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Greetings!
Welcome to the May issue of Residue News
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Upcoming Events |
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Foresite staff will be participating in some industry events in
the fall of 2009. We will keep you updated regarding where, when,
and what.
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Meet the Problem |
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Flux From a Nearby No-clean Hand-solder Operation
When using a squeeze bottle with a needle to apply flux to
hand-solder areas, it is typical for excess flux to travel over
nearby areas and through nearby vias. The performance-affecting
results can be seen in the photo. In this case, dendrites grew
between the two vias with a 1.5 volt difference within four weeks
of product usage in the field. Heavy flux usage does not improve
solderability; unfortunately operator training in rework and
repair does not always emphasize this important issue.
Data Discussion Samples from two assemblies,
built from the same process, six months apart, were tested. Each
test location was near a hand-solder area with visible flux
residues present. Both samples were from the top side of the via
and exhibited heavy visible flux. WOA (weak organic acid) levels
exceeded 300 µg/in2 on both test locations. The high
levels of WOA match the no-clean flux used for the solder
attachment; only the bottom side of the assembly was brushed
cleaned.
Recovery Plan Due to the presence of several
water-intolerant components on the assembly, a secondary thermal
exposure above activation temperatures was added, ensuring total
board and component surfaces were exposed to the same temperature.
All residues became benign.
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Foresite Expands Our "CSI" Capability |
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Foresite has always been focused on solving the crimes of reduced
product reliability and/or performance. Our failure analysis at
the "crime scene" reveals such process residue clues as flux
residues that are not fully activated or etch residues that have
not been properly cleaned from boards. These clues usually lead us
to a "culprit" manufacturing process - a process that has gone out
of control, needs optimization or perhaps drastic rehabilitation.
We have become adept at identifying ions that are detrimental,
in what concentrations, and tracking down the source(s). We are
continually exploring ways to enhance our failure analysis,
reliability and process optimization capabilities for our
customers. Foresite has succeeded in optimizing the column
technology in our ion chromatography (IC) systems, resulting in
better separation and identification of organic species that we
have learned negatively impact product performance.
The addition of electron microscopy inspection (SEM) and new
micro-sectioning equipment, to our X- ray Fluorescence (XRF)
capability, will allow us to uncover additional clues regarding
your process residues. Purchasing equipment is not enough, having
staff with the expertise and experience to collect pertinent data
and interpret the information is crucial. Lead Investigator, Paco
Solis, and Process Investigator, Lee Flasche, together have over
40 years of experience in failure analysis, reliability, and
metallurgical issues.
If you have a "crime scene" that needs investigating contact
Foresite. |
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New, Smaller Footprint, C3 Test Cell
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A new test cell for the C3 Critical Cleanliness Control has been
developed to fit over small components (0805 and smaller) and into
tight spots on electronic assemblies. This test cell fits into the
C3 steam head without modification. The new cell's rectangular
test area is 0.028 in2 (0.18 cm2) vs. the
standard test cell's circular test area of 0.110 in2
(0.71 cm2), a 75% reduction. The new footprint is
0.245" (6.2mm) x 0.355" (9.0mm) or 0.087 in2 (0.56 cm2)
as compared to the 0.625" (15.9mm) dia. or 0.307 in2
(1.98 cm2).
Optimized sample extraction from the test surface with this new
cell does require a new set of C3 operating test parameters that
can be easily entered into the C3's touch-screen controller.
The new test cell will be released for production in May and
initially have a six to eight week lead-time. |
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