Smooth-surface Tg140 lead-free PP bonding sheet and preparation process thereof

Abstract

The application discloses a kind of surface smooth Tg140 leadless PP bonding sheet and its preparation process, belong to copper-clad plate technical field.The surface smooth Tg140 leadless PP bonding sheet preparation raw material includes: brominated epoxy resin 30-50 parts, bisphenol A type epoxy resin 10-30 parts, multi-block copolymer 5-12 parts, benzocyclobutene resin 10-15 parts, phenolic resin 35-60 parts, composite filler 15-25 parts, thickening agent 0.5-1.5 parts, and paper base material or glass fiber cloth;Multi-block copolymer is ethylene-polybutadiene-glycidyl methacrylate-epoxy resin block copolymer.The application not only can significantly reduce the thermal expansion coefficient of the prepared bonding sheet, while avoiding its use performance reduction, also can keep surface smooth, using the bonding sheet can prepare green environmental protection, heat resistance is strong, high strength, low thermal expansion coefficient high-performance copper-clad plate.

Description

Technical Field

[0001] This invention belongs to the field of copper clad laminate technology, specifically relating to a smooth Tg140 lead-free PP adhesive sheet and its preparation process. Background Technology

[0002] Printed Circuit Boards (PCBs) are hailed as the mother of electronic products. They are key components in computers, mobile phones, and other electronic devices, serving as a bridge connecting various electronic components and circuits. They are widely used in numerous fields, including medical instruments, aerospace, new energy, automotive electronics, defense, communication terminals, and industrial control. With the rapid development of electronics and electrical appliances, PCBs are increasingly evolving towards smaller, more multifunctional, and more environmentally friendly designs, which undoubtedly places higher demands on the production and performance of copper-clad laminates (CCLs).

[0003] Copper clad laminate (CCL) is the core material for PCB manufacturing, responsible for the PCB's conductivity, insulation, and support functions. CCL is made by impregnating wood pulp paper or fiberglass cloth with resin to form a prepreg (PP). Several PP sheets are then combined, with copper foil applied to one or both sides, and cured under heat and pressure to form a sheet-like material. As a upstream product in the CCL production process, PP largely determines the overall performance of the CCL. Due to the requirement for harmless PCB manufacturing, only lead-free solder is permitted. This necessitates a soldering temperature approximately 20-30°C higher than that using lead-containing solder. Furthermore, this requires PP to have a lower coefficient of thermal expansion at higher temperatures to ensure the reliability and stability of the board.

[0004] To address the aforementioned issues and reduce the coefficient of thermal expansion, the industry typically employs methods such as increasing the amount of reinforcing materials like glass fiber, reducing the amount of resin, and incorporating fillers. These methods are all based on reducing the amount of raw materials with a high coefficient of thermal expansion and increasing the amount of raw materials with a low coefficient of thermal expansion. However, as a key raw material for PP, increasing the amount of glass fiber reduces electrical insulation, and increasing the amount of filler leads to roughness in the PP, thus affecting the subsequent lamination of PCBs. Therefore, further in-depth research is needed on the selection of PP raw materials and their amounts. Summary of the Invention

[0005] To address the problems mentioned in the background art, the present invention aims to provide a smooth Tg140 lead-free PP adhesive sheet and its preparation process. The present invention employs epoxy resin, phenolic resin, and other materials to construct a special primary curing system. Based on this special curing system, combined with special fillers and additives, it can not only significantly reduce the coefficient of thermal expansion of the prepared adhesive sheet, but also avoid the reduction in its performance, while maintaining a smooth surface. Through combined pressing, a high-performance copper-clad laminate can be obtained.

[0006] To achieve the above objectives, the present invention specifically adopts the following technical solution:

[0007] This invention provides a smooth, Tg140 lead-free PP adhesive sheet, comprising the following raw materials by weight:

[0008] 30-50 parts of brominated epoxy resin

[0009] 10-30 parts of bisphenol A type epoxy resin

[0010] 5-12 parts of multi-block copolymer

[0011] 10-15 parts of benzocyclobutene resin

[0012] 35-60 parts of phenolic resin

[0013] 15-25 parts of composite filler

[0014] Thickener 0.5-1.5 parts,

[0015] And paper-based materials or fiberglass cloth;

[0016] The multi-block copolymer is an ethylene-polybutadiene-glycidyl methacrylate-epoxy resin block copolymer.

