U.S. patent application number 15/857988 was filed with the patent office on 2019-07-04 for mechanical couplings designed to resolve process constraints.
The applicant listed for this patent is TEXAS INSTRUMENTS INCORPORATED. Invention is credited to Yuh-Harng CHIEN, Hung-Yu CHOU, Steven Alfred KUMMERL, Fu-Kang LEE.
Application Number | 20190206699 15/857988 |
Document ID | / |
Family ID | 67058522 |
Filed Date | 2019-07-04 |
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United States Patent
Application |
20190206699 |
Kind Code |
A1 |
CHIEN; Yuh-Harng ; et
al. |
July 4, 2019 |
MECHANICAL COUPLINGS DESIGNED TO RESOLVE PROCESS CONSTRAINTS
Abstract
An integrated circuit package having a shunt resistor with at
least one self-aligning member that protrudes from a first surface,
and a lead frame with at least one self-aligning feature that is a
cavity within which the at least one self-aligning member is
located, and an integrated circuit located on the lead frame.
Inventors: |
CHIEN; Yuh-Harng; (New
Taipei City, TW) ; CHOU; Hung-Yu; (Taipei City,
TW) ; LEE; Fu-Kang; (New Taipei City, TW) ;
KUMMERL; Steven Alfred; (Carrollton, TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
TEXAS INSTRUMENTS INCORPORATED |
Dallas |
TX |
US |
|
|
Family ID: |
67058522 |
Appl. No.: |
15/857988 |
Filed: |
December 29, 2017 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L 23/49551 20130101;
H01L 23/49517 20130101; H01L 23/49562 20130101; H01L 21/4842
20130101; H01L 23/49548 20130101; H01L 2924/19105 20130101; H01L
21/4825 20130101; H01L 2924/19043 20130101; H01L 23/62 20130101;
H01L 24/00 20130101 |
International
Class: |
H01L 21/48 20060101
H01L021/48; H01L 23/495 20060101 H01L023/495 |
Claims
1. An integrated circuit package, comprising: a shunt resistor
having at least one self-aligning member that protrudes from a
first surface of the shunt resistor; and a lead frame having at
least one self-aligning feature, wherein the self-aligning feature
is a cavity extending from a first surface of the lead frame facing
the first surface of the shunt resistor and the at least one
self-aligning member is located within the cavity that form the at
least one self-aligning feature; and an integrated circuit located
on said lead frame.
2. The integrated circuit package of claim 1, wherein the cavity is
a through hole that extends from the first side of the lead frame
through a second side of the lead frame that is opposite the first
side of the lead frame.
3. The integrated circuit package of claim 2, wherein an outermost
surface of the at least one self-aligning member has a surface area
that is greater than a surface area of the self-aligning feature of
the lead frame.
4. The integrated circuit package of claim 1, wherein the at least
one self-aligning member is affixed to the self-aligning feature of
the lead frame by solder coupling.
5. The integrated circuit package of claim 1, wherein the shunt
resistor has at least four self-aligning members.
6. An amplifier comprising: an integrated circuit package
comprising: a shunt resistor having at least two self-aligning
members, each self-aligning member being formed from the shunt
resistor material and as protrusions from a first surface of the
shunt resistor; and a lead frame having at two least self-aligning
features, wherein the self-aligning features are through holes
extending from a first surface of the lead frame facing the first
surface of the shunt resistor through a second surface of the lead
frame opposite the first surface, wherein each of the at least two
self-aligning members are located within and through a respective
self-aligning feature; and an integrated circuit located on said
lead frame.
7. The amplifier of claim 6, wherein at least a portion of at least
one of the self-aligning members that extends past the
self-aligning feature has a larger surface area than a surface area
of the self-aligning feature of the lead frame.
8. The amplifier of claim 6, wherein each of the at least two
self-aligning members are affixed to the self-aligning features of
the lead frame by solder coupling.
9. The amplifier of claim 6, wherein the shunt resistor has at
least four self-aligning members.
10. A method of making an integrated circuit package comprising:
providing a shunt resistor material having at least two
self-aligning members that protrude from the shunt resistor
material and extend from a first surface of the shunt resistor
material; and providing a lead frame having an integrated circuit
and at least two self-aligning features, wherein the self-aligning
features are cavities extending from a first surface of the lead
frame facing the first surface of the shunt resistor.
