Piezoresistive Silicon Diaphragm Doping and Strain Gauge Adhesion Defect Modes
Optimal piezoresistive stability requires heavy surface boron doping above 2e19 cm-3 combined with plasma-activated silane coupling to prevent delamination.
Wire Bond Pull Test
Bond Strength
A mechanical evaluation procedure measures the adhesive strength and integrity of wire bonds that connect a semiconductor die to its lead frame or package. During the wire bond pull test, a hook is placed under the bonding wire and pulled vertically until the bond or the wire breaks. This test is a critical quality control method used to verify the reliability of electrical connections in microelectronic assemblies.
Mechanical Pull
A calibrated bond pull tester applies a gradually increasing force to the wire loop while measuring the displacement and peak force. The angle and position of the hook are standardized to ensure consistent stress distribution across both the die bond and the lead frame bond. The force at which the assembly fails is recorded and compared against minimum pull-force specifications defined by industry standards.
This test can be performed as either a destructive or a non-destructive screening process.
Failure Mode
Analyzing the location and appearance of the fracture provides valuable information about the quality of the bonding process. For example, a break at the heel of the wire suggests over-deformation during the bonding step, while a separation at the bond pad interface indicates surface contamination or insufficient ultrasonic energy. These findings are used to adjust the bonding parameters in real time to maintain high process yield.
Sampling Strategy
The test is typically performed on a sampling basis during production due to its destructive nature. If a single bond fails below the required strength, the entire production lot is held for further inspection and potential rework.