DE2160821C3 - Process for the deposition of copper layers on molded articles made of polyimides - Google Patents

Description

The invention relates to a method for depositing firmly adhering copper layers on molded bodies Polyimides.

It is known that molded bodies made of electrically non-conductive plastics, e.g. B. from polystyrene, acrylonitrile-butadiene-styrene Mischpoiymerisaten (ABS plastics), polyolefins and polyesters, optionally after suitable pretreatment, electrolessly or galvanically with to provide thin metal coatings.

In this case, a method has proven particularly useful in which a very thin surface is applied to the plastic surface A layer of noble metal nuclei is deposited by sensitizing the surface with a noble metal salt solution and activating it with a solution of a reducing agent. On the precious metal nuclei then deposit cohesive metal layers by means of chemical or galvanic metallization baths.

You can such a pretreatment z. B. perform by first treating the surface with a palladium salt solution, e.g. B. PdCl ₂ , and then treated with a hydrazine hydrate solution. Small amounts of elemental palladium are deposited on the surface.

In order to firmly anchor the metal layers to be applied later, it is customary to mechanically fix the plastic surface prior to the aforementioned pretreatment or preferably to roughen chemically. With the ABS For plastics, chemical roughening is used e.g. B. with concentrated sulfuric acid, which may also contain an oxidizing agent.

In GB-PS 12 47 706 or FR-PS 20 37 988 processes are described in which polyester or polyimide surfaces before the electroless Application of a metal layer, in particular a nickel layer, as follows in the specified sequence to be pretreated: dry cleaning of the upper surface with acids or alkali solutions, sensitize with a SnClr solution and activation with a palladium salt solution.

If you use the previously known metallization process without the addition of halogenated fatty acid in the treatment treatment bath is applied to the copper plating of polyimide moldings, no firmly adhering ones are obtained Uppers.

From US-PS 35 61 995 the treatment of a large number of very different plastics, inter alia.

polyester with precious metal salts can also be removed in a large number of very different reaction media. As one of the many possible Compound types should also be possible for the treatment of plastics with halogenated fatty acids. the Treatment with the various reaction media takes place, however, the longer the lower the reaction temperature, d. H. a technologically interesting short one The reaction time can only be achieved with high bath temperatures, so that these solutions are used for is dangerous to the user and a significant corrosive effect of the solution is to be expected In addition, the use of the reaction media for polyimide surfaces is not described or suggested.

J5 In the earlier patent application P 20 62 2155-45 is already a process for the deposition of. Metal layers on molded articles made of polyesters have been proposed in which the surface of the molded article

a) sensitized with a precious metal salt solution, if necessary

b) activated with a reducing agent and

c) with a metal salt solution, e.g. B. a copper salt solution, chemically metallized

the order of a) and b) reversed can be. This is the first of the steps a) and b) or each of both steps or at least step a) carried out with a solution which additionally contains 5 to 25% by weight of a halogenated fatty acid from the group of trichloroacetic acid, Contains trifluoroacetic acid and 2,2,3-trichloropropionic acid, and the molded body immediately after Treatment with the halogen fatty acid-containing solution with heating, dried compared to the Prior art proceeds this suggested Process without significant corrosive effect the treatment in step a) with only brief heating of the molding.

The object of the invention was to provide a method - without the known disadvantages of the prior art find, after which firmly adhering copper layers are also deposited on molded articles made of polyimides can.

The invention is based on the older method for depositing copper layers on shaped bodies made of plastics, in which the surface of the molded body

a) with the solution of a noble metal salt and 5 to 25 wt .-% of a halogenated fatty acid from the

Trichloroacetic acid group, trifluoroacetic acid and 2Ä3-trichloropropionic acid sensitized and

b) activated with a solution of a reducing agent and

c) chemically metallized with a copper salt solution, whereby the order of a) and b) can be interchanged, and in which the shaped body is directly after step a) dries with heating

The inventive method is characterized in that a molded body from a Polyimide used

So it was found that it was determined Embodiments of the older method for metallizing polyester molded bodies can also be used for copper-plating polyimide molded bodies. the The method according to the invention is therefore carried out - apart from the restrictions that emerge from the definition above - largely analogous to the procedure of the earlier application.

