U.S. patent application number 16/176630 was filed with the patent office on 2020-04-30 for additive deposition low temperature curable magnetic interconnecting layer for power components integration.
The applicant listed for this patent is Texas Instruments Incorporated. Invention is credited to Luu Thanh Nguyen, Anindya Poddar, Ashok Prabhu, Yi Yan.
Application Number | 20200135381 16/176630 |
Document ID | / |
Family ID | 70327157 |
Filed Date | 2020-04-30 |
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United States Patent
Application |
20200135381 |
Kind Code |
A1 |
Yan; Yi ; et al. |
April 30, 2020 |
ADDITIVE DEPOSITION LOW TEMPERATURE CURABLE MAGNETIC
INTERCONNECTING LAYER FOR POWER COMPONENTS INTEGRATION
Abstract
Apparatus to form a transformer, an inductor, a capacitor or
other passive electronic component, with patterned conductive
features in a lamination structure, and one or more ferrite sheets
or other magnetic core structures attached to the lamination
structure via one or more inkjet printed magnetic adhesive layers
that join the magnetic core structure or structures to the
lamination structure.
Inventors: |
Yan; Yi; (Sunnyvale, CA)
; Nguyen; Luu Thanh; (San Jose, CA) ; Prabhu;
Ashok; (San Jose, CA) ; Poddar; Anindya;
(Sunnyvale, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Texas Instruments Incorporated |
Dallas |
TX |
US |
|
|
Family ID: |
70327157 |
Appl. No.: |
16/176630 |
Filed: |
October 31, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L 2224/48195
20130101; H01F 27/306 20130101; H01F 27/266 20130101; H01F 41/24
20130101; H01L 24/48 20130101; H01L 2223/6666 20130101; H01F
2027/2819 20130101; H01L 2224/48177 20130101; H01L 23/49589
20130101; H01L 23/495 20130101; H01L 23/66 20130101; H01F 27/2804
20130101; H01L 23/49575 20130101; H01L 23/3107 20130101; H01F 27/40
20130101 |
International
Class: |
H01F 27/26 20060101
H01F027/26; H01L 23/495 20060101 H01L023/495; H01L 23/00 20060101
H01L023/00; H01F 27/28 20060101 H01F027/28; H01F 41/24 20060101
H01F041/24; H01F 27/40 20060101 H01F027/40; H01L 23/66 20060101
H01L023/66 |
Claims
1. An apparatus, comprising: a lamination structure, including a
patterned conductive feature that forms a part of a passive
electronic component; a core structure; and a magnetic adhesive
layer that joins the core structure to the lamination
structure.
2. The apparatus of claim 1, wherein the lamination structure
includes a plurality of patterned conductive features.
3. The apparatus of claim 2, further comprising: a first magnetic
adhesive layer that joins a first magnetic core structure to a
first side of the lamination structure; and a second magnetic
adhesive layer that joins a second magnetic core structure to a
second side of the lamination structure.
4. The apparatus of claim 3, wherein the lamination structure
includes a plurality of patterned conductive layers.
5. The apparatus of claim 2, wherein the passive electronic
component is a transformer, and wherein the lamination structure
includes: a conductive primary winding; and a conductive secondary
winding magnetically coupled with the conductive primary winding by
the core structure and the magnetic adhesive layer.
6. The apparatus of claim 2, wherein the passive electronic
component is an inductor, and wherein the lamination structure
includes a conductive winding magnetically coupled with the core
structure and the magnetic adhesive layer.
7. The apparatus of claim 2, wherein the passive electronic
component is a capacitor, and wherein the lamination structure
includes first and second capacitor plates.
8. The apparatus of claim 1, further comprising: a first magnetic
adhesive layer that joins a first magnetic core structure to a
first side of the lamination structure; and a second magnetic
adhesive layer that joins a second magnetic core structure to a
second side of the lamination structure.
9. The apparatus of claim 8, wherein the lamination structure
includes a plurality of patterned conductive layers.
10. The apparatus of claim 1, wherein the lamination structure
includes a plurality of patterned conductive layers.
11. The apparatus of claim 1, wherein the core structure includes a
magnetic material.
12. A method, comprising: performing an inkjet printing process
that prints a magnetic ink epoxy on a magnetic core structure, or
on a lamination structure; and attaching the magnetic core
structure to the lamination structure via the magnetic ink
epoxy.
