Impact of Burnished and Brushed Surface Preparation on Gold Bond Pads: Bond Strength and Wire Bond Quality in Microelectronics

Wire bond strength depends on various factors beyond material selection, bonding machinery, and operational parameters. This study investigates how surface roughness of gold bond pads on a 99.6% Alumina Ceramic, TaN, TiW, Au plating stack affects bonding. Pads were solvent and argon plasma cleaned to reduce effects from residual contamination. Two mechanical surface preparations, burnishing and brushing, were compared to an unmodified control. While water contact angle, an indicator of possible surface contamination, was measured across all samples, it showed no statistically significant correlation with bond performance, suggesting cleanliness was not a limiting factor. Bonds were formed using 0.001” DIA 99.99% Au wire via the Crescent on Ball (COB) method, with nine bonds fabricated per test condition. Bond strength was evaluated using industry standards EIA/JESD22-B116 – Wire Bond Shear Test Method and MIL-STD-883E – Method 2011 Destructive Bond Pull. Destructive shear tests revealed a statistically significant improvement in bond strength with burnishing surface preparation: burnished bonds averaged 48.4 gf, brushed 40.4 gf, and control 34.5 gf. In one-tailed analysis, burnished pads yielded a Z-score of 1.853 (p = 0.032) against the control group, confirming statistical significance. Pull strength was unaffected by surface preparation, with 24 of 27 bonds breaking at the neckdown and 3 at the heel, ranging from 1.505 to 5.930 gf, with minimal mean variation and variance across groups. These results, along with water contact angle observations and surface imaging and roughness measurements of bonded surfaces, underscore that mechanical surface preparation —especially burnishing — can lead to statistically significant improvements in wire bond ball-shear test results, offering a practical path to reducing bond failures in high-reliability electronics.