U.S. patent application number 14/650331 was filed with the patent office on 2015-10-29 for method for connecting at least two components using a sintering process.
This patent application is currently assigned to Robert Bosch GmbH. The applicant listed for this patent is ROBERT BOSCH GMBH. Invention is credited to Andrea Feiock, Michael Guenther.
Application Number | 20150306669 14/650331 |
Document ID | / |
Family ID | 49304996 |
Filed Date | 2015-10-29 |
United States Patent
Application |
20150306669 |
Kind Code |
A1 |
Guenther; Michael ; et
al. |
October 29, 2015 |
METHOD FOR CONNECTING AT LEAST TWO COMPONENTS USING A SINTERING
PROCESS
Abstract
The invention relates to a method for connecting at least two
components (18, 20) using a sintering process. The aim of the
invention is to improve the sintering process. This is achieved in
that the method has the following method steps: a) providing a
starting material (10) of a sintering compound (22), comprising
particles (12) which can be sintered and have at least one metal or
at least one metal compound and comprising at least one polymeric,
polymerizable, and/or monomeric organic compound (14), wherein the
polymeric, polymerizable, and/or monomeric compound (14) has a flow
temperature which is higher than or equal to the room temperature
and lower than the sintering temperature, and the polymeric,
polymerizable, and/or monomeric organic compound (14) further has a
desorption temperature which is higher than the flow temperature
and lower than or equal to the sintering temperature; b) arranging
the starting material (10) between two components (18, 20) to be
connected; c) heating the starting material (10) to a temperature
(T1) which is higher than or equal to the flow temperature of the
polymeric, polymerizable, and/or monomeric organic compound (14)
and lower than the desorption temperature of the polymeric,
polymerizable, and/or monomeric organic compound (14) for a period
of time (t1); and d) heating the starting material (10) to a
temperature (T2) which is higher than or equal to the sintering
temperature of the particles (12) which can be sintered, optionally
under the influence of a sintering pressure, for a period of time
(t2), thereby forming a sintering compound (22).
Inventors: |
Guenther; Michael;
(Stuttgart, DE) ; Feiock; Andrea; (Pliezhausen,
DE) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
ROBERT BOSCH GMBH |
Stuttgart |
|
DE |
|
|
Assignee: |
Robert Bosch GmbH
Stuttgart
DE
|
Family ID: |
49304996 |
Appl. No.: |
14/650331 |
Filed: |
October 9, 2013 |
PCT Filed: |
October 9, 2013 |
PCT NO: |
PCT/EP2013/070991 |
371 Date: |
June 8, 2015 |
Current U.S.
Class: |
156/89.16 ;
156/89.28; 228/248.1 |
Current CPC
Class: |
B22F 7/064 20130101;
B22F 7/008 20130101; B22F 1/0059 20130101; B22F 1/0062 20130101;
B23K 35/0244 20130101; H01L 2924/12044 20130101; H01L 2224/29299
20130101; H01L 24/83 20130101; B22F 7/08 20130101; H01L 2924/12044
20130101; B23K 35/025 20130101; H01L 2924/00 20130101; H01L
2224/32013 20130101; H01L 2224/29399 20130101; B22F 7/062 20130101;
H01L 2224/29006 20130101; H01L 24/29 20130101; H01L 2224/8384
20130101; H01L 2224/2929 20130101 |
International
Class: |
B22F 7/06 20060101
B22F007/06; B22F 1/00 20060101 B22F001/00; B22F 7/00 20060101
B22F007/00 |
Foreign Application Data
Date |
Code |
Application Number |
Dec 6, 2012 |
DE |
10 2012 222 416.5 |
Claims
1. A method for connecting at least two components (18, 20) using a
sintering process, comprising: a) providing a starting material
(10) of a sintered connection (22), comprising sinterable particles
(12), comprising at least one metal or at least one metal compound,
and at least one polymeric, polymerizable and/or monomeric organic
compound (14), wherein the polymeric, polymerizable and/or
monomeric organic compound (14) has a flow temperature that is
greater than or equal to room temperature and less than a sintering
temperature of the sinterable particles, and wherein the polymeric,
polymerizable and/or monomeric organic compound (14) also has a
desorption temperature that is greater than the flow temperature
and less than or equal to the sintering temperature; b) arranging
the starting material (10) between two components (18, 20) to be
connected; c) heating the starting material (10) to a temperature
T1, which is greater than or equal to the flow temperature of the
polymeric, polymerizable and/or monomeric organic compound (14) and
less than the desorption temperature of the polymeric,
polymerizable and/or monomeric organic compound (14), for a time
t1; and d) heating the starting material (10) to a temperature T2,
which is greater than or equal to the sintering temperature of the
sinterable particles (12), for a time period t2, thereby forming a
sintered connection (22).
2. The method as claimed in claim 1, wherein the desorption
temperature is a boiling temperature, a decomposition temperature
or a reaction temperature of the polymeric, polymerizable and/or
monomeric organic compound (14) with the sinterable particles
and/or with sintered particles (12).
3. The method as claimed in claim 1, wherein the sinterable
particles (12) contain silver, gold, platinum, palladium and/or
copper, an organic metal compound, a metal oxide, or a mixture
comprising one or more of the aforementioned substances.
4. The method as claimed in claim 1, wherein the polymeric,
polymerizable and/or monomeric organic compound (14) comprises a
polyolefin, a polyethylene copolymer, a polyketone or a mixture
comprising one or more of the aforementioned substances.
5. The method as claimed in claim 1, wherein the polymeric,
polymerizable and/or monomeric organic compound (14) forms a
matrix, in which the sinterable particles (12) are embedded, or
wherein the polymeric, polymerizable and/or monomeric organic
compound (14) takes the form of a coating on the sinterable
particles (12).
