Ed,
Thanks for the due respect, I'll take it wherever I can get it. I do
not disagree with the points that you, Brian or Larry have raised, vapor
phase can have great benefits in certain instances. However, it is not a
process to move into without a good reason for doing so. And in the majority
of applications, a modern forced convection reflow system will achieve
desired results without the high costs that can be involved with vapor
phase. Brian's points regarding the GWP of these materials is another
negative looking towards future usage, it is just a matter of time before
they become heavily regulated, taxed and ultimately outlawed ala CFCs and
lead. Even 3M makes note of the high GWP of Fluorinert in their data sheets,
right after they trumpet the fact that they are VOC free. Finally, the
current selection of perfluorinated fluids will not exceed a temperature of
215C, ruling out use for high-temp alloy soldering. The FC-71 you mentioned
was discontinued by 3M without replacement back in 1989-1990 due to lack of
demand, and there is no other manufacturer I'm aware of making anything with
a boil point above 215C.
Mike McMonagle
PCBA Process Engineering
Telxon Corporation
(713) 307-2443
www.telxon.com
-----Original Message-----
From: Edward J. Valentine [mailto:[log in to unmask]]
Sent: Wednesday, March 01, 2000 2:34 PM
To: [log in to unmask]
Subject: Re: [TN] vapor phase reflow
Jason -
With all due respect to Mr. McMonagle, vapor phase reflow with preheating
(an integral part of many units since the mid-80's), can produce excellent
results in very dense assemblies and backplanes. The chief advantage is its
very even heat distribution over the assemble. The highest temperature
fluorinated liquid that I am familiar with is FC-71, which has a higher
boiling temperature than the 215C (419F), FC-70. The FC-71 is 250C (495F).
The liquids are very expensive, but the only fluids that were/are regulated
were the secondary fluids (Freons), not the Primary fluorinated fluids since
they are not a HFC or cause any effect on the ozone, nor are they a
regulated contaminant,but that may vary at some locales. Generally, forced
convection is the preferred reflow process, but it is not a panacea for all
applications.
If you would like to discuss some more, please feel free to contact me
offline.
Ed Valentine
Electronics Manufacturing Solutions
8612 Mourning Dove Road, Raleigh, NC 27615
Phone: (919) 270-5145, Fax: (919) 847-9971
Email: [log in to unmask]
Website: http://www.ems-consulting.com
----- Original Message -----
From: Jason Gregory <[log in to unmask]>
To: <[log in to unmask]>
Sent: Wednesday, March 01, 2000 8:53 AM
Subject: [TN] vapor phase reflow
> Hello techies!
>
> I am looking for anyone who has performed any qualifications on the
advantages/disadvantages of vapor phase reflow. Particularly dealing with
higher temp alloys. Is it the way to go? Is convection better? Who are the
major manufacturers? Are silicon castments to keep the bottomside components
from falling off mandatory? Any replies are GREATLY appreciated.
>
> Jason Gregory
> Production Manager
> Electrospec
> (713)784-4900
> (713)784-1194 fax
>
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