Gold-silver alloy bump nickel-palladium-gold plating corrosion prevention method based on segmented current electroplating

Abstract

The invention discloses a gold-silver alloy bump nickel-palladium-gold plating corrosion prevention method based on segmented current electroplating. The gold-silver alloy bump nickel-palladium-gold plating corrosion prevention method comprises the following steps that electroplating treatment is conducted on a base material in an Au / Ag alloy plating solution containing gold salt and silver salt; the electroplating process comprises two stages, and different current densities are set; in the first stage, alloy electro-deposition is carried out by adopting the first current density; in the second stage, electroplating is continued by adopting second current density in the later period of alloy layer formation; the current densities of the two stages are different, so that alloy bumps with components distributed in a gradient manner from bottom to top are formed; sequentially carrying out photoresist removal, seed gold layer etching and seed titanium tungsten layer etching treatment on the alloy bump; and carrying out chemical plating treatment on the treated alloy bump, wherein the chemical plating treatment step comprises the step of sequentially forming at least three metal layers on the surface of the alloy bump according to a preset sequence.

Description

TECHNICAL FIELD

[0001] The application is a gold-silver alloy bumping nickel-palladium-gold corrosion prevention method based on segmented current electroplating. BACKGROUND

[0002] Metal bumps are commonly used connection structures in microelectronic packaging, and have high requirements for their conductivity, mechanical strength and corrosion resistance. Traditional electroplating processes mostly use a single current density, which is difficult to balance the mechanical properties of the alloy bump bottom layer and the chemical stability of the surface layer, and is prone to corrosion, oxidation and reliability decline problems.

[0003] The segmented current electroplating technology can adjust the composition gradient distribution of the gold-silver alloy bump from the bottom to the top by setting different current densities at different stages, realize the enrichment of silver at the bottom to enhance the structural strength, and the enrichment of gold at the top to improve the corrosion resistance, so as to optimize the overall performance.

[0004] At the same time, the traditional protective layer of single-layer gold plating or nickel plating is easy to be damaged and fail, and is difficult to provide long-term protection. The chemical plating process does not require an external power supply and can continuously deposit nickel, palladium and gold on the surface of the bump to build a multi-layer corrosion barrier. The nickel layer provides basic protection, the palladium layer enhances the combination, and the gold layer provides inert protection and good conductivity.

[0005] Currently, there is no mature process to effectively combine segmented current control with a three-layer chemical plating protection structure. Therefore, a new method needs to be developed to balance the functional optimization of the bump structure and the high-stability corrosion resistance to meet the needs of high-end packaging. SUMMARY

[0006] The purpose of the present application is to solve the above problems of the prior art and provide a gold-silver alloy bumping nickel-palladium-gold corrosion prevention method based on segmented current electroplating.

[0007] A gold-silver alloy bumping nickel-palladium-gold corrosion prevention method based on segmented current electroplating, comprising the following steps:

[0008] Electroplating treatment of the substrate in an Au / Ag alloy plating solution containing gold salt and silver salt;

[0009] The electroplating process includes two stages with different current densities:

[0010] The first stage uses a first current density for alloy electrodeposition;

[0011] The second stage uses a second current density for electroplating in the later stage of alloy layer formation;

[0012] The current densities of the two stages are different to form an alloy bump with a composition gradient distribution from the bottom to the top;

[0013] The alloy bump is sequentially subjected to a glue removal process, a seed gold layer etching process and a seed titanium-tungsten layer etching process;

[0014] The treated alloy bump is subjected to a chemical plating process, which includes:

[0015] At least three metal layers are sequentially formed on the surface of the alloy bump in a preset order.

[0016] Further, the first current density is 0.2-0.8A / dm 2 , and the second current density is 1-5A / dm 2 .

[0017] Further, the duration of the second stage electroplating is 30-120 seconds.

[0018] Further, the duration of the first stage electroplating is 1000-2400 seconds.

[0019] Further, the thickness of the alloy bump is 5-11um, and the purity of gold in the top 1-2um thickness range is more than 80%.

[0020] Further, the electroplating solution maintains a flow rate of 10-15L / min and a shaking frequency of 10-30Hz during the entire electroplating process.

