SMTA International Conference Proceedings


Authors: Ursula Marquez de Tino, Linlin Yang and Denis Barbini
Company: Vitronics Soltec, Inc.
Date Published: 10/4/2009   Conference: SMTA International

Abstract: The appropriate selection of nozzle type and design utilized in selective soldering applications is critical to achieve exceptional soldering results. The physical properties of liquid lead free alloys employed in electronics assembly such as viscosity, melting temperature, surface tension combined with the nozzle material and process parameters effects the behavior of lead free alloys which ultimately determines the quality of the formed electric interconnect. This investigation evaluated the use of wettable and non-wettable nozzles with varying nozzle diameters for the purpose of soldering printed circuit boards. There are several distinctions between wettable and non-wettable nozzles.

The results of visual inspection and quantitative analysis of the electrical shorts formed during the designed experiment showed that wettable nozzles produced less bridging defects than non-wettable nozzles. Furthermore, bridging defects were minimized with the use of nozzle diameters equal to or greater than 6 mm along with the faster drag speed (2 mm/s). Soldering temperature did not exert an impact on bridging.

Results from X-ray analysis of through-hole penetration showed that vias soldered with the wettable nozzle were statistically filled and met the IPC 610D class 3 qualification for hole fill at a slightly higher rate than those vias soldered with non-wettable nozzles. Better through hole penetration was observed when soldering temperature of more than 3000C and nozzle diameters of 8 mm for the wettable and 4 mm for the non-wettable were used.

Key words: wettable nozzles, non-wettable nozzles, selective soldering, 5DX, through hole

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