DE1521435A1 - Bath and process for depositing copper layers - Google Patents

Description

The invention relates to a bath and a method for depositing copper layers without an external power supply, you The aim is to improve the stability of such auto-catalytically working baths. Another object of the invention is to reduce metal deposition on non-metallic To limit surfaces to those areas in which it is desired, and thus to metallize others To prevent areas largely or completely.

Common autocatalytic plating baths show one strong tendency to self-decomposition and a tendency to instability which rapidly increases with service life. Various bath additives and processes have been proposed in the past to improve stability. For example, it has been proposed that the bath solution

009849 / U60

BATH ORIGINAL

152U35

Adding gelatin and thus delaying the flocculation due to its effect as a protective colloid. Farther it was proposed to use carbonates as stabilizers. Finally, it has already been suggested that improve the bath stability by blowing air or oxygen through it. All known so far However, the methods and proposals that have become effective result in an improvement in stability which is inadequate for practical operation in normal production plants. You wise in addition, there are also a number of troublesome disadvantages. So blowing oxygen or air through it causes one substantial decrease in metal deposition rate. Additions of gelatin and other proteins result for co-deposition of the same and thus an undesirable structural change in the metal deposit. in the they also have a retarding effect on the desired metal deposition. In addition, the stability improvement only insufficient. The situation is similar for baths containing carbonate.

Furthermore, all of the autocatalytically operating baths known to date show a pronounced tendency, even on non- sensitized surfaces, for example those areas of non-conductors, copper in an irregular distribution, for example in shape

009849/1460

152H35

of metal points to be deposited. This uncontrolled copper deposition leads in numerous cases - so for example in the manufacture of printed circuit boards in the manner of printed circuits - too considerable Trouble. As a rule, the undesired metal deposition from the surface must be more expensive and uneconomical testing and correction work can be removed, if not the circuit boards are unusable at all are.

Another serious disadvantage of conventional autocatalytic baths is that they take longer Operating time Metallize the bottom and walls of the bath tank. This not only causes deterioration the efficiency of such baths, but can in certain cases lead to high bath instability. At the same time, the phenomena determine the layer thickness from the amount of copper used and Surface of the desired copper layer made practically impossible, which in turn entails the necessity brings to use costly and uneconomical layer thickness determination methods.

The present invention avoids all of the listed Defects. Bathroom compositions according to the invention are not

009849 / U60

152U35

only extremely stable, but have a pronounced ability to use copper only or almost exclusively to be deposited on such plastic surfaces that sensitized for this, i.e. provided with catalytically active germs. Even surfaces that last for a long time Periods of exposure to the bath liquid, such as the container walls, show no or only extremely low copper deposits.

This phenomenon can - without limiting it to this working hypothesis - be explained as follows: The non-metallic, for example plastic surfaces have small pores and holes and the like. With a sufficiently long exposure in an autocatalytic bath, hydrogen slowly accumulates in those holes, pores or cracks, which ultimately serves as a catalyst for the copper deposition and sets it in motion. Sulfur compounds of the type described here not only stabilize autocatalytic baths in general, but also substantially reduce this phenomenon or avoid it entirely. According to the working hypothesis , they either prevent the accumulation of hydrogen in pores or achieve that the catalytic activity of the accumulated hydrogen in pores alone is not sufficient to initiate separation.

009849 / U6Q - 5 -

• ORIGINAL BATHROOM

152H35

It is believed that the sulfur compounds are capable of forming stable but dissociable chelates. Suitable organic sulfur compounds are, for example: aliphatic sulfur-nitrogen compounds such as thiocarbonates, thioures, heterocyclic five-ring compounds with S-N in the ring such as thiazoles and iso-thiazo, or e.g. 2-mercapte-benzene-thiazole, dithols, e.g. 1,2-ethanedithiol, heterocyclic six-membered ring compounds with S-N in the ring such as 1,2-benzisothiazine, Thioamino acids such as methionine, cystine, cysteine, thio derivatives of alkyl glycol such as 2,2'-thiodiethanol, Dithiodiglycol, etc .; suitable inorganic compounds are, for example, alkali metal sulfides such as Sodium and potassium sulfide, sodium polysulfide, potassium polysulfide, alkali metal thiocyanates such as sodium and Potassium thiocyanate; Alkali metal dithionates such as sodium and potassium dithionate.

