TWI328052B - Electrolyte and method for depositing tin-bismuth alloy layers - Google Patents

Description

IX. Description of the invention: [Technical field to which the invention pertains] A method of using the electrolyte, a coating obtained by the method, and the use of the electrolyte for coating an electronic component. [Prior Art]

Manufacturing electrical and electronic assemblies often requires the use of components containing (for functional reasons) coatings with electrolytically deposited tin-stagger layers. Even after a relatively long shelf life, these coatings ensure that the components can be easily softened. However, the use of i electrical and electronic equipment is the risk of contamination of the material whenever the equipment is stored on a waste heap. The treatment of rot # can convert the fault of the solder joint into a water-soluble form, and (4) eventually cause groundwater pollution. Therefore, as of July 1, 2006, the European Union Directive will no longer permit (with a few exceptions) the use of lead-containing solder and electrolytically deposited tin (10) 3 years 四 (4)

The present invention relates to an acid electrolyte for depositing tin-bismuth alloys. The State Council and the Council of Europe Directive 2002/95/EC on the use of certain hazardous substances in electrical and electronic equipment).狻 ’ 狻 狻 _ _ _ _ _ _ U U U U U U U U U U U U U U U U U U The Ag) or tin is called 4% by weight of the tin alloy layer as an alternative coating. In terms of processing, pure tin coating is a simple technology and therefore the first choice for an economical alternative to tin 7 layers. However, the risk of crystal formation cannot be completely ruled out as a disadvantage. Must be grain boundary. . s refers to the needle-shaped single crystal of tin. These early bodies usually have a few micrometers of cold 丄 but can reach a length of several millimeters. The development of miniaturization of electronic components has led to the formation of crystals that can cause adjacent leads and short circuits. This can cause the electrical sub-electronics to fail again and cause a considerable economic loss of I09703.doc 1328052. The whisker formation in the tin layer can be prevented by co-depositing a very small amount of another metal. It has been confirmed here that co-depositing a small amount of lead (at least 3% by weight) is effective. However, as explained above, this co-deposition allows only a small amount of application. In addition, it has been confirmed that the deposit contains about 2-4 weights. /. The tin-bismuth alloy is a reliable method to avoid whiskers. Higher amounts of tantalum are disadvantageous because the ductility of the deposited layer is reduced, causing a risk of cracking in the coating if the pins of the electronic component are mechanically operated. Thus, the properties of the deposited layer such as ease of soldering and corrosion resistance are degraded. If co-deposited less than 2 weights of 0/〇 Bi ’, the formation of whiskers cannot be completely ruled out. A suitable commercially available method for depositing tin bismuth has been used in the manufacture of electronic components and is described in, for example, European Patent No. 255 558, European Patent No. 715 003, Japanese Patent No. 2 983 548, and Japanese Patent No. 2,132,894. However, 'the electrochemical potential of tin (·〇·12 volts) differs greatly from the electrochemical potential 隹 (+0.35 volts) of yttrium. Therefore, the yttrium in the form of dissolved metal ions in the electrolyte is deposited during charge exchange. For the more negative-powered Xiyang-pole. This reaction occurs according to the following reaction formula: 3Sn° + - 3Sn2* + 2Bi& i The ruthenium deposited in this charge-exchange reaction is deposited in the form of a porous, sponge-like coating that has undergone time to peel off from the anode, thereby permeating the electrolyte And therefore also penetrate the component to be coated. In this case, these ruthenium particles may be incorporated into the electrolytically deposited layer of 109703.doc 1328052, thus creating an extremely dendritic layer that is technically useless. This can also lead to production disruptions. Further, the above charge-exchange reaction causes the enthalpy of dissolution in the electrolyte to be continuously lost, so that the secret of dissolution has to be added, thereby increasing the processing cost. To ensure that the ruthenium is co-deposited within the required range of 2-4% by weight, it is necessary to continuously analyze the amount of money in the electrolyte and make up the amount accordingly. This process involves a lot of time and work. • If it is possible to prevent the loss caused by the charge-exchange reaction, the amount of the bismuth compound that meets the passing current can be filled by the combination of the automatic metering pump and the ampere-hour meter. This approach therefore makes the implementation simpler and more economical. In this case, only a more accurate analysis of the enthalpy in the electrolyte is required at lower frequent intervals. Another drawback associated with the charge-exchange reaction described above is that the reaction occurs not only on the tin anode, but also whenever the coating operation is interrupted (eg, due to system failure) and the assembly is immersed in the electrolyte for a short period of time without any current load. , and 1 also occurs on the already coated components. This can result in blackening of the surface. If the plating is subsequently continued, a so-called sandwich coating is produced. The thin layer of tantalum produced by charge exchange will be formed between two electrolytically deposited tin-germanium layers. If you talk about mechanical work, this sequence can cause crack formation and it can cause delamination of the layer and lead to poor solderability. ^ To prevent the deposition of ruthenium caused by the charge-exchange reaction, it is recommended to use an electrolyte composed of ruthenium acid and a tin and bismuth salt of the acid. This electrolyte contains an unsaturated carboxylic acid as an organic additive and is derived from polyethylene oxide/polyoxidation. A nonionic surfactant of the group of propylene octamers (US 2003/0132122 109 703. doc 1328052 A1). In the case of this electrolyte, the deposition of 雷 乂 确实 确实 确实 确实 确实 确实 确实 确实 确实 确实 确实 确实 铋 铋 铋 铋 铋 铋 铋 铋 铋 铋 铋 铋 铋 铋 铋 铋 铋 铋 铋 铋 铋