As polyimides, the surface of which can be metallized according to the invention, are essentially all high molecular weight condensation products of aromatic diamines with dianhydrides of aromatic tetracarboxylic acids into consideration examples of suitable are aromatic diamines

4,4'-diamino-diphenylpropane, 4,4'-diamino-diphenylmethane, benzidine, 4,4'-diamino-diphenyl sulfide, 4,4'-diamino-diphenyl sulfone, 4,4'-diamino-diphenyl ether, m-phenylenediamine, p-phenylenediamine and others.

As reactants are z. B. the dianhydrides of the following tetracarboxylic acids are suitable: 2,3,6,7-naphthalene tetracarboxylic acid, 3,3 ', 4,4'-DiphenyItetracarboxylic acid, bis- (3,4-dicarboxy-phenyl) -propane, Bis (3,4-dicarboxy-phenyl) -ether and pyromellitic acid.

Halogenated fatty acids are those from the trichloroacetic acid group, 2,2,3-trichloropropionic acid and trifluoroacetic acid is used, trichloroacetic acid is preferably used

The treatment solution containing the halogenated fatty acid preferably contains water as a solvent. The solvent can also consist of organic liquids, e.g. acetone, butanone, or their Mix with water.

The content of halogenated fatty acid, in particular trichloroacetic acid, in the noble metal salt solution is about 5 to 25% by weight, preferably 10 to 15% by weight.

The salts of platinum, palladium, gold or silver come into consideration as noble metal salts. Preferred Palladium chloride used, which in concentrations between 0.001 and 5 wt .-%, preferably between 0.005 and 0.5 wt%.

Tin-II-chloride is usually used as the reducing agent used, but it can also organic reducing agents such. B. hydrazine hydrate can be used. Tin (II) chloride is in hydrochloric acid aqueous solution in Concentrations between 0.1 and 10% by weight, preferably from 0.5 to 5% by weight, applied, hydrazine hydrate in alkaline aqueous solution in concentrations between 0.1 and 5% by weight, preferably from 0.5 to 1 Wt%.

Both the precious metal salt solutions and the Reducing agent solutions are left at room temperature for 10 seconds to 10 minutes, preferably 30 Work for seconds to 3 minutes.

Before the polyimide moldings are sensitized or activated, they are expediently one Cleaning or superficial hydrolysis, to achieve even wetting by the treatment solution. Cleaning can be done in in a known manner with organic solvents, with acids or alkalis.

A treatment with an aqueous solution which contains 1 to 5% by weight has proven to be particularly expedient.

to chromic acid, 30 to 60 wt .-% phosphoric acid and 30 contains up to 50% by weight sulfuric acid. The bath temperature is between 50 and 80 ° C. The exposure time is 5 to 15 minutes. The acid is rinsed off after the treatment and

π those still adhering to the surface of the polyimide body Chromic acid residues are expediently removed with an alkaline sodium thioside solution becomes an uncontrolled local reaction of the noble metal salt with adhering chromic acid residues

Avoid applying the sensitizing solution.

As molded bodies to be copper-plated come all types of rigid, z. B. manufactured by injection molding, molded articles made of polyimides into consideration but it can also z. B. fibers, threads and films made of polyimides after Process according to the invention are copper-plated. Especially with copper-plated foils, the widespread Find technical application, the process according to the invention is of particular advantage because it is natural in the case of flexible foils, the adhesion of a metal layer

jo poses a bigger problem than with rigid moldings.

All of the treatment solutions described are preferably wetting in a known manner improving substances added to a possible to achieve an even effect. The sensitizing solution containing halogen fatty acid used according to the invention is still used for constant wetting even during the drying process a small amount, e.g. B. 0.01 to 2%, a water-soluble Chen high molecular substance, e.g. B. polyvinyl alcohol, added. The wetting agent content of the solution can generally be about 0.1 to 5%. If as Activating solution, a hydrazine hydrate or tin (II) chloride solution is used, this solution is required no wetting agent to be added.

After the sensitizing solution containing halogen fatty acid has been applied, the molded body is at dried at elevated temperature. It is essential that the temperature of the treated

so surface when using a halogen fatty acid containing palladium salt solution does not exceed 150 ° C; generally 120 to 130.degree applied. The drying should not be done too quickly, as it seems that it takes a certain amount of time to take effect the treatment solution at an elevated temperature to achieve good adhesion of the copper layer the document is required. The drying time can generally be 1 to 3 minutes, e.g. B. 2 minutes, be. Drying can be done in hot air, they can also take place under infrared heaters.