[0021] Further, the gold layer, nickel layer and palladium layer are formed on the surface of the alloy bump by the following steps:

[0022] The alloy bump is pretreated, and the pretreatment includes pickling, micro-etching, dilute nitric acid cleaning and deionized water rinsing;

[0023] The pretreated alloy bump is subjected to at least two zinc displacement treatments to activate the surface;

[0024] The activated alloy bump is sequentially placed in a chemical nickel plating solution and a chemical palladium plating solution for reaction, respectively forming a continuous nickel layer and a palladium layer on the surface of the bump;

[0025] Chemical gold plating is performed on the surface of the palladium layer to form a continuous metal gold layer;

[0026] The alloy bump with a three-layer structure is rinsed and dried.

[0027] Further, the pickling uses a 5% citric acid solution for 1-5 minutes, the rinsing step uses 18MΩ·cm deionized water for rapid rinsing, and the drying step is hot air or nitrogen drying with a temperature control of 80-120℃.

[0028] Further, the gold plating solution is a non-electrolytic gold salt solution, the reaction temperature of the chemical gold plating step is 50-65℃, and the reaction time is 5-60 minutes; the plating nickel step is carried out at a temperature of 60±5℃, the reaction time is 10-30 minutes, and a nickel layer with a thickness of 1-5 μm is formed; the plating gold step is carried out at a temperature of 50-65℃, the reaction time is 5-60 minutes, and a gold layer with a thickness of 0.05-0.5 μm is formed; the plating palladium step is carried out at 50-60℃ for 5-30 minutes, and a palladium layer with a thickness of 0.05-0.5 μm is formed; the plating nickel step is carried out at 60±5℃ for 10-30 minutes, and a nickel layer with a thickness of 1-5 μm is formed; the plating gold step is carried out at 50-65℃ for 5-60 minutes, and a gold layer with a thickness of 0.05-0.5 μm is formed.

[0029] Further, the micro-etching is a surface layer corrosion for 10-60 seconds to remove the oxide film, and each zinc replacement treatment includes a dilute nitric acid cleaning and deionized water rinsing step.

[0030] Beneficial effects: Compared with the prior art, the present application effectively realizes the composition gradient control of the gold-silver alloy bump from the bottom to the top by introducing the segmented current density control electroplating process, so that the bottom has high silver content and dense structure, and the mechanical support and thermal conductivity are enhanced; the top has high gold content and excellent chemical inertness, which significantly improves the oxidation resistance and corrosion resistance of the bump, thereby overcoming the problem of uniform composition and single performance caused by traditional single current density electroplating.

[0031] In addition, the present application further combines a three-layer structure of a chemical plating metal protection system, and a nickel, palladium and gold three-layer dense and continuous metal film layer is formed on the surface of the alloy bump in sequence to build a multiple corrosion barrier system. This structure improves the overall protection performance, and also improves the interlayer adhesion strength and anti-interface failure capability. The chemical plating process does not require an external power supply, the process is stable, and the interlayer cleaning ensures the film layer bonding quality and avoids impurity inclusions or film layer peeling.

[0032] Through the synergistic effect of the above structure design and process optimization, the present application can significantly improve the mechanical strength, corrosion resistance and electrical performance of the metal bump, and is suitable for application fields such as microelectronic packaging, electrical interconnection and sensor devices that require high reliability and resistance to multiple environmental stresses, and has good industrial application prospects. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 is a flow chart of a gold-silver alloy bump chemical plating nickel-palladium-gold anti-corrosion method based on segmented current electroplating. DETAILED DESCRIPTION

[0034] In order to deepen the understanding of the present application, the present application will be further described below in conjunction with examples and drawings, which are only used to explain the present application and do not constitute a limitation on the protection scope of the present application.

[0035] A gold-silver alloy bumping nickel-palladium-gold plating corrosion prevention method based on segmented current electroplating, comprising the following steps:

[0036] Step 1: electroplating preparation

[0037] An Au / Ag alloy electroplating solution containing gold and silver salts is configured; the substrate is placed in the electroplating solution for alloy electrodeposition treatment.

