Smt chip processing, there are some small knowledge can not be ignored, which also belongs to smt chip processing common sense, it is easy to be overlooked by people. Jingbang technology below the technician gave you some finishing smt chip processing common sense.

1. ECN Chinese full name: Engineering Change Notice. SWR Chinese full name: special needs work orders. Need to be reviewed and signed by each functional department to take effect;

2. 5S specific content for the rectification ﹑ cleaning ﹑ cleaning ﹑ literacy;

3. The role of vacuum packaging PCB is moisture and dustproof;

4. The quality policy is: comprehensive quality control, compliance with rules and regulations to ensure the quality of the supply of customer needs; full participation ﹑ promptly deal with in order to achieve the goal of zero defect;

5. Quality "three noes" approach is: do not accept defective products, do not create defective products, not out of bad products;

6. "4M1H" means: human, machine, material, method, environment;

7. Paste ingredients include: metal powder ﹑ anti-drop agent ﹑ flux ﹑ solubilizer ﹑ active agent; by component, the metal powder accounted for 85-92%, according to the volume of metal powder accounted for 50%; during which the first metal powder Composition of tin and lead, accounting for 63%, 37%, melting point of 183 ° C;

8. Paste taken out of the freezer must be warmed at room temperature. The purpose is: Let the temperature of the cold solder paste return to normal temperature, to facilitate printing. If you do not back to warm, it is easy to produce tin beads in PCBA processing;

9. The supply of machine documents in the form of: preparatory form, priority exchange form, exchange form and quick connection form;

10. SMT chip processing PCB positioning methods are: vacuum positioning, mechanical hole positioning, positioning both sides of the folder and board edge positioning;

Screen printing is the resistance of 272, the resistance is 2700Ω, the resistance is 4.8MΩ, the resistance of the screen is 485;

12. BGA silk screen includes: manufacturers ﹑ ﹑ ﹑ datecode / (Lot No) and other manufacturers of information;

13. 208pinQFP pitch is 0.5mm;

14. The seven methods of QC testing, the fish bone map focuses on product traceability;

15. CPK: process capability under current processing conditions;

16. flux is in the beginning of the constant temperature zone, due to transpiration can chemically clean pcb board;

17. Cooling zone curve and the reflow zone curve was a mirror image;

18. RSS curve is warming → constant temperature → reflux → cooling curve;

19. Reflow the role of the temperature zone:

a. preheating zone; role: the solvent in the solder paste transpiration.

b. average temperature zone; role: activation of flux, remove oxides, transpiration flux remaining water.

c. back to the welding area; role: solder melting.

d. cooling zone; role: the formation of alloy solder joints, pins and components bonding pad as one;

20. SMT chip processing, resulting in tin beads are the main reasons: PCB pad design is unreasonable, unreasonable plate openings, patch depth or patch pressure is too large, the temperature rise curve is too large, the solder paste Collapse, paste viscosity is too low.