A novel pulse plating leveler for packaging substrates, copper electroplating solution and electroplating process

Abstract

This application relates to the technical field of metallization of packaging substrates, and in particular to a novel pulse electroplating leveling agent for packaging substrates. The agent comprises an active ingredient, which is a reaction product containing one or more imidazole compounds or their salts, one or more ditertiary amine compounds, and one or more dihaloalkyl ethers. Using the leveling agent provided in this application as a core additive in a copper plating solution, the beneficial technical effects include significantly shortening the plating time, reducing the surface copper thickness, and achieving excellent filling of vias with an aspect ratio greater than 10. The copper plating solution of this application also contains polyether additives, which, by applying a certain combination of forward and reverse pulse currents, greatly increase the copper deposition rate inside the vias.

Description

Technical Field

[0001] This application relates to the technical field of metallization of packaging substrates, and in particular to a novel pulse electroplating leveling agent, copper electroplating solution, and electroplating process for packaging substrates. Background Technology

[0002] As technology continues to advance, artificial intelligence places increasingly higher demands on the processing power of chips. Furthermore, the chip packaging hardware and materials required for electronic components are trending towards miniaturization and thinning. This means that substrates need to have finer wire widths and smaller diameter vias in their design and manufacturing.

[0003] Through-hole filling is one of the key technologies for achieving advanced packaging. The ideal state of through-hole filling is that highly planar through-holes are completely filled, meaning the interior of the through-hole is entirely filled with deposited copper, without voids or depressions. This provides optimal reliability and electrical performance while achieving the lowest possible copper thickness to provide optimal linewidth and impedance control in electronic components. Excessive copper thickness can negatively impact the electrical performance and reliability of the substrate, for example, leading to poor adhesion between the copper layer and the substrate, hindering subsequent fine-line patterning processes, and resulting in excessively high costs.

[0004] However, existing technologies often only specify current methods, including combinations of DC and pulse plating techniques, and further include periodic pulse, periodic normal phase pulse, and dual pulse current methods. While these methods can achieve complete via filling, they do not address techniques for controlling surface copper thickness or have a significant effect on reducing surface copper thickness. Especially for vias with high aspect ratios, such as 10:1 or higher, under certain current densities and plating times, existing technologies struggle to achieve complete via filling, resulting in voids and excessive surface copper thickness.

[0005] Therefore, the industry urgently needs a method for filling vias in packaging substrates, which can both completely fill the vias and minimize the increase in copper thickness on the substrate surface. Summary of the Invention

[0006] Therefore, it is necessary to provide a copper plating method for through holes in a packaging substrate to solve the problems of incomplete copper plating or excessive copper thickness on the substrate surface in existing through hole copper plating methods, especially for through hole filling with a large thickness-to-diameter ratio.

[0007] The above-mentioned objective of this application is achieved through the following technical solution:

[0008] In a first aspect, this application provides a novel pulse electroplating leveling agent for packaging substrates, comprising an active ingredient, said active ingredient being a reaction product containing one or more imidazole compounds or their salts, one or more ditertiary amine compounds, and one or more dihaloalkyl ethers.

[0009] In some embodiments, the imidazole compound has the structure shown in formula (1):

[0010]

[0011] R1, R2, and R3 are each independently selected from H, C1-C8 alkyl, or phenyl, wherein the C1-C8 alkyl or phenyl may optionally be further substituted with one or more C1-C6 alkyl groups; and R1, R2, and R3 are not all H at the same time.

[0012] The ditertiary amine compound has the structure shown in formula (2):

[0013]

[0014] Wherein, R4 is a C2-C10 straight-chain alkylene or a C2-C10 branched alkylene; R5, R6, R7 and R8 are each independently selected from: C1-C8 alkyl, or one or more hydroxyl-substituted C2-C8 alkyl.

[0015] The dihaloalkyl ether has the structure shown in formula (3):

[0016]

[0017] Where n is selected from any integer from 1 to 50, and X is a halogen.

[0018] The molar ratio of the imidazole compound, the ditertiary amine compound, and the dihaloalkyl ether is (0.1-2):(0.1).

[0019] -2):1.

