Tin or tin alloy plating liquid

Abstract

Tin or tin alloy plating liquid with a sufficient plated deposit can be formed in the opening without causing burns on the plated film surface or abnormal deposits, and which has a good via filling effect. When a specific , -unsaturated carbonyl compound is added into the tin or tin alloy plating liquid, the plating liquid with good via filling performance can be obtained, and the deposit which is substantially free of voids and burns or abnormal deposits on the deposit surface are reduced.

Claims

1. A method of electroplating comprising: a) providing a substrate comprising vias having diameters of 10-100 pm and depths of 10-100 pm; b) immersing the substrate comprising vias having diameters of 10-100 pm and depths of 10-100 pm in an electroplating liquid comprising a source of tin ions and at least one , -unsaturated carbonyl compound selected from the group consisting of citral, 4-hexene-3-one, -ionone, and 1-acetyl-1-cyclohexene, wherein the at least , -unsaturated carbonyl compound is in amounts of 0.01-0.5 g/L; and c) plating tin in the vias with the electroplating liquid.

2. The method of claim 1, further comprising an alloying metal ion source.

3. The method of claim 2, wherein alloying metals are chosen from silver, copper, gold, platinum, zinc, nickel, bismuth, indium, thallium, antimony, palladium, rhodium, iridium and lead.

4. The method of claim 1, wherein the electroplating liquid further comprises additives chosen from an antioxidant, a complexing agent, a pH adjusting agent, a brightener and a grain refiner.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 is the bright vision field microscope photo of the via cross section that was made in Example 1.

(2) FIG. 2 is the bright vision field microscope photo of the via cross section that was made in Comparison 1.

DETAILED DESCRIPTION OF THE INVENTION

(3) In this Description, plating liquid and plating bath are used interchangeably. C. is centigrade degree, g/L is gram per litter, mL/L is milliliter per litter, m is micro meter, m/min is meter per minute, A/dm.sup.2 is amps/per square decimeter. All numerical ranges are inclusive and combinable in any order, except where it is logical that such numerical ranges are constrained to add up to 100%.

(4) This invention is the tin or tin alloy electroplating liquid characterized by containing the compound of the following general formula (1).

(5) ##STR00002##

(6) In the formula, R.sup.1 can be chosen from hydrogen atoms; halogen atoms; substituted or non-substituted C.sub.1-C.sub.20 alkyl groups; C.sub.2-C.sub.20 alkenyl groups; C.sub.4-C.sub.20 dienyl groups; C.sub.3-C.sub.20 cyclo alkyl groups; C.sub.3-C.sub.20 cyclo alkenyl groups; and C.sub.4-C.sub.20 cyclo dienyl groups; and the amino groups represented by NR.sup.5R.sup.6. R.sup.5 and R.sup.6 can be each independently hydrogen atoms or substituted or non substituted C.sub.1-C.sub.20 alkyl groups. R.sup.2-R.sup.4 can be each independently chosen from hydrogen atoms; halogen atoms; substituted or non-substituted C.sub.1-C.sub.20 alkyl groups; C.sub.2-C.sub.20 alkenyl group; C.sub.4-C.sub.20 dienyl groups; C.sub.3-C.sub.20 cyclo alkyl groups; C.sub.3-C.sub.20 cyclo alkenyl groups; and C.sub.4-C.sub.20 cyclo dienyl groups. R.sup.2 and R.sup.4, or R.sup.1 and R.sup.3 may be bonded together to form a ring, and the formed ring may have one or more double bonds. When R.sup.1 is an amino group that can be indicated by the above mentioned formula NR.sup.5R.sup.6, the above mentioned ring is a hetero ring in which R.sup.5 or R.sup.6 bonded with R.sup.3. In the case when R.sup.1 is a substituted or non-substituted C.sub.1-C.sub.20 alkyl group, C.sub.2-C.sub.20 alkenyl group, or C.sub.4-C.sub.20 dienyl group, the above mentioned ring may be a hetero ring that has one oxygen atom between the carbonyl carbon and R.sup.1.

(7) The C.sub.1-C.sub.20 alkyl groups; C.sub.2-C.sub.20 alkenyl groups; C.sub.4-C.sub.20 dienyl groups; C.sub.3-C.sub.20 cyclo alkyl groups; C.sub.3-C.sub.20 cyclo alkenyl groups; and C.sub.4-C.sub.20 cyclo dienyl groups of the above mentioned R.sup.1-R.sup.4, and the C.sub.1-C.sub.20 alkyl groups of R.sup.5, R.sup.6 can have one or more substitution groups chosen from alkyl groups with 1-9 carbon atoms, alkenyl groups, alkoxy groups, amino groups, halogen atoms, hydroxyl groups, carbonyl groups, and cyano groups.