11. The method of claim 10, wherein the at least two self-aligning
members are formed by impacting the shunt resistor material with a
punch down tool and a complementary punch up tool.
12. The method of claim 10, wherein the at least two self-aligning
features are formed by impacting the lead frame with a punch down
tool and a clamp.
13. The method of claim 12, wherein the punch down tool forms
through holes in the lead frame that extend from a first surface of
the lead frame to a second surface opposite the first surface.
14. The method of claim 10 further comprising the step of inserting
each of the at least two self-aligning members into a respective
self-aligning feature.
15. The method of claim 14, wherein the at least two self-aligning
members extend past a second surface of the lead frame that is
opposite the first surface of the lead frame that faces the first
surface of the shunt resistor.
16. The method of claim 15 further comprising the step of impacting
portions of the at least two self-aligning members that extend past
the second surface of the lead frame.
17. The method of claim 16, wherein the impacting step forms
portions of the at least two self-aligning members that have a
surface area that is greater than a surface area of the through
hole forming the self-aligning feature of the lead frame.
18. The method of claim 10 further comprising the step of forming
at least two additional self-aligning members and at least two
additional self-aligning features.
19. A method of forming an amplifier having an integrated circuit
package comprising the steps of: forming a shunt resistor having a
plurality of self-aligning members that protrude from the shunt
resistor material and extend from a first surface of the shunt
resistor material; and inserting each of the plurality of
self-aligning members into respective self-aligning features formed
within a lead frame having an integrated circuit.
20. The method of claim 19, wherein the self-aligning features are
through holes that extend from a first surface of the lead frame to
a second surface opposite the first surface.
Description
BACKGROUND
[0001] Semiconductor devices can be used as amplifiers dedicated to
current or voltage sensing. The amplifier typically comprises an
integrated circuit (IC) package that is typically coupled to a lead
frame that is further attached to a shunt resistor to increase area
of the circuit board occupied by these elements. Attaching the lead
frame to the shunt resistor, however, has proven difficult, as the
alignment of the two components can be disrupted during the prior
art methods or processes of epoxy or solder attachment.
Accordingly, a device and process are needed to minimize the
misalignment of the lead frame and the shunt.
SUMMARY
[0002] One aspect of the present disclosure provides an integrated
circuit package. The package comprises a lead frame, an integrated
circuit located on the lead frame and a self-aligning shunt
resistor coupled to the lead frame and to the integrated circuit.
The shunt resistor coupled to the lead frame through the use of
self-aligning members. In one aspect of the disclosure, the shunt
has at least two self-aligning members that protrude from a first
surface facing the lead frame that extend past a second surface of
the lead frame opposite a first surface of the lead frame facing
the shunt. In a further aspect of the disclosure, the self-aligning
members extend through a self-aligning feature in the lead frame.
In still a further aspect of the disclosure, the self-aligning
members have at least a portion that extends past the self-aligning
feature and has a larger surface area than the self-aligning
feature of the lead frame.
[0003] In an alternative aspect of the disclosure, the
self-aligning members of the shunt extend past a surface of the
lead frame facing the shunt. In a further aspect of the disclosure,
the self-aligning features cavities forming at least two sidewalls.
In a further aspect of the disclosure, the self-aligning members
are affixed to the sidewalls of the self-aligning features. In a
further aspect of the disclosure, the self-aligning members are
affixed to the sidewalls of the self-aligning features by epoxy
coupling. In an alternative aspect of the disclosure, the
self-aligning members are affixed to the sidewalls of the
self-aligning features by solder coupling. In alternative aspects
of the disclosure, other methods of affixing the self-aligning
members are affixed to the sidewalls of the self-aligning features
can be used.
[0004] In a further aspect of the disclosure of the package, the
shunt has its own integrated external leads. In a further aspect of
the disclosure, the package is an amplifier for current or voltage
measurements. The amplifier comprises the above-described packages,
wherein the shunt has its own external leads, or, has a
low-resistance coupling to external leads of the lead frame. A mold
encompasses the lead frame, the shunt resistor, and the integrated
circuit, except for the integrated external leads of the lead frame
or the integrated external leads of the shunt resistor.