[0020] In some embodiments, the imidazole compound in the leveling agent is selected from one of 2-methylimidazole, 2-phenylimidazole, 4-phenylimidazole, 4-octylimidazole, 2-(4-methylphenyl)imidazole, 2,4-dimethylimidazole or 4-ethylimidazole;

[0021] and / or

[0022] The ditertiary amine compound is selected from one of N,N,N',N'-tetramethyl-1,6-hexanediamine, N,N,N',N'-tetraethyl-1,10-decanediamine, N,N-dimethyl-N',N'-di(2-hydroxypropyl)-1,3-propanediamine, and N,N,N',N',2-pentamethylpropane-1,3-diamine;

[0023] and / or

[0024] The dihaloalkyl ether is selected from one of the following: bis(2-chloroethyl) ether, 1,2-bis(2-chloroethoxy)ethane, diethylene glycol bis(2-chloroethyl) ether, and dichloro polyethylene glycol.

[0025] A second object of the present invention is to provide a copper electroplating solution containing the above-mentioned leveling agent.

[0026] A third objective of this invention is to provide an electroplating process for through-holes in a packaging substrate, comprising the following steps:

[0027] a) Make the substrate and at least one cathode and the copper plating solution into contact;

[0028] b) Perform electroplating on one side and the other side of the substrate from step a) until the through-hole is filled with metallic copper.

[0029] The substrate surface and the wall of the through hole described in step a) have a conductive layer;

[0030] The acidic copper plating solution described in step a) contains the aforementioned leveling agent;

[0031] The electroplating operation described in step b) includes the following steps in sequence:

[0032] 1) Pulse electroplating is performed on one side and the other side of the substrate, so that copper ions are deposited first in the center of the through hole. After the copper is deposited and connected in the center of the through hole, two opposing blind holes are formed in the through hole.

[0033] 2) Direct DC electroplating or pulse electroplating is performed to fill the two opposing blind holes formed in the through hole by pulse electroplating;

[0034] Step b) of step 1) of the pulse plating process includes applying a pulsed current to deposit copper ions onto one side and the other side of the substrate, wherein the current is applied as a pulse plating cycle comprising a repeatable sequence, wherein the repeatable sequence comprises a set of pulse plating cycles, each set of pulse plating cycles being performed in any order, including:

[0035] (i) at least the first positive pulse cycle;

[0036] (ii) at least the first reverse pulse cycle;

[0037] (iii) at least the second positive pulse small cycle;

[0038] In some embodiments, the substrate is one of glass, ceramic, organic material or organic-inorganic composite insulating material, the conductive layer is one or more alloys of titanium, copper, nickel, chromium, molybdenum, gold and silver, and the through holes are one or more.

[0039] In some embodiments, the forward current density in step 1) of pulse electroplating is 0.2 ASD to 7.0 ASD, the electroplating cycle uses a forward / reverse current ratio between 1:1 and 1:8, and the duration of the forward pulse is 50 ms to 500 ms and the duration of the reverse pulse is 5 ms to 200 ms, and the pulse frequency of the pulse electroplating is 1 Hz to 8 Hz.

[0040] In some embodiments, the electroplating method in step 2) of step b) is DC electroplating, wherein the current density of the DC electroplating is 0.2 ASD to 5.0 ASD;

[0041] In some embodiments, the electroplating method in step 2) of step b) is pulse electroplating, wherein the pulse electroplating is pulse electroplating with only positive pulses, the current density is 0.2 ASD to 5.0 ASD, and the duration of the positive pulse is 100 ms to 500 ms, the pulse frequency of the pulse electroplating is 2 Hz to 10 Hz, wherein the current is applied as a pulse electroplating cycle including a repeatable sequence, wherein the repeatable sequence includes a set of pulse electroplating cycles, each set of pulse electroplating cycles being performed in any order, including:

[0042] (i) at least the first positive pulse cycle;

[0043] (ii) at least the second positive pulse mini-cycle;

[0044] In some embodiments, the electroplating cycle uses a forward / reverse current ratio between 1:1 and 1:8, and the duration of the forward pulse is 50ms to 300ms and the duration of the reverse pulse is 5ms to 100ms.

[0045] In some embodiments, the DC plating current density is 0.2 ASD to 5.0 ASD.

[0046] In some embodiments, the current density of each small cycle of pulse electroplating in step 2) described in step b) is 0.2 ASD to 5.0 ASD.

[0047] A fourth objective of the present invention is to provide a substrate having the aforementioned copper-plated through-holes.

