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July 1997

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Thu, 17 Jul 1997 00:18:59 -0400 (EDT)
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Just a note to confirm that the use of SERA to quantitatively measure CuO
and Cu2O on inner layer cores prior to lamination works. We are in the final
stages of determining the actual levels of total reducable oxides as a
control limit for our oxide lines. Upon completion, we will establish
product and process limits in order to assure wedge-void free product.


Dave Rooke
Circo Craft - Pointe Claire
a division of ViaSystems

= = = = = = = = = = 

>     Hi TechNet -
>     
>     There is a tool available that can very accurately measure both the 
>     type and the quantity of copper oxide present on a surface in a 
>     nondestructive manner - Sequential Electrochemical Reduction Analysis 
>     (SERA). The ANSIJ-STD-003 PWB solderability committee recently 
>     completed a gauge R&R study on several SERA equipments and is in the 
>     process of submitting the test method for inclusion in the IPC-TM-650 
>     specification. Although the 003 committee's focus is on solderability, 
>     the SERA test method can also evaluate copper surface oxides. Contact 
>     the folks at ECI Technologies (201-773-8686) for more information. Use 
>     of this method could be used to eliminate the subjectiveness or as a 
>     supplement to copper oxide identification by visual appearance.
>     
>     
>     
>     Dave Hillman
>     Rockwell Collins
>     [log in to unmask]
>
>
>______________________________ Reply Separator
_________________________________
>Subject: Part II: Mechanism of Wedge Void Formation
>Author:  [log in to unmask] at ccmgw1
>Date:    7/15/97 5:14 PM
>
>
>Rudy Sedlak mentions that a reduction in oxide thickness from black to 
>brown to red in color assists in deterring wedge voids.
>     
>This trend could lead to a cosmetic difficulty.  Am I correct?
>     
>Matt Byrne states that reduced oxide helps:  Here I take this to be 
>reduction from cupric to cuprous ions which Rudy Sedlak confirms.
>     
>Richard Fudalewski states that reduced oxide brings in a problem of its 
>own, but I am uncertain which definition that Sedlak mentioned he is 
>referring.
>     
>****
>     
>New question:  At what minimal thickness does one entertain cupric ion 
>post oxide reduction with DMAB?  What are the trade offs cosmetically 
>versus functionality (w.r.t. wv's)?
>     
>Again thanks,
>Josep
>     
>P.S.  In direct answer to Byrne's question of reduction problem,  we see 
>wv problems intermittently.  The goal is to strive for a cosmetic black 
>coating.  Thickness entering DMAB is typically 0.28mg/cm2 (black not 
>brown before immersion).  Acid resistance (10% HCl) is greater than 2 
>hours.  
>     
>These wv issues are not related to layer counts.  I cannot as yet pin 
>the mechanism down but have not ruled out materials such as prepreg.
>     
>I'd like to understand more about the contact mechanism of prepreg 
>during lamination, whether other's verify Tg of lots, and if this has 
>ever been an issue in wv troubleshooting.
>     
>[log in to unmask]
>     
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