What are the reasons leading to PCBA patch processing patch poor
PCBA processing manufacturers PCBA chip processing production process, because of the influence of the error, it is easy to cause PCBA SMT defects, such as: air welding, short circuit, erect, short, tin beads, squatting, floating high, wrong parts, cold welding, reversal, the white/reverse, offset printing, the element damage, tin, tin, tin, gold finger glue, etc., need to analyze these defects, improve, improve product quality.
Analysis of machining defect of PCBA chip
First, air welding
1. Weak solder paste activity;
2. Poor opening of steel mesh;
3, copper or platinum spacing too large or large copper paste group;
4. Excessive blade pressure;
5. Uneven (warped and deformed) foot of components;
6. The reheating zone of the reflux furnace heats up too fast;
7,PCB copper platinum too dirty or oxidation;
8,PCB board water;
9. Deviation of machine placement;
10, solder paste printing offset;
11. The loose guide rail of the machine splint causes the mounting deviation;
12. MARK points are misaligned due to misalignment of components, resulting in blank welding;
Second, short circuit
1. The distance between the wire mesh and the PCB is too large, resulting in too thick and short solder paste printing;
2. The mounting height of components is set too low to squeeze the solder paste and cause a short circuit;
3. The heating furnace heats too fast;
4. Offset caused by component mounting;
5. Poor opening of steel mesh (too thick, too long lead opening, too large opening);
6. The solder paste cannot bear the weight of components;
7. The deformation of steel mesh or scraper causes the solder paste printing to be too thick;
8. Strong activity of solder paste;
9. The sealing tape at the empty paste point is rolled up to make the solder paste printing of peripheral components too thick;
10, reflux vibration is too large or not horizontal;
Third, upright
1. The copper and platinum on both sides of different sizes produce uneven tension;
2. The rate of preheating is too fast;
3. Deviation of machine placement;
4. Uneven solder paste printing thickness;
5. Uneven temperature distribution in the reflux furnace;
6, solder paste printing offset;
7, the machine track splint is not tight, resulting in placement deviation;
8. Shake the nose;
9. The solder paste is too active;
10. The furnace temperature is not set correctly;
11. The spacing between copper and platinum is too large;
12,MARK point misoperation caused yuan qu
Fourth, missing parts
1. Insufficient vacuum of carbon plate of vacuum pump, resulting in missing parts;
2. The nozzle is blocked or defective;
3. Improper component thickness detection or defective detector;
4. Improper placement height;
5, suction nozzle is too large or not blowing;
6. Improper nozzle vacuum setting (applicable to MPA);
7. The speed of placing special-shaped components is too fast;
8. Trachea head is very fierce;
9. Valve seals wear;
There are elements on the wipe plate of foreign body on the track side of reflow furnace;
Fifth, tin beads
1. Insufficient preheating of reflow welding and excessive heating;
2. Refrigerate the solder paste with incomplete temperature;
3. Solder paste absorbs spatter (excessive indoor humidity);
4. Too much water on PCB board;
5. Add excessive diluent;
6. Improper opening design of steel mesh; 7. Tin powder particles are uneven.
Sixth, offset
1. The positioning reference point on the board is not clear
2. The positioning reference point on the circuit board is not aligned with the reference point of the template.
3. The fixing clamp of the circuit board in the printing machine is loose, and the locating thimble is not in place.
4. The optical positioning system of the printing machine is faulty
5, the lack of solder paste template openings and circuit board design document is inconsistent
In order to improve the defects of the PCBA patch, it is necessary to carry out a rigorous inspection of all aspects to prevent problems of the previous process from flowing as little as possible into the next process.
