U.S. patent application number 14/832156 was filed with the patent office on 2017-02-23 for reducing directional stress in an orthotropic encapsulation member of an electronic package.
The applicant listed for this patent is International Business Machines Corporation. Invention is credited to Marcus E. INTERRANTE, Yi PAN, Hilton T. TOY, Jeffrey A. ZITZ.
Application Number | 20170053845 14/832156 |
Document ID | / |
Family ID | 58056802 |
Filed Date | 2017-02-23 |
United States Patent
Application |
20170053845 |
Kind Code |
A1 |
INTERRANTE; Marcus E. ; et
al. |
February 23, 2017 |
REDUCING DIRECTIONAL STRESS IN AN ORTHOTROPIC ENCAPSULATION MEMBER
OF AN ELECTRONIC PACKAGE
Abstract
Methods and apparatuses for reducing directional stress in an
orthotropic encapsulation member of an electronic package may
include attaching a stiffening frame to a carrier, the stiffening
frame comprising a central opening to accept a semiconductor chip
and a plurality of opposing sidewalls, electronically coupling the
semiconductor chip to the carrier concentrically arranged within
the central opening, and thermally contacting a directional heat
spreader to the semiconductor chip, the directional heat spreader
transferring heat from the semiconductor chip, wherein the
directional heat spreader is shaped to reduce a directional stress
along the opposing bivector direction.
Inventors: |
INTERRANTE; Marcus E.; (New
Paltz, NY) ; PAN; Yi; (The Woodlands, TX) ;
TOY; Hilton T.; (Hopewell Junction, NY) ; ZITZ;
Jeffrey A.; (Poughkeepsie, NY) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
International Business Machines Corporation |
Armonk |
NY |
US |
|
|
Family ID: |
58056802 |
Appl. No.: |
14/832156 |
Filed: |
August 21, 2015 |
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01L 23/3737 20130101;
H01L 23/373 20130101; H01L 21/4882 20130101; H01L 23/16 20130101;
H01L 21/50 20130101; H01L 23/562 20130101; H01L 23/498 20130101;
H01L 23/36 20130101 |
International
Class: |
H01L 23/16 20060101
H01L023/16; H01L 21/48 20060101 H01L021/48; H01L 21/50 20060101
H01L021/50; H01L 23/373 20060101 H01L023/373; H01L 23/498 20060101
H01L023/498 |
Claims
1. A method of reducing directional stress in an orthotropic
encapsulation member of an electronic package, the method
comprising: attaching a stiffening frame to a carrier, the
stiffening frame comprising a central opening to accept a
semiconductor chip, a base portion, and a plurality of opposing
sidewalls; electrically coupling the semiconductor chip to the
carrier concentrically arranged within the central opening; and
thermally contacting a directional heat spreader to the
semiconductor chip, the directional heat spreader transferring heat
from the semiconductor chip in an opposing bivector direction
towards opposing sidewalls, wherein the directional heat spreader
is shaped to reduce a directional stress along the opposing
bivector direction by forming: a hole in the directional heat
spreader in an area of the directional heat spreader proximal to
one of a plurality of opposing stiffener sidewalls; an elastomeric
column adhering the stiffening frame to the directional heat
spreader within the hole in the directional heat spreader.
2. The method of claim 1, wherein the directional heat spreader is
shaped to reduce the directional stress by tapering an end of the
directional heat spreader proximal to one of the plurality of
opposing stiffener sidewalls such that an area of the directional
heat spreader in contact with a portion of the stiffening frame is
less than an area of the directional heat spreader distal from the
one of the opposing sidewalls.
3. (canceled)
4. (canceled)
5. The method of claim 1, wherein the directional heat spreader is
loosely mechanically coupled to the electronic package such than an
area of the directional heat spreader adhered to the electronic
package proximal to an opposing sidewall of the stiffening frame is
less than an area of the directional heat spreader distal from the
opposing sidewall of the stiffening frame.
6. The method of claim 1, wherein the directional heat spreader is
shaped to reduce the directional stress by forming on a side of the
directional heat spreader proximal to the semiconductor chip an
attach structure operable to increase a contact radius between a
center area of the directional heat spreader and the semiconductor
chip.
7. The method of claim 6, wherein the attach structure comprises an
indentation on the side of the directional heat spreader proximal
to the semiconductor chip, the indentation of a shape to increase
and decentralize contact area between the directional heat spreader
and the semiconductor chip.
8. The method of claim 7, wherein the attach structure comprises a
local protrusion within the indentation from the side of the
directional heat spreader proximal to the semiconductor chip, the
protrusion located to contact the semiconductor chip at a
semiconductor chip hot spot.
