SMT Common Knowledge
SMT Common Knowledge
SMT Common Knowledge Introduction
1 . Generally speaking, the temperature of SMT workshop is 25±3℃.
2. Solder paste printing, the materials and tools needed to prepare the paste, steel plate, scraper, wipe paper, dust-free paper, cleaning agent, stirring knife.
3. generally used alloy composition of the paste is Sn / Pb alloy, and the alloy ratio of 63/37. 4.
4. The main components of the solder paste is divided into two major components of tin powder and flux. 5.
5 flux in the soldering of the main role is to remove the oxide, destroy the surface tension of molten tin, to prevent re-oxidation. 6.
6. The volume ratio of tin powder particles to Flux (flux) in solder paste is about 1:1, and the weight ratio is about 9:1.
7. The principle of taking solder paste is first in first out. 8.
8. when the paste is opened and used, it must go through two important processes: tempering and stirring.
9. The common production methods of steel plate are: etching, laser, electroforming.
10. The full name of SMT is Surfacemount (or mounting) technology, Chinese meaning for surface adhesion (or mounting) technology. 11.
11. the full name of ESD is Electro-static discharge, the Chinese meaning is electrostatic discharge.
12. When making SMT equipment program, the program includes five major parts, this five parts are substrate data; mounting data; loading data; component data; absorbing data, image data.
13. lead-free solder Sn/Ag/Cu 96.5/3.0/0.5 melting point of 217C. 14.
14. The controlled relative temperature and humidity of the parts drying oven is < 10%.
15. commonly used passive components (PassiveDevices) are: resistance, capacitance, point sense (or dipole), etc.; active components (ActiveDevices) are: crystals, IC, etc.
16. The material of the commonly used SMT steel plate is stainless steel.
17. The thickness of the commonly used SMT steel plate is 0.15mm (or 0.12mm).
18. The types of electrostatic charge generated by friction, separation, induction, electrostatic conduction, etc.; electrostatic charge on the electronics industry: ESD failure, electrostatic pollution; electrostatic elimination of the three principles of electrostatic neutralization, grounding, shielding.
19. imperial size LxW 0603=0.06inch*0.03inch, metric size LxW 3216=3.2mm*1.6mm.
20. The 8th code "4" of ERB-05604-J81 indicates 4 circuits with 56 ohms resistance value. Capacitor ECA-0105Y-M31 capacitance C = 106PF = 1NF = 1X10-6F.
21. ECN Chinese full name: engineering change notice; SWR Chinese full name: special requirements work order, must be countersigned by the relevant departments, the documentation center to distribute, in order to be effective.
22. 5S specific content for the organization, tidying, cleaning, cleanliness, literacy.
23. The purpose of PCB vacuum packaging is to prevent dust and moisture.
24. The quality policy is: **Quality control, implementation of the system, to provide the quality of customer needs; full participation, timely processing, to achieve the goal of zero defects.
25. The three no policies of quality are: do not accept ** products, do not manufacture ** products, and do not flow out ** products.
26. QC seven techniques in the fishbone check the cause of 4M1H are (Chinese): people, machines, materials, methods, environment.
27. The composition of the solder paste contains: metal powder, solution, flux, anti-drop agent, active agent; by weight, metal powder accounts for 85-92%, by volume metal powder accounts for 50%; where the main components of metal powder for tin and lead, the ratio of 63/37, the melting point of 183 ℃.
28. Solder paste must be taken out of the refrigerator when using back to temperature, the purpose is: let the refrigerated temperature of the paste back to room temperature, in order to facilitate printing. If not return to temperature in the PCBA into the Reflow easy to produce ** for tin beads.
29. the machine's file supply mode are: ready mode, priority exchange mode, exchange mode and quick connect mode.
30. SMT PCB positioning methods are: vacuum positioning, mechanical hole positioning, bilateral clamping positioning and board edge positioning.
31. The resistor with a silkscreen (symbol) of 272 has a resistance value of 2700Ω, and the resistor with a resistance value of 4.8MΩ has a symbol (silkscreen) of 485.
32. The silkscreen on the BGA body contains information such as manufacturer, manufacturer's part number, specification, and Datecode/(Lot No).
33. The pitch of 208pin QFP is 0.5mm.
34. the seven QC practices, the fishbone diagram emphasizes the search for cause-and-effect relationships;
35. CPK refers to the current process capability under actual conditions;
36. Flux starts to evaporate in the constant temperature zone for chemical cleaning act