What is Burn-In?

There are several types of burn-in systems in a variety of shapes and sizes that meet the need of various applications. With devices becoming more complex, manufacturers find it necessary to include some type of burn-in to reduce the number of failures in the final product.

Static burn-in applies extreme temperatures and voltages to each device in the chamber without operating or exercising any of the devices. The advantages of static burn-in are its low cost and simplicity. A major limitation of static burn-in is that it exercises fewer than half the circuit nodes on a device.

Dynamic burn-in applies various input stimuli to each device while the device is exposed to temperature and voltage extremes. The advantages of dynamic burn-in is the ability to stress more internal circuits causing additional failure mechanisms to occur. Dynamic burn-in is limited because it cannot completely stimulate what the device would experience during actual use, so all the circuit nodes may not get stressed.

Dynamic burn-in with test adds monitoring of device outputs at different points in the burn-in process, verifying that the devices are actually being exercised. Dynamic burn-in with test quickly determines burn-in fallout as a function of time, allowing the burn-in process to be terminated at an optimal point. Another advantage of burn-in with test is the ability to detect devices that fail under marginal conditions, but not at the normal operating point. Elimination of these devices early, significantly improves product quality.

Individual temperature control (ITC) per device is the most important development in burn-in technology. Now, burn-in users can be sure that the temperature of each device is monitored throughout the burn-in cycle (i.e., not allowing devices to become so hot that they are damaged or other devices not heating up enough to be adequately burned-in). These sophisticated burn-in systems are capable of monitoring and controlling the individual device temperatures of hundreds of devices at once with either the internal thermal diode temperature or external case temperatures. Now, all the devices will be stimulated to achieve the optimum temperature for stressing.

Burn-in systems are generally classified by the type of device accommodated, or by how the burn-in process is performed.

Logic burn-in with test involves the use of complex test vectors. These test vectors are basically truth tables provided by device simulations. The test vectors include input stimuli (1s and 0s) timing information with nanosecond resolution, and output compare data. The inputs are provided in parallel with up to 256 I/O or using fewer I/O through a JTAG port. Devices are configured through the test data in and then a built-in self-test (BIST) can be run at high frequencies (800+ MHz). This method provides good burn-in stimulation and fault coverage.

Memory burn-in is similar. These patterns load and read back sequential data in the memory array. The patterns used on today’s memories are large and time becomes an issue when running patterns on large memories. In many cases, the memory arrays are imbedded into a logic device and must be communicated to via a JTAG port.

Burn-in systems come in a variety of shapes and sizes to provide the acceleration to age semiconductors by applying heat and voltage stress through the burn-in boards in the chamber.

Burn-In Boards interface between the socket and the burn-in system. Each burn-in board connects directly to system architecture through a connector. Burn-in boards are designed according to a customer’s specific application, and they are usually complex multi-layer boards able to handle extreme temperatures.

Burn-In Sockets interface between the semiconductor device and the burn-in board. Burn-in sockets are customized to the device that will go through burn-in and test. Vendors that specialize in the design and manufacture of burn-in sockets often work directly with the device developer to achieve the best socket design for a valid burn-in outcome.