What Is Wave Soldering?
Wave solder is a batch soldering process used in printed circuit board manufacturing.The circuit board goes through a plate of melted solder, in which the solder produced by the pump surges upwards and looks like standing waves.The circuit board is in contact with this wave to solder the components to the circuit board.Through-hole printed circuit assemblies and surface mounting can both be soldered using the wave soldering technique.For the latter, the placement device glues the component to the surface of the printed circuit board (PCB) and then begins to melt the solder wave.This is called smt wave soldering.Miniature wave soldering is aimed at locally selective welding with high welding accuracy, while the primary purpose of wave soldering is to solder through-hole components, although surface-mounted components can also be soldered using this method.
Since through-hole components are almost superseded by surface-mount components, wave soldering is also give away to reflow soldering in many large electronic applications.Nevertheless, wave soldering still plays an important role in situations where surface-mount technology (SMT) is not viable or sufficient, such as with large power devices and connectors with high pin counts, or in cases where simple through-hole technology is predominant, such as with some major household appliances.
Application Field of wave slodering.
Wave soldering is a specialized soldering technique involved in the manufacture of printed circuit boards (PCBs).The process involves connecting the board to the PCB through a wave of melted solder. Areas of application for wave soldering include:
- Electronics Manufacturing:Wave soldering technology is a commonly employed method in the electronics sector for producing PCBs utilized in various industries such as consumer electronics, automotive electronics, telecommunications, aerospace, and defense.
- Industrial automation:The wave soldering machine plays a crucial role in the process of industrial automation as it is essential for achieving high-quality mass production.
- Medical devices:Wave soldering finds extensive application in the production of medical devices, including imaging systems, life support equipment, implantable devices, and more, which demand superior reliability and quality standards.
- Lighting industry:The manufacture of LED panels in the lighting industry involves utilizing wave soldering, which demands accurate soldering techniques to1. make certain superior durability and reliability.
- Automotive industry:The automotive sector employs wave soldering during the production of electronic components, including printed circuit boards for controlling systems, managing engines, and entertainment systems in cars.
How To Do Wave Soldering?
The steps of diy wave soldering include the following aspects:
What Is Reflow Soldering?
Reflow soldering is a process that utilizes a combination of flux and powdered solder, which is referred to as solder paste. This method temporarily attaches small electrical components to their corresponding contact pads. The entire assembly is then exposed to controlled heat, causing the solder paste to reflow and create long-lasting solder joints. This heating process can be achieved by passing the assembly through an infrared lamp or reflow oven, or by individually soldering each joint with a desoldering hot air pencil. Hot bar reflow soldering is a method that utilizes a hot head to apply heat and force in order to achieve the simultaneous heating and soldering of multiple connections.
Reflow ovens are the preferred method for soldering surface mount technology components (SMT) onto a printed circuit board (PCB). Benchtop reflow soldering is the process of conducting small-scale surface mount technology (SMT) reflow soldering within a space that is the size of a tabletop. In these ovens, each segment has a temperature that is regulated according to the specific thermal requirements of the assembly being soldered. Reflow ovens designed for soldering surface mount components are also capable of soldering through-hole components by filling the holes with solder paste and inserting the component leads through them.In contrast, wave soldering has traditionally been used to solder multileaded through-hole components onto a PCB primarily designed for surface-mount components.
How To Do Reflow Soldering?
During the reflow soldering process, a mixture of solder and flux known as solder paste is applied to the pads. Components are then placed onto the solder paste, creating a temporary connection. The PCB is subsequently heated in an oven using hot air, infrared radiation, or other forms of heat radiation. The oven temperature is carefully monitored and controlled to ensure that the solder paste melts and solidifies, forming stable solder joints.
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The typical flow for single-sided mounting involves the following steps:
solder paste printing > pick-and-place >reflow soldering > inspection. -
For double-sided mounting, the process includes the following steps:
solder paste printing on the A-side > pick-and-place > reflow soldering > solder paste printing on the B-side > another pick-and-place > another round of reflow soldering > finally inspection.
