Copper surface bonding compound with low electric loss and preparation method and application thereof

Abstract

The invention relates to the technical field of printed circuit board processing, in particular to a low-electric-loss compound for copper surface bonding and a preparation method and application of the low-electric-loss compound for copper surface bonding, the structural formula of the compound is as follows: # imgabs0 # is a polythiourea molecule with an azole structure, and the value of the polymerization degree n is 3-10. Benefited from the special structure (C = S and-NH2) of the compound, the bonding under the condition of no copper surface corrosion is effectively realized, and the smooth copper surface meets the transmission requirement of high-frequency signals.

Description

Technical Field

[0001] This application relates to the technical field of PCB copper surface treatment. More specifically, it relates to a copper surface bonding compound with low electrical loss, its preparation method and application. Background Art

[0002] As a basic component of electronic devices, the importance of the performance, quality and processing technology of PCB is becoming increasingly prominent. The current PCB copper surface treatment methods mainly include chemical methods: super roughening, medium roughening; or physical methods: grinding and brushing, sandblasting. However, they generally have the disadvantages of high cost and complex processes.

[0003] In the related art, in order to overcome the above disadvantages, a copper surface bonding agent is provided for replacement. Thanks to its many advantages, it has become the mainstream technology in the PCB manufacturing field. It significantly improves the adhesion between the copper surface and the resin layer and maintains stability by being compatible with chemical micro-etching and chemical bonding. However, in recent years, with the popularization and commercial implementation of 5G technology, the demand for lossless transmission of high-frequency signals during transmission has become higher and higher. Therefore, it can be concluded that the existing PCB pretreatment process is limited by the etching of its copper surface and can no longer meet the transmission requirements of high-frequency signals. In addition, from the analysis of the actual performance use, the rougher the copper surface, the more eddy current signals will be formed on the copper surface layer when the current flows on the copper surface, resulting in greater signal attenuation. Therefore, there is an urgent need to provide a copper surface bonding compound with low electrical loss, its preparation method and application. Summary of the Invention

[0004] To ensure the quality of the copper surface after using the copper surface bonding agent and make it meet the transmission requirements of high-frequency signals, this application specifically provides a copper surface bonding agent that does not etch copper and has low electrical loss, as well as its preparation method.

[0005] In the first aspect, this application provides a copper surface bonding compound with low electrical loss, adopting the following technical solution: A copper surface bonding compound with low electrical loss has the following structural formula: That is, a polythiourea molecule with a triazole structure, where the degree of polymerization n ranges from 3 to 10.

[0006] In the second aspect, this application provides a preparation method of a copper surface bonding compound with low electrical loss, adopting the following technical solution: A preparation method of a copper surface bonding compound with low electrical loss includes the following steps: S1. Dissolve 4H-1,2,4-triazole-3,4,5-triamine in CHCl without water 3 to obtain solution A for standby; Dissolve 1,1 - thiocarbonyl diimidazole in dehydrated CHCl 3 to obtain solution B for later use; S2. Dropwise add solution B to solution A in S1 and stir for reaction to obtain a reaction solution. Control the feeding ratio of 4H - 1,2,4 - triazole - 3,4,5 - triamine and 1,1 - thiocarbonyl diimidazole to be (1 - 1.1):1; S3. Wash the reaction solution obtained in S2 with saturated brine and deionized water by liquid - liquid separation to remove unreacted monomers and small - molecule by - products generated during the reaction, and then collect the organic phase; S4. First, dry the organic phase obtained in S3 with anhydrous sodium sulfate, then rotary evaporate to dryness to remove the solvent, and finally dry the obtained solid to obtain the compound shown in formula (I); The reaction route of the above - mentioned preparation steps is as follows:

[0007] Preferably, the mass percentage concentrations of solution A and solution B in S1 are as follows: The mass percentage concentration of 4H - 1,2,4 - triazole - 3,4,5 - triamine in solution A is 11 - 15%; The mass percentage concentration of 1,1 - thiocarbonyl diimidazole in solution B is 9 - 14%.

[0008] Preferably, the conditions for the stirring reaction in S2 are: The stirring speed is 2000 - 3000 r / min, and the reaction is carried out at room temperature for 24 - 36 h.

[0009] Preferably, 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 brine, shake well and let it stand, then pour out the lower - layer organic phase, and repeat the washing with saturated brine three times; Then, wash the obtained organic phase with deionized water three times to complete the collection of the organic phase.

