Characteristics of O-cresol Novolac epoxy resin

O-cresol Novolac epoxy resin is a multifunctional glycidyl ether type epoxy resin developed abroad in the 1970s to adapt to the rapid development of the semiconductor and electronic industries. Its molecular structure formula is as follows:

From the molecular structure, it can be seen that each benzene ring is connected to an epoxy group. Compared with bisphenol A-type epoxy resin with a softening point in the range of 70-80 ℃ (epoxy value of 0.2eq/100g), the epoxy value of ortho formaldehyde epoxy resin is as high as 0.5 eq/100g or more. When the resin is cured, it can provide 2.5 times the number of crosslinking points, making it easy to form a three-dimensional structure with high crosslinking density. In addition, the cured product is rich in phenolic skeleton, exhibiting excellent thermal stability, mechanical strength, electrical insulation performance, water resistance, and high glass transition temperature (Tg) of chemical resistance, as shown in the table. Electronic components encapsulated with high-purity resin can maintain their good electrical insulation performance even in harsh environments such as high temperature, humidity, and humidity. Another significant feature of this resin is that when the softening point changes, the epoxy value remains basically unchanged, and the melt viscosity is quite low, endowing the resin with excellent process stability and processability. Therefore, it is widely used as the main adhesive material for packaging materials such as LSI, VLSI integrated circuits, electronic components, and civilian weak current products (VTR, OP) in the semiconductor industry.

But the resin is brittle after curing and has been improved in the past 10 years through visionary modification. For example, using modified high-efficiency fillers, encapsulated toughening fillers, or adding rubber particles (such as CTBN, ATBN, organosilicon, etc.) to form a "sea island" structure to toughen and reduce thermal stress and thermal expansion index. In recent years, in order to further improve heat resistance, hydroxyl containing polydimethylsiloxane has been introduced into the molecular structure of ortho formaldehyde epoxy resin, which can increase the curing product's TG to 80-100 ℃, while reducing water absorption, improving corrosion resistance, and reducing internal stress.