Leadframe for semiconductor packages

Abstract

A leadframe for semiconductor packages. The leadframe includes a die pad, a side rail, a tie bar, and a plurality of leads. The side rail is around the die pad. The tie bar connects the die pad and the side rail. The leads extend from the side rail to close proximity to the die pad. Each lead has a corresponding lead relative to a predetermined center line. A predetermined pair of corresponding leads are substantial asymmetrical with each other in appearance relative to the predetermined center line.

1 . A leadframe for semiconductor packages, comprising: 
 a die pad;    a side rail around the die pad;    a tie bar connecting the die pad and the side rail; and    a plurality of leads extending from the side rail to close proximity to the die pad; wherein    every lead has a corresponding lead relative to a predetermined center line; and    a predetermined pair of corresponding leads are substantial asymmetrical with each other relative to the predetermined center line.    
     
     
         2 . The leadframe as claimed in  claim 1 , wherein the leads of the predetermined pair comprise substantially different lead lengths.  
     
     
         3 . The leadframe as claimed in  claim 1 , wherein the leads of the predetermined pair comprise substantially different lead widths.  
     
     
         4 . The leadframe as claimed in  claim 1 , wherein the leads of the predetermined pair comprise substantially asymmetrical extending traces.  
     
     
         5 . The leadframe as claimed in  claim 1 , wherein the leads of the predetermined asymmetrical pair are for impedance matching.