Through holes (THs) with different shapes were formed by laser drilling on a printed circuit board to evaluate the filling capability of two copper plating formulas. The shapes of these THs were cylindrical, V- and X-shaped. Two copper plating formulas, accelerator-free formula (AFF) and accelerator-containing formula (ACF), were employed in this work. The AFF contained only one organic additive and the ACF was composed of multiorganic additives. The electrochemical characteristics of the AFF were investigated by cyclic voltammetry, which could be utilized to explain the results of filling plating. The plating results showed that the cylindrical TH could be fully filled using AFF. However, the V- and X-shaped THs could be fully filled using ACF. TH and microvias could be simultaneously filled in one plating bath using the AFF. A filling mechanism based on an adsorption/consumption/diffusion mode was proposed to explain these plating results. (C) 2008 The Electrochemical Society. [DOI: 10.1149/1.2988134] All rights reserved

An economic and low toxicity gold plating process for bio-compatible device fabrication was investigated. A tiopronin-gold complex altered by mercaptothiodiazole or mercaptotriazole derivatives gave a form of the complex that could be reduced autocatalytically to enable electroless gold plating. Catalytic ca. 5 nm gold particles were selectively grafted into cycloolefin polymer and polyethylenenaphthalate film surfaces by adsorption of tiopronin-gold complex from solution into 20-30 nm deep ultra-violet light modified surface layers followed by reduction with sodium borohydride. Exposure of the catalyst adsorbed surfaces to baths composed of tiopronin-gold complex, mercaptothiodiazole and ascorbic acid resulted in selective electroless plating on the modified surfaces. Observation of the interface cross-section by transmission electron microscopy revealed that the gold deposits were physically anchored to the substrate by nanometer scale octopus trap like structures. Bio-compatible electronics for in vivo application represent an innovative field of medicine, offering ailment for life quality debilitating health complications. In the applications, sensors and transducers read or relay electronic input or output directly to or from living biological systems, like the brain. In retinal and cochlear neuroprosthesis, neural array implants facilitate direct stimulation of optic nerves with signals from a miniature camera, or direct stimulation of cochlear nerves with signals from a microphone. Research involving conscious neural control to operate external devices like prosthetic robots has also been undertaken. Neural electrode arrays also serve in therapeutic stimulation, bypass or diagnosis of specific neural systems in stroke and head injury patients and in patients suffering from Parkinson's disease, epilepsy, dystonia and severe clinical depression.1-10 Another important application for in vivo electronics is sensors and MEMS on catheters, allowing sensory feedback to the operator or manipulation of a MEMS device internally.11,12 Micro in vivo electronic sensors also offer a means of less invasive direct monitoring by wireless transmission or aid efficient pharmaceutical release. 13Non-toxic, non-allergenic and inert gold and platinum can be used as electrode materials; however toxins and allergens should be avoided in fabrication. Economic plating techniques that rely on bath components and construction materials that are toxic or allergenic introduce health risks and are therefore difficult to implement in fabrication. One approach for deposition of biocompatible gold patterns on poly(dimethylsiloxane) has been described using chemical plating and electrochemical etching. 14 In medicine, tiopronin (TPN) has been used therapeutically as a treatment of cystine disulfide related ailments like cystinuria and prophylaxis of renal cystine calculi, functioning based on an increase in solubility. 15,16 Tiopronin capped gold nanoclusters/nanoparticles (TPN-AuNP) have also been a center of attention in a broad spectrum...

Formation of interlayer connections in semiconductor and printed circuit board packaging can be accomplished by filling vias using three additive component electrolytic copper deposition. One of the essential additives that enables filling performance, bis-(3-sulfopropyl) disulfide (SPS) oxidized during electrolysis to give 1,3-propane disulfonic acid (PDS). In order to further elucidate the plating chemistry and improve performance, the electrochemical effects and the effects of PDS content in the electrolyte on resulting copper deposits were investigated. The crystallite structure and crystal structure transitions were investigated using X-ray diffractometry and the influence on physical properties of the deposit by internal strain analysis and extensibility. Combustioninfrared absorption spectrometry was used to determine the C and S content in the respective deposits. In all examinations, PDS content in the electrolyte was found to influence plating performance and deposit characteristics. The results suggested that PDS masked SPS and that co-deposition of PDS affected the deposit physical properties. In the late 1990s, package densification had been achieved by adoption of electrolytic copper sulfate via fill plating for interlayer connection in printed circuit board (PCB) manufacture. Since then, this technology has been used for fabrication of highly functionalized PCBs found in high-end electronic devices such as smartphones, and has been predicted to gain in importance. [1][2][3][4][5][6][7][8][9][10][11][12][13] The filling performance of the plating bath has been known to manifest from the action of organic additives.14-27 However due to additive decomposition, in industrial application periodic active carbon treatment and bath renewal is performed, where specifications have been determined by practical experience. With the more recent adoption of copper sulfate plating as an essential technology in semiconductor and high-end PCB manufacture, investigation of the bath aging phenomena and establishment of quantitative bath management methods may contribute to evolution of the technology.Due to the growing necessity for high performance via fill technology, decomposition mechanisms of the additives used in copper sulfate via fill plating and the effects of decomposition products on filling performance have been examined. The widely used additive bis-(3-sulfopropyl) disulfide (SPS) has been shown to decompose to 1,3-propane disulfonic acid (PDS) by oxidation during electrolysis. [28][29][30][31] Furthermore, detrimental effects of PDS on filling performance has been reported (Figure 1), where electrochemical analysis revealed that PDS countered the depolarizing effect of SPS on copper deposition (Figure 2). 32In consideration of the substantial influence of PDS on copper plating, analysis of the effects of PDS on the physical properties of copper deposits plated from baths containing PDS is necessary to achieve high performance from plating baths. To accomplish this, deposits from PDS containing baths we...

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Electrolytic copper via filling based on three additive component copper sulfate bath chemistry has been and currently is widely used in electronic packaging. Progression in copper sulfate plating chemistry is vital to development of smart phones among other devices. In order to further elucidate bath chemistry and possible methods to improve performance, degradation of the disodium 3,3'-dithiobis(1-propanesulfonate) (SPS) additive, which is employed as brightener, during copper via filling by electrodeposition and the influence of a byproduct on plating was investigated. Oxidative decomposition of SPS and formation of disodium 1,3-propanedisulfonate (PDS) at an IrO2 coated Ti insoluble anode during electrolysis was confirmed by NMR analysis. By addition to a fresh bath, PDS was then shown to compromise via filling performance. This study clarified the anodic oxidation of SPS to PDS under electrolytic filling conditions and that the PDS concentration correlated to the filling ability of the copper plating bath.