Tin-silver alloy electroplating solution as well as preparation method and application thereof

Abstract

The invention relates to the field of electroplating, and discloses a tin-silver alloy electroplating solution and a preparation method and application thereof.The electroplating solution comprises soluble stannous salt, soluble silver salt, a composite defoaming agent, an anti-scorching agent, free acid, an antioxidant, a complexing agent and a solvent, and the composite defoaming agent comprises a first defoaming agent and a second defoaming agent; the first defoaming agent is selected from naphthol sulfonic acid, and the second defoaming agent is selected from naphthol ether; the molar ratio of the first defoaming agent to the second defoaming agent is 1: (1-4). The tin-silver alloy electroplating solution provided by the invention contains the composite defoaming agent compounded by the naphthol sulfonic acid and the naphthol ether, so that foam can be effectively prevented from being formed, and meanwhile, the formed foam is destroyed, so that a tin-silver alloy bump is prevented from generating a cavity after backflow. In addition, the composite defoaming agent has good water solubility and high cloud point, does not cause turbidity of the electroplating liquid at a relatively high temperature, and can avoid influence on normal use of the electroplating liquid.

Description

Technical Field

[0001] The invention relates to the field of electroplating, and in particular to a tin-silver alloy electroplating solution and a preparation method and application thereof. Background Art

[0002] Wafer bump plating is mainly connected by electric welding, which has high temperature requirements. Pure metals cannot meet this requirement, but alloys can meet higher welding temperatures, so alloy plating is mainly used. Currently, tin-lead alloys and tin-silver alloys are mainly used, with a small amount of tin-indium alloys, tin-copper alloys, tin-silver-copper alloys, etc. From the perspective of solderability, wafer bump plating uses welding plating, which has high requirements for the solderable temperature range. The solderable temperature of tin-silver alloy is 200-250℃, which has a good match with the solderable temperature.

[0003] The mainstream tin-silver electroplating solution on the market currently uses a current density of about 1-10ASD. When the tin-silver electroplating solution continues to work at a medium-to-high current density, a large number of bubbles will be generated in the plating solution due to the occurrence of hydrogen evolution at the cathode and oxygen evolution at the anode. If the defoaming ability or foam suppression ability of the plating solution is poor, these generated bubbles cannot be dissipated in time and are enriched in large quantities on the surface and in the plating solution. This will cause the plating solution to overflow the electroplating tank of the machine and cause pollution to the machine and the working environment. In addition, when these generated bubbles cannot be dissipated in time, they will be mixed in the electroplating coating during the electroplating process. After reflow, these bubbles in the coating will cause void problems and reduce the yield rate. For example, as disclosed in JP11256390A, since the precious metal component (silver) is preferentially precipitated at low current density, the silver content increases sharply at locations where the current density is low and cannot be controlled. As a result of this phenomenon, the current density becomes uneven on the uneven surface to be plated, and the alloy composition of the plated film becomes uneven, making it difficult to control the physical properties of the film, such as solderability. In addition, when using insoluble materials such as platinum, platinum-plated titanium, titanium coated with precious metal oxides, carbon, etc. as anodes, the following problems will occur: (1) divalent tin ions are oxidized on the anode and tetravalent tin ions accumulate in the plating solution; (2) a large amount of indelible foam layer will appear on the anode, which will affect the conductivity of the plating solution and increase the voltage, that is, when an insoluble anode is used, there will be a problem of reduced current efficiency. In addition, when a soluble anode is used, there is also the problem of silver displacement and deposition on the surface of the tin electrode. In order to solve the electroplating problem caused by high foam, JP11229174A discloses a low-foaming Sn or Sn-Pb alloy electroplating solution, but it can only be applied to pure tin or tin-lead alloy plating solution systems. Therefore, in view of the above technical problems, it is necessary to provide a low-foaming tin-silver alloy electroplating solution.

