Statistical analysis of stencil technology for wafer-level bumping

Robert W Kay, Gerard Cummins, Thomas Krebbs, Richard Lathrop, Eitan Abraham, Marc Phillipe Yves Desmulliez

Research output: Contribution to journalArticle

Abstract

Purpose - Wafer-level stencil printing of a type-6 Pb-free SAC solder paste was statistically evaluated at 200 and 150 jam pitch using three different stencil manufacturing technologies: laser cutting, DC electroforming and micro-engineered electroforming. This investigation looks at stencil differences in printability, pitch resolution, maximum achievable bump height, print co-planarity, paste release efficiency, and cleaning frequency. The paper aims to discuss these issues.

Design/methodology/approach - In this paper, the authors present a statistical evaluation of the impact of stencil technology on type-6 tin-silver-copper paste printing. The authors concentrate on performances at 200 and 150 mu m pitch of full array patterns. Key evaluated criteria include achievable reflowed bump heights, deposit co-planarity, paste release efficiency, and frequency of stencil cleaning. Box plots were used to graphically view print performance over a range of aperture sizes for the three stencil types.

Findings - Fabrication technologies significantly affect print performance where the micro-engineered electroformed stencil produced the highest bump deposits and the lowest bump height deviation. Second in performance was the conventional electroformed, followed by the laser-cut stencil. Comparisons between the first and fifth consecutive print demonstrated no need for stencil cleaning in the case for the micro-engineered stencil for all but the smallest spacings between apertures. High paste transfer efficiencies, i.e. above 85 per cent were achieved with the micro-engineered stencil using low aperture area ratios of 0.5.

Originality/value - Stencil technology influences the maximum reflowed solder bump heights achievable, and bump co-planarity. To date, no statistical analysis comparing the impact of stencil technology for wafer-level bumping has been carried out for pitches of 200 mu m and below. This paper gives new insight into how stencil technology impacts the print performance for fine pitch stencil printing. The volume of data collected for this investigation enabled detailed insight into the limitations of the printing process and as a result for suitable design guidelines to be developed. The finding also shows that the accepted industry guidelines on stencil design developed by the surface mount industry can be broken if the correct stencil technology is selected, thereby increasing the potential application areas of stencil printing.

Original languageEnglish
Pages (from-to)71-78
Number of pages8
JournalSoldering and Surface Mount Technology
Volume26
Issue number2
DOIs
Publication statusPublished - 2014

Keywords

  • Interconnects
  • Pb-free
  • Solder joints
  • Stencil printing
  • Wafer-level package
  • SOLDER PASTE
  • PRINTING TECHNOLOGY
  • CHALLENGES

Cite this

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title = "Statistical analysis of stencil technology for wafer-level bumping",
abstract = "Purpose - Wafer-level stencil printing of a type-6 Pb-free SAC solder paste was statistically evaluated at 200 and 150 jam pitch using three different stencil manufacturing technologies: laser cutting, DC electroforming and micro-engineered electroforming. This investigation looks at stencil differences in printability, pitch resolution, maximum achievable bump height, print co-planarity, paste release efficiency, and cleaning frequency. The paper aims to discuss these issues.Design/methodology/approach - In this paper, the authors present a statistical evaluation of the impact of stencil technology on type-6 tin-silver-copper paste printing. The authors concentrate on performances at 200 and 150 mu m pitch of full array patterns. Key evaluated criteria include achievable reflowed bump heights, deposit co-planarity, paste release efficiency, and frequency of stencil cleaning. Box plots were used to graphically view print performance over a range of aperture sizes for the three stencil types.Findings - Fabrication technologies significantly affect print performance where the micro-engineered electroformed stencil produced the highest bump deposits and the lowest bump height deviation. Second in performance was the conventional electroformed, followed by the laser-cut stencil. Comparisons between the first and fifth consecutive print demonstrated no need for stencil cleaning in the case for the micro-engineered stencil for all but the smallest spacings between apertures. High paste transfer efficiencies, i.e. above 85 per cent were achieved with the micro-engineered stencil using low aperture area ratios of 0.5.Originality/value - Stencil technology influences the maximum reflowed solder bump heights achievable, and bump co-planarity. To date, no statistical analysis comparing the impact of stencil technology for wafer-level bumping has been carried out for pitches of 200 mu m and below. This paper gives new insight into how stencil technology impacts the print performance for fine pitch stencil printing. The volume of data collected for this investigation enabled detailed insight into the limitations of the printing process and as a result for suitable design guidelines to be developed. The finding also shows that the accepted industry guidelines on stencil design developed by the surface mount industry can be broken if the correct stencil technology is selected, thereby increasing the potential application areas of stencil printing.",
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author = "Kay, {Robert W} and Gerard Cummins and Thomas Krebbs and Richard Lathrop and Eitan Abraham and Desmulliez, {Marc Phillipe Yves}",
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Statistical analysis of stencil technology for wafer-level bumping. / Kay, Robert W; Cummins, Gerard; Krebbs, Thomas; Lathrop, Richard; Abraham, Eitan; Desmulliez, Marc Phillipe Yves.

