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I trust that the summer months have
been fun. Our family has recently
enjoyed a trip to the upper Midwest
in the lower part of Michigan.
In this newsletter you will find
several interesting teaser articles
with references to more complete
information on the topic. Take a
look at what's going with the RoHS
proposed legislation in
California-it will make your blood
boil. Please review your
specifications for cleanliness
requirements after reviewing our
brief discussion of cleanliness
testing methods. If you need further
direction on the repair of solder
mask after reading our comments on
this procedure please do not
hesitate to call.
Don't forget to take advantage of
our 10% discount for all training
sessions booked in September and
October! See the coupon below and
call Katy Radcliff to redeem your
discount.
Bob Wettermann, President
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Cleaning and BGA Reballing |
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After the reworking of
components, especially high
speed BGAs and CSPs, it is
important to maintain a
level of cleanliness post
processing. BEST has the
capability to either assure
or document a given level of
device cleanliness if your
specifications demand this.
The Omega Meter, Ionograph,
and ZeroIon are used by a
number of assemblers for
quality assurance purposes.
These instruments compare
the conductivity of the
extract solution before and
after testing. The "result"
of this testing is reported
as a sodium chloride (NaCl)
equivalent per unit area.
Ion Chromatography (IC) is a
tool that can be used for
precision testing and
process base lining. This
test system can quantify and
identify specific ionic
species that are present on
an electronic device. The
most common test method is
the IPC TM-650 2.3.28. The
device is placed into an
ionically-clean bag and is
immersed in an extract
solution of 75% alcohol and
25% deionized water at 80°C
for one hour. This is a much
more rigorous extraction
method than the methods used
by automated ROSE equipment.
The IC then separates and
detects each individual ion
for which it was calibrated.
Typical systems detect and
measure fluoride (F-),
chloride (Cl-), bromide
(Br-), nitrate (NO3-)
nitrite (NO2-), phosphate
(PO4-), sulfate (SO42-), and
weak organic acids (WOAs).
Results are reported in
µg/in2.
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Repairing Damaged Solder
Mask |
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Solder mask can be damaged
by a number of things
including but not limited to
board handling, hand
soldering, rework operations
or burned devices or even
the original board
manufacturing process.
The damaged mask can be
easily repaired by a skilled
PCB repair technician following the guidelines of
the IPC 7721 procedure.
The following TOOLS &
MATERIALS are required
for this repair: Brushes
Cleaner Liquid Mask Foam
Swabs UV Lamp Microscope
Wipes
PROCEDURE:
1. Clean the
area. Make sure the surfaces
to be coated are cleaned
prior to coating to ensure
adequate adhesion, minimized
corrosion, and optimized
electrical properties.
2. If
needed, apply Kapton tape to
outline the area where the
solder mask will be applied.
3. Apply the replacement
mask to the board surface as
required. A brush or foam
swab may be used to apply
and spread the epoxy or
replacement coating.
4. Cure
per the manufacturers'
suggested guidelines with a
UV spot curing system or by
placing under a UV lamp
Call BEST if you need
help with these or other
repair procedures.
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RoHS California Update |
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The RoHS machine grinds on.
It would seem though that
California's legislature is
beginning to craft its own
RoHS version. Assembly Bill
AB2202 is designed to mirror
most of the European
legislation's provisions.
The bill, as it stands right
now is due to go into affect
in 2010.
Here is an excerpt from the
draft :
(h) (1) The department shall
adopt regulations
establishing a process
whereby a manufacturer or
distributor of an electronic
device or component may seek
an exemption or time
extension to a sales
prohibition pursuant to this
section upon demonstration
to the department that the
device or component meets
the criteria developed
pursuant to paragraph (2).
(2) In developing a process,
including criteria, for
evaluating a request for
exemption and time
extension, the department
shall consult with effected
stakeholders, including
representatives from the
manufacturers, distributors,
and environmental groups.
As currently drafted the
California legislature will
consider its own exemption
process with its own
exemption board. It looks
like the bureaucrats
(another 49 similar ones to
follow???) keep creating
more governmental
regulations. Hopefully it
will use and actually allow
scientific evidence as
input.
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Nano Soldering Iron ??? |
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An atomic-scale conveyor
belt may be the smallest
soldering iron ever created.
The new device, discovered
by a researcher at the
University of California in
Berkeley, ferries molten
metal. It is made from
carbon nanotubes just 20
millionths of a millimetre
in diameter.
The discovery could pave the
way for nano-machines that
are pieced together from
smaller components, rather
than emerging from chemical
reactions.
"There has been a dream
for many years to build nano-structures
piece by piece, like
building a large-scale
machine," explains Alex
Zettl, who built the nano-soldering
iron. "Then the structure
is no longer constrained by
the chemistry of its
components", he says.
Currently, nano-probes can
nudge atoms one at a time
from one place to another.
But to generate the flow of
molten material necessary to
solder parts together,
hundreds of thousands of
atoms must be moved
Zettl begins by spraying
pure carbon nanotubes with
gaseous indium. The metal
then condenses into solid
droplets between one and 10
nanometers wide. Using a
nano-manipulator built in
his lab he connects the
tubes to a circuit and
applies a small voltage.
Heat from the resulting
current melts the droplets,
which move along the
nanotube's surface and
collect as a bubbling liquid
at the negative end.
Reversing the voltage shunts
indium to the other end,
meaning the movement is
driven by electricity rather
than a thermal effect. And
varying the voltage changes
the flow rate of liquid. The
liquid bubbles could be
wicked off the ends of the
tubes and used to solder
tiny parts together
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More BEST information |
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