CA2008801A1

CA2008801A1 - Process for the adhesive metallization of plastics resistant to high temperatures

Info

Publication number: CA2008801A1
Application number: CA 2008801
Authority: CA
Inventors: Michael Romer
Original assignee: Individual
Current assignee: Bayer Pharma AG
Priority date: 1989-01-30
Filing date: 1990-01-29
Publication date: 1990-07-30
Also published as: EP0380767A2; EP0380767A3; JPH02240272A; DE3902991A1

Abstract

ABSTRACT OF THE DISCLOSURE
The present invention provides for the pretreatment of plastics, particularly of polyether sulphones, for the adhesive chemical metallization, in which the plastics, dissolved with a quaternary base, are treated in an organic solvent.

Description

-"` Z0088(~1 The present invention relates to a process for the pretreatment of plastics, particularly of polyether sulphones for adhesive chemical metallization. By polyether sulphone are meant any plastics or industrial products that contain S02r ether and phenylene groups.

By pretreatment is meant the preparation or change of the plastics surface including the filler (for example, glass fibers) to completely and homogeneously assure the activation (seeding with (noble) metals or carbon) and thus posltively influencing the chemical metallization.
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The pretreatment of plastic based on polyesters, polyamides, sulphones, polyurethanes, and the like, for chemical metallization is known. This includes, for example, the 1~ treatment with alkaline purifiers, with S03 in the gas phase, with solvents containing wetting agents or with water-soluble organic dissolving intermediaries which solvate hydroxyl ions.

However, for the pretreatment of plastlcs based on 2U polyether sulphones, these methods of treatment are unsuitable since they result only in an unsatisfactory films.

The present invention provides a method of pretreatment for the above-mentioned kind of plastics, i.e., a pretreatment allowing an adhesive chemical metallization.

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According to the present invention there is provided a process for the pretreatment of plastics, for the adheslve chemical metallization, wherein the plastics, dissolved wlth a quaternary base, are treated in an organic solvent. Suitably a 30 Cl-C4 alkyl ammonium hydroxide, aryl ammonlum hydroxide, vinyl triaryl phosphonium hydroxide, tetraphenyl phosphonium hydroxlde or tetraphenyl arsonium hydroxide is used as quaternary base.
Desirably an organic solvent that is soluble in water, alcohols or ethers is used.

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: 2008801 The process according to the present invention advantageously allows an adhesive metallization of the surface of plastics.

Thus, the plastics are hydrophilized with surprising intensity and are prepared for the activation in a special manner !i while the surfaces simultaneously swell up and the attack of the etching agent is facilitated and thus reinforced.

By polyether sulphone is meant a thermoplastic polyether sulphone that contains aromatic ether groups as well u as, with periodic recurrence, SO2 groups and aromatic and/or aromatic bisphenol-A groups in the chain. On the market these products are known as polysulphones, polyarylene, (or polyphenylene) sulphones and polyether sulphones. When desired, these plastics may contain a glass fiber component or a mineral 1~ component or mixture of these two components.

The following quaternary bases to be used according to the present invention are mentioned specifically:

; ammonium hydroxide alkyl ammonlum hydroxide aryl ammonlum hydroxide 2~ vlnyl trlaryl phosphonlum hydroxide tetraphenyl phosphonium hydroxide and tetraphenyl arsonlum hydroxlde.

Furthermore, an outstanding effect is displayed by ; tetramethyl ammonium hydroxide.

The following bases and/or thelr salts whlch are used ~ointly wlth hydroxyl ions are suitable compounds:
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, -`~ 20088(~1 alkyl benzyl dimethyl ammonium chloride (-)-N-benzyl quinlnium chloride :
benzyl trlbutyl ammonlum bromlde benzyl tributyl ammonium chloride benzyl triethyl ammonium chloride benzyl triethyl ammonium hydroxide benzyl trimethyl ammonium chloride benzyl trimethyl ammonium hydroxide :Iu butyl triphenyl phosphonium chlorlde (-)-N-dodecyl-N-methyl ephedrinlum bromlde ethyl hexadecyl dlmethyl ammonium bromide ethyl trioctyl phosphonium bromide hexadecyl trlmethyl ammonium bromide hexadecyl trimethyl ammonium chloride . methyl trioctyl ammonium chloride tetrabutyl ammonium fluoride trlhydrate .. tetrabutyl ammonium hydrogen sulphate tetrabutyl ammonium hydroxlde ;; tetrabutyl ammonlum lodide 2~ tetrabutyl ammonlum tetrafluoroborate tetrabutyl ammonium phosphonlum bromlde tetrabutyl phosphonlum chlorlde tetraethyl ammonlum bromlde 3U tetraethyl ammonlum chlorlde tetraethyl ammonlum cyanlde tetraethyl ammonlum hydroxlde tetraethyl ammonlum fluroborate 3~