The required amount of active sulfur-containing compound is very small and depends on the respective Verbin dung from t, the upper limit is given by the fact that the copper deposition bath is at all prevented and the bath solution can not be autocatalyzed by copper · the under · limit results than that crowd

00M49 / UIQ

BATH ORIGINAL

152H35

which is sufficient to achieve the effect according to the invention. This amount is usually between traces and 300 χ 10 ~ parts by weight and more; for the majority of the active sulfur compounds, however, the upper limit is about 1 10 parts by weight and the lower limit is about 0.001 χ 10 "and the preferred concentration range is between 0.01 and 0.2 10"" ⁶ parts by weight.

Typical autocatalytic bath solutions, which can be modified according to the invention are those alkaline aqueous solutions containing (II) ions, and an active reducing agent a water soluble copper salt, a complexing agent for copper, without thereby all components are to be enumerated such a bath ·

Suitable copper salts are, for example, sulfates, chlorides, nitrates, acetates; a suitable reducing agent is formaldehyde; Rochelle salt, for example, or the mono-, di-, tri- or tetrasodium salt of ethylenediaminetatraacetic acid, nitrilotriacetic acid and its alkali acid, gluconic acid, gluconate, triethanolamine and

009849/1460

- 7 -

BATH ORIGINAL

152U35

other known complexing agents and mixtures of these such as N-hydroxyethylethylenediamine triacetate.

The concentration of the individual bath components can vary within wide limits; as an example of one useful work area is listed:

Copper salt formaldehyde

Complexing agent for copper (II) ions

Sulfur compound

Alkali hydroxide

water

0.002 to 0.60 moles 0.03 to 1.3 moles

0.7 to 2.5 times the amount of moles in copper

under 300 χ 10
share

-6

Weight

to get a pH of 10-14

to make 1 liter of bath fluid

Bath solutions according to the patent are particularly suitable No. modified according to the present invention by adding a suitable sulfur compound. Such baths contain cyanides and sulfur compounds side by side; as suitable for complex formation are cyanides capable of copper (I) ions

009849/1460

BATH

152U35

the alkali metal cyanides and the nitriles, for example sodium and potassium yanide, chloroacetonitrile, alphahydroxynitriles such as glyconitrile and lactonitrile, dinitriles such as succinonitrile, iminodiacetonitrile and 3,3'-iminodipropionitrile.

It is also possible to use compounds known from the literature which contain both sulfur and the cyan complex contain; an example is 3,3'-thiodipropionitrile and its homologues.

The concentration of the cyano compounds in the bath should be approximately between 0.00001 and 0.06 mol / l and is preferably from 0.00005 to 0.01 mol / l. The copper precipitates deposited from such bath solutions containing both an active sulfur compound and a cyano compound are shiny and ductile; At the same time, both the bath stability and the ability of the bath to differentiate between sensitized and non-sensitized non-metallic surfaces are significantly increased compared to bath solutions that contain only one of the two compounds.

These baths also have a relatively large variation

009849 / U60 - 9 -

BATH

area for the concentration of the constituents it contains. Let us serve as an example:

Soluble copper salt, preferably copper sulfate

Alkali metal hydroxide, preferably sodium hydroxide, sufficient for

formaldehyde

Copper (II) ion complex

preferred concentration

0.002 to 0.2 moles

Cyan id connection Sulfur compound Water, enough for

pH from 10 to 13

0.06 to 0.50 moles, 0.001 to 0.60 moles

(and usually at least 10% in a molar excess, based on the copper salt)

0.00005 to 0.01 moles

0.0001 to 1 χ 10 parts by weight

1 1 bath solution

-6

In practical operation it can be "wake up or necessary to replace the amount of copper used",

■ L;

001149/1410

- ίο -

BATH ORIGINAL

Ί52Η35

- ίο -

as well as adding the reducing agent and monitoring the pH and within the specified range Hold area; likewise the concentration of the sulfur and cyano compounds. Furthermore it has proved to be advantageous to add a wetting agent to the bath solutions. Phosphate esters, for example and oxyethylate sodium salts can be used. Such products are sold under the trade names GAFAG RE 610 and TRITON QS 15 offered on the market.