Co-deposition amount. Even in the electrolyte, the content of ruthenium in the deposited layer of A in the deposited layer relative to the total metal content is only about 415 to 2% by weight. SUMMARY OF THE INVENTION Accordingly, the present invention is based on the object of providing an entanglement system k for depositing an electrolyte of a tin alloy having an alloy content of at least 2 to 4% by weight, in which the electrolyte is interrupted in charge exchange. No secret deposits on the coated surface during this period. This object is solved by the use of an aqueous acidic electrolyte for depositing tin-manganese sheet metal. The electrolyte consists of one or more, pit-based decanoic acid and/or alkanolsulfonic acid, a plurality of soluble tin(II) salts. , a 锸 w w w a 4 夕 可 soluble 铋 (ΠΙ) salt, one or more non-ionic surfactants and a chelating agent and or a variety of thiazole and / or thiadiazole compounds. Therefore, by means of the electrolytic enthalpy of the present invention, the above object is solved as the one skilled in the art is concerned with the convulsions of seven people, because the electrolyte contained in the electrolyte has no electrode potential. Zhao Yu 4 shifts to a negative direction, which is used by the skilled person to prevent the deposition of the ^ ^ ^ ^ ^ ^ ^ ^ ^ ^ shellfish in a more negative metal pretreatment. Even when combined, the components contained in the electrolyte are not cited as the (f) cathode. "Anti-(4) deposited on freshly deposited tin _ = face: can not be explained electrochemically. There may be a kind of inhibition of joy, that is, the combination of the materials used, and no bond, but does not block M Electrolytic deposition. The squat or sputum-salt compound is not particularly limited. The term " 嗟. sitting 109098.doc 1328052 is in the electrolyte. Examples of such inorganic acid salts include sulfates and tetrafluoroborates. The sulfonate includes, for example, a methanesulfonate, an ethyl sulphate, a n- and iso-propionate, a methanesulfonate, a bromide, a 2,3-propanedisulfonate, and , 3-propanedisulfonate. Suitable alkanol sulfonates include 2. ethanesulfonate, 2-hydroxypropane sulfonate and 3-hydroxypropane sulfonate. Particularly preferred is methanesulfonic acid. Tin (Π) ^ The tin (Π) salt is preferably present in the electrolyte in an amount of 5 to 200 g / 丨 electrolyte, particularly preferably 10 to 100 g / Ι electrolyte (calculated as tin (π)). (III) The salt may be added to the electrolyte in any form which allows dissolution of the Bi(In) ion in the electrolyte. The addition can be dissolved (1) The form of the salt or in the form of a solid compound which can be converted into a soluble oxime compound in the presence of a free acid. Suitable examples of the salt of the compound (1) are inorganic acid salts (such as vaporized 'tetrafluorocarbon). Borate or nitrate), alkyl sulfonate (such as methanesulfonate, ethanesulfonate, methanedisulfonate, ethyl salt, 2,3-propanedisulfonate and l53-propanedisulfonate) An