U.S. patent application number 11/850531 was filed with the patent office on 2008-03-27 for method for producing flexible integrated circuits which may be provided contiguously.
This patent application is currently assigned to Fraunhofer-Gesellschaft zur Foerderung der angewandten Forschung e.V.. Invention is credited to Michael FEIL, Gerhard KLINK, Christof LANDESBERGER.
Application Number | 20080076209 11/850531 |
Document ID | / |
Family ID | 38859688 |
Filed Date | 2008-03-27 |
United States Patent
Application |
20080076209 |
Kind Code |
A1 |
KLINK; Gerhard ; et
al. |
March 27, 2008 |
METHOD FOR PRODUCING FLEXIBLE INTEGRATED CIRCUITS WHICH MAY BE
PROVIDED CONTIGUOUSLY
Abstract
The present invention provides a method for producing integrated
circuits which are mechanically flexible and can be provided
contiguously on a common flexible carrier substrate. The method
includes a step of continuously providing a first flexible
substrate which has conductor-line patterns, and a step of mounting
the integrated circuits on the first flexible substrate and
connecting the integrated circuits to the conductor-line patterns
of the first flexible substrate, and a step of covering the
circuits mounted on the first flexible substrate with a second
flexible substrate, recesses being provided in the first or second
flexible substrates in order to make the conductor-line patterns of
the first flexible substrate accessible. The step of covering has
the sub-step of continuously providing a flexible film with
recesses and laminating same onto the flexible integrated circuits
mounted on the first flexible substrate, or a sub-step of applying,
by a printing technique, a cover on the flexible integrated
circuits mounted on the first flexible substrate.
Inventors: |
KLINK; Gerhard;
(Furstenfeldbruck, DE) ; LANDESBERGER; Christof;
(Grafelfing, DE) ; FEIL; Michael; (Munchen,
DE) |
Correspondence
Address: |
SCHOPPE, ZIMMERMAN , STOCKELLER & ZINKLER
C/O KEATING & BENNETT , LLP, 8180 GREENSBORO DRIVE , SUITE 850
MCLEAN
VA
22102
US
|
Assignee: |
Fraunhofer-Gesellschaft zur
Foerderung der angewandten Forschung e.V.
Munich
DE
|
Family ID: |
38859688 |
Appl. No.: |
11/850531 |
Filed: |
September 5, 2007 |
Current U.S.
Class: |
438/112 ;
257/E21.502; 257/E23.062; 257/E23.065; 257/E23.069;
257/E23.178 |
Current CPC
Class: |
H01L 2924/01047
20130101; H01L 2924/181 20130101; H01L 2924/00011 20130101; H01L
2924/14 20130101; H05K 3/305 20130101; H01L 2924/12041 20130101;
H01L 2924/01074 20130101; H01L 23/5389 20130101; H01L 2924/15311
20130101; H05K 3/321 20130101; H05K 2201/10734 20130101; H01L
2924/01013 20130101; H01L 2924/014 20130101; H01L 2924/181
20130101; H01L 2224/16 20130101; H01L 2224/82039 20130101; H01L
2924/01005 20130101; H01L 23/49822 20130101; H01L 2224/81801
20130101; Y10T 29/49117 20150115; H01L 2924/00011 20130101; H01L
23/49816 20130101; H01L 2224/76155 20130101; H01L 2224/97 20130101;
H01L 2924/01068 20130101; H01L 2924/01082 20130101; H01L 2924/1532
20130101; H01L 2224/97 20130101; H01L 2924/00014 20130101; H01L
2924/01033 20130101; H05K 2201/10977 20130101; H01L 2924/15311
20130101; H01L 2224/81 20130101; H01L 2224/0401 20130101; H05K
3/005 20130101; H01L 2224/97 20130101; H01L 21/56 20130101; H01L
23/4985 20130101; H01L 24/97 20130101; H01L 23/3128 20130101; H01L
2224/2402 20130101; H01L 2924/00014 20130101; H01L 2924/12044
20130101; H01L 2924/01006 20130101; H01L 24/81 20130101; H01L
2224/0401 20130101; H01L 2924/00012 20130101 |
Class at
Publication: |
438/112 ;
257/E21.502 |
International
Class: |
H01L 21/56 20060101
H01L021/56 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 21, 2006 |
DE |
102006044525.2-33 |
Claims
1. A method for producing integrated circuits which are
mechanically flexible and can be provided contiguously on a common
flexible carrier substrate, comprising: continuously providing a
first flexible substrate having conductor-line patterns, mounting
the integrated circuits on the first flexible substrate and
connecting the integrated circuits to the conductor-line patterns
of the first flexible substrate, and covering the circuits mounted
on the first flexible substrate with a second flexible substrate,
recesses being generated in the first flexible substrate or being
provided or generated in the second flexible substrate in order to
make the conductor-line patterns of the first flexible substrate
accessible, comprising the following sub-steps: continuously
providing a flexible film with or without recesses and laminating
same onto the flexible integrated circuits mounted on the first
flexible substrate, or applying, by a printing technique, a cover
to the flexible integrated circuits mounted on the first flexible
substrate.