[0010] In the third aspect, the present application provides an application of the copper - surface bonding compound with low electrical loss and / or the compound prepared by any of the above - mentioned methods in bonding a copper surface and a resin layer.

[0011] In the fourth aspect, the present application provides a copper - surface bonding agent, adopting the following technical solution: A copper - surface bonding agent includes the copper - surface bonding compound with low electrical loss and / or the compound prepared by any of the above - mentioned methods.

[0012] Preferably, it includes 0.1 - 0.5‰ of the copper - surface bonding compound with low electrical loss and / or the compound prepared by any of the above - mentioned methods.

[0013] Preferably, the copper surface bonding agent is composed of components in the following parts per thousand by weight: 0.1-0.5‰ of a copper surface bonding compound with low electrical loss, 0-5‰ of a coupling agent, 0-3‰ of a wetting agent, and the balance being deionized water.

[0014] Preferably, the copper surface bonding agent is composed of components in the following parts per thousand by weight: 0.1-0.5‰ of a copper surface bonding compound with low electrical loss, 3-5‰ of a coupling agent, 1-3‰ of a wetting agent, and the balance being deionized water.

[0015] In summary, the present application has the following beneficial effects: 1. The unique bifunctional molecular design of the copper surface bonding compound with low electrical loss in the present application realizes stable chemical bonding between the two functional groups and the copper surface and the dry film respectively, significantly enhancing the bonding force between the copper surface and the dry film while keeping the copper surface smooth, and ensuring its use conditions. 2. Compared with the traditional copper surface treatment method, the copper surface bonding compound with low electrical loss in the present application has an overall environmentally friendly process and no copper ions in the wastewater, which not only reduces the negative impact on the environment, but also reduces the production cost, does not cause copper loss, and improves the production efficiency. 3. Thanks to the use of the copper surface bonding compound with low electrical loss and its adaptation to high-frequency and high-speed signal transmission, the copper surface bonding agent in the present application significantly reduces signal attenuation and improves the electrical performance of the PCB by optimizing the bonding force between the copper surface and the dry film. 4. The process operation design of the copper surface bonding agent in the present application takes into account the compatibility with the existing PCB manufacturing process, enabling it to be easily applied to the existing production line without major modifications to the equipment. At the same time, its operation process is relatively simple, reducing the operation difficulty and error rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 is a schematic diagram of the bonding connection between the copper surface bonding agent, the substrate, and the dry film in Example 1 of the present application; Figure 2 is the infrared spectrum of the copper surface bonding compound of the present application. DETAILED DESCRIPTION OF THE EMBODIMENTS The following is a further detailed description of the present application in conjunction with Figure 1-2 and examples.

[0018] Preparation Example 1 A copper surface bonding compound with low electrical loss has the following structural formula: That is, a polythiourea molecule with an azole structure, where the degree of polymerization n ranges from 3 to 10; And it is prepared by the following preparation steps: S1. Dissolve 4H-1,2,4-triazole-3,4,5-triamine in dehydrated CHCl 3 to obtain solution A with a mass percentage concentration of 11% for standby; Dissolve 1,1-thiocarbonyl diimidazole in dehydrated CHCl 3 to obtain solution B with a mass percentage concentration of 9% for standby; S2. Dropwise add solution B to solution A in S1 and stir for reaction. Stir at a speed of 2000 r / min and react at room temperature for 36 h to obtain a reaction solution. Control the feeding ratio of 4H-1,2,4-triazole-3,4,5-triamine to 1,1-thiocarbonyl diimidazole to be 1.05:1; S3. Wash the reaction solution obtained in S2 with saturated brine and deionized water by liquid separation to remove unreacted monomers and small molecule by-products generated during the reaction, and then collect the organic phase; The specific steps and conditions for collecting the organic phase are as follows: First, pour the reaction solution obtained in S2 into saturated brine, shake well and let it stand, then pour out the lower organic phase, and repeat the washing with saturated brine three times; Then, continue to wash the obtained organic phase with deionized water three times to complete the collection of the organic phase; S4. First, dry the organic phase obtained in S3 with anhydrous sodium sulfate, then rotary evaporate to dryness to remove the solvent, and finally dry the obtained solid at 60 °C for 24 h to obtain the compound shown in formula (I), with a purity of 90.5%, a yield of 93.2%, and the corresponding infrared spectrum as Figure 2 shown.

