30 questions about SMT patches
1 In general, the temperature specified in SMT workshop is 25 ± 3 ℃;
2. When printing solder paste, prepare the materials and tools needed for solder paste, steel plate, scraper, wiping paper, dust-free paper, cleaning agent and stirring knife;
3. The common solder paste alloy composition is tin lead alloy, and the alloy ratio is 63/37;
4. The main components of solder paste are divided into two parts: tin powder and flux.
The main role of flux in welding is to remove oxides, destroy the surface tension of molten tin and prevent reoxidation.
6. The volume ratio of tin powder partICles to the flux (flux) in the solder paste is about 1:1, and the weight ratio is about 9:1;
7. The principle of obtaining solder paste is first in first out;
8. When the solder paste is used, it must be reheated and stirred through two important processes;
9. Common steel plate production methods are: etching, laser, electroforming;
10. SMT is fully calLED surface mount (or installation) technology, which means surface bonding (or installation) technology in Chinese;

11. The full name of ESD is electrostatic discharge, which means electrostatic discharge in Chinese;
12. When making SMT equipment program, the project includes five main parts, which are PCB data; MARKing 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 control relative temperature and humidity of the part drying box are less than 10%;
15. Common passive components (passive components) include: resistance, capacitance, point induction (or diode), etc.; Active devices (active devices) include: transistors, integrated circuits, etc.;
16. Common SMT steel plate is stainless steel;
17. The thickness of common SMT steel plate is 0.15 mm (or 0.12 mm);
18. The types of static electricity generated include friction, separation, induction, static conduction, etc.; The impact of static electricity on the electronic industry is: electrostatic discharge failure, electrostatic pollution; The three principles of electrostatic elimination are electrostatic neutralization, grounding and shielding.
19. Inch dimension length x width 0603=0.06inch * 0.03inch, metric dimension length x width 3216=3.2mm * 1.6mm;
20. Exclude ERB-05604-J81 No. 8 code "4" indicates 4 circuits, and the resistance value is 56 ohms. The capacitance of capacitor ECA-0105Y-M31 is C=106PF=1NF=1X10-6F;
21. ECN full name in Chinese: engineering change notice; Full Chinese name of SWR: the work order with special requirements must be countersigned by relevant departments and distributed by the Archives Center before it becomes effective;
22. The specific content of 5S is sorting, rectification, cleaning, cleaning and completion;
23. The purpose of PCB vacuum packaging is to prevent dust and moisture;
24. The quality policy is: overall quality control, implementation of the system, and provision of quality required by customers; Full participation and timely handling to achieve the goal of zero defect;
25. 3 Non quality policy: do not accept unqualified products, do not manufacture unqualified products, and do not discharge unqualified products;
26. Among the seven quality control methods, 4M1H for the reason of fish bone inspection refers to (in Chinese): human, machine, data, method and environment;
27. The components of solder paste include: metal powder, solvent, flux, anti sagging agent and active agent; Metal powder accounts for 85-92% by weight and 50% by volume; The metal powder is mainly composed of tin and lead, with a ratio of 63/37 and a melting point of 183 ℃;
28. During use, the solder paste must be taken out of the freezer to restore its temperature. The purpose is to restore the temperature of the frozen solder paste to the normal temperature for printing. If the temperature does not recover, the defect that is easy to appear after PCBA enters reflow soldering is tin bead;
29. The file providing modes of the machine include: preparation mode, priority exchange mode, exchange mode and quick connection mode;
30. The SMT PCB positioning methods include: vacuum positioning, mechanical hole positioning, bilateral clamp positioning and plate edge positioning;

The above is the explanation given by the editor of PCB circuit board company.
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