2. The method according to claim 1, further comprising: providing a
bonding material in the recesses of the flexible first or second
substrates.
3. The method according to claim 1, further comprising:
continuously reeling up the packaged integrated circuits, which are
mechanically flexible and arranged contiguously on the common
flexible carrier substrate.
4. The method according to claim 1, wherein the recesses in the
flexible film are provided by means of plasma etching, laser
patterning and/or photolithographic patterning.
5. The method according to claim 1, wherein the step of applying by
means of a printing technique is performed by means of a screen
printing, thick-film or thin-film technique.
6. The method according to claim 1, wherein in the step of covering
the integrated circuits mounted on the first flexible substrate, an
adhesive layer is furthermore applied to the integrated circuits
mounted on the first flexible substrate.
7. The method according to claim 6, wherein the adhesive layer
comprises an insulating hot-setting adhesive.
8. The method according to claim 2, wherein the bonding material
comprises a conducting hot-setting adhesive material.
9. The method according to claim 1, further comprising:
hot-laminating the integrated circuits mounted on the first
flexible substrate and covered by the second flexible
substrate.
10. A method for producing electronic assemblies with packaged
integrated circuits which are mechanically flexible and can be
provided contiguously on a common carrier substrate, comprising:
continuously providing the flexible packaged integrated circuits,
the flexible packaged integrated circuits being arranged between
first and second flexible substrates and connected to
conductor-line patterns of the first flexible substrate, recesses
being provided in the first or second flexible substrates in order
to make the conductor-line patterns of the first flexible substrate
accessible, and mounting one of the provided packaged integrated
circuits on one of the electronic assemblies, comprising the
following sub-steps: mechanically and electrically connecting the
one packaged integrated circuit to the one electronic assembly; and
separating the packaged electrical circuit from the packaged
integrated circuits supplied contiguously.
11. The method according to claim 10, wherein the step of
continuously providing is performed by unreeling the packaged
integrated circuits from a reel arrangement.
12. The method according to claim 10, wherein the step of
separating is performed by die-cutting the packaged integrated
circuits.
13. The method according to claim 12, wherein the step of
die-cutting is performed by means of a heatable punching tool.
14. The method according to claim 10, wherein the steps of
mechanically and electrically connecting coincide in one
manufacturing step and are performed by means of soldering, gluing,
bonding and/or welding.
15. The method according to claim 10, wherein the steps of
mechanically and electrically connecting and of separating coincide
in one manufacturing step.
16. The method according to claim 10, wherein the step of
mechanically and electrically connecting comprises the following
sub-steps: applying a conductive thermoplastic bonding material as
the bonding material.
17. A method for producing packaged integrated circuits which are
mechanically flexible and can be provided contiguously on a common
flexible carrier substrate, comprising: continuously providing a
first flexible substrate having conductor-line patterns, mounting
the flexible integrated circuits on the first flexible substrate
and connecting the integrated circuits to the conductor-line
patterns of the first flexible substrate, and covering the circuits
mounted on the first flexible substrate with a second flexible
substrate, recesses being provided or generated in the second
flexible substrate in order to make the conductor-line patterns of
the first flexible substrate accessible, comprising the following
sub-steps: continuously providing a flexible film as the second
flexible substrate with or without recesses and laminating same
onto the flexible integrated circuits mounted on the first flexible
substrate, or applying, by a printing technique, a cover as the
second flexible substrate to the flexible integrated circuits
mounted on the first flexible substrate.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority from German Patent
Application No. 10 2006 044 525.2, which was filed on Sep. 21,
2006, and is incorporated herein in its entirety by reference.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The present invention refers to a method for producing
integrated circuits which are mechanically flexible and may be
provided contiguously on a common flexible carrier substrate, as
well as to their further processing.
