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September 2009

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Subject:
From:
Charlie Pitarys <[log in to unmask]>
Reply To:
TechNet E-Mail Forum <[log in to unmask]>, Charlie Pitarys <[log in to unmask]>
Date:
Mon, 21 Sep 2009 15:53:28 -0500
Content-Type:
text/plain
Parts/Attachments:
text/plain (198 lines)
Methylene chloride ships as a HAZ (more $$$ to transport) and extreme
measure should be employed when used. It will burn you on contact and likely
strip away all other surface coatings on components present. About as safe
as playing with bald-faced hornets.

Bottom line, the PCB's to be recovered need to have a high value in order to
be worth saving. 
To remove silicon CC with a "safe" solvent is a tough task to accomplish and
realistically a pipe dream. With 25 yrs in the biz I can say that with some
certainty
Probably cheaper in the long run to just throw them away.

I visited an automotive component recycle shop many years ago and they would
take the Delphi engine control modules into a spray booth and the guy in the
bunny suit would blast them with 3,000 psi wash water to physically remove
the silicone. I did not ask what "wash fluid" they were using.
Kyzen dabbled in alternative products for silicone conformal coat removal
years ago and the price for one raw material to formulate a finished good
cost more then we could realistically sell and sustain any finished product
for. HumiSeal may still have an offering or two available but check the Haz
menu and you best be sitting down before you ask for a price on 1-gallon.

Like a friend of mine used to say, "Were not baking cakes here"
  	
________________________________

	

-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Inge
Sent: Monday, September 21, 2009 3:16 PM
To: [log in to unmask]
Subject: Re: [TN] silicone conformal coat removal

This 'nPb'  sounds nasty. Methylene chloride isn't very healthy either, but 
I would use that. In fact, methylene chloride takes most CCs. If you can buy

it. As far as I know, some silicon based coatings don't lift for any 
chemicals.
/Inge


----- Original Message ----- 
From: "Stadem, Richard D." <[log in to unmask]>
To: <[log in to unmask]>
Sent: Monday, September 21, 2009 5:57 PM
Subject: Re: [TN] silicone conformal coat removal


> Thanks. Underscores my earlier posting; refer to the IPC recommendations 
> for conformal coat removal. Go by the industry standards. Avoid 
> "everybody's" ad hoc toilet cleaners, unsafe chemicals, untested methods, 
> etc.
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Brian Ellis
> Sent: Monday, September 21, 2009 10:48 AM
> To: [log in to unmask]
> Subject: Re: [TN] silicone conformal coat removal
>
> nPB is n-propyl bromide or 1-bromopropane, a substance that is
> ozone-depleting, but unfortunately unregulated under the Montreal
> Protocol. It is also a reproductive toxin, reducing sperm count and
> motility, and a neurotoxin, with anecdotal cases of severe effects. The
> US EPA have strict regulations how it can be used with recommended
> exposure values. OSHA have not officially pronounced on it. Various
> authorities have suggested exposure levels between 1 ppm and 100 ppm. My
> opinion is that a time-weighted value of 10 ppm may be OK with a ceiling
> short term exposure of 25 ppm. Every effort should be made to prevent
> evaporation into the atmosphere. Make sure that there is no skin
> contact, as it would seem that there may be considerable transdermal
> absorption and it is not known how such absorbed solvent is metabolised.
>
> Brian
>
> Stadem, Richard D. wrote:
>> What is nPb?
>>
>> -----Original Message-----
>> From: TechNet [mailto:[log in to unmask]] On Behalf Of Charlie Pitarys
>> Sent: Monday, September 21, 2009 9:47 AM
>> To: [log in to unmask]
>> Subject: Re: [TN] silicone conformal coat removal
>>
>> Guy, a cold soak in nPb will work. Trade offs are with the thickness of
>> the
>> coating and it still may require some manual work or you could luck out
>> and
>> it may swell and completely lift off the substrate.
>> Then of course you have the disposal issues.
>> Positives, It is relatively cheap and may suffice in this recovery
>> process
>> and at room temp should fare well on many components compatibility.
>>
>> ________________________________
>>
>>
>> -----Original Message-----
>> From: TechNet [mailto:[log in to unmask]] On Behalf Of Guy Ramsey
>> Sent: Monday, September 21, 2009 8:52 AM
>> To: [log in to unmask]
>> Subject: [TN] silicone conformal coat removal
>>
>> Is there a solvent that will help remove silicone coatings?
>>
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