INTRODUCTION
In precision electronic equipment, the fineness and stability of soldering are important indicators for assessing product quality. High-quality soldering process can ensure that the electrical connection between electronic components is both stable and reliable, thus enhancing product performance and extending service life.
SMT reflow oven soldering is a soldering process used in electronics manufacturing, mainly used to fix surface mount components on printed circuit boards.
Wave soldering oven is a kind of automated welding technology, its core principle is to let the soldering surface of the PCB directly contact with high temperature liquid tin (usually lead-tin alloy or lead-free alloy), through a special device to make the solder to form a wave-like flow pattern (i.e., "wave"), so as to complete the connection between the component pins and pads.
In this article, we will compare the advantages and disadvantages of reflow soldering and wave soldering for electronic enthusiasts and PCBA manufacturers to choose the appropriate welding method to provide reference.
I. Reflow machine
1. Reflow machine workflow
- Preheating stage: PCB into the preheating temperature zone, this stage of the solder paste in the solvent, the gas began to evaporate, while flux wetting pads, components of the solder end and pins. Solder paste gradually softens, collapses, covering the pad, and the pad, component pins and oxygen isolation, thereby preventing oxidation during the soldering process.
- Soldering Stage: As the PCB enters the actual soldering area, the temperature rises rapidly, usually at a rate of 2-3°C per second. During this process, the solder paste reaches a molten state, and the liquid solder wets, spreads, diffuses and reflows between the PCB's pads, component solder ends and pins, ultimately generating a metallic compound at the solder interface to form a solid solder joint.
- Cooling phase: After completing the soldering, the PCB will enter the cooling zone to solidify the solder joints, thus ensuring the strength and stability of the soldering.
2. Reflow machine materials used
- Solder Paste: A mixture of solder and flux. The solder is usually a tin-lead alloy or lead-free solder, and the flux is used to help remove oxides and facilitate soldering. The solder paste is heated and melted during the reflow process to make the connection between the electronic components and the PCB.
- PCB: The main substrate material for reflow soldering. It is usually made of epoxy resin, fiberglass, and other reinforcing materials and covered with copper foil.
3. Advantages
Reflow machine reduces oxidation and soldering defects (e.g., porosity, false soldering) and improves the strength and consistency of solder joints through precise temperature control (four phases: preheating, melting, refluxing, and cooling).
Reflow machine adapts to the trend of miniaturization of electronic products, and can handle high-density assembly of micro-components (e.g., SMD devices).
Reflow machine with a high degree of automation, reduce manual operation, shorten the welding cycle.
4. Disadvantages
Reflow machine is relatively expensive and requires regular maintenance and calibration, increasing production costs. In addition, the operation and maintenance of the equipment requires specialized technicians, increasing labor costs. During the reflow soldering process, the quality of soldering is affected by a variety of factors, such as improper setting of the temperature profile, inaccurate control of the preheating and cooling process, etc. These may lead to unstable soldering quality, which may affect the reliability and durability of the product.
II. Wave soldering oven
1. Overview of the workflow of wave soldering oven
- Preheating: PCB components preheated to a specific temperature range, which helps to minimize the thermal shock of the soldering process on the electronic components, but also helps the evaporation of solvents in the flux, to ensure that the soldering environment is more controlled and reliable.
- Wave Generation: Wave soldering ovens equipped with a solder pot generate waves of molten solder. The solder pot contains a molten solder alloy, usually lead-free, maintained at a specific temperature, usually 1-3°C. The solder pot can be adjusted for height and shape. The height and shape of the wave can be adjusted to suit the PCB design and component requirements, ensuring thorough wetting and coverage of the required solder joints.
- PCB Assembly Channel: The conveyor system moves PCB components over the crest in a controlled manner, allowing solder to flow and form strong connections. Through-hole components with leads passing through the PCB are particularly well suited for wave soldering because the wave soldering oven makes effective contact with the leads and creates a reliable solder joint.
- Cooling and Curing: After the PCB assembly passes through the wave, it enters the cooling zone. Proper cooling is critical to ensure that the solder joint solidifies, preventing the component from shifting before the solder is fully solidified. This cooling process helps minimize the occurrence of thermal shock and potential defects such as broken solder joints or damaged components due to rapid temperature changes.
