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Basic knowledge necessary for PCBA processing
2021-10-13
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Author:Frank

Basic knowledge necessary for PCBA processing
   After years of pcba processing, I have accumulated a lot of basic knowledge, including SMT chip processing knowledge, dip plug-in knowledge, wave soldering knowledge, including some component knowledge, PCB board judgment, and some processing skills for your reference. There are 107 in total.
    1. The hole pattern of the steel plate is square, triangle, round, star, and bevel shape;
  2. The raw material of the computer-side PCB currently in use is: glass fiber board FR4;
  3. What kind of substrate ceramic board should Sn62Pb36Ag2 solder paste be used for?
  4. There are four types of fluxes based on rosin: R, RA, RSA, RMA;
   5. SMT segment exclusion has or no directionality;
  6. The solder paste currently on the market only needs 4 hours of sticky time in practice;
  7. The full name of ESD is Electro-static discharge, which means electrostatic discharge in Chinese;
   8. When manufacturing SMT equipment program, the program includes five major ones, namely PCB data; Mark data; Feeder data; Nozzle data; Part data;
   9. The melting point of lead-free solder Sn/Ag/Cu 96.5/3.0/0.5 is 217C;
  10. The operating relative temperature and humidity of the parts drying box is <10%;
  11. Commonly used passive components include: resistors, capacitors, inductors (or diodes), etc.; active components include: transistors, ICs, etc.;
   12. The commonly used raw material of SMT steel plate is stainless steel;
   13. The thickness of commonly used SMT steel plate is 0.15mm;

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  14. There are conflicts, separation, induction, electrostatic conduction, etc. of the types of electrostatic charges; the impact of electrostatic charges on the electronics industry is: ESD failure, electrostatic pollution; the three principles of electrostatic elimination are electrostatic neutralization, grounding, and shielding.
   15. Inch size length x width 0603= 0.06inch*0.03inch, metric size length x width 3216=3.2mm*1.6mm;
   16. Exclusion ERB-05604-J81 No. 8 code "4" indicates that there are 4 circuits, and the resistance value is 56 ohms. The capacitance of the capacitor ECA-0105Y-M31 is C=106PF=1NF =1X10-6F;
    17. Generally speaking, the regular temperature of SMT chip processing workshop is 25±3℃;
   18. When printing solder paste, the materials and things needed to prepare solder paste, steel plate, scraper, wiping paper, dust-free paper, cleaning agent, mixing knife;
  19. The commonly used solder paste alloy composition is Sn/Pb alloy, and the alloy share is 63/37;
  20. The main components of solder paste are divided into two parts: tin powder and flux.
  21. The primary function of flux in soldering is to remove oxides, damage the surface tension of molten tin, and avoid re-oxidation.
  22. 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;
  23. The principle of obtaining solder paste is first in, first out;
  24. When the solder paste is opened and used, it must be heated and mixed through two important processes;
  25. Common manufacturing methods for steel plates are: etching, laser, electroforming;
  26. The full name of SMT chip processing is Surface mount technology, which means surface adhesion (or mounting) technology in Chinese;
  27. The full name of ECN in Chinese is: Engineering Change Notice; the full name of SWR in Chinese is: Specially Needed Work Orders, which must be countersigned by the relevant parts and distributed in the middle of the documents for their usefulness;
  28. The specific content of 5S is sorting, sorting, cleaning, cleaning, quality;
  29. The intention of PCB vacuum packaging is to prevent dust and moisture;
  30. The quality policy for all employees is: all quality control, follow the guidelines, and supply the quality required by customers; all employees participate and deal with it in a timely manner to achieve zero defects;
  31. The three-not quality policy is: do not accept defective products, do not manufacture defective products, and do not discharge defective products;
  32. Among the seven methods of QC, 4M1H refers to the reasons for fishbone investigation respectively (in Chinese): people, machines, materials, methods, and environment;
