阅读说明：本技术 一种稳定锡类化学镀液及其应用 (Stable tin chemical plating solution and application thereof ) 是由 张元正 于 2021-08-31 设计创作，主要内容包括：本发明涉及C23C18,更具体地,本发明涉及一种稳定锡类化学镀液及其应用。所述镀液的制备原料包括亚锡盐、有机酸、硫脲类促进剂和还原剂,所述有机酸包括C1～C5有机酸。本发明提供一种化学镀液,通过使用合适的硫脲促进剂和还原剂,在酸性条件下可实现连续镀锡,在较高厚度的锡层上实现较高光滑和光亮性。通过添加合适的分散剂,和有机酸等作用,可提高镀液稳定性的同时,减少对油墨的攻击性。通过本发明提供的镀液各组分共同作用,可实现较快镀速下的到致密的镀层,提高后续PCB板等电子元件的可焊性。(The invention relates to C23C18, in particular to a stable tin chemical plating solution and application thereof. The raw materials for preparing the plating solution comprise stannous salt, organic acid, thiourea promoter and reducing agent, wherein the organic acid comprises C1-C5 organic acid. The invention provides an electroless plating solution which can realize continuous tin plating under acidic conditions and realize higher smoothness and brightness on a tin layer with higher thickness by using a proper thiourea promoter and a proper reducing agent. By adding proper dispersant and organic acid, the stability of the plating solution can be improved and the attack to the ink can be reduced. Through the combined action of the components of the plating solution provided by the invention, a compact plating layer at a higher plating speed can be realized, and the weldability of electronic elements such as a subsequent PCB (printed circuit board) and the like is improved.)

1. The stable tin chemical plating solution is characterized in that the preparation raw materials of the plating solution comprise stannous salt, organic acid, thiourea promoter and reducing agent, wherein the organic acid comprises C1-C5 organic acid.

2. A stable tin electroless plating solution according to claim 1 wherein said organic acid further comprises a C10-C20 unsaturated acid, and wherein the weight ratio of said C10-C20 unsaturated acid to said C1-C5 organic acid is 1: (3-5).

3. A stable tin-based electroless plating solution according to claim 1, wherein the weight ratio of the organic acid to the stannous salt is (2.5 to 3): 1.

4. a stable tin electroless plating solution according to claim 1, wherein the thiourea based accelerator is selected from one or more of thiosemicarbazide, phenylthiourea, and vinylthiourea.

5. A stable tin electroless plating solution according to claim 1, wherein the weight ratio of the thiourea promoter to the stannous salt is (2.5 to 3): 1.

6. a stable tin electroless plating solution according to any of claims 1 to 5, wherein the plating solution is prepared from aliphatic alcohol amine, wherein the weight ratio of the thiourea promoter to the aliphatic alcohol amine is 1: (0.1-0.2).

7. A stable tin-based electroless plating solution according to claim 6, wherein the plating solution is prepared from raw materials further comprising a dispersant, wherein the weight ratio of the dispersant to the aliphatic alcohol amine is (0.2-0.6): 1.

8. a stable tin-based electroless plating solution according to claim 7, wherein the dispersant is selected from one or more of polyethers, sulfonates, and polyvinylamides.

9. The stable tin electroless plating solution of claim 1, wherein the plating solution is prepared from metal oxides, and the weight ratio of the metal oxides to the stannous salt is (0.1-0.2): 1.

10. use of a stable tin-based electroless plating solution according to any one of claims 1 to 9 for tin plating of electronic components and semiconductors.

Technical Field

The invention relates to C23C18, in particular to a stable tin chemical plating solution and application thereof.

Background

With the increase of the requirement of the welding performance of electronic components, the requirement of arranging a plating layer on the circuit of the electronic component, such as a tin layer, is increased, but the currently used tin-lead solder has the problems of high lead content, environmental pollution and the like, and the use of the tin solder is influenced.

