DE2256025A1 - METHOD AND COMPOSITION FOR THE GALVANIC DEPOSITION OF LEAD / TIN ALLOYS - Google Patents

Description

■ 2258025

K 23039 - Dr.Ε / Ρ ■ K-HD Case 937 ^ι

-CHSMICAIS-New York, H-.Y. V.St.A.

Process and composition for the electrodeposition of lead / tin alloys

Priority: December 20, 1971

United States of America

With the application of a lead / tin alloy, there is growing interest in glossier deposits for printed circuit boards, for rapid deposition on strips and wires, and for soldering contacts in electrical devices and printed circuit boards. The additives currently used in fluoborate baths are usually glue, gelatin or high proteose peptones. These prior art glancers are complex mixtures of materials, are generally poorly defined and vary in composition, and give off aggressive vapors in use due to the accumulation of degradation products. ^: ~

'309827/0993 ./.

BAO ORIGINAL

The most widely used additive for the electrodeposition of a tin / lead alloy is a peptone. When a peptone is used as additive, then a continuous, fairly fine-grained precipitate, instead of a discontinuously ^l ous spongy detrital covering is obtained which has in general a rather dark color and shows poor coverage in the low current density and a poor throwing power. The peptone tends to hydrolyze and can produce very unpleasant vapors in the galvanic bath.

The results obtained according to the invention are much "better than with the additional systems of the state of the art Technology are available.

The present invention provides the following specific improvements:

1 . The precipitates are much lighter in color and approach the white.

2. The precipitates are very uniform and show a considerable decrease in grain size.

3. The precipitates are much shinier, though not highly reflective.

4. The coverage at low current density is excellent and also the scattering power is improved.

The precipitates produced according to the invention are used in the electronics industry and other fields, in order to give the electroplated objects an improved appearance, in order to improve the solderability and to improve resistance to discoloration in use.

309827/0993

BAD ORI & NAL ' ^?

The aim of the invention is to create a new additional system for the galvanic deposition of tin / lead alloys, whereby this additional system consists of a chemical unit, which brings about a considerable improvement in the process over prior art systems.

Another object of the invention is to provide improved Baths for the production of tin / lead alloy precipitates with, an improved parbe and with 'improved Grain properties.

The present invention thus relates to an aqueous bath for the galvanic deposition of white, continuous fine-grained tin / lead alloys, with the characteristic therein lies that it contains the following:

a) 4 to 53 g / l divalent tin;

b) 1 to 85 g / l lead; :

c) 100 to 200 g / l free pluoboric acid;

d) 4 to 10 g / l of a polyether surfactant;

e) 0.5 to 1.0 g / l of an arylhydroxy compound selected from oaphthols and substituted phenols.

According to the invention there is also a method of manufacture of galvanic white, continuous fine-grained Tin / lead alloy precipitates have been proposed, which is carried out by going from an anode to a Metal cathode passes a current through an aqueous bath composition containing at least one water-soluble Tin (II) salt, at least one water-soluble lead salt, Fluoric acid, boric acid, at least one polyether surface

309827/0993 /

contains medium and at least one aryl! hydroxyl compound.

The compositions and methods are based on electroplating Deposition in drums, rails and on wires "applicable. The concentrations of tin and lead can be insane. generally fluctuate within the limits that are usual in this technique are. For example, baths can have a bivalent Tin content of 4 to 53 g / l and a lead content of 1 to 85 g / l are used together with the additives defined here v / earth.

Polyether surfactants which can be used in accordance with the invention include aromatic polyethers and aliphatic ^ Polyäxher. Preferably the wetting agent is a pclyalkoxylated one Alky! Phenol. Typical polyalkoxylated alkyl phenols are polyetrioxylated alky! phenols of the formula

O f- CHpCHpO A H

/ m

wherein R represents an alkyl group having 5 to 15 carbon atoms (preferably 9 carbon atoms) and m stands for an integer of at least 5 and preferably not more than 20,

Polyether surfactants are used in amounts of about 4 to 12 g / l (preferably about 8 g / l).

