2n d level reliability performance during drop impact is critical for Wafer Level Packages (WLP). Accompanying the popularization of portable and mobile phone products, high reliability under board level drop test is a great concern to semiconductor manufacturers. A O.4mm pitch Cu under bump metallization (UBM) type has been developed for mobile computing application. In this paper presents the impact on solder joint reliability with various approaches to achieve higher Drop Test (DT) robustness. Polymer Core solder ball, solder ball Sn1.2AgCu (additive Ni + a), polymer flux with SACI07 solder ball, solder ball Sn 1.2AgO.5Cu (doped), copper core solder ball, and additional 6J.!m passivation layer (poly imide ) have been investigated. The test vehicles were 49 pins and O.4mm ball pitch with Cu UBM. Ball shear test was carried out to measure the solder joint performance after reflow process and units were performed cross sectioned for IMC formation analysis. Board level drop test was performed as per JESD22-B III test method. The drop test results showed polymer core solder ball gives the best performance which is more than 1000 drops, followed by Sn1.2AgO.5Cu (doped) solder ball, polymer flux, additional 6um polyimide, Sn1.2AgCu (additive Ni + a) solder ball & copper core solder ball. It indicated the stress relaxation within IMC & strength improvement to achieve higher drop test performance for polymer core solder ball during drop test. On the other hand, copper core solder ball has the worst drop performance (66 drops) as it has rigid material (Cu) inside the ball and less solder amount that can absorb the drop impact and stress.
Miniaturization of portable and hand-held electronic devices is driving the need for smaller foot print on PCB. Wafer Level Package, WLP is an example that facing this challenge of package miniturisation. Units placement into carrier tape pocket has become critical for such products. WLP package with bump causing uneven contact between pick up tool and the package has made it more challenging to achieve accurate unit positioning in pocket during taping process. Additional challenges faced is existing machine was designed for minimum package size of 0.5mm x 0.5mm. This paper will share systematic approach to prevent tilted units in case of WLP package size less than 0.5mm x 0.5mm. DMAIC approach with 6 sigma tools has been applied. Material selection, process parameter setting and indexing track design are the 3 main areas that have been studied in detail. As for material selection, different types of cover tape and rubber tip have been evaluated. Because of small size and light weight, units tend to tilt easily if there is excessive vibration. Thus, vacuum setting has been evaluated in order to understand the impact on tilted units which caused by excessive vibration during taping. Apart from material selection and vacuum setting, indexing track design also has been studied. With the new error proof track design and optimum selection of materials, the tilted units have been reduced towards zero ppm.
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.