A study of SMT assembly processes for fine pitch CSP packages

Minna Arra (Flextronics, Tampere, Finland)
David Geiger (Flextronics, San Jose, California, USA)
Dongkai Shangguan (Flextronics, San Jose, California, USA)
Jonas Sjöberg (Flextronics, Linköping, Sweden)

Soldering & Surface Mount Technology

ISSN: 0954-0911

Publication date: 1 December 2004

Abstract

The surface mount technology (SMT) assembly process for 0.4 mm pitch chip scale package (CSP) components was studied in this work. For the screen printing process, the printing performance of different solder pastes, aperture shapes and sizes was investigated. Square apertures and a fine particle size in the solder paste provided a better paste release. Besides optimising the printing process capability and minimizing the printing defects such as bridging and missing paste, the total volume of solder consisting of the paste and the solder ball has to be considered in order to maximize the final process yield. For the pick & place process, the accuracy required for the placement equipment was determined by studying the self‐alignment of the lead‐free CSPs (with Sn/4.0Ag/0.5Cu balls) during the reflow process using lead‐free Sn/3.9Ag/0.6Cu paste. The components were intentionally misplaced up to ∼50percent off‐pad. After reflow, x‐ray inspection showed that the components had aligned to the pad. By considering the stack‐up of the printed circuit board pad location and size tolerances, the solder paste printing tolerances and the placement tolerances, the required alignment accuracy for the pick & place equipment was established to meet the total process capability requirement.

Keywords

Citation

Arra, M., Geiger, D., Shangguan, D. and Sjöberg, J. (2004), "A study of SMT assembly processes for fine pitch CSP packages", Soldering & Surface Mount Technology, Vol. 16 No. 3, pp. 16-21. https://doi.org/10.1108/09540910410562482

Download as .RIS

Publisher

:

Emerald Group Publishing Limited

Copyright © 2004, Emerald Group Publishing Limited

Please note you might not have access to this content

You may be able to access this content by login via Shibboleth, Open Athens or with your Emerald account.
If you would like to contact us about accessing this content, click the button and fill out the form.
To rent this content from Deepdyve, please click the button.