CN111534840B

CN111534840B - Electroplating method of PCB copper alloy

Info

Publication number: CN111534840B
Application number: CN202010509265.XA
Authority: CN
Inventors: 李翠芝
Original assignee: Shenzhen Prade Technology Co ltd
Current assignee: Shenzhen Prade Technology Co.,Ltd.
Priority date: 2020-06-07
Filing date: 2020-06-07
Publication date: 2021-12-17
Anticipated expiration: 2040-06-07
Also published as: CN111534840A

Abstract

The invention relates to a method for electroplating a copper alloy (such as CU-SN-ZN) of a PCB, which is characterized by comprising a plating solution of copper salt (such as copper sulfate, copper chloride, preferably copper sulfate), (zinc salt (such as zinc sulfate, zinc chloride, zinc nitrate, preferably zinc nitrate), and tin salt (such as stannous sulfate Sn2+, stannic chloride), wherein the process of preparing the plating solution before electroplating is carried out according to the following sequence, and the stannic sulfate and a chelating agent form a stannic chelate solution, and then are added into solutions of other components (other metal salts) to form a final plating solution, so that the content change of stannic can be controlled to change along a controllable direction in the electroplating process, and the control is facilitated.

Description

Electroplating method of PCB copper alloy

The technical field is as follows:

the invention relates to a method for electroplating copper-containing alloy, in particular to a method for controlling electroplating components of copper-containing alloy.

Background art:

copper and copper alloys are common plating species in the field of electroplating, and are used in many technical fields, such as PCBs, electronic terminals, switches, and the like. The existing copper alloy has detailed research whether the plating layer is thick or thin film. The literature on the study is listed here only by way of example as follows: the invention discloses a method for preparing a copper-zinc-tin-sulfur film by co-electrodeposition, which belongs to the technical field of new energy of photoelectric materials, and the method can be used for simultaneously depositing three metals in the same solution, obtaining precursor films of the three metals of copper, zinc and tin by one-step electrodeposition, easily controlling the components and the morphology, and then obtaining the copper-zinc-tin-sulfur film by heat treatment. The method comprises the following steps: 1) dissolving salt and complex containing three metal cations of copper, zinc and tin in water; 2) connecting the cathode and the anode with a conductive substrate and an inert anode respectively by using a three-electrode method, and placing a reference electrode in the solution without communicating the cathode and the anode; 3) turning on a power supply, and codepositing three metals of copper, zinc and tin by adopting a fixed potential; 4) taking out the deposited precursor and drying the precursor; 5) and carrying out heat treatment on the precursor to obtain the copper-zinc-tin-sulfur film. The method is safe and environment-friendly, and meanwhile, the electrodeposition method is simple in equipment, low in cost and easy for large-area industrial manufacturing. The technology relates to the general film coating process, and CN201510855333 discloses a gold imitation electroplating solution and an electroplating method thereof. The electroplating solution comprises the following components in mass volume concentration: 150-200 g/L potassium pyrophosphate, 40-50 g/L copper sulfate, 3-5 g/L tin pyrophosphate, 5-15 g/L zinc sulfate, 10-30g/L glycerol, 10-30g/L succinimide, 20-30 g/L nitrilotriacetic acid, 70-100 g/L pyrophosphoric acid and 6-10g/L benzotriazole, wherein the pH is adjusted to 7-9.3 by potassium hydroxide or sodium hydroxide, and the temperature of the electroplating solution is 20-55 ℃. The imitation gold electroplating solution is environment-friendly, adopts various coordination agents for coordination, and is good in stability and easy to maintain. The imitation gold layer obtained by the electroplating method has golden color, good brightness, good binding force with a plated piece base material, good leveling capability and excellent covering capability, and the method has wide current density application range and good repeatability. This process is typically directed to decorative copper-plated alloys. Furthermore, cyanate copper plating has traditionally been largely replaced, as CN201610423894 provides a low-cost cyanide-free copper-zinc-tin alloy electroplating solution. The water-soluble film is characterized by comprising copper salt, zinc salt, tin salt, strong base, EDTA complex and benzene sulfonate. The invention also discloses a process for producing the copper-zinc-tin alloy by adopting the low-cost cyanide-free electroplating copper-zinc-tin alloy solution. The copper-zinc-tin alloy electroplating solution does not contain components such as cyanide which have great harm to the environment and human bodies, reduces the environmental pollution and belongs to environment-friendly plating solution. The cost of each component in the copper-zinc-tin alloy electroplating solution is low. The electroplating copper-zinc-tin alloy system is stable and the production process is simple. The copper-zinc-tin alloy plating layer manufactured by using the electroplating solution has adjustable component content, and the content of copper, zinc and tin in the alloy plating layer is combined with the content of copper, zinc and tin salt in the electroplating solution according to the specific metal material application. Meanwhile, the copper-zinc-tin alloy coating has good binding force with a matrix, the surface of the coating is smooth and has no growth of dendrites, and the crystal is fine and bright.

