Gold-tin alloy electroplating method and circuit board

Abstract

The invention discloses a gold-tin alloy electroplating method and a circuit board, and belongs to the technical field of chemistry. The method comprises the steps that gold-plating electroplating liquid is prepared; preparing a tinning electroplating solution; the tin plating electroplating solution is added into the gold plating electroplating solution for mixing, and a gold-tin alloy electroplating solution is prepared; putting a plurality of metal substrates to be electroplated into an electroplating bath containing gold-tin alloy electroplating liquid, and electrifying the electroplating bath through a numerical control double-pulse power supply; electroplating is conducted through a two-electrode electrodeposition system, and pulse electrodeposition electroplating parameters are set; an ultrasonic device is arranged at the bottom end of the electroplating bath; and the gold-tin alloy electroplating liquid is heated through the ultrasonic device, so that electroplating of the multiple metal substrates to be electroplated is completed. The gold-tin alloy electroplated layer deposited through the electroplating method is not prone to falling off, and the electroplated layer is more uniform.

Description

Technical Field

[0001] The present application relates to the field of chemical technology, and more specifically, to a method for electroplating a gold-tin alloy and a circuit board. Background Art

[0002] The main electroplating methods for related gold-tin alloys mainly include solder paste reflow, solder preform, evaporation, sputtering, alloy electroplating, etc. However, there are relatively difficult problems in preparing gold-tin alloy thin films by the current electroplating methods: on the one hand, the gold-tin alloy electroplating solution is not stable enough, and the service life of the electroplating solution needs to be extended; on the other hand, the gold-tin alloy thin films prepared by the current electroplating methods are prone to falling off or having rough and uneven coatings after deposition. Summary of the Invention

[0003] In order to overcome the above technical defects, the purpose of the present application is to provide a method for electroplating a gold-tin alloy and a circuit board. The method includes: configuring a gold electroplating solution; configuring a tin electroplating solution; adding the tin electroplating solution to the gold electroplating solution for mixing to obtain a gold-tin alloy electroplating solution, wherein the molar ratio of gold ions to tin ions in the gold-tin alloy electroplating solution is (0.5 - 3):(0.5 - 2), and the volume ratio of the gold electroplating solution to the tin electroplating solution is (0.5 - 3):(0.5 - 2); putting a plurality of metal substrates to be electroplated into an electroplating tank containing the gold-tin alloy electroplating solution, and energizing the electroplating tank through a numerical control double-pulse power supply; performing electroplating through a two-electrode electrodeposition system and setting pulse electrodeposition electroplating parameters; arranging an ultrasonic device at the bottom of the electroplating tank; heating the gold-tin alloy electroplating solution through the ultrasonic device to complete the electroplating of a plurality of metal substrates to be electroplated. The gold-tin alloy electroplating layer deposited by the electroplating method of the present application is not prone to falling off and the electroplating layer is more uniform.

[0004] In a first aspect, the present application provides a method for electroplating a gold-tin alloy. The method includes:

[0005] Configuring a gold electroplating solution; configuring a tin electroplating solution;

[0006] Adding the tin electroplating solution to the gold electroplating solution for mixing to obtain a gold-tin alloy electroplating solution, wherein the molar ratio of gold ions to tin ions in the gold-tin alloy electroplating solution is (0.5 - 3):(0.5 - 2), and the volume ratio of the gold electroplating solution to the tin electroplating solution is (0.5 - 3):(0.5 - 2);

[0007] Putting a plurality of metal substrates to be electroplated into an electroplating tank containing the gold-tin alloy electroplating solution, and energizing the electroplating tank through a numerical control double-pulse power supply;

[0008] Performing electroplating through a two-electrode electrodeposition system and setting pulse electrodeposition electroplating parameters;

[0009] An ultrasonic device is provided at the bottom end of the electroplating bath;

[0010] The gold-tin alloy electroplating solution is heated by the ultrasonic device to complete the electroplating of a plurality of metal substrates to be electroplated.

[0011] Optionally, a gold electroplating solution is configured, including:

[0012] The gold electroplating solution includes potassium chloroaurate, sodium sulfite, ethylenediaminetetraacetic acid, and ammonium citrate;

[0013] Among them, the gold purity of the potassium chloroaurate solution > 51%, and the solution concentration is 10 - 15 g / L;

[0014] Sodium sulfite is used as a complexing agent, and the solution concentration is 40 - 45 g / L;

[0015] The solution concentration of ethylenediaminetetraacetic acid is 1.5 - 2.0 g / L;

[0016] The concentration of ammonium citrate is 100 - 110 g / L;

[0017] The purity of sodium sulfite, ethylenediaminetetraacetic acid, and ammonium citrate ≥ 99.0%.

[0018] Optionally, a tin electroplating solution is configured, including:

[0019] The tin electroplating solution includes stannous chloride dihydrate, potassium pyrophosphate, ammonium citrate, and 2,3,4,5,6 - pentahydroxy - 2 - hexenoic acid - 4 - lactone;

[0020] Among them, the concentration of the stannous chloride dihydrate aqueous solution is 15 - 20 g / L;

[0021] Potassium pyrophosphate is used as a complexing agent to promote the diffusion of tin ions in the negative electrode region, and the concentration of potassium pyrophosphate is 40 - 45 g / L;

[0022] The concentration of ammonium citrate is 100 - 110 g / L;

[0023] The concentration of 2,3,4,5,6 - pentahydroxy - 2 - hexenoic acid - 4 - lactone is 15 - 20 g / L.

[0024] Optionally, the pulse electro - deposition electroplating parameters include the current density of pulse electro - deposition, and the current density of pulse electro - deposition is 1.5 - 2.0 mA / cm 2 .