[0038] Step 2: segmented current density electroplating

[0039] The electroplating process is carried out in two stages to form a gold content gradient alloy bump from the bottom to the top:

[0040] First stage:

[0041] The current density is 0.2-0.8 A / dm 2 ; the electroplating time is 1000-2400 seconds; the bottom layer alloy structure is formed;

[0042] Second stage:

[0043] The current density is increased to 1-5 A / dm 2 ; the electroplating time is 30-120 seconds; the top gold content ratio is increased to improve the surface corrosion resistance.

[0044] During the entire electroplating process, the following is controlled:

[0045] Electroplating solution flow rate: 10-15 L / min; shaking frequency: 10-30 Hz.

[0046] Step 3: forming an alloy bump structure

[0047] The total thickness of the alloy bump is controlled to be 5-11 μm; the gold content purity in the range of 1-2 μm at the top of the bump reaches more than 80%.

[0048] Step 4: surface treatment

[0049] The alloy bump is sequentially treated as follows: degumming; etching the seed gold layer; etching the seed titanium-tungsten layer.

[0050] If it is an alloy bump, the following alternative treatment process is performed:

[0051] Step 5: chemical plating of three-layer metal protection structure

[0052] The treated alloy bump surface is sequentially chemically plated with nickel, palladium and gold, and each layer is rinsed with deionized water:

[0053] Electroless nickel plating:

[0054] Temperature: 60±5℃;

[0055] Time: 10-30 minutes;

[0056] Thickness: 1-5 μm;

[0057] Washing with 18 MΩ·cm deionized water;

[0058] Electroless palladium plating:

[0059] Temperature: 50-60℃;

[0060] Time: 5-30 minutes;

[0061] Thickness: 0.05-0.5 μm;

[0062] Washing with 18 MΩ·cm deionized water;

[0063] Electroless gold plating:

[0064] Temperature: 50-65℃;

[0065] Time: 5-60 minutes;

[0066] Thickness: 0.05-0.5 μm;

[0067] Step 6: Final rinsing and drying

[0068] Rinsing thoroughly with 18 MΩ·cm deionized water;

[0069] Drying using hot air or nitrogen, with temperature controlled at 80-120℃.

[0070] Working principle: By setting different current densities in two stages during electroplating, a composition gradient distribution of the gold-silver alloy bump from bottom to top is achieved, and a three-layer metal protection structure of nickel, palladium, and gold is formed on its surface in turn, thereby significantly improving its corrosion resistance and interface stability.

[0071] In the first stage, a lower current density is used for electrodeposition, which is conducive to the preferential growth of silver elements, making the bottom of the bump rich in silver and thus giving it good mechanical support and heat conduction performance; while in the second stage, a higher current density is used, which accelerates the deposition efficiency of gold elements on the top of the bump, forming a gold-rich layer on the top, which has stronger chemical inertness and corrosion resistance. Through this segmented current control technology, the alloy bump has a longitudinal gradient structure that gradually transitions from silver to gold, optimizing its overall functionality.

[0072] By setting appropriate plating solution flow rate and shaking frequency in the electroplating process, the solution interface update rate and electrode reaction uniformity can be effectively improved, composition segregation and deposition defects can be prevented, and the flatness and density of the bump surface can be improved.

[0073] In the post-electroplating processing link, the seed gold layer and titanium-tungsten layer are removed by etching, the exposed alloy bump surface is cleaned, and a continuous chemical plating process is implemented on the surface: a dense nickel layer is first formed as a main protective barrier, then a stable palladium layer is formed on it as a buffer and connecting layer, and finally an inert gold layer is formed to provide long-lasting oxidation resistance and electrical performance protection. Deionized water is used to clean between the three layers of metal plating, ensuring clean interfaces and firm interlayer bonding, effectively avoiding problems such as film peeling or inclusions.

[0074] In summary, this method uses segmented current density control to achieve a gradient alloy structure, and combines a three-layer chemical plating layer to build a multi-protection system, significantly improving the corrosion resistance, electrical conductivity, and structural stability of the gold-silver alloy bump. It is especially suitable for precise application scenarios such as microelectronic packaging, electrical connections, and sensors that require high reliability.