[0004] 2. Description of the Related Art
[0005] Integrated circuits are increasingly processed as
increasingly thinner chips. The reason for this is the demand for
assemblies which are as flat as possible, e.g. in portable devices,
in order to provide the highest possible functionality in a small
volume. The underlying technology for the production of these thin
ICs (IC=integrated circuit) is the thinning technique for
semiconductor wafers, by which the thickness of ICs can now be
reduced as a standard to thicknesses less than 100 .mu.m. The
possibility of producing ICs with a residual thickness within the
range of 10-20 .mu.m which, in this range, are becoming
increasingly flexible mechanically has also been demonstrated by
now.
[0006] This mechanical flexibility is advantageous in particular
for producing flat or flexible electronic systems and their
processing on film substrates. A well-known example is the
production of the so-called smart labels, wherein a substrate
provided with antenna structures is equipped with integrated
circuits for RF identification (RF=radio frequency). The IC is
directly connected, without packaging, mechanically to the
substrate and electrically to the antenna.
[0007] For more complex assemblies, very thin ICs have not yet
become generally accepted. The main reason for this is that
manufacturers are not in a position, in terms of technology, to
process non-packaged components, since this entails very strict
requirements in terms of accuracy of placement, structural accuracy
of the carrier and the interconnection technology. In the case of
extremely thin flexible ICs, there is also the fact that the
technique for handling these components becomes substantially more
complicated. Usually the manufacturers who process electronic
circuits further therefore may advantageously use packaged ICs,
which may be processed with a uniform assembly method and larger
structural dimensions. Common forms of packaging, however, are not
able to achieve the two substantial advantages of ultra-thin chips,
namely an extremely flat design and mechanical flexibility.
[0008] Packaged devices are provided for further processing in
different forms of packaging. To this end, packaged devices are
loaded into trays, rails, belts or the like and supplied in this
form to fitting machines for assembly. A drawback of the known
manufacturing methods for flexible integrated circuits is that a
direct and effective further processing cannot be achieved, since
the known forms of packaging do not permit a continuous
presentation due to lack of mechanical stability.
[0009] EP 1028436 describes, for example, thin integrated circuits
which are manufactured in a flexible package comprised of a
substrate film, wiring, thin IC and encapsulation. The method
provided there has the drawback that continuous manufacturing and
further processing of the flexible components is not possible,
since the flexible film packages used there do not have a
continuous coating.
[0010] EP 1256983 essentially describes, for example, a method for
producing flexible integrated circuits by a transfer method from a
semiconductor wafer to a polymer layer. The drawback of the method
introduced is that no solutions for the structure, bonding, or
contacting, and connection technique for integration into systems
can be indicated.
[0011] DE 19542883 introduces, e.g., a flexible chip package which
uses films. The chip itself is inserted into the film package by
means of lamination, but is itself thick and rigid, i.e. the
resulting package is, again, not flexible.
[0012] DE 19845296 describes, e.g., a method for bonding a circuit
chip. Isoplanar bonding techniques are used, by means of which
particularly flat designs are possible. The bonding is achieved by
means of a silk-screen printing or stamp-printing method, these
methods being used to apply a metallization to the thin circuit
fitted onto a carrier, in order to connect the pads of the circuit
chip to a conductive pattern arranged on the main surface of the
carrier substrate. The bonding of thin circuits during the
production of flat assemblies is described.
[0013] In Christians, W. et. Al.: "Embedded ultra-thin chips in
Flex, 4th int. Workshop on Flexible Electronic Systems, Nov. 23,
2005, IZM Munich, the authors describe a method for packaging
ultra-thin chips. In the case of the chips presented, a total
thickness of about 50-60 .mu.m is assumed, the thickness of the ICs
ranging between 20 and 30 .mu.m. The process cycle shall be
described more in detail with reference to FIG. 7. FIG. 7 shows 6
process steps 71 to 76, which illustrate the manufacturing method.
In a first step 71, a first polyimide layer 71b is initially spun
on a fixed carrier 71a, which may be made of glass, for example,
and is cured. In a second step 72, BCB (BCB=benzocyclobotene) 72a
is applied, by means of a dispenser, as an adhesive for fixing a
thin chip.
[0014] Then, in a following step 73, a thin chip 73a is placed in
the humid adhesive bed and the BCB 72a is cured. Then, in a step 74
a second polyimide layer 74a is spun. By means of a laser, openings
75a can then, in a step 75, be bored to the contact pads of the
chip 73a. The bonding, expansion of the connections and the
creation of the external contacts then occur in a metallization and
patterning process, in a step 76, which illustrates the mounting of
the contact surfaces 76a.
