ASTM F641-09(2014)

Standard Specification for Implantable Epoxy Electronic Encapsulants

ABSTRACT
This specification covers thermoset plastics based on diglycidyl ethers of bisphenol A and amino functional curing agents or amine catalysts for implantable epoxy electronic encapsulants. Encapsulants shall be classified depending on contact with tissues or physiological fluids. Chemical composition requirements may include additives, phthalate esters, amines, catalysts, and carbonates. The material shall be tested for the following physical properties: peak exotherm temperature, transparency, foreign particles, USP biological test plastic containers, USP pyrogen test, sterilant residues, cure shrinkage, embedment stress, tissue culture test, long-term immersion test, and accelerated immersion test. The material shall also be inspected with infrared spectroscopy, amine number, epoxide equivalent weight, spectrographic analysis, and total nitrogen.
SCOPE
1.1 This specification covers thermoset plastics based on diglycidyl ethers of bisphenol A and amino functional curing agents or amine catalysts.  
1.2 The epoxy encapsulants covered by this specification are intended to provide a tissue-compatible protective covering for implantable medical devices such as pulse generators, telemetry devices and RF receivers. The biocompatibility of epoxy plastics has not been established. Epoxy plastic is a generic term relating to the class of polymers formed from epoxy resins, certain curing agents or catalysts and various additives. Since many compositions and formulations fall under this category, it is essential that the fabricator assure safety of implantability of the specific composition or formulation for the intended use by current state-of-the-art test methods. This specification can be used as a basis for standardized evaluation of biocompatibility for such implantable encapsulants.  
1.3 The encapsulants covered by this specification are for use in devices intended as long-term implants.  
1.4 Limitations—This specification covers only the initial qualification of epoxy encapsulants for implantable electronic circuitry. Some of the requirements are not applicable to routine lot-to-lot quality control.  
1.5 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.  
1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.

General Information

• Status: Historical
• Publication Date: 31-Oct-2014
• ICS: 11.040.40 - Implants for surgery, prosthetics and orthotics
• Technical Committee: F04 - Medical and Surgical Materials and Devices
• Drafting Committee: F04.11 - Polymeric Materials

Standards Content (Sample)

NOTICE: This standard has either been superseded and replaced by a new version or withdrawn.
Contact ASTM International (www.astm.org) for the latest information
Designation:F641 −09 (Reapproved 2014)
Standard Specification for
Implantable Epoxy Electronic Encapsulants
ThisstandardisissuedunderthefixeddesignationF641;thenumberimmediatelyfollowingthedesignationindicatestheyearoforiginal
adoptionor,inthecaseofrevision,theyearoflastrevision.Anumberinparenthesesindicatestheyearoflastreapproval.Asuperscript
epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope 2. Referenced Documents
1.1 This specification covers thermoset plastics based on 2.1 ASTM Standards:
diglycidyl ethers of bisphenol A and amino functional curing D149Test Method for Dielectric Breakdown Voltage and
agents or amine catalysts. DielectricStrengthofSolidElectricalInsulatingMaterials
at Commercial Power Frequencies
1.2 The epoxy encapsulants covered by this specification
D150Test Methods forAC Loss Characteristics and Permit-
areintendedtoprovideatissue-compatibleprotectivecovering
tivity (Dielectric Constant) of Solid Electrical Insulation
for implantable medical devices such as pulse generators,
D257Test Methods for DC Resistance or Conductance of
telemetry devices and RF receivers. The biocompatibility of
Insulating Materials
epoxy plastics has not been established. Epoxy plastic is a
D570Test Method for Water Absorption of Plastics
generic term relating to the class of polymers formed from
D638Test Method for Tensile Properties of Plastics
epoxy resins, certain curing agents or catalysts and various
D790Test Methods for Flexural Properties of Unreinforced
additives. Since many compositions and formulations fall
and Reinforced Plastics and Electrical Insulating Materi-
under this category, it is essential that the fabricator assure
als
safety of implantability of the specific composition or formu-
D1042Test Method for Linear Dimensional Changes of
lation for the intended use by current state-of-the-art test
Plastics Caused by Exposure to Heat and Moisture
methods. This specification can be used as a basis for stan-
D1239Test Method for Resistance of Plastic Films to
dardized evaluation of biocompatibility for such implantable
Extraction by Chemicals
encapsulants.
