The contemporary magic pen Ma Liang mentioned today is Paul Eisler, the father of PCB. He is an Austrian, PCB printed circuit board. Printed circuit board, also known as printed circuit board, is the support of important electronic components and electronic components, and the carrier of electrical connection of electronic components. Because it is made by electronic printing, it is called "printed" circuit board. He used a printed circuit board in a radio in 1936.
Contemporary electronic equipment can not do without printed circuit board, so what are the benefits of it? The main advantages of using printed boards are:
1. Because the graphics have repeatability (reproducibility) and consistency, the errors of wiring and assembly are reduced, and the maintenance, commissioning and inspection time of the equipment are saved;
2. The design can be standardized to facilitate interchangeability;
3. High wiring density, small volume and light weight, which is conducive to the miniaturization of electronic equipment;
4. It is conducive to mechanized and automatic production, improves labor productivity and reduces the cost of electronic equipment.
What does a circuit board consist of?
The current circuit board mainly consists of the following components:
Circuit and pattern: the circuit is used as a tool for conducting between components. In the design, a large copper surface will be designed as the grounding and power layer. Lines and drawings are made at the same time.
Dielectric layer: used to maintain the insulation between lines and layers, commonly known as substrate.
Through hole / via: the through hole can make more than two layers of lines connect with each other. The larger through hole is used as a part plug-in. In addition, the non through hole (npth) is usually used for surface mounting and positioning, and used for fixing screws during assembly.
Solder resist ink (solder resist / solder mask): not all copper surfaces need to eat tin parts. Therefore, a layer of material (usually epoxy resin) to isolate the copper surface from tin will be printed in the non tin eating area to avoid short circuit between non tin eating lines. According to different processes, it is divided into green oil, red oil, blue oil, etc., as well as cherry blossom powder oil newly launched by hunting board.
Legend / marking / silk screen: This is an unnecessary composition. Its main function is to mark the name and location box of each part on the circuit board for maintenance and identification after assembly.
Surface finish: as the copper surface is easily oxidized in the general environment, it is unable to apply tin (poor solderability), so it will be protected on the copper surface to eat tin. The protection methods include HASL, ENIG, silver, tin and OSP. Each method has its own advantages and disadvantages, which are collectively referred to as surface treatment.
Each single layer must be pressed to produce a multilayer board. The pressing action includes adding an insulating layer between each layer and bonding each other. If there are guide holes through several layers, each layer must be treated repeatedly. The wiring on the outer two sides of the multilayer board is usually treated after the multilayer board is pressed.
How do we make PCB?
In the laboratory, we generally divide into the following steps: PCB layout - drawing printing and pasting - pasting - light irradiation - wait 15 or 30 minutes - prepare solution - corrosion and cleaning - Drilling - welding.
The modern chemical reactions here are: FeCl3 + Cu to produce FeCl2 + CuCl2. I made a brief introduction to the chemicals:
Copper chloride is toxic (low toxicity, commonly used for swimming pool disinfection), the solution is green (sometimes called blue-green), the dilute solution of copper chloride is blue, the ion is green, the solid is green, anhydrous copper chloride is brownish yellow, and often exists in the form of (CuCl2) n.
Ferrous chloride, chemical formula FeCl2. Green to yellow. Soluble in water, ethanol and methanol. There is tetrahydrate FeCl2 · 4H2O, which is a transparent blue-green monoclinic crystal. Density 1.93 g / cm3. Deliquescent. Soluble in water, ethanol, acetic acid, slightly soluble in acetone, insoluble in ether. In the air, part of it will be oxidized to grass green. It is gradually oxidized to ferric chloride in the air. Anhydrous ferrous chloride is a yellow green hygroscopic crystal, which dissolves in water to form a light green solution. Tetrahydrate salt. It becomes dihydrate when heated to 36.5 ℃.
Ferric chloride is a covalent compound. Chemical formula: FeCl3. Also known as ferric chloride, it is a black brown crystal and also has a sheet shape. Its melting point is 306 ℃ and boiling point is 315 ℃. It is easily soluble in water and has strong water absorption. It can absorb water in the air and deliquesce. FeCl3 precipitates from aqueous solution with six crystals. The water is FeCl3 · 6H2O, and ferric chloride hexahydrate is orange crystal. Ferric chloride is a very important iron salt.