Highly Dispersive Adsorption of Ag Nanoparticle Catalyst for Electroless Copper Plating

Koishikawa

et al. 2014

J. Electrochem. Soc.

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Ag nanoparticle catalysts having a Ag@SnO 2 core/shell structure were adsorbed from their colloidal solution on the smooth epoxy substrates conditioned with poly(diallyldimethylammonium chloride). The amounts and morphology of the adsorbed catalysts suggest the uniform monolayer adsorption and the formation of the agglomerated two-dimensional domains comprising several nanoparticles. Citrate acceleration of the adsorbed catalysts dissolved the SnO 2 shell of the catalysts, and somewhat increased the size of the agglomerated domains and the surface roughness of the substrate with adsorbed nanoparticles. Electroless Cu deposition rate on the substrates with adsorbed catalysts went through a maximum at the initial stage, and then decreased to its constant value. Isolated Cu particles were deposited at the initial stage, and they coalesced to form the continuous films after the deposition rates reached the constant value. On the substrates without the citrate acceleration, Cu particles were deposited only at the beginning, due to the desorption of catalysts into the plating bath. The citrate acceleration prevented the desorption, and hence increased the catalyst availability. This led to the higher deposition rate and the faster morphology development at the initial stage because of the rapid and progressive deposition of Cu particles.

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Section: Resultsmentioning

confidence: 99%

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confidence: 99%

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confidence: 99%

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Initial Stage of Electroless Cu Deposition on Epoxy Substrate Catalyzed with Ag Nanoparticles

Koishikawa

et al. 2014

J. Electrochem. Soc.

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“…Our preliminary study has shown that PDDA promotes the Ag nanoparticle adsorption onto a glass substrate. 15…”

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confidence: 99%

Adsorption Promotion of Ag Nanoparticle Using Cationic Surfactants and Polyelectrolytes for Electroless Cu Plating Catalysts

Sugaya

et al. 2010

J. Electrochem. Soc.

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Ag nanoparticles were adsorbed onto epoxy and fluorine-doped tin oxide ͑FTO͒ glass substrates by dipping them into a Ag nanoparticle colloidal solution to catalyze the substrate for electroless Cu plating. Before the Ag nanoparticle adsorption, the substrates were conditioned with either a cationic surfactant, stearyltrimethylammonium chloride ͑STAC͒, or a cationic polyelectrolyte, poly͑diallyldimethylammonium chloride͒ ͑PDDA͒, both having quaternary amine headgroups. The adsorbed Ag nanoparticles catalyzed the HCHO oxidation reaction, thereby allowing the electroless Cu deposition reaction to start. For both the epoxy and the FTO glass substrates, conditioning with the concentrated PDDA solution having a 100 ϫ 10 −3 mol L −1 quaternary amine concentration was the most effective in producing the largest amounts of Ag nanoparticles to be adsorbed and in providing the fastest initial deposition rate of the electroless Cu plating. When the diluted conditioners were used, a comparison between the diluted STAC and PDDA showed that STAC was the more effective conditioner for the epoxy substrates, while PDDA was more effective for the FTO glass substrates. The effectiveness of STAC was attributed to the strong hydrophobic interaction with the epoxy substrate surface. However, the effectiveness of PDDA was attributed to the strong electrostatic interaction with the FTO glass surface.Electroless plating on polymer substrates is widely used in the automotive and electronics industries. 1 In particular, electroless Cu plating on epoxy or polyimide substrates is a crucial process during printed wiring board ͑PWB͒ manufacturing. 2 Many stages during the pretreatment for the electroless plating are required, such as surface roughening, substrate conditioning, catalyzing, and accelerating. The catalyzing process is essential to initiate the electroless plating.Polymer substrates are usually catalyzed by the adsorption of Pd/Sn mixed colloids from a solution. 3 The Pd/Sn mixed colloidal catalysts, however, do not appreciably adsorb on the epoxy surface; 4 therefore, a conditioning process for the substrates is needed. Luke 5 pointed out that cationic surfactants neutralize the negative charge of the epoxy surface and promote the adsorption of the negatively charged Pd/Sn mixed colloidal catalysts. It has also been reported that cationic polyelectrolytes are effective as substrate conditioners for introducing a positive surface charge. 4,6 Recent trends in the PWB design, which require electroless Cu plating to fabricate the narrower circuit lines at a lower cost, have revealed some disadvantages of the Pd/Sn mixed colloid catalysts. 7 For example, residual Pd beneath the photoresist permits the electroless Cu to be deposited between the circuit lines and causes an insulation decrease and short circuits. 4 In addition, the material cost of Pd has become increasingly expensive in recent years. Ag and Ag nanoparticles are effective as alternative catalysts to the Pd/Sn mixed colloids. [7][8][9] In a previous paper, 10 we have propo...

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Activation of Ag Nanoparticle Catalysts and Stabilization of Electroless Cu Plating Bath by Sodium Citrate

Sugaya

Journal of The Surface Finishing Society of Japan

et al. 2010

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