13. The method of claim 12, further comprising: performing another
inkjet printing process that prints a second magnetic ink epoxy on
the lamination structure; and attaching a second magnetic core
structure to the lamination structure via the second magnetic ink
epoxy.
14. The method of claim 13, wherein performing the other inkjet
printing process includes performing the other inkjet printing
process multiple times to print the second magnetic ink epoxy as a
multilayer on the lamination structure.
15. The method of claim 14, wherein performing the inkjet printing
process includes performing the inkjet printing process multiple
times to print the magnetic ink epoxy as a multilayer on the
magnetic core structure, or on the lamination structure.
16. The method of claim 12, wherein performing the inkjet printing
process includes performing the inkjet printing process multiple
times to print the magnetic ink epoxy as a multilayer on the
magnetic core structure, or on the lamination structure.
17. A method, comprising; formulating a magnetic ink epoxy with
ferrite powders of different particle sizes; performing an inkjet
printing process that prints the magnetic ink epoxy on a magnetic
core structure; and attaching the magnetic core structure to a side
of a lamination structure via the magnetic ink epoxy.
18. The method of claim 17, further comprising: performing another
inkjet printing process that prints a second magnetic ink epoxy on
another side of the lamination structure; and attaching a second
magnetic core structure to the other side of the lamination
structure via the second magnetic ink epoxy.
19. The method of claim 17, wherein performing the inkjet printing
process includes performing the inkjet printing process multiple
times to print the magnetic ink epoxy as a multilayer on the
magnetic core structure.
20. The method of claim 17, wherein the magnetic ink epoxy is
formulated with ferrite powders having particle sizes in the range
of tens of nanometers to hundreds of nanometers.
21. A semiconductor product, comprising: a semiconductor die; and a
magnetic apparatus, including: a lamination structure, including a
patterned conductive feature that forms a part of a passive
electronic component, a core structure, and a magnetic adhesive
layer that joins the core structure to the lamination
structure.
22. A method for fabricating a semiconductor product, comprising:
performing an inkjet printing process that prints a magnetic ink
epoxy on a magnetic core structure, or on a lamination structure;
attaching the magnetic core structure to the lamination structure
via the magnetic ink epoxy; electrically interconnecting conductive
features of a semiconductor die, and conductive features of the
magnetic lamination structure; and enclosing the lamination
structure and the magnetic core structure in a package
structure.
23. The method of claim 22, further comprising; electrically
interconnecting further conductive features of the semiconductor
die with leads of a lead frame structure; and electrically
interconnecting further conductive features of the magnetic
lamination structure with further leads of the lead frame
structure; wherein enclosing the lamination structure and the
magnetic core structure further includes enclosing a portion of the
lead frame structure.
Description
BACKGROUND
[0001] High quality isolation transformers typically are wire wound
transformers, which are large and expensive. To shrink the size of
such transformers, while keeping high isolation rating is very
challenging for smaller footprint designs. There is a big demand
for a small, affordable isolation transformer which would be better
suited for module integration. Currently, many transformer
structure designs can meet these requirements. The planar
transformer structure, the planar transformer structure with center
post, as well as EI, UI, TU-shaped transformers structures, which
having a very high coupling, inductance density and quality factor.
However, the method of interconnecting the transformer core pieces
is dispensing the non-magnetic materials on the laminates for
electrical connection. This method will generate "gaps" of 20-25
.mu.m thickness between magnetic pieces and laminate winding
structures, which has adverse impact on the efficiency and
properties of the transformer structures. Better solutions are
needed for improved high frequency operation and low-cost
manufacturing of planar passive component structures.
SUMMARY
[0002] Described examples provide apparatus that includes one or
more patterned conductive features on laminate sheets of a
lamination structure, and an inkjet printed magnetic adhesive layer
that attaches a core structure to the lamination structure.
[0003] In one example, the core structure includes a magnetic
material. In one example, an apparatus includes a lamination
structure with a patterned conductive feature, a core structure,
such as a magnetic sheet, and a magnetic adhesive layer that joins
the core structure to the lamination structure. In one
implementation, the lamination structure includes multiple
patterned conductive features, for example, on different patterned
conductive layers of a multilayer lamination structure. The
apparatus in one example includes multiple core structures, such as
top and bottom magnetic sheets, attached to different sides of the
lamination structure using inkjet printed magnetic adhesive layers.
