Composite complexing agent and chemical copper plating solution

Abstract

The invention discloses a composite complexing agent and a chemical copper plating solution. Wherein the composite complexing agent comprises a heterocyclic complexing agent, linear fatty amine and an amino acid copolymer, and the amino acid copolymer is a copolymerization product of aspartic acid and glutamic acid. The chemical copper plating solution comprises a composite complexing agent, bivalent copper ions, a pH regulator, a stabilizer, a reducing agent and water. According to the invention, the problem of poor binding force between a copper plating layer prepared by a traditional chemical copper plating solution and a base material on the low-roughness base material is solved.

Description

Technical Field

[0001] The invention relates to the technical field of circuit board production, in particular to a composite complexing agent and a chemical copper plating solution. Background Art

[0002] Chemical copper plating solution includes complexing agent, divalent copper ion donor, alkali, stabilizer and reducing agent. The complexing agent is the most important. The addition of complexing agent inhibits the hydrolysis of copper ions in alkaline environment and ensures the stable reduction of copper salt on the surface of the substrate. The choice of complexing agent also determines the strength of the bonding between the chemical copper plating layer and the substrate surface to a large extent. The overall chemical reaction equation of chemical copper plating solution is far from as shown in formula (1):

[0003] Formula (I): Cu.L m 2+ +R→Cu.mL+O;

[0004] According to the prior art, the complexing agents used in the chemical copper plating solution can be summarized as the structure shown in the chemical formula (IV):

[0005] Chemical formula (IV): R in the structural formula is one or more of acetic acid, propionic acid, hydroxyethyl, and hydroxypropyl. The basic principle of the complexation is that two nitrogen atoms and four oxygen atoms form a 1:1 complex with copper. Among them, the more commonly used complexing agents are ethylenediaminetetraacetic acid (EDTA) and its derivatives, including hydroxyethylethylenediaminetriacetic acid, tetrahydroxyethylethylenediamineacetic acid, tetrahydroxypropylethylenediamine, and ethylenediaminetetrapropionic acid. In addition, triethanolamine and potassium sodium tartrate are also used as complexing agents.

[0006] The semi-additive process (SAP) is the mainstream manufacturing method for IC substrates. The steps are: first drill holes on the dielectric substrate, then remove the glue residue in the hole by chemical method, and then use chemical copper plating solution for chemical copper metallization, electroplating, and pattern transfer. Chemical copper, as a seed layer, is the direct bonding surface between the substrate and the copper metal layer, which has a significant impact on the reliability of the substrate. However, in the face of high-frequency and high-speed transmission requirements, the traditional chemical copper plating formula can no longer meet the needs. The reason is that the roughness of the substrate is getting lower and lower, and the lines are getting thinner and thinner. The lower the roughness of the substrate, the less contact area the copper metal layer has with it, and the smaller the bonding force between the two. Ultimately, it affects the performance of the plated product. Summary of the invention

[0007] In order to solve the above technical problems, the present invention provides a composite complexing agent and an electroless copper plating solution, which solves the problem of poor bonding between the copper plating layer prepared by the traditional electroless copper plating solution and the substrate on a low-roughness substrate.

[0008] The technical solution of the present invention is:

[0009] A composite complexing agent, characterized in that it comprises, by mass concentration ratio, heterocyclic complexing agent: linear fatty amine: amino acid copolymer = (30-120): (2-40): 1;

[0010] The chemical general formula (I) of the heterocyclic complexing agent is as follows:

[0011] The general chemical formula (I) is:

[0012] Wherein, R1=H; R2=H, alkyl;

[0013] The R1 and R2 are H, and the heterocyclic complexing agent is 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid;

[0014] The R1 is H, the R2 is tert-butyl, and the heterocyclic complexing agent is tri-tert-butyl 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid;

[0015] The chemical formula (II) of the linear fatty amine is as follows:

[0016] The general chemical formula (II) is

[0017] Wherein, n=an integer from 1 to 5;

[0018] The general chemical formula (III) of the amino acid copolymer is shown below:

[0019] The general chemical formula (III) is

[0020] Wherein, x=an integer from 3 to 8, and y=an integer from 3 to 9.

[0021] Preferably, the heterocyclic complexing agent: the linear fatty amine: the amino acid copolymer=(44-100):(8-40):1.