[0017] Preferably, the preparation method of the ethylene-polybutadiene-glycidyl methacrylate-epoxy resin block copolymer is as follows: butadiene is subjected to free radical polymerization under the conditions of initiator and catalyst, ethylene is added and polymerization is continued to obtain ethylene-polybutadiene block copolymer; glycidyl methacrylate is added to the ethylene-polybutadiene block copolymer for graft polymerization, and finally epoxy resin is added for blending to obtain ethylene-polybutadiene-glycidyl methacrylate-epoxy resin multi-component block copolymer.

[0018] Preferably, the raw materials for preparing the ethylene-polybutadiene-glycidyl methacrylate-epoxy resin multi-block copolymer are, by weight, 24-30 parts of ethylene, 100 parts of butadiene, 2-6 parts of glycidyl methacrylate, and 25-32 parts of epoxy resin.

[0019] Preferably, the initiator is benzoyl peroxide, the catalyst is dibutyltin dilaurate, and the epoxy resin is bisphenol A type epoxy resin.

[0020] Preferably, the composite filler is composed of aluminum hydroxide, silicon carbide, polyimide microspheres, and tin selenide.

[0021] As a preferred option, the mass ratio of aluminum hydroxide, silicon carbide, polyimide microspheres, and tin selenide in the composite filler is 10:(5-7):(0.2-0.6):(1-1.5).

[0022] Preferably, the thickener is a polyurea thickener.

[0023] This invention also provides a method for preparing the above-mentioned smooth Tg140 lead-free PP adhesive sheet, comprising the following steps:

[0024] Step 1: Weigh out each ingredient according to the formula and set aside;

[0025] Step 2: Take a portion of the composite filler and add brominated epoxy resin, bisphenol A type epoxy resin, benzocyclobutene resin and thickener in sequence. Shear at high speed at 55-65℃. Then add the remaining composite filler, multi-component block copolymer and phenolic resin to the resulting mixture and maintain constant temperature for 8-12 h to obtain resin solution.

[0026] Step 3: Impregnate the paper substrate or fiberglass cloth in the above resin solution and dry to obtain lead-free PP adhesive sheet.

[0027] Preferably, before adding the composite filler to the resin in step two, an accelerator and a diluent should be added and mixed evenly; the composite filler is aluminum hydroxide and silicon carbide, and the remaining composite filler is polyimide microspheres and tin selenide.

[0028] Preferably, the lead-free PP adhesive sheet obtained in step three has a resin content of 50%-55%.

[0029] Tg refers to the temperature at which a board material transforms into a rubber-like elastic deformation state during heating, that is, the temperature required for it to change from a solid to a molten state, i.e., the glass transition temperature. Tg is a key indicator for measuring the heat resistance of PP, and it indirectly affects the mechanical, electrical, and chemical properties of PCB materials. High-Tg bonding sheets have excellent comprehensive performance to meet the needs of high-end fields, but their preparation requires the use of higher-grade resin raw materials, which significantly increases the raw material and process costs, resulting in low cost-effectiveness. Therefore, this invention uses conventional resins as raw materials to prepare an improved Tg140-grade bonding sheet. This invention uses brominated epoxy resin as the main resin. Brominated epoxy resin has excellent heat resistance, electrical insulation, and adhesion. Combining it with phenolic resin to construct the main curing system can maintain the basic viscosity of the adhesive and the basic strength and heat resistance of the bonding sheet. To meet the requirements of higher processing temperatures and lower coefficients of thermal expansion for lead-free solders, this invention adds appropriate amounts of bisphenol A type epoxy resin and benzocyclobutene resin in combination with brominated epoxy resin. Simultaneously, an ethylene-polybutadiene-glycidyl methacrylate-epoxy resin multi-block copolymer is prepared, which can coordinate the interactions between the mixed resin systems, further improving the system's heat resistance and strength to meet the processing requirements of lead-free solders. Furthermore, this invention uses aluminum hydroxide, silicon carbide, polyimide microspheres, and tin selenide as a composite filler. Aluminum hydroxide and silicon carbide can reduce the coefficient of thermal expansion of the adhesive, while polyimide microspheres and tin selenide not only further improve the thermal stability of the adhesive but also, in conjunction with the polyurea thickener selected in this invention, promote full compatibility between the composite filler and the mixed resin system. This allows the resin adhesive to effectively coat the composite filler while maintaining good flowability, thereby preparing a smooth-surfaced PP adhesive sheet.

