Inline microscopy

Fraunhofer IPM has many years of experience in the further development and automation of microscopy methods for various applications. This includes the investigation of defects; for example, on solar cells, and the development of automatic microscopes such as the analysis of cell cultures in the incubator. On the basis of commercial components, special microscopes with extraordinary properties have been developed. The goal is the integration of complex microscopy systems into production. The development of very sophisticated image analysis algorithms enables the analysis of microscopic structures in real time.

Application example: Optical inspection of the core component of an inhalation device

With the propellant-free inhaler Respimat®, the pharmaceutical company Boehringer Ingelheim has achieved a technical innovation. This is based primarily on a tiny component: a special micro nozzle for nebulization of the drug. In order to be able to precisely control the quality of this microfluidic component during production, Fraunhofer IPM has developed an optical inline inspection system.

The uniblock is a small microstructured silicon component capped with glass. The inspection of such a series product manufactured as a high-volume component requires in addition to a high spatial resolution in also very high inspection speeds. The system developed at the Fraunhofer IPM checks various properties and possible defects of the uniblock during production: Structural defects, i.e., deviations of the microstructure from the desired geometry and missing structures, impurities, bonding defects in the connection of the silicon structure with the glass cover, sawing errors as a cause of faulty external dimensions of the component, defects and breakouts at the edges. In order to be able to reliably inspect even the finest structures of so called filter channels, measuring accuracies in the lower micrometer range are required.

The test system uses a laser scanning microscope, which performs all measurements through the glass cover with a clock rate of 1.3 seconds. A focused laser beam scans the surface of the uniblock. The laser focus is displayed on a small opening, the pinhole, in the microscope, so that almost exclusively light from a sample plane reaches the detector. Unlike a conventional optical microscope, the laser scanning microscope detects the edge of the uniblock very precisely at the level of the silicon surface under the glass. Only in this way can the system check the position of the microstructure relative to the outer edges - an important prerequisite for an essential part of the inspection.

In co-operation with a manufacturer of automation systems, the delivery of several inline inspection systems took place, inspecting 100 percent of the components today.