6. The method as claimed in claim 1, wherein the starting material
(10) is applied to at least one component to be connected by
printing, doctor blading or dispensing.
7. The method as claimed in claim 1, wherein the starting material
(10) has a transfer layer (24), which is arranged between at least
two protective layers (26, 28).
8. The method as claimed in claim 7, wherein the protective layers
(26, 28) are removed before or during method step b).
9. The method as claimed in claim 7, wherein the protective layers
(26, 28) comprise polyethylene terephthalate.
10. The method as claimed in claim 1, wherein the starting material
(10) is provided in the form of a paste, a powder, granules or a
film.
11. The method as claimed in claim 1, wherein the polymeric,
polymerizable and/or monomeric organic compound (14) is discharged
or removed during or after method step c).
12. The method as claimed in claim 1, wherein the polymeric,
polymerizable and/or monomeric organic compound (14) contains at
least one additive that reacts with the sinterable particles (12),
while reducing the sintering temperature.
13. The method as claimed in claim 1, wherein a sintered connection
(22) that has an electrical conductivity of from greater than or
equal to 30 MS/m is produced, and/or wherein a sintered connection
(22) that has a thermal conductivity of from greater than or equal
to 200 W/mK to less than or equal to 300 W/mK is produced.
14. The method as claimed in claim 1, wherein an electronic
component is used as one of the components to be connected and a
substrate is used as another of the components (20) to be
connected.
15. The use of a method as claimed in claim 1 for producing an
electronic component.
16. The method as claimed in claim 1, wherein method step d)
includes heating the starting material (10) to a temperature T2
under the effect of a sintering pressure.
17. The method as claimed in claim 1, wherein the sinterable
particles (12) contain silver, gold, platinum, palladium and/or
copper, an organic metal compound, comprising silver carbonate,
silver lactate or silver stearate, a metal oxide, comprising silver
oxide, or a mixture comprising one or more of the aforementioned
substances.
18. The method as claimed in claim 1, wherein the polymeric,
polymerizable and/or monomeric organic compound (14) comprises a
polyolefin, comprising polyethylene and/or polypropylene, a
polyethylene copolymer, a polyketone or a mixture comprising one or
more of the aforementioned substances.
19. The method as claimed in claim 1, wherein the starting material
(10) has a transfer layer (24), which is arranged between at least
two protective layers (26, 28), comprising a polymeric,
polymerizable and/or monomeric organic compound.
20. The method as claimed in claim 1, wherein the polymeric,
polymerizable and/or monomeric organic compound (14) contains at
least one additive that reacts with the organic metal compound,
while reducing the sintering temperature.
21. The method as claimed in claim 1, wherein a sintered connection
(22) that has an electrical conductivity of from greater than or
equal to 30 MS/m to less than or equal to 45 MS/m is produced,
and/or wherein a sintered connection (22) that has a thermal
conductivity of from greater than or equal to 200 W/mK to less than
or equal to 300 W/mK is produced.
22. The method as claimed in claim 1, wherein a sintered connection
(22) that has an electrical conductivity of from greater than or
equal to 36 MS/m to less than or equal to 44 MS/m is produced,
and/or wherein a sintered connection (22) that has a thermal
conductivity of from greater than or equal to 220 W/mK to less than
or equal to 275 W/mK is produced.
23. The method as claimed in claim 1, wherein an electronic
component is used as one of the components to be connected and a
substrate, comprising a copper compound, is used as another of the
components (20) to be connected.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates to a method for connecting at
least two components using a sintering process.
[0002] Power electronics are used in many areas of technology.
Especially in electrical or electronic devices, in which great
currents flow, the use of power electronics is indispensable. The
current intensities that are necessary in power electronics lead to
a self-heating of the electrical or electronic components
contained. In addition, the components of power electronics can be
used at locations that are constantly subjected to an elevated
temperature. Control devices in the automotive sector, which are
arranged directly in the engine compartment or in the transmission
compartment, may be mentioned as examples. In this case, the
control device is also exposed to a continual change of
temperature, whereby the electrical and/or electronic components
contained undergo great thermal loading. Generally, temperature
changes in a range up to a temperature of 200.degree. C. are usual.
However, operating temperatures that go beyond this are also
increasingly being required. As a result, altogether increased
requirements are being demanded of the reliability and functional
dependability of electrical or electronic devices with power
electronics.
[0003] Electrical or electronic components are usually joined
together--for example on a carrier substrate--by a connecting
layer. Soldered connections, for example lead-free soldered
connections of tin-silver or tin-silver-copper, are known as such
connecting layers. In cases of higher operating temperatures,
lead-containing soldered connections can be used. However, for
reasons of environmental protection, lead-containing soldered
connections are greatly restricted with respect to their
permissible technical applications by legal regulations.
Alternatively, lead-free hard solders are suitable for use at
elevated or high temperatures, in particular over 200.degree. C.
Lead-free hard solders generally have a higher melting point than
200.degree. C.
[0004] Sintered connections, which can already be processed at low
temperatures and are nevertheless suitable for operation at
elevated temperatures, are also used. Such sintered connections
offer the advantage of an increased selection of electrical or
electronic components that come into consideration as parts to be
joined on account of the lower processing temperature. Also
advantageous in the case of sintered connections is that no creep
takes place in the connecting layer, and consequently no crack
formation, whereby failure of an assembly having such a connection
can be reduced further.
[0005] Thus, the patent application DE 10 2007 046 901 A1 shows
such sintered connections. To produce a sintered connection, a
starting material in paste form comprising readily decomposable
silver compounds and silver flakes or nano silver is used.
Furthermore, copper for example may be contained in the starting
material.
