U.S. patent application number 11/164411 was filed with the patent office on 2006-09-07 for laser-based technique for the fabrication of embedded electrochemical cells and electronic components.
This patent application is currently assigned to The Government of the USA, as represented by the Secretary of the Navy Naval Research Laboratory. Invention is credited to Craig B. Arnold, Ray Auyeung, Michael Nurnberger, Alberto Pique.
Application Number | 20060197194 11/164411 |
Document ID | / |
Family ID | 33567582 |
Filed Date | 2006-09-07 |
United States Patent
Application |
20060197194 |
Kind Code |
A1 |
Arnold; Craig B. ; et
al. |
September 7, 2006 |
LASER-BASED TECHNIQUE FOR THE FABRICATION OF EMBEDDED
ELECTROCHEMICAL CELLS AND ELECTRONIC COMPONENTS
Abstract
A method is provided for embedding electronic components
including electrochemical cells within a circuit board substrate.
The method includes micromachining the printed circuit board
substrate to a selective depth to form a recess. A component is
inserted into the recess and an electrical connection is
established between the electrical component and a metallized
pattern of the circuit board substrate using, e.g., laser
direct-write.
Inventors: |
Arnold; Craig B.;
(Alexandria, VA) ; Pique; Alberto; (Crofton,
MD) ; Auyeung; Ray; (Alexandria, VA) ;
Nurnberger; Michael; (Alexandria, VA) |
Correspondence
Address: |
NAVAL RESEARCH LABORATORY;ASSOCIATE COUNSEL (PATENTS)
CODE 1008.2
4555 OVERLOOK AVENUE, S.W.
WASHINGTON
DC
20375-5320
US
|
Assignee: |
The Government of the USA, as
represented by the Secretary of the Navy Naval Research
Laboratory
Naval Research Laboratory 4555 Overlook Ave, SW; Code
1008.2
Washington
DC
|
Family ID: |
33567582 |
Appl. No.: |
11/164411 |
Filed: |
November 22, 2005 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
10868448 |
Jun 9, 2004 |
6986199 |
|
|
11164411 |
Nov 22, 2005 |
|
|
|
60478471 |
Jun 11, 2003 |
|
|
|
Current U.S.
Class: |
257/665 |
Current CPC
Class: |
Y10T 29/49117 20150115;
H05K 2201/10037 20130101; H05K 2203/107 20130101; H05K 3/0038
20130101; H05K 2203/1469 20130101; H05K 1/16 20130101; H05K 1/183
20130101; Y10T 29/4913 20150115; Y10T 29/49124 20150115 |
Class at
Publication: |
257/665 |
International
Class: |
H01L 23/62 20060101
H01L023/62 |
Claims
1. An electronic device comprising: a substrate having a conductive
pattern on a top surface thereof; a first micromachined recess
formed in said substrate; at least one electronic component
disposed in said first recess; and an electrical connection between
said at least one electronic component and said conductive
pattern.
2. The device of claim 1, wherein said at least one electronic
component is an electrochemical cell.
3. The device of claim 2, wherein said electrochemical cell
comprises an aqueous material.
4. The device of claim 1, wherein said at least one electronic
component comprises a complete electronic or opto-electronic
component.
5. The device of claim 1, wherein said at least one electronic
component is comprised of a film comprising layers of
electrochemically active material, electrolyte, current collector
and an encapsulating material.
6. The device of claim 1, wherein said at least one electronic
component is comprised of a multilayer film comprising a current
collector, an electrochemically active material, one of an
electrolyte or a separator, a second electrochemically active
material, a second current collector, and an encapsulating
material.
7. The device of claim 1, wherein said at least one electronic
component comprises a transmission line.
8. The device of claim 1 further comprising a second micromachined
recess in said substrate and said at least one electronic component
comprises one electronic component in each of the recesses.
9. The device of claim 8 wherein said second micromachined recess
is disposed adjacent to said first recess, and formed through a
same side of said substrate.
10. The device of claim 8 wherein said second micromachined recess
is formed in said substrate on a side opposite from where said
first recess is located.
11. The device of claim 32, further comprising a via is formed
between said first recess and said second recess.
12. The device of claim 1, wherein said at least one electronic
component comprises two electronic components stacked on top of
each other and disposed in said first recess.