Other polyether surfactants which are known to be used in amounts from L to 12 g / l (preferably about 8 g / l) are nitrogen-containing aliphatic polyethers, which can be represented by the following general formula

3098 2 7/0993

BATH

■ · 5 - ■ i

where TL, R _? and R, stands for a straight or branched alkyl group with 3 to 15 carbon atoms, η stands for an integer of at least 5 and not more than 10 "and -Iu stands for a cation consisting of hydrogen, sodium, potassium and ammonium is selected.

According to "" the invention, a galvanic bath for ■ the galvanic deposition of a tin / lead alloy beaten, which contains a water-soluble 21nn (II) salt, a water-soluble lead salt and the following additives:

A). a polyether surfactant of at least 5 and not more than 20 ether oxygen atoms per molecule, and

B) an arylhydrox3 ^r compound,

with which a continuous, microcrystalline, uniform Precipitation with excellent coverage in the low Current density range is obtained. "■

The aryl phenols used in accordance with the invention are naphthols and substituted phenols. The aryl hydroxy compound should be present in an amount of 0.5 to 1 g / l.

üie I-taphthol compounds contain one or more hydroxyl groups. Lie liaphtholverbindungen can inert "substituents, as for example 3 .. contain chlorine, but should not contain any nega ^ civ charges Have substituents ..

3 0982 7/099 3 ■. '

• / I

BATH

O -

The Paenolverbindungen have one ceer several hydrcy groups. The Phenolverbir.dungen can have one or more, but less than 4 inert substituents per benzene ring, and they can be inert linking groups, such as s.B. Sulion— groups (-SOp-), but should not contain negatively charged Own group.

The additives therefore consist of at least one polyether surface agent and at least one aryl hydroxide. The surfactant is used to get loosely adherent, stained, sometimes dendritic ^ crystalline tin / lead alloy deposits of an additive-free bath in dense, continuous, adhesive, to transform microlcristalline precipitate. The aryl hydroxide bev, there is a great improvement in the coverage in the area of low current density and in the scattering.

Typical examples of naphthols and phenols that have been found to be effective are:

β-naphthol α-naphthol

1,1'-Bi-2-naphthol

- CH

2,7-liaphthalenediol

309827/0993

BAD ORlßlNKt

2,4, c-Tricilorcpaenol

-, ρ'-Z-Dihydroxydiphenylsulfon HO- /. . V-S-

OH

0 0

_JES divalent tin- in the solution supplies aas tin, which is present in the deposited tin / lead alloy. Jn a freshly prepared bath, welcties 10 g / l tin and 90 g / l of lead contains, are about 85 io of tin in zv. ^T eivalent state, with the remainder consisting of tetravalent tin ". L? In such a bath produces a boiling impact that contains 10 f = tin." Enr. the kenge of tetravalent tin, increases, and the amount of divalent tin aTmircmt, then the percentage of tin in precipitate falls 'below 10 5i.' However, at higher concentrations, for example 50 g / l tin and 35 g / l lead, there is less tendency - that tetravalent tin in the bath -

de χ

In normal operation of the bathroom, the bivalent content remains Linn ν, -exciting constant, causing a precipitate with a even tin content is obtained. "¥ ¥ however the solution is out of order for some time then it is advisable to use the bathroom too filter and protect it as much as possible from the ingress of air. to keep the formation of tetravalent tin to a minimum.

Lead dissolved as? Lucborate provides the lead contained in the precipitated tin / 31ei alloy.

■■ Free luccric acid is therefore contained in the bathroom that the necessary Activity arises that the conductivity increases

309827/0993 '' ■

BATH ORIGINAL

_ "J

becomes that a fine-grained precipitate is obtained and that tree formation is prevented. The content can be 100 to 200 g / l be.

The boric acid is added to the bath to maintain the stability of the bath. Approximately 25 g / l boric acid have been found to be Proven useful, but this concentration is not critical.

The preferred operating conditions, as s.B. pH, temperature and current density, can depend on the particular bath composition and according to the nature of the object on which the tin / lead alloy is to be deposited by electroplating. Generally good galvanic Tin / lead alloy precipitates obtained within a specific range of working conditions.

