PCBA Tech - Common knowledge in SMT chip processing and production

1. Generally speaking, the temperature specified in the SMT workshop is 25±3°C;

2. When printing solder paste, the materials and tools needed to prepare solder paste, steel plate, scraper, wipe paper, dust-free paper, cleaning agent, stirring knife;

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

4. The main components in the solder paste are divided into 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 to 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 opened and used, it must go through two important processes to rewarm and stir;

9. The common production methods of steel plates are: etching, laser, 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 SMT equipment program, the program includes five major parts, these five parts 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 controlled relative temperature and humidity of the parts drying box is <10%;

15. Commonly used passive components (Passive Devices) include: resistance, capacitance, point sense (or diode), etc.; Active Devices (Active Devices) include: transistors, ICs, etc.;

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

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

18. The types of electrostatic charge generated include friction, separation, induction, electrostatic conduction, etc.;

The impact of the industry is: ESD failure, electrostatic pollution; the three principles of electrostatic elimination are electrostatic 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. Exclusion ERB-05604-J81 No. 8 code "4" means 4 circuits, the resistance value is 56 ohms. capacitance

The capacitance value of ECA-0105Y-M31 is C=106PF=1NF =1X10-6F;

21. The full name of ECN in Chinese: Engineering Change Notice; the full name of SWR in Chinese: Special Requirements Work Order,

It must be countersigned by relevant departments and distributed by the document center to be valid;

22. The specific content of 5S is sorting, rectifying, cleaning, cleaning and accomplishment;

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

24. The quality policy is: comprehensive quality control, implementation of the system, providing quality required by customers; full participation, timely

Deal with it to achieve the goal of zero defects;

25. The quality three no policy is: do not accept defective products, do not manufacture defective products, do not flow out defective products;

26. Among the reasons for fishbone inspection in the seven QC methods, 4M1H respectively refers to (in Chinese): people, machines, materials,

27. The components of solder paste include: metal powder, solvent, flux, anti-sagging agent, activating agent; by weight,

Metal powder accounts for 85-92%, and metal powder accounts for 50% by volume; the main components of metal powder are tin and lead, the ratio is 63/37, and the melting point is 183 degree Celsius;

28. The solder paste must be taken out of the refrigerator to return to temperature when it is used. The purpose is: to restore the temperature of the refrigerated solder paste to normal temperature.

Eliminate printing. If it does not return to temperature, the defects that are likely to occur after PCBA enters Reflow are tin beads;

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;

31. The silk screen (symbol) is 272 resistor, the resistance value is 2700Ω, and the resistance value is 4.8MΩ.

The number (silk screen) is 485;

32. The silk screen on the BGA body contains information such as manufacturer, manufacturer's part number, specification and Datecode/(Lot No);

33. The pitch of 208pinQFP is 0.5mm;

34. Among the seven methods of QC, the fishbone diagram emphasizes the search for causality;

37. CPK refers to: current process capability under actual conditions;

38. The flux starts to volatilize in the constant temperature zone for chemical cleaning;

39. The ideal mirror image relationship between the cooling zone curve and the reflux zone curve;

40. The RSS curve is heating - constant temperature - reflux - cooling curve;

41. The PCB material we are using is FR-4;

42. PCB warpage specification does not exceed 0.7% of its diagonal