U.S. patent application number 16/564331 was filed with the patent office on 2020-05-14 for component carrier with improved bending performance.
The applicant listed for this patent is AT&S (China) Co. Ltd.. Invention is credited to Mikael Tuominen, Nick Xin.
Application Number | 20200154558 16/564331 |
Document ID | / |
Family ID | 67836368 |
Filed Date | 2020-05-14 |
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United States Patent
Application |
20200154558 |
Kind Code |
A1 |
Xin; Nick ; et al. |
May 14, 2020 |
Component Carrier With Improved Bending Performance
Abstract
A component carrier, wherein the component carrier includes: i)
a layer stack with at least one electrically conductive layer
structure and/or at least one electrically insulating layer
structure, ii) a bendable portion which forms at least a part of
the layer stack, and iii) a metal layer which forms at least a part
of the bendable portion. Hereby, the metal layer extends over at
least 75% of the area of the bendable portion.
Inventors: |
Xin; Nick; (Shanghai,
CN) ; Tuominen; Mikael; (Pernio, FI) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
AT&S (China) Co. Ltd. |
Shanghai |
|
CN |
|
|
Family ID: |
67836368 |
Appl. No.: |
16/564331 |
Filed: |
September 9, 2019 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H05K 1/0281 20130101;
H05K 1/0298 20130101; H05K 1/038 20130101; H05K 3/361 20130101;
H05K 1/0277 20130101; H05K 1/148 20130101; H05K 1/181 20130101;
H05K 1/0283 20130101; H05K 2201/058 20130101; H05K 2201/055
20130101; H05K 2201/046 20130101; H05K 1/0393 20130101; H05K 3/4691
20130101; H05K 1/0278 20130101; H05K 1/118 20130101; H05K 1/028
20130101; H05K 2201/05 20130101; H05K 2201/056 20130101 |
International
Class: |
H05K 1/02 20060101
H05K001/02; H05K 1/18 20060101 H05K001/18; H05K 1/03 20060101
H05K001/03 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 14, 2018 |
CN |
201821878788.6 |
Claims
1. A component carrier, wherein the component carrier comprises: a
layer stack comprising at least one electrically conductive layer
structure and/or at least one electrically insulating layer
structure; a bendable portion which forms at least a part of the
layer stack; and a metal layer which forms at least a part of the
bendable portion; wherein the metal layer extends over at least 75%
of the area of the bendable portion.
2. The component carrier according to claim 1, wherein the metal
layer is a continuous layer that extends over the whole area of the
bendable portion.
3. The component carrier according to claim 1, wherein the metal
layer is a patterned layer.
4. The component carrier according to claim 1, wherein the metal
layer is a metal foil, in particular a copper foil.
5. The component carrier according to claim 1, wherein the metal
layer is an outermost layer of the layer stack.
6. The component carrier according to claim 1, wherein the metal
layer is in direct contact with a solder mask, and wherein the
solder mask is an outermost layer of the layer stack.
7. The component carrier according to claim 1, wherein the metal
layer is configured as an antenna structure.
8. The component carrier according to claim 1, wherein the metal
layer is configured for carrying an electric signal, in particular
during operation of the component carrier.
9. The component carrier according to claim 1, wherein the metal
layer has a tensile strength of at least 170 MPa.
10. The component carrier according to claim 1, wherein the
component carrier is configured as a purely flexible component
carrier or as a semi-flexible component carrier.
11. The component carrier according to claim 1, wherein the layer
stack comprises a recessed portion, and wherein the bendable
portion is formed at the recessed portion.
12. The component carrier according to claim 11, wherein at least
one non-recessed portion of the layer stack is formed as a rigid
portion which is not bendable.
13. The component carrier according to claim 12, wherein the
bendable portion is formed between a first rigid portion and a
second rigid portion.
14. The component carrier according to claim 13, wherein the bottom
of the bendable portion is flush with the bottom of the first rigid
portion and the bottom of the second rigid portion.
15. The component carrier according to claim 13, wherein the metal
layer is formed at the bottom of the bendable portion, and wherein
the metal layer is not flush with the bottom the first rigid
portion and the bottom of the second rigid portion.
16. The component carrier according to claim 11, wherein the
recessed portion is formed in a viewing direction being parallel to
the main directions of extension of the component carrier, and/or
wherein the recessed portion is formed in a viewing direction being
perpendicular to the main directions of extension of the component
carrier.
17. The component carrier according to claim 13, wherein at least
one layer of the layer stack extends from the first rigid portion
through the bendable portion to the second rigid portion.
18. The component carrier according to claim 13, wherein the rigid
portions are connected to the bendable portion via a rigid
connection.
19. The component carrier according to claim 1, wherein the bending
portion comprises a further metal layer, and at least one
electrically insulating layer structure arranged between the metal
layer and the further metal layer.
