Today's electronic device packaging is getting smaller and smaller, coupled with the reality that the thermal stress of the current lead-free process of water-soluble solder wire and the brittleness of lead-free solder wire solder joints have increased significantly, and the solder joint cracking caused by excessive bending during the manufacturing process The probability of occurrence increases accordingly. For package substrates with all surface finishes, excessive strain can cause damage to the solder joints. These failures include solder ball cracking, wire damage, pad lift, and substrate cracking during PCBA fabrication and testing.

The stress acting on the solder joints of PCBA water-soluble solder wire is not non-mechanical stress and thermal stress. Mechanical stress refers to the stress generated by the interaction between various parts in an object when it is deformed by an external force. Thermal stress refers to the stress generated by an object that cannot expand and contract completely freely due to external constraints and mutual constraints between internal parts when the temperature changes. Electrical strain measurement technology is mainly used in the evaluation of mechanical stress damage of PCBA water-soluble solder wire solder joints. PCBA strain measurement involves attaching strain gages to a printed board, and then subjecting the PCBA with the attached strain gages to different testing and assembly process operations. Testing and assembly steps that exceed strain limits are considered overstrain and are identified and remedial actions taken during production.