9. An integrated circuit chip module comprising: a carrier
comprising a top surface and a bottom surface configured to be
electrically connected to a motherboard; a stiffening frame
attached to the carrier top surface, the stiffening frame
comprising a central opening that accepts a semiconductor chip, a
base portion, and a plurality of opposing sidewalls; a
semiconductor chip electrically connected to the carrier top
surface and concentrically arranged within the central opening; and
a directional heat spreader thermally contacting the semiconductor
chip, the directional heat spreader transferring heat from the
semiconductor chip in an opposing bivector direction towards
opposing sidewalls, wherein the directional heat spreader is shaped
to reduce a directional stress along the opposing bivector
direction by forming: a hole in the directional heat spreader in an
area of the directional heat spreader proximal to one of a
plurality of opposing stiffener sidewalls; an elastomeric column
adhering the stiffening frame to the directional heat spreader
within the hole in the directional heat spreader.
10. The integrated circuit chip module of claim 9, wherein the
directional heat spreader is shaped to reduce the directional
stress by tapering an end of the directional heat spreader proximal
to one of a plurality of opposing stiffener sidewalls such that an
area of the directional heat spreader in contact with a portion of
the stiffening frame is less than an area of the directional heat
spreader distal from the one of the opposing sidewalls.
11. (canceled)
12. (canceled)
13. The integrated circuit chip module of claim 9, wherein the
directional heat spreader is loosely mechanically coupled to the
electronic package such than an area of the directional heat
spreader adhered to the electronic package proximal to an opposing
sidewall of the stiffening frame is less than an area of the
directional heat spreader distal from the opposing sidewall of the
stiffening frame.
14. The integrated circuit chip module of claim 9, wherein the
directional heat spreader is shaped to reduce the directional
stress by forming on a side of the directional heat spreader
proximal to the semiconductor chip an attach structure operable to
increase a contact radius between a center area of the directional
heat spreader and the semiconductor chip.
15. The integrated circuit chip module of claim 14, wherein the
attach structure comprises an indentation on the side of the
directional heat spreader proximal to the semiconductor chip, the
indentation of a shape to increase and decentralize contact area
between the directional heat spreader and the semiconductor
chip.
16. The integrated circuit chip module of claim 14, wherein the
attach structure comprises a local protrusion within the
indentation from the side of the directional heat spreader proximal
to the semiconductor chip, the protrusion located to contact the
semiconductor chip at a semiconductor chip hot spot.
17. A method of reducing directional stress in an orthotropic
encapsulation member of an electronic package, the method
comprising: electrically connecting a IC chip module to a
motherboard, the IC chip module comprising: a carrier comprising a
top surface and a bottom surface configured to be electrically
connected to a motherboard; a stiffening frame attached to the
carrier top surface, the stiffening frame comprising a central
opening that accepts a semiconductor chip, a base portion, and a
plurality of opposing sidewalls; a semiconductor chip electrically
connected to the carrier top surface and concentrically arranged
within the central opening; and a directional heat spreader
thermally contacting the semiconductor chip, the directional heat
spreader transferring heat from the semiconductor chip in an
opposing bivector direction towards opposing sidewalls, wherein the
directional heat spreader is shaped to reduce a directional stress
along the opposing bivector direction by forming: a hole in the
directional heat spreader in an area of the directional heat
spreader proximal to one of a plurality of opposing stiffener
sidewalls; an elastomeric column adhering the stiffening frame to
the directional heat spreader within the hole in the directional
heat spreader; thermally contacting a heat sink to the IC chip
module.
18. The method of claim 17, wherein the directional heat spreader
is shaped to reduce the directional stress by tapering an end of
the directional heat spreader proximal to one of a plurality of
opposing stiffener sidewalls such that an area of the directional
heat spreader in contact with a portion of the stiffening frame is
less than an area of the directional heat spreader distal from the
one of the opposing sidewalls.
19. (canceled)
20. The method of claim 17, wherein the directional heat spreader
is shaped to reduce the directional stress by forming on a side of
the directional heat spreader proximal to the semiconductor chip an
attach structure operable to increase a contact radius between a
center area of the directional heat spreader and the semiconductor
chip.
Description
BACKGROUND
[0001] The present disclosure is generally related to electronic
packaging, or, more specifically, methods, apparatus, and products
for reducing directional stress in an orthotropic encapsulation
member of an electronic package.
DESCRIPTION OF RELATED ART
[0002] As electronic packages continue to decrease in size,
additional hurdles are discovered in the effective and efficient
manufacturing and operation of electronic packages. For example,
some current electronic packages use various conductive materials
such as copper as a heat sink or heat transfer as a means of
dissipating heat from an active semiconductor chip within the
electronic package. In order to increase efficiencies in
manufacturing, new materials and methods are sought out to replace
traditional conductive materials. For example, certain types of
graphite have been proposed for use in various parts of electronic
packages, including as heat transfer structures. However, the use
of these new materials presents new difficulties in manufacturing
due to the particular nature of those materials.