The electrodeposition of the tin / lead alloy using the compositions of the invention can be (preferably 15 to 2C ⁰ C) is carried out either with or without agitation at temperatures of about ⁰ C to 6C TC. The temperature of the galvanic solution is usually room temperature, for example 35 C or below. At lower temperatures, such as 15 to 20 C, optimal results are obtained. In some working methods in which a considerable cell line is used, which results in a temperature increase, cooling must be carried out in a suitable manner, for example by cooling water flowing through an immersed cooling coil, by cooling machines, etc. Using average current densities of 0.5 to 5.0 A / dm, tin / lead alloy deposits with an average thickness of 0.25 to 25 μ are obtained in deposition times of an average of 0.1 to 10 minutes.

If necessary, for a uniform movement of the. galvanic Bads are taken care of, either by a mechanical movement of the object to be coated or by

309827/0993

BATH ORIGINAL

solution stirring during electrodeposition. £ i: i Such agitation can the "use van high 'ADscheidungsstroriaichten on the electrically au" be coated permit. ■.

During the galvanic deposition of. Tin / lead alloys. l'Cönner. the parts are coated on rails ,, ie holders \ * ^r elk single or multiple part holds en ", the. -can generally be the same, but they also have a different size, - different geometrical shape, etc., know. The parts can also be coated in rotating drums as Hasse. 3 In this type of coating, which is usually used to coat smaller ropes, which in themselves result in a drum effect, the drum is usually loaded from the same ropes, although mixed loads can also be used. Because of the number _{t of the} size and the shape of the parts. it is important * that the galvanic bath applied in this way. As large a current density range as possible, in which a semi-gloss is obtained. I5s is atich important that the limiting current density, d "h _{f c is} the current density at which the! Tieder- ■ suggest not have a healthy structure and no healthy look more, as high as possible, to account for the wide variations in ICatodenstromdichte ,, which due to the size and the complicated shape of the to be viewed. trending parts can be encountered. . .

The polyether surfactant ,,. such as, 3. Tergitol ilon-Ionic aP-35 can be added as a concentrated aqueous base solution, for example 100 g / l, in whatever form it is. in a concentration of 40 to 80 ml / l or 4 to 3 IiCoI. -fi ■ ztige— ■ ■ sets v / he can «

Lie Zirfindung is explained in more detail by the following examples. _;

309827./0J9M
ÖAD ORIGIISIAt

49-

A galvanic bath for the deposition of an alloy with cO γ> tin and 40 pounds of lead with the following composition was produced:

Zinii (II) fluorate concentrate (49.6 wt .- *;) 16.2 VcIv-S

31eifluoborate concentrate (50% by weight) 6.3 % by volume

Fluoboric acid (49 wt .- ^) 15.0 YcI.- ;. '

Boric acid 15.6 g / l

Water 62.5 YcI, - ^

that makes

divalent tin 52 g / l

Lead 30 g / l.

free fluoboric acid 100 g / l free boric acid 25 g / l

The PIull cell deposition conditions were as follows:

solution volume 267 ml

Temperature. 20 ⁰ G

Stirring magnetic stirring

Cell current 1 A

Time 5 min

Anode plate made of an alloy

with 60 fo tin and 40>> lead

Polished brass cathode

8 g / l of a nonylphenol / ethylene oxide condensate were added to the above pad added, which is about 15 J-EthylenoxydiTrurer. per molecule (sold by Union Carbide Chemical Corporation as Tergitol Kon-Ionic IIP-35).

The precipitates from this system were wai; 3, throughreaond and fine-grained. 309827/0993

BATH ORIGINAL ^;

Example 2 . .

