Multi-layer material comprising flexible graphite which is reinforced mechanically, electrically and thermally by a metal and a process for the production thereof

A multi-layer material comprises at least two layers of flexible material, including one layer based on electrically conductive, expanded recompressed graphite and another layer based on a metal, wherein the layer of graphite has at least one face thereof covered at every point by a layer of metal and in direct electrical contact with the layer of metal, and wherein the layer of metal is obtained by electrodeposition or by chemical deposit of at least one metal on the layer of graphite in such a way that the layer of metal adheres directly to the layer of graphite and closely matches the micro-relief thereof.

FIELD OF THE INVENTION 
The present invention concerns a flexible multi-layer material comprising 
expanded, recompressed graphite reinforced by a metal, which is intended 
either for the production of sealing members, or for protection from 
electromagnetic radiation, or for the production of heat sinks, and the 
process for the production thereof. 
STATE OF THE ART 
The attraction of expanded, recompressed graphite, commonly referred to as 
flexible graphite, is known in many uses and in particular as a material 
for a sealing member. However one of the problems involved in the use of 
that material is its low level of mechanical strength so that endeavours 
are made to reinforce flexible graphite by means of a layer of metal. 
Thus, German patent No. 3 309 338 describes a multi-layer material for a 
sealing member comprising a central metal reinforcement in the form of a 
strip of steel or aluminium, and two layers of flexible graphite on 
respective sides of the metal reinforcement, each layer of graphite 
covering a face of the metal reinforcement and being secured thereto by 
means of a layer of adhesive. 
Likewise European patent No. 155 083 describes a multi-layer strip for a 
sealing member comprising a central metal reinforcement formed by a strip 
of electroformed nickel or iron of small thickness, the connection between 
the reinforcement and the layers of flexible graphite being made by an 
adhesive or possibly by the use of a metal reinforcement apertured with 
holes in such a way that the two layers of flexible graphite which are 
self-sticking are in contact with each other at certain locations. 
Thus, in accordance with the prior art, the connection between the layers 
of flexible graphite and the metal reinforcement strip is made either by 
an adhesive or by mechanical means. There are increasingly numerous uses 
which require materials affording a high level of chemical, thermal and 
dimensional stability, which are used under conditions of temperature, 
pressure, chemical corrosiveness or non-contamination such that the use of 
an adhesive must be limited, if it is not prohibited. In fact, adhesives 
are products which are capable of creep, or suffering degradation for 
example by chemical attack or thermally. 
Moreover the use of a metal reinforcement with holes therethrough does not 
constitute a satisfactory solution to that problem, for three reasons: 
it does not permit the adhesion between the layers of flexible graphite and 
the mechanical strength of the multi-layer strip to be varied 
independently of each other (the greater the number of holes, the higher 
the degree of adhesion between the layers of graphite but the lower the 
level of mechanical strength of the strip); 
a joint produced from such a material is heterogenous in respect of 
thickness since locally there may or may not be a metal reinforcement 
thickness, which is not favourable in terms of a sealing effect; and 
it lends itself poorly to continuous production. 
It is known moreover that the protection of electronic equipment from 
electromagnetic radiation involves the provision of continuous conductive 
walls, for example by applying coatings of the type consisting of 
conductive paints to the enclosures of plastics material or to the walls 
of a room to be protected, or by using seals or joints consisting of 
conductive elastomers at the locations of discontinuities which are 
constituted in particular by display screens. In that use, the 
effectiveness of the protection afforded, which is characterised by 
measurement of the degree of attenuation of waves in the course of passing 
through the shielding may be estimated on the basis of measurement of its 
electrical resistance since the absorption attenuation effect is 
proportional to the square root of the electrical conductivity of the 
layer. In practice, the "resistance per square unit" which symbolically 
represented by R.quadrature. and which is equal to the quotient of 
resistivity by the thickness of the coating is currently used. Thus in the 
case of nickel-bearing paints which make it possible to achieve levels of 
attenuation effect of between 30 and 65 dB, the resistance per square unit 
is generally between 2000 and 400 m.OMEGA. respectively for a thickness of 
25 .mu.m. 
