BT-Epoxy belongs to the group of thermoset resins used in printed circuit boards (PCBs). It is a mixture of epoxy resin, a common raw material for PCBs and BT resins. BT stands for Bismaleimide-Triazine resin. This is in turn a mixture of bismaleimide, which is also used as a raw material for PCBs and cyanate ester.

Bismaleimide resins are known for their high-strength and high-temperature performance. They are widely used as matrix resins for high-performance (fiber-reinforced) composites in electronic and aerospace industries. They also find applications as high performance adhesives.

Thermosetting bismaleimide (BMI) resins have been widely used as a matrix for advanced composites in aerospace and astronautics. BMI resins possess excellent thermal and oxidative stability, as well as electrical and mechanical properties and a relatively low propensity for moisture absorption.

Epoxy resins are classified as thermoset polymers that have unique characteristics when manufacturing, such as low pressure required to make products, very small cure shrinkage, and low residual stresses. For applications as matrices of composite materials, conventional difunctional epoxy is used.

Thermosetting resins use a chemical reaction to cure. There are three curing stages, which are called A, B, and C. A stage: The components of the resin (base material and hardener) have been mixed but the chemical reaction has not started.

All resins will absorb some moisture, adding to a laminate’s weight, but what is more significant is how the absorbed water affects the resin and resin/fibre bond in a laminate, leading to a gradual and long-term loss in mechanical properties.

epoxy, Any of a class of thermosetting polymers, polyethers built up from monomers with an ether group that takes the form of a three-membered epoxide ring. The familiar two-part epoxy adhesives consist of a resin with epoxide rings at the ends of its molecules and a curing agent containing amines or anhydrides.

Thermosetting resins describe a generic family of products that includes unsaturated polyesters, vinyl esters, epoxy, and polyurethane resins. The materials used with them are generally described as hardeners, curing agents, peroxide initiators, isocyanates, fillers, and flexibilizers.

The main characteristic of thermosets (literally setting under heat) is that they require curing, when they undergo a molecular cross-linking process which is irreversible and renders them infusible. They therefore offer high thermal stability, good rigidity and hardness, and resistance to creep.

ABF is a three- layer polymer system, with a polyethylene terephthalate (PET) support film, a resin layer, and a cover film. One can deposit copper on the thin to create interconnect traces. Ajinomoto has evolved its ABF to remove the halogens, lower the coefficient of thermal expansion, and allow for narrower vias.

Printed circuit boards (PCB) using Ajinomoto build-up films (ABF) as insulating layers are widely used as package sub- strates. Along with the increasing demand for downsizing electronic devices with advanced functions, package substrates are strongly required to be miniaturized with high-density circuit wirings.

Bismaleimides Bismaleimides are addition-type polyimides used in high-performance structural composites that require higher temperature use and increased toughness. Monomers are usually synthesized from maleic anhydride and an aromatic diamine and the bismaleamic acid formed is cyclo-dehydrated to a bismaleimide resin (Figure 13.6).

Using liquid molding processes such as RTM can also readily process bismaleimides. One potential usage problem with bismaleimides and any polymer containing the imide end-group is a phenomenon known as “imide corrosion.” This is a form of hydrolysis that results in degradation of the polymer itself.

They process similar to epoxies, by curing through addition reactions at 350 °F. To obtain their high-temperature properties, they are given free-standing post-cures at 450–475 °F to complete the polymerization reactions. BMI composites can be processed by autoclave curing, filament winding and resin transfer molding.

This type of thermosetting polyimide provides several unique characteristics such as excellent physical property retention at elevated temperatures and in wet environments, constant electrical properties over a vast array of temperature settings, and nonflammability properties as well.