Baths invention are übβ * 1icherweise used at temperatures between 25 and 70 ⁰ C, but this does not exclude to use them at lower or higher temperatures. In general, increasing the temperature pre-increases the rate of deposition and slightly increases the ductility. Particularly with bath compositions that contain both sulfur and CN compounds, however, bath operation is possible without special precautions, with a wide temperature range being available. The efficiency of the baths according to the invention is usually at least 90%, based on the copper concentration,

The invention is described below using individual examples

be shown

009849 / U6Q

- li -

BATH ORIGINAL

152U35

. - 11 - 5 g • 5 g EXAMPLE 1 Copper sulfate 15 ml Trisodium-N-hydroxyethyl- 15 ml 0.01 mg ethylenediamine triacetate 6 ml 6 ml (41% solution) ι g ι g Formaldehyde (37%) 2 g 2 g Wetting agent 0.01 mg 1 1 bath liquid Sodium hydroxide 1 1 bath liquid - 12 - Thiourea Water for EXAMPLE 2 Copper sulfate TrJ-sodium-N-hydroxyethyl- ethylenediamine acetate Potassium polysulfide formaldehyde Wetting agent Sodium hydroxide Water for 009849 / U60

BATH ORIGINAL

EXAMPLE 3 152U35 5 g - 13 - - 12 - Copper sulfate Trisodium nitrilotr 2 3 ml acetic acid (40% solution) 0.07 to 0.1 mg 2-mercaptobenzenethiazole 10 ml Formaldehyde (37%) 2.1 g Sodium hydroxide 2.5 g Wetting agent 1 1 bath liquid Water for EXAMPLE 4 14 g Copper sulfate 70 g Rochelle salt 20 g Sodium hydroxide 40 ml Formaldehyde (37%) 0.001 ml Thoglycolic acid 1 g Wetted 1 1 bath liquid Water for EXAMPLE S 14 g Copper sulfate 70 g Rochelle salt Q09849 / U6Q

1-52H35

Sodium hydroxide 20 g Formaldehyde (37%) 40 ml Thioglycolic acid (70%) 0.001 ml Sodium cyanide 10 mg Wetting agent 1 g Water for 1 1 bathroom preferred bath temperature 30 ⁰ C

EXAMPLE 6

Copper sulfate

5 g

Trisodium N-hydroxyethylethylenediamine triacetate (41%) 15 ml

Sodium cyanide 10 mg Ammonium thiocyanate 3.2 mg Formaldehyde (37%) 6 ml Wetting agent ι g Sodium hydroxide 2 g Water for 1 1 bath liquid Bath temperature 45 ° C

EXAMPLE 7

Copper sulfate

lü σ

009849/1460

- 14 -ORIGiNAL INSPECTED

152H35

Tetrasodium ethylene 20 g diamine tetra acetate 20 mg Succinonitrile 0.02 mg Thiourea 6 ml Formaldehyde (37%) 1 g Wetting agent 3 g Sodium hydroxide 1 1 bath liquid Water for 60 ⁰ C Bath temperature

EXAMPLE 8 Copper Sulphate

Trisodium N-hydroxyethylethylenediamine triacetate

Sodium hydroxide Formaldehyde (37%) Thiodiethanol Sodium cyanide Wetting water for bath temperature

5 g

15 ml

2 g

6 ml

0.000015 ml 10 mg 1 g 1 1 bath liquid 45 ° C

009849/14 6 Q

- 15 -

ORfGfNAL INSPECTED

EXAMPLE 9

Like example 8, but with

0.07 to 0.1 mg of 2-mercaptobenzenethiazole as a sulfur compound

2 g of chloroacetonitrile as CN compound

EXAMPLE 10

Like example 7, but with

2-mercaptobenzenethiazole, 0.1 mg as a sulfur compound

30 mg lactonitrile as CN compound

Bath temperature 55 ° C

EXAMPLE 11

Like example 3, but with

0.07 to 0.1 mg of 2-mercaptobenzenethiazole as a sulfur compound

Glyconitrile, 12 mg, as a CN compound

Bath temperature 20 ⁰ C

- 16 -

0098A9 / U60

152U35

EXAMPLE 12

As in Example 8, but with 0.01 mg of potassium polysulphide as the sulfur compound,

For the use of the autocatalytic bath solutions described, the surfaces to be plated must be free be of fat and other substances that hinder the separation. Shall non-metallic surfaces clad they must be made aware of this in a known manner. This can be done, for example, by Treatment with tin (I) chloride solution and with dilute palladium chloride solution done or advantageously with a bath liquid containing both chlorides, namely the tin chloride in a stoichiometric excess, contains. Such pre-treatment is not necessary for metal surfaces and is usually sufficient it is to degrease them and then treat the surface with an acid such as hydrochloric acid or phosphoric acid to free from oxide layers. Then the prepared surface is in one of the inventive Brought bath solutions and left in this until the copper layer reaches the desired thickness Has. '

