Au to Au Thermosonic Flip Chip

The preliminary assumption was that a flip chip IC attached with gold bumps would have improved electrical performance over the standard IC interconnects. Additional assumptions were that there would be varied and different performance between the available flip chip techniques. These techniques included gold plated bumps on IC, gold plated bumps on thin film substrates and gold stud bumps on thin film substrates. Last was the assumption that an available flip chip bonder would be versatile enough to perform all applications using either thermocompression or Thermosonic bond processes as well as the traditional solder bump process.

The objective was to use a Finetech "Lambda" machine to flip chip attach two different devices using both thermocompression and Thermosonic bond processes. These two devices would apply different concepts in flip chip design: Standard gold plated bumps to the chip, gold plated bumps to the thin film and gold stud bumps to substrate. This would demonstrate the feasibility of performing multiple processes with this one machine as well as allowing the opportunity to evaluate the mechanical and electrical performance of the devices.

While there are many f/c machines on the market, the majority are targeted towards high volume low mix markets. This bench top machine is actually targeted towards low volume, high mix production.

The conclusion of this report is that this process does have the capability to place all three types of products with fine pitch accuracy and with both TC and TS bond processes. It was found that thermocompression had limited potential but the Thermosonic process was successful on all product samples evaluated.