Breaking the bonds

Marek Dragon, contamination control engineer for Xolox Corporation, has good things to say about CO₂ composite spray cleaning technology.

“We provide crash stop and actuator assemblies to the hard disk drive industry,” explained Dragon.  “Because our components go into hard disk drives, they must be very clean.  We have different requirements for different parts.  For example, a significant portion of our parts are allowed to have 250,000- to 0.5- micron particles (or smaller).  However, our requirements for other parts, such as our magnetic parts, are more stringent.  Our requirement for allowable magnetic particles is basically zero.”

According to Dragon, the company routinely subjects parts to particle- counting tests to confirm cleanliness.  Parts are also subject to a nonvolatile residue test (NVR).  Two to three micrograms of NVR per square centimeter is the upper limit.

“In the past, we attempted to use compressed ionized air to remove particles,” Dragon stated.  “We found the ionized air process to be effective at removing the larger particles, but ineffective at removing the smaller particles.  It was totally ineffective at removing the magnetically charged particles.  A few years ago we found the CO₂ composite spray cleaning process to be very effective at removing all particles, including magnetically charged submicron particles.”

According to Dragon, the new process is meeting company requirements at approximately 3 to 5 seconds per piece.  The system has also proven itself easily adaptable to the automated processes within the operation and is used for many different applications.

“The CO₂ used in the system is a recycled by-product, so for us there are no environmental concerns associated with the process,” remarked Dragon.  He added, however, that “since CO₂ has the ability to deplete oxygen, you do need to consider the area of use.”

Xolox put a CO₂ composite spray cleaning system into their operation and currently use it approximately 4 to 24 hours per day, depending on production.  “When properly applied with the appropriate fixturing, we could reduce our scrap rate by 90 percent,” claimed Dragon.  “That translates into a good yield improvement.”

Source:
“Today’s Forecast: It Looks like Snow”, Precision Cleaning, May 1999