The four major performance indicators of prepreg are: resin content, soluble resin content, volatile matter content, and fluidity.

1.Effect of resin content on electromechanical property

The dielectric properties of laminates increase with the increase in resin content. When the resin content is increased to a certain value, the resin content will not increase below 60%. When the resin content increases, the electrical performance will increase. When it reaches 60%, the resin content will increase and the electrical performance will increase. The improvement is not obvious. The resin content also affects the mechanical and physical properties of epoxy boards. The mechanical properties of epoxy laminates increase as the resin content increases, but the optimal value of mechanical strength appears when a certain value is reached, and then increases with the resin content Instead, the mechanical strength decreases. When the resin content is less than 35%, the mechanical properties are reduced, and it is considered that the adhesion is not good; when the resin content is more than 35%, as the resin content increases, the effect of the resin is prominent, and the strength of the resin is lower than that of the reinforcing material. many. For example, the tensile strength of phenolic resin is only 35 ~ 50MPa, and the epoxy resin is 65 ~ 80MPa; the impact strength is lower, such as epoxy resin is 10 ~ 20kJ / m2; the mechanical strength of reinforcing materials is very high, such as electrical Glass fiber single yarn has a tensile strength of 50MPa.

The resin content also has a greater effect on the water absorption and relative density of the laminate. As the resin content increases, the voids of the reinforcing material in the laminate are filled by the resin. Water absorption of phenolic resin is 0.12% ~ 0.36%, and epoxy resin is 0.10%. The water absorption of the laminate decreases with the increase of the resin content, but when the resin fills all the voids of the fiber material, the water absorption reaches a constant value and does not decrease any more. The relative density of the laminate decreases with increasing resin content, which is determined by the relative density of the resin. For example, the relative density of phenolic resin is 1.30 ~ 1.32, and the relative density of epoxy resin is 1.15. Epoxy laminate is a composite of resin and reinforcing material, so its performance is related to the ratio of the two. Generally, the resin content of the prepreg required for laminates that require electrical properties is larger; the resin content is required to be smaller for those that require high mechanical properties. Generally, the glass cloth laminate is controlled at about 40%, because Flow glue and volatiles overflow

2.Effect of soluble resin content on performance

The soluble resin content refers to the mass fraction of the resin that can be dissolved in the solvent in the prepreg. If the content of the soluble resin is large, the prepreg is relatively tender. If the content of the soluble resin is small, the pre-dip stain is old. The soluble resin content is large, the resin fluidity is large, the penetration ability is strong, and the adhesiveness is excellent, but the glue is easy to flow during pressing, if the pressing is too fast, it is easy to cause the stack and steel plate to slip out from the hot plate of the press The pressing time should be increased accordingly. At the same time, the pressure should be moderately released during the preheating stage (open the hot plate) to ensure that the volatiles overflow. The soluble resin content is small, the adhesion is not good, the mechanical strength is severely reduced, and the laminate is cracked between layers.

3.Effect of volatile content on the property of laminates

The volatile content of prepreg refers to the mass ratio of volatile substances, such as water, solvents, and low molecular substances, remaining in the prepreg to the prepreg. The volatile content has a significant effect on the electrical properties of the laminate. The volatiles content increased from 4% to 5%, and its tan6 doubled. Its dielectric strength and internal resistance both decreased due to the large volatiles. Not only that, but also makes the thermal deformation temperature of the laminate lower, which causes defects such as blistering, cracking and surface pattern of the laminate. Therefore, the pressure should be lowered during preheating, and the temperature will rise a little faster, so that its volatiles will easily overflow, and the pressure will be gradually increased during the hot pressing stage

Therefore, the prepreg should be stored in a constant temperature, humidity and dust-free warehouse.

4. As for the fluidity, it is similar to the soluble resin content, but because the test method is more intuitive, it has a guiding effect on the pressing process, and the effect on product performance is similar to the soluble resin content.