[0005] Another aspect of the present disclosure is method of
manufacturing the above-described integrated circuit packages. The
method comprises forming a lead frame, forming self-aligning
features in the lead frame, forming a shunt, forming at least two
self-members on the shunt. The method further comprises coupling
the shunt to the lead frame by inserting the self-aligning members
of the shunt into the self-aligning features of the lead frame. The
method further comprises forming an outermost surface of at least
one self-aligning member having a surface area that is greater than
a surface area of the self-aligning feature of the lead frame.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] For a detailed description of various examples, reference
will now be made to the accompanying drawings in which:
[0007] FIG. 1 illustrates an aspect of the disclosure of an
integrated circuit package having a shunt and a lead frame are
coupled together;
[0008] FIGS. 2A-2F illustrate an aspect of the disclosure of
fabricating the FIG. 1 integrated circuit package;
[0009] FIGS. 3A-3B illustrates a second aspect of the disclosure of
a shunt and a lead frame are coupled together;
[0010] FIG. 4 illustrates a precursor of the FIG. 3A/3B device;
and
[0011] FIGS. 5A-5B illustrate block diagrams of another aspect of
the present disclosure of an amplifier having an integrated circuit
package having a shunt and a lead frame are coupled together.
DETAILED DESCRIPTION
[0012] Certain terms have been used throughout this description and
claims to refer to particular system components. As one skilled in
the art will appreciate, different parties may refer to a component
by different names. This document does not intend to distinguish
between components that differ in name but not function. In this
disclosure and claims, the terms "including" and "comprising" are
used in an open-ended fashion, and thus should be interpreted to
mean "including, but not limited to . . . ." Also, the term
"couple" or "couples" is intended to mean either an indirect or
direct wired or wireless connection. Thus, if a first device
couples to a second device, that connection may be through a direct
connection or through an indirect connection via other devices and
connections.
[0013] As part of the present disclosure, it was recognized that
prior methods of epoxy and/or solder coupling of a shunt to a lead
frame resulted in non-alignment or rotation during the liquid phase
of the solder reflow process. Similarly, a shunt can rotate as a
result of epoxy coupling to a lead frame.
[0014] To prevent such an occurrence, it was found that forming
self-aligning members and self-aligning features in the shunt and
lead frame, respectively, can alleviate and minimize the rotation
that typically occurs with prior methods of coupling the two
components.
[0015] FIG. 1 illustrates an integrated circuit package 100 in
accordance with this disclosure. The integrated circuit package 100
has a shunt 110 and a lead frame 120. The shunt has at least one
self-aligning member 115 that protrudes from a first surface of the
shunt 111 facing the lead frame and extend past a second surface
122 of the lead frame opposite a first surface 121 of the lead
frame facing the shunt 121. In the example shown, the two
self-aligning members 115 have at least a portion 116 that extends
past the self-aligning feature 125 and has a first width 117 that
is greater than a second width 127 of the self-aligning feature 125
of the lead frame 120.
[0016] FIGS. 2A-2F show an aspect of the disclosure of fabricating
the integrated package 100 of FIG. 1. As illustrated in FIG. 2A, a
shunt precursor 110' and a lead frame precursor 120' are both
depicted. FIG. 2B shows the formation of self-aligning members 115
protruding from the shunt 110 and the formation of self-aligning
features 125 within the lead frame 120. While the self-aligning
members 115 is described as being formed from the shunt precursor
110' material, it should be understood that the self-aligning
members 115 are not so limited. For example, self-aligning members
could be formed of a different material, and can be affixed to a
surface of the shunt 111 (FIG. 1) facing the lead frame 120.
Alternatively, the self-assembled members could be formed through
molding of the shunt in a manner having the self-aligned members.
The illustrated self-aligning members 115 of FIG. 2B are made from
a punch down tool 170 and a complementary punch up tool 180.
[0017] Similarly, the FIG. 2B self-aligning features 125 of the
lead frame 120 are illustrated as being formed by a punch down tool
190 and clamp 195. It should be noted that such an example is not
limiting. For example, other methods of forming the self-aligning
features 125 can be used like conventional etching. Alternatively,
the lead frame can be molded to include the self-aligning features
upon formation. In the example illustrated, the self-aligning
features 125 are shown as through holes, but it should be
understood that the illustration is not so limiting. For example,
in an alternative example, the self-aligning feature can be a
cavity having at least two sidewalls and no through hole. Like the
example illustrated in FIG. 2B, these alternative examples can be
formed with a punch down tool 190 and a clamp 195, with the
difference being the height of the punch down tool (the height
being measured from a first surface 121 of the lead frame facing
the shunt 110 to the second surface 122 of the lead frame opposite
the first surface 121). In the alternative example, the
cross-sectional height of the punch down tool would be less than
the cross-sectional height of the lead frame within which the
cavities would be formed.
