DE2122263A1 - Process for the production of a primary brightener for acid electroplating tinning baths - Google Patents

Description

Priority: 6.5 * 1970 - DSA

Luster deposits produced from acid galvanic tin-plating baths are increasingly being used in the electronics industry for printed circuits, for other electrical contacts and also for devices which "serve for example in the packaging of food products". In printed circuits, it is extremely important that the deposits are shiny Such shiny deposits give better protection and shiny deposits can be soldered more easily (for unknown reasons) c

Boi the deposition of shiny tin on printed Circuits and also, in other applications, this is done in a maesan production technology, with thousands of the the same items can be produced in a single operation. For this reason it is important that the Baths for the separation of tin have a high degree of constancy and can be operated easily, otherwise dio Mass production cannot be carried out economically can.

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BATH

The deposition of shiny tin on mass-produced goods is going on for example carried out so that the objects on can be hung on a rail ^ which is then immersed in the bath. Drum processes are also used for Maasen tinning into consideration.

When electroplating it is important that the used Bath within the largest possible current density range shiny separations result in the ones to be electroplated Parts can have a wide variety of shapes and have to be processed in a wide variety of quantities. Farther it is important that the current density (the current density at which no good separation is obtained) as high as possible to accommodate the large cathode current densities which can occur due to the shape and size of the electroplated parts.

In the previous acidic galvanic tinning baths, tar and tar fractions, obtained by dry distillation of wood * used. Such electrolysis are difficult with the required To produce reproducibility, and for this reason it is not easy to use shiny pewter cladding of constant quality for long periods * Furthermore, the tin deposits that were caused by many of the baths known heretofore were obtained, not sufficiently shiny. After all, many well-known baths suffer under certain operational difficulties, such as extreme sensitivity to agitation. Incorrect stirring intensity often resulted in streaky deposits.

According to the invention it has now been found that tin deposits with an improved gloss and in one fully reproducible whiteness can be obtained »if one in acidic galvanic tinning baths known per se as cooperating addition incorporates the product which one

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obtained by converting furfural and grotonaldehyde and which in the following is referred to as the primary shimmer "" Furthermore, the primary shiners of the invention work with known additives such as ZcB. secondary glossers and wetting agents well together, considering their gloss effect and the permissible in their use; to shiny deposits leading l & thoden current density range to expand «Bb is so a lot when using the glossers according to the invention

the

less maintenance required / especially in mass production important is.

It has also been found that when using the shine according to the invention in a customary acidic Electroplating, a current interruption is very usefulc This is carried out in a certain cycle, with deposits with an even greater uniformity and even greater gloss than using a steady stream.

The additives, which together with the inventive Primary glossers used are, for example, non-ionic alkoxylated products (wetting agents) and formaldehyde (secondary glasses). The use of such substances is well known. The wetting agent has the consequence that not a loosely adhering stained and sometimes dentritic critical liner 2.innniederschlag is obtained, but a dense, continuous., adherent, microcrystalline precipitate formaldehyde acts as a cathode depolarizing agent » when used together with the wetting agent, When formaldehyde alone with a wetting agent (in the absence of the primary luster according to the invention) is used, then only unsatisfactory precipitates are produced obtain.

It should be noted that the present invention in the most varied of "known acidic galvanic

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BATHROOM ORIGINAL

Tin baths are useful, such as baths that contain divalent tin salts (tin sulfate or tin fluoborate) and an acid (sulfuric acid or fluoboric acid). The invention is applicable to both drum processes and processes in which the objects to be electroplated are suspended on rails. The concentration of the tin and the free acid can be within the usual limit values, for example in the case of the known baths which contain sulfate, fluoborate or aromatic sulfonate and which have a tin content of 10 to 100 g / l and a free acid concentration of 20 to 200 _{The baths can contain sulfuric acid e} fluoboric acid or aromatic sulfonic acid as acids in a known manner.

