La protection de cartes électroniques avec des revêtements

Protection des cartes électroniques
avec des Revêtements Ultra-Fins
Fluoropolymères
Jeudi 2 Avril 2015
Julie Boizot – Ingénieur d’application 3M
La protection de cartes électroniques avec
des revêtements ultra-fins
On observe une demande croissante pour:
– appareils électroniques plus compacts, portables avec de
multiples fonctionnalités
– Utilisables dans tous types d’environnements extérieurs
– Besoin de protection des composants sensibles contre
l’humidité, les souillures
Les vernis de tropicalisation comme réponse possible:
– résine réticulable UV ou à chaud, permanents
– Polymère acrylique, PU, silicone, époxy
– épaisseur de 12,5µm ou +
3©April
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Les revêtements ultra-fins ne sont
pas des vernis de tropicalisation
2
s
Agenda
• Description des revêtements ultra fins fluoropolymères
• Performances suivant les tests de l’IPC – CC- 830B
• Performances en conditions de corrosion à criticité croissante
• Les méthodes de mise en œuvre
• Contrôle du process
• Opérations possibles après dépôt du revêtement
La protection de cartes électroniques avec
des revêtements ultra-fins fluoropolymères
• Polymère en solution dans un solvant fluoré très fluide
• Fluides porteurs diélectriques, ininflammables,
inertes, sans phrase de risque pour l’homme
• Une chimie durable: faible PRP, PACO=0
• Existent sous la gamme 3MTM NovecTM
• S’appliquent par trempage ou pulvérisation
• Sèchent à l’air ambiant en qqs secondes
• Forment une couche de protection hydrophobe
et oléophobe de l’ordre de 1µm d’épaisseur
• Protègent de l’humidité, atmosphères soufrées
• Existent avec traceur UV
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4
Résultats de tests suivant la norme IPC-CC-830B
• Humidité : 160h de cycles à 65°C 85%HR pdt 3h / 25°C pdt 2h
 A l’inspection visuelle, aucun endommagement du film NovecTM n’est
observé, la résistance électrique maintenue
• Choc thermique : 100 cycles de -65°C pdt 15min / 125°C pdt 15min => A
l’inspection visuelle au microscope ne montre aucun endommagement du
film
Il existe un rapport
de test issu d’un
laboratoire externe:
Trace Laboratories
Test Report
• Vieillissement température et humidité : 120jours à 85°C et 98%HR =>
Pas d’endommagement du film observé
• Peut supporter 175°C à 200°C pendant 24h et maintenir son
imperméabilité à une huile silicone chlorée (selon norme MIL-B81744AA)
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5
La protection contre la corrosion en brouillard salin
Acier
inox non
traité
Après
16h
Selon ASTM B117-09
Température : 35°C
Humidité : 95%
Solution saline: 5% NaCl en
aspersion
• pH=6.5~7
•
•
•
•
Après
44h
Revêtement fluoré ultra fin –
traceur UV
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6
La protection contre la corrosion
en atmosphère soufrée
• Selon l’ASTM B809: FoS : Flower of Sulfur
• Test conçu pour recréer atmosphère de gaz soufrés
• et d’humidité que l’on retrouve dans de nombreuses
industries
• Test sur coupons standards IPC -B-25A
• Revêtements appliqués par trempage sur coupons placés
ensuite dans la chambre saturée en atmosphère soufrée
• 3 configurations testées avec le même fluoropolymère en
solution dans un solvant (T°eb: 76°C):
Nom
Epaisseur du dépôt
% massique du polymère en solution
F-1
0,1µm
1%
F-2
0,5µm
4%
F-3
1,0µm
8%
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7
Réduction de corrosion en atmosphère soufrée
sur coupons protégés selon ASTM B809
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8
Protection en atmosphère soufrée
• Finition ImSnPb –34 jours
Il existe un livre
blanc sur le sujet
pour en savoir plus:
• Finition ImAg –10 jours
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Coating Corrosion
Protection of Metal
Surfaces from Sulfur
9
La protection en milieu aqueux selon l’IPX7
• Revêtement appliqué par pulvérisation
• Dépôt de 2µm épaisseur
• Les coupons sont immergés dans l’eau ou
• dans l’eau salée pendant 30 à 60 minutes
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Méthode de Milieu
test
d’immersion
Temps
Sous tension
(min)
IPX7
Eau
30
Non
3M - A
Eau
60
3 Volts
3M - B
Eau à 5% NaCl
60
3 Volts
10
La protection en milieu aqueux selon l’IPX7
• Méthode 3M-A:
• Immersion dans l’eau,
pendant 60min, sous 3
Volts
• Méthode 3M-B:
• Immersion dans l’eau salée,
pendant 60min sous 3 Volts
Non testé
(référence)
Non protégé
Il existe un livre blanc sur le sujet pour en savoir plus:
Protégé avec
revêtement
de 2µm
Protection of Circuit Boards, Electronic Components from Water
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11
La protection en milieu acide d’un appareil sous alimentation
• Revêtement appliqué
par pulvérisation
• appareil mis en marche
Non protégé
Protégé avec
un revêtement de 5µm
• Sueur de synthèse
appliquée sur les zones
critiques de la carte
• Durée du test: 4h
• Sur les cartes non
revêtues, on observe
une corrosion
significative en fin de
test
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12
Les méthodes d’application en production
Flexibilité de la méthode d’application
Variété de concentrations
• Trempage, pulvérisation, seringue