(8) Compounds of general formula (1) include but are not limited to: , -unsaturated aldehydes; , -unsaturated ketones; , -unsaturated halides; , -unsaturated lactones (cyclic esters); , -unsaturated amides; and , -unsaturated lactams (cyclic amides). Among these, , -unsaturated aldehydes and , -unsaturated ketones are preferred. When R.sup.1 is a hydroxyl group, it becomes an , -unsaturated carboxylic acid, however, the compound has poor via filling ability, therefore it is not included in this invention. Also, , -unsaturated carboxylic acid anhydrides and , -unsaturated carboxylic acid esters, excluding where the , -unsaturated carboxylic acid ester is a cyclic ester, have poor via filling ability, therefore they are not included in this invention. Further, the aromatic aldehydes and aromatic ketones which do not have an unsaturated group in the , position are not included in this invention, because the obtained plated film surface has dendrites, burns or skip plating, and those are not preferred. , -unsaturated aldehyde is a general name for compounds which have an unsaturated double bond between the position and the position of the carbon atoms looking at it from the carbonyl group, and this is the same for the other , -unsaturated compounds as well.

(9) Examples of compounds covered by the general formula (1) include the compounds shown below:

(10) ##STR00003##

(11) When R.sup.2 and R.sup.4 in the general formula (1) bond to form a ring, the compound that can be indicated by general formula (1) may have the structure having the following general formula (2) as well.

(12) ##STR00004##

(13) In the general formula (2), R.sup.7 can be a substituted or non-substituted C.sub.1-C.sub.40, C.sub.1-C.sub.20, or C.sub.1-C.sub.10 alkylene, or C.sub.2-C.sub.40, C.sub.2-C.sub.20 or C.sub.2-C.sub.10 alkene di-yl that has one or more double bonds, and R.sup.7 can have one or more substitution groups chosen from alkyl groups with 1-9 carbon atoms, alkenyl groups, alkoxy groups, amino groups, halogen atoms, hydroxyl groups, carbonyl groups and cyano groups.

(14) Compounds of general formula (2), include, but are not limited to the following compounds:

(15) ##STR00005##

(16) Also, when R.sup.1 and R.sup.3 in the general formula (1) are bonded to form a ring, the compounds that can be indicated by the general formula (1) may be the structure that can have the following general formula (3) as well.

(17) ##STR00006##

(18) In the general formula (3), R.sup.8 can be a substituted or non-substituted C.sub.1-C.sub.40, C.sub.1-C.sub.20, or C.sub.1-C.sub.10 alkylene, or C.sub.2-C.sub.40, C.sub.2-C.sub.20 or C.sub.2-C.sub.10 alkene di-yl that has one or more double bonds, and it may form a hetero cycle that includes one or more atoms chosen from nitrogen atoms and oxygen atoms as the hetero atom between the carbonyl carbon and R.sup.1, and also R.sup.8 can have one or more substitution groups chosen from alkyl groups with 1-9 carbon atoms, alkenyl groups, alkoxy groups, amino groups, halogen atoms, hydroxyl groups, carbonyl groups and cyano groups.

(19) Compounds that are included by general formula (3) are the compounds below:

(20) ##STR00007##

(21) Among these, -ionone; 1-acetyl-1-cyclohexene; citral; 4-hexene-3-one; -ionone and -damascone which are , -unsaturated aldehydes or , -unsaturated ketones, are preferred.

(22) In the tin or tin alloy electroplating liquid of this invention, the , -unsaturated carbonyl compound that can be indicated by the general formula (1) should be included in the range of 0.0001-10 g/L, preferably 0.0005-5 g/L, more preferably 0.001-1 g/L, and more preferably it should be included in the range of 0.01-0.5 g/L.

(23) The tin or tin alloy electroplating liquid of this invention includes a tin ion source and an acid in addition to the above mentioned , -unsaturated carbonyl compound, and further, it may include a second metal ion source that forms an alloy with tin, and other additives too.