[0048] This application has at least the following beneficial effects:

[0049] This application discloses a novel pulse electroplating leveling agent for packaging substrates and a copper electroplating solution containing the same, and also provides an optimized pulse via electroplating process. The beneficial technical effects of this application include significantly shortening the electroplating time, reducing the surface copper thickness, and achieving excellent filling of vias with a thickness-to-diameter ratio greater than 10. The electroplating method of this application not only achieves via filling at the hundred-micron level, but also exhibits superior filling effects for vias with smaller diameters, at the ten-micron level, resulting in smaller depression values. This is due to two factors: firstly, the design of the pulse current waveform; and secondly, the carefully designed core leveling agent component in the organic additive adjusts the current distribution inside and outside the via. Both of these factors promote current flow into the via, accelerating the filling process. Therefore, it has a significant beneficial effect on filling vias with smaller diameters, achieving smaller depression values ​​and thinner surface copper. Attached Figure Description

[0050] To more clearly illustrate the technical solutions in the specific embodiments of this application or the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0051] Figure 1 A flowchart illustrating the pulse electroplating through-hole process for the packaging substrate of this application;

[0052] Figure 2 This is a cross-sectional view of the through hole in the electroplated glass plate of Embodiment 6 of this application. Detailed Implementation

[0053] To facilitate understanding of this application, the following detailed description is provided in conjunction with specific embodiments. However, this application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of this application.

[0054] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application.

[0055] In this application, "and / or" means any and all combinations of one or more of the related listed items. "At least one" means one or more, such as one, two, or more. "Multiple" or "several" means at least two, such as two, three, etc., and "multi-layered" means at least two layers, such as two, three, etc., unless otherwise expressly and specifically defined. In the description of this application, "several" means at least one, such as one, two, etc., unless otherwise expressly and specifically defined.

[0056] When a numerical range is disclosed in this application, the range is considered continuous and includes the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to an integer, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be merged. In other words, unless otherwise specified, all ranges disclosed in this application should be understood to include any and all subranges to which they are included.

[0057] In this application, "above" or "below" includes the number itself. For example, "below 1" includes 1.

[0058] Unless otherwise specified, the temperature parameters in this application are permitted to be either constant-temperature treatment or variations within a certain temperature range. It should be understood that the constant-temperature treatment allows temperature fluctuations within the precision range of the instrument control, such as ±5℃, ±4℃, ±3℃, ±2℃, or ±1℃.

[0059] In this application, room temperature refers to indoor temperature, normal temperature, or general temperature. Generally, room temperature can be any of the following temperature ranges: 23℃±2℃, 25℃±5℃, or 20℃±5℃.

[0060] In this application, the substrate is a glass substrate, the conductive layer on the substrate is preferably a copper layer, the thickness of the conductive layer is preferably 0.01μm to 1μm, and the number of vias can be one or more.

[0061] In this application, the reactant raw materials such as imidazole compounds, ditertiary amine compounds, and dihaloalkyl ethers required for the synthesis of the leveling agent can be purchased through various existing channels, such as Sigma-Aldrich or prepared by referring to existing published literature, such as "Research on the Synthesis and Application of Imidazole Compounds" published by Wu Xiaochun et al. in 2010, "Research on Hydrogenation Amination Reaction of Polyether and Diethylamine" published by Wu Feifei et al. in 2014, and "Research on the Synthesis of Chlorinated Polyethylene Glycol by Reaction of Polyethylene Glycol and Thionyl Chloride" published by Wang Yitao et al. in 2017.

[0062] In the synthesis of the leveling agent of this application, the molar ratio of the three monomers can be in the range of (0.1-3):(0.1-3):1, preferably (0.1-2):(0.1-2):1. The leveling agent can be obtained by the following preparation method: mixing an imidazole compound, a ditertiary amine compound, an inorganic base and a water-soluble aprotic organic solvent, and adding a dihaloalkyl ether after the imidazole compound and the ditertiary amine compound are completely dissolved;

[0063] Then heat to 60℃-100℃, stir for 10h-24h, stop the reaction, cool, filter to remove solids, and obtain leveling agent solution.

[0064] The water-soluble aprotic organic solvents used include acetonitrile, N,N-dimethylformamide, tetrahydrofuran, acetone, 2-butanone, 1,4-dioxane, and N-methylpyrrolidone. The inorganic bases used include sodium carbonate.