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tetraoctyl ammonium bromide tetraphenyl phosphonium bromide tetraphenyl phosphonium chloride :
tetrapropyl ammonium bromide tetrabutyl hexadecyl phosphonium bromide tributyl methyl ammonium chloride .
tetrapentyl ammonium bromide tetramethyl ammonium hydroxide :I.u tetrapropyl ammonium hydroxide (aqueous solution) tetrahexyl ammonium bromide tetradecyl trimethyl ammonium bromide methyl tridecyl ammonium chloride 1~;
These compounds are used in concentrations of 0.05 to 200 g per litre.

:~ 2U It is understood that the pretreatment agents according to the present invention can be applied as such - or when desired in the form of their salts in the presence of hydroxyl ions, from which the quaternary bases are liberated in the presence of hydroxyl ions. .

For example, the following media are suitable as organic solvents and/or dissolving intermediaries:

N-methyl formamlde 3~ N-methyl acetamlde propylene carbonate ethylene carbonate acetonltrile ,.
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dlmethyl sulphoxide N,N-dimethyl formamide dimethyl acetamide N-methyl pyrrolidone methylene chloride acetic ethyl ester 1,4-dioxane diethyl carbonate :Iu ~ -butyrolactone ethylene glycol ethylene glycol monomethyl ether ethylene glycol monoethyl ether ethylene glycol monobutyl ether ethylene glycol monolsopropyl ether ethylene glycol monoisobutyl ether 2U ethylene glycol mono-tert-butyl ether ethylene glycol mono-n-hexyl ether ethylene glycol mono (2-aminoethyl)-ether ethylene glycol diglycide ether z~ ethylene glycol monophenyl ether ethylene glycol monoacetate ethylene glycol diacetate ethylene glycol monoethyl ether-acetate 3U ethylene glycol monoallyl ether ethylene glycol dimethyl ether ethylene glycol monobutyl ether acetate ethylene glycol monobenzyl ether 3~

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ethylene glycol monoisoamyl ether methanol ethanol n-propanol i-propanol n-butanol glycerol glycerol aldehyde :Iu glycerol glycide ~:
glycerol monomethyl ether glycerol monoethyl ether dlethylene glycol 1~ dlethylene glycol monomethyl ether diethylene glycol monoethyl ether dlethylene glycol monobutyl ether 2U diethylene glycol dlethyl ether dlethylene glycol dimethyl ether trlethylene glycol trlethylene glycol monoethyl ether 2~ triethylene glycol monomethyl ether The solvents are suitably used in concentratlons of 10 to 100% by weight. When deslred, these solvents can also be mixed with water or low alcohols.
3u The solutions to be used according to the present invention are alkaline and have a pH value of 11 to 14.

The treatment of the plastics is suitably carried out :
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'~3~U3 at temperatures of lo to 90C, preferably at 25C.

The process according to the present invention is carried out by conventional immersion of the plastic articles, such as sheets, in;ection moulded articles, copper-laminated extruded panels or moulded parts, in the pretreatment solution according to the present invention.

The treatment time depends on the plastics concerned and usually is 3 to 10 minutes, preferably 5 minutes. The u pretreated parts are then rinsed, whereupon they can be further processed. On an article thus pretreated water no longer beads.

