Optimising lead-free screen-printing and reflow process parameters

Claire Ryan, Shane O'Neill, John Donovan, Jeff Punch, Bryan Rodgers, Eamonn Murphy

Research output: Contribution to conferencePaperpeer-review

Abstract

Introducing a lead-free solder replacement requires studies, to be conducted by electronic assembly manufacturers in order to determine process alteration requirements and suitability of current equipment. This paper presents the results of an investigation of the screen-printing and reflow steps of the surface mount technology (SMT) manufacturing process. Experiments were conducted to investigate these two processes using a tin-silver-copper (95.5Sn3.8Ag0.7Cu) solder and a baseline of standard tin-lead (63Sn37Pb). 10×10 array micro Ball Grid Arrays (BGAs) mounted on 8-layer FR4 printed wiring boards (PWBs) were used with an organic solderability preservative (OSP) finish for use with lead-free components, and a hot air solder level (HASL) finish for use with tin-lead components. The screen-printing experiment investigated the deposition of the solder paste on the board. The parameters used in the investigation were print speed, squeegee pressure, snap-off distance, separation speed and cleaning interval with the responses being measurements of paste height and volume. Optimum screen-printer settings were determined which give adequate paste volume and height and a good print definition. The reflow experiment investigated the following parameters of the temperature profile; preheat, soak and reflow temperatures, and conveyor speed. The solder joints were examined using cross-section analysis and x-ray techniques in order to determine the presence of defects. The outcome of the investigation is a set of optimum settings for the screen-printer and reflow oven for use with SnAgCu lead-free solder.

Original languageEnglish
Pages664-668
Number of pages5
Publication statusPublished - 2004
EventITherm 2004 - Ninth Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems - Las Vegas, NV, United States
Duration: 1 Jun 20044 Jun 2004

Conference

ConferenceITherm 2004 - Ninth Intersociety Conference on Thermal and Thermomechanical Phenomena in Electronic Systems
Country/TerritoryUnited States
CityLas Vegas, NV
Period1/06/044/06/04

Keywords

  • Ball Grid Array (BGA) package
  • Cross-section
  • Designed experiment
  • PWB
  • Reliability
  • Solder

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