Printing Solder Paste Test - China PCBA Supplier

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To ensure the quality of the printing, it needs to monitor the printing press parameters: printing speed / squeegee pressure / printing gap / separation distance / clean frequency / paste thickness / the viscosity. All these parameters should be met the specification. The thinkness and viscosity of the paste should be also met the specification.

The specifications of the thickness of the stencil and tin coating:

0.12mm 0.11 ~ 0.17mm 0.18mm 0.15 ~ 0.23mm

0.15mm 0.13 ~ 0.21mm 0.20mm 0.17 ~ 0.25mm

Paste neither is a solid, not a liquid, it is a mixed paste objects, the main component is the solder powder (tin powder) and the flux (flux)

To achieve a good printing durability, it is required to solder paste viscosity at the low level when printing. So that the stecil is easier to fall the paste and demould.After demoulding, in order to ensure that the solder paste does not collapse, it needs a higher viscosity, so it should add the solder paste thixotropic agent. The thixotropic agent can make the the viscosity of the solder paste at a sharp decline during exercise. When stopping motion, the viscosity will soon recover. So that it can achieve good printability.

(1) Printing Red Glue

The red glue is usually kept in the refrigerator at the optimum temperature. It should be remove thawed at room temperature before using. And then open and stir to use.The dosage shoulbe be not to exceed two hours. It also needs to check if the red glue printed on the bottom of the PCB mounting components with full and moderate. So that there is no infiltration of red glue mount to the the pad and connectors (or pins). At the same time, the red glue can make the components bonding and fastening. So that when wave soldering, the components are not easy to fall.

(2) Printing Solder Paste

The solder paste is usually kept in the at the refrigerator proper temperature. Be fore using, it should be removed from the refrigerator and thawed to room temperature. And then open and stir until uniform, smooth and put into use. It also needs to check after printing the solder paste is uniform amount printed on the PCB pads, with or without collapse and scattered at the surface of the PCB to ensure good reflow soldering components. And there is no beads scattered on the plate surface.