Description
CROSS REFERENCE TO RELATED APPLICATIONS
[0001] This application is a divisional application of U.S. patent
application Ser. No. 10/868,448, filed on Jun. 9, 2004, allowed,
which claims priority to U.S. Provisional Patent Application No.
60/478,471, filed on Jun. 11, 2003, both incorporated herein by
reference.
FIELD OF THE INVENTION
[0002] The present invention relates to electronic devices and
components and methods for fabricating electronic devices and
components, and in particular, to embedded electronic devices and
components and methods for fabricating electronic devices and
components by embedding an electrical component in a recess formed
in a circuit board substrate.
DESCRIPTION OF RELATED ART
[0003] The size and weight of small, unobtrusive devices is
dominated by the size and weight of the internal circuit boards,
the electrical components which are mounted on the surface of
circuit boards, and by the energy storage devices such as batteries
that supply the power to the various electronic components. The
surface area of the internal circuit board is considered very
valuable as there is only a finite amount of space for adding
components. Of course, as components are added to the internal
circuit board, the height and mass of the device increases.
[0004] In order to address the dimensional limitations of
electronic devices, previous techniques, such as the use of thin
film printing techniques as well as techniques for embedding
electronic components in to a circuit board, have been developed to
reduce the thickness of electronic components. However, previous
techniques for embedding components have relied primarily on the
addition of material around the discrete electronic components,
thereby effectively building a laminated circuit board from the
bottom up.
[0005] These prior art approaches are inherently limited as they
require special development and optimization for each individual
circuit design, involve a significant cost increase to circuit
board manufactures and reduce the ability to add additional
components to an existing circuit board or modify the circuit
design.
BRIEF SUMMARY OF THE INVENTION
[0006] The present invention relates to a method for embedding
electronic components including electrochemical cells into a
circuit board. The method can be adapted to use a standard
commercially available circuit board which is then micromachined,
in one embodiment using a laser, for example, to form a recess to a
controlled depth. The recess provides a location within the
thickness of the circuit board for a thin, electronic component.
After micromachining, the electric component or components such as,
for example, a surface mount capacitor or resistor, are placed in
the machined region of the circuit board. Electrical contacts to
the component are made using a non-contact, low-temperature,
direct-write technique that connects the surface mount component
disposed in the machined region to metallized patterns on the
circuit board. One important feature of the invention is that the
method can be carried out using a single machine, in contrast to
prior art methods wherein additional processing steps/machines are
required.
[0007] In accordance with one aspect form of the present invention,
a method is provided for fabricating an electronic device. The
method includes providing a substrate having a metallized or
conductive pattern on a top surface and micromachining the
substrate from the top surface to a selected depth so as to form a
first recess in the substrate. At least one electronic component is
inserted into the first recess, and electrical connections are
established between at least one electrical component and the
metallized pattern on the substrate using laser directed writing
(or any other method) of conductive material. It will be understood
that while in the foregoing description the substrate is described
as having a metallized pattern thereon, any conductive pattern can
be used and the conductive pattern can, in general, be added at any
time.
[0008] In accordance with another aspect form of the present
invention, a method is provided for fabricating an electronic
device which includes providing a substrate having a metallized or
conductive pattern on a top surface. The substrate is micromachined
from the top surface to a selected depth so as to form a recess in
the substrate, and conductive material is deposited into the recess
to form a first conductive line. A dielectric material is added
into the recess on top of the conductive line and a second
conductive line is written on the dielectric material using laser
(or other means of) directed writing of conductive material. In one
embodiment, this method is used for the fabrication of embedded
waveguides for the transmission of RF signals and also for other RF
structures.
[0009] According to yet another aspect of the invention, there is
provided an embedded electronic device which comprises a substrate
having a metallized pattern on a top surface. A micromachined first
recess is formed in the substrate and at least one electronic
component is disposed in the first recess. An electrical connection
connects at least one electronic component and the metallized
pattern together.
[0010] One important feature of the invention is that it allows the
embedding of dissimilar components such as passive and active
electronic components as well as electrochemical cells using a
common approach or method.
