Rohde & Schwarz: Fine assembly in the new cleanroom

Fine assembly under the microscope in the new cleanroom.

The rapidly advancing miniaturization with ever smaller structures, whether in fine assembly, adjustment, or bonding processes under the microscope, continuously increases the requirements for the working environment. Therefore, a new cleanroom compliant with ISO 14644-1:1999/ISO 7 has been integrated into the micromanufacturing area at Rohde & Schwarz's Teisnach plant. The electronics company invested over 500,000 euros for this purpose.

"Covering 312 square meters, there is a wet area for pre-treating the individual parts to be assembled, as well as three production areas focused on different technologies, including protection against electrostatic discharge (ESD) for sensitive components. An access control for personnel and materials is a prerequisite for minimizing contamination," said Stefan Brandl, Head of Cleanroom and Micromanufacturing Cost Center, at the opening in the presence of Dr. Dirk-Eric Loebermann, Head of Production and Material Management from the headquarters in Munich, the Teisnach plant manager Johann Kraus, and the responsible segment manager Tobias Herzog.

The temperature in the room is constantly maintained at 21 degrees Celsius, and the relative humidity is 50 percent. The room air is processed 25 times within an hour. The maximum permissible particle count is monitored at 44 measurement points. The fully integrated lighting of the workspaces with 40 assembly and soldering stations provides 1000 lux of illumination.

Assembling under the Microscope

The fine assembly takes place in the rooms integrated into the new Production Hall VI of the Teisnach plant, where gold- or silver-plated parts are assembled under a microscope with up to 1000x magnification. Brandl explains: "Components, some only as large as a matchstick head, are soldered, glued, or connected using clamping and joining techniques within the thousandth of a millimeter range."

Gold-plated precision turned parts with a diameter of, for example, 0.43 millimeters are fitted into turned parts with a bore diameter of one millimeter and glued. The required end-face offset of the two parts is 0.01 millimeters, with a tolerance of plus/minus three thousandths. The thickness of a human hair is about six hundredths in comparison. Specially developed bonding fixtures guarantee the process-safe adherence to this requirement.

Important Certifications

25 employees work in the micromanufacturing department at the Teisnach plant. "In addition to activities in the cleanroom, we assemble, for example, measuring devices for paper production, which are used to determine the charge content of the paper pulp or to measure the flow potential," Stefan Brandl explained. The portfolio also includes plasma cleaning, temperature cycling tests (burn-in tests, thermal shock tests), protective gas chambers, and embedding of components.

Rohde & Schwarz Teisnach is certified according to IPC J-STD-001, the standard for materials, methods, and testing criteria for the manufacture of high-quality soldered connections, and EN 9100, which describes comprehensive quality management systems for suppliers in the aerospace industry.