20. A method for manufacturing a component carrier, the method
comprising: forming a layer stack comprising at least one
electrically conductive layer structure and/or at least one
electrically insulating layer structure; forming a bendable portion
which forms at least a part of the layer stack; and forming a metal
layer as at least a part of the bendable portion such that the
metal layer extends over at least 75% of the area of the bendable
portion.
Description
TECHNICAL FIELD
[0001] The invention relates to a component carrier. In particular
the invention relates to a component carrier comprising a bendable
portion. Furthermore, the invention relates to a method of
manufacturing a component carrier.
TECHNOLOGICAL BACKGROUND
[0002] In the context of growing product functionalities of
component carriers equipped with one or more electronic components
and increasing miniaturization of such electronic components as
well as a rising number of electronic components to be mounted on
the component carriers such as printed circuit boards, increasingly
more powerful array-like components or packages having several
electronic components are being employed, which have a plurality of
contacts or connections, with ever smaller spacing between these
contacts. Removal of heat generated by such electronic components
and the component carrier itself during operation becomes an
increasing issue. At the same time, component carriers shall be
mechanically robust and electrically reliable so as to be operable
even under harsh conditions. Furthermore, it is also desirable for
specific requirements to provide component carriers which are
semi-flexible or purely flexible. These at least partially bendable
component carriers are suitable for a large variety of
applications. For example, the need to provide additional cables
could be overcome by implementing a flexible component carrier.
Flexible component carriers may thus be used to replace wiring and
connectors, allowing for connections and geometries that are not
possible with rigid component carriers. However, there are still
problems with flexible component carriers. In particular, providing
a component carrier with a flexible portion, wherein the flexible
portion is resistant against stress and strain, is still a
challenge.
SUMMARY
[0003] There may be a need to provide a component carrier with an
improved bending performance.
[0004] A component carrier and a method for manufacturing a
component carrier according to the independent claim are
provided.
[0005] According to an aspect of the invention, a component carrier
is provided, wherein the component carrier comprises: i) a layer
stack comprising at least one electrically conductive layer
structure and/or at least one electrically insulating layer
structure, ii) a bendable portion which forms at least a part of
the layer stack, and iii) a metal layer which forms at least a part
of the bendable portion. Hereby, the metal layer extends over at
least 75% of the area of the bendable portion.
[0006] According to a further aspect of the invention, a method for
manufacturing a component carrier is provided. The method
comprises: i) forming a layer stack comprising at least one
electrically conductive layer structure and/or at least one
electrically insulating layer structure, ii) forming a bendable
portion which forms at least a part of the layer stack, and iii)
forming a metal layer as at least a part of the bendable portion
such that the metal layer extends over at least 75% of the area of
the bendable portion.
OVERVIEW OF EMBODIMENTS
[0007] In the context of the present application, the term
"component carrier" may particularly denote any support structure
which is capable of accommodating one or more components thereon
and/or therein for providing mechanical support and/or electrical
connectivity. In other words, a component carrier may be configured
as a mechanical and/or electronic carrier for components. In
particular, a component carrier may be one of a printed circuit
board (PCB), an organic interposer, a substrate-like-PCB (SLP), and
an IC (integrated circuit) substrate. A component carrier may also
be a hybrid board combining different ones of the above-mentioned
types of component carriers. Furthermore, the component carrier may
be a flexible component carrier, a semi-flexible component carrier,
or a rigid-flex component carrier.
[0008] In the context of the present application, the term
"bendable portion" may particularly denote any structure in a layer
stack that is suitable to be bended. In other words, the term
"bendable portion" may denote every portion of a component carrier
that is flexible such that a bending of said portion is possible.
For example, a component carrier may comprise a layer stack with
e.g. ten layers. A recess may be formed into the layer stack (e.g.
in the middle or center) in order to provide a recessed part. Said
recessed part may comprise e.g. only four layers, thereby being
much thinner than the non-recessed parts of the layer stack.
Because the recessed portion is very thin, it is also flexible with
respect to the non-recessed parts of the layer stack, which are
thicker and therefore rigid. The properties of the recessed portion
may also be influenced by the material that is used for building
the layers of the bendable portion. The use of flexible material
may further improve the bendability. The described bendable portion
may connect two rigid, non-bendable portions of the layer stack
such that the rigid, non-bendable portions can be moved with
respect to each other, when the bending portion between them is
bended.
