[Ellen]

I bought a bottle of Techspray 99% pure isopropyl alcohol to use to clean up circuit boards after soldering. However, I notice that it leaves this yucky white film on the boards, my fingers, everything. Is this normal?

 

[JMT]

Unfortunately, yes. I usually dry off the excess before it has a chance to dry completely.

 

[Gariver]

Hi Ellen:

One of the reasons I like to use Cardas Quad Eutectic Solder is this: It solders clean! That is, it does not leave flux residues to clean up. Oh, I still use 99% Isopropyl Alcohol to clean up, but my Q-Tips hardly get dirty.

The "quad" refers to 4 metals: Tin, Lead, Silver and Copper.

Michael Percy sells Cardas Quad Eutectic Solder...
--1/2 lb = $22.00
--1/4 lb = $11.00

http://www.percyaudio.com

If you feel the Cardas solder is too expensive, you can use Kester No-Clean solder in an eutectic mix of 63SN/37PB. You can buy this over at Mouser. The No-Clean refers to the fact that this solder does not leave behind flux residues to clean up. In this respect, this Kester solder and the Cardas solder are very, very similar. Cardas does beat the Kester in conductivity. In this dept, Cardas solder is the best I have tried.

http://www.mouser.com

Cold Solder Joints....
With 60SN/40PB solder, it is easy to get cold solder joints (joints that do not work). Why? This solder has a 15 degree pasty state. So any tiny movement will give you poor joints. On the other hand, eutectic solders do NOT have a pasty state. They go from liquid to solid instantly, reducing the likelyhood of bad solder joints. Thus, I highly recommend that newbies use eutectic solders (63SN/37PB).

Oh, least I forget: Try to make a good mechanical connection before you solder. I use 4" miniature needle point Xcelite pliers to press the parts together for good contact. Then I solder the joint.

Hmm...lots of info. Well, I do type very fast!

Buena Suerte!

 

[morsel]

Try 99% isopropyl alcohol from a drug store. I am guessing it will be purer, and probably cheaper too.

 

[tangent]

I don't get residue, but I've heard that alcohol will combine with certain rosins to produce a residue. This is different from the water impurities in lesser grades of alcohol.

Something you might try before you give up on that alcohol/rosin combo is to scrub the board with a toothbrush loaded up with alcohol until the board is fully wet and all the goo is suspended in the alcohol. Then take a can of compressed "air" and blow the sullied alcohol off the board. It may be that the alcohol is just evaporating and leaving behind altered rosin compounds. If you blow it off, the alcohol carries the rosin with it.

 

[timoteus]

Quote:

Originally posted by Ellen I bought a bottle of Techspray 99% pure isopropyl alcohol to use to clean up circuit boards after soldering. However, I notice that it leaves this yucky white film on the boards, my fingers, everything. Is this normal?

All alcohols will leave a slight film or residue. The one exception is denatured alcohol which will evaporate 100% and leave nothing behind. This is the only alcohol that I trust to clean tape heads.

 

[morsel]

On the contrary, denatured alchohol is ethyl alcohol with additives to make it unpotable. This usually means impurities that leave a residue.

 

[timoteus]

That has not been my experience. I have used denatured alcohol since the '70s because that is what was recommended by studio techs to clean tape heads if you don't want to spend the money on a professional cleaner. I also use about 2 gallons a year to clean aluminum molds. Cotton will absorb all the surface gunk and the alcohol evaporates and doesn't even leave any streaking behind.

I believe denatured means that anything other than alcohol has been removed. There should not be any additives. Just like denatured water means that the minerals have been removed leaving nothing but pure H2O.

 

[morsel]

http://www.m-w.com/cgi-bin/netdict?v...ook=Dictionary

Main Entry: de·na·ture
Pronunciation: (")dE-'nA-ch&r
Function: verb
Inflected Form(s): de·na·tured; de·na·tur·ing /-'nA-ch(&-)ri[ng]/
Date: 1685
transitive senses
1 : DEHUMANIZE
2 : to deprive of natural qualities : change the nature of: as a : to make (alcohol) unfit for drinking (as by adding an obnoxious substance) without impairing usefulness for other purposes b : to modify the molecular structure of (as a protein or DNA) especially by heat, acid, alkali, or ultraviolet radiation so as to destroy or diminish some of the original properties and especially the specific biological activity
intransitive senses : to become denatured

 

[Gariver]

Kester's "245" No-Clean solder leaves very little flux residue behind. The residues of "245" are designed to be left on the board with no post soldering cleaning.

Here's the easy way to try some...

Kester No-Clean Pocket Pak = $1.30
Kester "245" NCF in 63Sn/37Pb
Diameter = 0.020"
Mouser part# = 533-82-5000-0046

http://www.mouser.com

 

[timoteus]

Quote:

Originally posted by morsel On the contrary, denatured alchohol is ethyl alcohol with additives to make it unpotable. This usually means impurities that leave a residue.

The additive is methyl alcohol which makes it poisonous. That's what makes it unpotable and also allows you to buy it without having to pay liquor taxes.

Anyways, I'm just saying that in my experience denatured alcohol evaporates clean. I also know what Ellen means by the white residue left behind when using Techspray. I had the same problem when I used Caigkleen (sp).

 

[Ellen]

Thanks for all of the tips! You folks have given me a lot of options to try. I appreciate the advice.

 

[ck42]

Looks like I got in kinda late on this topic but I'll comment anyway.

Ellen, if the flux used on the pcb was of the 'no-clean' alchohol based variety, using IPA will leave what appears to be a white residue that is VERY hard to remove in some cases.

If it's a rosin based or OA, the IPA should work ok.....but it really depends on several factors, some of which have NOTHING to do with the type of flux used on the pcb.

No-clean flux doesn't mean that it leaves NO flux residue...it just means that whatever left behind is non-active (not corrosive). Many rosin based fluxes are ok to leave on as well...but not all of them.

The remaining types of fluxes require washing with either water or detergent mixes since the residues are corrosive.

bottom line....the white residue you're seeing is GOING to happen if you try to clean boards using IPA when an alcohol based no-clean flux was used.

If you really want to clean the board, there ARE cleaners in a can that are forumlated specifically for this type application.

 

[Budgie]

Alcohol will leave a film, but also will cause bad breath.

 

[tangent]

Quote:

Alcohol will leave a film, but also will cause bad breath.

The haze isn't really there, Budgie. You have to STOP DRINKING IT if you want the haze to go away.