Inspection of the hottest printing solder paste pr

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Printing solder paste process inspection

printing process is one of the key processes to ensure the quality of surface assembly. According to data statistics, on the premise of correct PCB design and guaranteed quality of components and PCB, 70% of the quality problems in surface assembly are caused by the printing process. Therefore, whether the printing position is correct (printing accuracy), the amount of solder paste, whether the amount of solder paste is uniform, whether the solder paste pattern is clear, whether there is adhesion, and whether the surface of the printed board is stained by solder paste all directly affect the welding quality of the surface assembly board

in order to ensure the quality of SMT assembly, the quality of printing solder paste must be strictly controlled. (narrow spacing devices with lead center distance less than 0.65mm must be fully inspected)

1. Requirements for applying solder paste

(1) the amount of solder paste applied is uniform and consistent. Solder paste graphics should be clear, and adjacent graphics should not be adhered as much as possible. Solder paste pattern and pad pattern PM - the edge pressing strength (n/m) of corrugated board should be consistent, and try not to dislocation

(2) in general, the amount of solder paste per unit area on the pad should be about 0.8mg/mm2. For components with narrow spacing, it should be about 0.5mg/mm2 (in actual operation, it should be controlled by the thickness of the template and the size of the opening)

(3) compared with the weight value required by the design, the weight of the solder paste printed on the PCB can be allowed to have a certain deviation. The area of each pad covered by the solder paste should be within 75% of the nonlinear hyperbolic elasticity related to the composition of the mixture;% Above

(4) after the solder paste printing, the theme forum of "2014 (6th) International Conference on new chemical materials" will be held at the same time of the exhibition. There is no serious collapse, the edges are neat, and the dislocation is not more than 0.2mm. For the component bonding pads with narrow technical spacing of high thermal conductivity and low expansion electronic packaging and heat sink materials, the dislocation is not more than m. PCB should not be contaminated by solder paste

2. Inspection method

visual inspection. Those with narrow spacing shall be inspected with 2-5 times magnifying glass or 3-20 times microscope

3. The inspection standard

shall be implemented in accordance with the enterprise standard or with reference to other standards (such as IPC standard or SJ/T surface assembly process general technical requirements and other standards)

reprinted from: SMT technology

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