The process variables, such as the desired rate of deposition as well as the shape of the object to be coated, in many cases determine the exact composition of the baths, as is well known. Can Further, known antioxidants that were used in the previous acidic galvanic Verzinnungsbädern also be used herein in small amounts "The temperature of the Verzinnungsbads is in general 'room temperature, it is preferably below 35 ⁰ C and in particular in a range between about 15 ° and 20 ⁰ C, in order to achieve an optimal working behavior of the bath.

It should be noted that, in order to achieve good results, the primary shine according to the invention is roughly the same Quantities is used, such as the already known primary Glänzero When preparing the baths, the quantities and / or Concentrations of the secondary brightener and the wetting agent vary considerably.

The following bath composition is an example of one 5Qad working well:

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TinndD sulfate (SnSO ₄ ) 30th g / l Concentrated sulfuric acid 105 ml / 1 (P. 1.84) Primary shimmer 0.25 s / i carrier 4th g / l Secondary shimmer 10 ml / 1

The secondary Glä.nzer preferably consists au ⁸ formaldehyde in a 37 # ~ solution. The carrier can be a known non-ionic alkoxylated wetting agent, such as, for example, polyoxyethylated nonylphenol with an average of 15 oxyethylene groups. The detergent is usually used as an aqueous base solution with a concentration of 400 g / l and added to the bath in a concentration of 40 ml / l, which results in 4 YoI .- # »The primary gloss is generally also in the form of a base solution in one organic solvents, such as ethylene glycol monoethyl ether, are added, their concentration preferably being 25 g / l. The basic solution is added to the bath at a concentration of 10 ml / l, which gives 0.25% by volume.

As already indicated, it has been found that a periodic current interruption during electroplating results in an even better shine Cathode is used, then surprisingly good results are obtained if the current is interrupted periodically every 10 βθο for 2 seconds ,, This cycle is preferred »but good results can also be obtained if current periods of approximately 10 to 20 seconds through currentless periods of about ! interrupted up to 5 aec.

Z'fi'xv can rlli Z troBiUni; · be AuihUnsjeschiend _fi js also /e.-veadot when working with a Troirjnel ', but they I3T of beüonderem benefits; .rbr <ichung rsowohl be Ln Working with oimr:

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BATH ORIGINAL

when working with a hanging rail, because this one Usually stirred only by moving the cathode which procedure is not always sufficient Stir results in order to etch the correct concentration of gloss maintain near the cathode surface,

When applying a power interruption in the inventive On the other hand, it was found that during the power interruption Sufficient brightening additives diffuse into the cathode film, which restores the brightener concentration there is increased, which leads to an improved gloss of the deposit.

The preparation of the erfindungegemäßen Glänzere can be carried out by reacting furfural and Orotonaldenyd reacted in approximately equimolar amounts, with a molar excess of 15% and in particular 10 $ Turfural is preferred Ea is preferably conducted in the presence of a catalytic amount of an "alkali, preferably sodium hydroxide, worked. It is also preferred to work in an aqueous medium, although organic solvents can also be used, such as, for example, ethylene glycol monoethyl ether or dioxane.

For example, 1.1 moles of furfural and 1 mole of crotonaldehyde can be converted. An excess of orotonaldehyde should be avoided, as it has been found that higher orotonaldehyde concentrations can result in self-polymerization of the product, which should be avoided since single products result in streaky Abaoheidungen. The reaction temperature is generally maintained in the range of about -5 ⁰ C and 5O ⁰ C and preferably between about O ⁰ C and 25 ⁰ O. Although good results have also been obtained at higher temperatures, it has been found that the primary gloss is obtained in higher concentrations when working at lower temperatures,

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Example 1 below explains the production of the inventive Glänzers using equimolecular amounts of furfural and crotonaldehyde.

example 1

41.4 ml of furfural (0.5 mol) and 45 ml of 90 # crotonaldehyde (0.5 mol) were added to 200 ml of water. The resulting suspension was cooled in an ice / salt bath to a temperature ranging between about ⁰ C -1 and +4 ⁰ C "4 g of sodium hydroxide (0.1 mol) were dissolved in 50 ml of water. The sodium hydroxide solution was then added dropwise to the aldehyde suspension with cooling and stirring. After the addition of the Katriumhydroxidlösung, during which a maximum temperature of 15 ⁰ C was reached, stirring was further continued st 2 Then, the solution with glacial acetic acid to litmus was acidified. The lower layer of the product was extracted three times with 150 ml of chloroform each time. The chloroform extract was then dried over anhydrous magnesium sulfate and filtered. Then the volatile components were removed under a water pump vacuum, the bath was maintained at a temperature between 70 ° and 8O ⁰ C. 83 g of reaction product were obtained. The product was a slightly viscous yellow-brown liquid.

