Ruben - I believe it may be time (overdue, in fact) for a solder paste evaluation. Nothing against the Qualitek formulation but you may find a solder paste that behaves a lot better in all regards in your process and in your environment. My company performs a lot of solder paste evaluations and one of the things we look for is residue level - thickness and clarity. Some fluxes are susceptible to what you have when there is a high peak temp. You may or may not be able to avoid this, depending upon the thermal ability of your oven and the complexity (particularly mass and surface geometry) of your application. Suffice it to say that there is a big difference among the pastes we've tested of late - particularly the very low- and ultra low- residue formulations that don't, by the way, require inert atmosphere. I strongly recommend that you undertake a thorough solder paste evaluation program, using your current formulation as a benchmark. Besides residue levels, test for wetting angle, printability, solder balls, work life and tact time as a minimum. When was the last time you qualified your solder paste, anyway? Phil Zarrow ITM, Inc. Durham, NH [log in to unmask] ################################################################ TechNet E-Mail Forum provided as a free service by IPC using LISTSERV 1.8c ################################################################ To subscribe/unsubscribe, send a message to [log in to unmask] with following text in the body: To subscribe: SUBSCRIBE TechNet <your full name> To unsubscribe: SIGNOFF TechNet ################################################################ Please visit IPC web site (http://jefry.ipc.org/forum.htm) for additional information. For the technical support contact Dmitriy Sklyar at [log in to unmask] or 847-509-9700 ext.311 ################################################################