Getting the paste isn't too hard. But, reflow (25-40 degrees above
liquidous) temperature for those alloys is hazardous for FR-4, and many
components. Ceramic chip caps and thick film resistors might be okay but
this is clearly over the top for most plastic IC packages. We have done
some experimenting with direct attach and forming-gas to ceramic using
these alloys. One day we ran an FR-4 board though the oven without
thinking. What came out of the oven would best be described as ash with
body.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Steve Gregory
Sent: Friday, September 06, 2002 3:20 PM
To: [log in to unmask]
Subject: Re: [TN] High temp pastes for wave soldering...
Hi Steve,
Hope you don't mind, I put a subject in the subject box for your post...
As far as through-put issues with your dispenser, why not print your
epoxy. You would do the whole board in well less than 30-seconds, and
have much better accuracy and consistency than you could ever expect
from a dispenser.
As far as high temperature pastes go, you would need one of the
high-lead alloys in order to be above the typical solder pot temperature
of 500° F (260° C). Getting these alloys in paste form is going to be
challenge as well, you can bet that it's going to be a custom order with
a minimum buy too.
A few of those alloys are:
° F ° C
Sn10Pb90 514 - 576 268 - 302
Sn10Pb88Ag02 514 - 570 268 - 299
Sn05Pb92.5 Ag2.5 536 280
My two-cents...
-Steve Gregory-
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