A low-electrical-loss copper-surface bonding compound, its preparation method and application

Abstract

This application relates to the field of printed circuit board processing technology, and more specifically, to a low-electrical-loss copper bonding compound, its preparation method, and its application. The compound has the following structural formula: a polythiourea molecule with a nitrazole structure, wherein the degree of polymerization n is 3-10. This application benefits from the compound's special structure (C=S and -NH2), effectively achieving bonding under copper-free etching conditions, and the smooth copper surface meets the requirements for high-frequency signal transmission.

Description

Technical Field

[0001] This application relates to the field of PCB copper surface treatment technology, and more specifically, it relates to a low-electrical-loss copper bonding compound, its preparation method, and its application. Background Technology

[0002] As a fundamental component of electronic devices, the performance, quality, and processing technology of PCBs are becoming increasingly important. At present, the main methods for PCB copper surface treatment include chemical methods: ultra-roughening and medium-roughening; or physical methods: grinding and sandblasting. However, these methods generally have the disadvantages of high cost and complex processes.

[0003] To overcome the above-mentioned drawbacks, copper bonding agents have been provided as alternatives in related technologies. Thanks to their many advantages, they have become the mainstream technology in the PCB manufacturing field. By being compatible with chemical micro-etching and chemical bonding, they significantly improve the adhesion between the copper surface and the resin layer and maintain stability.

[0004] However, in recent years, with the promotion and commercialization of 5G technology, the demand for lossless transmission of high-frequency signals has been increasing. Therefore, it can be concluded that the existing PCB pre-processing technology is limited by the etching of its copper surface and can no longer meet the transmission requirements of high-frequency signals.

[0005] Furthermore, from the perspective of practical performance, the rougher the copper surface, the more eddy current signals will be formed on the surface of the copper when the current flows through it, resulting in greater signal attenuation. Therefore, there is an urgent need to provide a low-electrical-loss compound for copper bonding, its preparation method, and its application. Summary of the Invention

[0006] To ensure the quality of the copper surface after the application of the copper bonding agent, so that it can meet the transmission requirements of high-frequency signals, this application provides a copper surface bonding agent that does not bite into copper and has low electrical loss, as well as its preparation method.

[0007] In a first aspect, this application provides a low-electrical-loss compound for copper-face bonding, employing the following technical solution: A low-electrical-loss compound for copper-face bonding, with the following structural formula:

[0008]

[0009] That is, a polythiourea molecule with a nitrazole structure, wherein the degree of polymerization n takes the value of 3-10.

[0010] Secondly, this application provides a method for preparing a low-electrical-loss copper-surface bonding compound, employing the following technical solution:

[0011] A method for preparing a low-electrical-loss copper-face bonding compound includes the following steps:

[0012] S1. Dissolve 4H-1,2,4-triazol-3,4,5-triamine in dehydrated CHCl3 to obtain solution A for later use;

[0013] Dissolve 1,1-thiocarbonyldiimidazole in dehydrated CHCl3 to obtain solution B for later use.

[0014] S2. Add solution B dropwise to solution A in S1 and stir to react, to obtain a reaction solution. Control the feed ratio of 4H-1,2,4-triazole-3,4,5-triamine and 1,1-thiocarbonyldiimidazole to be (1-1.1):1.

[0015] S3. Wash the reaction solution obtained in S2 with saturated saline and deionized water to remove unreacted monomers and small molecule byproducts produced in the reaction, and then collect the organic phase.

[0016] S4. First, dry the organic phase obtained in S3 with anhydrous sodium sulfate, then evaporate to dryness to remove the solvent, and finally dry the obtained solid to obtain the compound shown in formula (I).

[0017] The reaction route for the above preparation steps is as follows:

[0018]

[0019] Preferably, the mass percentage concentrations of solution A and solution B in S1 are as follows:

[0020] The mass percentage concentration of 4H-1,2,4-triazole-3,4,5-triamine in solution A is 11-15%.

[0021] The mass percentage concentration of 1,1-thiocarbonyldiimidazole in solution B is 9-14%.

[0022] Preferably, the conditions for the stirring reaction in S2 are:

[0023] Stirring speed 2000-3000 r / min, reaction at room temperature for 24-36 h.

[0024] Preferably, the specific steps and conditions for collecting the organic phase in step S3 are as follows:

[0025] First, pour the reaction solution obtained in S2 into saturated saline solution, shake well and let stand. Then pour out the lower organic phase and wash it three times with saturated saline solution.