A substantial effect for a good adhesion can be attained even after the solderlng passage when on completing the 1~ pretreatment the plastics are roughened by means of an etching bath, preferably a bath containing an acid oxidizing agent, and, are then further processed in the usual manner. Apart from chromosulphuric acid and chromic acid, chloric acid, hydrogen peroxide and peroxodisulphuric acid can also be used as an acid 2U oxidizing agent.
k, The activation and the chemical metallization of the plastic articles pretreated according to the present invention are carried out in a convention manner, 2~
The activation can be carried out, for example, by means of a palladium activator, which is present in the ionic form or in the form of colloidal pparticles. When required, the palladium ions are reduced on the substrate surfaces, for 3U example, by the action of dimethyl aminoborane or sodlum - hydroxide. Colloidal palladium nuclei can be freed from the protective colloid by means of borofluoric acid or caustic soda solutlon.

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Z()088~1 The surfaces thus treated are then chemically metallized by means of conventional methods, using currentless nickel, cobalt, silver, palladium, tin, gold or copper baths.
For example, the copper - or nickel-plated plastics article can be subjected to tempering at a temperature of 80 to 120C for the purpose of strengthening the bond and, when required, for removing water or solvent. This can take up to approximately one hour.

Depending on the required shape of the metallized plastics articles the layer thickness of the metal can be u chemically or galvanically reinforced and processed by means of conventional structuring methods. The composite metal-plastics is distinguished by its great stability and the adhesive strength of the metal layer on the substrate surface.
-The process according to the present invention is particularly suitable for the production of printed circuits in electrical engineering and electronics.

The printed circuits thus produced have the special advantage of a low microroughness and high adhesive strength.
This is a great aavantage.

The plastics articles produced according to the present invention have high adhesive strength values of up to 15N/cm.
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A partlcularly surprising advantage of the present lnventlon lles ln that not only does the attack of the hydroxide ions dissolved in the solvent and/or swelling agent increase the adhesive strength values of the composite system metal-plastics 3U but it also produced uniformly reproducible adhesive strength values. Thus, even at lengthy operating cycles no poor adhesive strength values were observed in the composite metal-plastics, as was occasionally noticed ln a pretreatment of the plastlcs with a swelling agent alone (chromosulphuric acid).
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The present invention will be illustrated by the following Examples:

Example 1 A polyether-sulphone panel having a glass-fiber component of 20%
!i iS immersed in a solution of loog/litre of tetramethyl ammonium hydroxide in N,N-dimethyl formamide/isopropanol (70:30) for 30 seconds at room temperature and then rinsed, whereupon it is immersed for 12 minutes in a commercial sulphuric chromium-VI-oxide etching bath having a temperature of 70C. Following the -~ etching action the panel is rinsed for 2 minutes and the hexavalent chromium still present on the substrate surface is reduced to chromium-III by means of a 10% aqueous NaHSO3 solution.

1~On completion of the treatment, the substrate surface is very slightly roughened and is found to be well wetted with the water. Thereafter the pane~ is activated with an iongenic palladlum-II complex, reduced with sodium boron hydride and chemically copper-plated in a conventional thin copper bath to a 2~ layer thickness of 0.2 ~m. On tempering the chemically copper-plated polyether-sulphonate panel for one hour at 100C it ls holohedrally copper-plated in a commercial sulphuric copper electrolyte to a layer thickness of 35 ~m. The copper coating, which is finally tempered for 2 hours at 130C, has an adhesive 2~strength value of 14 to 15 N/cm ln the peel test (DIN Standard 53 494).

Example 2 3~ A polyether-sulphone panel having a glass-fiber component of 10%
and a mineral component of 10% is immersed in a solution of 80g/litre of tetramethyl ammonium hydroxide in N,N-dimethyl formamide/isopropanol (70:30) for 30 seconds at room temperature analogously to Example 1 and is copper-coated to a layer g _ ,.

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thickness 35 ~ m as described in Example 1.

The adhesive strength value according to DIN Standard 53 494 is 12 to 13 N/cm.
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; Example 3 A polyether-sulphone panel having a glass fiber component of 20%
is immersed for 1 minute in a solution of N,N-dimethyl formamide/H2O (90:10), at room temperature, rinsed and then Lu immersed for 15 minutes in a commercial chromosulphuric acid etching solution having a temperature of 70C.

