CH621152A5 - Process for metallising surfaces - Google Patents

Description

621 152

PATENT CLAIMS

1. A method for metallizing surfaces according to claim I of the main patent, characterized in that the reducible metal salt is applied in the form of an aqueous solution to the base material, the pH of which is between 1.5 and 4, and the one compared to the amount of the reducible metal salt contains a small amount of halogen ions.

2. The method according to claim, characterized in that the reduction of the metal salt is started by the action of visible light.

3. The method according to claim, characterized in that the reduction of the metal salt is started by UV radiation.

4. The method according to claim, characterized in that the reduction of the metal salt with a co-used reducing agent, for example with a light-sensitive, reducing compound from the group of iron salts, anthraquinones, glycine and ascorbic acid.

5. The method according to claim, characterized in that the metal salt solution, the pH value of which is preferably between 2.5 and 3.8, contains a secondary reducing agent, for example a polyhydric alcohol such as sorbitol.

6. The method according to claim 4, characterized in that the reducing agent contains anthraquinone-2,6-disulfonic acid disodium salt.

7. The method according to claim, characterized in that the reducing agent-containing aqueous solution of the reducible metal salt contains citric acid and a polyhydric alcohol from the group of glycerol, sorbitol, pentaerythritol and mesoerythritol.

8. The method according to claim, characterized in that a metal layer of copper, nickel, cobalt, silver, gold, tin, rhodium or zinc is deposited on the metal seed layer from an electroless metal depositing bath.

9. The method according to claim 8, characterized in that the surface treated with the solution of the reducible metal salt is dried before the reduction initiated by the action of radiation, and that the surface is brought into a rinsing bath after the reduction under the action of radiation and before the electroless metal deposition becomes.

10. The method according to claim 5, characterized in that said solution contains a bromide, for example copper bromide.

11. The method according to claim 5, characterized in that said solution contains a wetting agent.

The main patent no. 606 485 describes a method for metallizing surfaces, which is characterized in that the surface of a base material is sensitized by coating it with a layer of one or more metal salts from the series of copper, nickel, cobalt and iron salts, which can be converted to a layer of metal nuclei by the action of energy or a chemical reducing agent, which is itself non-conductive, but can catalyze the deposition of metal from an electroless plating bath and then the applied metal salt by the action of energy or reduced from a reducing agent to catalytically active metal nuclei, and that a metal layer is subsequently deposited in the areas sensitized in this way by means of an electroless metal-depositing bath.

It has now been found that this process can still be improved if the reducible metal salt is applied to the base material in the form of an aqueous solution, the pH of which is between 1.5 and 4, and the one compared to the amount of the reducible Metal salt contains small amounts of halogen ions.

According to the invention, the solution containing the reducible salt has a pH of 1.5 to 4.0, preferably 2.5 to 3.8. Acids and acidic salts are suitable for setting this value. In addition, a small amount of halogen ions, in particular chlorine, bromine or iodine ions, is added to the solution compared to the amount of the reducible metal salt. These two conditions together have a surprising effect on the density and the intensity of the image created after the reduction process. The agent used for the pH adjustment does not only have to serve the pH adjustment, it can perform several functions at the same time. For example, a radiation-sensitive reducing agent can simultaneously have an acidic nature, such as ascorbic acid. The halogen ion can also be added in the form of an acid such as hydrochloric acid. In general, the following may be mentioned as suitable substances for adjusting the pH of the solution: fluoroboric acid, citric acid, lactic acid, phosphoric acid, sulfuric acid, acetic acid, formic acid, boric acid, hydrochloric acid, nitric acid and the like.

A large number of halogen compounds have proven to be usable as halogen ion sources. Examples include: copper bromide, nickel chloride, potassium iodide, sodium iodide, cobalt and copper chloride, lithium chloride, magnesium bromide, sodium bromide and the like. In general, bromides are preferred to the other halides because experience has shown that they produce denser and darker metal seed layers.

The amount of halogen ions represents only a small percentage of the total components in the solution. It is generally between 0.045 and 1.6%, preferably between 0.13 and 0.45%, or 0.9 to 25 milliequivalents per liter of sensitizing solution, preferably 2.5 to 9 milliequivalents, for example 0.3 to 1.0 g / liter of copper bromide. It has been shown that a further increase in the halogen ion content has a negative effect on the image intensity, that is to say it reduces the sensitization effect. It has also been found that the amount of halogen ions must be small compared to the amount of reducible metal salt. The ratio of reducible metal ion to halogen ion should be at least 2: 1, but preferably 4: 1 to 100: 1. A partial replacement of the chloride, bromide or iodide with fluoride can increase the sensitizing effect of the solution.