[0022] Furthermore, the amino acid copolymer is a copolymerization product of aspartic acid and glutamic acid.

[0023] Aspartic acid and glutamic acid both have amino and carboxyl groups, and the two can copolymerize to form polyamino acids, whose polyamino acid monomer units are connected by amide bonds (amino and carboxyl groups minus small molecular water). In terms of its molecular structure itself, it is a macromolecular complexing agent.

[0024] Furthermore, R1 and R2 are H, and the heterocyclic complexing agent is 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid.

[0025] Furthermore, the R1 is H, the R2 is tert-butyl, and the heterocyclic complexing agent is tri-tert-butyl 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid.

[0026] Furthermore, the viscosity average molecular weight Mv of the amino acid copolymer is 1000-1500.

[0027] The present invention also provides a chemical copper plating solution, which comprises 21-44 g / L of a composite complexing agent, 1.5-3.0 g / L of divalent copper ions, 5-13 g / L of a pH regulator, 3-15 mg / L of a stabilizer, 3-10 g / L of a reducing agent, and the balance is water.

[0028] The composite complexing agent of the present invention is a complexing agent prepared by compounding three components of a heterocyclic complexing agent, a linear fatty amine and an amino acid copolymer in a specific ratio. It can refine the grains, increase the density of the copper plating layer, and enable the chemical copper plating solution of the present invention to have a higher deposition rate.

[0029] Furthermore, the divalent copper ion donor includes at least one of copper sulfate pentahydrate and copper chloride dihydrate.

[0030] Furthermore, the pH regulator is sodium hydroxide.

[0031] The pH value of the chemical copper plating solution of the present invention is controlled by the pH regulator to be between 11 and 14.

[0032] Furthermore, the stabilizer is 2-2'-bipyridine and potassium ferrocyanide, and the mass concentration ratio is 2-2'-bipyridine:potassium ferrocyanide=1:(1.4-5).

[0033] The stabilizer is a sulfur-containing compound that has a strong adsorption effect on copper. It plays the role of poisoning the active center in chemical copper, and ultimately inhibits the violent reaction of chemical copper.

[0034] Furthermore, the reducing agent is formaldehyde.

[0035] The beneficial technical effects of the present invention are:

[0036] On the one hand, by utilizing the heterocyclic complexing agent and the straight-chain fatty amine in the chemical copper plating solution system of the present invention, the copper plating layer prepared on the substrate with low roughness has uniform grain size and high density, and the copper plating layer has high bonding force with the substrate; on the other hand, the amino acid copolymer in the chemical copper plating solution system of the present invention, i.e., the aspartic acid and glutamic acid copolymer, can accelerate the copper deposition rate of the chemical copper plating solution system of the present invention, so that the chemical copper plating solution of the present invention has high deposition rate and good backlight property, thus meeting the actual use requirements of plated parts. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Figure 1 is a schematic diagram of the surface morphology of Example 5 (resolution × 1000);

[0038] Figure 2 Schematic diagram of the surface morphology of Comparative Example 1 (resolution × 1000);

[0039] Figure 3 This is a schematic diagram of the surface morphology of Comparative Example 4 (resolution × 1000);

[0040] Figure 4 This is a schematic diagram of the surface morphology of Comparative Example 6 (resolution × 1000);

[0041] Figure 5 This is a schematic diagram of the surface morphology of Comparative Example 7 (resolution × 1000);

[0042] Figure 6 This is a schematic diagram of the surface morphology of Comparative Example 9 (resolution × 1000). DETAILED DESCRIPTION

[0043] In order to more clearly understand the technical means of the present invention and implement it according to the contents of the specification, the specific implementation methods of the present invention are further described in detail below in conjunction with the drawings and examples. The following examples are used to illustrate the present invention but are not used to limit the scope of the present invention.

[0044] The invention provides a composite complexing agent, which comprises a hybrid complexing agent, a linear fatty amine and an amino acid copolymer, wherein the mass concentration ratio is heterocyclic complexing agent: linear fatty amine: amino acid copolymer=(30-100):(2-12):1.

[0045] Preferably, the mass concentration ratio of heterocyclic complexing agent: linear fatty amine: amino acid copolymer is (44-100): (8-40): 1.

