Hello Phil,
Most flux residues (liquid and solder paste) are soluble in alcohols. This includes methanol, ethanol, isopropanol, etc. As flux residues are heated they become more difficult to clean. Longer and higher temperature reflow profiles make cleaning more difficult. Some fluxes also contain ingredients that are not truly soluble in alcohols, but are able to be washed off by alcohols. In this case, the alcohol will lift off the residue, but it might redeposit on other areas of the circuit board.
The evaporation rate of the alcohol is also a concern. As the alcohol molecular weight decreases (IPA > Ethanol > Methanol) the evaporation rate increases. Methanol evaporates faster than IPA. As the alcohol evaporates, the dissolved flux residues will redeposit on the circuit board. IPA is commonly used due to it’s relatively low evaporation rate, ability to dissolve flux residues, and it's safety concerns.
The trick is to wash the residues off fast enough to prevent re-deposition, and to follow with a rinse of clean alcohol to ensure that there are no residues left when the board dries. This can be done with liquid alcohol along with some type of wipes or Q-tips as Patrick stated.
I know that Kyzen, Zestron, and others have done a lot of work to formulate cleaners for just about every type of residue. You might want to ask your local cleaning chemical rep for some suggestions if you are open to using a proprietary cleaner.
Best regards,
Tony Lentz
FCT Assembly
Field Application
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970-566-0360 Mobile
-----Original Message-----
From: TechNet [mailto:[log in to unmask]] On Behalf Of Nutting, Phil
Sent: Friday, April 24, 2015 10:31 AM
To: [log in to unmask]
Subject: Re: [TN] methanol for cleaning
Ok, so if I am spot washing flux off a circuit board or cleaning the face of an epoxy insulator to remove silicone dielectric grease what am I supposed to use?
Brian, I know you are very environmentally concerned. IPA and the like have been used for years by our industry and it is usually the default cleaner for everything. And yes I know alcohols do a better job of spreading contaminates than removing them. What then, if spot cleaning, should be used? (I know, "it depends".) Manufacturing is always complaining that Engineering creates designs and processes that take too much time, but they work if done as designed. Finding a practical solution and changing the mindset is no small task.
I look forward to your sage wisdom.
Phil
-----Original Message-----
From: Brian Ellis [mailto:[log in to unmask]]
Sent: Friday, April 24, 2015 12:18 PM
To: TechNet E-Mail Forum; Nutting, Phil
Subject: Re: [TN] methanol for cleaning
Yes! absolutely! And it is highly toxic, to boot, with ingress to the body by all means, including cutaneous. IMHO, avoid it!
Brian
On 24/04/2015 18:12, Nutting, Phil wrote:
> We have had many posts regarding the ability of alcohol to evenly distribute flux and other contaminates over the surface of the board or part. Does methanol do that same thing?
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