Addition of yon £ - naphthol

Zine solution of β-l-taphthol was prepared in that 144.2 g (1 KoI) powdered ß-Uaphthol from U.S ..? - purity were added to water with mechanical stirring. then 50 g of chemically pure NaCH pellets, which were previously in 2CO ml Water dissolved before the goods were added. The stirring was continued "until the ß-haphthol dissolved v / ar. Then were 3 g activated carbon (Darco S 51-Red Label or equivalent Karke) was added and stirring was continued for 1 hour, whereupon was filtered. The filtrate was made up to 1440 ml with water diluted so that a solution containing 100 g / l ß-ifaphthol is obtained became. 1 part by volume of purified 100 g / l ß-caphthol base solution was nit 1-YoI.-Teil 100 g / l basic solution of Tergitol ΙΓοη— Ionic IiI-35 mixed. .. -..- ,.

10 nl / 1 of the basic solution give the bath composition of Example 1 added, with 0.5 g / l ß-iaphthol being obtained. The β-naphthol was completely dissolved and the result Precipitation v / ar white, semi-glossy, microcrystalline, continuous and fine-grained and showed no defects whatsoever a much better coverage at low current density than in the example "1. -" ■

Example 5

(7-like) -

A system identical to that of Example 1 · but contained no polyether surfactant gave a dendritic, loose, adherent, spongy, discontinuous I-Tie the strike, with very poor coverage in the area low current density on both the front side and on the back of the cathode.

309827/0993

BAÖ

The three above examples show that the electrodeposition of a tin / lead alloy in a Flucbcratbad a combination of a non-ionic polyether surfactant, such as Tergitol Non-ionic IIP-35, and off ß-Naphthol finer-grained, glossier and whiter precipitates as well as a greatly improved coverage in the area of low current density results, which is especially true in the case of printed Circuits in which deposited through the holes, which is important.

v.'enn "for example the Zirm / lead pluoborate bath the equivalent from 4 to 1/2 g / l of, for example, Tergitol Non-ionic NP-35 is added, then instead of a dendritic, spongy, discontinuous precipitate, which occurs in an additive-free bath in the Hull cell, a fine-grained, semi-glossy, white solid precipitate obtained. 77enn the naphthol or phenol compound in one Concentration of, for example, 0.5 to 1 g / l is added, then all the good precipitation properties are retained. but in addition an excellent coverage in the area of low current density is obtained. If the tin / lead pluoboratbac. only 0.5 to 1 g / l naphthol or phenol and none Polyether surface agent is added (the naphthol or Phenol can be added in the form of a solution in a solvent such as cellosolve or as an aqueous solution of the sodium salt whereupon most of the naphthol or phenol: can precipitate, with a fairly low saturation concentration of, for example, less than 0.1 g / l is obtained), then the precipitate can be white, continuous and fine-grained and have good coverage in the low current density range, but at the end of the high current density range there is then a high probability that the precipitation is dendritic or spongy, with holes in the other ropes in the area, such as voids, stripes, etc., may occur. In order to explain this, let us use the folks Examples given:

30982 7/0993

BATH

Example 4 (comparison)

- 43

Addition of ary! Alcohol; alone '-

The system is identical to that of Example 2, except that the Polyether surface element had been omitted gave one faulty precipitation occurring in the area-high current density dendritic v / ar. - '■ -. . .

Example 5 (comparison) ■■ "." -.

A fluoborate tinning bath was prepared which had the following composition: - ^: ₍

Tin (ii) fluoborate concentrate - (49.6 <p) ■ .25.2 vol .-? 1 fluoboric acid (49 5 $), 14.2 vol .- ^ - '

Water · 60.6 vol. - ^c ß>

(which gives 81 g / l tin and -100 g / l free 'fluoboric acid).

This system resulted in a porous, discontinuous one It precipitation with very poor coverage in the area low current density. '-

Example 6 (comparison) ' . '

To a S'luoboratzinnbad that with that of Example 5 was identical ', 8 g / l of an I-tonylphenol / ethylene oxide condensate were added, v / elches-about 15 ethylene oxide groups contained per molecule. The precipitate obtained tended to ■ "an ifecrol crystallinity and had very bad coverage in the area of low current density.

Example 7 (comparison) '-''

"Every 10 ml / 1 of a basic solution of β-ITaphthol (prepared as in Example-2) were added to the bath of Example 6, then a white, fairly fine-grained, continuous-

3 0 9827/0993

ßA0 ORIOjNAL, ..,.

prefer precipitation, but the concern penetrated in the area lower Current density was bad.

