TW584674B - A tin electroplating solution and its process - Google Patents

Abstract

The present invention relates to a tin electroplating solution comprising (1) 5-60 g/L of stannous ion, (2) complexing agent, (3) surfactant, and (4) 0.01-0.5 g/L of bismuth ion (trivalent), wherein pH of the solution is 1.5-6.0. Said tin electroplating soluting can-provide improved levels of solder-wettability without using harmful lead or organic brighteners. In addition, the present-invention relates to a tin electroplating process using the tin electroplating solution.

Description

Printed by the Consumer Cooperative of the Intellectual Property Bureau of the Ministry of Economic Affairs 584674 Α7 Β7 V. Description of the invention (2) Copper and tin-bismuth gold-containing electroplating bath, the precipitation potential of bismuth to tin is closer than that of silver. The tin-silver alloy electroplating solution has better stability, and the content ratios (ie, copper and bismuth) of each current density also change less. However, the tin-copper alloy coating has a problem that the copper content is increased and the melting point is also increased, which reduces the solder wettability. In addition, the tin-bismuth alloy coating film has a low melting point, so it has excellent solder wettability, but it has the disadvantage of being very brittle. Therefore, considering the reliability of the joint plus M, it is necessary to reduce the eutectic rate of bismuth (usually 2 ~ 10 weight X) For this reason, there is a strong need for improvement in tin plating technology. However, tin-lead alloys have a lower melting point than tin, and lead can act as a glossing agent during electroplating, which can make the precipitation dense and the coating's time (over time) It has the advantages of less change and maintaining welding wettability. For this reason, tin plating has the problems of rough precipitation and poor welding wettability. In addition, the use of organic gloss agents such as aldehyde stripe compounds or ammonium halide as the representative Although it can make the precipitation denser and improve the wettability of the solder, it increases the amount of eutectoid of organic matter in the coating, which leads to the decrease of the wettability of the solder over time. Electronic parts made of ceramics, glass, plastic and other materials When a tin-plated layer or a solder-plated film is applied to the electrode, if the shape of the part is larger than that of the 1005 type H (chip), each plating film is not affected by the difference in solder wettability, but under the 105 type M Small chip, The tin-plated film layer may cause problems in bonding. In addition, if the wafer is made of ceramics or glass, problems such as erosion of the material or precipitation of gold tincture on the material may occur. Therefore, it is necessary to use weak acidity or even medium. It is not suitable for use. Especially the ammonium salt is highly corrosive to the material, so it should not be used. Therefore, the technology of tin electroplating, which is less corrosive and has the same solder wettability as tin-lead alloy, is generally required. Applicable to China National Standard (CNS) Al Specification αίΟ X 297mm) · -------- Order --------- Line '(Please read the precautions on the back before filling this page) Economy Printed by the Consumer Cooperative of the Ministry of Intellectual Property Bureau 584674 Λ7 —.- ______IE______ 5. Description of the Invention (5) There is no special limitation on the salt, as long as the trivalent form of bismuth K can be introduced into the tin-electricity ferment, such as K methosulfide Salt forms such as bismuth acid, bismuth sulfate, and bismuth tartrate are introduced into the plating solution. The pH of the tin plating of the present invention is preferably from 1.5 to 6.0, and most preferably from 3.5 to 4.5. In this pH range, even if the constituent material of the electronic part is ceramic or glass, it will not erode the material, and at the same time, gold tincture will not precipitate on the material, and a good coating can be obtained. In the present invention, additives such as an oxidation inhibitor, a conductive agent, and an ion dissolving agent may be blended into the plating solution as needed. The oxidation inhibitor has the effect of preventing tin from changing from divalent to tetravalent ions, forming hydroxides, and the like to cause precipitation. Antioxidants used for this purpose are, for example, hydroquinone, catechol, resorcinol and ascorbic acid. The concentration of the oxidation inhibitor in the tin plating solution is 0.2 to 5.0 g / liter, and preferably 0.5 to 2.0 g / liter. The conductivity agent is used by the user to reduce the voltage during plating. As long as the purpose can be achieved, the type is not limited. For example, various compounds such as methanesulfonic acid, sulfuric acid, and gluconic acid are applicable. The concentration of the conductive agent in the tin plating solution is 20 to 200 g / L, preferably 50 to 150 g / L. The anode dissolving agent is used to dissolve the anode smoothly and keep the metal concentration constant. Any compound having this function is suitable, such as methanesulfonic acid, sulfuric acid, and gluconic acid. The concentration of the anode dissolving agent in the tin plating solution is 20 to 200 g / liter, preferably 50 to 150 g / liter. The tin plating solution of the present invention is preferably a plated electronic component with M. Electronic zero ~ 8-This paper size is applicable to China National Standard (CNS) A4 specification (210 X 297 mm) · -------------- Order ----- ^ --- -Line- (Please read the precautions on the back before filling out this page) 584674 B7 Printed by the Consumer Cooperatives of the Intellectual Property Bureau of the Ministry of Economic Affairs. 5. Description of the invention (6 pieces including chip capacitors, chip capacitors, and cymbals. Various electronic parts, etc. The tin plating solution of the present invention can form a tin plating film on electronic parts and the like under the following plating conditions.

