U.S. patent application number 14/880976 was filed with the patent office on 2017-04-13 for integrated circuit package mold assembly.
The applicant listed for this patent is Texas Instruments Incorporated. Invention is credited to Hiep Xuan Nguyen.
Application Number | 20170103904 14/880976 |
Document ID | / |
Family ID | 58499896 |
Filed Date | 2017-04-13 |
United States Patent
Application |
20170103904 |
Kind Code |
A1 |
Nguyen; Hiep Xuan |
April 13, 2017 |
INTEGRATED CIRCUIT PACKAGE MOLD ASSEMBLY
Abstract
An integrated circuit ("IC") package mold includes an upper mold
platen that defines an upper mold cavity for receiving an upper
substrate having a die attach side with a plurality of dies mounted
thereon and a non-attach side with no dies mounted thereon. The die
attach side of the upper substrate faces upwardly. A lower mold
platen defines a lower mold cavity for receiving a lower substrate
having a die attach side with a plurality dies mounted thereon and
a non-attach side with no dies mounted thereon. The die attach side
of the lower substrate faces downwardly.
Inventors: |
Nguyen; Hiep Xuan; (Grand
Prairie, TX) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Texas Instruments Incorporated |
Dallas |
TX |
US |
|
|
Family ID: |
58499896 |
Appl. No.: |
14/880976 |
Filed: |
October 12, 2015 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L 2924/19043
20130101; H01L 21/565 20130101; H01L 2224/97 20130101; H01L 21/561
20130101; H01L 2224/85005 20130101; H01L 2924/00014 20130101; H01L
2924/19041 20130101; H01L 2924/3511 20130101; H01L 2924/14
20130101; H01L 2924/15311 20130101; H01L 2924/00014 20130101; H01L
2224/48091 20130101; H01L 24/97 20130101; H01L 2224/48227 20130101;
H01L 24/85 20130101; H01L 21/6835 20130101; H01L 23/49537 20130101;
H01L 2224/73265 20130101; H01L 2224/45099 20130101; H01L 2224/45099
20130101; H01L 2924/00014 20130101; H01L 2224/48247 20130101; H01L
2224/97 20130101; H01L 23/3121 20130101; H01L 2924/19042 20130101;
H01L 2924/19105 20130101; H01L 24/48 20130101; H01L 2224/48091
20130101; H01L 2224/85 20130101 |
International
Class: |
H01L 21/56 20060101
H01L021/56; H01L 21/78 20060101 H01L021/78 |
Claims
1. An integrated circuit ("IC") package mold assembly comprising:
an upper mold platen defining an upper mold cavity for receiving an
upper substrate having a die attach side with a plurality of dies
mounted thereon and a non-attach side with no dies mounted thereon,
wherein said die attach side is facing upwardly; and a lower mold
platen defining a lower mold cavity for receiving a lower substrate
having a die attach side with a plurality dies mounted thereon and
a non-attach side with no dies mounted thereon, wherein said die
attach side of said lower substrate is facing downwardly.
2. The assembly of claim 1 wherein said upper and lower mold
platens comprises at least one pair of aligned projections
extending into said mold cavities for engaging said upper and lower
substrates therebetween.
3. The assembly of claim 1 further comprising a single runner in
fluid communication with said upper and lower mold cavities.
4. An integrated circuit ("IC") package mold assembly comprising:
an upper mold platen defining an upper mold cavity; a lower mold
platen defining a lower mold cavity; an upper substrate positioned
in said upper mold cavity and having a plurality of integrally
connected substrate portions, each said upper substrate portion
having a die attach side and a non-attach side, IC dies being
mounted on said die attach sides of said plurality of upper
substrate portions; and a lower substrate positioned in said lower
mold cavity and having a plurality of integrally connected lower
substrate portions, each lower substrate portion having a die
attach side and a non-attach side, IC dies being mounted on said
die attach sides of said plurality of lower substrate portions;
wherein said upper and lower substrates are positioned with said
non-attach sides of said substrate portions thereof positioned in
facing relationship.
5. The assembly of claim 4 wherein said upper and lower substrates
comprise upper and lower leadframe substrates and further
comprising a liner positioned between said upper and lower
leadframe substrates.
