Surface Mount Technology
SMT is Surface Mount Technology (Surface Mounted Technology abbreviation), is the electronics assembly industry's most popular form of technology and processes.
What are the characteristics of high density SMT assembly, electronic products small size, light weight, chip component size and weight of traditional instrumentation components only 1 / 10, the general use of SMT, the electronic product size decreased 40% to 60%, weight reduce 60% ~ 80%. High reliability, anti-vibration capability. Solder joint defect rate. Good high frequency characteristics. Reduce electromagnetic and RF interference. Easy to automate and improve production efficiency. Reduce costs by 30% to 50%. Saving materials, energy, equipment, manpower and time.
The pursuit of miniaturization of electronic products, used previously perforated plug components are not reduced. More complete electronic product features, using integrated circuit (IC) is no longer piercing components, especially large-scale, highly integrated IC, had to use surface mount components. Product volume, production automation, factory to low cost high yield, producing quality products to meet customer demand and enhance market competitiveness the development of electronic components, integrated circuits (IC) development of multiple applications of semiconductor materials. Electronic technology revolution inevitable international trend chasing.
Print (or dispensing) -> mount - "(curing) -> reflow soldering -> cleaning -> testing -> repair printing: its role is to paste or glue were missing to the PCB SMT the pad, in preparation for the welding of components. The SMT process equipment for the printing shop (solder paste printing press), in the forefront of SMT production lines. Dispensing: for now mostly used for double-sided circuit board placement, in order to prevent secondary recycled components when the input side due to fusion of solder paste off again, so the input surface to install dispensers, it is the glue drip onto the PCB fixed position, its main role is to be fixed to the PCB board components. Equipment used for the dispenser, at the forefront of SMT production line or testing equipment behind. Sometimes, because of customer requirements also need to dispensing output side, and now many small factories do not have dispenser, if the input is large artificial surface component dispensing. Mount: its role is to install the surface mount components to the PCB and accurate fixed position. Equipment used for the placement machine, in the SMT production line in the press behind. Curing: its role is to patch plastic melting, so surface mount components and PCB board firmly bonded together. Equipment used for the curing oven, in the SMT placement machine production line in the back. Reflow soldering: solder paste melts its role is to make surface mount components and PCB board firmly bonded together. Equipment used for the reflow oven, in the SMT placement machine production line in the back. Cleaning: The role of the PCB board will be assembled above harmful residues such as welding flux and removed. Equipment used for the washing machine, the location may not be fixed, online, or not online. Detection: its role is assembled PCB board assembly quality of the welding quality and testing. The equipment has a magnifying glass, microscope, on-line tester (ICT), flying probe tester, automatic optical inspection (AOI), X-RAY inspection system, functional tester. Position according to the needs of detection, can be configured in the production line where appropriate. Repair: its role is to detect failure of the PCB board to rework. The use of iron tools, rework stations and so on. Configuration in the production line anywhere.
1 In general, SMT workshop provides a temperature 23 ± 3 ℃.
2. Solder paste printing, materials and tools needed to prepare the paste, steel, scraper, clean paper, wipes, cleaning agents, mixing knife.
3. Commonly used solder alloy composition for the Sn / Pb alloy, and alloy ratio of 63/37.
4. Solder paste is divided into two major components in the solder powder and flux.
5. Flux in the welding of the main role is to remove the oxide, tin melt surface tension damage and prevent further oxidation.
6. Solder paste in the tin powder particles and Flux (flux) of the volume ratio of about 1:1, the weight ratio of about 9:1. 7. Paste the access principle is FIFO.
8. Solder paste used in Kaifeng, an important process to go through two back temperature and stir.
9. Steel common production methods are: etching, laser, electroforming.
10. SMT stands for Surface mount (or mounting) technology, the Chinese meaning for surface (or mount) technology. 11. ESD stands for Electro-static discharge, electrostatic discharge Chinese meaning.
12. Produce SMT equipment program, the program includes five parts, this five-part data for the substrate; patch data; loading data; component data; draw data, image data.