[0004] Generally speaking, in high-speed electroplating tin-silver alloy plating solutions, in order to ensure that the plating solution can work normally at high current density, cationic surfactants such as ester-based quaternary ammonium salts or dialkyl and trialkyl ammonium salts are added to the plating solution to suppress the deposition rate of stannous ions at high current density, thereby preventing the occurrence of scorching and powdering problems at high current density. However, this type of cationic surfactant tends to make the plating solution more prone to bubbles, and these bubbles will not dissipate in a short time. If some non-ionic surfactants are added to suppress bubbles, these non-ionic surfactants often have poor solubility and low turbidity. Adding them to the plating solution will cause the plating solution to become turbid, affecting the normal use of the plating solution. In addition, TW202202661A discloses that it uses amphoteric surfactants of the betaine type, which are prone to a large amount of foam during the electroplating process. If too much foam is generated during the electroplating process, the tin-silver alloy bumps will have void problems after reflow, which will affect subsequent functional problems such as solderability and uniformity. Summary of the invention

[0005] In order to overcome the problem in the prior art that a large amount of foam is easily generated in the tin-silver alloy electroplating solution during the electroplating process, resulting in voids in the tin-silver alloy bumps obtained by electroplating after reflow, the present invention provides a tin-silver alloy electroplating solution and a preparation method and application thereof. The tin-silver alloy electroplating solution comprises a composite defoamer prepared by mixing naphthol sulfonic acid and naphthol ether, which can effectively prevent the formation of foam and destroy the formed foam, thereby avoiding the formation of voids in the tin-silver alloy bumps after reflow.

[0006] In addition, the composite defoamer has good water solubility and a high cloud point, and will not cause turbidity in the electroplating solution at a higher temperature, thereby avoiding affecting the normal use of the electroplating solution.

[0007] In order to achieve the above-mentioned object, the first aspect of the present invention provides a tin-silver alloy electroplating solution, wherein the electroplating solution comprises a soluble stannous salt, a soluble silver salt, a composite defoamer, an anti-scorching agent, a free acid, an antioxidant, a complexing agent and a solvent, wherein the composite defoamer comprises a first defoamer and a second defoamer; The first defoamer is selected from naphthol sulfonic acid, and the second defoamer is selected from naphthol ether; The molar ratio of the first defoaming agent to the second defoaming agent is 1:1-4.

[0008] The second aspect of the present invention provides a method for preparing the tin-silver alloy electroplating solution provided by the first aspect of the present invention, the method comprising: in the presence of a solvent, mixing a soluble stannous salt, a soluble silver salt, a composite defoaming agent, a free acid, an antioxidant, a complexing agent, an anti-scorching agent and an optional brightener to obtain the tin-silver alloy electroplating solution.

[0009] The third aspect of the present invention provides a use of the tin-silver alloy electroplating solution provided by the first aspect of the present invention in electroplating.

[0010] The beneficial technical effects of the present invention are: The tin-silver alloy electroplating solution provided by the present invention comprises a composite defoamer prepared by mixing naphthol sulfonic acid and naphthol ether, which can effectively prevent the formation of foam and destroy the formed foam, thereby avoiding the formation of voids in the tin-silver alloy bumps after reflow.

[0011] In addition, the composite defoamer has good water solubility and a high cloud point, and will not cause turbidity in the electroplating solution at a higher temperature, thereby avoiding affecting the normal use of the electroplating solution. BRIEF DESCRIPTION OF THE DRAWINGS

[0012] Figure 1 The X-Ray CT image of the tin-silver alloy bump obtained by the electroplating solution of Example 1 after reflow; Figure 2 X-Ray CT image of the tin-silver alloy bump obtained by the electroplating solution of Comparative Example 1 after reflow; Figure 3 This is a scanning electron microscope image of a section of a tin-silver alloy bump obtained by the electroplating solution of Example 1 after reflow; Figure 4 This is a scanning electron microscope image of a section of the tin-silver alloy bump obtained by the electroplating solution of Comparative Example 1 after reflow. DETAILED DESCRIPTION

[0013] The endpoints and any values ​​of the ranges disclosed in this article are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoint values ​​of each range, the endpoint values ​​of each range and the individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered as specifically disclosed in this article.