Current density 0. 05 ~ 0 · 5 A / dtf Temperature 20 ~ 301C Time 2 4 0 ~ 24 minutes (coating thickness 5 to 5) The bismuth content of the tin coating film obtained by the method of the present invention is 0.1 weight X Μ, this tin content Compared with tin-bismuth alloy plating, the eutectoid rate of 2 ~ 10 and 5Ϊ is far lower, so the coating is not brittle and has coating characteristics close to that of tin coating. In addition, the coating is extremely dense and the solder wettability is the same as tin-lead coating. Can replace solder in applications where solder is used. A nickel coating is usually formed on this coating by further ore. _____f ________. — S j8c Example 1 Composition of tin electric ore liquid stannous sulfate (M tin ion meter) sodium polyoxyethylene / polyoxypropylene (ethylene oxide: average 10 moles, propylene oxide) ： Bisphthalate bismuth mesylate (M Bismuth ion meter) Distilled water PH 9-This paper size applies to China National Standard (CNS) A4 (210 X 297 mm) 15 g / L 140 g / L 100 g / 2.0 grams per liter / 4 mols on average) 0.5 grams per liter 0.05 gram per liter of excess. -------------- Order ----- 1-- --Line 1 (Please read the notes on the back before filling this page) Printed by the Consumer Cooperatives of the Intellectual Property Bureau of the Ministry of Economic Affairs 2 40 g / L 45 g / L 30 g / L 15 g / L 140 g / L 100 G / litre 5.0 g / litre 584674 A7 117 Description of invention (7)

Composition of nickel electroplating solution Sulfuric acid-nickel nickel chloride boric acid PH coating specifications Thickness of nickel coating Thickness of tin coating Electroplating process (i) Put parts to be mined into the drum (ii) Washing (iii) Acid activation treatment (v) Nickel plating (0 · 4 A / dra2, 60 minutes) ΓνΤ7 water ^ (vii) Tin plating (0 · 1 ~ 0 · 3 A / drf, 120 ~ 40 minutes) (viii) Washing (ix) Drying Example 2 Tin Composition of electroplating bath stannous sulfate (K tin ion meter) potassium citrate sodium polyoxyethylene nonyl ether methanesulfonate (ethylene oxide: average 9 mol) -10- This paper size applies to Chinese National Standard (CNS) Al size (210 X 297 mm) (Please read the notes on the back before filling this page)

Balance 2 40 g / L 45 g / L 30 g / L 584674 _______B7__ V. Description of the invention (8) Hydroquinone 1.0 g / L Bismuth mesylate (K bismuth meter) 0. 05 g / L Distilled water PF

