The hottest laser welding of ceramics and polymers

Laser welding of ceramics and polymers

a novel welding process was developed by the Fraunhofer Institute for material and beam technology in Germany with the assistance of the Fraunhofer Institute for ceramic technologies and systems, It aims to improve the manufacturing process of Microsystem engineering in the field of Biochemistry and chemical analysis. Here, we focus on the use of laser technology to directly weld polymers and ceramics. This research and development project aims to develop a cheap and multifunctional sensor system by integrating sensors based on low temperature co fired ceramics (LTCC) and actuation technology using low-cost polymer micro jets. Through laser technology, various objects of different materials are strongly and permanently combined. Laser technology also contributes to the micro imaging and surface functionalization of low-temperature CO fired ceramics and polymers

low temperature co fired ceramic technology

multilayer LTCC technology of ceramics is a widely recognized production technology for manufacturing microelectronics, sensors (such as pressure sensors, pH detection, conductivity and resistance measurement) and actuators (such as piezoelectric actuators). This technology can produce three-dimensional, high-power electronic circuits, which can be used in the automotive and telecommunications industries

flexible foil in unsintered materials is the basis of LTCC technology. These individual foils can be machined or laser ablated to generate geometry. For example, electrical components on the surface of each single foil can be generated by silk printing. Next, the preformed foil is stacked, flattened and sintered at 900 ℃. One disadvantage of low temperature co fired ceramic technology is that it is not transparent enough, which makes it difficult to monitor the process by optical means

scientists in pharmaceutical and biological circles are trying to use sensor systems to optically monitor processing processes. By installing transparent polymer windows, the ceramic induction system will be able to optically monitor the internal processing process. Complex microfluidic systems are usually not manufactured by LTCC technology. Materials and manufacturing technology make this kind of ceramic components more widely used than polymer components of the same grade

cutting edge technology

industrial manufacturing usually uses different connection technologies to join polymer and ceramic components, such as bonding or mechanical connection technology. Adhesives are often used in industrial production to bond different objects, and finally play a good role in sealing the suture. One of the disadvantages of this technology is that it uses additional chemicals as bonding materials, which has an unnecessary impact on the function of the final system, such as biomedical reactions. Scientists using single-chip experimental systems or biomedical systems are very interested in using optical methods to monitor the internal conditions from the outside. They usually use adhesives to install a transparent window on the ceramic body to observe the internal conditions. In the long run, many such bonding interfaces are not stable and firm enough, and forms often peel off or leak

mechanical connection generally uses screws, clamps or similar tools, which provides another option for connecting ceramics and polymers. In this case, two connected parts need to be considered at the same time in places such as holes or bayonets, which increases the workload. In addition, sealing washers are also required to complete the seamless assembly between polymer and ceramic parts without leakage of liquid and air

laser welding is another recognized polymer component welding process in the industry. The two parts that need to be fused are composed of similar thermoplastic polymers. The energy of the laser beam is absorbed by the second after passing through the first welding part. Combined with the external pressure, the two parts can be closely connected to form a powerful contact. The absorbed laser energy melts and binds the components in the contact area. After the connection area is cured, it shows the same properties as the base material

novel fusion technology

a new technology developed by the Fraunhofer Institute of materials and beam technology in Germany, which can directly and firmly weld ceramics and polymers. At first glance, it seems difficult to directly weld two objects with different melting points. The melting point of ordinary thermoplastic polymers is below 250 ℃, and a high temperature of more than 400 ℃ is required for thermal decomposition. In contrast, the melting point of ceramics is above 1000 ℃. The widely different heating and physical performances of these two materials pose a challenge to this fusion technology

the basic idea of this novel fusion technology (see Figure 1) is to push the polymer into the holes and bumps on the surface of solid ceramic materials by partially melting it. The welding process is divided into two steps: the surface is only suitable for the test and inspection modification of a large number of the same samples or finished products, and the thermal connection is carried out by laser radiation

