Soldering defect: printing defect (solder paste)

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Detailed information

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  Printing defects Among the printing defects, those caused by solder paste mainly fall into two categories: (1) Transfer failure This phenomenon occurs when the required amount of solder paste is not transferred to the substrate, leading to insufficient wetting and strength at the soldering points. (2) Printing smearing This phenomenon occurs when the shape of the solder paste collapses or is excessively transferred after printing. It can cause bridging in chip side balls and narrow pitch areas.

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  Causes of Printing Defects The cause of these defects is the change in viscosity of the solder paste. An increase in viscosity leads to transfer defects, while a decrease causes printing smearing.

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  Countermeasures for Printing Defects There are countermeasures for solder paste and equipment settings. (a) Countermeasures using solder paste By using solder paste with minimal viscosity changes even during long continuous printing, both transfer defects and printing smearing can be addressed. (b) Countermeasures through equipment settings Managing the temperature and humidity within the printing machine can serve as a countermeasure. When the temperature inside the printing machine is high, the viscosity of the solder paste temporarily decreases, leading to printing smearing. However, over time, the chemical reaction between the flux and solder powder causes the viscosity to increase, resulting in transfer defects. Conversely, when the temperature is low, the viscosity of the solder paste decreases, leading to transfer defects. High humidity inside the printing machine can cause deterioration of the solder paste due to moisture absorption, resulting in increased viscosity and transfer defects. Additionally, low humidity can cause the solvent in the flux to evaporate, increasing the viscosity of the paste and leading to transfer defects.

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  We offer solder paste with stable printability that experiences minimal viscosity changes even during long printing sessions, so please feel free to contact us.