[0018] FIG. 2C illustrates the shunt 110 and the lead frame 120
without the punch down and punch up tools 170, 180, 190, and clamp
195.
[0019] As illustrated in FIG. 2D, the self-aligning members 115 are
inserted through the self-aligning features 125 such that they
extend past a second surface 122 of the lead frame 120 opposite a
first surface 121 of the lead frame facing the shunt. As discussed
above, the example is not limiting. For example, the example
illustrated in FIG. 2D shows self-aligning features 125 as through
holes. As discussed above, the self-aligning features could also be
formed as cavities having at least two sidewalls and not having a
through hole. The self-aligning members would be complimentary in
height to the cavities (with the height being measured from a first
surface 121 of the lead frame facing the shunt 110 to the second
surface 122 of the lead frame opposite the first surface 121). In a
further alternative example, the self-aligning members can be
affixed to the self-aligning features of the lead frame either by
epoxy or solder or some other fastening mechanism.
[0020] The insertion of self-aligning members 115 into the
self-aligning features 125 minimizes and possibly eliminate any
rotation of the shunt 110 relative to the lead frame 120 as with
the prior art. Because there are at least two self-aligning members
115 inserted into the self-aligning features 125, any rotation
during further processing steps can be minimized and/or
eliminated.
[0021] In a further example of the fabrication process illustrated
in FIG. 2E, portion 116' of the self-aligning members 115 extend
past a second surface 122 of the lead frame 120 that is opposite
the first surface 121 of the lead frame 120 that faces the shunt
110. A punch up tool 197 is positioned underneath the lead frame
120 having feet 198 aligned with the self-aligning members 115
extending through the self-aligning features. A clamp 199 is
positioned over the shunt 110 to act as a backstop for the impact
that the punch up tool 197 would create upon impact on the portions
116' of the self-aligning members 115. The impact of the punch up
tool 197 creates portions 116 of the self-aligning members 115
having a larger surface area 117 (FIG. 2F) than the surface area
127 (FIG. 2F) of the opening that forms the self-aligning feature
125 of the lead frame 120. The self-aligning members 115 act as
couplings to couple the shunt 110 to the lead frame 120.
[0022] The resulting device is illustrated in FIG. 2F.
[0023] By having self-aligning members 115 that mate with
self-aligning features 125, the risks of rotation during assembly
are minimized by up to 50% relative to prior methods using epoxy or
solder coupling. The self-aligning members 115 and self-aligning
features 125 allow for interlocking that can also shorten
production time by eliminating the time-consuming process of epoxy
or solder coupling step, which requires heating, attachment, and
cooling of the epoxy or solder used to hold the materials together.
In addition, it eliminates the expense of epoxy and solder that are
required for prior methods of coupling the shunt to the lead
frame.
[0024] In another example depicted in an angled plan view in FIG.
3A, an integrated circuit package 200 has a lead frame 220 placed
over a shunt 210. In this example, the shunt has at least four
self-aligning members 215 that are shown to extend through the
self-aligning features 225 of the second surface 222 of the lead
frame 220 opposite the first surface 221 of the lead frame. As
illustrated, two portions 216' of two self-aligning members 215 are
depicted prior to the punch up tool (197 of FIG. 2E) and clamp (199
of FIG. 2E) have deformed those portions. The other two portions
216 of two self-aligning members 215 are depicted after the punch
up tool (197 of FIG. 2E) and clamp (199 of FIG. 2E) have deformed
those portions. As illustrated, those portions 216 have larger
surface areas 217 than the surface areas 227 of the self-aligning
feature 225 of the lead frame 220. In the example illustrated, the
surface areas 217 and 227 are equivalent to the circular diameters
(as measured from a top plan view of FIGS. 3A and 3B) of portions
216 of the self-aligning members 215 and the self-aligning features
225, respectively. It should be noted that this is not intended to
be limiting. For example, the surface areas 217 and 227 could have
a top plan view shape of a rectangle, triangle, or some other
shape.