[0009] In the context of the present application, the term "metal
layer" may particularly denote any structure that consists of metal
and is designed as a layer. For example, the metal layer may be
formed as a foil, e.g. a copper foil. The layer may hereby be a
continuous layer or a patterned layer. The layer may be designed as
a thick copper layer, a so-called "full copper" layer. The metal
layer may be formed together with the other layers of the layer
stack in a build-up laminating process. Hereby, the metal layer may
be formed by electroplating (galvanic plating) and/or electro-less
plating. When the bending portion is viewed from a top view, i.e.
from a viewing direction being perpendicular to the main extension
directions of the component carrier (in other words: a viewing
direction being parallel to a normal vector of a plane, which plane
is parallel to the two main extension directions of the component
carrier), then the metal layer covers at least 75% of the area of
the bending portion. As a consequence, the metal layer may indeed
be seen as a layer (continuous or patterned) and not as a metal
trace. The thickness of the metal layer may be in the range 1 .mu.m
to 100 .mu.m, in particular 12 .mu.m to 36 .mu.m.
[0010] According to an exemplary embodiment, the invention is based
on the idea that, with the implementation of an additional metal
layer within a bendable portion of a layer stack, the bending
performance of a component carrier is highly improved and the
formation of defects, such as cracks, is reduced (i.e. material
stress reduction). Conventionally, a bendable portion within a
component carrier is realized with a plurality of resin layers,
especially the outermost layers of said bendable portion are resin
layers (resin/solder mask interface). This design leads to a poor
bending performance with a high strain (e.g. a deformation of
5.8%), in particular at a resin/solder mask interface, and crack
formation. Hereby, it has to be taken into account that the maximum
allowable strain deformation of resin is below 2%. It has now been
surprisingly found that, by forming a metal layer which extends
over at least 75% of the area of the bendable portion (thereby
being formed as an at least partially continuous layer and not only
as a metal trace), the bending performance is highly improved,
while the formation of defects, such as cracks, is highly
decreased. The bending behavior of the component carrier is thereby
optimized and the formation of asymmetries during the bending can
be avoided. Especially at a metal/solder mask interface, the strain
deformation may be optimized (e.g. to 3.7% in the case of copper).
In contrast to resin, the maximum allowable strain of metal is very
large, e.g. larger than 10% in the case of copper. The bending
radius, e.g. in a semi-flexible component carrier, may also be
improved in this manner with a highly reliable capability.
Furthermore, the described solution can be implemented into high
volume production technologies in a straightforward manner. These
technical effects are in particular surprising because metal, e.g.
copper, is generally not considered as a flexible material.
[0011] In the following, further exemplary embodiments of the
method and the component carrier will be explained.
[0012] According to an exemplary embodiment, the metal layer is a
continuous layer that extends over the whole area of the bendable
portion. This may provide the advantage that the bending
performance of the component carrier is further improved. The
implementation of at least one metal layer provides surprising
advantages over the conventionally applied resin (see discussion
above). When applying the metal layer to the whole area (when seen
from a top view) of the bendable portion, the advantageous effects
may also arise at the whole area of the bendable portion.
Furthermore, a continuous portion is more robust than a patterned
structure or traces. The metal layer may also extend further than
the area of the bendable portion and may also extend over areas of
non-bendable, rigid portions of the layer stack. A continuous metal
layer could also be used as an electromagnetic radiation shielding
structure in different applications.
[0013] According to a further exemplary embodiment, the metal layer
is a patterned layer. This may provide the advantage that the metal
layer can be used in a flexible manner for different advantageous
applications. For example, a plurality of electric contacts may be
realized, when a patterned metal layer is used. Several parts of
the pattern may thereby be realized as connection pads or
terminals. These pads/terminals could e.g. be contacted with
interconnections such as vias. A via (vertical interconnection
access) is an electrical connection between layers in a physical
electronic circuit that goes through the plane of one or more
adjacent layers. A complex and cost-efficient circuitry may be
provided in this manner. In another example, the metal layer could
be patterned such that it can be used as an antenna structure.
[0014] According to a further exemplary embodiment, the metal layer
is a metal foil, in particular a copper foil. This may provide the
advantage that the metal layer can be manufactured in a
straightforward and cost-efficient manner using known and
established processes. A metal foil can for example be manufactured
with electroplating and/or electro-less plating, in particular
copper plating. This process step may be directly included into a
production line. In this manner, the metal foil may be manufactured
during a layer build-up, when the layer stack is produced.
[0015] According to a further exemplary embodiment, the metal layer
is an outermost layer of the layer stack. This may provide the
advantage that the bending performance of the component carrier is
further improved. During bending of the bending portion, the stress
and strain may be strongest at the outermost layer. When providing
the metal layer with its advantageous effects at the position with
the strongest stress and strain forces, these forces may be
compensated in the best possible manner.