[0026] Then, the obtained organic phase is washed three more times with deionized water to complete the organic phase collection.

[0027] Thirdly, this application provides the application of the low electrical loss copper bonding compound and / or the compound prepared by any of the above methods in bonding copper surfaces and resin layers.

[0028] Fourthly, this application provides a copper bonding agent, which adopts the following technical solution:

[0029] A copper bonding agent comprising the aforementioned low-electrical-loss copper bonding compound and / or a compound prepared by any of the above methods.

[0030] Preferably, it includes 0.1-0.5‰ of the aforementioned low-electric-loss copper bonding compound and / or compounds prepared by any of the above methods.

[0031] Preferably, the copper bonding agent is composed of the following components in parts by weight: 0.1-0.5‰ of a low-electrical-loss copper bonding compound, 0-5‰ of a coupling agent, 0-3‰ of a wetting agent, and deionized water as the balance.

[0032] Preferably, the copper bonding agent is composed of the following components in parts by weight: 0.1-0.5‰ of a low-electric-loss copper bonding compound, 3-5‰ of a coupling agent, 1-3‰ of a wetting agent, and deionized water as the balance.

[0033] In summary, this application has the following beneficial effects:

[0034] 1. The low electrical loss copper surface bonding of this application uses a unique bifunctional molecular design in the compound. By forming stable chemical bonds between the two functional groups and the copper surface and the dry film respectively, the bonding force between the copper surface and the dry film is significantly enhanced while maintaining the smoothness of the copper surface, thus ensuring its use conditions.

[0035] 2. Compared with traditional copper surface treatment methods, the low-electrical-loss copper bonding compound in this application has a more environmentally friendly overall process and produces copper-free wastewater. This not only reduces the negative impact on the environment but also lowers production costs, eliminates copper loss, and improves production efficiency.

[0036] 3. The copper bonding agent in this application benefits from the use of a low-current-loss copper bonding compound and its suitability for high-frequency and high-speed signal transmission. By optimizing the adhesion between the copper surface and the dry film, it significantly reduces signal attenuation and improves the electrical performance of the PCB.

[0037] 4. The process design of the copper bonding agent in this application takes into account compatibility with the existing PCB manufacturing process, so that it can be easily applied to the existing production line without major modifications to the equipment. At the same time, its operation is relatively simple, reducing the difficulty of operation and the error rate. Attached Figure Description

[0038] Figure 1 This is a schematic diagram of the bonding connection between the copper bonding agent and the substrate and dry film in Embodiment 1 of this application;

[0039] Figure 2This is the infrared spectrum of the compound used for copper bonding in this application. Detailed Implementation

[0040] The following combination Figure 1-2 The present application will be further described in detail with reference to the embodiments.

[0041] Preparation Example 1

[0042] A compound for copper-face bonding with low electrical loss has the following structural formula:

[0043]

[0044] That is, a polythiourea molecule with a nitrazole structure, wherein the degree of polymerization n takes the value of 3-10;

[0045] It was prepared using the following steps:

[0046] S1. Dissolve 4H-1,2,4-triazol-3,4,5-triamine in dehydrated CHCl3 to obtain solution A with a mass percentage concentration of 11% for later use.

[0047] Dissolve 1,1-thiocarbonyldiimidazole in dehydrated CHCl3 to obtain a 9% (w / w) solution B for later use.

[0048] S2. Add solution B dropwise to solution A in S1 and stir to react. Stir at 2000 r / min and react at room temperature for 36 h to obtain the reaction solution. Control the feed ratio of 4H-1,2,4-triazole-3,4,5-triamine and 1,1-thiocarbonyldiimidazole to be 1.05:1.

[0049] S3. Wash the reaction solution obtained in S2 with saturated saline and deionized water to remove unreacted monomers and small molecule byproducts produced in the reaction, and then collect the organic phase.

[0050] The specific steps and conditions for collecting the organic phase are as follows:

[0051] First, pour the reaction solution obtained in S2 into saturated saline solution, shake well and let stand. Then pour out the lower organic phase and wash it three times with saturated saline solution.

[0052] Then, the obtained organic phase is washed three more times with deionized water to complete the organic phase collection;

[0053] S4. First, dry the organic phase obtained in S3 with anhydrous sodium sulfate, then rotary evaporate to dryness to remove the solvent. Finally, dry the obtained solid at 60℃ for 24 h to obtain the compound shown in formula (I), with a purity of 90.5% and a yield of 93.2%. The corresponding infrared spectrum is shown below. Figure 2 As shown.