Example 8

4 ml / l of eifluoborate concentrate were added to the bath of Example 7 admitted. The resulting precipitate was white, fine-grained and continuous and showed excellent coverage in the range of low current density *

This is the case with a pluoborate tinning bath with an additive for example 4 to 8 g / l polyether surfactant ' plus 0.5 to 1 g / l ß-naphthol a white, macrocrystalline dull precipitation, which is continuous, in the Hull-Sellen- ■ test received and not the coarsely crystalline discontinuous porous (there are only scattered islands of a tin crystal precipitation present) Precipitation from the additive-free bath. However, the coverage is in the "low" current density range bad. When adding lead fluoborate in a "low Concentration so that a precipitate with 2 to 5 wt. Lead is obtained, a white, microcrystalline, uniform continuous precipitate is obtained, which is also a shows excellent coverage in the low current density range, that is, the addition of lead has a remarkable effect on improving precipitation in the area lower Current density.

Similar results are obtained with a different phenol and ηit obtained another naphthol. The making of two other typical basic solutions is as follows:

Example 9 Preparation of a solution of 2,4,6-trichlorophenol

100 g 2,4,6-trichlorophenol and 25 g NaOH were in approx. 900 ml of water dissolved. The solution was 3 st with 3 g of active

"■■ - ·. · ■ ■. /.

BATH ORIGINAL

-. -4ε-

charcoal "and then filtered, whereupon the express occurred was diluted to 1 l with water. For the preparation of the additional basic solution v / urde 1 vol. part of the solution with 1 part by volume of a 1CC g / 1 basic solution of Tergitol Non-ionic 1TP-35 mixed.

Example 10 -

Preparation of a solution of 4,4'-Sihycro: £ yQiphen7flsulfon

100 g 4,4'-I) ihydrGxydiphenylsulfon and. 40 g of KaOH were in about 900 ml of water dissolved. The solution was 3 st with 3 g activated charcoal "treated and filtered, and the Piltrat v / urde diluted to 1 liter with water. To prepare the additional base solution, 1 tol.-iil of the solution obtained was added with 1 part by volume of a 100 g / 1 basic solution of Tergitol lon-Ionic NP-35 mixed. -

Patent application:

3 0 9 8 2 7?% 9φ Ö ^f ORIGINAL

Claims (28)