[0014] A first aspect of the present invention provides a tin-silver alloy electroplating solution, the electroplating solution comprising a soluble stannous salt, a soluble silver salt, a composite defoamer, an anti-scorching agent, a free acid, an antioxidant, a complexing agent and a solvent, the composite defoamer comprising a first defoamer and a second defoamer; The first defoamer is selected from naphthol sulfonic acid, and the second defoamer is selected from naphthol ether; The molar ratio of the first defoaming agent to the second defoaming agent is 1:1-4.

[0015] The tin-silver alloy electroplating solution provided by the present invention comprises a composite defoamer prepared by mixing naphthol sulfonic acid and naphthol ether, which can effectively prevent the formation of foam and destroy the formed foam, thereby avoiding the formation of voids in the tin-silver alloy bumps after reflow.

[0016] According to the present invention, preferably, the molar ratio of the first defoaming agent to the second defoaming agent is 1:1.5-3.

[0017] According to a preferred embodiment of the present invention, the first defoaming agent is selected from at least one of the substances represented by formula (I): (I) Among them, R 1 -R 8 are independently selected from H, a halogen atom, a substituted or unsubstituted C1-C 20 Alkyl, C2-C 20 Alkenyl, C4-C 20 Diene, C3-C 20 Cycloalkyl, C3-C 20 Cycloalkenyl, C4-C 20 Cycloalkadienyl, alkoxy, amino, nitro, nitroso, azo, diazo, aniline, hydroxyl and -SO3M x One of, M is H or the first metal ion, and x is a stoichiometric number that satisfies charge balance; R 1 -R 8 has at least one hydroxyl group and at least one -SO3M x .

[0018] In the present invention, there is no particular limitation on the valence state of the first metal ion, and the first metal ion may be monovalent, divalent, or higher valent. For example, M is a monovalent metal ion (Na + , K + In order to satisfy the charge balance, x=1; M is a divalent metal ion (Mg 2+ , Ca 2+ etc.), to satisfy charge balance, x=1 / 2.

[0019] Specifically, R 1 -R 8 Each is independently selected from H, a halogen atom, a substituted or unsubstituted C1-C6 alkyl group, a C2-C6 alkenyl group, a C4-C8 dienyl group, a C3-C8 cycloalkyl group, a C3-C8 cycloalkenyl group, a C4-C8 cycloalkadienyl group, an alkoxy group, an amino group, a nitro group, a nitroso group, an azo group, a diazo group, an anilino group, a hydroxyl group and -SO3M x One of them.

[0020] According to a preferred embodiment of the present invention, the second defoaming agent is selected from at least one of the substances represented by formula (II): (II) Among them, R 9 is C1-C6 alkylene, R 10-N y or a C1-C6 alkyl group, N is H or a second metal ion, and y is a stoichiometric number satisfying charge balance.

[0021] The valence state of the second metal ion is not particularly limited in the present invention, and the second metal ion may be monovalent, divalent, or higher valent. For example, N is a monovalent metal ion (Na + , K + In order to satisfy the charge balance, y=1; N is a divalent metal ion (Mg 2+ , Ca 2+ etc.), to satisfy charge balance, y=1 / 2.

[0022] According to the present invention, more preferably, the first defoaming agent is selected from at least one of naphthol ethoxy sulfonic acid, 1-naphthol-5-sulfonic acid, 1-amino-2-naphthol-4-sulfonic acid, 2-nitroso-1-naphthol-4-sulfonic acid, 2-diazo-1-naphthol-4-sulfonic acid, 7-anilino-1-naphthol-3-sulfonic acid, 2-naphthol-6,8-disulfonic acid, 6-nitro-1-amino-2-naphthol-4-sulfonic acid and their salts.

[0023] Wherein, when the first defoaming agent is naphthol ethoxy sulfonic acid, R 1 -R 8 Middle: R 1 is ethoxy, R 2 is hydroxyl group, R 4 is sulfonic acid group, and the rest are H.