33. 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; among them, metal powder is the most important The ingredients are tin and lead, the share is 63/37, and the melting point is 183°C;
  34. When solder paste is used, it is necessary to take it out of the refrigerator and return it to temperature. The intention is to restore the temperature of the solder paste in refrigeration to normal temperature to facilitate printing. If it does not return to temperature, the defects that are likely to occur after PCBA enters Reflow are tin beads;
  35. The document supply form of the machine includes: preparation form, priority communication form, communication form and quick connection form;
  36. SMT PCB positioning methods include: vacuum positioning, mechanical hole positioning, two-side clamp positioning and board edge positioning;
   37. The silk screen (symbol) is 272 resistance, the resistance value is 2700Ω, and the resistance value is 4.8MΩ, the resistance symbol (silk screen) is 485;
  38. The silkscreen on the BGA body includes information such as manufacturer, manufacturer's part number, standard, and Datecode/(Lot No);
  39. The pitch of 208pinQFP is 0.5mm;
  40. The correct component and volume ratio of tin powder to flux in the solder paste composition is 90%:10%, 50%:50%;
  41. Early external surface bonding skills originated in the military and avionics category in the mid-1960s;
  42. The contents of Sn and Pb in the solder paste most commonly used in SMT are: 63Sn+37Pb;
  43. The feeding distance of a common paper tape tray with a width of 8mm is 4mm;
  44. In the early 1970s, a new type of SMD was introduced in the industry, which was a "sealed footless chip carrier", often replaced by HCC;
  45. The resistance of the component with symbol 272 should be 2.7K ohms;
  46. The capacitance value of the 100NF component is the same as 0.10uf;
  47. The eutectic point of 63Sn+37Pb is 183℃;
  48. The most widely used electronic component raw material for SMT is ceramics;
  49. The maximum temperature of the reflow furnace temperature curve is 215C, which is the most suitable;
  50. When the tin furnace is inspected, the temperature of the tin furnace is 245C;
  51. SMT parts are packaged with tape and reel diameter of 13 inches, 7 inches;  
    52. Among the seven methods of QC, the fishbone diagram focuses on finding causal connections;
  53. CPK refers to: process capability under current practice;
  54. The flux starts to evaporate in the constant temperature zone for chemical cleaning;
  55. The ideal cooling zone curve and the reflux zone curve are mirrored;
  56. The RSS curve is heating → constant temperature → reflux → cooling curve;
  57. The PCB raw material we are using is FR-4;
  58. PCB warpage standard does not exceed 0.7% of its diagonal;
  59. STENCIL manufacturing laser incision is a method that can be reworked;
  60. The diameter of the BGA ball commonly used on computer motherboards is 0.76mm;
  61. ABS system is a positive coordinate;
  62. The error of the ceramic chip capacitor ECA-0105Y-K31 is ±10%;
  63. The voltage of Panasert's full active placement machine is 3~200±10VAC;
  64. The diameter of the reel for SMT parts packaging is 13 inches and 7 inches;
  65. SMT steel plate openings are usually 4um smaller than PCB PAD to avoid the appearance of bad solder balls;
  66. According to the "PCBA Inspection Regulations", when the dihedral angle is greater than 90 degrees, it indicates that there is no adhesion between the solder paste and the wave solder body;
  67. After the IC is unpacked, the humidity on the display card indicates that the IC is damp and absorbs moisture when the humidity on the card is greater than 30%
  68. The additional air pressure normally used by SMT equipment is 5KG/cm2;
  69. The front PTH, which welding method is used when passing through the tin furnace with SMT, spoiler double wave welding;
  70. Common inspection methods for SMT: visual inspection, X-ray inspection, machine vision inspection
  71. The heat conduction method of ferrochrome repair parts is conduction + convection;
  72. The current BGA data, the main component of the solder ball is Sn90 Pb10;
  73. Steel plate manufacturing methods: laser cutting, electroforming, chemical etching;
  74. The temperature of the arc welding furnace is as follows: Use a thermometer to measure the applicable temperature;
