U.S. patent application number 14/937022 was filed with the patent office on 2017-05-11 for systems and methods for package on package through mold interconnects.
The applicant listed for this patent is Intel Corporation. Invention is credited to Siddarth Kumar, Shubhada H. Sahasrabudhe, Sandeep B. Sane, Shalabh Tandon.
Application Number | 20170133350 14/937022 |
Document ID | / |
Family ID | 58663735 |
Filed Date | 2017-05-11 |
United States Patent
Application |
20170133350 |
Kind Code |
A1 |
Sahasrabudhe; Shubhada H. ;
et al. |
May 11, 2017 |
SYSTEMS AND METHODS FOR PACKAGE ON PACKAGE THROUGH MOLD
INTERCONNECTS
Abstract
Discussed generally herein are methods and devices for more
reliable Package on Package (PoP) Through Mold Interconnects
(TMIs). A device can include a first die package including a first
conductive pad on or at least partially in the first die package, a
dielectric mold material on the first die package, the mold
material including a hole therethrough at least partially exposing
the pad, a second die package including a second conductive pad on
or at least partially in the second die package the second die
package on the mold material such that the second conductive pad
faces the first conductive pad through the hole, and a shape memory
structure in the hole and forming a portion of a solder column
electrical connection between the first die package and the second
die package.
Inventors: |
Sahasrabudhe; Shubhada H.;
(Gilbert, AZ) ; Sane; Sandeep B.; (Chandler,
AZ) ; Kumar; Siddarth; (Siddarth, AZ) ;
Tandon; Shalabh; (Chandler, AZ) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Intel Corporation |
Santa Clara |
CA |
US |
|
|
Family ID: |
58663735 |
Appl. No.: |
14/937022 |
Filed: |
November 10, 2015 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L 24/81 20130101;
H01L 2225/06513 20130101; H01L 23/3128 20130101; H01L 2224/16057
20130101; H01L 2224/1607 20130101; H01L 2225/1023 20130101; H01L
25/0657 20130101; H01L 2224/81951 20130101; H01L 23/49811 20130101;
H01L 24/17 20130101; H01L 2924/15331 20130101; H01L 2924/1815
20130101; H01L 2924/15311 20130101; H01L 25/50 20130101; H01L
2224/16227 20130101; H01L 2225/06527 20130101; H01L 23/3107
20130101; H01L 2224/81815 20130101; Y02P 80/30 20151101; H01L
2225/1082 20130101; H01L 2224/16145 20130101; H01L 2224/16055
20130101; H01L 2224/81193 20130101; H01L 25/105 20130101; H01L
2224/81365 20130101; H01L 2224/16225 20130101; H01L 23/49833
20130101; H01L 21/565 20130101; H01L 23/5389 20130101; H01L
2225/1058 20130101 |
International
Class: |
H01L 25/065 20060101
H01L025/065; H01L 21/56 20060101 H01L021/56; H01L 25/00 20060101
H01L025/00; H01L 23/31 20060101 H01L023/31; H01L 23/00 20060101
H01L023/00 |
Claims
1. A device comprising: a first die package including a first
conductive pad on or at least partially in the first die package; a
dielectric mold material on the first die package, the mold
material including a hole therethrough, the hole at least partially
exposing the first conductive pad; a second die package including a
second conductive pad on or at least partially in the second die
package, the second die package on the mold material such that the
second conductive pad faces the first conductive pad through the
hole; and a shape memory structure in the hole and forming a
portion of a solder column electrical connection between the first
die package and the second die package, the shape memory structure
formed of a shape memory alloy material that, when heated above an
austenite temperature, reverts to a programmed shape.
2. The device of claim 1, wherein the shape memory structure
includes a spring that is configured to expand in austenite phase,
the shape memory alloy material that includes two or more of
nickel, titanium, silver, cadmium, copper, aluminum, tin, iron,
zinc, silicon, platinum, manganese, cobalt, gallium, niobium,
hafnium, and palladium.
3. The device of claim 2, wherein the shape memory structure is a
two-way shape memory structure that is configured to lengthen
towards the second die package to a first programmed shape when
sufficiently heated and retract away from the second die package to
a second, different programmed shape when sufficiently cooled.
4. The device of claim 1, wherein the solder column includes solder
from a first solder ball and solder from a second solder ball and
wherein the shape memory structure is suspended in the solder
column.
5. The device of claim 1, wherein the shape memory structure is
attached to the first conductive pad by a conductive adhesive, and
wherein the solder column includes solder from only a single solder
ball.
6. The device of claim 1, wherein: the first die package includes a
plurality of first conductive pads on or at least partially in the
first die package; the mold material includes a plurality of holes
therethrough to at least partially expose each of the plurality of
first conductive pads; the solder column is one of a plurality of
solder columns, each solder column in a respective hole of the
plurality holes, each solder column including solder from a
respective second solder ball of a plurality of second solder
balls; the second die package includes a second plurality of
conductive pads on or at least partially in the second die package;
and the shape memory structure is one of a plurality of shape
memory structures in respective holes of the plurality holes.