[0016] According to an exemplary embodiment, the metal layer is in
direct contact with a solder mask, and the solder mask is an
outermost layer of the layer stack. This may provide the advantage
that the bending performance of the component carrier is further
improved, while the metal layer is efficiently protected. A solder
mask (or solder resist) may be a thin lacquer-like layer of polymer
that is applied to the metal traces of a component carrier for
protection against corrosion, oxidation, mechanical destruction,
and to prevent solder bridges from forming between closely spaced
solder pads. The solder mask thus protects the metal layer against
corrosion, oxidation, mechanical destruction, and from solder
bridges (in particular, when the metal layer is patterned into
electric contacts). An interface between resin and solder mask is
very prone to high stress and strain (see discussion above). In the
case that a metal layer/solder mask interface is provided, the
stress and strain (and hence also the crack formation) is reduced,
and a highly improved bending performance may be achieved, also
when providing an additional solder mask layer. The solder mask may
comprise epoxy resin, for example epoxy acrylate.
[0017] According to a further exemplary embodiment, the metal layer
is configured as an antenna structure. This may provide the
advantage that the metal layer can be used in a flexible manner for
specific functions. Besides its advantageous effects with respect
to the bending behavior of the component carrier, the metal layer
may additionally be used to fulfill a variety of technical
functions. One of these functions may be an antenna function. There
are many ways of how the metal layer could be patterned in order to
receive an antenna structure.
[0018] The term "antenna structure" may particularly denote an
arrangement of metallic conductor elements electrically connected
for instance through a transmission line to a receiver or
transmitter. Hence, an antenna structure may be denoted as an
electrical member which converts electric power into radio waves,
and/or vice versa. An antenna structure may be used with a
controller (for instance a control chip) such as a radio
transmitter and/or radio receiver. In transmission, a radio
transmitter may supply an electric current oscillating at radio
frequency (i.e. a high frequency alternating current) to the
antenna structure's terminals, and the antenna structure may
radiate the energy from the current as electromagnetic waves (in
particular radio waves). In a reception mode, an antenna structure
may intercept some of the power of an electromagnetic wave in order
to produce a tiny voltage at its terminals, that may be applied for
example to a receiver to be amplified. In embodiments, the antenna
structure may be configured as a receiver antenna structure, a
transmitter antenna structure, or as a transceiver (i.e.
transmitter and receiver) antenna structure. In an embodiment, the
antenna structure may be used for a radar application. The antenna
structure may, for example, comprise a dipole antenna, a folded
dipole antenna, a ring antenna, a rectangular loop antenna, a patch
antenna, or a coplanar antenna. The antenna structure may also
comprise a Yagi antenna or a fractal antenna. A Yagi antenna may be
a multi-beam directional antenna for so-called mm wave
applications. A fractal antenna may be another type of antenna that
uses a self-similar design to maximize the length of a material in
a total surface area. A fractal antenna may be compact and wideband
and can act as an antenna for many different frequencies.
[0019] According to a further exemplary embodiment, the metal layer
is configured for carrying an electric signal, in particular during
operation of the component carrier. This may provide the advantage,
that the metal layer, besides its advantageous effects with respect
to the bending performance, also provides electrical
functionalities. The metal layer may for example be at least
partially patterned such that electric signals could be carried
through different traces of the metal layer. Furthermore, the metal
layer may comprise pads/terminals which could be connected to other
conductor traces and/or vias. In the case that the metal layer is a
continuous layer, the whole layer could function as one electric
signal carrier. When the component carrier is in operation, the
bendable portion, in particular the metal foil, may not only allow
for connections and geometries that are not possible with rigid
component carriers, but additional wirings and connectors may also
be further reduced as they can be implemented in a straightforward
manner into the metal layer.
[0020] According to a further exemplary embodiment, the metal layer
has a tensile strength of at least 170 MPa. In particular, the
tensile strength is at least 200 MPa. This may provide the
advantage that the metal layer is especially robust against stress
and strain. The (ultimate) tensile strength may be the capacity of
a material or structure to withstand loads tending to elongate,
i.e. the property to resist a tension force before breaking. While
resin generally has a tensile strength around 50 MPa, copper has
for example a tensile strength of around 210 MPa. As a consequence,
metal (e.g. copper) is very suitable to withstand stress and strain
under bending conditions.
[0021] According to a further exemplary embodiment, the component
carrier is configured as a purely flexible component carrier or as
a semi-flexible component carrier. This may provide the advantage
that the favorable bending properties of the described bending
portion can be transferred directly to the component carrier in a
straightforward manner. The difference between purely flexible and
semi-flexible component carriers may be seen in that semi-flexible
component carriers may be more limited in their bending radius than
flexible component carriers. The bending radius of a semi-flexible
component carrier may for example be smaller than 5 mm, in
particular 3 mm. The use of a standard thin laminate may provide
semi-flexible component carriers as an especially cost-effective
alternative. A so-called "rigid-flex" component carrier may
furthermore combine the advantages of flexible and rigid printed
circuit boards, by yielding benefits for signal transmission, size
and stability.