However, the study of the above-mentioned plating species is not limited to this type of application, and further, US9586381B1 provides a device further having a hydrophobic and/or hydrophilic surface treatment layer (33), preferably a hydrophobic surface treatment layer, disposed on the metal plate. The metal coating has an outer surface with small dimensional irregularities that is not machined. Preferred is the use as orthopedic implants, especially orthopedic rods, the preferred composition being a copper alloy layer: the metal plating layer comprises about 45 wt% copper, about 45 wt% tin, and about 10 wt% zinc.

The above-mentioned research is extensive and more intensive and is not limited to common countries and regions, as the patent of AT509459B1 by austria miba glette ltd provides an anti-fretting layer (5) of a multilayer sliding bearing (1), said anti-fretting layer being composed of a copper-based alloy containing, in addition to copper as a main alloying element, AT least one element selected from the group consisting of germanium, tin, indium, zinc, nickel, cobalt, bismuth, lead, silver, antimony and inevitable impurities resulting from production, wherein the total proportion of said alloying elements is AT least 1 wt% and AT most 30 wt%, and wherein copper mixed crystal particles formed of copper and said AT least one element are present in said copper alloy, wherein said copper mixed crystal particles are oriented in such a way that an orientation index M { hkl } according to the following formula (I) satisfying each of the group { hkl } has a value of less than 3.0, wherein I { hkl } represents the X-ray diffraction intensity of the { hkl } crystal plane of the fretting wear resistant layer and I0{ hkl } represents the X-ray diffraction intensity of a completely unoriented copper powder sample.

Regardless of the research and application, the coating of copper alloys requires the provision of complexing agents, and there are many developments and applications of cyanide-free complexing agents, such as potassium hydroxide, potassium pyrophosphate, in addition to the conventional cyanate copper plating mentioned above, even though copper (I) pyrophosphate and zinc (II) pyrophosphate have been used as copper and zinc salts added and added since long ago as document SU 1177400A. The addition of tin (III) pyrophosphate and a specific wetting agent (IV) to the Cu-Zn-Sn alloy electroplating electrolyte increases the uniformity of the coating and the stability of its composition. The electrolyte comprises (g/l): (I)4.8 to 9.8, (II)21.1 to 31.6, (III)0.17 to 4.23, (IV)0.05 to 0.2 and pyrophosphoric acid K (V) 250-30035 to 55 ℃ and 0.4 to 1.8A/dm 2. Na 2-2- (N-3-decyloxypropyl-N-diethylsuccinic acid) succinamide sulfonate was used as (IV). A typical electrolyte comprises (in g/l): (I)4.8, (II)27.9, (III)1.5, (IV)0.1 and (V) 300. The nickel content is 70-83% and a typical coating contains 76% copper, 19% zinc and 5% tin.

However, the above is only one research or technical application and the control of the alloy composition cannot be studied. For example, it is deeply recognized in "discussion of mixed lead and lead-free process" (electronic process technology) that the control of the alloy composition in the electroplating process needs to be strict, the electroplating process is complex, the precise control of the alloy composition is challenged, and how the discussed mixed use of the lead and lead-free components can ensure the welding quality of the lead and lead-free components can be simultaneously influenced, and the change of the coating composition of course objectively influences the welding quality. In addition, the further research is that the Shanghai university of transportation shows that pure tin is adopted in order not to control the alloy components in the feasibility research of introducing a new electroplating process by AB company. Control of the alloy composition can be seen to be challenging.