CN101705482A provides an alkyl sulfonic acid chemical tinning liquid and a tinning process based on the chemical tinning liquid, which comprises organic sulfonic acid tin salt, organic acid, a complexing agent, a reducing agent, a surfactant, an antioxidant, a noble metal salt and a brightening agent.

However, the brightness and the stability of the plating layer after tin plating are affected due to the problems of oxidation of tin and the like in the tin plating process, and in the tin plating process, a thicker tin layer is difficult to realize due to higher potential of tin, and the adhesion is lower.

Disclosure of Invention

In order to solve the above problems, the first aspect of the present invention provides a stable tin-based electroless plating solution prepared from raw materials including a stannous salt, an organic acid, a thiourea-based accelerator, and a reducing agent.

As a preferable technical scheme of the invention, the mass of the stannous salt in 1L of plating solution is 20-30 g.

As a preferred technical solution of the present invention, the stannous salt is selected from one or more of stannous sulfate, stannous fluoroborate, stannous halide and stannous methanesulfonate.

As a preferable technical scheme of the invention, the weight ratio of the organic acid to the stannous salt is (2.5-3): 1.

in a preferred embodiment of the present invention, the organic acid includes C1-C5 organic acid, and the C1-C5 organic acid is one or more selected from methanesulfonic acid, citric acid, and tartaric acid. Preferably methanesulfonic acid and citric acid, in a weight ratio of 1: (6-8).

In a preferred embodiment of the present invention, the organic acid further comprises a C10-C20 unsaturated acid, and the weight ratio of the C10-C20 unsaturated acid to the C1-C5 organic acid is 1: (3-5).

As a preferable technical scheme of the invention, the unsaturated acid C10-C20 is selected from one or more of oleic acid, 9-octadecenoic acid, 2-hexadecenoic acid, 2-tetradecenoic acid and 9-hexadecenoic acid.

In a preferred embodiment of the present invention, the reducing agent is selected from one or more of hydrazine hydrate, ascorbic acid, sodium hypophosphite and ammonium hypophosphite. Preferably ascorbic acid and sodium hypophosphite in a weight ratio of 1: (4-6).

As a preferable technical scheme of the invention, the weight ratio of the reducing agent to the stannous salt is (1.5-2): 1.

in a preferred embodiment of the present invention, the thiourea accelerator is one or more selected from thiosemicarbazides, phenylthioureas, and vinylthioureas.

According to a preferable technical scheme of the invention, the weight ratio of the thiourea accelerant to the stannous salt is (2.5-3): 1.

in the process of tinning a PCB (printed circuit board), because tin has high potential, the tin is difficult to replace copper, and when a reducing agent is used for reduction, continuous reduction is difficult to realize to obtain a tin layer, in addition, because stannous is easy to oxidize, the problem of blackening possibly occurs in the electroplating process, and the bright smoothness of a plating layer is influenced.

The inventor finds that the small molecular organic acid with higher dosage is needed to provide more stable chelating sites in order to avoid oxidation blackening in the tin plating process, but the higher dosage of the small molecular organic acid also increases the coordination stability of stannous chelate, influences the further replacement with copper and influences the thickening of a tin layer, and the inventor finds that the unsaturated medium-chain organic acid is added to stabilize stannous by citric acid and the like, and simultaneously the medium-chain organic acid participates in the stannous, the unsaturated medium-chain organic acid is used for regulating and controlling the number of citric acid, methyl sulfonic acid and the like and stannous chelate, so that the citric acid and the like tend to form a one-coordination and two-coordination structure with the stannous, the realization of more coordination structures is reduced, continuous tin plating is promoted, and a brighter plating layer with proper thickness is obtained.

As a preferable technical scheme, the preparation raw material of the plating solution also comprises a dispersant, and the weight ratio of the dispersant to the aliphatic alcohol amine is (0.2-0.6): 1.

in a preferred embodiment of the present invention, the dispersant is one or more selected from polyether, sulfonate and polyvinyl amide. Preferably polyether and sulfonate, in a weight ratio of 1: (2-3).