[0006] The document EP 2 278 593 A1 discloses a sintered connection
which is produced from a paste that contains particles of a silver
compound.
[0007] The document US 2008/0211095 A1 also discloses a
semiconductor component which has a connection between a
semiconductor element and an electrode that is formed by an
electrically conductive adhesive.
[0008] The document U.S. Pat. No. 6,832,915 B2 also discloses a
thermally conductive adhesive connection between two
components.
[0009] The document DE 10 2007 27 999 A1 also discloses a transfer
film for the transfer of a silver sintered layer.
[0010] The document DE 10 2004 019 567 B3 also describes a method
for securing electronic components, in which the components are
secured on a substrate by means of pressure sintering using a pasty
layer.
[0011] The document JP 63258084 A also discloses a carrier film
with a sintering paste for joining electronic components.
[0012] U.S. Pat. No. 6,951,666 shows the production of different
sintered connections. General possibilities for combining different
starting elements are thereby described. Included among the
elements mentioned as starting elements are molecular metals,
numerous metallic particles of nano or micro size, coatings,
solvents, additives, reducing agents, crystallization inhibitors,
wetting agents and others.
SUMMARY OF THE INVENTION
[0013] The subject of the present invention is a method for
connecting at least two components using a sintering process,
having the method steps of:
[0014] a) providing a starting material of a sintered connection,
comprising sinterable particles, comprising at least one metal or
at least one metal compound, and at least one polymeric,
polymerizable and/or monomeric organic compound, wherein the
polymeric, polymerizable and/or monomeric organic compound has a
flow temperature that is greater than or equal to the room
temperature and less than the sintering temperature, and wherein
the polymeric, polymerizable and/or monomeric organic compound also
has a desorption temperature that is greater than the flow
temperature and less than or equal to the sintering
temperature;
[0015] b) arranging the starting material between two components to
be connected;
[0016] c) heating the starting material to a temperature T1, which
is greater than or equal to the flow temperature of the polymeric,
polymerizable and/or monomeric organic compound and less than the
desorption temperature of the polymeric, polymerizable and/or
monomeric organic compound, for a time t1; and [0017] d) heating
the starting material to a temperature T2, which is greater than or
equal to the sintering temperature of the sinterable particles,
possibly under the effect of a sintering pressure, for a time
period t2, thereby forming a sintered connection.
[0018] The method described above can make it possible in
particular to carry out a sintering process particularly easily and
thereby produce a particularly stable and reliable sintered
connection.
[0019] For this purpose, according to a method step a), the
previously described method involves providing a starting material
of a sintered connection, comprising sinterable particles,
comprising at least one metal or at least one metal compound, and
at least one polymeric, polymerizable and/or monomeric organic
compound, wherein the polymeric, polymerizable and/or monomeric
organic compound has a flow temperature that is greater than or
equal to the room temperature and less than the sintering
temperature, and wherein the polymeric, polymerizable and/or
monomeric organic compound also has a desorption temperature that
is greater than the flow temperature and less than or equal to the
sintering temperature.
[0020] Consequently, according to method step a), first a starting
material that is intended in the further course of the method to
form the sintered connection is provided. The starting material
thereby comprises a sintering base material, which after the
sintering can represent the actual sintered connection or at least
forms a large proportion of the sintered connection. This sintering
base material may be in particular at least one metal or at least
one metal compound. Furthermore, the starting material comprises at
least one polymeric, polymerizable and/or monomeric organic
compound. The polymeric, polymerizable and/or monomeric organic
compound may in this case serve the purpose of keeping the
sintering base material together, and thus allow the starting
material to be provided for example as a compact, for example
moldable, for instance thermoplastic, molded body.
[0021] A polymeric organic compound may in this case be regarded
for example, and not restrictively, as meaning a hydrocarbon-based
compound that is polymerized. Consequently, a polymerizable organic
compound may for example, and not restrictively, be understood as
meaning such a compound, in particular a hydrocarbon-based
compound, that can in particular as a result of having specific
functional groups be subjected to a polymerization. An organic
monomeric compound may furthermore be understood for example, and
not restrictively, as meaning such a compound that likewise may be
hydrocarbon-based, but need not have any groups suitable for
polymerization.
[0022] Such provision of a starting material of a sintered
connection allows the starting material to be provided as a
transportable and storable material, which can be applied at any
time and without any special effort. In other words, the starting
material is produced in advance and stored and is supplied for use
immediately before carrying out the method. This makes possible
very dynamic and variable production processes that can be adapted
directly to the desired requirements.
[0023] In this case, the starting material may for example be
provided as a material of a large surface area, from which a
material part of a suitable size can be separated, for example
punched out or cut out, in each case before use. As a result, just
one starting material can be provided for a great range of
applications, which can improve the costs for the previously
described method still further.
[0024] Furthermore, the starting material may be provided for
instance by film casting or injection molding, initially for
example as a particularly flexible film, which keeps the handling
requirements very low. As a result, the starting material can be
handled by conventional handling systems, which can allow
particularly good incorporation of the starting material in
existing process peripherals.
[0025] In this case, during or after application of the starting
material to a component or during arrangement of the starting
material between the components to be connected, it is possible, as
described below, to adapt the starting material optimally to
potentially existing irregularities of the parts to be joined, such
as for example substrate irregularities or component
irregularities, so that a particularly intimate contact becomes
possible, which can also be accompanied by a particularly stable
sintered connection.
[0026] In this case, the polymeric, polymerizable and/or monomeric
organic compound and the sintering base material or the at least
one metal or the at least one metal compound may in particular be
made to match one another in such a way that the polymeric,
polymerizable and/or monomeric organic compound has a flow
temperature that is greater than or equal to the room temperature
and less than the sintering temperature of the sintering base
material, and wherein the polymeric, polymerizable and/or monomeric
organic compound also has a desorption temperature that is greater
than the flow temperature and less than or equal to the sintering
temperature of the sintering base material.