[0065] (Na2CO3), potassium carbonate (Na2CO3), sodium hydroxide (NaOH), and potassium hydroxide (KOH).

[0066] Table 1 lists the composition of the acidic copper plating solution used for through-hole plating in this application:

[0067] Table 1. Composition and concentration of acidic copper plating solution

[0068]

[0069]

[0070] Then, the substrate comes into contact with the aforementioned acidic copper plating solution. The technical solution of this application achieves the effect of one-step filling of through-holes while ensuring minimal increase in copper thickness on the substrate surface. This includes the first step of depositing and connecting copper at the center of the through-hole, and the second step of using copper solution and plating conditions to fill the two opposing blind holes thus formed.

[0071] The electroplating operation includes (1) pulse electroplating for a first time period, wherein the pulse electroplating uses two pulse forms on both sides of the substrate, wherein these pulse forms exhibit phase shift; and then (2) DC electroplating using a forward current for a second time period.

[0072] The copper ion source in the acidic copper plating solution is preferably copper sulfate pentahydrate. As the concentration increases, the resistivity of the copper plating solution increases. As the sulfuric acid concentration increases, the solubility of copper sulfate decreases. The concentration of copper sulfate in the acidic copper plating solution is typically maintained in the range of about 50 g / L to about 300 g / L, more preferably about 190 g / L to about 270 g / L, and most preferably about 220 g / L to about 260 g / L.

[0073] The role of sulfuric acid is to provide maximum solution conductivity. The concentration of sulfuric acid in acidic copper plating solutions is typically maintained in the range of about 20 g / L to about 230 g / L, more preferably about 30 g / L to about 90 g / L, and most preferably about 40 g / L to about 70 g / L.

[0074] The acidic copper plating bath also contains halide ions, most preferably chloride ions. Chloride is added in the form of sodium chloride or diluted hydrochloric acid. The concentration of chloride ions in the acidic copper plating bath is typically maintained in the range of about 20 ppm to about 150 ppm, more preferably about 30 ppm to about 100 ppm, and most preferably about 40 ppm to about 60 ppm.

[0075] One or more leveling agents, brighteners, and wetting agents can be added to the acidic copper plating solution to provide the desired copper plating effect. In this invention, the concentration of the leveling agent is 10ppm to 50ppm, the concentration of the brightener is 4ppm to 8ppm, and the concentration of the wetting agent is 500ppm to 2000ppm. The brightener and wetting agent can be conventional organic additives, such as short-chain organic molecules containing thiol and sulfonic acid groups, like polydisulfide dipropane sulfonate (SPS) and 3-mercapto-1-propane sulfonate (MPS), and the wetting agent can be a polyether surfactant. For ease of explanation, in the embodiments, the leveling agent is the reaction product of an imidazole compound, a ditertiary amine compound, and a dihaloalkyl ether disclosed in this application; the brightener is sodium polydisulfide dipropane sulfonate (SPS); and the wetting agent is polyethylene glycol (PEG-6000).

[0076] In a broad sense, the term "pulse electroplating" as used in this invention can refer to pulse electroplating with both forward and reverse current densities, or pulse electroplating with only a forward current density.

[0077] The substrate used in the following embodiments is a glass substrate with a thickness between 0.05 mm and about 2 mm, more preferably between about 0.1 mm and about 1.0 mm. The diameter of the vias is typically between about 0.005 mm and about 0.5 mm, preferably between about 0.01 mm and about 0.3 mm, and most preferably between about 0.01 mm and about 0.10 mm. Therefore, the technical solution of this application is applicable to via filling, where the vias have a thickness-to-diameter ratio between about 0.5:1 and about 50:1, more preferably between about 2:1 and about 30:1. The conductive layer on both sides of the substrate and the inner surface of the vias can be one of copper, nickel, tin, silver, gold, copper-phosphorus alloy, nickel-phosphorus alloy, and nickel-tungsten alloy, preferably a conductive copper layer, with a thickness preferably ranging from 0.1 μm to 1.2 μm.

[0078] The electroplating parameters used in this application, including the electroplating step parameters for DC and pulse electroplating, are shown in Table 2.