Composition of nickel plating solution Nickel sulfate nickel chloride boric acid PH coating specifications Thickness of nickel coating Thickness of tin coating Electroplating process (Ϊ) Put the zero companion to be electroplated into (茼) Water washing (iii) Acid activation treatment (iv) Water washing (v) Nickel plating (0.4 A / dnf, 60 minutes) (vi) Water washing (vii) Tin plating (0.1 to 0.3 A / dm2, 120 to 40 minutes) (viii) Water washing (ix) Drying Example 3 Tin Composition of electroplating bath-11- This paper size is applicable to China National Standard (CNS) A4 (210 X 297 mm) -------- Order --------- Line | (Please read first Note on the back, please fill in this page again) Printed by the Employees' Cooperative of the Intellectual Property Bureau of the Ministry of Economic Affairs 584674 Λ7 B7 V. Invention Description Sodium methanesulfonic acid, sodium polyoxyethylene lauryl ether phthalate, bismuth methanesulfonate (M bismuth ion meter), distilled water, pH, composition of nickel plating solution, nickel sulfate, nickel chloride, boric acid, pH, leanness ~ thickness of nickel coating: 5 ^ ιη Thickness of tin coating: 5uin Plating process (i) Put the parts to be plated into the drum (ϋ) Wash (iii) Pickling Chemical treatment (iv) Washing (v) Nickel plating (0.4 A / dra2, 60 minutes) (vi) Washing (vii) tin plating (0 · 1 ~ 0 · 3 A / dm2, 120 15 g / litre 140 g / Litre 100 g / litre 2.0 g / litre 0.5 g / litre 0.05 g / litre balance 2 40 g / litre 45 g / litre 30 g / litre 40 min) # (Please read the notes on the back before filling in This page) Order ----- 1 ---- line | 12- This paper size applies to Chinese National Standard (CNS) A4 (210 x 297 mm) 584674 Λ7 Β7 V. Description of invention (10 Intellectual property of the Ministry of Economic Affairs Printed by the Consumer Cooperative of the Bureau (vi ii) Washed (ix) Drying Example 4 Composition of tin electroplating solution stannous sulfate (K tin ion meter) sodium gluconate methanesulfonate sodium polyoxyethylene lauryl ether hydroquinone methanesulfonate Bismuth acid (calculated as bismuth) Composition of distilled water PH nickel plating solution Sulfuric acid line Nickel chloride boric acid PH coating specification Thickness of nickel coating ·· 5 / i ® Thickness of tin coating: 5 / i ηι The plating process (i) will be waited Plating parts into the drum (ii) Washing (iii) Acid activation treatment 15 g / L 140 g / L 100 g / L 2.0 g / L 1.0 g / L 0.05 g / L Quantity ΤίΊΓg / open 45g / litre 30g / litre # (Please read the precautions on the back before filling out this page) Order ---------- Line {13- This paper applies the national standard of Shen Guo (CNS) A4 specification (210 X 297 mm) 45 g / litre 140 g / litre 100 g / litre 2.0 g / litre 1.0 g / litre 0.05 g / litre balance 584674 ____B7_ V. Description of the invention (11) (i V ) Washed (v) Nickel-plated (0 · 4 A / dnf, 60 minutes) (vi) Washed (vii) Tin-plated (0 · 1 ~ 0.3 A / dm2, 120 ~ 40 minutes) (viii) Washed (ix ) Drying Example 5 Composition of tin electroplating solution stannous sulfate (M tin ion meter) sodium gluconate sodium mesylate polyoxyethylene lauryl ether hydroquinone bismuth mesylate (K bismuth meter)

Distilled water PH

Composition of Nickel Plating Solution Nickel Sulfate Nickel Chloride Boric Acid PH Coating Specifications