[0022] According to a further exemplary embodiment, the layer stack
comprises a recessed portion, and the bendable portion is formed at
the recessed portion. This may provide the advantage that the
bendable portion can be manufactured in an easy and cost-efficient
manner. In an embodiment, a layer stack may be manufactured, for
example with ten layers. Then, a recessed portion may be provided
by forming a cavity, for example by laser drilling, sand-blasting,
photolithography, etching, or a combination thereof. After forming
the cavity, the layer stack at the recessed portion may comprise
less layers than non-recessed portions (e.g. only four). Due to the
reduced number of layers, the recessed portion may be more flexible
than the non-recessed portions. Therefore, the recessed portion may
form the bendable portion. However, there are also other
possibilities to provide a recessed portion. For example, there may
be more layers laminated on the non-recessed portions positions
than on the recessed portion position. In another embodiment, the
non-recessed portions and the recessed portion may be manufactured
separately and are then attached to each other in a later process
step.
[0023] According to a further exemplary embodiment, a non-recessed
portion of the layer stack is formed as a rigid portion which is
not bendable. This may also provide the advantage that the bendable
portion can be manufactured in an easy and cost-efficient manner.
The rigid portion(s) may be manufactured as described above.
[0024] According to a further exemplary embodiment, the bendable
portion is formed between a first rigid portion and a second rigid
portion. This may provide the advantage that the component carrier
is at the same time very flexible and still robust. In the final
component carrier, the rigid portions may then be moved relative to
each other, when bending the flexible, recessed portion arranged
between them.
[0025] According to a further exemplary embodiment, the bottom of
the bendable portion is flush with the bottom of the first rigid
portion and the bottom of the second rigid portion. This may
provide the advantage that the component carrier may be provided
with a robust and practicable design which can be manufactured in a
straightforward manner.
[0026] According to a further exemplary embodiment, the metal layer
is formed at the bottom of the bendable portion, and the metal
layer is not flush with the bottom the first rigid portion and the
bottom of the second rigid portion. This may provide the advantage
that the bending performance is further improved. In an embodiment,
the bendable portion may be flush with the bottoms of the rigid
portions. The metal layer, however, may be configured as an
additional layer which is arranged below the other layer(s) of the
bendable portion. In this embodiment, specific effects with respect
to the bending performance and/or stability may be achieved.
[0027] According to a further exemplary embodiment the recessed
portion is formed in a viewing direction being parallel to the main
directions of extension of the component carrier, and/or the
recessed portion is formed in a viewing direction being
perpendicular to the main directions of extension of the component
carrier. This may provide the advantage that the bending portion
can be provided in a flexible manner, wherein the size and position
of the bendable portion can be adjusted to different requirements.
For example, when the bendable portion is meant to be very bendable
and/or manufactured very cost-efficiently, a very large recess may
be chosen. In another example, wherein the bendable portion is
meant to be not very bendable, the bendable portion may be designed
by providing a very small recess. In one embodiment, the recessed
portion is formed only in one direction, and in another embodiment,
the recessed portion is formed in two directions. For example, in a
top view, in which the area of the bendable portion is completely
visible, one recessed portion may be formed above the bendable
portion (and between the first rigid portion and the second rigid
portion) and another recessed portion may be formed below the
bendable portion (and between the first rigid portion and the
second rigid portion) such that the bendable portion is at least
partially at a center position between the rigid portions. In
another embodiment, in a cross-sectional view, in which the area of
the bendable portion is not completely visible, one recessed
portion may be formed above the bendable portion (and between the
first rigid portion and the second rigid portion) and another
recessed portion may be formed below the bendable portion (and
between the first rigid portion and the second rigid portion) such
that the bendable portion is at least partially at a center
position between the rigid portions. These described embodiments
could also be combined together.
[0028] According to a further exemplary embodiment, at least one
layer of the layer stack extends from the first rigid portion
through the bendable portion to the second rigid portion. This may
provide the advantage that a robust component carrier can be
provided by using a straightforward manufacturing process. In this
manner, at least the layers shared by the rigid and the bendable
portions may be manufactured in one and the same process steps. By
providing continuous layers that extend through the rigid and the
bendable portions, the structure of the component carrier may be
very robust.
[0029] According to a further exemplary embodiment, the rigid
portions are connected to the bendable portion via a rigid
connection. This may provide the advantage that the component
carrier can be assembled in a flexible manner. According to an
embodiment, the rigid portions and the bendable portions may be
manufactured separately and are assembled later-on. In this case,
the different portions can be attached to each other individually
with respect to the requirements of the final component
carrier.
[0030] According to a further embodiment, the bending portion
comprises a further metal layer, and at least one electrically
insulating layer structure arranged between the metal layer and the
further metal layer. In this embodiment, an electrically insulating
layer structure of the layer stack may extend through the bendable
portion. Furthermore, also the metal layer and/or the further metal
layer may extend through the layer stack.