If the surface treated with the described sensitizing solution is reduced after drying, for example irradiated with UV, the reduction is generally complete and the surface has now proven to be catalytically effective for metal deposition from electroless baths. It has proven to be advantageous to bring the catalytically active surfaces into the electroless metal separating bath very soon after the reduction and, if appropriate, the development. In the event that the treated plastic plate is provided with perforations, the perforated walls, if they have not been protected against the action of the reducing agent or the radiation, are also catalytically effective for the metal deposition from electroless baths. The hole walls metallized in this way then represent metallically conductive connections between the two surfaces of the plate.

2nd

5

10th

15

20th

25th

30th

35

40

45

50

55

60

65

3rd

621152

The reduction of the metal salt applied can be initiated, for example, by the action of visible light, UV radiation or reducing agents.

The baths suitable for electroless metal deposition on the surfaces pretreated according to the invention generally consist of aqueous solutions in which the metal to be deposited is contained in the form of a water-soluble salt. They also contain a reducing agent for this metal salt and a complexing agent for the metal ions. This complexing agent forms a water-soluble complex with the metal ions.

Moreover, the corresponding electroless copper, nikkei, cobalt, silver, gold, tin, rhodium and zinc baths are well known to those skilled in the art.

A typical example of electroless copper deposition i is given here:

Copper sulfate 0.03 mol / 1

Sodium hydroxide 0.125 mol / 1

Sodium cyanide 0.0004 mol / 1;

Formaldehyde 0.08 mol / 1

T etra sodium ethylenediamine

tetraacetate 0.036 mol / 1

Make up to 11 with water.

The working temperature of the bath is preferably set to; Kept at 55 ° C. After 51 hours, the layer thickness of the ductile, deposited copper is 28 | i.

In a further embodiment, for example, only a thin copper layer is deposited on the metal seed layer from the electroless copper plating bath mentioned above and then electrolytically plated to the desired layer thickness. It goes without saying that any other metal, such as copper, nickel, silver, gold, rhodium, tin or alloys of these metals, can also be plated onto the electrolessly deposited copper layer. For printed circuits, however, copper conductors are generally used as the base, which can optionally have more noble metal coatings as corrosion protection.

For example, the following can be used as the galvanic copper bath:

Copper fluoroborate Cu (BF.t) 2 fluoroboric acid HBFt boric acid H3BO3 pH value

Working temperature current density

225-450 g / 1 2-15 g / 1

12-15 g / 1 4

0.6-1.2 25-50 ° C

25-70 amp / 1000 cm2

For example, the following can be proposed as a galvanic silver plating bath:

AgCN

KCN

K2CO3

Brightener of your choice pH

Working temperature current density

50 g / 1

HO g / 1 55

45 g / 1

11.5-12 25-35 ° C

5-15 amp / 1000 cm2 60

The following is proposed as a galvanic nickel plating bath:

Ni SO4 • 6 H2O 240 g / 1

Ni CI2 • 6 H2O 45 g / 1

Boric acid 30 g / 1

pH 4.5-5.5

Working temperature 45 ° C

Current density 20-65 amp / 1000 cm2

The generally customary baths can be used for all other metals.

Examples 1 to 4

An unclad epoxy glass press plate is pretreated as follows:

a) The plate is immersed for 1 minute in a mixture of 1: 1 (by volume) of 1,1,1-trichloroethane and dimethylformamide (with a wetting additive of about 1 g).

b) The excess trichloroethane is evaporated in the fume hood, while a damp coating of dimethylformamide remains on the plate.

c) The plate is then immersed in the following mixture at 45 ° C. for 10 minutes:

Cr03 100g / liter

Make up H2SO4 (concentrated) 300 ml / liter with water to 1 liter.

This mixture is heated to 100 ° C for one hour and cooled to 45 ° C before use. D) The well drained plate is then immersed in the following neutralizing solution:

Sodium bisulfite 20g / liter

Wetting agent 1 g / liter

Make up sulfuric acid to a pH value of 4 with water to one liter.

e) The plate is immersed in a second neutralization bath of the same composition for 10 minutes.

f) The plate is then rinsed under running tap water for 10 minutes.

g) It is then immersed in an alkaline rinse bath at 100 ° C. for 15 minutes. The bath consists of 75 g / liter NaOH and 0.5 g / liter wetting agent.

h) Last rinse under running water.

i) Drying at room temperature.