• On peut également revêtir intégralement une
pièce
• Les pièces peuvent être revêtues
sélectivement
• Différents extraits secs et/ou différents
mélanges de solvants porteurs pour optimiser
performance et process
• On peut appliquer plusieurs couches
• par pulvérisation
Trempage
Séchage à
l’air ambiant*
Cartes
nettoyées
Pulvérisation
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Les cartes sont
prêtes pour
l’étape suivante
* Une polymérisation à chaud peut être
requise pour certaines références
13
Process de mise en oeuvre
Trempage à température ambiante
Pulvérisation
• Bain non thermostaté
• Confinement des vapeurs par un circuit de
refroidissement
• Buse spécifique
• Durée d’immersion de 30 sec
• Hauteur/vitesse de la buse
• Séchage à l’air ambiant en quelques secondes
• Nombre de passages
• La vitesse de retrait influe sur l’épaisseur du
dépôt
• Pas de suivi de bain
• Influent sur l’épaisseur:
Partenariat avec:
Pour la distribution et la mise en œuvre des produits
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14
Contrôle du process d’application
Avec lampe UV 254 nm
• De la couverture de la pièce
Revêtement
• par contrôle UV
• De la tension de surface
• par encre de test de 28 dynes
Pas de revêtement
• De l’épaisseur:
• AFM, Ellipsométrie, Profilométrie, MEB coupe transversale
• Mesure de changement de masse
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15
Manipulations possibles après revêtement
• Pour des opérations de réparations:
• Dévernissage possible de la carte par immersion
dans bain de Fluide Novec pur
• Réparations locales par soudures possibles à travers
le revêtement
• L’épargne des connecteurs peut ne pas être
nécessaire
• Manipulations par toucher/pression
n’endommagent pas le revêtement.
3©April
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16
Une technologie de l’ultra-fin pour la protection des cartes, des LED
et des écrans
• Les revêtements ultra fins constituent une nouvelle catégorie de vernis de protection des
cartes
• Les revêtements ultra fins fluoropolymères protègent les cartes de l’humidité, des
atmosphères corrosives, de l’immersion en milieu aqueux
• Ces revêtements peuvent être appliqués sur des LED, conforme CREE - livre blanc à
paraître
• Il existe une technologie de revêtements encore plus fins (10nm) en solution à 0,1% pour
protéger les écrans tactiles
• => Revêtement hydrophobe et oléophobe pour faciliter le nettoyage des écrans
3©April
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17
s
Merci de votre attention
s
Annexes
La gamme des revêtements 3M™ Novec™
Application
Area
Internal
Protection
Designed to protect
printed circuit boards,
solder alloys,
components, metals,
composites
Novec
Coating
Solids
(%)
1700
2
1901
1902
1904
1908
2704
1
2708
Designed to protect
glass, steel, aluminum,
ceramics
4
3M™ Novec™ 7100
Engineered Fluid
8
4
8
Dry Time
Cure Time
Dip
5-30 seconds
No cure is
required
  

5-30 seconds
No cure is
required
  

5-30 seconds
No cure is
required
  

UV
Detectable
AntiSmudge
Easy Clean
Spray or Dip
3M™ Novec™
7100 and 7200
Engineered Fluids Blend
Spray or Dip
Spray or Dip
Dip
3M™ Novec™ 7200
Engineered Fluid2
Spray or Dip
Dip

Spray or Dip
30-90 seconds
Cure at 70150°C for 15-60
minutes
0.1
3M™ Novec™ 7100
Engineered Fluid
Dip or Spray
5-15 seconds
Cure at 70150°C for 15-60
minutes


0.2
3M™ Novec™ 7200
Engineered Fluid
Spray
5-15 seconds
Cure at 185°C for
60 minutes


2
3M™ Novec™ 7200
Engineered Fluid
1720
2202
2702
External
Protection
2
Solvent
PCB
ACF
Moisture Connection
AntiProtection Protection Migration Removable
Preferred Application
Methods1


1 All Novec coatings can be applied using spray, dip or syringe methods. For spray
application, 3M recommends using engineered controls or PPE to minimize worker
exposure.
2 Contains
< 5% by weight PGMEA, a VOC. See SDS for specific product information.
3©April
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20
3M™ Novec™ Electronic Grade Coatings
External Protection
Application
Area
External
Protection
Novec Solids
Coating (%)
1720
0.1
3M™ Novec™
7100 Engineered
Fluid
Dip or Spray
0.2
3M™ Novec™
7200 Engineered
Fluid
Spray
Designed to protect glass,
steel, aluminum, ceramics
2202
1
Solvent
All Novec coatings can be applied using spray, dip or syringe methods. For
spray application, 3M recommends using engineered controls or PPE to
minimize worker exposure.
3©April
3M 2015 . All Rights Reserved. 3M Confidential.
Preferred
Application Dry Time
Anti1
Methods
Cure Time Smudge
5-15
seconds
Cure at 70150°C for
15-60
minutes
5-15
seconds
Cure at
185°C for
60 minutes
Easy
Clean




21
Les revêtements 3M™ Novec™
Contacts:
• Catherine Sol – 3M France
• Développement de Marché Fluides et Gaz
• csol@mmm.com
• Julie Boizot – 3M France
• Ingénieur Support Technique Fluides et Gaz
• jboizot@mmm.com
• Jonathan Cetier – Inventec
• Responsable Grands Comptes
• jcetier@inventec.dehon.com
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22
Informations complémentaires
Le montage ou l’utilisation du produit 3M décrit dans le présent document implique des
connaissances particulières et ne peut être réalisé que par un professionnel compétent.
