AUTOMOTIVE
Autonomous driving calls for high cleanliness standards
Fully autonomous and assisted driver systems have advanced rapidly in recent years, and the pace of development continues to accelerate. Doris Schulz explains.
V
ision systems are key, and their ability to function properly and reliably is heavily dependent on the cleanliness of the
components used. The scalable CO2 snow- jet technology quattroClean has established itself as an efficient and reliable solution for cleaning delicate image sensors and system housings. The dry-cleaning process is highly suited to automation, and for integration into manufacturing systems, including cleanrooms. Roadworks and lane departure warning systems, glare-free high beam, brake assistant, rear view assistant and traffic sign recognition; these are just some of the many driver assistance systems that ensure greater safety and comfort in today’s vehicles. Modern, ever-more sophisticated sensors and increasingly intelligent camera systems detect the situation respectively. Collected data is processed by a control unit and converted within fractions of a
second either into optical/acoustic signals for the driver or into active reactions, such as braking and steering interventions. Artificial intelligence and machine learning, combined with technologies such as cloud computing and image recognition, further optimise assistance systems for autonomous or assisted driving. However, it is paramount that they function safely and reliably. This in turn is largely dependent on the cleanliness of the various components. For obvious reasons, wet chemical cleaning is not an option, and conventional blow-cleaning with compressed air is often unable to remove all, if any, of the adhering particles and filmic contaminants. This method is unable to meet today’s cleanliness requirements in a reliable and reproducible manner.
Removing submicron particles and filmic contaminants
The scalable quattroClean snow jet technology ensures that image sensors with the highest par- ticulate and filmic cleanliness requirements are cleaned in a dry, gentle, and residue-free manner.
With its scalable quattroClean snow jet technology, acp systems AG offers a dry, gentle, and residue-free solution to this dilemma. It has already proven itself over a number of years in serial applications for cleaning image sensors, such as CCD or CMOS, including their (often-flexible) control and processing circuit boards. It is residues from the production process that need to be removed, such as flux or adhesive residues, particles, fibers, dust, and abrasion. A few years ago, typical cleanliness demands were still “no particles larger than five micrometers”; nowadays, it is specifications in the two-to- three-digit nanometer range that must be met. At the same time, neither the active sensor, contacts, nor printed circuit board may be damaged by the cleaning step. Due to the huge increase in cleanliness requirements, the dry process is now often used to clean housings for camera systems. Regardless of whether the parts are made of metal or injection-molded plastic, they are subjected to mechanical vibrations and temperature fluctuations during their subsequent operation. As a result, any particles that were not removed, or substances outgassing from processing media residues (in the case of metals) and release agents (in
16 MARCH 2024 | ELECTRONICS FOR ENGINEERS
Particles and filmic contaminants on the image sensor as well as on the PCB can be reliably and reproducibly removed thanks to the quattroClean snow jet technology.
the case of plastics) could impair the function of the sensor.
Dry, gentle, residue-free, and climate-neutral cleaning process
The technology, which has already been implemented in more than 1,500 cleaning systems, uses liquid carbon dioxide as a cleaning medium. Non-corrosive, non- flammable and with an indefinite shelf life, it is formed as a by-product from chemical manufacturing processes and biogas energy generation, thus making it climate neutral. The heart of the cleaning system is a wear- free two-component ring nozzle. The media, which are appropriately purified to meet the high product cleanliness requirements, flow through this. On exiting the nozzle, the carbon
dioxide expands to form fine CO2 snow, which is then bundled by a separate jacketed jet of compressed air and accelerated to supersonic speed.
The easily focused jet of snow and compressed air impacts the surface to be cleaned at a temperature of minus 78.5°C, triggering a combination of thermal, mechanical, sublimation and solvent effects. The interaction of these four mechanisms
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