WO2007038915A1

WO2007038915A1 - Passivator and lubricant for gold, silver, and copper surfaces, and method for using the same

Info

Publication number: WO2007038915A1
Application number: PCT/DE2006/001739
Authority: WO
Inventors: Uwe Landau; Ingo Jolk
Original assignee: Otb Oberflächentechnik In Berlin Gmbh & Co
Priority date: 2005-10-05
Filing date: 2006-10-04
Publication date: 2007-04-12
Also published as: DE502006003913D1; DE102005047843A1; EP1969157A1; ATE433000T1; EP1969157B1

Abstract

Disclosed is a passivator and lubricant for gold, silver, and copper surfaces and corresponding alloy surfaces. Said passivator and lubricant comprises an aqueous emulsion with a linear fatty alcohol as an emulsifier, especially at least one C12-C14 fatty alcohol containing about 8 ethoxy units. Preferably, the concentration of the fatty alcohol amounts to about 25 to 35 g/l. An organic hydrophobic thiol compound, particularly hexadecanethiol and/or octadecanethiol, is dissolved in said aqueous emulsion as an inhibitor at a preferred concentration of about 6 to 12 g/l. In order to prepare said emulsion, the emulsifier is first dissolved in a certain amount of water. Said solution is then thoroughly mixed and is preferably heated to a temperature ranging from about 42 to 49°, whereupon the inhibitor is added. The resulting solution is then further mixed until a uniform milky emulsion is obtained. Silver and copper surfaces that are to be passivated are initially treated with said aqueous emulsion and are then rinsed with water, the temperatures of the emulsion and the water being selected so as to exceed the melting point of the inhibitor.

Description

Passivation and lubricant for GoId. Silver and copper surfaces and

Method for its use

The present invention relates to a passivation and lubricating agent for gold, silver, and copper surfaces as well as corresponding alloy surfaces. It also relates to a manufacturing method of this composition and a method of its use.

As a result of the formation of poorly soluble silver sulfide layers, silver and silver alloy surfaces generally become more or less spotty in use after a short time in use. This tarnishing is not only undesirable from an aesthetic point of view, but also has a negative effect on the application properties. In electrical or electronic applications, for example, it leads to an undesirable deterioration of the solderability of silvered components and to an undue increase in the contact resistance of silver contact materials. In silver-containing electrical connectors also makes an undesirable high coefficient of friction often quite disadvantageous noticeable.

The use of thiols, in particular hexadecanethiol, has long been proven as protection against tarnishing and for reducing the friction on silver surfaces (see, for example, the review article "Tarnishing and friction reduction with thiols on silver surfaces" by D. Kartlüke, RR Scholz, MJ Funk and ME Baumgärtner in Galvanotechnik , D-7967 Saulgau, 83, (1992) No. 6), the thiols are in this case first in a suitable solvent, such as chlorinated hydrocarbons, alkanes or alcohols, dissolved and then, for example by simply immersing the silver surfaces to be treated in the solution In order to prevent the tendency of undesired crystallization, the correspondingly treated surfaces are then rinsed, usually in the same solvent in which the thiol is present in the passivating agent.The thiol coatings can also be applied to water-based emulsions be applied surfaces. Although aqueous emulsions are preferable from an environmental point of view, good thiol coatings are usually the most difficult to achieve with them.

In order to prevent unwanted tarnishing of silver and copper surfaces, it is known from EP 0 492 487 B1 to passivate the surfaces by applying an aqueous emulsion with a pH of 1-10 and subsequent rinsing with water. The temperatures of the emulsion and the water are chosen in this case, that they are above or below the inhibitor melting point. The known emulsion comprises 2 to 20 g / l of an emulsifier, 2 to 20 g / l of a hydrophobic inhibitor and 0 to 2 g / l of an anionic or nonionic surfactant. The emulsifier comes from the group of branched alkoxylated - preferably ethoxylated - fatty alcohols. with 4 to 20 carbon atoms and a degree of alkoxylation of 2 to 10. The initiator used is a long-chain aliphatic thio compound having at least one SH group and at least 12 C atoms from the group of thio alcohols and their esterification products.

The object of the present invention is to provide a novel, improved passivation and lubricant for gold, silver and copper surfaces as well as corresponding alloy surfaces, which is not only very simple, inexpensive and quick to produce and convenient and safe to use, but also a ensures lasting and reliable tarnish protection. The agent sought should be as environmentally sound as possible and in particular suitable for electrical or electronic applications. It should therefore not only form a thin and stable passivation layer, but also lead to a significant reduction in the friction value of gold, silver and copper surfaces and of corresponding alloy surfaces, without causing an increase in contact resistance. The object is also to provide a manufacturing method for the agent sought and a method for its application.