The invention content is as follows:

although each coating achieves a certain composition of the alloy, it is clear that it is not intended for this purpose, or that the composition of the alloy can be controlled or regulated precisely. The invention therefore aims to refine the control of the electroplating process for such alloy compositions and to provide an innovative solution for this purpose. The technical scheme of the invention is described in detail as follows:

in one aspect of the present invention, there is provided a method for electroplating a copper alloy (e.g., CU-SN-ZN), which comprises a plating solution of a copper salt (e.g., copper sulfate, copper chloride, preferably copper sulfate), (zinc salt (e.g., zinc sulfate, zinc chloride, zinc nitrate, preferably zinc nitrate)), and a tin salt (e.g., stannous sulfate SN2+, tin chloride), wherein the plating solution is prepared before electroplating, particularly in the following order, tin sulfate and a chelating agent are mixed to form a tin chelate solution, and then the tin chelate solution is added to a solution of other components (other metal salts) to form a final plating solution, thereby controlling the change in the tin content in a controllable direction during electroplating.

The chelating agent is hydroxybenzene sulfonic acid and its salt (such as sodium, potassium, etc.).

pH 10-14。

The addition amount of the chelating agent (the hydroxybenzene sulfonic acid and the salt thereof) is 0.1-0.15mol/L calculated by the whole plating solution.

The current density is 5-10A/dm²。

The copper salt is 10-50g/L, the tin salt is 1-5g/L, and the zinc salt is 10-30 g/L.

The second aspect of the invention relates to the electroplating technology, in particular to the copper salt of 10-50g/L, the tin salt of 1-5g/L, the zinc salt of 10-30g/L, the addition amount of the chelating agent (the hydroxybenzene sulfonic acid and the salt thereof) of 0.1-0.15mol/L calculated by the whole plating solution, and the current density of 5-10A/dm²pH 10-14, WenThe temperature is 15-35 deg.C, and the electroplating time is 5-10 min.

The third aspect of the present invention also relates to an electroplating bath characterized by comprising a bath of a copper salt (e.g., copper sulfate, copper chloride, preferably copper sulfate), (zinc salt (e.g., zinc sulfate, zinc chloride, zinc nitrate, preferably zinc nitrate), and a tin salt (e.g., stannous sulfate Sn2+, stannic chloride), the copper salt being 10 to 50g/L, the tin salt being 1 to 5g/L, the zinc salt being 10 to 30g/L, and the tin chelating agent (hydroxybenzenesulfonic acid or a salt thereof) being added in an amount of 0.1 to 0.15mol/L in terms of the entire bath.

And the copper complexing agent is potassium hydroxide, potassium pyrophosphate and the like, and the content is 0.1-0.2 mol/L.

The zinc complexing agent is citric acid, tartaric acid and sodium salt thereof, and the content is 0.1-0.2 mol/L.

The invention has the beneficial effects that: 1 to the plating bath, the chelating agent also plates copper alloys in the bath, and the deposition of tin does not increase positively with the concentration in the bath, as opposed to the prior art one-pot addition of metal salts, however, the inventors have discovered that in addition to the complexing sequence capability of the complexing agent, the controlled addition of tin to the bath after complexing tin with the complexing agent, particularly hydroxybenzenesulfonic acid or a salt thereof, increases the tin content.

The specific implementation mode is as follows:

example 1:

1) sequentially adding potassium pyrophosphate, copper sulfate, citric acid and zinc nitrate into a solution bottle with 500mL of water, stirring for 1-2min, adding potassium hydroxide,

2) dissolving a tin chelating agent, namely hydroxybenzene sulfonic acid in 500mL of water, then adding 1g of stannous sulfate, stirring for 3-5min, standing for 1-2min, and then stirring for 1-2 min; the tin chelate solution of step 2 is then added to step 1,

3) and adjusting the pH value with ammonia water, and then electroplating according to the set parameters of the table 1. And the composition of the plating was analyzed.

Examples 2-5 were prepared according to the method of example 1, with the remaining differences being seen in table 1.

Comparative examples 1-2 were formulated as a one-pot process, i.e., the chelating agent and the metal salt were added together to the solution.