(24) Any tin ion source may be used as long as it can provide tin ions in the plating liquid, and it may be an inorganic salt, an organic salt, a complex, or metallic tin. Tin ion sources include, but are not limited to tin salts of inorganic acids such as sulfuric acid; borofluoric acid; silicofluoric acid; sulfamic acid, hydrochloric acid; pyro phosphoric acid, and tin salts or tin complexes of methane sulfonic acid; 2-propanol sulfonic acid; phenol sulfonic acid; sulfo succinic acid; acetic acid; oxalic acid; malonic acid; succinic acid; glycolic acid; tartaric acid; citric acid; gluconic acid; glycine; mercapto succinic acid; ethylene diamine tetra acetic acid; imino di-acetic acid; nitrilo tri acetic acid; di-ethylene tri amine penta acetic acid; tri ethylene tetramine hexa acetic acid; ethylene di-oxy bis(ethyl amine)-N,N,N,N-tetra acetic acid; glycol ethylene di-amine tetra acetic acid; and N-(2-hydroxy ethyl)ethylene di-amine tri acetic acid. Also, in the case of using metallic tin, the metallic tin can be used as the anode electrode in electroplating. Among these tin ion sources, tin sulfate; tin chloride; tin methane sulfonate and tin phenol sulfonate are preferred.

(25) The amount of the tin ion source to be used should be 5-500 g/L, preferably 20-200 g/L as tin ions in the plating liquid.

(26) Concerning the acid, already known compounds can be used, for instance, the acid component that is used for the above mentioned tin salt or tin complex can be used. The amount of acid to be used should be 1-500 g/L, preferably 20-200 g/L in the plating liquid.

(27) In addition to the tin ion source, the plating liquid of this invention may include an alloying metallic ion source (second metal ion source) other than tin. Depending on the targeted tin alloy, the second metal includes but is not limited to: silver; copper; gold; platinum; zinc; nickel; bismuth; indium; thallium; antimony; palladium; rhodium; iridium; and lead. As the second metallic ion source, inorganic salts, organic salts or complexes of these metals can be used, and for instance, the salts of the acids described in the above mentioned tin salts or tin complexes, can be used. Also, two or more can be used as the second metal ion.

(28) The amount of the second metal ion source can vary depending on the type of the plating bath, the type of metal to make the alloy and the alloy composition; however, it should be in the range of 0.1-500 g/L. For instance, in the case of making a near eutectic composition of tin-silver by adding a slight amount of silver into tin, it should be 0.1-3.5 g/L in the plating liquid, and in the case of conducting the plating of a tin-indium alloy with a low melting temperature, it needs to be 1-500 g/L. When two or more metals are used as the second metal ion sources, the same is also true.

(29) The plating liquid of this invention can include other additives too. Such additives include, but are not limited to an antioxidant, a surfactant, a complexing agent, a pH adjusting agent, a brightener, and grain refiners.

(30) Antioxidant include, but are not limited to: catechol; resorcinol; hydroquinone; pyrogallol; oxy hydroquinone; fluoro glucine; 3,4,5-tri hydroxy benzoic acid; p-phenol sulfonic acid; cresol sulfonic acid; catechol sulfonic acid; and hydroquinone sulfonic acid. The amount of antioxidant should be 0.015 g/L, preferably 0.12 g/L, in the plating liquid.

(31) Surfactants which may be used are those that solubilize the , -unsaturated carbonyl compound used in this invention and has the function of restricting deposits at the high current density area. Such surfactants include known cationic surfactants, anionic surfactants, nonionic surfactants and amphoteric surfactants; however, the preferred ones are non-ionic surfactants. Non-ionic surfactants include, but are not limited to poly oxy alkylene alkyl ethers or esters; poly oxy alkylene phenyl ethers; poly oxy alkylene alkyl phenyl ethers; poly oxy alkylene naphthyl ethers; poly oxy alkylene alkyl naphthol ethers; poly oxy alkylene styrenated phenyl ethers or poly oxy alkylene styrenated phenyl ether where a poly oxy alkylene chain is further added onto the said phenyl group; poly oxy alkylene bis phenol ethers; poly oxy ethylene poly oxy propylene block polymers; poly oxy alkylene sorbitan fatty acid esters; poly oxy alkylene sorbit fatty acid esters; poly ethylene glycol fatty acid esters; poly oxy alkylene glycerin fatty acid esters; poly oxy alkylene alkyl amines; poly oxy alkylene condensation-added material of ethylene diamine; poly oxy alkylene fatty acid amides; poly oxy alkylene castor oil and/or hardened castor oil; poly oxy alkylene alkyl phenyl formalin condensed material; glycerin or poly glycerin, fatty acid esters; penta erythritol fatty acid esters; sorbitan mono, sesqui and tri-fatty acid esters; high rank fatty acid mono and di ethanol amides; alkyl.alkylol amides; and oxy ethylene alkyl amines. The amount of these surfactants should be 0.05-25 g/L, preferably 0.1-10 g/L in the plating liquid.

