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PCB Reverse Engineering

PCBA reverse FAQ summary

1. In general, PCBA reverse & SMT workshop temperature of 25 ± 3 ℃;
2. Paste printing, the required preparation of materials and tools Paste, steel plate, scraper, clean paper, clean paper, cleaning agent, mixing knife;
3. The commonly used solder paste alloy composition for the Sn / Pb alloy, and the alloy ratio of 63/37;
4. Paste in the main components are divided into two parts of the tin powder and flux.
5. The main role of flux in welding is to remove the oxide, destroy the surface tension of molten tin, to prevent re-oxidation.
6. The ratio of the volume of tin powder particles to Flux (flux) is about 1: 1, the weight ratio is about 9: 1;
7. Paste the principle of access is first-in first out;
8. Paste in Kaifeng use, to go through two important processes back to temperature, stirring;
9. Common production methods are: etching, laser, electroforming;
10. SMT full name is Surface mount (or mounting) technology, the Chinese means for the surface adhesion (or placement) technology;
11. ESD full name is Electro-static discharge, the Chinese meaning for the electrostatic discharge;
12. The production of SMT equipment program, the program includes five parts, the five parts of the PCB data; Mark data; Feeder data; Nozzle data; Part data;
13. Lead-free solder Sn / Ag / Cu 96.5 / 3.0 / 0.5 has a melting point of 217C;
14. Parts of the oven control relative humidity and humidity <10%;
15. Common passive components (Passive Devices) are: resistance, capacitance, point (or diode); active components (Active Devices) are: transistors, IC, etc .;
16. The commonly used SMT steel plate is made of stainless steel;
17. The thickness of the commonly used SMT steel plate is 0.15mm (or 0.12mm);
18. PCBA reverse Electrostatic charge generated by the type of friction, separation, induction, electrostatic conductivity, etc .; electrostatic charge on the electronics industry: ESD failure electrostatic pollution; static elimination of the three principles of static electricity and grounding, shielding.
19. inch size length x width 0603 = 0.06inch * 0.03inch, metric length x width 3216 = 3.2mm * 1.6mm;
20. Exclusion ERB-05604-J81 8 "4" is expressed as 4 loops with a resistance of 56 ohms. Capacitance ECA-0105Y-M31 ​​Capacitance is C = 106PF = 1NF = 1X10-6F;
21. ECN Chinese full name: engineering change notice; SWR Chinese full name: special needs work orders, must be signed by the relevant departments, the document center distribution, party is valid;
22. 5S specific content for finishing, rectification, cleaning, cleaning ﹑ quality;
23. PCB vacuum packaging is the purpose of dust and moisture;
24. Quality policy: a comprehensive quality control, implement the system to provide the quality of customer needs; full participation, timely processing, to achieve the goal of zero shortcomings;
25. Quality three no policy: do not accept bad products, do not create bad products ﹑ not out of bad products;
26. QC seven practices in the fish bone check the reasons 4M1H are (Chinese): people, machinery, materials, methods, the environment;
The composition of the solder paste comprises: metal powder, solvent, flux, anti-flooding agent and active agent; the metal powder is 85-92% by weight, 50% by volume of metal powder; The composition of tin and lead, the ratio of 63/37, the melting point of 183 ℃;
28. Paste use must be removed from the refrigerator back to warm, the purpose is: to cool the temperature of the solder paste back to room temperature, in order to facilitate printing. If not back in the PCBA into Reflow after the easy to produce bad for the tin beads;
29. The machine supply mode of the machine is: preparation mode, priority exchange mode, exchange mode and quick access mode;
30. PCBA reverse  positioning methods are: vacuum positioning, mechanical hole positioning, bilateral clamp positioning and edge positioning;
31. The screen (symbol) is a resistance of 272, the resistance is 2700Ω, the resistance of 4.8MΩ resistance of the symbol (silk screen) to 485;
32. The silk screen on the BGA body contains information such as the manufacturer, the manufacturer's reference number, the specifications and the datecode / (Lot No)
33. 208pinQFP pitch is 0.5mm;
34. QC seven practices, fish bone figure emphasizes the search for causal relationship;
37. CPK refers to the current process conditions of the process capacity;
38. Flux begins to evaporate in the constant temperature zone for chemical cleaning.
39. Ideal cooling zone curve and recirculation zone curve mirror relationship;
40. RSS curve for the temperature → constant temperature → return → cooling curve;
41. We are using the PCB material FR-4;
42. PCB warpage specifications do not exceed 0.7% of its diagonal;
43. STENCIL laser cutting is the way to re-engineering;
44. At present the computer motherboard is often used BGA ball diameter of 0.76mm;
45. ABS system is absolute coordinates;
46. ​​Ceramic chip capacitors ECA-0105Y-K31 error of ± 10%;
47. Panasert Panasonic automatic placement machine with a voltage of 3? 200 ± 10VAC;
48. SMT parts packaging Tape reel diameter of 13 inches, 7 inches;
49. SMT general steel plate hole than the PCB PAD 4um can prevent the phenomenon of poor solder ball;
50. In accordance with the "PCBA test" Fan when the diagonal> 90 degrees, said solder paste and wave soldering without adhesion;
51. After the unpacking of the IC, the humidity on the card indicates that the IC is moisture and moisture is more than 30%
52. The weight ratio and volume ratio of tin powder to flux in the solder paste composition are 90%: 10%, 50%: 50%
53. Early surface adhesion technology originated in the mid-1960s military and aeronautical electronics;
54. At present SMT is the most commonly used solder paste Sn and Pb content are: 63Sn +37Pb;
55. The common bandwidth of 8mm paper tape tray feeding distance of 4mm;
56. In the early 1970s, a new SMD in the industry was "sealed without foot chip carrier", often with HCC;
57. The resistance of the component with symbol 272 should be 2.7K ohms;
58. The 100NF component has the same value as 0.10uf;
59. The eutectic point of 63Sn + 37Pb is 183 ° C;
60. SMT the largest use of electronic parts material is ceramic;


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