Comparative examples 3-4, methods of formulation the order of copper example 1.

It can be seen from table 1 that, as the stannous sulfate content increases, basically, every 1g of the plating solution increases, the tin plating layer content correspondingly increases by about 1% in a controllable manner, while the comparative examples 1 and 2 do not have the same rule, that is, the tin in the plating layer can be controlled by improving the preparation method, especially in the ternary alloy of copper, tin and zinc, and the copper content is not obviously changed, and the increase of the tin is mainly compensated by the decrease of the zinc content.

In addition, a comparison was made with the commonly used chelating agent EDTA, and it was found that even if a mixed complex solution was formed by adding EDTA and tin first and then added to the plating solution, tin formation could not be controllably formed as with hydroxybenzenesulfonic acid.

The understanding of the above phenomena is helpful in further understanding the influence of the chelating agent in the complexation of metal ions, and whether the ability of the chelating agent to form a complex with metal ions by being added first is to be determined whether the ability to substitute or attack other metal ions in the bath subsequently competes with the same conditions of the one-pot process, although the obvious fact is that the content of the tin coating can be controllably varied by the pre-addition of tin and hydroxybenzenesulfonic acid according to the present invention, thereby allowing a range of copper alloys to be obtained.

TABLE 1

Claims

1. A Cu-Sn-Zn alloy electroplating method is characterized by comprising a copper salt, a zinc salt and a tin salt plating solution, wherein the copper salt is copper sulfate or copper chloride, the zinc salt is zinc sulfate, zinc chloride or zinc nitrate, and the tin salt is stannous sulfate, the plating solution preparation process before electroplating is carried out according to the following sequence, stannous sulfate and a tin chelating agent form a tin chelate solution, and then the tin chelate solution is added into solutions of other metal salts to form a final plating solution, so that the content change of tin can be controlled to change along a controllable direction in the electroplating process, and the tin chelating agent is hydroxybenzene sulfonic acid and salts thereof.

2. The plating method as recited in claim 1, wherein the copper salt is copper sulfate, the zinc salt is zinc nitrate, and the hydroxybenzenesulfonate salt is a sodium salt or a potassium salt.

3. The plating method according to any one of claims 1 to 2, wherein the pH of the plating solution is from 10 to 14.

4. The plating method according to any one of claims 1 to 2, wherein the tin chelating agent is added in an amount of 0.1 to 0.15mol/L in terms of the whole plating solution.

5. Electroplating method according to any of claims 1-2, characterised in that the current density is 5-10A/dm²。

6. The plating method according to any one of claims 1 to 2, wherein the copper salt is 10 to 50g/L, the tin salt is 1 to 5g/L, and the zinc salt is 10 to 30 g/L.

7. The electroplating method according to any one of claims 1-2, wherein the copper salt is 10-50g/L, the tin salt is 1-5g/L, the zinc salt is 10-30g/L, the tin chelating agent is added in an amount of 0.1-0.15mol/L in terms of the whole bath, and the current density is 5-10A/dm²The pH value is 10-14, the temperature is 15-35 ℃, and the electroplating time is 5-10 min.

8. The plating solution is characterized by comprising copper salt, zinc salt and tin salt, wherein the copper salt is copper sulfate or copper chloride, the zinc salt is zinc sulfate, zinc chloride or zinc nitrate, the tin salt is stannous sulfate, the copper salt is 10-50g/L, the tin salt is 1-5g/L, the zinc salt is 10-30g/L, the adding amount of a tin chelating agent is 0.1-0.15mol/L calculated by the whole plating solution, the tin chelating agent is hydroxybenzene sulfonic acid and salts thereof, and the preparation process of the plating solution is as follows: stannous sulfate is formed into a tin chelate solution with the tin chelator and then added to a solution of other metal salts to form the final plating bath.

9. The plating solution of claim 8, further comprising a copper complexing agent which is potassium hydroxide or potassium pyrophosphate and is contained in an amount of 0.1 to 0.2 mol/L.

10. The plating solution of any of claims 8 to 9, further comprising a zinc complexing agent which is citric acid in an amount of 0.1 to 0.2 mol/L.