[0030] Compared with the prior art, the beneficial effects of the present invention are:

[0031] This invention overcomes the shortcomings of existing conventional copper-clad laminates, which cannot meet the performance requirements of current PCB development due to their insufficient performance. It adopts a multi-resin synergistic construction of the main curing system, combined with a special filler combination and thickener, while optimizing the raw material dosage and preparation process. This not only significantly reduces the thermal expansion coefficient of the bonded sheet, but also avoids the reduction of its performance and maintains a smooth surface. Using this bonded sheet, high-performance copper-clad laminates with green environmental protection, high heat resistance, high strength and low thermal expansion coefficient can be prepared. Attached Figure Description

[0032] Figure 1 The appearance of the PP adhesive sheet sample prepared in Example 1 of the present invention.

[0033] Figure 2 The appearance of the PP adhesive sheet sample prepared in Example 2 of the present invention.

[0034] Figure 3The appearance of the PP adhesive sheet sample prepared in Example 3 of the present invention.

[0035] Figure 4 The appearance of the PP adhesive sheet sample prepared in Comparative Example 1 of this invention.

[0036] Figure 5 The appearance of the PP adhesive sheet sample prepared in Comparative Example 2 of this invention.

[0037] Figure 6 The appearance of the PP adhesive sheet sample prepared in Comparative Example 3 of this invention. Detailed Implementation

[0038] To make the objectives, technical solutions, and advantages of this invention clearer, the technical solutions of this invention will be clearly and completely described below in conjunction with embodiments. Where specific conditions are not specified in the embodiments, conventional conditions or conditions recommended by the manufacturer shall apply. Reagents or instruments whose manufacturers are not specified are all conventional products that can be purchased commercially.

[0039] 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. The terminology used in this specification is for the purpose of describing particular embodiments only and is not intended to limit the invention. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0040] The raw materials used in this invention are: brominated epoxy resin NPEB-400; bisphenol A type epoxy resin NPEL-128; phenolic resin 2123; polyurea thickener Anjeka 4410A; and 7628 glass fiber cloth (thickness 0.173 mm, unit area mass 204.4 g / m²). 2 ).

[0041] Example 1

[0042] 1. At 70℃, 100 parts of butadiene were dissolved in 120 parts of tetrahydrofuran, and 0.8 parts of benzoyl peroxide and 0.5 parts of dibutyltin dilaurate were added. The polymerization reaction was carried out for 2 hours. While maintaining a constant temperature, 28 parts of ethylene were added and the polymerization reaction was carried out for 2.5 hours to obtain an ethylene-polybutadiene block copolymer. At 80℃, 4 parts of glycidyl methacrylate were added to the obtained ethylene-polybutadiene block copolymer and grafted for 2 hours. Then, 30 parts of bisphenol A epoxy resin were added and blended. After cooling, the reaction product was washed and dried to obtain an ethylene-polybutadiene-glycidyl methacrylate-epoxy resin multi-block copolymer.

[0043] 2. Weigh out 40 parts by weight of brominated epoxy resin, 20 parts by weight of bisphenol A type epoxy resin, 10 parts by weight of the above-mentioned multi-component block copolymer, 12 parts by weight of benzocyclobutene resin, 50 parts by weight of phenolic resin, 20 parts by weight of composite filler (composed of aluminum hydroxide, silicon carbide, polyimide microspheres, and tin selenide in a mass ratio of 10:6:0.4:1.4), and 1 part by weight of polyurea thickener.