Finally, the cooling of ceramic boards must have recourse to materials 
which simultaneously exhibit good thermal conductivity and a low 
coefficient of expansion. Such a compromise in respect of characteristics 
is achieved for example with a co-rolled copper-invar-copper material, 
although the rigidity thereof is not compatible with the fragility of the 
ceramic, so that there is generally a contact between the two materials 
which does not provide for good thermal transfer. 
OBJECT OF THE INVENTION 
A first object of the invention is a multi-layer material based on flexible 
graphite reinforced by a metal with a view to improving its mechanical 
strength and in certain cases reducing its electrical resistance or 
enhancing its thermal conductivity, which permits it to be used in 
particular for the production of seals with a reduced or even zero content 
of adhesive as economic materials for shielding in relation to 
electromagnetic radiation or as particular heat sinks. 
A sheet of flexible graphite of 0.2 mm in thickness, which has a resistance 
per square unit of from 50 to 60 m.OMEGA., which, just from the electrical 
point of view, would be appropriate for shielding purposes, cannot be used 
for this application by virtue of its inadequate mechanical strength. In 
the same manner a thin sheet of copper which is 5 .mu.m in thickness and 
whose resistance per square unit is 3.5 m.OMEGA. would be perfectly 
appropriate from the electrical point of view but the use thereof either 
directly on the inside wall of enclosures of plastics material or at the 
surface of a flexible film of plastics material is delicate to carry into 
effect or even burdensome. The association of two elements consisting of 
flexible graphite and a thin sheet of conducting metal, typically copper, 
then makes it possible simultaneously to achieve under economic conditions 
a low level of electrical resistance and a high degree of facility of 
handling. 
The same flexible graphite-copper association also presents an array of 
attractive properties: good thermal conductivity, a low coefficient of 
expansion and a high degree of flexibility. That array of characteristics 
is particularly suitable for thermal transfer situations. 
Another object of the invention is a process for the economic production of 
multi-layer materials based on flexible graphite which is reinforced by a 
metal. 
DESCRIPTION OF THE INVENTION 
According to the invention the multi-layer material is formed by at least 
two layers of flexible materials of which one, identified by the letter C 
in this description, is based on expanded, recompressed graphite while the 
other is a layer of metal, characterised in that at least one of the faces 
of the layer of material C based on electrically conductive flexible 
graphite is covered at all points on its surface by a layer of metal M and 
is in direct electrical contact with said layer of metal M, and that said 
layer of metal M is produced by electrodeposit or by chemical deposit of 
metal M on said layer of material C in such a way that the metal M 
directly to the layer of material C and closely matches the micro-relief 
thereof. 
For the sake of convenience the same symbol will be used in this 
application to identify a material and the layer formed by said material. 
According to the invention the material C is an electrically conductive 
flexible graphite which is known for example by the name PAPYEX, being a 
registered trademark (R) of the company LeCarbone Lorraine, of a specific 
gravity of between 0.3 and 1.5 and being of a thickness of between 0.1 and 
10 mm, depending on the final use. That material is manufactured 
industrially and occurs in the form of a wound strip of great length and 
of a width which can exceed 1 m. 
The metal M which is deposited on the layer of flexible material C is 
selected from metals which can be electrodeposited or which can be 
deposited by chemical means. If the final use requires good resistance to 
corrosion on the part of the metal M, nickel will preferably be selected 
while in the opposite case, other metals will equally be appropriate: 
copper, zinc, iron etc. Nickel is preferred in a sealing member use while 
copper which is a better electrical and thermal conductor will preferably 
be employed for electromagnetic shielding or heat sink uses. 
The thickness of the layer of metal M is adapted either to the desired 
mechanical strength or to the desired electrical or thermal conductivity. 
It is generally between 1 and 200 mm and is preferably between 3 and 50 
.mu.m. For example, if there is a wish for a material having elevated 
mechanical characteristics, the thickness of the layer of metal M will be 
increased and conversely, the thickness of the layer of metal M will be 
chosen thin if flexibility of the multi-layer material is a priority 
consideration. 
If the situation involves using the electrical characteristics of the 
multi-layer material for shielding purposes, it appears that a layer of 
copper of a few .mu.m is sufficient to reduce the initial resistance of 
the flexible graphite so that it is superfluous, just from the electrical 
point of view, to deposit more than 5 .mu.m of copper or more than 15 
.mu.m of nickel. 
