Cleaning under cleanroom conditions

In order to properly specify the cleanliness of a machine in advance, it is necessary to analyse the entire process chain from the production of individual parts to the complete machine. This results in the respective requirements for the conditions under which production, cleaning and packaging take place.

The time aspect plays a significant role when considering the process chain. The longer an individual process lasts, the higher the quality of the environmental cleanliness must be. This can be achieved in many different ways:

• through a cleanroom with the appropriate classification
• through constant repeat cleaning to remove the contamination again and again
• by packing the products before each work break and unpacking them for further processing as well as regular cleaning 

From a pragmatic point of view in itself, the question arises as to whether a final cleaning of the entire machine would not be sufficient. However, as hardly any machine is designed so simply that you can reach all areas during cleaning, this is usually not a suitable measure. If it is done anyway, contamination is literally ‘built in’ and thus becomes a long-term risk. These contaminants do not adhere firmly to the surfaces for all time. Ageing processes, changes in the surface charge (electrostatics), changes in humidity and temperature, etc. cause a change in the adhesive forces on the surface and give the contamination an unpredictable dynamic.

You can find more information on the cleanroom technology overview page.

Single part cleaning

Any cleaning of individual parts always depends on the following factors:

• Kind of contamination
• Material
• Surface properties and their sensitivity to mechanical influences
• Impact of fluids

Ultrasonic cleaning has proven itself for many applications. It protects the components as much as technically possible and is fully developed. 

However, many parts cannot be cleaned ultrasonically. This includes, optics, ceramics, materials with porous surfaces and soft materials. In these cases, mechanical cleaning is used, which can be supported by suction and blowing. 

There are also numerous other cleaning methods such as CO2 cleaning, baking, fishing, brushing and adhesive films.

Component cleaning

The high complexity of assemblies requires a high proportion of mechanical cleaning processes. For example, adhesions cannot be cleaned ultrasonically or if the assembly consists of different materials, all of which have to be treated differently. There may be also a risk of cleaning media remaining in the assembly, as 100% drying is not possible. The cleaning of assemblies is only efficient if the individual parts have also been cleaned beforehand.

Machine Cleaning

In machine cleaning, a distinction is made between basic cleaning and maintenance cleaning. Comparable to the cleaning of cleanrooms.

Basic cleaning following assembly

Before a machine is packed, it has to be cleaned completely by the manufacturer - regardless of previous cleaning steps for individual parts and assemblies. This cleaning requires the machine to be well understood by the cleaning personnel. The various areas of the machine must be cleaned using the appropriate cleaning methods, and sensitive assemblies may be excluded from the final cleaning. In this case, these should be protected accordingly in advance. Immediately after the final cleaning, the machine must be provided with the first protective cover (e.g. a film).

A pre-acceptance test can be carried out before the packaging process, which can identify contamination problems in-house. If increased values are detected, they can be eliminated in-house, which can be realised at this point with less effort than in the customer's cleanroom. These pre-acceptance tests are also suitable for documenting the quality achieved to the customer.

Basic cleaning before commissioning

After unpacking the machine at the customer's premises in accordance with regulations, it is subjected to a further basic cleaning to remove any contamination that may have got onto the machine during transport. No machine should be brought into the cleanroom without this cleaning. Unpacking and cleaning instructions are advantageous for this.
After cleaning, it is advisable to check the surface cleanliness at random. If the limit values are met, the machine can be installed in the appropriate place in the cleanroom.

Maintenance cleaning

Maintenance cleaning is included in the customer's cleaning plan. It ensures the necessary cleanliness over time. That means that despite production in the cleanroom, the machines must always be returned to their original condition. This is because the cleanroom environment only prolongs the time it takes for the surfaces of the process equipment to become contaminated again. In addition, the operation of the machine constantly generates contamination that settles on surfaces. 

It is difficult to present generalised procedures for cleaning individual parts, assemblies and machines. The variety of parts is too great and the requirements are too different. Basically, the individual cleaning steps should be carried out under firmly documented environmental conditions by well-trained personnel. Quality control helps to continuously improve the processes.

Find out in our white paper what you need to pay attention to when designing processes under cleanroom conditions - from component cleaning to the finished product.