Some mechanical properties of copper electrodeposited from commercial pyrophosphate and acid copper sulfate solutions

Both acid copper and pyrophosphate baths have been used extensively in electroforming applications. We required electrodeposits that retained their yield strength and hardness after baking at high temperatures. However, we found in our experiments that deposits from a bright acid copper bath decreased in hardness from an original range of 210 to 220 DPH/sub 100g/ to 150 at 150/sup 0/C and 105 at 250/sup 0/C. Later tests with copper deposited at an outside source showed that acid copper deposits can retain their hardness after baking 8 h at 250/sup 0/C. However, the elongation was below 3%, indicating an excess of brightener in the bath. Deposits from a commercial pyrophosphate bath will retain their hardness (210 to 220 DPH/sub 100g/) at 250/sup 0/C for 2 h, providing sufficient brightener is present. We studied the effect of brightener concentration on hardness, yield strength, and tensile strength in a commercial copper pyrophosphate solution. By increasing the brightener from 0 to 5X normal, we raised the hardness from 80 to 225 DPH, the yield strength from 130 MPa (19.5 ksi) to 389 MPa (56.5 ksi), and the ultimate strength from 235 MPa (34 ksi) to 625 MPa (91.2 ksi). The higher values are retainedmore » after baking 2 h at 250/sup 0/C when the brightener is 5X normal.« less