As examples of the polyether, polyoxyethylene ether, polyoxypropylene ether, polyoxyethylene polyoxypropylene block copolymer may be cited. The weight average molecular weight of the polyether is 2000-4000, and the HLB value is 12-18. There are exemplified polyoxyethylene polyoxypropylene block copolymers of sea weed, such as L45 (weight average molecular weight of 2400, HLB value of 15), L65 (weight average molecular weight of 3500, HLB value of 15), L64 (weight average molecular weight of 2900, HLB value of 13).

In a preferred embodiment of the present invention, the sulfonate is one or more selected from disodium 4-octadecenyl 2-sulfosuccinate, calcium bis (2-ethylhexyl) succinate sulfonate, magnesium bis (2-ethylhexyl) succinate sulfonate, and disodium 4-isodecyl 2-sulfosuccinate, preferably calcium bis (2-ethylhexyl) succinate sulfonate and magnesium bis (2-ethylhexyl) succinate sulfonate.

In addition, the inventor finds that the problem of etching of a copper surface windowing part is easy to occur in the process of tin immersion of the PCB, so that ink needs to be added on the PCB to reduce the influence on the windowing part, but the ink is attacked by a plating solution, particularly an acidic plating solution, and the stability of the ink can be further improved while the attack on the ink is effectively reduced by adding polyether and sulfonate.

This is probably because, in the tin plating process, by using a polyether having an appropriate molecular weight and HLB value, the dissolution of the polyether in the bath water and the spreading property of the ink portion and copper surface of the PCB are improved, and at the same time, the attack of the bath on the ink layer is reduced and the stability of the bath is promoted by the action of a sulfonate, particularly a sulfonate containing a divalent ion such as magnesium and calcium, and an organic acid, and the inventors have found that, by adding a di-branched sulfonate and a polyoxyethylenepolyoxypropylene block copolymer containing a poly-oxygen and a multi-branched chain, the attack of the bath on the ink layer can be further reduced and the stability of the bath in standing can be improved.

As a preferred technical scheme of the invention, the preparation raw material of the plating solution further comprises aliphatic alcohol amine, and the weight ratio of the thiourea promoter to the aliphatic alcohol amine is 1: (0.1-0.2).

In a preferred embodiment of the present invention, the aliphatic alcohol amine is selected from aliphatic mono-alcohol amine and/or aliphatic di-alcohol amine.

In a preferred embodiment of the present invention, the aliphatic monoethanol amine is selected from one or more of lauric acid monoethanol amide, stearic acid monoethanol amide, myristic acid monoethanol amide, and oleic acid monoethanol amide.

In a preferred embodiment of the present invention, the aliphatic diol amine is one or more selected from lauric acid diethanolamide, stearic acid diethanolamide, myristic acid diethanolamide, and oleic acid diethanolamide.

The inventor finds that when the polyether long chain is added, the compactness and the adhesiveness of tin layer deposition are influenced, and the adhesion of a tin coating and a PCB is influenced, and the inventor finds that the adhesion of the coating can be improved and a full-bright coating can be further obtained by adding proper aliphatic alcohol amine, particularly aliphatic mono-alcohol amine.

The reason for this is probably that through adding aliphatic mono-alcohol amine, because the interaction and competitive adsorption of the aliphatic chain and the long chain of polyether, and the structure of the NHROH bond of mono-alcohol amine, can be chelated with copper and the like to further reduce the potential, promote the replacement effect, so that polyether and aliphatic mono-alcohol amine are formed in the initial stage of tin plating and are adsorbed in a cross way, thereby promoting the lattice formation and lattice density of the initial tin deposition, and in the process of continuing reaction, the potential reduction of thiourea accelerant and the competitive action of calcium, magnesium and the like in sulfonate and stannous are utilized to improve the reaction activity and concentration of stannous, thereby forming a coating with better adhesiveness and compactness, and promoting the improvement of the coating adhesion and brightness.

