A Comparison of Coating Requirements IPC-J-STD

A Comparison of Coating Requirements
IPC-J-STD-001 Rev E vs Rev F
Doug Pauls
Principal Materials and Process Engineer
Rockwell Collins
Chair: IPC Cleaning and Cleanliness Committees
[email protected]
1
Background
• Conformal coating requirements in J1E and earlier were
somewhat anemic or outdated
– Far too much emphasis on cosmetics
– Coating, Encapsulation, and Staking
– Never let a bunch of soldering people make up a spec on conformal
coatings
• Leadership of J1/610 asked the conformal coating committees
to improve those requirements
• Proposed to the committee – January 2014
• Became part of the published standard in August 2014
2
What Coatings Are Used
•
•
•
Conformal coating material shall
[D1D2D3] conform to the material
specification (IPC-CC-830 or
equivalent).
The coating manufacturers supplier’s
instructions or other documented
process shall [D1D2D3] be followed.
•
When curing conditions
(temperature, time, Infra Red (I.R.)
intensity, etc.) vary from supplier
recommended instructions, they
shall [D1D2D3] be documented and
available for review.
•
Conformal coating material shall
[D1D2D3] conform to IPC-CC-830 or
equivalent.
–
•
•
BS EN 61086 Parts -1, -2, -3
The material specification/data sheet
or other documented procedure shall
[D1D2D3] be followed for mixing and
curing.
When processing varies from supplier
recommended instructions, they shall
[D1D2D3] be documented and
available for review.
J-STD-001 Appendix C – “Guidance on
Objective Evidence of Material
Compatibility”
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3
How You Mix and Cure
•
•
The material specification or other
documented procedure shall
[D1D2D3] be followed for mixing
and curing. The material shall
[D1D2D3] be used within the time
period specified (both shelf life and
pot life) or used within the time
period indicated by a documented
system the manufacturer has
established to mark and control agedated material.
Equipment used for measuring
viscosity, mixing, applying and curing
silicone material shall not [D1D2D3]
be used for processing other
material.
•
The material shall [D1D2D3] be used
within the time period specified
(both shelf life and pot life) or used
within the time period indicated by a
documented system to control agedated material.
•
Items exposed to uncured silicone
material shall not [D1D2D3] be used
for processing other material.
An authorized exception is allowed
only in cases where equipment is
used for co-curing processes and the
manufacturer has demonstrated
through system tests that nonsilicone material properties have not
changed and design requirements are
met.
Objective evidence shall [D1D2D3] be
maintained and available for review.
•
•
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Components
•
When coating or encapsulation
materials are applied to glass body
components, the components shall
[D1D2D3] be sleeved to prevent
cracking, unless the material has
been selected so as not to damage
the components/assembly in its
service environment.
•
•
The coating fillets should be kept to
a minimum.
•
Conformal Coating on Components
When coating material is applied to
glass bodied components, the
components shall [D1D2D3] be
sleeved when specified to prevent
cracking unless the material has been
selected so as not to damage the
components/ assembly in its service
environment.
Coating fillets should be kept to a
minimum.
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Where Does Coating Go?
•
•
•
Coating shall [D1D2D3] be applied in
a continuous manner to all areas
designated for coverage on the
assembly drawing/documentation.
When used, masking materials shall
[D1D2D3] have no deleterious effect
and shall [D1D2D3] be removable
without leaving contaminant
residue.
Dimensions of masked areas shall
not [D1D2D3] be decreased in
length, width, or diameter by more
than 0.75 mm [0.0295 in] by
application of conformal coating.
•
Coating shall [D1D2D3] be applied only
to areas designated for coverage on the
assembly drawing/ documentation.
Assembly drawing/ documentation
should indicate all areas to be kept free
of conformal coating and the tolerance
on the keep-out zone.
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What is Not Coated
•
•
•
The adjustable portion of adjustable
components, as well as electrical
and mechanical mating surfaces
such as connector contacts, probe
points, screw threads, bearing
surfaces (e.g., card guides) shall
[D1D2D3] be left uncoated as
specified on the assembly
drawing(s)/ documentation.
