U.S. patent application number 11/708382 was filed with the patent office on 2008-05-15 for overmolded electronic module with an integrated electromagnetic shield using smt shield wall components.
This patent application is currently assigned to Skyworks Solutions, Inc.. Invention is credited to Larry D. Pottebaum, Philip H. Thompson.
Application Number | 20080112151 11/708382 |
Document ID | / |
Family ID | 39710898 |
Filed Date | 2008-05-15 |
United States Patent
Application |
20080112151 |
Kind Code |
A1 |
Thompson; Philip H. ; et
al. |
May 15, 2008 |
Overmolded electronic module with an integrated electromagnetic
shield using SMT shield wall components
Abstract
An electronic module with an integrated electromagnetic shield
using surface mount shield wall components has been disclosed. Each
surface mount shield wall component provides side shielding of
circuitry within the overmolded electronic module and provides an
exposed conductive shield wall section to which a top conductive
shield can be applied. By including the shield structure as part of
the overmolded electronic module, the need for a separate shield
and separate process steps for installing the separate shield can
be eliminated. Each surface mount shield wall component comprises a
non-conductive portion that provides stability during a reflow
soldering process, but at least a sacrificial portion of the
non-conductive portion can be removed to reduce the amount of area
occupied by the overmoldable shield structure.
Inventors: |
Thompson; Philip H.; (Solon,
IA) ; Pottebaum; Larry D.; (Marion, IA) |
Correspondence
Address: |
FARJAMI & FARJAMI LLP
26522 LA ALAMEDA AVENUE, SUITE 360
MISSION VIEJO
CA
92691
US
|
Assignee: |
Skyworks Solutions, Inc.
|
Family ID: |
39710898 |
Appl. No.: |
11/708382 |
Filed: |
February 19, 2007 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
10793618 |
Mar 4, 2004 |
7198987 |
|
|
11708382 |
|
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Current U.S.
Class: |
361/818 ;
257/E23.005; 257/E23.114; 257/E23.125 |
Current CPC
Class: |
Y10T 29/49144 20150115;
Y02P 70/611 20151101; H01L 2924/01029 20130101; H05K 2201/10636
20130101; H01L 2924/19042 20130101; H01L 2924/01006 20130101; H05K
9/0088 20130101; H05K 2201/10204 20130101; H01L 2224/97 20130101;
H01L 2924/19043 20130101; H01L 2224/48227 20130101; H01L 2924/14
20130101; H05K 3/3405 20130101; Y02P 70/50 20151101; Y10T 29/4913
20150115; H01L 23/552 20130101; H01L 23/3121 20130101; H01L
2924/19041 20130101; H05K 3/0052 20130101; H05K 3/3442 20130101;
H01L 2924/181 20130101; H05K 2201/10371 20130101; H01L 2924/3025
20130101; H01L 2924/01033 20130101; H01L 2924/014 20130101; H01L
24/97 20130101; H01L 2224/97 20130101; H01L 2224/85 20130101; H01L
2924/181 20130101; H01L 2924/00 20130101 |
Class at
Publication: |
361/818 ;
257/E23.005 |
International
Class: |
H05K 7/00 20060101
H05K007/00 |
Claims
1. A surface mount shield wall component for providing side wall
shielding for an electronic module and suitable for connection to a
top conductive shield of said electronic module, said surface mount
shield wall component comprising: at least one conductive shield
wall section suitable for attachment to a conductive circuit board
pad of said electronic module; a non-conductive portion, including
a non-conductive sacrificial portion, attached to said at least one
conductive shield wall section; wherein said conductive shield wall
section provides said side wall shielding and is suitable for
connection to said top conductive shield.
2. The surface mount shield wall component of claim 1 wherein said
surface mount shield wall component is positioned on a circuit
board panel by an SMT pick and place process.
3. The surface mount shield wall component of claim 1 wherein said
non-conductive portions provides mechanical stability for said
surface mount shield wall component during an overmolding
process.
4. The surface mount shield wall component of claim 1 wherein said
non-conductive portion lies in a saw street between two adjacent
module circuit boards on a circuit board panel, so as to facilitate
removal of said sacrificial portion by sawing.
