IEC 61249-4-1:2008

IEC 61249-4-1 ®
Edition 1.0 2008-01
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Materials for printed boards and other interconnecting structures –
Part 4-1: Sectional specification set for prepreg materials, unclad (for the
manufacture of multilayer boards) – Epoxide woven E-glass prepreg of defined
flammability
Matériaux pour circuits imprimés et autres structures d'interconnexion –
Partie 4-1: Série de spécifications intermédiaires pour matériaux préimprégnés,
non plaqués (pour la fabrication des cartes multicouches) – Tissu de verre
époxyde préimprégné de type E d’inflammabilité définie

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IEC 61249-4-1 ®
Edition 1.0 2008-01
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Materials for printed boards and other interconnecting structures –
Part 4-1: Sectional specification set for prepreg materials, unclad (for the
manufacture of multilayer boards) – Epoxide woven E-glass prepreg of defined
flammability
Matériaux pour circuits imprimés et autres structures d'interconnexion –
Partie 4-1: Série de spécifications intermédiaires pour matériaux préimprégnés,
non plaqués (pour la fabrication des cartes multicouches) – Tissu de verre
époxyde préimprégné de type E d’inflammabilité définie

INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
M
CODE PRIX
ICS 31.180 ISBN 978-2-88910-463-5
– 2 – 61249-4-1 © IEC:2008
CONTENTS
CONTENTS .2
FOREWORD.3
1 Scope.5
2 Normative references .5
3 Materials and construction.5
3.1 Reinforcement.6
3.2 Epoxide resin .6
4 Properties.6
4.1 Properties related to the appearance of the prepreg .6
4.1.1 Dewetted areas (fish eyes) .6
4.1.2 Broken filaments.6
4.1.3 Distortion.6
4.1.4 Creases.6
4.1.5 Edge conditions.6
4.2 Properties related to B stage prepreg .7
4.2.1 Resin content .7
4.2.2 Treated weight.7
4.2.3 Resin flow .7
4.2.4 Scaled flow thickness .7
4.2.5 Melting viscosity .8
4.2.6 Gel time.8
4.2.7 Volatile content.8
4.3 Properties of prepregs after curing to C stage .8
4.3.1 Electric strength .8
4.3.2 Flammability .8
4.3.3 Relative permittivity and dissipation factor .9
4.3.4 Cured thickness.9
5 Delivery form .9
5.1 Rolls.9
5.2 Sheets.9
5.3 Cut panels.9
6 Quality assurance.10
6.1 Quality system.10
6.2 Responsibility for inspection .10
6.3 Qualification inspection .10
6.4 Quality conformance inspection.10
6.5 Certificate of conformance.10
6.6 Safety data sheet .10
7 Packaging and marking .10
8 Shelf life.11
9 Ordering information.11
Bibliography.12

Table 1 – Flammability.9

61249-4-1 © IEC:2008 – 3 –
INTERNATIONAL ELECTROTECHNICAL COMMISSION
_____________
MATERIALS FOR PRINTED BOARDS AND OTHER
INTERCONNECTING STRUCTURES –
Part 4-1: Sectional specification set for prepreg materials,
unclad (for the manufacture of multilayer boards) –
Epoxide woven E-glass prepreg of defined flammability

FOREWORD
1) The International Electrotechnical Commission (IEC) is a worldwide organization for standardization comprising
all national electrotechnical committees (IEC National Committees). The object of IEC is to promote
international co-operation on all questions concerning standardization in the electrical and electronic fields. To
this end and in addition to other activities, IEC publishes International Standards, Technical Specifications,
Technical Reports, Publicly Available Specifications (PAS) and Guides (hereafter referred to as “IEC
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agreement between the two organizations.
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6) All users should ensure that they have the latest edition of this publication.
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expenses arising out of the publication, use of, or reliance upon, this IEC Publication or any other IEC
Publications.
8) Attention is drawn to the Normative references cited in this publication. Use of the referenced publications is
indispensable for the correct application of this publication.
9) Attention is drawn to the possibility that some of the elements of this IEC Publication may be the subject of
patent rights. IEC shall not be held responsible for identifying any or all such patent rights.
International Standard IEC 61249-4-1 has been prepared by IEC technical committee 91:
Electronics assembly technology.
This bilingual version, published in 2009-08, corresponds to the English version.
The text of this standard is based on the following documents:
FDIS Report on voting
91/739/FDIS 91/747/RVD
Full information on the voting for the approval of this standard can be found in the report on
voting indicated in the above table.