In one example, the lamination structure includes a conductive
primary winding, and a conductive secondary winding that is
magnetically coupled with the conductive primary winding by the
core structure and the magnetic adhesive layer. In one example, the
passive electronic component is an inductor, and the lamination
structure includes a conductive winding that is magnetically
coupled with the core structure and the magnetic adhesive layer. In
one example, the passive electronic component is a capacitor, and
the lamination structure includes first and second capacitor
plates.
[0004] Further described examples provide processes or methods for
fabricating an apparatus. The method in one example includes
performing an inkjet printing process that prints a magnetic ink
epoxy on a magnetic core structure, or on a lamination structure,
and attaching the magnetic core structure to the lamination
structure via the magnetic ink epoxy. One example also includes
performing another inkjet printing process that prints a second
magnetic ink epoxy on the lamination structure, and attaching a
second magnetic core structure to the lamination structure via the
second magnetic ink epoxy.
BRIEF DESCRIPTION OF THE DRAWINGS
[0005] FIG. 1 is a perspective view of an example transformer
apparatus with a multilayer lamination structure and upper and
lower core structures attached to the lamination structure by
magnetic ink epoxy.
[0006] FIG. 2 is a partial sectional side elevation view of the
transformer apparatus of FIG. 1.
[0007] FIG. 3 is a flow chart of a method to fabricate an
apparatus.
[0008] FIGS. 4-11 show the example transformer apparatus of FIGS. 1
and 2 at various stages of fabrication according to the method of
FIG. 3.
[0009] FIGS. 12 and 13 respectively show side elevation and top
plan views of a packaged semiconductor product with a transformer
apparatus with a multilayer lamination structure and upper and
lower core structures attached to the lamination structure by
magnetic ink epoxy.
DETAILED DESCRIPTION
[0010] In the drawings, like reference numerals refer to like
elements throughout, and the various features are not necessarily
drawn to scale. In the following discussion and in the claims, the
terms "including", "includes", "having", "has", "with", or variants
thereof are intended to be inclusive in a manner similar to the
term "comprising", and thus should be interpreted to mean
"including, but not limited to . . . " Also, the term "couple" or
"couples" is intended to include indirect or direct electrical or
mechanical connection or combinations thereof. For example, if a
first device couples to or is coupled with a second device, that
connection may be through a direct electrical connection, or
through an indirect electrical connection via one or more
intervening devices and connections.
[0011] FIGS. 1 and 2 show an isolation transformer apparatus 100.
The apparatus 100 includes a first core structure 101, a second
core structure 102 and a lamination structure 104. The lamination
structure 104 and the core structures 101, 102 are generally planar
in the illustrated example, although not required for all
implementations. The lower first core structure 101 is attached to
at least a portion of the bottom side of the lamination structure
104 via a first magnetic adhesive layer 106, and the upper second
core structure 102 is attached to at least a portion of the top
side of the lamination structure 104 via a second magnetic adhesive
layer 108.
[0012] The lamination structure 104 in one example is a multilayer
structure with patterned conductive features 111, 112 and 113 that
form parts of a passive transformer electronic component. In one
example, a first patterned conductive feature 111 forms a
transformer primary winding, a second patterned conductive feature
112 forms a first transformer secondary winding, and the patterned
conductive feature 113 forms a second secondary winding. The
patterned conductive features 111, 112 and 113 in this example have
components on multiple layers of a multilayer lamination structure
104, although not required of all possible implementations. In
addition, the patterned winding turns of the individual primary and
secondary windings in this example extend on different layers of
the lamination structure 104, although not required of all possible
implementations. Moreover, the individual patterned winding
features 111, 112 and 113 include multiple turns in a spiral
pattern on the individual layers of the lamination structure 104,
although other implementations are possible, such as single turn
winding structures on a single layer. Furthermore, the example
patterned conductive features forming the transformer primary and
secondary windings include end connection features allowing
interconnection of the windings to external circuitry (not shown).