Figure 1. Principle of the new welding process

in the first step of processing, the surface of the ceramic object is patterned, for example, a dense composite of two objects is formed by laser ablation. In the next thermal processing process, the laser beam melts a thin layer of polymer surface within the connection range. The laser passes through the transparent polymer part and is absorbed by the ceramic part, contributing to the selective melting of the ceramic surface. The heat conduction between the melting points keeps the polymer heating up, and the molten part of the polymer can flow into the surface structure of the ceramic through external pressure (see Figure 2). After waiting for the temperature to drop and solidify, the two objects are tightly fused. The key points to complete this fusion are: the connection of polymer to the microstructure of ceramic surface through mechanical anchoring, and the adhesion between contact objects

Figure 2. Illustration of connection mechanism (mechanical fixation and bonding)

the latest research work investigated and optimized the influence of different processing parameters on the hot fusion process, including laser power, processing speed, connection pressure, connection area temperature, etc. In order to effectively monitor and control the bonding temperature, a high temperature measuring instrument and a laser power controller are installed in the system. So far, two different laser sources have been used: rod nd:yag laser and fiber laser system. In comparison, fiber lasers have higher beam quality than solid-state lasers. In general, other laser sources, such as semiconductor lasers, can also be applied

due to the great potential of LTCC technology in micro and sensor systems, the R & D department focuses on this type of ceramics. Different polymer materials have been successfully tested and compared, such as PC, PMMA, San and PETG. The surface pattern of the fused object (in our case, ceramic) has an important impact on the strength and durability of the fusion. By using different short pulse laser sources, surface patterns in different fields are created, connected and compared. Structural dimensions such as length and width are different for different geometries, such as single craters or straight grooves. Different structures and processing parameters affect each other, and the attributes of docking points also play a role. The treatment and preparation of raw materials will also affect the final performance. In order to achieve the best welding effect, it is very important to optimize and adjust all the interrelated parameters. A sealed connection with a tensile strength of 25 n/mm2 is thus produced

single chip experimental system

based on this new fusion technology, some bioreactors and single chip experimental systems have been manufactured for research and testing. Using optimized connection technology, LTCC based ceramic sensors are combined with transparent polymers, such as planar windows or microfluidic components. The Fraunhofer Institute of ceramic technology and systems has assisted in the development of ceramic components containing different sensors and microfluidic system components. It can be seen from the single chip experimental system in Figure 3 that the growth of cells in the integrated microbial reactor can be monitored and controlled under customized heat and biochemical conditions. B. by tightening or replacing the sealing gasket of the upper frame at the oil leakage place and using a transparent polymer window, the system can now monitor the internal process through an optical microscope. Another option is to use spectrophotometry, such as fluorescence analysis, to analyze the biochemical changes inside the reactor

Figure 3. The single chip experimental system is equipped with LTCC based multi electrode sensor and polymer microfluidic cavity

Figure 4 shows that an integrated multi electrode array ceramic polymer flow sensor is used to measure the electronic signals emitted during cell culture. Ceramic sensors are connected to a polymer microfluidic element by a new fusion technology. During culture, cells can absorb nutrient solutions and various reactants transported by polymer fluid

Figure 4. The single chip experimental system based on LTCC is equipped with a polymer window

in another research and development work when it is necessary to strengthen the rust prevention of instrument firmware, the Fraunhofer Institute of materials and beam technology in Germany developed a pulsed laser that can make the polymer surface patterned and functionalized in the active gas environment. This will affect the proliferation of cells on specific surfaces, making it possible for the polymer to be biologically functionalized before it is connected to the sensing system

this new welding process has a broad application prospect and market, covering the fields of chemical and biological analysis, such as screening used in pharmaceutical companies, environmental analysis in chemical facilities, analysis in food industry and medical technology

future prospects

one of the purposes of the ongoing research activities of the Fraunhofer Institute of materials and beam technology in Germany is to improve the tensile strength of the connection point. Further optimize surface patterning and surface pretreatment. Future research will also transfer the connection process to the fusion of other objects, such as other polymers or new ceramics, or use this technology to connect polymers with semiconductors or metals. Through this 5 Whether there is wear on the working surface of the hanging bolt and hook is a way to expand the application scope of this technology to the field of micro system technology and microelectronics. (end)