[0025] Optionally, the pulse electro - deposition electroplating parameters include the electro - deposition time of pulse electro - deposition, and the electro - deposition time range of pulse electro - deposition is 30 - 40 min.

[0026] Optionally, the pulse electroplating parameters include the ratio of the pulse-on time to the pulse-off time, and the ratio of the pulse-on time to the pulse-off time is 1:4.

[0027] Optionally, the gold-tin alloy electroplating solution is heated by ultrasonic energy conversion, and the temperature of the gold-tin alloy electroplating solution is 40 - 42 °C.

[0028] Optionally, after placing a plurality of metal substrates to be electroplated into an electroplating tank containing a gold-tin alloy electroplating solution, it includes:

[0029] Setting electroplating fixtures for the plurality of metal substrates to be electroplated;

[0030] Processing the main frame of the electroplating fixture with a titanium-clad copper material, fixing the plurality of metal substrates to be electroplated with the electroplating fixture, and making the current of the pulse electroplating evenly distributed among the plurality of metal substrates to be electroplated by the method of applying electricity to multiple points of the metal substrates to be electroplated.

[0031] Optionally, before completing the electroplating of the plurality of metal substrates to be electroplated, it includes:

[0032] Classifying the plurality of metal substrates to be electroplated according to the electroplating area, and electroplating the plurality of metal substrates with the same electroplating area with the gold-tin alloy in the same batch.

[0033] In a second aspect, the present application provides a circuit board, and the circuit board is electroplated according to the gold-tin alloy electroplating method of any one of the first aspect.

[0034] Compared with the prior art, the gold-tin alloy electroplating method and the circuit board provided by the present application at least achieve the following beneficial effects:

[0035] The technical solution provided by the embodiments of the present application introduces a numerically controlled dual-pulse power supply and an ultrasonic device, adopts an electro-deposition system with two electrodes, combines electroplating fixtures and electroplating process parameters, adjusts parameters such as the ion concentration of the electroplating solution, current density, electro-deposition time, the temperature of the gold-tin alloy electroplating solution, and the pulse on-off ratio, etc., to make the performance, thickness, and component ratio of the gold-tin alloy electroplating layer reach the target values; through the regulation of electroplating process parameters, the deposited alloy is not easy to fall off or the electroplating layer is smoother and more uniform; at the same time, the present application mainly makes innovations and optimizations in the electroplating and soldering processes of lead-free gold-tin alloys for eutectic soldering, which can effectively reduce R & D costs, improve the production process efficiency of enterprises, and has extraordinary significance for the field of electronic packaging.

[0036] Of course, it is not necessary for any product implementing the present application to simultaneously achieve all the above technical effects.

[0037] Through the following detailed description of the exemplary embodiments of the present application with reference to the accompanying drawings, other features and advantages of the present application will become clear. Brief Description of the Drawings

[0038] The drawings incorporated in and forming a part of this specification illustrate embodiments of the present application and, together with the description thereof, are used to explain the principles of the present application.

[0039] Figure 1 is a flowchart of the electroplating method for gold-tin alloy provided by the present application;

[0040] Figure 2 is a flowchart of the overall metal packaging method;

[0041] Figure 3 is a structural diagram of the electroplating system for gold-tin alloy;

[0042] Figure 4 is a structural diagram of the electroplating fixture for gold-tin alloy;

[0043] Reference Numerals in the Drawings:

[0044] 1. Gold plating electroplating solution; 2. Tin plating electroplating solution; 3. Gold-tin alloy electroplating solution; 4. Electrode; 5. Electroplating tank; 6. Numerical control dual-pulse power supply; 7. Ultrasonic device. Detailed Embodiments

[0045] Now, various exemplary embodiments of the present application will be described in detail with reference to the drawings. It should be noted that: Unless otherwise specifically stated, the relative arrangements, numerical expressions, and numerical values of the components and steps set forth in these embodiments do not limit the scope of the present application.

[0046] The following description of at least one exemplary embodiment is merely illustrative in nature and is in no way a limitation on the present application or its application or use.

[0047] Technologies, methods, and devices known to those of ordinary skill in the relevant art may not be discussed in detail, but where appropriate, such technologies, methods, and devices should be regarded as part of the specification.

[0048] In all the examples shown and discussed herein, any specific values should be construed as merely exemplary and not as a limitation. Thus, other examples of the exemplary embodiments may have different values.

[0049] It should be noted that: Similar reference numerals and letters denote similar items in the following drawings. Therefore, once an item is defined in one drawing, it does not need to be further discussed in subsequent drawings.

[0050] Here, the gold-tin alloy is a binary alloy composed of gold and tin, which is widely used in the electronic field, especially in the soldering of lead frames and leads plated with gold or gold alloys. The gold-tin alloy solder belongs to lead-free hard solder, and its components are 80 wt.% gold (Au) / 20 wt.% tin (Sn).

[0051] At the same time, the gold-tin alloy is an environmentally friendly, high-performance, highly reliable and pollution-free lead-free solder, which has excellent thermal conductivity and mechanical properties, has a low melting point and reflux temperature, has a low viscosity and good wettability after melting, and does not require a soldering flux for soldering. It is widely used in the assembly and packaging of high-power heat dissipation components and has broad market potential and development prospects in future electronic packaging materials.

