Multibenzocyclobutene Functionalized Silane for Low-k Polyarylsilane Thermosets with Low Coefficient of Thermal Expansion and High Thermostability

Abstract

Highly cross-linked thermosets have been extensively studied for their good thermostability and low coefficient of thermal expansion (CTE). Herein, multibenzocyclobutene (multi-BCB) functionalized silane monomers and the related thermosets as polyarylsilane are reported. These silane monomers can be cured at a high temperature above 200 °C. After curing, the corresponding transparent thermosets showed good thermal property. The results indicated that more benzocyclobutene (BCB) groups on the corresponding silane monomer induced a higher cross-linked structure, which contributes to improve heat resistance, glass transition temperature (T g), and dimensional stability. Particularly, the cured tetra­(benzocyclobutene-4-yl) silane (SiB4) showed extremely high T g over 400 °C, high initial storage modulus, and good thermostability (T d5 = 532 °C). The cured SiB4 also showed excellent thermomechanical properties with a low CTE at 24 ppm/°C. These polymers also showed good dielectric properties with a low k below 2.70. The low-k material with a low CTE may be a good candidate for high-performance composite resin matrix and high-density substrates.

Di(bicyclo[4.2.0]octa-1(6),2,4-trien-3-yl)dimethylsilane

“…The resulting monomer diBCB-DMS is polymerized when heated above 200 • C. It is known that the mechanism of polymerization of benzocyclobutene derivatives is multivariable [2,4,6,7,10]. Benzocyclobutene fragments in thermo-induced o-xylylene form can react with active double bonds.…”

“…Recently, a direction has been developed associated with the use of multi-benzocyclobutene functionalized silane and siloxane monomers, which provide more dense crosslinking, high thermal stability, and low coefficient of thermal expansion. In particular, polymers are known based on tri-(benzocyclobuten-4-yl) phenylsilane and tetra-(benzocyclobuten-4-yl)silane [7] or their siloxane analogs [6]. However, it is a surprise that there are no data about the synthesis or physical and chemical properties of a simpler analogue, namely di(bicyclo[4.2.0]octa-1(6),2,4-trien-3-yl)dimethylsilane.…”

Phosphorus-Containing Flame-Retardant Benzocyclobutylene Composites with High Thermal Stability and Low CTE

“…Small molecules will not be produced during the curing process, which will not affect the process and the internal structure of the resin. At the same time, due to the highly cross-linked structure after curing, − the cured resin usually has good thermal stability and good dimensional stability . Meanwhile, the benzene ring contained in the BCB monomer is a rigid structure, which can provide certain mechanical properties to the resin and has a certain elastic modulus and hardness.…”

Facile Strategy for Preparing a Rosin-Based Low-k Material: Molecular Design of Free Volume

“…Since the advent of integrated circuits (ICs) in the 1960s, IC components have been developing toward miniaturization, which can cause interconnection signal delay (RC delay), power dissipation, and crosstalk noise. − The Semiconductor Industry Association believes that in order to take this challenge, the development of high-performance low- k ( k < 2.5) and ultra-low k ( k < 1.9) materials is urgently necessary. , Benzocyclobutene (BCB) resins, an important class of low- k materials, have attracted much attention for many years. BCB polymers exhibit high thermostability, good mechanical properties, and a low dielectric constant. − Therefore, benzocyclobutene polymers have been widely used in electronic and microelectronic industries. − “Cyclotene” (DVS-BCB) developed by DOW Chemical Company has been successfully commercialized and utilized in microelectronics. , With the continuous miniaturization of ICs components, the k value of DVS-BCB resin (2.65) cannot meet the performance requirements. ,,, Theoretically, two main strategies are usually used to decrease the k value of materials: (1) decreasing the polarizability by introducing low polarity bonds such as C–H, C–C, C–Si, and so on, and (2) introducing pores to decrease the density of materials. , In particular, the introduction of pores can reduce the k value of materials below 2.0 because the k value of air is approximately 1. ,, However, excessive pores can decrease the mechanical properties and water resistance of materials, thereby, increasing the k value. ,, It is significant to develop a new system to decrease the k value and ensure the material with good hydrophobicity and mechanical properties. Notably, the k value of materials can be reduced by introducing bulky groups into the polymer, such as aromatic ring, adamantane, polyhedral oligomeric silsesquioxane (POSS), and so on. − This is because introducing bulky groups can increase the free volume of polymers that weakens the polar interaction between molecular chains, reducing the dielectric constant. ,, Free volume is essentially different from the porous structure, which is a subnanometer-scale space.…”