Wave soldering is a widely used and efficient process for soldering through-hole components onto printed circuit boards. Here's an overview of the wave soldering process:
- Flux Application:
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Cleaning and Activation: The PCB is pre-cleaned to remove any contaminants, and then a flux is applied to the areas where soldering will take place. The flux serves to remove oxidization, facilitate solder wetting, and improve solder joint formation.
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Preheating:
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Heat Preparation: The PCB is passed through a preheating stage to gradually raise the temperature of the board and components. This preheating stage helps in driving off moisture and flux solvents, as well as reducing the thermal shock to the components during solder wave contact.
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Wave Soldering:
- Solder Wave Formation: The PCB is then moved over a bath of molten solder. The solder wave is typically made of a eutectic alloy with a relatively low melting point, such as Sn63/Pb37 (63% tin, 37% lead) or lead-free alternatives like SAC305 (96.5% tin, 3% silver, 0.5% copper).
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Solder Contact: As the PCB passes over the solder wave, the exposed pads and leads of through-hole components come into contact with the solder, forming strong and reliable solder joints.
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Solder Fillet Formation:
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Capillary Action: The molten solder wicks up through the holes in the PCB, forming a solid solder fillet on the components' leads and the PCB pads. This creates a reliable electrical and mechanical connection.
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Cooling:
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Solidification: The PCB then goes through a cooling process to solidify the solder joints. Rapid cooling helps ensure that the solder solidifies in a well-formed, shiny, and reliable manner.
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Post-solder Cleaning:
- Flux Residue Removal: Some PCB assemblies may require post-solder cleaning to remove any remaining flux residue. This step is essential to prevent long-term board and component degradation due to residual contaminants. Alternatively, "no-clean" fluxes may be used, eliminating the need for post-solder cleaning.
By properly following these steps, the wave soldering process can effectively establish reliable solder connections for through-hole components on a printed circuit board, significantly streamlining the assembly of electronic devices and ensuring the robust electrical and mechanical integrity of the solder joints.