Production of Microelectronics Cleanroom
01 May 2021

Production of Microelectronics Cleanroom

Microelectronics technology is increasingly ubiquitous, even within the human body, as medical researchers develop new approaches  to monitoring and treating a growing array of illnesses and injuries. A variety of implantable medical devices are now used routinely, ranging from intraocular lenses to electroencephalography (EEG) recorders and many others. The companies that design these devices require specific capabilities and qualifications from a potential medical device manufacturer. These requirements typically cover topics like experience in medical device manufacturing, the types of equipment necessary to manufacture, assemble and package the product, parts tracking methods, employee qualifications and/or specialised training, required  industry and governmental certifications, etc. However, as comprehensive as these requirements might appear, some of them fail to include an aspect that’s critical for some categories of medical microelectronics device manufacturing: a microbial-controlled cleanroom.

In-house Microbial-Controlled Cleanrooms

A microbial-controlled cleanroom allows medical device manufacturers to handle the complete manufacturing process. By eliminating the need to ship finished devices to a third-party vendor for cleaning or packaging prior to sterilisation, an in-house cleanroom helps to shorten the supply line, save time, and contain costs. Choosing a manufacturer without one increases the potential for production/delivery delays, product routing/tracking confusion or errors, accidental device contamination, and other problems. Having in-house cleanrooms of this type streamlines the production process and reduces opportunities for finger-pointing if a question arises with a product in the field.

Why Device Sterilisation Alone Isn’t Enough

For microelectronic devices designed for either permanent or temporary implantation in the human body, the use of a microbial-controlled cleanroom to control the microbial (sometimes referred to as bioburden) level during final device assembly and pouching is essential to avoid exposing patients to danger. Bioburden refers to the number of contaminating bacteria on a certain amount of material before it is sterilised. Although implantable medical devices are thoroughly sterilised prior to shipment to the healthcare facility where they will be used (typically using gamma radiation or ethylene oxide [EtO]), sterilisation should be thought of as a “necessary but not sufficient” step. Yes, sterilisation will kill any living moulds, bacteria, etc. on the device and its packaging. However, even after sterilisation, pyrogenic (fever-causing) substances can remain in the cell walls of these dead organisms, posing an unacceptable risk to the patient after the device is implanted.

Cleanrooms Defined

It is a common misconception that cleanrooms clean things but this is not the case. A cleanroom can be defined most simply as an enclosed environment with a low level of pollutants like dust, airborne microorganisms, aerosol particles, and chemical vapors. Cleanrooms can only be as clean as the people, products, packaging and cleaning materials introduced into them. The facilities, people, tools, cleaning chemicals, and the product being manufactured can all contribute to contamination. All potential sources of contamination must be tightly controlled. A quick overview of the different types of cleanrooms that medical device manufacturers may have in their facilities may be helpful.

Cleanrooms are widely used in semiconductor manufacturing, biotechnology,  the life sciences—anywhere there are products or processes that are sensitive to environmental contamination. The air entering a cleanroom is filtered to exclude dust; once inside, it is recirculated constantly through high efficiency particulate air (HEPA) and/or ultra-low penetration air (ULPA) filters to remove particulate contaminants generated inside the cleanroom itself.

In a typical city, the outdoor atmosphere contains 35 million particles that are 0.5 microns in diameter or larger per cubic meter, which corresponds to an International Organization for Standardization (ISO) Class 9 cleanroom. In contrast, an ISO Class 1 cleanroom allows no particles in that size range and only 12 particles that are 0.3 microns or smaller per cubic meter.

In order for a cleanroom to be certified by the U.S. Food and Drug Administration (FDA), it must meet the standards for controlled environments set forth in FED-STD-209E or ISO 14644-1. Although the US FED STD 209E was officially cancelled more than a decade ago, the classification numbers are still widely used.