[0015] Thereupon, the finished film package is then separated from
the rigid carrier, and a flexible chip package is thus obtained. A
drawback of the described method is that due to the use of the
rigid carrier, a manufacturing process with a continuous provision
of the carrier is not possible. Another drawback of this technique
is the high requirements placed upon the manufacturing of the
openings and the contacts, which result from the fact that an
expansion of the contact structures does not occur until after
manufacturing of the chip contacts. Another drawback resides in the
open expansion of the contact structures. In order to avoid
short-circuits with the substrate wiring, either an insulating
intermediate sheet must be used, or a structural concept is applied
wherein only the contacts on the film package are open.
SUMMARY OF THE INVENTION
[0016] According to an embodiment, a method for producing
integrated circuits which are mechanically flexible and can be
provided contiguously on a common flexible carrier substrate may
have the steps of: continuously providing a first flexible
substrate having conductor-line patterns, mounting the integrated
circuits on the first flexible substrate and connecting the
integrated circuits to the conductor-line patterns of the first
flexible substrate, and covering the circuits mounted on the first
flexible substrate with a second flexible substrate, recesses being
provided or generated in the first or second flexible substrates in
order to make the conductor-line patterns of the first flexible
substrate accessible, having the sub-steps of: continuously
providing a flexible film with or without recesses and laminating
same onto the flexible integrated circuits mounted on the first
flexible substrate, or applying, by a printing technique, a cover
to the flexible integrated circuits mounted on the first flexible
substrate.
[0017] According to another embodiment, a method for producing
electronic assemblies with packaged integrated circuits which are
mechanically flexible and can be provided contiguously on a common
carrier substrate may have the steps of: continuously providing the
flexible packaged integrated circuits, the flexible packaged
integrated circuits being arranged between first and second
flexible substrates and connected to conductor-line patterns of the
first flexible substrate, recesses being provided in the first or
second flexible substrates in order to make the conductor-line
patterns of the first flexible substrate accessible, and mounting
one of the provided packaged integrated circuits on one of the
electronic assemblies, having the sub-steps of: mechanically and
electrically connecting the one packaged integrated circuit to the
one electronic assembly; and separating the packaged electrical
circuit from the packaged integrated circuits supplied
contiguously.
[0018] According to another embodiment, a method for producing
packaged integrated circuits which are mechanically flexible and
can be provided contiguously on a common flexible carrier substrate
may have the steps of: continuously providing a first flexible
substrate having conductor-line patterns, mounting the flexible
integrated circuits on the first flexible substrate and connecting
the integrated circuits to the conductor-line patterns of the first
flexible substrate, and covering the circuits mounted on the first
flexible substrate with a second flexible substrate, recesses being
generated in the first flexible substrate or being provided or
generated in the second flexible substrate in order to make the
conductor-line patterns of the first flexible substrate accessible,
having the sub-steps of: continuously providing a flexible film as
the second flexible substrate with or without recesses and
laminating same onto the flexible integrated circuits mounted on
the first flexible substrate, or applying, by a printing technique,
a cover as the second flexible substrate to the flexible integrated
circuits mounted on the first flexible substrate.
[0019] According to another embodiment, a method for producing
packaged integrated circuits which are mechanically flexible and
can be provided contiguously on a common flexible carrier substrate
may have the steps of: continuously providing a first flexible
substrate having conductor-line patterns, mounting the flexible
integrated circuits on the first flexible substrate and connecting
the integrated circuits to the conductor-line patterns of the first
flexible substrate, and covering the circuits mounted on the first
flexible substrate with a second flexible substrate, recesses being
provided or generated in the second flexible substrate in order to
make the conductor-line patterns of the first flexible substrate
accessible, having the sub-steps of: continuously providing a
flexible film as the second flexible substrate with or without
recesses and laminating same onto the flexible integrated circuits
mounted on the first flexible substrate, or applying, by a printing
technique, a cover as the second flexible substrate to the flexible
integrated circuits mounted on the first flexible substrate.