This object is achieved by a passivating and lubricating agent according to claim 1, a manufacturing method according to claim 11 and an application method according to claim 16. Preferred embodiments or variants of the method can be found in the respective dependent claims.

The passivating and lubricating agent according to the invention comprises an aqueous emulsion with at least one unbranched fatty alcohol as emulsifier. The emulsifier comprises in this case preferably one or more C ₈ - Ci _S fatty alcohols having from about 6 - 10 ethoxy units, preferably C ₁₂ - C ₁₄ fatty alcohols having from about 8 - 10, in particular 8 ethoxy units. Its concentration is preferably about 25-35 g / l, in particular about 25-30 g / l.

In this aqueous emulsion, an inhibitor is dissolved, which comprises an organic hydrophobic thiol compound, preferably a hexa and / or octadecanethiol. Its concentration is preferably about 6 to 12 g / l, more preferably about 8 to 10 g / l. The pH of the emulsion according to the invention is typically between about 4 and 9, in particular between about 6 and 7.

The operating temperature of the emulsion according to the invention in treating a part or workpiece to be passivated is preferably about 42 to 49 ⁰ C, wherein a temperature value of about 46 ⁰ C proves to be particularly favorable.

To prepare this passivation agent and lubricant according to the invention, the emulsifier is first dissolved in water, in particular deionized water (DI water). This solution is now thoroughly mixed and preferably heated to a temperature of about 42 - 49 ⁰ C. Optionally, however, the emulsifier can also be stirred into already appropriately heated water. Subsequently, the inhibitor is added. The resulting solution is then further mixed until a uniform, milky, ready-to-use emulsion is formed. Optionally, the heating can also take place only after the addition of the inhibitor or may even be omitted altogether.

The emulsifier is preferably first dissolved in only about 85-95%, in particular about 90%, of the required amount of water. The remaining amount of water is added only after the metered addition of the inhibitor.

The pH of the emulsion according to the invention is preferably adjusted to a value between about 4 and 9, in particular between about 6 and 7, by addition of phosphoric acid or sodium hydroxide solution.

To be passivated surfaces are preferably first degreased and cleaned before treatment with the passivation and lubricating agent according to the invention initially to eliminate any adhering fat and unwanted oxide layers. Sufficiently clean surfaces, e.g. freshly silvered and rinsed surfaces, but can also be treated without additional degreasing and cleaning directly in the manner according to the invention described below.

The clean surfaces are first treated in a manner known per se with the passivation and lubricant according to the invention and then rinsed off with water. The temperature of the passivating agent is chosen so that it is above the inhibitor melting point. In contrast to the known state of Technique according to the invention, the temperature of the water is chosen so that it is above the inhibitor melting point.

For the passivating agent, a use or treatment temperature between about 42 and 49 ⁰ C has proved to be particularly advantageous, with the optimum temperature value is about 46 ⁰ C. For heating the passivation and lubricant to the desired operating temperature, a suitable heating device, such as a simple immersion heater made of titanium, quartz or Teflon, can be used. For rinsing, preferably water with a temperature of about 55-65 ⁰ C is used.

Treating the surfaces preferably comprises a first immersion in the passivating and lubricating agent for typically about 7 seconds to 2 minutes, more preferably about 7 seconds to 30 seconds, as this can provide particularly reliable and durable passivation. For special applications, however, longer dipping times may prove useful. For the passivation agent and lubricant according to the invention, a bath container made of polyethylene, polypropylene, rigid PVC or the like is preferably used here. To ensure good passivation during immersion, the parts to be treated are preferably moved back and forth in the passivating agent. Alternatively or in addition to this, however, a relative movement between the surfaces and the passivation and lubricant can also be generated by exciting a suitable liquid movement in the treatment bath.

However, the surface treatment may optionally also include spraying or painting with the passivating agent and lubricant of the present invention or by any other suitable aqueous emulsion application process.

Rinsing preferably comprises a first rinse cycle at a water temperature of about 55 - 65 ⁰ C. The surfaces may in this case for example simply for about 5 - s are immersed in a static rinse 10th The substance added to the first economy sink can be used to supplement the process bath.

The surfaces can then be rinsed a second time, for example in a flow rinse, with water that has about room temperature. Used rinse water can be subjected to purification of cyanide poisoning followed by neutralization.