Avant toute utilisation, il est recommandé de réaliser des tests et/ou de valider la bonne
adéquation du produit au regard de l'usage envisagé.
Les informations et préconisations inclues dans le présent document sont inhérentes au
produit 3M concerné et ne sauraient être appliquées à d’autres produits ou
environnements. Toute action ou utilisation des produits faite en infraction de ces
indications est réalisée aux risques et périls de leur auteur.
Le respect des informations et préconisations relatives aux produits 3M ne dispense pas
de l’observation d’autres règles (règles de sécurité, normes, procédures…)
éventuellement en vigueur, relatives notamment à l’environnement et moyens
d’utilisation. Le groupe 3M, qui ne peut vérifier ni maîtriser ces éléments ne saurait être
tenu pour responsable des conséquences, de quelque nature que ce soit, de toute
infraction à ces règles, qui restent en tout état de cause extérieures à son champ de
décision et de contrôle.
Les conditions de garantie des produits 3M sont déterminées dans les documents
contractuels de vente et par les dispositions impératives applicables, à l’exclusion de
toute autre garantie ou indemnité.
3©April
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23
3M™ Novec™ Electronic Grade Coatings
Technical Paper
Protection of Printed Circuit Boards and Electronic Components from
Water and Salt Water by Using 3M™ Novec™ Electronic Grade Coatings
Introduction
Experiment Overview
Protection against water – both vapor and liquid – has become
increasingly critical to the lifetime performance of electronic
devices. This is especially true as electronics become more mobile
and are used in more challenging environments.
Testing began by applying the coating over rigid printed circuit
boards with electrical test patterns. The circuit boards were then
connected to an external power supply that maintained a constant
voltage. Based on a modification of the IPX71, 2 testing standard
(see IPX7 Test Method and 3M Modifications plus Test Results),
powered test boards were immersed in water or salt water for
an extended time period. The resistance of the circuit was then
measured over time and charted to determine the effect of the
water on the circuitry.
One effective method of providing this protection is to coat the
internal surfaces of the electronic device components, including its
printed circuit boards and connections. To demonstrate this, tests
were conducted to show the capability of 3M™ Novec™ Electronic
Grade Coatings (EGC) to protect metals against moisture, liquids
and corrosion under a variety of water and salt water immersion
conditions.
3M™ Novec™ Electronic Grade Coatings (EGC) are thin, low
viscosity coatings designed to protect printed circuit boards
and electronic components from moisture and corrosion. These
polymer coatings dry to thin, transparent films with excellent
hydrophobic and oleophobic properties. Available in both thermal
curing and non-curing versions, they are easy to apply – whether
by liquid dipping, spraying (controlled) or brush. These coatings
are non-ozone depleting and RoHS compliant.
Test Boards
For this study, IPC-Association Connecting Electronics Industries
approved printed test boards IPC-B-25A3 were used. The IPC-B25A test board meets guidelines for testing solder masks (IPC-SM804C) and conformal coatings (IPC-CC-830B) and is shown in
Figure 1.
The 3M™ Novec™ Electronic Grade Coatings portfolio includes
a number of coatings. For this evaluation, 3M™ Novec™ 1710 and
2708 Electronic Grade Coatings were chosen for testing. These
coatings are fluorinated polymers delivered as a solution in a
segregated-hydrofluoroether 3M™ Novec™ Engineered Fluid.
These low viscosity and low surface tension solutions allow
for easy wetting over a variety of surfaces, helping to ensure
outstanding coverage.
At 8% solids content, Novec 2708 coating is recommended as
a final coating. A yellow-orange dye is incorporated into the
polymer backbone. This dye will fluoresce under UV light, thus
aiding inspection and detection in the quality control process.
Although used in this trial for experimentation purposes, at 10%
solids content, Novec 1710 coating is recommended to be used as a
concentrate to replenish coating solids in application baths or as a
component with other materials to create unique liquid solutions,
rather than as a final coating.
In this testing, both of the Novec coatings added considerable
protection to the components to which they were applied. The
protection they provided substantially reduced the effect of water,
corrosion and other contaminants that could electrically shorten
the lifetime and performance of the electronic device.
Figure 1. The IPC-B-25A printed test board
Board Preparation and Coating Application
The boards were cut vertically to isolate the test pattern D from
patterns E and F. Test patterns D, E and F were then used separately
in the water immersion test.
Prior to coating, the boards were cleaned with 3M™ Novec™ 72DA
Engineered Fluid in a vapor degreaser. Novec 72DA fluid is effective
at removing surface contaminants and particulates that, if left on the
circuit board, might impact coating performance.
3
3M™ Novec™ Electronic Grade Coatings
3M recommends either spray coating (in a controlled environment)
or dip coating as application methods. For this study, both methods
were used to demonstrate the flexibility of application options and
to measure any differences resulting from the application methods.
For testing, boards with different targeted thicknesses of the
coatings were generated by spraying, dipping or a combination of
these processes.