[0052] As Figure 1 shown, this application provides a plating method for gold-tin alloy, and the method includes:

[0053] Step S1: Configure the gold plating bath;

[0054] Step S2: Configure the tin plating bath;

[0055] Step S3: Add the tin plating bath to the gold plating bath for mixing to obtain a gold-tin alloy plating bath. Among them, the molar ratio of gold ions to tin ions in the gold-tin alloy plating bath is (0.5 - 3):(0.5 - 2), and the volume ratio of the gold plating bath to the tin plating bath is (0.5 - 3):(0.5 - 2);

[0056] Preferably, the molar ratio of gold ions to tin ions in the gold-tin alloy plating bath here is 1:1, and the volume ratio of the gold plating bath to the tin plating bath is 1:1;

[0057] Step S4: Place several metal substrates to be plated into the plating bath containing the gold-tin alloy plating bath;

[0058] Step S5: Fix and distribute several metal substrates to be plated through a plating fixture;

[0059] Step S6: Connect the positive electrode of the numerically controlled dual-pulse power supply to the platinum electrode of the plating bath and the negative electrode of the numerically controlled dual-pulse power supply to the cupronickel electrode of the plating bath by energizing the plating bath through the numerically controlled dual-pulse power supply;

[0060] Step S7: Perform plating through a two-electrode electrodeposition system and set the pulse electrodeposition plating parameters;

[0061] Step S8: Set an ultrasonic device at the bottom of the plating bath;

[0062] Step S9: Suppress the generation of bubbles during the electroplating hydrogen evolution process through the ultrasonic device and heat the gold-tin alloy plating bath through the conversion of ultrasonic energy;

[0063] Step S10: Classify several metal substrates to be electroplated according to the electroplating area of the metal substrate to be electroplated, and electroplate the same batch of gold-tin alloy on several metal substrates with the same electroplating area.

[0064] Step S11: Electroplate the gold-tin alloy on several metal substrates to be electroplated.

[0065] It can be understood that the present application provides a method for preparing a gold-tin alloy by a numerically controlled dual-pulse power supply superimposed ultrasonic device. By separately configuring a gold plating electroplating solution, a tin plating electroplating solution, and a lead-free gold-tin alloy electroplating solution, introducing a numerically controlled dual-pulse power supply and an ultrasonic device, adopting an electro-deposition system with two electrodes, combining electroplating jigs and electroplating process parameters, adjusting parameters such as the ion concentration of the electroplating solution, current density, electro-deposition time, temperature of the gold-tin alloy electroplating solution, and pulse on-off ratio, a gold-tin alloy solder film is successfully electroplated on the metal substrate, and the process of metal packaging is completed.

[0066] It can be understood that the preparation and soldering process of the lead-free gold-tin alloy solder film provided by the present application mainly innovates and optimizes the preparation and soldering process of the eutectic solder of the lead-free gold-tin alloy; it can effectively reduce the R & D cost, improve the production process efficiency of the enterprise, and has extraordinary significance for the field of electronic packaging.

[0067] Such as Figure 2 shown, the metal packaging process flow: wafer inspection → front side film pasting → back side grinding → back side metallization → back side film pasting → cutting → plasma cleaning → eutectic soldering (electroplating) → plasma cleaning → wire bonding → internal visual inspection → pre-baking → sealing → fine leak detection → external visual inspection → marking → screening.

[0068] Among them, the eutectic soldering process introduces a numerically controlled dual-pulse power supply and an ultrasonic device, adopts an electro-deposition system with two electrodes, combines electroplating jigs and electroplating process parameters, and adjusts parameters such as the ion concentration of the electroplating solution, current density, electro-deposition time, temperature of the gold-tin alloy electroplating solution, and pulse on-off ratio to achieve the target values of the performance, thickness, and component ratio of the electroplated layer.

[0069] Optionally, configuring the gold plating electroplating solution includes:

[0070] The gold plating electroplating solution includes potassium chloroaurate, sodium sulfite, ethylenediaminetetraacetic acid, and ammonium citrate;

[0071] Among them, the gold purity of the potassium chloroaurate solution > 51%, and the solution concentration is 10 - 15 g / L;

[0072] Taking sodium sulfite as a complexing agent, the solution concentration is 40 - 45 g / L;

[0073] The solution concentration of ethylenediaminetetraacetic acid is 1.5 - 2.0 g / L;

[0074] The concentration of ammonium citrate is 100 - 110 g / L;

[0075] The purity of sodium sulfite, ethylenediaminetetraacetic acid, and ammonium citrate is ≥99.0%.

[0076] Specifically, prepare a gold plating electroplating solution: The components are potassium chloroaurate K(AuCl 4 ), sodium sulfite Na 2 SO 3 , ethylenediaminetetraacetic acid C 10 H 16 N 2 O 8 , and ammonium citrate C 6 H 5 O 7 (NH 4 ) 3 ;

[0077] The potassium chloroaurate solution is the matrix solution, with the purity of gold Au > 51% and the concentration of 10 - 15 g / L;

[0078] Sodium sulfite Na 2 SO 3 is the complexing agent, which forms complex salts of metal ions in the electroplating solution, and the solution concentration is 40 - 45 g / L;

[0079] Ethylenediaminetetraacetic acid C 10 H 16 N 2 O 8 plays the role of antioxidant and stabilizing the electroplating solution, which is beneficial to improving the storage time of the gold plating electroplating solution, and the solution concentration is 1.5 - 2.0 g / L;

[0080] Ammonium citrate C 6 H 5 O 7 (NH 4 ) 3 plays the role of buffer, maintaining and improving the stability of metal ions in the electroplating solution, and the concentration is 100 - 110 g / L;

[0081] Sodium sulfite Na 2 SO 3 , ethylenediaminetetraacetic acid C 10 H 16 N 2 O 8 , and ammonium citrate C 6 H 5 O 7 (NH 4 ) 3 The purity is ≥99.0%.