The surface pretreated in this way is then coated with a metal salt layer using the immersion method. The metal salt solution has the following composition.

The plate thus coated with a reducible metal salt layer is irradiated with ultraviolet light for 1 to 2 minutes. A metal seed layer forms. Subsequently, a firmly adhering, shiny ductile copper layer is deposited from an electroless copper depositing bath. The bath can have the following composition, for example:

The following is proposed as a galvanic gold plating bath:

Na Au (CN) 2 20-30 g / 1 dibasic ammonium citrate

(N H4) 2CöH507 25-100 g / 1

pH 5-7

Working temperature 45-60 ° C

Current density 5-15 amps / 1000 cm2

Mol / liter

Copper sulfate 65 sodium hydroxide sodium cyanide formaldehyde

Top up tetrasodium ethylenetetraacetate with water to one liter.

0.02

0.125

0.0004

0.08

0.036

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4th

The surface of the plate and any inner walls of the hole are covered with a firmly adhering, shiny ductile copper layer.

Paper or woven material can also be used instead of the press material. 5

The solutions used to apply the metal salt layer had the following composition:

Example 1 10

Copper formate 10 g

Antrachinone-2,6-disulfonic acid disodium salt 3 g

Water 450 ml

Glycerin 30 ml

Citric acid 30 g 15

Tin chloride 1 g

Wetting agent 0.25 g

Example 2

Partial solutions A and B are prepared separately and 20 are then mixed:

Tin chloride wetting agent

Make up to 11 with water.

0.5 g 0.5 g

A copper nuclei layer forms on heating, on which metal is subsequently deposited from a bath that deposits electroless metal.

Example 6

The same procedure as in Example 1 is repeated, but nickel is deposited on the copper seed layer from an electroless bath. The nickel plating bath has the following composition:

Nickel chloride

Sodium hypophosphite

Glycolic acid

Sodium hydroxide

Make up to 11 with water.

30 g 10 g 25 g 12.5 g

Partial solution A

Copper gluconate

water

Partial solution B

Wetting agent

Glycerin

citric acid

Anthraquinone-2,6-disulfone-

acid disodium salt

Tin chloride

water

15 g 200 g 25

0.1g 30g 30g3o

2 g lg 250 g

The pH is adjusted to 4.5 and the bath temperature is kept at 95 ° C. A nickel layer is deposited on the copper nuclei.

Example 7

The same procedure as described in Example 1 is repeated with an electroless cobalt bath. The cobalt bath has the following composition:

Cobalt chloride N atrium hypophosphite N atrium citrate dihydrate Ammonium chloride Make up to 11 with water.

30 g 20 g 20 g 50 g

Examples 3 and 4

As in Example 2, two partial solutions are prepared, which are then mixed. However, they have the following composition:

The pH is adjusted to 9.5 and the bath temperature is 90 ° C. A cobalt layer is deposited on the copper seed layer.

40 Example 8

The process according to Example 1 is carried out instead of using a

Partial solution A

3rd

4th

los copper depositing bath with an electroless gold

Copper acetate

15 g

depositing bath repeated. The gold plating bath has

Copper nitrate

15 g the following composition:

water

200 g

200 g

45

Gold chloride hydro

0.01 mol / 1

Partial solution B

3rd

4th

chloride trihydrate

Wetting agent

0.25 g

0.25 g

Sodium hypophosphite

0.014 mol / 1

Glycerin

30 g

30 g

Dimethylaminoborane

0.013 mol / 1

citric acid

30 g

30 g

50 sodium cyanide

0.4 mol / 1

Anthraquinone-2,6-

3g

3g

Make up to 11 with water.

disulfonic acid disodium

salt

The pH is set to 13, the bath temperature

water

250 g

250 g is 60 ° C. A gold layer builds up on the copper seed layer

Tin chloride lg lg

55 shifts.

Example 5

The process as described above is carried out with a metal salt solution of the composition described below, using L-ascorbic acid as the radiation-sensitive reducing component:

Silver nitrate

Copper acetate 4 g sodium potassium tartrate

L-ascorbic acid 5 g 65 sodium cyanide

Pentaerythritol 25 g dimethylamine borane.

Sorbitol 30 g Make up to 11 with water.