Finally, the passivated surfaces are preferably dried with hot air or by blowing off with compressed air. The drying can be carried out for example for about 4 to 6 minutes at about 75 to 85 ^° C. in a centrifuge.

The quality of the applied passivation layer can be tested by second immersing the surfaces in an ammonium sulfide solution. The passivated surfaces must not start for a certain immersion time. Preference is given to using an approximately 1 to 3% active ammonium sulphide solution which has been used for a maximum of 10 minutes beforehand, in which the surfaces must not start for about 30 to 45 seconds. If dark spots appear on the passivated surfaces, the treatment or passivation bath should be renewed or supplemented with concentrate.

The passivating and lubricating agents according to the invention are distinguished by very good, durable and reliable passivation and lubricating properties with very short treatment times. It is particularly suitable for electrical and electronic applications. Because it is water-based and contains no halogenated hydrocarbons or chromium compounds, it is also a fairly environmentally friendly product. The agent can be made ready for use by the user simply by stirring appropriate commercially available inhibitor and emulsifier concentrates in water and is therefore quite inexpensive, easy, quick and easy to produce. It can be applied by simply dipping, spraying or painting the surfaces and is therefore also easy and safe to use.

The present invention will now be exemplified again by way of a preferred embodiment of the invention.

To prepare a passivating treatment bath according to the invention, first a carefully cleaned bath container made of polyethylene, polypropylene, rigid PVC or the like is filled with deionized water (DI water), but initially only 90% of the desired total treatment bath volume of water is added. Per liter of treatment bath of a nonionic surfactant are added as the emulsifier then 30 ml (ie, about 27 g / l) consisting of a defined mixture of unbranched C ₂ - is C ₁₄ fatty alcohols with 8 ethoxy units. This solution is then thoroughly mixed for about 1 h and heated to 46 by means of a titanium, quartz or Teflon immersion heater ⁰ C heated or heated. Per liter of treatment bath 10 ml (ie about 8 g / l) hexadecanethiol (Ci ₆ H ₃₃ SH, melting point: about 18 - 20 ⁰ C) are then added with stirring as an inhibitor, the resulting solution is then stirred until a forms a uniform milky emulsion. This is then filled by adding the remaining 10% of deionized water to the total treatment bath volume. The pH of the emulsion is adjusted to an optimum value between 6 and 7 by addition of phosphoric acid or sodium hydroxide solution.

With the attached treatment bath or the emulsion can be treated per liter about 10 m ² surface. The actual consumption of emulsion depends on its composition, the respective process sequence and on the geometry of the parts or workpieces to be treated.

Since the surfaces of the passivated parts should be as fat and oxide-free as possible when applying the passivation layer, they are first cleaned. However, freshly silvered or gilded, clean surfaces can also be treated directly.

The clean parts or workpieces are immersed in the treatment bath or emulsion to apply the desired passivation layer for a given treatment time. This treatment time is chosen appropriately depending on the geometry of the parts. It is typically about 7 - 3O s. However, in exceptional cases, longer treatment times of up to about 2 minutes may be required to achieve proper passivation. To improve the surface contact, the parts are moved back and forth on immersion in the treatment bath. Alternatively or additionally, however, a relative movement between the treatment bath and the parts to be treated can also be generated by exciting a bath flow.

After the treatment in the treatment bath, the parts are first immersed for about 5 to 10 s in a stationary sink with 60 ^C C warm water and then rinsed in a flow rinse at room temperature with water.

The rinsed parts are then finally dried for about 5 min at about 80 ⁰ C for in a centrifuge. However, drying may also be accomplished, for example, by blowing off the surfaces with compressed air or by any other suitable conventional drying method. Finally, to verify that the passivation has taken place, the treated parts are submerged in a 2% ^' active ammonium sulfide solution not more than 10 minutes previously used, in which they must not start within 45 seconds.

The described passivation process according to the invention forms a very thin, firmly adhering, transparent, durable protective film on gold, silver or copper surfaces, by means of which it is reliably protected against tarnishing for several months. The gloss and the color of the surfaces are retained even after the passivation according to the invention. The good material properties of the parts, e.g. the contact resistance and the conductivity are changed only slightly.

The applied passivating protective film also has good lubricating properties, which is particularly advantageous, for example, in certain electrical connectors. Due to the applied passivating protective film, therefore, the insertion and removal forces in electrical connectors can be significantly reduced.

