Wave Soldering Defects and Measures to resolve

Wave soldering is one of the most widely used techniques in PCB assembly, yet soldering defects remain one of the most common challenges that can impact the quality and reliability of the final product.

These defects include bridging solder, incomplete soldering, excess solder, voids or porosity, cold soldering, and more. Typically, these issues arise from improper process parameters, equipment conditions, or material choices.

PCB with through-hole components and coils after wave soldering process
PCB with through-hole components and coils after wave soldering process (Image source: online)

The Causes of Soldering Defects in Wave Soldering

Improper Control of Flux Preheat Temperature

  • Low Preheat Temperature: Insufficient activation of the flux, resulting in poor soldering performance.
  • High Preheat Temperature: Flux evaporates before reaching the soldering area, which negatively affects soldering quality.

Inadequate or Uneven Flux Application

  • Insufficient or uneven flux can cause bad wettability to the solder joints, increasing the likelihood of soldering defects.

Incorrect Settings of Solder Pot Temperature

  • Excessively High Temperature: Flux is consumed too quickly, losing its protective properties.
  • Excessively Low Temperature: The flowability of solder is reduced, hindering proper separation of solder and potentially causing bridging.

Soldering Time Issues

  • Long Soldering Time: Excessive evaporation of flux, leading to reduced wettability of solder joints.
  • Short Soldering Time: Inadequate soldering, resulting in poor joint formation.

How to Resolve Wave Soldering Defects?

  • Optimize Flux Preheat Temperature

Set the flux preheat temperature within an optimal range to activate the flux sufficiently without causing premature evaporation.

Wave soldering temperature curve
Wave soldering temperature curve (Image source: online)
  • Control Flux Application Process with Precision

Adjust spray parameters, including nozzle speed and flux volume, to ensure uniform coverage of the solder joint area.

flux dispenser nozzle for precise flux application in soldering process
flux dispenser nozzle for precise flux application in soldering process (Image source: online)
  • Adjust Track and Wave Heights

Control solder volume and wave height to prevent excess solder from leading to bridging issues.

adjusting wave height and track height to prevent solder bridging in wave soldering
adjusting wave height and track height to prevent solder bridging in wave soldering (Image source: online)
  • Strict Control of Solder Pot Temperature

The recommended solder temperature range is 260-265°C (500-509°F), though testing is essential to ensure the temperature is optimal to have excellent flowability in reflow.

strict control of solder pot temperature between 260-265℃ for optimal solder flow
strict control of solder pot temperature between 260-265℃ for optimal solder flow (Image source: online)
  • Properly Control Soldering Time

Adjust the soldering time based on conveyor speed to avoid excessive flux evaporation or insufficient solder joint wetting. This ensures optimal flux wettability and solder extendability, improving soldering quality.

solder joints on through-hole components after proper soldering time control
solder joints on through-hole components after proper soldering time control (Image source: online)

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