In: Soldering and Surface Mount Technology, Vol. 26, No. 2, 2014, p. 71-78.

Research output: Contribution to journalArticle

TY - JOUR

T1 - Statistical analysis of stencil technology for wafer-level bumping

AU - Kay, Robert W

AU - Cummins, Gerard

AU - Krebbs, Thomas

AU - Lathrop, Richard

AU - Abraham, Eitan

AU - Desmulliez, Marc Phillipe Yves

PY - 2014

Y1 - 2014

N2 - Purpose - Wafer-level stencil printing of a type-6 Pb-free SAC solder paste was statistically evaluated at 200 and 150 jam pitch using three different stencil manufacturing technologies: laser cutting, DC electroforming and micro-engineered electroforming. This investigation looks at stencil differences in printability, pitch resolution, maximum achievable bump height, print co-planarity, paste release efficiency, and cleaning frequency. The paper aims to discuss these issues.Design/methodology/approach - In this paper, the authors present a statistical evaluation of the impact of stencil technology on type-6 tin-silver-copper paste printing. The authors concentrate on performances at 200 and 150 mu m pitch of full array patterns. Key evaluated criteria include achievable reflowed bump heights, deposit co-planarity, paste release efficiency, and frequency of stencil cleaning. Box plots were used to graphically view print performance over a range of aperture sizes for the three stencil types.Findings - Fabrication technologies significantly affect print performance where the micro-engineered electroformed stencil produced the highest bump deposits and the lowest bump height deviation. Second in performance was the conventional electroformed, followed by the laser-cut stencil. Comparisons between the first and fifth consecutive print demonstrated no need for stencil cleaning in the case for the micro-engineered stencil for all but the smallest spacings between apertures. High paste transfer efficiencies, i.e. above 85 per cent were achieved with the micro-engineered stencil using low aperture area ratios of 0.5.Originality/value - Stencil technology influences the maximum reflowed solder bump heights achievable, and bump co-planarity. To date, no statistical analysis comparing the impact of stencil technology for wafer-level bumping has been carried out for pitches of 200 mu m and below. This paper gives new insight into how stencil technology impacts the print performance for fine pitch stencil printing. The volume of data collected for this investigation enabled detailed insight into the limitations of the printing process and as a result for suitable design guidelines to be developed. The finding also shows that the accepted industry guidelines on stencil design developed by the surface mount industry can be broken if the correct stencil technology is selected, thereby increasing the potential application areas of stencil printing.

AB - Purpose - Wafer-level stencil printing of a type-6 Pb-free SAC solder paste was statistically evaluated at 200 and 150 jam pitch using three different stencil manufacturing technologies: laser cutting, DC electroforming and micro-engineered electroforming. This investigation looks at stencil differences in printability, pitch resolution, maximum achievable bump height, print co-planarity, paste release efficiency, and cleaning frequency. The paper aims to discuss these issues.Design/methodology/approach - In this paper, the authors present a statistical evaluation of the impact of stencil technology on type-6 tin-silver-copper paste printing. The authors concentrate on performances at 200 and 150 mu m pitch of full array patterns. Key evaluated criteria include achievable reflowed bump heights, deposit co-planarity, paste release efficiency, and frequency of stencil cleaning. Box plots were used to graphically view print performance over a range of aperture sizes for the three stencil types.Findings - Fabrication technologies significantly affect print performance where the micro-engineered electroformed stencil produced the highest bump deposits and the lowest bump height deviation. Second in performance was the conventional electroformed, followed by the laser-cut stencil. Comparisons between the first and fifth consecutive print demonstrated no need for stencil cleaning in the case for the micro-engineered stencil for all but the smallest spacings between apertures. High paste transfer efficiencies, i.e. above 85 per cent were achieved with the micro-engineered stencil using low aperture area ratios of 0.5.Originality/value - Stencil technology influences the maximum reflowed solder bump heights achievable, and bump co-planarity. To date, no statistical analysis comparing the impact of stencil technology for wafer-level bumping has been carried out for pitches of 200 mu m and below. This paper gives new insight into how stencil technology impacts the print performance for fine pitch stencil printing. The volume of data collected for this investigation enabled detailed insight into the limitations of the printing process and as a result for suitable design guidelines to be developed. The finding also shows that the accepted industry guidelines on stencil design developed by the surface mount industry can be broken if the correct stencil technology is selected, thereby increasing the potential application areas of stencil printing.

KW - Interconnects

KW - Pb-free

KW - Solder joints

KW - Stencil printing

KW - Wafer-level package

KW - SOLDER PASTE

KW - PRINTING TECHNOLOGY

KW - CHALLENGES

U2 - 10.1108/SSMT-07-2013-0017

DO - 10.1108/SSMT-07-2013-0017

M3 - Article

VL - 26

SP - 71

EP - 78

JO - Soldering and Surface Mount Technology

JF - Soldering and Surface Mount Technology

SN - 0954-0911

IS - 2

ER -