5. The surface mount shield wall component of claim 1 wherein said
electronic module is substantially overmolded with a mold compound
so as to form an overmolded electronic module.
6. The surface mount shield wall component of claim 5 wherein said
mold compound is removed from a top portion of said at least one
conductive shield wall section so as to expose said top portion for
connection to said top conductive shield.
7. The surface mount shield wall component of claim 6 wherein said
top conductive shield is placed on said overmolded electronic
module for connection to said at least one conductive shield wall
section.
8. The surface mount shield wall component of claim 1 wherein said
conductive circuit board pad is coupled to a ground plane of a
module circuit board supporting said electronic module.
9. The surface mount shield wall component of claim 1 wherein said
conductive circuit board pad is coupled to a package pin of said
electronic module, said package pin being coupled to a ground plane
of a module circuit board supporting said electronic module.
10. An overmolded electronic module comprising: a plurality of SMT
shield wall components arranged on periphery of a module circuit
board; at least one integrated circuit situated in said module
circuit board; a top conductive shield connected to an exposed top
portion of at least one of said plurality of SMT shield wall
components.
11. The overmolded electronic module of claim 10 further including
at least one passive SMT component situated in said module circuit
board.
12. The overmolded electronic module of claim 10 wherein said top
conductive shield is situated on a mold compound encapsulating said
electronic module, and wherein said exposed top portion is not
covered by said mold compound.
13. The overmolded electronic module of claim 10 wherein said at
least one of said plurality of SMT shield wall components includes
a conductive shield wall section.
14. The overmolded electronic module of claim 13 wherein an exposed
top portion of said conductive shield wall section is connected to
said top conductive shield.
15. The overmolded electronic module of claim 13 wherein said
conductive shield wall section is attached to a conductive circuit
board pad of said module circuit board.
16. The overmolded electronic module of claim 15 wherein said
conductive circuit board pad is coupled to a ground plane of said
module circuit board.
17. The overmolded electronic module of claim 13 wherein said
conductive shield wall section comprises tin plated copper.
18. The overmolded electronic module of claim 10 wherein at least
one additional SMT shield wall component is situated inside said
module circuit board.
19. The overmolded electronic module of claim 10 wherein said mold
compound comprises a polymer resin.
Description
[0001] This application is a continuation in part of, and claims
benefit of the filing date of, and hereby incorporates fully by
reference, the pending parent application entitled "Overmolded
Semiconductor Package with an Integrated EMI and RFI Shield" Ser.
No. 10/793,618, filed Mar. 4, 2004, and assigned to the assignee of
the present application.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] The invention relates generally to electronic device
manufacturing and more particularly to techniques for providing
shielding for electronic components.
[0004] 2. Related Art
[0005] Portable electronic devices such as cell phones typically
utilize electronic modules to provide a high level of functionality
in a small package. The electronic module can include, for example,
any combination of one or more integrated circuits and one or more
passive devices such as resistors, capacitors, and inductors
mounted on a module circuit board. The components of the electronic
module can be encapsulated using a non-conductive material to form
an overmolded electronic module package. Electronic circuits within
an electronic module typically receive, transmit, and/or internally
utilize time-varying electromagnetic signals. Such electromagnetic
signals can radiate through the non-conductive packaging material
of the electronic module and affect other electronic devices (e.g.,
cause interference), exceed regulatory limits, and/or be subject to
interception. Also, externally present electromagnetic energy of
either natural or artificial origin may penetrate non-conductive
packaging material of an electronic module to adversely affect the
circuitry within the electronic module. Accordingly, good
engineering practices dictate that electromagnetic shielding be
provided to attenuate electromagnetic energy to limit potentially
adverse effects. Typically electromagnetic shielding is provided by
surrounding the electronic module with a conductive material such
as a structure that is stamped or otherwise formed out of a thin
sheet of metal. However, such a shield typically takes up
substantial space around the electronic module. Such a stamped
shield needs to be large enough to avoid mechanically interfering
with the electronic module. Moreover, the dimensions of the shield
have to be sufficient to accommodate manufacturing tolerances of
the electronic module, as well as those of the shield. The
additional size required by a stamped shield limits miniaturization
of products including such electronic modules. Another disadvantage
of a stamped shield is that attaching the shield involves an
additional manufacturing step that cannot be performed until after
installing the electronic module.
