 . An apparatus for underfilling a gap between a multi-sided die and a substrate with a dispenser operative for dispensing an encapsulant material adjacent to at least one side edge of the die to encapsulate a plurality of electrical connections formed therebetween, comprising: 
 a heat source operative to non-uniformly transfer heat energy to one of the die and the substrate so that said one of the die and the substrate non-uniformly transfers heat to the encapsulant material moving in the gap between the multi-sided die and the substrate.    
     
     
         2 . The apparatus of  claim 1  wherein said heat source is adapted to transfer heat to the heated one of the die and the substrate with a plurality of temperature zones distributed to promote non-uniform heat transfer to the encapsulant material.  
     
     
         3 . The apparatus of  claim 1  wherein said heat source is configured to conductively transfer heat energy to the heated one of the die and the substrate.  
     
     
         4 . The apparatus of  claim 3  wherein said heat source comprises: 
 a support block having a surface coupled in thermal communication with the heated one of the die and the substrate; and    at least one heating element coupled in thermal communication with said support block, said at least one heating element adapted to transfer heat energy to said surface.    
     
     
         5 . The apparatus of  claim 1  wherein said heat source is configured to convectively transfer heat energy to the heated one of the die and the substrate.  
     
     
         6 . The apparatus of  claim 5  wherein said heat source is capable of directing a flow of a heated gas toward the heated one of the die and the substrate.  
     
     
         7 . The apparatus of  claim 6  wherein said heat source comprises: 
 a first porous element and a second porous element positioned between said heat source and the heated one of the die and the substrate, said first and second porous elements having a different porosity effective to control the flow of the heated gas to the heated one of the die and the substrate.    
     
     
         8 . The apparatus of  claim 1  wherein said heat source is configured to radiatively transfer heat energy to the heated one of the die and the substrate.  
     
     
         9 . The apparatus of  claim 8  wherein said heat source is operative to provide a radiative flux of electromagnetic energy incident on the heated one of the die and the substrate.  
     
     
         10 . The apparatus of  claim 9  wherein said heat source comprises: 
 a mask positioned between said heat source and the heated one of the die and the substrate, said mask including a pattern of openings configured to transmit the radiative flux to the heated one of the die and the substrate.    
     
     
         11 . The apparatus of  claim 9  wherein said heat source comprises: 
 a laser providing an area of radiative flux dimensionally smaller than a surface area of the heated one of the die and the substrate; and    a reflective device for moving the area of radiative flux relative to the heated one of the die and the substrate in a manner effective to non-uniformly transfer heat energy.    
     
     
         12 . The apparatus of  claim 9  wherein said heat source comprises: 
 a thermal transfer element covering the heated one of the die and the substrate and operative to absorb said radiative flux, said thermal transfer element formed of a thermally-conductive material having a pattern of thicknesses that varies so as to alter a path length for heat conduction from said thermal transfer element to the heated one of the die and the substrate.    
     
     
         13 . The apparatus of  claim 1  further comprising: 
 a dispenser operative for dispensing the encapsulant material adjacent to at least one side edge of the die.    
     
     
         14 . The apparatus of  claim 13  wherein said heat source is adapted to non-uniformly transfer heat energy to one of the die and the substrate before said dispenser operates to dispense the encapsulant material.  
     
     
         15 . The apparatus of  claim 13  wherein said heat source is adapted to non-uniformly transfer heat energy to one of the die and the substrate after said dispenser operates to dispense the encapsulant material.  
     
     
         16 . The apparatus of  claim 13  said heat source is adapted to non-uniformly transfer heat energy to one of the die and the substrate when said dispenser operates to dispense the encapsulant material.  
     
     
         17 . An apparatus for underfilling a gap between a die and a substrate with an encapsulant material, comprising: 
 a heat source including a plurality of regions each adapted to transfer heat energy to the heated one of the die and the substrate, at least two of said regions operative to transfer heat energy to heat encapsulant material in the gap between the die and the substrate to different temperatures as the encapsulant material moves within the gap.