In the illustrated example, the individual patterned conductive
features 111, 112 and 113 include end connections for external
connection of the individual transformer windings, such as for wire
bonding connections in a packaged semiconductor product as shown in
FIGS. 12 and 13 below. In one example, the magnetic adhesive layers
106 and 108 are inkjet printed using magnetic epoxy ink. In the
illustrated example, the upper and lower core structures 101, 102
are attached to the lamination structure by magnetic ink epoxy 106,
108 to form a magnetically coupled transformer apparatus. The
magnetic ink epoxy 106, 108 provides magnetic coupling between the
windings formed by the patterned conductive features 111, 112 and
113 without an undesirable non-magnetic gap between the lamination
structure 104 and the core structures 101 and 102. In other
examples, one of the upper or lower core structures 101, 102 and
the corresponding magnetic ink epoxy 106, 108 can be omitted, with
the remaining core structure and magnetic epoxy providing magnetic
coupling for the passive electronic component or components of the
apparatus 100. The lamination structure 104 includes a top or first
side 121 and a bottom or second side 122. The second core structure
102 includes a bottom or first side 131 that is attached to the
first side 121 of the lamination structure 104 via the magnetic
adhesive layer 108, and a top or second side 132. The first core
structure 101 includes a bottom or first side 141, and a second or
top side 142 that is attached to the second side 122 of the
lamination structure 104 via the first magnetic adhesive layer 106.
The individual core structures (e.g., magnetic sheets) and the
lamination structure 104 are attached to one another via mechanical
bonding through adhesion provided by the magnetic ink epoxy 106,
108, and may, but need not, contact one another. Where not in
direct structural contact, the lamination structure 104 and the
core structure(s) are joined by the epoxy material 106, 108 that
provides a continuous magnetic structure with enhanced high
frequency performance compared to the use of non-magnetic
epoxy.
[0013] In other transformer examples, the lamination structure
includes the primary winding 111 and a single secondary winding,
and the further secondary winding 113 can be omitted. In other
examples, a single patterned conductive feature can be provided to
form a single conductive winding of an inductor, and the inductor
winding is magnetically coupled with one or more core structures
via magnetic adhesive layer material. In another example, a passive
capacitor electronic component can be constructed, in which the
lamination structure 104 includes first and second capacitor plates
separated by a dielectric material of the multilayer lamination
structure.
[0014] The inkjet printing of magnetic epoxy ink 106, 108
advantageously provides controlled materials usage during
manufacturing, thereby reducing waste and controlling manufacturing
cost of the apparatus 100 compared with screen printing. In
addition, the magnetic epoxy ink 106, 108 performs the attachment
(e.g., bonding or mechanical attachment) function for adhering the
core structure or structures 101, 102 to the lamination structure,
while mitigating or avoiding the non-magnetic material gap found in
other structures manufactured using non-magnetic epoxy. The
improved magnetic coupling via the magnetic epoxy ink structures
106, 108 enhances the transformer performance, and facilitates high
frequency operation of the transformer component formed by the
apparatus 100. The magnetic coupling of the patterned conductive
features 111, 112 and 113 with the core structure(s) and/or with
one another can be modified for design changes by simply changing
the inkjet printing programming for printing the magnetic ink epoxy
106 and/or 108. In one example, the printing programming provides a
continuous or solid magnetic ink epoxy layer 106 and/or 108, and
the thickness and/or material properties of the material 106, 108
can be varied for a given magnetic coupling design. In other
examples, discontinuous patterns of the material 106, 108 can be
programmed for inkjet printing to achieve a desired magnetic
circuit for a given apparatus design.
[0015] In one example, the core structures 101, 102 are magnetic
ferrite sheets. Any suitable magnetic material can be used for the
core structures 101, 102, including ferrous materials. Any material
can be used that can provide a magnetic coupling for one or more
patterned conductive features, for example, to create a transformer
or an inductor. In one example, the core structures 101, 102 are
sheets of ferrous material (e.g., ferrite sheets). In one example,
the core structures 101, 102 are a mixture of Bismaleimide-Triazine
(BT) epoxy resin. In one example, the first and second magnetic
epoxy ink structures 106, 108 include a magnetic paste with
magnetic particles mixed in a thermal set polymer matrix, inkjet
printed onto one or more sides and/or surfaces of the lamination
structure 104 and/or onto one or more sides or surfaces of the core
structures 101, 102.
[0016] The disclosed approach provides a solution to limited
micro-transformer performance because of non-magnetic
interconnecting material by selective printing of magnetic
ink/epoxy to form the attachment layers 106, 108.
