Hi TechNet! It sounds like the flux in your solder paste is loosing its suspension properties because of the shearing action during deposition onto your assembly. The flux in solder paste isn't suppose to do that (unless you formulate it too)! I suggest conducting the basic material tests on your paste (viscosity, slump, tack) and also contacting the solder paste vendor. This "spreading" of the flux element of the solder paste has been reported on in the literature (and I have observed it too) but the solder paste flux was breaking down leading to solder defects. Good luck. Dave Hillman Rockwell Collins [log in to unmask] ______________________________ Reply Separator _________________________________ Subject: assy:spreading of paste flux Author: [log in to unmask] at ccmgw1 Date: 11/23/96 9:33 AM Date : 23/11/96 16:56 Msg From: PROCESS ENGINEERING hello, we are facing a problem of spreading of paste flux (water soluble paste) on either side of the pad just after printing (contact printing using 6 mil laser cut stencil). This is clearly observed under 4x magnification, particularly for 20 mil pitch component. is there any flux spread test for solder paste . regards nalin altos india ltd. altos india ltd. *************************************************************************** * TechNet mail list is provided as a service by IPC using SmartList v3.05 * *************************************************************************** * To unsubscribe from this list at any time, send a message to: * * [log in to unmask] with <subject: unsubscribe> and no text. * *************************************************************************** *************************************************************************** * TechNet mail list is provided as a service by IPC using SmartList v3.05 * *************************************************************************** * To unsubscribe from this list at any time, send a message to: * * [log in to unmask] with <subject: unsubscribe> and no text. * ***************************************************************************