Solder Paste Dispensing on Printed Circuit Boards: Challenges and Solutions

In the complex world of PCB (Printed Circuit Board) assembly, solder paste dispensing is a critical process that demands precision and consistency. Whether you're an experienced engineer or a technician new to the field, understanding the challenges and solutions associated with solder paste application can significantly impact the quality and reliability of your electronic products. Let's look into these aspects, particularly focusing on the advanced solutions offered by marco’s StepDot Dispensing Head and the marc1 Gantry System, our inline robotic system.

Challenges in the solder paste dispensing

1. Precision and consistency: The primary challenge is to achieve consistent and precise deposition of solder paste on the PCB. Inconsistent application can lead to issues like poor solder joints, bridging, or insufficient solder, which affect the performance and reliability of the final product.
2. Speed and throughput: High-speed production lines require solder paste dispensing systems that can keep up without sacrificing accuracy. Traditional methods often struggle to balance speed with precision.
3. Adaptability to different PCB designs: Modern electronics feature a wide variety of PCB designs, each with unique requirements for solder paste volume and placement. A flexible dispensing system is essential to handle diverse design specifications.
4. Minimizing waste material: Efficient use of solder paste not only reduces material costs but also minimizes environmental impact. However, achieving this efficiency without compromising on quality is a significant challenge.

Examples of different requirements at solder paste dispensing:

Solutions with marco's StepDot dispensing head and marc1 Gantry System

Piezo actuator-based system technology

Piezo-actuator based systems like our StepDot dispensing head offer an advanced solution for precision solder paste dispensing. marco systems valves are designed with the TorqueBlock actuator, using piezoelectric materials to control the flow of solder paste with exceptional accuracy. With frequencies up to 100 Hz and interchangeable valve seats, we dispense dots and lines with diameters or line widths down to 120 µm – extremely fine and precise.

Here you can see how piezo valve technology solves typical dispensing challenges:

• High precision: Piezo-actuator based systems can dispense minute quantities of solder paste with remarkable precision, ensuring uniform application even on the smallest pads. This precision significantly reduces defects like bridging and insufficient solder.
• Consistent flow control: The advanced control mechanisms in piezo valves build the foundation to be able to maintain a consistent flow of solder paste, enabling every deposit to be identical. This consistency is crucial for high-quality solder joints.
• Speed: Piezo valves are capable of higher frequency dispensing, making them suitable for fast-pace production lines. They maintain accuracy even at fast dispensing rates, thus enhancing throughput without compromising quality.

High-speed precision with small dot sizes

Micro-dispensing of solder paste dots – in this example – with diameters around 180 µm is carried out using the StepDot dispensing head from marco systems. Operating at dispensing frequencies of up to 100 Hz, the system ensures consistent dot formation with high repeatability and process stability.

The StepDot dispensing head is compatible with a wide range of solder paste types and does not rely on specific brands. The example images show dot dispensing using a Type 6 solder paste from a Chinese supplier, applied through a 65 µm tungsten nozzle.

The marc1 Gantry System: A new standards for inline robotic systems

Integrating inline robots with piezo valve dispensers brings another layer of efficiency and precision to the solder paste dispensing process:   

• Automation and efficiency: Inline robots automate the movement of the dispensing head along the PCB,  ensuring precise alignment and consistent paste application.This automation reduces manual intervention, thereby increasing efficiency and reducing the risk of human error.
• Adaptability: Robots can be programmed to handle different PCB designs and solder paste requirements with ease. This adaptability allows for quick changeovers between different products, making the production line more versatile.
  
• Enhanced throughput: The combination of robotic speed and piezo valve precision ensures that high-volume production runs are completed quickly and accurately. This synergy boosts overall throughput and productivity.
• Waste reduction: Inline robots combined with piezo valves, that allow for precise control over the dispensing process, reduce solder paste waste. The piezo valve ensures a precise dispensing volume, minimizing excess and thereby lowering material costs.

Closed-loop control with integrated inspection

The StepDot dispensing head from marco features an integrated high-performance camera system that captures the solder paste dispensing process. This enables real-time, inline inspection of dot dimensions during live operation.

The system operates in fully closed-loop control mode, using data inspection. In the event of nozzle clogging, the system stops immediately – minimizing potential damage to the board and ensuring maximum process reliability for the end user.

Advantages of using a StepDot dispensing head for solder paste dispensing

1. Greater flexibility with product variants

• No stencil changes required – layout modifications (e.g., component sizes or positions) can be easily implemented digitally.
• Especially beneficial for frequently changing product variants or prototype production.

2. No stencil wear, minimum downtime, low running costs

• Stencils can wear out, bend or clog over time - this cannot happen when dispensing.
• Less maintenance and lower running costs for consumables and cleaning agents.
• Main parts (valve seat, nozzle, fluid body) are modular. This means you need to change only the worn or clogged part. This saves time and lowers service costs.
• Nozzle and valve modules can be replaced in seconds, minimizing downtime.
• The marco systems’ cleaning kit helps to clean and replace with the necessary tools.

3. Precise volume control

• Each solder paste deposit can be dispensed individually with adjustable volume.
• Ideal for components with varying pad sizes or heights, such as in 3D-MID, LED assembly, or power electronics.

4. Improved process reliability for complex or critical pads

• No risk of stencil smearing or misprints – especially important for small or densely packed pads.
• Better repeatability and accuracy with demanding geometries.

5. Reduced waste in small batch production

• No material loss due to stencil printing on test boards.
• Dispensing only on actual solder pads → lower solder paste consumption in small or highly customized production runs.

6. Automation-ready and inline-compatible

• Easy integration into automated SMT lines, e.g., as part of inline dispensing systems.
• Ideal for Industry 4.0 concepts with data-driven process optimization.

7. No printing process - fewer process parameters

• Screen printing involves many parameters (squeegee pressure, speed, angle, stencil support, etc.).
• Dispensing processes are more stable and easier to monitor and control.

Best suited for:

• Prototype manufacturing
• Small to medium batch sizes with frequent layout changes
• Applications with high precision or quality requirements

Conclusion for the solder paste dispensing

By integrating piezo valve technology with inline robotic systems, PCB manufacturers can overcome the traditional challenges of solder paste dispensing. This advanced approach offers unmatched precision, consistency, and efficiency, ensuring high-quality solder joints and reliable electronic products. The long-term benefits in terms of reduced defects, increased throughput, and material savings make it a worthwhile consideration marco’s system solution for any forward-thinking manufacturer.

The investment in piezo valve and inline robot technology from marco not only improves your production capabilities, but also positions your operation at the forefront of innovation in PCB manufacturing. This solution was by marco to meet the demands of modern electronics manufacturing and gives you the tools you need to succeed in a competitive market.