[0024] When the first defoaming agent is 1-naphthol-5-sulfonic acid, R 1 -R 8 Middle: R 4 is a sulfonic acid group, R 8 is hydroxyl and the rest are H.

[0025] When the first defoaming agent is 1-amino-2-naphthol-4-sulfonic acid, R 1 -R 8 Middle: R 1 is an amine group, R 2 is hydroxyl group, R 4 is sulfonic acid group, and the rest are H.

[0026] When the first defoaming agent is 2-nitroso-1-naphthol-4-sulfonic acid, R 1 -R 8 Middle: R 1 is hydroxyl group, R 2 is nitroso, R 4 is sulfonic acid group, and the rest are H.

[0027] When the first defoaming agent is 2-diazo-1-naphthol-4-sulfonic acid, R1 -R 8 Middle: R 5 is a sulfonic acid group, R 7 is a diazo group, R 8 is hydroxyl and the rest are H.

[0028] When the first defoaming agent is 7-anilino-1-naphthol-3-sulfonic acid, R 1 -R 8 Middle: R 4 is an aniline group, R6 is a hydroxyl group, R 8 is sulfonic acid group, and the rest are H.

[0029] When the first defoaming agent is 2-naphthol-6,8-disulfonic acid, R 1 -R 8 Middle: R 3 is hydroxyl group, R 6 and R 8 is sulfonic acid group, and the rest are H.

[0030] When the first defoaming agent is 6-nitro-1-amino-2-naphthol-4-sulfonic acid, R 1 -R 8 Middle: R 3 For nitro, R 5 is an amine group, R 6 is hydroxyl group, R 8 is sulfonic acid group, and the rest are H.

[0031] In the present invention, when the first defoaming agent is selected from the above preferred range, it can further improve the stability of stannous ions while suppressing and defoaming, and prevent stannous ions from being oxidized to tin ions, thereby further improving the stability and service life of the plating solution.

[0032] Further preferably, the first defoaming agent is selected from at least one of naphthol ethoxy sulfonic acid, 1-naphthol-5-sulfonic acid, 1-amino-2-naphthol-4-sulfonic acid and 2-naphthol-6,8-disulfonic acid.

[0033] According to the present invention, more preferably, the second defoaming agent is selected from at least one of ethyl 1-naphthoxyacetate, methyl 2-(1-naphthoxy)propionate, ethyl 2-(1-naphthoxy)propionate and tert-butyl 2-(1-naphthoxy)propionate.

[0034] Wherein, when the second defoaming agent is ethyl 1-naphthyloxyacetate, R 9 is methylene, R 10 It is ethyl.

[0035] When the second defoaming agent is methyl 2-(1-naphthyloxy)propionate, R 9 is 1,2-ethylene, R 10It is methyl.

[0036] When the second defoaming agent is ethyl 2-(1-naphthyloxy)propionate, R 9 is 1,2-ethylene, R 10 It is ethyl.

[0037] When the second defoamer is tert-butyl 2-(1-naphthyloxy)propionate (CAS: 1519509-92-2), R 9 is 1,2-ethylene, R 10 It is tert-butyl.

[0038] In the present invention, when the second defoaming agent is selected from the above more preferred range, it can further improve the anti-foaming and defoaming effects without affecting the silver ion deposition rate.

[0039] Further preferably, the first defoaming agent is ethyl 1-naphthyloxyacetate.

[0040] According to a preferred embodiment of the present invention, the content of the composite defoamer in the electroplating solution is 5-20 g / L.

[0041] In the present invention, when the content of the composite defoamer in the electroplating solution is within the above range, the formation of foam can be better suppressed and the formed foam can be destroyed.

[0042] More preferably, the content of the composite defoamer in the electroplating solution is 8-15 g / L.

[0043] According to a specific embodiment of the present invention, the soluble stannous salt is selected from at least one of stannous methanesulfonate, stannous sulfate and stannous fluoroborate.