[0011] Further features and advantages of the present invention
will be set forth in, or apparent from, the detailed description of
preferred embodiments thereof which follows.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 is a cross-section schematic view of an embedded
electronic component in the form of an electrochemical cell in
accordance with one embodiment of the present invention;
[0013] FIG. 2 is a cross-section schematic view of another
electrochemical cell in accordance with a further embodiment of the
present invention;
[0014] FIG. 3 is a cross-section schematic view of an embedded
surface mount electronic component in accordance with another
embodiment of the present invention;
[0015] FIG. 4 is a cross-section schematic view of a stacked
electronic component in accordance with yet another embodiment of
the present invention;
[0016] FIG. 5 is a cross-section schematic view of an embedded
coaxial waveguide electronic component;
[0017] FIG. 6 is a cross-section schematic view of a stacked
two-component embedded electronic component device; and
[0018] FIG. 7 is a cross-section schematic view of an embedded
multilayered electronic component in accordance with a further
embodiment of the present invention.
DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS
[0019] The present invention will now be described in relation to
the preferred embodiments thereof as depicted in the several
figures wherein similar components have the same reference number
increased by one hundred so as to correspond with the figure
number.
[0020] Referring now to FIG. 1, device 100 includes an
electrochemical cell formed in a circuit board substrate 102.
Substrate 102 can, for example, be any suitable circuit board,
including but not limited to, metals, semiconductors, insulators,
ceramics, and multilayered structures which include previously
embedded structures. Advantageously, the substrate 102 may be
chemically resistant and have low processing temperatures such as
is characteristic of many plastics or commonly available circuit
board materials. The shape of the substrate 102 although depicted
as planar, may be of any arbitrary three-dimensional shape,
including planar, spherical or complex curved.
[0021] Substrate 102 includes a bottom metallic layer 104 having an
exterior surface 104a and interior surface 104b, an intermediate
insulating layer 108 and a top surface layer 112 which includes a
metallized pattern. The metallized pattern includes but is not
limited to passive and active electronic circuits or
opto-electronic circuits.
[0022] The top surface 112 is micromachined to form multiple
adjacent recesses 120, 122, and 124. A micromachining system
suitable for forming the recesses 120, 122, and 124 includes an
apparatus which can remove top surface 112 and insulating material
which composes intermediate layer 108. Advantageously, this can be
done by using a dual-laser system in which one high peak-power
(pulsed) laser removes the metallic material and a second pulsed or
cw laser, operating at a different wavelength, removes the
insulating material either solely or with the aid of the first
laser. The laser beams from the two lasers co-propagate along or
nearly along the same optical axis towards the sample. A second
laser operating in pulsed mode and at a wavelength with a higher
absorption in the insulating material than the first laser can have
enough fluence to completely ablate and remove this material.
Alternatively, the second laser can operate in cw mode (and also at
a different wavelength than the first laser) to convert part or all
of the insulating material into a liquid and/or vapor phase before
the other high peak-power laser beam arrives to completely remove
the material.
[0023] One advantage of using the dual-laser system is that the
time and spatial offset between the laser pulses coming from each
laser is variable in duration and in order. Therefore, the amount
and duration of thermal and ablative processes acting on the sample
can be controlled. Advantageously, in one preferred dual-laser
system, the temperature of the machined substrate 102 is monitored
by a temperature sensor whose output is fed back to control the
interaction time, and power of the dual-laser system. This feedback
is used to prevent catastrophic damage to the substrate during the
machining processes.
[0024] It will be understood that although the dual laser system
has advantages in certain applications (e.g., when used with
particular substrate materials), a single laser is, in general,
sufficient for the purposes of the invention.
[0025] In an alternative method of machining substrate 102 to form
the recesses 120, 122, and 124 and depositing material, rather than
using laser micromachining, any available machining process known
in the art for manufacturing circuit boards may be employed,
including but not limited to, mechanical machining or milling,
etching, and laser machining combined with an additive direct-write
process which includes ink-jet, micro-pen and laser
direct-write.
[0026] After the recesses 120, 122, and 124 are formed, individual
electronic components are inserted into the recesses 120, 122, and
124 to form an electrochemical cell 130. First, electrically
conductive materials are deposited in the recesses 120, 122, and
124 to form an electrochemical cathode 131a, 131b and anode 132.