[0079] Table 2:

[0080]

[0081]

[0082] The pulse electroplating rectifier in the blind via formation stage of this application can be configured to have multiple steps in the plating process, including at least two steps or up to eight steps. For ease of explanation, in this embodiment, the rectifier is configured with four steps, which define a single pulse plating cycle. These four steps, in any order, include the following steps:

[0083] 1) A first pulse with a first positive duration and a first positive intensity;

[0084] 2) A second pulse with a second positive duration and a second positive intensity;

[0085] 3) The third pulse with the first positive duration and the first positive intensity;

[0086] 4) The fourth pulse with reverse duration and reverse intensity;

[0087] The pulse electroplating rectifier for the blind via filling stage of this application can be configured to have multiple steps in the plating process, including at least two steps or up to four steps. For ease of explanation, in this embodiment, the rectifier is configured with three steps, which define a single pulse plating cycle. These three steps, in any order, include the following steps:

[0088] 1) A first pulse with a first positive duration and a first positive intensity;

[0089] 2) A second pulse with a second positive duration and a second positive intensity;

[0090] 3) The third pulse with the first positive duration and the first positive intensity;

[0091] Because all components of the plating solution are lost during the electroplating process, it is necessary to replenish each material during the electroplating process to maintain the concentration of each component. In the embodiments of this application, copper oxide is manually added to maintain the concentration of copper sulfate by chemical titration analysis, and the concentrations of sulfuric acid and chloride ions are replenished by chemical titration analysis.

[0092] The concentrations of brightener, leveling agent, and wetting agent are automatically replenished by monitoring cyclic voltammetry (CVS).

[0093] Table 3 describes the electroplating parameters of the pulse plating cycle in the blind hole formation stage of the four steps of this invention.

[0094] Table 3: Pulse plating cycle parameters.

[0095] Step 1 Step 2 Step 3 Step 4 Side A (ASD) 1J-1.2J 1J-2J 1J-1.2J (-2J)-(-5J) Side A (ms) 50ms-150ms 5ms-50ms 50ms-150ms 5ms-50ms Side B (ASD) 1J-1.2J (-2J)-(-5J) 1J-1.2J 1J-2J Side B (ms) 50ms-150ms 5ms-50ms 50ms-150ms 5ms-50ms

[0096] In the table, J represents the set single-sided current density; the number before J represents the multiple of the set single-sided current density.

[0097] Table 4 describes the electroplating parameters of the pulse plating cycle in the blind hole filling stage of the three steps of the present invention.

[0098] Table 4: Pulse plating cycle parameters.

[0099] Step 1 Step 2 Step 3 Side A (ASD) 1J-1.2J 1J-2J 1J-1.2J Side A (ms) 20ms-200ms 20ms-200ms 20ms-200ms Side B (ASD) 1J-1.2J 1J-2J 1J-1.2J Side B (ms) 20ms-200ms 20ms-200ms 20ms-200ms

[0100] In the table, J represents the set single-sided current density; the number before J represents the multiple of the set single-sided current density.

[0101] The following description is further illustrated with specific embodiments and comparative examples. Unless otherwise specified, the raw materials involved in the following specific embodiments and comparative examples are all commercially available. Unless otherwise specified, the instruments used are all commercially available. Unless otherwise specified, the processes involved are conventionally selected by those skilled in the art.

[0102] Example 1: Preparation of leveling agent (reactant molar ratio: 0.7:0.3:1)

[0103] Add 2.03 g (14.07 mmol) of 2-phenylimidazole, 1.04 g (6.03 mmol) of N,N,N',N'-tetramethyl-1,6-hexanediamine, 2.25 g (16 mmol) of anhydrous potassium carbonate, and 40 mL of acetonitrile. Stir for 10 minutes, then add 3.82 g (20.10 mmol) of 1,2-bis(2-chloroethoxy)ethane. Heat in an oil bath and stir at 80 °C for 12 hours. Stop the reaction, cool to room temperature, and filter using a Buchner funnel to remove the solid, yielding a brownish-red liquid. Dilute with water to the required ratio for electroplating applications.

[0104] To perform 1H NMR spectroscopy, 10 ml of the filtrate was taken and the acetonitrile was removed under reduced pressure using a rotary evaporator, yielding a brown oily substance.