[0020] The present invention creates a method for producing
integrated circuits which are mechanically flexible and can be
provided together on a common flexible carrier substrate,
comprising a step of continuously providing a first flexible
substrate, which has conductor-line patterns, and a step of
mounting the integrated circuits on the first flexible substrate
and connecting the integrated circuits to the conductor-line
patterns of the first flexible substrate. The method for producing
integrated circuits includes, furthermore, a step of covering the
circuits mounted on the first flexible substrate with a second
flexible substrate, recesses in the first or second flexible
substrates being provided or generated in order to make the
conductor-line patterns of the first flexible substrate accessible,
and having a sub-step of continuously providing a flexible film
with or without recesses and laminating same on the flexible
integrated circuits mounted on the first flexible substrate, or a
sub-step of technically applying a cover to the flexible integrated
circuits mounted on the first flexible substrate.
[0021] The present invention creates, furthermore, a method for
producing electronic assemblies with packaged integrated circuits,
which are mechanically flexible and may be provided contiguously on
a common carrier substrate, comprising a step of continuously
providing the flexible packaged integrated circuits, the flexible
packaged integrated circuits being arranged between a first and a
second flexible substrate and connected to conductor-line patterns
of the first flexible substrate, recesses being provided in the
first or second flexible substrates in order to make the
conductor-line patterns of the first flexible substrate accessible.
The method for producing electronic assemblies furthermore
comprises a step of mounting one of the provided packaged
integrated circuits to one of the electronic assemblies, comprising
a sub-step of mechanically and electrically connecting the one
packaged integrated circuit to the one electronic assembly, and a
sub-step of separating the one packaged electrical circuit from the
packaged integrated circuits supplied contiguously.
[0022] The finding of the present invention consists in the fact
that thinned integrated circuits are fitted for further processing
on a film provided with conductor lines as an intermediate carrier.
The production may then advantageously occur on continuous
substrates by a reel-to-reel method, wherein an isoplanar or
flip-chip bonding can be used accordingly, which is substantially
easier to control than conventional bonding techniques.
[0023] Embodiments of the present invention have the advantage that
the flexible integrated circuits can be manufactured continuously,
and that subsequently flexible packaged integrated circuits are at
hand. These flexible packaged integrated circuits can also be
provided continuously, during further processing, for example by a
reel-to-reel method. The IC packaging has an extremely flat design.
Thanks to the use of continuous processes, i.e. to continuous
provision of the assemblies without these having to be separated
first, the production becomes very economical and efficient. The
packaged integrated circuits remain mechanically flexible. This
results in possibilities of use in flexible electronic systems.
[0024] Embodiments of the present invention furthermore provide
higher reliability as regards thermomechanical stresses. The
production of the IC packaging can occur directly by a continuous
reel-to-reel process. Further processing, for example component
tests, markings and assembly, can furthermore occur in a reel-fed
manner. Sorting into belts for automatic component insertion is
omitted, since the devices manufactured according to the method of
the invention can, thanks to their increased flexibility, be
further stored for example in a reeled-up condition.
[0025] The assembly of flexible or flat assemblies is made easier
for the user by the method according to the invention. No special
tools are needed for the handling and fitting of the ultra thin
ICs. For processing the flexible package, standard processes of SMD
mounting (SMD=surface mounted devices) can be used. An important
advantage of the present invention resides in the easy mounting of
the flexible IC packages, which can be mounted to the assemblies
e.g. by means of hot lamination.
BRIEF DESCRIPTION OF THE DRAWINGS
[0026] Embodiments of the present invention will be detailed
subsequently referring to the appended drawings, in which:
[0027] FIGS. 1a-c show an embodiment of a production method
according to the invention;
[0028] FIG. 2 shows an embodiment of a flexible circuit
manufactured by the method according to the invention;
[0029] FIG. 3 shows another embodiment of a flexible integrated
circuit manufactured by the method according to the invention;
[0030] FIG. 4 shows an embodiment of a flexible integrated circuit
manufactured by the method according to the invention;
[0031] FIG. 5 shows an embodiment of a schematic flow of a further
processing method according to the invention;
[0032] FIGS. 6a and b show an embodiment of a further processing
method enabled by the present invention; and
[0033] FIG. 7 shows the steps of a known method for producing
integrated flexible circuits.
DETAILED DESCRIPTION
[0034] The following figures serve to explain embodiments according
to the invention of production methods for producing integrated
circuits. In the following figures, same elements will be
designated by same reference numerals, so that the respective
descriptions of these elements are interchangeable.
[0035] FIG. 1a shows a first reel 100, a second reel 110 and a base
substrate 120 which is provided with conductor lines 130 and which
has flexible integrated circuits 140 applied to it.
