Method for screening semiconductor devices for contact coplanarity

Abstract

A method for determining contact coplanarity of packaged semiconductor devices having a plurality of contacts. The method includes the steps of measuring the relative positions of the contacts on a subject semiconductor device; calculating from the measurements seating planes 64 formed by tilting the device to one or more of its corners and/or sides such that each said plane comprises contacts at or adjacent to the corners of the device; using the measured relative contact positions and the calculated seating planes to determine the highest deviation from contact coplanarity for the semiconductor device.

We claim:  
     
         1 . A method for determining contact coplanarity of packaged semiconductor devices having a plurality of contacts, comprising the steps of: 
 measuring the relative positions of said contacts on a subject semiconductor device;    calculating from said measurements seating planes formed by tilting said device to one or more of its corners and/or sides such that each said plane comprises contacts at or adjacent to the corners of said device;    using said measured relative contact positions and said calculated seating planes to determine the highest deviation from contact coplanarity for said semiconductor device.    
     
     
         2 . The method of  claim 1 , wherein said step of measuring comprises measuring the relative positions of said contacts using a 3-point seating plane method.  
     
     
         3 . The method of  claim 1 , wherein said contacts are leads extending in a gull-wing pattern from said packaged semiconductor device.  
     
     
         4 . The method of  claim 1 , wherein said contacts are solder balls attached to a bottom side of said packaged semiconductor device.  
     
     
         5 . A method for screening for contact coplanarity packaged semiconductor devices having a plurality of contacts, comprising the steps of: 
 measuring the relative positions of said contacts on a subject semiconductor device;    calculating from said measurements seating planes formed by tilting said device to one or more of its corners and/or sides such that each said plane comprises contacts at or adjacent to the corners of said device;    using said measured relative contact positions and said calculated seating planes to determine the highest deviation from contact coplanarity for said semiconductor device; and    comparing said highest deviation from contact coplanarity to a pre-determined specification.    
     
     
         6 . The method of  claim 5 , further comprising the step of sorting packaged semiconductor devices that have a highest deviation at or in excess of said pre-determined specification from packaged semiconductor devices that have a highest deviation less than said pre-determined specification.  
     
     
         7 . The method of  claim 5 , wherein said step of measuring comprises measuring the relative positions of said contacts using a 3-point seating plane method.  
     
     
         8 . The method of  claim 5 , wherein said contacts are leads extending in a gull-wing pattern from said packaged semiconductor device.  
     
     
         9 . The method of  claim 5 , wherein said contacts are solder balls attached to a bottom side of said packaged semiconductor device.  
     
     
         10 . A semiconductor test apparatus, comprising: 
 a tool operable to measure the relative positions of contacts on a packaged semiconductor device;    a computer operable to use said relative positions to determine seating planes formed by tilting said device to one or more of its corners and/or sides such that each said plane comprises contacts at or adjacent to the corners of said device; said computer further operable to calculate a highest deviation from contact coplanarity using said measured relative contact positions and said seating planes.    
     
     
         11 . The apparatus of  claim 10 , where said computer is further operable to compare said highest deviation from contact coplanarity to a pre-determined specification.  
     
     
         12 . The apparatus of  claim 11 , further comprising a device for separating packaged semiconductor devices having deviations from contact coplanarity that exceed said pre-determined specification from packaged semiconductor devices that do not exceed said pre-determined specification.  
     
     
         13 . The apparatus of  claim 10 , wherein said contacts on a packaged semiconductor device comprise leads extending in a gull-wing pattern from said device.  
     
     
         14 . The apparatus of  claim 10 , wherein said contacts on a packaged semiconductor device comprise solder balls extending from a bottom side of said device.