[0019] The reaction route of the above preparation steps is as follows: Select the copper surface bonding agent prepared in each example and comparative example as the detection object for standby, and then carry out bonding and circuit processing according to the following usage method; Sample conditions: Plate type: IT 968G of ITEQ Electronics Co., Ltd. (base copper 18 μm), dry film type: YQ40MP of Asahi Kasei Corporation; Processing process: A1) Pickling: Remove the copper surface oxide with a sulfuric acid solution with a sulfuric acid mass content of 3% at room temperature (25 °C ± 1 °C) for 30 s; A2) Water washing: Wash with deionized water for 20 s; A3) Treatment with the copper surface bonding agent prepared in the examples and comparative examples: Form an organic bonding film on the copper surface by spraying, with a treatment temperature of 28 °C and a treatment time of 40 s; A4) Water washing: Wash with deionized water for 20 s; A5) Pickling: Remove the copper surface oxide using a sulfuric acid solution with a sulfuric acid mass content of 3% at room temperature (25°C ± 1°C) for 10 s; A6) Water washing: Wash with deionized water for 10 s to 20 s; A7) Drying: The drying temperature is 85°C and the drying time is 30 s; A8) Film attachment: Use the Hongshengxiang CSL-M25E full-automatic film laminating machine to attach the Asahi Kasei Corporation YQ40MP dry film at a pressure of 4 kg, a temperature of 105°C, and a film laminating speed of 1.4 m / min; A9) Exposure: Use the Orbotech Xpress-9i full-automatic LDI exposure machine to attach the film negative in a Class 10,000 clean workshop environment with a temperature of 25°C and a humidity of 50%. Adjust the vacuum degree to 0.08 MPa, the distance from the exposure light source to the board surface to 15 cm, and the exposure energy to 100 mJ / cm 2 , and the time to 6 s; A10) Development: Develop using a sodium carbonate aqueous solution with a mass percentage concentration of 1% at 28°C for 1 minute, and then wash twice with water and enter the next etching process; A11) Etching: Spray and vacuum etch the copper in a mixed aqueous solution of 370 g / L copper dichloride dihydrate & 2.0 Mol / L hydrochloric acid at 50°C for 3 minutes, then wash twice with water and enter the next film removal process; A12) Film removal: Remove the film in a sodium hydroxide aqueous solution with a mass percentage concentration of 4% at 52°C for 2 min, wash twice with water and then blow dry to obtain the final circuit board.

[0020] Blank group The processing flow is the same as above, where the copper surface bonding agent is replaced by an equal amount of water as the blank control group.

[0021] Micro-etching control group The processing flow is the same as above, where the copper surface bonding agent is replaced by an equal amount of micro-etching solution (80 g / L sodium persulfate, 20 g / L sulfuric acid, and the solvent is water) as the micro-etching control group.

[0022] Medium roughening control group The processing flow is the same as above, where the copper surface bonding agent is replaced by an equal amount of medium roughening solution as the micro-etching control group. The components of the medium roughening solution are: 20 g / L hydrogen peroxide, 20 g / L ME-358 (Shenzhen Songbai Science and Industry) medium roughening micro-etching solution, and the solvent is pure water.

[0023] Then, respectively test the copper surface micro-etching amount, peel strength after bonding, and electrical signal loss amount of each example group, comparative example group, and control group. The test samples and detection steps at each stage are as follows: Copper surface micro-etching amount 1) Weigh the IT 968G (base copper 18um) of Lianmao Electronics Co., Ltd. in advance and calculate it as G1; 2) Then take out the plate treated by the above steps A1-A7, place it in an oven at 105±5℃ and dry it for 15 minutes, cool it to room temperature in a dryer, weigh it on a balance, and calculate it as G2; 3) Measure the area S of the test board (the sum of the areas of both sides, unit: cm2); Calculation: Micro-etching amount (um) = [(G1-G2) / 8.96×S]×10000.

