Conditioning Agent for the Treatment of Base Materials

The invention concerns a conditioning agent for the treatment of base materials in preparation for a subsequent complete and uniform chemical metallization, containing a quaternary organic nitrogen compound, and a process for the conditioning of base materials for subsequent complete and uniform chemical metallization, performed at temperatures from 15.degree. to 30.degree. C.

The term conditioning is meant to include the preparation or alteration of a substrate surface, including any filler material (for example, glass fibers), with the aim of positively influencing the chemical metallization by guaranteeing a complete and uniform activation (i.e. seeding).

It is known that the pre-treatment, tuned by a suitable activator, can promote satisfactory results in the metallization, whereby the adhesion between the substrate and the metal, is extensively dependent upon the particular etching, adapted to the corresponding material.

It is therefore an object according to the present invention to make available a conditioning agent for the pretreatment of base materials, having outstanding characteristics.

This object is attained according to the present invention by a conditioning agent of the above designated type, which is thereby characterized in that it contains a quaternary organic nitrogen compound.

The conditioning agent according to the present invention effects an increased activation of the surfaces of base materials compared to agents known from the state of the art, and thereby makes possible their complete and uniform chemical metallization.

It is of particular advantage that the conditioning agent according to the present invention makes possible equally good metallizations with all known activator systems, according to the following general operational procedure:

1. conditioning;

2. metal etching;

3. activation; and

4. chemical metallization.

As a rule, a cleaning is still a prerequisite for the conditioning. However, the cleaning can also be performed simultaneously with the conditioning.

Generally, the activation is undertaken with palladium-containing solutions, but can, however, also be performed with other precious metal salt solutions, such as for example the silver salts.

The quaternary organic nitrogen compounds according to the present invention are known per se or can be prepared according to known methods.

These compounds correspond to the general formula ##STR2## represents a cyclical nitrogen compound,

R is hydrogen, C.sub.1 -C.sub.4 -alkyl or hydroxy-C.sub.l -C.sub.2 -alkyl,

n is 0 or 1, and

.sub.X (-) is the anion of an inorganic or an organic acid.

Compounds with particularly outstanding activity include, for example,

N-methyl-N'-vinylimidazolium chloride,

N-methyl-N'-vinylpyrrolidonium chloride,

N-methyl-N'-allylimidazolium iodide,

N-methyl-N-vinyl-.crclbar.-caprolactam-quaternary salt,

N-butyl-N'-allylbenzimidazolium methosulfate, and

N-methyl-N'-vinylimidazolium-bromide or methane sulfonate.

The employment of these compounds follows preferably in aqueous solutions, in conentrations from 0.01 to 10 g/l.

The compounds according to the present invention are suitable for the pre-treatment of all known base materials, such as for example epoxide resin papers, phenol resin, polyimide, polyamide, polystyrene, polyethylene, polyvinylchloride, polycarbonate, acrylate, acrylonitrile-butadiene-styrene block polymerizate, polysulfone, polyester, teflon, glass or ceramic.

The pre-treatment includes any means of thoroughly contacting the conditioning agent with the base material, such as for example, steeping, soaking, immersing, wiping on with a sponge or towel, spraying on, and the like.

The activity of the compounds to be employed according to the present invention can be increased, in surprising manner, when they are employed in combination with dicarboxylic acid, preferably oxalic acid, malonic acid, succinic acid, glutaric acid, adipic acid or maleic acid, advantageously in concentrations from 1 up to 10 g/l, and preferable 5 g/l.

The simultaneous presence of a cleaning agent based upon a non-ionogenic wetting agent, preferably alkylphenolpolyglycolether, is possible without more, so that the cleaning operation can be combined with the conditioning, which is technically advantageous.

The composition according to the present invention is employed at temperatures from about 15.degree. to 30.degree. C., preferably 20.degree. C. However, the operational temperature has no noteworthy influence upon the coating results.

The conditioning agent according to the present invention finds use in the production of conductor plates and circuits in the fields of electronics and electrical engineering.

The invention will be more closely illustrated and described by the following non-limitative examples of specific embodiments:

A chemical metallization process is performed with a bored, copper-coated epoxide-glass fiber material, as follows:

A non-ionogenic wetting agent, for example based upon alkylphenolpolyglycolether, which is suitable for epoxide, is employed as conventional cleaner. However, the cleaner contains no addition of a compound with conditioning characteristics.

