Hi Albert! I suspect that you are driving off/volatilizing some type of ionic contamination with your baking procedure. One method investigating this is to bake a set of boards at 90 C for 65 minutes, run the omegameter test and compare results. A temperature of 150 C is high enough to volatilize a number of different ionic contaminates species. Doesn't such a high bake temperature result in solderability problems for your pwbs? Good Luck. Dave Hillman Rockwell Collins [log in to unmask] Albert Mok <[log in to unmask]> on 04/14/99 07:48:44 PM Please respond to "TechNet E-Mail Forum." <[log in to unmask]>; Please respond to Albert Mok <[log in to unmask]> To: [log in to unmask] cc: Subject: [TN] ionic contamination Good morning, technetters, We aer using Alpha 600SMD for detecting the ionic contamination of bare PCB. All boards are D.I. rinse and dried prior for the testing. The reading come out is about 10ug NaCl/sq.in. However, when the boards sent to baking at 110 C for four hours and the boards are tested again, the reading drop to 3ug NaCl/sq. in. We do not suspect inadequate baking at the first time. We bake the boards at 150 C for 65 mins. The solder mask is photoimagable solder mask. This is not a single case. Everytime when the contamination is failed, then bake the boards again, the result turn to positive. However, if we prolong the baking time at the first baking, it does have this result apparently. Do you have this experience? ################################################################ 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's web site (http://www.ipc.org) "On-Line Services" section for additional information. For technical support contact Hugo Scaramuzza at [log in to unmask] or 847-509-9700 ext.312 ################################################################ ################################################################ 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's web site (http://www.ipc.org) "On-Line Services" section for additional information. For technical support contact Hugo Scaramuzza at [log in to unmask] or 847-509-9700 ext.312 ################################################################