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2009/11/23
學
生：陳立偉
指導教授：林克默
 1. Introduction
 2. Experimental
 3. Results and discussion
 4. Summary
1. Introduction
 According to the EU (RoHS) Directive on the restriction of the
use of certain hazardous substances, it is believed that
requirement of environment- friendly ribbon assembled in the
crystalline silicon solar system should be an important issue in
the near future.
 Before the characteristic study on electronics packaging, little
work has been done on the wettability of solders on solar cells.
Herefore, it is of great interest to study the wettability of two
lead (SnAgPb (SAP) and SnPb (SP)) and one lead-free
(SnAgCu (SAC)) solders, and the effects of soldering
temperature were also monitored for comparison in this paper.
2. Experimental
 Solders：Sn–28Pb、Sn–2.6Ag–24.3Pb and
Sn–3.5Ag–0.8Cu in at%.
 Low-solid non-clean flux (Kester, 955).
 The temperatures at 190–240℃ for lead solders and at 230–
280 ℃ for lead-free solder.
 Analyzed by the contact angle (CA) system (VCA-
2500XE, VISUAL CONTACT ANGL-236).
 Microstructure analyses were performed using scanning
electron microscopy (Hitachi S-4800).
 Composition analyses were carried out by energydispersive spectrometry (EDX).
3. Results and discussion
Fig. 1. Contact angle measurement of solders detected at high temperatures.
Fig. 2. Contact angle measurement of solders at room temperatures.
Fig. 3. Contact angles of solders on substrates measured at various temperatures.
Fig. 4. Cross-sectional images of SnAgPb soldering with Ag paste at (a)190℃, and higher
magnification of (b).
Fig. 5. Cross-sectional BEI micrographs of SnPb soldering with Ag paste at (a)
190℃ and (b) its local higher magnification, at (c)215 ℃ and (d) its local
higher magnification.
(Pt.1) has mostly Sn
(76.7%), high amounts
of Cu (19.0%), and
low Ag (4.3%). (Pt. 2)
mostly Ag with minor
amounts of other alloy
elements dissolved in.
Fig. 6. Cross-sectional image of SnAgCu soldering with Ag paste at (a)
255℃, (b) 280℃, and higher magnification of (c).
4. Summary
1. Lead-free SAC solder generally has lower CA values
than lead SP and SAP solders, implying that SAC solder
has better wettability.
2. CA values of SAC solder decreased with increasing
soldering temperatures; conversely, leaded SP and SAP
solders have higher CA values when soldered at high
temperatures.
3. Based on the BEI micrographs, IMC was significantly
observed in the SAC solder/busbar interface, while no
evidence of IMC formed between the SP solder and the
substrate was detected.
Thank you for your attention