Someone with less scruples or sophistication than me might infer you are
using smear tactics to get new business.
Dewey

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Werner Engelmaier /*
Sent: Thursday, August 07, 2008 11:26 AM
To: [log in to unmask]
Subject: Re: [TN] Smear and rework failure

Hi Pradeep,
NO, smear will not form uniformly.
YES, smear will affect the quality and reliability of the PCBs at every
stage 
of subsequent work and operational use.
THEREFORE, effective desmear is a must. 
HOWEVER, that does not mean that you need a lot of positive etchback,
because 
that too degrades quality and reliability. 

You need to be aware that desmearing Pb-free soldering compatible PCB
base 
materials, typically phenolic cured, do not respond to smear removal
like the 
traditional FR-4 PCBs.

All of this, and of course much more, is detailed in my White Paper 
"Recommendations for PCB FAB Notes and Specifications in Printed Circuit
Board Drawings 
for SnPb and Lead-Free Soldering Assemblies, the Qualification of PCB
Shops 
and Activities to Assure Continued Quality."



Werner
Future workshops:
Reliability Issues with Lead-Free Soldering Processes, September 22, 
Schaumburg
Failure Mode and Root Cause Analyses Reliability (Fatigue, Brittle
Fracture, 
ENIG), September 22, Schaumburg
Solder Joint Reliability: Parts 1 & 4, Oct. 9, Moscow, Russia
Solder Joint Reliability: Part 4, Oct. 17, Timisoara, Rumania
Solder Joint Reliability: Parts 1 & 4, Oct. 22, Tallinn, Estonia



**************
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