13. Lead-free solder Sn / Ag / Cu 96.5/3.0/0.5 the melting point of 217 ℃ ~ 220 ℃
14. Parts oven control temperature and relative humidity was <10%.
15. Commonly used passive components (Passive Devices) includes: resistors, capacitors, inductors (or diodes), etc.; active components (Active Devices) are: transistor, IC and so on.
16. Commonly used SMT steel plate is made of stainless steel.
17. Commonly used SMT steel plate thickness: 0.15mm 0.12mm 0.13mm 0.10mm.
18. The types of electrostatic charge generated friction, separation, sensors, electrostatic transduction; electrostatic charge on the impact of the electronics industry to: ESD failure, electrostatic pollution; static elimination in the three principles for the static and, grounding, shielding.
19. Inch Size length x width 0603 = 0.06inch * 0.03inch, metric dimensions length x width 3216 = 3.2mm * 1.6mm.
20. Exclusion ERB-05604-J81 8 code "4" is expressed as four loop resistance is 56 ohms. Capacitors ECA-0105Y-M31 capacity value C = 106PF = 1NF = 1X10-6F.
21. ECN Chinese full name: Engineering Change Notice; SWR full name in Chinese: the work of the special needs of single, must be countersigned by the relevant departments, documents distributed by the Centre to be valid.
22. 5S specific content of the order, rectification, cleaning, clean, quality.
23. PCB vacuum packaging is dust and moisture.
24. Quality policy: overall quality control, implement the system, to provide the quality of customer demand; full participation, in time, to achieve the goal of zero defects.
25. Quality of Three No policy: not to accept defective products, not create bad products, not defective products.
26. QC practices in seven causes of fish bone check 4M1H are means (in Chinese): people, machines, materials, methods and environment.
27. Paste ingredients include: metal powder, solvent, flux, resistance to vertical flow agent, active agent; by weight points, accounting for 85-92% of metal powder, metal powder by volume fraction 50%; of which the main metal powder components for the tin and lead, the ratio of 63/37, the melting point of 183 ℃.
28. Solder paste used to remove the back from the refrigerator temperature to: solder paste temperature response to cold storage at room temperature, to facilitate printing. If the temperature does not return after Reflow in the PCBA into the negative as easy to produce solder balling.
29. Machine paper supply pattern: preparation mode, first switching mode, switching mode and speed of access mode. 30. SMT for PCB positioning methods are: vacuum positioning, mechanical hole location, orientation and edge bilateral clip positioning.
31. Silk screen (symbols) for the 272 resistance, resistance to 2700Ω, resistance to 4.8MΩ symbol of resistance (screen printing) at 485.
32. BGA body on the screen contains the manufacturer, vendor part numbers, specifications and Datecode / (Lot No) and other information.
33. 208 pin QFP the pitch is 0.5mm.
34. QC seven tools, the fish bone diagram emphasizes find causation;
35. CPK means: the actual state of the current process capability;
36. Flux evaporation in the heated area on the chemical cleaning action;
37. Ideal curve of the cooling zone and the recirculation curve mirror relationship;
38. Sn62Pb36Ag2 of solder paste on the ceramic plates the main trial;
39. rosin-based flux divided into four types: R, RA, RSA, RMA;
40. RSS curve of temperature → temperature → return → cooling curve;
41. We are using the PCB is made of FR-4;
42. PCB warpage specification not exceeding the diagonal of 0.7%;
43. STENCIL production laser cutting is another method of Heavy Industry;
44. now common computer motherboard BGA ball diameter of 0.76mm;
45. ABS system for absolute coordinates;
46. ceramic chip capacitors ECA-0105Y-K31 error of ± 10%;
47. current computer PCB, the material is: glass MDF;
48. SMT parts packaging of its reel disc diameter of 13 inches, 7 inches;
49. SMT PCB PAD generally smaller than the plate openings to prevent the solder balls can be bad 4um phenomenon; 50. in accordance with the "PCBA test specification" When the dihedral angle> 90 degrees, said solder paste and wave solder body no adhesion;
Preview: What's copy pcb?
[ Author: admin ] [ Date: 2013-7-30 ] [ Hits: ]