Metal-polymer composites for molded interconnect devices (MID)
The market constantly demands the extension of the functional features of electronic devices and this leads to the application of new materials. Polymers represent an innovative potential due to their favorable properties for packaging. The MID technology represents a new growing potential in the electronic packaging (Forschungsvereinigung and Feldmann, 2004). Metal-polymer bonds are the key issue for this technology. For the quality and reliability of a metal-polymer component the adhesive strength of the metal-polymer composite is a critical factor. Normally, it is usual to pretreat either the polymer or the metal surface by physical or chemical methods to promote strong interactions between metal and polymer. Among the various pretreatment processes the plasma modification of the polymer surface wins a key position (Friedrich et al., 2002). Reactions between plasma species and polymer surface make it possible to form polar groups on the polymer surface. Polar chemical groups like C-OH, CO, CHO, COOH are reactive chemically, can form chemical bonds and therefore can cause an increase of the surface energy and the wetting quality. This work deals with investigation results of the adhesion between polyamide 6 and polyamide 6.6 and typical of MID Technology metals like copper and silver. The following procedure shows the methods and opportunities for the improvement and characterization of the metal-polymer adhesion.
Adhesion of Thermoplastics to Materials used in Electronics (Tin)
Electronics manufacturers are under legislative pressure to find alternatives to non-recyclable thermoset PCBs for production of electronics. A candidate process being developed at Loughborough University uses injection over-moulding to embed components in a polymer matrix, prior to interconnection by electroplating of the moulding or by printing of a conductive ink. Crucial to the manufacturing quality and reliability of products made using the process will be the adhesion/interaction between the metallisation surfaces, such as tin, of the electronic components and the overmould. In this work, a set of experimental procedures developed to study the interaction forces and adhesion between tin and thermoplastics in the melt and in the solid state are reported. Direct adhesion force measurements in the solid state will be undertaken using Atomic Force Microscopy (AFM) with tin functionalized probes. A novel method of functionalisation using a Focused Ion Beam (FIB) apparatus is described. Trials of a Wilhelmy plate method for measuring the contact angle between thermoplastic melt and tin foils are also described, together with a wetting force method which is in development. Finally trials of in situ injection moulding methods for creating artifacts suitable for tensile adhesion strength measurements are described.
Evaluation of buckling load and dynamic performance of steel shear wall retrofitted with strips made of shape memory alloy
One of the most imperfections of the steel shear wall is out of plane displacements that cause severe damage in both structural and non-structural elements. In this paper, the effects of shape-memory alloys on steel shear walls are investigated. First, a numerical analysis using the finite element method in ABAQUS software has been carried out according to an experimental test. The results of the numerical analysis have been verified with experimental results. Next, shape-memory alloy fibers have been added vertically and horizontally to various parts of the steel shear wall. The results show that retrofitting with the shape-memory alloy reduces the out-of-plane displacement of the steel shear wall under both cyclic and seismic loadings. Besides, the buckling load in the steel shear wall increases when it is retrofitted with the shape-memory alloy. Also, the total out-of-plane movement (accumulated absolute displacements) of the steel shear wall and non-structural damage are controlled by the characteristic of a shape-memory alloy material called “super-elastic”.