{HEAD ~ Solder ball reflow soldering methods} are used to connect the electronic device to the secondary substrate and to connect {TAIL ~ the secondary substrate} to the primary substrate 
are used to connect
{ HEAD ~ Solder ball reflow soldering methods } are used to connect the electronic device to the secondary substrate and to connect { TAIL ~ the secondary substrate } to the primary substrate
HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL REL OTH OTH OTH OTH OTH OTH OTH OTH OTH OTH REL REL TAIL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH