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Causes-and-Solutions-of-SMT-Solder-Beads-and-Pinholes
Solder beads and pinholes are common process defects duringSMT printingand reflow process. They not only affect board appearance, but also may cause circuit short circuit, which must be strictly controlled in daily production.

1. Solder Beads

Phenomenon: Round tiny solder particles appear on non-soldering areas of PCB.
Main Causes

  1. Insufficient warm-up time leads to residual moisture inside solder paste.

  2. Unreasonable reflow temperature profile and too fast heating speed.

  3. Improper and oversized stencil aperture design.

  4. Moisture on PCB surface after printing.

Solutions

  1. Follow standard warm-up procedure before using solder paste.

  2. Optimize reflow temperature settings for stable heating.

  3. Adjust stencil aperture size reasonably.

  4. Keep production workshop dry and moisture-proof.

2. Pinholes

Phenomenon: Tiny pin-shaped holes appear on printed solder paste surface.
Main Causes

  1. Insufficient squeegee pressure results in uneven printing.

  2. Worn and deformed squeegee affects printing effect.

  3. Impurities mix into solder paste due to irregular storage.

  4. Inadequate stirring causes air bubbles inside solder paste.

Solutions

  1. Set proper squeegee pressure to obtain smooth solder paste layer.

  2. Replace damaged squeegee regularly.

  3. Standardize solder paste storage and usage rules.

  4. Stir solder paste fully to eliminate internal air bubbles.

Most solder beads and pinholes are caused by improper material management and wrong machine parameters. Standard operation and precise adjustment can effectively avoid these defects.
Globalwell implements complete solder paste management rules and maintains printing equipment regularly, effectively reducing various printing and soldering defects and ensuring stable production quality.


 

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