November 21, 2017
Cleanliness Standards for Electronic Components
I work as a supplier engineer in our automotive
division and we are very concerned about cleanliness for electronic
components. We have a very stringent humidity and temp test from one
of our OEM's that causes dendrites almost every time we run the test.
I have been looking for cleanliness standards for
electronic components but the only thing I have been able to find is for PWB
cleanliness. To date I have not been able to find any standards
regarding cleanliness specifications for ionics for electronic components
specifically.
Are there for
electronic component cleanliness in the industry currently or are there plans
to review cleanliness requirements for components?
D.D.
Component
cleanliness is "sort of" covered within the JEDEC standards, but typically they
will reference MIL-PRF-STDs for component cleanliness. Two JEDEC standards I
can recommend you begin your search with are JEDEC STD 22-B102E, and JESD9B,
specifically section 8.1 which uses the words "metallization" to cover any
conductive condition, including under-etched metal, crystallization, dendrites,
and so forth.
Anyone
can get the JEDEC standards by simply going to www.jedec.org
and registering; it is free of charge.
Also
they are cheaper than sleeping pills, and more effective.
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Richard D. Stadem
Advanced Engineer/Scientist
General Dynamics
Richard D. Stadem is an advanced engineer/scientist for General Dynamics and is also a consulting engineer for other companies. He has 38 years of engineering experience having worked for Honeywell, ADC, Pemstar (now Benchmark), Analog Technologies, and General Dynamics.
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Try IPC/JEDEC J-STD-033,
Handling, Packing, Shipping and Use of
Moisture/Reflow Sensitive Surface Mount Devices,
see image below, of IPC Standards,
you should find what you are looking for under "Storage and Handling."
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Kishan Sarjoo
Process Engineering Manager - Electronics
Altech UEC, South Africa
Currently with Altech UEC and responsible for technology road map in PCBA electronic manufacturing and technical support for PCBA electronic manufacturing for Altech UEC and its JDM's. Over 7 years in SMT, Radial Insertion, Wave solder & Test Applications.
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I
have not seen any other document that provides specs for component cleanliness
other than IPC but you are not the only one experiencing this phenomena.
Dendrites will form when current & moisture are introduced to two
adjacent conductors.
Even distilled water can caused dendrites if the
right conditions are met. You did not mention if these components are
going to be conformal coated. You could avoid formation of dendrites if
you provide a conformal coat to the components or area surrounding them.
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Edithel Marietti
Senior Manufacturing Engineer
iDirect
Edithel is a chemical engineer with 20 year experience in manufacturing & process development for electronic contract manufacturers in US as well as some major OEM's. Involved in SMT, Reflow, Wave and other assembly operations entailing conformal coating and robotics.
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From
a humidity standpoint, the dewing test is a difficult one.
As
a materials company who supplies solder paste to automotive applications where
the no-clean residue is not cleaned off post-reflow, we have pastes that pass
the BMW dewing test.
From
a temperature standpoint, we have seen instances of dendritic growth under
flat-bottom components for dry heat testing (120 deg C for 21 days).
The
ionics and residue characteristics of the solder paste can be engineered to
address this issue.
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Karthik Vijay
Technical Manager - Europe
Indium Corp.
Currently with Indium Corporation and responsible for technology programs and technical support for customers in Europe. Over 15 yrs experience in SMT, Power, Thermal & Semiconductor Applications. Masters Degree in Industrial Engg, State University of New York-Binghamton.
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There are no present standards for how clean a component has to be to have long term reliability, either in IPC or IEC. There are some standards for how clean assemblies need to be, but those standards are presently being updated and the old standards are being obsoleted. Ion Chromatography is the tool of choice for determining component cleanliness.
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Doug Pauls
Principal Materials and Process Engineer
Rockwell Collins
Doug Pauls has a bachelors in Chemistry & Physics, Carthage College, BSEE, Univ of Wisc Madison. He has 9 years working experience for US Navy - Materials Lab, Naval Avionics Center Indianapolis. 8 years Technical Director, Contamination Studies Laboratories. 11 years Rockwell Collins Advanced Operations Engineering.
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