[0082] Optionally, configure a tin plating bath, including:

[0083] The tin plating bath includes stannous chloride dihydrate, potassium pyrophosphate, ammonium citrate, and 2,3,4,5,6 - pentahydroxy - 2 - hexenoic acid - 4 - lactone;

[0084] Among them, the concentration of the stannous chloride dihydrate aqueous solution is 15 - 20 g / L;

[0085] Use potassium pyrophosphate as a complexing agent to promote the diffusion of tin ions in the negative electrode region, and the concentration of potassium pyrophosphate is 40 - 45 g / L;

[0086] The concentration of ammonium citrate is 100 - 110 g / L;

[0087] The concentration of 2,3,4,5,6 - pentahydroxy - 2 - hexenoic acid - 4 - lactone is 15 - 20 g / L.

[0088] Specifically, configure the tin plating bath: The components are stannous chloride dihydrate SnCl 2 ·2H 2 O, potassium pyrophosphate K 4 P 2 O 7 ·3H 2 O, ammonium citrate C 6 H 5 O 7 (NH 4 ) 3 , 2,3,4,5,6 - pentahydroxy - 2 - hexenoic acid - 4 - lactone C 6 H 8 O 6 ;

[0089] The concentration of the stannous chloride dihydrate aqueous solution is 15 - 20 g / L;

[0090] Potassium pyrophosphate K 4 P 2 O 7 ·3H 2 O inhibits the oxidation of divalent tin ions in the plating bath, serves as a complexing agent, promotes the diffusion of tin ions in the negative electrode region, and deposits at the cathode, with a concentration of 40 - 45 g / L;

[0091] Ammonium citrate C 6 H 5 O 7 (NH 4 ) 3 plays a role in protecting and stabilizing the plating bath, with a concentration of 100 - 110 g / L;

[0092] 2,3,4,5,6 - pentahydroxy - 2 - hexenoic acid - 4 - lactone C 6 H 8 O6 Maintain the stability of Sn2+ in the stannous chloride dihydrate aqueous solution, playing an antioxidant and reduction role, with a concentration of 15 - 20 g / L.

[0093] Optionally, prepare a lead-free gold-tin alloy electroplating solution: Slowly pour the pre-prepared tin electroplating solution into the gold electroplating solution to prepare a lead-free gold-tin alloy electroplating solution.

[0094] The molar ratio of gold ions to tin ions in the gold-tin alloy electroplating solution is 1:1, and the volume ratio of the solution is 1:1.

[0095] Optionally, the pulse electro-deposition electroplating parameters include the current density of pulse electro-deposition, and the current density of pulse electro-deposition is 1.5 - 2.0 mA / cm 2 。

[0096] Optionally, the pulse electro-deposition electroplating parameters include the electro-deposition time of pulse electro-deposition, and the electro-deposition time range of pulse electro-deposition is 30 - 40 min.

[0097] Optionally, the pulse electro-deposition electroplating parameters include the ratio of pulse conduction time to disconnection time, and the ratio of pulse conduction time to disconnection time is 1:4.

[0098] Optionally, heat the gold-tin alloy electroplating solution through ultrasonic energy conversion, and control the temperature of the gold-tin alloy electroplating solution to be 40 - 42 °C.

[0099] Specifically, as Figure 3 shown, connect the positive and negative electrodes of the numerical control double-pulse power supply 6 to the platinum electrode and the cupronickel electrode in the electroplating bath 5 respectively, and use the electro-deposition system of the two electrodes 4. The preparation method of superimposing continuous pulse electro-deposition with the ultrasonic device 7 is used for electroplating; during the pulse electro-deposition process, the conduction and disconnection of the current occur, greatly improving the polarization effect generated by the electroplating solution in the cathode region; the energy of the ultrasonic process can not only inhibit the generation of bubbles during the hydrogen evolution process, making the morphology of the gold-tin alloy coating more uniform and dense, and there are few defects such as cracks and holes in the cross-section, but also convert the ultrasonic energy into heat energy to accelerate the diffusion of ions in the electroplating solution, which is beneficial to the formation of polarization near the cathode, making the gold-tin alloy precipitate on the cathode.

[0100] Here, the electroplating process parameters:

[0101] The current density of pulse electro-deposition is 1.5 - 2.0 mA / cm 2 ;

[0102] The electro-deposition time range of pulse electro-deposition is 30 - 40 min;

[0103] The temperature of the gold-tin alloy electroplating solution is 40 - 42 °C;

[0104] The pulse conduction time to disconnection time ratio is 1:4.

[0105] Optionally, electroplating jigs are set for several metal substrates to be electroplated.

[0106] The main frame of the electroplating jig is processed with a titanium-clad copper material, and several metal substrates to be electroplated are fixed by the electroplating jig. The current of pulse electro-deposition is evenly distributed among several metal substrates to be electroplated by applying power to multiple points on the metal substrates to be electroplated.

[0107] Specifically, as Figure 4 shown, the electroplating jig is a device used to fix and support the metal substrate during electroplating, ensuring that the metal substrate can be evenly electroplated in the electroplating solution; the design and use of the electroplating jig have an important impact on electroplating quality and efficiency. The main frame of the electroplating jig is processed with a titanium-clad copper material; the current of pulse electro-deposition is evenly distributed among several metal substrates to be electroplated by applying power to multiple points on the metal substrates to be electroplated. For example, at least 4 points of power application are required for a 2-inch square piece (metal substrate to be electroplated).

[0108] Optionally, electroplate in batches: Before electroplating, the metal substrates should be classified according to the electroplating area of the metal substrates, and only the metal substrates with similar areas to be plated can be electroplated in the same batch; because the actual current densities distributed on the surfaces of workpieces with different areas to be plated vary greatly, which will lead to a large difference in the composition of the gold-tin alloy and is extremely likely to cause poor electroplating layer performance and low product qualification rate.