6. The assembly of claim 4 wherein said upper and lower substrates
comprises nFBGA (New Fine Pitch Ball Grid Array) substrates.
7. The assembly of claim 4 wherein said upper and lower substrates
comprises flex-tape substrates.
8. The assembly of claim 4 wherein said upper and lower substrates
have aligned holes extending therethrough.
9. The assembly of claim 8 further comprising a liner positioned
between said upper and lower substrates and having holes therein
aligned with said holes in said upper and lower substrates.
10. The assembly of claim 9 wherein each of said upper and lower
substrates comprise leadframe sheet substrates with leadframe
corner connection structures that connect leadframe portions on
each corresponding leadframe sheet substrate; wherein said
leadframe corner connection structures have openings therein that
are aligned with corresponding ones of said holes extending through
said liner.
11. The assembly of claim 8, said upper and lower mold cavities
being filled with mold compound that fills said aligned holes
extending through said substrates.
12. A method of making integrated circuit ("IC") packages
comprising: placing first and second IC package substrates having a
plurality of individual portions associated with individual IC
packages in non-attach side facing, mirror image relationship;
placing the first and second substrates in a mold having upper and
lower cavities with the first substrate positioned in an upper mold
platen cavity and the second substrate positioned in a lower mold
platen cavity that is in fluid communication with the upper mold
platen cavity; and filling the upper and lower mold cavities with
molten mold compound.
13. The method of claim 12 further comprising engaging aligned
portions of the first and second IC package substrates with
opposite mold platen projections.
14. The method of claim 13 further comprising producing a plurality
of holes extending through aligned portions of the first and second
substrates.
15. The method of claim 14 further comprising flowing mold compound
into the mold to mold the two substrates including flowing mold
compound through the plurality of holes to form connecting
structures to hold the two molded substrates together.
16. The method of claim 15 further comprising: curing the mold
compound; and removing connecting structures holding the molded
substrates together.
17. The method of claim 16 further comprising separating the molded
substrates.
18. The method of claim 17 further comprising dicing the separated
molded substrates.
19. The method of claim 15 further comprising dicing the connected
molded substrates.
20. The method of claim 19 further comprising removing the
connecting structure during said dicing.
Description
BACKGROUND
[0001] Integrated circuits, also referred to as "IC's" or
"semiconductor chips" or simply "chips," are electronic circuits
made by diffusion of trace elements into the surface of thin
substrates of semiconductor material. Integrated circuits were
first produced in the mid 20.sup.th Century. Because of their small
size and relatively low production cost, integrated circuits are
now used in most modern electronics. Semiconductor chips are
typically mass produced in the form of a single wafer that contains
a large number of identical integrated circuits. The wafer is cut
("singulated") into a number of individual semiconductor chips
referred to as "dies" or "dice."
[0002] Dies and sometimes other components such as passive devices
are "packaged" to prevent damage to the dies and to facilitate
attachment of the dies to circuit boards. Various packaging
materials and processes have been used to package integrated
circuit dies. One conventional packaging method involves mounting
individual dies in a predetermined pattern on a substrate strip.
The dies mounted on the substrate strip are then encapsulated in a
plastic material, such as by a transfer molding process. Next, the
encapsulated dies are singulated into individual integrated circuit
packages by cutting the encapsulated die/substrate strip in
accordance with the predetermined die mounting pattern. Typical
cutting tools include saws and punches. Each integrated circuit
package generally includes at least one die and the underlying
portion of the substrate strip on which it was mounted. The
underlying substrate strip is sometimes a leadframe to which the
die is electrically connected.
SUMMARY
[0003] An integrated circuit ("IC") package mold assembly includes
an upper mold platen defines an upper mold cavity for receiving an
upper substrate having a die attach side with a plurality of dies
mounted thereon and a non-attach side with no dies mounted thereon.
The die attach side faces upwardly. A lower mold platen defines a
lower mold cavity for receiving a lower substrate having a die
attach side with a plurality dies mounted thereon and a non-attach
side with no dies mounted thereon. The die attach side of the lower
substrate faces downwardly.