[0024] Peel strength after bonding Take out the plate after the above-mentioned A1-A10 process, and then select the tensile testing machine suitable for testing the peel strength equipment accuracy requirements between the PCB dry film coating and the substrate according to the standard "PC-TM-650 2.4.8". The test steps and methods are as follows: fix the extracted plate on the test device, clamp the peeling end with a clamp, start the tensile testing machine, and stretch the test strip vertically upward at a speed of 50.8mm / min to record the minimum load (N / cm) during the peeling process. Randomly select 10 points for the test and take the average value of the results.

[0025] Electrical signal loss % Use a German vector network analyzer to test the panels treated with A1-A12, and test the insertion loss in Delta IL3.0 mode (the test line is designed as three groups of differential lines of different lengths and the same impedance. The lengths of the test lines are 2 inches, 5 inches, and 10 inches respectively, and the frequencies are 4G, 8G, and 12.89G respectively. Example

[0026] Examples 1-5 A copper surface bonding agent, wherein each component and its corresponding weight per 1 kg are shown in the following table, and is prepared by dispersing and mixing at normal temperature and pressure conditions; The compound for copper surface bonding was prepared by 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.

[0027] Table: Components and weights of copper surface bonding agents in Examples 1-5 (g) Comparative Example 1 A copper surface bonding agent, which is different from Example 1 in that its copper surface bonding compound is replaced by an equal amount of a nitrogen-containing heterocyclic copolymer, and the nitrogen-containing heterocyclic copolymer is prepared by the following process: It is obtained by blending 60 g of 4-methyl-5-vinylthiazole, 30 g of 2-hydroxyethyl acrylate, 10 g of acrylamide, 300 g of absolute ethanol and 0.3 g of azobisisobutyronitrile at 80 °C and reacting for 6 hours.

[0028] Extract the copper surface bonding agents in Examples 1-5 and Comparative Example 1 above, and test their copper surface micro-etching amount (μm) and peel strength after bonding (lb / inch) according to the above measurement steps. The test results are recorded in the following table.

[0029] Table: Performance test results of Examples 1-5 and Comparative Example 1 Extract the copper surface bonding agents in Examples 1-5 and Comparative Example 1 above, and test their electrical signal loss amounts (%) at different lengths and frequencies according to the above measurement steps. The test results are recorded in the following table.

[0030] As can be seen from the above table and Figure 1 it can be seen that the copper surface bonding agents prepared in Examples 1-5 achieved bonding under the condition of no copper surface etching, the copper surface micro-etching amount was 0 μm, and the peel strength after bonding was 1.35 - 1.39 lb / inch, showing varying degrees of improvement compared to Comparative Example 1 and the control group; In addition, from the electrical signal loss amount data in the above table, it can also be known that the copper surface treated with the copper surface bonding agents obtained in Examples 1-5 can effectively meet the transmission requirements of high-frequency signals, specifically as follows: 1) When the test line length is 2 inches, the electrical signal loss amount at 4G is only -1.002 to -1.058%, the electrical signal loss amount at 8G is only -1.924 to -2.052%, and the electrical signal loss amount at 12.89G is -4.172 to -4.514%; 2) When the test line length is 5 inches, the electrical signal loss amount at 4G is only -2.123 to -2.209%, the electrical signal loss amount at 8G is only -4.072 to -4.343%, and the electrical signal loss amount at 12.89G is -6.617 to -7.076%. The loss below 5% at 4G and 8G can be ignored; 3) When the test line length is 10 inches, the electrical signal loss amount at 4G is only -3.801 to -4.071%, the electrical signal loss amount at 8G is only -6.971 to -7.542%, and the electrical signal loss amount at 12.89G is -11.843 to -12.752%; In summary, it can be seen from the above data that when the test lengths are 2 inches and 5 inches, the line losses of both 4G and 8G are relatively small. Only the 10-inch test line has a relatively high line loss at a relatively high frequency (12.89G), but this frequency is not basically involved in the current applications and is only used for comparison of over-limit performance here. The comprehensive calculation of the line loss rates of the 4G and 8G signals on the copper surface treated with the copper surface bonding agent in this application is about 50% lower than that of Comparative Example 1, the micro-etching control group, and the medium roughening control group. Moreover, the longer the line and the higher the frequency, the more obvious the difference. It can be seen that the copper surface bonding agent in this application has great advantages in 5G signal transmission and is beneficial to reducing the conductor loss caused by the skin effect.

