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Development of solder paste jetting processes for advanced packaging

: Thomas, Tina; Voges, Steve; Fliess, M.; Becker, Karl-Friedrich; Reiners, Philipp; Koch, Mathias; Bauer, Jörg; Braun, Tanja; Lang, Klaus-Dieter

Fraunhofer-Institute for Electronic Nano Systems -ENAS-, Chemnitz; Fraunhofer-Institut für Zuverlässigkeit und Mikrointegration -IZM-, Berlin:
Smart Systems Integration 2015 : 9th International Conference and Exhibition on Integration Issues of Miniaturized Systems - MEMS, NEMS, ICs and Electronic Components, Copenhagen, Denmark, 11 - 12 March 2015
Aachen: Apprimus-Verlag, 2015
ISBN: 978-3-86359-296-7
Smart Systems Integration Conference (SSI) <2015, Copenhagen>
International Conference & Exhibition on Integration Issues of Miniaturized Systems - MEMS, NEMS, ICs and Electronic Components <9, 2015, Copenhagen>
Conference Paper
Fraunhofer IZM ()

During the last years, jetting processes for higher viscosity materials have gained widespread interest in microelectronics manufacturing. Main reasons for this interest are high throughput/productivity of jetting, contactless material deposition, high volume precision and freely designable deposition patterns. In previous studies we have demonstrated the jetability of different resin-based materials, being exemplary for unfilled adhesive, for low viscous Underfill resin and for higher viscosity Glob Top materials. The focus of our previous work was on the dosing of various encapsulants - Underfill material with low viscosity and near Newtonian behavior and Glob Top resins, being non-newtonian fluids due to higher matrix viscosity and higher filler content (up to 70 wt%) with resulting increased filler/filler and filler/matrix interaction [i]. During the last years jetting has become widely used and has been applied to the dosing of much more complex materials, combining high viscosity matrix materials with odd shaped and compressive particles. Examples for these materials are conductive adhesives and also solder pastes, where the jetting system developed by Swedish company Mycronic sets the current standard for solder paste jetting in a manufacturing environment. In previous reports, also the basic feasibility of solder paste jetting was reported, in this technological study solder paste jetting using different jetting systems is investigated in comparison to solder paste dispensing and solder paste printing, especially material rheological behaviour and the correspondence to processability have been evaluated in detail. [ii] To illustrate the potential of solder paste jetting as a flexible and powerful tool for electronic system prototyping, a test vehicle has been designed, containing areas for SMD soldering and for process reproducibility. Within the project VersoJet, a "KMU Innovative" supported research project between the TU Berlin and Vermes Microdispensing the possibility of using standard jet technology for contactless dosing of solder pastes was investigated and solder paste modification as well as jet valve optimization have been investigated. To determine process quality not only basic process data on droplet diameter, resulting material depot size and positioning accuracy have been evaluated, but also statistical means have been employed to determine process homogeneity and stability depending on the respective parameter set. Summarized this paper gives a detailed insight into solder jet process development and describes material rheology demands and limitations and thus allows the optimized use of advanced solder jetting technology for electronic assemblies.