Mating connector surfaces of
printed circuit assemblies shall
[D1D2D3] be free of conformal
coating.
The mating (contact) surface of
brackets or other mounting devices
shall not [D1D2D3] be coated with
conformal coating unless specifically
required by the assembly
drawing(s)/documentation.
•
•
Mating surfaces (electrical and
mechanical) of connectors shall
[D1D2D3] remain free of conformal
coating.
The mating (contact) surface of
brackets or other mounting devices
shall not [D1D2D3] be coated with
conformal coating unless specifically
required by the assembly
drawing(s)/documentation.
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Coating Thickness
•
•
•
The thickness of the conformal
coating shall [D1D2D3] be as shown
in Table 10-1 for the type specified
(see IPC-2221):
Note: Table 10-1 of this standard is
to be used for printed circuit
assemblies.
The coating thickness requirements
in IPC CC-830 Table 4-2 are to be
used only for test vehicles associated
with coating material testing and
qualification.
•
•
Unless otherwise specified, the
coating thickness shall [D1D2D3] be
in accordance with Table 10-1.
Coating thickness is a result of the
coating process and is expected to
vary on and around components and
may not meet the values in Table 101.
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How Coating is Measured
•
•
•
The thickness is measured on a flat,
unencumbered, cured surface of the
printed circuit assembly or a coupon
that has been processed with the
assembly.
Coupons may be of the same type of
material as the printed board or may
be of a nonporous material such as
metal or glass.
As an alternative, wet film or
viscosity measurement may be used
to establish the coating thickness
provided there is documentation
that correlates dry film thickness to
the alternate measurement
technique.
•
•
•
The thickness is to be measured on a
flat, unencumbered, cured surface of
the printed circuit assembly or a
coupon that has been processed with
the assembly.
Coupons may be of the same type of
material as the printed board or may
be of a nonporous material such as
metal or glass.
As an alternative, a wet thickness or
other measurement may be used to
establish the coating thickness
provided there is documentation that
correlates the measurement to the
dry thickness.
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Coating Coverage
• Conformal coating shall
[D1D2D3]:
– a. Be completely cured and
homogeneous.
– b. Cover only those areas
specified on the assembly
drawing(s)/documentation.
– c. Be free of blisters, or breaks
that could affect the operations
of the assembly or sealing
properties of the conformal
coating.
– d. Be free of cracks, crazing,
voids, bubbles, mealing,
peeling, wrinkles or foreign
material which expose
component conductors, printed
circuit conductors, (including
ground planes) or other
conductors and/or violates
design electrical clearance.
•
Conformal coating shall [D1D2D3] be
completely cured and homogeneous.
•
See later section
•
Later
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Coating Inspection
• Inspection of conformal coating
shall [A1P2D3] be performed
(see Table 11-2) and may be
performed without
magnification. Inspection for
conformal coating coverage may
be performed under an
ultraviolet (UV) light source
when using conformal coating
material containing a UV tracer.
Magnification up to 4X may be
used for referee purposes.
• Inspection of conformal coating
shall [A1P2D3] be performed in
accordance with the requirements
in Table 12-2.
• The referee magnification for
conformal coating inspection shall
[A1P2D3] be 4X maximum.
• Conventional coatings that contain
a fluorescing agent should be
examined under ultraviolet light to
verify coverage.
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Coating Rework
• Procedures which describe the
removal and replacement of
conformal coating shall
[N1D2D3] be documented and
available for review.
•
•
•
•
Procedures which describe the
removal and replacement or manual
rework/ touchup of conformal
coating shall [N1D2D3] be
documented and available for review.
The coating rework or touchup areas
shall [D1D2D3] meet the
requirements of the assembly
drawing(s)/ documentation.
If thickness measurements are
required in the reworked area, the
validation process shall [D1D2D3] be
documented and available for review.
Note: Conformal coating buildup on
or around some component types
such as glass or ceramic bodied
components may cause damage.
Coating touch-up should be applied
as close to the original coating
thickness as possible.