[0044] 3. Take 0.5 parts of 2-methylimidazole, 1.5 parts of DMF, and mix with the above-mentioned aluminum hydroxide, silicon carbide, brominated epoxy resin, bisphenol A type epoxy resin, benzocyclobutene resin, and polyurea thickener. Shear at 60°C and 500 rpm for 15 min. Add polyimide microspheres, tin selenide, multi-component block copolymer, and phenolic resin to the resulting mixture. Maintain constant temperature and cure for 10 h to obtain a resin solution. Impregnate glass fiber cloth in the obtained resin solution and dry to obtain a lead-free PP adhesive sheet with a resin content of 52%. The PP adhesive sheet prepared in this example has the following appearance: Figure 1 As shown, its surface is smooth.

[0045] Example 2

[0046] 1. At 70℃, 100 parts of butadiene were dissolved in 120 parts of tetrahydrofuran, and 0.8 parts of benzoyl peroxide and 0.5 parts of dibutyltin dilaurate were added. The polymerization reaction was carried out for 2 hours. While maintaining a constant temperature, 24 parts of ethylene were added and the polymerization reaction was carried out for 2.5 hours to obtain an ethylene-polybutadiene block copolymer. At 80℃, 2 parts of glycidyl methacrylate were added to the obtained ethylene-polybutadiene block copolymer and grafted for 2 hours. Then, 25 parts of bisphenol A epoxy resin were added and blended. After cooling, the reaction product was washed and dried to obtain an ethylene-polybutadiene-glycidyl methacrylate-epoxy resin multi-block copolymer.

[0047] 2. Weigh out 30 parts by weight of brominated epoxy resin, 30 parts by weight of bisphenol A type epoxy resin, 5 parts by weight of the above-mentioned multi-component block copolymer, 10 parts by weight of benzocyclobutene resin, 45 parts by weight of phenolic resin, 15 parts by weight of composite filler (composed of aluminum hydroxide, silicon carbide, polyimide microspheres, and tin selenide in a mass ratio of 10:6:0.4:1.4), and 0.8 parts by weight of polyurea thickener.

[0048] 3. Take 0.5 parts of 2-methylimidazole, 1.5 parts of DMF, and mix them with the above-mentioned aluminum hydroxide, silicon carbide, brominated epoxy resin, bisphenol A type epoxy resin, benzocyclobutene resin, and polyurea thickener. Shear the mixture at 60°C and 500 rpm for 15 min. Add polyimide microspheres, tin selenide, multi-block copolymer, and phenolic resin to the resulting mixture. Maintain a constant temperature and allow it to mature for 10 h to obtain a resin solution. Impregnate glass fiber cloth in the obtained resin solution and dry it to obtain a lead-free PP adhesive sheet with a resin content of 53%. The PP adhesive sheet prepared in this example has the following appearance: Figure 2 As shown, its surface is smooth.

[0049] Example 3

[0050] 1. At 70℃, 100 parts of butadiene were dissolved in 120 parts of tetrahydrofuran, and 0.8 parts of benzoyl peroxide and 0.5 parts of dibutyltin dilaurate were added. The polymerization reaction was carried out for 2 hours. While maintaining a constant temperature, 30 parts of ethylene were added and the polymerization reaction was carried out for 2.5 hours to obtain an ethylene-polybutadiene block copolymer. At 80℃, 6 parts of glycidyl methacrylate were added to the obtained ethylene-polybutadiene block copolymer and grafted for 2 hours. Then, 32 parts of bisphenol A epoxy resin were added and blended. After cooling, the reaction product was washed and dried to obtain an ethylene-polybutadiene-glycidyl methacrylate-epoxy resin multi-block copolymer.