– 4 – 61249-4-1 © IEC:2008
The French version of this standard has not been voted upon.
This publication has been drafted in accordance with the ISO/IEC Directives, Part 2.
A list of all parts belonging to the IEC 61249 series, under the general title Materials for
printed boards and other interconnecting structures, can be found on the IEC website.
The committee has decided that the contents of this publication will remain unchanged until
the maintenance result date indicated on the IEC web site under "http://webstore.iec.ch" in
the data related to the specific publication. At this date, the publication will be
• reconfirmed;
• withdrawn;
• replaced by a revised edition, or
• amended.
61249-4-1 © IEC:2008 – 5 –
MATERIALS FOR PRINTED BOARDS AND OTHER
INTERCONNECTING STRUCTURES –
Part 4-1: Sectional specification set for prepreg materials,
unclad (for the manufacture of multilayer boards) –
Epoxide woven E-glass prepreg of defined flammability

1 Scope
This part of IEC 61249 gives requirements for properties of prepreg that is mainly intended to
be used as bonding sheets in connection with laminates according to IEC 61249-2-7 when
manufacturing multilayer boards in line with IEC 62326-4. This material may be also used to
bond other types of laminates.
Prepreg according to this standard is of defined flammability (vertical burning test). The
flammability rating on fully cured prepreg is achieved through the use of brominated fire
retardants contained as an integral part of the polymeric structure. After lamination according
to the supplier’s instructions, the glass transition temperature is defined as being 120 °C
minimum.
2 Normative references
The following referenced documents are indispensable for the application of this document.
For dated references, only the edition cited applies. For undated references, the latest edition
of the referenced document (including any amendments) applies.
IEC 61189-2:2006, Test methods for electrical materials, printed boards and other
interconnection structures and assemblies – Part 2: Test methods for materials for
interconnection structures
IEC 61189-3:1997, Test methods for electrical materials, printed boards and other
interconnection structures and assemblies – Part 3: Test methods for interconnection
structures (printed boards)
IEC 61249-2-7:2002, Materials for printed boards and other interconnecting structures –
Part 2-7: Reinforced base materials clad and unclad – Epoxide woven E-glass laminated
sheet of defined flammability (vertical burning test), copper-clad
IEC 62326-4, Printed boards – Part 4: Rigid multilayer printed boards with interlayer
connections – Sectional specification
ISO 9000:2005, Quality management systems – Fundamentals and vocabulary
ISO 11014-1:1994, Safety data sheet for chemical products – Part 1: Content and order of
sections
ISO 14001:2004, Environmental management systems – Requirements with guidance for use
3 Materials and construction
The prepreg consists of a reinforcing E-glass fabric which is impregnated with epoxide resin
and partially cured to the B stage.

– 6 – 61249-4-1 © IEC:2008
3.1 Reinforcement
NOTE Woven E-glass is intended to be specified in the future IEC 61249-6-3.
3.2 Epoxide resin
Majority di-functional epoxide resin with a glass transition temperature of ≥120 °C when cured
according to the manufacturer’s recommendation.
Contrast agents may be added to enhance processing such as optical inspection. Its flame
resistance is defined in terms of the flammability requirements of 4.3.2.
4 Properties
4.1 Properties related to the appearance of the prepreg
The prepreg shall be substantially free from defects that may have an impact on the material’s
fitness for use for the intended purpose.
For the following specific defects, the requirements given shall apply when inspection is made
in accordance with IEC 61189-3, method 3V01: Visual examination 3× magnification.
4.1.1 Dewetted areas (fish eyes)
Dewetted areas with a diameter >5 mm are not permissible.
Dewetted areas with a diameter ≤5 mm are permitted to an extent of a maximum 10 fish eyes
in any 300 mm × 300 mm area of the prepreg.
4.1.2 Broken filaments
When judging the presence of broken filaments their sizes and frequency of occurrence are
important for assessing acceptability but also the flow characteristic of the prepreg must be
taken into consideration. The acceptance conditions for broken filaments shall be as agreed
upon between the user and supplier.
4.1.3 Distortion
When the prepreg is tested in accordance with test method 2M29 the distortion of the fill
yarns in the glass fabric shall not exceed 10 % measured over any 300 mm test distance.
NOTE 2M29 is intended to be specified in a future edition of IEC 61189-2.
4.1.4 Creases
Creases caused by handling of the prepreg where only a negligible loss of resin has occurred
are permitted.
Creases where the glass yarns are exposed due to loss of resin are not permitted.
4.1.5 Edge conditions
Cut-to-size panels shall have even edges and shall not show loss of resin at the edge due to
the cutting process more than 2 mm. Excessive occurrence of resin dust released during the
cutting shall be removed before packaging for shipment.