Thickness of nickel coating: 5 / im Thickness of tin coating ... 5 to IB -14- This paper size applies Chinese National Standard (CNS) / V1 specification αίο X 297 mm) ----------------- ------ ^ ---- 1 ---- (Please read the notes on the back before filling out this page) 2 4 0 g / L 45 g / L 30 g / L Employees of Intellectual Property Bureau, Ministry of Economic Affairs Printed by the cooperative 584674 Λ7 B7 V. Description of the invention (12) Plating process Printed by the consumer cooperative of the Intellectual Property Bureau of the Ministry of Economic Affairs Printed by the cooperative (i) Put the parts to be plated into the drum (ϋ) Washed (iii) Acid activation treatment (iv) Washed (v) Mineral nickel (0 · 4 A / dm2, 60 minutes) (vi) Washed (vii) Tinned (0 · 1 ~ 0 · 3 A / dm2, 12C 1 ~ 40 minutes) (viii) Washed (ix ) Drying Example 6 Composition of tin electroplating bath: stannous sulfate (M tin ion meter) 15 g / liter sodium citrate 140 g / liter sodium mesylate 100 g / liter polyoxyethylene lauryl ether 2.0 g / liter benzene O-diphenol 0.5 g / L bismuth mesylate (K bismuth ion meter) 0.05 g / L distilled water balance PH 4.0. Composition of nickel plating solution Nickel sulfate 24 0 g / L nickel chloride 45 g / L Boric acid 30grams / litre # (Please read the precautions on the back before filling this page) Order --------- line < this paper size applies Chinese National Standard (CNS) A4 specification (210x297 mm) 584674 A7 B7 Five Inventions (13 Printed by the Consumer Cooperatives of the Intellectual Property Bureau of the Ministry of Economic Affairs, pH coating specifications, thickness of nickel coating: 5 // m, thickness of tin coating: 5 // 81, plating process (i) put parts to be plated into the drum (ii) Water washing (iii) Acid activation treatment (iv) Water washing (v) Nickel plating (0.4 A / dm2, 60 minutes) (vi) Water washing (vii) Tin plating (0.1 · (viii) Water washing (i X) Qianhuan Comparative Example 1 (without bismuth) Composition of tin electroplating solution Tin sulphate (W tin ion meter) Sodium gluconate sodium polyoxyethylene lauryl ether phthalic acid distilled water pH Composition of nickel electroplating solution 0 · 3 A / difl2, 120 ~ 40 minutes) 27 g / litre 140 g / litre 100 g / litre 2.0 g / litre 0.5 g / litre margin. '-------- Order ------ ---- Line * (Please read the notes on the back before filling out this page) 16 This paper size applies Chinese National Standard (CNS) A4 specification αίο X 297 mm) 584674 V. Description of the invention (14) A7 B7 Nickel sulfate 240 g / L nickel chloride 45 g / L boric acid 30 g / L PH 4.5 printed by the Ministry of Intellectual Property Bureau's Consumer Cooperative, thickness of nickel coating: 5 / iin thickness of tin coating: 5 ^ Into the plating process (i) Put the parts to be plated into the drum (ii) Water washing (iii) Acid activation treatment (iv) Water washing (v) Nickel plating (0 · 4 A / dm2, 60 minutes) (vi) Water washing ( vii) Tin plating (0 · 1 to 0.3 A / dra2, 120 to 40 minutes) (viii) Washing (ix) Drying Comparative Example 2 (without bismuth) Composition of tin plating solution stannous sulfate (calculated as tin ion) 15 G / litre ammonium citrate 140 g / litre ammonium sulfate 50 g / litre polyoxyethylene lauryl ether 2.0 g / litre phthalic acid 0.5 g / litre 17- This paper size applies to China National Standard (CNS) A4 specifications ( 210X 297 mm) (Please read the notes on the back before filling this page)

584674 A7 B7 V. Description of the invention (15)

Distilled water PH 2 40 g / L 45 g / L 30 g / L Composition of nickel plating solution Nickel sulfate Nickel chloride Nickel boric acid

PH coating specifications Thickness of nickel coating Thickness of tin coating Plating process (i) Put parts to be plated into the drum (ii) Washing