[0051] 2. Weigh out 50 parts by weight of brominated epoxy resin, 10 parts of bisphenol A type epoxy resin, 12 parts of the above-mentioned multi-component block copolymer, 15 parts of benzocyclobutene resin, 50 parts of phenolic resin, 25 parts of composite filler (composed of aluminum hydroxide, silicon carbide, polyimide microspheres, and tin selenide in a mass ratio of 10:6:0.6:1), and 1 part of polyurea thickener.

[0052] 3. Take 0.5 parts of 2-methylimidazole, 1.5 parts of DMF, and mix with the above-mentioned aluminum hydroxide, silicon carbide, brominated epoxy resin, bisphenol A type epoxy resin, benzocyclobutene resin, and polyurea thickener. Shear at 60°C and 500 rpm for 15 min. Add polyimide microspheres, tin selenide, multi-component block copolymer, and phenolic resin to the resulting mixture. Maintain constant temperature and cure for 10 h to obtain a resin solution. Impregnate glass fiber cloth in the obtained resin solution and dry to obtain a lead-free PP adhesive sheet with a resin content of 52%. The PP adhesive sheet prepared in this example has the following appearance: Figure 3 As shown, its surface is smooth.

[0053] Comparative Example 1

[0054] Referring to the steps and parameters of Example 1, the difference is that the block copolymer prepared below is used instead of the ethylene-polybutadiene-glycidyl methacrylate-epoxy resin multi-block copolymer.

[0055] Specifically: at 70°C, 100 parts of butadiene were dissolved in 120 parts of tetrahydrofuran, and 0.8 parts of benzoyl peroxide and 0.5 parts of dibutyltin dilaurate were added for polymerization reaction for 2 hours. While maintaining a constant temperature, 28 parts of ethylene were added for polymerization reaction for 2.5 hours to obtain ethylene-polybutadiene block copolymer. At 80°C, 30 parts of bisphenol A type epoxy resin were added to the obtained ethylene-polybutadiene block copolymer for blending. After cooling, the reaction product was washed and dried to obtain ethylene-polybutadiene-epoxy resin block copolymer.

[0056] The PP adhesive sheet prepared in this comparative example has the following appearance: Figure 4 As shown, its surface is rough.

[0057] Comparative Example 2

[0058] The procedure parameters are the same as in Example 1, except that the following packing composition is used instead of the composite packing.

[0059] That is, aluminum hydroxide, silicon carbide, and hollow vitrified microspheres are combined in a mass ratio of 10:6:1.8 to form a filler composition. Step 3 is adjusted as follows: 0.5 parts of 2-methylimidazole, 1.5 parts of DMF, the filler composition, brominated epoxy resin, bisphenol A type epoxy resin, benzocyclobutene resin, and polyurea thickener are mixed and sheared at 60°C and 500 rpm for 15 min. Multi-component block copolymer and phenolic resin are added to the resulting mixture, and the mixture is kept at a constant temperature for 10 h to obtain a resin solution. Glass fiber cloth is impregnated in the obtained resin solution and dried to obtain a lead-free PP adhesive sheet with a resin content of 52%.

[0060] The PP adhesive sheet prepared in this comparative example has the following appearance: Figure 5 As shown, its surface is rough.

[0061] Comparative Example 3

[0062] Referring to the steps and parameters in Example 1, the difference lies in adjusting the amount of raw materials as follows:

[0063] 40 parts brominated epoxy resin, 20 parts bisphenol A type epoxy resin, 10 parts multi-component block copolymer, 12 parts benzocyclobutene resin, 50 parts phenolic resin, 30 parts composite filler (composed of aluminum hydroxide, silicon carbide, polyimide microspheres, and tin selenide in a mass ratio of 10:6:0.4:1.4), and 0.1 parts polyurea thickener.

[0064] The PP adhesive sheet prepared in this comparative example has the following appearance: Figure 6 As shown, its surface is rough.