[0036] As the base substrate 120, both plastic films and composite
films made of metal and an insulating plastic layer may be used
here. The latter are advantageous in particular for components
having a relatively high energy dissipation, in which improved heat
evacuation or heat dissipation of the system can be achieved by
means of the metallic carrier material. The film substrate, i.e.
the base substrate 120, is provided, for example by methods of the
thick-film or thin-film technique, with conductor lines or a wiring
pattern 130, which serve in particular to expand the close
connection grid of the IC and to thus simplify the subsequent
mounting to an assembly. On this base substrate 120 is then
mounted, according to FIG. 1a, the thin IC 140, e.g. by means of
the flip-chip technique.
[0037] The flip-chip technique is a mounting method of the field of
the mounting and connecting technique (AVT--Aufbau- und
Verbindungstechnik) in microelectronics for bonding unpackaged
semiconductors by means of bumps, or contact bumps. The chip is
mounted directly and without further connecting leads with the
active bonding side down toward the substrate/circuit carrier. This
results in particularly small dimensions of the package and short
conductor lengths. In the case of very complex circuits, this
technology often provides the only useful possibility of
connection, because several hundred contacts are implemented. In
wire bonding, this is not possible, because the wires would
intersect and would very probably come into contact with each
other. Furthermore, in wire bonding, the connections are
established successively. With the flip-chip technique, the
connection of all contacts occurs at the same time and thus results
in time saving.
[0038] Alternatively, for very thin ICs, isoplanar bonding can also
be used, bondings being printed on by a silk-screen printing
method, an ink-jet method or a stamp-printing method. By means of
these methods, a metallization is applied to the thin circuit
mounted on a carrier in order to connect the pads of the circuit
chip to a conductor pattern arranged on the main surface of the
carrier substrate.
[0039] According to FIG. 1a, the base substrate is unreeled from
the first reel 100 and reeled up, after the process steps described
below have been performed, onto a second reel 110. Thus, the
embodiment of a method for producing integrated circuits also
enables the subsequently packaged circuits to be mechanically
flexible and to be provided together on a common flexible carrier
substrate 120 for further processing, the continuity of provision
being achieved, in the embodiment of the present invention
considered here, by the reels 100 and 110. During the continuous
provision of the first flexible substrate 120, which, according to
the above description, already has conductor-line patterns 130, the
mounting of the integrated circuits 140 occurs on the first
flexible substrate 120. Also, at the same time, the integrated
circuits 140 are connected to the conductor-line patterns 130 of
the base substrate 120.
[0040] A next step of the embodiment of the method according to the
invention is shown in FIG. 1b. FIG. 1b shows now in addition, with
respect to FIG. 1a, a third reel 150 and a second flexible
substrate 160, which will also be referred to as protection or top
layer hereinafter. According to the invention, via the third reel
150 the second flexible substrate 160 is applied to the flexible
integrated circuits 140 mounted on the first substrate 120. In this
way, the mounted flexible integrated circuits 140 receive a
protection or top layer 160. What is thus performed, according to
the invention, is a process step of covering the circuits 140
placed on the first flexible substrate 120 with a second flexible
substrate 160, recesses 165 being provided or generated in the
first flexible substrate 120 or in the second flexible substrate
160, in order to make the conductor-line patterns 130 of the first
flexible substrate 120 accessible. This can occur for example by
means of a sub-step of continuously providing a flexible film, i.e.
the second flexible substrate 160, with recesses 165, the flexible
film being fixed by laminating same on the flexible integrated
circuits 140 placed on the first flexible substrate 120.
Alternatively, the application of the second flexible substrate 160
can occur by applying, using printing techniques, a top layer on
the flexible integrated circuits 140 placed on the first flexible
substrate 120.
[0041] The protective layer or the second flexible substrate 160
can thus be obtained by laminating a top film or by means of
coating processes, openings 165 or recesses for wiring the carrier
film being provided or generated. For example, the latter can be
applied in a particular efficient way by printing methods, such as
for example screen printing, since this provides the possibility of
applying the protection layer or the second flexible substrate 160
already with the openings 165 in one processing step. The pattern
definition of such printing methods is limited, so that no
arbitrarily small openings or recesses 165 can be achieved. In
order to obtain smaller openings 165, in other embodiments of the
present invention, a full-surface top film or coating, i.e. the
second flexible substrate 160, can be applied, and the openings can
then be made by means of known plasma-etching or laser-patterning
methods. In another embodiment of the method according to the
invention, a photosensitive material could alternatively be used
for the top layer, i.e. for the second flexible substrate 160 and,
after the coating, be patterned directly by photolithographic
methods. In these methods are used, for example, photosensitive
plastics which are applied in a liquid state on the assemblies and
are then cured by irradiation, for example with laser or UV-light
(UV=ultra violet).