After the deposition of noble metal nuclei on the surface of the polyimide molded body, the copper can be deposited without electricity on the surface of the polyimide molded body from a reducing agent-containing copper salt bath.

After a copper layer thickness of the order of 0.2 to 03 μιη has been achieved, the further reinforcement of the copper layer galvanically or

again take place without current in a known manner.

The conditions and mode of operation for the described Metallization steps are known per se and are not the subject of the present invention.

According to the method according to the invention, firmly adhering copper layers can be applied to part of the surface or applied to the entire surface of the molded body. So foils z. B. one and be copper-plated on both sides. The adhesion of the copper layer to the base decreases in the first time metal deposition increases and reaches its final maximum value after 1 to 3 days.

For the galvanic reinforcement of the approximately 0.2 to 0.3 μm thick copper layers deposited according to the invention Galvanic baths with and without the addition of leveling and smoothing agents are suitable. the Copper is deposited in the electroplating baths at current densities between 0.1 and 2 A / qdm. The electrodeposited copper layers adhere together with the electrolessly deposited lower layer firmly on the polyimide base.

The copper layers obtained according to the invention adhere so firmly to the substrate that they, even if the copper-plated moldings are stored for weeks in an atmosphere saturated with water vapor, keep their good adhesion.

If a polyimide film is the same treatment process like the foil treated according to the invention, but is subjected to the noble metal salt solution If no halogen fatty acid is added, then either there is no copper deposition at all in the electroless bath instead (if the foil is treated first with palladium chloride and then with reducing agent has been), or there is copper deposition in the electroless bath instead (if the foil first with Reducing agent and then treated with palladium chloride), but after amplifying the electroless After the deposited layer in the electroplating bath, the reinforced copper layer can easily be removed from the base separate. The galvanically reinforced layers then adhere in air saturated with water vapor back sharply within three days.

Because of the extremely good heat resistance of the polyimide films, copper-plated polyimide films z. B. used for the production of printed circuits. You can use the galvanic foils reinforced with copper or emanating from the foils, which are only the thin, electrolessly deposited Wear copper layer.

The process according to the invention is illustrated using the following examples. Percentages are when nothing else is indicated, percentages by weight.

example 1

A 100 μm thick polyimide film made from the polycondensate of diaminodiphenyl ether and pyromellitic dianhydride was 7 minutes in an aqueous, Bathed at 70 ° C, the 1.7% chromic acid, 49.0% phosphoric acid, 40.0% sulfuric acid and 9.3% Containing water and 0.005% perffuorooctanecarboxylic acid as a wetting agent.

The film was rinsed with water for 1 minute and in a 40 ° C. aqueous solution for 5 minutes bathed, which contained 3% sodium hydroxide and 1% sodium thiosulfate.

The film was again rinsed with water for 1 minute and then for 30 seconds at room temperature bathed in an aqueous solution containing 0.15% palladium chloride, 0.25% hydrogen chloride, 0.5% polyvinyl alcohol with a K value of 30 and a residual acetyl group content of 12%, 0.4% sodium dodecylbenzenesulfonate and contained 13% trichloroacetic acid

The bathed film was dried at 130 ° C. for 2 minutes. The dried film was 30 seconds bathed at room temperature in an aqueous solution containing 0.6% hydrazine hydrate and 1.25% sodium hydroxide contained. The foil was sprayed off and placed in a 49 ° C electroless copper bath for 2 minutes brought, which had the following composition:

6.2 g
0.1g
15 g

CuSO ₄ -SH ₂ O
NiSO ₄ -7 Fi ₂ O
formaldehyde
Sodium hyposulfil
13.5 g sodium hydroxide
6 g sodium tartrate
8.5 g of N, N, N ', N'-tetra (2-hydroxypropyl) ethylenediamine

0.25 g adduct of ethylene oxide with isopropanol,
made up to 1 liter with water

A 03 μπι separated on the film surface thick copper layer. When in this with the razor blade a cross pattern of fine, spaced about 1 mm vertical lines and then the pattern was pasted over with a pressure-sensitive adhesive tape, no copper came off the base when the adhesive strip was jerked off.