[0046] Among them, the amino acid copolymer in the present invention is a copolymerization product of aspartic acid and glutamic acid, which is prepared by referring to the preparation method described in "Zhu Ling, Research on Copolymerization of Aspartic Acid and Glutamic Acid, China's Outstanding Master and Doctoral Dissertations, 2006", which will not be repeated here; the other reagents in the present invention are all commercially available reagents.

[0047] The general chemical formula (I) of the heterocyclic complexing agent is shown below:

[0048] Chemical formula (I): Among them, R1=H; R2=H, tert-butyl.

[0049] When R1 and R2 are both H, the heterocyclic complexing agent is 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid; when R1=H and R2 is tert-butyl, the heterocyclic complexing agent is tri-tert-butyl 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid.

[0050] The chemical formula (II) of straight chain fatty amine is as follows:

[0051] The general chemical formula (II) is Wherein, n=an integer from 1 to 5. When n=1, 2, 3, 4, 5, the straight-chain fatty amine is diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexamine, hexaethyleneheptamine, respectively.

[0052] The general chemical formula (III) of the amino acid copolymer is shown below:

[0053] The general chemical formula (III) is

[0054] Wherein, x=an integer from 3 to 8, and y=an integer from 3 to 9.

[0055] The present invention also provides a chemical copper plating solution, which includes 15-40 g / L of a heterocyclic complexing agent, 2-7 g / L of a linear fatty amine, 0.1-1 g / L of an amino acid copolymer, 1.5-3.0 g / L of a divalent copper ion, 5-13 g / L of a pH regulator, 3-15 mg / L of a stabilizer, 3-10 g / L of a reducing agent, and the balance is water.

[0056] Preferably, the heterocyclic complexing agent is preferably 20-35 g / L, the linear fatty amine is preferably 4-6 g / L, and the amino acid copolymer is preferably 0.3-0.8 g / L.

[0057] The divalent copper ion donor of the invention is copper sulfate pentahydrate; the pH regulator is sodium hydroxide; the stabilizer is 2-2'-bipyridine and potassium ferrocyanide, wherein, by mass concentration, 2-2'-bipyridine:potassium ferrocyanide=1:(1.4-5); the reducing agent can be formaldehyde.

[0058] The chemical copper plating solution is added into deionized water in the order of the above reagents, and stirred to dissolve to form the chemical copper plating solutions of Examples 1-7, whose specific components and the addition amount of each component are shown in Table 1.

[0059] Table 1: Compositions of chemical copper plating solutions of Examples 1-7 and the amount of each component added (mass concentration g / L)

[0060]

[0061]

[0062]

[0063] In addition, the present invention also designs chemical copper plating solutions of comparative examples 1-9, whose specific components and the addition amounts of each component are shown in Table 2.

[0064] Table 2: Comparative Examples 1-9 Chemical Copper Plating Solution Compositions and Addition Amounts of Each Component (Mass Concentration g / L)

[0065]

[0066]

[0067]

[0068] The present invention has made the following performance evaluation on the chemical copper plating and copper dissolving of the above-mentioned embodiments 1-7 and comparative examples 1-9, wherein an ABF substrate with a roughness of 0.08 μm is selected in the following performance evaluation experiment, and the test panels used are all made by the SAP process of the prior art for chemical copper plating process, which will not be repeated here.

[0069] 1. Copper deposition rate test

[0070] (1) Take a 69mm×69mm ABF sample and bake it in an oven at 120℃ for 1h; (2) Take it out and put it in a desiccator to cool for 10min, then weigh it to the accuracy of 0.0001g (G1); (3) Deposit chemical copper by SAP process; (4) Put the copper deposited sheet into an oven at 120℃ for 1h, take it out and put it in a desiccator to cool for 10-15min, then weigh it to the accuracy of 0.0001g (G2); (5) Calculation formula:

[0071]

[0072] Where ρ represents the copper density, 8.9 g / cm 3 , S is the board area cm 2 , T represents time. The copper deposition rate of 0.6-1um / 15min is considered qualified.

[0073] 2. Backlight test

[0074] The test panels made by SAP process were backlit and ground. The ground test panels were about 6mm wide and were considered qualified with a backlight level of 9.5 or above.