[0042] Afterwards, it is only contacts 170 for the electrical
connections of the package that are implemented. This operation is
represented in FIG. 1c. In an embodiment of the present invention,
the contacts 170 can be implemented, for example, by means of
suitable soldering bumps 170, which may be used to carry out direct
mounting, by means of welding, on a subsequent assembly. Other
known bonding techniques, such as for example gluing or welding,
are also feasible, however.
[0043] An embodiment of a flexible integrated circuit which can be
produced with an embodiment of a method according to the invention
is shown in FIG. 2.
[0044] FIG. 2 shows a film substrate 120 to which wiring pattern is
applied in the form of conductor lines 130, as described above. On
the wiring pattern 130 is then mounted the thin IC 140 according to
the above description. Alternatively, in the case of an optional
film lamination, an adhesive layer 220 can then be applied between
the mounted thin IC 140 and the top layer 160. In the top layer 160
there are openings or recesses 165, through which a contact
material 170 for bonding the wiring pattern 130 is applied. FIG. 2
shows an embodiment of the package having so-called soldering bumps
170, in which a protected chip 140 is formed in the form of a
flexible film package. Alternatively, the contacts can also be
established on the side of the carrier film 120 after applying the
top layer 160.
[0045] This embodiment is represented in FIG. 3. FIG. 3 shows, in
turn, a film substrate 120 with a wiring pattern 130. On the wiring
pattern 130 a thin IC 140 is mounted on which an adhesive layer 220
is optionally present and which is then covered as a whole with a
top layer 160. The embodiment represented in FIG. 3 has openings
165 in the film substrate 120, through which the wiring pattern 130
can be bonded by means of a contact material 170. The arrangement
in FIG. 3 shows an embodiment of the flexible integrated circuit,
which is, in this case, bonded by the carrier material, i.e. the
film substrate 120. The embodiment shown in FIG. 3 allows a
particularly plane package surface on the mounting side. The
concept represented allows producing a chip module which has
approximately plane-parallel surfaces. This is particularly
advantageous, since forces exerted from the outside then will act
not only on the chip, but will be evenly distributed across the
module. This is also important when the packaged modules are to be
reeled up onto a reel in the form of a chip-module tape, since
breaks can otherwise occur in the chip. The embodiment of the
present invention represented in FIG. 3 thus enables the advantage
of storing a reeled-up chip-module tape.
[0046] Another embodiment of a flexible chip which can be produced
with an embodiment of the manufacturing method according to the
invention is represented in FIG. 4. FIG. 4 shows a film substrate
120 to which a wiring pattern 130 is applied. A thin IC 140 is
mounted on the wiring pattern 130. The mounted thin IC 140 is, in
the embodiment in FIG. 4, surrounded by a passivation layer 420,
which can contribute for example to the insulation and additional
protection of the IC 140. in the embodiment of FIG. 4, an
insulating hot adhesive 430, which both surrounds the passivation
layer 420 of the mounted thin IC 140 and insulates the wiring
pattern 130 at the limits of the module, serves as a top layer. In
the present embodiment, a conductive hot adhesive 440 serves as a
contact material.
[0047] In the embodiment represented in FIG. 4, the film substrate
120 with the mounted thin IC 140 can be coated, on the mounting
side, with a top layer of thermoplastic adhesive 430 which can be
in the form of, e.g., hot-setting adhesive or hot-melt adhesive,
which, again, is provided with openings or recesses 165 for
creating electrical connections. An electrically conductive
thermoplastic adhesive 440 is then introduced into these openings
165. In this context, it is advantageous that the same
thermoplastic adhesive can be used for both applications. In the
case of the conductive thermoplastic adhesive 440, electrically
conductive particles, for example, such as, e.g., silver, may be
introduced into the thermoplastic adhesive 440.
[0048] During the mounting of the film package on an assembly, both
the insulating and the electrically conductive adhesive layers are
melted, so that both the electrical and the mechanical connection
to the component-group carrier can occur in one single process
step. The mounting of the flexible film packaging can thus also be
integrated very easily into a continuous manufacturing process,
i.e. into a reel-to-reel process, in which the melting occurs in a
similar way as in film-laminating processes by hot-laminating
systems, wherein the hot adhesive can for example be melted via
heatable metal rollers and is at the same time distributed or
pressed by means of a rotary roller.