[0044] According to a specific embodiment of the present invention, the soluble silver salt is selected from at least one of silver methanesulfonate, silver acetate and silver sulfate.

[0045] According to a specific embodiment of the present invention, the content of soluble stannous salt in the electroplating solution is 60-100 g / L, and the content of soluble silver salt is 0.8-4 g / L, calculated as metal ions.

[0046] More specifically, in terms of metal ions, the content of soluble stannous salt in the electroplating solution is 80-95 g / L, and the content of soluble silver salt is 1-3 g / L.

[0047] According to a specific embodiment of the present invention, the free acid is selected from at least one of methanesulfonic acid, sulfuric acid and formic acid.

[0048] According to the present invention, specifically, the hydrogen ion concentration of the electroplating solution is 0.5-1.6 mol / L.

[0049] More specifically, the hydrogen ion concentration of the electroplating solution is 0.8-1.2 mol / L.

[0050] According to the present invention, specifically, the antioxidant is selected from at least one of catechol, hydroquinone, potassium hydroquinone monosulfonate, potassium hydroquinone sulfonate, sodium 2-naphthol-7-sulfonate, pyrogallol, antipyrine, hydroquinone, catechol sulfonic acid, resorcinol sulfonic acid, catechol, aminocatechol, potassium hydroquinone sulfonate, methylhydroquinone, hydroquinone sulfonic acid, potassium hydroquinone sulfonate, and ascorbic acid.

[0051] More specifically, the antioxidant is antipyrine.

[0052] According to the present invention, specifically, the content of the antioxidant in the electroplating solution is 1-10 g / L.

[0053] More specifically, the content of the antioxidant in the electroplating solution is 1-5 g / L.

[0054] According to the present invention, specifically, the complexing agent is selected from at least one of a thiol compound, a sulfide compound and a thiourea compound, such as 3,6-dithio-1,8-octanediol, thiodiglycol, thiourea, 4,4'-dihydroxydiphenyl sulfide, 3,6-dithiooctane-1,8-diol, thiobis(triglyceride), 1,10-diamino-4,7-dithiohexadecane, 4,7-dithiohexadecane-1,2,9,10-tetraol, thiobis(dodecaethylene glycol), thioethylene glycol, 4,7-dithiodecane At least one of hexadecane-1,10-diol, thiobis(twentyethylene glycol), 3,6-dithiooctane-1,8-diol, 1,10-diamino-4,7-dithiodecane, thiobis(twelveethylene glycol), thiobis(decaethylene glycol), 4,7-dithio-1,10-diol, dithiobis(pentadecaethylene glycol), dithiobis(decaglycerol), 1-(2-dimethylaminoethyl)-5-mercaptotetrazole, 1-(m-sulfophenyl)-5-mercapto-1H-tetrazole sodium salt and octyl dimethyl ethyl ammonium sulfate.

[0055] More specifically, the complexing agent is thiodiglycol.

[0056] According to the present invention, specifically, the molar ratio of the complexing agent to the soluble silver salt calculated as silver ions in the electroplating solution is 2-30:1.

[0057] More specifically, the molar ratio of the complexing agent to the soluble silver salt in terms of silver ions in the electroplating solution is 10-20:1.

[0058] According to a preferred embodiment of the present invention, the anti-scorching agent is a cationic surfactant and / or an amphoteric surfactant.

[0059] More preferably, the anti-scorching agent is selected from at least one of dodecyldimethylbenzylammonium chloride, hexadecyldimethylbenzylammonium chloride, lauryldimethylammonium oxide, dodecyltrimethylammonium bromide, octadecyltrimethylammonium chloride, laurylhydroxysulfobetaine, laurylsulfobetaine, stearylsulfobetaine, hexadecyltrimethylammonium hydroxide, tetrabutylammonium hydroxide, tri(2-hydroxyethyl)methylammonium hydroxide, benzyltrimethylammonium hydroxide, polyoxyethylene bisphenol ether, polyoxyethylene phenyl ether, N,N,N',N'-tetrakis(2-hydroxypropyl)ethylenediamine, ethoxylated phenol and ethoxylated bisphenol.

