Lift-off phenomenon in wave soldering

The mechanism of lift-off, which is the serious defect formation that the solder fillet is peeled off from a Cu land pad on a printed wiring board in wave soldering, has been examined primarily by using basic Sn–Bi alloys (Sn at 2–5 wt%) and solidification simulation. The probability of lift-off inc...

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Bibliographic Details
Published in:Acta materialia 2000-12, Vol.48 (18-19), p.4475-4481
Main Authors: Suganuma, K, Ueshima, M, Ohnaka, I, Yasuda, H, Zhu, J, Matsuda, T
Format: Article
Language:English
Subjects:
Applied sciences
Brazing. Soldering
Computer simulation
Exact sciences and technology
Interface
Joining, thermal cutting: metallurgical aspects
Lift-off phenomenon
Metals. Metallurgy
Microstructure
Segregation
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Summary:The mechanism of lift-off, which is the serious defect formation that the solder fillet is peeled off from a Cu land pad on a printed wiring board in wave soldering, has been examined primarily by using basic Sn–Bi alloys (Sn at 2–5 wt%) and solidification simulation. The probability of lift-off increases with increasing Bi content. Lift-off results from the segregation of Bi, which diffuses in a short distance, in the interfacial region between a Sn–Bi alloy and a Cu land pad during dendritic structure formation. A higher fillet results in a more severe lift-off—the top side of a printed wiring board, where the fillet is low, seldom shows lift-off. The solidification simulation indicates that the solidification of the solder fillet rapidly propagates from a lead wire to a fillet edge. A Cu land acts as a heat sink, with heat flowing from the inner through-hole to the land pad. Both rapid cooling and annealing at high temperature can effectively prevent lift-off.
ISSN:1359-6454
1873-2453
DOI:10.1016/S1359-6454(00)00234-2