7. The device of claim 6, wherein: each solder column further
includes solder from a first solder ball of a plurality of first
solder balls and a shape memory structure of the plurality of shape
memory structures.
8. The device of claim 6, wherein: each solder column further
includes a shape memory structure of the plurality of shape memory
structures and conductive adhesive.
9. A method comprising: heating a first solder ball on a first
conductive pad attached to a first die package to soften the first
solder ball; situating a shape memory structure at least partially
into the softened solder ball, the shape memory structure formed of
a shape memory alloy material that, when sufficiently heated,
reverts to a programmed shape; situating a second die package over
the first die package to situate a second solder ball attached to a
second conductive pad attached to the second die package near the
first solder ball; and reflowing the first and second solder balls
together to form a solder column connected to the first and second
conductive pads, the solder column including the shape memory
structure at least partially embedded therein.
10. The method of claim 9, wherein the shape memory structure
includes a spring shape, the shape memory alloy material that
including two or more of nickel, titanium, silver, cadmium, copper,
aluminum, tin, iron, zinc, silicon, platinum, manganese, cobalt,
gallium, niobium, hafnium, and palladium.
11. The method of claim 10, wherein the shape memory structure is a
two-way shape memory structure that is configured to lengthen
towards the second die package to a first programmed shape when
sufficiently heated and retract away from the second die package
and revert to a second, different programmed shape when
sufficiently cooled.
12. The method of claim 11, further comprising cooling the shape
memory structure to cause the shape memory structure to retract and
revert to the second programmed shape.
13. The method of claim 12, further comprising pressing the second
die package into a dielectric mold material between the first die
package and the second die package while cooling the shape memory
structure.
14. The method of claim 13, further comprising: situating the mold
material over the first solder ball and the first die package; and
removing a portion of the mold material to create a through mold
hole that exposes the first solder ball and at least a portion of
the first conductive pad, prior to heating the first solder
ball.
15. A method comprising: attaching, using a conductive adhesive, a
shape memory structure on a first conductive pad attached to a
first die package, the shape memory structure formed of a shape
memory alloy material that, when sufficiently heated, reverts to a
programmed shape; situating a second die package over the first die
package to situate a solder ball attached to a second conductive
pad attached to the second die package near the shape memory
structure; and reflowing the solder ball to form a solder column
connected to the first and second conductive pads, the solder
column including the shape memory structure at least partially
embedded therein.
16. The method of claim 15, wherein the shape memory structure
includes a spring shape, the shape memory alloy material including
two or more of nickel, titanium, silver, cadmium, copper, aluminum,
tin, iron, zinc, silicon, platinum, manganese, cobalt, gallium,
niobium, hafnium, and palladium.
17. The method of claim 16, wherein the shape memory structure is a
two-way shape memory structure that is configured to lengthen
towards the second die package to a first programmed shape when
sufficiently heated and retract away from the second die package
and revert to a second, different programmed shape when
sufficiently cooled.
18. The method of claim 17, further comprising cooling the shape
memory structure to cause the shape memory structure to retract and
revert to the second programmed shape.
19. The method of claim 18, further comprising pressing the second
die package into a mold material between the first die package and
the second die package while cooling the shape memory
structure.
20. The method of claim 19, further comprising: situating the mold
material over the shape memory structure and the first die package;
and removing a portion of the mold material to create a through
mold hole that exposes the shape memory structure and at least a
portion of the first conductive pad, prior to attaching the shape
memory material to the first conductive pad.
Description
TECHNICAL FIELD
[0001] This disclosure relates generally to semiconductor packaging
that includes one or more Package-on-Package (PoP) through mold
interconnects (TMI). More specifically, one or more embodiments can
include a shape memory structure situated in a TMI hole to help
ensure electrical contact between packages in a PoP TMI.
BACKGROUND ART
[0002] Package-on-Package (PoP) is a technology that can be used to
stack a first die package on a second die package. In some
instances, the one die package is a memory package and the other
die package is a logic die package. Package flatness properties of
a surface of the first and second die packages can impact product
yield, such as can be due to Through Mold Interconnect (TMI)
failure. In instances that include a second die package that
includes a surface mount technology (SMT) interconnect for mounting
on the first die package, yield depends upon a shape of the first
die package, the second die package, as well as the alignment
between the two packages during a reflow process. Some common
failure modes are ball bridging, non-contact opens (NCO), and
head-on-pillow (HOP) failure. Thinner form-factor packaging
increases a challenge provided by warpage, further impacting the
device assembly manufacturing processes and the corresponding
product yield. The thinner packaging has a smaller bump pitch, thus
reducing product yield and increasing product cost. Existing
solutions to address one or more of these electrical interconnect
issues includes addition of flux in TMI through holes to help with
NCO and HOP failures. Although the flux solution helps improve
yield, the flux only helps when the gap between the PoP packages is
less than fifteen micrometers.
BRIEF DESCRIPTION OF THE DRAWINGS
[0003] FIG. 1 illustrates, by way of example, a block diagram of an
embodiment of a PoP package with ball bridging, NCO, and HOP
failures.
[0004] FIG. 2 illustrates, by way of example, a block diagram of an
embodiment of a PoP package that includes a shape memory structure
to help reduce ball bridging, NCO, and/or HOP failures.