[0109] Optionally, by maintaining the pH value of the gold-tin alloy electroplating solution between 4.5 and 6.5, the quality decline of the gold-tin alloy coating is prevented, including:

[0110] Regularly measure the electroplating solution with a high-precision pH meter to ensure the stability of the pH value;

[0111] Add buffers to stabilize the pH value. Among them, the buffers include boric acid and phosphates;

[0112] When the pH value of the electroplating solution < 4.5, then add dilute sodium hydroxide or sodium carbonate solution to increase the pH value of the electroplating solution;

[0113] When the pH value of the electroplating solution > 6.5, then add dilute sulfuric acid or hydrochloric acid solution to decrease the pH value of the electroplating solution;

[0114] Gradually add regulators to avoid violent fluctuations in the pH value of the electroplating solution;

[0115] Keep the electroplating solution uniform by stirring and filtering to prevent local pH value changes.

[0116] Meanwhile, record in detail the pH measurement and adjustment each time, analyze the pH change trend through data analysis, and take measures in advance. Through the above measures, the pH value of the gold-tin alloy electroplating solution can be effectively controlled to ensure the quality of the gold-tin alloy electroplating layer.

[0117] On the other hand, the present application provides a circuit board, which is electroplated according to the following electroplating method of gold-tin alloy. The electroplating method of gold-tin alloy includes:

[0118] Configure a gold electroplating solution;

[0119] Configure a tin electroplating solution;

[0120] Add the tin electroplating solution to the gold electroplating solution for mixing to obtain a gold-tin alloy electroplating solution. Among them, the molar ratio of gold ions to tin ions in the gold-tin alloy electroplating solution is 1:1, and the volume ratio of the solution is 1:1;

[0121] Put several metal substrates to be electroplated into the gold-tin alloy electroplating solution;

[0122] Fix and distribute several metal substrates to be electroplated through an electroplating fixture;

[0123] Connect the positive electrode of the numerical control double-pulse power supply to the platinum electrode of the electroplating tank, and connect the negative electrode of the numerical control double-pulse power supply to the cupronickel electrode of the electroplating tank;

[0124] Perform electroplating through a two-electrode electrodeposition system and set the pulse electrodeposition electroplating parameters;

[0125] Set an ultrasonic device at the bottom of the electroplating tank;

[0126] Suppress the generation of bubbles during the electroplating hydrogen evolution process through the ultrasonic device, and heat the gold-tin alloy electroplating solution through the conversion of ultrasonic energy to electroplate the gold-tin alloy on several metal substrates to be electroplated.

[0127] Example 1:

[0128] First, configure a gold electroplating solution. The gold purity of the potassium chloroaurate solution is 52%, and the solution concentration is 13 g / L; the concentration of the sodium sulfite solution is 41 g / L; the concentration of the ethylenediaminetetraacetic acid solution is 1.6 g / L; the concentration of ammonium citrate is 105 g / L. The purity of sodium sulfite, ethylenediaminetetraacetic acid, and ammonium citrate is ≥99.0%.

[0129] Secondly, configure a tin electroplating solution. The concentration of the stannous chloride dihydrate aqueous solution is 16 g / L; the concentration of potassium pyrophosphate is 42 g / L; the concentration of ammonium citrate is 105 g / L; the concentration of 2,3,4,5,6-pentahydroxy-2-hexenoic acid-4-lactone is 17 g / L.

[0130] Reconfigure the lead-free gold-tin alloy electroplating solution: Slowly pour the tin electroplating solution into the gold electroplating solution to configure the lead-free gold-tin alloy electroplating solution.

[0131] The molar ratio of gold ions to tin ions in the gold-tin alloy electroplating solution is 1:1, and the volume ratio of the solution is 1:1.

[0132] Finally, prepare the gold-tin alloy coating. Connect the positive and negative electrodes of the numerical control double-pulse power supply to the platinum electrode and the cupronickel electrode in the electroplating tank respectively. Adopt a two-electrode electrodeposition system, and use the ultrasonic superposition for the preparation method of continuous pulse electrodeposition.

[0133] The current density of pulse electrodeposition is 2.0 mA / cm 2 ;

[0134] The electrodeposition time of pulse electrodeposition is 35 min;

[0135] The temperature of the electroplating solution is 40 °C;

[0136] The ratio of pulse conduction time to disconnection time is 1:4.

[0137] Example 2:

[0138] First, configure the gold electroplating solution. The gold purity of the potassium chloroaurate solution is 53%, the solution concentration is 11 g / L; the concentration of the sodium sulfite solution is 42 g / L; the solution concentration of ethylenediaminetetraacetic acid is 1.7 g / L; the concentration of ammonium citrate is 104 g / L. The purity of sodium sulfite, ethylenediaminetetraacetic acid, and ammonium citrate is ≥99.0%.

[0139] Secondly, configure the tin electroplating solution. The concentration of the stannous chloride dihydrate aqueous solution is 15 g / L; the concentration of potassium pyrophosphate is 41 g / L; the concentration of ammonium citrate is 104 g / L; the concentration of 2,3,4,5,6-pentahydroxy-2-hexenoic acid-4-lactone is 16 g / L.

[0140] Reconfigure the lead-free gold-tin alloy electroplating solution: Slowly pour the tin electroplating solution into the gold electroplating solution to configure the lead-free gold-tin alloy electroplating solution.

[0141] The molar ratio of gold ions to tin ions in the gold-tin alloy electroplating solution is 1:1, and the volume ratio of the solution is 1:1.

[0142] Finally, prepare the gold-tin alloy coating. Connect the positive and negative electrodes of the numerical control double-pulse power supply to the platinum electrode and the cupronickel electrode in the electroplating tank respectively. Adopt a two-electrode electrodeposition system, and use the ultrasonic superposition for the preparation method of continuous pulse electrodeposition.