(32) A complexing agent is suitable especially when making the tin alloy plating liquid for dissolving a second metal. Complexing agents include, but are not limited to: thiourea; allyl thiourea; and 3,6-di-thiaoctane-1,8-diol. The amount to be used should be 0.01-50 g/L, preferably 0.1-10 g/L.

(33) As described above, the tin or tin alloy plating liquid of this invention has a good effect for via filling. Normally, when the plating is performed for the material that has indented parts, the plated film tends to be formed on outer surfaces other than the indented part, and only very thin plate is formed in the indented part, or the surface is closed even though the deposition of plating is insufficient in the indented part and the plated film with void spaces tends to be formed. However, when the plating liquid of this invention is used, the plating is deposited selectively in the indented part; therefore, the deposited plating which practically does not have void spaces can be obtained. Also, when the tin or tin alloy plating liquid of this invention is used, the plated surface that was formed does not experience burns or abnormal deposits. Therefore, the plated film which is practical and has good appearance, excellent soldering ability and excellent color change resistance is obtained. Therefore, the plating liquid of this invention is suitable for bump formation which includes via filling processes, and for forming tin and tin alloy bumps.

(34) One embodiment of the method of this invention is the method for filling vias on the surface of the material to be plated with the plating deposit. It is characterized by electroplating using the tin or tin alloy plating liquid of this invention. The material to be plated has at least one via formed, and the size is not limited. The method of this invention preferably fills vias which have diameters from 10-100 m with depths of 10-100 m. The material to be plated includes but is not limited to electric substrates and electronic components such as semiconductor chips. Substrates that have electrodes are preferred since sufficient plated deposit can be formed on the opened part provided in the electrode position on the substrate.

(35) Also, another embodiment of this invention is the method to form bumps that contain tin or tin alloy on the substrate. This embodiment includes the following processes:

(36) (1) Forming a protection layer that has an opened part on the substrate, and

(37) (2) Forming the plate deposit on the above mentioned opened part using the tin or tin alloy electroplating liquid of this invention.

(38) The protection layer is the layer which is formed prior to the plating on the place where the deposit should not be made on the substrate, and both the layer that is peeled after the plate deposit is formed (this is also called a resist), and the layer that will remain without being peeled, are included. Concerning the forming of the protection layer that has the opening on the substrate, any existing method can be used, however, the method which uses a photosensitive resin or a thermosetting resin as the protection layer, is preferred. In this invention, photosensitive resin means a resin that reacts with various light sources such as visible light, UV, X-rays or electron beams. The resin becomes soluble or insoluble in the developing solution, and either the negative type or positive type can be used. Also, after the thermosetting resin is cured by heat, the opening can be formed by a laser or other conventional process.

(39) Concerning the specific method for forming the opening, as was described in the description of U.S. Pat. No. 7,098,126, a barrier layer is formed on the contact pad, and the solder mask is formed on the places where the plate deposit is not necessary, and the patterning is done, and the barrier layer on the contact pad is exposed, and after the metal conductive layer is formed by physical vapor deposition (PVD), chemical vapor deposition (CVD), or electro or electroless plating beforehand, the patterning is done using the resist and the opening is formed. Also, as was described in Kokai patent No. 2012-506628, using the negative type photoresist, the solder mask layer is exposed and the opening is formed, and thereafter, the conductive layer is formed on the entire body of the opening and the solder mask layer.

(40) The above mentioned opening can be any size, however, generally, it is a via of which the diameter is 10-100 m, and the depth is 10-100 m. It is preferred that the conductive layer is formed at least on the bottom part of the opening of the protection layer before electroplating using the plating liquid of this invention. The above mentioned conductive layer can be the layer that is comprised of copper; tin; cobalt; tin-lead alloy; chromium-copper alloy; titanium/nickel (bi-metal), tin/copper; chromium/chromium-copper alloy/copper; or nickel/tin/copper. The conductive layer can be formed by PVD or CVD, or electroless plating or electroplating. For instance, after the catalyst that contains noble metal ions such as palladium is attached, the electroless copper plating or nickel electroplating is done to form the conductive layer.

