SMT necessary know question (section 2)


SMT necessary know question (section 2).jpg

21. ECN Chinese full name: engineering change notice; SWR Chinese full name: special needs worksheet, must be countersigned by the relevant departments, document center distribution, is effective;


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


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 the quality of customer needs; full participation, timely processing, in order to achieve the goal of zero defects;


25. The quality three non-policy policy is: no accept bad products, no produce bad products, no leak out bad products;


26. 4M1H in QC's Seven Large-scale Techniques refers to (Chinese): Person, Machine, Material, Method, Environment;


27. Paste contains: metal powder, solvent, flux, anti-sagging agent, active agent; by weight, metal powder accounts for 85-92%; by volume, metal powder accounts for 50%; the main components of the metal powder are tin and lead, the ratio is 63/37, and the melting points is 183°C.


28. Paste must be removed from the refrigerator when used. The purpose is to allow the refrigerated paste to return to room temperature for printing. If you do not return to the temperature after the PCBA into the Reflow easy to produce bad beads;


29. The document supply modes of the machine include: preparation mode, preferential exchange mode, exchange mode and quick connect mode;


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


31. The resistance of silk screen (symbol) is 272, the resistance is 2700Ω, the resistance of the resistance value of 4.8MΩ (silk screen) is 485;


32. The silkscreen on the BGA body contains information such as manufacturer, vendor part number, specifications, and Date code/(Lot No);


33. The pitch of the 208pinQFP is 0.5mm;


34. In QC's seven techniques, fish bone maps emphasize the search for causality;


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


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


39. Ideal mirror image of the cooling zone curve and the reflow zone curve;


40. RSS curve for temperature constant temperature reflux cooling curve;


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


42. PCB warpage specifications do not exceed 0.7% of its diagonal;


43. STENCIL makes laser cutting a method that can be reworked;


44. The current BGA ball diameter often used on computer motherboards is 0.76mm;


45. The ABS system is absolute coordinates;


46. The error of the ceramic chip capacitor ECA-0105Y-K31 is ±10%;


47. Panasert Panasonic automatic placement machine voltage is 3?; 200 ± 10VAC;


48. SMT parts packaging tape diameter of 13 inches, 7 inches;


49. SMT plate opening is generally 4 μm smaller than PCB PAD to prevent bad solder balls;


50. According to "PCBA inspection specification", when the dihedral angle is > 90 degrees, there is no adhesion between the solder paste and the wave solder body.