The rinse water, which can accumulate by carryover with silver and cyanide ions, is subjected to cyanide poisoning with subsequent neutralization after use. The spent emulsion, however, is fed to a wastewater treatment.

Claims

claims

1. passivating and lubricating agent for gold, silver and copper surfaces and for corresponding alloy surfaces with an organic hydrophobic thiol compound as an inhibitor and a water-soluble emulsifier emulsified in water, characterized in that the emulsifier comprises an unbranched fatty alcohol.

2. passivating and lubricating agent according to claim 1, characterized in that the unbranched fatty alcohol comprises 8 - 16 carbon atoms with 6 - 10 ethoxy units.

Passivating and lubricating agent according to claim 2, characterized in that the unbranched fatty alcohol comprises 12-14 carbon atoms with 8 ethoxy units.

4. Passivierungs- and lubricant according to any one of the preceding claims, characterized in that the concentration of the emulsifier 25 - 35 g / l.

5. passivating and lubricating agent according to any one of the preceding claims, characterized in that the inhibitor comprises hexa and / or octadecanethiol.

6. Passivierungs- and lubricant according to any one of the preceding claims, characterized in that the concentration of the inhibitor is 6 - 12 g / l.

7. Passivierungs- and lubricant according to claim 6, characterized in that the concentration of the inhibitor is 8 - 10 g / l.

8. Passivierungs- and lubricant according to any one of the preceding claims, characterized in that the pH is 4-9.

9. Passivierungs- and lubricant according to claim 8, characterized in that the pH is 6 - 7.

10. Passivierungs- and lubricant according to any one of the preceding claims, characterized in that the temperature is 42 - 49 ⁰ C.

11. A process for the preparation of the passivating and lubricating agent according to one of the preceding claims with the following process steps:

Dissolving the emulsifier in water; Addition of the inhibitor; and mixing the solution.

12. The method according to claim 11, characterized in that the water or the emulsion is heated to 42 - 49 ⁰ C.

13. The method according to claim 11 or 12, characterized in that the emulsifier is dissolved only in 85 - 95% of the amount of water; and that the remaining water is added after the inhibitor.

14. The method according to any one of claims 11-13, characterized in that the pH of the passivation and lubricant is adjusted by metered addition of phosphoric acid or sodium hydroxide to a value of 4-9.

15. The method according to claim 14, characterized in that the pH is adjusted to a value of 6-7.

A method of passivating and lubricating gold, silver and copper surfaces and corresponding alloy surfaces by treating the surfaces with the passivating and lubricating agent of any one of claims 1-10, and then first rinsing the surfaces with water, the Temperatures of the passivating agent and the water are above the inhibitor melting point.

17. The method according to claim 16, characterized in that the treatment of the surfaces comprises a first immersion in the passivation and lubricant.

18. The method according to claim 17, characterized in that the immersion time is 7 s - 2 min.

19. The method according to claim 18, characterized in that the immersion time is 7 s - 30 s.

20. The method according to any one of claims 17 - 19, characterized in that upon immersion, a relative movement between the surfaces and the passivation and lubricant is generated.

21. The method according to any one of claims 17 - 20, characterized in that the temperature of the passivation and lubricant is adjusted by means of a Tauchwärmers of titanium, quartz or Teflon.

22. The method according to any one of claims 16 - 21, characterized in that the first rinsing takes place at 55 - 65 ⁰ C.

23. The method according to claim 22, characterized in that the surfaces are dipped for the first rinsing for 5 - 10 s in a stationary rinse.

24. The method according to any one of claims 16 - 23, characterized that the surfaces are then rinsed a second time with water that has room temperature.

^• 25, Method according to claim 24, characterized in that the second rinsing takes place in a flow rinse.

26. The method according to any one of claims 16-25, characterized in that used rinse water is subjected to cyanide poisoning with subsequent neutralization.

27. The method according to any one of claims 16 - 26, characterized in that the treated surfaces are finally dried with hot air or by blowing off with compressed air.

28. The method according to claim 27, characterized in that the surfaces are dried at 75-85 ⁰ C for 4-6 min in a centrifuge.

29. The method according to any one of claims 16-28, characterized in that the passivation of the surfaces is tested by a second immersion in an ammonium sulfide solution.

30. The method according to claim 29, characterized in that the second immersion time is 30-45 s.

31. The method according to claim 29 or 30, characterized in that a 1-3% active ammonium sulfide solution is used.

32. The method according to any one of claims 16 - 31, characterized that the surfaces are first degreased and cleaned before treatment with the passivation and lubricant.