BRIEF DESCRIPTION OF THE DRAWINGS
[0004] FIG. 1 is a cross-sectional elevation view of a prior art
mold assembly.
[0005] FIG. 2 is a cross-sectional elevation view of an example
embodiment of a mold assembly that includes a mold with a double
cavity configuration.
[0006] FIG. 3 is a cross-sectional elevation view of another
example embodiment of a double cavity mold assembly.
[0007] FIG. 4 is a detail isometric view of a portion of the double
cavity mold assembly of FIG. 3.
[0008] FIG. 5 is a cross-sectional elevation view of a portion of
another example embodiment of a double cavity mold assembly.
[0009] FIG. 6 is a flow chart that illustrates a method of making
integrated circuit ("IC") packages.
DETAILED DESCRIPTION
[0010] FIG. 1 is a cross-sectional elevation view of a prior art
mold assembly 10. The mold assembly 10 includes a mold 11, such as
an injection mold, that has an upper mold platen 12 and a lower
mold platen 14. The upper mold platen 12 has a mold cavity 16
therein in fluid communication with a mold runner 18. The mold
assembly 10 also includes a leadframe sheet 22 that is positioned
within the mold cavity 16. The mold assembly 10 further includes a
plurality of integrated circuit (IC) dies 24, 26, 28, etc., which
are attached to different portions 25, 27, 29, etc., of the
leadframe sheet 22. Each of these portions 25, 27, 29 is associated
with a separate IC package that will ultimately be formed by
singulating ("dicing") the leadframe sheet 22.
[0011] Each of the dies 24, 26, 28 is electrically connected to an
associated leadframe portion 25, 27, 29 of the leadframe sheet 22.
In the assembly 10 of FIG. 2 the dies are electrically connected to
the leadframe sheet 22 by bond wires 30. Each bond wire 30 has a
first end 32 attached to an associated die, e.g., die 24, and a
second end 34 attached to the leadframe portion, e.g., portion 25,
on which the die is mounted.
[0012] After insertion of the leadframe sheet 22 and attached wire
bonded dies 24, etc., the mold 10 is closed and the mold cavity 16
is filled with molten mold compound 40. The mold compound 40 flows
under pressure into the cavity 16 through the runner 18, which is
conventionally connected to a pressurized source of molten mold
compound 40. After the mold compound 40 has filled the cavity,
curing of the mold compound commences, initially while the mold 10
is closed, and subsequently after it is has been opened and the
entire assembly of leadframe sheet 22, dies 24, etc. and mold
compound 40 has been removed. After removal from the mold 10, the
portion of the mold compound 40 that was in the runner 18 is
removed from the portion of the mold compound covering the
leadframe sheet 22. The portion of the mold compound that was in
the runner is scrapped as waste. This waste is typically around 40%
of the total amount of mold compound injected in a molding
operation.
[0013] After the molded leadframe assembly has completed curing it
is singulated along saw streets 36, 38, etc., indicated by dashed
lines in FIG. 1, into separate IC package units.
[0014] FIG. 2 is a cross-sectional elevation view of an example
embodiment of a mold assembly 110 that includes a mold 111 with a
double cavity configuration. The mold 111 includes upper and lower
mold platens 112, 114 having upper and lower mold cavities 116,
118, respectively. A single mold runner 120 is in fluid
communication with both mold cavities 116, 118.
[0015] The mold assembly 110 includes an upper substrate 122, which
may be a leadframe sheet substrate. Hereafter "leadframe sheet
substrate" is referred to by the shorter phrase "leadframe sheet."
It is to be understood that substrates other than leadframe sheets
may be used in the embodiments described in FIGS. 2, 3 and 5.
[0016] The substrate 122 has a first end 124 and a second end 126
and has a die attach side 128 and an opposite or "non-attach side"
129. A lower substrate 132, which in this embodiment may be a
leadframe sheet, has a first end 134 and a second end 136 and also
includes a die attach side 138 and an opposite or non-attach side
139. The upper substrate 122 and the lower substrate 132 each
comprise a plurality of corresponding separate substrate portions
140 and 142, respectively, which are vertically aligned.