alkanol sulfonate (such as 2-hydroxyethanesulfonate and 3-hydroxypropane sulfonate). Particularly preferred is ruthenium methanesulfonate (in). When added as a solid (111), Preferably, slaves (in) or cerium oxide (111) are used. These compounds are dissolved in the electrolyte in the presence of an alkyl and/or alkanol acid to form a soluble Bi(in) compound. The amount required for the obtained tin-bismuth alloy and the selected tin (9) salt concentration. The electrolyte preferably contains a ruthenium (ΙΠ) salt which enables deposition of a tin-bismuth alloy having an alloy composition of two genera. The concentration of Bi ions is preferably 36%, particularly preferably 5%, relative to the selected tin (II) concentration. 109703.doc 132 8052 The alkyl-based acid and the alkanolsulfonic acid preferably have 1 to 10 carbon atoms, particularly preferably 1 to 5 carbon atoms. As an example, 曱4 acid, ethyl benzoic acid, n-propionic acid, and different ' Mic acid m B: sulfonic acid, 2,3 • propionate acid, and propyl sulfonate can be used as alkyl sulfonic acid. Examples of suitable alkanol sulfonic acids include 2-feyl hexanoic acid, 2 thiol Alkanoic acid and 3 or alkanoic acid. The alkyl group and/or the alkanolsulfonic acid is preferably present in the electrolyte in a concentration ranging from 5 Å to 3 Åg/1 of the electrolyte, particularly preferably from 100 to 200. In addition, in order to prevent oxidation of tin, the electrolysis f may contain a conventional antioxidant such as a mono- or poly-compound compound (such as catechu, niobium and acid). Better use of life. The concentration of such antioxidants may be from 5 Å to 2, _ ¥ electrolyte, preferably from 500 to 1, 00 〇 mg/b. The electrolyte may also contain various additives such as crystal grains commonly used for depositing an acidic electrolyte t of a tin alloy. Refine additives, wetting agents and/or brighteners. The grain refining additive is preferably present in an amount of from 1 to 5 Torr of the electrolyte, preferably from 1 to 10 g / Torr of the electrolyte. The humectant may be present in an amount of from M to 5 G g/1 of electrolytic f, preferably from 〇5 to 1 〇g/Ι of the electrolyte. The value of ρίί of the acidic electrolyte is preferably from 〇 to less than 1. Further 'provided on the basis of the present invention A method for electrolyzing a substrate with a tin alloy, which uses the electrolyte of the present invention, a metal tin anode, a cathode made of a substrate to be coated, for depositing the coating, in this method, a straight peach The coating obtained by using this method J09703.doc 丄3.28052 is also provided on the basis of the present invention. The current density can be (MA/dm2 (barrel plating or rack plating method) up to 1 〇〇A/dm2 (high speed system). The temperature of the electrolyte is preferably in the range of 〇 to 7 (rc), particularly preferably in the range of up to 5 Å. Any material commonly used in the manufacture of electronic components (such as copper, copper containing)

