Patrick: How fresh is the paste being used? Also, how wet has the weather been during the time of this phenomenon? In other words, has the paste had the chance to absorb moisture before screen printing? One mechanism for solder splatter MIGHT be that during the preheating operation, entrapped moisture in the paste could rapidly expand and "explode" from within the deposited paste, especially if a damp surface layer of paste is spatulated into the jar before placing it on the screeen printer. This rapid expansion of moisture COULD send solder balls flying to nearby areas on the board (e.g. gold fingers). They probably result in melted spots of ~0.005" - 0.010" in diameter and are probably located on the end of the finger nearest the deposited solder paste, right? An experiment you could run to prove or disprove the theory is: 1) Tape the fingers of a several boards with Kapton tape. 2) Paste and reflow one set of boards with paste that has been allowed to sit open for a period of time to collect moisture from the air. 3) Paste and reflow another set of taped boards with fresh paste from the supplier. 4) Carefully inspect the gold finger area under a microscope and see how many solder balls are present on the tape for each set. The N2 environment should have no direct affect on the phenomenon you are seeing. In either case, the gold fingers would be protected while the data is being collected, so the product quality would NOT be compromised. When or if you find the root cause of the splatter, I would appreciate it if you would let me know the results. Good luck! Bill Fabry Plantronics, Inc. [log in to unmask] ______________________________ Reply Separator _________________________________ Subject: [TN] ASSY, solder residues on gold fingers Author: "TechNet Mail Forum." <[log in to unmask]> at INTERNET