[0031] In an embodiment, an electronic component may be embedded in
the component carrier. The electronic component can be selected
from a group consisting of an electrically non-conductive inlay, an
electrically conductive inlay (such as a metal inlay, preferably
comprising copper or aluminum), a heat transfer unit (for example a
heat pipe), a light guiding element (for example an optical
waveguide or a light conductor connection), a die, or combinations
thereof. For example, the component can be an active electronic
component, a passive electronic component, an electronic chip, a
storage device (for instance a DRAM or another data memory), a
filter, an integrated circuit, a signal processing component, a
power management component, an optoelectronic interface element, a
light emitting diode, a photocoupler, a voltage converter (for
example a DC/DC converter or an AC/DC converter), a cryptographic
component, a transmitter and/or receiver, an electromechanical
transducer, a sensor, an actuator, a microelectromechanical system
(MEMS), a microprocessor, a capacitor, a resistor, an inductance, a
battery, a switch, a camera, a logic chip, a light guide, and an
energy harvesting unit. However, other components may be embedded
in or surface mounted on the component carrier. For example, a
magnetic element can be used as a component. Such a magnetic
element may be a permanent magnetic element (such as a
ferromagnetic element, an antiferromagnetic element or a
ferromagnetic element, for instance a ferrite coupling structure)
or may be a paramagnetic element. However, the component may also
be a substrate, an interposer or a further component carrier, for
example in a board-in-board configuration. Moreover, also other
components, in particular those which generate and emit
electromagnetic radiation and/or are sensitive with regard to
electromagnetic radiation propagating from an environment, may be
used as component.
[0032] In an embodiment, the at least one electrically insulating
layer structure comprises at least one of the group consisting of
resin (such as reinforced or non-reinforced resins, for instance
epoxy resin or Bismaleimide-Triazine resin, cyanate ester,
polyphenylene derivate, glass (in particular glass fibers,
multi-layer glass, glass-like materials), prepreg material (such as
FR-4 or FR-5), polyimide, polyamide, liquid crystal polymer (LCP),
epoxy-based Build-Up Film, polytetrafluoroethylene (Teflon), a
ceramic, and a metal oxide. Reinforcing materials such as webs,
fibers or spheres, for example made of glass (multilayer glass) may
be used as well. Although prepreg particularly FR4 are usually
preferred for rigid PCBs, other materials in particular epoxy-based
Build-Up Film for substrates for substrates may be used as well.
For high frequency applications, high-frequency materials such as
polytetrafluoroethylene, liquid crystal polymer and/or cyanate
ester resins, low temperature cofired ceramics (LTCC) or other low,
very low or ultra low DK-materials may be implemented in the
component carrier as electrically insulating layer structure.
[0033] In an embodiment, the component carrier comprises a stack of
at least one electrically insulating layer structure and at least
one electrically conductive layer structure. For example, the
component carrier may be a laminate of the mentioned electrically
insulating layer structure(s) and electrically conductive layer
structure(s), in particular formed by applying mechanical pressure
and/or thermal energy. The mentioned stack may provide a
plate-shaped component carrier capable of providing a large
mounting surface for further components and being nevertheless very
thin and compact. The term "layer structure" may particularly
denote a continuous layer, a patterned layer or a plurality of
non-consecutive islands within a common plane.
[0034] In an embodiment, the component carrier is shaped as a
plate. This contributes to the compact design, wherein the
component carrier nevertheless provides a large basis for mounting
components thereon. Furthermore, in particular a naked die as
example for an embedded electronic component, can be conveniently
embedded, thanks to its small thickness, into a thin plate such as
a printed circuit board.
[0035] In an embodiment, the component carrier is configured as one
of the group consisting of a printed circuit board, and a substrate
(in particular an IC substrate).
[0036] In the context of the present application, the term "printed
circuit board" (PCB) may particularly denote a plate-shaped
component carrier which is formed by laminating several
electrically conductive layer structures with several electrically
insulating layer structures, for instance by applying pressure
and/or by the supply of thermal energy. As preferred materials for
PCB technology, the electrically conductive layer structures are
made of copper, whereas the electrically insulating layer
structures may comprise resin and/or glass fibers, so-called
prepreg such as FR4 material. The various electrically conductive
layer structures may be connected to one another in a desired way
by forming through-holes through the laminate, for instance by
laser drilling or mechanical drilling, and by filling them with
electrically conductive material (in particular copper), thereby
forming vias as through-hole connections. Apart from one or more
components which may be embedded in a printed circuit board, a
printed circuit board is usually configured for accommodating one
or more components on one or both opposing surfaces of the
plate-shaped printed circuit board. They may be connected to the
respective main surface by soldering. A dielectric part of a PCB
may be composed of resin with reinforcing particles (such as
reinforcing spheres, in particular glass fibers).
