IWLPC (Wafer-Level Packaging) Conference Proceedings


Author: Steve Steps
Company: Aehr Test Systems
Date Published: 10/10/2004   Conference: IWLPC (Wafer-Level Packaging)

Abstract: Burning-in semiconductor devices (especially memory devices such as SDRAMs) to increase their reliability has been a common practice for many years. This burn-in has been done primarily after the devices are packaged. Wafer-Level Burn-In and Test (WLBT) is a method for burning-in devices while they are still unpackaged. This has many advantages, one of which is the production of burned-in, Known Good Die (KGD.)

Consumers are demanding higher capability portable electronic devices ranging from cellular telephones with built in cameras to PDAs that are miniature computers. Consumers are willing to pay a premium for reduced size and weight. Achieving this reduced size and weight normally requires the use of advanced packaging technologies such as System In Package (SIP) that use multiple bare die.

The reliability of the overall package will be shown to be highly dependent upon the reliability of each of the bare die. The usual method for achieving highly reliable parts is through burn-in to sort out early failures. However, there are very few alternatives for burning-in unpackaged (bare) die. These few alternatives are compared in terms of the cost per burned-in die versus wafer volume. Recent improvements are reviewed that have significantly reduced the cost per die.

Finally, this paper discusses one of the major challenges of WLBT: full wafer contact. Data is shown to demonstrate that full wafer contact not only possible, but can also be very reliable.

Key words: WLBT, KGD, reliability, burn-in, Wafer-Level Burn-in.

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