The following examples 2 and 3 illustrate further preparation in each case of the primary gloss according to the invention "

Example 2

205 ml of furfural (2.5 mol), 225 ml of 90% crotonaldehyde (2.5 mol) and 500 ml of water were mixed and cooled in a bath / salt bath. After the temperature had dropped to ^{0 ° C., a} A solution of 20 g of sodium hydroxide (0.5 mol) as a solution in 150 ml of water was added dropwise with stirring and cooling. The reaction temperature was kept ^{below 20 ° C.}

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When the sodium hydroxide solution was added, the resulting solution was stirred for an additional 3 hours. Then 35 ml of glacial acetic acid were added (a slight excess of 0.5 mol) added with stirring. The reaction mixture was poured into a 2 liter separatory funnel brought in. 200 ml of saturated sodium chloride solution was added to allow the two layers to separate facilitate. The lower layer, which is the active component contained was separated. She weighed 394 g

The aqueous layer was extracted with chloroform, and 28 g of a thick yellow-brown liquid was obtained * That means a total yield of 422 g of primary gloss "

Example 3

Reaction container ι 95 1 stainless steel container, immersed in a 380 1 plastic tank which was filled with ice.

Materialet

! Furfural crotonaldehyde water sodium hydroxide (dissolved in 3.8 1 water) glacial acetic acid

Process furfural, crotonaldehyde and water were stirred and cooled ^{to 1 ° C.} The HaOH solution was slowly added to the mixture. After 800 ml was added, the temperature began to rise. At a temperature of 45 ⁰ C, a cooling coil made of tantalum, which duroh tap water flowed at 4 ⁰ C was immersed. The temperature rose within about 1 st to a maximum of 50 ⁰ C. After about 1 st the temperature had fallen back to about 15 ⁰ C, after which the rest dor LÖ3ung NaOH was added with no further temperature increase occurred.

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22.8 1 190 1 38 1 840 G 1700 ml

The mixture was then stirred for 4 hours, with 1700 ml of glacial acetic acid were added in small portions to bring the pH to approximately 6.0. The reaction mixture was then left to stand and the upper aqueous layer was siphoned off. The thick remaining material was put in 13 polyethylene containers with a fit of 3.3 l each. These were left standing for another separation of the water, which was then decanted off »The total weight of the products was approximately 54.5 kg.

Although aqueous solutions were used in the above 3 examples, but it is also within the scope of the invention to carry out synthesis in organic solvents such as e.g. Ethylene glycol monoethyl ether or dioxane to run. at this practice is only a trace of sodium hydroxide necessary to get the reaction going. The products are essentially the same as when they were used an aqueous medium. Whether the products are in an aqueous or in an organic solvent they are equally well suited to all primary ones Glancerο

The exact composition and the exact content of the reaction products are not known. Ea is, however, assumed that the product consists of several components which all work together to achieve good results in the to allow galvanic deposition of tin.

Although these components are not known, it is assumed that they contain the following components: 2-Purylacrolel, 2-Purylpentadienal, 2- (1-Hydroxyethyl) -3- (2-furyl) -acrolel, and acetaldehyde, as well as presumably some unreacted Auogangsmaterialien _ü In Versuohen was found, however, that dia mögllohen individual components, such as 2-Purylacrolein, ^ iri'ural. and grotonaldehyde ^ do not produce any gloss effect in a.'iureu pre-simmering baths. Even in combination, the suspected components did not produce any gloss effect. It can therefore be said that the

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total reaction product resulting from the implementation of the Examples 1 to 3 is obtained, is necessary to the invention Achieve results.

