U.S. patent application number 16/174299 was filed with the patent office on 2020-04-30 for shielded semiconductor device and lead frame therefor.
The applicant listed for this patent is NXP USA, INC.. Invention is credited to Lee Fee Ngion, Zi-Song Poh, Michael B. Vincent.
Application Number | 20200131030 16/174299 |
Document ID | / |
Family ID | 68289883 |
Filed Date | 2020-04-30 |
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United States Patent
Application |
20200131030 |
Kind Code |
A1 |
Ngion; Lee Fee ; et
al. |
April 30, 2020 |
SHIELDED SEMICONDUCTOR DEVICE AND LEAD FRAME THEREFOR
Abstract
A shielded semiconductor device is assembled using a lead frame
having a die receiving area, leads disposed around the die
receiving area, and a bendable strip formed in the die receiving
area. Each lead has an inner lead end that is spaced from but near
to one of the sides of the die receiving area and an outer lead end
that is distal to that side of the die receiving area. An IC die is
attached to the die receiving area and electrically connected to
the inner lead ends of the leads. An encapsulant is formed over the
die and the electrical connections and forms a body. The strip is
bent to extend vertically to a top side of the body. A lid is
formed on the top side of the body and is in contact with a distal
end of the vertical strip.
Inventors: |
Ngion; Lee Fee; (Melaka,
MY) ; Poh; Zi-Song; (Melaka, MY) ; Vincent;
Michael B.; (Chandler, AZ) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
NXP USA, INC. |
Austin |
TX |
US |
|
|
Family ID: |
68289883 |
Appl. No.: |
16/174299 |
Filed: |
October 30, 2018 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L 23/49582 20130101;
B81C 2203/0154 20130101; H01L 2224/73265 20130101; H01L 2224/48091
20130101; B81B 2201/0264 20130101; B81B 7/007 20130101; H01L
2924/3025 20130101; H01L 23/3107 20130101; B81C 1/00309 20130101;
B81C 1/00301 20130101; G01L 9/0042 20130101; H01L 2224/48247
20130101; H01L 23/552 20130101; H01L 21/561 20130101; B81C
2203/0792 20130101; H01L 2224/97 20130101; H01L 23/49551 20130101;
B81B 2207/012 20130101; B81B 7/0061 20130101; H01L 2224/32245
20130101; B81B 7/0064 20130101; B81B 2207/098 20130101; H01L
2224/32145 20130101; H01L 2224/48145 20130101; H01L 2224/73265
20130101; H01L 2224/32145 20130101; H01L 2224/48145 20130101; H01L
2924/00012 20130101; H01L 2224/73265 20130101; H01L 2224/32245
20130101; H01L 2224/48247 20130101; H01L 2924/00012 20130101; H01L
2224/48091 20130101; H01L 2924/00014 20130101; H01L 2224/97
20130101; H01L 2224/85 20130101; H01L 2224/97 20130101; H01L
2224/83 20130101 |
International
Class: |
B81B 7/00 20060101
B81B007/00; B81C 1/00 20060101 B81C001/00; G01L 9/00 20060101
G01L009/00 |
Claims
1. An article of manufacture, comprising: a lead frame, wherein the
lead frame includes a die receiving area, a plurality of leads
disposed on at least one side of the die receiving area and that
are generally perpendicular to the at least one side of the die
receiving area, wherein each lead of the plurality of leads has an
inner lead end that is spaced from but near to the at least one
side of the die receiving area and an outer lead end that is distal
to the at least one side of the die receiving area, and a strip
formed in the die receiving area that is bendable to a
substantially vertical position for electrical connection to a
package lid, and wherein the die receiving area, the plurality of
leads, and the strip are all formed of the same electrically
conductive sheet material.
2. The article of claim 1, wherein the strip is formed along one
side of the die receiving area.
3. The article of claim 1, wherein the strip has a width of 0.05 mm
to 0.20 mm, and a length of 0.50 mm to 2.0 mm.
4. The article of claim 1, wherein the lead frame is formed from a
copper sheet that is plated with a non-corrosive metal or metal
alloy.
5. The article of claim 1, wherein the die receiving area is
rectangular.