2. Materials Used in Wave Soldering oven
The materials used in wave soldering oven mainly include solder bars and fluxes. Solder bar is the core material of wave soldering, usually using tin or tin-lead alloy bar. The main component of the solder bar is Sn, and sometimes Pb is added to lower the melting point and improve soldering performance. Tin-lead alloys such as Sn-37Pb eutectic alloy is widely used because of its narrow melting temperature range, good wettability, excellent mechanical and physical properties.
3. Wave soldering oven benefits
- High-Speed Soldering: The wave soldering process is very efficient because multiple components can be soldered at the same time as the PCB passes through the solder wave. This reduces assembly time and makes it an ideal solution for high volume production.
- Soldering of through-hole components: Wave soldering oven is particularly suitable for through-hole components, where the wave soldering makes efficient contact with the leads and creates a strong solder joint.
- Reliable solder joints: The wave soldering process ensures good wetting and reliable solder joints due to the full contact of the melted solder with the component leads and PCB pads.
4. Disadvantages
Wave soldering is difficult with small components. Surface mount components have small, delicate leads or pads that can be easily damaged or displaced by high temperature molten wave soldering.
The wave soldering oven process may limit access to specific areas of the PCB, making it difficult to solder components that require precise placement or fine soldering techniques. In such cases, selective soldering or manual filler methods may be required to ensure proper soldering in tight or hard-to-reach areas.
III. Comprehensive Comparison
1. Analysis of Applicable Scenarios
1.1 Application scenarios for Reflow oven
- High-density, miniaturized PCB design: for surface mounted components.
- Hybrid integrated circuit board assembly: Reflow soldering process can meet the welding needs of high-density components of hybrid integrated circuit boards.
- Miniaturized electronic products: With the increasing miniaturization of electronic products, reflow soldering technology has become an important means of manufacturing miniaturized electronic products.
1.2 Application scenarios of wave soldering machine
Wave soldering machine is widely used in the welding of various electronic components, including resistors, capacitors, inductors, diodes, transistors, integrated circuits and so on.
Wave soldering machine can efficiently complete the welding of connectors to ensure a solid connection between the connector pins and circuit board pads, thereby improving the stability and reliability of the entire electronic system.
2. Cost-benefit analysis
2.1 Equipment investment costs
- Reflow soldering oven: usually higher prices, especially high-end formation furnace and multi-temperature reflow soldering machine. Initial investment is large and may take up a high budget. Suitable for high production and high complexity of welding needs, its long-term use of the return may make up for the initial investment.
- Wave soldering oven: Relatively low initial investment, suitable for small to medium-sized manufacturers. Wave soldering is suitable for large-scale simple soldering, but may require additional equipment configuration when working with complex boards.
2.2 Maintenance Costs
- Reflow soldering machine: Regular maintenance and calibration is required to ensure soldering quality and efficiency. This may involve expenditure on specialized technicians. Due to the complexity of the technology, breakdowns may take longer to repair, leading to production downtime, thus increasing potential overhead costs.
- Wave soldering oven: Maintenance is relatively simple and routine inspection and cleaning is usually sufficient. In most cases, basic maintenance and troubleshooting can be performed by the operator. Due to the relative maturity of the equipment structure, the cost of repairing common faults is low, and the equipment is generally easier to replace and upgrade.
2.3 Long-Term Cost Benefits
- Reflow Soldering oven: The high quality welds and low defect rates offered by the Reflow Soldering System for high-density and high-precision soldering needs may result in long term savings in rework and QC costs. As the production scale increases, the economic benefits gradually appear, especially in the manufacture of precision electronic products, high-quality solder joints to enhance product reliability.
- Wave soldering: Ideal for mass production, the lower cost-per-solder gives it a competitive advantage when dealing with high volumes. In simple and standardized production processes, its fast soldering speed and affordable maintenance keep long-term costs low.
Summarize
Our selection of the right welding process should be based on actual production needs. We hope that this article will help you clarify your thoughts and make an informed choice that better fits your situation. Feel free to share your experience and views, so that we can discuss the future development and application of welding technology.
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.