1.1 The role of PCB The function of PCB is to provide a base for completing the first-level assembly of components and other necessary electronic circuit parts to form a module or finished product with specific functions. Therefore, in the entire electronic product, the PCB plays the role of integrating and connecting all the functions of the assembly. Therefore, the PCB is often the first to be questioned when the electronic product malfunctions. 1.2 The evolution of PCB 1. As early as 1903, Mr. Albert Hanson pioneered the use of the concept of 'circuit' (Circuit) to be applied to the telephone switch system. It is cut into circuit conductors with metal foil and glued to paraffin paper , and a layer of paraffin paper is also pasted on it, which has become the prototype of the current PCB mechanism. 2. To 1936, Dr Paul Eisner really invented the PCB manufacturing technology and also issued a number of patents . Today's print-etch (photoimage transfer) technology follows its invention . 1.3 PCB types and manufacturing methods diversification in materials, levels, and manufacturing processes to suit different electronic products and their special needs. The following summarizes some common differences, to briefly introduce the classification of PCB and its manufacturing method. 1.3.1 PCB type A. Classified by material a. Organic material Phenolic resin, glass fiber/epoxy resin, Polyimide, BT/Epoxy, etc. are all included. B. Inorganic materials aluminum, Copper-invar-copper, ceramic, etc. are all of them. Mainly take its heat dissipation function B. Differentiate between soft and hard finished products Board D. Divided by purpose: communication/consumable electronics/military/computer/semiconductor/electrical test board... BGA. There is another kind of injection molded three-dimensional PCB, which is not introduced here because of less use.