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Abstract : Vol.39No.2(2004.6)
Research Report
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| P.34 |
Aluminum
Protected Silicon Anisotropic Etching
Technique Using TMAH with an Oxidizing Agent and Dissolved
Si |
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Norio Fujitsuka, Kanae Hamaguchi,
Hirofumi Funahashi, Eishi Kawasaki,
Tsuyoshi Fukada
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Silicon anisotropic etching using TMAH containing dissolved
Si and an oxidizing agent was investigated. The focus
of this investigation was on the aluminum etching rate
and the formation of micropyramids. It was previously
reported that Si anisotropic etching could be achieve
with TMAH with Si and ammonium persulfate. In addition
to this method, Si anisotropic etching without the occurrence
of aluminum etching was achieved by dissolving Si and
ammonium nitrate in TMAH. Surface analysis of the etched
aluminum revealed that thin oxide layers, which cannot
be etched by TMAH, form on the aluminum surface. This
formation of micropyramids is dependent on the (111)/(100)
etching rate ratio. Herein, we demonstrate that micropyramid
formation can be prevented by increasing the (111)/(100)
etching rate ratio. The Si(100) etching rate and the
occurrence of micropyramids changes according to the
sequence that the materials are dissolved in Silicon
anisotropic etching using TMAH with Si and ammonium
persulfate. Consequently, dissolving Si before ammonium
persulfate was determined to be crucial to the prevention
of aluminum etching.
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| P.41 |
Development
of Wettability Evaluation Technique
Applying Contact Angle Measurement during Soldering |
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Hisaaki Takao, Toshihiko Tsukada, Keiichi
Yamada,
Masahiko Yamashita, Hideo Hasegawa
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A new wettability evaluating system was developed by
combining a contact angle measurement instrument, which
optically and in-situ measures the contact angle of
molten solder, with a conventional wettability tester
(meniscograph). Using this new evaluation system, a
well-known experiential knowledge that the wettability
for Sn-3.5Ag, a typical Pb-free solder, is inferior
to that for Sn-37Pb is quantitatively confirmed by the
result that the contact angle for Sn-3.5Ag is twice
of that for Sn-37Pb. The cause for this wettability
difference is attributed to the difference in the surface
tensions of the solders (the solder-flux interfacial
tension). The influences of alloying elements (1%Cu,
1%Zn, 5%Bi, 5%In), fluxes and Au coating on a Cu substrate
on the wettability for the Sn-3.5Ag are discussed. In
the discussion, three interfacial tensions among the
solder, flux and substrate are separately estimated
to analyze the mechanisms which make differences in
wettability.
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| P.49 |
Mechanical
Properties and Solder Joint Reliability of Low-Melting
Sn-Bi-Cu Lead Free Solder Alloy |
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Hisaaki Takao, Akira Yamada, Hideo Hasegawa
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The influence of alloy composition of low-melting Sn-Bi-Cu
lead-free solder alloys on mechanical properties and
solder joint reliabilities were investigated. The mechanically
optimum alloy composition is Sn-40Bi-0.1Cu (mass%).
The addition of 40mass%Bi improves the ductility and
restrains the fillet-lifting, which are problems of
lead-free solders with Bi. The addition of copper improves
both the ductility and Cu leaching resistance of Sn-40Bi.
The joint strength and thermal fatigue resistance of
the Sn-40Bi-0.1Cu solder joints are superior to those
of Sn-37Pb.
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| P.57 |
Numerical
Prediction of the Spring-Back Behavior of Stamped Metal
Sheets |
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Noritoshi Iwata, Hideo Tsutamori,
Naomori Suzuki, Atsunobu Murata
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This paper describes our study of
the spring-back behavior of a sheet that has been bent
into a hat shape, with the goal of establishing a system
for predicting all the shape defects that may occur
in formed sheet products. We also examine the stamping
of a three-dimensional rail panel that would normally
be expected to twist. For the sake of computational
efficiency, we used the dynamic explicit method in our
simulation of the forming process, after which we applied
the static implicit method for the unloading process.
The most notable finding arising from this study is
that, in order to precisely predict the spring-back
behavior, the non-linear properties of the sheet material
during unloading must be taken into consideration. We
propose methods for measuring the nonlinearity, as well
as a material model for expressing the characteristic
behaviors (i.e., the strain-dependent pseudo-elastic
modulus and the Bauschinger effect). The results obtained
with the proposed methods (together with the proposed
material model) are compared with those obtained experimentally.
Furthermore, we also applied the proposed method to
the elastic deformation of dies, and the shape obtained
theoretically was compared with actual measurements.
We confirmed that the proposed method can precisely
predict the spring-back shape.
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