[0025] FIG. 3B illustrates a further aspect of the disclosure in
which a conductive paste 250 is placed on the shunt 210 or lead
frame 220. After coupling, conductive paste 250 can fill any
mechanical gaps between the shunt 210 and lead frame 220. This can
enhance the electrical and thermal conductivity of the device.
[0026] FIG. 4 illustrates a blown-apart depiction of a shunt 310
over a lead frame 320 with a punch up tool 397. In this example,
the shunt 310 has four self-aligning members 315 (only two of which
are illustrated). The self-aligning members 315 are shown prior to
their deformation by the punch up tool 397. It should be noted that
once the punch up tool 397 is removed, an integrated circuit can be
coupled to the lead frame. Alternatively, an integrated circuit can
be seated on the lead frame prior to the punch up tool 397
step.
[0027] FIGS. 5A and 5B illustrate block diagrams of another aspect
of the present disclosure. An amplifier 600 for current or voltage
measurements comprises an IC package 610. The package 610 can be
any of the above-described examples of the IC packages. The package
610 includes a lead frame 620, IC 622 on the lead frame 620, and
shunt resistor 624. The shunt resistance 624 is coupled to the lead
frame 620 (as discussed above) and electrically connected to the IC
622. The lead frame 620 and shunt resistor 624 are coupled together
through self-aligning members and self-aligning features as
described above with respect to FIGS. 1-4. The shunt resistor 624
can have its own external leads, or, has a low-resistance coupling
to external leads of the lead frame. Additionally, the package 610
includes a mold 626 that encompasses the lead frame 620, shunt
resistor 624, and IC 622, except for the external leads of lead
frame 620 or shunt resistor 624.
[0028] One of ordinary skill in the art would be familiar with
various possible configurations the amplifier 600 could have to
facilitate a current- or voltage-sensing function. For example, the
shunt resistor 624 can be coupled via its own external leads, or,
via external leads of the lead frame 620, to an input device 630
and to a load device 635. FIG. 5A presents a low-side sensing
configuration. FIG. 5B presents a high-side sensing configuration.
One skilled in the art would appreciate the other sensing
configurations that could be used. In some examples, to measure the
current (I.sub.device) passing through the input device 630, the
voltage potential drop (V.sub.in) across the shunt resistor 624, is
read as an input to the IC 622, to produce an output voltage
(V.sub.out) from which I.sub.device can be calculated.
[0029] The amplifier 600 can further comprise additional components
to facilitate the measurement of current or voltage. For example,
the amplifier 600 can also include a calibration circuit 640 that
is electrically connected to the IC 622. The calibration circuit
640 can also be encompassed by the mold 626, or, can be external to
the mold 626. The calibration circuit 640 can be configured to
facilitate adjustment of the gain of the amplifier IC 622, using
procedures well known to those skilled in the art. E.g., the
calibration circuit 640 can include a network of parallel
resistors, each resistor having a different value in a desired
range governed by design considerations. In some examples, the
parallel resistors of the calibration circuit 640 comprise the same
low TCR material used to form the shunt resistor 624, or, in other
cases is included in other topological configurations. The
calibration circuit 640 can be connected via conventional
input/output lead 645 to the IC 622, and via a data bus 650, to a
conventional calibration system 660 that is external to the package
610.
[0030] The above discussion is meant to be illustrative of the
principles and various examples of the present invention. Numerous
variations and modifications will become apparent to those skilled
in the art once the above disclosure is fully appreciated. For
example, it should be noted that the lead frame could include an
epoxy or solder coupling in addition to the self-aligning members
and self-aligning features that couple the shunt to the lead frame.
It should also be noted that the shunt and/or lead frame can be
made of a material having a high temperature co-efficient of
resistivity (TCR). It should also be noted that while certain
examples above have been illustrated as a quad flat no-lead package
(QFN), other conventional type of lead-containing package,
including plastic dual in-line integrated circuit packages (PDIP),
small outline integrated circuits (SOICs), quad flat packages
(QFP), thin QFPs (TQFPs), low profile QFPs (LPQFPs), Small Shrink
Outline Plastic packages (SSOP), thin SSOPs (TSSOPs), thin very
small-outline packages (TVSOPs), or other packages well known to
those skilled in the art. It should also be noted that other layers
not shown can be included in the packages described above. In
addition, it should be understood that other components including
bonding wires, mounting pads, tie bars, and other components can be
included in the examples described above.
[0031] It is intended that the following claims be interpreted to
embrace all such variations and modifications.
* * * * *