Method and process of contact to a heat softened solder ball array

Abstract

A method for enhancing temporary solder ball connection comprises the application of thermal energy to the solder balls, heating them to a submelting “softening” temperature, whereby the compression force required to connect all balls in a BGA is achieved at much reduced force, avoiding damage to the package, insert, substrate and support apparatus. Several forms of heating apparatus, and temperature measuring apparatus are disclosed.

1 . A method for forming a portion of a solder bump of an array of solder bumps of a device to a contact site of a plurality of contact sites of a member, comprising: 
 providing the solder bump of the array of solder bumps at a temperature Ts below a melting temperature of the solder bump; and    moving the solder bump of the array of solder bumps of the device using a pressure less than substantially 22 grams-force for contacting the contact site.    
   
   
       2 . The method of  claim 1 , wherein the melting temperature of the solder bump of the array of solder bumps is T° C. higher than an ambient temperature To, and wherein the softening temperature Ts is in the range of about 0.5 T to 0.95 T above the ambient temperature To.  
   
   
       3 . The method of  claim 1 , wherein the solder bump of the array of solder bumps contacts the contact site of the plurality of conductive contact sites at a pressure not substantially exceeding about 10 grams-force.  
   
   
       4 . The method of  claim 1 , wherein the solder bump of the array of solder bumps contacts the plurality of conductive contact sites at a pressure in the range of about 2 to 10 grams-force.  
   
   
       5 . The method of  claim 1 , wherein the semiconductor device having the array of solder bumps is heated by one of hot air convection and infrared radiation.  
   
   
       6 . The method of  claim 1 , wherein the member having the plurality of conductive contact sites is heated by one of hot air convection, conduction from a heated object, and infrared radiation.  
   
   
       7 . The method of  claim 1 , wherein the semiconductor device and the member are placed in a temperature-controlled oven for heating to the softening temperature Ts.  
   
   
       8 . The method of  claim 1 , wherein the semiconductor device is held in a chuck, the chuck being heated.  
   
   
       9 . The method of  claim 1 , wherein the member is held in a chuck, the chuck being heated.  
   
   
       10 . The method of  claim 1 , wherein the member having the plurality of conductive contact sites is heated by electrical resistance wires.  
   
   
       11 . The method of  claim 1 , wherein the member and a substrate are mounted on a mounting board having an integral heater, the integral heater controlled to heat the member to the softening temperature Ts.  
   
   
       12 . The method of  claim 1 , wherein the array of solder bumps comprises Sn—Pb solder having a lead content in the range of about 40 to about 98 percent, and the softening temperature Ts comprises a range of about 140 to 180° C.  
   
   
       13 . The method of  claim 1 , wherein heating comprises predetermining a heating time X to heat the solder bump of the array of solder bumps to the softening temperature Ts, and heating for the time X.  
   
   
       14 . The method of  claim 1 , wherein heating comprises initiating the heating, measuring a temperature of one of the member and the semiconductor device, and stopping the heating to limit a temperature of the solder bump of the array of solder bumps to no more than the softening temperature Ts.  
   
   
       15 . An apparatus for connecting a solder ball to a contact site comprising: 
 a first member having a solder ball thereon;    a second member having a contact site;    apparatus moving the first member against the second member for contact of the solder ball to the contact site, the first member contacting the second member at a pressure less than substantially 22 grams-force for the solder ball; and    apparatus for increasing the temperature of the solder ball and the contact site to a solder-softening temperature Ts.    
   
   
       16 . The apparatus of  claim 15 , wherein the contact site comprises one of a substantially flat surface, a recess for receiving a portion of a solder ball, and a recess having at least one projection therein for deforming a solder ball inserted therein.  
   
   
       17 . Testing apparatus for a semiconductor package having at least one solder ball on a surface thereof, the apparatus comprising: 
 an insert formed of generally noncompliant material having a first surface including at least one contact site for contacting the at least one solder ball and having a second surface;    a substrate having a first surface, having a second surface, the second surface of the insert secured to the first surface of the substrate, and having at least one lead on the substrate for connecting to at least one lead in a socket;    at least one electrical lead connecting the at least one contact site of the insert with the at least one lead of the substrate;    a test board having the socket with at least one contact lead connected to a testing circuit, the substrate and the insert for insertion into the socket for contact of the at least one lead of the substrate with the at least one contact lead of the socket; and    apparatus associated with at least one of the substrate, the insert, and the socket to increase the temperature thereof to a predetermined level.    
   
   
       18 . The apparatus of  claim 17 , further comprising temperature-sensing apparatus attached to one of the substrate, the insert, and the semiconductor package.  
   
   
       19 . The apparatus of  claim 18 , further comprising a temperature controller for controlling the apparatus to increase the temperature of the substrate, the insert, and the socket.