[0017] The mold assembly 110 also includes upper and lower
substrate dies. The upper substrate dies 152 are mounted on the
upper substrate portions 140 of the upper substrate 124 and are
electrically connected thereto, as by upper bond wires 154.
Similarly lower substrate dies 162 are attached to the separate
substrate portions 142 of the lower substrate 134 and are connected
thereto by lower leadframe bond wires 164. As illustrated in FIG.
2, a liner 170 may be used in some embodiments to separate the
upper and lower substrates. In some embodiments when the respective
substrates are, for example, nFBGA (New Fine Pitch Ball Grid Array
packages) substrates or uBGA (Ultra FineLine Ball-Grid Array
packages) substrates, rather than leadframe sheets, no liner is
needed. The liner 170 engages the non-attach sides 129, 139 of the
substrates 122, 132.
[0018] As further illustrated by FIG. 2, the mold assembly also
includes heated mold compound 178 that is injected into the single
mold runner and flows therethrough to fill both the upper and lower
mold cavities 116, 118. The mold compound 178 is initially allowed
to cure within the mold cavities 116, 118. Subsequently, the entire
substrate/die/bond wire/mold compound assembly, including the mold
compound 178 within the runner 120, is removed from the mold 111.
The solidified mold compound 178 within the runner 120 is then
removed and scrapped. Because there is a single runner 120
associated with both mold cavities 116, 118, the scrap produced by
this new process is substantially reduced as compared to the scrap
produced in the conventional process illustrated in FIG. 1.
[0019] Next the upper and lower molded substrates 122, etc., 132,
etc., are separated and the liner 170, if used, is removed. Each
substrate 122, etc., 132, and associated dies and mold compound,
etc., is then singulated by conventional methods to provide a
plurality of separate IC packages.
[0020] FIG. 3 is a cross-sectional elevation view of another
example embodiment of a double-sided mold assembly 210 including a
mold 211 that has upper and lower mold platens 212, 214 having
upper and lower mold cavities 216, 218, respectively. The mold 211
has a single runner 220. The assembly 210 illustrated in FIG. 3 is
similar to that illustrated in FIG. 2, and similar structures
therein are given the identical reference numerals as in FIG. 2,
except that the reference numerals are 200 series rather than 100
series. The structures include: runner 220, upper substrate 222
having a first and second ends 224, 226 and die attach side 228 and
non-attach side 229 and upper leadframe portions 240; a lower
substrate 232 with a first and second ends 234, 236 and with a die
attach side 238 and non-attach side 139 and separate upper and
lower substrate portions 240 and 242; upper dies 252, which may be
electrically connected to the upper substrate by bond wires 254;
lower dies with bond wires 264; liner 270; and mold compound 278.
One difference in the assembly of FIG. 3 is that upper and lower
passive components 253, 255 (e.g., resistors, capacitors and/or
inductors) are also operably mounted on each substrate portion 240
or 242 and electrically connected to the die(s) on the associated
portion 240 or 242. Another difference in the assembly of FIG. 3
from that of FIG. 2 is that holes 280 have been bored through the
two substrates 222, 232 and liner sheet 270 after initially
sandwiching the liner sheet 270 between the two substrates 222, 232
and before insertion of this substrate/liner assembly into the mold
210. These holes 280 may be bored at each corner intersection of
the substrates when they comprise leadframe sheets 222, 232. Four
separate leadframe portions are integrally connected. (The
illustrated embodiment shows the holes located at corner
intersections of the sheets 222, 232, but the holes 280 may be
provided at other locations. For example, if the binding feature is
larger than corner space allows, several of the dies may be
eliminated and the holes can be located on the leadframes, or other
substrates, where the dies have been eliminated.)
[0021] FIG. 4 is a detail isometric view illustrating a portion of
structure located around the holes 280 shown in FIG. 3. This
structure includes a rectangular frame structure 284. The
rectangular frame structure laterally connects first, second, third
and fourth upper leadframe portions 286, 288, 290, 292,
respectively, of the upper leadframe sheet 222. The lower leadframe
sheet 232 has an identical configuration (not shown) lying directly
below that of sheet 222. The hole 280 passes through the center of
this rectangular frame portion 284 and an aligned portion 282 of
the liner 270.
