Electroless copper plating compositions and methods for electroless plating copper on substrates

Abstract

Stable electroless copper plating baths include pyridinium compounds to improve rate of copper deposition on substrates. The copper from the electroless plating baths can be plated at low temperatures and at high plating rates.

Description

FIELD OF THE INVENTION[0001]The present invention is directed to electroless copper plating compositions and methods for electroless plating copper on substrates, wherein electroless copper plating has a high electroless copper plating rate at low temperatures and the electroless copper plating compositions are stable. More specifically, the present invention is directed to electroless copper plating compositions and methods for electroless plating copper on substrates, wherein electroless copper plating has a high electroless copper plating rate at low temperatures and the electroless copper plating compositions are stable, wherein the electroless copper plating compositions include pyridinium compounds or salts thereof.BACKGROUND OF THE INVENTION[0002]Electroless copper plating baths are in widespread use in metallization industries for depositing copper on various types of substrates. In the manufacture of printed circuit boards, for example, the electroless copper baths are used...

AI Technical Summary

Benefits of technology

The patent is about a new way to increase the speed of electroless copper plating at low temperatures. This is done by using pyridinium compounds, which help the plating process to work better. The method also allows for better coverage of holes in materials and reduces the amount of chemicals used, making the process more stable and cost-effective. The pyridinium compounds can be used in high concentrations without affecting the performance of the plating composition, which makes it easier to manage and control.

Problems solved by technology

Control of the baths to maintain high plating rates with substantially uniform copper deposits over long periods of time is exceedingly difficult.

In general, electroless copper plating rates of equal to or greater than 0.6 μm / 5 min. are highly desirable (preferably desired for current horizontal plating applications) but rarely achieved, especially at low electroless plating temperatures, such as below 40° C. Consumption and replenishment of bath components over several metal turnovers (MTO) can also contribute to bath instability, for example, through the buildup of side products.

Therefore, such baths, and particularly those having a high plating potential, i.e. highly active baths, tend to become unstable and to spontaneously decompose with use.

Such electroless copper bath instability can result in non-uniform or discontinuous copper plating along a surface.

Such discontinuity of the copper deposit can ultimately lead to mal-functioning of any electrical device in which the defective printed circuit board is included.

However, many stabilizers lower electroless copper plating rates, and, also, at high concentrations can be catalyst poisons, thus reducing plating rates or inhibiting plating and compromising the performance of the plating bath.

Low plating rates are detrimental to electroless copper plating performance.

However, increasing the operating temperatures can decrease the stability of the electroless copper bath by increasing the buildup of byproducts as well as increasing the rate of generation of byproducts by side reactions, thus negating some of the effects of increasing the stabilizer concentration.

Furthermore, a more stable formulation, which is afforded by lowering the working temperature, results in lower maintenance requirements.

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