Tech blog

Most cleanroom professionals understand that FFUs capture contaminants that degrade particle-sensitive samples. But they also remove bacteria and many viruses and mold spores that contribute to a host of infections.

Most common bacteria are contained by the 0.3-micron pore size of high-efficiency particular air (HEPA) filters. Ultra-Low Penetration Air (ULPA) filters, which are rated 99.999% efficient at retaining particles of 0.12 microns and larger in diameter, capture ultra-fine contaminants, including many large viruses and mold spores.

These filters also remove aerosol-born pathogens—germs that hitch a ride on larger particles and liquid droplets that are captured in a HEPA or ULPA filter. HEPA- or ULPA-based Fan/Filter Units (FFUs) thus can play an impor

Flush-mount pass-throughs, including CleanMount CleanSeam and CleanMount BioSafe, can be installed and ready for operation in a few minutes once the wall cut-out is prepared. The unique integral bracket mounts the chamber flush against the cleanroom wall without the use of any external fasteners or the need for caulking. With no horizontal surfaces to collect dust, the chamber exterior helps maintain the most critical cleanroom requirements.

Refer to the Operatin

Fire-Rated and Ruggedized wall-mount pass-throughs can be installed and ready for operation in a few minutes once the wall cut-out is prepared. The process for contractors is straightforward, requiring the parts received from Terra, two people and the following additional supplies:

• Phillips screwdrivers
• Level
• Fastener hardware appropriate for wall material (drywall or masonry, as examples). The number of fasteners needed will depend on the chamber size
• Sealant or caulking appro

Activated charcoal, the most common purification filtration medium, adsorbs chemicals with a molecular weight above 30 and a boiling point above 60°C. Carbon filters are also effective with many other chemicals because of their particular molecular structure.

Adsorption takes place in the active filter zone, the small cross-section of the filter bed in which the material to be removed comes in contact with the filtering medium (see illustration). This active filter zone moves upward as the filter becomes saturated. When it reaches the filter's top surface, there is an initial breakthrough by the contaminant gas; thereafter the percentage of contaminant gas that escapes filtration increases until total

Door Alignment

Proper alignment of doors will prevent excessive gas escape and ensure door sensor alignment. Some leakage, however, is normal. Because cabinets operate under varying degrees of positive pressure, Terra door gaskets are designed to allow controlled gas escape.

All cabinets are checked prior to packaging to ensure proper door alignment. However, they can come out of alignment during shipping due to the inherent flexibility of plastic.

Doors feature sensor magnets that must be aligned with the associated sensor on the desiccator door. If these magnets are misaligned, the Dual Purge™ system may not function properly, and door seals may not seat properly, allowing nitrogen leakage.

Standard wall-mount pass-throughs such as CleanSeam™, BioSafe® and Terra’s plastic and intermittent-seam welded steel chambers can be installed and ready for operation in a few minutes once the wall cut-out is prepared. Refer to the Operating Manual for full installation details.

The process is straightforward, requiring the parts you receive from Terra, tw

• What is electrostatic discharge?
• How is it generated?
• How does it damage microelectronic devices?
• How can it be controlled?
• What are the advantages and disadvantages of static control methods available today?

Why all the Static?

Static electricity is an excess or deficiency of electrons on a surface. The total number of deficient or excess electrons determines the charge on that surface. A surface exhibiting an excess of electrons is charged negatively, and an electron-deficient surface is charged positively.

How are Electrostatic Charges Generated?

Electrostatic charges are usually generated by friction between and/or separation of two dissimilar materials, at least one of which is a nonconductor or a poor conductor of electricity. The accumulated charge (stat

Terra offers a comprehensive range of application-specific desiccator cabinets and nitrogen control systems. These performance concepts will help you select the system right for your application.

Nitrogen is the standard medium for contamination-free storage because it is relatively inert—it neither reacts with stored materials nor carries moisture—and because it can be isolated and purified relatively inexpensively.

Desiccator cabinets must be set up so that an appropriate flow of nitrogen forces out all moisture- and contamination-laden air. Because nitrogen has a lower specific gravity than air, it is introduced into the upper section of the desiccator; the h

As critical components become smaller and more sophisticated, their susceptibility to moisture damage increases.

Once absorbed by sensitive components, water creates a number of potentially disastrous conditions. Even minute traces of oxidation, the most notorious result of moisture exposure, can degrade soldering and other manufacturing processes. Because water dissolves ionic contaminants, it also alters the conductivity of the material, which in turn can degrade electrical function. Water also combines with other materials, causing harmful chemical reactions that degrade pharmaceutical samples and chemical mixtures.

"Popcorn Effect": Moisture Damage in IC Production

One particularly costly example of moisture-related damage is the "popcorn" effect that occurs during reflow soldering of IC packages.

Although the vast majority of integrated circu