Papers

ICMCTF2007 Session G1-2: Innovations in Surface Coatings and Treatments

Tuesday, April 24, 2007 1:30 PM in Room Royal Palm 4-6

Tuesday Afternoon

Start	Invited?	Item
1:30 PM		G1-2-1 Optimisation of the Ni-P Electroless Plating on Aluminium Silicon Carbide for Electronic Packaging A. Ureña, M.V. Utrilla, J. Rams, M. Ferrer (Rey Juan Carlos University, Spain) The application of metal matrix composites, with high contents of ceramic reinforcement in packaging for electronics is being investigated since the late 80s. The most important candidates within this family are the Al matrix composites reinforced with SiC particles because combine the most fitted CTEs, jointly a high thermal conductivity, reduced densities and outstanding values of specific strength and stiffness. Usually, they must be coated with alloys of Au or/and Ni, to protect the systems against corrosion and to facilitate the join with the electronic stages. Therefore, these new materials must fulfil the demanded requirements for plating. In this study, we focus mainly on the nickel plating for the surface preparation of the AlSiC substrates previous of the microelectronic components integration. The chosen method was the application of a continuous and adherent Ni-P coating on the AlSiC surface by electroless plating (EN), followed by the application of heat treatment to optimize the anti-corrosion and adhesion properties by means the change of coating microstructure. The content of SiC particles in the tested composite as substrate was high up to 75% volume, so activation pre-treatments were necessary to make the electroless plating possible and to enhance the interfacial adhesion between the nickel coatings and the substrate. Nevertheless a non activated EN plating method was also studied. Effects of EN plating conditions, such as temperature, pH and plating time on coating characteristics were evaluated, and the optimal conditions were chosen considering the microstructure and durability of the produced coatings. Environmental durability of the coatings was determined by tests of corrosion polarization, continuous saline fog and accelerated weathering. Mechanical properties of the deposited coatings were evaluated by means of nanoindentation and adhesion tests. Mechanisms of EN coating formation and growing were studied by means of AFM.
1:50 PM		G1-2-2 Characterization and Mechanical Properties of Electroless Ni-P-ZrO₂ Coatings P. Gay (Institute Microtechology of Surfaces, Switzerland); L.J.M. Limat (University of Besancon, France); P.A. Steinmann (University of Applied Sciences, China); J. Pagetti (University of Besancon, France) Ni-P-ZrO₂ composite coatings were produced using a classical electroless Ni-P and wet agent with added ZrO₂ particles. Plating parameters, particle concentration and the stirring rate of the bath were systematically investigated in order to calculate the incorporation rate Vp of the particles in the deposit. It was found that the relationships between Vp and stirring rate were related to the particle concentration in the bath. The morphology of deposits was studied by SEM and Vp was mesured by EDS. Moreover, it was established that the mechanical, tribological properties coating composite after heat treatment, like hardness, friction coefficient, wear resistance and corrosion resistance of composite Ni-P-ZrO₂ increased with the increase of incorporation rate Vp.
2:10 PM		G1-2-3 Evaluation of Chemical Mechanical Polishing for Fabrication of Tunable Photonic Crystals S.H. Ng (Singapore Institute of Manufacturing Technology, Singapore); W. Cheng, F. Chollet, D.L. Butler (Nanyang Technological University, Singapore) Traditionally, chemical mechanical polishing (CMP) has been used to remove semiconductor materials and metals such as silicon, silicon oxide, tungsten, aluminum and copper. Increasingly, polymers and elastomers are being employed as part of micro devices for structural purposes and for specific functions such as optical transmission. In MEMS and microfluidics, the availability of thick photoresists like the Microchem SU-8, the JSR THB and the Clariant AZ4620 has also been timely. There has been some interest in the utilization of CMP to removal polymeric materials from such hybrid devices. In this paper, we present the experimental study to characterise the performance of CMP on a polymer (SU-8) matrix with micro-pillars structure embedded and to evaluate the feasibility of CMP in achieving the desired material removal, roughness and flatness, which are required for our fabrication of two-dimensional (2D) photonic crystals within a polymer layer. The polymer thickness needs to match the thickness of the pillars quite precisely to confine the waveguiding in the PCs. Also, good planarity or flatness and low roughness are required to reduce scattering loss. The roughness, flatness and removal rate were measured under different parameters (force, speed) of CMP. In our experiment, micro silicon pillars are made by etching the silicon wafer using deep reactive ion etching. Photoresist SU-8 25 is spin-coated on the wafers at a speed of 1800 rpm, which results in approximately 25 µm of photoresist thickness. Experimental results show that it is possible to achieve satisfactory roughness and flatness and controllable removal rate. The average roughness is about 30 nm for a scan area of 5 µm x 5 µm, flatness is within 200 nm and removal rate is about 1 µm per minute under CMP parameters of 200 N and 150 rpm.