(41) The bump that contains tin or a tin alloy is formed by using the above mentioned tin or tin alloy plating liquid. As was described above, the plating liquid of this invention exhibits good via fill performance, therefore, it can form a column-like deposit which practically does not have voids. The bump that contains tin or a tin alloy means the bump of which the main component is tin or a tin alloy, and for instance, it may be the bump comprised of two layers where the foundation of the bump is made first by another metal plating liquid, and on top of this, the tin or tin alloy column is formed, or it may be the one in which the bump containing two layers is reflowed and both are mixed as one body. The bump means a protrusion that is formed on the semiconductor chip or substrate, and it becomes the terminal to connect the semiconductor chip and substrate. Generally, the bump can be of any size. Typically the diameter is from 10-100 m, and the height is from 10-100 m.

(42) When the bump of this invention is contains a tin alloy, the tin and the second metal that forms the alloy are the metals that were previously described above for the tin alloy plating liquid. Concerning the composition of the alloy, the content of the second metal should be 0.1-50%, preferably 1-5% with the remainder tin.

Example 1

(43) A copper clad FR4 substrate was submerged in the pre-treatment liquid (CIRCUBOND 187 treatment solution available from Dow Electronic Materials, Marlborough, Mass.) for 2 minutes at 45 C., and the copper clad surface was made rough. On top of this, a photosensitive insulation resin (MultiPosit 9500cc photosensitive resin available from Dow Electronic Materials) was coated by a spin coater, and exposure, baking and development were done, and thus, a via with a depth of 20 m and a diameter of 50 m was formed.

(44) Thereafter, it was washed with a surface cleansing agent at 70 C. (CIRCUPOSIT MLB 211 cleaning agent available from Dow Electronic Materials) and then washed with water, and it was desmeared at 80 C. with CIRCUPOSIT MLB 213 solution (available from Dow Electronic Materials) for 2.5 minutes, and continuously, it was treated at 45 C. with a neutralizing agent (CIRCUPOSIT MLB 216 solution available from Dow Electronic Materials) for 5 minutes. Thereafter, electroless plating was conducted with an electroless copper plating liquid (CUPOSIT 328 copper plating bath available from Dow Electronic Materials) at 30 C. for 40 minutes, and a 1 m thick seed layer was formed. The substrate with the via was used as the evaluation substrate and the following test was conducted and the leveling performance was evaluated.

(45) The following tin plating liquid was prepared:

(46) Tin methane sulfonate: as tin ions, 45 g/L

(47) Methane sulfonic acid (79% solution): 85 mL/L

(48) Surfactant (poly oxy ethylene poly oxy propylene alkyl ether (Pegnol D-210Y, available from

(49) Toho Kagaku Kogyo K.K.): 0.5 g/L

(50) -ionone: 0.07 g/L

(51) Catechol: 2 g/L

(52) The evaluation substrate was submerged in 10 mL/L of a methane sulfonic acid solution (70% solution) for 1 minute, and the surface was activated. Thereafter, it was washed with de-ionized water for 2 minutes, and using this evaluation substrate as the cathode, electroplating was conducted for 11 minutes at 1 A/dm.sup.2 using the above mentioned plating liquid while stirring at a speed of 2 m/min After plating, and after washing with de-ionized water and drying, the via of the substrate was cut, and it was observed with a bright field microscope.

Example 2

(53) Example 1 was repeated except that 1-acetyl-1-cyclo hexene was used at 0.12 g/L instead of -ionone, and the via cross section was observed.

Example 3

(54) Example 1 was repeated except that citral was used at 0.2 g/L instead of -ionone, and surfactant 1 at 0.15 g/L and surfactant 2(-naphthol ethoxylate, commercial product Lugalvan BNO 12 available from BASF Co.) at 0.5 g/L were used as the surfactants, and the via cross section was observed.

(55) ##STR00008##

Example 4

(56) Example 1 was repeated except that 4-hexene-3-one was used at 0.3 g/L instead of -ionone, and that the concentration of surfactant 1 was changed to 2 g/L, and the via cross section was observed.

Example 5

(57) Example 1 was repeated except that -damascone was used at 0.02 g/L instead of -ionone, and that the concentration of surfactant 1 was changed to 0.75 g/L, and the via cross section was observed.