D1434TestMethodforDeterminingGasPermeabilityChar-
1.3 The encapsulants covered by this specification are for
acteristics of Plastic Film and Sheeting
use in devices intended as long-term implants.
D2240TestMethodforRubberProperty—DurometerHard-
1.4 Limitations—This specification covers only the initial ness
D2471PracticeforGelTimeandPeakExothermicTempera-
qualification of epoxy encapsulants for implantable electronic
circuitry. Some of the requirements are not applicable to tureofReactingThermosettingResins(Withdrawn2008)
D2562Practice for Classifying Visual Defects in Parts
routine lot-to-lot quality control.
Molded from Reinforced Thermosetting Plastics
1.5 The values stated in SI units are to be regarded as
D2566Test Method for Linear Shrinkage of CuredThermo-
standard. No other units of measurement are included in this
setting Casting Resins During Cure (Withdrawn 1993)
standard.
D2734TestMethodsforVoidContentofReinforcedPlastics
1.6 This standard does not purport to address all of the
D3137Test Method for Rubber Property—Hydrolytic Sta-
safety concerns, if any, associated with its use. It is the 3
bility (Withdrawn 0)
responsibility of the user of this standard to establish appro-
F74Practice for Determining Hydrolytic Stability of Plastic
priate safety and health practices and determine the applica- 3
Encapsulants for Electronic Devices (Withdrawn 1994)
bility of regulatory limitations prior to use.
1 2
This specification is under the jurisdiction of ASTM Committee F04 on For referenced ASTM standards, visit the ASTM website, www.astm.org, or
Medical and Surgical Materials and Devices and is the direct responsibility of contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM
Subcommittee F04.11 on Polymeric Materials. Standards volume information, refer to the standard’s Document Summary page on
Current edition approved Nov. 1, 2014. Published November 2014. Originally the ASTM website.
approved in 1979. Last previous edition approved in 2009 as F641–09. DOI: The last approved version of this historical standard is referenced on
10.1520/F0641-09R14. www.astm.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
F641−09 (2014)
F135TestMethodforEmbedmentStressCausedbyCasting 5. Physical Properties
Compounds on Glass-Encased Electronic (Withdrawn
5.1 Type I Encapsulants:
1997)
5.1.1 Peak Exotherm Temperature (Test Method D2471)—
F602Criteria for Implantable Thermoset Epoxy Plastics
The peak exotherm temperature during cure shall be kept
F748PracticeforSelectingGenericBiologicalTestMethods
below the maximum acceptable value for the lowest tempera-
for Materials and Devices
ture rated component of the device.
F895TestMethodforAgarDiffusionCellCultureScreening
5.1.2 FullyCuredSpecimens—Therequiredpropertiesmea-
for Cytotoxicity
sured on fully cured specimens conditioned as in 6.1 are as
F981Practice for Assessment of Compatibility of Biomate-
follows:
rials for Surgical Implants with Respect to Effect of
5.1.2.1 Transparency—In cases where no fillers or rein-
Materials on Muscle and Bone
forcements are used, the encapsulant shall have sufficient
2.2 AAMI Standard:
transparency so that the circuitry may be visually inspected
EOS-DE-O Sterilization Standard
after encapsulation.
2.3 ISO Standard:
5.1.2.2 Foreign Particles—No foreign particles, particulate
ISO 10993Biological Evaluation of Medical Devices
matter,orgrosscontaminationshallbeobservedwhenchecked
under 2× wide field magnification.