IPX7
A
B
Immersion
Depth
Liquid Media
Time
(Min)
Powered
1 Meter
1 Meter
1 Meter
Water
Water
5% aqueous NaCl
30
60
60
No
3 Volts
3 Volts
Table 1: IPX7 and 3M test conditions A and B
Using a Solartron™ model 1287 potentiostat8 in conjunction with
a Solartron™ model 1260 impedance analyzer, a constant current
of 3 volts was applied to the test pattern. Current leakage across
the open comb structure test pattern (D, E or F from Figure 1)
during the 60 minute immersion test was then measured. After
60 minutes, the board was removed, rinsed with water and
evaluated. The 3M system for Test Methods A and B is depicted
in Figure 2.
Ammeter
A
For dip coating, the process began with a chamber filled with
3M™ Novec™ Electronic Grade Coating. The chamber was on a
table which moved up and down at a controlled rate. The removal
rate of the boards controlled the thickness of the coating. In general,
the faster the board is removed, the thicker the coating. To coat
the boards, they were dipped, held in solution for 30 seconds and
removed from the coating solution at a rate of 12 inches per minute.
The boards were allowed to dry and then wire leads were soldered
to the board’s contacts. These contacts and the lead connected to
the open structure comb pattern were insulated by covering with
100% silicone, leaving just the comb structure test pattern exposed.
The board was then placed in the immersion test chamber.
Test
Method
Power Supply
3V
Voltmeter
V
Comb
Structure
Spray coating can be done manually or by automated spray
equipment (3M does not recommend manual spray application
without worker exposure control).* For this study, boards were
coated using a hand operated air driven sprayer. The volume of
coating applied was varied so a thickness of 2µm (2 microns) or
less was achieved. Wire leads were then soldered to the boards and
insulated with silicone as described above.
Figure 2. Electrical wiring for Test Methods A and B
IPX7 Test Method and 3M Modifications
While the IPX7 is a test to show water ingress, our testing
eliminated the enclosure, ensuring that test boards were completely
exposed to the aqueous solutions.
The water immersion test was based on a modification of the
IPX7 test standard that has been established by the International
Electrotechnical Commission (IEC).4, 5 The IP Code, sometimes
referred to as the Ingress Protection Rating,6, 7 classifies the degree
of protection against intrusion into the interior of a device. The IPX
standard and tests have been used by the electronics industry for
evaluating the ability of water, dirt, dust and other contaminants
to ingress into an enclosure. Protection from these contaminants
is critical as they have the potential to create conditions that could
shorten the service life of an electronic device.
Although there are multiple levels of IPX protection classifications,
IPX7 is often referenced for water immersion testing. It provides
an indication as to how well an electronic device would survive
if immersed in water. This test calls for an unpowered electronic
device to be immersed in 1 meter of water for 30 minutes. After
the 30 minutes, the device is removed and the power turned on. If
it operates as it was designed, the device is considered to meet the
IPX7 classification.
Test Results
To make the testing more aggressive, modifications were made
beyond the IPX7 protocol: 1) immersing in both water and salt
water, 2) powering the electronics during testing and 3) extending
the immersion time to 60 minutes. In all of these cases, the coated
sample boards did not demonstrate the corrosion and degradation
of the metal traces to the extent that the uncoated samples
boards showed.
Test Method A was used to test IPC-B-25A printed test board
patterns D, E and F coated with Novec 1710 or 2708 coating. There
was no corrosion, dendritic growth, copper loss or line thinning
observed (Figure 3). When Test Method A was used on uncoated
test patterns, there was significant corrosion and line thinning
(Figure 4).
While the IPX7 test method uses actual commercial devices,
device enclosures can vary in their design and ingress capability.
For this reason, this study eliminated the enclosure and evaluated
the performance of coatings applied directly on exposed test
boards.
To test at a rigorous level (beyond the IPX7 test protocol), testing
in salt water was also carried out. To ensure that a device’s
electronics would survive these conditions, plus add another level
of performance requirements, the sample boards were tested under
power. A comparison of these test methods are described in Table 1.
No corrosion or
copper loss on
the “+” lead
* Before using this product, please read the current product Material Safety Data Sheet (available
through your 3M sales or technical service representative or at www.3M.com/Novec) and the
precautionary statement on the product package. Follow all applicable precautions and directions.
Always practice smart and safe industrial hygiene practices.
Figure 3. Example: Test patterns coated with Novec 1710 coating and Novec
2708 coating performed similarly after Test Method A.
2
3M™ Novec™ Electronic Grade Coatings
Test Method B
0.30
0.25
Current (Amps)
Test Method B replaced the water with a 5% aqueous sodium
chloride solution. This method made for an extremely aggressive
test, as exemplified by the striping of the copper trace lines from
the test boards during the immersion time. Even within this
environment, the Novec coatings protected the surfaces.
When Test Method B was used to test boards coated with
3M™ Novec™ 1710 or 2708 Electronic Grade Coating, there was
minimal corrosion in spots along the edge of copper traces.
Uncoated test patterns, when tested with Test Method B, were
completely corroded and much of the copper tracings were
removed from the board, thus creating electrical connection
opens (Figure 4).
Uncoated
Failed
0.20
0.15
0.10
0.05
Novec 1710 Coated
Novec 2708 Coated
0.00
Test Method A
0
10
20
30
Time (Min)
40
50
60
Figure 5: Solartron™ potentiostat data showing current flow
Not Tested
Uncoated
Novec 2708
Novec 1710
Uncoated
Novec 2708
Novec 1710
Uncoated test boards had extensive corrosion when immersed in
both water and salt water. This was evident by observing current
flow immediately across the test pattern when exposed to the
test fluid. In contrast, test boards coated with Novec 1710
coating or Novec 2708 coating showed no current flow even
after 60 minutes.