61249-4-1 © IEC:2008 – 7 –
4.2 Properties related to B stage prepreg
A number of characteristics can describe thickness, reactivity and rheology of B stage prepreg.
The choice of characteristics to be used as qualification and quality conformance testing as
well as the nominal performance levels are as agreed upon between the user and supplier.
Several of the characteristics shown below are interrelated and should not be specified
individually. Ordering requirements should preferably be restricted to the glass style, one
characteristics marked (a) in combination with one characteristic marked (b). A maximum of
one optional characteristic (c) of B stage prepreg may be included.
Glass style
Thickness parameter
• Resin content (a)
• Treated weight (a)
Reactivity/rheology parameter
• Resin flow (b)
• Scaled flow thickness (b)
• Melt viscosity (b)
• Cured thickness (b)
Optional parameter
• Volatile content (c)
• Gel time (c)
4.2.1 Resin content
When tested in accordance with test method 2C03 or 2C10 of IEC 61189-2, the nominal resin
content shall be as agreed upon between the user and supplier.
The tolerance around the ordered nominal value shall be ±3 %, e.g. (45 ± 3) %.
4.2.2 Treated weight
When tested in accordance with test method 2C03 of IEC 61189-2, the nominal treated weight
shall be as agreed upon between the user and supplier.
The tolerance around the ordered nominal value shall be ±3 %, e.g. (16,8 ± 0,5) g.
4.2.3 Resin flow
When tested in accordance with test method 2M09 of IEC 61189-2, the nominal resin flow
shall be as agreed upon between the user and supplier.
The tolerance around the ordered nominal value shall be ±5 %, e.g. (25 ± 5) %.
4.2.4 Scaled flow thickness
When tested in accordance with test method 2M26 of IEC 61189-2, the nominal scaled flow
and the tolerance shall be as agreed upon between the user and supplier.

– 8 – 61249-4-1 © IEC:2008
4.2.5 Melting viscosity
When tested in accordance with test method 2C09 of IEC 61189-2, the nominal melt viscosity
shall be as agreed upon between the user and supplier.
The tolerance around the ordered nominal value shall be ±20 mPa s, e.g. (240 ± 20) mPa s.
4.2.6 Gel time
When tested in accordance with test method 2C02 of IEC 61189-2, the nominal gel time shall
be as agreed upon between the user and supplier.
The tolerance around the ordered nominal value shall be ±20 s, e.g. (160 ± 20) s.
4.2.7 Volatile content
When tested in accordance with test method 2C04 of IEC 61189-2, the volatile content shall
be 0,5 % maximum.
4.3 Properties of prepregs after curing to C stage
4.3.1 Electric strength
A total of 2 plies of prepreg of minimum size 300 mm × 300 mm shall be bonded together and
cured in accordance with the manufacturer’s recommendations whereupon the thickness shall
be determined using a micrometer.
When tested in accordance with test method 2E11 of IEC 61189-2, the minimum electric
strength shall be 25 V/μm.
4.3.2 Flammability
A number of plies of minimum size 300 mm × 300 mm of the prepreg under test shall be
bonded together and cured in accordance with the manufacturers’ recommendations. The
number of plies shall be chosen so that a specimen thickness of 0,4 mm – 0,5 mm is obtained
as measured with a micrometer.
When tested in accordance with test method 2C06 of IEC 61189-2, the flammability shall meet
the requirements as shown in Table 1.