3. Classification
5.1.2.3 Biocompatibility Testing—While cell culture meth-
3.1 Encapsulants shall be classified as follows: ods as described in Test Method F895 may be appropriate for
3.1.1 Type I—Those encapsulants which contact the tissue
the lot-to-lot screening of fully cured specimens, the basic
directly or indirectly. recipe used should have been qualified for its overall tissue
3.1.2 Type II—Those encapsulants used only within her-
response by methods such as those suggested in Practice F748
metically sealed containers. The epoxy encapsulant has no or ISO 10993 for the intended application, including testing
contact with tissues or physiological fluids.
according to Practice F981.
(1)Biocompatibility testing should be performed on speci-
4. Chemical Composition
mens that have been processed and sterilized per the methods
intended for the final device.
4.1 Additives (Type I Encapsulants Only):
5.1.2.4 USP Bacterial Endotoxin Test or other Pyrogen
4.1.1 Reactive Diluents—The following compounds when
methods which have been demonstrated to be of equal or
used as reactive diluents shall not be used in concentrations
greater sensitivity—Pass.
greater than 12 parts per hundred resin (phr).
5.1.2.5 Sterilant Residues (AAMI EOS-D)—Where
4.1.1.1 Butyl glycidyl ether (BGE).
applicable, the concentration of ethylene oxide, ethylene
4.1.1.2 Phenyl glycidyl ether (PGE).
chlorohydrin,ethyleneglycol,anddichlorodifluoromethane(or
4.1.2 OtherAdditives(seeNote1)—Otheradditivesshallbe
the equivalents) at the time of implantation shall be shown to
showntobenonextractablein37°Cphysiologicalsalineforthe
be within safe limits prescribed by the device manufacturer.
device design life in concentrations sufficient to significantly
5.1.2.6 The cure shrinkage (Test Method D2566) or embed-
affect the properties of the encapsulant or to produce a
ment stress (Test Method F135) shall be≤2%. The stress shall
significant biological reaction.
not exceed the limits of the most pressure-sensitive compo-
NOTE 1—Other additives, as indicated in Criteria F602, include
nents.
compounds such as nonreactive diluents, fillers, release agents, and the
5.1.2.7 Tissue CultureTest (Agar Overlay) orTest Method
like.
F895—Pass.
4.1.3 Phthalate Esters—Phthalate esters such as dibutyl
5.1.3 Required Cured Properties Measured in Long-Term
phthalate shall not be used in concentrations ≥10 phr.
Immersion Tests for Type I Encapsulants—Thepropertyvalues
4.2 Mix Ratios (Type I and Type II Encapsulants):
prescribed in Table 1 shall be obtained at 22 6 3°C and 50 6
4.2.1 Amines—The mix ratio shall be maintained at 65
10% relative humidity on specimens conditioned as in 6.3.
equivalent% of stoichiometry.
Samples shall be wiped dry prior to test with a lint-free tissue,
4.2.2 Catalysts—The mix ratio shall be maintained within
as appropriate.
the ranges recommended by the formulator.
5.1.4 Optional cured properties measured after accelerated
4.3 Carbonates (Type I and Type II Encapsulants)—The immersion for Type I encapsulants may be determined for
encapsulant shall be poured under conditions such that the screening purposes after conditioning as in 6.2.
formation of amine carbonates is minimized. The device
5.2 Type II Enca
...

This document is not an ASTM standard and is intended only to provide the user of an ASTM standard an indication of what changes have been made to the previous version. Because
it may not be technically possible to adequately depict all changes accurately, ASTM recommends that users consult prior editions as appropriate. In all cases only the current version
of the standard as published by ASTM is to be considered the official document.
Designation: F641 − 09 F641 − 09 (Reapproved 2014)
Standard Specification for
Implantable Epoxy Electronic Encapsulants
This standard is issued under the fixed designation F641; the number immediately following the designation indicates the year of original
adoption or, in the case of revision, the year of last revision. A number in parentheses indicates the year of last reapproval. A superscript
epsilon (´) indicates an editorial change since the last revision or reapproval.
1. Scope
1.1 This specification covers thermoset plastics based on diglycidyl ethers of bisphenol A and amino functional curing agents
or amine catalysts.