[0006] Thus, a technique for providing electromagnetic shielding
that avoids such disadvantages is needed.
SUMMARY OF THE INVENTION
[0007] The present invention is directed to a method and apparatus
for providing an overmolded electromagnetic shield for an
electronic module. The invention addresses and resolves the need in
the art for a cost effective shield for an overmolded electronic
module that does not substantially increase the module size and
overcomes the need for a separate shield, such as a stamped shield,
and a separate process for installing the separate shield.
[0008] According to one exemplary embodiment, an overmolded
electronic module includes any combination of one or more
integrated circuits and passive SMT (surface mount technology)
components situated on a module circuit board. The overmolded
electronic module further includes one or more SMT shield wall
components situated on the same module circuit board where the SMT
shield wall components form the side walls of an electromagnetic
shield. The overmolded electronic module further includes an
overmold material used to encapsulate the components within the
electronic module. The overmolded electronic module further
includes a conductive layer situated on the top surface of the
overmold material where the conductive layer forms the top of an
electromagnetic shield. According to this exemplary embodiment, the
conductive layer that forms the top of the electromagnetic shield
is electrically connected to the SMT shield wall components which
in turn are electrically connected to SMT pads on the module
circuit board in such a way that the components within the
electronic module are surrounded by the shielding structure.
[0009] In accordance with at least one embodiment, the SMT shield
wall components have form factors compatible with existing SMT
component assembly requirements. For example, the SMT shield wall
components may be implemented in a size and shape similar to a
typical SMT component, such as a resistor or capacitor, but with a
body of sacrificial, nonconductive material joining the conductive
shield wall sections. Accordingly, the SMT shield wall components
may be placed in an electronic module using typical SMT component
assembly processes, for example typical SMT pick and place
processes.
[0010] Multiple module circuit boards can be arranged in an array
on a circuit board panel or strip with a space between the module
circuit boards that is used as a saw street when the module circuit
boards go through a singulation process. The design of the SMT
shield wall components allows them to be placed between module
circuit boards in the saw street such that one SMT shield wall
component can provide a first shield wall section for a given
module circuit board and a second shield wall section for an
adjacent module circuit board. The result is a shield wall
component that has a footprint that is large enough relative to the
height of the shield wall component to be easy to manufacture and
to provide mechanical stability and withstand subsequent
overmolding processes while occupying minimal space in the final
completed overmolded electronic module since much of the SMT shield
wall component (e.g., a sacrificial portion) is situated in the saw
street and is removed during the singulation process.
[0011] Other features and advantages of the present invention will
become more readily apparent to those of ordinary skill in the art
after reviewing the following detailed description and accompanying
drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIGS. 1A, 1B, 1C, and 1D are diagrams of a surface mount
technology (SMT) shield wall component comprising two conductive
wall sections that are situated at the ends of a non-conductive,
sacrificial portion in accordance with at least one embodiment.
FIG. 1A is a top view diagram of the SMT shield wall component.
FIG. 1B is an end view diagram of the SMT shield wall component.
FIG. 1C is a side view diagram of the SMT shield wall component.
FIG. 1D is a perspective view diagram of the SMT shield wall
component.
[0013] FIG. 2 is a plan view diagram of a circuit board panel for
overmolded electronic modules with an integrated electromagnetic
shield using SMT shield wall components that includes multiple
module circuit boards arranged in an array with saw streets
situated between the individual module circuit boards in accordance
with at least one embodiment.
[0014] FIG. 3A is a top view diagram of a module circuit board with
exposed conductive portions of SMT shield wall components in
accordance with at least one embodiment.
[0015] FIG. 3B is a side view diagram of a module circuit board
with exposed conductive portions of SMT shield wall components in
accordance with at least one embodiment.
[0016] FIG. 4A is a top view diagram of a module circuit board with
a top conductive shield coupled to exposed conductive portions of
SMT shield wall sections in accordance with at least one
embodiment.
[0017] FIG. 4B is a side view diagram of a module circuit board
with a top conductive shield coupled to exposed conductive portions
of SMT shield wall sections in accordance with at least one
embodiment.
