Testing in the world’s cleanest cleanroom

Welcome to Fraunhofer IPA’s department for Ultraclean Technology and Micro manufacturing. This is the world-leading research and testing facility for clean production. It is also where Glamox tests cleanroom luminaires.

If you have visited the Fraunhofer Institute for Manufacturing Engineering and Automation testing facilities in Stuttgart, you can also boast that you have been inside the cleanest cleanroom in the world. For more than 30 years, the institute, which is located close to the University of Stuttgart, has been the centre for research on clean environments. Glamox visited Fraunhofer IPA in Stuttgart late August last year. We wanted to see for ourselves the reputed cleanroom environment where serious manufacturers of cleanroom interior and equipment test their products. Everything from ceiling systems to robots and process tools are subjects for the different cleanroom tests Fraunhofer IPA has to offer. For Glamox it is important to have our cleanroom luminaires tested here. The cleanroom certification offered by Fraunhofer gives an objective and reliable assessment of our products. This gives our customers good grounds for decision-making when comparing our solution with other alternatives. 

The first step of the particle emission test is to locate the points where dust and dirt is most likely to accumulate. This is done with an optical laser particle counter.

When an adequate number of test points are located, probe heads from the particle counters are placed next to each point. 

2100 tested cleanroom products

In Stuttgart we were met and shown around the facilities by Group Leader, Dr. Frank Bürger and his co-worker Jasmin Mettmann, who holds a Master of Science.“We can offer more than 40 different tests depending on the product and the application, and we have more than 2100 tested cleanroom products in our database from the last 10 years”, said Dr. Bürger who started working for Fraunhofer IPA 13 years ago. He was recruited from an American company in the semiconductor manufacturing industry, which is incidentally the industry with the highest requirements for cleanroom suitability. Product testing is only a part of the activity conducted by the department for Ultraclean Technology and Micro manufacturing  of the institute. Applied research and science is the main focus area. This involves making sure that the standards that guide the cleanroom industry are kept up to date. “We are the driving force in developing and improving the international standards that are used to test cleanroom products”, Dr. Bürger says. Dr. Bürger foresees an increasing demand for cleanroom testing in the years to come. “We see that more and more branches of industry need to manufacture their products under defined clean conditions”, he said. 

Particle emission testing

There are especially two tests that Glamox sees as important for a cleanroom luminaire. The first test is the particle emission test performed and classified according to ISO 14644-14 and ISO 14644-1. This test is carried out in the Fraunhofer IPA’s own cleanroom, which is at least ten times cleaner than the requirement for air cleanliness of ISO 1 class. To achieve such an extreme level of cleanliness, a laminar airflow is needed. This means that the air only flows downwards from ceiling to floor. The floor is perforated to give the air passage and there are filters in the ceiling that intercept particles. In order to provide the ideal conditions for a reference cleanroom, the air in the 250 square metre room is replaced every 12 seconds.It can be hard to get your head around the small size and quantity of particles that this test has to be able to detect. For ISO class 1 only 10 particles no bigger than 0.1 micrometre (1 micrometre equalling one thousandth of a millimetre) in size may be present in one cubic metre of air. But when you consider that a speck of dust in a semiconductor manufacturing facility can ruin millions worth of microchips, it’s easy to see why the high level of cleanliness is needed. The particle emission testing starts out with a round of particle source localization which is unceremoniously referred to as “sniffing”. This involves a particle counter that uses laser to measure the size and count the number of airborne particles. The counter is equipped with a probe head that has a suction capacity of 28.3 litres of air per minute. The operator moves around the luminaire in order to detect points that are accumulating particles. Once an adequate number of measurements points are located, probe heads are placed in fixed positions close to each measurement point and left there for a 100 minutes test period. 

To assess the cleanability of the luminaires, a mixture with riboflavin is applied to the surfaces of the luminaire. The contamination is fluorescent yellow in colour and clearly visible.

 After cleaning, the success of the cleaning procedure is evaluated based on the presence of any residual contamination. 

Cleanability test

The second test is equally as important to Glamox. This is a cleanability test. To assess the cleanability of the luminaires, a mixture with riboflavin is applied to the surfaces of the luminaire. The contamination is fluorescent yellow in colour and clearly visible with ultraviolet light. The contamination is subsequently removed using a reproducible cleaning process. For flat surfaces, a cleaning simulator is used in order to gain comparable results. The success of the cleaning procedure is evaluated based on the presence of any residual contamination. The use of a fluorescent pigment enables areas that are difficult to clean to be clearly visualised.  This test is carried out according to the VDMA information sheet “Riboflavin test for low-germ or sterile process technologies – Fluorescence test for examination of cleanability”.