It is found that the adhesion of the metal M which is electro-deposited or 
deposited chemically on the layer of flexible material C is excellent and 
is superior to the internal cohesion of the layer C, at the usual specific 
gravities of the latter: the inter-layer adhesion of the multi-layer 
material M/C is greater than the internal cohesion of the material C (M/C 
represents the succession of the layers of materials along the axis which 
is perpendicular to the plane of the strip of multi-layer material and 
designates that strip of multi-layer material itself). 
The multi-layer materials of type C/M or M/C/M can be used as they are as a 
material for sealing members, for electromagnetic shielding or for heat 
sink purposes, but in certain cases better results will be achieved with 
more complex multi-layer materials comprising a greater number of layers. 
For that purpose, at least one of the two faces of a multi-layer material 
of type C/M or M/C/M is covered with a joining or bonding layer L of a 
thickness of between 1 and 10 .mu.m, so as to be able to secure said face 
to another layer either of metal M or of flexible material C. 
In accordance with a first embodiment of the invention the bonding layer L 
is formed by a metal LM having a melting point which is lower than that of 
the metal M serving as reinforcement, the layer of metal LM being 
deposited by any known means on at least one of the faces of the 
multi-layer materials C/M or M/C/M which were obtained previously so as to 
provide the following multi-layer materials: C/M/LM, LM/C/M, LM/C/M/LM, 
LM/M/C/M, LM/M/C/M/LM. The thickness of the layer of metal LM may be very 
small, between 1 and 5 .mu.m, that layer not acting as a structural 
material intended to impart mechanical characteristics but only acting as 
a layer for bonding purposes or to provide protection from oxidation of 
the metal M. 
The bonding metal LM is selected in dependence on the reinforcing metal M. 
If the latter is nickel or copper, the bonding metal used may be tin or a 
soft brazing alloy containing for example tin, lead or indium. 
The multi-layer materials of which at least one of the faces is formed by 
bonding metal LM may also be used as they are as materials for seals, as 
materials for electromagnetic shielding or as a heat sink. Thus for 
example they can be applied to a metal support and they can be caused to 
adhere to the support by heating and a light pressure, which are applied 
for example by means of an ironing iron. 
However, when using the material as a material for a sealing member in 
particular, the association of a plurality of layers of flexible material 
C may be desirable, in particular in order to provide a multi-layer 
material whose two external faces are of flexible material C, being a 
material which is chemically more inert than metals. 
In order to illustrate some possible modes of association, the following 
multi-layer materials may be mentioned: C/M/LM/C, C/LM/C/M, C/LM/C/M/LM/C, 
C/LM/M/C/M, C/LM/M/C/M/LM/C, C/M/LM/M/C, C/M/LM/C/LM/M/C, C/M/LM/C/M/LM/C, 
C/LM/C/M/LM, C/LM/M/C/LM. 
FIG. 4 illustrates the multi-layer material C/M/LM/M/C. 
FIG. 6 illustrates the multi-layer material C/M/LM/C. 
FIG. 7 illustrates the multi-layer material C/LM/M/C/M/LM/C. 
This first embodiment of the invention makes it possible to provide a 
multi-layer material which is totally free from thermolabile organic 
material. 
In accordance with a second embodiment of the invention the bonding layer L 
is a layer of adhesive LA which is capable of causing adhesion of a layer 
of metal M and a layer of flexible material C. The adhesive LA is selected 
from known adhesives for adhering to carbon-bearing surfaces and to metals 
and alloys and is preferably based on phenol, epoxy, polyimide, acrylic 
and polyurethane resin. That thus provides the following multi-layer 
materials by the deposit of adhesive LA on at least one face of the 
multi-layer materials C/M or M/C/M: LA/C/M, C/M/LA, LA/C/M/LA, LA/M/C/M, 
LA/M/C/M/LA. The thickness of the layer is between 10 and 1 .mu.m and will 
preferably be less than 5 .mu.m. 
Generally those multi-layer materials having at least one of the two faces 
covered with a layer of adhesive LA cannot be handled as such and are 
stuck to a layer of flexible material C which may be different from the 
initial layer of flexible material C in regard to thickness and/or 
specific gravity, to give the following multi-layer materials: C/LA/C/M, 
C/LA/M/C/M, C/LA/C/M/LA/C, C/LA/M/C/M/LA/C. However it is possible for the 
adhesive LA chosen to be an adhesive of the "hot-melt" type, that is to 
say an adhesive which can be applied hot and which after cooling gives a 
layer which is non-adhesive and therefore handleable but which can be 
reactivated by reheating. In that case the multi-layer materials having an 
external layer of adhesive LA can be handled and stored. 
