Recently, I met one very interesting issue with my board and connector. substrate of the board is copper with immersion silver, pad size is about 3x1mm. we print lead-free paste on the pad, then put the connector on the paste. The board was reflowed under a profile wiht a 65 sec of dwell time, some leads of the connector (at a ppm level)was pull out with the solder. all the solder was totally sticked to the lead and pell off from the pad, nothing was left on the pad. under the micoscope, it was observed the solder was reflowed and wet well. for the good joint, the solder will stick to the pad if we try to pull out the lead from the joint. anyone have ever meet the issue like this, any idea about this issue, what is the possible reason for this issue? waiting for your reply!!