Known-Good-Die Process Flows
The following diagram shows a simplified assembly and test process flow for IC manufacture. The probe environment is different (with respect to parasitic electrical elements) than that of the application environmen so the probe test step is usually kept simple to enhance throughput and to discourage false negative results, thereupon scrapping "good" die. Full electrical test is where the rigorous operational and performance testing is performed, after the device has been packaged and is ready for shipment.
For bare die sales that utilize the IC fabricator's normal production flow, the die are simply shipped to the customer after the wafer saw step.
The quality and reliability expectation of bare die that have seen no final test nor burn-in should be fully understood by the customer. If the use application requires higher quality or better reliability than offered by bare die, there are several KGD processes to be considered.
Moving all testing back to the probe test area holds promise for lowering cost and improving quality for all IC devices, not only those slated for die products markets. The customer should be aware that unless specifically part of the full electrical routing, these probe test methods are not intended to improve reliability. The supplier may institute special test methods at the probe step that will detect potential infant mortality devices through outlier detection. If burn-is needed to achieve reliability goals, the IC manufacturer may consider using a temporary carrier, which acts as the package during test and burn-in, and then allows the die to be removed for assembly into the application.
The drawing shows a commercially available carrier that may used for full test and burn-in of bare die. A set of test points on the substrate provide electrical contact to bond pads or solder bumps on the die. Routing on the substrate lead to contacts that mate with a PCB socket.
Wafer level test methods and reliability screening offers the potential of lowering the number of "test insertioins", which could lower costs for die products. There are tradeoffs to consider in the cost of equipment and potential negative yield impacts of relying on outlier detection as a reliability screen.