FIG. 2 illustrates the multi-layer material C/M/LA/C. 
FIG. 3 illustrates the multi-layer material C/LA/M/C/M/LA/C. 
The multi-layer materials according to the invention occur in the form of a 
strip which is wound in a roll or in the form of stackable formats, 
depending on the final use and depending on the flexibility of the 
multi-layer material. For the majority of uses envisaged, the multi-layer 
material in strip or format form will be subjected to a further cutting 
operation. In the case of electromagnetic shielding for enclosures or 
rooms however the multi-layer material may be used as it is by juxtaposing 
successive strips as if it were wallpaper. 
In order to facilitate the work to be done by the user, it is important for 
the multi-layer material to be provided with means which permit 
positioning thereof or fixing thereof to the support chosen by the final 
user. With that aim in mind the multi-layer material of the invention may 
have an external layer of adhesive for permitting fixing thereof to the 
usual materials: plastics materials, glass, metal, wood, plaster, paper, 
etc. . . . , and in that case, the multi-layer material of the invention 
may be in the form of a commercially available adhesive strip. 
The adhesive may be of the "hot-melt" type and in that case the multi-layer 
material, for example in the form of formats or sheets, which does not 
stick at ambient temperature, can be applied to the support chosen by the 
user, for example by means of an ironing iron. 
Another mode of procedure involves depositing an external layer of adhesive 
which is active at ambient temperature and covering it with a peelable 
film in such a way that it can be wound in the form of a roll if it is in 
strip form, or it can be stacked if it is in the form of formats or 
sheets, without involving any problem in regard to sticking thereof when 
removing it from the roll or from the stack. Paper or a plastics material 
can be used as the material of the peelable film. 
The multi-layer materials according to the invention make it possible to 
provide sealing members which exhibit excellent resistance to crushing. 
Reference may be made for example to the crushing curve (FIG. 8) of a 
joint obtained with the material prepared in Example 1. 
The materials according to the invention are particularly well suited to 
the production of electromagnetic shielding joints which are used for 
example at the locations of discontinuities such as the opening systems or 
the display screens. They can also be used for covering the walls of a 
room when it is to be converted into a Faraday cage. 
The materials according to the invention are particularly suitable for the 
manufacture of heat sinks formed for example by a format or sheet of 
flexible multi-layer material of type M/C/M or LM/M/C/M/LM, to the two 
faces of which two ceramic boards to be cooled are applied or brazed. 
A second object of the invention is a process for the economic production 
of multi-layer material, whether it is in the form of a strip or a format 
or sheet. 
According to the invention the metal M is deposited on at least one face of 
a layer of flexible material C which is generally in strip form. 
That deposit operation can be effected by electrodeposit: a layer of metal 
M is deposited on the electrically conductive flexible material C which 
serves as a cathode by the electrolytic reduction of a soluble salt of 
that metal M which is contained in the bath: in the case of nickel 
deposit, it is possible to use nickel sulphamate but other salts are 
equally suitable. That deposit procedure is known per se and is described 
in "Techniques de l'ingenieur" - M 1610. It is thus possible to produce 
the products C/M and M/C/M depending on whether a deposit was formed on 
one or both faces of the layer of flexible material C. 
The current densities applied may vary within a wide range and affect the 
speed of deposit of the metal. The treatment time is selected in such a 
way as to produce the required thickness of metal. 
It is also possible to produce the deposit of metal by a chemical 
procedure. In that case, reduction of the cation of the metal to be 
deposited is effected by a chemical reducing agent. When depositing 
nickel, the most widely used reducing agents are hypophosphite, compounds 
of boron, hydrazine or salts thereof. 
Those deposits, by an electrodeposit process or by a chemical procedure, 
are preferably produced on a strip of flexible graphite (material C) of a 
width which can exceed 1 m and with automatic monitoring and regulation of 
the chemical and/or electrical parameters of the bath as well as the speed 
of movement of the strip so as to produce a layer of metal M of regular 
and predetermined thickness. 