Citric acid 20 g

Example 9

The process according to Example 1 is repeated instead of using an electroless copper plating bath using an electroless silver 60 plating bath. The silver bath has the following composition:

1.7 g 4.0 g

1.8 g 0.8 g

5

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The pH is adjusted to 13, the bath temperature is 80 ° C. A silver layer builds up on the copper seed layer.

In the same way as the copper seed layers, nickel, cobalt and iron seed layers can also be built up, on which metals from electroless baths can subsequently be deposited in the same way.

Examples 1 to 9 shown here illustrate

that a metal salt layer can be reduced by radiation energy or heat to metal nuclei, which are catalytically effective for the metal deposition from electroless baths. The electrolessly deposited metal layers can be further reinforced.

Example 10 15

A resin pressed board is pretreated as in Examples 1 to 4 and provided with holes. The plate is coated with the following metal salt solution:

Sorbitol

Anthraquinone-2,6-disulfone-

acid disodium salt

Copper bromide

Copper acetate

Wetting agent

40% fluoroboric acid to adjust the pH

Make up to 11 with water.

120 g

16 g 0.5 g 8 g 1.5 g 3.5

Copper acetate anthraquinone-2,6-disulfonic acid disodium salt sorbitol

citric acid

Tin chloride

Wetting agent

Make up to 11 with water.

8g20

16 g 60 g 40 g 0.5 g 25 lg

The plate is then dried at 50-60 ° C for 5 minutes. The dried salt layer on the upper side of the plate is then exposed to a UV light source for 2 minutes. The inner walls of the hole are also hit by UV radiation. As a next step, the unirradiated areas of the surface are removed by rinsing with warm water. The plate is then placed in a electroless copper plating bath, from which copper is deposited on the surface and on the inner walls of the hole. If desired, it can then be electroplated by switching the plate to be coppered as the cathode. 40

A plurality of cleaned and pretreated epoxy glass pressed sheets which are provided with holes are sensitized according to the method described in Examples 1 to 4 and then, as described there, provided with a copper layer from an electroless copper depositing bath.

The pretreated plate is immersed in the sensitizing solution at a temperature of 40 ° C. for 3-5 minutes, carefully drained, all liquid removed from the holes, dried, brought to normal conditions (room temperature at 30-60% relative humidity), irradiated with UV and developed during 2 minutes under cold, running water, that is, the unexposed, i.e. not reduced, metal salt is rinsed off. (Make sure that only yellow light is used.) The UV radiation is carried out using a mercury lamp (4800 watts at a distance of 20 cm).

In a comparative experiment under the same conditions, but with the omission of the copper bromide and the fluoroboric acid to adjust the pH, it was found that the image density or the copper seed density is significantly lower than in the previous experiment.

The sensitizing solution described in Example 12 is characterized by good stability. It remains usable up to 6 months after preparation if the following is observed. The solution must be filtered daily, the pH and density must be measured weekly and readjusted if necessary. It is important to keep the copper acetate concentration at 7.8-8.5 g / 1 and the anthraquinone salt concentration at 15-16 g / 1.

Example 11

An insulating material plate is coated with an adhesive resin layer using the immersion method. The adhesive resin has the following composition:

Acrylonitrile butadiene copolymer

Phenolic resin

Methyl ethyl ketone

72 g 14 g 1200 g

Examples 13 to 30

A number of appropriately pretreated epoxy glass pressed sheets are sensitized as described in Example 12, with the difference that the exposure is carried out by a UV light source with 1500 watts and by a Stouffer wedge. The composition of the comparison solution is as follows:

The adhesive resin layer is cured, then treated with chromosulfuric acid and finally coated with a reducible salt by dipping into the solution described in Example 10. The plate is then dried at 55-60 ° C. for 5 minutes and then exposed to UV radiation for 2 minutes. A copper seed layer forms on the adhesive resin layer. Electroless copper can also be deposited on this, which can subsequently be reinforced by electroplating if desired. This method achieves particularly good adhesive strengths of the metal layer on the base.

Example 12

A further sensitizing solution is prepared as follows: the following substances are added to 800 ml of water in the order given at room temperature:

50 sorbitol

Anthraquinone-2,6-disulfonic acid disodium salt

Potassium bromide

Copper acetate

Wetting agent

55 Make up to 11 with water, pH 5.62.

120 g 16.2 g 1.0 g 9.0 g 1.5 g

The Stouffer wedge has 21 squares of graduated optical density from complete light transmission (No. 0) to complete light transmission (No. 20). After the test plates have been developed and dried, the number of quadrilaterals shown is determined and a measure of the sensitization intensity of the individual sensitization solutions obtained. An image number of at least 5, preferably 7, is desirable.