[0027] In the sense of the present invention, a flow temperature
may be understood in particular as meaning a specific temperature
or a temperature range from which the polymeric, polymerizable
and/or monomeric organic compound is flowable, and consequently can
flow, that is to say can remove itself from the joining zone of its
own accord by a flowing process. In this case, a flow temperature
may be understood in particular as meaning a melting temperature or
a melting range or a glass transition temperature or a glass
transition range.
[0028] By such a selection of the sintering base material or the
polymeric, polymerizable and/or monomeric organic compound,
significant advantages in conducting the process can be made
possible.
[0029] In detail, it can be made possible by the selection in
particular of the polymeric, polymerizable and/or monomeric organic
compound that the starting material has a good adhesive force, and
consequently can adhere well to the components to be joined, such
as for instance a substrate and a component, in particular because
of the polymeric, polymerizable and/or monomeric organic compound.
In other words it is possible for instance as a result of the
polymeric, polymerizable and/or monomeric organic compound or a
further auxiliary substance, such as for instance a solvent, for
the starting material to have a suitable adhesiveness that allows
the starting material to adhere to the parts to be joined. This
allows particularly good applicability, since the starting
material, once arranged, can remain securely in place. For example,
such an adhesive force or adhesiveness can be obtained at
temperatures below the flow temperature, that is to say purely by
way of example at temperatures in the range of less than or equal
to 100.degree. C.
[0030] In addition, the polymeric, polymerizable and/or monomeric
organic compound may serve the purpose of preventing cold fusing of
the particles and also of making it possible for the film material
to be shaped.
[0031] After providing a starting material designed as described
above, according to method step b) this starting material is
arranged between two components to be connected. This may take
place for example in a fully automated manner. In this case, the
starting material may for example be arranged between a substrate
and an electronic component to be secured on the substrate.
[0032] According to method step c), in a further step heating of
the starting material takes place to a temperature T1, which is
greater than or equal to the flow temperature of the polymeric,
polymerizable and/or monomeric organic compound and less than the
desorption temperature of the polymeric, polymerizable and/or
monomeric organic compound, for a time t1. This method step allows
an adhesive attachment of the starting material to the components
to be connected to be improved still further. In this case, such a
temperature T1 may, depending on the chosen polymeric,
polymerizable and/or monomeric organic compound, already lie at
temperatures of less than or equal to 100.degree. C., for instance
in a range of from greater than or equal to 30.degree. C. to less
than or equal to 80.degree. C. In detail, for example, an
adhesiveness or an adhesive force of the polymeric, polymerizable
and/or monomeric organic compound can be further increased or such
an adhesiveness can be formed in the first place by a flowability.
Consequently, in this step it can be made possible that the
starting material firmly adheres between the components to be
connected, and consequently already forms an arrangement that
already has good stability for the further sintering operation.
[0033] It can consequently be made possible by this method step
that the starting material is arranged at a desired position, and
furthermore remains there. As a result, particularly defined
products can be obtained. In this case, by increasing the
temperature beyond the flow temperature of the polymeric,
polymerizable and/or monomeric organic compound, the starting
material can be held in its position by particularly stable forces.
Consequently, an additional fixing medium is not necessary, which
allows the previously described method to be made particularly
simple and inexpensive.
[0034] Furthermore, in particular in the flowable state, the
polymeric, polymerizable and/or monomeric organic compound may
serve as a dispersing medium, in order to create a homogeneous
starting material.
[0035] In addition, it can be made possible by a flowability of the
polymeric, polymerizable and/or monomeric organic compound that the
starting material comes into close contact with the components to
be connected, and otherwise, as a result of a softening, in
particular reversible softening, of the polymeric, polymerizable
and/or monomeric organic compound as a result of the temperature
increase beyond the flow temperature, a good adaptation between the
layer of the starting material and the parts to be joined is
produced. In this way equally an intimate contact of the metallic
compound or of the sintering base material with the components to
be joined can be allowed. This may contribute to a particularly
stable arrangement being produced after a sintering process, as is
explained below.
[0036] Since, however, only a very small amount of polymeric,
polymerizable and/or monomeric organic compound is necessary for an
adhesiveness or close contactability and the fixing of the starting
material between the parts to be joined, it is possible to achieve
the further advantage that the majority of the polymeric,
polymerizable and/or monomeric organic compound is removed from the
joining zone as a result of flowability. As a result, it can be
achieved that a subsequent removal or desorption of the polymeric,
polymerizable and/or monomeric organic compound from the joining
region does not cause a development or significant development of
reaction gases that could possibly expand in the joint, and thereby
counteract the formation of a material-bonded connection.
Furthermore, for example, and depending on the desorption chosen,
no oxygen is required, whereby the sintered connection can also
take place with the exclusion of oxygen. This can avoid all the
involved parts to be joined undergoing a change or damage during a
thermal treatment. In addition, the necessity of supplying gases or
the necessity of removing gases can be prevented. It is
consequently not disadvantageous in the case of the previously
described method that, particularly in the case of connections over
a large surface area, the gas transport is limited by the
impermeability of the joining material, and consequently for
example in the case of production of a sealed connection the
material is pressed by mechanical pressure, and consequently
specifically inhibits transport of the gas. Consequently, to sum
up, the disadvantages of removal of such a matrix according to the
prior art can be prevented by a temperature increase above the flow
temperature of the polymeric, polymerizable and/or monomeric
organic compound.
