No abstract

There are three areas to consider when designing/implementing wire bonding to advanced ULSI damascene-copper chips having copper metallization and low dielectric-constant polymers embedded beneath them (Cu/LoK). These are: 1) the copper-pad top-surface oxidation inhibitor coatingmetal/organic/inorganic. (Current work involves evaluating the metal and inorganic options); 2) the low dielectric constant materials available; 3) under-pad metal/polymer stacks and support structures necessary for bondability and reliability. There are also various polymer/metallurgical interactions, resulting in long term packaged-device reliability problems, that can occur as the result of the wire bonding process over low modulus, LoK materials with barriers. These include cracked diffusion barriers, copper diffusion into the LoK polymers, cracking/spalling/crazing of the LoK materials, and bond pad indentation ("cupping"). Low-K polymer materials, with high expansion coefficients and low thermal conductivities, can also increase the stress and further extend any existing damage to barriers. Many of the above problems have previously been encountered when bonding to pads over polymers (MCM-D, polymer buildup-layers on PCBs, PBGAs, flex circuits, etc.), and they share some of the same solutions. Well designed LoK and the underpad structures should have no negative effect on bonding parameters and be invisible to the bonding process.

We describe a material that allows for high spatial resolution pH mapping through tissue using X-ray excited luminescence chemical imaging (XELCI). This is especially useful for detecting implant associated infection and elucidating how the local biochemical environment changes during infection and treatment. To acquire one pixel in the image, a focused X-ray beam irradiates a small region of scintillators coated on the implant and the X-ray excited optical luminescence spectrum is modulated by indicator dyes to provide a chemically sensitive measurement with low background. Scanning the X-ray beam across the implant surface generates high spatial resolution chemical measurements. Two associated challenges are 1) to make robust sensors that can be implanted in tissue to measure local chemical concentrations and specifically for metal orthopedic implants, and 2) to conformally coat the implant surface with scintillators and pH indicator dyes in order to make measurements over a large area. Previously, we have physically pressed or glued a pH-sensitive hydrogel sensor to the surface of an implant, but this is impractical for imaging over large irregular device areas such as an orthopedic plate with holes and edges. Herein we describe a chemically sensitive and biocompatible XELI sensor material containing scintillator particles (Gd 2 O 2 S:Eu) and a pH sensitive hydrogel coating using a roughened epoxy coating. A two-part commercial grade epoxy film was tested and found to make the coating of pH sensitive layer adhere better to the titanium surface. Sugar and salt particles were added to the surface of the epoxy as it cured to create a roughened surface and increase surface area. On this roughened surface, a secondary layer of diacrylated polyethylene glycol (PEG) hydrogel, containing a pH sensitive dye, was polymerized. This layer was found to adhere well to the epoxy-coated implant unlike other previously tested polymer surfaces which delaminated when exposed to water or humidity. The focused X-ray beam enabled 0.5 mm spatial resolution through 1 cm thick tissue. The pH sensor coated orthopedic plate was imaged with XELCI through tissue with different pH to acquire a calibration curve. The plates were also imaged through tissue with low pH region from a Staphylococcus aureus biofilm grown on one section. These studies demonstrate the use of pH sensor coated orthopedic plates for mapping the surface pH through tissue during biofilm formation using XELCI.

Atrial Fibrillation (AF) is a common disease that may occur in the heart, especially as we age. AF is due to non-normal myocardial ectopic foci that then causes an uncoordinated atrium contraction. This effectively reduces the atrial kick to the ventricles, which can account for up to 20% of ventricular filling. While not an immediately fatal disease, it can cause reduced quality of life for patients and also puts them at increased risk for stroke. AF as a disease, is expected to affect over 50 million people in the United States alone by 2050 [1].

Glassy (amorphous) metals have some unique properties that may render them attractive candidates for the coating of metal-implant bearing surfaces. Metastable glasses of metal alloys, with uniform compositions and homogeneous structures that are not attainable under usual quasi-equilibrium processing conditions, can often be made to produce alloys with exceptional corrosion resistance and high hardness. The absence of secondary phases argues for resistance to abrasive and asperity-initiated wear. One method of producing glassy alloys is electrodeposition. Glassy coatings from nanometers to millimeters thick can be produced. Unique compositions, such as single-phase, amorphous, cobalt-phosphorus alloys [3,9] or glass-like coatings of cobalt-chromium-carbon [6,7] alloys (those referred to by this name throughout the text have layers of amorphous chromium and cobalt that are known to have carbon dispersed throughout the chromium), can be made.