Ipc 7351b Pdf Free
The solder for lead free processes must:
Glass-metal laminate packages are limited to operation temperatures larger than 250° C. The use of silver particles in solder paste applied to the BGA and paste underfill helps to minimize the variability in the solder joint reliability. The use of vacuum dipping to impart tension to the laminate is less effective for lead free solder joint formation, as compared to the tensile strength imparted by the lead.
BGA packaging is one of the greatest challenges for the SMT process. Precious metal finishes will not form a good joint with most lead free solders. Furthermore, the organic material of the polymer usually prevents the wetting of the surface which leads to low joint reliability. Many resins are commonly used in combination with some type of silver, including polyurethane, epoxy and phenolic, but all of these must be metallized by sputtering to ensure a complete wetting of the die.