- 17 -

009 8 49 / USS

152U35

In a further development of the invention it was found that the effective sulfur compound is not directly the Bath liquid needs to be added; under certain circumstances it is more advantageous in terms of the preliminary proceedings that to be covered surface of non-metals to equip with a layer that such a connection in contains a corresponding amount. This also results in a deposition of copper the districts that are particularly sensitive to this will remain limited.

009149/1410

18 INSPECTED

Claims (1)

152U35 Expectations 1. Bad sum deposition of copper coatings on any Surfaces without external power supply, which contains a bath stabilizing additive, im essentially consisting of such and water, a water-soluble copper salt, a Complexing agent for copper (II) ions, an alkali metal hydroxide and formaldehyde, thereby characterized in that there is a small amount of a stabilizing, divalent Contains sulfur compound. 2. Bath according to claim 1, characterized in that the concentration of the copper salt between 0.00? and 0.6 mol / l, that of the complexing agent for copper (II) ions 0.7 to 2.5 times the amount of Mole dos copper salt and that of formaldehyde is between 0.03 and 1.3 mol / l and the amount of alkali metal hydroxide is such that dBR is in the Bathroom floors have a pH value between 10.0 and 14 adjusts and the bath liquid next to the divalent - 19 - 009849 / USQ ORIGINAL INSPECTED Sulfur compound is a cyanide compound in at a concentration of 0.00001 to 0.06 mol / l. 3. Bath according to claim 1 or 2, characterized in that that the sulfur compound is taken from the group is, the aiis thio derivatives dec alkyl glycol, aliphatic S-N compounds, heterocyclic five-ring compounds that contain S-N in the ring, Thioamino acid, alkali sulfides, alkali polysulfides, Alkalithiocyp.atcn, Alkalidithionaten or mixtures thereof. 4. Bath according to at least one of claims 1 to 3, characterized in that the cyano compound is an inorganic cyanide or an organic citrile. 5. Had according to claim 3 or 4 _t, characterized in that the aqueous bath liquid contains a water-soluble copper salt in an amount of 0.002 to 0.2 mol / l, a complexing agent for copper (II) ions in an amount of 0.001 to 0, 50 mol / l, formaldehyde in an amount of 0.06 to 0.50 mol / l 009849/1460 BATHROOM ORIGlNAt. 152U35 Alkali metal hydroxide in a colchcr. Amount DNSS calibration pin pH between 1C and 1 ¹ adjusts NVI _r "r-jtir flume amount of a divalcnton Schvefel- v rb ir. Contains dung that a stable dissociable ·? Chelate with copper (1) ion to form ahead. f. Had according to claim 5, characterized in that it has a cyanic content in an amount between 0.00005 and 0.01 mol / l . 7. Bath according to claim 5 or 6, characterized in that that the active sulfur compound in a con -6 centering of about 1 χ 10 is essential. Parts by weight 8. Process for the deposition of copper layers on any suitable surface without power supply from the outside, characterized in that a bath liquid is used for its production, the composition of which is at least one of the preceding Meets requirements 9 · Process according to claim β for producing copper * layers on here sensitized surface 009649 / U60 -Bl- SAD ORIGINAL 152U35 layers of non-metals, characterized in that that the amount of divalent sulfur compound present in the bath solution is such that a deposit on non-sensitized surfaces is largely or entirely prevented. 10. The method according to claim 8 or 9, characterized in that the divalent sulfur compound is located in the carrier material surface to be partially coated with copper. 11. The method according to claim 10, characterized in that the surface to be provided with a copper pattern is first provided with a preferably non-conductive intermediate layer, which is up to -6 300 χ 10 parts by weight of a divalent sulfur compound contains that this intermediate layer is then sensitized in the areas predetermined for the electroless metal deposition and that then the entire surface is exposed to an electroless copper plating bath. 12. The method according to claim 10, characterized in that that the effective amount of the sulfur compound is preferably between 0.01 and 0.2 χ 10 and below 1 χ 10 " Parts by weight is 001148/1460 BATH ORIGINAL