[0037] The time period t1, for which the temperature T1 is
maintained, may in this case be chosen in dependence on the
starting material that is specifically used. In particular, the
time period should be chosen to be long enough for a sufficient
flowability of the polymeric, polymerizable and/or monomeric
organic compound to be realizable, and consequently for it to be
possible for the aforementioned advantages to be achieved in a
particularly advantageous way.
[0038] In a further method step d), a previously described method
involves heating the starting material to a temperature T2, which
is greater than or equal to the sintering temperature of the
sinterable particles, possibly under the effect of a sintering
pressure, for a time period t2, thereby forming a sintered
connection. In this method step, consequently, the actual sintered
connection is produced.
[0039] In this case, the particles, for example chemically
stabilized particles, are burned out, for instance until the
joining temperature or sintering temperature is reached, so that
the particles or released metal atoms can come into direct contact
with one another and with the material of the parts to be joined.
Then, a connection that is stable at high temperatures already
forms at low temperatures as a result of solid diffusion
processes.
[0040] For this purpose, the starting material is heated on its own
or together with at least one joining region of the components to
be connected to a temperature T2, for instance by a heating source
or electromagnetic radiation. In this case, the temperature T2 is
greater than or equal to the sintering temperature of the
sinterable particles, that is to say the particles comprising at
least one metal or at least one metal compound. In this case, the
temperature T2 is maintained for a predetermined time period t2,
which is sufficient for a stable sintered connection to be able to
form.
[0041] In this case, the stability of the sintered connection
formed can be increased still further by the fact that the
polymeric, polymerizable and/or monomeric organic compound also has
a desorption temperature, that is to say a specific desorption
temperature or a broad desorption temperature, that is to say a
desorption range, that is greater than the flow temperature and
less than or equal to the sintering temperature. In detail, the
polymeric, polymerizable and/or monomeric organic compound is
desorbed both by the sinterable particles and by the components to
be joined, that is to say in the sense of the present invention is
removed. In this way it can be ensured that, after the forming of
the sintered connection, it substantially comprises only the
sintered particles or sintered products thereof. Therefore, the
polymeric, polymerizable and/or monomeric organic compound does not
disturb the stability of the sintered connection, as a result of
which particularly stable products can be obtained.
[0042] To sum up, the previously described method makes possible in
particular a particularly simple and defined production of a
sintered connection between two components to be connected, with it
also being possible for the sintered connection that is formed to
be particularly stable.
[0043] Within the scope of a refinement, the desorption temperature
may be the boiling temperature, decomposition temperature or a
reaction temperature of the polymeric, polymerizable and/or
monomeric organic compound with the sinterable particles and/or
with sintered particles. In particular in this refinement, it can
be advantageously ensured that, in the case of method step d), the
polymeric, polymerizable and/or monomeric organic compound can be
removed completely, or without any residue, and the polymeric,
polymerizable and/or monomeric organic compound consequently does
not adversely influence the stability of the sintered connection.
The fact that at least a certain proportion or advantageously a
majority of the polymeric, polymerizable and/or monomeric organic
compound is no longer arranged in the direct joining zone during
method step d) means that even a vaporization, decomposition or
combustion or a reaction, such as for instance an oxidation, by a
constituent part of the sintering material, of the polymeric,
polymerizable and/or monomeric organic compound arranged in
particular outside the joining zone cannot cause the risk of a
significant production of gas adversely influencing the sintering
process. The proportion of polymeric, polymerizable and/or
monomeric organic compound that is still located in the joining
zone can in this case be in particular so small that there is no
need for the occurrence of any significant gas transport, which
adversely influences the sintered connection that is forming or the
stability of the sintered connection that has formed. Consequently,
here even a removal by the aforementioned processes can be possible
without any problem, or else it is possible for the polymeric,
polymerizable and/or monomeric organic compound to remain in the
joining zone without adversely influencing the sintering
process.
[0044] Within the scope of a further refinement, the sinterable
particles may contain silver, gold, platinum, palladium and/or
copper, an organic metal compound, in particular silver carbonate,
silver lactate or silver stearate, a metal oxide, in particular
silver oxide, or a mixture comprising one or more of the
aforementioned substances. Such particles may be particularly
advantageously suitable for forming a highly stable and
electrically conductive sintered connection. In this case, both the
pure metals and corresponding metal compounds may be provided. The
metals may in this case allow in particular a material-bonded
connection between the parts to be joined to be obtained directly
by a heat input or an input of pressure, and thereby make a stable
sintered connection possible. With respect to the metal compounds
mentioned, they can decompose during a thermal treatment of the
starting material, for instance in a range of less than 300.degree.
C., to form the elemental metal, and form the sintered connection.
When using the starting material described, electrical contacting
can already take place with low pressing pressures of the parts to
be contacted, which consequently can allow mild reaction
conditions, and consequently a simple and inexpensive method.
[0045] Within the scope of a further refinement, the polymeric,
polymerizable and/or monomeric organic compound may comprise a
polyolefin, in particular comprising polyethylene and/or
polypropylene, a polyethylene copolymer, a polyketone or a mixture
comprising one or more of the aforementioned substances. In
particular, such polymeric, polymerizable and/or monomeric organic
compounds may have the advantage that, with respect to their flow
temperature or with respect to their desorption behavior, they can
be integrated well into a sintering process, in particular in
combination with the aforementioned sintering base materials, that
is to say in particular metals or metal compounds. Consequently,
the aforementioned polymeric, polymerizable and/or monomeric
organic compounds may be particularly advantageously suitable for
taking up the sintering base material and also being removed
substantially without any residue from a component to be joined by
a desorption process. In addition, the aforementioned polymeric,
polymerizable and/or monomeric organic compounds are stable under
ambient conditions, that is to say even in an oxidative atmosphere
and/or in a moist atmosphere, so that particularly advantageous
storability can be made possible for the starting material, even
over a long period of time.