6. The article of claim 5, wherein the plurality of leads includes
leads disposed on each of the sides of the die receiving area.
7. The article of claim 1, further comprising: a first integrated
circuit die attached to the die receiving area and electrically
connected to the inner lead ends of the plurality of leads; and an
encapsulant formed over the first die, the electrical connections
between the first die and the plurality of inner lead ends, wherein
the encapsulant forms a body, and wherein the strip is bent
vertically and extends to an upper edge of the body.
8. The article of claim 7, further comprising the package lid
formed on the upper edge of the body and in contact with the
strip.
9. The article of claim 8, wherein the package lid comprises a
metal sputter coated on the top edge of the body.
10. The article of claim 7, wherein the first die is electrically
connected to the inner lead ends with bond wires.
11. The article of claim 10, further comprising a second integrated
circuit die attached to a top surface of the first die and
electrically connected to at least one of the first die and the
plurality of leads.
12. The article of claim 11, wherein the first die comprises a
microcontroller unit and the second die comprises a pressure
sensor, wherein there is a void in the encapsulant above the second
die and a hole in the package lid that is in communication with the
void such that the second die is exposed to the ambient environment
outside of the body by way of the hole and the void.
13. The article of claim 12, wherein the package lid is attached to
the upper edge of the body with a conductive adhesive and the
vertical strip is in contact with the conductive adhesive.
14. A shielded semiconductor device comprising: a lead frame
including a die receiving area, a plurality of leads disposed on at
least one side of the die receiving area and that are generally
perpendicular to the at least one side of the die receiving area,
wherein each lead of the plurality of leads has an inner lead end
that is spaced from but near to the at least one side of the die
receiving area and an outer lead end that is distal to the at least
one side of the die receiving area, and a strip formed in the die
receiving area that is bent to a substantially vertical position,
and wherein the die receiving area, the plurality of leads, and the
strip are all formed of the same electrically conductive sheet
material; a first integrated circuit die attached to the die
receiving area and electrically connected to the inner lead ends of
the plurality of leads; an encapsulant formed over the first die
and the electrical connections between the first die and the
plurality of inner lead ends, wherein the encapsulant forms a body,
and wherein the strip extends vertically to an upper edge of the
body; and a package lid formed on the upper edge of the body and in
contact with a distal end of the vertical strip such that the
vertical strip is in electrical communication with the package
lid.
15. The shielded semiconductor device of claim 14, further
comprising a second integrated circuit die attached to a top
surface of the first die and electrically connected to at least one
of the plurality of leads and the first die, and covered with the
encapsulant.
16. A method of assembling a shielded semiconductor device,
comprising: providing a lead frame including a die receiving area,
a plurality of leads disposed on at least one side of the die
receiving area and that are generally perpendicular to the at least
one side of the die receiving area, wherein each lead of the
plurality of leads has an inner lead end that is spaced from but
near to the at least one side of the die receiving area and an
outer lead end that is distal to the at least one side of the die
receiving area, and a strip formed in the die receiving area that
is bent to a substantially vertical position for electrical
connection to a package lid, and wherein the die receiving area,
the plurality of leads, and the strip are all formed of the same
electrically conductive sheet material; attaching a first
integrated circuit (IC) die to the die receiving area of the lead
frame; electrically connecting the first IC die to the inner lead
ends of the plurality of leads; encapsulating the first IC die, the
electrical connections and the lead frame with a molding compound,
wherein the molding compound forms a body and wherein the distal
ends of the plurality of leads are exposed along at least one
lateral side of the body and a distal end of the vertical strip is
exposed at a top surface of the body; and forming a metallic lid on
the top surface of the body, wherein the exposed distal end of the
vertical strip contacts the package lid such that the vertical
strip is in electrical communication with the package lid.
17. The method of claim 16, further comprising: attaching a second
IC die to an upper surface of the first IC die and electrically
connecting the second IC die to at least one of the first IC die
and the inner lead ends of the plurality of leads, wherein the
second IC die is covered with the molding compound.
18. The method of claim 17, wherein a void is formed over the
second IC die and the package lid includes a hole that is in
communication with the void such that the second IC die is exposed
to the ambient environment by way of the hole and the void.