Test Method B
Not Tested
Summary and Conclusions
3M™ Novec™ Electronic Grade Coatings provide an effective
barrier for metals and surfaces including electronic circuit
boards, helping to protect them from moisture, liquids, corrosion,
line thinning and dendritic growth. This protection adds to the
performance and longevity of the surfaces, metal connections
and an electronic device’s service life.
Figure 4: Summary of Novec 1710 and Novec 2708-coated test patterns after
Test Method A and Test method B. Note that the uncoated lines show signs
of loss of the copper traces.
For the coated boards, current leakage (as measured by the
potentiostat) across the test circuit was negligible at less than
0.01 amps. In contrast, for the uncoated boards, current leakage
across the test circuit was immediate and significant (exceeding
2 amps) when using either Test Method A and B. The uncoated
test pattern under these conditions typically failed within
60 minutes as shown by complete copper loss on the positively
charged side of the pattern. Boards coated with Novec 1710 or
2708 coatings did not fail (Figure 5).
References
The IP Code is a test standard published by International Electrotechnical Commission (IEC) and
describes the level of protection provided by an enclosure. For an explanation of the IP code see:
http://www.ce-mag.com/archive/06/ARG/bisenius.htm
1
Test Method A
2
IP Code Defined: http://www.osram.com/media/resource/hires/342330/technical-applicationguide---ip-codes-in-accordance-with-iec-60529-gb.pdf
3
IPC-Association Connecting Electronics Industries is an organization that sets standards used by
the electronics manufacturing industry: https://www.ipc.org/default.aspx
0.50
IEC 60529: Degrees of protection provided by enclosures (IP Code). International Electrotechnical
Commission, Geneva: http://www.iec.ch/
4
0.40
Current (Amps)
Uncoated
IP Ratings vs. NEMA Ratings: http://www.bisonprofab.com/ip-ratings-explained.htm
5
0.30
6
0.20
7
Interpreting the acronym officially in the standard text: http://www.iso.org/iso/iso_catalogue/
catalogue_tc/catalogue_detail.htm?csnumber=39578
0.10
8
Solartron Analytical is a manufacturer of electronic instruments: http://solartronanalytical.com/
Understanding the IP (Ingress Protection) Ratings: http://www.maximintegrated.com/app-notes/
index.mvp/id/4126
Novec 1710 or 2708 Coated
0.00
0
10
20
30
Time (Min)
40
50
60
3
3M™ Novec™ Electronic Grade Coatings
For Additional Information
To request additional product information or sales assistance,
contact 3M Customer Service at one of the numbers below or
visit 3M.com/Novec.
For other 3M global offices or information on other 3M products
for electronics, visit our website at 3M.com/electronics.
Product Comparison Summary
Property
3M™ Novec™ 1710 Electronic Grade Coating
3M™ Novec™ 2708 Electronic Grade Coating
Solids
Solvent
Shelf Life
10 wt% fluoropolymer
3M™ Novec™ 7100DL Engineered Fluid
4 years from date of manufacture in unopened container
8 wt% fluorinated polymer
3M™ Novec™ 7200 Engineered Fluid
1 year from date of manufacture in unopened container
Clear, colorless to light-colored liquid solution
1.5 g/mL
61°C (142°F)
None (per closed cup method)
Transparent, orange, liquid solution
1.4 g/mL
79°C (174°F)
None (per closed cup method)
Low in toxicity, non-ozone depleting, nonflammable, VOC exempt
(U.S. EPA), RoHS compliant, contains no chlorine or bromine
Low in toxicity, non-ozone depleting, nonflammable, low-VOC,
RoHS compliant, contains no chlorine or bromine
One Part
One Part
Transparent, colorless
Typically 1 to 10 microns (depending on application method)
Yes
44.5°C (112°F)
Can withstand 175°C for 24 hours and maintain repellency
Transparent, light yellow to orange (depending on thickness)
Typically 0.5 to 25 microns (depending on application method)
Yes
53°C (127°F)
Can withstand 175°C for 24 hours and maintain repellency
105° (water), 65° (hexadecane)
105° (water), 65° (hexadecane)
Yes
Yes
Coating Solution
Appearance
Specific Gravity
Boiling Point of Solvent
Flash Point
Environmental
System
Dry Fluoropolymer Coating
Appearance
Coating Thickness
Solvent & Chemical Resistance
Tg (glass transition temperature)
Thermal Stability of Dry Film
Contact Angles
(static, dip coated/dried on glass substrate)
Solder-Through Repairability
The 3M™ Novec™
Brand Family
The Novec brand is the hallmark for a variety of patented 3M compounds. Although each has its own unique formula and performance properties, all Novec
products are designed in common to address the need for safe, effective, sustainable solutions in industry-specific applications. These include precision and
electronics cleaning, heat transfer, protective coatings and surface modifiers, fire protection, lubricant deposition and several specialty chemical applications.
3M™ Novec™ Engineered Fluids 3M™ Novec™Aerosol Cleaners 3M™ Novec™1230 Fire Protection Fluid 3M™ Novec™ Electronic Grade Coatings 3M™ Novec™ Electronic Surfactants
■
United States
3M Electronics Materials
Solutions Division
800 810 8513
China
3M China Ltd.
86 21 6275 3535
■
Europe
3M Belgium N.V.
