Board Talk is presented by ITM Consulting
Phil Zarrow, ITM Consulting
With over 35 years experience in PCB assembly, Phil is one of the leading experts in SMT process failure analysis. He has vast experience in SMT equipment, materials and processes.
Jim Hall, ITM Consulting
A Lean Six-Sigma Master Blackbelt, Jim has a wealth of knowledge in soldering, thermal technology, equipment and process basics. He is a pioneer in the science of reflow.
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And welcome to Board Talk. This is Jim Hall and Phil Zarrow, the Assembly Brothers. We are here to discuss process issues, problems, situations and whatever might be plaguing your mind in the electronic assembly arena.
Let's take a look at this one, Jim. P.N. writes, we are located in India. We manufacture and assemble circuit boards used in watches. We are currently using a mix of trichloroethylene and IPA for cleaning in the ratio of 10 to 90. e are looking to eliminate the use of trichloroethylene and request your input.
Fortunately for you P.N. you have about 25 years of experience of the rest of the world getting rid of trichloroethylene and Freon solvent.
For those of us who are old, like Phil and I, we remember those days when we cleaned with chlorinated solvents and did a great job. he Montreal protocol in 1989 made them illegal to use. Virtually everyone has either gone no-clean or water-soluble.
There are a few legacy products, which may include you, which are still using the old RMA fluxes. If that is the case, you will either have to find an alternative solvent, one of these non-ozone depleting advanced hydro-carbons or other exotic solvents. Or go to an aqueous cleaner with a strong saponifier which will dissolve the natural resins in your RMA paste.
If you are using a more recent solder paste, if it is no-clean you obviously don't have to clean and if its not there are a variety of very friendly, engineered aqueous materials that you can use in combination with water to remove the flux residues.
Yeah, chances are if you are making a consumer product like watches you may have a great application for no-clean. Wow, man this is like back to the future. Fond memories of trichloroethylene and leaning over a vapor degreaser and ingesting the fumes. But anyway, we digress.
It is actually rare that we see anybody using trichloroethylene. Actually it is rare that there are countries out there allowing the use of trichloroethylene. What can I say P.N., welcome to the future.
Jim, anything you want to add to that?
As with cleaning, or the soldering that comes before it, don't do it like my brother.
Oh, and please don't solder like my brother.
Phil and Jim are probably not the best techies to answer this question as they have confused 1,1,1 trichloroethane with trichloroethylene (TCE). TCE has never been banned for its ozone depletion properties (there are none) and it is a solvent currently legal to use in the USA, Europe, and most of the world. TCE does have some issues with its cancer causing properties, so the exposure to the solvent must be controlled. |
Better yet, use one of the dozens of other safe, nonflammable, halogenated, solvent blends that are widely available. My favorite is an HFE / alcohol azeotrope with sky high polarity that cleans ionics, oils, etc. But for a lower priced product, check out stabilized n-propyl bromide and use it in a newish vapor degreaser to reduce solvent emissions and personnel exposure. Nothing like cleaning with hot solvent vapor to clean those type spaces in a watch.
Rick Perkins, ChemLogic
There are more sustainable solvent options for replacing TCE. Contrary to what is stated above, TCE was not regulated by the Montreal Protocol (TCE is not a significant ozone depleter, unlike its close cousin TCA, trichloroethane) and there are many companies still using this chemical. TCE is coming under scrutiny due more to its exposure guidelines and health effects. 3M, as well as other manufacturers, have new chemistry that have no ozone depletion potential (ODP), low global warming potential (GWP, a focus of the Kyoto Protocol) and much higher exposure guidelines to make them safer alternatives to TCE. These chemicals can be drop-in replacements for flux removal or other precision cleaning applications where vapor degreasing equipment is already in place.
Karl Manske, 3M Company