Introduction to SMT Common Knowledge (1)

Source:Junze Electronics      Browse:      Time:2018-09-20

1. In general, the temperature specified in the SMT workshop is 23 ± 7 °C.

2. When preparing solder paste, the materials and tools to be prepared: 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 the solder paste are divided into two parts: tin powder and flux.

5. The main role of flux in soldering is to remove oxides, destroy the surface tension of molten tin, and prevent reoxidation.

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

7. The principle of access to solder paste is FIFO.

8. When the solder paste is used in the opening, it must be warmed and stirred through two important processes.

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

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

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

12. When making an SMT device 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 relative humidity of the parts drying oven is < 10%.

15. Common passive components (PassiveDevices) are: resistors, capacitors, inductors (or diodes), etc. Active components (ActiveDevices) are: transistors, ICs, etc.

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

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

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

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

20. Exclusion ERB-05604-J81 8th code "4" is represented as 4 loops with a resistance of 56 ohms. The capacitance of the capacitor ECA-0105Y-M31 ​​is C=106PF=1NF =1X10-6F.

21. ECN Chinese full name: engineering change notice; SWR Chinese full name: special demand work order, must be signed by all relevant departments, file center distribution, to be effective.

22. The specific content of 5S is finishing, rectifying, cleaning, cleaning and literacy.

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

24. The quality policy is: comprehensive quality control, implementation of the system, quality of customer demand; full participation, timely processing, to achieve zero shortcomings.

25. The policy of quality three is: not accepting defective products, not manufacturing defective products, and not discharging defective products.

26. The QC seven methods refer to checklists, layering methods, Plato, causal maps, scatter plots, histograms, and control charts.

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

28. When using the solder paste, it must be taken out of the refrigerator to restore the temperature of the refrigerated solder paste to normal temperature for printing. If you do not return to temperature, the defect that is easily generated after PCBA enters Reflow is tin beads.

29. The file supply modes of the machine are: 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 edge positioning.

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