32 3 250 7521
■
Japan
Sumitomo 3M Limited
813 3709 8250
■
Korea
3M Korea Limited
82 2 3771 4114
Singapore
3M Singapore Pte. Ltd.
65 64508888
Taiwan
3M Taiwan Limited
886 2 2704 9011
Technical Information: The technical information, recommendations and other statements contained in this document are based upon tests or experience that 3M believes are reliable, but the
accuracy or completeness of such information is not guaranteed.
Product Use: Many factors beyond 3M’s control and uniquely within user’s knowledge and control can affect the use and performance of a 3M product in a particular application. Given the variety
of factors that can affect the use and performance of a 3M product, user is solely responsible for evaluating the 3M product and determining whether it is fit for a particular purpose and suitable for
user’s method of application.
Warranty, Limited Remedy, and Disclaimer: Unless an additional warranty is specifically stated on the applicable 3M product packaging or product literature, 3M warrants that each 3M product
meets the applicable 3M product specification at the time 3M ships the product. 3M MAKES NO OTHER WARRANTIES OR CONDITIONS, EXPRESS OR IMPLIED, INCLUDING, BUT NOT LIMITED
TO, ANY IMPLIED WARRANTY OR CONDITION OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE OR ANY IMPLIED WARRANTY OR CONDITION ARISING OUT OF A COURSE OF
DEALING, CUSTOM OR USAGE OF TRADE. If the 3M product does not conform to this warranty, then the sole and exclusive remedy is, at 3M’s option, replacement of the 3M product or refund of
the purchase price.
Limitation of Liability: Except where prohibited by law, 3M will not be liable for any loss or damage arising from the 3M product, whether direct, indirect, special, incidental or consequential,
regardless of the legal theory asserted, including warranty, contract, negligence or strict liability.
3
Electronics Materials Solutions Division
3M Center, Building 224-3N-11
St. Paul, MN 55144-1000
www.3M.com/novec
1-800-810-8513
Please recycle. Printed in USA.
© 3M 2014. All rights reserved.
Issued: 7/14 9851HB
60-5002-0725-7
Solartron is a trademark of Lloyd Instruments Limited.
3M and Novec are trademarks of 3M Company.
Used under license by 3M subsidiaries and affiliates.
3M™ Novec™ Electronic Grade Coatings
Technical Paper
Corrosion Protection of Metal Surfaces from Sulfur by Using
3M™ Novec™ Electronic Grade Coatings
Introduction
A study was conducted to show the capability of 3M™ Novec™
2701, 2704 and 2708 Electronic Grade Coatings to mitigate
corrosion of exposed metal on printed circuit boards and
electronic components under harsh environmental conditions.
Novec 2701, 2704 and 2708 electronic grade coatings are
fluorinated polymers carried in segregated-hydrofluoroether
fluids sold by 3M under the Novec trade name. These polymer
coatings are designed for protection of printed circuit boards,
components and a variety of surfaces from moisture and corrosion.
Novec 2701, 2704 and 2708 electronic grade coatings dry to a
thin, transparent film with excellent hydrophobic and oleophobic
properties. They do not require thermal curing and are easy to
apply – whether by liquid dipping, spraying (controlled) or brush
applying. The solution and polymer are both low in toxicity, nonozone depleting and RoHS compliant. These coatings incorporate
a yellow-orange dye into the polymer backbone that is designed to
fluoresce under UV light to aid inspection and the quality control of
the coating process.
boards with ImAg and bare copper (Cu) finishes were both treated
with Novec electronic grade coatings and tested. Additionally,
some with ImSnPb finish, vias and solder mask were also tested.
Boards of each surface finish that were not treated with Novec
electronic grade coatings were used as control samples and tested
under the same conditions as the boards which were treated.
It has been stated by some groups that flux residues, which result
from the board construction process, may be necessary to simulate
the dendritic growth involved in creep corrosion in the laboratory.1
Because of this, in our study some boards were treated with flux
and reflowed before being coated and tested. It was found that
boards with no flux residues were just as susceptible to creeping
corrosion as boards with flux residues. Therefore, the focus
remained on the clean IPC-B-25A test vehicles, shown in
Figure 1 below.
Background
During the transition away from printed circuit board finishes
that contain lead, many industries have reported corrosion
when using circuitry plated with metals such as silver and tin.1,2,3
Industries that have cited these issues include petrochemical,
water treatment, and rubber manufacturing.3 Circuitry subjected
to the harsh environments associated with these and other
industries is susceptible to corroding relatively quickly.1,2,3
In addition, geographic location can contribute heavily to this
problem.3 The creep corrosion from exposure to these harsh
environments often leads to electrical shorts and failures quickly
because the characteristic dendritic growth can cause bridging.1,2,3
For industries that rely heavily on the use of electronics to function,
creep corrosion needs to be mitigated, especially in cases where
electronics must meet high minimum requirements.
Figure 1. The IPC-B-25A test vehicle.
Experiment
Coating Process
Test Boards
The IPC-B-25A test boards were cut in half vertically in order
to accommodate the ASTM test conditions and the limited
space in the test chamber. The cut boards were then cleaned
with 3M™ Novec™ 72DA Engineered Fluid in a vapor degreaser.
Novec 72DA fluid is effective at removing surface contaminants
and particulate that, if left on the board, may have an impact on
metal corrosion rates.
Standard IPC-B-25A test boards are commonly available and
were used in the study. These printed circuit boards (PCBs)
meet guidelines for the testing of solder masks (IPC-SM-804C)
and conformal coatings (IPC-CC-830A).