[0017] FIG. 2 shows an example multilayer lamination structure 104
in the transformer apparatus 100. The lamination structure 104
includes a first conductive feature 200 on the bottom side of a
first laminate layer 202, and the bottom side 122 of the laminate
layer, including the conductive feature 200, is attached to the top
side 142 of the first core structure 101 via the first magnetic ink
epoxy 106. A patterned conductive feature 204 extends on the top
side of the laminate layer 202, and a subsequent laminate layer 206
is attached to the top side of the first laminate layer 202 and to
the conductive feature 204. A further conductive feature 208
extends on the top side of the laminate layer 206, and a center or
core laminate layer 210 is attached to the top side of the laminate
layer 206 and the conductive feature 208. Another patterned
conductive feature 212 extends on the top side of the center
laminate layer 210, and a further laminate layer 214 is attached to
the top side of the center laminate layer 210 and the conductive
feature 212. Another conductive feature 216 extends on the top side
of the laminate layer 212, and a subsequent laminate layer 218 is
attached to the top side of the laminate layer 214 and to the
conductive feature 216.
[0018] In this example, a final conductive feature 220 extends on
the top side of the laminate layer 218. The upper second core
structure 102 is attached to the uppermost laminate layer 218 and
the associated conductive feature 220 via the second magnetic ink
epoxy 108 to complete the structure. In one example, the first and
second core structures 101 and 102 are 30 .mu.m thick, and the
patterned conductive features or layers 200, 204, 208, 212, 216 and
220 include copper with a thickness of 23 .mu.m. In one example,
the first magnetic ink epoxy material 106 has a thickness of 20
.mu.m, and the second magnetic ink epoxy material 108 has a
thickness of 40 .mu.m. In one example, the center core laminate
layer 210 has a thickness of 60 .mu.m, the laminate layers 206 and
214 have thicknesses of 50 .mu.m, and the outermost laminate layers
202 and 218 have thicknesses of 45 .mu.m.
[0019] The example of FIGS. 1 and 2 uses a lamination structure 104
with six metal layers to provide the patterned conductive
transformer winding features 111, 112 and 113. In one example, the
pattern conductive features 208 and 212 in FIG. 2 are used for the
patterned primary winding structure 111. The patterned conductive
features 216 and 220 are used for the patterned first secondary
winding structure 112, and the two lowermost patterned conductive
features 200 and 204 are used for the second secondary winding
structure 113.
[0020] FIG. 3 shows an example method 300 for fabricating an
apparatus with one or more electronic components, such as the
apparatus 100 of FIGS. 1 and 2. In one example, the lamination
structure 104 is preassembled before the processing 300 is
performed. The apparatus 100 can include any type or form of
passive electronic component or components, such as capacitors,
inductors, resistors, transformers, and hybrid circuits.
[0021] The method 300 begins at 302 in FIG. 3 with formulation of
the magnetic ink epoxy (e.g., for use in printing the magnetic ink
epoxy 106 and 108 in FIGS. 1 and 2). In one example, the magnetic
ink epoxy is formulated at 302 as a ferrite film. The formulation
at 302 can be tailored to adjust film thickness, adhesive and
magnetic material properties for ease of integration with a given
apparatus design. In certain implementations, the inkjet printing
of the magnetic ink epoxy includes printing multiple layers to
provide a desired final layer thickness of the epoxy layers 106
and/or 108. The magnetic ink can be fabricated at 302 using ferrite
powders with different particle sizes to vary properties of the
structure layer by layer. The same or different magnetic ink epoxy
formulations can be used for printing different layers in some
examples. The property and thickness adjustability of the method
300 provides significant advantages compared with other dispensing
methods, such as screen printing. In one example, the particle size
of the magnetic powders is in the range of tens of nanometers to a
few hundred nanometers for inkjet printing.
[0022] The following table lists three example magnetic adhesive
layer pastes, which have varied properties based on the magnetic
particle types and sizes, where B.sub.s is the saturation flux
density in Tesla units (T), and .mu. is the relative permeability
of the magnetic particles:
TABLE-US-00001 Saturation flux Magnetic density of Particle
Magnetic particle Relative magnetic sizes Ink properties
permeability ink (T) (nm) Finemet in B.sub.s = 1 to 1.6 T, 20
Unknown 200 epoxy .mu. = 4,000 to 150,000 @ 1 KHz Finemet in
B.sub.s =1 to 1.6 T, 200 Approximately 500 silicone .mu. = 4,000 to
0.35 (Magnetic) 150,000 @ 1 KHz @ 100 MHz Fe-Metallic B.sub.s = 1
to 1.6 T, 12 Approximately 800 glasses in .mu. = 3,000 to 0.20
(Magnetic) silicone 18,000 @ 1 KHz @ 100 MHz
[0023] At 304, the magnetic ink epoxy is installed in an inkjet
printer. In one example, the lamination structure 104 is separately
processed before performing the method 300 in FIG. 3.