[0054] The reaction route for the above preparation steps is as follows:

[0055]

[0056] The copper bonding agent prepared in each embodiment and comparative example was selected as the test object for performance testing. Then, bonding and circuit processing were carried out according to the following usage method.

[0057] Sample conditions: Board material type: Lianmao Electronics Co., Ltd. IT 968G (18um base copper); Dry film type: Asahi Kasei Corporation YQ40MP; Processing flow:

[0058] A1) Pickling: Remove the oxides on the copper surface with a 3% sulfuric acid solution at room temperature (25℃±1℃) for 30 seconds;

[0059] A2) Water wash: Wash with deionized water for 20 seconds;

[0060] A3) Copper surface bonding agent treatment prepared in the examples and comparative examples: an organic bonding film is formed on the copper surface by spraying, the treatment temperature is 28°C, and the treatment time is 40s.

[0061] A4) Water wash: Wash with deionized water for 20 seconds;

[0062] A5) Pickling: Remove the oxides on the copper surface using a 3% sulfuric acid solution at room temperature (25℃±1℃) for 10 seconds;

[0063] A6) Water wash: Wash with deionized water for 10s to 20s;

[0064] A7) Drying: Drying temperature 85℃, drying time 30s;

[0065] A8) Film application: Using the Hongshengxiang CSL-M25E fully automatic laminating machine, apply Asahi Kasei Corporation YQ40MP dry film at a pressure of 4 kg, a temperature of 105 degrees, and a laminating speed of 1.4 m / min.

[0066] A9) Exposure: Film negatives were mounted using an Orbold Xpress-9i fully automatic LDI exposure machine in a Class 10,000 cleanroom environment at 25°C and 50% humidity. The vacuum was adjusted to 0.08MPa, the distance from the exposure light source to the board surface was 15 cm, and the exposure energy was 100 mJ / cm². 2 Time: 6 seconds;

[0067] A10) Development: After development using a 1% sodium carbonate aqueous solution at 28 degrees Celsius for 1 minute, the product undergoes two water rinses before proceeding to the next etching process.

[0068] A11) Etching: Copper is sprayed and vacuum etched in a mixed aqueous solution of 370 g / L copper chloride dihydrate and 2.0 mol / L hydrochloric acid at 50°C for 3 minutes, followed by two water washes before proceeding to the next film removal process.

[0069] A12) Film removal: Remove the film in a 4% sodium hydroxide aqueous solution at 52°C for 2 minutes, rinse twice with water and then blow dry to obtain the final circuit board.

[0070] Blank group

[0071] The processing procedure is the same as above, except that the copper bonding agent is replaced by an equal amount of water, which serves as a blank control group.

[0072] Micro-etching control group

[0073] The processing procedure is the same as above, except that the copper bonding agent is replaced by an equal amount of micro-etching solution (80g / L sodium persulfate, 20g / L sulfuric acid, and water as solvent), which serves as a micro-etching control group.

[0074] Medium coarsening control group

[0075] The processing procedure is the same as above, except that the copper bonding agent is replaced by an equal amount of roughening solution as a micro-etching control group. The composition of the roughening solution is: hydrogen peroxide: 20g / L, ME-358 (Shenzhen Songbai Science & Technology) roughening micro-etching solution: 20g / L, and pure water as the solvent.

[0076] Then, the copper surface micro-etching amount, post-bonding peel strength, and electrical signal loss were tested for each example group, comparative example group, and control group. The test samples and detection steps for each stage are as follows:

[0077] Copper surface micro-etching amount

[0078] 1) Weigh the IT 968G (base copper 18um) of Lianmao Electronics Co., Ltd. on a balance beforehand and record it as G1;

[0079] 2) Then, take the boards processed by the above A1-A7 processes, place them in an oven and dry them at 105±5℃ for 15 minutes, cool them to room temperature in a desiccator, weigh them on a balance, and record them as G2.

[0080] 3) Measure the area S of the test plate (the sum of the areas of both sides, unit: cm2);

[0081] Calculation: Micro-erosion amount (um) = [(G1-G2) / 8.96×S]×10000.

[0082] Post-bonding peel strength

[0083] Extract the board material processed through the above A1-A10 steps, and then select a tensile testing machine with the required accuracy for testing the peel strength between the PCB dry film coating and the substrate, according to standard "PC-TM-650 2.4.8". The test steps and methods are as follows: Fix the extracted board material on the test device, clamp the peeling end with a clamp, start the tensile testing machine, and vertically pull the test strip upward at a speed of 50.8 mm / min. Record the minimum load (N / cm) during the peeling process. Randomly select 10 points for testing and take the average value of the results.

