The Importance of Having a Clean Slate in the SMT Assembly Process

The Importance of Having a Clean Slate in the SMT Assembly Process
The paper covers an experiment to improve upon the defect ratio of their PCB assembly process by utilizing a bare board cleaner before the paste printer.
Analysis Lab


Authored By:

Charlie Fujikawa, Michelle Ogihara
Seika Machinery, Inc.


The miniaturization of electronics and globalization of the SMT industry have introduced a number of challenges to the manufacturing process. Despite improvements to many aspects of SMT manufacturing, one of the crucial components of a smooth and efficient process is often overlooked. The industry strives to minimize the number of voids and defects that can occur during production and starting with a clean surface on the PCB is an important step in accomplishing this.

This generation of SMT manufacturing has seen the introduction of nearly microscopic chips and components that populate PCBs at higher densities than ever before. The smallest bit of debris can cause major problems and interfere with the solder pads that have been screen printed over it. Hair and dust contribute to voids and errors during the reflow process. PCB manufacturing has become a major point of growth on a worldwide scale. The number of PCBs being produced continues to grow and the technology of the boards also advances. This mass production of bare boards has led to losses of quality control resulting in a rise of cases where excess of substrate material debris is being left on the PCBs. That loose material, if left on the surface, can interfere with printing and burn up during reflow. There is no guarantee that the PCB is completely free of contaminants when it enters into production.

Implementing a method of cleaning the PCB surface before it enters the screen-printing machine is an ideal step in Process Control. This step ensures that the PCB surface is free from debris & contaminants, and prepares the surface of the pads to make clean contact with the solder.

The white paper will cover an experiment and evaluation conducted by a well-known Japanese manufacturer of automotive electronics to improve upon the defect ratio of their PCB assembly process by utilizing a bare board cleaner before the paste printer. The evaluation will depict the conditions of their assembly process before using the cleaner and results after testing with cleaning system. This study will cover the effects and observations of reflowing PCBs, while comparing the results of the effectiveness of using a bare PCB surface cleaner.


In conclusion, the need for cleaning bare PCBs (Printed Circuit Boards) in Surface Mount Technology (SMT) assembly is essential for several compelling reasons.

First and foremost, PCB cleaning is essential to ensure the integrity of the soldering process. Contaminants, such as dust, hair, leftover & routed substrate material, dirt, and other foreign particles, can interfere with the adhesion of solder paste during the screen-printing phase. Insufficient adhesion can lead to defective solder joints, including weak connections and solder bridges, jeopardizing the overall reliability and functionality of electronic assemblies. Debris and particles can burn during the reflow process, causing voiding, misalignment and dislodging of components.

Furthermore, proper cleaning of bare PCBs is critical for maintaining the quality and consistency of the SMT production process. Clean PCBs provide a uniform starting point for component placement and soldering, contributing to consistent results across production runs. This consistency is essential for achieving low defect rates and high-quality electronic products.

Clean PCBs are crucial for long-term reliability. Contaminants left on the PCB surface can lead to electrical shorts, corrosion, and compromised insulation resistance over time. By ensuring that bare PCBs are thoroughly cleaned before component placement, manufacturers can enhance the longevity and durability of their electronic assemblies.

Additionally, as environmental regulations become stricter, PCB cleaning plays a role in promoting eco-friendly manufacturing practices. Proper cleaning helps decrease the wasting of material and resources due to misprints and defective PCBs. This leads to a reduction in the environmental impact of the electronic production processes.

In summary, the need for bare PCB cleaning in SMT is driven by the importance of maintaining soldering quality, achieving production consistency, ensuring long-term reliability, and adherence to environmental standards. Embracing effective cleaning practices is a fundamental step toward producing high-quality, reliable, and environmentally responsible electronic products in the ever-evolving world of electronics manufacturing.

Initially Published in the SMTA Proceedings


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