ASTM F641-98a(2003)
(Specification)Standard Specification for Implantable Epoxy Electronic Encapsulants
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 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
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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: F 641 – 98a (Reapproved 2003)
Standard Specification for
Implantable Epoxy Electronic Encapsulants
This standard is issued under the fixed designation F 641; 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 (e) indicates an editorial change since the last revision or reapproval.
1. Scope D 257 Test Methods for dc Resistance or Conductance of
Insulating Materials
1.1 This specification covers thermoset plastics based on
D 570 Test Method for Water Absorption of Plastics
diglycidyl ethers of bisphenol A and amino functional curing
D 638 Test Method for Tensile Properties of Plastics
agents or amine catalysts.
D 790 TestMethodsforFlexuralPropertiesofUnreinforced
1.2 The epoxy encapsulants covered by this specification
and Reinforced Plastics and Electrical Insulating Materi-
are intended to provide a tissue-compatible protective covering
als
for implantable medical devices such as pulse generators,
D 883 Terminology Relating to Plastics
telemetry devices and RF receivers. The biocompatibility of
D 1042 Test Method for Linear Dimensional Changes of
epoxy plastics has not been established. Epoxy plastic is a
Plastics Under Accelerated Service Conditions
generic term relating to the class of polymers formed from
D 1239 Test Method for Resistance of Plastic Films to
epoxy resins, certain curing agents or catalysts and various
Extraction by Chemicals
additives. Since many compositions and formulations fall
D 1434 Test Method for Determining Gas Permeability
under this category, it is essential that the fabricator assure
Characteristics of Plastic Film and Sheeting
safety of implantability of the specific composition or formu-
D 1763 Specification for Epoxy Resins
lation for the intended use by current state-of-the-art test
D 1898 Practice for Sampling of Plastics
methods. This specification can be used as a basis for stan-
D 2240 Test Method for Rubber Property—Durometer
dardized evaluation of biocompatibility for such implantable
Hardness
encapsulants.
D 2471 Test Method for Gel Time and Peak Exothermic
1.3 The encapsulants covered by this specification are for
Temperature of Reacting Thermosetting Resins
use in devices intended as long-term implants.
D 2562 Practice for Classifying Visual Defects in Parts
1.4 Limitations—This specification covers only the initial
Molded from Reinforced Thermosetting Plastics
qualification of epoxy encapsulants for implantable electronic
D 2566 Test Method for Linear Shrinkage of Cured Ther-
circuitry. Some of the requirements are not applicable to
mosetting Casting Resins During Cure
routine lot to lot quality control.
D 2734 Test Method for Void Content of Reinforced Plas-
1.5 This standard does not purport to address all of the
tics
safety concerns, if any, associated with its use. It is the
D 3137 Test Method for Rubber Property—Hydrolytic Sta-
responsibility of the user of this standard to establish appro-
bility
priate safety and health practices and determine the applica-
F 74 Practice for Determining Hydrolytic Stability of Plas-
bility of regulatory limitations prior to use.
tic Encapsulants for Electronic Devices
2. Referenced Documents
F 135 Test Method for Embedment Stress Caused by Cast-
ing Compounds on Glass-Encased Electronic Compo-
2.1 ASTM Standards:
nents
D 149 Test Method for Dielectric Breakdown Voltage and
F 602 Criteria for Implantable Thermoset Epoxy Plastics
Dielectric Strength of Solid Electrical Insulating Materials
F 748 Practice For Selecting Generic Biological Test Meth-
at Commercial Power Frequencies
ods for Materials and Devices
D 150 Test Methods for ac Loss Characteristics and Permit-
tivity (Dielectric Constant) of Solid Electrical Insulating
Materials
Annual Book of ASTM Standards, Vol 08.01.
Annual Book of ASTM Standards, Vol 15.09.
Discontinued; See 1997 Annual Book of ASTM Standards, Vol 08.01.
This specification is under the jurisdiction of ASTM Committee F04 on
Annual Book of ASTM Standards, Vol 09.01.
Medical and Surgical Materials and Devices and is the direct responsibility of
Annual Book of ASTM Standards, Vol 08.02.
Subcommittee F04.11 on Polymeric Materials.
Discontinued; See 1992 Annual Book of ASTM Standards, Vol 08.02.
Current edition approved Apr. 10, 2003. Published May 2003. Originally
Discontinued; See 1994 Annual Book of ASTM Standards, Vol 10.04.
approved in 1979. Last previous edition approved in 1998 as F 641 – 98a.
