NDLI: Feasibility and reliability study on the electroless nickel bumping and stencil solder printing for low-cost flip chip electronic packaging

Content Provider	IEEE Xplore Digital Library
Author	Chow, Y.M. Lau, W.M. Schetty, R.E. Karim, Z.S.
Copyright Year	2000
Description	Author affiliation: Adv. Interconnect Technol. Ltd., China (Chow, Y.M.)
Abstract	We present a study on the feasibility and reliability of a low-cost flip chip technology using a combination of electroless nickel bumping and stencil solder printing. Circular aluminum bump pads of diameter 250 /spl mu/m and pitch 400 /spl mu/m with 200 /spl mu/m openings in the passivation layer were patterned for the study. Since it has been suggested that phosphorus from the electroless nickel solution will degrade the adhesion of solder, three types of electroless nickel deposits were prepared as the under bump metallurgy (UBM) consisting of electroless nickel-high phosphorous (EN-HP), electroless nickel-low phosphorous (EN-LP) and electroless nickel-boron (EN-B). Eutectic lead-tin solder paste of composition 63Sn-37Pb was screen-printed on the electroless nickel UBM followed by reflow at a peak temperature of 230/spl deg/C. The final solder bump height achieved was 155/spl plusmn/8 /spl mu/m. The shearing strength was found to decrease in the order of EN-B (1857.5 g/bump)>EN-LP (178/spl plusmn/8.7 g/bump)>EN-HP (170/spl plusmn/8.1 g/bump). Furthermore, multiple reflow caused a decrease of the shearing strength within 20%, indicating a satisfactory reliability of electroless nickel/stencil printed solder in wafer bumping. It was found by SEM/EDX analysis that the fracture occurred within the solder regardless of the type of electroless nickel. Further evaluation on bump height uniformity has indicated that the use of stencil printing technique for screen-printed bumps can be an effective low-cost method for fabrication of solder bumps on wafers.
Starting Page	79
Ending Page	85
File Size	864518
Page Count	7
File Format	PDF
ISBN	0780366549
DOI	10.1109/EMAP.2000.904136
Language	English
Publisher	Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Publisher Date	2000-11-30
Publisher Place	China
Access Restriction	Subscribed
Rights Holder	Institute of Electrical and Electronics Engineers, Inc. (IEEE)
Subject Keyword	Nickel Printing Shearing Flip chip Aluminum Passivation Degradation Adhesives Lead Temperature
Content Type	Text
Resource Type	Article

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