The copper layer was applied at room temperature in the following electroplating bath at 1 A per square decimeter Current density increased to 30 μm in 3 hours.

3 ^r > bathroom composition:

250 g CuSO ₄ SH ₂ O
50 g sulfuric acid (98%)
made up to 1 liter with water

A 1 cm wide film strip was used to peel off the copper layer from the polyimide film According to DIN 40 802, a pull-off force cannot be measured, since the attempt to remove the copper foil from the polyimide foil separate, this split before the copper layer tore.

If the electrodeposited copper layer was only 10 μm thick, it could also not be removed from the Loosen the pad.

Example 2

The film degreased as in Example 1 and rinsed with alkaline sodium thiosulphate solution was first activated for 5 minutes at room temperature in an aqueous solution containing 0.5% by weight Tin (II) chloride and 0.7% by weight hydrogen chloride contained

The film was rinsed with water for 1 minute, then bathed at room temperature for 30 seconds in an aqueous solution containing 0.15% palladium chloride, 0.25% hydrogen chloride, 0.5% polyvinyl alcohol as in Example I _{1 and} 0.4% sodium dodecylbenzenesulfonate Contained 13% trichloroacetic acid. The bathed film was dried at 130 ° C. for 2 minutes. It was placed in the 49 ° C. copper bath of Example 1 for 2 minutes.

The copper layer thickness was 0.24 μm. The layer inseparably adhered in the adhesive tape test described in Example 1.

The galvanic reinforcement of this layer was as in Example 1 up to a layer thickness of 30 μm carried out.

As in Example 1, a force for peeling off the copper layer could not be measured.

If the electrodeposited copper layer was only Ιϋμίτι thick, it could be removed from the base not solve.

Example 3

8 polyimide films were used in the examples
or 2 described manner treated.

Tabel

The table shows the test results with different orders of the sensitization solution a) and the reducing solution b) with and without the addition of trichloroacetic acid (TCE) to the solutions a) and b).

A = copper deposits in the electroless copper bath (0.2 to 0.3 μΐη) and adhesion of the electroless deposited copper layer.

in B = reinforcement of layer A in the galvanic copper bath to 10 μπι and adhesion of the galvanic reinforced copper layer.

attempt 1st step 2nd step A. B. I. Palladium chloride Tin-II-chloride
or hydrazine hydrate no Cu deposition - Il Tin-ll-chloride
or hydrazine hydrate Palladium chloride Cu deposition more or
less separable separable III Palladium chloride / TCE Tin-II-chloride
or hydrazine hydrate Cu deposition
inseparable inseparable IV Tin-II-chloride
or hydrazine hydrate Palladium chloride / TCE Cu deposition
inseparable inseparable V Palladium chloride Tin-II-Chloride / TCE no Cu deposition - VI Tin-II-Chloride / TCE Palladium chloride Cu deposition
separable separable VII Palladium chloride / TCE Tin-II-Chloride / TCE no Cu deposition - VIII Tin-II-Chloride / TCE Palladium chloride / TCE Cu deposition
separable separable

Inseparable adhesion is only achieved when the trichloroacetic acid is the only solution of the palladium chloride is added.

Claims (6)

21 60 82ί Claims: 1. Process for the production of copper layers on molded articles made of plastics, in which the Surface of the molding a) with the solution of a noble metal salt and 5 to 25% by weight of a halogenated fatty acid the group of trichloroacetic acid, trifluoroacetic acid and 2 ^, 3-trichloropropionic acid and sensitized b) activated with the solution of a reducing agent and c) is chemically metallized with a copper salt solution, wherein the order of a) and b) can be interchanged, and in which the shaped body is dried with heating immediately after step a), characterized in that that a molded body made of a polyamide is used. 2. The method according to claim 1, characterized in that trichloroacetic acid is used as the halogenated fatty acid. 3. The method according to claim 2, characterized in that the trichloroacetic acid in aqueous Solution is used. 4. The method according to claim 1, characterized in that a palladium salt is used as the noble metal salt is used. 5. The method according to claim 4, characterized in that a solution containing 0.005 to 0.5 wt .-% palladium chloride is used. 6. The method according to claim 1, characterized in that the drying at a below 150 ° C lying temperature is made.