How Cleaning Really Works, Part 1
By Controlled Environments
Created 2010-05-27 21:42
When I teach cleaning science, I try to decompose that amalgam into components so I can reduce the complexity. I have developed four “laws” which let me communicate the basics of cleaning without using chemical structures or mathematical formulas. Two will be covered this month, and two in the next C4 column.
KESEY’S LAW OF CLEANING
The most important law is often attributed (falsely I believe) to the novelist Ken Kesey, author of One Flew Over the Cuckoo’s Nest. It is also attributed to someone named Imbesi (and called their “Law of Fifth”). And it’s simple:
Whenever something becomes clean, something else becomes dirty.
We don’t clean the particles from semiconductor surfaces. We don’t clean the pyrogens from medical implants. We just move (hopefully) the particles and the pyrogens from where they are to where we want them to be. The particles are suspended in a moving stream of fluid, which can infect another surface. The pyrogens are bound by intermolecular force to a detergent soluble in water, which can also infect another surface.
It’s the aqueous detergent or organic solvent which gets dirty–when our parts become clean(er).
Success in cleaning is really two things: first moving the soil from the base surface, and second, moving it from the place we put it (the cleaning agent) to the place we want it (usually some recovery process).
So, cleaning processes often fail when they produce clean parts for a while, but don’t get the soil out of the cleaning machine–so later-cleaned parts aren’t fully so.
CLEANING ISN’T ATOMIC SCIENCE
The second law of surface cleaning is a modification of the first:
Soil is like entropy–never destroyed, always created.
A perfectly designed cleaning machine doesn’t destroy soil. It doesn’t convert it to CO2 and water. It doesn’t convert it to protons, neutrons, and electrons. It doesn’t convert it to energy. It just moves it from one place to another.
This second law is important to you, as:
That’s half of the “basic principles” of cleaning at the critical, or any, level of soil removal. The remaining two will be covered in the next C4 column.
KESEY’S LAW OF CLEANING
The most important law is often attributed (falsely I believe) to the novelist Ken Kesey, author of One Flew Over the Cuckoo’s Nest. It is also attributed to someone named Imbesi (and called their “Law of Fifth”). And it’s simple:
Whenever something becomes clean, something else becomes dirty.
We don’t clean the particles from semiconductor surfaces. We don’t clean the pyrogens from medical implants. We just move (hopefully) the particles and the pyrogens from where they are to where we want them to be. The particles are suspended in a moving stream of fluid, which can infect another surface. The pyrogens are bound by intermolecular force to a detergent soluble in water, which can also infect another surface.
It’s the aqueous detergent or organic solvent which gets dirty–when our parts become clean(er).
Success in cleaning is really two things: first moving the soil from the base surface, and second, moving it from the place we put it (the cleaning agent) to the place we want it (usually some recovery process).
So, cleaning processes often fail when they produce clean parts for a while, but don’t get the soil out of the cleaning machine–so later-cleaned parts aren’t fully so.
CLEANING ISN’T ATOMIC SCIENCE
The second law of surface cleaning is a modification of the first:
Soil is like entropy–never destroyed, always created.
A perfectly designed cleaning machine doesn’t destroy soil. It doesn’t convert it to CO2 and water. It doesn’t convert it to protons, neutrons, and electrons. It doesn’t convert it to energy. It just moves it from one place to another.
This second law is important to you, as:
- The more solder you apply to a junction, the more flux residue will need to be cleaned, and your bill for materials will be higher.
- Since soil isn’t destroyed in the cleaning bath, when you mix rinse fluid with cleaning agent, you’re just recycling dirt–albeit at a low concentration.
- Poorly designed cleaning machines drain the dirty cleaning agent into the rinse tank. Since the soil wasn’t converted to energy or atoms, Kesey’s Law applies. You’re just reapplying it in a diluted form to the parts.
- The Resource Conservation and Recovery ACT (RCRA) states that if you put the soil on the parts, you own the soil. If you outsource your cleaning work to a contract cleaner, the soil they remove is yours–forever. So when you sign a contract for outside cleaning service, make sure ownership of that liability is transferred (with your money) to the service provider. The EPA will respect that contract.
That’s half of the “basic principles” of cleaning at the critical, or any, level of soil removal. The remaining two will be covered in the next C4 column.