[0105] The 1H NMR spectrum of the reaction product (using heavy water as solvent, 300MHz) showed the following peaks: δppm: 7.76-7.40 (m, 7H), 3.75-3.50 (m, 17.1H), 3.40-3.25 (m, 5.14H), 1.70-1.20 (m, 5.14H), confirming the structure.

[0106] Preparation of leveling agent in Examples 2-5

[0107] The preparation method is the same as in Example 1, except that the types and molar ratios of the imidazole compounds, ditertiary amine compounds, and dihaloalkyl ethers are specified in Table 4.

[0108] Table 4

[0109]

[0110] Comparative Example 1: Preparation of Leveling Agent

[0111] The reaction is basically the same as in Example 1, except that the ditertiary amine monomer “N,N,N',N'–tetramethyl-1,6-hexanediamine” in the reaction raw materials is replaced by “triethylamine”.

[0112] Comparative Example 2: Preparation of Leveling Agent

[0113] The reaction is basically the same as in Example 1, except that the dihaloalkyl ether monomer "1,2-bis(2-chloroethoxy)ethane" in the reaction raw materials is replaced by "1,4-butanediol diglycidyl ether".

[0114] Example of through-hole filling effect:

[0115] The industry requirements for the effect of through-hole filling are as follows: (1) The average value of the micro-convexity on both sides of the copper pillar of the through-hole filling is <5μm, the average value of the micro-concaveness is <15μm, and the copper pillar is uniform and free of voids. The average value of the micro-convexity is the average value of the most protruding points at both ends of the through-hole, and the average value of the micro-concaveness is the average value of the most concave points at both ends of the through-hole; (2) The average value of the surface copper thickness of the substrate after through-hole filling is <25μm. The average value of the surface copper thickness is the average value of the surface copper thickness measured at two points on both sides of the substrate.

[0116] Example 6

[0117] Acidic copper electrolyte was prepared according to the following parameters:

[0118] Element Concentration range Copper sulfate 240g / L sulfuric acid 50g / L chloride ions 50ppm Leveling agent (prepared in Example 1) 20ppm SPS 5ppm wetting agent 800ppm bath temperature 24℃

[0119] In this embodiment, a glass substrate with a thickness of approximately 400 μm is used, the diameter of the through-hole is approximately 100 μm, and the thickness-to-diameter ratio is approximately 4:1 (see Appendix). Figure 1 The substrate has a 0.3 μm thick conductive copper layer on both sides and the inner surface of the vias. Pulse plating is performed at a current density of 1.6 ASD for 60 minutes to form zipper-like copper interconnects in the vias, followed by DC plating at a current density of 2.0 ASD for 60 minutes until the vias are filled using the vertical plating method.

[0120] The pulse plating waveforms on the first and second sides of the substrate follow the following sequence:

[0121]

[0122] Finally, cross-sectional observation of the electroplated glass plate through-holes showed good and uniform copper plating with no voids in the copper pillars and an average concave orifice diameter of about 3.84 μm, and an average copper thickness of about 16.24 μm.

[0123] Examples 7 to 10

[0124] Following the copper plating solution and electroplating parameters of Example 6, Examples 7 through 10 performed electroplating filling operations on the same through-hole substrates, with the only difference being that Examples 7 through 10 used the leveling agents prepared in Examples 2 through 5, respectively. The through-hole filling effects obtained in each electroplating effect example after the through-hole filling operation are shown in the table below:

[0125]

[0126] Example 11

[0127] The copper plating solution and electroplating parameters were used in Example 6, with the only difference being that a 600 μm thick glass substrate was used in this example, with a through-hole diameter of 20 μm and a thickness-to-diameter ratio of 30:1. Ultimately, cross-sectional observation of the through-hole in the electroplated glass plate showed good and uniform copper plating with no voids within the copper pillars and a micro-recess of approximately 7.3 μm, and an average copper thickness of approximately 21.4 μm.

[0128] Example 12

[0129] The copper plating solution and plating parameters of Example 6 are used, except that pulse plating is performed at a current density of 1.6 ASD for 60 minutes to form a zipper-like copper connector in the through hole, followed by pulse plating at a current density of 2.0 ASD to fill the two opposing blind holes formed in the through hole for 60 minutes, until the through hole is filled in the vertical plating method.

[0130] The pulse plating waveforms on the first and second sides of the substrate follow the following sequence:

[0131]

[0132] Finally, cross-sectional observation of the electroplated glass plate through-holes showed good and uniform copper plating with no voids in the copper pillars and an average convexity of about 2.17 μm at the orifice opening, and an average copper thickness of about 17.92 μm.

