13 March 2007 Micro welding of electronic components with 532nm laser radiation
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Laser micro-welding of electronic components using the wavelength &lgr;= 1064 nm is state-of-the-art technology. However, in these parts some metals that needs to be welded, especially copper and gold, show high reflection and hence low absorption rates of under 4 % for the infrared wavelength range. Further, for increasing temperatures above the melting point of these metals, the absorption rate rises erratically. Since the fusion time point is dependent on different factors, it cannot be calculated precisely beforehand. This makes process control difficult and decreases the required process window for laser micro-welding of these materials. On the other hand, these metals show a ten-times higher absorption rate for the wavelength &lgr; = 532 nm, meaning the use of a frequency-converted Nd:YAG laser becomes interesting for micro-welding. In this paper, investigations on laser micro-welding using a frequency-converted laser at the wavelength of &lgr; = 532 nm were carried out. In order to evaluate the laser process, on a demonstrator board electrical components (TSSOP) with a pitch of 0.5 mm were welded directly onto the copper strip conductors with heights of d = 70 μm. The laser welding process with &lgr; = 532 nm delivered constant results. Within the characterization by a shear tester an average shear force of F = 5.5 N per lead could be realized.
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F. Otte, F. Otte, U. Stute, U. Stute, A. Ostendorf, A. Ostendorf, } "Micro welding of electronic components with 532nm laser radiation", Proc. SPIE 6458, Photon Processing in Microelectronics and Photonics VI, 645804 (13 March 2007); doi: 10.1117/12.705385; https://doi.org/10.1117/12.705385

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