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February 2009

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Subject:
From:
"David D. Hillman" <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, [log in to unmask]
Date:
Fri, 6 Feb 2009 07:38:31 -0600
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Hi Mike, Brian and gang!  I'll go chase down Brian's InterNepcon '69 paper 
and the book chapter segment. Our Rockwell Collin's Technical Reference 
database is pretty extensive but I was striking out on this one. I haven't 
heard back from ITRI yet and was getting impatient so I thought I would 
ask TechNet for help. The reason I am chasing that reference is that I 
have finally gotten feed up with addressing the issue of well intended but 
misguided internal/external customers using "Pearl Pink" erasers as a 
surface finish oxide/discoloration removal protocol. The pink erasers come 
from multiple sources, have uncharacterized chemical compositions and 
leave contamination on the printed board surfaces that have been 
"cleaned". My co-op students and I have completed a small investigation 
demonstrating the issues using SEM and FTIR results on a variety of 
printed wiring board surface finishes and now I am just pulling together 
the external data sets on the topic that other investigators have 
published. Oddly, it seems to be a topic that everyone fully understood in 
the late '60s but has been erased (what a pun!) from the industry tribal 
knowledge pool. The pumice and ScotchBrite information has been captured 
in the external data sets as well so I am going to include that 
information in the our paper. Probably something that I'll publish at one 
of the IPC or SMTA conferences.  Looks like I'll be giving the TechNet an 
acknowledgement for everyone's most valuable assistance! Thanks to 
everyone for their assistance - TechNet is such a great tool!

Dave



Mike Fenner <[log in to unmask]> 
Sent by: TechNet <[log in to unmask]>
02/06/2009 06:04 AM
Please respond to
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To
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Subject
Re: [TN] In Search of a Technical Reference






I remember Colin Thwaites's paper very well and Brian's, was grateful for
them, but no longer have copies. 
I would be surprised if the ITRI people don't find a copy. I asked them 
for
an actual reference to some information of the industry legend type -
meaning everyone knows it but not why or how they know it - and they found
first references in early 1940s. 

Regards
 
 
Mike
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Brian Ellis
Sent: Friday, February 06, 2009 7:30 AM
To: [log in to unmask]
Subject: Re: [TN] In Search of a Technical Reference

Dave

I hadn't realised that Colin Thwaites had published such a paper. I
believe that his research of the subject may have been instigated by
myself, following publication of the paper I presented at Inter/Nepcon
'69, in Brighton, England, 'New Aspects on the Solderability of Printed
Circuits'. Unfortunately, I no longer have a copy of the Technical
Proceedings but, as I remember it (40 years is a long time ago!!!), I
evoked the problems caused by both pumice and ScotchBrite cleaning,
whereby the abrasive particles were embedded into the copper pore
structure and then the copper was swaged over them. The only way they
could be released was with a light persulfate etch and forceful rinse,
without which dewetting was inevitable after abrasive cleaning.

Having written this, I then re-read what I wrote in Section 7.2.4 (p.
76) of my book and found that it's similar in essence but more complete,
so my aged memory can't be that bad! Whatever, abrasives and
solderability make poor bedmates!

Hope this helps.

Brian

David D. Hillman wrote:
> Hi gang! Ok, I am in search of a technical reference and my usual, 
"always

> works" sources have failed me. I am looking for the following technical 
> reference:
> 
> Thwaites, C. J. and Mackay, C. A. , " Some Effects of Abrasive Cleaning 
on

> the Solderability of Printed Circuits", Metal Finishing Journal, Sept. 
> 1968, pp. 291-294, (also may be listed as ITRI Publication 386)
> 
> 
> Anyone have a copy or can direct me to where a copy can be obtained? And 

> yes, I have sent a request to the ITRI folks already (International Tin 
> Research Institute)
> 
> Dave Hillman
> Rockwell Collins
> [log in to unmask]
> 
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