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New Elements in Rev F not in Rev E
• All assemblies shall [N1N2D3] be clean before processing. After cleaning,
prior to processing, assemblies shall [N1N2D3] be handled to prevent
contamination.
• 10.1 Conformal Coating for Tin Whisker Risk Mitigation: Conformal
Coating requirements used for tin whisker risk mitigation shall [D1D2D3]
be as agreed between user and supplier.
• 10.2 Conformal Coating – Masking: When used, masking materials shall
(D1D2D3) have no deleterious effect and shall [D1D2D3] be removable
without leaving contaminant residue. Dimensions of masked areas shall
not [D1D2D3] be decreased in length, width, or diameter by more than
0.75 mm [0.03 in] by application of conformal coating.
• 10.3.3 Uniformity: Coating distribution and uniformity will depend partly
on the method of application and may affect visual appearance and corner
coverage. Some variation in visual appearance of the conformal coating is
expected and is acceptable.
– Example: Assemblies coated by dipping may have a drip line or localized buildup of the edge of the board. This build-up may contain a small amount of
bubbles but it will not affect the functionality or reliability of the coating.
13
New Elements in Rev F not in Rev E
• 10.3.4 Transparency: Transparency is controlled by the coating material
standard and shall [D1D2D3] meet 10.1. (IPC-CC-830 or equivalent)
– Linda Woody – Lockheed Martin research – darkening/yellowing does not negatively
impact coating integrity
• 10.3.5 Bubbles and Voids: Cured coating should be free of bubbles and
voids.
– When present, bubbles and voids shall not [D1D2D3]:
• Bridge non-common leads or conductors.
• Expose one or more conductors.
• When bubbles and voids are present and do not meet the defect criteria, they shall
[P1P2P3] be considered as process indicators
• 10.3.6 Delamination: The cured coating should be free of blisters and
delamination.
– Delamination shall not [D1D2D3]:
• Bridge non-common leads or conductors.
• Expose one or more conductors.
14
New Elements in Rev F not in Rev E
•
•
10.3.7 Foreign Objects Debris FOD in the cured coating shall not [D1D2D3] bridge
conductive surfaces or violate minimum electrical clearance between components,
lands or conductive surfaces.
10.3.8 Other Visual Conditions: The coating shall [D1D2D3] be free of dewetting,
mealing, peeling, wrinkles (non-adhering areas), cracks, ripples or fisheyes that
bridge non-common conductors.
15
Conformal Coating in A-610F
• Conformal coatings should be transparent, uniform in color and
consistency and uniformly cover the board and components. Uniform
coating distribution depends partly on the method of application and may
affect visual appearance and corner coverage. Assemblies coated by
dipping may have a drip line or localized build-up of the edge of the board.
This build-up may contain a small amount of bubbles but it will not affect
the functionality or reliability of the coating.
16
610F: Coverage
17
610F: Coverage Defects
• Coating is not cured.
• Coating is not applied to required areas.
• Coating is on areas required to be free of coating, e.g., mating
surfaces, adjustable hardware, wicking into connector housings, etc.
• Bridging of adjacent lands or exposed conductive surfaces caused
by:
–
–
–
–
–
–
–
–
Loss of adhesion
Voids or bubbles
Dewetting
Cracks
Ripples
Fisheyes
Orange peel
Flaking
• Any entrapped material that bridges lands or adjacent conductive
surfaces, exposes circuitry or violates minimum electrical clearance
between components, lands or conductive surfaces.
• Discoloration or loss of transparency.
18
19
610F Thickness
• The thickness is to be measured on a flat, unencumbered, cured surface
of the printed circuit assembly or a coupon that has been processed with
the assembly. Coupons may be of the same type of material as the printed
board or may be of a nonporous material such as metal or glass. As an
alternative, a wet film thickness measurement may be used to establish
the coating thickness provided there is documentation that correlates the
wet and dry film thickness.
• Acceptable if it meets this table, and a defect if it does not.
