DE2205869C3 - Aqueous alkaline bath for chemical copper deposition - Google Patents

Description

HOf A-

where R, R 'and R "are each individually divalent alkylene, cycloalkylene, alkylene ether or arylene radicals and these radicals have 1 to 12 carbon atoms, A is an alkylene radical with 2 to 5 carbon atoms and η is an integer between 1 and 100.

2. Bath according to claim 1, characterized in that R, R 'and R "are alkylene radicals.

3. Bath according to claim 1, characterized in that R, R 'and / or R "by a polar Group are substituted.

4. Bath according to claim 3, characterized in that the polar group is an —NH ₂ -,

- SO ₃ OH-, - COOH-, -NO ₃ -, -Cl-, -Br-,

- J or - F group.

5. Bath according to claim 1, characterized in that η varies between 5 and 50.

6. Bath according to claim 1, characterized in that it is the polyether in an amount of Contains 1 to 2000 parts per million parts bath.

7. Bath according to claim 6, characterized in that it is the polyether in an amount of Contains 25 to 200 parts per million bath parts.

8. Bath according to claim 1, characterized in that the polyether has the formula

CH ₂ -CH,
CH ₃ -CH ₂ -CH, -CH-CH-C = CH

45

where χ varies between about 45 and 50.

9. Bath according to claim 1, characterized in that the polyether has the formula

CH,
CH, - CC ^ CH

; O -CH ₂ - CH ₂ JrOH

owns.

10. Bath according to claim I. wherein the stabilizer has the following formula:

55

60

HC = C - R -EO - A3v OH characterized in that A is an alkylene radical with

65

869

2 to 5 carbon atoms and n. Is an integer between 1 and 100.

11. Bath according to claim 10, characterized in that R is an alkylene radical and A is a Is ethylene radical

12. Bath according to claim 11, characterized in that that π varies between 5 and 50 and the polyether in the bath in an amount from 25 to 200 parts per million parts is included.

The invention relates to an aqueous alkaline bath for chemical copper deposition, containing a Source of copper (II) ions, formaldehyde as reducing agent, a complexing agent, sufficient hydroxide to adjust the pH value as well a stabilizer containing alkynyl groups.

Chemical copper deposition is the electroless application of copper coatings to active ones Understanding surfaces. Baths and processes suitable for this are already known and are being used extensively Extent technically applied. They are described in numerous patents, for example in U.S. Patents 3,011,920 and 3,457,089.

The known copper plating baths contain four components dissolved in water, namely (1) one Source of copper (II) ions, usually copper sulfate, (2) formaldehyde as a reducing agent, (3) alkali, im generally an alkali metal hydroxide, preferably sodium hydroxide, in an amount sufficient to give the bath the required pH, and (4) a complexing agent for the copper so that it does not precipitate in alkaline solution.

A wide variety of compounds can be used as complexing agents, such as, for example in the above-mentioned US patents and in US patents 28 74072, 30 75 856, 31 19 709 and 30 75 855 are described.

Those described above containing both an oxidizing agent and a reducing agent However, copper plating baths have limited stability and a tendency to undergo reduction almost all of the copper in solution not only on the substrate to be coated, but also to decompose spontaneously on the walls of the container, the stirrer and the like. It has therefore proved to be useful. Add stabilizers to prevent spontaneous decomposition prevent and widen the range of usable concentration and temperature without affecting the Ability of the solutions, through reduction on catalytic surfaces in contact with them Depositing copper is impaired. For example, in US Pat. No. 3,457,089, copper plating baths are disclosed described, which contain a soluble, low molecular weight alkynol as a stabilizer, in which the acetylenic group, especially a group containing an active hydrogen atom, presumably the effective part is. Such a stabilizer is generally used in the copper plating bath added in an amount between 2.5 and 2000 parts per million bath depending on the Molecular weight of the alcohol used, with the higher molecular weight alcohols in the bath being less are more soluble than the low molecular weight alcohols.

The object of the invention is now to provide an aqueous specify an alkaline bath for chemical copper deposition that is even more resistant to decomposition than the previously known copper plating baths and that to copper coatings with an improved Appearance leads.

The invention relates to an aqueous alkaline bath for chemical copper deposition, which contains a source of copper (ir) ions, formaldehyde as a reducing agent, a complexing agent, sufficient hydroxide to adjust the pH and a stabilizer containing alkynyl groups and is characterized in that that the stabilizer is a polyether of the following formula:

• 5

HC = C - R -f O -

OH

HO-tA

'- C = CR "-fO - Afc-OH

wherein R, R 'and R "are each individually divalent alkylene , cycloalkylene, alkylene ether or arylene radicals and these radicals have 1 to 12 carbon atoms, A is an alkylene radical with 2 to 5 carbon atoms and η is an integer between 1 and ICiO means.