[0024] The method 300 includes performing an inkjet printing
process at 306 that inkjet prints the magnetic ink epoxy as a die
attach material on the top side of the first magnetic core
structure (e.g., the first core structure 101, such as a sintered
ferrite sheet). FIGS. 4-6 show an example inkjet printing process
400 that prints the first magnetic adhesive layer 106 on the second
side 142 of the first core structure 101. In one example, a
multi-layer printing process 400 is used as shown in FIGS. 4-6 to
form the first magnetic ink epoxy 106. FIG. 4 illustrates the
process 400 using an inkjet print head 402 traveling along a
programmed or predetermined pattern path 404. FIG. 5 illustrates
the completion of the first inkjet print process 400 to complete
the first magnetic ink epoxy layer 106. FIG. 6 shows a top view of
the inkjet printing process 400 as the print head 402 is traversed
along a raster printing path 404 beginning in the lower left, and
printing a series of connected rows (e.g., along the X direction)
on the top surface of the first magnetic core structure 101. In one
example, the pattern substantially covers the entire top surface of
the first core structure 101 in which the lamination structure 104
will be attached. In other examples, different patterns can be used
for inkjet printing the first magnetic adhesive layer 106.
[0025] At 308 in FIG. 3, the bottom side of the lamination
structure 104 is attached to the top side of the first magnetic
core structure 101 via the printed ink epoxy 106. FIGS. 7 and 8
show an example attachment process 700 in which the lower or second
side 122 of a preassembled lamination structure 104 is initially
brought downward in FIG. 7 toward the upper or second side 142 of
the first core structure 101 (e.g., along the negative Y
direction), and then the magnetic ink epoxy 106 bonds the lower
side 122 of the lamination structure 104 to the upper side 142 of
the first core structure 101 as shown in FIG. 8. In one example,
the printed first magnetic ink epoxy layer 106 is cured at 309, for
example, by heating the printed material 106, or by ultraviolet
(UV) exposure of UV-curable material 106, or by other suitable
curing means. In other examples, the separate curing at 309 can be
omitted.
[0026] At 310 in FIG. 3, the method 300 further includes inkjet
printing another magnetic ink epoxy as a die attach material on the
lamination structure. FIGS. 9 and 10 show an example where the
inkjet printing process 400 is again performed, this time to form
the second magnetic ink epoxy 108 on the upper first side 121 of
the lamination structure 104. In this example, a multi-layer inkjet
printing process 400 is used, although not a requirement of all
possible implementations.
[0027] At 312 in FIG. 3, the second magnetic core structure 102 is
attached to the top side of the lamination structure via the
printed second ink epoxy. FIG. 11 shows an example second
attachment process 700, which attaches the upper second magnetic
core structure 102 to the upper first side 121 of the lamination
structure 104 via the printed second magnetic ink epoxy 108. In one
example, the completed structure is then heated (e.g., co-fired) at
313 to cure the inkjet printed magnetic ink epoxy 108 (and 106, if
previously uncured). This provides the transformer apparatus
example 100 as shown in FIGS. 1 and 2 above, with no non-magnetic
gaps between the lamination structure 104 and the core structures
101 and 102.
[0028] In one example, the method 300 further provides a complete
process for manufacturing a package semiconductor device that
includes the example transformer apparatus 100 or other integrated
magnetic apparatus. In this example, the method 300 further
includes attaching the magnetic assembly (e.g., the transformer
apparatus 100) to one or more die attach pads at 314, as well as
attaching one or more semiconductor dies to the die attach pad at
316.
[0029] At 318, the semiconductor product fabrication example
further includes electrical interconnection of one or more external
conductive features of a lead frame or other package structure with
one or more conductive features of the attached semiconductor die
or dies, and conductive features of the magnetic assembly. In one
example, the interconnection includes wire bonding at 318. In other
examples, the interconnection can include soldering, such as in a
flip-chip product fabrication, or various structural
interconnections in forming a wafer chip scale packages (WCSP). At
320, the interconnected assembly is enclosed at least partially
within a package structure, such as by molding portions of the
assembly, while leaving leads or other conductive features exposed
for ultimate soldering to an external structure, such as a printed
circuit board.