[0005] FIG. 3A illustrates, by way of example, an exploded view
diagram of a shape memory structure situated on a ball in a TMI
through hole of a PoP package.
[0006] FIG. 3B illustrates, by way of example, an exploded view
diagram of a shape memory structure situated on a pad in a TMI
through hole of a PoP package.
[0007] FIGS. 4A, 4B, and 4C illustrate, by way of example, block
diagrams of an embodiment of a process for forming an electrical
connection between packages of a PoP package using a shape memory
structure.
[0008] FIG. 5 illustrates, by way of example, an embodiment of a
method for forming an electrical connection between packages of a
PoP package using a shape memory structure.
[0009] FIGS. 6A, 6B, and 6C illustrate, by way of example, block
diagrams of another embodiment of a process for forming an
electrical connection between packages of a PoP package using a
shape memory structure.
[0010] FIG. 7 illustrates, by way of example, an embodiment of a
method for forming an electrical connection between packages of a
PoP package using a shape memory structure.
[0011] FIG. 8 shows a block diagram example of an electronic device
which can include an electrical connection between packages using a
shape memory structure as disclosed herein.
DESCRIPTION OF THE EMBODIMENTS
[0012] The following description and the drawings sufficiently
illustrate specific embodiments to enable those skilled in the art
to practice them. Other embodiments can incorporate structural,
logical, electrical, process, or other changes. Portions and
features of some embodiments can be included in, or substituted
for, those of other embodiments. Embodiments set forth in the
claims encompass all available equivalents of those claims.
[0013] Embodiments discussed herein use a shape memory structure
(e.g., a spring, pin, or other shape memory structure that expands
when sufficiently heated) to help overcome warpage, misalignment,
or other issues in creating a PoP package that includes a Through
Mold Interconnect (TMI). In one or more embodiments, the shape
memory structure includes a shape memory alloy (SMA) material. An
SMA material includes a combination of materials, such as can
include two or more of nickel, titanium, silver, cadmium, copper,
aluminum, tin, iron, zinc, silicon, platinum, manganese, cobalt,
gallium, niobium, hafnium, and palladium. One common SMA material
is nitinol, which is a combination of nickel and titanium.
[0014] Displacement between solder balls in a through hole in a
dielectric mold material is controlled in a manner using the shape
memory structure. The shape memory structure increases the chance
of a good solder joint formation, such as to form a reliable
electrical connection between packages of a PoP package. The shape
memory structure effectively reduces the displacement between one
or more solder balls in the mold material through hole of the PoP
package. The shape memory structure is situated on, or at least
partially in, a solder ball or on a package pad. The shape memory
structure can provide a path for reflowed solder to join. In
embodiments, the shape memory structure can automatically stretch
to its memory shape, such as by being heated as a natural byproduct
of a reflow process. The shape memory structure (e.g., the
stretched spring, straightened pin, or other longer shape memory
structure) acts as a molten solder wick that aids in creating a
reliable electrical interconnect. The shape memory structure being
compliant, such as with a controlled elastic constant, can help
compensate for a range of gaps between packages of the PoP package,
thus decreasing yield losses from connection failures. This SMA
incorporation can be accomplished in at least two different ways,
such as can include attaching the shape memory structure on a
solder ball and attaching the shape memory structure on a pad of
the package, as is discussed in more detail herein.
[0015] FIG. 1 illustrates, by way of example, a block diagram of an
embodiment of a PoP package 100 with ball bridging, NCO, and HOP
failures. The PoP package 100 includes a first die package 102 and
a second die package 104 on the first die package, with a mold
material 108 separating the die packages 102 and 104. In one or
more embodiments, the first die package 102 can include a die 106
attached to pads on a surface thereof.
[0016] The first die package 102 as illustrated includes solder
balls 112 on a surface thereof and the second die package 104
includes mating solder balls 110 on a surface that faces the
surface of the first die package 102 that include the solder balls
112. The die 106 is connected to the first die package 102 through
solder balls 116. The first die package 102 can be connected to a
printed circuit board, or other electrical substrate with contact
pads through solder balls 118.
[0017] The mold material 108 as illustrated includes a plurality of
through holes 114 extending all the way through the mold material
108 to a pad and/or surface of the first die package 102. The
solder connections between the first and the second die packages
102 and 104 are formed in the holes 114 between pairs of aligned
solder balls 110 and 112. The solder balls 110 and 112 (from bottom
to top) of FIG. 1 are illustrated as forming a reliable electrical
connection, a HOP connection (a weak, unreliable connection), an
open, and two of the solder balls 112 are bridged.
[0018] FIG. 2 illustrates, by way of example, a block diagram of an
embodiment of a PoP package 200 that includes shape memory
structures 220 to help reduce ball bridging, NCO, and/or HOP
failures. The package 200 is illustrated prior to a reflow process
being performed to melt the solder balls 110 and 112 and form a
solder column (a reliable TMI). The shape memory structures 220 of
FIG. 2 are illustrated as being partially in the solder balls 112.
