Toughening Modification Of Cyanate Ester Resins For Electronic Packaging

Cyanate ester (CE) resins possessed many excellent properties such as heat-resistance, high glass transition temperature, low dielectric constant and dielectric loss, low water absorption and good dimensional stability because of the existence of large amounts of highly cross-linked triazine and aromatic rings. CE resin is a type of ideal materials for the packaging of electronic devices, however, its high brittleness, ascribed to the rigid structure and the highly regularity of the network, limits its applications in the area of electronic packaging under the condition of high alternating load and high frequency. So, the resin needs to be modified to reduce its brittleness and improve the toughness.In this paper, polyether glycol, amine-terminated polyether and hydroxyl-terminated polyurethane prepolymer with flexible segments are used to modify the bisphenol-A dicyanate resin (BADCy). Differential scanning calorimetry (DSC) and MATLAB software are used to investigate the curing behavior of modified system; Fourier-Transform infrared spectroscopy (FT-IR) is utilized to track the process of curing reaction. The curing mechanism of the modified system is analyzed; the curing conditions are determined; the cured modified resins are prepared; the mechanical property, dielectric property and moisture absorption rate are measured. The toughening mechanism of modified system was discussed. The thermal decomposition prosess of the cured modified system is tracking tested by Simultaneous Thermal Analyzer (STA) and FT-IR. The specific research contents and the results obtained are as follows:1. Polyethylene glycol (PEG600) and polypropylene oxide glycol (DL1000) were used to modify the BACDy resin. Results showed that the addition of modifiers significantly reduced the curing temperature of the modified systems compared with that of pure BACDy. The curing reaction process of modified systems experienced two stages:chemical reaction kinetics controlled stage and diffusion dynamics controlled stage. The appearance of-O-C(=NH)-O- structure in the curing process indicated that the modifier participated the curing reaction. The mechanical properties including flexural strength, tensile strength and Fracture toughness index(Kic and GIC) of the cured modified resin were increased, indicating improvement of the toughness for cured modified system. With increasing content of the modifiers, the glass transition temperatures and the dielectric properties decreased while the water absorption rates increased. The present of modifier reduced the initial thermal decomposition temperature of modified resins which course of thermal decomposition experienced 3 stages.2. Amine-terminated polyether (DA2000) and Amine-terminated polyether (TA5000) were used to modify the BACDy resin. Compared with that of pure BACDy, the addition of DA2000 distinctly reduced the curing temperature of the modified systems, but it also lowered the heat release and the maximum curing reaction rate. The curing process of the modified system was successively controlled by chemical reaction and diffusion. The structure of-O-C(=NH)-NH-was detected by FT-IR in the curing process, indicating the participation for modifiers to the formation of curing network structures. The mechanical properties such as flexural strength, tensile strength and Fracture toughness index (Kic and GIC) of the cured modified resin were increased, showing that the toughness for modified resins was enhanced. With increasing content of the modifiers, the glass transition temperatures and dielectric properties of cured modified resins were declined and its water absorption rates increased. The properties including he glass transition temperatures, dielectric and water absorption of cured TA5000 system were better than those of cured DA2000 system. The original thermal decomposition temperature of the modified cured resins was decreased for addition of modifiers. The thermal decomposition of the cured modified resin can be divided into 2 stages.3. Hydroxyl-terminated polyurethane prepolymer (PUDL) were used to modify the BACDy resin. Results indicated that the addition of PUDL reduced the curing temperature of the modified systems, while the heat release and the maximum curing reaction rate declined. The curing process of the modified system was successively controlled by chemical reaction and diffusion. The structure of -O-C(=NH)-O-was found in the curing process, indicating that the PUDL took part in the curing reaction. The bending strength, tensle strength and Fracture toughness index (Kic and GIC) of the cured modified resin were increased, demonstrating the toughness of the cured resins was improved. With increasing content of the modifiers, the glass transition temperatures and dielectric properties declined and the water absorption rates increased. The modifiers degraded the initial thermal decomposition of the modified cured resins and the thermal decomposition of the cured modified resin included 2 stages.4. Among the above three kinds of modifiers, amine-terminated polyether showed the best modification effect. The modified system containg TA5000 possessed the optimal properties which was suitable to be used as toughness-high temperature resistant materials in electronic packaging field. Both the cured resins respectively containing 10% modifier and 20% modifier showed outstanding properties and fracture toughness, the glass transition temperature of the both cured resins were more than 230?; The dielectric constant annd the dielectric loss were respectively inferior to 2.82 and 0.00475 when the frequency was 160MHz; the water absorption rate was lower to 2.05%.