As a preferable technical scheme of the invention, the preparation raw material of the plating solution also comprises metal oxide, and the weight ratio of the metal oxide to the stannous salt is (0.1-0.2): 1.

in a preferred embodiment of the present invention, the metal oxide is selected from Na₂WO₄、CuSb₂O₆、Na₂SnO₃One or more of (a).

The inventor finds that a tin coating with a proper thickness can be obtained by using a certain amount of polyether and sulfonate as a dispersion machine and adding metal powder for combined action, the formation and growth of crystals in the tin coating process can be adjusted, a smooth and full-bright coating can be obtained, and the binding force of the coating can be improved by using thiourea and alcohol amine to promote the replacement of stannous and copper while using a higher amount of organic acid to stabilize stannous and carrying out continuous deposition through a proper reducing agent.

In a second aspect, the invention provides the use of said stable tin-based electroless plating solution for tin plating of electronic components and semiconductors.

Compared with the prior art, the invention has the following beneficial effects:

(1) the invention provides an electroless plating solution which can realize continuous tin plating under acidic conditions and realize higher smoothness and brightness on a tin layer with higher thickness by using a proper thiourea promoter and a proper reducing agent.

(2) By adding proper dispersant and organic acid, the stability of the plating solution can be improved and the attack to the ink can be reduced.

(3) By adding proper amide, dispersing agent and the like, the ink is prevented from being attacked, and the bonding capability and the brightness are improved.

(4) Through the combined action of the components of the plating solution provided by the invention, a compact plating layer at a higher plating speed can be realized, and the weldability of electronic elements such as a subsequent PCB (printed circuit board) and the like is improved.

Detailed Description

Examples

Example 1

The embodiment provides a plating solution, the preparation raw materials of the plating solution comprise stannous salt, organic acid, thiourea accelerator and reducing agent, in 1L of the plating solution, the mass of the stannous salt is 30g, the stannous salt is stannous methanesulfonate, and the weight ratio of the organic acid to the stannous salt is 3: 1, the organic acid comprises C1-C5 organic acid, the C1-C5 organic acid is methanesulfonic acid and citric acid, and the weight ratio is 1: 8, the organic acid also comprises C10-C20 unsaturated acid, and the weight ratio of the C10-C20 unsaturated acid to the C1-C5 organic acid is 1: 3, C10-C20 unsaturated acid is 9-octadecenoic acid, and the reducing agent is ascorbic acidThe weight ratio of the ascorbic acid to the sodium hypophosphite is 1: 6, the weight ratio of the reducing agent to the stannous salt is 2: 1, the thiourea promoter is phenylthiourea, and the weight ratio of the thiourea promoter to the stannous salt is 3: 1, the preparation raw materials of the plating solution also comprise a dispersant, and the weight ratio of the dispersant to the aliphatic alcohol amine is 0.5: 1, the dispersing agent is polyether L45 and sulfonate, and the weight ratio is 1: 3, the sulfonate is calcium bis (2-ethylhexyl) succinate sulfonate, the preparation raw material of the plating solution also comprises aliphatic alcohol amine, and the weight ratio of the thiourea accelerator to the aliphatic alcohol amine is 1: 0.2, the aliphatic alcohol amine is lauric acid monoethanolamide, the preparation raw materials of the plating solution also comprise metal oxide, and the weight ratio of the metal oxide to the stannous salt is 0.2: 1, the metal oxide is Na₂WO₄。

