Suppressing the Formation of Cracks in Conventional Copper Additive Baths by Ultrasound
Original Publication Date: 1985-Mar-01
Included in the Prior Art Database: 2005-Feb-18
For producing conductors in circuit boards, additive baths are used for copper plating. Defects, such as cracks, in the growth phase are prevented by ultrasound. Example: In a controlled additive pilot bath with a contents of about 1800 1, rate sites are treated at a temperature of about 60ŒC for about 12 hours with and without ultrasound. For ultrasound treatment, an immersion oscillator is used with a frequency of 25 kHz and a maximum capacity of about 2 W/cm2 . Copper deposited under the influence of ultrasound has noticeably finer grains than conventionally deposited copper. The structure of the copper layers is shown in the micrographs of Figs. 1A and 1B. The embedded particles result from impurities that dissolved during the test. Normally, grain boundary defects or cracks occur at such points.