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Plating bath composition for electroless plating of gold and a method for depositing a gold layer

a plating bath and electroless technology, applied in the direction of metallic material coating process, liquid/solution decomposition chemical coating, coating, etc., can solve the problems of insufficient stability of gold plating bath, many challenges unresolved, and undesirable, and achieve high the effect of improving the stability of electroless aqueous gold plating bath and sufficient plating ra

Pending Publication Date: 2020-07-23
ATOTECH DEUT GMBH
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

The present invention provides a stable electroless aqueous gold plating bath that has a longer lifespan compared to existing baths. Additionally, the invention allows for high plating rates, resulting in more economically feasible processes. The aqueous gold plating baths form homogeneous deposits with little layer thickness diversion, regardless of the substrate size. The patent reference several products available from Atotech Deutschland GmbH, such as Pallabond® CLN, Pallabond® ME, PalleBond® Pre Dip, PallaBond® Aktivator, and PallaBond® ACT V3 STD.

Problems solved by technology

Even though these techniques have been established some time ago, there are still many challenges unresolved.
Such challenges are the corrosion of nickel layers which are placed between gold and copper lines (nickel corrosion) and insufficient stabilities of gold plating baths which is highly undesirable due to the cost of said baths.
Due to the minuscule sizes of electrical components nowadays, it is not possible to use electrolytic processes which require electrical connections to the substrates.
This is a distinct disadvantage of immersion plating because deposition of thicker layers is normally limited by the layer porosity.
However, such gold plating solution lack sufficient stability and plating rate and are thus not applicable in industrial processes (see example 4).
But again, the plating baths described therein lack plating rate and stability (see example 4).

Method used

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  • Plating bath composition for electroless plating of gold and a method for depositing a gold layer
  • Plating bath composition for electroless plating of gold and a method for depositing a gold layer
  • Plating bath composition for electroless plating of gold and a method for depositing a gold layer

Examples

Experimental program
Comparison scheme
Effect test

example 5 (

Inventive): Stability and Life-Time of Gold Plating Baths

[0078]The gold plating baths of examples 1 to 3 were used to deposit gold on substrates for a prolonged time. The stability of the gold plating baths and the plating rate were monitored over time. If a plate-out occurred the solution was filtered and re-used. Every day during the experiment, the pH value was measured and adjusted to 7.1 with KOH and / or H3PO4 if necessary. During plating, the source of gold ions, the source of cyanide ions and the plating enhancer compound were continuously replenished.

[0079]Table 6 provides information on the stability of gold plating baths containing different plating enhancer compounds. The plating baths were visually inspected directly after make-up (day 0) and for one week on a daily basis. The gold plating baths were also used to deposit gold on substrates every day during this test period. These results are summarized in Table 7. The values given in said table are the deposit thickness i...

example 6 (

Inventive): Ratio of Plating Enhancer Compound to Reducing Agent for Gold Ions

[0081]A gold plating baths containing the following components was prepared by dissolving all components in water:

Water100 mLpotassium hydroxide12.4 g / LN1,N2-di-iso-propylethane-1,2-diaminesee table 8complexing agent89 mmol / Lsulphur based stabilising agent1.5 mg / Lthallium ions4.4 mg / Lpotassium cyanide 42 mg / Lformaldehyde 0.3 g / Lgold ion source1.47 g / L

[0082]The gold plating bath was adjusted with KOH / H3PO4 to a pH value of 7.1. A substrate was subjected to the process as described in table 1 wherein the electroless gold plating step was carried out for 10 min only.

[0083]The process was repeated several times with different gold plating baths containing increasing amounts of plating enhancer compounds whereby the amount of reducing agent for gold ions was kept at the same level. The results are provided by table 8.

TABLE 8Ratio of plating enhancer compound and reducing agent for gold ions.Molar ratio of N1,N2...

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Abstract

An electroless aqueous gold plating bath, comprising at least one source of gold ions and at least one reducing agent for gold ions, characterized in that it comprises at least one ethylenediamine derivative as plating enhancer compound according to formula (I)wherein the residues R1 and R2 comprise 2 to 12 carbon atoms and are selected from the group consisting of branched alkyl, unbranched alkyl, cycloalkyl or combinations thereof wherein the individual residues R1 and R2 are the same or different and a method of depositing of gold. The electroless aqueous gold plating bath is suitable to provide soft gold layers useful for wire bonding and soldering applications which are required for electronic components.

Description

FIELD OF THE INVENTION[0001]The present invention relates to electroless aqueous gold plating bath compositions for electroless plating of gold layers onto a substrate and a method for depositing gold. The plating bath is particularly suitable in the manufacture of printed circuit boards, IC substrates, semiconducting devices, interposers made of glass and the like.BACKGROUND OF THE INVENTION[0002]Gold layers are of paramount interest in the manufacturing of electronic components and in the semiconductor industry. Gold layers are frequently used as solderable and / or wire bondable surfaces in the manufacture of printed circuit boards, IC substrates, semiconducting devices and the like. Typically, they are used as a final finish before soldering and wire bonding. In order to provide electrical connections of sufficient conductivity and robustness between the copper lines and wires that are bonded thereto while providing a good strength for wire bonding, there are various layer assembl...

Claims

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Application Information

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IPC IPC(8): C23C18/44
CPCC23C18/44C23C18/1844C23C18/1637
Inventor SPREEMANN, ROBERTNÖTHLICH, CHRISTIANGRUNOW, SABRINAVOLOSHYN, DMYTROJANSSEN, BORIS ALEXANDERLAUTAN, DONNY
Owner ATOTECH DEUT GMBH
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