Innovative LDS technology replaces silicon wafers
The market for sensor applications is large: microsystems are used in large quantities in the IT and telecommunications industries, the automotive and aerospace industries as well as in plant and mechanical engineering. The basis of these electronic components are so-called wafers – thin discs, usually made of silicon, on which thin films are deposited. The production and further processing of silicon wafers is very complex and highly expensive. The Institute for Microproduction Technology at Leibnitz University Hannover (IMPT) has investigated alternative production methods for sensor applications. A study showed that modified polyetheretherketone (PEEK) can replace high-priced substrates such as silicon. The material TECACOMP PEEK LDS black 1047045, a high-performance compound from Ensinger, was used for the production of a functional demonstrator (temperature and magnetic field sensor) by injection moulding with laser direct structuring (LDS).
Injection moulding and laser direct structuring: three instead of seven production steps
The production of a housed sensor, which can be easily integrated into PCB assembly processes, involves three production steps with the LDS process:
In the first step, the substrates are made of laser-activatable plastic by injection moulding. Predefined sensor structures as well as vertical electrically conductive connections (VIA) for vias are taken into account. The next step is laser drilling of recesses as well as activation of the LDS-compatible polymer by electroless selective deposition of metals. Subsequently, an unstructured sensor layer is applied by means of cathode sputtering. The required structures are then exposed in a CMP process (chemical mechanical polishing).
This process chain significantly reduces the complexity of manufacturing and packaging. Unlike classic silicon-based wafer production, a clean room environment and photolithography are not required.
Picture 1: Magnetic field sensor, produced by injection moulding with laser direct structuring (LDS). The substrate used is the high-performance polymer TECACOMP PEEK LDS black 1047045 from Ensinger (Photo: Ensinger / IMPT).
Thermoplastics enable cost-effective sensor production
The use of laser-activatable high-performance polymers instead of silicon as a substrate for wafer production can bring significant cost advantages in production in addition to a reduction in the number of process steps. Stefan Bur, Application Segment Manager MID/LDS at Ensinger, sees great potential in this innovative application: “In the electronics industry, the polymer PEEK in particular is gaining in importance due to its special properties. The IMPT study showed that our compound TECACOMP PEEK LDS, which is unique on the market, can be used as a wafer material. In initial applications, the sensor had around 75 percent of the performance of a sensor conventionally built on silicon. In terms of manufacturing costs, potential savings of 90 per cent were shown.” Ensinger is confident that in the future, medium-sized companies will also be able to produce low-cost wafers for microsystems technology using the LDS process. “For this reason, we are investing in further development of these compounds. Our new product, TECACOMP PEEK LDS grey, is already optimised for applications with particularly high surface requirements,” explains Stefan Bur.
Areas of application
TECACOMP PEEK LDS compounds can be of interest for sensors in electrical engineering, mechanical engineering and medical technology. Possible fields of application are position sensors (AMR and GMR sensors), eddy current sensors, temperature sensors for measurements in the laboratory or industrial processes (thin-film PT sensors) or DC/DC converters.
Property profile: TECACOMP PEEK LDS black 1047045 compound
The LDS process places particularly high demands on the polymer when manufacturing microsystems. Ensinger has been developing thermoplastic compounds for laser direct structuring for many years and is currently the only plastics specialist that can offer PEEK certified by LPKF Laser & Electronics AG for the LDS method. TECACOMP PEEK LDS black 1047045 is optimised with mineral fillers. The material is extremely temperature-resistant (permanently up to 260°C), has very good weld line strength, good adhesive strength and shows high chemical resistance to solvents. In addition, TECACOMP PEEK LDS has a very low coefficient of thermal linear expansion, which is closer to metals than that of many other plastics.
Picture 2: Eddy current sensor. The compound TECACOMP PEEK LDS grey is used for production in the LDS process. This development grade from the plastics processor Ensinger meets particularly high surface requirements (Photo: Ensinger / IMPT)
Picture 3: The illustration shows microstructures (Bragg gratings) on a sensor. The compound TECACOMP PEEK LDS black 1047045 produced by Ensinger is extremely temperature-resistant, has very good weld line strength, good adhesive strength and shows high chemical resistance to solvents. In addition, the material has a very low coefficient of thermal linear expansion (Photo: Ensinger / IMPT)
The Ensinger Group is engaged in the development, production and distribution of compounds, semi-finished products, composites, finished parts and profiles made of engineering plastics. Ensinger uses a variety of manufacturing processes to process the thermoplastic construction and high-performance polymers, including extrusion, machining, injection moulding, mould casting, sintering and pressing. With a total of 2,700 employees at 35 locations, the family-owned company has manufacturing facilities or sales offices in all major industrial regions worldwide.