In one or more other embodiments, one or more of the shape memory
structures 220 can be attached to pads on a surface of the first
die package 102. In such embodiments, the solder balls 112 may be
unnecessary and not used in the formation of a PoP TMI electrical
connection. Embodiments in which the shape memory structure 220 is
attached to the solder ball 112 and attached to the pad on the
surface of the first die package 102 are discussed in turn.
[0019] FIG. 3A illustrates, by way of example, an exploded view
diagram of a shape memory structure 220 situated partially in a
solder ball 112 in a TMI through hole 114 of a PoP package 300A.
FIG. 3A is an exploded view diagram of a portion of the package 200
of FIG. 2 outlined with a dashed box labelled "FIG. 3A".
[0020] The package 300A as illustrated includes the first and
second die packages 102 and 104, the solder balls 110 and 112 in
the through hole 114 in the mold material 108 (mold not shown in
FIG. 3A), and the shape memory structure 220 attached to the solder
ball 112. The first die package 102 includes a conductive contact
pad 324 facing a corresponding contact conductive pad 322 on, or at
least partially in, the second die package 104. The shape memory
structure 220 reduces a gap (indicated by the arrows 326) which
solder from the solder balls 110 and 112 would need to traverse to
create a reliable electrical connection during a reflow process.
The shape memory structure 220 can act as a wick for the solder
from the solder balls 110 and 112 to flow together and form a
reliable electrical connection. More details regarding creating an
electrical connection using a shape memory structure attached to a
solder ball, such as depicted in FIG. 3A, are provided with regard
to FIGS. 4A, 4B, 4C, and 5.
[0021] FIG. 3B illustrates, by way of example, an exploded view
diagram of a shape memory structure 220 attached to a pad 324 in a
TMI through hole 114 of a PoP package 300B. FIG. 3B is an exploded
view diagram, similar to FIG. 3A, with FIG. 3B illustrating the
shape memory structure 220 attached directly to the pad 324 instead
of the solder ball 112.
[0022] The package 300B as illustrated includes the first and
second die packages 102 and 104, the solder ball 110 in the through
hole 114 in the mold material 108 (mold not shown in FIG. 3B), and
the shape memory structure 220 attached to the pad 324. The shape
memory structure 220 can be attached to the pad 324 using a
conductive adhesive 328, such as solder, curable conductive paste,
a conductive tape, or other conductive adhesive. The first die
package 102 includes a conductive contact pad 324 facing a
corresponding contact conductive pad 322 on, or at least partially
in, the second die package 104. The spring 220 takes the place of
the solder ball 112 and reduces a gap (indicated by the arrows 326
in FIG. 3A) which solder from the solder balls 110 and 112 would
need to traverse to create a reliable electrical connection during
a reflow process. The shape memory structure 220 can act as a wick
for the solder from the solder ball 110 to flow to the pad 324
and/or the conductive adhesive 328 and form a reliable electrical
connection. More details regarding creating an electrical
connection using a spring attached to a pad, such as depicted in
FIG. 3B, are provided with regard to FIGS. 6A, 6B, 6C, and 7.
[0023] In one or more embodiments, the shape memory structure 220
is electrically conductive, such as to help current to flow from
one die package to another die package. In such embodiments, a
reliable electrical connection can be made between the first die
package 102 and the second die package 104 even if solder from the
balls 110 and/or 112 do not reach the other solder ball or the
opposing pad 324 or 322. A reliable electrical connection can be
formed through solder from the solder ball 110 contacting the
spring 220, such as without contacting the solder of the solder
ball 112, the conductive adhesive 328, or the pad 324. In such
embodiments, the shape memory structure 220 provides a path through
which electrical current can flow between the die packages 102 and
104.
[0024] FIGS. 4A, 4B, and 4C illustrate, by way of example, block
diagrams of an embodiment of a process for forming an electrical
connection between packages of a PoP package using a shape memory
structure. Each of the FIGS. 4A-4C illustrate PoP packages 400A,
400B, and 400C, respectively, at various stages of an electrical
connection formation process. The packages 400A-C each include a
first die package 102, a second die package 104, pads 132 and 134
on respective die packages 104 and 102, and a shape memory
structure 220.
[0025] The package 400A including the shape memory structure 220
attached to and partially embedded in the solder ball 112 attached
to the pad 134. The solder balls 110 and 112 and the shape memory
structure 220 are situated in a mold through hole 114. FIG. 4B
illustrates the device 400B that includes the device 400A after the
shape memory structure 220 and solder ball 110 have been heated.
Heating the shape memory structure 220 causes the spring to morph
into a shape that has been "programmed" into the spring 220.
Heating the shape memory structure 220 and the solder balls 110 and
112 can be done during a solder reflow process.
[0026] With shape memory materials, a shape is programmed into the
material by heating the material, forming the material into the
desired (programmed) shape, and then cooling the material. In the
cooled state the material can be formed into a different shape.
Then, when sufficient heat is applied to the material, the material
returns to its programmed shape. Thus, in the example of FIGS.
4A-C, the shape memory structure 220 as shown in FIGS. 4B-C is in
its programmed state and the shape memory structure 220 as shown in
FIG. 4A is in a deformed, cooled state.