No 100% coating, mainly of the glass fibers, could be observed, after a copper deposition of 5 .mu.m, not only when there was a simple alkaline cleaning, but also even when there was acid, or neutral cleaning, or even a combined double stage cleaning (alkaline/acid, or the reverse).

Example 1 is repeated, however with addition to the single-stage strongly alkaline cleaner (pH=greater than 13) of 10 mg/l of a quaternary organic nitrogen compound based upon N-methyl-N'-vinylimidazolium methosulfate.

A closed metallization is produced on the base material after deposition of about 5 .mu.m copper.

Example 2 is repeated, using an addition to the cleaner of 100 mg/l of N-methyl-N'-vinylimidazolium methosulfate.

A 100% coating is achieved after deposition of about 3 .mu.m copper.

Example 2 is repeated, using an addition to the cleaner of 250 mg/l of N-methyl-N'-vinylimidazolium chloride.

A closed copper coating is obtained already after a layer thickness of about 0.5 .mu.m.

Example 2 is repeated, using an addition to the cleaner of 1 g/l of N-methyl-N'-vinylimidazolium methosulfate.

A 100% coating is obtained already after a layer thickness of about 0.5 .mu.m.

Example 2 is repeated, using an addition to the cleaner of 10 g/l of N-methyl-N'-vinylimidazolium methosulfate.

A closed metallization is obtained after a layer thickness of approximately 0.5 .mu.m.

Example 4 is repeated, using a further addition to the cleaner of 5 g/l succinic acid.

An improved conditioning is observed. The copper coating is 100% already after an approximate layer thickness of 0.2 .mu.m.

Example 2 through 7 are repeated, using a single-stage strongly acid cleaner (pH=less than 1), to which is added either 10 mg/l, 100 mg/l, 1 g/l or 10 g/l of a quaternary organic nitrogen compound based upon N-methyl-N'-vinylimidazolium methosulfate.

The test findings correspond to the results set forth in Examples 2 through 7.

Example 8 is repeated, using a single-stage cleaner in a neutral medium, containing an addition of a compound based upon N-methyl-N'-vinylimidazolium methosulfate.

Here, too, improvements in the metallizations are observed.

Example 7 is repeated, using a double-stage alkaline/acid cleaner pre-treatment.

A closed, 100% chemical coppering is obtained already after a layer thickness of about 0.1 .mu.m.

A repeat of test 10, with a double-stage acid/ alkaline cleaner pre-treatment provides analogous results.

The tests of Example 2 through 11 are repeated, using plasma-etched, multiple layered circuits (multilayers). A complete coating with electroless copper (i.e. chemical metallization) is obtained already after a layer thickness of about 0.2 .mu.m.

Results similar to those of test 12 are obtained when multiple layer circuits (multilayers) are etched with concentrated sulfuric acid, chromic acid, or with an alkaline potassium permanganate solution.

Results analogous to those of Examples 2 through 11 are obtained when the palladium content in the ionogenic activator is lowered from 200 mg/l to 75 mg/l.

Results analogous to those of Examples 2-11 are obtained when the palladium concentration in a colloidal, tin(II)-containing and acid activator is reduced from 200 mg/l to 100 mg/l.

A repeat of Examples 1 through 11, with silver-containing and copper-containing activators, provides comparable results.

Examples 10 and 11 are repeated, using as base material, epoxide resin paper, phenol resin, polyimide, polyamide acrylonitrile-butadiene-styrene block polymerizate (ABS), polysulfone, teflon and porcelain. Analogous results are obtained.

Examples 2 through 17 are repeated, using a chemical nickel bath. The conditioning agent according to the present invention causes a coating-promoting activity when the metallization is effected with electroless nickel baths.

While the invention has been described and illustrated as embodied in a conditioning agent for the treatment of base materials, it is not intended to be limited to the details shown, since various modifications and structural changes may be made without departing in any way from the spirit of the present invention.

Without further analysis, the foregoing will so fully reveal the gist of the present invention that the skilled man of the art will be able to practice the same without undue experimentation and without omitting features that, from the standpoint of prior art, fairly represent the generic or specific aspects of the present invention.