Example 2

The embodiment provides a plating solution, the preparation raw materials of the plating solution comprise stannous salt, organic acid, thiourea accelerator and reducing agent, in 1L of the plating solution, the mass of the stannous salt is 25g, the stannous salt is stannous methanesulfonate, and the weight ratio of the organic acid to the stannous salt is 2.8: 1, the organic acid comprises C1-C5 organic acid, the C1-C5 organic acid is methanesulfonic acid and citric acid, and the weight ratio is 1: 7, the organic acid also comprises C10-C20 unsaturated acid, and the weight ratio of the C10-C20 unsaturated acid to the C1-C5 organic acid is 1: 4, C10-C20 unsaturated acid is 2-hexadecenoic acid, the reducing agent is ascorbic acid and sodium hypophosphite, and the weight ratio is 1: 5, the weight ratio of the reducing agent to the stannous salt is 1.8: 1, the thiourea promoter is phenylthiourea, and the weight ratio of the thiourea promoter to the stannous salt is 2.6: 1, the preparation raw materials of the plating solution also comprise a dispersant, and the weight ratio of the dispersant to the aliphatic alcohol amine is 0.4: 1, the dispersing agent is polyether L65 and sulfonate, and the weight ratio is 1: 2.5, the sulfonate is calcium bis (2-ethylhexyl) succinate sulfonate, the preparation raw material of the plating solution also comprises aliphatic alcohol amine, and the weight ratio of the thiourea accelerator to the aliphatic alcohol amine is 1: 0.15, the aliphatic alcohol amine is stearic acid monoethanolamide, and the preparation raw materials of the plating solution also comprise metal oxideA compound, wherein the weight ratio of the metal oxide to the stannous salt is 0.15: 1, the metal oxide is Na₂WO₄。

Example 3

The embodiment provides a plating solution, the preparation raw materials of the plating solution comprise stannous salt, organic acid, thiourea accelerator and reducing agent, in 1L of the plating solution, the mass of the stannous salt is 20g, the stannous salt is stannous methanesulfonate, and the weight ratio of the organic acid to the stannous salt is 2.5: 1, the organic acid comprises C1-C5 organic acid, the C1-C5 organic acid is methanesulfonic acid and citric acid, and the weight ratio is 1: 6, the organic acid also comprises C10-C20 unsaturated acid, and the weight ratio of the C10-C20 unsaturated acid to the C1-C5 organic acid is 1: 5, C10-C20 unsaturated acid is 2-tetradecenoic acid, the reducing agent is ascorbic acid and sodium hypophosphite, and the weight ratio is 1: 4, the weight ratio of the reducing agent to the stannous salt is 1.5: 1, the thiourea promoter is phenylthiourea, and the weight ratio of the thiourea promoter to the stannous salt is 2.5: 1, the preparation raw materials of the plating solution also comprise a dispersant, and the weight ratio of the dispersant to the aliphatic alcohol amine is 0.4: 1, the dispersing agent is polyether L64 and sulfonate, and the weight ratio is 1: 2, the sulfonate is magnesium bis (2-ethylhexyl) succinate sulfonate, the preparation raw material of the plating solution further comprises aliphatic alcohol amine, and the weight ratio of the thiourea accelerator to the aliphatic alcohol amine is 1: 0.1, the aliphatic alcohol amine is myristic acid monoethanolamide, the preparation raw materials of the plating solution also comprise metal oxide, and the weight ratio of the metal oxide to the stannous salt is 0.1: 1, the metal oxide is Na₂WO₄。

Example 4

The embodiment provides a plating solution, the preparation raw materials of the plating solution comprise stannous salt, organic acid, thiourea accelerator and reducing agent, in 1L of the plating solution, the mass of the stannous salt is 25g, the stannous salt is stannous methanesulfonate, and the weight ratio of the organic acid to the stannous salt is 2.8: 1, the organic acid comprises C1-C5 organic acid, the C1-C5 organic acid is methanesulfonic acid and citric acid, and the weight ratio is 1: 7, the organic acid also comprises C10-C20 unsaturated acid, andthe weight ratio of the C10-C20 unsaturated acid to the C1-C5 organic acid is 1: 4, C10-C20 unsaturated acid is 2-hexadecenoic acid, the reducing agent is ascorbic acid and sodium hypophosphite, and the weight ratio is 1: 5, the weight ratio of the reducing agent to the stannous salt is 1.8: 1, the thiourea promoter is phenylthiourea, and the weight ratio of the thiourea promoter to the stannous salt is 2.6: 1, the preparation raw materials of the plating solution also comprise a dispersant, and the weight ratio of the dispersant to the aliphatic alcohol amine is 0.4: 1, the dispersing agent is polyether L65 and sulfonate, and the weight ratio is 1: 2.5, the sulfonate is calcium bis (2-ethylhexyl) succinate sulfonate, the preparation raw material of the plating solution also comprises metal oxide, and the weight ratio of the metal oxide to the stannous salt is 0.15: 1, the metal oxide is Na₂WO₄。