[0065] Test case

[0066] Copper-clad laminates (CPs) were prepared by laminating the bonding sheet samples obtained in Examples 1-3 and Comparative Examples 1-3 (6 PP sheets and 2 copper foil sheets were laminated to form a 1.4 mm thick CP). Performance was tested (IPC-TM-650). The results are shown in the table below:

[0067] Table 1

[0068]

[0069] In summary, the adhesive system of this invention exhibits good fluidity, resulting in a smooth surface on the PP adhesive sheet. The copper-clad laminate prepared by laminating the PP adhesive sheet produced by this invention exhibits excellent heat resistance, high strength, and a very low coefficient of thermal expansion, meeting the current performance requirements for copper-clad laminate development.

[0070] The embodiments described above are merely preferred embodiments of the present invention, and while the descriptions are specific and detailed, they are not intended to limit the present invention. It should be noted that various changes and modifications can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the concept and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A smooth-surfaced, Tg140 lead-free PP adhesive sheet, characterized in that, The following raw materials are included by weight: 30-50 parts of brominated epoxy resin 10-30 parts of bisphenol A type epoxy resin 5-12 parts of multi-block copolymer 10-15 parts of benzocyclobutene resin 35-60 parts of phenolic resin 15-25 parts of composite filler Thickener 0.5-1.5 parts, And paper-based materials or fiberglass cloth; The multi-block copolymer is an ethylene-polybutadiene-glycidyl methacrylate-epoxy resin block copolymer; the composite filler is composed of aluminum hydroxide, silicon carbide, polyimide microspheres and tin selenide, and the mass ratio of aluminum hydroxide, silicon carbide, polyimide microspheres and tin selenide in the composite filler is 10:(5-7):(0.2-0.6):(1-1.5).

2. The smooth-surfaced, Tg140 lead-free PP adhesive sheet according to claim 1, characterized in that, The preparation method of the ethylene-polybutadiene-glycidyl methacrylate-epoxy resin block copolymer is as follows: butadiene is subjected to free radical polymerization under the conditions of initiator and catalyst, ethylene is added and polymerization is continued to obtain ethylene-polybutadiene block copolymer; glycidyl methacrylate is added to the ethylene-polybutadiene block copolymer for graft polymerization, and finally epoxy resin is added for blending to obtain ethylene-polybutadiene-glycidyl methacrylate-epoxy resin multi-block copolymer.

3. The smooth-surfaced Tg140 lead-free PP adhesive sheet according to claim 2, characterized in that, The raw materials for preparing the ethylene-polybutadiene-glycidyl methacrylate-epoxy resin multi-block copolymer are, by weight, 24-30 parts of ethylene, 100 parts of butadiene, 2-6 parts of glycidyl methacrylate, and 25-32 parts of epoxy resin.

4. The smooth-surfaced Tg140 lead-free PP adhesive sheet according to claim 2, characterized in that, The initiator is benzoyl peroxide, the catalyst is dibutyltin dilaurate, and the epoxy resin is bisphenol A type epoxy resin.

5. The smooth-surfaced, Tg140 lead-free PP adhesive sheet according to claim 1, characterized in that, The thickener is a polyurea thickener.

6. The method for preparing a smooth Tg140 lead-free PP adhesive sheet as described in any one of claims 1-5, characterized in that, Includes the following steps: Step 1: Weigh out each ingredient according to the formula and set aside; Step 2: Take a portion of the composite filler and add brominated epoxy resin, bisphenol A type epoxy resin, benzocyclobutene resin and thickener in sequence. Shear at high speed at 55-65℃. Then add the remaining composite filler, multi-block copolymer and phenolic resin to the resulting mixture and maintain constant temperature for 8-12 hours to obtain resin solution. Step 3: Impregnate the paper substrate or fiberglass cloth in the above resin solution and dry to obtain lead-free PP adhesive sheet.

7. The method for preparing a smooth Tg140 lead-free PP adhesive sheet according to claim 6, characterized in that, The lead-free PP adhesive sheet obtained in step three has a resin content of 50%-55%.

8. The application of the surface-smooth Tg140 lead-free PP adhesive sheet as described in any one of claims 1-5 in the preparation of copper-clad laminates.

Images