Flex Board Heller Profile

Recently started running flex board with tin lead connectors. The problem being that when we receive the parts incoming connectors are all bright and shiny. Now after going thru the heller we encountered cold solder. At this time peak temp was at 186c using tamura 60-30 paste (which incidentally does not come in contact with the above mentioned connector)By slowly increasing the temp to peak at 213c no more cold solder but the connectors now look dull. Remembering that tin-lead content melting point is at 183c i have been very carefull not to warp and damage the flex. Suprising thing is that after applying heat @200c using a heatgun the connectors clearup leaving it shinny as before. I would really appreciate it if someone here could help me troubleshoot this prob. If you have a similar product perhaps you could advice me on the profile. TIA.

sukhdev

reply »