Example 6

(58) Example 1 was repeated except that tin methane sulfonate at 20 g/L and silver methane sulfonate at 0.5 g/L were used as the metal ion sources, and that -damascone was used at 0.02 g/L instead of -ionone, and 3,6-dithia-1,8-octane diol which has the structure shown below, was used at 2.6 g/L as the complexing agent, and the via cross section was observed.

(59) ##STR00009##

(60) The compositions of Examples 1-6, the via fill performance and the appearance are shown in Table 1. Also, a bright field microscopic photo of the cross section of the via that was made in Example 1 is shown in FIG. 1.

(61) TABLE-US-00001 TABLE 1 Example 1 2 3 4 5 6 Metal ion Tin methane 45 45 45 45 45 20 source (g/L sulfonate as metal Silver methane 0.5 ions) sulfonate Acid (mL/L) Methane sulfonic 85 85 85 85 85 34 acid , - -ionone 0.07 unsaturated 1-acetyl 1 cyclo 0.12 carbonyl hexene compound Citral 0.2 (g/L) 4-hexene-3-one 0.3 -damascone 0.02 0.02 Oxidation Catechol 2 2 2 2 2 2 inhibitor (g/L) Surfactant 1 0.5 0.5 0.15 2 0.75 1 (g/L) 2 0.5 Complexing 3,6-dithia-1,8- 2.6 agent (g/L) octane diol Result Degree of leveling Perfect Perfect Perfect Perfect Perfect Perfect Condition of No No No No No No deposited film problems problems problems problems problems problems surface Surfactant 1: Poly oxy ethylene poly oxy propylene alkyl ether, commercial name: Pegnol D-210Y (available from Toho Kagaku Kogyo K. K.) Surfactant 2: -naphthol ethoxylate, commercial mane. Lugalvan BNO 12 (available from BASF Co.)
Comparative 1

(62) Example 1 was repeated except that di-hydro--ionone was used at 0.2 g/L instead of -ionone, and the via cross section was observed. Filling of the via was insufficient.

(63) ##STR00010##
Comparative 2

(64) Example 1 was repeated except that citronellal having the structure shown below was used at 0.5 g/L instead of -ionone, and the via cross section was observed. Filling of the via was insufficient.

(65) ##STR00011##
Comparative 3

(66) Example 1 was repeated except that the acetone having the structure shown below was used at 1 g/L instead of -ionone, and the via cross section was observed. Filling of the via was insufficient.

(67) ##STR00012##
Comparative 4

(68) Example 1 was repeated except that the methacrylic acid having the structure shown below was used at 1 g/L instead of -ionone, and surfactant 2 was used at 7 g/L, and the via cross section was observed. Filling of the via was insufficient.

(69) ##STR00013##
Comparative 5

(70) Example 1 was repeated except that benzaldehyde was used at 0.025 g/L instead of -ionone, and surfactant 2 was used at 7 g/L instead of surfactant 1, and the via cross section was observed. The via was filled but many areas of skip plating and burns were observed and it was insufficient for practical use.

(71) Comparative 6

(72) Example 1 was repeated except that 3-chloro acetophenone was used at 0.3 g/L instead of -ionone, and the via cross section was observed. The via was filled but many areas of skip plating and burns were observed and it was insufficient for practical use.

(73) The compositions of Comparisons 1-6 and the results (via fill performance and appearance) are shown in Table 2. Also, a bright field microscopic photo of the cross section of the via made in Comparison 1 is shown in FIG. 2.

(74) TABLE-US-00002 TABLE 2 Comparative 1 2 3 4 5 6 Metal ion Tin methane 45 45 45 45 45 85 source (g/L sulfonate as metal ions) Acid (mL/L) Methane sulfonic 85 85 85 85 45 85 acid Leveling Di-hydro - 0.2 agent ionone (g/L) Citronellal 0.5 Acetone 1 Methacrylic acid 1 Benz aldehyde 0.025 3-chloro 0.3 acetophenone Oxidation Catechol 2 2 2 2 2 2 preventer (g/L) Surfactant 1 0.5 0.5 0.5 0.5 (g/L) 2 7 7 Result Degree of Some Some Some Some Poor Poor leveling what what what what poor poor poor poor Condition of No No No No Dendrite Dendrite deposited film problem problem problem problem deposits deposits surface Surfactant 1: Poly oxy ethylene poly oxy propylene alkyl ether, commercial name: Pegnol D-210Y (available from Toho Kagaku Kogyo K. K.) Surfactant 2: -naphthol ethoxylate, commercial name: Lugalvan BNO 12 (available from BASF Co.)