  75. When the semi-finished products of the SMT chip processing of the arc welding furnace are exported, the welding condition is that the parts are fixed on the PCB;
  76. The development process of modern quality management TQC-TQA-TQM;
  77. The ICT test is a needle bed test;
  78. The ICT test can test electronic parts and select static tests;
  79. The characteristics of soldering tin are that the melting point is lower than other metals, the physical properties are satisfactory for welding conditions, and the fluidity at low temperature is better than other metals;
  80. The change of process conditions for the replacement of parts in the arc welding furnace must be measured from the beginning;
  81. It can be produced without LOADER in the SMT process;
  82. The SMT process is a board feeding system-solder paste printer-high-speed machine-general purpose machine-recirculation soldering-rewinding machine;
  83. When the temperature and humidity sensitive parts are opened, the color inside the circle of the humidity card is blue, and the parts can be used;
  84. The standard 20mm is not the width of the strip;
85. Causes of short circuit due to poor printing during the manufacturing process: insufficient metal content of the solder paste, excessive openings in the formed steel plate, excessive amount of tin, poor quality of the steel plate, poor soldering, change the laser cutting template, and there is solder paste on the reverse side of Stencil , Decrease the pressure of the scraper, choose the appropriate VACCUM and SOLVENT
    86. The solder paste thickness gauge uses Laser light to measure: solder paste degree, solder paste thickness, solder paste printed width;
  87. SMT parts supply methods include oscillating feeder, disc feeder, tape feeder;
  88. Which organizations are used in SMT equipment: cam organization, side rod organization, screw organization, sliding organization;
  89. If the visual inspection section cannot be recognized, the BOM, manufacturer’s recognition, and sample board shall be followed;
  90. If the parts packaging method is 12w8P, the counter Pinth scale must be adjusted to 8mm each time;
  91. Varieties of arc welding machines: hot air arc welding furnace, nitrogen arc welding furnace, laser arc welding furnace, infrared arc welding furnace;
  92. Optional methods for trial use of SMT parts samples: streamlined production, hand-printing machine mounting, and hand-printing hand mounting;
  93. Commonly used MARK shapes are: round, "cross", square, diamond, triangle, and swastika;
  94. Due to improper setting of Reflow Profile in SMT section, it is the preheating zone and cooling zone that can form part microcracks;
  95. The two ends of the SMT section parts are heated unevenly and easy to form: empty welding, offset, and stone stele;
  96. SMT parts repair things include: soldering iron, hot air extractor, suction gun, tweezers;
  97. QC is divided into: IQC, IPQC, .FQC, OQC;
  98. Siemens 80F/S belongs to more electronic control transmission;
  99. High-speed placement machine can mount resistors, capacitors, ICs, and transistors;
  100. The characteristics of static electricity: small current, greatly affected by humidity;
  101. The cycle time of high-speed machines and general-purpose machines should be balanced as much as possible;
  102. The true meaning of quality is to do well the first time;
  103. The placement machine should first paste small parts, and then paste large parts;
  104. BIOS is a basic input and output system, in English: Base Input/Output System;
  105. SMT parts can be divided into LEAD and LEADLESS according to the presence or absence of parts;
  106. There are three basic types of common active placement machines, continuous placement type, continuous placement type and many handover placement machines. The general purpose of each section of the reflow furnace profile is:
   Preheating zone; transpiration of the solvent in the solder paste. Homogeneous temperature zone; flux is activated to remove oxides; remaining moisture is evaporated. Reflow zone; the solder melts. Cooling zone; composed of alloy solder joints, and the part feet and the pads are connected as a whole;
107. In the SMT chip processing process, the primary reasons for the occurrence of solder balls: poor PCB PAD drawing, poor drawing of steel plate openings, excessive placement depth or placement pressure, excessive rise of the rofile curve, solder paste collapse, and solder paste The viscosity is too low.