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October 2007

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Subject:
From:
Graham Collins <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, [log in to unmask]
Date:
Tue, 30 Oct 2007 11:14:06 -0300
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As always, Doug is the man!

We use this philosophy.  We have an Ionograph (modified ROSE) that we
use for process monitoring - I know what reading I expect, if the result
is higher then expected - something has changed in our system.

When we purposefully change something (e.g. we changed solder paste
recently) we do ion chromatography testing to verify that we can
maintain or improve our cleaning - typically that means running some
control and some test samples, getting both batches IC tested and
comparing them.  The ionograph isn't good enough for this as it won't
tell you what flavors of contaminants are on the board.  If the residues
on control and test are pretty much the same then we should have a
reasonable expectation of similar results at the ionograph.  We also
ionograph some identical samples to check our ionograph baseline.  

We don't do IC testing in-house, we use an outside lab. So in terms of
costs, we have the ongoing costs of running an ionograph (purchase
price, plus periodic replacement of the filters), and occasionally we
pay someone to do ion chromatography testing for us.

 - Graham Collins

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Douglas O. Pauls
Sent: Tuesday, October 30, 2007 10:28 AM
To: [log in to unmask]
Subject: Re: [TN] cleaning concerns

Phil, since you already says "It Depends", I won't.
If you state a required level of cleanliness, you MUST also quote by
what method, which then generally tells you what equipment. 

If you said that the assembly must be less that 1.56 ug/cm2 NaCl
equivalence when measured by IPC-TM-650, method 2.3.25, then the
equipment is determined for you.  If you said that you had to have less
than 2.5
ug/cm2 of chloride when measured by method 2.3.28, that likewise gives
you 
the general equipment you need.    You might look at IPC-5701 which 
discusses the issue in more depth.

A simple but effective test?  Mutually exclusive terms in my view. 

About the simplest test I would recommend is the modified ROSE
procedure, using a temperature-compensated dip probe in place of an
ionic cleanliness tester.  And I would only use it for process control,
not product acceptance.  If you REALLY want to know if product is
acceptable going out your door, you need an IC system (IMNSHO).  It does
not have to have all the bells and whistles that the salesman will tell
you you absolutely MUST have, without breaking the bank.

Doug Pauls




Phil Nutting <[log in to unmask]> Sent by: TechNet
<[log in to unmask]>
10/29/2007 03:11 PM
Please respond to
TechNet E-Mail Forum <[log in to unmask]>; Please respond to Phil Nutting
<[log in to unmask]>


To
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Subject
Re: [TN] cleaning concerns






Dewey,

This dovetails into what I'm looking into.  So if I state a required
level of cleanliness, what equipment do I have to buy to prove it? 
I know "it depends" so it should be tailored to what is simple yet
effective.  Mercedes or BMW type equipment is out of range.  I'm
thinking something just above the diesel Chevette level. 

Phil

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Whittaker, Dewey
(EHCOE)
Sent: Monday, October 29, 2007 1:26 PM
To: [log in to unmask]
Subject: Re: [TN] cleaning concerns

That's a week answer. The real answer will cost me another royalty
donation to the Doug Paul's Defense Fund for Battered Chickens, but it
depends. The range of time could be from ASAP (a maximum one hour) to
eternity (meaning never). Some of the things to consider are as follows:

*         Laminate

*         Final surface finish

*         Solder Mask

*         Spacing

*         Component orientation

*         Assembly surface topography

*         Material compatibilities

*         Cleaning chemistries

*         Solvency capabilities

*         Flux chemistries

*         Cleaning process residuals and their chemical make-up

*         Thermal excursion exposures during processing

*         Cleanliness requirements

*         Conformal coating or not

*         Testing requirements

*         End use environment

*         Warranty issues

*         Cost

 

Dewey

 

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Linda Langley
Sent: Tuesday, October 23, 2007 11:40 AM
To: [log in to unmask]
Subject: [TN] cleaning concerns

 

 

Can anyone tell me or direct me to documentation that specify how long
flux residue from WS609 63/37 can be left on a board before washing?

 

I was informed that it could be left on for 7 days . 

 

Linda Langley 

Jabil Circuit 

Training Specialist 

(248) 292-6176 

 

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