In the SMT (Surface Mount Technology) industry, mastering the necessary basics is crucial for every worker. Whether you’re a beginner or an experienced professional, this article will provide you with 100 essential facts about the SMT industry to help you navigate your work with greater ease. We’ll cover key concepts, workflows, common issues, and solutions in the SMT industry to help you better understand and apply SMT technology. Let’s dive in together, hone your skills, and become experts in the SMT industry!
1. Generally speaking, the specified temperature for an SMT workshop is 25±3°C.
2. Materials and tools required for solder paste printing: solder paste, steel stencil, squeegee, wiping paper, lint-free paper, cleaning solution, and mixing spatula.
3. The most commonly used solder paste alloy is a Sn/Pb alloy with a ratio of 63/37.
4. The main components of solder paste are divided into two categories: tin powder and flux.
5. The primary functions of flux in soldering are to remove oxides, break the surface tension of molten solder, and prevent re-oxidation.
6. The volume ratio of tin powder particles to flux in solder paste is approximately 1:1. The weight ratio is approximately 9:1.
7. Solder paste is dispensed on a first-in, first-out basis.
8. Before use, solder paste must undergo two important processes: conditioning (2–4 hours to bring it to room temperature and prevent it from absorbing moisture from the air) and stirring (to increase the viscosity of the solder paste and thoroughly mix the metal particles and organic components within it).
9. Common methods for producing steel plates include etching, laser cutting, and electroforming.
10. SMT stands for Surface Mount (or Mounting) Technology.
11. The full form of ESD is "Electro-static discharge," which means "electrostatic discharge" in Chinese.
12. When creating SMT equipment programs, the program consists of five main sections: PCB data, Mark data, Feeder data, Nozzle data, and Part data.
13. The melting point of lead-free solder (Sn/Ag/Cu 96.5/3.0/0.5) is 217°C.
14. The controlled relative temperature and humidity in the parts drying oven is <10%.
15. Common passive components include resistors, capacitors, inductors [or diodes], etc. Active components include transistors, ICs, etc.
16. The material commonly used for SMT steel plates is stainless steel.
17. The standard thickness for SMT steel plates is 0.15 mm (or 0.12 mm or 0.13 mm), which is generally determined by the IC with the smallest pitch. For a 0.5 mm pitch, the thickness is 0.15 mm; for a 0.4 mm pitch, 0.13 mm or 0.12 mm is used.
18. Static electricity can be generated through friction, separation, induction, and conduction, among other means. The effects of static electricity on the electronics industry include ESD-related failures and electrostatic contamination. The three principles of static electricity dissipation are static neutralization, grounding, and shielding. The drier the air, the more likely static electricity is to build up; the general humidity requirement for SMT is 45–75%.
19. Imperial dimensions (length x width) 0603 = 0.06 inch × 0.03 inch = metric dimensions 1608 = length 1.6 mm × width 0.8 mm; metric dimensions (length x width) 3216 = 3.2 mm × 1.6 mm.
20. For resistor ERB-05604-J81, the “4” in the 8th digit indicates 4 circuits, with a resistance of 56 ohms. For capacitor ECA-0105Y-M31, the capacitance is C = 106 pF = 1 nF = 1 × 10⁻⁶ F.
21. The full Chinese name for SWR is: Special Needs Work Order. It is valid only after being co-signed by all relevant departments and distributed by the Document Center.
The specific components of 22.5S are Sorting, Straightening, Sweeping, Sanitizing, and Self-Discipline.
23. The purpose of vacuum-sealing PCBs is to protect them from dust and moisture.
24. Our quality policy is: comprehensive quality control, strict adherence to procedures, and delivering the quality that meets customer needs; full employee participation, prompt resolution of issues, and achieving the goal of zero defects.
25. The "Three No's" Quality Policy is: Do not accept defective products, do not produce defective products, and do not release defective products.
26. In an SMT workshop, people, machines, materials, methods, and the environment are closely integrated from a management perspective.
27. The components of solder paste include: metal powder, solvents, flux, anti-sag agents, and activators; by weight, metal.
The powder accounts for 85–92%, and by volume, the metal powder accounts for 50%; the metal powder consists primarily of tin and lead in a ratio of 63:37. Its melting point is 183°C.
28. Solder paste must be removed from the refrigerator and allowed to come to room temperature before use. The purpose of this is to bring the refrigerated solder paste back to room temperature to facilitate printing. If it is not allowed to come to room temperature, solder balls are likely to form on the PCBA after reflow.
29. The machine's file supply modes include: Ready Mode, Priority Exchange Mode, Exchange Mode, and Quick Connect Mode.
30. The PCB positioning methods used in SMT include: vacuum positioning, mechanical hole positioning, dual-side clamping positioning, and board-edge positioning.
