Know more about polyimide used in engineering plastics?

There are many classification methods for 6051 polyimide film special engineering plastics. This article only discusses the polyimide used as engineering plastics, and it is only classified according to the physical structure characteristics and chemical structure characteristics.

According to its physical properties, it can be divided into crystalline type and amorphous type. Most polyimides are amorphous, and only a few polyimides are crystalline and semi-crystalline. The crystalline form has an obvious melting point, relatively low melt viscosity and processability above the melting point, and is the preferred structure type for the development of thermoplastic polyimide. Because amorphous polyimide has no melting point, the melt viscosity above the glass transition temperature (Tg) is still high, and it is generally molded.

According to chemical properties, it can be conventionally divided into thermoplastic and thermosetting. Thermoplastic is like ordinary plastics that can be heated and melted, can be injected, extruded, molded, PI100 series, PI200 series, YS20 of Shanghai Resin Institute, P100 of Takasaki, etc. The thermosetting ones contain groups such as double bonds or acetylene groups, similar to unsaturated resins, epoxy resins and other materials, which require high temperature or heating to be cured and formed, such as bismaleimide (BMI), containing benzene Acetylene-terminated polyimides, etc., are mainly used in adhesives and composites.

Multilayer PCBs are constructed on flexible insulating substrates, and the finished product must be formable, not continuously flexible: such multilayer flexible PCBs are made of flexible insulating materials. Although it is made of soft materials, it is limited by electrical design such as thick conductors for the required conductor resistance, or between the signal and ground planes for the required impedance or capacitance insulating isolation, so it is already formed when the finished product is applied. The term "formable" is defined as a multi-layer flexible PCB component that has the ability to be formed into a desired shape and can no longer be flexed during application. Application in avionics unit internal wiring.

At this time, stripline or three-dimensional design conductors with low resistance, minimal capacitive coupling or circuit noise, and a smooth 90° bend at the interconnect ends are required. A multilayer flexible PCB made of polyimide film material achieves this routing task. Because polyimide films are high temperature resistant, flexible, and have good overall electrical and mechanical properties. In order to realize all the interconnections of this component section, the wiring part can be further divided into a plurality of multi-layer flexible circuit components and bonded together with adhesive tapes to form a printed circuit bundle.

A multi-layer PCB is formed on a flexible insulating substrate, and the finished product is not required to be flexed: this type of multi-layer flexible PCB is laminated with a soft insulating material, such as a polyimide film, into a multi-layer board. The inherent flexibility is lost after lamination. This type of flexible PCB is used when the design requires maximum use of the insulating properties of the film, such as low dielectric constant, uniform thickness dielectric, lighter weight, and continuous processing. For example, a multilayer PCB made with polyimide film insulation is about one-third lighter than a rigid epoxy glass cloth PCB.