(Tii) Acidification I (iv) Water washing (v) Nickel plating (0.4 A / drf, 60 minutes) (vi) Water washing (vii) Tin plating (0.1 to 0.3 A / dm2, 120 to 40 minutes ) Printed by the Consumer Cooperative of the Intellectual Property Bureau of the Ministry of Economic Affairs (viii) Washed (ix) Drying Comparative Example 3 (Tin-Pb alloy) Composition of tin plating solution Tin methanesulfonate (M tin ion meter) 15 g / L methanesulfonate Lead acid (M lead meter) 1 g / L-18-This paper size applies to Chinese National Standard (CNS) A4 (210X 297 mm) 584674 A7 B7 V. Description of the invention (16) Sodium gluconate 140 g / Liter sodium methanesulfonate 100 g / L polyoxyethylene lauryl ether 2.0 g / L 0.5 g / L balance phthalic acid distilled water

PH 2 4 0 g / L 45 g / L 30 g / L

Composition of nickel plating solution Nickel sulfate nickel chloride boric acid PH coating specifications Thickness of nickel coating Λ Thickness of film: 5 "m Plating process (i) Put parts to be plated into the drum (ii) Washing (iii) Acid activity Printed by the Consumer Cooperative of the Intellectual Property Bureau of the Ministry of Economic Affairs (iv) Washed (v) Nickel-plated (0 · 4 A / dra2, 60 minutes) (vi) Washed (vii) Tin-lead alloy (0.1 ~ 0.3 A / dra2, 120 ~ 40 points) (viii) Washing (ix) Drying-19- This paper size applies Chinese National Standard (CNS) A4 specification (210X 297 mm) 584674 Α7 Β7 V. Description of the invention (17) Implemented by The coatings obtained in the examples all have a uniform matte or micro-gloss appearance. For these coatings, the zero-cross time was measured by the Meniscograph method using a solder wettability tester (commercial solder checker), and the soldering was evaluated. Wettability. The measurement conditions are as follows: Zero-cross time measurement conditions Solder bath: Sn / Pb = 60/40 Plating bath temperature: 2 3 0 Its immersion depth: 0.1 mm Immersion speed: 1 ffl / second Immersion time: 5 seconds Flux: pine resin-based inactive moisture resistance Test: The results obtained by performing the above test for 96 hours at a temperature of 60 ° C and a humidity of 90% are shown in Table 10. From the mercury on the surface of the junction, the cross-over time of the rain is less than 1 second, which proves that it is related to tin The lead alloy coating has almost the same degree of solder wettability. Please read the precautions before filling