[0060] In the present invention, when the anti-scorching agent is selected within the above range, it can better prevent scorching during electroplating under high current density, while refining the grains on the surface of the coating, thereby improving the overall uniformity of the coating.

[0061] More preferably, the anti-scorching agent is selected from at least one of dodecyl dimethyl benzyl ammonium chloride, hexadecyl dimethyl benzyl ammonium chloride, lauryl dimethyl ammonium oxide, lauryl hydroxysulfobetaine and dodecyl dimethyl benzyl ammonium bromide.

[0062] According to the present invention, preferably, the content of the anti-scorch agent in the electroplating solution is 2-10 g / L.

[0063] More preferably, the content of the anti-scorch agent in the electroplating solution is 2-6 g / L.

[0064] According to a specific embodiment of the present invention, the electroplating solution further comprises a brightener, and the brightener is selected from at least one of 1-acetyl-1-cyclohexene, 4-hexene-3-one, pentahydroxyflavone, benzalketone, benzaldehyde, cinnamaldehyde, β-ionone, benzalketone, benzoyl acetone, benzalketone, mulberry pigment and quercetin.

[0065] More specifically, the brightener is benzalkyne acetone.

[0066] According to the present invention, specifically, the content of brightener in the electroplating solution is 5-60 mg / L.

[0067] More specifically, the content of brightener in the electroplating solution is 30-50 mg / L.

[0068] In the present invention, the solvent is preferably water, but the technical solution provided by the present invention does not exclude the applicability of non-aqueous solvents, such as polar organic solvents and ionic liquids.

[0069] The second aspect of the present invention provides a method for preparing the tin-silver alloy electroplating solution provided by the first aspect of the present invention, the method comprising: in the presence of a solvent, mixing a soluble stannous salt, a soluble silver salt, a composite defoaming agent, a free acid, an antioxidant, a complexing agent, an anti-scorching agent and an optional brightener to obtain the tin-silver alloy electroplating solution.

[0070] According to a specific embodiment of the present invention, the method comprises the following steps: (1) In the presence of a solvent, a free acid, an antioxidant, a complexing agent, a soluble tin salt and a soluble silver salt are added in sequence; (2) The solution obtained in step (1) is mixed with a composite defoamer, an anti-scorch agent and an optional brightener to obtain the electroplating solution.

[0071] The third aspect of the present invention provides a use of the tin-silver alloy electroplating solution provided by the first aspect of the present invention in electroplating.

[0072] The present invention will be described in detail below through examples.

[0073] In the following examples, the turbidity of the plating solution was measured by a Hach TL2310 turbidity meter using 90° scattered light, with a light source wavelength of 830-890 nm; The void fraction after bump reflow was measured by X-ray computed tomography (X-Ray CT).

[0074] Unless otherwise specified, all reagents and raw materials were purchased from commercial sources.

[0075] Examples and Comparative Examples (1) At room temperature, add free acid, antioxidant, chelating agent, soluble tin salt and soluble silver salt to water in sequence and stir for 30 seconds. (2) Adding a defoaming agent, an anti-scorching agent and an optional brightener to the solution obtained in step (1) in sequence, stirring for 60 seconds, to obtain the electroplating solution.

[0076] The specific types and contents of the above substances are shown in Table 1.

[0077] Table 1

[0078] Table 1 (continued)

[0079] Table 1 (continued)

[0080] Table 1 (continued)

[0081] Table 1 (continued)

[0082] Test Example 1 100 mL of the plating solution obtained in the above embodiment and comparative example were taken respectively and placed in a 1 L glass measuring cylinder, the measuring cylinder was built with a conduit with an inner diameter of 5 mm, and the outlet of the conduit was about 5 mm from the bottom of the measuring cylinder. After standing for 10 min, when there was no visible foam in the plating solution, air was introduced through the conduit at a flow rate of 0.5 L / min. When the height of the plating solution foam was observed to be stable and no longer increased, the introduction of air was stopped and the timing was started at the same time, and the maximum cylinder scale reached by the foam and the time taken for all visible foam to be completely eliminated were recorded. The results are shown in Table 2.