[0022] With reference to FIG. 3, the holes 280 through the
assembled sheets 222, 270, 232 provide a path for molten mold
compound 278. The mold compound 278 that flows through the holes
280 forms a connecting structure that holds the two sheets 222, 232
together and in alignment during curing, including the curing phase
that takes place after removal of the molded leadframe/die/bond
wire structure from the mold 211. The holes 280 may also help to
provide pressure equalization between the upper and lower mold
cavities 216 and 218 as molten mold compound flows into these
cavities. The corner frame structure 284 and the mold compound 278
passing through the holes 280 are bored or cut out and removed
after curing to allow the leadframe sheets 222, 232 to be separated
and subsequently singulated. In another embodiment, the corner
structure remains intact until singulation and the two connected
molded leadframe sheets 222, 232 and liner 270 are all singulated
simultaneously with deeper singulation cuts. The upper and lower IC
package pairs, thus formed, are then separated. In this case,
singulation removes the corner structure and connecting mold
compound structure.
[0023] The prior art structure, as shown by FIG. 1, has a metal
leadframe sheet 22 on one side of the assembly, and epoxy
encapsulant compound 40 on the other side. Due to a mismatch in
thermal expansion of these two materials, when the assembly is
ejected from the mold 11 and cools down from a high mold
temperature, the encapsulated leadframe sheet 22 tends to warp.
Such warping makes the prior art leadframe sheet 22 difficult to
work with and, in some cases, is so severe that the molded
leadframe sheet 22 must be scrapped. In the assembly of FIG. 3, the
connecting structure formed by the mold compound 278 after it
solidifies in holes 280, combined with the symmetry of the two
substrates, prevents warping of the substrates 222, 232.
[0024] FIG. 5 is a cross-sectional elevation view of a portion of
another example embodiment of a double-sided mold assembly 310. The
mold assembly 310 includes a mold 311 that comprises upper and
lower mold platens 312, 314 having upper and lower mold cavities
316, 318, respectively. The mold 311 may be identical to the mold
211 illustrated in FIG. 3, except that upper projections 317 and
lower projections 319 extends from the upper and lower mold
platens, like symmetrical stalactites and stalagmites, to form a
clamping assembly that sandwiches and holds upper and lower
leadframes/substrates 322, 332 therebetween. These projections 317,
319 may be provided by ribs that are integrally formed with the
respective upper and lower mold platens 312, 314 or may be provided
by pins inserted through the walls of the mold platens or may be
formed by other means. The projections may engage the
leadframes/substrates 322, 332 at the boundaries of adjacent
substrate portions, such that any irregularities in the mold
compound layer formed by the projections 317, 319 is trimmed off
during subsequent singulation.
[0025] This clamping assembly 317, 319 vertically supports the
leadframes 322, 332, counteracting a tendency of the leadframes to
droop under their own weight prior to the inflow of mold compound
(not shown in FIG. 5).
[0026] As used herein terms such as up, down, above, under,
vertical, horizontal, etc., are used in a relative sense to explain
the physical relationship between various structures shown in the
drawings, rather than in an absolute sense indicating an
orientation of objects within a gravitational field.
[0027] FIG. 6 is a flow chart that illustrates a method of making
integrated circuit ("IC") packages. The method includes, as shown
at 601, placing first and second IC package substrates having a
plurality of individual portions associated with individual IC
packages in non-attach side facing, mirror image relationship. The
method also includes, as shown at 602, placing the first and second
substrates in a mold having upper and lower cavities with the first
substrate positioned in an upper mold platen cavity and the second
substrate positioned in a lower mold platen cavity that is in fluid
communication with the upper mold platen cavity. As shown at 603,
the method further includes filling the upper and lower mold
cavities with molten mold compound.
[0028] Certain specific embodiments of double cavity mold
assemblies and methods of use thereof have been expressly described
in detail herein to aid those reading this disclosure to understand
the inventive concepts involved. Alternative embodiments of such
mold assemblies and methods will occur to those skilled in the art
after reading this disclosure. It is intended that the language of
the appended claims be broadly construed to cover such alternative
embodiments, except as limited by the prior art.
* * * * *