Hello everyone, We have a Malcom PM-2A handheld viscometer here, and I'm trying to make use of it, however I'm having difficulty obtaining stable readings when testing solder paste. IPC TM-650 Test Methods Manual sect 2.4.34.3 says to take a reading when output data is stable for at least 1 minute. When I insert the spiral cylinder into the paste, after a few minutes it seems to just dig a hole into the paste and then begins to rotate freely and the viscosity reading steadily drops. The paste from the surrounding just doesn't seem to "flow" into the void space. However, when I rotate the paste container, or use a spatula to push the solder to fill in the voids, the readings seem to shoot up after a little delay, and then steadily decrease after that. At other times, if left alone for a while. the readings fluctuate a little (ie between 171-177). Is this considered "stable", and if so should I just take the middle value in that range, and how long would one recommend I wait before taking a measurement? Since solder paste is thixotropic, my understanding is that under constant shear for extended period of time, the viscosity will slowly decline. I'm not sure how quickly this effect takes place and how that would effect the stability of the readings. Any comments/suggestions will be greatly appreciated, (Thanks!) Toby --------------------------------------------------- Technet Mail List provided as a free service by IPC using LISTSERV 1.8e To unsubscribe, send a message to [log in to unmask] with following text in the BODY (NOT the subject field): SIGNOFF Technet To temporarily halt or (re-start) delivery of Technet send e-mail to [log in to unmask]: SET Technet NOMAIL or (MAIL) To receive ONE mailing per day of all the posts: send e-mail to [log in to unmask]: SET Technet Digest Search the archives of previous posts at: http://listserv.ipc.org/archives Please visit IPC web site http://www.ipc.org/html/forum.htm for additional information, or contact Keach Sasamori at [log in to unmask] or 847-509-9700 ext.5315 -----------------------------------------------------