• These are the default thicknesses if your engineering drawing does not
specify thickness. If your engineering drawing specifies thickness, the
engineering drawing predominates
20
New for 610F: Electrical Insulation Coating
• Coverage:
– This material is used to provide insulation to an exposed conductor when conformal
coating is insufficient to provide enough protection and encapsulation is too much.
– All of the considerations used for conformal coating are applicable for insulation coating,
except the surface where insulation coating is applied is generally not smooth enough
for a uniform coating surface. Thin coating is not a target attribute. See 10.5.2.2.
– There are no illustrations for these criteria.
• Thickness
– Acceptable – Class 1,2,3
• Complete coverage with no exposed metal.
– Defect – Class 1,2,3
• Exposed metal.
– Note: The thickness requirements of 10.8.3 do not apply.
21
NASA J-STD-001FS Space Addendum
• This addendum currently at the ballot stage
• All assemblies shall be cleaned before processing. After cleaning, prior to
processing, assemblies shall be handled to prevent contamination.
• A mix record is required for multi-part coatings. The record includes:
– The date mixed, supplier’s part number and date/lot code, shelf-life expiration date (of
all parts of the mix), the mix ratio for all constituents used, traceability to the hardware
the material is being applied to, test specimen acceptance test results, and material
supplier’s datasheet acceptance criteria.
– As an exception, manufacturers that use continuous run processes shall have a
documented process for mixing and traceability.
• For one part coatings:
– For one-part polymers, the supplier’s part number and lot/date code, and shelf life
expiration date shall be documented.
• Regarding Silicone Materials:
– Equipment and work areas, including lab coats/smocks, used for processing silicone
material shall not be used for processing other material.
• Regarding Mixing:
– Non-porous containers and mixing tools shall be used. Containers and mixing tools shall
be selected such that their use in combination cannot introduce contamination into the
mix, e.g., a metal stirrer can scrape shavings from a plastic container.
22
NASA J-STD-001FS Space Addendum
• Dryness
– Fillers, e.g., thickening agents, thermal property enhancers, etc., shall
be treated to remove detrimental moisture and other volatiles prior to
adding to any polymer.
– After final cleaning and prior to coating or encapsulating, the assembly
shall be treated to remove detrimental moisture.
• Processing
– Staking and bonding shall be performed prior to conformal coating.
– Tapes and other maskants with conductive material in the adhesive
shall not be used to mask over PCB conductor patterns.
– When coating, encapsulation, or staking materials are applied to
through-hole glass, ceramic, or hermetic components, the
components shall be protected to prevent cracking unless the material
has been selected so as not to damage the components/assembly in
its service environment.
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NASA J-STD-001FS Space Addendum
• Cure
– Materials shall be cured in accordance a documented cure schedule
and within the thermal limitations of the hardware.
– Objective evidence of full cure for each batch of material shall be
documented.
• Coat 2” square aluminum plate – thickness. Tack free to cotton glove
touch
– A witness sample may be used for this verification.
• Inspection
– When fluorescent conformal coating materials are used, coverage and
location shall be determined by UV-light examination.
• Rework
– Procedures that describe the removal and replacement of conformal
coating shall be documented and available for review. Chemical
stripping processes shall be approved by the User prior to use.
24
IPC Coating Activities
• IPC SMTA Cleaning and Coating Conference
– 18-20 Nov 2014, Schaumburg, Illinois
– Excellent conference, great papers, checking on availability
• IPC Conformal Coating Material & Application “State of the Industry”
Assessment Project, led by Dave Hillman, Rockwell Collins
– Expect completion in 2016
• IPC-CC-830 Revision C drafting – incorporation of ultrathin coatings and
new classes of coatings
– Expected completion – Fall 2015
– May start working with DoD after that for update of MIL-I-46508
• IPC 5-33 AWG (Ad-hoc Working Group)
– How to test and evaluate conformal coating performance beyond material
characterization tests
– Input into design standards for conformal coating
– Group that addresses new coating technology
• Apex 2015 meeting in San Diego, California
– Half day workshop on how coatings are tested and evaluated
– IPC Task Group committee meetings
– New group on low pressure molding materials and processes
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Questions
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