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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.
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