PCB board commonly used raw material knowledge popular science

　　Pcb plate commonly used raw materials are mainly: substrate, copper foil, PP, photosensitive material, anti-welding paint and substrate, etc.

　　1. The substrate

　　In addition to some special uses will use ceramic materials as a substrate, organic insulation materials are usually used as a substrate.We know that pcb is both rigid and flexible, and the corresponding organic insulation materials can be divided into thermosetting resin and thermoplastic polyester.Commonly used thermosetting resin are phenolic resin and epoxy resin; commonly used thermoplastic polyester are polyimide and polytetrafluoroethylene.

　　2. Copper foil

　　Most of the metal foil covered on pcb is copper foil made by calendering or electrolytic method.Copper foil thickness is generally 0.3mil-3mil(0.25oz/ft2-2oz/ft2), and how to choose it should be determined according to the bearing current size and etching accuracy.Copper foil has an influence on the product quality, specifically manifested in the product surface dents and pits, anti-peeling strength, etc.

　　3.PP

　　The B-order resin for making multiple layers of pcb is an indispensable interlayer adhesive.

　　4. Photoreceptor materials

　　Generally divided into photoresist and photosensitive film, according to the words of the industry insiders, it is the wet film and dry film.The coating of the wet film on the copper-coated plate changes chemically at a certain wavelength of light, thus changing the solubility in the development solution (solvent).Wet film and light decomposition type (positive) and photic polymerization type (negative), photopolymeric resist can be dissolved in the developer before not exposure, and the polymer converted after exposure can not dissolve in the development fluid; the photodecomposition resist, the polymer can be dissolved in the development solution.Dry film also has the positive and negative characteristics, namely the difference between light decomposition type and light polymerization type, they are very sensitive to ultraviolet light.In the future, dry film is possible to replace wet film because they provide high precision lines and etching.

　　5. Anti-welding paint (ink)

　　A welding der, a common liquid photosensitive material with no affinity for liquid solder, changes and harden under specific light conditions.There are many kinds of ink colors, the most common resistance welding resistance color is green.

　　6. negatives (Philin)

　　Similar to the photographic lipid substrate, they are a material that uses photosensitive materials to record image data.Phililin's contrast, sensitivity and resolution are quite high, but requires a low speed.In order to meet the fine lines and dimensional stability, glass can be used as the bottom plate.

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