Flexible PCB
:Introduction to Terminology
The world of flexible PCBs (FPCs) involves many specialized terms. This page provides explanations for commonly searched terms related to FPC materials and manufacturing processes, particularly helpful for those new to flexible PCBs.
Key Differences Between 2-Layer and 3-Layer FPCs
In 3-layer FPCs, an adhesive is used to bond the base film and copper foil of the copper-clad laminate. In contrast, 2-layer FPCs achieve this without using adhesive.
There are three primary bonding methods used in 2-layer FPCs: casting, lamination, and metallization.
Learn more about the differences
between 2-layer and 3-layer FPCs
What Is Etching?
Compared to cutting or grinding, etching allows for the removal of extremely fine layers, making it ideal for precision surface processing.
Learn more about the types and process of etching
What Is Coverlay?
A coverlay is a surface protection film or ink applied to Flexible PCBs to shield their circuitry. It not only shields the circuitry but also reinforces the structure of the FPC itself.
About Coverlay
FPC Copper Foils: Rolled, Electro-Deposited, and Plated
Flexible PCBs are designed to bend repeatedly or stay flexed during use, so the copper foil used must be both thin and flexible. Common copper types used in FPCs include rolled copper foil, electro-deposited copper foil, and plated copper foil.
Learn more about copper foils used in FPCs
Differences in FPC Manufacturing Methods: Subtractive vs. Additive
There are two main approaches to forming circuit patterns in FPC manufacturing. Major plating methods include electroplating and electroless plating. Various metals can be used in these processes.
Learn more about subtractive and additive methods
FPC Plating Methods, Including Electroplating
FPC Plating
FPC plating includes processes such as adding copper layers to the base, forming circuit traces, plating through holes, and surface finishes. Major plating methods include electroplating and electroless plating. Various metals can be used in these processes.
Learn more about plating techniques for FPCs
Substrate Materials Like Polyimide and Liquid Crystal Polymer
Flexible PCB substrates require flexibility, durability, heat resistance, dimensional stability, electrical insulation, and chemical resistance. To meet these demands, films like polyimide, liquid crystal polymer (LCP), and PET are commonly used.
Learn more about materials like polyimide and LCP used in FPCs
Differences in Mounting Methods: SMT vs. Through-Hole
Standard PCB mounting techniques include Surface Mount Technology (SMT), where components are soldered onto exposed copper lands, and Through-Hole Technology (THT), where components are inserted into plated holes and soldered. FPC mounting often requires an additional support board, which differs from rigid PCBs.
Learn more about SMT and THT mounting differences
What Is Pitch?
In PCB manufacturing, "pitch" refers to the distance between component leads or between conductor traces. When the spacing between traces and the trace width are each below 70μm, it is called "fine pitch."
