| Autor: |
J. H. Wu, T. B. Lim, X. F. Zong, J. C. Lu, Y. S. Li, Y. H. Tay |
| Rok vydání: |
1998 |
| Předmět: |
|
| Zdroj: |
Journal of Electronics Manufacturing. :173-179 |
| ISSN: |
0960-3131 |
| DOI: |
10.1142/s0960313198000161 |
| Popis: |
The occurrence of flux residue is a manufacturing and reliability concern for flip chip assemblies. In this paper, removal of flux residue by laser cleaning before chip attachment to board is carried out. In the flip chip process, 63%Sn37%Pb solder paste with a water soluble flux was printed on wafer by stencil and subjected to infrared reflow. Instead of washing with water, flux residue on the chips after wafer sawing was removed by ablation of pulsed ultraviolet (UV) lasers with wavelengths of 248 nm and 355 nm respectively. Some parameters in the cleaning process such as the energy density of laser and number of pulses irradiated on the chips had been optimized. It was found that the laser beams also etched polyimide passivation on the chips. After laser etching, the passivation surface became cleaner. The rate of etching was measured by a surface profilometer. To conclude, we discuss the advantages of laser cleaning over wet chemical cleaning in the removal of flux residue. |
| Databáze: |
OpenAIRE |
| Externí odkaz: |
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