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November 1997

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Subject:
From:
David D Hillman <[log in to unmask]>
Reply To:
TechNet Mail Forum.
Date:
Wed, 26 Nov 1997 07:35:17 -0600
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Hi Lee - two items to think about as you venture into double sided
assembly: your reflow oven capabilities and the robustness of your pwb
surface finish.  Reflow ovens that have both top and bottom side heating
provide some recipe flexibility to keep your "first pass and now bottom
side" of the pwa from reaching reflow temperature. Surface tension will
keep many components attached to the pwa so avoiding bottomside reflow
isn't a requirement but it does keep the solder joint intermetallic
thickness minimized. Secondly your "second pass and now top side" of the
pwa has seen one thermal exposure - the surface finish (OSP, tin/lead,
gold/nickel, etc.) needs to maintain its solderability so that successful
soldering can be completed during the second pass. Good Luck.

Dave Hillman
Rockwell Collins
[log in to unmask]





[log in to unmask] on 11/25/97 07:28:11 AM

Please respond to [log in to unmask]

To:   [log in to unmask]
cc:    (bcc: David D Hillman/CedarRapids/Collins/Rockwell)
Subject:  [TN] Double sided assembly methods




Gentlemen,
I am looking for advise, checkpoints, pit falls, etc. on double sided
PCB assembly methods.  I have recently been informed by our
engineering department that we will be advancing our board
circuit densities by extending our bottom side component population
from simple chip cap/resistors to active integrated components.  I
would greatly appreciate a few words from anyone presently
producing high density, mixed technology, double sided boards, that
can provide process insights.

Lee McCuistion
Manufacturing Engineer
Cubix Corporation
2800 Lockheed Way
Carson City, NV  89706
702-888-1000 x237 (voice)
702-888-1002 (fax)
[log in to unmask] (e-mail)
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