LATEST DEVELOPMENTS IN BUMPING TECHNOLOGIES FOR FLIP CHIP AND WLCSP PACKAGINGAuthors: Dionysios Manessis and Lars Böttcher,et al.
Company: Microperipheric Research Center, Technical University Berlin and Fraunhofer Institute for Reliability and Microintegration (IZM) Berlin
Date Published: 10/4/2009 Conference: SMTA International
Paste-in-Resist technology has been developed as an alternative to stencils in order to overcome the manufacturing difficulties of making extremely small apertures. Paste is printed in resist apertures which have been opened by photolithographic processes. In this way, bumping has been demonstrated up to 50µm pitches. Complimentary to stencil printing processes, IZM has developed balling technologies up to 400µm pitch up to 8” wafers with a thickness of 150µm. Solder balling can be achieved either by “perform ball print” using conventional stencil printers with specially designed stencils or by "ball drop" techniques. Balling technologies have demonstrated the application of 300µm and 250µm Sn-Pb and Pb-free balls at respective area array pitches of 500µm and 400µm, the main I/O pitches for WL-CSP bumping.
Key words: flip chip bumping, solder balling, WLCSP packaging, stencil printing, solder paste.
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