[0027] The temperatures at which the solder flows and the shape
memory structure 220 returns to its programmed shape need to be
controlled so that the shape memory structure 220 does not fall to
the pad 134 when or the shape memory structure 220 needs to become
sufficiently long so as to make contact with solder of the solder
ball 110. Such temperatures are solder material and spring material
dependent and can be determined by evaluating a specification
regarding the solder material or shape memory structure material,
experimenting with the solder material and/or shape memory
structure material, and/or contacting a solder material and/or
shape memory structure material manufacturer.
[0028] FIG. 4C illustrates a device 400C that includes the device
400B after the solders from the respective solder balls 110 and 112
have become molten and flowed together, by way of being wicked by
the shape memory structure 220, to form a solder column 430. The
solder column 430 forms a contiguous pathway for electrical current
to flow between the pads 132 and 134, and thus between the packages
102 and 104.
[0029] FIG. 5 illustrates, by way of example, an embodiment of a
method 500 for forming an electrical connection between packages of
a PoP package using a shape memory structure. The method 500 as
illustrated includes: attaching a solder ball on a first die
package, at operation 502; situating a mold material on the first
die package, at operation 504; exposing the solder ball attached to
the first die package, at operation 506; heating the exposed solder
ball on the first die package, at operation 508; at least partially
inserting a shape memory structure into the heated solder ball, at
operation 510; optionally adding flux to the exposed ball and/or
the inserted shape memory structure, at operation 512; situating a
second die package on the mold material (such that a solder ball of
the second die package is aligned with the shape memory structure
and in a hole that exposes the solder ball of the first die
package), at operation 514; and reflowing the package so as to join
solder of the two solder balls and form a solder column, at
operation 516.
[0030] The operation 506 can include drilling (e.g., laser of
mechanical drilling), chemical etching, or other method of removing
mold material on the solder ball, such as to expose the solder
ball. The operation 510 can include inserting the shape memory
structure to a depth sufficient to not interfere with the operation
514 and still allow the shape memory structure to contact a solder
ball on the second die package when sufficiently heated. If the
shape memory structure is not deep enough into the solder ball, the
shape memory structure will make contact with the solder ball of
the second package during operation 514 and create alignment
issues. The operation 516 generally includes pre-heating the solder
and spring to make a temporary connection between the shape memory
structure and the solder ball of the second die package, such as to
align the first and second die packages relative to each other,
heating the solder and the shape memory structure to make the
solder molten and expand the shape memory structure to its
programmed shape, and then cooling the newly formed solder column
electrical connection to permanently join the two solder balls and
solidify the shape memory structure, at least partially, into the
solder column, such as shown in FIG. 4C.
[0031] FIGS. 6A, 6B, and 6C illustrate, by way of example, block
diagrams of another embodiment of a process for forming an
electrical connection between packages 102 and 104 of a PoP package
600A, 600B, and 600C, respectively, using a shape memory structure
220, such as a spring, pin, or other shape memory structure that
can reduce a gap between electrical contacts (e.g., pad(s) and/or
solder ball(s)) when heated. Each of the FIGS. 6A-6C illustrate PoP
packages 600A, 600B, and 600C, respectively, at various stages of
an electrical connection formation process. The packages 600A-C
each include a first die package 102, a second die package 104,
pads 132 and 134 on respective die packages 104 and 102, and a
shape memory structure 220.
[0032] The package 600A includes the shape memory structure 220
attached to the pad 134 using a conductive adhesive 328. FIG. 6B
illustrates the package 600B that includes the package 600A after
the shape memory structure 220 and solder ball 110 have been
heated. Heating the shape memory structure 220 causes the spring to
morph into a shape that has been "programmed" into the shape memory
structure 220. Heating the shape memory structure 220 and the
solder ball 110 can be done during a solder reflow process. In the
examples of FIGS. 6A-C, the shape memory structure 220 as shown in
FIGS. 6B-C is in its programmed state and the shape memory
structure 220 as shown in FIG. 6A is in a deformed and/or cooled
state.
[0033] The temperatures at which the solder of the solder ball 110
flows, the conductive adhesive 328 flows, and the shape memory
structure 220 morphs to its programmed shape should be controlled
so that the shape memory structure 220 does not fall over, or
otherwise tilt, so as to help ensure that the shape memory
structure 220 expands towards the solder ball 110 and does not
create a bridge, NCO, or HOP failure. Such temperatures are solder
material, conductive adhesive material, and spring material
dependent and can be determined by evaluating a specification
regarding the solder material or spring material, experimenting
with the solder material and/or spring material, and/or contacting
a solder material and/or spring material manufacturer.
[0034] FIG. 6C illustrates a device 600C that includes the package
600B after the solder from the solder ball 110 has become molten
and flowed to the pad 134, by way of being wicked by the shape
memory structure 220, to form a solder column 632. The solder
column 632 forms a contiguous pathway for electrical current to
flow between the pads 132 and 134, and thus between the packages
102 and 104.