[0049] For mounting integrated circuits thus packaged within a
film, the components can be supplied for mounting directly from the
reel. FIG. 5 schematically shows such a process according to
another embodiment of the present invention. FIG. 5 shows an
assembly 500 on which is mounted a flexible film package 510. To
this end, from the film with the ICs 520, it is in one process step
that the latter are separated by means of a punching tool 530 and
mounted. The method represented in FIG. 5 for producing electronic
assemblies with packaged integrated circuits 510, which are
mechanically flexible and may be provided contiguously on a carrier
substrate 120, includes the step of continuously providing the
flexible packaged integrated circuits 510, the flexible packaged
integrated circuits being arranged between first 120 and second
flexible substrates 160 and connected to conductor-line patterns
130 of the first flexible substrate 120, recesses or openings 165
being provided in the first 120 or second flexible substrates 160
in order to make the conductor-line patterns 130 of the first
flexible substrate 120 accessible.
[0050] The process according to the invention for producing
electronic assemblies includes, furthermore, a step of mounting one
of the provided packaged integrated circuits 510 on an electronic
assembly 500, comprising a sub-step of mechanically and
electrically connecting the packaged integrated circuit 510 to the
electronic assembly 500, as well as a step of separating the
packaged electrical circuit 510 from the packaged integrated
circuits 520 run contiguously. The separation can occur for example
by means of a heated punching tool 530, wherefore the steps of
separating and of mechanically and electrically coupling can be
combined into one single process step. The mechanical and
electrical coupling occurs by melting the soldering bumps by means
of the heatable punching tool 530.
[0051] According to the FIG. 5, in the embodiment of the method
according to the invention, after placing the package, the
component is separated from the film through die-cutting or
cutting, and is connected by means of a mounting tool, for example
a punching tool 530, with the necessary application to pressure and
temperature, to the assembly 500. What is advantageous here is that
the die-cutting and mounting operations can be combined into one
single process step. According to the different mounting methods, a
plurality of configurations or embodiments may be produced for such
a reel-to-reel package, for example according to the preceding
embodiments, and may be subsequently processed according to the
embodiment of the further processing method in FIG. 5.
[0052] Another embodiment of the production method according to the
invention is represented in FIGS. 6a and 6b. Each of FIGS. 6a and
6b represent an assembly 500 onto which the flexible integrated
circuit 510 is to be mounted. A heatable tool 530 first of all
holds the integrated circuit 510 to be mounted, according to the
representation in FIG. 6a. In FIG. 6b, the integrated flexible
circuit 510 is pressed to the assembly 500 by the heatable tool
530, and is heated. The heating is represented in FIG. 6b by the
zigzag-shaped arrows. By pressing the integrated flexible circuit
510 onto the assembly 500 and simultaneously heating, the contact
surfaces 170 of the integrated flexible circuit 510 melt and get
bonded with the contact surfaces 610 of the assembly. The flexible
integrated circuit 510 is thus, in one process step, both separated
and electrically and mechanically coupled to the assembly 500.
[0053] Embodiments of the present invention provide the advantage
that the IC package has an extremely flat design. According to the
embodiments of the present invention, the production is very
economical and efficient thanks to the use of continuous processes,
i.e. the continuous provision of the packaged flexible integrated
circuits. The packages are mechanically flexible, which results in
possibilities of using them in flexible electronic systems.
Furthermore, it is assumed that a higher level of reliability is
achieved as regards thermomechanical stresses.
[0054] Another advantage of the present invention is that it allows
a production of the IC package directly in a reel-to-reel method or
process. Further processing, such as for example component tests,
markings and assembly, can furthermore occur in a reel-fed way.
Therefore, the sorting into belts for automatic component insertion
is omitted.
[0055] Furthermore, embodiments of the present invention have the
advantage that the assembly of flexible or flat assemblies is
simplified for the user. He/She does not need special tools for
handling and placing ultra thin ICs. For processing the flexible
package, standard methods of SMD assembly can be used. In
principle, embodiments of the present invention provide the
possibility of a simple assembly of a flexible IC package,
according to the embodiments described above, for example by means
of hot-lamination onto an assembly.
[0056] While this invention has been described in terms of several
embodiments, there are alterations, permutations, and equivalents
which fall within the scope of this invention. It should also be
noted that there are many alternative ways of implementing the
methods and compositions of the present invention. It is therefore
intended that the following appended claims be interpreted as
including all such alterations, permutations and equivalents as
fall within the true spirit and scope of the present invention.
* * * * *