[0143] The current density of pulse electrodeposition is 1.9 mA / cm 2 ;

[0144] The electroplating time of pulse electroplating is 34 min;

[0145] The temperature of the electroplating solution is 41 °C;

[0146] The ratio of pulse conduction time to disconnection time is 1:4.

[0147] Comparative Example 1:

[0148] First, prepare a gold electroplating solution. The gold purity of the potassium chloroaurate solution is 52%, the solution concentration is 13 g / L; the concentration of the sodium sulfite solution is 41 g / L; the solution concentration of ethylenediaminetetraacetic acid is 1.6 g / L; the concentration of ammonium citrate is 105 g / L. The purity of sodium sulfite, ethylenediaminetetraacetic acid, and ammonium citrate ≥ 99.0%.

[0149] Secondly, prepare a tin electroplating solution. The concentration of the stannous chloride dihydrate aqueous solution is 16 g / L; the concentration of potassium pyrophosphate is 42 g / L; the concentration of ammonium citrate is 105 g / L; the concentration of 2,3,4,5,6-pentahydroxy-2-hexenoic acid-4-lactone is 17 g / L.

[0150] Then prepare a lead-free gold-tin alloy electroplating solution: Slowly pour the tin electroplating solution into the gold electroplating solution to prepare a lead-free gold-tin alloy electroplating solution.

[0151] The molar ratio of gold ions to tin ions in the gold-tin alloy electroplating solution is 1:1, and the solution volume ratio is 1:1.

[0152] Finally, prepare a gold-tin alloy coating. A numerical control double-pulse power supply and an ultrasonic device are not introduced, and an ordinary direct current connection between two electrodes is used for electroplating preparation.

[0153] The electroplating time is 35 min;

[0154] The temperature of the electroplating solution is 40 °C.

[0155] Experimental results:

[0156]

[0157] From the experimental results of Example 1 and Comparative Example 1, it can be seen that the introduction of a numerical control double-pulse power supply and an ultrasonic device in the eutectic soldering process can make the gold-tin alloy coating electroplated uniform, delicate, smooth, and without spots, etc.; it meets the requirement that the average total thickness of the coating is not less than 50 μm; the coating has no peeling, peeling or blistering phenomenon; there are no signs of black, green, or red corrosion on the surface of the specimen; the deposited gold-tin alloy is not easily detached and the coating is uniform.

[0158] Comparative Example 2:

[0159] First, configure the gold plating electroplating solution. The gold purity of the potassium chloroaurate solution is 52%, the solution concentration is 13 g / L; the concentration of the sodium sulfite solution is 41 g / L; the concentration of the ethylenediaminetetraacetic acid solution is 1.6 g / L; the concentration of ammonium citrate is 105 g / L. The purity of sodium sulfite, ethylenediaminetetraacetic acid, and ammonium citrate is ≥99.0%.

[0160] Secondly, configure the tin plating electroplating solution. The concentration of the stannous chloride dihydrate aqueous solution is 16 g / L; the concentration of potassium pyrophosphate is 42 g / L; the concentration of ammonium citrate is 105 g / L; the concentration of 2,3,4,5,6-pentahydroxy-2-hexenoic acid-4-lactone is 17 g / L.

[0161] Then, configure the lead-free gold-tin alloy electroplating solution: Slowly pour the tin plating electroplating solution into the gold plating electroplating solution to configure the lead-free gold-tin alloy electroplating solution.

[0162] The molar ratio of gold ions to tin ions in the gold-tin alloy electroplating solution is 1:1, and the solution volume ratio is 1:1.

[0163] Finally, prepare the gold-tin alloy coating. Connect the positive and negative electrodes of the numerical control dual-pulse power supply to the platinum electrode and the cupronickel electrode in the electroplating tank respectively, adopt the two-electrode electrodeposition system, and use the preparation method of continuous pulse electrodeposition with ultrasonic superposition.

[0164] The current density of pulse electrodeposition is 3.5 mA / cm 2 ;

[0165] The electrodeposition time of pulse electrodeposition is 35 min;

[0166] The temperature of the electroplating solution is 40 °C;

[0167] The ratio of pulse conduction time to disconnection time is 1:4.

[0168] Comparative Example 3:

[0169] First, configure the gold plating electroplating solution. The gold purity of the potassium chloroaurate solution is 52%, the solution concentration is 13 g / L; the concentration of the sodium sulfite solution is 41 g / L; the concentration of the ethylenediaminetetraacetic acid solution is 1.6 g / L; the concentration of ammonium citrate is 105 g / L. The purity of sodium sulfite, ethylenediaminetetraacetic acid, and ammonium citrate is ≥99.0%.

[0170] Secondly, configure the tin plating electroplating solution. The concentration of the stannous chloride dihydrate aqueous solution is 16 g / L; the concentration of potassium pyrophosphate is 42 g / L; the concentration of ammonium citrate is 105 g / L; the concentration of 2,3,4,5,6-pentahydroxy-2-hexenoic acid-4-lactone is 17 g / L.

[0171] Re-prepare the lead-free gold-tin alloy electroplating solution: Slowly pour the tin electroplating solution into the gold electroplating solution to prepare the lead-free gold-tin alloy electroplating solution.

[0172] In the gold-tin alloy electroplating solution, the molar ratio of gold ions to tin ions in the solution is 1:1, and the volume ratio of the solution is 1:1.

[0173] Finally, prepare the gold-tin alloy coating. Connect the positive and negative electrodes of the numerical control double-pulse power supply to the platinum electrode and the cupronickel electrode in the electroplating bath respectively. Adopt a two-electrode electrodeposition system, and use the preparation method of continuous pulse electrodeposition with ultrasonic superposition.