65 A bath solution as described above is divided into a corresponding amount of test batches and with different acids to demonstrate the influence of the pH and the acids used to adjust the pH

621152

and amounts of acid added. I and II serve as comparative tests with extremely low pH values. In Table I below, the result is first determined without any addition of acid. Then different amounts of

Citric acid, fluoroboric acid and phosphoric acid are added to the above solution and the pH is determined, and the level of sensitization is determined by the above-mentioned method.

Example acid addition no.

Table I

pH measured values the mean

. Sensitization- Strength Sensitization-

strength

Check no addition

4.62

6

5

7

6.0

attempt

I *

citric acid

1.4

3rd

5

5

4.3

13

citric acid

2.05

6

6

7

6.3

14

Citric acid 45 g / 1

2.1

7

-

-

7.0

15

Citric acid 22.5 g / 1

2.4

8th

-

-

8.0

16

citric acid

2.5

10th

10th

11

10.3

17th

Citric acid 10 g / 1

2.6

10th

-

-

10.0

18th

citric acid

2.92

8th

9

11

9.3

19th

citric acid

3.5

8th

8th

9

8.3

20th

citric acid

3.96

8th

8th

10th

8.6

II *

Fluoroboric acid 40%

1.06

0

0

0

0

21st

Fluoroboric acid

2.20

8th

10th

9

9.0

22

Fluoroboric acid

2.5

8th

10th

9

9.0

23

Fluoroboric acid

2.9

-

10th

9

10.5

24th

Fluoroboric acid

2.96

8th

10th

11

9.6

25th

Fluoroboric acid

3.5

-

10th

10th

10.0

26

Fluoroboric acid

3.7

7

7

7

7.0

27th

Fluoroboric acid

4.0

7

8th

8th

7.7

28

Phosphoric acid 80%, 200 drops / 1

2.05

8th

-

-

8.0

29

phosphoric acid

3.15

10th

-

-

10.0

30th

sulfuric acid

2.0

7

-

-

7.0

* Experimental approaches for comparison purposes

45

According to Table I it can be stated that the whole solution The starting solution without special acid additives obviously has a dependency between sensitization and a pH of 4.78 and is composed as follows:

strength and pH is present, and that apparently for everyone

Acid determine an optimal pH value or pH value range - sorbitol 120 g / 1 bar is 50 anthraquinone-2,6-disulfone

It was also possible to ascertain - specifically with the acid disodium salt 16 g / 1

Use of glass instead of pressed boards - that the adhesive copper acetate 8 g / 1

strength of the resulting metal nuclei a certain amount of copper bromide 0.5 g / 1

acid additive and phosphorus wetting agents show 2.0 g / 1

and fluoroboric acid have a better adhesive strength than lemon and fill up to 11 with water.

Sulfuric acid. It goes without saying that the acid additives can be combined in such a way that the result obtained with this starting solution is optimal in terms of both density and adhesion. Table II is also referred to as a comparative test. an experiment with fluoroboric acid and particularly low

The following examples, which - unless 60 pH of 0.82 (comparative experiment III) and experiments IV particularly mention - make use of the mentioned method, and make V with particularly high pH values. (The setting - the effect of the acid and the halogen additives was demonstrated. The pH was determined by NaOH.) The photosensitivity, as described here before, was determined with Stouffer Wedge Examples 31 to 52. In contrast to those summarized in Table I

Further tests on the effect of the acid and the 65 tests made, the intensity according to the pH value on the image intensity are measured in Table II electroless plating of a thin copper layer.

7

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Table II

Example No. Acid addition pH

Measured values of sensitization before application after application

the Cu layer to the Cu layer

Comparative no additional attempt

31

Fluoroboric acid

32

Fluoroboric acid

33

Fluoroboric acid

34

Fluoroboric acid

35

Fluoroboric acid

36

Fluoroboric acid

37

Fluoroboric acid

Comparative

Fluoroboric acid experiment III

38

Lactic acid

39

Lactic acid

40

Lactic acid

41

Lactic acid

42

Lactic acid

43

Lactic acid

44

Lactic acid

45

citric acid

46

citric acid

47

citric acid

48

citric acid

49

citric acid

50

Citric acid 20 g / 1

51

Citric acid 30 g / 1

52

Citric acid 40 g / 1

Comparative

(NaOH)

