Ball grid assembly with solder columns

Abstract

A method of making a ball grid assembly and the assembly wherein a mask ( 1 ) is provided which is not wettable by solder and through which a pattern of parallel holes ( 3 ) is provided extending to at least one of a pair of opposing surfaces. A magnet ( 5 ), preferably an electromagnet, is disposed at the other one of the opposing surfaces. Solderable magnetic pins ( 7 ) are caused to enter the holes by magnetic attraction by positioning the one surface of the mask over the pins with a portion of each of the pins extending out of the hole into which it has entered. A layer of solder ( 11 ) is formed on the portion of each of the pins extending out of a hole in the mask and this layer of solder is reflowed over the pins and over a grid of solder adherable elements ( 13 ) on the package ( 15 ) and then allowed to set. The mask is removed from the pins when the solder is again set.

1 . A method of making a ball grid assembly comprising the steps of: 
 (a) providing a mask which is not wettable by a solder to be used in conjunction therewith and through which a pattern of parallel holes is provided extending to at least one of a pair of opposing surfaces with a magnet disposed at the other of said opposing surfaces;    (b) providing one of solderable or solder-coated magnetic pins;    (c) causing said pins to enter said holes by magnetic attraction by positioning said one surface over said pins with a portion of each of said pins extending out of the hole into which it has entered;    (d) forming a layer of solder on the portion of each of said pins extending out of a said hole;    (e) causing said layer of solder to reflow over said pins and over a grid of solder adherable elements and then set; and    (f) removing said pins from said mask.    
     
     
         2 . The method of  claim 1  wherein said grid is a plurality of solder pads disposed on a package.  
     
     
         3 . The method of  claim 1  wherein said magnet is an electromagnet.  
     
     
         4 . The method of  claim 2  wherein said magnet is an electromagnet.  
     
     
         5 . The method of  claim 1  wherein said solderable magnetic pins have a magnetizable core which is coated with a solderable metal.  
     
     
         6 . The method of  claim 4  wherein said solderable magnetic pins have a magnetizable core which is coated with a solderable metal.  
     
     
         7 . The method of  claim 1  wherein said solderable magnetic pins are a core of an alloy of steel coated with a material taken from the class consisting of copper, gold or palladium.  
     
     
         8 . The method of  claim 4  wherein said solderable magnetic pins are taken from the class consisting of an alloy of steel coated with a material taken from the class consisting of copper, gold or palladium.  
     
     
         9 . A package which comprises: 
 (a) a surface having a plurality of electrically conductive pads thereon; and    (b) a solder-coated solderable magnetic pin secured to each of said pads.    
     
     
         10 . The package of  claim 9  wherein said pads are one of solder pads or lands.  
     
     
         11 . The package of  claim 9  wherein each said solder-coated magnetic pin is secured to said pad by solder coated on said pin.  
     
     
         12 . The package of  claim 10  wherein each said solder-coated magnetic pin is secured to said pad by solder coated on said pin.  
     
     
         13 . The package of  claim 9  wherein each said pin is disposed normal to said surface.  
     
     
         14 . The package of  claim 10  wherein each said pin is disposed with its major axis normal to said surface.  
     
     
         15 . The package of  claim 11  wherein each said pin is disposed with its major axis normal to said surface.  
     
     
         16 . The package of  claim 12  wherein each said pin is disposed with its major axis normal to said surface.  
     
     
         17 . A method of making a ball grid assembly comprising the steps of: 
 (a) providing a mask which is not wettable by a solder to be used in conjunction therewith and through which a pattern of parallel holes is provided extending to at least one of a pair of opposing surfaces with a magnet disposed at the other of said opposing surfaces;    (b) providing solderable pins;    (c) causing said pins to enter said holes with a portion of each of said pins extending out of the hole into which it has entered;    (d) forming a layer of solder on the portion of each of said pins extending out of a said hole;    (e) causing said layer of solder to reflow over said pins and over a grid of solder adherable elements and then set; and    (f) removing said pins from said mask.    
     
     
         18 . The method of  claim 17  wherein said solderable pins are taken from the class consisting of a magnetizable core coated with a solderable metal.  
     
     
         19 . The method of  claim 17  wherein said solderable pins are taken from the class consisting of a core of an alloy of steel coated with a solderable metal taken from the class consisting of gold, copper or palladium.