Example 5

The embodiment provides a plating solution, the preparation raw materials of the plating solution comprise stannous salt, organic acid, thiourea accelerator and reducing agent, in 1L of the plating solution, the mass of the stannous salt is 25g, the stannous salt is stannous methanesulfonate, and the weight ratio of the organic acid to the stannous salt is 2.8: 1, the organic acid comprises C1-C5 organic acid, the C1-C5 organic acid is methanesulfonic acid and citric acid, and the weight ratio is 1: 7, the organic acid also comprises C10-C20 unsaturated acid, and the weight ratio of the C10-C20 unsaturated acid to the C1-C5 organic acid is 1: 4, C10-C20 unsaturated acid is 2-hexadecenoic acid, the reducing agent is ascorbic acid and sodium hypophosphite, and the weight ratio is 1: 5, the weight ratio of the reducing agent to the stannous salt is 1.8: 1, the thiourea promoter is phenylthiourea, and the weight ratio of the thiourea promoter to the stannous salt is 2.6: 1, the preparation raw materials of the plating solution also comprise a dispersant, and the weight ratio of the dispersant to the aliphatic alcohol amine is 0.4: 1, the dispersant is polyether L65, the preparation raw material of the plating solution also comprises aliphatic alcohol amine, and the weight ratio of the thiourea accelerator to the aliphatic alcohol amine is 1: 0.15, the aliphatic alcohol amine is stearic acid monoethanolamide, the preparation raw materials of the plating solution also comprise metal oxide, and the weight ratio of the metal oxide to the stannous salt is 0.15: 1, the metal oxide is Na₂WO₄。

Evaluation of Performance

1. Testing the ink aggressiveness; after the PCB with the ink layer was chemically plated in a plating solution at 45 ℃ to obtain a 3 μm plating layer, a microscope was used to observe whether the ink on the PCB was loose, and the results are shown in Table 1.

2. The appearance of the plating layer: after the PCB board containing the ink layer is chemically plated in a plating solution at 45 ℃ to obtain a plating layer with the thickness of 3 microns, whether the plating layer is full-bright and flat is observed, and the result is shown in table 1.

3. Stability: the plating solution was left at room temperature for 5 days, and the presence of precipitation, delamination, and the like was observed, and the results are shown in Table 1.

4. The binding force is as follows: after a plating layer of 3 μm was obtained by electroless plating at 45 ℃ on a copper plate, the tin-plated substrate was heated to 250 ℃ for 1 hour and immersed in cold water at 20 ℃ to observe whether or not the plating layer was blistered, and the results are shown in Table 1.

TABLE 1

Examples	Ink aggressiveness	Morphology of the coating	Stability of	Binding force
					1	Without loose	Full brightness	No turbidity	No foaming and peeling
2	Without loose	Full brightness	No turbidity	No foaming and peeling
					3	Without loose	Full brightness	No turbidity	No foaming and peeling
4	-	Most of the light is	-	Slight bubbling
					5	Slightly loose	Most of the light is	Slightly turbid	-

The plating solution provided by the invention has high stability and tinning capacity, and can obtain a tinned layer with high brightness and adhesive force.

It is to be understood that the embodiments described herein are to be considered in a descriptive sense only and not for purposes of limitation. Descriptions of features, advantages, or aspects within various embodiments should be considered as available for other similar features, advantages, or aspects in other embodiments.