[0037] In the context of the present application, the term
"substrate" may particularly denote a small component carrier
having substantially the same size as a component (in particular an
electronic component) to be mounted thereon. More specifically, a
substrate can be understood as a carrier for electrical connections
or electrical networks as well as component carrier comparable to a
printed circuit board (PCB), however with a considerably higher
density of laterally and/or vertically arranged connections.
Lateral connections are for example conductive paths, whereas
vertical connections may be for example drill holes. These lateral
and/or vertical connections are arranged within the substrate and
can be used to provide electrical and/or mechanical connections of
housed components or unhoused components (such as bare dies),
particularly of IC chips, with a printed circuit board or
intermediate printed circuit board. Thus, the term "substrate" also
includes "IC substrates". A dielectric part of a substrate may be
composed of resin with reinforcing spheres (such as glass spheres).
Furthermore, the component carrier may be configured as a
substrate-like-printed circuit board (SLP).
[0038] The substrate or interposer may consist of at least a layer
of glass, Silicon (Si) or a photo-imageable or dry-etchable organic
material like epoxy-based Build-Up films or polymer compounds like
Polyimide, Polybenzoxazole, or Benzocyclobutene.
[0039] In an embodiment, the at least one electrically conductive
layer structure and/or the electrically conductive structure
comprises at least one of the group consisting of copper, aluminum,
nickel, silver, gold, palladium, cobalt, and tungsten. Although
copper is usually preferred, other materials or coated versions
thereof are possible as well.
BRIEF DESCRIPTION OF THE DRAWINGS
[0040] FIG. 1 illustrates a cross-sectional view of a component
carrier according to an exemplary embodiment of the invention.
[0041] FIG. 2 illustrates a cross-sectional view of a component
carrier according to a further exemplary embodiment of the
invention.
[0042] FIG. 3 illustrates a top view of a component carrier
according to a further exemplary embodiment of the invention.
[0043] FIG. 4 illustrates a cross-sectional view of a component
carrier according to a further exemplary embodiment of the
invention.
[0044] FIGS. 5a to 5c illustrate experimental data with respect to
the strain occurring at a bendable portion of a prior art example
and of a component carrier according to an exemplary embodiment of
the invention.
DETAILED DESCRIPTION OF ILLUSTRATED EMBODIMENTS
[0045] The aspects defined above and further aspects of the
invention are apparent from the examples of embodiment to be
described hereinafter and are explained with reference to these
examples of embodiment.
[0046] The illustrations in the drawings are schematically
presented. In different drawings, similar or identical elements are
provided with the same reference signs.
[0047] FIG. 1 illustrates a cross-sectional view (along the Y-axis,
see axis indicated in the Figure) of a component carrier 100
according to an exemplary embodiment. The component carrier 100
comprises a layer stack 101 having electrically conductive layer
structures 104 and electrically insulating layer structures 102.
Furthermore, the component carrier 100 comprises a bendable portion
120 which forms at least a part of the layer stack 101. The layer
stack 101 comprises hereby a recessed portion 122, and the bendable
portion 120 is formed at the recessed portion 122. Non-recessed
portions 121, 123 of the layer stack 101 are formed as a first
rigid portion 121 and a second rigid portion 123 which are not
bendable. The bendable portion 120 is formed between the two rigid
portions 121, 123, and the bottom of the bendable portion 120 is
flush with the bottoms of the rigid portions 121, 123 which are
arranged next to the bendable portion 120. The recessed portion 122
is formed in a viewing direction being parallel to one of the main
directions of extension of the component carrier 100. In other
words, the recessed portion 122 is formed along the indicated
Z-axis. The main directions of extension of the component carrier
are hereby along the X and Y axis. Two layers 102, 104 of the layer
stack 101 extend from the first rigid portion 121 through the
bendable portion 120 to the second rigid portion 123. Hereby, a
metal layer 130 forms a part of the bendable portion 120 and of the
layer stack 101. The metal layer 130 is a continuous layer and
covers the whole area of the bendable portion 120 and is a
configured as a copper foil. The area of the bendable portion 120
is along the main directions of extension of the component carrier
100 and the layer stack 101, which extend along the X- and the
Y-axis. In this exemplary embodiment, the metal layer 130 extends
from the first rigid portion 121 through the bendable portion 120
to the second rigid portion 123.
[0048] FIG. 2 illustrates a cross-sectional view (along the Y-axis)
of a component carrier 200 according to a further exemplary
embodiment. The component carrier 200 according to FIG. 2 is very
similar to the component carrier 100 of FIG. 1, however, the metal
layer 230 is formed at the bottom of the bendable portion 120, and
the metal layer 230 is not flush with the bottom of the neighboring
rigid portions 121, 123. The bendable portion 120, without the
metal layer 230, is flush with the bottoms of the rigid portions
121, 123. The metal layer 230 is configured as an additional layer
which is arranged below the other layers of the bendable portion
120.
