Top 9 Tips for Improving Reflow Oven Efficiency

Introduction

Reflow oven is a SMT that utilizes high temperature for a short period of time to act on the connection parts coated with solder paste on electronic components and PCBs to achieve soldering. Reflow soldering machine has a high degree of automation, high-quality welding and applicability of a wide range of advantages, in electronics manufacturing, automotive electronics, communications equipment and other fields have a wide range of applications.

Reflow soldering machine role:

• High degree of automation: Allows for a high degree of automation, improving productivity and consistency.
• High-quality soldering: Produces uniform, reliable solder joints and improves soldering quality.
• Wide applicability: Applicable to various types of electronic components and printed circuit boards.

I. Understanding the basic principles of reflow oven

1. Reflow oven workflow

SMT machine to complete the placement, the PCB board into the reflow soldering equipment, heating and welding.

• Preheating stage: PCB gradually warmed up to the appropriate welding temperature, to avoid sudden changes in temperature caused by component damage or poor welding.
• Soldering stage: the process of melting solder, usually between 220-240 ℃ for several minutes.
• Thermal cycling stage: Cooling of the soldered PCB to promote crystallization of the solder joints and enhance mechanical strength.
• Cooling Stage: After completing the heating, the PCB is cooled naturally or through a cooling zone for rapid cooling.
• Inspection stage: The operator visually inspects the soldered PCB or uses SMT AOI inspection machine to confirm that the soldering quality meets the requirements.

2. Reflow oven in the introduction of common materials and equipment

2.1 Common Materials

• Solder Paste: Usually composed of solder powder, flux and carrier, solder paste in the reflow process to melt and form solder joints. Common solder paste, including lead-free solder paste, tin-lead solder paste.
• Solder Wire: Material used for manual soldering, commonly used for repair and small batch production. Includes different diameters and compositions of solder wire.
• PCBs: Substrates usually made of FR-4, HF-, or HF materials.
• Cleaner: Used to clean PCBs or assemblies, removing flux and other contaminants left over from the soldering process.

2.2 Common Equipment

• Solder Stencil Printer: Used to uniformly print the solder paste onto the PCB.
• Reflow Oven: PCB printed with solder paste is heated, so that the solder paste melts and combines the electronic components.
• Temperature profile monitoring equipment: Used to monitor temperature changes during the reflow process in real time to ensure compliance with the preset temperature profile.
• Defect detection equipment: AOI equipment for detecting soldering defects, unsoldered or false solder joints to improve the efficiency of quality control.

II. 9 tips to improve efficiency

1. Optimization of printed circuit board design

• Layout: Adopt a compact functional partition layout to tightly integrate circuit modules with similar functions and reduce wasted gaps between modules.
• Reasonable use of space: PCB edge area can be arranged for some small, space-critical components or circuits. Not only meet the functional requirements, but also do not take up the limited square space inside, making the overall PCB layout more compact and efficient.
• Wiring: Adopt high-density wiring technology and accurately plan the wiring usage of each layer. Shorten the wiring length as much as possible, especially for high-speed signals and high-current paths, to reduce signal delay and line loss.
• Component selection: Select components in miniaturized packages.

2. Selection of suitable solder paste

• Activity: Select different levels of flux according to the cleanliness of the printed board surface.
• Granularity: For fine-pitch printing, select the appropriate granularity of the solder paste.
• Melting point: When soldering thermal components or components that cannot withstand high temperatures, choose a solder paste with a low melting point.
• No-clean process: Select a no-clean solder paste that does not contain chlorine ions or other strong corrosive compounds for no-clean processes.
• Viscosity: Good viscosity to ensure that in the SMT workflow, from printing to enter the reflow heating process, the solder paste is not deformed, components do not shift.

3. Adjust the preheating temperature and time

Reflow oven preheating is the reflow furnace in the front of a temperature zone, the main function is to remove the solder paste in the volatile solvents, cut down on the thermal shock of the components, together with the flux is fully activated, and make the temperature difference becomes smaller. Preheating zone temperature and time settings need to be based on the actual PCBA heat capacity of the largest parts, PCB area, PCB thickness and the function of the solder paste used to determine.

As far as the reflow heating phase is concerned, a slow rate of rise in the temperature range between room temperature and melting point temperature is expected to cut down most of the defects.

4. Configure the appropriate reflow settings

4.1 Proper setting of the reflow temperature profile requires the following considerations:

• Preheating phase: The temperature rise rate is recommended to be no more than 3°C/s to prevent the paste from collapsing or bubbling as a result of too rapid a temperature change. The preheat temperature is usually 70°C to 90°C, the purpose is to allow the PCB and components to gradually warm up and reduce thermal shock.
• Holding phase: The temperature is held near the preheat temperature for a period of time (usually 2 minutes to 5 minutes) to ensure that the PCB and components are at a uniform temperature.
• Reflow phase: The temperature rises rapidly to the peak temperature, but not more than a 3°C/s ramp rate. Peak temperatures for lead-free soldering are typically between 245°C and 260°C, depending on the type of lead-free solder paste used and equipment recommendations.
• Cooling phase: Rapid cooling for good solder strength and appearance, the cooling rate is not strictly limited, but should be avoided to avoid rapid cooling resulting in thermal shock to the components. Temperature down to room temperature stage does not require special control, natural cooling can be.

4.2 Temperature requirements for different soldering materials

• Leaded solder paste: Reflow soldering temperature of about 215 ℃.
• Lead-free solder paste: Due to the higher melting point of lead-free solder paste, the reflow soldering temperature is usually around 245°C.

5. Regular maintenance and calibration of equipment

• Regular Maintenance and Inspection: Reflow soldering machines require regular maintenance and inspection to ensure their long-term stability and accuracy. This includes cleaning the equipment, replacing worn parts, checking electrical connections, etc.
• Calibration Records and Reports: After each calibration, calibration results should be recorded and a calibration report generated. This helps track changes in equipment performance and make adjustments or repairs when needed.

6. Enhance Employee Training

Develop staff training programs to improve equipment efficiency and operator skills.

7. Real-time monitoring and data analysis

• Early Failure Detection: Real-time monitoring can instantly identify problems in the welding process, such as abnormal temperatures and poor atmospheres, thus reducing scrap rates and rework costs.
• Improve product consistency: Real-time monitoring ensures that the welding parameters of each batch comply with the design standards, reducing product quality fluctuations.

8. Timely adjustment of production rhythm

According to the product demand reasonable arrangement of SMT production line, to avoid overproduction and waste.

9. Collect feedback and continuous improvement

Through the establishment of a good feedback mechanism, implementation of systematic improvement, staff training and information sharing, the quality and efficiency of welding can be further improved to meet the needs of the market and customers, and realize the sustainable development of the enterprise. Enterprises are encouraged to always maintain an improvement mindset in their daily management to meet the ever-changing industry challenges.

Conclusion

Improving reflow oven efficiency is not only a technical issue, but also an important strategy for enterprise competitiveness and market survival. Achieving this goal will help enterprises stand out in the fierce market competition while creating greater value for customers and society.

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. 

with global presence in over 130 countries, the excellent performance, high accuracy and reliability of NeoDen PNP machines make them perfect for R&D, professional prototyping and small to medium batch production. We provide professional solution of one stop SMT equipment.

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.