Printed by the Consumers ’Cooperative of the Intellectual Property Bureau of the Ministry of Economic Affairs-20- This paper size is applicable to the Chinese National Standard (CNS) A4 specification (210X297 mm) 584674 A7 B7 Description of the invention (18) Table 10 Etching Ceramic Department Zero-crossing time of wettability of metal precipitation welding (seconds) Before moisture resistance test After moisture resistance test Example 1 0.000.3 0.7 Example 2 0.000.3 0.8 Example 3 0.000.3 0.6 Example 4 0.000.3 0.7 Example 5 0.000.3 0.8 Example 6 0.000.3 0.6 * Comparative Example 1 0.00 0.3 2.2 * Comparative Example 2 XX 0.3 &gt; 5.0 * Comparative Example 3 0.00. 2 0.6 (Please read the note on the back first Please fill in this page again) [Note] Erosion of the ceramics section ... No erosion X ..... Precipitation of gold ions that eroded the ceramics section ... No precipitation X .... Precipitation <Industrial use possibility 〉 The tin plating solution of the present invention printed by the Consumer Cooperative of the Intellectual Property Bureau of the Ministry of Economics has high safety because it does not contain lead of harmful components. In addition, because of the non-alloy plating solution, the management of the plating solution is easy, and at the same time, there is no change in the characteristics of the mineral film due to the change in the content rate, and a uniform coating can be obtained. In particular, the formed tin plating film has good solder wettability and is easy to solder, so it is very suitable for use as a bonding material. 2-1-This paper size is in accordance with Chinese National Standard (CNS) Al specification (210 X 297 mm) Application period --- C = * --- Case No. 0 (丄 I 13. Category Note by this bureau) A4 C4 Intellectual property of the Ministry of Economic Affairs (U-Patent Specification 584674 printed by the Industrial and Consumer Cooperatives) Inventions I. Touch name Chinese tin plating solution and plating method English A TIN ELECTROPLATING SOLUTION AND ITS PROCESS Name (1) 2) Kondo Keiichi, Invention 1 | 4 # — Nationality said his country's residence and residence (1) 2-4-1, Sakuma, Saitama, Saitama, Japan (2) 2-4-26, Kamei, Saitama, Saitama, Japan (Name) Rebirna Co., Ltd. f Nationality Resident National III. Applicant's residence and domicile (office) 6-3, Sanbancho, Chiyoda-ku, Tokyo, Japan Representative name Ichida Tetsu also draws a line 'This paper size Applicable to China National Standard (CNS) A4 specification (210X297 mm) * Installed by the Intellectual Property Bureau of the Ministry of Economic Affairs and printed by the Consumer Cooperatives 584674 A7 Γ-Just, ...... Γ: — ____B7_ Bu .... V. Description of the invention () &lt; FIELD OF THE INVENTION The present invention relates to a tin plating solution and a tin electric shovel method. More specifically, the present invention relates to a lead-free tin plating solution, and a tin plating film suitable for bonding electronic parts and having good solderability. Tin plating method. &Lt; Background Technology &gt; As is well known, tin-lead alloys have good bonding properties, are inexpensive, have excellent electrical characteristics, and have good solder wettability, and have been widely used as solders for electronic parts and the like. Electronic parts made of ceramics, glass, plastic and other materials have traditionally used tin plating or solder plating, such as tin plating or lead plating (solder plating), in order to improve the solder wettability of their electrodes. However, solder contains a large amount of lead ( For example, 5 to 40% by weight), it is not ideal from the viewpoints of maintenance of the working environment or the natural environment. In recent years, some people have replaced tin-plating solutions such as silver-silver alloy, tin, copper alloy, or tin-bismuth alloy with tin- Lead alloys form a coating film as a lead-free plating solution. However, because tin-silver alloy plating solutions are more precious than tin (high-potential metals), silver ions are returned due to the oxidation of tin ions. In the past, metallized silver deposits affect the life of the plating solution. In addition, in order to make tin and silver less likely to be deposited as alloys, a complexing agent is added to reduce the silver precipitation potential to The humble di rect ion moves to eutectic with tin, but in this method, the silver content rate tends to increase in the low current density part, especially when the silver content rate is 3.5% by weight or more. The higher the rate, the higher the melting point of the coating, resulting in a reduction in welding wettability and increasing welding difficulty. In addition, if it is a tin-copper alloy plating solution, the paper size is applicable to the Chinese National Standard (CNS) A4 specification (210 X 297 mm) 1 丨 d 丨 丨 丨-丨 丨 丨 丨 丨 ------. .. Orders 丨 丨 丨 I 丨 丨 丨 · line (please read the notes on the back before filling this page) 584674 Printed by the Consumer Cooperatives of the Intellectual Property Bureau of the Ministry of Economic Affairs A7 B7 V. Invention Description () 1… For this reason, An object of the present invention is to provide a tin electroplating solution and a tin electroplating method having no solder lead and no organic glossing agent and soldering wettability equal to or better than tin-lead alloy (solder). &lt; Disclosure of the invention &gt; ‘The present inventors have made intensive investigations in order to achieve the above-mentioned problems and found that the above-mentioned objects and effects can be achieved by the following constitutions, thereby completing the present invention. That is, this invention is an invention which has the following structures. 