[0083] Table 2

[0084] Test Example 2 The electroplating solutions obtained in the above examples and comparative examples were respectively placed in a constant temperature water bath at 55° C. and heated for 360 h. The appearance of the electroplating solutions and whether there was precipitation were observed. The turbidity of the electroplating solutions was measured with a turbidity meter. The results are shown in Table 3.

[0085] Table 3

[0086] Test Example 3 A copper patterned wafer with a photoresist seed layer was cut from a 12-inch diameter wafer. The wafer size is 6.25 cm × 6.25 cm and contains 3 × 3 DIEs (9 DIEs) in total. The area of ​​a single DIE is about 0.64 cm 2 The photoresist thickness is 80 μm, the aperture is 85 μm, and the opening ratio is 12%.

[0087] Take 500 mL of the electroplating solution obtained in the above embodiment and comparative example respectively, and perform electroplating in a constant temperature water bath at 30° C. according to the following segmented current density conditions: The first stage: a current density of 1 ASD, a plating time of 1 min, and a stirring speed of 15 m / min were used; The second stage: a current density of 4 ASD, an electroplating time of 8 min 45 s, and a stirring speed of 15 m / min; The third stage: a current density of 7 ASD, a plating time of 37 s, and a stirring speed of 15 m / min were used; The fourth stage: using a current density of 7 ASD, an electroplating time of 8 min 20 s, and a stirring speed of 60 m / min to obtain tin-silver alloy bumps.

[0088] After the electroplating is completed, the test piece is cleaned with deionized water and blown dry; then, the surface photoresist is removed with a degumming solution. The degummed test piece is subjected to a reflow treatment, specifically: in a nitrogen atmosphere, the test piece is heated from room temperature to 200°C at a rate of 2°C / s, maintained for 80s; then heated to 240°C at a rate of 2°C / s, maintained for 110s, and finally cooled naturally to room temperature. X-Ray CT is used to detect whether there are voids and the void ratio of the tin-silver alloy bumps after reflow, and the results are shown in Table 4.

[0089] Table 4

[0090] Figure 1 , Figure 2 X-Ray CT images of the tin-silver alloy bumps obtained by the plating solutions of Example 1 and Comparative Example 1 after reflow.

[0091] Figure 3 , Figure 4 The cross-section scanning electron microscope images of the tin-silver alloy bumps obtained by the electroplating solutions of Example 1 and Comparative Example 1 after reflow.

[0092] pass Figure 1-Figure 4 It can be seen that the tin-silver alloy bumps obtained by the electroplating solution of Example 1 have no voids after reflow, while the tin-silver alloy bumps obtained by the electroplating solution of Comparative Example 1 have obvious voids after reflow.

[0093] It can be seen from the results in Tables 2-4 that the composite defoamer provided by the present invention comprising naphthol sulfonic acid and naphthol ether can effectively prevent the formation of foam in the electroplating solution and destroy the formed foam, thereby avoiding the formation of voids in the tin-silver alloy bumps after reflow.

[0094] In addition, the composite defoamer provided by the present invention has good water solubility and a high cloud point, and will not cause turbidity in the electroplating solution at a relatively high temperature, thereby avoiding affecting the normal use of the electroplating solution.

[0095] The preferred embodiments of the present invention are described in detail above, but the present invention is not limited thereto. Within the technical concept of the present invention, the technical solution of the present invention can be subjected to a variety of simple modifications, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be regarded as the contents disclosed by the present invention and belong to the protection scope of the present invention.