As described in Example 1, the hydrophilic roughened surface is reinforced to a copper layer thickness of 35 ~ m. The adhesive strength value according to DIN Standard 53 494 is 10 N/cm. A comparison of the Examples 3 and 4 clearly shows the effect of the substance tetramethyl ammonium hydroxide on the adhesive strength of the composite copper-polyether sulphone.

Example 4 A polyether-sulphone panel having a glass fiber component of 30%
is immersed for 30 seconds in a solution of 40g/litre of tetramethyl ammonium hydroxide in dimethyl sulphoxide/water 2~ (90 I0)~ rinsed and subsquently treated for 15 minutes in a commercial sulphuric chromiun -VI- oxide etching solution having a temperature of 65C.

The further sequence of operation up to the finlsh of 3~ 35~ m of galvanic copper ls evident from Example 1.

The adhesive strength value according to DIN Standard - 53 494 is 9 to 11 N/cm.

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Claims

1. A process for the pretreatment of plastics, for the adhesive chemical metallization, wherein the plastics, dissolved with a quaternary base, are treated in an organic solvent.

2. A process as in claim 1, wherein a quaternary ammonium, phosphonium or arsonium hydroxide is used as quaternary base.

3. A process as in claim 1, wherein a C1-C4 alkyl ammonium hydroxide, aryl ammonium hydroxide, vinyl triaryl phosphonium hydroxide, tetraphenyl phosphonium hydroxide or tetraphenyl arsonium hydroxide is used as quaternary base.

4. A process as claimed in the claims 1, 2 or 3, wherein tetramethyl ammonium hydroxide is used as quaternary base.

5. A process as claimed in claim 1, wherein the quaternary bases are formed from their salt in the presence of hydroxyl ions.

6. A process as claimed in claim 5, wherein the halides, tetrafluoro-(hydro,phenyl)-borates, periodates, hydrosulphates, dihydrogen phosphates or hexafluorophosphates are used as salts.

7. A process as claimed in claim 5, wherein the hydroxyl ions are formed from alkali metal hydroxides.

8. A process as claimed in claim 1, wherein an organic solvent that is soluble in water, alcohols or ethers is used.

9. A process as claimed in claim 8, wherein the organic solvent is used simultaneously as a swelling agent for the plastics.

10. A process as claimed in claim 9, wherein alkyl sulphoxides, dialkylsulphoxides, dialkyl carbonates, dialkyl lactamides, N,N-dialkyl formamides, pyrollidone, alcohols and/or ethers are used as solvents or swelling agents or both.

11. A process as claimed in claim 8, 9 or 10, wherein the solvents or swelling agents or both are used in mixture with water of low alcohols.

12. A process as in claim 1, wherein the quaternary base is used in concentrations of 0.05 to 200 g per liter.

13. A process a in claim 1, wherein the organic solvent is used in concentrations of 10 to 100 percent by weight.

14. A process as claimed in claim 1, 2 or 3, wherein the treatment is carried out at temperatures of 10 to 90%.

15. A process as claimed in claim 1, wherein on completed pretreatment the plastics are roughened by means of an etching bath.

16. A process as claimed in claim 1, wherein on completed pretreatment the plastics are roughened by means of an etching bath containing an acid oxidizing agent.

17. A process as in claim 15 or 16, wherein an etching bath containing sulphuric chromium -VI- oxide is used.

18. A process as in claim 1, wherein on completed pretreatment the plastics are activated and chemically metalized.

19. A process as in claim 18, wherein the activation is carried out with a solution containing colloidal or ionic palladium, which is freed from protective colloid or is reduced to the zero value metal.

20. A process as in claim 1, 2 or 3, wherein the chemical metallization is carried out by means of a copper,silver, palladium, gold, tim, cobalt or nickel bath.

21. A process as in claim 1, 2 or 3, wherein an amorphous aromatic high temperature-resistant thermoplastic polyether sulphone is used including any industrial product containing SO2 ether and phenylene groups.

22. A process as in claim 1, 2 or 3 wherein the plastics are present in the form of a sheet, an injection molded article copper-laminated extruded panel or as a moulded article.

23. A process as in the claim 1, in which a printed circuit is produced.

24. A printed circuit produced by the process as claimed in claim 1, 2 or 3.

25. A process as claimed in claim 1, 2 or 3, in which the plastics is of a polyester sulphide.