2 Discontinued; See 1996 Annual Book of ASTM Standards, Vol 10.02.
Annual Book of ASTM Standards, Vol 10.01.
Annual Book of ASTM Standards, Vol 13.01.
Copyright © ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959, United States.
F 641 – 98a (2003)
F 895 Test Method forAgar Diffusion Cell Culture Screen- 5.1.2.1 Transparency—In cases where no fillers or rein-
ing for Cytotoxicity forcements are used, the encapsulant shall have sufficient
F 981 Practice for Assessment of Compatibility of Bioma- transparency so that the circuitry may be visually inspected
terials for Surgical Implants with Respect to Effect of after encapsulation.
Materials on Muscle and Bone 5.1.2.2 Foreign Particles—No foreign particles, particulate
2.2 AAMI Standard: matter and gross contamination shall be observed when
EOS-D E-O Sterilization Standard checked under 23 wide field magnification.
5.1.2.3 USP Biological Tests Plastic Containers, Class
3. Classification
IV —Pass.
5.1.2.4 USP Pyrogen Test or other Pyrogen methods
3.1 Encapsulants shall be classified as follows:
which have been demonstrated to be of equal or greater
3.1.1 Type I—Those encapsulants which contact the tissue
sensitivity—Pass.
directly or indirectly.
5.1.2.5 Sterilant Residues (AAMI EOS-D)—Where appli-
3.1.2 Type II—Those encapsulants used only within her-
cable, the concentration of ethylene oxide, ethylene chlorohy-
metically sealed containers. The epoxy encapsulant has no
drin, ethylene glycol, and dichlorodifluoromethane (or the
contact with tissues or physiological fluids.
equivalents) at the time of implant shall be shown to be within
4. Chemical Composition safe limits prescribed by the device manufacturer.
5.1.2.6 The cure shrinkage (Test Method D 2566) or em-
4.1 Additives (Type I Encapsulants Only):
bedment stress (Test Method F 135) shall be#2%. The stress
4.1.1 Reactive Diluents—The following compounds when
shall not exceed the limits of the most pressure-sensitive
used as reactive diluents shall not be used in concentrations
components.
greater than 12 parts per hundred resin (phr).
5.1.2.7 TissueCultureTest(AgarOverlay) orTestMethod
4.1.1.1 Butyl glycidyl ether (BGE).
F 895—Pass.
4.1.1.2 Phenyl glycidyl ether (PGE).
5.1.2.8 While cell culture methods as described in Test
4.1.2 OtherAdditives(seeNote1)—Otheradditivesshallbe
Method F 895 may be appropriated for the batch-to-batch
showntobenonextractablein37°Cphysiologicalsalineforthe
screening of fully cured specimens, the basic recipe used
device design life in concentrations sufficient to significantly
should have been qualified for its overall tissue response by
affect the properties of the encapsulant or to produce a
methods such as those suggested in Practice F 748 for “Im-
significant biological reaction.
planted Devices Principally Contacting Tissue and Tissue
NOTE 1—Other additives, as indicated in Criteria F 602, include
Fluid” including testing according to Practice F 981.
compounds such as nonreactive diluents, fillers, release agents, and the
5.1.3 Required Cured Properties Measured in Long-Term
like.
ImmersionTestsforTypeIEncapsulants—The property values
4.1.3 Phthalate Esters—Phthalate esters such as dibutyl
prescribed in Table 1 shall be obtained at 22 6 3°C and 50 6
phthalate shall not be used in concentrations$10 phr.
10 % relative humidity on specimens conditioned as in 6.3.
4.2 Mix Ratios (Type I and Type II Encapsulants):
Samples shall be wiped dry prior to test with a lint-free tissue,
4.2.1 Amines—The mix ratio shall be maintained at 65
as appropriate.
equivalent % of stoichiometry.
5.1.4 Optional cured properties measured after accelerated
4.2.2 Catalysts—The mix ratio shall be maintained within
immersion for Type I encapsulants may be determined for
the ranges recommended by the formulator.
screening purposes after conditioning as in 6.2.
4.3 Carbonates (Type I and Type II Encapsulants)—The
5.2 Type II Encapsulants:
encapsulant shall be poured under conditions such that the
5.2.1 Peak Exotherm Temperature (Test Method D 2471)—
formation of amine carbonates is minimized. The device
The peak exotherm temperature during cure shall be kept
manufacturer may specify maximum limits of carbon diox
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