19. The method of claim 18, wherein the first IC die is a
microcontroller unit and the second IC die is a pressure
sensor.
20. The method of claim 16, wherein the lid is formed by
sputtering.
Description
BACKGROUND
[0001] The present invention relates generally to semiconductor
devices and semiconductor device packaging and, more particularly,
to semiconductor device packages with electromagnetic interference
shielding.
[0002] Semiconductor device packages or integrated circuit chip
carriers are used in many high-density electronics applications.
The integrated circuits or semiconductor devices are protected from
the external environment by encapsulation with an epoxy material or
transfer molding a thermoplastic resin about the device. However,
as circuits become smaller, denser, and operate at higher
frequencies and in harsher environments, there is a growing need to
shield the circuits from radiation, such as radio frequency
interference (RFI) and electromagnetic interference (EMI). For
example, cell phones and other mobile devices need to be protected
from such radiation. Automotive circuits, such as microcontrollers
that are mounted near the spark plugs also need to be shielded, and
the plastic encapsulant does not provide EMI or RFI shielding.
[0003] Conventional shielding systems use a conductive metallic
enclosure that surrounds the circuit to be shielded. The enclosure
protects the internal circuit from EMI and RFI and prevents the
escape of RFI or EMI signals generated by the circuit. Another
solution is to place a metal cap over a semiconductor device either
before or after molding the package. This solution is applicable to
ball grid array (BGA) packages that have a large semiconductor die
(i.e., at least one inch squared). Yet another solution is to
provide a metal coating over the encapsulated device. However, all
of these solutions have some drawbacks. For instance, using a
conductive metal enclosure adds to the overall size of the package
and requires an additional soldering step to attach the metal
shield to the device, with the heat generated by the additional
soldering process potentially harming the device.
[0004] Therefore, a need exists for cost-effective, component level
shielding that can be used in a variety of packages with any
semiconductor die size.
BRIEF DESCRIPTION OF THE DRAWINGS
[0005] Embodiments of the invention will become more fully apparent
from the following detailed description, the appended claims, and
the accompanying drawings. The drawings are not necessarily to
scale, as some elements may be relatively smaller or larger than
other elements, with such differences being to highlight the
features of the invention. In the drawings, like reference numerals
identify similar or identical elements.
[0006] FIG. 1 is an enlarged cross-sectional side view of a
semiconductor device in accordance with an embodiment of the
present invention;
[0007] FIG. 2 is a top plan view of a lead frame used to form the
semiconductor device of FIG. 1;
[0008] FIG. 3 is a series of cross-sectional side views
illustrating a method of assembling the semiconductor device of
FIG. 1; and
[0009] FIG. 4 is an enlarged cross-sectional side view of a
pressure sensor semiconductor device in accordance with an
embodiment of the present invention.
DETAILED DESCRIPTION
[0010] Detailed illustrative embodiments of the invention are
disclosed herein. However, specific structural and functional
details disclosed herein are merely representative for purposes of
describing example embodiments of the invention. The invention may
be embodied in many alternate forms and should not be construed as
limited to only the embodiments set forth herein. The terminology
used herein is for the purpose of describing particular embodiments
only and is not intended to be limiting of example embodiments of
the invention.
[0011] As used herein, the singular forms "a," "an," and "the," are
intended to include the plural forms as well, unless the context
clearly indicates otherwise. It further will be understood that the
terms "comprises," "comprising," "includes," and/or "including,"
specify the presence of stated features, steps, or components, but
do not preclude the presence or addition of one or more other
features, steps, or components. It also should be noted that in
some alternative implementations, the functions/acts noted may
occur out of the order noted in the figures. For example, two
figures shown in succession may in fact be executed substantially
concurrently or may sometimes be executed in the reverse order,
depending upon the functionality/acts involved.
[0012] The present invention provides a semiconductor device having
a lid that provides EMI and RFI shielding. The device is formed
with a lead frame that includes a vertical strip formed in a die
pad of the lead frame. The vertical strip contacts and is in
electrical communication with the lid. In one embodiment, the
present invention is an article of manufacture, including a die
receiving area, a plurality of leads disposed on at least one side
of the die receiving area and that are generally perpendicular to
the at least one side of the die receiving area, and a strip formed
in the die receiving area that is bendable to a substantially
vertical position for connection to a package lid. Each of the
leads has an inner lead end that is spaced from but near to the at
least one side of the die receiving area and an outer lead end that
is distal to the at least one side of the die receiving area.