Electrochemically active material 133 is deposited on cathode 131a,
131b and anode 132, and an electrolyte material 134 is deposited on
top of the electrochemically active material 133. The electrolytic
material 134 can be either a solid or an aqueous material. Finally,
an encapsulating potting material 135 is deposited over the
electrolytic material 134.
[0027] It will be understood that in a workable implementation the
metallized layer 104 would not short circuit the anode region 132
and cathode regions 131a, 131b as appears to be shown in FIG. 1. In
practice, the metallized layer 104 is machined or patterned such
that the anode 132 and cathode 131a, 131b are electrically
isolated. Thus, in FIG. 1, material (not shown) would be removed
from layer 104 below the separating walls between anode 132 and
cathode 131a, 131b.
[0028] It will also be appreciated that the order of formation
described above (cathode, then separator and then anode) can be
reversed so that the anode is formed first, then the substrate and
finally the cathode. Alternatively, the entire final sample can be
"dipped" in a liquid (e.g., a thermosetting or thermoplastic liquid
or the like) which would completely seal and cover up the embedded
components upon drying.
[0029] Referring now to FIG. 2, an alternative electrochemical cell
is fabricated using the present method in which electronic device
200 comprises a circuit board 202 in which recess 220 is
micromachined from top surface 212 through intermediate insulating
layer 208 to an interior surface 204b of a bottom metallic layer
204 which also has an exterior surface 204a. In forming recess 220,
the circuit board 202 is micromachined using a dual wavelength
laser which incorporates ultraviolet laser light and infrared laser
light to remove substrate materials of the intermediate insulating
layer 208 and top layer 212 in a method similar to the one used in
accordance with the embodiment depicted in FIG. 1.
[0030] An electronic component in the form of electrochemical cell
230 is inserted into the recess 220 by depositing a single
multilayer film which comprises layers of a current collector 231,
an electrochemically active material 233, an electrolyte 234, a
second electrochemically active material 236, a second current
collector 232 and an encapsulating material 235. The first current
collector 231 layer forms a cathode and the second current
collecting layer 232 forms the anode of the embedded
electrochemical cell 230.
[0031] It is pointed out that the drawing in FIG. 2 can be
simplified. Because the circuit board is metallized, element 231
can be viewed as the electrochemically active materials, elements
233, 234 and 236 lumped together as the electrolyte/separator, 232
as the other electrochemical material and 235 as the current
collector. In this case the current collector acts as the
encapsulating material.
[0032] Examples of some electrochemical cells which can be embedded
using the present method include hydrous ruthenium oxide
supercapacitors, lithium-ion batteries and other alkaline
cells.
[0033] Referring now to FIG. 3, the present method may be used to
form the electronic device 300 which includes an embedded surface
mount component 330. The electronic component 300 is formed in
substrate 302 which includes bottom layer 304, intermediate
insulating layer 308 and top surface 312 having a metallized
pattern. Recess 320 is formed by micromachining using the technique
described above with regard to the embodiments of FIGS. 1 and 2.
The surface mount component 330 is embedded or inserted into recess
320 as a complete electronic or opto-electronic component.
Subsequently, connection tabs 350 and 352 are deposited on the
electronic device 300 by laser direct-write deposition of metal or
conductive ink, although other methods can also be used. The
connection tabs 350, 352 provide an electrical connection between
the surface mount component 320 and the metallized pattern present
on the top surface 312.
[0034] The surface mount component 330 may be any known electronic
or opto-electronic component known to one of ordinary skill in the
art which can be embedded into the recess of a circuit board
machined as described herein. Such components include but are not
limited to a capacitor, resistor, inductor, active device such as
LEDs, diodes, transistors and other semiconductor devices,
microdevices such as MEMS or MOEMS, or IC dies and other RF
components.
[0035] Referring now to FIG. 4, the present method is used to form
an electronic device 400 which includes a stacked structure formed
from two multilayer films 430, 440. The electronic device 400 is
formed by micromachining two recesses 420, 422 in the top surface
412 and bottom layer 404, respectively, using the method described
above with regard to the embodiments of FIGS. 1 and 2. A single
multilayer film 430, 440 is inserted into recesses 420, 422,
respectively. The multilayer film 430, 440 is composed of layers:
current collection layer 431, 441 electrochemically active layer
436, 446, electrolyte layer 434, 444 and encapsulating layer 435,
445. Current collector 431 forms a cathode and current collector
441 forms an anode. The intermediate substrate 408 acts as a
separator between the cathode and the anode.
