To lower the manufacturing cost of quad flat no-lead (QFN) packages, the number of QFN packages on a leadframe must be increased. However, the increased number of packages or changes to the layout of QFN packages on the leadframe can impact the mold compound flow behavior, which will, in turn, affect warpage, and the generation of voids inside the mold compound. In this paper, both simulation and experimental approaches were conducted to study the behaviors of QFN packages on a leadframe strip. For simulation, we will demonstrate and present an analysis methodology to account for the in-line processing parameters, especially the step of manufacturing and processing the mold compound material to form the QFN packages on a leadframe strip. The in-line manufacturing parameters, such as pressure, temperature, shrinkage, and processing timing, were all considered and modeled. A commercial finite element tool was used. For the experiment, we measured the warpages and the voids of QFN packages as a function of the package location on the leadframe. The warpage of the package, and the voids generation of QFN packages at different locations on the leadframe strip were studied. In conclusion, the experiment vs. modeling data was correlated, and the study proved to be very useful for the prediction of warpage, and void generations.
In this paper, a novel flip chip interconnect structure called Bond-On-Lead (BOL) and its ability to reduce stress in the sensitive sub-surface ELK (Extra Low K) layers of the die is presented. BOL is a new low cost flip chip packaging solution which was developed by STATSChipPAC to dramatically reduce the cost of flip chip packaging. The BOL solution allows for efficient substrate routing by virtue of the use of narrow BOL pads and the removal of solder mask in the area of the BOL pads, which eliminates the limitations associated with solder mask opening sizes and positional tolerances. In addition to the compelling cost benefits, modeling results are confirmed with empirical reliability testing data to show that BOL is superior to the traditional Bond-on-Capture Pad (BOC) configuration from a mechanical stress and reliability perspective. The focus of this paper is on the theoretical analysis of the stress, strain, and warpage associated with the BOL configuration compared with the traditional BOC structure. For the package deformation, the global finite element method is used to simulate the package warpage. For the local bumping reliability, the focus is on the ELK layers which are the critical locations affecting the package's reliability. The local finite element simulation is conducted to compare the critical ELK layers stresses with BOL structure vs. with traditional BOC structure.
Three dimensional finite element analysis (FEA) is performed to assess the board level temperature cycling reliability for lead-free solder Sn96.5Ag3Cu0.5 (SAC305) used in eWLB packages. With Anand viscoplastic constitutive model used for the solder material, the chosen damage parameters, i.e. accumulated creep strain or accumulated creep strain energy density, can be derived from the finite element analysis (FEA) models and then can be correlated with the solder fatigue life obtained from the temperature cycling tests.In this study, a surface-based tie constraint technique is employed in the FEA models to facilitate mesh transition requirements at various interfaces of incompatible meshes. It is particularly the case arising from the die edges overlie the circular solder pads in the models. To deal with such situations, the FEA model for the entire package-to-board assembly can be strategically split into two parts and then connected to each other with tie constraints for the ease of meshing effort. It is found that this technique can help in managing a more uniform mesh distribution over the regions of interest, such as solder joints and dielectric layers with refine meshes, and yet allow a relatively coarse mesh to be assigned elsewhere for model size reduction. Thus, the computational efficiency for these tie-constraint models can be improved significantly as compared with their corresponding single part models with fine meshes and yet the model accuracy for the critical solder joint fatigue life estimation can be preserved. A model validation and numerical case study will be provided to illustrate the application of this modeling technique.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
customersupport@researchsolutions.com
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.