As stated earlier, when using this Reaction products as primary shine in otherwise conventional acidic bright tinning baths get improved results. The primary Glänaer result together with the other usual additives, shiny deposits within a wide range of current densities. The degree of AbseheiauE £ - depends on the intensity of the stirring Concentration of the shimmer and the current conduction. the periodic current interruption mentioned above increases the Gloss formation. The deposits are very shiny. You can have a light veil that is aesthetic Appearance. In addition, auctfiA-edigen current densities get a good shine. The deposit adheres well to the coated metallic substrate. It can be a big one Series of metal substrates coated in accordance with the invention such as bis, copper, lickel, cobalt and the most diverse Alloys of these metals uew,

The concentration range of the primary gloss in the bath can vary greatly - depending on the desired results and the other additives and components of the bath. Obviously, too much shine does not result in any Sohaden; However, there is then an increased consumption of glosser, which increases the process costs

an be increased, in general it can be said that / area of the primary gloss in the bath between 0.1 g / l and 1 g / l, preferably between approximately 0.2 g / l and 0.4 g / l, a good one Effect.

The invention will now be further illustrated by means of examples, those with Hull cells using the reaction products

BATH 109850/1590

of Examples 1 to 3 were carried out.

Example 4

Into a standard Hull cell equipped with a magnetic stirrer which gave moderate agitation, 250 ml of an acidic dilution base solution containing 30 g / l SnSO ^ and 105 ml / l concentrated sulfuric acid (S ₀ O. 1 , 84) "To the solution was added 4 g / l of a non-ionic surfactant. A polished brass plate was cleaned, immersed in an oyanide copper plating bath for 1 min and rinsed. It was then briefly dipped in acid and rinsed with water. Then it was used at room temperature at a current of 1 ampere for 5 minutes in the Hull cell «,

The precipitate obtained was dull white, uniform and smooth and gave coverage only within a narrow one Current density range "

Example 5

Example 4 was repeated using 10 ml / l 37 # formaldehyde solution as an additional bath component became.

The first third of the plate in the high current density area had a non-uniform dark spotty deposit, whereas, as in Example 4, the remainder of the plate was matte white.

Example 6

Example 5 was repeated after the bath additionally Ο, 25 g / l of the primary gloss of Example 1 in the form of a 25 g / l basic solution in ethylene glycol monoethyl ether added became.

The precipitate obtained was glossy over the entire current density range of 0 Ma 6 A / dm ² and had an extremely good gloss.

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Example 7

Example 6 was repeated, but with the primary one Shine used the .Product of Example 2 in the form of a 25 g / l base solution in ethylene glycol monoethyl ether ο This precipitate, too, was uniformly glossy over the entire current density range and had an extremely good glossy appearance.

Example β

Example 6 was repeated except that the primary Shine from example 3 as 25 g / l basic solution in ethylene glycol monoethyl ether was used * Essentially the same results would be obtained.,

Example 9

In a rectangular glass tray (2O ⁰ C approximately) was added 4 1 subjected to acid Verzinnungsgrundlösung having a concentration of 30 g / l SnSOi and 105 ml / l concentrated sulfuric acid (SG 1.84) an electrolysis at room temperature. A tin plate of 99 »99% purity was suspended in the solution on a titanium wire as anode. The cathode consisted of a polished brass strip with the dimensions 20.3 ι 2.54 x 0.1 cm. After cleaning, the cathode was immersed in the plating bath to a depth of 18 cm, at a distance of 10 cm from the anode »with the front of the cathode parallel to the anode» The cathode was moved in a plane perpendicular to the anode with a stroke of 5 cm, with a total running speed of 160 cm / min »

To the 4 l bath, 0.25 g of the primary gloss from Example 2, 4 g / l of a nonionic surfactant and 10 ml / l of a 37% formaldehyde solution were added. A current of 2.5 A was applied for 10 minutes

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. ., · Z122263

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The deposit was uniformly glossy and had a milky appearance throughout,

Example 10

Example 9 was repeated, with a periodic current interruption, namely 10 eeo deposition, 2 seconds without current, and a current of 2.5 A was applied for a total of 12 minutes. This resulted in the same time of separation As in Example 9. Per precipitate obtained was essential shinier than in example 9.