[0174] The current density of pulse electrodeposition is 2.0 mA / cm 2 ;

[0175] The electrodeposition time of pulse electrodeposition is 20 min;

[0176] The temperature of the electroplating solution is 40 °C;

[0177] The ratio of pulse conduction time to disconnection time is 1:4.

[0178] Comparative Example 4:

[0179] First, prepare the gold electroplating solution. The gold purity of the potassium chloroaurate solution is 52%, the solution concentration is 13 g / L; the concentration of the sodium sulfite solution is 41 g / L; the solution concentration of ethylenediaminetetraacetic acid is 1.6 g / L; the concentration of ammonium citrate is 105 g / L. The purity of sodium sulfite, ethylenediaminetetraacetic acid, and ammonium citrate is ≥99.0%.

[0180] Secondly, prepare the tin electroplating solution. The concentration of the stannous chloride dihydrate aqueous solution is 16 g / L; the concentration of potassium pyrophosphate is 42 g / L; the concentration of ammonium citrate is 105 g / L; the concentration of 2,3,4,5,6-pentahydroxy-2-hexenoic acid-4-lactone is 17 g / L.

[0181] Re-prepare the lead-free gold-tin alloy electroplating solution: Slowly pour the tin electroplating solution into the gold electroplating solution to prepare the lead-free gold-tin alloy electroplating solution.

[0182] In the gold-tin alloy electroplating solution, the molar ratio of gold ions to tin ions in the solution is 1:1, and the volume ratio of the solution is 1:1.

[0183] Finally, prepare the gold-tin alloy coating. Connect the positive and negative electrodes of the numerical control double-pulse power supply to the platinum electrode and the cupronickel electrode in the electroplating bath respectively. Adopt a two-electrode electrodeposition system, and use the preparation method of continuous pulse electrodeposition with ultrasonic superposition.

[0184] The current density of pulse electrodeposition is 2.0 mA / cm 2 ;

[0185] The electroplating time of pulse electroplating is 35 min;

[0186] The temperature of the electroplating solution is 25 °C;

[0187] The ratio of pulse conduction time to disconnection time is 1:4.

[0188] Comparative Example 5:

[0189] First, prepare a gold electroplating solution. The gold purity of the potassium chloroaurate solution is 52%, and the solution concentration is 13 g / L; the concentration of the sodium sulfite solution is 41 g / L; the solution concentration of ethylenediaminetetraacetic acid is 1.6 g / L; the concentration of ammonium citrate is 105 g / L. The purity of sodium sulfite, ethylenediaminetetraacetic acid, and ammonium citrate is ≥99.0%.

[0190] Secondly, prepare a tin electroplating solution. The concentration of the stannous chloride dihydrate aqueous solution is 16 g / L; the concentration of potassium pyrophosphate is 42 g / L; the concentration of ammonium citrate is 105 g / L; the concentration of 2,3,4,5,6-pentahydroxy-2-hexenoic acid-4-lactone is 17 g / L.

[0191] Then prepare a lead-free gold-tin alloy electroplating solution: Slowly pour the tin electroplating solution into the gold electroplating solution to prepare a lead-free gold-tin alloy electroplating solution.

[0192] The molar ratio of gold ions to tin ions in the gold-tin alloy electroplating solution is 1:1, and the solution volume ratio is 1:1.

[0193] Finally, prepare a gold-tin alloy coating. Connect the positive and negative electrodes of the numerical control double-pulse power supply to the platinum electrode and the cupronickel electrode in the electroplating tank respectively, adopt a two-electrode electroplating system, and use an ultrasonic superposition for continuous pulse electroplating preparation.

[0194] The current density of pulse electroplating is 2.0 mA / cm 2 ;

[0195] The electroplating time of pulse electroplating is 35 min;

[0196] The temperature of the electroplating solution is 40 °C;

[0197] The ratio of pulse conduction time to disconnection time is 1:1.

[0198] Experimental results:

[0199]

[0200] From the experimental results of Example 1 and Comparative Example 2, it can be seen that when the current density of pulse electroplating is not within 1.5 - 2.0 mA / cm 2When it is outside the range, the coating will be rough and there will be a relatively uneven distribution of light and dark on the surface; the difference in the coating thickness of the sample is slightly large, and the average total thickness is about 46.28 μm; the bonding between the coating and the metal part to be plated is poor; from the experimental results of Example 1 and Comparative Example 3, when the electro-deposition time of pulse electro-deposition is not within the range of 30 - 40 min, the coating will be uneven and rough, with local cracks; the difference in the coating thickness of the sample is slightly large, and the average total thickness is about 46.91 μm; the bonding between the coating and the metal part to be plated is poor; from the experimental results of Example 1 and Comparative Example 4, when the temperature of the electroplating solution is not within the range of 40 - 42 °C, the coating will be rough and accompanied by holes and cracks, with local cracks and no coating; the difference in the coating thickness of the sample is slightly large, and the average total thickness is about 45.16 μm; the bonding between the coating and the metal part to be plated is poor; from the experimental results of Example 1 and Comparative Example 5, when the ratio of the pulse on-time to the off-time is not 1:4, the coating will be rough and there will be many defects such as holes and cracks on the surface of the sample; the difference in the coating thickness of the sample is slightly large, and the average total thickness is about 47.55 μm; the bonding between the coating and the metal part to be plated is poor.

[0201] In summary, the eutectic soldering process of the present application introduces a numerically controlled dual-pulse power supply and an ultrasonic device, uses an electroplating fixture to fix the metal substrate, and batches the electroplating of the metal substrate according to the electroplating area of the metal substrate. The electroplating process parameters are as follows:

[0202] The current density of pulse electro-deposition is 1.5 - 2.0 mA / cm 2 ;

[0203] The electro-deposition time range of pulse electro-deposition is 30 - 40 min;

[0204] The temperature of the electroplating solution is 40 - 42 °C;

[0205] The ratio of the pulse on-time to the off-time is 1:4.