1.2 The epoxy encapsulants covered by this specification are intended to provide a tissue-compatible protective covering for
implantable medical devices such as pulse generators, telemetry devices and RF receivers. The biocompatibility of epoxy plastics
has not been established. Epoxy plastic is a generic term relating to the class of polymers formed from epoxy resins, certain curing
agents or catalysts and various additives. Since many compositions and formulations fall under this category, it is essential that
the fabricator assure safety of implantability of the specific composition or formulation for the intended use by current
state-of-the-art test methods. This specification can be used as a basis for standardized evaluation of biocompatibility for such
implantable encapsulants.
1.3 The encapsulants covered by this specification are for use in devices intended as long-term implants.
1.4 Limitations—This specification covers only the initial qualification of epoxy encapsulants for implantable electronic
circuitry. Some of the requirements are not applicable to routine lot-to-lot quality control.
1.5 The values stated in SI units are to be regarded as standard. No other units of measurement are included in this standard.
1.6 This standard does not purport to address all of the safety concerns, if any, associated with its use. It is the responsibility
of the user of this standard to establish appropriate safety and health practices and determine the applicability of regulatory
limitations prior to use.
2. Referenced Documents
2.1 ASTM Standards:
D149 Test Method for Dielectric Breakdown Voltage and Dielectric Strength of Solid Electrical Insulating Materials at
Commercial Power Frequencies
D150 Test Methods for AC Loss Characteristics and Permittivity (Dielectric Constant) of Solid Electrical Insulation
D257 Test Methods for DC Resistance or Conductance of Insulating Materials
D570 Test Method for Water Absorption of Plastics
D638 Test Method for Tensile Properties of Plastics
D790 Test Methods for Flexural Properties of Unreinforced and Reinforced Plastics and Electrical Insulating Materials
D1042 Test Method for Linear Dimensional Changes of Plastics Caused by Exposure to Heat and Moisture
D1239 Test Method for Resistance of Plastic Films to Extraction by Chemicals
D1434 Test Method for Determining Gas Permeability Characteristics of Plastic Film and Sheeting
D2240 Test Method for Rubber Property—Durometer Hardness
D2471 Practice for Gel Time and Peak Exothermic Temperature of Reacting Thermosetting Resins (Withdrawn 2008)
D2562 Practice for Classifying Visual Defects in Parts Molded from Reinforced Thermosetting Plastics
D2566 Test Method for Linear Shrinkage of Cured Thermosetting Casting Resins During Cure (Withdrawn 1993)
D2734 Test Methods for Void Content of Reinforced Plastics
D3137 Test Method for Rubber Property—Hydrolytic Stability (Withdrawn 0)
This specification is under the jurisdiction of ASTM Committee F04 on Medical and Surgical Materials and Devices and is the direct responsibility of Subcommittee
F04.11 on Polymeric Materials.
Current edition approved Aug. 1, 2009Nov. 1, 2014. Published September 2009November 2014. Originally approved in 1979. Last previous edition approved in 20032009
as F641 – 98aF641(2003). –09. DOI: 10.1520/F0641-09.10.1520/F0641-09R14.
For referenced ASTM standards, visit the ASTM website, www.astm.org, or contact ASTM Customer Service at [e-mail]. For Annual Book of ASTM Standards
volume information, refer to the standard’s Document Summary page on the ASTM website.
The last approved version of this historical standard is referenced on www.astm.org.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959. United States
F641 − 09 (2014)
F74 Practice for Determining Hydrolytic Stability of Plastic Encapsulants for Electronic Devices (Withdrawn 1994)
F135 Test Method for Embedment Stress Caused by Casting Compounds on Glass-Encased Electronic (Withdrawn 1997)
F602 Criteria for Implantable Thermoset Epoxy Plastics
F748 Practice for Selecting Generic Biological Test Methods for Materials and Devices
F895 Test Method for Agar Diffusion Cell Culture Screening for Cytotoxicity
F981 Practice for Assessment of Compatibility of Biomaterials for Surgical Implants with Respect to Effect of Materials on
Muscle and Bone
2.2 AAMI Standard:
EOS-D E-O Sterilization Standard
2.3 ISO Standard:
ISO 10993 Biological Evaluation of Medical Devices
3. Classification
3.1 Encapsulants shall be classified as follows:
3.1.1 Type I—Those encapsulants which contact the tissue directly or indirectly.
3.1.2 Type II—Those encapsulants used only within hermetically sealed containers. The epoxy encapsulant has no contact with
tissues or physiological fluids.