[0084] Electrical signal loss %

[0085] Using a vector network analyzer, the board material after A1-A12 treatment was tested. Insertion loss was tested in Delta IL3.0 mode (the test lines were designed as three sets of differential lines of different lengths but with the same impedance, with test line lengths of 2 inches, 5 inches and 10 inches, and frequencies of 4 GHz, 8 GHz and 12.89 GHz, respectively).

[0086] Example

[0087] Examples 1-5

[0088] A copper bonding agent, with its components and corresponding weights per 1 kg as shown in the table below, was prepared by dispersion and mixing under normal temperature and pressure conditions.

[0089] The copper bonding compound was prepared in Preparation Example 1; the coupling agent was 2-methyl-2,4-pentanediol, purchased from Arkema, France; and the wetting agent was ED3060, purchased from Clariant.

[0090] Table: Components and weights (g) of copper bonding agents in Examples 1-5

[0091]

[0092] Comparative Example 1

[0093] A copper bonding agent, differing from Example 1 in that its copper bonding compound is replaced by an equal amount of a nitrogen-containing heterocyclic copolymer, which is prepared by the following process:

[0094] The product is obtained by mixing 60g of 4-methyl-5-vinylthiazole, 30g of hydroxyethyl acrylate, 10g of acrylamide, 300g of anhydrous ethanol and 0.3g of azobisisobutyronitrile at 80℃ for 6 hours.

[0095] Extract the copper bonding agent from Examples 1-5 and Comparative Example 1 above, and test its copper surface micro-etching amount (um) and post-bonding peel strength (lb / inch) according to the above measurement steps. The test results are recorded in the table below.

[0096] Table: Performance test results of Examples 1-5 and Comparative Example 1

[0097]

[0098] Extract the copper bonding agent from Examples 1-5 and Comparative Example 1 above, and test the electrical signal loss (%) at different lengths and frequencies according to the above measurement steps. The test results are recorded in the table below.

[0099]

[0100]

[0101] From the table above and Figure 1 As can be seen, the copper bonding agents prepared in Examples 1-5 achieved bonding under conditions without copper surface etching, with a copper surface micro-etching amount of 0 μm, and a peel strength of 1.35-1.39 lb / inch after bonding, which are all improved to varying degrees compared with Comparative Example 1 and the control group.

[0102] Furthermore, the data on electrical signal loss in the table above also shows that the copper surface treated with the copper bonding agent obtained in Examples 1-5 can effectively meet the transmission requirements of high-frequency signals, as detailed below:

[0103] 1) When the test line length is 2 inches, the electrical signal loss at 4G is only -1.002 to -1.058%, the electrical signal loss at 8G is only -1.924 to -2.052%, and the electrical signal loss at 12.89G is -4.172 to -4.514%.

[0104] 2) When the test cable length is 5 inches, the signal loss at 4G is only -2.123 to -2.209%, at 8G it is only -4.072 to -4.343%, and at 12.89G it is -6.617 to -7.076%. The losses at 4G and 8G are less than 5% and can be ignored.

[0105] 3) When the test line length is 10 inches, the electrical signal loss at 4G is only -3.801 to -4.071%, the electrical signal loss at 8G is only -6.971 to -7.542%, and the electrical signal loss at 12.89G is -11.843 to -12.752%.

[0106] In summary, the data shows that when the test length is 2 inches and 5 inches, the line loss for 4G and 8G is relatively small. Only the 10-inch test line has a higher loss at a higher frequency (12.89G), but this frequency is not currently used in applications and is only used here for comparison of over-limit performance.

[0107] The line loss rate of 4G and 8G signals on the copper surface treated with the copper bonding agent in this application is reduced by about 50% compared with Comparative Example 1, the micro-etching control group and the medium roughening control group. The difference is more obvious as the line is longer and the frequency is higher. It can be seen that the copper bonding agent in this application has great advantages in 5G signal transmission and is conducive to reducing the conductor loss caused by the skin effect.

[0108] The reasons are as follows: The copper bonding compound in this application, through its unique bifunctional molecular design, forms stable chemical bonds with the copper surface and the dry film respectively, thereby significantly enhancing the bonding force between the copper surface and the dry film while maintaining the smoothness of the copper surface, thus ensuring its application conditions.

