Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:

 

Laser glass soldering for low-temperature, durably stable packaging of electronic components

10.03.2010
Electronic and electrical products have to meet a diverse range of increasingly exacting demands, including high integration density and the combination of various materials with specific functionality.

Hermetic packaging poses particular challenges for the production technology, which can no longer be met by conventional methods such as gluing and soldering. The Fraunhofer Institute for Laser Technology ILT has developed an innovative packaging process for microcomponents and electronic parts based on laser glass soldering, which is suitable for use in mass production and fulfils the stringent environmental regulations of the EU's RoHS Directive.

Precision products such as semiconductors, sensors or optical and medical system components contain highly sensitive electronic elements. In most cases they must not come into contact with water, oxygen and other elements and therefore have to be hermetically sealed. Gas-tight packaging of the complex interior poses a great challenge for the joining process in microcomponents.

High-temperature processes such as anodic bonding and glass frit bonding are widely used methods for hermetically sealing components made of silicon and glass. The heat needed for joining is introduced into the component by a kiln process at temperatures of 300 to 600°C. As the most temperature sensitive component determines the maximum temperature of the entire system, these two processes cannot be used for temperature-sensitive functional elements. They are, for example, unsuitable for encapsulating OLEDs because the functional organic layers would be destroyed at a temperature of even 100 °C.

At present temperature-labile components are usually glued, but long-time tests on semiconductors and OLEDs have shown that the durability of the glued connection is limited. Oxygen and moisture gradually penetrate the interior of the component and affect its function. The limited durability and the temperature sensitivity of glued connections are a problem, especially for components used in the medical sector, as they cannot withstand, for example, sterilization processes in autoclaves. Electronic components such as sensors in implants can often only be replaced by performing a surgical operation on the patient. The manufacturers of these and other precision components are therefore seeking a way of prolonging the durability of their products. As high-temperature and gluing processes do not meet the requirements for joining microelectronic components to various materials, manufacturers are looking for a reliable low-temperature process.

Laser-based soldering with glass solder materials offers a suitable solution. This is a relatively new joining technique which subjects the total component to only minimal thermal loading. Research scientists at the Fraunhofer ILT are currently developing the technique with the aim of introducing it soon into series production. In this joining method the solder consisting of a glass particle paste is first applied precisely to the cover of the component using a print mask. The solder is then pre-vitrified in a kiln at a temperature of 350 - 500 °C depending on the type of glass paste used, so that the binders in the paste evaporate. After the solder has cooled the electronic component is joined to the cover. A defined and locally limited temperature increase is achieved by scanning the solder seam with a laser beam. The rest of the component is not affected by this application of heat. Owing to the high scanning speed of up to 10,000 mm per second, the joining process is quasi-simultaneously controlled. The entire solder contour is evenly heated, the cover can sink into the liquid solder bath and is thus hermetically connected to the component. Compared with gluing, the laser-based method achieves a considerable increase in the durability of the entire microcomponent, and the permeability of liquids and gases is practically zero. What's more, the solder seam is completely free of bubbles and cracks. For the medical sector in particular this means a significant increase in safety. "A further advantage of laser-based glass soldering is that the solder seam is very narrow, measuring just 300-500 µm, whereas glued seams have a width of several millimeters," explains Heidrun Kind, project manager at the Fraunhofer ILT. "This fact becomes increasingly important with the advancing miniaturization of precision components. Wide glued seams on OLEDs for example are regarded as visual defects. On sensors used in implants they can change the entire component geometry detrimentally. In environmental terms, too, the technique has a bright future. We are now able to use completely lead-free solder, which means that our method meets the requirements of the EU's RoHS Directive for the minimization of hazardous substances in electrical and electronic components."

Thanks to the maximum flexibility provided with regard to component size and shape, the process is highly suitable for industrial series production. It can be used to seal microsystem components as well as to join large components measuring 200 x 200 mm2. In addition to glass/glass components, substrates with MAM or ITO layers as well as glass/silicon components can be hermetically connected to each other.

