Cold Ball Pull Testing

Procedure Logic

Clamping an individual solder ball and applying a vertical tensile force until separation occurs defines the execution of this diagnostic. While hot pull methods test the joint near reflow temperatures, cold ball pull testing focuses on the durability of the solidified attachment during standard handling or transport. The gripper tool must exert enough pressure to hold the ball without deforming it to a degree that invalidates the measurement.

Different tip designs accommodate various ball diameters and pitch dimensions found on modern high density substrates. Use of a specialized load cell ensures that the force is applied consistently across a large sample size of components from a single production batch.

Failure Mode

Analysis of the fracture surface after the pull event categorizes the weakness into specific types such as pad lifting or interfacial fracture. When cold ball pull testing results show a break at the nickel or copper interface, it often points to contamination or improper plating thickness. Solder joints that exhibit ductile failure within the bulk solder itself generally indicate a strong bond and a well controlled assembly process.

Brittle fractures at the bond line suggest brittle intermetallic growth which could lead to field failures under mechanical shock.

Compliance Requirement

Standard operating procedures for testing must align with industry norms such as JESD22 B115 to ensure data consistency across multiple manufacturing sites. Although Chinese national standards often reference these international protocols, the specific acceptance criteria remain subject to the contract between the original equipment manufacturer and the contract manufacturer. Periodic auditing of test equipment calibration ensures that the load cells provide accurate readings for every batch.

Technical documentation produced from these tests supports the final product certification for high reliability applications.