DETAILED DESCRIPTION OF THE INVENTION
[0018] The present invention is directed to a method and apparatus
for an electronic module with an overmolded electromagnetic shield
using SMT shield wall components. The following description
contains specific information pertaining to the implementation of
the present invention. One skilled in the art will recognize that
the present invention may be implemented in a manner different from
that specifically discussed in the present application. Moreover,
some of the specific details of the invention are not discussed in
order not to obscure the invention. The specific details not
described in the present application are within the knowledge of a
person of ordinary skill in the art.
[0019] The drawings in the present application and their
accompanying detailed description merely describe exemplary
embodiments of the invention. To maintain brevity, other
embodiments of the invention which use the principles of the
present invention are not specifically described in the present
application and are not specifically illustrated by the present
drawings. It should be noted that similar numerals generally refer
to similar elements in the various drawings.
[0020] The method and apparatus for providing an electromagnetic
shield structure using an SMT shield wall component that can be at
least partially integrated within an overmolded part, for example,
an electronic module within a module circuit board which includes
integrated circuits, and surface mount components. Surface mounted
components within the electronic module are typically attached to a
module circuit board residing in a circuit board panel using a pick
and place process. A reflow soldering process is used to solder the
surface mount components to the circuit board. To provide a top
conductive shield connection a conductive structure is needed
that-extends above the height of the integrated circuits and/or
surface mount components. However, tall conductive structures tend
to lose mechanical stability and become misaligned during the
reflow soldering process. If an attempt is made to increase the
width of the tall conductive structure to increase its stability,
the additional width could reduce usable surface area of the
circuit board which results in a significant increase in the size
of the circuit board and the complete electronic module.
[0021] According to at least one embodiment, a SMT shield wall
component is provided that is similar enough to form factors of
existing components to allow compatibility with SMT pick and place
processes, but which provides a sacrificial non-conductive portion
that provides increased stability during reflow soldering processes
but can be subsequently removed if the SMT shield wall component is
mounted so that the sacrificial portion is located over the saw
street. This reduces the size of the SMT shield wall component to
an optimal size for providing a side wall shielding structure and
shielding structure interconnect to a top conductive shield
structure. The SMT shield wall component comprises a non-conductive
sacrificial portion and a first conductive shield wall section
coupled to the non-conductive sacrificial portion. The surface
mount component typically comprises a second conductive shield wall
section coupled to the non-conductive sacrificial portion opposite
the first conductive shield wall section.
[0022] Unlike traditional surface mount components, a SMT shield
wall component would not need conductive internal portions. Rather,
providing a non-conductive sacrificial portion coupled to a
conductive shield wall section would allow the non-conductive
sacrificial portion to be removed (e.g., by sawing) without
releasing conductive debris that might settle and form undesired
electrical connections. Preferably, the non-conductive sacrificial
portion comprises epoxy or another polymer resin similar to the
nonconductive overmold material used for overmolding the entire
electronic module. One or more conductive shield wall sections
remain after removal of the non-conductive sacrificial portion of
the SMT shield wall component to provide side wall shielding and
connection to a top conductive shield. The one or more conductive
shield wall sections preferably comprise metal (e.g., tin plated
copper) that may be preferably soldered to the conductive circuit
board pads upon which the SMT shield wall components may be
mounted. The conductive circuit board pads are preferably connected
to a ground plane within the circuit board. The conductive circuit
board pads are optionally connected to package pins on the
electronic module that are subsequently connected to a ground plane
within the module circuit board on which the electronic module is
mounted.
[0023] The presently available pick and place process for mounting
surface mount components can be used to mount surface mount shield
wall components as well as other passive and/or discrete surface
mount components, which are preferably mounted and reflow soldered
before mounting and wirebonding any integrated circuits that may be
included in the electronic module.
[0024] After being populated with components (e.g., integrated
circuits and/or passive SMT components), an environmentally
protective material (e.g., a mold compound) may be applied to the
circuit board panel (e.g., by injection molding) to cover the one
or more electronic modules residing on the circuit board panel.