The reflow soldering process consists of several crucial steps, each of which is necessary to ensure that the board is heated to the correct temperature without requiring any adjustments or thermal shocks. Maintaining the proper temperature in the reflow chamber or tunnel is critical for producing high-quality solder joints. The steps of diy reflow soldering include the following aspects:
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Preheat
It is crucial to ensure that the board is exposed to the appropriate temperature during reflow soldering. If the temperature is too high, there is a risk that the board’s components or the board itself may be damaged due to thermal stress. Similarly, introducing the board to the temperature too rapidly can result in certain areas not receiving the required amount of heat due to thermal mass. Conversely, if the board is introduced too slowly, it may be difficult to achieve the desired temperature. Generally, the recommended temperature increase rate for infrared reflow soldering is between 2-3 degrees/sec, although this rate can occasionally be adjusted to 1 degree/sec. -
Thermal soak
Following the board’s exposure to the right temperature, the subsequent step is commonly referred to as thermal soaking. This process involves maintaining the board at the optimal temperature for a set period. There are several reasons for thermal soaking. Firstly, it ensures that any sections of the board that were not adequately heated due to shadowing are brought up to the correct temperature. Secondly, it eliminates any solvents or volatile content from the solder paste and activates the flux. The soak phase typically lasts anywhere from 60 to 120 seconds, depending on the mass differential of the assembly and the types of components present. The duration of the soak can be shortened if heat transfer during this phase is more efficient. -
Reflow
The reflow stage is the crucial part of the soldering process where the desired temperature is attained, and the solder melts to form the required joints. During this stage, the flux works to reduce surface tension, particularly at the metal junctions, to facilitate a metallurgical bond. -
Cooling
The final step of the soldering process is to cool the board down, and it must be done carefully to prevent stress on the components. Effective cooling is essential to avoid the formation of thermal shock and excessive intermetallic compounds. Typically, cooling takes place in an area with a temperature range of 86-212 degrees Fahrenheit. This temperature range allows for rapid cooling while ensuring that strong joints are formed.
What's The Difference Between Reflow And Wave Soldering?
The dissimilarities between wave soldering and reflow soldering are significant, and it is crucial to understand the distinctions before choosing which method to use in PCB assembly services. Any alterations made to the soldering process can result in changes to the entire manufacturing process, including production efficiency, costs, time-to-market, profits, among others.
Wave soldering and reflow soldering have notable distinctions in their core soldering process.
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Complexity:
In terms of complexity, wave soldering is considerably more intricate. The process involves placing the board on a conveyor belt to pass over the solder wave, which requires careful handling and adjustments to achieve optimal results. The worker or handler must have expertise in the process. In contrast, reflow soldering is a much simpler process. -
Environmental conditions:
Environmental conditions are vital in both wave and reflow soldering processes as any fluctuations can affect the quality of solder joints. However, in reflow soldering, maintaining all the conditions can be challenging. The wave of solder must be in optimal environmental conditions to function correctly. Reflow soldering involves careful preheating of the board under controlled conditions before applying the molten solder at the required temperature to ensure optimal fluidity. Temperature shifts during this process can result in defects and imperfections in the soldering, highlighting the importance of stable environmental conditions.
Compared to wave soldering, it is simpler to maintain the necessary conditions for reflow soldering as the reflow oven only needs to melt the solder in the paste, making controlling the environmental factors easier. -
Constraints:
In both wave and reflow soldering, there are constraints beyond just temperature that must be carefully controlled. The quality of the soldering in reflow soldering is influenced by the length of time that the board is subjected to heat. The timing must be precise, as exceeding the limits can result in excess solder or insufficient solder for some components. Maintaining the correct pad shape, size, and orientation is also crucial in wave soldering. Controlling the exposure time in reflow soldering is also necessary, but it is comparatively easier than wave soldering. -
Speed:
Wave soldering is a faster process than reflow soldering, making it the preferred choice for high-volume PCB production. This is because in wave soldering, the flux is sprayed, and the PCBs pass over the solder wave quickly. Nonetheless, the use of a stencil to apply solder paste and the requisite extended exposure of the PCB inside the reflow oven during reflow soldering can lead to time-consuming processing. -
Cost:
When it comes to cost, wave soldering is a more economical choice than reflow soldering, particularly for large volume orders. Reflow soldering is a more expensive option due to the need for special stencil production and the higher cost of the reflow oven compared to a wave soldering machine. -
Usage:
Through-hole components are ideally suited for wave soldering, while SMDs are better suited for reflow soldering.
What Factors Control The Quality Of Wave/Reflow Soldering?