31. The screen-printed [symbol] for a resistor with a resistance of 2700 Ω is 272, and the screen-printed [symbol] for a resistor with a resistance of 4.8 MΩ is 485.
32. The silkscreen on the BGA package includes information such as the manufacturer, manufacturer's part number, specifications, and date code/(lot number).
33. Generally speaking, the pitch of a 208-pin QFP is 0.5 mm, that of a 216-pin QFP is 0.4 mm, and that of a 256-pin QFP is 0.35 mm.
34. Among the Seven QC Tools, the fishbone diagram emphasizes identifying cause-and-effect relationships.
35. CPK refers to: the process capability under current actual conditions.
36. In the constant-temperature zone, the flux begins to volatilize and undergoes a chemical cleaning process. The typical temperature range is between 140°C and 180°C, with the highest activity occurring between 170°C and 180°C.
37. The cooling zone curve and the reflux zone curve are mirror images of each other.
38. The standard temperature profile is set as follows: heating → isothermal → reflux → cooling.
39. The PCB warpage tolerance shall not exceed 0.51 TP3T–0.71 TP3T of its diagonal.
40. The tolerance for the ECA-0105Y-K31 ceramic chip capacitor is ±101 TP3T.
41. The SMT component packaging comes in tape-and-reel reels with diameters of 13 inches and 7 inches.
42. On SMT steel plates, the holes are generally 4 µm smaller than the PCB pads to prevent solder ball defects.
43. According to the “PCBA Inspection Specifications,” when the dihedral angle is greater than 90 degrees, it indicates that the solder paste does not adhere to the wave soldering fixture.
44. After unpackaging the IC, if the humidity reading on the humidity display card exceeds 30%, it indicates that the IC has been exposed to moisture and has absorbed moisture.
45. Which of the following is the correct weight ratio and volume ratio of tin powder to flux in solder paste: 90%:10% or 50%:50%?
46. Early surface-mount technology originated in the military and avionics sectors in the mid-1960s.
47. Currently, the most commonly used leaded solder paste in SMT has a composition of 63% Sn and 37% Pb, while lead-free solder paste has a composition of 96.5% Sn, 3% Ag, and 0.5% Cu.
For 48.0805 and 0603 component packaging, the common tape width is 8 mm, and the feed pitch for paper tape reels is 4 mm; for 0402 component packaging, the common tape width is 8 mm, and the feed pitch for paper tape reels is 2 mm. 48. In the early 1970s, a new type of SMD emerged in the industry: the “hermetically sealed leadless chip carrier,” commonly abbreviated as HCC.
49. The resistance of the component labeled 272 should be 2.7 kΩ.
The capacitance of the 50.100NF component is the same as that of 0.10 uF.
The melting point of 51.63Sn+37Pb is 183°C, and the eutectic point is approximately 200°C.
52. The most commonly used material for electronic components in SMT is ceramic.
53. In lead-containing production, generally speaking, a maximum temperature of 225°C on the reflow oven temperature curve is considered appropriate.
54. When inspecting the tin bath, a temperature of 245°C is most appropriate.
55. SMT components packaged on tape-and-reel, including adhesive tape and paper tape packaging.
56. The types of openings in steel plates include square, triangular, circular, star-shaped, and diamond-shaped.
57. Generally speaking, the open area ratio of a steel mesh ranges from 0.8 to 1.2. If it is too small, there will be insufficient solder; if it is too large, it will waste solder paste and make solder balls more likely to form.
58. The resistors in the SMT section are not oriented.
59. The solder paste currently available on the market actually has a pot life of only 4 hours; therefore, printed circuit boards must be reflow-soldered within 4 hours, though the standard requirement is typically 2 hours.
60. The standard rated air pressure for SMT equipment is generally 5 kg/cm².
61. For components mounted on the front side, what soldering method is used on the reverse side when passing through the SMT wave soldering machine to prevent turbulence in the dual-wave soldering process?
62. Common SMT inspection methods: visual inspection, X-ray inspection, and machine vision inspection.
63. Heat transfer in ferromanganese repair parts occurs through a combination of conduction and convection.
64. Currently, the tin balls in BGA materials are primarily composed of 90% tin and 10% lead.
65. The main reason why the temperature rise rate in a reflow oven must not exceed 3°C/s is that it is determined by the physical properties of the components; if the temperature rises too quickly, it can easily cause the components to crack.
66. The temperature settings for a reflow oven are generally determined by referring to the standard curve for solder paste and combining that with the actual products being manufactured to establish the temperature curve that yields the most accurate soldering results.