[0133] Comparison of through-hole filling plating effect: Example 3:

[0134] The results were basically the same as in Example 6, except that the leveling agent in the copper plating solution was replaced with the leveling agent prepared in Comparative Example 1. The final through-hole plating results showed that the copper plating inside the holes was uneven and there were voids.

[0135] Comparison of through-hole filling plating effect, Example 4:

[0136] The results were basically the same as in Example 6, except that the leveling agent in the copper plating solution was replaced with the leveling agent prepared in Comparative Example 2. The final through-hole filling results showed that the copper plating inside the hole was uniform and without voids, but the average thickness of the copper on the surface was about 26.3 μm, which did not meet the requirements of subsequent processes.

[0137] Comparison of through-hole filling plating effect: Example 5:

[0138] The results were basically the same as in Example 6, except that the leveling agent in the copper plating solution was replaced with "1000ppm PEG600 + 30ppm ethylenediamine". The final through-hole filling results showed that the copper plating inside the hole was uniform and without voids, but the average thickness of the copper on the surface was about 30.8μm, which did not meet the requirements of subsequent processes.

[0139] Comparison of through-hole plating effect, Example 6:

[0140] Acidic copper electrolyte was prepared according to the following parameters:

[0141] Element Concentration range Copper sulfate 240g / L sulfuric acid 90g / L chloride ions 80ppm SPS 0.85ppm PEG600 10ppm ethylenediamine 2ppm bath temperature 23℃

[0142] Copper oxide was manually added to maintain the copper sulfate concentration using chemical titration analysis, and the concentrations of sulfuric acid and chloride ions were replenished using the same chemical titration analysis.

[0143] The concentrations of SPS, PEG600, and ethylenediamine are automatically replenished by monitoring cyclic voltammetry (CVS).

[0144] In this embodiment, a 600μm thick glass substrate is used, with a via diameter of 20μm and a thickness-to-diameter ratio of 30:1. A 0.3μm thick conductive copper layer is applied to both sides of the substrate and the inner surface of the vias. The rectifier programming is adjusted to accommodate the following pulse plating current parameters: pulse plating is performed at a current density of 2.4 ASD for 60 minutes to form a zipper-like copper interconnect in the vias, followed by DC plating at a current density of 2.5 ASD for 60 minutes until the vias are filled using the vertical plating method.

[0145] The pulse plating waveforms on the first and second sides of the substrate follow the following sequence:

[0146]

[0147]

[0148] The final through-hole filling results showed that the copper plating inside the holes was uniform and without voids, but the average copper thickness on the surface was about 37.1 μm, which did not meet the requirements of subsequent processes.

[0149] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0150] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are specific and detailed, they should not be construed as limiting the scope of protection of this application. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these modifications and improvements all fall within the scope of protection of this application. Therefore, the scope of protection of this application should be determined by the appended claims.

Claims

1. A novel pulse electroplating leveling agent for packaging substrates, characterized in that, It includes an active ingredient, which is a reaction product containing one or more imidazole compounds or their salts, one or more ditertiary amine compounds, or one or more dihaloalkyl ethers.

2. The leveling agent as described in claim 1, characterized in that, The imidazole compounds have the structure shown in formula (1): R1, R2, and R3 are each independently selected from H, C1-C8 alkyl, or phenyl, wherein the C1-C8 alkyl or phenyl may optionally be further substituted with one or more C1-C6 alkyl groups; and R1, R2, and R3 are not all H at the same time. The ditertiary amine compound has the structure shown in formula (2): Wherein, R4 is a C2-C10 straight-chain alkylene or a C2-C10 branched alkylene; R5, R6, R7 and R8 are each independently selected from: C1-C8 alkyl, or one or more hydroxyl-substituted C2-C8 alkyl. The dihaloalkyl ether has the structure shown in formula (3): Where n is selected from any integer from 1 to 50, and X is a halogen; The molar ratio of the imidazole compound, the ditertiary amine compound, and the dihaloalkyl ether is (0.1-2):(0.1-2):

1.