Claims

1. A tin-silver alloy electroplating solution, characterized in that: The electroplating solution comprises a soluble stannous salt, a soluble silver salt, a composite defoamer, an anti-scorching agent, a free acid, an antioxidant, a complexing agent and a solvent, and the composite defoamer comprises a first defoamer and a second defoamer; The first defoamer is selected from naphthol sulfonic acid, and the second defoamer is selected from naphthol ether; The molar ratio of the first defoaming agent to the second defoaming agent is 1:1-4.

2. The electroplating solution according to claim 1, characterized in that The first defoaming agent is selected from at least one of the substances represented by formula (I): (I) Among them, R 1 -R 8 are independently selected from H, a halogen atom, a substituted or unsubstituted C1-C 20 Alkyl, C2-C 20 Alkenyl, C4-C 20 Diene, C3-C 20 Cycloalkyl, C3-C 20 Cycloalkenyl, C4-C 20 Cycloalkadienyl, alkoxy, amino, nitro, nitroso, azo, diazo, aniline, hydroxyl and -SO3M x One of; M is H or the first metal ion, and x is the stoichiometric number that satisfies the charge balance; R 1 -R 8 has at least one hydroxyl group and at least one -SO3M x .

3. The electroplating solution according to claim 1 or 2, characterized in that: The second defoaming agent is selected from at least one of the substances represented by formula (II): (II) Among them, R 9 is C1-C6 alkylene, R 10 -N y or a C1-C6 alkyl group, N is H or a second metal ion, and y is a stoichiometric number satisfying charge balance.

4. The electroplating solution according to claim 1 or 2, characterized in that: The first defoaming agent is selected from at least one of naphthol ethoxy sulfonic acid, 1-naphthol-5-sulfonic acid, 1-amino-2-naphthol-4-sulfonic acid, 2-nitroso-1-naphthol-4-sulfonic acid, 2-diazo-1-naphthol-4-sulfonic acid, 7-anilino-1-naphthol-3-sulfonic acid, 2-naphthol-6,8-disulfonic acid, 6-nitro-1-amino-2-naphthol-4-sulfonic acid and salts thereof; And / or, the second defoaming agent is selected from at least one of ethyl 1-naphthoxyacetate, methyl 2-(1-naphthoxy)propionate, ethyl 2-(1-naphthoxy)propionate and tert-butyl 2-(1-naphthoxy)propionate.

5. The electroplating solution according to claim 1 or 2, characterized in that: The content of the composite defoamer in the electroplating solution is 5-20 g / L.

6. The electroplating solution according to claim 1 or 2, characterized in that: The electroplating solution contains 60-100 g / L soluble stannous salt and 0.8-4 g / L soluble silver salt in terms of metal ions. and / or, the hydrogen ion concentration of the electroplating solution is 0.5-1.6 mol / L; and / or, the content of antioxidant in the electroplating solution is 1-10 g / L; And / or, the molar ratio of the complexing agent to the soluble silver salt calculated as silver ions in the electroplating solution is 2-30:

1.

7. The electroplating solution according to claim 1 or 2, characterized in that: The anti-scorching agent is a cationic surfactant and / or an amphoteric surfactant; And / or, the content of the anti-scorch agent in the electroplating solution is 2-10 g / L.

8. The electroplating solution according to claim 1 or 2, characterized in that: The electroplating solution further comprises a brightener, wherein the brightener is selected from at least one of 1-acetyl-1-cyclohexene, 4-hexene-3-one, pentahydroxyflavone, benzalketone, benzaldehyde, cinnamaldehyde, β-ionone, benzylideneacetone, benzoylacetone, benzalketone, morin and quercetin; And / or, the content of brightener in the electroplating solution is 5-60 mg / L.

9. A method for preparing the tin-silver alloy electroplating solution according to any one of claims 1 to 8, characterized in that: The method comprises: mixing soluble stannous salt, soluble silver salt, composite defoamer, free acid, antioxidant, complexing agent, anti-scorch agent and optional brightener in the presence of solvent to obtain the tin-silver alloy electroplating solution.

10. Use of the tin-silver alloy electroplating solution according to any one of claims 1 to 8 in electroplating.

Images