If you have worked in the SMT of an electronics factory, you must understand these

If you have worked in the SMT of an electronics factory, you must understand these

Generally speaking, the specified temperature in the SMT workshop is 25±3℃.
2. Materials and tools required for solder paste printing: solder paste, steel plate, scraper, wiping paper, lint-free paper, cleaning agent, and stirring knife;
3. The commonly used alloy composition of solder paste is Sn/Pb alloy, and the alloy ratio is 63/37.
4. The main components of solder paste are divided into two major parts: solder powder and flux.
5. The main function of flux in soldering is to remove oxides, break 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 approximately 1:1, and the weight ratio is approximately 9:1.
7. The principle for taking solder paste is first in, first out.
8. When solder paste is opened and used, it must go through two important processes: warming up and stirring.
9. The common manufacturing methods of steel plates are: etching, laser, and 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 static electricity discharge in Chinese.
12. When making the SMT equipment program, the program includes five major parts, and 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 217 ° C.
14. The relative temperature and humidity of the parts drying oven is less than 10%.
15. Commonly used Passive Devices include resistors, capacitors, point inductors (or diodes), etc. Active Devices include: transistors, ics, etc.
16. The commonly used material for SMT steel plates is stainless steel.
17. The commonly used thickness of SMT steel plates is 0.15mm(or 0.12mm);
18. The types of electrostatic charges generated include friction, separation, induction, electrostatic conduction, etc. The influence of electrostatic charge on the electronics industry is :ESD failure, electrostatic pollution; The three principles of static elimination are static neutralization, grounding and shielding.
19. The imperial size is 0603 (length x width) = 0.06inch*0.03inch, and the metric size is 3216 (length x width) =3.2mm*1.6mm.
20. The 8th code "4" of the resistor ERB-05604-J81 indicates 4 circuits, with a resistance value of 56 ohms. The capacitance value of the capacitor ECA-0105Y-M31 is C=106 pF =1NF =1 × 10-6F.
21. The full Chinese name of ECN is: Engineering Change Notice. The full Chinese name of SWR is "Special Needs Work Order". It must be co-signed by all relevant departments and distributed by the document center to be valid.
22. The specific contents of 5S are sorting, straightening, sweeping, cleaning and self-discipline.
23. The purpose of vacuum packaging for PCBS is to prevent dust and moisture.
24. The quality policy is: comprehensive quality control, implementation of systems, and provision of quality that meets customer demands. Full participation, timely handling, to achieve the goal of zero defects;
25. The "Three No" policy for quality is: no acceptance of defective products, no manufacturing of defective products, and no release of defective products.
26. Among the seven QC techniques, the 4M1H in the fishbone cause examination refer to (in Chinese) : person, machine, material, method, and environment.
27. The components of solder paste include: metal powder, solvent, flux, anti-sagging agent and active agent; By weight, metal powder accounts for 85-92%, and by volume, it accounts for 50%. Among them, the main components of the metal powder are tin and lead, with a ratio of 63/37, and the melting point is 183℃.
28. When using solder paste, it must be taken out of the refrigerator to warm up. The purpose is to bring the temperature of the refrigerated solder paste back to room temperature to facilitate printing. If the temperature is not warmed up, the defect that is likely to occur after Reflow in the PCBA is the solder beads.
29. The file supply modes of the machine include: preparation mode, priority exchange mode, exchange mode and quick access mode.
30. The PCB positioning methods of SMT include: vacuum positioning, mechanical hole positioning, double-sided clamp positioning and board edge positioning.
31. The symbol (silk-screened) for a resistor with a value of 272 is 2700Ω, and the symbol (silk-screened) for a resistor with a value of 4.8MΩ is 485.
32. The silk-screen printing on the BGA body contains information such as the manufacturer, manufacturer part number, specification and Datecode/(Lot No);
33. The pitch of the 208-pin QFP is 0.5mm;
Among the seven QC techniques, the fishbone diagram emphasizes the search for causal relationships.
37. CPK refers to: the process capability under the current actual situation;
38. The flux begins to volatilize in the constant temperature zone to carry out the chemical cleaning action.
39. The ideal mirror image relationship between the cooling zone curve and the reflux zone curve;
40. The RSS curve is the curve of heating up → constant temperature → reflux → cooling.
41. The PCB material we are currently using is FR-4;
42. The warpage specification of the PCB shall not exceed 0.7% of its diagonal.
43. STENCIL's laser cutting is a method that can be reworked.
44. Currently, the commonly used BGA ball diameter on computer motherboards is 0.76mm.
45. The ABS system is in absolute coordinates;
46. The error of the ceramic chip capacitor ECA-0105Y-K31 is ±10%.
47. The voltage of the Panasert fully automatic surface mount machine from Panasonic is 3Ø200±10VAC.
48. The diameter of the tape reel for SMT component packaging is 13 inches or 7 inches.
49. Generally, the holes in SMT steel plates should be 4 μ m smaller than those in PCB pads to prevent the phenomenon of poor solder balls.
50. According to the "PCBA Inspection Specifications", when the dihedral Angle is greater than 90 degrees, it indicates that the solder paste has no adhesion to the wave solder body.
If you have worked in the SMT of an electronics factory, you must understand these
51. After the IC is unpacked, if the humidity on the humidity display card is greater than 30%, it indicates that the IC is damp and absorbing moisture.
52. The correct weight ratio and volume ratio of solder powder to flux in the solder paste composition are 90%:10% and 50%:50%.
53. The early surface mount technology originated in the military and avionics fields in the mid-1960s;
54. Currently, the contents of Sn and Pb in the most commonly used solder pastes for SMT are respectively: 63Sn+37Pb;
55. The common feeding distance for paper tape trays with a width of 8mm is 4mm.
56. In the early 1970s, a new type of SMD emerged in the industry, known as "sealed pin less chip carrier", which was often abbreviated as HCC.