[0049] FIG. 3 illustrates a top view (along the Z-axis) of a
further exemplary embodiment of a component carrier 300. The
component carrier 300 according to FIG. 3 is very similar to the
component carrier 100 of FIG. 1, however, the recessed portion 122
is formed in a viewing direction being parallel to one of the main
directions of extension of the component carrier 100 and the
recessed portion 122 is formed in a viewing direction being
perpendicular to the main directions of extension of the component
carrier 100. In other words, the recessed portion is formed in the
direction along the indicated Z-axis of FIG. 1 and in the direction
along the indicated Y-axis of FIG. 3. In this example, the bendable
portion 120 is arranged at a center position between the rigid
portions 121, 123. It can be seen in the FIG. 3, that the metal
layer 130 is not restricted to the bendable portion 120 but extends
also into the rigid portions 121, 123 of the layer stack 101, which
rigid portions 121, 123 are arranged next to the bendable portion
120. The area 331 of the bendable portion 120 is along the main
directions of extension of the component carrier 100 and the layer
stack 101, which extend along the X- and the Y-axis.
[0050] FIG. 4 illustrates a cross-sectional view of the bendable
portion 420 of a component carrier 400 according to an exemplary
embodiment. The bendable portion 420 is build-up of the following
layer stack from bottom to top: i) a solder mask 450, e.g. made of
epoxy acrylate, which forms the outermost layer of the bendable
portion 420, ii) a first metal layer 130a, e.g. a copper foil,
being arranged directly in contact with the solder mask 450, iii) a
first electrically insulating layer structure 102a, e.g. made of
prepreg, iv) a second (further) metal layer 130b, and v) a second
electrically insulating layer structure 102b, e.g. also made of
prepreg. In this exemplary embodiment, the bendable portion 420 and
the rigid portions 421, 423 are connected via a rigid connection.
The layers of the bendable portion 420 are only present in said
bendable portion 420 and do not extend through the rigid portions
421, 423. The height of the rigid portion 421, 423 is for example
around 1.6 mm.
[0051] FIGS. 5a to 5c illustrate experimental data with respect to
the strain occurring at the bendable portion of a prior art example
and of a component carrier according to an exemplary embodiment of
the invention.
[0052] FIG. 5a: a component carrier 500 comprises two rigid
portions 521, 523 which are flexibly connected to each other via a
bendable portion 520. The indicated square shows a region of
interest, which is further shown in detail in FIGS. 5b and 5c, at
an interface between the first rigid portion 521 and the bendable
portion 520. The rigid portions 521, 523 are hereby shifted
90.degree. with respect to each other such that a large strain
occurs at the bending portion 520. Strain is hereby a measure of
deformation representing the displacement between particles in the
body relative to a reference length. The result is hereby given in
percent.
[0053] FIG. 5b: in this example from the prior art, the outermost
layer of the bendable portion is made of a resin layer covered with
a solder mask. When investigating the strain, it can be seen that,
at the resin/solder mask interface, there occurs a strain of 5.8%.
This is highly critical, because the strain in a resin layer should
not be more than 2%. Thus, the failure rate (e.g. formation of
cracks) is significantly high in this case. Hereby, the reserve
factor (factor of safety, defined by the failure load divided by
the effective load) is <1).
[0054] FIG. 5c: in this exemplary embodiment of the invention, the
outermost layer of the bendable portion 520 is a metal layer (full
copper) covered with a solder mask. When investigating the strain,
it can be seen that, at the copper/solder mask interface, there
occurs a strain of 3.7%. This is not at all critical, because the
strain in a copper layer could even be larger than 10%. Thus, the
failure rate is significantly lower in this case (reserve factor
>2).
[0055] It should be noted that the term "comprising" does not
exclude other elements or steps and the article "a" or "an" does
not exclude a plurality. Also, elements described in association
with different embodiments may be combined.
[0056] Implementation of the invention is not limited to the
preferred embodiments shown in the figures and described above.
Instead, a multiplicity of variants is possible which use the
solutions shown and the principle according to the invention even
in the case of fundamentally different embodiments.
REFERENCE SIGNS
TABLE-US-00001 [0057] 100, 200, 300, 400, 500 Component carrier 101
Layer stack 102, 102a, 102b Electrically insulating layer structure
104 Electrically conductive layer structure 120, 420, 520 Bendable
portion 121, 421, 521 First rigid (non-recessed) portion 122
Recessed portion 123, 423, 523 Second rigid (non-recessed) portion
130, 130a, 230 Metal layer 130b Further metal layer 331 Area of the
bendable portion 450 Solder mask
* * * * *