With the introduction of its XM5 series solder paste, Cobar is fighting the tombstone issue of small SMDs. Here, due to a problem with paste activation, tiny two-pole passive chip components flip-up on one end during soldering, due to a problem with paste activation, but can also result from uneven paste deposition. This contributes to uneven solder surface tensions and non-uniform reflow. As passives get even lighter, tombstoning becomes more acute, and the defects must be reworked, adding cost and delays and reducing yield. The paste is formulated with an anti-tombstoning combination of alloy powder (Sn63/ Sn62) and a polymer flux system. This formula has proven to be thermally stable, ensuring that the paste activity survives process heat, delivering zero-defect level soldering performance. The printing properties are characterized by high speed at low pressure. The material can also be used in closed print heads.
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