[0030] FIGS. 12 and 13 show side elevation and top plan views of a
packaged semiconductor product 1200 with a transformer apparatus
100 as described above in connection with FIG. 1, including a
multilayer lamination structure 104, as well as a lower core
structure 101 and an upper core structure 102 attached to the
lamination structure 104 by magnetic ink epoxy 106, 108. The
packaged product 1200 includes a first die attach pad 1201 and a
second die attach pad 1202. A lead frame structure is provided,
including leads 1204 extending outside the product for external
connection, such as soldering to a circuit board (not shown). The
illustrated example includes gull wing leads, but j-type or other
leads or external connections can be provided in other
implementations. A first semiconductor die 1206 is mounted on the
first die attach pad 1201, and a second semiconductor die 1208 is
mounted on the second die attach pad 1202. In this example, the
transformer apparatus 100 is also mounted to the second die attach
pad 1202. The example semiconductor product 1200 in FIGS. 12 and 13
is a wire-bonded device, although flip-chip, wafer chip scale
packages (WCSP), or other designs are possible in different
implementations. In the illustrated example, the product 1200
includes bond wires 1210, 1212, 1214 and 1216 interconnecting
various conductive features.
[0031] The illustrated example provides a high voltage circuitry
including the first semiconductor die 1206 and associated leads
1204 on the left side of the product 1200. The product 1200 in this
example also includes low voltage circuitry including the second
semiconductor die 1208 and associated leads 1204 on the right side
of the product 1200. In one example, the product 1200 is a DC-DC
converter, in which the first semiconductor die 1206 includes a
switch configured to perform primary-side switching of a DC input
voltage. In certain examples, the first semiconductor die 1206 also
includes control circuitry to provide a switching control signal to
operate the switch. The second semiconductor die 1208 in one
example includes one or more rectifier diodes configured for
secondary-side rectification to provide a DC output signal. In one
example, the second semiconductor die 1208 further includes one or
more additional electronic components, such as an output capacitor.
In this example, the bond wires 1210 connect high-voltage side
leads 1204 to the first semiconductor die 1206, and bond wires 1212
connect conductive features of the first semiconductor die 1206 to
primary side patterned conductive features 112 of a transformer
primary implemented by the transformer apparatus 100. In this
example, the wire bonding interconnects leads 1204 associated with
a DC input voltage to a primary-side switching device (e.g., a
MOSFET), and the input signal and the switching device are
connected to primary windings of the transformer apparatus 100.
[0032] One or more bond wires 1210 in this example connect
conductive features of the second semiconductor die 1208 to
corresponding low-voltage leads 1204. Bond wires 1216 connect
conductive features of the second semiconductor die 1208 to
patterned conductive features 111 and 113 of the transformer
apparatus 100, for example, to interconnect rectifier diodes of the
semiconductor die 1208 with first and second secondary winding
circuits of the transformer apparatus 100. The product 1200
includes a molded package 1218 that encloses the dies 1206 and 1208
as well as the bond wires and the transformer apparatus 100. The
package 1218 also encloses portions of the leads 1204, while
leaving portions of the leads 1204 exposed for soldering to an
external structure (e.g., a printed circuit board, not shown).
[0033] The inkjet printed magnetic ink epoxy 106 and 108 of the
apparatus 100 advantageously facilitate manufacturing without the
need for screen printing or masks, with ease of adjustment for
different designs, and significantly reduced materials usage
compared with screen printing techniques. Moreover, described
examples advantageously reduce or mitigate non-magnetic material
gaps between the lamination structure 104 and the magnetic core
structures 101, 102. Moreover, direct inkjet printing of magnetic
ink epoxy 106 and 108 allows accurate additive deposition and
formation of fine pitch features, for example, with dimensional
accuracies up to +/-5 .mu.m in some implementations. Described
examples combine the advantages of good high frequency performance
and small package sizes, along with magnetic circuit performance
improvements by reducing or eliminating non-magnetic material gaps,
together with the material usage advantages of inkjet printing
compared with screen printing approaches.
[0034] The above examples are merely illustrative of several
possible embodiments of various aspects of the present disclosure,
wherein equivalent alterations and/or modifications will occur to
others skilled in the art upon reading and understanding this
specification and the annexed drawings. Modifications are possible
in the described embodiments, and other embodiments are possible,
within the scope of the claims.
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