3. The leveling agent as described in claim 2, characterized in that, The imidazole compound in the leveling agent is selected from one of 2-methylimidazolium, 2-phenylimidazolium, 4-phenylimidazolium, 4-octylimidazolium, 2-(4-methylphenyl)imidazolium, 2,4-dimethylimidazolium, or 4-ethylimidazolium; and / or The ditertiary amine compound is selected from one of N,N,N',N'-tetramethyl-1,6-hexanediamine, N,N,N',N'-tetraethyl-1,10-decanediamine, N,N-dimethyl-N',N'-di(2-hydroxypropyl)-1,3-propanediamine, and N,N,N',N',2-pentamethylpropane-1,3-diamine; and / or The dihaloalkyl ether is selected from one of the following: bis(2-chloroethyl) ether, 1,2-bis(2-chloroethoxy)ethane, diethylene glycol bis(2-chloroethyl) ether, and dichloro polyethylene glycol.

4. A copper electroplating solution, characterized in that, The electroplating solution contains the leveling agent as described in any one of claims 1-3.

5. An electroplating process for through-holes in a packaging substrate, characterized in that, Includes the following steps: a) Make the substrate and at least one cathode and the copper plating solution into contact; b) Perform electroplating on one side and the other side of the substrate from step a) until the through-hole is filled with metallic copper. The substrate surface and the wall of the through hole described in step a) have a conductive layer; The acidic copper plating solution mentioned in step a) is the copper plating solution described in claim 4; The electroplating operation described in step b) includes the following steps in sequence: 1) Pulse electroplating is performed on one side and the other side of the substrate, so that copper ions are deposited first in the center of the through hole. After the copper is deposited and connected in the center of the through hole, two opposing blind holes are formed in the through hole. 2) Direct DC electroplating or pulse electroplating is performed to fill the two opposing blind holes formed in the through hole by pulse electroplating; Step 1) of step b) includes pulse plating, which involves applying a pulsed current to deposit copper ions onto one side and the other side of the substrate, wherein the current is applied as a pulse plating cycle comprising a repeatable sequence, wherein the repeatable sequence comprises a set of pulse plating cycles, each set of pulse plating cycles being performed in any order, including: (i) at least the first positive pulse cycle; (ii) at least the first reverse pulse cycle; (iii) At least the second positive pulse small cycle.

6. The electroplating process as described in claim 5, characterized in that, The substrate is made of glass, ceramic, organic material or organic-inorganic composite insulating material, the conductive layer is one or more alloys of titanium, copper, nickel, chromium, molybdenum, gold and silver, and there are one or more through holes.

7. The electroplating process as described in claim 5, characterized in that, In step b), the forward current density in step 1) of the pulse electroplating is 0.2 ASD to 7.0 ASD, the electroplating cycle uses a forward / reverse current ratio between 1:1 and 1:8, and the duration of the forward pulse is 50 ms to 500 ms and the duration of the reverse pulse is 5 ms to 200 ms, and the pulse frequency of the pulse electroplating is 1 Hz to 8 Hz. and / or The electroplating method in step 2) described in step b) is DC electroplating, wherein the current density of the DC electroplating is 0.2 ASD to 5.0 ASD; and / or The electroplating method in step 2) described in step b) is pulse electroplating, wherein the pulse electroplating is pulse electroplating with only positive pulses, the current density is 0.2 ASD to 5.0 ASD, and the duration of the positive pulse is 100 ms to 500 ms, the pulse frequency of the pulse electroplating is 2 Hz to 10 Hz, and the current is applied as a repeatable sequence of pulse electroplating cycles, wherein the repeatable sequence includes a set of pulse electroplating cycles, each set of pulse electroplating cycles being performed in any order, including: (i) at least the first positive pulse cycle; (ii) at least the second positive pulse cycle.

8. The electroplating process as described in claim 5, characterized in that, In step b), the electroplating cycle of step 1) uses a forward / reverse current ratio between 1:1 and 1:8, and the duration of the forward pulse is 50ms to 300ms and the duration of the reverse pulse is 5ms to 100ms.

9. The electroplating process as described in claim 5, characterized in that, The DC electroplating current density in step 2) of step b) is 0.2 ASD to 5.0 ASD; or / and The current density of each small cycle of the pulse electroplating in step 2) described in step b) is 0.2 ASD to 5.0 ASD.

10. A substrate, characterized in that, It contains a copper-plated through-hole as described in any one of claims 1-7.

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