The copper deposition bath according to the invention has better stability than the previously known copper deposition baths, and it leads to electrolessly deposited copper coatings with a better appearance. It is believed that this is due to the fact that the polyether adducts used in accordance with the invention have better solubility in the copper plating bath than the alkynols from which they are made, which is why higher molecular weight alcohols can also be used, and that the better appearance of the copper plating is due to the increased surface activity of the nonionic hydrophobic part of the polyether which is formed during the epoxidation of the alkylene oxide.

The polyether used as a stabilizer according to the invention is an adduct which is composed of the constituents alkynol and alkylene oxide. The following alkynols can be used to produce such an adduct:

HC == C - R - OH

HO-R '- C = R "- OH

where R, R 'and R "each denote divalent alkylene, cycloalkylene, alkylene ether or arylene radicals having 1 to 12 carbon atoms. Suitable examples of alkyne alcohols corresponding to the formulas given above are the following:

55

2. methylbutynol

CH ₃

CH ₃ -C = CH

OH

3. methyl pentinol

CH ₃

CH ₃ -CH ₂ -CC =

OH

4. Dimethylhexynol

CH ₃ CH ₃

CH ₃ - CH - CH ₂ - C - C == CH

OH

5. 2-butyne-1,4-diol

C - CH ₂ - OH

II

C-CH ₂ -OH

6. Dimethylhexynediol

CH ₃ CH,

CH ₃ - C - C = C - C - CH

OH OH

7. Propargyl alcohol

HC ξξ C - CH ₂ - OH

8. Bis-hydroxylethylbutynediol ether

HO - - CH, - CH ₂ - O - CH ₂ - C ξ = - C

'- rn - η - ι

CH ₂ -O-CH ₂ -CH ₂ OH 9. Hexynol

CH ₂ - CH ₂ - CH ₂ - CH - C = CH

OH

10. Ethyl octinol

CH ₂ -CH ₃

CH ₃ -CH ₂ -CH ₂ -CH ₂ -CH-Ch-C = CH

OH

Ethynylcyclohexanol

H ₁ C

CH ₁ -CH,

CH, -CH,

C CH

OH

In the compounds mentioned above , the radicals represented by R, R 'and R "can be further substituted by groups which have a

Effect solubility in water. For example, each radical can be substituted by -NH ₂ , _{-SO 3} OH, -COOH, -NO ₃ , - Cl, - J, - Br, F and the like.

Low molecular weight alkylene oxides having 2 to 5 carbon atoms can be used to form the adducts . Examples of such oxides are ethylene oxide, propylene oxide, isobutylene oxide and 1,2-epoxybutane. The adducts are formed by an epoxidation reaction with cleavage of the epoxy group of the alkylene oxide

5 ^6th

by forming the OH group of the alcohol. The stability of the solution provided was under of polyether. The adducts can be obeyed by using the palladium chloride drop test Formulas are reproduced: it is correct for which 50 drops of a 0.5 weight

percent palladium chloride solution of a sample of

I. HCsC-R-EOJhrA-OH 5 30cm ^{3 of} the composition of Example 1 are added. The 50 drops come with a

^and speed of 10 drops / 30 seconds below

II. HO-FA-OJ ^ -R'-C = C-R "-FO-A ^ OH added to constant stirring to prevent local decomposition or to prevent precipitation. Currently-

worir R, R 'and R "are the above-mentioned loading, ₀ point for the spontaneous decomposition will have starting importance, A is an alkylene radical having 2 to from the time at which the addition of Palla-5 carbon atoms, and π is an integer between With regard to the addition 1 and 100, preferably between 5 and 50, means the composition of Example 1 decomposed These adducts are new compounds, those of the previous ones did not occur within 48 hours.
Compounds corresponding to formula II according to the formula II Example 1 was again less preferred without the addition of the adduct, since it brings less than half as much. Decomposition occurred within an hour. The procedure of Example 1 was repeated. Formula I shown above. however, the adduct was replaced by athyloctinol.

The adducts are formed according to the epoxidation reactions customary for alcohols and alkylene due to its limited solubility. In 20 times about 25 ppm of the AthyloctinoJs in solution. In general, elevated temperatures occur, for example the remainder formed an insoluble phase in the solution. 50 to 150 C and elevated pressures, e.g. B. over 1, preferred The solution was applied to the palladium chloride dropwise over 2 atmospheres. Typically it decomposes in about 18 hours, which is possibly also an epoxidation catalyst. B. BCl ₃ or a tertiary amine is used. The 25 sensitizer is due.
The ratio of the alkylene oxide to the alcohol depends on the number of OH groups on the alcohol and using the usual pretreatment for the desired chain length of the polyether, namely cleaning, conditioning and, in accordance with the methods known to those skilled in the art, catalyzing a single stage palladium-tin. Details of the formation of polyether acid catalyst. The substrate was plated by dew adducts of alcohols and alkylene oxides found in the composition of Example 1, found in Jelinek, CF, and Mey Hew, RL, "In- The surface so plated had a shiny industrial engineering chemistry", 46 ( 1954) what to look at.

