SMT Patch Processing: Poor Solder Paste Printing Phenomena and Cause Analysis

In SMT patch processing, solder paste printing is a critical step in ensuring welding quality. However, according to statistics, up to 60-70% of welding defects are caused by poor solder paste printing. Therefore, a thorough understanding and identification of the potential adverse phenomena during the solder paste printing process, as well as their underlying causes, is crucial for improving the yield of SMT patch processing.

One common adverse phenomenon is the collapse of the solder paste edges after printing. When the solder paste fails to maintain a stable shape during the printing process, its edges gradually spread outward towards the outer side of the solder pad, and even form connections between adjacent solder pads. If this collapse phenomenon is not corrected in time, it will lead to welding shorts during the reflow soldering process, seriously affecting product quality.

So, what causes this solder paste collapse phenomenon? Hunan Charmhigh Electromechanical will discuss the poor solder paste printing phenomena and their causes in SMT patch processing. Interested friends, let's take a look together.

Firstly, excessive squeegee pressure is an important cause. Excessive pressure can cause the solder paste to be excessively squeezed, allowing it to flow into the gap between the stencil and the PCB. In severe cases, the solder paste of adjacent solder pads may connect, resulting in collapse defects.

Additionally, the viscosity of the solder paste is a key factor affecting printing quality. If the viscosity of the solder paste is too low, its edges can easily become loose after printing, leading to collapse. This collapse phenomenon is more likely to cause solder paste shorts, especially for fine-pitch components.

High metal content is another cause of poor solder paste printing. When the solder paste is left on the stencil for too long or recycled solder paste is used, the diluent components may evaporate while the metal content remains unchanged. This can lead to a decrease in the viscosity of the solder paste, thereby increasing the risk of collapse.

Moreover, the size of the solder particle also affects the quality of the solder paste printing. Solder paste with smaller particle sizes has better tin filling properties under the stencil, but its ability to maintain the shape of the solder paste after printing may be poorer. During the printing process, metal particles are more likely to spread under the stencil, increasing the risk of solder paste shorts.

Furthermore, the hygroscopicity of the solder paste is also a factor that needs to be addressed. When the air humidity is high or the solder paste is exposed to the air for too long, it may absorb moisture from the air and become diluted. This can lead to a decrease in the viscosity of the solder paste, making it unable to maintain a stable shape and prone to collapse.

Lastly, the ambient temperature also has an impact on the quality of solder paste printing. When the ambient temperature is too high, the viscosity of the flux in the solder paste may decrease, leading to collapse after printing. Moreover, if the time is too long, the diluent components in the solder paste may further evaporate, resulting in increased viscosity and making printing difficult.

In summary, the occurrence of poor solder paste printing phenomena is closely related to multiple factors. To ensure the yield and quality of SMT patch processing, we need to closely monitor these factors and take corresponding measures to prevent and correct the occurrence of poor solder paste printing phenomena.

Hunan Charmhigh Electromechanical is a professional manufacturer of SMT placers. If you have a demand for SMT placers, please contact us, and we will provide you with efficient and professional services. If you want to become our local dealer, we will provide you with a mutually beneficial agency plan.WhatsApp : +8618100733752 / WeChat : 86 18100733752 / Skype : 86 18100733752