67. When SMT semi-finished products from the reflow oven are exported, the components are soldered and secured to the PCB.
68. Lead-free solder paste [Sn96.5+Ag3+Cu0.5] is characterized by a high melting point, low flowability, and high solder joint strength; however, the surface of the solder joints is prone to oxidation during soldering, so N₂ is generally used to prevent oxidation.
69. ICT testing refers to pin-bed testing.
70. ICT testing can be used to test electronic components; static testing is generally employed.
71. Solder is characterized by a lower melting point than other metals, physical properties that meet soldering requirements, and better fluidity at high temperatures than other metals.
72. When replacing parts or changing process conditions in a remote welding furnace, the calibration curve must be remeasured.
73. Δt refers to the temperature difference between different measurement points on the temperature curve at the same moment.
74. A solder paste thickness gauge uses a laser to measure the solder paste level, thickness, and width of the printed solder paste.
75. SMT component feeders include vibratory feeders, reel feeders, and tape feeders.
76. What types of mechanisms are used in SMT equipment: cam mechanisms, link mechanisms, screw mechanisms, and sliding mechanisms.
77. If the visual inspection criteria cannot be confirmed, which of the following should be used: the BOM, manufacturer confirmation, or sample board?
78. Assuming the parts are packaged in 12w8P units, the Pinth counter must be adjusted to advance 8 mm each time.
79. Types of brazing machines: hot-air brazing furnaces, nitrogen brazing furnaces, laser brazing furnaces, and infrared brazing furnaces.
80. Methods that can be used for SMT component sample prototyping: flow-line production, manual placement with a machine, and manual placement by hand.
81. Commonly used MARK shapes include: circles, crosses, squares, diamonds, triangles, and swastikas.
82. In the SMT section, improper reflow profile settings may cause microcracks in components during the preheat and cool-down zones.
83. Uneven heating at both ends of components in the SMT section can easily lead to: cold solder joints, misalignment, and tombstone defects.
84. Tools used for SMT component repair include: a soldering iron, a hot-air desoldering tool, a desoldering sucker, and tweezers.
85. Quality control (QC) is divided into: IQC, IPQC, FQC, and OQC.
86. High-speed surface-mount placement machines can place resistors, capacitors, ICs, and transistors.
87. Characteristics of static electricity: high voltage, low current, and significant sensitivity to humidity.
88. The cycle times of high-speed machines and general-purpose machines should be as balanced as possible.
89. The true meaning of quality is getting it right the first time.
90. The placement machine should place small components first, followed by large components; low components should be placed first, followed by tall components.
91. BIOS stands for Basic Input/Output System.
92. SMT components are classified into two types—LEAD and LEADLESS—based on whether they have leads.
93. There are three basic types of automatic placement machines: sequential placement machines, continuous placement machines, and high-volume transfer placement machines.
94. Production in the SMT process is possible even without a loader or unloader.
95. The standard SMT process consists of the board feeder system, solder paste printer, high-speed placement machine, general-purpose placement machine, reflow oven, inspection and testing, and board collector.
96. The body of an IC typically features markings indicating the 1# pin. For SOP-package ICs, the 1# pin is the first pin counterclockwise from the indented notch; for QFP, PLCC, and similar packages, the 1# pin is the first pin counterclockwise from a small dot, or the pin indicated by a small triangle.
97. QE, IE, PE, ME, TE, and RE refer to Quality Engineer, Industrial Engineer, Process Engineer, Product Engineer, Mechanical Engineer, Test Engineer, and Maintenance Engineer, respectively.
98.BOM物料清单(BillofMaterial)以基本数据类型来描述产品结构的资料就是物料清单，贴片加工厂要求的BOM包含原材料名称、需求量、贴片位号，BOM是贴片机编程及IPQC确定的关键步骤。
99.DIPDIP封装(DualIn-linePackage)也叫双列直插入式封装技术，指采用双列直插方式封装的集成电路IC芯片，绝大多数中小规模集成电路均采用这类封装类型，其引脚数一般不超过100.
100.SMT表层贴片技术(SurfaceMountTechnology)将表层贴片电子元器件贴、焊到印制电路板表层要求位上的电路装联技术。
通过这篇博客文章，我们详细介绍了SMT行业打工人必备的100个常识。从SMT技术的基本概念到工作流程中的注意事项，我们希望这些知识能够帮助您在SMT行业中更加自信和熟练。
在SMT行业中，不断学习和更新知识是至关重要的，因为这个行业一直在不断发展和创新。我们希望这篇文章能成为您不断进步和成长的指南，帮助您在SMT行业中取得更大的成功。感谢您的阅读，期待与您共同探索SMT行业的更多精彩！
