The surfaces have been wiped and the obvious question is: How clean are they? Start with what you see. Do the surfaces look visibly clean? If not, the wiping activity is not yet done. Wipe to the absence of visible soil on both the surface and the wiper. Keep wiping until the last wiper shows [Read More…]
In a cleanroom, cleaning floors and walls is like cleaning other surfaces, only more so – larger surface areas and corresponding larger wiping cloths. Let’s start with floors. The same principles apply to wiping floors as described previously in Particles on Surfaces Part 4 – use linear wiping strokes and wipe from clean to dirty. To achieve [Read More…]
Before we address wiping techniques, we might well question the need for wiping. After all, if capillary forces hold particles to surfaces strongly enough that the particles can’t easily get airborne, why the great concern to remove the particles by wiping? The simple answer is embodied in two words: Contact Transfer. That’s the means by which [Read More…]
In Particles on Surfaces – Part 2, we learned that thin liquid layers between particles and surfaces serve as the binding forces between the two. By lowering the surface tension of this liquid layer – typically water – we can decrease the binding force and assist in the removal of particles. Isopropyl alcohol (IPA) – as [Read More…]
In Particles on Surfaces – Part 1, witness wafer and settling plate data showed that particles and bacteria (i.e. viable particles) will settle on cleanroom surfaces. From this we can infer that particles do NOT behave as hard microscopic billiard balls, striking surfaces and rebounding into the air. Rather, through inelastic collisions with the surface, they [Read More…]
Surely cleanrooms qualify. Air filtered everywhere. Operators garbed from head to foot with only a portion of their faces exposed. Spotless stainless steel and plastic surfaces everywhere. No paper or cardboard anywhere. Manufactured product protected. Surely this is cleanliness next to Godliness. Appearances are deceiving. Despite the advances made in the High Efficiency Particle Air [Read More…]
Web searches for “Lint Free Wipes” provide some interesting information. A Google search returns 82,300 hits. A search of “lint-free” on the American Society for Testing Materials (ASTM) site returns 265 hits, and a search of “lint-free” on the United States Pharmacopeia (USP) site returns 737 hits. Of these, three are contained in the <797> document on [Read More…]
The Customer An aluminum wheel manufacturer is currently using Choice® SuperSorb 12×12″ (30x30cm) disposable wipes for their powder coating applications. The Applications Oil, aluminum oxide and other contaminants in the pre-treatment (surface preparation) process can adversely affect the quality of the final product. Wiping down the bare metal after cleaning and prior to coating will [Read More…]
The Issue Of Ion Contamination In Electronics Manufacturing Processes Is Of Critical Importance. Therefore It Is Incumbent On Manufacturers To Be Vigilant In Detecting And Minimizing Ionic Contamination. By Howard Siegerman, Ph.D BIG PROBLEMS WITH SMALL IONS THE ISSUE OF ION CONTAMINATION in microelectronics is of critical importance because electronic device failures have been directly linked [Read More…]
YOU CAN BUY SOLVENTS like acetone and turpentine from a hardware store, but you really shouldn’t. Solvents sold in the hardware store are not refined to the level required for cleanroom cleaning. When applied to surfaces, the hardware store variety of solvents will leave visible residues behind after they have evaporated. Cleaning With Acetone Or Turpentine [Read More…]
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