[0036] Viewing FIG. 4 differently, 441 and 431 could be the
electrochemically active materials and 436 and 446 the current
collectors; separate electrolyte layers are not actually necessary
in that the electrolyte is mixed in with the electrochemically
active materials.
[0037] Next, metallic connection tabs 450, 452 and 454, 456 are
deposited on films 440, 430, respectively, so as to make contact
with the rest of the circuit board 402 and in particular a
metallized pattern on the top surface 412 and a metallized pattern
in bottom layer 404, respectively. The metallic connection tabs
450, 452, 454, and 456 are preferably deposited using the same
method described above with regard to the device 300 of FIG. 3.
[0038] Referring now to FIG. 5, an electronic device 500 is
provided which preferably comprises an embedded coaxial waveguide
or stripline or transmission line, indicated generally at 530.
[0039] The device 500 is fabricated by first forming recess 520 by
micromachining through the substrate layer 508 of the circuit board
substrate 502. Next, insulating layer 513 is deposited over the
substrate including in the recess 520. Then a complete coaxial
waveguide 530 which includes a feed line 532 and dielectric
material 533 is inserted into recess 520. Subsequently, a second
conductive line 560 is laser written on the dielectric material 533
of the coaxial waveguide 530 within the recess 520.
[0040] It will be appreciated that the specific embodiment shown in
FIG. 5 is an inverted microstrip line. By changing layer 513 (or at
least the portion thereof in recess 520) to metal, a coaxial
waveguide or stripline transmission line results. With additional
layers, an embedded coplanar waveguide or coplanar strip
transmission line is produced. Thus, it will be understood that the
invention is not in any way limited to the specific embodiment
illustrated in FIG. 5.
[0041] Referring now to FIG. 6, in yet another embodiment, device
600 is formed in circuit board substrate 602 having recess 620
micromachined through a top surface 624 and a second recess 622
formed through bottom layer 604 in accordance with the method
described above with regard to device 100.
[0042] An electronic component 630 is inserted in recess 620 and
electronic component 640 is inserted in recesses 622. A via 624 is
formed in the intermediate layer 608 separating the recesses 620
from recess 622 using any conventional via fabrication method known
in the art. Electrical connection 626 electrically couples
electronic component 630 with the electronic component 640.
[0043] Metallic connection tabs 650, 652 and 654, 656 are deposited
using the same method as described above with regard to device 300
of the embodiment depicted in FIG. 3.
[0044] Referring now to FIG. 7, electronic device 700 is formed in
circuit board substrate 702 which has a recess 720 formed therein
using the method described above with regard to the embodiment
depicted in FIG. 1. An electrically conductive layer 772, an
electrically insulating layer 773, an electrically conducting layer
774, an electrically insulating layer 775, and an electrically
conducting layer 776 are deposited in order in the recess 720.
Metallic connection tabs 750, 752 are formed using non-contact,
low-temperature, laser (or non-laser) direct-write technique to
conductively connect the component 770 to the metallized pattern on
the top surface 724 of the circuit board substrate 702.
[0045] In an alternative embodiment of the one shown in FIG. 7,
rather than depositing electrically conducting material 772, layer
772 may alternatively be a resistive, semiconducting,
piezoelectric, dielectric, ferrite or any other type of depositable
material known in the art and in keeping with the spirit and scope
of the present method.
[0046] Referring to any of the embodiments, the present laser
micromachining method is adapted to micromachine to a particular
depth which if desired can remove all circuit board material and
leave only exposed the metallic layer from a bottom layer of a
circuit board. Such is the case in the electronic device 200 of
FIG. 2. Subsequently, interconnects can be made through the
resulting circuit board using low temperature laser or other
direct-write techniques described herein to make contact between
both sides of the circuit board, i.e., from both bottom layer 204
and top surface 212. For example, this technique may be used for
radio frequency (RF) and antenna applications.
