Good advice. Thank you, Ahne, for the response!
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Subject: RE: [TN] Assy: stencil cleaning liquid temps
Author: "Ahne Oosterhof" <[log in to unmask]> at Internet
Date: 11/6/98 2:00 PM
Hi Jeff,
HEAT: Stencil epoxies are chosen for a variety of reasons, the main one is
whether or not the epoxy holds the metal in place. Another one has to do
with whether or not it will be possible to remove the epoxy and allow
re-use. For most situations, don't exceed 140F or the epoxy may come off.
The temperature levels you are talking about have no impact on the stencil
metal.
ULTRASONIC CLEANING: I have not seen a negative impact on the stencils from
ultrasonic cleaning.
CLEANERS and LIQUIDS: Some cleaners, especially those with high pH, "eat"
epoxies, some cleaners even attack aluminum. I don't know what your choices
and alternatives are. Make at least sure the stencil is well rinsed and
maybe even dried, before putting it away.
Have fun,
Ahne Oosterhof, (503)641-9428.
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Jeff Hempton
Sent: Friday, November 06, 1998 6:39 AM
To: [log in to unmask]
Subject: [TN] Assy: stencil cleaning liquid temps
We are evaluating heated, ultrasonic stencil cleaners and liquids.
We are evaluating detergent based liquids, and heating them to 120
deg. F greatly enhances their cleaning capabilities.
We are using no-clean solder paste, type mesh 3, at .020" pitch
components.
I am aware that you must stay below certain temperatures and times at
temp to keep the epoxy from de-bonding from the stencil to the wire
mesh, but, from articles I've read ("...recommend keeping liquid temps
below 110 deg. F"), this seems somewhat ridiculous to me, so I want to
ask:
Is there a concern that temps could
"expand/warp/change pitch/permanently deform" stainless steel (we use
.006") in the fine-pitch or ultra-fine pitch areas?
United Technology Electronic Controls
Jeff L. Hempton, Sr. SMD Engineer
E-mail: [log in to unmask]
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