Challenges of manual screen printing

In the process of manually screen-printing solder paste onto PCBs, one of the decisive factors in guaranteeing the quality and regularity of the deposit is the mechanical stability of the printed circuit board during the squeegee movement.  Let's imagine a board with no lateral support. When the squeegee presses down, it applies a longitudinal downward force. This force, concentrated across the width of the squeegee, pushes directly against the edges of the board. Since the PCB is often thin (typically 1.6 mm or less), it will flex slightly, especially if the support surface (stencil) is not perfectly rigid (thin stencil)

This deformation results in:

• A loss of flatness: the squeegee follows a curved trajectory instead of a straight line
• Unequal pressure: stronger in the centre, weaker at the edges
• Fluctuating deposit thickness: areas of excess thickness when the squeegee is straightened, or areas without solder paste due to poor contact

In the CIF system with bars, these problems are mechanically eliminated. The side bars act as rigid interfaces on which the squeegee is partially supported. They create a fixed reference plane, parallel to the surface of the board. In this way, regardless of any possible micro-deformations in the board, the squeegee is guided in a stable manner and applies a constant pressure parallel to the surface. This firm, continuous contact between the ends of the squeegee and the bars ensures that the pressure is evenly distributed, creating a constant, flat contact surface across the entire width of the board. The deposit is then controlled with greater precision. In addition, anti-bending pins placed under the board reinforce this stability, by supporting the centre of the board against any vertical bending.

In addition to traditional anti-bending pins, the systems have been equipped with new complementary anti-bending pins since April 2025. These new pins provide lateral support with a 0.8 mm high ergonomic design that allows them to be positioned in certain vias or around the edges of PCBs with non-rectilinear shapes to ensure perfect support and clamping. They are therefore compatible with PCB thicknesses greater than or equal to 8/10 mm.

The real challenge in manual screen printing is not simply to apply the solder paste, but to apply it in a controlled, homogenous and reproducible way. Thanks to our reinforced system with side bars, you can transform a traditional operation into a much more reliable and industrial process, while retaining the flexibility and low cost of manual operation. It's a technical compromise that ensures deposit quality close to that of semi-automated systems, without the heavy investment.

⚖️ Technical comparison between two manual screen-printing systems:

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