57. The resistance value of the component with the symbol 272 should be 2.7K ohms.
58. The capacitance value of the 100NF component is the same as that of 0.10uf.
The eutectic point of 59.63Sn +37Pb is 183℃.
60. The most widely used electronic component material in SMT is ceramic.
61. The temperature curve of the reflow soldering furnace has a maximum curve temperature of 215 ° C, which is the most suitable.
62. When inspecting the tin furnace, a temperature of 245 ° C is more appropriate.
63. The diameter of the tape reel for SMT component packaging is 13 inches or 7 inches.
64. The opening types of steel plates are square, triangular, circular, star-shaped and Ben Lai-shaped.
65. The material of the PCB currently in use on the computer side is: fiberglass board;
66. What kind of substrate ceramic plates is Sn62Pb36Ag2 solder paste mainly used for?
67. Rosin-based fluxes can be classified into four types: R, RA, RSA, and RMA.
68. Is there any directionality in the SMT section resistance?
69. Currently, the solder paste available on the market actually only has a adhesion time of 4 hours.
70. The rated air pressure generally used for SMT equipment is 5KG/cm ².
71. What kind of soldering method should be used for the front PTH and the back SMT when passing through the soldering furnace? What kind of soldering method is the disturbed double-wave soldering?
72. Common inspection methods for SMT: visual inspection, X-ray inspection, and machine vision inspection
73. The heat conduction mode of chromite repair parts is conduction + convection.
74. Currently, the main components of the tin balls in BGA materials are Sn90 Pb10.
75. The manufacturing methods of steel plates include laser cutting, electroforming and chemical etching.
76. The temperature of the reflow furnace is determined by using a thermometer to measure the applicable temperature.
77. When the SMT semi-finished products of the reflow oven are exported, their soldering condition is that the parts are fixed on the PCB.
78. The Development Process of Modern Quality Management: TQC-TQA-TQM;
79. ICT testing is needle-bed testing;
80. The testing of ICT can measure electronic components through static testing.
81. The characteristics of solder are that its melting point is lower than that of other metals, its physical properties meet the welding conditions, and its fluidity at low temperatures is better than that of other metals.
82. When the parts of the reflow furnace are replaced and the process conditions change, the measurement curve needs to be remeasured.
83. Siemens 80F/S belongs to more electronic control drive;
84. The solder paste thickness gauge uses Laser light to measure: solder paste degree, solder paste thickness, and the width of the solder paste print.
85. The feeding methods for SMT parts include vibrating feeders, disc feeders and tape feeders.
86. Which mechanisms are used in SMT equipment: CAM mechanism, side rod mechanism, screw mechanism, and sliding mechanism;
87. If the visual inspection section cannot be confirmed, which operation BOM, manufacturer confirmation, and sample board should be followed?
88. If the packaging method of the part is 12w8P, the Pinth size of the counter needs to be adjusted by 8mm each time.
89. Types of re-welding machines: hot air re-welding furnace, nitrogen re-welding furnace, laser re-welding furnace, infrared re-welding furnace;
90. Methods that can be adopted for the trial production of SMT component samples: streamlined production, hand-printed machine mounting, and hand-printed hand mounting;
91. Commonly used MARK shapes include: circle, cross, square, rhombus, triangle, and swastiform.
92. In the SMT section, due to improper setting of the Reflow Profile, it is the preheating zone and the cooling zone that may cause micro-cracks in the parts.
93. Uneven heating at both ends of the components in the SMT section can easily lead to: empty soldering, misalignment, and tombstones.
94. The tools for SMT component repair include: soldering iron, hot air extractor, solder suction gun, and tweezers.
95. QC is divided into :IQC, IPQC,.FQC and OQC;
96. High-speed surface mount machines can mount resistors, capacitors, ics, and transistors.
97. 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 much as possible.
99. The true meaning of quality is to do it well the first time.
100. The surface mount technology (SMT) machine should place small parts first and then large ones.
101. BIOS is a basic Input/Output System. Its full English name is: Base Input/Output System;
102. SMT components are classified into two types based on the presence or absence of component pins: LEAD and LEADLESS.
103. There are three basic types of common automatic placement machines: successive placement type, continuous placement type and mass transfer placement machine.
104. Production can be carried out in the SMT process without a LOADER.
105. The SMT process is as follows: board feeding system - solder paste printing machine - high-speed machine - general-purpose machine - reflow soldering machine - board receiving machine;
106. When opening temperature and humidity sensitive parts, the color displayed inside the circle of the humidity card should be blue before the parts can be used.
107. The size specification of 20mm is not the width of the tape.
108. Reasons for short circuits caused by poor printing during the manufacturing process :a. Insufficient metal content in solder paste, resulting in collapse b. 1. The holes in the steel plate are too large, resulting in excessive tin content. n2. The quality of the steel plate is poor, and the tin discharge is not good. Replace the laser cutting template. n3. There is residual solder paste on the back of the pencil. Reduce the pressure of the scraper and use appropriate VACCUM and SOLVENT
109. The main engineering purposes of each zone in the general reflow furnace Profile :a. Preheating zone; Project objective: Evaporation of the solvent in the solder paste. b. Uniform temperature zone Engineering objective: Activation of flux and removal of oxides; Evaporate the excess water. c. Re-welding area Project objective: Solder melting. d. Cooling zone Engineering objective: To form alloy solder joints and integrate the part feet with the solder pads as one.
110. In the SMT process, the main reasons for the generation of solder beads are: poor design of PCB pads, poor design of openings on steel plates, excessive placement depth or placement pressure, excessive rising slope of the Profile curve, solder paste collapse, and too low viscosity of solder paste.