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October 2011

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Subject:
From:
Gerald Bogert <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, [log in to unmask]
Date:
Wed, 12 Oct 2011 08:43:42 -0400
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October 12, 2011

You may be able to argue that the use of ORH1 flux violates J-STD-001E,
paragraph 3.3 unless the supplier can provide the data demonstrating
compatibility, regardless of whether or not flux residue is or is not
present.

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Douglas Pauls
Sent: Wednesday, October 12, 2011 8:29 AM
To: [log in to unmask]
Subject: Re: [TN] ORH1 flux residues

Phil,
It depends.  You knew it was coming.

It would be very hard to argue that you don't meet J-STD-001.  I doubt
you would have enough of the ORH1 residues present to make you fail the
ROSE requirement.  And since you probably can't see the flux residue
during inspection, you don't violate the visible flux requirements.  If
I were an auditor, trying to reject an assembly based on residues I
thought MIGHT be there, but which I could not see and which I could not
prove, I would be justifiably laughed out of the building.

But if I were in your shoes, assuming your shoes are size 10D, I would
be more concerned about the potential impact of the residues on the
reliability of my product.  I would certainly want to investigate it to 
see if there was a problem or not.   You might take 1-2 assemblies and 
subject them to 85/85 for a week. Then take the parts off.  Do you see
any corrosion taking place?  If so, then you have a problem that will
manifest in the field and some remedial cleaning measures, possibly with
ultrasonics to get into those tight areas, to address the residues.

Doug Pauls



Phil Bavaro <[log in to unmask]> Sent by: TechNet
<[log in to unmask]>
10/11/2011 06:54 PM
Please respond to
TechNet E-Mail Forum <[log in to unmask]>; Please respond to
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To
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Subject
Re: [TN] ORH1 flux residues






Update:  Thanks to all who have chimed in.  Obviously this is not a good
problem to have.
We did change the process to only use RMA core solder (no external flux)
as soon as we found the problem.
The question at hand now is this:

Does having ANY flux residue trapped beneath the component violate the
J-STD-001 and/or J-STD-001DS?
IMO, the answer is yes as paragraph 8.0 states that all flux residues
shall be cleaned but then I am old (school).
I don't consider this to be encapsulated (8.1) but my management is
interested to see how the Technet community feels.
I think they are trying to weigh the acceptance of the condition where
we have trapped RMA (ROL0) under other flush mounted hand soldered
parts.  Our mechanical engineering department has a long history of
mounting parts flush with thermal pads beneath the parts (TO3, TO5,
etc).

-----Original Message-----
From: [log in to unmask]
[mailto:[log in to unmask]] 
Sent: Tuesday, October 11, 2011 11:16 AM
To: [log in to unmask]; Bavaro, Phillip @ MWG - TW
Subject: RE: [TN] ORH1 flux residues

October 11, 2011

As others have stated, any ORH1 flux is bad news unless in a perfect
world it is completely removed by the post soldering cleaning process
but as folks know we do not live in a perfect world.  Also, the go
forward fix to just make larger access holes in the gasket may not
prevent flux residue from traveling under the gasket. 

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Phil Bavaro
Sent: Monday, October 10, 2011 7:49 PM
To: [log in to unmask]
Subject: [TN] ORH1 flux residues

I have a PWA with a gasket beneath a large thru hole power device. 
The gasket has holes punched in it for each of the pins. 
The device is hand soldered flush to the PWB. 
The operator uses external liquid flux along with core solder with flux
in it. 
The assembly is later washed and it passes ionics testing. 

The problem is that this gasket effectively seals the top side solder
connections from the cleaning process. 


My question is this:

How much should I be worrying about the existing hardware which has flux
residues sealed under the power device?
The assembly is stored with the power off.
The flux used is water soluble and classified as ORH1.
For future builds we are modifying the gasket so that the topside
connections can be cleaned (cutout "u" shape intead of round holes).








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