After the overmold process is complete, the conductive shield wall
sections of the SMT shield wall components are exposed (e.g. by
milling or planing the top surface of the overmolded circuit board
panel) in order to provide an electrical connection to the top
conductive shield. Thereafter, a conductive material is applied to
the top surface of the module circuit boards to form the top
conductive shield. After the conductive material is applied to form
the top conductive shield, the circuit board panel is singulated
into individual electronic modules, each residing in a respective
module circuit board. During singulation, a saw cuts through a saw
street, which is a sacrificial margin between module circuit boards
defined on a circuit board panel. The singulation saw, while
removing the circuit board material and mold compound along the saw
street, also removes the non-conductive sacrificial portion of the
SMT shield wall component.
[0025] Surface mount shield wall components may be mounted around a
periphery of an electronic module circuit board. Alternatively or
in conjunction with ones mounted around the periphery, surface
mount shield wall components may be mounted internal to an
electronic module circuit board, for example to provide intramodule
shielding.
[0026] The SMT shield wall components in accordance with at least
one embodiment described herein are useful for electronic modules
that transmit, receive, or internally utilize electromagnetic
energy, for example, signals in the 100 MHz to 5 GHz range. An
example of a module circuit board for which the SMT shield wall
components would be useful is a radio-frequency (RF) module, for
example, a power amplifier module (PAM), a transmit front-end
module (TXFEM), a voltage-controlled oscillator (VCO), a RF mixer,
etc.
[0027] FIGS. 1A, 1B, 1C, and 1D show different views of a surface
mount technology (SMT) shield wall component comprising a
non-conductive sacrificial portion in accordance with at least one
embodiment. FIG. 1A is a top view diagram of the SMT shield wall
component. The SMT shield wall component comprises conductive
shield wall section 102 and, optionally, conductive shield wall
section 103, as well as non-conductive portion 101, including
non-conductive sacrificial portion 104. Non-conductive portion 101
is coupled to conductive shield wall sections 102 and, if present,
shield wall section 103. Sacrificial portion 104 of the SMT shield
wall component need not be of precise width, but may vary in width,
for example, depending on process parameters, such as singulation
saw kerf width. For some uses (e.g., intramodule shielding),
sacrificial portion 104 need not be removed, but may be left
intact.
[0028] FIG. 1B is an end view diagram of the SMT shield wall
component. While the SMT shield wall component comprises
non-conductive portion 101, including non-conductive sacrificial
portion 104, only shield wall section 102 is depicted in this end
view diagram. FIG. 1C is a side view diagram of the SMT shield wall
component. Conductive shield wall section 102, non-conductive
portion 101, and optional conductive shield wall section 103 are
depicted in FIG. 1C. FIG. 1D is a perspective view diagram of the
SMT shield wall component. Shield wall section 102, non-conductive
portion 101, and optional shield wall section 103 are depicted in
FIG. 1D.
[0029] FIG. 2 is a plan view diagram of circuit board panel 201 in
accordance with at least one embodiment. Circuit board panel 201
comprises module circuit boards 202, 203, 204, and 205. Conductive
pads are provided on module circuit boards 202, 203, 204, and 205,
either around the periphery of the module circuit boards and/or
internal to the module circuit boards, to allow mounting of SMT
shield wall components. FIG. 2 depicts SMT shield wall components
mounted on such pads, for example, SMT shield wall components 206
through 241 are mounted around the periphery of module circuit
boards 202 through 205 and SMT shield wall components 248 and 249
mounted internal to module circuit board 203.
[0030] As illustrated, by using SMT shield wall components having a
first conductive shield wall section on one end coupled to a
non-conductive sacrificial portion in the middle, which is in turn
coupled to a second conductive shield wall section on the opposite
end, the first conductive shield wall section (e.g., the first
conductive shield wall section of SMT shield wall component 214)
can be mounted on a pad at the periphery of a first module circuit
board (e.g., module circuit board 202), while the second conductive
shield wall section (e.g., the second conductive shield wall
section of SMT shield wall component 214) can be mounted on a pad
at the periphery of a module second circuit board (e.g., module
circuit board 204). Such bridging of adjacent module circuit boards
by a SMT shield wall component allows the first conductive shield
wall section of the SMT shield wall component to be used to provide
side wall shielding and coupling to a top conductive shield for the
module first circuit board while using the second conductive shield
wall section of the SMT shield wall component to be used to provide
side wall shielding and coupling to a top conductive shield for the
second module circuit board. The non-conductive sacrificial portion
of the SMT shield wall component between the first and second
conductive shield wall sections of the SMT shield wall component
can be removed along with circuit board material between the module
first circuit board and the second module circuit board by
singulating the module circuit boards, for example, using a
singulation saw. Singulation can occur along paths through the
circuit board and/or SMT shield wall components, for example,
cutting paths 242, 243, 244, 245, 246, and/or 247 depicted in FIG.