Example 11

Using the 4 l solution from Example 9 (including additives), drum tinning was carried out, wherein a small plastic drum was used, which is rotated horizontally * Your description is as follows »

Hexagonal cross-section

Length 25 cm

Diameter 10 cm, rotating speed 5 rpm

Anodes outside, plates with

99 »99 # pure tin

310 g steel nails with a length of 3.3 cm each and one

ο
Total surface of 930 cm was cleaned and placed in the drum. The feed was balanced 1 et using a 5 amp cell flow. (Diee means an average cathode current density of 0.5 A / da ² ). After the coating, it was carefully rinsed and dried. The hailstones were plain and shiny. The hiedersole thickness was approximately

Example 12

Example 11 was repeated, but using a current of 10 A for 30 minutes. The resulting precipitate was uniform and glossy and possessed as well

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H-

an average tick of 6.4 ^.

To further explain the invention, a life test was carried out with the bath of Example 9 for 3 weeks. Eb was worked 8 hours a day "Occasionally , the additives were added" For 3 weeks, the bathroom continued to work excellently. No accumulation of harmful decomposition products of the additives could be observed .

BATH

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Claims (17)

Claims 1. Process but production of a primary shine for acidic galvanic tinning baths, characterized in that furfural and crotonaläehyd in amounts of equimolecular "up to 15 $ excess of furfural at a temperature of about -5 ° to 50 ⁰ C in the presence of a catalytic amount of one Converts alkali, acidifies the reaction mixture and separates the reaction products » 2. The method according to claim 1, characterized in that an excess of about 10 i * KoI furfural is used. Process according to Claim 1 or 2, characterized in that the reaction components are added before they are brought together dissolves in water » 4 ·. Method according to one of claims 1 to J>, characterized in that τη "η the reaction at a temperature" wipe about 0 ° and performs 25 ⁰ C. 5. The method according to any one of claims 1 to 4, characterized in that that the reaction is carried out in the presence of an aqueous solution of sodium hydroxide, 6. The method according to claim 5, characterized in that an aqueous solution of the reactants is first prepared and then the aqueous sodium hydroxide solution is added dropwise _r while the reaction mixture is stirred « 7. Verfa'hren according to one of the preceding claims, characterized characterized in that the acidification of the reaction mixture after the reaction with a slight excess run by glacial acetic acid. 109850/1590 BAD ORlOtHAL - 16 - 8. The method according to any one of the preceding claims, characterized characterized in that the separation of the reaction product is carried out by removing the reaction product extracted with chloroform and the chloroform separated off. 9. The method according to any one of claims 1 to 7, characterized in that that the extraction of the product is carried out by adding an aqueous solution of sodium chloride will" 10. Use of the reaction products according to one of the claims 1 "to 9f ia acidic galTanic tinning baths as primary shimmer. 11. Use according to claim 10, characterized in that formaldehyde is used as a secondary shimmer «, 12 = Use according to claim 10 or 11, characterized in that a wetting agent is also used. 13. Use according to claim 12, characterized in that a nonionic wetting agent is used as the wetting agent. 14. Use according to claim 13 »characterized in that a polyoxyethylated nonylphenol with an average of 15 oxyethylene groups is used as the hardening agent, 15. Use according to any one of claims 10 to 14, characterized in that the current is periodically interrupted will. 16. Use according to claim 15 «characterized in that the current flows between about 10 and about 20 seconds and then interrupted between about 1 and about 5 seconds. 109850/1590 BATH - 17 - 17. Use according to claim 16, characterized in that the current flows for 10 seconds and is then interrupted for 2 seconds. PATENT ADVOCATE! .H.FINCKE. 0IPL.-lNO.aaOH * 109850/1590