[0075] Backlighting is a magnified visual inspection method to check whether the copper wall of the through hole is intact. It is also a convenient way to indirectly feedback whether the copper coating is uniform. If the chemical copper hole wall is intact without any holes or pinholes, the copper layer can block the light and appear dark under the microscope. Once there is a hole in the copper wall, there will be light leakage.

[0076] 3. Binding strength test

[0077] After the test board is electroplated with SAP process, it is electroplated with a thickness of 25μm.

[0078] Adhesion test process: The adhesion test area is a copper surface test area with a width of 1cm, a length of 10cm and a plating thickness of 25μm made by dry film, exposure and development and electroplating processes. Use a tensile tester (Shimadzu AGS10KNX) to pull up the test strip at a speed of 51mm / min in a fixed 90° direction and read the tensile value, which is the adhesion value of the copper plating layer and the substrate surface. Adhesion ≥0.45kgf / cm is considered qualified.

[0079] The test results of the chemical copper plating solutions of Examples 1-7 and Comparative Examples 1-9 are shown in Table 3.

[0080] Table 3

[0081]

[0082]

[0083] From the above test results, it can be seen that the backlight level of the chemical copper plating solutions of Examples 1-7 is 10, indicating that the chemical copper plating layers of each chemical copper plating solution are uniform and have good coverage; the copper deposition rates of the chemical copper plating solutions of Examples 1-7 are all between 0.6-1.0um / 15min, and the binding forces of the chemical copper plating solutions of Examples 1-7 are all more than 0.45kgf / cm, which can meet the actual use requirements. Among them, the chemical copper plating solutions of Examples 3-5 have better performance.

[0084] In the chemical copper plating solutions of Comparative Examples 1-3, traditional complexing agents were used. Although their backlight levels were all 10 and their copper deposition rates were all between 0.6-1.0um / 15min, the binding forces measured by the chemical copper plating solutions of Comparative Examples 1-3 were all less than 0.45kgf / cm, indicating that when the traditional complexing agent acts on a substrate with a relatively low roughness, its binding force performance cannot meet the actual use requirements.

[0085] For this, first of all, from the perspective of molecular structure, the heterocyclic complexing agent of the present invention has two more nitrogen atoms than EDTA, and the four nitrogen atoms in the heterocyclic complexing agent form a hybrid. According to the empirical deduction of the 1:1 complexing of EDTA and copper ions, the two extra nitrogen atoms in the heterocyclic complexing agent of the present invention can complex new copper ions, so that the ratio of complexing agent required for the heterocyclic complexing agent to complex copper ions is less than 1:1. Therefore, compared with EDTA, the complex structure formed by the heterocyclic complexing agent and copper ions in the present invention is more complex, and the formed heterocyclic structure is also more stable. In addition, the straight-chain fatty amine of the present invention, as an auxiliary complexing agent, may be embedded in the complex formed by the above-mentioned heterocyclic complexing agent and copper ions, forming a complex complex of a polyhedron. Thus, the stability of the complex formed by the heterocyclic complexing agent and the copper ion is further improved. When the complex of this structure is reduced, the speed of the copper ion precipitation in the complex is more stable, so that the crystallization of the copper ion precipitation is more delicate, and the copper crystal layer is also more compact, so that the precipitated copper crystals are more easily filled in some recessed places of the substrate, and finally the bonding force between the copper coating and the substrate is improved. In addition, the amino acid copolymer of the present invention is a copolymerization product of aspartic acid and glutamic acid. According to its molecular structure characteristics, it can also be used as a macromolecular complexing agent, but from the test results of Examples 1-7, it can better play the role of accelerating the copper deposition rate of the chemical copper plating solution system of the present invention.

[0086] Further from Figure 1 to Figure 2 It can be seen that the copper layer on the surface of the copper plating layer on the test board corresponding to the chemical copper plating solution of Example 5 has a smaller crystal size and a uniform grain size, presenting a smoother surface structure; the copper layer on the surface of the copper plating layer on the test board corresponding to the chemical copper plating solution of Comparative Example 1 is coarse, and the grain size is uniform.