[0031] The reasons are analyzed as follows: In the copper surface bonding compound in this application, through its unique bifunctional molecular design, it forms stable chemical bonds with the copper surface and the dry film respectively, achieving the simultaneous maintenance of the smoothness of the copper surface and the significant enhancement of the bonding force between the copper surface and the dry film, thus ensuring its application conditions. Therefore, compared with the traditional copper surface treatment methods, the copper surface bonding compound with low electrical loss 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, that is, non-etching bonding. Moreover, the overall process is environmentally friendly and pollution-free, which not only reduces the negative impact on the environment but also lowers the production cost and does not cause copper loss.

[0032] In addition, from Examples 1-5, it can also be seen that it is preferably composed of the following components in parts per thousand by weight: 0.1-0.5‰ of the copper surface bonding compound with low electrical loss, 3-5‰ of the coupling agent, 1-3‰ of the wetting agent, and the balance being deionized water. Moreover, the use of the coupling agent and the wetting agent is beneficial to further improving the performance. In other embodiments, the coupling agent and the wetting agent can also be replaced with conventional components, which should not be regarded as a limitation to this application. As for adding or deleting other additives, if their performance can be reasonably expected according to the conventional knowledge of those skilled in the art, it should also fall within the protection scope of this application.

[0033] This specific embodiment is only an explanation of this application and does not limit this application. Those skilled in the art can make modifications without creative contributions to this embodiment after reading this specification, but as long as they are within the scope of the claims of this application, they are protected by the patent law.

Claims

1. A low electrical loss copper surface bonding compound, characterized in that: The structural formula is as follows: That is, a polythiourea molecule with an azole structure, wherein the degree of polymerization n is 3-10.

2. The method for preparing the compound for copper surface bonding with low electrical loss as claimed in claim 1, characterized in that: The following steps are involved: S1. Dissolve 4H-1,2,4-triazole-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, adding solution B to solution A in S1 and stirring to react to obtain a reaction solution, wherein the feed ratio of 4H-1,2,4-triazole-3,4,5-triamine and 1,1-thiocarbonyldiimidazole is controlled to be (1-1.1):1; S3, washing the reaction solution obtained in S2 with saturated saline and deionized water, removing unreacted monomers and small molecular by-products produced by the reaction, and collecting the organic phase; S4, first drying the organic phase obtained in S3 with anhydrous sodium sulfate, then rotary evaporating to dryness to remove the solvent, and finally drying the obtained solid to obtain the compound represented by formula (I); The reaction scheme of the above-mentioned preparation steps is as follows:

3. The method for preparing a compound for copper surface bonding with low electrical loss according to claim 2, characterized in that: The mass percentage concentrations of solution A and solution B in S1 are as follows: The mass percentage concentration of 4H-1,2,4-triazole-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 a compound for copper surface bonding with low electrical loss according to claim 2, characterized in that: The conditions for the stirring reaction in S2 are: The stirring speed is 2000-3000r / min and the reaction is carried out at room temperature for 24-36h.

5. The method for preparing a compound for copper surface bonding with low electrical loss 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, shake well and let stand, then pour out the lower organic phase, and repeat washing with saturated saline three times; Then, the obtained organic phase was continuously washed with deionized water for three times, and the collection of the organic phase was completed.

6. Use of the low-electrical-loss copper surface bonding compound described in claim 1 and / or the compound prepared by any of the methods described in claims 2 to 5 in bonding a copper surface and a resin layer.

7. A copper surface bonding agent, characterized in that: The invention comprises the copper surface bonding compound with low electric loss as claimed in claim 1 and / or the compound prepared by any one of the methods of claims 2-5.

8. The copper surface bonding agent according to claim 7, characterized in that: Calculated by weight percentage, it includes 0.1-0.5‰ of the copper surface bonding compound with low electrical loss described in claim 1 and / or the compound prepared by any method in claims 2-5.

9. The copper surface bonding agent according to claim 8, characterized in that: The invention is composed of the following components in thousandths by weight: 0.1-0.5‰ of a copper surface bonding compound with low electric loss, 0-5‰ of a coupling agent, 0-3‰ of a wetting agent, and the balance is deionized water.

10. The copper surface bonding agent according to claim 9, characterized in that: The invention is composed of the following components in thousandths by weight: 0.1-0.5‰ of a copper surface bonding compound with low electric loss, 3-5‰ of a coupling agent, 1-3‰ of a wetting agent, and the balance is deionized water.

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