PCB News - 110 tips for SMT patch production

110 tips for SMT patch 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,

Method 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 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;

43. STENCIL production of 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. ABS system is absolute coordinates;

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

47. The voltage of the 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 general steel plate openings are 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;

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

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

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

54. At present, the contents of Sn and Pb in the solder paste most commonly used in SMT are: 63Sn+37Pb;

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

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

57. The resistance of the component with symbol 272 should be 2.7K ohms;

58. The capacitance value of the 100NF component is the same as 0.10uf;

59. The eutectic point of 63Sn+37Pb is 183 degree Celsius;

60. The most widely used electronic component material for SMT is ceramic;

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

62. When inspecting the tin furnace, the temperature of the tin furnace is 245C;

63. SMT parts are packaged with a tape-and-reel reel with a diameter of 13 inches and 7 inches;

64. The hole pattern of the steel plate is square, triangle, round, star, and benley shape;

65. The computer-side PCB currently in use is made of: fiberglass board;

66. The solder paste of Sn62Pb36Ag2 is mainly used for what kind of substrate ceramic board;

67. The flux mainly based on rosin can be divided into four types: R, RA, RSA, RMA;

68. Whether SMT segment exclusion is directional or not;

69. The solder paste currently on the market has only 4 hours of tack time;

70. The rated air pressure for SMT equipment is generally 5KG/cm2;

71. What welding method is used when PTH on the front side and SMT on the back side go through the tin furnace, spoiler double wave soldering;

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

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

74. At present, the main components of BGA material and its solder balls are Sn90 Pb10;

75. Steel plate production methods: laser cutting, electroforming, chemical etching;

76. The temperature of the arc welding furnace is as follows: Use a thermometer to measure the applicable temperature;

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

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

79. ICT test is a needle bed test;

80. ICT test can test electronic parts using static test;

81. The characteristics of soldering tin are that the melting point is lower than that of other metals, the physical properties meet the welding conditions, and the fluidity at low temperatures is better than other metals;

82. The measurement curve must be re-measured when the process conditions of the replacement of the parts of the welding furnace are changed;

83. Siemens 80F/S is a relatively electronic control drive;

84. The solder paste thickness gauge uses Laser light to measure: solder paste degree, solder paste thickness, solder paste printed width;

85. SMT parts supply methods include vibrating feeder, disc feeder, tape feeder;

86. Which mechanisms are used in SMT equipment: cam mechanism, side rod mechanism, screw mechanism, sliding mechanism;

87. If the visual inspection section cannot be confirmed, the BOM, manufacturer's confirmation, and sample board should be followed;

88. If the part packaging method is 12w8P, the counter Pinth size must be adjusted to 8mm each time;

89. Types of arc welding machines: hot air arc welding furnace, nitrogen arc welding furnace, laser arc welding furnace, infrared arc welding furnace;

90. The methods that can be used for sample trial production of SMT parts: streamlined production, hand-printing machine mounting, hand-printing hand mounting;

91. Commonly used MARK shapes are: round, "cross", square, diamond, triangle, and swastika;

92. Due to improper setting of Reflow Profile in SMT section, it is the preheating zone and cooling zone that may cause micro-cracking of parts;

93. The uneven heating of the two ends of the SMT section is easy to cause: empty welding, offset, tombstone;

94. SMT parts repair tools include: soldering iron, hot air extractor, suction gun, tweezers;

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

96. High-speed placement machine can mount resistors, capacitors, ICs, and transistors;

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

98. The cycle time of high-speed machines and general-purpose machines should be balanced as far as possible;

99. The true meaning of quality is to do well the first time;

100. The placement machine should first paste small parts, and then paste large parts;

101. BIOS is a basic input and output system, all in English: Base Input/Output System;

102. SMT parts can be divided into LEAD and LEADLESS according to the presence or absence of parts;

103. There are three basic types of common automatic placement machines, continuous placement type, continuous placement type and mass transfer type placement machine;

104. It can be produced without LOADER in the SMT process;

105. The SMT process is a board feeding system-solder paste printing machine-high-speed machine-general purpose machine-recirculation welding-board receiving machine;

106. When the temperature and humidity sensitive parts are opened, the color displayed in the circle of the humidity card is blue, and the parts can be used;

107. The size specification 20mm is not the width of the strip;

108. Reasons for short circuits due to poor printing in the manufacturing process:

a. The solder paste has insufficient metal content, causing collapse

b. The steel plate has too large a hole, resulting in too much tin

c. The quality of the steel plate is poor, and the tin is poor. Change the laser cutting template

d. There is solder paste remaining on the back of Stencil, reduce the pressure of the squeegee, and use appropriate VACCUM and SOLVENT

109. The main engineering purpose of each section of the general reflow furnace profile:

a. Preheating zone; project purpose: the solvent in the solder paste volatilizes.

b. Uniform temperature zone; engineering purpose: flux activation, remove oxides; evaporate excess water.

c. Reflow area; project purpose: solder melting.

d. Cooling zone; engineering purpose: the formation of alloy solder joints, the part feet and the pads are connected as a whole;

110. In the SMT process, the main reasons for the occurrence of solder balls: poor PCB PAD design, poor steel plate opening design, excessive placement depth or placement pressure, excessive profile curve rising slope, solder paste collapse, and solder paste viscosity is too low .
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