In order to produce multi-layer materials which are better suited to their 
final use, at least one face of the multi-layer materials M/C or M/C/M may 
be covered with bonding metal LM. For that purpose the bonding metal LM 
may be deposited by an electrodeposit process in a bath containing a 
soluble salt of the metal LM, as described in "Techniques de l'ingenieur" 
- M 1620 and 2020, in the case of tin. 
It is also possible to produce a deposit by a chemical procedure, in 
particular when using tin. Whether the deposit of metal LM is produced 
chemically or electrochemically, it is advantageous, as in the case of 
depositing the metal M, for it to be produced continuously with automatic 
monitoring of the bath, and on strips of a great width which can exceed 1 
m. The baths for the electrolytic deposit or chemical deposit of metal M 
and metal LM may advantageously be disposed in series. 
It is thus possible to produce the following multi-layer materials: C/M/LM, 
LM/C/M, LM/C/M/LM, LM/M/C/M, LM/M/C/M/LM. 
There are other procedures for depositing metal M or LM which can be used 
for carrying the invention into effect, such as immersion in a molten 
metal bath or deposit by the spraying of liquid metal, by thermal 
projection, deposits under vacuum or CVD (chemical vapour deposition) but 
often those procedures do not permit continuous treatment of a strip of 
great length or they do not make it possible to master the small 
thicknesses required while in addition they are often more burdensome than 
the preferred procedures of the invention. 
In the case where the bonding effect is produced by adhesive LA, the 
deposit of the layer of adhesive LA is produced by any known process, for 
example by coating followed by sticking, so as to produce for example the 
product C/M/LA/C from a strip of C/M and a strip of C, in a single passage 
of the strip, thus providing for deposit and assembly of the materials. In 
the case of a multi-layer material comprising two layers of adhesive LA, a 
double-face application is produced and the material is assembled by 
sticking the different parts of the multi-layer material: thus for example 
C/LA/M/C/M/LA/C is produced in a single passage by application of the 
adhesive LA to the two faces of M/C/M, followed by sticking in line of a 
layer of flexible material C on each face. 
It is however possible to produce a deposit of adhesive LA without having 
it followed directly by a sticking phase. In that case the adhesive is of 
the "hot-melt" type. That situation may occur when the adhesive is applied 
to a strip continuously and it is necessary to effect assembly and final 
sticking in format or sheet form, in a discontinuous procedure, for 
example by virtue of the final thickness of the multi-layer material being 
excessive. 
Preferably the adhesive LA, irrespective of its chemical nature, is 
deposited continuously and with monitoring and regulation of the deposited 
thickness. It is possible to deposit a layer of adhesive LA which is 
continuous in a plane by coating or spraying. 
However it may be preferable to have a layer of adhesive which is 
discontinuous but regularly distributed, typically being in the form of a 
grid of fine mesh size, each mesh having a side length in the case of a 
square shape which can be between 0.1 and 10 mm, so as to have a degree of 
covering of the surface to be covered by the adhesive of between 5 and 50% 
of said surface; reference may be made to FIG. 11. 
That type of discontinuous deposit is typically produced by screen 
printing. The advantages of a discontinuous deposit with a mesh 
configuration are as follows: reduction in the weight of adhesive 
deposited in relation to surface area, which is an attractive 
consideration both in terms of a saving on expensive material and as a 
reduction in the risk of pollution by organic materials which are raised 
to high temperatures, while in addition the fine mesh configuration 
results in the formation of a very large number of small "dishes", the rim 
of which is formed by the adhesive LA and which are isolated from each 
other in such a way that the sealing effect with that type of deposit is 
superior to that obtained with a deposit of uniform thickness, a preferred 
linkage path never being excluded in the latter situation. 
The multi-layer materials of which at least one face is formed by a bonding 
layer LM or LA are assembled to at least one layer of flexible material C, 
sometimes with themselves, in such a way that the bonding layer LM or LA 
becomes an internal layer, but, with certain types of adhesives LA, the 
deposit and assembly operations are performed virtually simultaneously, as 
mentioned hereinbefore. Generally speaking the assembly operation is 
effected either continuously by passing movement of the materials to be 
joined together, in the form of a strip, between pressing cylinders, or by 
a discontinuous procedure using a press from materials to be assembled 
which have been cut into formats or sheets, with an assembly pressure of 
between 1 and 100 MPa depending on the assembly procedures used and the 
materials to be assembled, and with an assembly temperature of lower than 
600.degree. C. in the case of a bonding layer of type LM and lower than 
300.degree. C. in the case of a bonding layer of type LA. 
