The causes of solder balls in robotic soldering

EMP 2026 Electronics Manufacturing & Production Handbook Manufacturing / Production Technology, Hardware & Services

Solder balls (also known as solder splatter) are a major concern in many production sites. As solder forms balls (spheres), they can move across the board and potentially cause shorts, leading to long-term impacts on product reliability. Hence, solder balls are highly undesirable defects caused by incorrect soldering techniques.

The three main causes of solder ball generation through localised heating during robotic soldering are:

• Soldering tip contact.

• Incorrect solder supply.

• Moisture on the board caused by high humidity.

Tip contacting

The first cause is the impact when the tip contacts the PCB. Solder balls attached to the soldering tip may drop off due to the shock of contact. This may also occur when the soldering tip is retracted as heated solder may pop out from the tip forming small spatters onto the board.

To prevent this, it is vital to maintain a clean soldering tip with a regular maintenance routine. Another method to reduce this problem is by reducing the speed of contact or altering the contact angle.

Solder feeding

The second cause is the speed at which solder is fed onto the soldering tip and pad. If the solder feed is too rapid, the flux inside the solder can gasify causing the solder to pop thereby forming solder balls. Conversely, if the solder feeding is too slow, overheating of the solder occurs, which can cause the flux inside the molten solder to also gasify, leading to the formation of solder balls.

To prevent this, it is important to properly set the optimal solder feeding speed. Another effective method is to make a slit (notch) longitudinally down the length of the solder wire to allow any gases to more easily escape without causing the solder to pop.

Moisture in PCBs

The third cause is moisture in PCBs often caused by high humidity environments. When this moisture in the PCB is heated, it pops and is released outwards, resulting in the creation of solder balls.

To prevent this, it is important to manage both the condition of the PCBs and components, and the environment itself. This can be accomplished using dehumidifying equipment to remove any moisture before the soldering process commences.

For more information visit www.japanunix.com

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