DIE-CRACKING RISKS IN ADDING A HEATSLUG TO A QFP PACKAGE
Author: S. H.-K. Lee Company: HK U. of Science Technology Date Published: 1/25/2000
Pan Pacific Symposium
Abstract: The intensive growth in portable electronic products leads to the development of different packaging technologies. Various packages have been developed for different products and purposes. Quad-Flat-Pack (QFP) package is one of the most cost-effective packages especially for the low performance and low-pin-count electronic components. However, one drawback of the QFP package is its relatively high thermal resistance. To compensate for this, manufacturers typically add a heatslug to the QFP package. Thus, the resulting package can offer a cost-effective solution to meet a mid-range thermal requirement. However, as shown by the present work, the addition of the heatslug decreases the package reliability by introducing the risk of die cracking. The die cracking phenomena is well documented in the literature, but it has seldom been linked to the addition of a heatslug. In addition, most of the previous studies were not able to successfully explain the randomness of the die-cracking phenomenon. As a result, such random failure is typically attributed to quality control issues at the assembly house. The present study documents the rate of occurrence of die cracking for a heatslug QFP package. Simulations were performed to ascertain the effect of adding the heatslug. Furthermore, experimental measurements were made which for the first time demonstrate the effect of scratch mark orientations. These marks were the result of wafer backside quality and the above-mentioned orientation effects can account for the seemingly random die-cracking phenomenon. Finally, results were also obtained to show the acceptable level of die backside roughness as well as the corrective actions that can be taken to rectify die with excessive roughness.