[0046] Within the scope of a further refinement, the polymeric,
polymerizable and/or monomeric organic compound may form a matrix,
in which the sinterable particles are embedded, or the polymeric,
polymerizable and/or monomeric organic compound may take the form
of a coating on the sinterable particles. These are particularly
advantageous refinements for surrounding the sinterable particles
by the polymeric, polymerizable and/or monomeric organic
compound.
[0047] With respect to a matrix in which the sinterable particles
are embedded, it is thus possible to produce a molded body that can
be adapted in all dimensions to the desired application area. In
detail, such a body can be adapted in its length, width and height
to the components to be joined. As a result, the method can be made
even more simple and inexpensive. For example, in this way a
moldable composition that can adhere to itself, and in particular
can be handled well, can be produced. In this case, such a starting
material may for instance be producible by melting the polymeric,
polymerizable and/or monomeric organic compound followed by mixing
with the sintering base material and final cooling.
[0048] With respect to a coating, the proportion of the polymeric,
polymerizable and/or monomeric organic compound can be kept
particularly low, so that the composition leaving the joining
region when there is an increase in temperature beyond the flow
temperature of the polymeric, polymerizable and/or monomeric
organic compound can be kept particularly small. Consequently, the
method can be carried out in a particularly time-saving manner. In
this case, the coating of the particles may already be applied
during the production of the particles, in particular in order to
prevent a reaction of the sinterable particles with one another,
for instance cold fusing. For example, the metal particles, which
are produced for example as silver particles by a gas-phase
deposition or precipitation in a solvent, are coated by the solvent
comprising a corresponding coating material, for example as a
surface-active material. After removal of the solvent, for example,
the starting materials comprising the sinterable particles, which
for instance as a powder are in a form that can be handled, can be
obtained with the coating, in particular chemically or physically
bonded coating.
[0049] In these refinements, the starting material can thus be
applied, or brought into contact with the components to be joined,
as a powder or as a pressed body of the powder or else as a paste
with a solvent by means of methods that are known in principle,
such as for instance placement of the green body. Also in these
refinements, the viscosity of the polymeric, polymerizable and/or
monomeric organic compound can be set by means of a temperature
control, so that the viscosity is controllable by a temperature
setting and in that case a temperature increase can have the effect
that the compound can be removed from the joint, in particular by
capillary forces, and in a further method step can be completely
removed or desorbed.
[0050] Within the scope of a further refinement, the starting
material may be applied to at least one component to be connected
by printing, doctor blading or dispensing. These are particularly
simple and well-established processes for applying the starting
material to at least one of the components to be connected. In
these refinements, a particularly precise and highly accurate
arrangement of the starting material is possible, which can make
highly stable sintered connections possible even in components of
small dimensions. In this case, the starting material may be
applied both to only one of the components to be connected or to
both starting components to be used.
[0051] Within the scope of a further refinement, the starting
material may have a transfer layer, which is arranged between at
least two protective layers, in particular comprising a polymeric,
polymerizable and/or monomeric organic compound. For example, the
transfer layer may comprise the sintering base material or the
sinterable particles and possibly the polymeric, polymerizable
and/or monomeric organic compound. In this case, the polymeric,
polymerizable and/or monomeric organic compound of the transfer
layer may be the same compound as the compound of the protective
layers. Alternatively, it is possible to dispense with the
polymeric, polymerizable and/or monomeric organic compound in the
transfer layer, which may enclose the sinterable particles
directly, for instance as a coating or as a matrix, so that the
sinterable particles are only surrounded by the protective layers
comprising a polymeric, polymerizable and/or monomeric organic
compound. In this refinement, the starting material can be handled
particularly easily and nevertheless be arranged very precisely at
the desired location. In this case, the transfer layer is protected
particularly well from external influences, and as a result is
particularly storable.
[0052] In this case, arranging the starting material on one of the
components to be joined can be realized by way of example, and not
restrictively, by the protective layers being removed before or
during method step b). In this case, as an example, it may be that
first a protective layer is removed and the exposed side of the
transfer layer arranged on the component, and then the further
protective layer is removed. In this way, the starting material may
have in particular a transfer layer that is surrounded on two
opposite sides by the protective layer. In this case, the
protective layers may also be formed in such a way that
substantially the entire transfer layer is surrounded by protective
layers. It may be that this can be realized by providing more than
two protective layers and also by a corresponding form of the at
least two protective layers.
[0053] In this case it is possible in this refinement in particular
to dispense with applying the sintering base material by printing,
dispensing or doctor blading with a subsequent thermal treatment
for drying the applied layer. Therefore, in this refinement in
particular, the previously described method can do without some
steps in the process, which can save production costs of the
components to be produced and also time for producing such
components.
[0054] Within the scope of a further refinement, the protective
layers may comprise polyethylene terephthalate. In particular,
polyethylene terephthalate may serve as a stable protective layer,
in order to protect the transfer layer reliably from external
influences, such as for example mechanical influences. In addition,
it is inert with respect to the materials occurring in the transfer
layer, so that no adverse influencing of the transfer layer is to
be expected, even over a prolonged period of time. Furthermore,
polyethylene terephthalate can be obtained inexpensively, so that
also in this refinement the method can be realized particularly
inexpensively.
[0055] Within the scope of a further refinement, the starting
material may be provided in the form of a paste, a powder, granules
or a film. Such forms of the starting material can be handled
easily, inexpensively and by known methods, so that in these
refinements in particular the method can be possible particularly
simply and inexpensively. In addition, storage is unquestionably
possible, so that the advantages with respect to production in
advance and use or provision immediately before the method are
possible without any problem.