Reflow and wave soldering have different process conditions, but both are critical to achieve good solder joints.The following are essential process conditions to consider:
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Temperature:
The temperature must be high enough to melt the solder and form a reliable solder joint. For wave soldering, the typical temperature range is between 240°C and 260°C, while for reflow soldering, it ranges from 220°C to 240°C. -
Atmosphere:
The atmosphere inside the soldering oven must be inert and free from oxygen and moisture, typically achieved by using nitrogen gas. Nitrogen reflow soldering is a method of soldering that utilizes pure nitrogen in a reflow oven. -
Time:
Wave soldering has a relatively constant time interval, while reflow soldering depends on the size of the component being soldered and is calculated based on ramp rate and hold time. -
Flux:
Flux is required to remove oxides from the surface of the component or PCB, enabling better wetting of the solder and improved solder joints. -
Solder paste:
Solder paste is a mixture of solder and flux applied to PCB surface-mount pads, melted during reflow soldering to form a solder joint. Proper use of solder paste enhances process consistency and simplifies solder joint quality. -
Conveyor speed:
Conveyor speed is crucial in maintaining the appropriate dwell time of components and achieving good solder joints. -
Component placement:
Components must be correctly placed on the PCB, with sufficient spacing to avoid shorts and attain adequate solder joint formation. -
Cleaning:
Thorough cleaning of PCB and components is necessary to prevent contaminants that hinder good solder joint formation. -
High-quality PCB stencil:
A PCB stencil made of stainless steel with laser-cut openings accurately deposits the right amount of solder on the technology pads, resulting in perfect alignment and excellent mechanical strength and electrical connections for users.
What Precautions Should Be Taken When Doing Manual Wave/Reflow Soldering?
To ensure your safety when performing wave/reflow soldering, it is crucial to follow the guidelines provided by your employer, local and state laws, and equipment manufacturers regarding proper safety protocols and precautions. However, you can take general precautions to enhance your safety, including:
Soldering Iron:
- Avoid touching the element of the soldering iron, which can reach temperatures of up to 400°C.
- Instead of using your bare hands, employ tweezers or clamps to hold the wires that need to be heated.
- Keep the cleaning sponge moist during usage.
- When not in use, store the soldering iron in its stand and avoid placing it on the workbench.
- Turn off and disconnect the device when not in use.
Solder, flux, and cleaners:
- Wear eye protection to prevent injuries from solder “spitting”.
- Whenever possible, use rosin-free and lead-free solders.
- Dispense cleaning solvents from bottles.
- After soldering, wash your hands with soap and water.
Lead exposure:
- Lead can cause severe health effects if ingested accidentally. Wear gloves when in direct contact with solder.
- Soldering may generate limited fumes that contain lead.
Rosin exposure:
- Rosin is a resin in solder flux that produces visible fumes during soldering, leading to eye, throat, and lung irritation, nose bleeds, and headaches.
- Repeated exposure to rosin can cause respiratory and skin sensitization, exacerbating asthma.
- Rosin is a significant occupational health hazard.
Ensure personal protection: It is crucial to wear appropriate protective gear such as goggles, gloves, and clothing to prevent injuries during wave/reflow soldering.
Maintain a clean, obstruction-free work area: Keep your work area clean and unobstructed to prevent accidents.
Use correct equipment: Always use proper equipment that meets safety standards, and conduct regular maintenance checks.
Follow manufacturer’s instructions: Adhere to the manufacturer’s instructions when operating soldering equipment to minimize accidents.
Keep a first aid kit nearby: In case of an injury, keep a readily available first aid kit and ensure someone trained in administering first aid is present.
Proper ventilation: Ensure proper ventilation at your workplace as wave and reflow soldering produce harmful fumes.
Prevent fire hazards: Avoid placing flammable objects such as paper, plastics, and liquids near the soldering equipment to prevent fire.
Provide training and supervision: The supervisor/line manager should educate the user regarding the dangers of welding, implement effective controls, and enforce their proper use. All welds should receive proper training and supervision.
Ensure electrical safety:To guarantee electrical safety, make sure to utilize soldering irons that have no apparent damage to the body, cable, or plug. Furthermore, all soldering irons must have undergone electrical safety (PAT) testing within the past twelve months. Also, keep the soldering station free of cables to prevent damage to the heating tip. If a short circuit is possible, use a grounding socket and grounding pin.
Dispose of waste properly: Collect waste solder in containers with lids and label them hazardous waste.Dispose of used solder sponges and contaminated rags by placing them in sealable bags and appropriately discarding them.
Remember safety at all times: Always prioritize safety, follow safety procedures, and ensure you are working under safe conditions.