[0013] In another embodiment, the present invention is a shielded
semiconductor device, including a lead frame, an integrated circuit
(IC) die, an encapsulant, and a lid. The lead frame has a die
receiving area, a plurality of leads disposed on at least one side
of the die receiving area and that are generally perpendicular to
the at least one side of the die receiving area, and a strip formed
in the die receiving area that is bent to a substantially vertical
position for connection to a package lid. Each of the leads has an
inner lead end that is spaced from but near to the at least one
side of the die receiving area and an outer lead end that is distal
to the at least one side of the die receiving area. The IC die is
attached to the die receiving area and electrically connected to
the inner lead ends of the plurality of leads. The encapsulant is
formed over the first die and the electrical connections between
the first die and the plurality of inner lead ends and forms a
body. The strip extends vertically to an upper edge of the body.
The lid is formed on the upper edge of the body and is in contact
with a distal end of the vertical strip.
[0014] In yet another embodiment, the present invention provides a
method of assembling a shielded semiconductor device. The method
includes providing a lead frame including a die receiving area, a
plurality of leads disposed on at least one side of the die
receiving area and that are generally perpendicular to the at least
one side of the die receiving area, and a strip formed in the die
receiving area that is bent to a substantially vertical position
for connection to a package lid. Each of the leads has an inner
lead end that is spaced from but near to the at least one side of
the die receiving area and an outer lead end that is distal to the
at least one side of the die receiving area. The method also
includes attaching an IC die to the die pad of the lead frame,
electrically connecting the IC die to the inner lead ends of the
plurality of leads, and encapsulating the IC die, the electrical
connections and the lead frame with a molding compound. The molding
compound forms a body and the distal ends of the leads are exposed
on one or more sides of the body and a distal end of the vertical
strip is exposed on a top side of the body. The method also
includes forming a metallic lid on the top side of the body. The
exposed distal end of the vertical strip contacts the lid.
[0015] Referring now to FIG. 1, a cross-sectional side view of a
packaged semiconductor device 10 in accordance with an embodiment
of the present invention is shown. The semiconductor device 10 has
a body 12 formed with a plastic mold compound and a plurality of
leads 14 that extend outwardly from the housing 12. The
semiconductor device 10 may house various kinds of integrated
circuits 16, such as a power device, an application specific IC
(ASIC), etc., and the leads 14, although shown as extending
straight out of two opposing sides of the device 10, may extend
from one, two, three, or even all four sides of the device 10.
Moreover, the leads 14 may be bent into different shapes, such as
J-leads or Gull Wing leads, or be even with the housing, thereby
forming a QFN (Quad Flat No-Lead) device.
[0016] The device 10 is a lead frame-based device, where the lead
frame includes the leads 14 and a die receiving area 16. The leads
14 generally extend perpendicularly away from the sides of the die
receiving area 16. Each lead 14 thus has an inner lead end 18 that
is spaced from but near to the side of the die receiving area 16
and an outer lead end 20 that is distal to the side of the die
receiving area 16, and as discussed above, the distal ends 20 of
the leads 14 may extend outwardly from the lateral sides of the
device 10.
[0017] The die receiving area 16 is sized and shaped to support one
or more semiconductor integrated circuit (IC) dies. In the
embodiment shown, a first IC die 22 is attached to a top surface of
the die receiving area 16 and a second IC die 24 is stacked on top
of the first IC die 22. The second IC die 24 is optional and may be
located adjacent to the first IC die 22. Furthermore, there could
be one or more stacked dies and one or more adjacent dies. The
first IC die 22 is electrically connected to the leads 14 with bond
wires 26 that are connected at one end to a bonding pad on an
active surface of the first IC die 22 and at the other end to the
inner lead ends 18 of the leads 14. The second IC die 24 is
attached to the top surface of the first IC die 22 using
conventional methods and electrically connected to one or both the
first IC die 22 and one or more of the leads 14 also using bond
wires 26.
