Introduction to common knowledge of SMT (1)


1. Generally speaking, the temperature specified in the SMT workshop is 23±7°C.

2. Materials and tools required for solder paste printing: solder paste, steel plate, scraper, wiping paper, dust-free paper, cleaning agent, mixing knife.

3. The commonly used solder paste composition is Sn96.5%/Ag3%/Cu0.5%.

4. The main components of solder paste are two parts: tin powder and flux.

5. The main function of flux in soldering is to remove oxides, destroy the surface tension of molten tin, and prevent re-oxidation.

6. The volume ratio of tin powder particles and Flux (flux) in solder paste is about 1:1, and the weight ratio is about 9:1.

7. The principle of taking solder paste is first in first out.

8. When the solder paste is opened and used, it must go through two important processes of warming up and stirring.

9. Common production methods for steel plates are: etching, laser, and electroforming.

10. The full name of SMT is Surface mount (or mounting) technology, which means surface adhesion (or mounting) technology in Chinese.

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

12. When making an SMT equipment program, the program includes five parts, 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 control relative temperature and humidity of the parts drying oven is < 10%.

15. Commonly used passive components (PassiveDevices) include: resistors, capacitors, inductors (or diodes), etc.; active components (ActiveDevices) include: transistors, ICs, etc.

16. The commonly used SMT steel plate is made of stainless steel.

17. The thickness of the commonly used SMT steel plate is 0.15mm (or 0.12mm).

18. The types of electrostatic charge include friction, separation, induction, electrostatic conduction, etc.; the impact of electrostatic charge on the electronics industry is: ESD failure, electrostatic pollution; the three principles of static electricity elimination are static neutralization, grounding, and shielding.

19. Inch size length x width 0603=0.06inch*0.03inch, metric size length x width 3216=3.2mm*1.6mm.

20. ERB-05604-J81 No. 8 code "4" means 4 loops, and the resistance value is 56 ohms. The capacitance of the capacitor ECA-0105Y-M31 is C=106PF=1NF=1X10-6F.

21. The full Chinese name of ECN is: Engineering Change Notice; the full Chinese name of SWR is: Special Requirements Work Order, which must be countersigned by relevant departments and distributed by the document center to be valid.

22. The specific content of 5S is sorting, straightening, sweeping, cleaning, and quality.

23. The purpose of PCB vacuum packaging is to prevent dust and moisture.

24. The quality policy is: comprehensive quality control, implement the system, and provide the quality required by customers; full participation, timely processing, to achieve the goal of zero defects.

25. The quality three-no policy is: do not accept defective products, do not manufacture defective products, and do not export defective products.

26. The seven QC techniques refer to the checklist, stratification method, Plato, cause and effect diagram, scatter diagram, histogram, and control diagram.

27. The ingredients of solder paste include: metal powder, solvent, flux, anti-sagging agent, and active agent; by weight, metal powder accounts for 85-92%, and by volume metal powder accounts for 50%; among them, metal powder mainly The composition is tin and lead, the ratio is 63/37, and the melting point is 183°C.

28. Solder paste must be taken out of the refrigerator to return to temperature when used. The purpose is to restore the temperature of the refrigerated solder paste to normal temperature for printing. If the temperature is not returned, the defect that is likely to occur after the PCBA enters Reflow is tin balls.

29. The file supply modes of the machine include: preparation mode, priority exchange mode, exchange mode and quick connection mode.

30. SMT PCB positioning methods include: vacuum positioning, mechanical hole positioning, bilateral clamp positioning and board edge positioning.


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