Fred Fenner originally posted some questions about this subject 12/15/95. Mike Frederickson here at the EMPF gave this initial response, and went looking for additional info. He was finally able to discuss this with Alpha Metals today, and they indicated that they have a good knowledge of the subject, and are very willing to discuss at depth. Contact Andy Maki (Mackey?) at Alpha 201.434.6778. ---------- From: Frederickson, Mike D. To: Crawford, John A. Subject: RE: FWD: Air entrapment in pastes Date: 18 Dec 95 11:17AM He's looking for specifications or test methods. I'm unsure of any for this type of concern. From a mechanistic viewpoint, entrapped air will provide more available Oxygen that will alter the flux-powder interface which can and will have an impact of the solderability of the powder and the rheology. This effect of entrapped air is measureable electrochemically - not so sure on the resolution of a viscometer. From a practical viewpoint, as the paste is being worked on the printer, there is little room for static air pockets to exist. In manufacturing, paste is mixed sufficiently such that the probability of air pocket survival is small. I guess the only real concern is the possibility of entrapped air in the process of packing the syringes - which is highly possible. From my understanding, this is a manual task -- which would increase the level of inconsistency from syringe to syringe. Given that entrapped air has a finite amount of available oxygen, I believe that the impact is minimal. I will call Alpha and get their viewpoint. ------------------------------------- SUBJECT: Air entrapment in pastes MESS-ID: 951215234606(u)100760.351(u)GHV136-1(a)CompuServe.COM DATE: 1995-12-15 19:30:09 FROM: [log in to unmask]@PMDF@MBIN01 TO: [log in to unmask]@PMDF@MBIN01 sender: [log in to unmask] From: Mike Fenner, BSP 100760,[log in to unmask] Fax: +441 295 720 937 For a project: I would be interested to hear from anyone who has knowledge of specifications/procedures for determining the maximum amount of entrapped air in pastes (solder, adhesives or otherwise) as supplied and methods for measuring same. I am concerned with all aspects, eg possible effects on rheology of beaten in air/gas, as well as gross bubbles in syringes. Alternatively suggestions for measuring techniques and max limits for "packaged air" particularly would be welcome.