2.
[0031] FIG. 3A is a top view diagram of electronic module 301 with
exposed conductive shield wall sections of the SMT shield wall
components in accordance with at least one embodiment. The top
portions of conductive shield wall sections of the SMT shield wall
components may be exposed either by using an overmolding process
that allows them to remain exposed or by using a material removal
process after overmolding to expose the conductive shield wall
sections of the SMT shield wall components. Examples of such
material removal processes include milling, grinding, lasing,
and/or planing. With the conductive shield wall sections 306, 307,
308, 309, 310, 311, 312, 313, 314, 315, 316, and 317 of the SMT
shield wall components exposed, the remaining components on module
circuit board 318 preferably remain encapsulated within the mold
compound, as depicted in side view FIG. 3B.
[0032] FIG. 3B is a side view diagram of electronic module 301 with
exposed conductive portions of the SMT shield wall components in
accordance with at least one embodiment. In accordance with at
least one embodiment, the tops of conductive shield wall sections,
such as exemplary shield wall sections 310, 311, 312, and 313 are
flush with the top of the encapsulant, i.e. mold compound 330 of
electronic module 301. The tops of other surface mount components,
such as exemplary SMT components 319, 320, and 321 are below the
tops of the conductive shield wall sections, such as exemplary
shield wall sections 310, 311, 312, and 313, and are preferably
covered with encapsulant, i.e., mold compound 330.
[0033] FIGS. 4A and 4B are top and side view diagrams of electronic
module 301 with top conductive shield 401 coupled to exposed
conductive shield wall sections of the SMT shield wall components
in accordance with at least one embodiment. With the conductive
shield wall sections 306 through 317 of the SMT shield wall
components exposed, top conductive shield 401 can be applied over
the exposed conductive shield wall sections 306 through 317 of the
SMT shield wall components and preferably over the mold compound
that remains. For example, top conductive shield 401 may be a
conformal coating, such as a conductive paint or conductive epoxy,
or a thin layer of metal, which may attached (e.g. soldered) to the
exposed conductive shield wall sections 306 through 317 of the SMT
shield wall components.
[0034] Thus, as described above and according to the present
invention, multiple module circuit boards can be arranged in an
array on a circuit board panel or strip with a space between the
module circuit boards that is used as a saw street when the module
circuit boards go through a singulation process. Prior to the
singulation process, the SMT shield wall components may be placed
in the saw streets between module circuit boards using typical SMT
component assembly processes, for example typical SMT pick and
place processes. The design of the SMT shield wall components
allows them to be placed between module circuit boards in the saw
street such that one SMT shield wall component can provide a first
shield wall section for a given module circuit board and a second
shield wall section for an adjacent module circuit board. The
result is a shield wall component that has a footprint that is
large enough relative to the height of the shield wall component to
be easy to manufacture and to provide mechanical stability and
withstand subsequent overmolding processes while occupying minimal
space in the final completed overmolded electronic module since
much of the SMT shield wall component (e.g., a sacrificial portion)
is situated in the saw street and is removed during the singulation
process.
[0035] From the above description of the invention it is manifest
that various techniques can be used for implementing the concepts
of the present invention without departing from its scope.
Moreover, while the invention has been described with specific
reference to certain embodiments, a person of ordinary skill in the
art would appreciate that changes can be made in form and detail
without departing from the spirit and the scope of the invention.
Thus, the described embodiments are to be considered in all
respects as illustrative and not restrictive. It should also be
understood that the invention is not limited to the particular
embodiments described herein but is capable of many rearrangements,
modifications, and substitutions without departing from the scope
of the invention.
[0036] Thus, a method and apparatus for an overmolded electronic
module with an integrated electromagnetic shield using SMT shield
wall components has been described.
* * * * *