Contacts at the Fraunhofer ILT
If you have any questions our experts will be pleased to assist:
Dipl.-Ing. Heidrun Kind
Expert Group Ablation and Joining
Phone +49 241 8906-490
heidrun.kind@ilt.fraunhofer.de
Dr.-Ing. Arnold Gillner
Manager of Expert Group Ablation and Joining
Phone +49 241 8906-148
arnold.gillner@ilt.fraunhofer.de
Fraunhofer Institute for Laser Technology Lasertechnik ILT
Steinbachstrasse 15
52074 Aachen
Phone +49 241 8906-0
Fax. +49 241 8906-121

Axel Bauer | Fraunhofer Gesellschaft
Further information:
http://www.ilt.fraunhofer.de

More articles from Materials Sciences:

nachricht New design improves performance of flexible wearable electronics
23.06.2017 | North Carolina State University

nachricht Plant inspiration could lead to flexible electronics
22.06.2017 | American Chemical Society

All articles from Materials Sciences >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Can we see monkeys from space? Emerging technologies to map biodiversity

An international team of scientists has proposed a new multi-disciplinary approach in which an array of new technologies will allow us to map biodiversity and the risks that wildlife is facing at the scale of whole landscapes. The findings are published in Nature Ecology and Evolution. This international research is led by the Kunming Institute of Zoology from China, University of East Anglia, University of Leicester and the Leibniz Institute for Zoo and Wildlife Research.

Using a combination of satellite and ground data, the team proposes that it is now possible to map biodiversity with an accuracy that has not been previously...

Im Focus: Climate satellite: Tracking methane with robust laser technology

Heatwaves in the Arctic, longer periods of vegetation in Europe, severe floods in West Africa – starting in 2021, scientists want to explore the emissions of the greenhouse gas methane with the German-French satellite MERLIN. This is made possible by a new robust laser system of the Fraunhofer Institute for Laser Technology ILT in Aachen, which achieves unprecedented measurement accuracy.

Methane is primarily the result of the decomposition of organic matter. The gas has a 25 times greater warming potential than carbon dioxide, but is not as...

Im Focus: How protons move through a fuel cell

Hydrogen is regarded as the energy source of the future: It is produced with solar power and can be used to generate heat and electricity in fuel cells. Empa researchers have now succeeded in decoding the movement of hydrogen ions in crystals – a key step towards more efficient energy conversion in the hydrogen industry of tomorrow.

As charge carriers, electrons and ions play the leading role in electrochemical energy storage devices and converters such as batteries and fuel cells. Proton...

Im Focus: A unique data centre for cosmological simulations

Scientists from the Excellence Cluster Universe at the Ludwig-Maximilians-Universität Munich have establised "Cosmowebportal", a unique data centre for cosmological simulations located at the Leibniz Supercomputing Centre (LRZ) of the Bavarian Academy of Sciences. The complete results of a series of large hydrodynamical cosmological simulations are available, with data volumes typically exceeding several hundred terabytes. Scientists worldwide can interactively explore these complex simulations via a web interface and directly access the results.

With current telescopes, scientists can observe our Universe’s galaxies and galaxy clusters and their distribution along an invisible cosmic web. From the...

Im Focus: Scientists develop molecular thermometer for contactless measurement using infrared light

Temperature measurements possible even on the smallest scale / Molecular ruby for use in material sciences, biology, and medicine

Chemists at Johannes Gutenberg University Mainz (JGU) in cooperation with researchers of the German Federal Institute for Materials Research and Testing (BAM)...

All Focus news of the innovation-report >>>

Anzeige

Anzeige

Event News

Plants are networkers

19.06.2017 | Event News

Digital Survival Training for Executives

13.06.2017 | Event News

Global Learning Council Summit 2017

13.06.2017 | Event News

 
Latest News

Quantum thermometer or optical refrigerator?

23.06.2017 | Physics and Astronomy

A 100-year-old physics problem has been solved at EPFL

23.06.2017 | Physics and Astronomy

Equipping form with function

23.06.2017 | Information Technology

VideoLinks
B2B-VideoLinks
More VideoLinks >>>