4. Chemical Composition
4.1 Additives (Type I Encapsulants Only):
4.1.1 Reactive Diluents—The following compounds when used as reactive diluents shall not be used in concentrations greater
than 12 parts per hundred resin (phr).
4.1.1.1 Butyl glycidyl ether (BGE).
4.1.1.2 Phenyl glycidyl ether (PGE).
4.1.2 Other Additives (see Note 1)—Other additives shall be shown to be nonextractable in 37°C physiological saline for the
device design life in concentrations sufficient to significantly affect the properties of the encapsulant or to produce a significant
biological reaction.
NOTE 1—Other additives, as indicated in Criteria F602, include compounds such as nonreactive diluents, fillers, release agents, and the like.
4.1.3 Phthalate Esters—Phthalate esters such as dibutyl phthalate shall not be used in concentrations ≥10 phr.
4.2 Mix Ratios (Type I and Type II Encapsulants):
4.2.1 Amines—The mix ratio shall be maintained at 65 equivalent % of stoichiometry.
4.2.2 Catalysts—The mix ratio shall be maintained within the ranges recommended by the formulator.
4.3 Carbonates (Type I and Type II Encapsulants)—The encapsulant shall be poured under conditions such that the formation
of amine carbonates is minimized. The device manufacturer may specify maximum limits for carbon dioxide or water vapor, or
both, in the atmosphere in which the encapsulant is being mixed or poured.
5. Physical Properties
5.1 Type I Encapsulants:
5.1.1 Peak Exotherm Temperature (Test Method D2471)—The peak exotherm temperature during cure shall be kept below the
maximum acceptable value for the lowest temperature rated component of the device.
5.1.2 Fully Cured Specimens—The required properties measured on fully cured specimens conditioned as in 6.1 are as follows:
5.1.2.1 Transparency—In cases where no fillers or reinforcements are used, the encapsulant shall have sufficient transparency
so that the circuitry may be visually inspected after encapsulation.
5.1.2.2 Foreign Particles—No foreign particles, particulate matter, or gross contamination shall be observed when checked
under 2× wide field magnification.
5.1.2.3 Biocompatibility Testing—While cell culture methods as described in Test Method F895 may be appropriate for the
lot-to-lot screening of fully cured specimens, the basic recipe used should have been qualified for its overall tissue response by
methods such as those suggested in Practice F748 or ISO 10993 for the intended application, including testing according to Practice
F981.
(1) Biocompatibility testing should be performed on specimens that have been processed and sterilized per the methods
intended for the final device.
5.1.2.4 USP Bacterial Endotoxin Test or other Pyrogen methods which have been demonstrated to be of equal or greater
sensitivity—Pass.
Available from Association for Advancement of Medical Instrumentation, 1500 Wilson Blvd., Suite 417, Arlington, VA 22209.
Available from American National Standards Institute (ANSI), 25 W. 43rd St., 4th Floor, New York, NY 10036, http://www.ansi.org.
U.S. Pharmacopeia, USP-NF, <85>, available from U.S. Pharmacopeia (USP), 12601 Twinbrook Pkwy., Rockville, MD 20852-1790, http://www.usp.org.
F641 − 09 (2014)
5.1.2.5 Sterilant Residues (AAMI EOS-D)—Where applicable, the concentration of ethylene oxide, ethylene chlorohydrin,
ethylene glycol, and dichlorodifluoromethane (or the equivalents) at the time of implantation shall be shown to be within safe limits
prescri
...