In SMT assembly line, many processes require adjustments to the processing equipment, with the most critical steps summarized into 7 key steps.
I. Graphic Alignment
Using a solder paste printer on the workbench, align the optical MARK points with the steel mesh and steel mesh. Then fine-tune the X, Y, and θ parameters to ensure the pad patterns on the steel mesh and steel mesh perfectly match.
II. Angle Between the Squeegee and Steel Mesh
The smaller the angle between the squeegee and steel mesh, the greater the downward pressure, which can easily inject solder paste into the steel mesh and also easily squeeze solder paste into the bottom of the steel mesh, causing solder paste adhesion. The angle is typically between 45° and 60°. Nowadays, most automatic and semi-automatic solder paste printing machine systems use.
III. Squeegee Force
Squeegee force is also a critical factor affecting print quality. Squeegee pressure management essentially refers to the depth of the squeegee’s descent. If the pressure is too low, the squeegee cannot adhere to the stencil surface, effectively increasing the thickness of the printed material during SMT machine placement. Additionally, if the pressure is too low, a layer of solder paste may remain on the stencil surface, potentially causing printing defects such as deformation or adhesion issues.
IV. Printing Speed
Since squeegee speed is inversely proportional to solder paste viscosity, when solder paste density is high, spacing narrows, and printing speed slows down. If the squeegee moves too quickly, the mesh opening time is short, and solder paste cannot fully penetrate the mesh openings, leading to defects such as uneven solder paste distribution or missed printing. Printing speed is related to squeegee pressure, the descent speed equals the pressure application speed. Appropriately reducing the pressure application speed can increase printing speed. The optimal squeegee processing speed and pressure control method is to scrape the solder paste off the steel mesh surface.
V. Printing Gap
The printing gap is the distance between the printed circuit board and the PCB, which is related to the amount of solder paste left on the PCB.
VI. Separation Speed Between Steel Mesh and PCB
The separation speed is the instantaneous speed at which the steel mesh leaves the PCB after solder paste printing. It is a key factor affecting print quality, particularly important in high-density printing. Advanced SMT solder paste printers have a small pause process (or multiple pauses) when the steel mesh leaves the solder paste pattern, known as multi-stage demolding, to ensure optimal print results. If the separation rate is too high, the solder paste viscosity decreases, and the pad viscosity is low, causing some solder paste to adhere to the bottom surface of the steel mesh and the opening walls, resulting in printing quality issues such as reduced printing volume and printing collapse. If the separation speed slows down, the solder paste viscosity increases, and the viscosity is good and cohesive, making it easier for the solder paste to separate from the steel mesh and opening walls, resulting in better printing quality.
VII. Cleaning production mode and frequency
Screen cleaning is also a factor that ensures print quality. The cleaning method and frequency should be determined based on the solder paste material, screen thickness, and aperture size. Steel mesh contamination (set dry cleaning, wet cleaning, single-use reciprocation, wiping speed, etc.). If data is not cleaned promptly, it will contaminate the PCB surface, and residual solder paste around the steel mesh openings will harden, potentially blocking the openings in severe cases.
Conclusion
In SMT manufacturing facilities, many detailed parameter settings are not achieved overnight, they require long-term practical experience to summarize lessons learned, enhance management of quality control details, and continuously optimize processes.
Company Profile
Zhejiang NeoDen Technology Co., Ltd. has been manufacturing and exporting various small pick and place machines since 2010. Taking advantage of our own rich experienced R&D, well trained production, NeoDen wins great reputation from the world wide customers.
In our global Ecosystem, we collaborate with our best partners to deliver a more closing sales service, high professional and efficient technical support.
We believe that great people and partners make NeoDen a great company and that our commitment to Innovation, Diversity and Sustainability ensures that SMT automation is accessible to every hobbyist everywhere.
Post time: Jul-31-2025