[0109] Therefore, compared with traditional copper surface treatment methods, the low electrical loss copper bonding compound in this application significantly reduces signal attenuation and improves the electrical performance of the PCB by optimizing the bonding method between the copper surface and the dry film, i.e., non-etching bonding. Moreover, the overall process is more environmentally friendly and pollution-free, which not only reduces the negative impact on the environment, but also reduces production costs and does not produce copper loss.

[0110] Furthermore, as can be seen from Examples 1-5, the preferred composition is the following components in weight percentages: 0.1-0.5‰ low electrical loss copper bonding compound, 3-5‰ coupling agent, 1-3‰ wetting agent, and deionized water as the balance. The use of coupling agent and wetting agent is beneficial to further improving performance.

[0111] In other embodiments, the coupling agent and wetting agent may be replaced with conventional components, which should not be regarded as a limitation of this application. As for the addition or deletion of other additives, if their performance can be reasonably expected based on the conventional understanding of those skilled in the art, they should also fall within the protection scope of this application.

[0112] This specific embodiment is merely an explanation of this application and is not intended to limit it. After reading this specification, those skilled in the art can make modifications to this embodiment without contributing any inventive step, but such modifications are protected by patent law as long as they fall within the scope of the claims of this application.

Claims

1. A compound for copper surface bonding with low electrical loss, characterized in that, The structure is as follows: Formula (I); That is, a polythiourea molecule with a nitrazole structure, wherein the degree of polymerization n takes the value of 3-10.

2. The method for preparing the low-electrical-loss copper-surface bonding compound as described in claim 1, characterized in that, Includes the following steps: S1. Dissolve 4H-1,2,4-triazol-3,4,5-triamine in dehydrated CHCl3 to obtain solution A for later use; Dissolve 1,1-thiocarbonyldiimidazole in dehydrated CHCl3 to obtain solution B for later use. S2. Add solution B dropwise to solution A in S1 and stir to react, to obtain a reaction solution. Control the feed ratio of 4H-1,2,4-triazole-3,4,5-triamine and 1,1-thiocarbonyldiimidazole to be (1-1.1):

1. S3. Wash the reaction solution obtained in S2 with saturated saline and deionized water to remove unreacted monomers and small molecule byproducts produced in the reaction, and then collect the organic phase. S4. First, dry the organic phase obtained in S3 with anhydrous sodium sulfate, then evaporate to dryness to remove the solvent, and finally dry the obtained solid to obtain the compound shown in formula (I). The reaction route for the above preparation steps is as follows: 。 3. The method for preparing the low-electrical-loss copper-surface bonding compound according to claim 2, characterized in that, The mass percentage concentrations of solutions A and B in S1 are as follows: The mass percentage concentration of 4H-1,2,4-triazol-3,4,5-triamine in solution A is 11-15%. The mass percentage concentration of 1,1-thiocarbonyldiimidazole in solution B is 9-14%.

4. The method for preparing the low-electrical-loss copper-surface bonding compound according to claim 2, characterized in that, The conditions for the stirring reaction in S2 are as follows: Stirring speed 2000-3000 r / min, reaction at room temperature for 24-36 h.

5. The method for preparing the low-electrical-loss copper-surface bonding compound according to claim 2, characterized in that, The specific steps and conditions for collecting the organic phase in S3 are as follows: First, pour the reaction solution obtained in S2 into saturated saline solution, shake well and let stand. Then pour out the lower organic phase and wash it three times with saturated saline solution. Then, the obtained organic phase is washed three more times with deionized water to complete the organic phase collection.

6. The use of the low electrical loss copper bonding compound as described in claim 1 in bonding copper surfaces and resin layers.

7. A copper-face bonding agent, characterized in that, Including the low electrical loss copper bonding compound as described in claim 1.

8. The copper bonding agent according to claim 7, characterized in that, The compound for copper bonding with low electrical loss as described in claim 1 comprises 0.1-0.5‰ by weight.

9. The copper bonding agent according to claim 8, characterized in that, It consists of the following components in weight per thousand: 0.1-0.5‰ low electrical loss copper bonding compound, 0-5‰ coupling agent, 0-3‰ wetting agent, and deionized water as the balance.

10. The copper bonding agent according to claim 9, characterized in that, It consists of the following components in weight per thousand: 0.1-0.5‰ low electrical loss copper bonding compound, 3-5‰ coupling agent, 1-3‰ wetting agent, and deionized water as the balance.

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