Stencil printing is a critical first step in surface mount assembly. However, its robustness can be called into question because of the fact that about 50% or more of the defects found in the assembly of printed circuit boards (PCBs) are attributed to stencil printing 1. Manufacturing techniques for the assembly of certain flip chips, chip scale packages, 0201s, and fine pitch ball grid arrays are testing the limits of current stencil printing capabilities. This paper focuses on understanding the release of solder paste from the stencil, based on experimental and modeling approaches. The primary goal of the study is to characterize the performance of various aperture sizes and geometries based on release efficiencies and to compare them to predictions. The resulting model validation helps us better understand the print process for small features and offers options for increasing print yields. The study is divided into two phases. The first phase examines the release performance of various solder pastes from a variety of aperture sizes and geometries. The focus of this study is a comparison of square versus circular apertures when the nominal volume of paste to be deposited is kept constant. The second phase consists of developing a model that predicts paste-release efficiencies from small apertures and validating the model with experimental results.

1.
Clouthier
,
R.
, 1997, “
SMT Printing Process for Fine Pitch and Ultrafine Pitch
,”
Proc. of Surface Mount International Conference
, SMTA, Edina, MN, pp.
674
683
.
2.
Painaik
,
M.
,
Santos
,
D.
, and
McLenaghan
,
J.
, 2001, “
Guideline for Fine Feature Stencil Printing
,”
Proc. of SMTA International
, SMTA, Edina, MN, pp.
39
48
.
3.
Muffadal
,
M.
,
Santos
,
D.
,
McLenaghan
,
J.
, and
Kerrick
,
N.
, 2001, “
Evaluation and Optimization of the Speedline MPM Closed-Loop Rheometric Pump Head
,”
Proc. of SMTA International
, SMTA, Edina, MN, pp.
76
84
.
4.
Riemer
,
D. E.
, 1988, “
Analytical Engineering Model of the Screen Printing Process: Part I
,”
Solid State Technol.
0038-111X
31
(
8
), pp.
107
111
.
5.
Riemer
,
D. E.
, 1988, “
Analytical Engineering Model of the Screen Printing Process: Part II
,”
Solid State Technol.
0038-111X
31
(
9
), pp.
85
90
.
6.
Hanrahan
,
T. F.
,
Monaghan
,
P. F.
, and
Babikian
,
R. D.
, 1992, “
Modeling of a Solder Paste Flow With a Free Surface in Stencil Printing
,”
ASME J. Electron. Packag.
1043-7398
114
, pp.
587
592
.
7.
Sahay
,
C.
,
Head
,
L. M.
,
Shereen
,
R.
,
Dujari
,
P.
,
Constable
,
J. H.
, and
Westby
,
G.
, 1995, “
Study of Print Release Process in Solder Paste Printing
,”
ASME J. Electron. Packag.
1043-7398
117
, pp.
230
234
.
8.
Rodriguez
,
G.
, and
Baldwin
,
D.
, 1999, “
Analysis of Solder Paste Release in Fine Pitch Stencil Printing Process
,”
ASME J. Electron. Packag.
1043-7398
121
, pp.
271
276
.
9.
Partridge
,
J.
, and
Gunn
,
R.
, 1998, “
Paste Printing and Characterization for Chip Scale Package Assemblies
,”
Proc. of Surface Mount International Conference
, San Jose, CA, SMTA, Edina, MN, pp.
405
416
.
10.
Clech
,
J.
, 1997, “
Flip-Chip/CSP Assembly Reliability and Solder Volume Effects
,”
Proc. of Surface Mount International Conference
, SMTA, Edina, MN, pp.
315
324
.
11.
Johnson
,
A.
, and
Flori
,
A.
, 2001, “
High Density and Fine Feature Solder Paste Printing
,”
Proc. of APEX 2001
, IPC, Banneckburn, IL, MP2-3, pp.
1
5
.
12.
Kennedy
,
J.
, and
Ros
,
J.
, 1999, “
Solder Paste Printing Requirements for CSP Packages
,”
Proceedings of SMTA International
, SMTA, Edina, MN, pp.
105
115
.
13.
Burr
,
D.
, 1998, “
Printing Guideline for BGA and CSP Assemblies
,”
Proceedings of Surface Mount International Conference
, San Jose, CA, SMTA, Edina, MN, pp.
417
424
.
14.
Kelley
,
R.
, and
Tan
,
D.
, 2001, “
A 3-D Solder Paste Inspection Strategy for CSPs and 0201s
,” http://www.gsilumonics.com/electronics/pdfs/spi_3d.pdfhttp://www.gsilumonics.com/electronics/pdfs/spi_3d.pdf
15.
Coleman
,
W.
, 2001, “
Paste Release Vs. Print Area Ratio
”,
Proc. of APEX 2001
, IPC, Banneckburn, IL, MP2-2, pp.
1
8
.
16.
Zimon
,
A. D.
, 1982,
Adhesion of Dust and Powder
,
2nd. Edition
,
Plenum Press
, New York, translated by R. K. Johnston, Consultants Bureau.
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