Immersion silver (ImAg) finish is used in electronics as an
alternative to lead-tin finishes.1 Therefore, IPC-B-25A test
3
3M™ Novec™ Electronic Grade Coatings
Each board was coated by a dip coating process. The process
began with a chamber filled with one of the 3M™ Novec™ 2701,
2704 or 2708 Electronic Grade Coatings. The chamber sat on a
table which moved up and down at a controlled rate. The rate at
which the boards were removed controlled the thickness of the
coating. In general, the faster the board is removed, the thicker
the coating. The boards were dipped, held in solution for 30
seconds and removed from the coating solution at a rate of 12
inches per minute. The boards were allowed to dry and then
placed into a flowers-of-sulfur test chamber as described below.
To simulate the type of conditions that might occur in the field,
some boards were treated with flux prior to being tested. To do
this, the coating process was modified slightly for boards that
would be treated with flux. These test vehicles were first cleaned
as stated above, the chosen flux was applied and the boards
were then reflowed. The boards were allowed to cool to room
temperature and then coated by the dip coating process as
described above.
High Humidity - High Sulfur Test
“Flowers-of-Sulfur” (FoS)
A variety of methods can be used to test the porosity of coatings
and protective finishes. The ASTM B809 method provides a
standard method by which to induce the corrosion of various
metal finishes.4 The test is designed to recreate the problematic
high hydrogen sulfide gas and high humidity environment found
in many industries.
The testing setup is shown in Figure 2. A 10 L glass desiccator
was used as the test vessel. Grease was never used to seal the lid
to the chamber and there was a vented stopper which allowed for
equilibration of the system without pressure buildup. The test
vessel contained a potassium nitrate solution in which there was
a Petri dish containing elemental sulfur floats. The samples were
suspended at least 75 mm above the sulfur powder. The samples
were held in place above the sulfur source by an apparatus and
the clips were not affected by the sulfur.
Vented Stopper
PCB Samples
Elemental Sulfur
Saturated KNO3 solution
Figure 2. Samples in the flowers of sulfur chamber setup as described in the
ASTM B809 test method.
Data
“Flowers-of-Sulfur” (FoS)
The FoS test method was used to study how the finish of a circuit
board behaves in a corrosive, sulfur-containing environment.
The method was designed to show whether attempts to mitigate
corrosion, specifically creep corrosion, with a protective coating
were successful.
Treated and untreated Cu finish test vehicles were exposed to the
corrosive high sulfur environment in this study. After 10 days of
exposure to the FoS test, untreated Cu finish boards were found to
have succumbed to severe tarnish and creeping corrosion.
Cu finish boards that were treated with Novec 2708 coating,
however, had minimal tarnish and no creep corrosion after 10 days
of exposure. There was also substantially less tarnish and corrosion
on Cu finish boards which were treated with Novec 2704 and 2701
“Flowers-of-Sulfur” (FoS) Chamber Test Results (60°C, >90% RH)
Cu - Time = 0
Cu/uncoated = 10 days
Cu w/Novec 2701 = 10 days
Cu w/Novec 2704 = 10 days
Cu w/Novec 2708 = 10 days
Figure 3. The pictures on the top and bottom left show uncoated Cu finish B-25A test vehicles before and after 10 days exposure in the FoS chamber. The three larger
pictures on the right show Cu finish B-25A test vehicles which were coated with 3M™ Novec™ 2701, 2704 and 2708 Electronic Grade Coatings after 10 days exposure
in the FoS chamber.
2
3M™ Novec™ Electronic Grade Coatings
ImAg
Treated with Kester® 984 Flux
coatings after 10 days than on untreated boards. The testing showed
that the characteristic dendritic growth of creep corrosion was
drastically reduced by the presence of 3M™ Novec™ 2701, 2704 and
2708 Electronic Grade Coatings.
The conclusion was that treatment of circuitry with Novec
coatings mitigated damages caused by exposure to the corrosive
environment inside the FoS chamber. This difference in corrosion
growth is shown in Figures 3 and 4.
Flowers-of-Sulfur (FoS) Chamber Test Results
(60°C, >90% RH) 10 Days
Cu - Time = 0
Coated with Novec 2704
Uncoated
Figure 5. The pictures on the top left and right pictures show coated and
uncoated ImSnPb finish test vehicles after 34 days exposure in the FoS chamber,
respectively. The bottom left and right pictures show ImAg finish B-25A test
vehicles coated and uncoated after 10 days exposure in the FoS chamber,
respectively.
Summary and Conclusions
Cu – Novec 2708 at 10 days
Cu – Uncoated at 10 days
Creep corrosion can be driven by many factors and is an increasing
concern for many industries, end customers and the circuit board
industry. Tests were completed to demonstrate whether coating
printed circuit board circuitry would help to reduce the progress of
creeping corrosion caused by sulfur in the environment.
In this study, 3M™ Novec™ 2701, 2704 and 2708 Electronic Grade
Coatings were applied over a variety of metal and metal finished
electronic circuitry surfaces. Uncoated versions were used as a
control and compared over time to the coated versions.
A FoS chamber was chosen as the test method for inducing creep
corrosion. It simulated the high hydrogen sulfide gas and high
humidity environments in which circuitry is increasingly
being used.