[0047] In addition, the present method may be adapted to form a
recess for components on opposite sides of a single substrate which
may be either electrically isolated from one another or
electrically connected through conductive vias or through
holes.
[0048] Further, the present method may be adapted for use with
particularly porous circuit board materials where the circuit
boards can be presoaked with a polymer solution to fill in pores
making the circuit board more able to contain aqueous components of
electrochemical cells.
[0049] In order to provide a better understanding of the present
method, the following non-limiting embodiments provide further
examples of modifications and adaptations of the present method and
resulting electronic and electrochemical cells formed using the
various adaptations of the present method.
[0050] The present method may be used for forming an embedded
transmission line within a substrate which includes micromachining
a substrate to form a recess, depositing an electrically conducting
layer in the recess, depositing an electrically conducting
material, depositing an additional insulting material and
depositing additional conductive material.
[0051] The present method may be adapted to make an embedded
antenna or transmission line within a substrate which includes
micromachining the substrate to form a recess, depositing
electrically conducting, resistive, superconducting, piezoelectric,
dielectric, ferrite or any other type of material into the recess,
and depositing an encapsulating material into the recess.
[0052] Further, the present method may be used for forming an
embedded sensor within a substrate which includes micromachining a
substrate to form a recess, depositing a sensor material into the
recess, depositing one or more electrical contacts into the recess,
depositing selective porous encapsulating material into the
recess.
[0053] As should now be apparent to one of ordinary skill in the
art, the present method may be used to form an electronic device
having an electronic component which includes but are not limited
to an alkaline battery, lithium battery, ultracapacitor,
transmission line or strip, resonator, passive or active antenna,
sensor, and a passive and active electronic circuit or
opto-electronic circuit.
[0054] Further, the present method may be adapted to remove and add
components at various locations on a substrate using the present
laser system.
[0055] As will be further apparent to one of ordinary skill in the
art, the present method provides features and advantages not
present in prior methods. For example, the present method provides
for embedding electronic components, such as electrochemical cells
to reduce the size and weight of devices utilizing circuit boards
or other substrates with surface mount components. By directly
embedding the electronic component into the circuit board, the
resulting device is more autonomous while having a lower profile.
Unlike prior devices wherein components are embedded directly into
circuit boards and materials are added to the surface to build up a
component in and around the circuit board, the present method
provides for using any currently available circuit board or
substrate and modifying that board as necessary to embed the
component using techniques including both the removing of portions
of the existing circuit board using micromachining and then
building up other portions of that circuit board using laser
writing or other means of direct writing.
[0056] Further, using the present laser micromachining process, one
is able to accurately control the depth by which one produces a
recess in the circuit board substrate. Further, using the present
laser direct-write process, one can add metallic conducting lines
above an embedded element to make electric contact to the rest of
the circuit board.
[0057] An additional feature and advantage of the present method is
provided through using a low temperature process for making
electrical contact.
[0058] Further, the present method can produce electrochemical
cells which may be either layered or planar structures embedded
within the circuit board material.
[0059] A further feature relates to now being able to embed
electrochemical cells having aqueous electrolyte material whereas
prior techniques for embedding electrochemical cells permitted only
solid electrolytes.
[0060] In addition, unlike prior embedded electrochemical cells
which required large areas, the present method provides for a
reduction in size of these components to a sub-millimeter
scale.
[0061] Further, the present method in one form or embodiment uses a
dual wavelength laser to accurately micromachine and remove circuit
board material down to the metal layer of the bottom surface of a
circuit board. Prior techniques have used screen printing and
contact methods for adding material to existing circuit boards but
these methods are not viable for use on existing circuit boards
with attached components. However, the present method provides for
adding material which is non-contact and conformable so one can add
material on almost any circuit board substrate.
[0062] In addition, the present method allows for laser
direct-write technique for adding material directly where required
thus eliminating the need for lithography or patterning. Further,
the present laser machining and laser direct-write deposition have
advantages over other prior non-lithographic techniques in that the
present laser machine and laser direct-write deposition provides
for higher resolution such as around approximately 10
micrometers.
[0063] Although the invention has been described above in relation
to preferred embodiments thereof, it will be understood by those
skilled in the art that variations and modifications can be
effected in these preferred embodiments without departing from the
scope and spirit of the invention.
* * * * *