Introduction to common knowledge of SMT (2)


Nowadays, SMT electronic components have been deeply applied to all walks of life, and each electronic manufacturer has its own strengths. Let us continue to learn the common knowledge of SMT!

31. The resistor whose silk screen (symbol) is 272 has a resistance value of 2700Ω, and the symbol (silk screen) of a resistor with a resistance value of 4.8MΩ is 485. SMT

32. The silk screen on the BGA body contains information such as the 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;

35. CPK refers to: the process capability under the current actual situation;

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

37. Ideal cooling zone curve and reflow zone curve mirror image relationship;

38. The solder paste of Sn62Pb36Ag2 is mainly used on ceramic boards;

39. Rosin-based flux can be divided into four types: R, RA, RSA, RMA;

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

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

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

43. Laser cutting by STENCIL can be reworked;

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

45. The ABS system is an absolute coordinate;

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

47. The PCB of the computer currently in use is made of: glass fiber board;

48. The diameter of tape and reel for SMT parts packaging is 13 inches and 7 inches;

49. The opening of the SMT general steel plate is 4um smaller than that of the PCB PAD to prevent the phenomenon of bad solder balls;

50. According to the "PCBA Inspection Specification", when the dihedral angle > 90 degrees, it means that the solder paste has no adhesion to the wave soldering body;

51. After the IC is unpacked, if the humidity on the display card is greater than 30%, it means that the IC is damp and absorbs moisture;

52. The weight ratio and volume ratio of tin powder and flux in the solder paste composition are correct 90%:10%, 50%:50%;

53. The early surface mount technology originated from the military and avionics fields in the mid-1960s;

54. At present, the contents of Sn and Pb in the most commonly used solder paste for SMT are: 63Sn 37Pb; the eutectic point is 183°C

55. The feeding distance of the common paper tape tray with a bandwidth of 8mm is 4mm;

56. In the early 1970s, a new type of SMD appeared in the industry, which was a "sealed footless chip carrier", often replaced by LCC;

57. The resistance value of the component marked 272 should be 2.7K ohms;

58. The capacitance of 100NF components is the same as that of 0.10uf;

60. The most widely used electronic component material in SMT is ceramics;

61. The temperature curve of the reflow furnace is most suitable for the maximum temperature of 215C;

62. During the tin furnace inspection, the temperature of the tin furnace is 245°C;

63. The opening pattern of the steel plate is square, triangle, circle, star, and epitome;

64. Whether the exclusion of SMT segment is directional or not;

65. The solder paste currently on the market actually only has a sticking time of 4 hours;

66. The rated air pressure generally used by SMT equipment is 5KG/cm2;

67. Tools for SMT parts maintenance include: soldering iron, hot air extractor, tin suction gun, tweezers;

68. QC is divided into: IQC, IPQC,. FQC, OQC;

69. High-speed placement machines can mount resistors, capacitors, ICs, and transistors;

70. The characteristics of static electricity: small current, greatly affected by humidity;

71. What kind of welding method is used when the front PTH and the back SMT pass through the tin furnace;

72. Common inspection methods for SMT: visual inspection, X-ray inspection, machine vision inspection

73. The heat conduction mode of ferrochrome repair parts is conduction convection;

74. At present, the main components of solder balls in BGA materials are Sn90 Pb10, SAC305, SAC405;

75. Laser cutting, electroforming, and chemical etching of steel plates;

76. The temperature of the welding furnace is pressed: use the temperature detector to measure the applicable temperature;

77. When the SMT semi-finished products of the welding furnace are exported, the welding status is that the parts are fixed on the PCB;

78. The history of modern quality management development TQC-TQA-TQM;

79. The ICT test is a bed of needles test;

80. ICT testing can test electronic components using static testing;

This is the end of today's learning content. In the next issue, the editor will continue to introduce the common knowledge of SMT, so stay tuned!


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