PCB News - The second half of the 50 common sense of SMT processing factory!

The second half of the 50 common sense of SMT processing factory!
At present, the country has higher and higher requirements for environmental protection and greater efforts in link governance. This is a challenge but also an opportunity for PCB factories. If the PCB factory is determined to solve the problem of environmental pollution, then FPC flexible circuit board products can be at the forefront of the market, and the PCB factory can get the opportunity to develop again.
25. The three-not quality policy is: do not accept defective products, do not manufacture defective products, and do not discharge defective products.
26. Among the seven QC methods, 4M1H refers to (in Chinese): people, machines, materials, methods, and environment.

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 by volume metal powder accounts for 50%; among them, metal powder is mainly The composition is tin and lead, the ratio is 63/37, and the melting point is 183°C.

28. The solder paste must be taken out of the refrigerator to return to temperature during use. The purpose is to restore the temperature of the refrigerated solder paste to normal temperature to facilitate printing. If the temperature is not restored, the defects that are prone 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 symbol (silk screen) of the resistance value 4.8MΩ is 485.

32. The silkscreen on the BGA body contains information such as manufacturer, manufacturer part number, specification, and Datecode/(LotNo).

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: process capability under current actual conditions.

38. The flux begins 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.

43. STENCIL laser cutting is a method that can be reworked.

44. At present, the diameter of the BGA ball commonly used on computer motherboards is 0.76mm.

45. The ABS system is absolute coordinates.

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

47. The voltage of Panasert Panasonic automatic placement machine is 3~200±10VAC.

48. SMT parts are packaged with tape-and-reel diameters of 13 inches and 7 inches.

49. SMT steel plate openings are generally 4um smaller than PCB PAD to prevent bad solder balls.

50. According to the "PCBA Inspection Regulations", when the dihedral angle is greater than 90 degrees, it means that the solder paste has no adhesion to the wave solder body.