Semiconductor package having flash-free contacts and techniques for manufacturing the same

Abstract

Techniques for forming packaged semiconductor devices having top surfaces with flash-free electrical contact surfaces are described. According to one aspect, a molding cavity is provided which has a molding surface that is sufficiently smooth such that when placed in contact with an electrically conductive contact, gaps between the conductive contact and the mold cavity surface do not form.

1 . A semiconductor molding chamber comprising: 
 a top molding cavity having a molding surface that has a surface roughness of less than 1.2 R a ; and    a bottom molding cavity configured to support a semiconductor die, whereby the top and bottom molding cavity enclose the semiconductor within the molding chamber.    
   
   
       2 . A semiconductor molding chamber as recited in  claim 1  wherein the molding surface has a surface roughness of approximately equal to or less than 0.5 R a .  
   
   
       3 . A semiconductor molding chamber as recited in  claim 1  wherein the molding surface has a surface roughness of approximately equal to or less than 0.1 R a .  
   
   
       4 . A semiconductor molding chamber as recited in  claim 1  wherein the molding surface of the top molding cavity contains surface imperfections, the molding chamber further comprising: 
 a surface coating formed over the molding surface of the top molding cavity that substantially smoothens the surface imperfections.    
   
   
       5 . A semiconductor molding system comprising: 
 a semiconductor die having a top surface and a bottom surface, at least one deformable electrically conductive contact on the top surface;    a top molding cavity having a molding surface that has a surface roughness of approximately equal to or less than 1.2 R a , wherein the molding surface is in contact with the deformable electrically conductive contact; and    a bottom molding cavity that supports the semiconductor die.    
   
   
       6 . A semiconductor molding system as recited in  claim 5  wherein the molding surface has a surface roughness of approximately equal to or less than 0.5 R a .  
   
   
       7 . A semiconductor molding system as recited in  claim 5  wherein the molding surface has a surface roughness of approximately equal to or less than 0.1 R a .  
   
   
       8 . A semiconductor molding system as recited in  claim 5  wherein the molding surface of the top molding cavity contains surface imperfections, the molding system further comprising: 
 a surface coating formed over the molding surface of the top molding cavity that substantially smoothens the surface imperfections.    
   
   
       9 . A semiconductor molding system as recited in  claim 5  wherein the deformable electrically conductive contact is a solder ball.  
   
   
       10 . A method of packaging a semiconductor die comprising: 
 providing a top molding cavity that has a top molding surface with a surface roughness of less than 1.2 R a ;    providing a bottom molding cavity that has a bottom molding surface, wherein the top and the bottom molding cavity form a molding chamber;    placing the semiconductor die having one or more deformable electrically conductive contacts on a top surface of the die into the molding chamber;    lowering the top molding cavity onto the deformable electrically conductive contacts such that the top molding surface deforms the contacts and creates an empty space between the top surface of the semiconductor die and the top molding surface; and    injecting a molding compound into the molding chamber such that the molding compound surrounds the deformable electrically conductive contacts and fills the empty space between the top surface of the semiconductor die and the top molding surface in a way that no flash forms on a top surface of each of the deformable electrically conductive contacts.    
   
   
       11 . A method as recited in  claim 10  wherein the molding compound is injected into the molding chamber such that the molding compound flows through the molding chamber at 1.16 kg/mm 2 .  
   
   
       12 . A method as recited in  claim 10  wherein the deformable electrically conductive contacts are solder balls.  
   
   
       13 . A method as recited in  claim 10  wherein the packaged semiconductor die is formed after the injecting operation, the method further comprising: 
 attaching a secondary device to a top surface of the packaged semiconductor die such that electrical contacts of the secondary device make contact with the top surface of each of the deformable electrically conductive contacts, wherein the attaching operation is the next operation after the injecting operation.