[0035] FIG. 7 illustrates, by way of example, an embodiment of a
method 700 for forming an electrical connection between packages of
a PoP package using a spring. The method 700 as illustrated
includes: attaching a shape memory structure on a pad of a first
die package (e.g., using a conductive adhesive), at operation 702;
situating a mold material on the first die package, at operation
704; exposing the shape memory structure (and at least a portion of
the pad) attached to the pad of the first die package, at operation
706; optionally adding flux to the exposed ball and/or the inserted
shape memory structure, at operation 708; situating a second die
package on the mold material (such that a solder ball of the second
die package is aligned with the shape memory structure and in a
hole that exposes the solder ball of the first die package), at
operation 710; and reflowing the package so as to form a solder
column between a pad of the second die package and the pad of the
first die package, at operation 712.
[0036] The operation 706 can include drilling (e.g., laser of
mechanical drilling), chemical etching, or other method of removing
mold material on the shape memory structure and/or the pad, such as
to expose the shape memory structure and/or the pad. The operation
712 generally includes pre-heating the solder and shape memory
structure to make a temporary connection between the shape memory
structure and the solder ball of the second die package, such as to
align the first and second die packages relative to each other,
heating the solder and the shape memory structure to make the
solder molten and lengthen the shape memory structure to its
programmed shape, and then cooling the newly formed solder column
electrical connection to permanently join the pads and solidify the
shape memory structure into the solder column, such as shown in
FIG. 7C.
[0037] While embodiments described herein illustrate the shape
memory structure as a spring, other shapes can be used that are not
considered springs. Other shapes that lengthen in the proper
direction can be used. For example, a pin, spiral, helix, arch,
question mark (without the dot), wave, or other shape that can
lengthen into its programmed state can be used in place of a spring
shaped shape memory structure. A spring shape can have advantages
over other shapes, such as can include the spring shape may be
compliant with a wider range of package shapes (e.g., warpage
shapes). This is because a pin, for example, has a fixed dimension
and may not work for a same range of package shapes as a spring,
which has a wide range of length dimensions. A weight of the second
package on the spring can limit the amount the spring expands in
going into its programmed shape.
[0038] As long as the length of the shape memory structure is
sufficient, the elastic nature (compressibility) of the shape
memory structure allows it to adjust to any warpage shape, thus
helping ensure a good TMI electrical connection. Embodiments
discussed herein exploit the shape memory properties of SMA alloys,
such as nitinol. At temperatures below an austenite phase
transition temperature of the shape memory structure, the shape
memory structure exhibits an elastic-plastic constitutive behavior
(the martensite phase) the shape memory structure is in a
contracted state at room temperature), however, heating the shape
memory structure above the austenite temperature makes the shape
memory structure revert to its "programmed" shape which happens to
be longer than its length in its martensite in this application,
thus aiding in the solder wicking process. The length, as used
herein, refers to its dimension in the direction indicated by the
arrows 326 in FIG. 3A. Wicking redirects the solder, thus aligning
the one or more solder balls and corresponding pads on which the
solder balls are attached, leading to a reliable electrical
connection formation. Cooling the joint below the austenite phase
transformation temperature causes the shape memory structure (in
the case of a two-way shape memory alloy) to revert to its
Martensite phase (elastic-plastic behavior) which allows
compression of the shape memory structure as the second die package
(e.g., a memory, such as a dynamic random access memory (DRAM)) is
pressed on the first die package (e.g., system on a chip
(SoC)).
[0039] In one or more embodiments, a compressed or otherwise
retracted shape memory structure in martensite phase can be
attached (e.g., on selected solder balls or pads) at locations with
known electrical connection failure issues. After the through mold
holes are formed in the mold material, this shape memory
structure-on-ball attachment can be achieved using localized laser
heating on a few joints and aligning shape memory structure into
soft, not molten, solder.
[0040] During the second die package attachment phase, the higher
reflow temperature can cause the shape memory structure to go into
austenite phase, thus stretching to some programmed form. The
stretched dimension of the shape memory structure at austenite
phase can be chosen such that it covers sufficient distance between
the bumps to allow wicking of solder and enable reliable electrical
connections. As the stretched spring touches the top molten solder,
solder wicks down the shape memory structure forming an electrical
connection. Such a solution can accommodate a wide range of package
form factors and warpage shapes.
[0041] In one or more embodiments, a compressed shape memory
structure in martensite phase is attached directly on the
conductive pad of the first die package instead of a solder bump.
During a second die package attachment phase, at the reflow
temperature the spring will go into austenite phase stretching to
its programmed form. The stretched dimension of the shape memory
structure at austenite phase can be chosen such that it covers
sufficient distance between the solder bump of the second die
package and the conductive pad of the first die package to allow
wicking of solder along the spring and enable reliable electrical
connections. As the stretched shape memory structure touches the
top molten solder, solder wicks below forming a joint. This
solution may have one or more advantages over embodiments in which
the shape memory structure is attached to a solder ball as TMI bump
pitch nears about 0.4 millimeters or less and/or electrical
connection joints include a diameters of about seven millimeters or
less.
[0042] FIG. 8 shows a block diagram example of an electronic device
which can include an electrical connection between packages using a
shape memory structure as disclosed herein. An example of an
electronic device using one or more packages with a shape memory
structure aided PoP TMI electrical connection is included to show
an example of a device application for the present disclosure. FIG.