[0018] A key feature of the invention is a bendable strip 28 that
is bent to extend vertically from the die receiving area 16 to a
top surface of the body 12. The device 10 also includes a lid 30
that is formed over the top surface of the body 12. The vertically
bendable strip 28 then extends to and is connected with the lid 30.
In one embodiment, the lid 30 comprises a metal, e.g., Copper, that
is sputter coated onto the top surface of the body 12. If
necessary, the body 12 may be subjected to grinding to expose the
strip 28 so that when the lid 30 is formed on the top surface of
the body 12, the strip 28 will contact the lid 30. Although in the
presently preferred embodiment the lid 30 is sputter-coated onto
the top surface of the body 12, a preformed lid may be attached to
the top surface of the body 12 using an adhesive. Further, the lid
30 may extend at least partially over the sides of the body 12.
[0019] FIG. 2 is a top plan view of a lead frame 32 in accordance
with an embodiment of the present invention is shown. The lead
frame 32 preferably is formed from a copper sheet by punching,
stamping, cutting or etching, as is known in the art, and the
underlying metal (e.g., Cu), may be plated with one or more other
metals or an alloy, such as Ni, Pd, and Au. The lead frame 32
includes the leads 14, the die receiving area 16, and the bendable
strip 28.
[0020] In the presently preferred embodiment, the strip 28 is
formed along one side of the die receiving area 16 and includes a
joint 34 from which the strip 28 may be bent to the vertical
position. The joint 34 may be formed by etching and progressive
mechanical forming or upset tool. The length of the strip 28 is
sized to the height of the body 12. In one embodiment, the strip 28
has a width of about 0.050 mm to about 0.200 mm, and a length of
about 0.50 mm to about 2.0 mm. However, it will be understood by
those of skill in the art that the strip 28 may be formed in other
locations of the lead frame, and that the dimensions of the strip
will be influenced by the size of the package, the size of the die
receiving area, and the size of the die(s) attached to the die
receiving area.
[0021] The die receiving area 16 may be rectangular and the leads
14 are disposed on each of the sides of the die receiving area and
extend perpendicularly away from the respective sides of the die
receiving area 16, as is known in the art. The inner lead ends 18
of the leads 14 are spaced from, but near to the respective sides
of the die receiving area 16.
[0022] FIG. 2 also shows the outline of the body 12, or rather
where in one embodiment, the body 12 is located. However, it will
be understood by those of skill in the art that the size of the
body may be slightly larger or smaller depending on the sizes of
the components covered by the body and how much of the outer lead
ends 20 is desired to extend outwardly from the body 12.
[0023] FIG. 3 is a series of figures illustrating the assembly of
the semiconductor device 10 shown in FIG. 1. Starting at the upper
left side, a portion of a lead frame sheet 36 including a plurality
of the lead frames 32 is shown. Each of the lead frames 32 includes
leads 14, die receiving area 16, and the bendable strip 28, which
has been bent to a vertical position by bending the strip 28 at the
joint 34.
[0024] In the middle figure on the left side, first dies 22 have
been attached to the die receiving areas 16 and second dies 24 have
been attached to the upper surfaces of the first dies 22. Each of
the first and second dies 22 and 24 also has been electrically
connected to the leads 14 with bond wires 26. The first die 22 may
be attached to the die receiving area 16 using known die attach
methods, including solder, glue, or tape, and the second die 24 may
be attached to the surface of the first die 22 also using known
methods. In the embodiment shown, bond wires 26 are used to
electrically connect the bonding pads (not shown) on an active
surface of the first die 22 to the inner lead ends 18, and to
connect bond pads of the second die 24 to either or both of
selected ones of the bond pads of the first die 22 and the inner
lead ends 14. Alternatively, if the first die is a flip-chip die,
then the first die could rest atop the leads with the die bonding
pads directly connected to the inner leads ends, such as with
conductive bumps or balls. Further, a molding process has been
performed to cover the dies 22 and 24 and bond wires 26 with a
molding compound to form the body 12.