Discontinuous assembly is effected by means of a press at a temperature 
which is slightly higher than the melting temperature of the metal LM or 
the activation temperature of the adhesive LA. For example that 
temperature is 240.degree. C. when the metal LM is tin which melts at 
232.degree. C. The assembly pressure is of the order of 30 MPa. 
Continuous assembly is effected by passing the array of layers of the 
multi-layer material, which are possibly preheated, between two heated 
cylinders and applying a pressure thereto so as locally to produce 
substantially the same conditions in respect of temperature and pressure 
as in the discontinuous assembly process. 
In the case of a bonding metal LM, it is also possible according to the 
invention simultaneously to provide for the deposit of metal LM and 
assembly of the various layers by spraying molten liquid metal between the 
layers to be assembled, which have been preheated beforehand, that 
operation being followed by cooling of the assembly; see FIG. 9. 
Generally speaking, the thickness of the multi-layer material varies little 
as a result of the compression effect insofar as the pressure applied is 
not greater than that to which the flexible material C has already been 
subjected. 
In the case of multi-layer materials produced in accordance with the 
invention and comprising on one of the two faces an adhesive which is 
intended to facilitate, from the point of view of the final user, the 
operation of positioning the multi-layer material or the joint or seal 
produced from that material, it is advantageous, as in the case of the 
deposit of adhesive LA, to deposit a layer of the adhesive, which is 
discontinuous but regularly distributed, preferably by means of a screen 
printing process, which makes it possible to produce a deposit in the form 
of a grid of fine mesh size, so as to provide a degree of covering of the 
surface to be covered of between 5 and 50% thereof. 
In addition to the advantages already mentioned above, in regard to the 
deposit of adhesive LA by means of the same procedure, that process has 
the advantage of not electrically insulating the subjacent layer, which is 
an attractive consideration in regard to the electromagnetic screening 
use. In addition when the external layer of adhesive is covered by a 
peelable film, a film of small thickness can be used without being torn 
when peeled off. 
The process according to the invention has many advantages, in particular: 
it permits metal M to be deposited directly on the layer of flexible 
material C, which makes it possible to eliminate a bonding layer, in 
particular an adhesive-based bonding layer, which is a favourable 
consideration in regard to many uses; 
the direct deposit of metal M on the layer of flexible material C permits 
the material to adapt to and closely match the micro-roughness of the 
surface of the flexible material C, which contributes to excellent 
adhesion between those two layers, hence affording the possibility of 
handling the multi-layer material and the final joint or seal without the 
risk of causing damage thereto; 
the deposit of metal LM makes it possible to produce a multi-layer material 
without any adhesive, which opens new areas of use in particular when the 
sealing members are to be used at high temperature and under conditions of 
non-contamination, for example in the electronic industry. In addition, 
with that type of joint, the risk of creep is totally eliminated; 
the procedures used for deposit of the metal M make it possible to provide 
as desired and in accordance with requirements a multi-layer material with 
the optimum thickness of metal M and of uniform thickness whereas the 
prior art requires stocks of strips of metal of different thicknesses to 
be kept; 
finally the process according to the invention permits a high degree of 
productivity since: 
the different phases of the process can be carried out continuously and 
over a great width which is at least equal to 1 m whereas electroformed 
nickel strips are available in a width not exceeding 50 cm; 
all of the phases of the process can be carried out in a line and in a 
single passage of the different layers of material; and 
the different phases of the process can be easily automated and regulated, 
thus permitting easy quality control. 
To sum up, the invention permits the flexible and economic manufacture of 
multi-layer materials which are versatile in terms of their use, whether 
they are materials for fluid-tight seals, whether they are for providing a 
sealing effect in relation to electromagnetic waves or whether the 
situation involves promoting heat transfer effects. These materials can 
also meet severe requirements and in particular requirements in respect of 
non-contamination at medium to elevated temperatures.