8 shows an example of an electronic device 800 incorporating a
shape memory structure aided PoP TMI electrical connection.
Electronic device 800 is merely one example of a device in which
embodiments of the present disclosure can be used. Examples of
electronic devices 800 include, but are not limited to, personal
computers, tablet computers, supercomputers, servers,
telecommunications switches, routers, mobile telephones, personal
data assistants, MP3 or other digital music players, radios, etc.
In this example, electronic device 800 comprises a data processing
system that includes a system bus 802 to couple the various
components of the system. System bus 802 provides communications
links among the various components of the electronic device 800 and
can be implemented as a single bus, as a combination of busses, or
in any other suitable manner.
[0043] An electronic assembly 810 is coupled to system bus 802. The
electronic assembly 810 can include a circuit or combination of
circuits. In one embodiment, the electronic assembly 810 includes a
processor 812 which can be of any type. As used herein, "processor"
means any type of computational circuit, such as but not limited to
a microprocessor, a microcontroller, a complex instruction set
computing (CISC) microprocessor, a reduced instruction set
computing (RISC) microprocessor, a very long instruction word
(VLIW) microprocessor, a graphics processor, a digital signal
processor (DSP), multiple core processor, or any other type of
processor or processing circuit.
[0044] Other types of circuits that can be included in electronic
assembly 810 are a custom circuit, an application-specific
integrated circuit (ASIC), or the like, such as, for example, one
or more circuits (such as a communications circuit 814) for use in
wireless devices like mobile telephones, pagers, personal data
assistants, portable computers, two-way radios, and similar
electronic systems. The IC can perform any other type of
function.
[0045] The electronic device 800 can include an external memory
820, which in turn can include one or more memory elements suitable
to the particular application, such as a main memory 822 in the
form of random access memory (RAM), one or more hard drives 824,
and/or one or more drives that handle removable media 826 such as
compact disks (CD), digital video disk (DVD), and the like.
[0046] The electronic device 800 can also include a display device
816, one or more speakers 818, and a keyboard and/or controller
830, which can include a mouse, trackball, touch screen,
voice-recognition device, or any other device that permits a system
user to input information into and receive information from the
electronic device 800.
Additional Notes and Examples
[0047] In Example 1 a device can include a first die package
including a first conductive pad on or at least partially in the
first die package, a dielectric mold material on the first die
package, the mold material including a hole therethrough at least
partially exposing the pad, a second die package including a second
conductive pad on or at least partially in the second die package
the second die package on the mold material such that the second
conductive pad faces the first conductive pad through the hole, and
a shape memory structure in the hole and forming a portion of a
solder column electrical connection between the first die package
and the second die package.
[0048] In Example 2, the device of Example 1 includes, wherein the
shape memory structure includes a spring that is configured to
expand in austenite phase.
[0049] In Example 3, the device of Example 2 includes, wherein the
shape memory structure is a two-way shape memory structure that is
configured to lengthen towards the second die package when
sufficiently heated and retract away from the second die package
when sufficiently cooled.
[0050] In Example 4, the device of at least one of Examples 1-2
includes, wherein the solder column includes solder from a first
solder and solder from second solder and wherein the first die
package includes the first solder ball on the first conductive pad
and the second die package includes the second solder ball on the
second conductive pad, wherein the shape memory structure is
attached to the first solder ball and wherein the shape memory
structure is configured to expand to the second solder ball and
wick the solder from the first and second solder balls together
when sufficiently heated.
[0051] In Example 5, the device of at least one of Examples 1-4
includes, wherein the shape memory structure is attached to the
first conductive pad by a conductive adhesive, and wherein the
solder column includes solder from a second solder ball attached to
the second conductive pad, and wherein the shape memory structure
is configured to expand to contact the second solder ball and wick
solder from the second solder ball to the first conductive pad to
form the solder column.
[0052] In Example 6, the device of at least one of Examples 1-5
includes, wherein the first die package includes a plurality of
first conductive pads on or at least partially in the first die
package, wherein the mold material includes a plurality of holes
therethrough to at least partially expose each of the plurality of
first conductive pads, wherein the solder column is one of a
plurality of solder columns, each solder column in a respective
hole of the plurality holes, each solder column including solder
from a second solder ball, wherein the second die package includes
a second plurality of conductive pads on or at least partially in
the second die package and the plurality of solder balls attached
to a respective second conductive pad of the plurality of second
conductive pads, each solder ball situated at least partially in a
hole of the plurality of holes, and wherein the shape memory
structure is one of a plurality of shape memory structures in
respective holes of the plurality holes, each of the shape memory
structures located at areas of the first die package or the second
die package known to warp.
[0053] In Example 7, the device of Example 6 includes, wherein each
solder column further includes solder from a first solder ball of a
plurality of first solder balls and a shape memory structure of the
plurality of shape memory structures, the plurality of first solder
balls attached to a respective first conductive pad of the
plurality of first conductive pads, and each shape memory structure
is attached to a respective first solder ball of the plurality of
first solder balls.
