“We are considering using copper wire as a replacement for gold wire in the interconnect of the diode to the lead frame. Is it best to use premixed cylinders of forming gas or blend the forming gas on the back pad?”
The supply of the forming gas (5% H2/95% N2) is wholly dependent on your production scale and number of bonding systems that you will be using. Cost is also a major criterion that one must consider. Premixed cylinders are usually more expensive than blending the forming gas, however if your production scale is small, then the cost may not be an issue. Blend panels, although not a high cost, may not be warranted if your production is small. Also if the supply of hydrogen in your location is not available, then premixed cylinders may be your only alternative.