try IV

Comparative

(NaOH)

try V

4.78

3rd

4th

4.00

7

7

3.75

8th

8th

3.50

9

8.5

3.00

8th

8th

2.50

7

7

2.00

6

6

1.50

6

6

0.82

4th

3rd

4.00

6

7

3.75

8th

8th

3.50

8th

8th

3.00

7

7

2.50

7

7

2.00

6

6

1.60

3rd

3rd

4.10

7

7

3.70

10th

8th

3.48

11

9

3.00

8th

7

2.50

7

7

1.90

7

6

1.68

6

5

1.62

6

4th

6.40 *

2nd

1

11.50 *

0

0

Note: At a pH of 6.4, a precipitate forms, which is dissolved again with a higher acidity.

Tables I and II show that the addition of halogen significantly increases the image intensity and that there is a specific pH range for each acid in which ■ the best values with regard to the level of sensitization are achieved. In general, it can be said that useful results are achieved in pH ranges between 1.5 and 4.0, and generally the best results are in pH ranges between 2.5 and 3.8 .

Examples 53 to 64

The following examples are intended to show the influence of halogen ions on the sensitization intensity. The procedure of Examples 31 to 52 is followed, but the sensitizing solution contains other halogen compounds instead of copper bromide. The sensitizing solution is composed as follows without acid and halide:

acid disodium salt

Copper acetate

Wetting agent

Make up to 11 with water.

16 g / 1 8 g / 1 2 g / 1

Sorbitol

Anthraquinone-2,6-disulfone-

This starting solution is divided into a number of samples 55, and 4.5 milliequivalents of different halides are added to each of these. This amount corresponds to 0.5 g / 1 copper bromide. The pH of the test solutions is adjusted to 3.5 with fluoroboric acid. Experiments 54 and 56 are exceptions, since here the hydrochloric acid and the hydroiodic acid 60 perform both functions, namely that of adding the halide and adjusting the pH, so that these samples contain significantly more halide and no fluoroboric acid. Test solutions 63 and 64 each contain 2.25 milliequivalents of copper bromide and sodium fluoride or 120 g / 1 65 sodium iodide. The test results are summarized in Table III.

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Table III

Example-

Halide

pH

Measured values of the sensitivity

No.

additive

intensity

Comparative no addition

3.5

3rd

attempt

53

HCl

3.5

4th

54

HCl

3.5

4th

55

CuCh

3.5

6

56

HI

3.4

4th

57

Nal

3.5

7

58

Nal **

3.5

6

Comparative

Nal

6.0

2nd

try VI

Comparative

Nal

11.5

2nd

try VII

59

AI

3.3

6

60

AI

1.5

0

61

Bromine water

3.5

7

62

CuBn

3.5

8th

63

CuBr2 + NaF

3.5

9

64

CuBn + Nal

3.5

7

** The sensitizing solution is filtered beforehand.

Fluoride as the only halide additive does not cause the same test solution as in the previous amplification. It is understandable that the addition of iodide causes 53-64 and the pH of this initial solution causes the copper to precipitate and is therefore less suitable. Solution adjusted to 3.5 with fluoroboric acid. This solution is in

10 samples were divided and, as shown in Table IV, various examples 65 to 73 30 den of amounts of copper bromide were added. The sensitization

In order to obtain a better assessment of the effect of the cone intensity, the method described in Examples 31 to the concentration of the halide additive is again determined, 52 again.

Table IV

Example No. CuBrcg / l pH readings

Sensitization strength after applying a copper film

Comparative

-

3.5

2nd

attempt

65

0.5

3.5

8th

66

1.0

3.5

7

67

1.5

3.5

6

68

1.75

3.5

6

69

2.0

3.5

6

70

2.5

3.5

6

71

3.0

3.5

4th

72

4.0

3.5

3rd

73

5.0

3.5

0

The measured values in Table IV show a certain dependency of the sensitization intensity on the bromide concentration of the solution. Optimal values are achieved between 0.5 g / 1 and 2.5 g / 1.

From the previous series of experiments it can be seen that the presence of a halide ion, preferably a bromide, crucially affects the intensity of the

Solution achieved sensitization or on the number of copper nuclei formed on the surface to be sensitized after UV irradiation, which have a catalytic effect on the subsequent metal deposition from electroless baths, also follows from the fact that compliance with certain pH value limits between 1.5 and 4.0 is essential for the effectiveness of the sensitization solution.

G