It's actually the prose and cons of our can-do attitude.
Dewey
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Bev Christian
Sent: Thursday, May 22, 2008 6:00 AM
To: [log in to unmask]
Subject: [TN] NTC RE: [TN] Are these substances OK for use in electronics
Eric,
That's almost a poem!
Bev
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Eric CHRISTISON
Sent: Thursday, May 22, 2008 8:58 AM
To: [log in to unmask]
Subject: Re: [TN] Are these substances OK for use in electronics
Hmmmm,
So some will enlarge the hole in the ozone layer and thus give us skin
caner.
Some will poison us if burnt.
Some will cause global warming.
Some will do all three.
Tricky.
Bev Christian wrote:
> Guy,
> No it is not, though not quite correct. The newer fluorine compounds are bad from a global warming perspective because they do not break down quickly enough. However, as Brian points out, if they break down quickly pyrolytically without good ventilation, you are in some serious trouble.
>
> The suppliers keep pointing out that their new solvents are CFC free and ozone friendly. They do not point out the global warming potentials that Brian I and keep harping on (him more eloquently of course :) ).
>
> I learned something today about the status of trans-DCE, which I did not know. Thank you, Brian.
> Bev
> RIM
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Guy Ramsey
> Sent: Thursday, May 22, 2008 7:56 AM
> To: [log in to unmask]
> Subject: Re: [TN] Are these substances OK for use in electronics
>
> I am seeing a reoccurring theme here.
>
> HFC, HCFC, HFE manufacturers are making claims about their solvents, out of
> the can. But, over time these chemicals breakdown. As they break the
> attributes of the resulting chemicals are not desirable.
>
> The makers of these chemicals don't tell us about that part of the product
> life cycle. We need to get that information elsewhere.
>
> Is this to much of a simplification?
>
> -----Original Message-----
> From: TechNet [mailto:[log in to unmask]] On Behalf Of Brian Ellis
> Sent: Thursday, May 22, 2008 7:46 AM
> To: [log in to unmask]
> Subject: Re: [TN] Are these substances OK for use in electronics
>
> OK, the HFCs are severe greenhouse gases, with GWPs of 300-1500 (CO2=1) and
> are controlled substances under the Kyoto Protocol. They are not aggressive
> cleaning solvents and, by themselves, are not good flux removers. They are
> almost non-toxic. They should not be used near soldering equipment as
> pyrolytic decomposition may occur at >200°C and the resultant by-products
> are VERY toxic (carbonyl fluoride and hydrogen fluoride).
>
> The trans-DCE is quite similar to trichloroethylene and is fairly toxic:
> it is added to make the mix a better solvent for oils and greases. This was
> used in preference to other chlorocarbon solvents because it is the only one
> for which OSHA do not have an official PEL, as epidemiological studies on
> its toxicity have not been conducted: it is therefore in that legal limbo
> where manufacturers can suggest their own exposure limits which may or may
> not be safe. Because it is a lot cheaper than HFCs, it tends to pull the
> price of the blend down. It is hardly ozone-depleting and is not a
> controlled substance. It attacks many plastics.
>
> The methanol is added to widen the dissolution spectrum and to improve the
> dissolution of rosin and some organic ionic materials. It is highly toxic
> and damages the central nervous system and the damage is cumulative. It is
> very easily absorbed through the skin, as well as by respiration (hopefully
> not to be ingested!). Of course it is flammable.
>
> The nitromethane is a stabiliser to prevent the trans-DCE from hydrolysing
> into hydrochloric acid. Normally, it would be present in very small
> quantities. It is violently flammable and toxic, but this is not your worry.
>
> The use of spray cans to achieve good cleaning is very difficult.
> Normally, you will have to hold the board at about 45° from the horizontal
> (coincidentally, about 45° to the vertical, as well!!!!) and spray the area
> to be cleaned very liberally, until the liquid well and truly starts to
> stream off the edge of the board. Pause a few tens of seconds and repeat n
> times (n >5), until the desired level of cleanliness is achieved. Never
> allow the solvent to dry on the board, as this will just spread the residues
> where they will cause more harm than if you had not tried to clean in the
> first place. Spray cans, used properly, are an expensive cleaning method.
>
> Brian
>
> Ioan Tempea wrote:
>
>> Dear Technos,
>>
>>
>>
>> I've got one for the chemists: a customer of ours requests us to clean
>> their boards with 2 spray canned products. Here's the stuff that's
>> inside of them:
>>
>> 1,1,1,2,3,4,4,5,5,5-Decafluoropentane
>>
>> Trans,1,2-Dichloroethylene
>>
>> Methanol
>>
>> Nitromethane
>>
>> 1,1,1,2-Tetrafluoroethane
>>
>>
>>
>> Are they safe for the product? What about the production personnel and
>> the environment?
>>
>>
>>
>> Thanks,
>>
>>
>>
>> Ioan
>>
>>
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--
Eric Christison Msc
Mechanical Engineer
Consumer & Micro group
Imaging Division
STMicroelectronics (R&D) Ltd
33 Pinkhill
Edinburgh EH12 7BF
United Kingdom
Tel: +44 (0)131 336 6165
Fax: + 44 (0)131 336 6001
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