Claims Process for the production of galvanic white, continuous, fine-grained tin / lead alloy deposits, which have excellent coverage in the area of low current density, characterized in that r.an passing a stream from an anode to a metal cathode through an aqueous bath which is at least one water-soluble Tin (II) salt, at least one water-soluble lead salt and, as additives, at least one polyether surface agent and contains at least one arylhydroxy compound. 2. The method according to claim 1, characterized in that that the polyether surfactant has the formula where R is an alkyl group having 5 to 15 carbons material atoms and m is an integer from, 5 to 20. 3. The method according to claim 1, characterized in that the water-soluble oxyalkylated wetting agent is the general formula R ₂ -C- where R ₁ , R ₂ and R each represent a straight or a branched alkyl group with 3 to 10. "carbon atoms, η represents 15 and M represents a cation consisting of hydrogen, sodium, potassium and Ammonium selected _is 309827/0993 BAD ORlGINAtI - ⁷ 4. The method according to claim 1, characterized in that the water-soluble tin (II) salt consists of tin (II) fluoborate and that the water-soluble lead salt consists of lead fluoborate. , 5. The method according to claim 1, characterized in that the tin / 31ei alloy consists essentially of 60 fo tin and 40 fo lead. 6. The method according to claim 2, characterized in that the .Polyatheroberflächemittel from a lionylpheno ^ / ethylene oxide condensate consists, which has about 15 ethylene oxide groups per molecule. "- 7. The method according to claim 1, characterized in that the arylhydroxy compound is selected from haphthols and substituted phenols. 8. The method according to claim 7, characterized in that the arylhydroxy compound consists of ß-l-taphthol. 9 »Method according to claim 7, characterized in that the arylhydroxy compound consists of -2,4,6-trichlorophenol ,. 10. The method according to claim 7, characterized in that the arylhydroxy compound from ρ, ρ'-dihydroxydiphenyl sulfone consists.' 1-1. Process according to claim 7, characterized in that the arylhydroxy compound consists of 2,7-naphthalenediol. 12. The method according to claim 7, characterized in that, the aryihydroxy compound consists of 1, 1 '-Bi' ^ - naphthol. 13. "The method according to claim 7, characterized in that the Arylr-ydrbxyverbindunfr consists of oc-naphthol :. 3EH9827 / G993, BATH 14. Process for the galvanic deposition of galvanic, white, continuous, fine-grained tin / 3iei alloy deposits, characterized in that rr.an a current from an anode to a cathode through a bath which contains the following: (a) 4 "to 53 g / L zv / egg-valent tin; (b) 1 to 5 g / l lead; (c) 100 to 200 g / l free pluoboric acid; (d) 4 to 10 grams per liter of a polyether surfactant; and (e). 0.5 to 1.0 g / l of an aryl hydroxy compound consisting of Naphthols and substituted phenols. 15. Composition for the, production of galvanic white, continuous, fine-grained tin / lead alloy deposits, characterized in that it consists of a bath which contains at least one water-soluble tin (II) salt, at least one water-soluble lead salt and at least one polyether surfactant and at least one aryl hydroxy compound contains. 16. The composition of claim 15, characterized in that the polyether surface agent has the following range on v / eist: -0- (CH ₂ CH ₂ O) _1n H where R is an alkyl group having 5 to 15 carbon atoms and m is an integer from 5 to 20. 17. The composition according to claim 15, characterized in that the polyether surfactant has the following formula having: 309827/0993 BADORfQINAt ι ¹ R ₀ -C - RH- (CH ₀ CH ₀ O) SO ~ M wherein R 1, R ₂ and R each represent a straight or branched alkyl group each having 3 to 10 carbon atoms, η represents 5 to 10 and M represents a cation selected from hydrogen, sodium, potassium and ammonium. 18. Composition according to claim 15, characterized in that that the water-soluble tin (II) salt, from tin (II) fluc- borate and the water-soluble lead salt consists of lead fluoborate consists. 19. Composition according to claim 15, characterized in that "that the arylhydroxy compound from iaphthols and substituted Phenols is selected. 20. Composition according to claim 15 »characterized in that the tin / lead alloy consists essentially of 60 % tin and 4-0 fS lead. ; i - 21. Composition according to claim 16, characterized in that that the polyether surfactant is made from a! Tony! phenol / Ethylene oxide condensate, which has about 15 ethylene oxide groups per molecule. .22. Composition according to Claim 19, characterized in that the aryl hydroxy compound consists of β-haphthol. 23. Composition according to claim 19, characterized in that that the aryl hydroxy compound from 2,4-, 6-trichlorophenol consists. '■' - ■ - 24. Composition according to claim 19, characterized in that that the aryl hydroxy compound from p, p'-dihydroxydiphenyl sulfone consists. 309827/0993 25. Composition according to claim 19, characterized in that that the aryl hydroxy compound from 2,7-iIaphthalenediol. consists. 26. Composition according to claim 19 »characterized in that the aryl hydroxy compound ■ from 1.1 ^! -3i-2-naphthol consists. 27. Composition according to claim 19 »characterized in that that the aryl hydroxy compound consists of (^ -naphthol. 28. Composition for making a galvanic white, continuous, fine-grained tin / lead alloy precipitate, consisting of a bath that contains: (a) 4 to 53 g / L divalent tin; (b) 1 to 85 g / l lead; (c) 100 to 200 g / l free pluoboric acid; (d) 4 to 10 grams per liter of a polyether surfactant; and (e) 0.5 to 1.0 g / l of an aryl hydroxy compound selected from Naphthols and substituted phenols. 309 8 27/0 99 3 BAD ORlGiNAL