Flexible circuit manufacturing Additive

Furthermore, the overall properties of the base materials for circuit boards are determined essentially by the joint between the copper foil and the laminate. This joint can be realized by both an added adhesive and by the laminating resin itself, which additionally, acts as adhesive. An additional adhesive is needed in the manufacture of flexible circuit boards (e.g., polyimide/copper) or of paper-based rigid circuit boards. During this process the adhesive is deposited on the bottom side of the copper foil after... 

Historically, copper-clad laminates with acrylic or epoxy adhesives have been the major materials for flexible circuits. Each manufacturer has developed a special resin grade or special additives to ensure reliable flexibility and bond strength. Other adhesive materials such as phenol resin or silicon resin have been developed however, they have not become standard adhesive materials in flexible circuits. 

High-density flexible circuits, which have been developed since the mid-1990s, have special constructions and therefore require supplemental processes. In addition, high-grade manufacturing technologies are required to generate finer circuits. Sometimes, they are called HDI... 

Furthermore, ultra high-density flexible circuits have been considered recently as the necessary substrate materials for the next generation electronics packaging. Their circuit densities will be under 20 micron pitches with 20 micron diameter via holes. They need completely new manufacturing technologies, such as an additive process instead of traditional subtractive process. Ultra high-density flexible circuits will be considered separately. 

A thick-film circuit is a type of additive manufacturing process. If an organic resin matrix is used, the conductor can be flexible, and this process has been applied in flexible circuits. 

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