1. A tin plating solution with a pH of 1.5 to 6.0 and containing the following components: (1) 5 ~ 60 g / L stannous ion; (2) complexing agent; (3) surfactant and (4) 0.01 to 0.5 g / liter of bismuth ion (trivalent). 2. The above-mentioned wound plating solution contains-electricity and salt), anode dissolving agent or oxidation inhibitor. 3. In the above-mentioned tin plating solution, it is characterized that the surfactant is a nonionic surfactant. 4. A tin electroplating method featuring electroplating of electronic parts using the plating solution described in item 1 above. -&Lt; Best Mode for Carrying Out the Invention &gt; The present invention will be described in detail below. The tin plating solution of the present invention is composed of stannous ions, complexing agents, surfactants, and bismuth ions. The stannous ion is a divalent tin ion. Any compound that can provide this kind of ions in the liquid can be applied, such as sulfuric acid, hydrochloric acid, methanesulfonic acid, citric acid, malic acid, tartaric acid, etc. This paper size applies Chinese National Standard (CNS) A4 specification (210 X 297 mm) ) --J ---- ^ --- II · I ------ ^-111111-- &lt; Please read the notes on the back before filling out this page) Printed by the Consumer Cooperatives of the Intellectual Property Bureau of the Ministry of Economic Affairs 584674 —— ~ .—_ 一 ...... ㈣ 上 ～ ㈣α: A7 year, month, day, one + — B7 ：:::-? '-· J 、 &gt; t, j V. Description of the invention (The stannous salt of an inorganic or organic acid. The concentration of stannous is 5 ~ 60 g / liter, and it is best to use it at a concentration of 10 ~ 30 g / liter. The complexing agent is to keep the stannous ion safely in tin It can be used in power mineral liquid. Inorganic acid can also be pyrophosphoric acid. In addition, organic acid can also use gluconic acid. These complexing agents can be used in the form of a salt, for example, in the form of an alkali metal salt such as sodium or potassium. In the present invention The complexing agent in the tin plating solution can be used in the range of 20 to 10 times mol / liter of stannous ions, preferably 4 to 6 times mol / liter. The concentration is 40 to 300 g / liter, preferably 80 to 200 g / liter. The surfactant used in the tin electric ore liquid of the present invention is used to make the appearance of the coating film uniform. The suitable surfactant is For example, non-ionic interfacial active agents, anionic interfacial active agents, and cationic interfacial active agents, among which non-ionic I surface active agents are the most preferred. This non-ionic interfacial active agent can be specifically exemplified by polyvinyl laurate, Polyoxyethylene polyoxyalkenyl glycol (eg, ethylene oxide: 10 moles on average, propylene oxide: 4 moles on average) and polyoxyethylene nonphenyl ether (eg, ethylene oxide on average 9 moles) These surfactants can be used alone or in combination. The concentration of the surfactant in the tin plating solution of the present invention is (^ 丨 ~ 丨 g / L, preferably 0.5 ~ 5.0 g / L. The bismuth ion system is improved The welding of the coating is wet and user-friendly. However, if the bismuth is excessively present in the tin plating solution, the disadvantage of the tin-bismuth plating solution will result in the embrittlement of the coating, so its concentration should be 0.01 ~ 0.5 g / liter, preferably 0.02 ~ 2 g / L range. Bismuth ion The salt is introduced into the plating solution. This' paper size is applicable to the Chinese National Standard (CNS) A4 specification (210 X 297 mm) \: -------- ^ --------- ^^ 1 (Please read the notes on the back before filling this page)

Claims (1)

584674 A8 B8 C8 D8 VI. Application for patent scope 1. A tin plating solution with a pH of 5 ~ 6 and containing the following components: U) 5 ~ 60 g / L of stannous ions; (2) of the above stannous ions 2-10 times mole / liter of complexing agent; (3) 0.1-20 g / liter of surfactant; and (4) 0.01 to 0.5 g / liter of bismuth ion (trivalent). 2. For the tin electric ore liquid of item 1 of the scope of patent application, it further contains a conductive salt, an anode dissolving agent or an oxidation inhibitor. 3. For example, the tin plating solution in the scope of patent application, wherein the interfacial agent is a nonionic surfactant. 4. A tin electric ore method, which is characterized in that the electroplating of electronic parts is performed by using a tin plating solution in the scope of patent application 1. lit,; -------------- ^ ---- I ---- (Please read the notes on the back before filling out this page) Printed by the Consumer Cooperatives of the Intellectual Property Bureau of the Ministry of Economic Affairs -22- The size of this paper applies to China National Standard (CNS) A4 (210 X 297 mm)