[0056] Within the scope of a further refinement, the polymeric,
polymerizable and/or monomeric organic compound may be discharged
or removed during or after method step c). In this refinement, the
effect occurring in principle as a result of flowability of the
polymeric, polymerizable and/or monomeric organic compound, whereby
the compound already leaves the joining zone by flowing away, can
be further enhanced or assisted.
[0057] With respect to discharging of the polymeric, polymerizable
and/or monomeric organic compound, one or a plurality of collecting
containers may be provided for example, such as for instance
cavities, into which the flowable compound can be discharged, that
is to say guided. For this purpose, channels may be provided for
example, arranged in such a way that the compound flows in a
flowable state, or the collecting containers may themselves be
directly arranged in such a way that the flowable compound flows in
there. In this case, the collecting containers may for instance be
arranged directly alongside the components to be joined and the
channels may for instance reach into the joining region.
[0058] With respect to removal of the polymeric, polymerizable
and/or monomeric organic compound, the flowable compound may for
example be taken up and carried away by means of a suitable
device.
[0059] Sponge-like devices or capillary bundles, which can take up
or suck in the compound by means of capillary forces, may for
example be used for this purpose. This can bring about particularly
low-stress removal of the compound, and as such not adversely
influence the sintering process.
[0060] Within the scope of a further refinement, the polymeric,
polymerizable and/or monomeric organic compound may contain at
least one additive that reacts with the sinterable particles, in
particular with the organic metal compound, while reducing the
sintering temperature. In this refinement in particular, a
particularly low-stress method can be made possible, since low
temperatures may already be sufficient for a sintering process. As
a result, even such components that should not be exposed to
temperatures that are all that high can be connected to one
another. In addition, polymeric, polymerizable and/or monomeric
organic compounds that have a relatively low desorption temperature
can also be used, which can for example increase the selection of
such compounds, including with respect to conventional polymers.
Oxidizable organic compounds, such as for instance fatty acids, for
example stearic acid or lauric acid, in particular in combination
with the aforementioned sintering base materials, such as for
instance silver, may be mentioned as exemplary and nonrestrictive
examples of such additives.
[0061] Within the scope of a further refinement, it is possible to
produce a sintered connection that has an electrical conductivity
of from greater than or equal to 30 MS/m to in particular less than
or equal to 45 MS/m, in particular from greater than or equal to 36
MS/m to in particular less than or equal to 44 MS/m, and/or to
produce a sintered connection that has a thermal conductivity of
from greater than or equal to 200 W/mK to less than or equal to 300
W/mK, in particular from greater than or equal to 220 W/mK to less
than or equal to 275 W/mK. Such sintered connections in particular
may be customary for a large number of electronic components that
are possibly used in power electronics. Such conductivities may for
example be achievable by the use of the previously described
sintering base materials.
[0062] Within the scope of a further refinement, an electronic
component may be used as one of the components to be connected and
a substrate, for instance comprising a copper compound, may be used
as another of the components to be connected. In this refinement,
electronic components in particular may be applied to the
corresponding substrates. In the case of such applications in
particular, a very stable connection, which is additionally
electrically conductive, is beneficial. Therefore, in this
refinement in particular it is of advantage that the sintered
connection can be positioned highly accurately, and furthermore no
gas transporting processes have a significant adverse influence on
the forming of a stable connecting layer. For example, in this
refinement in particular an electronic component of power
electronics can be produced.
[0063] With regard to further technical features and advantages of
the method according to the invention, reference is hereby made
explicitly to the explanations in connection with the use according
to the invention, the figures and the description of the
figures.
[0064] The subject of the present invention is also a use of a
method refined in the way described above for producing an
electronic component, in particular an electronic circuit. In the
case of this use, an electronic component or an electronic circuit
can consequently be produced by a component, in particular an
electronic component, being secured on a substrate by a sintering
process. In this case, power semiconductors or integrated circuits
may for example be secured as electronic components on the
substrate by the sintered connection. In particular, the previously
described method can be used in the case of components to be joined
that should only be exposed to low thermal loading, since the
temperatures that are necessary for flowability or desorption of
the polymeric, polymerizable and/or monomeric organic compound and
are necessary for sintering the sintering base material can
likewise be kept low in the case of a previously described method
on account of the selection of the starting material. For example,
in this refinement silicon chips or silicon carbide components,
which can withstand temperatures of for example 250.degree. C. or
350.degree. C., respectively, can be joined without any problem,
such as for example in the so-called "die attach" process.
[0065] In principle, this refinement consequently comprises a use
of the previously described method in the region of electronic
construction technology or connection technology, in particular as
a low-temperature sintering technique. For example, diffusion
soldering or active soldering can be replaced by the previously
described method.
[0066] With regard to further technical features and advantages of
the use according to the invention, reference is hereby made
explicitly to the explanations in connection with the method
according to the invention, the figures and the description of the
figures.
BRIEF DESCRIPTION OF THE DRAWINGS
[0067] Further advantages and advantageous refinements of the
subjects according to the invention are illustrated by the examples
and drawings and are explained in the description that follows. It
should be noted here that the examples and drawings only have a
descriptive character and are not intended to restrict the
invention in any form. In them:
[0068] FIGS. 1a, 1b and 1c show a schematic representation of
production of one embodiment of a starting material for a method
according to the invention;
[0069] FIGS. 2a, 2b and 2c show a schematic representation of a
method according to the invention using a starting material
according to FIG. 1; and
[0070] FIGS. 3a, 3b and 3c show a schematic representation of a
method according to the invention using a further refinement of a
starting material.
