. . . . .
2-9317-372-00-0 Bravo™ 8105 Programming and Operations Guide 8-123
Tombstoning (cont.) Uneven paste deposit, a vision system designed to measure solder deposition height
may rectify the problem
Time above liquideous too long
Insufficient tack force of the solder to hold the component in place during reflow (typically
a result of temperature and humidity). Avoid extremes in environmental conditions.
ae
Excessive movement during and immediately after the reflow process
af
Exceptionally
high ramp rates cause accelerated heating.
ag
Inaccurate component placement — the greater wetting force exerted on one end of an
incorrectly placed component will pull it up on end, creating a tombstoning effect.
ah
Excessive pad size — A greater amount of paste relative to the surface area of the part’s
terminal can result in tombstoning. Also a greater wetting force can be created during
reflow in the case of an uneven deposition of paste on the pads.
ai
Pad size/component mismatch
Laminate Discoloration Excessive maximum reflow temperature
Reflow cycle too long
Leaching Excessive maximum reflow temperature
Reflow cycle too long
a. Dr. Jennie S. Hwang, “Pathways to SMT: Soldering,” Surface Mount Technology (Aug 1998): 155.
b. Kurt Rajewski, “SMT Process Recommendations: Defect Minimization Methods for a No–Clean SMT
Process,”January 13, 1997, <http://www.kester.com/smtrec.htm> (January 25, 1999), 1.
c. Rajewski.
d. Michael R. McMonagle <McMongIM@KTELEC>”Pin–in–paste problem”, Feb. 25, 1999, TechNet dis-
tribution list, accessed Feb. 25, 1999.
e. Sonora Manufacturing Group, “A Gallery of ‘Bad Actors’,” Special Supplement to SMT Back to Basics,
(July, 1998): 34.
f. Hwang, 157
g. Brian Deram, “Solder Balls & Low Solder Fluxes,” January 13, 1997, <http:www.kester.com/sold-
ball.htm> (January 27, 1999).
h. Deram
i. David Scheiner, “Solder Materials,” Special Supplement to SMT Back to Basics, (July 1998): 15.
j. Rajewski.
k. Rajewski, 2.
l. Brian Smith, Greg Miller, “Understanding Solder Paste Survivability and Failure Modes,” Surface Mount
Technology (Aug 1998): 124
m. “Solder Balling,” <http://www.aimsolder.com/Troubleshooting%20guide/balling.htm> (May 12, 1999)
n. “Solder Beading,” <http://www.aimsolder.com/Troubleshooting%20guide/beading.htm> (May 12, 1999)
o. ibid.
p. ibid.
q. Sonora Manufacturing Group.
r. Hwang, 158.
s. Hwang.
t. Ray Chartrand, “Reflow Solder Workshop,” presented to Speedline Electrovert, Camdenton, MO, October
30, 1998.
u. Hwang.
Problem Possible Cause(s)
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