61249-4-1 © IEC:2008 – 9 –
Table 1 – Flammability
Requirement
Test method
Property
Designation
IEC 61189-2
FV0 FV1
Flammability (vertical burning test): nominal material 2C06

thickness ≥0,4 mm
1. Flaming combustion time after each application of the ≤10 s ≤30 s
flame for each test specimen
2. Total flaming combustion time for the 10 flame
≤50 s ≤250 s
applications for each set of five specimens
3. Glowing combustion time after the second removal of the ≤30 s ≤60 s
flame
4. Flaming or glowing combustion up to the holding clamp None None
5. Dripping flaming particles that ignite the tissue paper None None

4.3.3 Relative permittivity and dissipation factor
A total of 2 plies of prepreg of minimum size 300 mm × 300 mm shall be bonded together and
cured in accordance with the manufacturer’s recommendations whereupon the thickness shall
be determined using a micrometer.
When tested in accordance with test method 2E10 of IEC 61189-2, the relative permittivity
and dissipation factor shall be 5,4 and 0,035 minimum, respectively.
4.3.4 Cured thickness
The nominal thickness and the tolerance of the cured prepreg using the user’s lamination
cycle shall be as agreed upon between the user and supplier.
5 Delivery form
Prepreg may be ordered and delivered as rolls, sheets or cut panels.
5.1 Rolls
Roll sizes shall be as agreed upon between the user and supplier. For rolls ≥50 m in length,
cut-outs from quality conformance inspection are allowed. The size of the roll delivered by the
+20
supplier shall not deviate more than mm in the width and ±5 m in the length from the
ordered size.
5.2 Sheets
Sheet sizes shall be as agreed upon between the user and supplier. The size of the sheet
+20
delivered shall not deviate more than mm from the ordered size.
5.3 Cut panels
Cut panel sizes shall be as agreed upon between the user and supplier. The size of the cut
panels delivered shall not deviate more than ±3 mm from the ordered size.

– 10 – 61249-4-1 © IEC:2008
6 Quality assurance
6.1 Quality system
The supplier shall operate a quality system, ISO 9000 or similar, to support quality
conformance inspection. The supplier shall maintain a Management System for Environmental
Control in compliance with ISO 14001 or similar, to support environmental considerations.
6.2 Responsibility for inspection
The supplier is responsible for all inspection of the manufactured material. Inspection is
auditable by the purchaser or an appointed third party.
6.3 Qualification inspection
Prepregs furnished under this specification shall be qualified. Qualification testing shall be
performed to demonstrate the manufacturer’s ability to meet the requirements of this standard.
Qualification testing shall be conducted at a laboratory compliant with IEC laboratory
requirements. The manufacturer shall retain on file the data which supports that the materials
meet this specification and shall be readily available for review upon request.
6.4 Quality conformance inspection
The supplier shall operate a quality plan to assure product conformance to this standard.
Such a quality plan, when appropriate, should utilize statistical methods rather than lot-by-lot
inspection. It is the responsibility of the supplier based on the quality plan to determine the
frequency of test to assure conforming products.
A combination of the following techniques may be used to show compliance with the
requirements which can be used to reduce the frequency of testing. The data supporting the
reduction of testing frequency shall be available for review upon request:
• in process parameter control;
• in process inspection;
• periodic final inspection;
• final lot inspection.
6.5 Certificate of conformance
The supplier shall on request from the purchaser issue a certificate of conformance to this
standard in electronic or paper format.
6.6 Safety data sheet
A safety data sheet in accordance with ISO 11014-1 shall be available for products
manufactured and delivered against this standard.
7 Packaging and marking
Prepreg in rolls, sheets and cut panels shall be packaged in a manner, which will provide
adequate protection against deterioration and physical damage during shipment and storage.
If not otherwise specified in the purchase order, prepreg shall be marked on the smallest
package with the manufacturer’s designation, lot number and date of manufacture.
The shipping container shall have a label that shall remain securely affixed and legible during
normal handling. Location of the label and the type of marking shall be as specified in the

61249-4-1 © IEC:2008 – 11 –
drawing or ordering data, or if not specified, shall be the supplier’s standard labelling and
marking. The following information shall be included:
a) type of material
b) manufacturer’s designation
c) lot number
d) quantity
e) dimensions
f) gross weight
g) date of manufacture
h) manufacturer’s name and address
i) date packed
8 Shelf life
Prepreg shall be capable of being stored at either of the beneath conditions for the specified
time and still be fit for its intended use.
Condition 1: Temperature ≤10 °C, relative humidity not specified
...