EXAMPLES 
Example 1 
In a nickel sulphamate nickel-plating bath, a 10 .mu.m layer of nickel was 
deposited on each face of a sheet of flexible graphite (Papyex - 
registered trademark) of a thickness of 0.5 mm. Each face of the sheet 
when nickel-plated in that way was coated with an epoxy resin-based 
adhesive, to which a sheet of flexible graphite 0.5 mm in thickness was 
applied (see FIG. 3). That resulted in a material which was 1.5 mm in 
thickness. The crushing tests under a load of 100 MPa as well as the 
sealing tests in respect of a joint or seal produced with that material 
are excellent (see FIG. 8). 
Example 2 
A sheet of flexible graphite measuring 0.5 mm in thickness was 
nickel-plated over one face to a thickness of 10 .mu.m as in Example 1 and 
then the nickel-plated face was plated with a thickness of 1 .mu.m of tin. 
A second sheet of 0.5 mm flexible graphite was assembled to the preceding 
sheet (tin side) in the hot condition at 240.degree. C. and under a 
pressure of 30 MPa. After cooling, the result obtained was a material 
measuring 1 mm in thickness (see FIG. 6). The crushing tests in respect of 
a seal produced with that material are excellent under a loading of 100 
MPa. 
Example 3 
Two sheets of flexible graphite measuring 0.5 mm in thickness were 
nickel-plated, each on one face to a thickness of 5 .mu.m, then each 
nickel-plated face was plated with a thickness of 1 .mu.m of tin. Those 
two sheets were then pressed together under 30 MPa at a temperature of 
240.degree. C., with the plated faces being in contact with each other. 
After cooling the result is a multi-layer material measuring 1 mm in 
thickness, of the structure C/M/ML/M/C; see FIG. 5. 
Example 4 
A sheet of flexible graphite measuring 0.5 mm in thickness was 
nickel-plated to a thickness of 5 .mu.m and then tin-plated to a thickness 
of 1 .mu.m on its two faces. Two sheets of flexible graphite measuring 0.5 
mm in thickness were applied on respective sides of the nickel-plated and 
tin-plated graphite sheet. Those three sheets were pressed under a loading 
of 30 MPa at 240.degree. C. After cooling the result obtained was a 
multi-layer material of a thickness of 1.5 mm; see FIG. 7. The crushing 
tests under a loading of 100 MPa in respect of joints produced with the 
materials of Examples 3 and4 gave excellent results. 
Example 5 
A sheet of flexible graphite measuring 0.2 mm in thickness was 
nickel-plated to different thicknesses on one face. The resistance 
R.quadrature. of the material was then measured (resistance in a direction 
parallel to the sheet of a square with a side length of 50 .mu.m): 
______________________________________ 
Test No. Thickness Ni (.mu.m) 
R(m.OMEGA.) 
______________________________________ 
5-1 5 13.5 
5-2 10 7.3 
5-3 15 5.0 
______________________________________ 
Those materials are suitable for electromagnetic shielding and as a heat 
sink. 
Example 6 
This Example only differs from Example 5 in that the sheet of flexible 
material is 0.5 mm in thickness instead of 0.2 mm. 
______________________________________ 
Test No. Thickness Ni (.mu.m) 
R(m.OMEGA.) 
______________________________________ 
6-1 5 12.0 
6-2 10 6.8 
6-3 15 4.3 
______________________________________ 
Those materials are suitable for electromagnetic shielding and as a heat 
sink. 
Example 7 
A sheet of flexible graphite measuring 0.2 mm in thickness was 
copper-plated to different thicknesses on one face and then the resistance 
was measured as in Example 5. 
______________________________________ 
Test No. Thickness Cu (.mu.m) 
R(m.OMEGA.) 
______________________________________ 
7-1 2 49.0 
7-2 5 3.3 
7-3 7 2.3 
______________________________________ 
These materials are suitable for electromagnetic shielding and as a heat 
sink. 
Example 8 
Example 8 differs from Example 7 only in regard to the thickness of the 
sheet of graphite of 0.5 mm instead of 0.2 mm in Example 7. 
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Test No. Thickness Cu (.mu.m) 
R(m) 
______________________________________ 
8-1 2 21.0 
8-2 5 4.5 
8-3 7 2.3 
______________________________________ 
These materials are suitable for electromagnetic shielding and as a heat 
sink.