Kohei Murakami

Development of laser marking for IC packages

Laser marking is expected to apply to the production of IC packages, which are made of black composite resin. YAG laser and CO2 laser can be used for marking. It is considered that YAG laser marks are clearer than CO2 laser marks generally. But the difference of the visibility between YAG laser marks and CO2 laser marks is not obvious at present. Therefore, the effect of the wavelength of lasers on the visibility of the marks is investigated.In the experiment, the specimens were marked by YAG laser and CO2 laser irradiation. And the visibilities, the removed volumes and the microstructures of marked specimens were evaluated with an optical microscope, a surface profiling instrument and SEM. The characteristics of the absorbed laser energy of specimens were evaluated with a spectro-photometer.The YAG laser mark was clearer than the CO2 laser mark; the former was light brown and the latter was dark brown. The visibility of the laser marks did not depend on the removed volume, but depended on the contrast between irradiated region and other region. From the microstructures of the marks, it was deduced that the matrix resin was decolorized by YAG laser irradiation.Laser marking is expected to apply to the production of IC packages, which are made of black composite resin. YAG laser and CO2 laser can be used for marking. It is considered that YAG laser marks are clearer than CO2 laser marks generally. But the difference of the visibility between YAG laser marks and CO2 laser marks is not obvious at present. Therefore, the effect of the wavelength of lasers on the visibility of the marks is investigated.In the experiment, the specimens were marked by YAG laser and CO2 laser irradiation. And the visibilities, the removed volumes and the microstructures of marked specimens were evaluated with an optical microscope, a surface profiling instrument and SEM. The characteristics of the absorbed laser energy of specimens were evaluated with a spectro-photometer.The YAG laser mark was clearer than the CO2 laser mark; the former was light brown and the latter was dark brown. The visibility of the laser marks did not depend on the removed volume, but depended on the contrast be...

Fluxless soldering with laser for assembly of TCP

The fluxless soldering using a YAG laser for tape carrier package (TCP) has been investigated. We developed the fluxless soldering using the sputtering effect of laser irradiation with high power density (31 W, ϕ150 μm) and the reduction of hydrogen gas (5 vol%) for the removal of oxide film. The removal of the oxide film on the solder surface by the laser sputtering was investigated by Auger electron spectroscopy (AES). The laser irradiation time without the heat damage to PCB was optimized using the general finite elements analysis program, ANSYS. The results of the fluxless soldering were comparable with that in air using rosin mildly activated (RMA) flux.The fluxless soldering using a YAG laser for tape carrier package (TCP) has been investigated. We developed the fluxless soldering using the sputtering effect of laser irradiation with high power density (31 W, ϕ150 μm) and the reduction of hydrogen gas (5 vol%) for the removal of oxide film. The removal of the oxide film on the solder surface by the laser sputtering was investigated by Auger electron spectroscopy (AES). The laser irradiation time without the heat damage to PCB was optimized using the general finite elements analysis program, ANSYS. The results of the fluxless soldering were comparable with that in air using rosin mildly activated (RMA) flux.

Laser soldering for fine-pitch leads in SMT assembly

This paper describes the development of a new laser soldering technique for surface mount assemblies. The new technique, using a focused YAG laser beam, has superior performance. It can be applied to tape carrier package (TCP) assemblies for fine pitch leads and offers a no-bridge soldering process.In this paper, the performance of the new technique is evaluated experimentally. First, the new technique is compared with the conventional laser-soldering technique for TCP assemblies, and the no-bridge soldering concept is proved. Second, to obtain more flexibility in assembly, the solder flow is investigated by beam scanning. The beam-resting time on the pads of the printed circuit board (PCB), is optimized by the theoretical and experimental analysis of the volume of melted solder. The reducing atmosphere (H2-N2gas) is considered to achieve a no-clean soldering process. From these experiments, the new laser soldering technique offers the ability to assemble high lead count, fine pitch ICs such as TCPs.This paper describes the development of a new laser soldering technique for surface mount assemblies. The new technique, using a focused YAG laser beam, has superior performance. It can be applied to tape carrier package (TCP) assemblies for fine pitch leads and offers a no-bridge soldering process.In this paper, the performance of the new technique is evaluated experimentally. First, the new technique is compared with the conventional laser-soldering technique for TCP assemblies, and the no-bridge soldering concept is proved. Second, to obtain more flexibility in assembly, the solder flow is investigated by beam scanning. The beam-resting time on the pads of the printed circuit board (PCB), is optimized by the theoretical and experimental analysis of the volume of melted solder. The reducing atmosphere (H2-N2gas) is considered to achieve a no-clean soldering process. From these experiments, the new laser soldering technique offers the ability to assemble high lead count, fine pitch ICs such as TCPs.