is referred to here. Looking at the A phenolic substrate was made with the foregoing Formulas shows that this adducts composition of Example 1 was plated but was are not individual compounds, but that they replace the adduct with athyloctynol; one received Reaction products Mixtures with about Poisson - a glossy coating, but not so represent a shear distribution. was shiny as it was made from the adduct

The above polyether adducts are obtained in the solution
used in amounts that improve the 40th
The stability and appearance of the deposit are sufficient or the performance of the bath is otherwise impaired
improve; however, the quantities should not be so large
that the deposition is prevented. Suitable

Quantities are generally between 2.0 and 45 The procedure of Example 1 was repeated,

2000 parts per million bath on a weight basis, however with the adduct of Example 1 being replaced by the

calculated although the preferred range between the following compound in an amount of 100 parts

is about 25 and 2000 parts per million parts. The per million parts solution was replaced:
Maximum amount of any given adduct that can be used in the
Solution that can be given depends on the ethoxy 50

degree of lation, ie the chain length of the polyether. q ^

In general, the amount of Addukis present in the | ³

Bath can be dissolved, the larger, the higher the CH ₃ - C - C = CH

Degree of ethoxylation is. I.

Example 1 ⁵⁵ LfO-CH ₂ -CH ₂ JyOH

Copper sulfate pentahydrate 7.5 g

Sodium hydroxide 5.0 g

Formaldehyde 2.5 g If the palladium drop test is used, it

Rochelle Salt 12.0 g 60 did not settle the bath within 30 hours.

Adduct ¹ ) 50 ppm

Water on 1 1

,, CH ₂ -CH ₃ Example 3

CH ₁ -CH, -CH, -CH ₂ -CH-CH-C = CH 65

I Using the composition and the

LfO-CHi-CH ₂ -J-OH procedure of Example 1 was the adduct of

(v = 45 to 50). * Example 1 through the following connection in one

Replaced amount of 75 parts per million parts of solution :

CH, CH,

1 "I '

CH, - CH - CH ₂ -C = CH

O - CHXH - OH

CH,

In the palladium drop test, the bath did not degrade within 36 hours.

In the above examples, instead of the specified complexing agents and sources other known ones are used for copper (II) ions will. For example, those listed in the aforementioned patents provide useful ones Solutions.

The concentrations of the above ingredients are not critical and are usually in the areas known for chemical copper deposition solutions. There has to be one to achieve a sufficient Deposition sufficient amount of copper and so much alkali are used that the required high pH, usually 10-14. The formaldehyde must act as a reducing agent sufficient for the copper in the presence of a catalytically active surface - and there must be so much Complexing agent must be present that a precipitation of copper in the alkaline solution during storage and use is avoided. Generally, those in the following table have been found given concentrations for these substances proved to be the most suitable:

Concentrations

Cu ⁺⁺ 0.02-0.12MoI liters

Alkali 0.17-1.15 mol liter

HCHO 2-20 mole liters Cu " ⁺

Complexing agent .. .1.1-5 mol liters Cu ^{+ +}

When using the adducts described here, these are likely via the acetylene group effective to remove impurities, e.g. copper (I) compounds, keep in the activated form. The ethoxylation of the alkynol probably gives the Improvement, as this makes higher molecular weight alkynols soluble in the solution, which are more effective stabilizers for the chemical deposition bath. The polyether thus formed also acts as a surface-active MiUeI in the solution, which probably causes the improved appearance.

Of the adducts described, those with the - C = ^ CH group are at least twice as effective such as those with the —C = C group and thus represent a preferred embodiment of the invention. This is probably due to the greater reactivity of the —C = CH group. The following example explains this.

Example 4

The composition of Example 1 was used, but using the adduct of Example 1 has been replaced by the following:

CH ₃ CH ₃ CH ₃ CH ₃

1 * 1 i i

CH ₃ -CH-CH ₂ -CCCC-Ch ₂ -CH-CH ₃

A solution containing the above compound in an amount less than 75 ppm internally decomposed about 8 hours after the palladium chloride drop test; if the adduct was replaced by the diol, se 15 ppm went into solution and decomposition occurred in about 3 hours. The no stabilization center containing solution decomposed in a little less than an hour.

409 640/150

Claims (1)

Claims: 22 1. Aqueous alkaline bath for chemical copper deposition containing a source of Copper (IIHonen, formaldehyde as reducing agent, a complexing agent, sufficient hydroxide to adjust the pH value as well a stabilizer containing alkynyl groups, characterized in that the stabilizer a polyether of the following formula