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October 2007

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Subject:
From:
Phil Nutting <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Phil Nutting <[log in to unmask]>
Date:
Thu, 4 Oct 2007 12:47:39 -0400
Content-Type:
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Brian,

Thanks for the round-about "it depends".

Your comments match what I was thinking.  I had forgotten about the
no-clean + cleaning being a possible issue.

Phil 

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Brian Ellis
Sent: Thursday, October 04, 2007 12:10 PM
To: [log in to unmask]
Subject: Re: [TN] operational sweet spot for no-clean flux

How long is a piece of string?

I certainly would not choose "no-clean" where the voltage gradient would

exceed about 50 V/mm where hi-rel is needed. Nor would I choose it if I 
were to clean it afterwards. I may choose it if the end product is 
consumer, with no specific reliability criteria, no high voltages, no 
bad climate exposure etc. Each job would have to be judged on its own 
merits.

Remember "no-clean" + cleaning is sometimes worse than either straight 
"no-clean" or cleanable flux + cleaning.

Brian

Phil Nutting wrote:
> Hello Techsperts,
> 
> Is there a range in which no-clean is best NOT used?  For example,
very
> low current circuits or high voltages greater than 110 up to 25 kV?
Our
> primary problem seems to be with SMT boards and from more than one
> vendor. 
> 
> I know a lot of companies use no-clean, but for those who insist on
> washing boards even those with no-clean flux, what is the reasoning?
> Simply esthetics or an actual circuit related requirement?
> 
> I'm trying to determine if all our boards must be washed or if there
are
> any that would be a don't care. 
> 
> Thanks in advance,
> 
> Phil
> 
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