SMT Assembly using a novel pure nanocopper metal adhesive - Dr. Alfred Zinn, Lockheed Martin Space Systems
A nanocopper-based SMT material was developed as a robust, high-performance alternative to solder. This new solder-free nanocopper material overcomes the inherent limitations of traditional solders, wherein the operating temperature is limited by the processing temperature. For the first time, an interconnect material is capable of operating at temperatures not only equal to but even far above its original processing temperature. Being pure copper, the material can form contacts with 5-10x the thermal and electrical conductivity of typical solder systems. The material rheology can be tuned for drop-in replacement of solder on standard PCB assembly lines and other industrial paste dispensing equipment. Such nanoparticle based interconnects can exhibit improved creep resistance and enhanced reliability in low- and high-temperature operating environments. A readily dispensable nanocopper paste was formulated to bond commercial LEDs to a thermal heat sink. To evaluate the quality of the formed bulk copper interconnects, a large number of test samples was fabricated to measure mechanical strength. Shear strengths exceeding 70 MPa have been achieved.
Bonding process using Cu nanoparticles for high-temperature applications - Prof. Hiroshi Nishikawa, Joining and Welding Research Institute, Osaka University, Osaka, Japan
Recently, sintering behavior of nanoparticles has attracted significant interest, because it is well known that nanoparticles of metals such as Au and Ag have lower sintering and melting temperatures than the bulk metal. Nanoparticle bonding is proposed as a solder alternative to establish a new bonding technology for high-temperature applications. In this study, Cu nanoparticle paste was experimentally applied and the effect of bonding conditions on the joint strength of Cu-to-Cu joint using Cu nanoparticle paste was mainly investigated. As a result, it was found that the Cu-to-Cu joining using Cu nanoparticle paste was successfully achieved, and there was a large effect of joining conditions such as heating temperature and bonding atmosphere on the joining strength of the Cu-to-Cu joint.
Silver nanoparticles for inkjet-printed conductive structures in electronic packaging - Prof. Jan Felba, Microsystem Electronics and Photonics; Wroclaw University of Technology
Packaging of today’s miniaturized electronics is based on conductive microstructures and contacts with dimensions in the range of tens of micrometers. Such lines or much more complicated patterns are possible with advanced nanoparticle technologies. Printing is one of the key technologies which is used in microelectronics manufacturing. Printed electronics can be divided into two basic categories – contact or noncontact. In noncontact methods, e.g. inkjet printing, liquid flows freely between a dispenser and a substrate. The technology needs a special liquid, usually termed “ink,” which should satisfy at least the following three requirements: has very low viscosity, can be treated as a “true solvent” without component separation during high acceleration, and is able to make electrically conductive structures. One of the most popular are nanoparticle inks, which are metallic nanoparticle suspensions with some additives to prevent particle agglomeration and sedimentation. This presentation deals with inkjet printing technology using ink containing silver nanoparticles and in particular presents the following issues:
• Methods of silver nanoparticles production which can be used for preparation of filler for inkjet-printed formulations.
• Materials and the principle of inkjet printing
• Electrical conductivity of printed microstructures
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