The global trend to eliminate lead from electronic devices is driven by legislative and marketing pressures based on environmental, health and social concerns on the cumulative effects of lead in waste streams. Tin and tin-rich alloys are the forerunning replacements for tin-lead solders.However, pure tin electrodeposits have a tendency to form tin whiskers that may cause short-circuiting, metal vapor arcing and failure of the component. The major cause of whisker growth is thought to be compressive stress in pure tin deposits after DC plating. Faraday Technology, Inc. has developed an electrically mediated electrochemical process for depositing lead-free solders, based on non-steady state electric fields to control the deposition process and consequently the physical properties of the deposit. Results of electrically mediated tin deposits are presented and compared to DC deposits in terms of grain size, internal stress type/magnitude and surface roughness.

Many factors contribute to uniform electrochemical processing in industrial applications. The electrochemical cell provides the foundation for the process and as such an effective geometry is critical to obtain desired properties and to maximize process efficiency. A non-traditional cell geometry has been engineered to provide a uniform boundary layer thickness to dampen uneven localized current distributions and promote consequent plating uniformity for full size printed circuit board panels. This tank has been extensively characterized for thickness distribution under direct current plating conditions and compared with commercial plating cell geometries that utilize both educator flow and/or air sparging agitation. Compared to the conventional cells, the variation of copper deposit thickness across the panel in the non-traditional is significantly less, and meets the requirement of the printed circuit board industry. Cell geometry, panel features and operating parameters have been modeled and show good agreement with experimental data. The results of this study suggest that through hole patterns on a printed circuit board increase the non-uniformity of the boundary layer thickness. In the manufacture of printed circuit boards (PCBs), copper electrodeposition plays an important role in the final product's reliability and performance. Deposits that are non-uniform may induce reliability issues and ultimately hamper device performance. Furthermore, copper deposits with columnar grain structures are prone to cracking and may result in device failure. As such, implementation of a robust process that provides high levels of uniformity and the desired grain structure promotes higher throughput and higher quality products, decreasing manufacturing costs.Processing conditions such as agitation mechanism, electrolyte composition and electric field parameters control the properties of copper deposits as well as governing the uniformity of metallization over the PCB surface. Conventionally, much emphasis has been placed on electrolyte composition, specifically use of organic additives (in parts-per-million (ppm) concentrations), as a means to help control copper deposit uniformity and improve throw/fill within the micron size features. However, regardless of the electrolyte composition used, optimization of the plating cell geometry and agitation mechanism may greatly enhance the uniformity achieved in the copper electrodeposition process.In traditional plating cells, air sparging, and more recently eductor flow, is used as the primary agitation mechanism. Other agitation schemes (lateral oscillation, knife-edge oscillation and vibration of the panel) have been added in attempts to achieve a time averaged boundary layer thickness, which yields uniform current distribution and consequently uniform plating thicknesses. Another technology for controlling solution flow in a plating cell uses a paddle to create a turbulent wave of electrolyte that moves back and forth across the surface of the workpiece, 1 in an attempt to cre...

Plating cell geometry and uniform solution flow are the foundation for a uniform plating process for printed circuit board and electronic packaging applications. Currently, the plating cells used for copper metallization for these applications utilize a number of agitation methods to reduce the thickness of the diffusion boundary layer as well as fostering solution movement into and through small features. In order to achieve a uniform diffusion boundary layer, a requirement for uniform plating thickness, a uniform diffusion layer must be established by flow/agitation method within the cell. A novel plating cell geometry that provides a thin uniform diffusion boundary layer and consequently uniform plating thickness is disclosed. Results from cell characterization in terms of diffusion boundary layer thickness and deposit thickness uniformity is also reported.

This paper will discuss progress in development by Faraday of an integrated technology to recover and recycle metals from electrochemical machining (ECM). ECM is suited for low mass removal, high value-added manufacturing steps that cannot be easily performed using conventional machining, whether due to workpiece material properties, tooling limitations, or high surface integrity requirements. Sludge byproducts formed during conventional ECM processes are difficult to recover from the electrolyte, and discarding the sludge results in the loss of potentially valuable “waste” metal as well as entrained electrolyte salts and water. Results will be presented demonstrating a “Recycling ECM” technology, which is based upon patented cell designs and pulsed waveforms, targeting alloys including: C18000 copper, SAE4150 alloy steel, 316L stainless steel, and INCONEL® 718. These metals were machined in electrolyte to concentrations between 800-3500 ppm and subsequently recovered by electrowinning in solid, metallic form devoid of hydroxides/hydrated oxides, without intermediate electrolyte processing.

Faraday Technology, Inc. has developed a number of novel processing cells based on an innovative cell geometry that results in high levels of processing uniformity. This geometry is comprised of a number of unique attributes for the uniform electrodeposition or electroetching of metals across large planar substrates as well as fine features that are utilized for printed circuit board (PCB) and electronic packaging applications. The cell has been characterized with a 457 mm x 610 mm substrate. A coefficient of variation of 5.3% was achieved in FARADAYIC® ElectroCell over a 457 mm x 610 mm substrate; these values were compared to a commercial system. This cell design has been applied to a number of industrial processes, including electroplating of copper, trivalent chromium and platinum and electroetching of copper for interlayer circuit board applications. The current work outlines the importance of various cell components and resulting uniformity.