[0087] In the chemical copper plating solution in Comparative Example 4, the composite complexing agent only includes 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid, and in the chemical copper plating solution in Comparative Example 5, the composite complexing agent includes tri-tert-butyl 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid and pentaethylenehexamine, and the copper deposition rate of both is less than 0.6um / 15min, and the backlight level is 9, indicating that the copper layer coverage of the two chemical copper plating solutions is not complete, resulting in weak final bonding. In Comparative Example 6, the composite complexing agent includes 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid and an amino acid copolymer, and its copper deposition rate and backlight level both meet the qualified requirements, but its bonding strength is only 0.37kgf / cm. Comparing the chemical copper plating solutions of Comparative Examples 4-6 with the above Examples 1-7, it can be seen that the components of the composite complexing agent of the present invention have a strong synergistic effect, and the lack of any component will affect the above-mentioned comprehensive performance.

[0088] Depend on Figure 3-4 It can be seen that the copper layer crystals on the surface of the copper plating layer on the test board corresponding to the chemical copper plating solution of Comparative Example 4 are not as fine as the copper layer crystals in Example 5, and due to its low copper deposition rate and thin copper layer, its copper layer is not as smooth as the copper layer in Example 5; the copper layer crystals on the surface of the copper plating layer on the test board corresponding to the chemical copper plating solution of Comparative Example 6 are also coarse.

[0089] In Comparative Examples 7 and 8, small molecule amino acids, aspartic acid or glutamic acid, are used. Although they can play a certain acceleration role compared with Comparative Example 5, the copper deposition rate is still less than 0.6um / 15min. Figure 5 It can be seen that the corresponding copper layer crystals are coarser than those in Example 5 and the surface is uneven.

[0090] In Comparative Example 9, the amino acid copolymer of the present invention and EDTA were used to compound, and the speed was improved to a certain extent compared with Comparative Example 1, but the Figure 6 It can be seen that the copper layer corresponding to Comparative Example 9 has relatively rough crystals, that is, the chemical copper plating solution system cannot improve the morphology of the copper layer.

[0091] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. It should be pointed out that a person skilled in the art can make several improvements and modifications without departing from the technical principles of the present invention, and these improvements and modifications should also be regarded as within the scope of protection of the present invention.

Claims

1. A composite complexing agent, characterized in that: The invention comprises a mass concentration ratio of heterocyclic complexing agent: linear fatty amine: amino acid copolymer = (30-120): (2-40): 1; The chemical general formula (I) of the heterocyclic complexing agent is as follows: The general chemical formula (I) is: Wherein, R1=H; R2=H, one of alkyl; R1 and R2 are the same or different; The chemical formula (II) of the linear fatty amine is as follows: The general chemical formula (II) is Wherein, n=an integer from 1 to 5; The general chemical formula (III) of the amino acid copolymer is shown below: The general chemical formula (III) is Wherein, x=an integer from 3 to 8, and y=an integer from 3 to 9.

2. The composite complexing agent according to claim 1, characterized in that Calculated by mass concentration ratio, the heterocyclic complexing agent: the linear fatty amine: the amino acid copolymer = (44-100): (8-40):

1.

3. The composite complexing agent according to claim 1, characterized in that The amino acid copolymer is a copolymerization product of aspartic acid and glutamic acid.

4. The composite complexing agent according to claim 1, characterized in that The alkyl group is tert-butyl.

5. The composite complexing agent according to claim 1, characterized in that: The viscosity average molecular weight Mv of the amino acid copolymer is 1000-1500.

6. A chemical copper plating solution, characterized in that The invention comprises 21-44 g / L of the composite complexing agent described in any one of claims 1 to 5, 1.5-3.0 g / L of divalent copper ions, 5-13 g / L of a pH regulator, 3-15 mg / L of a stabilizer, 3-10 g / L of a reducing agent, and the balance is water.

7. The chemical copper plating solution according to claim 6, characterized in that The divalent copper ion donor includes at least one of copper sulfate pentahydrate and copper chloride dihydrate.

8. The chemical copper plating solution according to claim 6, characterized in that The pH regulator is sodium hydroxide.

9. The chemical copper plating solution according to claim 6, characterized in that: The stabilizer is 2-2'-bipyridine and potassium ferrocyanide, and the mass concentration ratio is 2-2'-bipyridine:potassium ferrocyanide=1:(1.4-5).

10. The chemical copper plating solution according to claim 6, characterized in that: The reducing agent is formaldehyde.

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