[0075] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A method for corrosion protection of gold-silver alloy bumping with nickel-palladium-gold plating based on segmented current electroplating, characterized in that, Includes the following steps: Electroplating of the substrate in an Au / Ag alloy plating bath containing gold and silver salts; The electroplating process includes two stages, each with a different current density: The first stage uses the first current density for alloy electrodeposition; In the second stage, electroplating continues at a second current density during the later stage of alloy layer formation; The current densities in the two stages are different to form alloy bumps with a compositional gradient distribution from bottom to top; The alloy bumps are sequentially subjected to adhesive removal, seed gold layer etching, and seed titanium-tungsten layer etching. The treated alloy bumps undergo a chemical plating process, the chemical plating process including: At least three metal layers are formed sequentially on the surface of the alloy bump in a predetermined order.

2. The electroless nickel-gold plating corrosion protection method according to claim 1, characterized in that, The first current density is 0.2-0.8 A / dm³. 2 The second current density is 1-5 A / dm. 2 .

3. The electroless nickel-gold plating corrosion protection method according to claim 2, characterized in that, The duration of the second stage of electroplating is 30-120 seconds.

4. The electroless nickel-gold plating corrosion protection method according to claim 3, characterized in that, The first stage of electroplating lasts for 1000-2400 seconds.

5. The electroless nickel-gold plating corrosion protection method according to claim 4, characterized in that, The alloy bumps are 5-11 μm thick, and the gold content in the top 1-2 μm thickness range is over 80% pure.

6. The electroless nickel-gold plating corrosion protection method according to claim 5, characterized in that, The electroplating solution maintains a flow rate of 10-15 L / min and an agitation frequency of 10-30 Hz throughout the entire electroplating process.

7. The electroless nickel-gold plating corrosion protection method according to claim 1, characterized in that, The steps for forming a gold layer, a nickel layer, and a palladium layer on the surface of the alloy bump are as follows: The alloy bumps are pretreated by pickling, micro-etching, dilute nitric acid cleaning and deionized water rinsing. The pretreated alloy bumps are subjected to at least two zinc replacement treatments to activate the surface; The activated alloy bumps were sequentially placed in a chemical nickel plating solution and a chemical palladium plating solution to react, forming continuous nickel and palladium layers on the surface of the bumps, respectively. Chemical gold plating is performed on the surface of the palladium layer to form a continuous metallic gold layer; The alloy bumps with the completed three-layer structure are rinsed and dried.

8. The electroless nickel-gold plating corrosion protection method according to claim 7, characterized in that, The pickling process uses a 5% citric acid solution for 1–5 minutes. The rinsing step involves rapid rinsing with 18 MΩ·cm deionized water. The drying step is performed using hot air or nitrogen, with the temperature controlled at 80–120°C.

9. The electroless nickel-gold plating corrosion protection method according to claim 7, characterized in that, The gold plating solution is a non-electrolytic gold salt solution. The chemical gold plating step is carried out at a temperature of 50–65℃ for a reaction time of 5–60 minutes. The nickel plating step is carried out at a temperature of 60±5℃ for a reaction time of 10–30 minutes, forming a nickel layer with a thickness of 1–5 μm. The gold plating step is carried out at a temperature of 50–65℃ for a reaction time of 5–60 minutes, forming a gold layer with a thickness of 0.05–0.5 μm. The palladium plating step is carried out at a temperature of 50–60℃ for a reaction time of 5–30 minutes, forming a palladium layer with a thickness of 0.05–0.5 μm. The nickel plating step is carried out at a temperature of 60±5℃ for a reaction time of 10–30 minutes, forming a nickel layer with a thickness of 1–5 μm. The gold plating step is carried out at a temperature of 50–65℃ for a reaction time of 5–60 minutes, forming a gold layer with a thickness of 0.05–0.5 μm.

10. The electroless nickel-gold plating corrosion protection method according to claim 7, characterized in that, The micro-etching involves surface etching of the metal surface for 10–60 seconds to remove the oxide film. Each zinc replacement treatment includes a dilute nitric acid cleaning and deionized water rinsing step.

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