Several material classifications for PCB circuit boards

　　PCB circuit board substrates from PCB prototyping manufacturers can be divided into several types based on quality, material, and fire rating: PCB circuit boards

　　94HB cardboard: The most common cardboard material, mostly used to make low-grade single panels, with a cheap price. Due to its lack of flame retardant properties, it cannot be used for a series of products with fire protection requirements such as power supplies.

　　94V0 cardboard: A cardboard material with flame retardant properties, which contains flame retardant additives in its composition compared to 94HB cardboard material.

　　22F single-sided composite substrate: single-sided semi fiberglass board.

　　CEM-1 single-sided composite substrate: This material requires CNC drilling.

　　CEM-3 double-sided composite substrate: Low end double-sided board material, belonging to semi fiberglass material.

　　FR-4 epoxy resin glass fiber board: the most commonly used PCB board material.

　　PCB circuit board fire rating classification: According to the UL standard, the substrate combustion characteristics can be divided into the following four categories from high to low: UL-94V0 UL-94V1、UL-94V2、UL-94HB。

　　Semi cured film: used for making multi-layer PCB boards, commonly used models include 1080, 2116, 7628 and other specifications.

　　Knowledge points of SMT surface mount processing

　　Generally speaking, the temperature requirement for SMT surface mount processing workshops for circuit board sampling is 25 ± 3 ℃;

　　2. When printing solder paste, the necessary materials and items include solder paste, steel plate, scraper, wiping paper, dust-free paper, cleaning agent, and mixing knife;

　　3. The commonly used solder paste alloy composition is Sn/Pb alloy, and the alloy proportion is 63/37;

　　The primary components of solder paste are divided into two main parts: solder powder and soldering flux.

　　The primary function of flux in welding is to remove oxides, damage the surface tension of the melted tin, and prevent further oxidation.

　　6. The volume ratio of tin powder particles to Flux in solder paste is approximately 1:1, and the weight ratio is approximately 9:1;

　　The principle of using solder paste is first in, first out;

　　8. When using solder paste in Kaifeng, two important processes must be carried out: reheating and mixing;

　　9. Common manufacturing methods for steel plates include etching, laser, and electroplating;

　　10. The full name of SMT surface mount processing is Surface mount (or mounting) technology, and SMT surface mount welding means surface adhesion (or mounting) skill in Chinese;

　　11. The full name of ESD is Electro static discharge, which means electrostatic discharge in Chinese;

　　When manufacturing SMT equipment programs, the program includes five major components, which are PCB data; Mark data; Feeder data; Nozzle data; Part data;

　　13. The melting point of lead-free solder Sn/Ag/Cu 96.5/3.0/0.5 is 217C;

　　14. The relative temperature and humidity of the parts drying oven should be controlled to be less than 10%;

　　15. Common passive devices include resistors, capacitors, point inductors (or diodes), etc; Active devices include transistors, ICs, etc;