[0206] Test Example 1:

[0207]

[0208]

[0209] As can be seen from the above embodiments, the electroplating method of the gold-tin alloy provided by the present application has at least achieved the following beneficial effects:

[0210] The technical solution of this application introduces a numerically controlled dual-pulse power supply and an ultrasonic device, adopts an electroplating system with two electrodes, combines electroplating fixtures and electroplating process parameters, and adjusts parameters such as the ion concentration of the electroplating solution, current density, electroplating time, temperature of the gold-tin alloy electroplating solution, and pulse on-off ratio, so as to achieve that the performance, thickness and component ratio of the gold-tin alloy electroplating layer reach the target values; through the regulation of electroplating process parameters, the deposited alloy is not likely to fall off or the electroplating layer is smoother and more uniform; at the same time, this application mainly innovates and optimizes the electroplating and soldering processes of lead-free gold-tin alloys for eutectic soldering, which can effectively reduce R & D costs, improve the production process efficiency of enterprises, and has extraordinary significance for the field of electronic packaging.

[0211] Although some specific embodiments of this application have been described in detail by way of examples, those skilled in the art should understand that the above examples are for illustration purposes only and not for limiting the scope of this application. Those skilled in the art should understand that the above embodiments can be modified without departing from the scope of this application. The scope of this application is defined by the appended claims.

Claims

1. A method for electroplating a gold-tin alloy, characterized in that: The method comprises: Prepare gold plating solution; Prepare tin plating solution; Adding the tin plating solution to the gold plating solution and mixing them to obtain a gold-tin alloy plating solution, wherein the molar ratio of gold ions to tin ions in the gold-tin alloy plating solution is (0.5-3):(0.5-2), and the volume ratio of the gold plating solution to the tin plating solution is (0.5-3):(0.5-2); Placing a plurality of metal substrates to be electroplated into an electroplating tank containing the gold-tin alloy electroplating solution, and energizing the electroplating tank through a digitally controlled double-pulse power supply; Electroplating is performed by a two-electrode electrodeposition system, and pulse electrodeposition plating parameters are set; An ultrasonic device is arranged at the bottom end of the electroplating tank; The gold-tin alloy electroplating solution is heated by the ultrasonic device to complete the electroplating of the plurality of metal substrates to be electroplated.

2. The gold-tin alloy electroplating method according to claim 1, characterized in that: The gold plating solution is configured, comprising: The gold plating solution comprises potassium chloroaurate, sodium sulfite, ethylenediaminetetraacetic acid and ammonium citrate; Wherein, the gold purity of the potassium chloroaurate solution is greater than 51%, and the solution concentration is 10-15 g / L; The sodium sulfite is used as a complexing agent, and the solution concentration is 40-45 g / L; The solution concentration of EDTA is 1.5-2.0 g / L; The concentration of the ammonium citrate is 100-110 g / L; The purity of the sodium sulfite, ethylenediaminetetraacetic acid and ammonium citrate is ≥99.0%.

3. The gold-tin alloy electroplating method according to claim 1, characterized in that: The tin plating solution is configured, including: the tin plating solution includes stannous chloride dihydrate, potassium pyrophosphate, ammonium citrate and 2,3,4,5,6-pentahydroxy-2-hexenoic acid-4-lactone; Wherein, the concentration of the stannous chloride dihydrate aqueous solution is 15-20 g / L; The potassium pyrophosphate is used as a complexing agent to promote the diffusion of tin ions in the negative electrode region, and the concentration of the potassium pyrophosphate is 40-45 g / L; the concentration of the ammonium citrate is 100-110 g / L; The concentration of the 2,3,4,5,6-pentahydroxy-2-hexenoic acid-4-lactone is 15-20 g / L.

4. The gold-tin alloy electroplating method according to claim 1, characterized in that: The pulse electrodeposition plating parameters include the current density of the pulse electrodeposition, and the current density of the pulse electrodeposition is 1.5-2.0 mA / cm 2 .

5. The gold-tin alloy electroplating method according to claim 1, characterized in that: The pulse electrodeposition electroplating parameters include the electrodeposition time of the pulse electrodeposition, and the electrodeposition time of the pulse electrodeposition is in the range of 30-40 minutes.

6. The gold-tin alloy electroplating method according to claim 1, characterized in that: The pulse electrodeposition plating parameters include a ratio of a pulse on time to an off time, and the ratio of the pulse on time to the off time is 1:

4.

7. The gold-tin alloy electroplating method according to claim 1, characterized in that: The gold-tin alloy electroplating solution is heated by ultrasonic energy conversion, and the temperature of the gold-tin alloy electroplating solution is 40-42°C.

8. The gold-tin alloy electroplating method according to claim 1, characterized in that: After placing a plurality of metal substrates to be electroplated into an electroplating tank containing the gold-tin alloy electroplating solution, the method comprises: Setting a plating fixture for the plurality of metal substrates to be electroplated; The main frame of the electroplating fixture is processed by titanium-copper-clad material, the several metal substrates to be electroplated are fixed by the electroplating fixture, and the metal substrates to be electroplated are electrified at multiple points to make the pulse electrodeposition current evenly distributed among the several metal substrates to be electroplated.

9. The gold-tin alloy electroplating method according to claim 1, characterized in that: Before completing the electroplating of the plurality of metal substrates to be electroplated, the process includes: The plurality of metal substrates to be electroplated are classified according to their electroplating areas, and the gold-tin alloy is electroplated in the same batch on the plurality of metal substrates with the same electroplating areas.

10. A circuit board, characterized in that: The circuit board is electroplated according to the gold-tin alloy electroplating method according to any one of claims 1 to 9.

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