[0025] In the lower figure on the left side, the top surface of the
package body (i.e., the mold compound) is subjected to grinding to
expose the strip 28. Then, as shown in the lower right-side
drawing, the lid 30 is formed on the top surface of the body 12,
with the lid 30 contacting the exposed portion of the strip 28. As
previously noted, the lid 30 preferably is formed by sputtering a
layer of Copper on the top surface of the body 12. Finally, in the
top right side, individual devices 10 are formed by singulating the
simultaneously formed devices.
[0026] As will be understood by those of skill in the art, trim and
form processes also are performed in which outer portions of the
lead frames 32 are cut away and the outer lead ends 20 of the leads
14 extend beyond an outer edge of the body 12, thereby providing
the packaged semiconductor device 10. The outer lead ends 20 may or
may not extend beyond the outer edge of the body 12 depending on
design requirements and may be bent into desired shapes such as
Gull Wing and J-leads.
[0027] Referring now to FIG. 4, a cross-sectional side view of a
packaged semiconductor device 40 in accordance with another
embodiment of the present invention is shown. The semiconductor
device 10 has a body 42 formed with a plastic mold compound and a
plurality of leads 44 that are exposed at the sides and bottom of
the housing 42, such that the device 40 is a QFN type package.
There is a die receiving area 46 and a microcontroller die 48
attached to a surface of the die receiving area 46. The die
receiving area 46 comprises a lead frame flag. A pressure sensor
die 50 is attached to a top surface of the microcontroller die 48.
The microcontroller die 48 is electrically connected to the leads
44 with first bond wires 54 and the pressure sensor die 50 is
electrically connected with the microcontroller die 48 with second
bond wires 56.
[0028] There is a bendable strip 56 that extends from the die
receiving area 46 vertically to a top of the body 42. A lid 58 is
secured to the top surface of the body 42 with a conductive glue
60. The lid 58 includes a hole 62, and the body 42 includes a void
64. The void 64 is formed over the pressure sensor die 50 during
molding. The hole 62 in the lid 58 is in fluid communication with
the void 64 such that the top surface of the pressure sensor die 50
is exposed to the ambient environment. In one embodiment, a gel
(not shown) at least partially fills the void and covers the
pressure sensor die 50.
[0029] As will now be apparent, the present invention provides a
packaged semiconductor device that has a bendable strip that
extends vertically from a die receiving area to a lid formed on a
top surface of the package. The strip being connected to the lid
provides EMI and RFI shielding. The bendable strip is part of a
lead frame. The lead frame thus includes a bendable joint for
bending the strip to the vertical position. The lead frame may be
fabricated by a lead frame supplier and the lead frame supplier may
supply the lead frame with the strip either in a flat position or
already bent and in a vertical position.
[0030] Unless explicitly stated otherwise, each numerical value and
range should be interpreted as being approximate as if the word
"about" or "approximately" preceded the value or range. Also,
although labels such as top and bottom have been used, it is
understood that such are relative terms, so such surfaces or
orientations are not absolute. Furthermore, although stacked die
devices are shown and described, the invention is not limited to
stacked die devices, as a single die device, a device with
side-by-side dies, or a device with a combination of stacked dies
and side-by-side dies may be assembled that include a vertical
strip that extends to and is connected with a package lid.
[0031] It will be further understood that various changes in the
details, materials, and arrangements of the parts that have been
described and illustrated in order to explain embodiments of this
invention may be made by those skilled in the art without departing
from embodiments of the invention encompassed by the following
claims.
[0032] In this specification including any claims, the term "each"
may be used to refer to one or more specified characteristics of a
plurality of previously recited elements or steps. When used with
the open-ended term "comprising," the recitation of the term "each"
does not exclude additional, unrecited elements or steps. Thus, it
will be understood that an apparatus may have additional, unrecited
elements and a method may have additional, unrecited steps, where
the additional, unrecited elements or steps do not have the one or
more specified characteristics.
[0033] Reference herein to "one embodiment" or "an embodiment"
means that a particular feature, structure, or characteristic
described in connection with the embodiment can be included in at
least one embodiment of the invention. The appearances of the
phrase "in one embodiment" in various places in the specification
are not necessarily all referring to the same embodiment, nor are
separate or alternative embodiments necessarily mutually exclusive
of other embodiments. The same applies to the term
"implementation."
* * * * *