The halogen-free copper clad laminate prepared by using the phenoloxazine resin having a broad molecular weight release and the modified phenol resin having a high nitrogen content has good heat resistance (Td5%>350° C., T288>60 min), moisture absorption heat resistance, and Good bending strength; the toughness of the board is good, and the crack is less when the panel is sheared.
Key words: broad molecular weight released benzoxazine resin, high nitrogen content modified phenolic resin, copper clad laminate performance
I. Introduction
Two EU directives have promoted the development of a halogen-free, lead-free CCL market with good heat resistance, CAF resistance and low dielectric loss tangent, especially from benzoxazine resin systems. The halogen-clad copper plate is popular among users because of its good moisture absorption and heat resistance. However, regardless of the halogen-free copper clad laminate, the halogen-free copper clad laminate prepared therefrom is relatively brittle and difficult to process and drill due to the structural rigidity of the resin material used and the addition of the inorganic filler. The purpose of this paper is to develop a high-toughness halogen-free copper-clad laminate, which can improve the toughness of the copper-clad laminate while fully maintaining the advantages of good heat resistance, CAF resistance and low dielectric loss tangent of the halogen-free copper-clad laminate. Overcome the brittleness, so that it has better processing properties.
Second, development ideas
Benzooxazine is a novel phenolic resin which is widely used in the preparation of halogen-free copper-clad laminates due to its abundant nitrogen content and excellent performance of cured products cured with other materials. In this study, we used a broad molecular weight distribution of benzoxazine resin. The resin can make the glue have better sizing and pressing process; the second is to make the cured product of the glue have a more perfect cross-linked network structure, thereby obtaining a copper clad board with better comprehensive performance. The phenolic resin acts as a curing agent, so that the copper clad laminate is greatly improved in heat resistance and reaches the lead-free requirement. We make full use of the advantages of phenolic resin as a curing agent and modify it into a nitrogenous phenolic resin with a higher nitrogen content. Thus, while maintaining good heat resistance of the copper clad laminate, flame retardancy is also increased, and the addition of the inorganic filler is reduced, and a copper clad laminate having good workability and toughness is obtained.
Third, the experimental process
Raw material: benzoxazine resin, trade name: WL-0910, Huashuo Technology Co., Ltd. (Hubei Chemical Research Institute) produces nitrogen-containing phenolic resin, trade name: WL-0812, Huashuo Technology Co., Ltd. (Hubei Province) Chemical Research Institute) Production of benzoxazine resin, nitrogen-containing phenolic resin, epoxy resin, surface-treated inorganic filler, curing accelerator and solvent into a container according to a certain ratio, stirring until evenly mixed, sizing 7628 type glass The cloth is clothed, baked and a certain number of bonded sheets and copper foils are pressed and formed at a certain temperature and gradually heated, and finally heat-treated at a temperature of 190 ° C for 90 minutes, and then cooled and tested.
Fourth, the results and discussion
1. Glue water glue, pressing process
1.1 glue water glue process
The above-mentioned glued water-based glue 7628 fiberglass cloth has good wettability to the fiberglass cloth; after baking at 150 ° C for 5 minutes, the surface of the prepreg is smooth without powder. 1118-1343-2047-8194-3937-3220
1.2 Rheological curve of semi-cured resin
Figure 1 is a rheological graph of a resin removed from a prepreg. It can be seen from Fig. 1 that the glue has a wide processing window and good viscosity after baking, indicating that the glue will have a better pressing process and leveling property after baking.
1.3 Post-treatment conditions for pressing into a board
A certain amount of the bonding sheets are stacked and covered with copper foil on both sides, and after pressing and forming at a certain temperature, the temperature is gradually increased, and finally heat-treated at a temperature of 190 ° C for 1.5 hours, and then the plate is cooled. There is no dry flower or resin shortage on the subsurface of the laminate, and the comprehensive performance of the copper clad laminate is better (Table 1), indicating that the resin system has mild post-treatment conditions.
2. CCL performance
2.1 PCT test
The copper-clad plate after etching copper is cut into a small piece of a certain size and placed in a pressure cooker. After cooking at 105 kPa, 121 ° C, and 180 min, the PCT (tin bath 288 ° C) is tested, and the time is less than 5 min. Layered, showing good water-resistant cooking performance of CCL.
2.2 Thermal weight loss analysis
The copper-clad copper plate has been subjected to a small weight loss test (TGA analysis). The test results show that the weight loss temperature of 5% wt is 371 ° C, and the surface of the copper plate has good heat resistance, which can achieve lead-free requirements.
2.3 bending strength and toughness
The halogen-free copper-clad laminate is generally brittle due to the rigid structure of the nitrogen-containing and phosphorus-containing resin and the addition of the filler, and is susceptible to cracking during the processing of the printed circuit. We indirectly observed the toughness of the plate by shearing the plate and testing its bending strength. We found that when the 1.6 mm plate was sheared, the edge of the plate was almost crack-free; the bending strength test was 608 MPa, 613 MPa, and 532 MPa in the transverse direction. 525MPa, its bending strength value is large. From the shear crack and bending strength values, it can indirectly reflect that the copper clad laminate has better toughness.
2.4 alkali resistance
After the plate was placed in a 10% NaOH solution at 80 ° C for 1 hour, the plate was excellent in appearance, no delamination, no blistering, and no obvious change in appearance. Table 1, part of the performance of copper clad laminate
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