110 knowledge points of SMT chip processing – Part 1
1. Generally speaking, the temperature of SMT chip processing workshop is 25 ± 3 ℃;
2. Materials and things needed for solder paste printing, such as solder paste, steel plate, scraper, wiping paper, dust-free paper, detergent and mixing knife;
3. The common composition of solder paste alloy is Sn / Pb alloy, and the alloy share is 63 / 37;
4. There are two main components in solder paste, some are tin powder and flux.
5. The primary role of flux in welding is to remove oxide, damage the external tension of molten tin and avoid reoxidation.
6. The volume ratio of tin powder particles to flux is about 1:1 and the component ratio is about 9:1;
7. The principle of solder paste is first in first out;
8. When the solder paste is used in Kaifeng, it must be rewarming and mixing through two important processes;
9. The common manufacturing methods of steel plate are: etching, laser and electroforming;
10. The full name of SMT chip processing is surface mount (or mounting) technology, which means appearance adhesion (or mounting) technology in Chinese;
11. The full name of ESD is electro static discharge, which means electrostatic discharge in Chinese;
12. When manufacturing SMT equipment program, the program includes five parts: PCB data; mark data; feeder data; puzzle data; part data;
13. The melting point of Sn / Ag / Cu 96.5 / 3.0 / 0.5 is 217c;
14. The operating relative temperature and humidity of parts drying oven is < 10%;
15. Passive devices commonly used include resistance, capacitance, point inductance (or diode), etc.; active devices include transistors, IC, etc;
16. The raw material of commonly used SMT steel plate is stainless steel;
17. The thickness of commonly used SMT steel plate is 0.15mm (or 0.12mm);
18. The varieties of electrostatic charge include conflict, separation, induction, electrostatic conduction, etc.; the influence of electrostatic charge on electronic industry is ESD failure and electrostatic pollution; the three principles of electrostatic elimination are electrostatic neutralization, grounding and shielding.
19. The length x width of English system is 0603 = 0.06inch * 0.03inch, and that of metric system is 3216 = 3.2mm * 1.6mm;
20. Code 8 “4″ of erb-05604-j81 indicates that there are 4 circuits, and the resistance value is 56 ohm. The capacitance of eca-0105y-m31 is C = 106pf = 1NF = 1×10-6f;
21. The full Chinese name of ECN is engineering change notice; the full Chinese name of SWR is: work order with special needs, which is necessary to be countersigned by relevant departments and distributed in the middle, which is useful;
22. The specific contents of 5S are cleaning, sorting, cleaning, cleaning and quality;
23. The purpose of PCB vacuum packaging is to prevent dust and moisture;
24. The quality policy is: all quality control, follow the criteria, supply the quality required by customers; the policy of full participation, timely handling, to achieve zero defect;
25. The three no quality policies are: no acceptance of defective products, no manufacturing of defective products and no outflow of defective products;
26. Among the seven QC methods, 4m1h refers to (Chinese): human, machine, material, method and environment;
27. The composition of solder paste includes: metal powder, Rongji, flux, anti vertical flow agent and active agent; according to the component, the metal powder accounts for 85-92%, and the volume integral metal powder accounts for 50%; among them, the main components of the metal powder are tin and lead, the share is 63 / 37, and the melting point is 183 ℃;
28. When using solder paste, it is necessary to take it out of the refrigerator for temperature recovery. The intention is to make the temperature of the solder paste return to normal temperature for printing. If the temperature is not returned, the solder bead is easy to occur after PCBA enters reflow;
29. The document supply forms of the machine include: preparation form, priority communication form, communication form and quick connection form;
30. The PCB positioning methods of SMT include: Vacuum positioning, mechanical hole positioning, double clamp positioning and board edge positioning;
31. The resistance with 272 silk screen (symbol) is 2700 Ω, and the symbol (silk screen) of resistance with resistance value of 4.8m Ω is 485;
32. Silk screen printing on BGA body includes manufacturer, manufacturer’s part number, standard and Datecode / (lot no);
33. Pitch of 208pinqfp is 0.5mm;
34. Among the seven QC methods, fishbone diagram focuses on finding causal relationship;
37. CPK refers to the process capability under current practice;
38. Flux began to transpiration in the constant temperature zone for chemical cleaning;
39. The ideal cooling zone curve and the reflux zone curve are mirror images;
40. RSS curve is heating → constant temperature → reflux → cooling;
41. The PCB material we are using is FR-4;
42. PCB warpage standard does not exceed 0.7% of its diagonal;
43. The laser incision made by stencil is a method that can be reprocessed;
44. The diameter of BGA ball which is often used on the main board of computer is 0.76mm;
45. ABS system is positive coordinate;
46. The error of ceramic chip capacitor eca-0105y-k31 is ± 10%;
47. Panasert Matsushita full active Mounter with a voltage of 3? 200 ± 10vac;
48. For SMT parts packaging, the diameter of the tape reel is 13 inches and 7 inches;
49. The opening of SMT is usually 4um smaller than that of PCB pad, which can avoid the appearance of poor solder ball;
50. According to PCBA inspection rules, when the dihedral angle is more than 90 degrees, it indicates that the solder paste has no adhesion to the wave solder body;
51. After the IC is unpacked, if the humidity on the card is greater than 30%, it indicates that the IC is damp and hygroscopic;
52. The correct component ratio and volume ratio of tin powder to flux in solder paste are 90%: 10%, 50%: 50%;
53. The early appearance bonding skills originated from the military and Avionics fields in the mid-1960s;
54. The contents of Sn and Pb in solder paste which are most commonly used in SMT are different
Post time: Sep-29-2020