Figure 4. The pictures on the top and bottom right show uncoated Cu finish
IPC-B-25A test vehicles before and after 10 days exposure in the FoS chamber,
respectively. The bottom left picture shows a Cu finish IPC-B-25A test vehicle
which was coated with 3M™ Novec™ 2708 Electronic Grade Coating after 10 days
exposure in the FoS chamber.
Since ImAg and other finishes are often used to protect Cu
circuitry, alternate finishes were also included in the study.
Figure 5 shows results of coated and uncoated boards with
these alternate finishes.
The IPC-B-25A design was used for the ImAg finish boards
and a 3M-designed test board was used for the ImSnPb finished
boards. The latter was done in addition to the IPC-B-25A boards
to determine whether the creep corrosion phenomena could be
mitigated on a typical solder mask, which is present on circuit
boards in most cases. The coatings did mitigate corrosion on both
alternate finishes tested.
This testing procedure resulted in a dramatic difference with the
coated versions showing significantly less corrosion development.
The conclusion was that Novec 2701, 2704 and 2708 electronic
grade coatings help mitigate the formation of creeping corrosion
of exposed metal on circuit boards caused by exposure to high
levels of sulfur and humidity.
Xu, C., Smetana J. Franey, G. Guerra, D. Flemming, W. Reents, Dennis Willie, Alfredo Garcia,
Guadalupe Encinas, and Jiang Xiaodong. “Creep Corrosion of PWB Final Finishes: Its Cause
and Prevention.” IPC APEX EXPO Proceedings (n.d.): n. pag. Web.
1
Kenny, Jim, Karl Wengenroth, Ted Antonellis, ShenLian Sun, Cai Wang, PhD, Edward Kudrak, and
Joseph Abys, PhD. “PWB Creeping Corrosion Mechanism and Mitigation Strategy.” Enthone Inc.,
Crookstone Electronics, n.d. Web.
2
Schueller, Randy, PhD. “Creep Corrosion on Lead-Free Printed Circuit Boards in High.”
Dfrsolutions.com. SMTA International Proceedings, Oct. 2007. Web. 19 Aug. 2013.
3
“ASTM B809 - 95(2008).” Standard Test Method for Porosity in Metallic Coatings by Humid
Sulfur Vapor (“Flowers of Sulfur”). N.p., n.d. Web. 15 Aug. 2013.
4
Flowers-of-Sulfur (FoS) Chamber Test Results
(60°C, >90% RH) Alternate Finishes After 34 days
ImSnPb
No Flux
Coated with Novec 2704
Uncoated
3
3M™ Novec™ Electronic Grade Coatings
The 3M™ Novec™
Brand Family
The Novec brand is the hallmark for a variety of patented 3M compounds. Although each has its own unique formula and performance properties, all Novec
products are designed in common to address the need for safe, effective, sustainable solutions in industry-specific applications. These include precision and
electronics cleaning, heat transfer, protective coatings and surface modifiers, fire protection, lubricant deposition and several specialty chemical applications.
3M™ Novec™ Engineered Fluids 3M™ Novec™Aerosol Cleaners 3M™ Novec™1230 Fire Protection Fluid 3M™ Novec™ Electronic Coatings 3M™ Novec™ Electronic Surfactants
■
United States
3M Electronics Markets
Materials Division
800 810 8513
China
3M China Ltd.
86 21 6275 3535
■
Europe
3M Belgium N.V.
32 3 250 7521
■
Japan
Sumitomo 3M Limited
813 3709 8250
■
Korea
3M Korea Limited
82 2 3771 4114
Singapore
3M Singapore Pte. Ltd.
65 64508888
Taiwan
3M Taiwan Limited
886 2 2704 9011
Technical Information: The technical information, recommendations and other statements contained in this document are based upon tests or experience that 3M believes are reliable, but the
accuracy or completeness of such information is not guaranteed.
Product Use: Many factors beyond 3M’s control and uniquely within user’s knowledge and control can affect the use and performance of a 3M product in a particular application. Given the variety
of factors that can affect the use and performance of a 3M product, user is solely responsible for evaluating the 3M product and determining whether it is fit for a particular purpose and suitable for
user’s method of application.
Warranty, Limited Remedy, and Disclaimer: Unless an additional warranty is specifically stated on the applicable 3M product packaging or product literature, 3M warrants that each 3M product
meets the applicable 3M product specification at the time 3M ships the product. 3M MAKES NO OTHER WARRANTIES OR CONDITIONS, EXPRESS OR IMPLIED, INCLUDING, BUT NOT LIMITED
TO, ANY IMPLIED WARRANTY OR CONDITION OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE OR ANY IMPLIED WARRANTY OR CONDITION ARISING OUT OF A COURSE OF
DEALING, CUSTOM OR USAGE OF TRADE. If the 3M product does not conform to this warranty, then the sole and exclusive remedy is, at 3M’s option, replacement of the 3M product or refund of
the purchase price.
Limitation of Liability: Except where prohibited by law, 3M will not be liable for any loss or damage arising from the 3M product, whether direct, indirect, special, incidental or consequential,
regardless of the legal theory asserted, including warranty, contract, negligence or strict liability.
3
Electronics Markets Materials Division
3M Center, Building 224-3N-11
St. Paul, MN 55144-1000
www.3M.com/novec
1-800-810-8513
Please recycle. Printed in USA.
© 3M 2014. All rights reserved.
Issued: 4/14 9728HB
60-5002-0724-0
Kester is a registered trademark of ITW Kester.
3M and Novec are trademarks of 3M Company.
Used under license by 3M subsidiaries and affiliates.