The Comparative Study to Enhance Board Level Reliability Performance of Wafer Level Package At 0.25 mm Pitch Using Micro-Ball Drop and Electroplated Solder Technology
In this study, the board level reliability of WLP at 0.25mm pitch has been evaluated by employing board level reliability test following JEDEC include thermal cycling, drop shock and cyclic 4-point bend tests to verify the performance of shrunk bump size. The WLP test vehicle has been designed with 4-layer stack up structure, 4.0 × 4.0 mm die size and 15 × 15 ball array. The shrunk bumps of test vehicles were formed by using micro-ball drop and electroplated lead free solder bumping process after UBM plating completed. The shrunk bump size in WLP at 0.25mm ball pitch will enhance the risk of board level solder joint fatigue due to lower standoff height and smaller diameter of solder joint (higher bump stress concentration). In this work, we also evaluated different 4-layer WLP stack up structures for key design parameters including polyimide, RDL and UBM layers to reduce solder joint stress and thus enhance BLR performance All the study legs passed drop test with the 1st fail >100 drops and passed 200K times cyclic bend test without any failure. The TCT performance of micro-ball drop bumped legs showed better results with 1st fail passed 500X cycles. The drop, bend test and TCT performance are improved by new bump stack-up designs.
Enhanced Design and Reliability Analysis of Copper Post Wafer Level Package
In this study, the board level reliability (BLR) performance of different copper (Cu) post wafer level package (WLP) structures without epoxy or molding encapsulation have been evaluated and compared to standard WLP. The Cu post WLP test vehicle has been performed on different stack up structures of 4.7 x 7.1 mm2 package size at 0.4 mm ball pitch. The Cu post bumps of test vehicles were manufactured through main-stream production technologies including standard ball drop and electro-plated lead free solder after Cu post completed. The Cu post WLP will enhance the risk of board level solder joint fatigue due to thick Cu post without encapsulation will increase bump site stress. The optimized design parameters of package stack up with low temperature cured polyimide are implemented to accommodate the increased stress. In this work, we also evaluated a novel Cu post WLP stack up structure for fast package cycle time and fine pitch application. The improved BLR performance of large die size Cu post WLP is demonstrated in this investigation. The failure modes analysis and Weibull failure statistics are presented for the BLR results and recommendations as to the preferred Cu post WLP structure are also included.
The MR-TOF-MS isobar separator for the TITAN facility at TRIUMF
At TRIUMF’s Ion Trap for Atomic and Nuclear Science (TITAN) a multiple-reflection time-of-flight mass spectrometer (MR-TOF-MS) will extend TITAN’s capabilities and facilitate mass measurements and in-trap decay spectroscopy of exotic nuclei that so far have not been possible due to strong isobaric contamination. This MR-TOF-MS will also enable mass measurements of very short-lived nuclides (half-life > 1 ms) that are produced in very low quantities (a few detected ions overall). In order to allow the installation of an MR-TOF-MS in the restricted space on the platform, on which the TITAN facility is located, novel mass spectrometric methods have been developed. Transport, cooling and distribution of the ions inside the device is done using a buffer gas-filled RFQ-based ion beam switchyard. Mass selection is achieved using a dynamic retrapping technique after time-of-flight analysis in an electrostatic isochronous reflector system. Only due to the combination of these novel methods the realization of an MR-TOF-MS based isobar separator at TITAN has become possible. The device has been built, commissioned off-line and is currently under installation at TITAN.