Difference between denatured ethanol and Isopropyl to clean IC Rosin Residue? - Page 1
Forum section: electronics / repair

author: martys
author_rank: Regular Contributor
timestamp: March 30, 2018, 01:20:15 pm
content: I have salvaged some ic's using Ersin Rosin core solder but now the residue completely obscures the parts number on the unsoldered ICs. I tried mixing denatured ethanol or methanol with acetone but still can't see the part number etched on the ic's (They were clearly visible before desoldering) .Does isopropyl alcohol work much better?

author: Fsck
author_rank: Super Contributor
timestamp: March 30, 2018, 01:25:37 pm
content: did you use mechanical action to clean? flux is pretty sticky and often times you need to scrub it to fully dissolve.shouldn't be a huge difference between ethanol and isopropanol. I've never used methanol or acetone myself for cleaning flux.

author: martys
author_rank: Regular Contributor
timestamp: March 30, 2018, 01:28:00 pm
content: Thanks, but I have scrubbed hard with the solvents mentioned using Q-tips.

author: Ian.M
author_rank: Super Contributor
timestamp: March 30, 2018, 02:06:23 pm
content: If they were old-style paint/ink marked ICs, your agressive solvent mixture has probably totally stripped the markings.Assuming modern ICs, you've probably scrubbed the brown burnt epoxy residue out of the microscopic pits left by the laser marking, so reducing the contrast till the markings are virtually invisible. If so, try applying a dot from a light coloured or metallic paint marker and smearing it over the top of the IC with your fingertip, then wiping off the excess with cartridge paper moistened with WD40. Done with care, some paint residue will remain in the microscopic pits and improve the contrast.

author: martys
author_rank: Regular Contributor
timestamp: March 30, 2018, 04:01:12 pm
content: Thanks, Ian.M, they are modern ICs.Unfortunately, I've had my metal pain marker taken away from me. (I still have a few pleasure markers left.)What in the world is cartridge paper? Is it something to make your own bullets?

author: SeanB
author_rank: Super Contributor
timestamp: March 30, 2018, 04:47:26 pm
content: Cartridge paper is simply the slightly thicker paper towel like you get in a large roll at the garage, used to wipe down things there. More robust than the good old single ply toilet paper that is typically used for this.

author: Ian.M
author_rank: Super Contributor
timestamp: March 30, 2018, 05:24:57 pm
content: Not quite. Cartridge paper is basically thick good quality art paper. It has a slightly rough surface, and is generally free from surface coatings and sizings.Cut up a strong envelope and use a slip of paper from that without creasing or folding it. You specifically want something much stiffer and harder than tissue or paper towel, without loose surface fibres, so it doesn't dig into the paint in the laser marking pits so much, but with enough surface texture that it readily picks up the paint off the flat surface of the rest of the top of the chip.I tested the procedure I described with a PIC16F88-I/P that had been sitting in a breadboard for a long time and had very indistinct markings, and a genuine Sharpie Silver Metallic Fine Point Permanent Marker. The PIC now has clearer markings than when it was factory fresh.

author: martys
author_rank: Regular Contributor
timestamp: March 31, 2018, 12:12:25 am
content: Thanks again Ian.M,I will certainly try that metallic marker idea. Unfortunately, because of the holidays, there isn't a slightest chance to find a store open to buy one until tomorrow.

author: igendel
author_rank: Frequent Contributor
timestamp: March 31, 2018, 12:28:25 am
content: Quote from: martys on March 30, 2018, 04:01:12 pmWell, I had to check, and according to Wikipedia this is indeed what the original Cartridge paper was used for!https://en.wikipedia.org/wiki/Paper_cartridge

author: daedalux
author_rank: Contributor
timestamp: March 31, 2018, 02:36:39 pm
content: Ethanol is cheap and will work most times, it's not such a strong solvent. Suitable for non critical work.Acetone will disolve lots of plastics and masks. Don't use it ever. If you are at it the circuit will have more chances of surviving with soap and water. You have the same problem with zero residue contact cleaner that is usually quite strong too.Isopropanol is usually considered the good stuff and what is in any single user wipes used for electrical purposes. You can get a very pure one that is usually the cleanest cleaning solvent available. It's very volatile and smelly.

author: I_Code_4_Hugs
author_rank: Newbie
timestamp: April 01, 2018, 03:35:20 pm
content: FWIW, the MG Chemicals 4140 flux remover is a mix of 94% ethanol, 5% isopropanol, and 1.5% ethyl actetate:https://www.mgchemicals.com/downloads/msds/01%20English%20Can-USA%20SDS/sds-4140-l.pdfThe "heavy duty" 413b version is 63% ethyl acetate, 25% acetone, and 12% isopropanol:https://www.mgchemicals.com/downloads/msds/01%20English%20Can-USA%20SDS/sds-413b-l.pdf