DETAILED DESCRIPTION
[0071] In FIG. 1c, a starting material 10 for a method according to
the invention for connecting at least two components using a
sintering process is shown. In the refinement according to FIG. 1c,
the starting material 10 of a sintered connection comprises
sinterable particles 12, comprising at least one metal or at least
one metal compound. Furthermore, the starting material 10 comprises
at least one polymeric, polymerizable and/or monomeric organic
compound 14, which according to FIG. 1 is arranged as a coating on
the sinterable particles 12. In this case, the sinterable particles
12 and/or the polymeric, polymerizable and/or monomeric organic
compound 14 are chosen in such a way that the polymeric,
polymerizable and/or monomeric organic compound 14 has a flow
temperature that is greater than or equal to the room temperature,
that is to say according to the invention is greater than or equal
to 22.degree. C., and less than the sintering temperature of the
sinterable particles, and the polymeric, polymerizable and/or
monomeric organic compound 14 also having a desorption temperature
that is greater than the flow temperature and less than or equal to
the sintering temperature.
[0072] In this case, an exemplary production process for the
starting material 10 is shown in FIG. 1. In FIG. 1a, a sinterable
particle 12 that has been produced in a solvent 16 is shown. The
sinterable particle 12 may for example be a silver particle. In
FIG. 1b, it is also shown that a coating of a polymeric,
polymerizable and/or monomeric organic compound 14 is arranged on
the sinterable particle 12. This coating may be produced by the
polymeric, polymerizable and/or monomeric organic compound 14 being
added to the solvent 16, for example dissolved or dispersed. By way
of example, a colophony resin, which can serve as a fluxing agent,
may be used as the polymeric, polymerizable and/or monomeric
organic compound 14. This has the advantage with respect to the
method according to the invention that it is soft and adhesive at
slightly elevated temperatures of well below 100.degree. C., but in
the further course of conducting the process evaporates virtually
without any residue by decomposing and can be produced as a preform
at 25.degree. C. The completed starting material 10, obtained as
described above by evaporating the solvent, is shown in FIG.
1c.
[0073] Such a starting material 10 may be arranged directly between
two components 18, 20 to be connected, as is shown in FIG. 2a. In
this case, the starting material 10 may be applied to at least one
component 20 to be connected by printing, doctor blading or
dispensing. For example, the component 20 may be a substrate,
whereas the component 18 may be an electronic component, such as
for instance a power semiconductor component.
[0074] In FIG. 2b, a first thermal treatment step is shown. In
detail, a state after a method step comprising heating of the
starting material 10 to a temperature T1, which is greater than or
equal to the flow temperature of the polymeric, polymerizable
and/or monomeric organic compound 14 and less than the desorption
temperature of the polymeric, polymerizable and/or monomeric
organic compound 14, for a time t1 is shown in FIG. 2. This results
in part of the polymeric, polymerizable and/or monomeric organic
compound 14 being removed from the joining zone and arranging
itself on the component 20 or wetting the surface of the component
20. In this case, the polymeric, polymerizable and/or monomeric
organic compound 14 can be discharged or removed during or after
this method step of the first heat treatment.
[0075] In FIG. 2c, furthermore, a formed sintered connection 22 of
the two components 18, 20 is shown. Such a sintered connection 22
is formed by sintered sinterable particles 12, by a further method
step involving heating the starting material 10 to a temperature
T2, which is greater than or equal to the sintering temperature of
the sinterable particles 10, possibly under the effect of a
sintering pressure, for a time period t2, thereby forming a
sintered connection 22. For example when using silver as sinterable
particles 12, the sintered connection 22 may have an electrical
conductivity of from greater than or equal to 30 MS/m to in
particular less than or equal to 45 MS/m, in particular from
greater than or equal to 36 MS/m to in particular less than or
equal to 44 MS/m, and/or may have a thermal conductivity of from
greater than or equal to 200 W/mK to less than or equal to 300
W/mK, in particular from greater than or equal to 220 W/mK to less
than or equal to 225 W/mK. Furthermore, sintering may by way of
example take place at a sintering pressure of less than or equal to
10 MPa, for example of less than or equal to 1 MPa and/or at a
sintering temperature in a range of less than or equal to
300.degree. C., for example less than or equal to 250.degree.
C.
[0076] In FIGS. 3a to 3c, a further refinement of a starting
material 10 and a method performed with it is shown. In the
refinement according to FIG. 3a, the polymeric, polymerizable
and/or monomeric organic compound 14 forms a matrix, in which the
sinterable particles 12 are embedded. In this case, the polymeric,
polymerizable and/or monomeric organic compound 14 is arranged
together with the sinterable particles 12 in a transfer layer 24,
for instance as an adhesive film. The transfer layer 24 is in this
case arranged between at least two protective layers 26, 28, in
particular comprising a polymeric, polymerizable and/or monomeric
organic compound 30.
[0077] In order to form a sintered connection 22, it may be the
case that first a protective layer 28 is removed and the starting
material 10 is transferred to the first component 20. After the
removal of the second protective layer 26 or of all the protective
layers still present, the second component 18 is correspondingly
positioned on the starting material 10 or on the transfer layer 14.
In this case, reference is made here, and possibly also in respect
of further method steps, to the starting material 10, even though
sometimes only part of the starting material is present, which
however can be included in the sense of the invention by referring
to starting material 10. This state is shown in FIG. 3b.
[0078] This may be followed by a first thermal treatment, in which
the polymeric, polymerizable and/or monomeric organic compound 14
melts, and for example may become adhesive. In the sintering
process, the polymeric, polymerizable and/or monomeric organic
compound 14 can be removed and, furthermore, as a result of the
elevated temperature, the sintered sinterable particles can form a
sintered connection 22, as is shown in FIG. 3c.
* * * * *