[0054] In Example 8, the device of Example 6 includes, wherein each
solder column further includes a shape memory structure of the
plurality of shape memory structures, and each shape memory
structure is attached by a conductive adhesive to a respective
first conductive pad of the plurality of first conductive pads.
[0055] In Example 9 a method can include heating a first solder
ball on a first conductive pad of a first die package to soften the
first solder ball, situating a shape memory structure at least
partially into the softened solder ball, situating a second die
package over the first die package to situate a second solder ball
attached to a second conductive pad of the second die package near
the first solder ball, and reflowing the first and second solder
balls together to form a solder column connected to the first and
second conductive pads, the solder column including the shape
memory structure at least partially embedded therein.
[0056] In Example 10, the method of Example 9 includes wherein the
shape memory structure includes a spring shape.
[0057] In Example 11, the method of Example 10 includes, wherein
the shape memory structure is a two-way shape memory structure that
is configured to lengthen towards the second die package when
sufficiently heated and retract away from the second die package
when sufficiently cooled.
[0058] In Example 12, the method of Example 11 includes cooling the
shape memory structure to cause the shape memory structure to
retract.
[0059] In Example 13, the method of Example 12 includes pressing
the second die package into a mold material between the first die
package and the second die package while cooling the shape memory
structure.
[0060] In Example 14, the method of Example 13 includes situating
the mold material over the first solder ball and the first die
package, and removing a portion of the mold material to create a
through mold hole that exposes the first solder ball and at least a
portion of the first conductive pad, prior to heating the first
solder ball.
[0061] In Example 15, a method can include attaching, using a
conductive adhesive, a shape memory structure on a first conductive
pad of a first die package, situating a second die package over the
first die package to situate a solder ball attached to a second
conductive pad of the second die package near the shape memory
structure, and reflowing the solder ball to form a solder column
connected to the first and second conductive pads, the solder
column including the shape memory structure at least partially
embedded therein.
[0062] In Example 16, the method of Example 15 includes, wherein
the shape memory structure includes a spring shape.
[0063] In Example 17, the method of Example 16 includes, wherein
the shape memory structure is a two-way shape memory structure that
is configured to lengthen towards the second die package when
sufficiently heated and retract away from the second die package
when sufficiently cooled.
[0064] In Example 18, the method of Example 17 includes cooling the
shape memory structure to cause the shape memory structure to
retract.
[0065] In Example 19, the method of Example 18 includes pressing
the second die package into a mold material between the first die
package and the second die package while cooling the shape memory
structure.
[0066] In Example 20, the method of Example 19 includes situating
the mold material over the shape memory structure and the first die
package, and removing a portion of the mold material to create a
through mold hole that exposes the shape memory structure and at
least a portion of the first conductive pad, prior to attaching the
shape memory material to the first conductive pad.
[0067] The above description of embodiments includes references to
the accompanying drawings, which form a part of the description of
embodiments. The drawings show, by way of illustration, specific
embodiments in which the invention can be practiced. These
embodiments are also referred to herein as "examples." Such
examples can include elements in addition to those shown or
described. However, the present inventors also contemplate examples
in which only those elements shown or described are provided.
Moreover, the present inventors also contemplate examples using any
combination or permutation of those elements shown or described (or
one or more aspects thereof), either with respect to a particular
example (or one or more aspects thereof), or with respect to other
examples (or one or more aspects thereof) shown or described
herein.
[0068] In this document, the terms "a" or "an" are used, as is
common in patent documents, to include one or more than one,
independent of any other instances or usages of "at least one" or
"one or more." In this document, the term "or" is used to refer to
a nonexclusive or, such that "A or B" includes "A but not B," "B
but not A," and "A and B," unless otherwise indicated. In this
document, the terms "including" and "in which" are used as the
plain-English equivalents of the respective terms "comprising" and
"wherein." Also, in the following claims, the terms "including" and
"comprising" are open-ended, that is, a system, device, article,
composition, formulation, or process that includes elements in
addition to those listed after such a term in a claim are still
deemed to fall within the scope of that claim. Moreover, in the
following claims, the terms "first," "second," and "third," etc.
are used merely as labels, and are not intended to impose numerical
requirements on their objects.
[0069] The above description is intended to be illustrative, and
not restrictive. For example, the above-described examples (or one
or more aspects thereof) can be used in combination with each
other. Other embodiments can be used such as by one of ordinary
skill in the art upon reviewing the above description. The Abstract
is provided to allow the reader to quickly ascertain the nature of
the technical disclosure. It is submitted with the understanding
that it will not be used to interpret or limit the scope or meaning
of the claims. Also, in the above description of embodiments,
various features can be grouped together to streamline the
disclosure. This should not be interpreted as intending that an
unclaimed disclosed feature is essential to any claim. Rather,
inventive subject matter can lie in less than all features of a
particular disclosed embodiment. Thus, the following claims are
hereby incorporated into the description of embodiments, with each
claim standing on its own as a separate embodiment, and it is
contemplated that such embodiments can be combined with each other
in various combinations or permutations. The scope of the invention
should be determined with reference to the appended claims, along
with the full scope of equivalents to which such claims are
entitled.
* * * * *