What is the raw material of PCB (printed circuit board)? We know there is something called "glass", this kind of material in our daily life. Obviously, such as core fireproof cloth, fireproof felt is glass fiber, glass fiber and resin is easy to combine, we put into the tree structure of glass fiber cloth and high strength grease, hardening has heat insulation PCB, not easy to bend the substrate -- if the PCB board is broken, white edge delamination, enough to prove that the material is glass fiber resin.
Mainly based on two reasons: one is the uniform copper foil can have very uniform temperature coefficient of resistance, low dielectric constant, which can make the signal transmission loss is smaller, and the capacitance of different capacitance requirements of high dielectric constant, so as to accommodate higher capacity in a finite volume, why is aluminum capacitor capacitance is smaller, after all is a high dielectric constant! Second, the thin copper foil through the high current temperature rise is small, which for heat dissipation and component life is very good, digital integrated circuit copper wire width is better than 0.3cm, this is also the truth. The finished product plate PCB well is very uniform, soft luster (because the brush on the surface of the solder resist), the naked eye can see, but honestly look at the copper coated base plate can be seen or not many people really, unless you are experienced in the factory inspection.
We can't transmit electrical signals just as insulation plates, so we need to cover the surface with copper. So we call the PCB board a copper clad substrate. In the factory, the common copper substrate in this code is FR-4, each card manufacturers which in general there is no difference, so we can think of everyone at the same starting line, of course, if it is best to use high frequency board, copper clad PTFE glass cloth laminate high cost. The process of copper is very simple, generally can be made by rolling and electrolytic solution, the so-called rolling is Gao Chundu (>99.98%) of the copper rolling method on the PCB substrate, because the adhesive has excellent epoxy resin and copper foil, copper foil adhesive strength and high working temperature, can be no bubble dip in the molten tin is 260 DEG C in. This process is like rolling dumpling wrappers, but the dumpling wrappers are thin and thin. The thinnest is less than 1mil (industrial unit: mil, 1/1000 inches, equivalent to 0.0254mm)! If the dumpling wrappers are so thin, the pot must leak! The so-called electrolytic copper in junior high school chemistry has learned, CuSo4 electrolyte can continuously manufacture a layer of "copper foil", this is more easy to control the thickness, the longer the copper foil the more thick! Usually the factory has strict requirements on the thickness of copper foil, usually between 0.3mil and 3mil, and has a dedicated copper foil thickness tester to test its quality. Like old radios and amateur PCB, copper is especially heavy, and the quality of the factory is far worse than the computer board.