Gold, a nickel-iron alloy (e.g., alloy 42) or a nickel-plated material can be used as the substrate to be coated. The electrolyte according to the invention can be used to coat electronic components. [Embodiment] The present invention will now be explained on the basis of the following examples and comparative examples. EXAMPLES An electrolyte was prepared containing: 15 〇 g / 甲 methanesulfonic acid, 70 〇 / 0 80 g / 1 tin [Sn (CH3S 〇 3) 2)]

3·5 g/Ι 铋[Bi(CH3S03)3)]] 1 g/1 catechol

4 g/1 E〇/PO block polymer (Pluronic PE 6400 from BASF, molecular weight about 2,9 〇〇) 1 g/1 methacrylic acid 200 mg/1 2-mercaptobenzothiazole. In this electrolyte, the coating of the copper flakes was carried out under the following conditions:

Temperature · 40 °C Current Rating · lOA/dm 109703.doc 12 13-28052 Movement: Magnetic Stirring, 700 rpm Duration: 2 minutes The tin-sand coating obtained in this way has a layer thickness of 1〇 and 2 8 % Bi (residual Sn) alloy content.

To test the ruthenium deposition during charge exchange, other test sheets were coated under the same conditions. After 2 minutes of deposition, the current was turned off and the sheets were respectively left in the electrolyte for 30, 6 Torr, 120, and 180 seconds. The alloy composition was then determined by X-ray light analysis. Duration of power failure exposure (s) Alloy composition f% by weight Bi]* 0 2.8 30 2.9 60 2.9 1 〇Λ -- 12U 3.0 1 ΟΛ iiSU *Residual Sn - 3.0

All surfaces have a metallic appearance that is half the light. Comparative Example Self-deposition under the same conditions as in Example 1: Electrolyte having the following composition was carried out in the form of 150 g/l of citric acid, 70% by weight of 8 〇g/1 of tin [Sn(CH3S03)2)] 3.5 g/Ι铋[Bi(CH3S〇3)3)]] 1 δ71 catechol 5 g/1 Naphthol ethoxylate of Lugalva group with 12 EO-based BASF (from n bn〇.12) 109703.doc -13* 0.5 g/1 Naphthalenesulfonic acid formaldehyde condensate (Tamol NN 4501 from BASF) Duration of power failure exposure (S) Alloy composition [% by weight ug 1]* 0 2.08 30 2.21 60 2.73 120 4.00 180 6.15 Residual Sn 13.28052 The surface of such samples deposited in this manner exhibits a substantial degree of dark discoloration as a function of exposure duration after a power outage exposure. After the exposure lasted for 180 seconds, the surface was velvet black.

109703.doc 14-

Claims (1)

A • 13^805^〇95113052 Patent Application Replacement of Chinese Patent Application (November 1998) X. Patent Application Range: 1. A water-soluble acidic electrolyte for depositing tin-silver alloy, which contains. One or more alkyl sulfonic acids and/or alkanol sulfonic acids in a concentration range of 50 to 300 g/丨 electrolyte, 9 or more soluble tin (II) salts, 50 to 2 〇〇 g/l The amount of electrolyte (calculated as tin (Π)), one or more soluble cerium (m) salts, wherein the concentration of Bi ions is 3% to 6% relative to the selected tin (Π) concentration, one or more nonionic The surfactant is a concentration in the range of j to 5 〇g/1 of the electrolyte, and or a concentration of the thiazole and/or thiadiazole compound in the range of 5 to 1 Torr of the electrolyte. % 2. The electrolyte of claim 1, wherein the thiazole compound is selected from the group consisting of benzothiazole, 2-aminobenzothiazole, 6-aminobenzothiazole, 2-hydroxybenzothiazole, 6-hydroxybenzothiazole 2-methyl benzothiazole, 2 mercapto benzothiazole, 6-methoxy 2 -aminobenzothiazole and 2 thiazoline thiol-2. The electrolyte of month length 1 wherein the thiadiazole compound is selected from the group consisting of 2·amino-5-fyl-1,3,4_嗟2. Sit, 2_amino _5_ thiol^cardiac diazole, 2_mercaptomethyl-1,3,4-thiadiazole, 2-amino-1,3,4-thiadiazole and 2 5 two sparse-i, 3, 4- sold two saliva. 4', such as ° electrolyte, the electrolyte of #1, the thiazole and / or thiadiazole octopus is present in the electrolyte at a concentration of (10). ° System 5.= Begging! The electrolyte, wherein the nonionic surfactant is a polyethylene oxide/polyoxypropylene copolymer. 109703-981126.doc 6. == Electrolyte 'where the polyoxyethylene acetylene/poly oxidized two-co-H-(〇CH2-CH2)m-(〇CH(CH3)-CH2)n_〇H Polyoxidation: an olefin/polyoxypropylene copolymer wherein _ is an integer between 5 and 6 Å and the copolymer has a weight average component of 2,000 to 1 Torr. Knife 7. 7. Electrolysis f of claim 6 wherein the polyoxyethylene propylene oxide copolymer has a cloud point greater than 30 °C. 8. The electrolyte of the request, wherein one or more polyphenolic compounds are additionally present. 9' The electrolyte of claim 8, wherein the polyhydric phenol compound is catechol. 10. A method for electrolytically coating a substrate with a tin-bismuth alloy, wherein the electrolyte is passed by using the electrolyte according to any one of claims 1 to 9, additionally by using a metal tin anode and by using Coating is performed by making one of the cathodes of the substrate to be coated. U. The use of the electrolyte according to any one of claims 1 to 9 for coating an electronic component. 109703-981126.doc