Wire Bond Challenges of Stacked Dice Devices

The integration of stacked dice into convention packaging formats provides a promising capability in reducing the cost, weight and size of the package while increasing the overall functionality of the system. It has been well accepted as enabling approach for smaller handheld devices such as cellular phones and digital camera. Among the various process steps in the packaging of these devices, wire bonding forms one of the critical processes. It applies a combination of mechanical force, ultrasonic power, and thermal energy to thin and, often, unsupported silicon die. This paper outlines the use of finite element in the design and development of a viable wire bonding approach for the interconnection of stacked dice in packages. We also show how improvements in the wire bonder are made to meet the needs of stacked die packaging.