SUMMARY
[0003] Methods and apparatuses for reducing directional stress in
an orthotropic encapsulation member of an electronic package are
disclosed. These may include attaching a stiffening frame to a
carrier, the stiffening frame comprising a central opening to
accept a semiconductor chip, a base portion, and a plurality of
opposing sidewalls, electronically coupling the semiconductor chip
to the carrier concentrically arranged within the central opening,
and thermally contacting a directional heat spreader to the
semiconductor chip, the directional heat spreader transferring heat
from the semiconductor chip in an opposing bivector direction
towards a first opposing sidewalls, wherein the directional heat
spreader is shaped to reduce a directional stress along the
opposing bivector direction.
[0004] The foregoing and other objects, features and advantages
described herein will be apparent from the following more
particular descriptions of example embodiments as illustrated in
the accompanying drawings wherein like reference numbers generally
represent like parts of example embodiments.
BRIEF DESCRIPTION OF THE DRAWINGS
[0005] FIG. 1 illustrates an example IC chip module configured to
spread heat away from a semiconductor chip using an orthotropic
material, in accordance with certain embodiments of the present
disclosure.
[0006] FIG. 2 illustrates a first step in forming example IC chip
module, in accordance with certain embodiments of the present
disclosure.
[0007] FIG. 3 illustrates a second step in forming example IC chip
module, in accordance with certain embodiments of the present
disclosure.
[0008] FIG. 4 illustrates a third step in forming example IC chip
module, in accordance with certain embodiments of the present
disclosure.
[0009] FIG. 5 illustrates a fourth step in forming example IC chip
module, in accordance with certain embodiments of the present
disclosure.
[0010] FIG. 6 illustrates an example underside of a directional
heat spreader configured to reduce directional stress in the
orthotropic encapsulation member, in accordance with certain
embodiments of the present disclosure.
[0011] FIG. 7 depicts a flow chart illustrating an example method
for reducing directional stress in an orthotropic encapsulation
member of an electronic package, in accordance with certain
embodiments of the present disclosure.
[0012] FIG. 8 depicts a flow chart illustrating the usage of an
electronic package within an electronic device, in accordance with
certain embodiments of the present disclosure.
DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS
[0013] An embodiment of the present invention is related to an
integrated circuit ("IC") chip module that includes a carrier, a
stiffening frame, an IC chip (or "semiconductor chip"), and a
directional heat spreader. The carrier has a top surface and a
bottom surface configured to be electrically connected to a
motherboard. The stiffening frame includes an opening that accepts
the IC chip and may be attached to the top surface of the carrier.
The IC chip is concentrically arranged within the opening of the
stiffening frame. The directional heat spreader is attached to the
stiffening frame and to the IC chip and generally removes heat in
an opposing bivector direction. The directional heat spreader is
shaped to reduce a directional stress along the opposing bivector
direction.
[0014] Example methods, apparatus, and products for reducing
directional stress in an orthotropic encapsulation member of an
electronic package in accordance with certain embodiments described
herein with reference to the accompanying drawings. FIGS. 1-5
illustrate the results of performing a set of example steps for
forming an example IC chip module (200) configured to spread heat
away from a semiconductor chip using an orthotropic material.
Although the words "first," "second," third," etc., are used with
reference to FIGS. 1-5 to aid in understanding, one of ordinary
skill in the art would understand that such terms are not limiting
and that more, fewer, and/or different steps may be used without
departing from the scope of the present disclosure.
[0015] FIG. 1 illustrates an example IC chip module (200)
configured to spread heat away from a semiconductor chip using an
orthotropic material, in accordance with certain embodiments of the
present disclosure. In some embodiments, the IC chip module (200)
may include a carrier (206), a stiffening frame (220), a
semiconductor chip, and one or more directional heat spreaders. The
IC chip module (200) illustrated in FIG. 1 includes a first
directional heat spreader (210) and a second directional heat
spreader (216). However, in alternative embodiments, one, more,
and/or different directional heat spreaders may be present within a
given configuration or orientation without departing from the scope
of the present disclosure.
[0016] FIG. 2 illustrates a first step in forming an example IC
chip module (200), in accordance with certain embodiments of the
present disclosure. The IC chip module (200) depicted in FIG. 2
includes a carrier (206) that is coupled to a stiffening frame
(220). The carrier (206) may be composed of organic materials. In
some embodiments, the carrier (206) may include multiple layers of
metallization and dielectric materials. Depending upon the
configuration of layers, the carrier (206) may be a coreless, thin
core, or standard core design. The dielectric materials may be, for
example, epoxy resin with or without fiberglass fill. In various
embodiments, the carrier (206) may interconnect with other devices
such as a socket (pin grid array, land grid array, ball grid array,
and the like).
[0017] The carrier (206) depicted in FIG. 2 includes a stiffening
frame (220) that is coupled to the carrier (206) using a high
strength adhesive, such as an epoxy, and the like. The stiffening
frame (220) improves the flatness of the carrier (206), and in
particular improves the flatness of an underside (199) of the
carrier (206). The stiffening frame (220) may also improve the
flatness of a topside (201) of the carrier (206). The flatness of
carrier (206) at least partially allows for more efficient assembly
or installation of the IC chip module (200) at a next level of
assembly (e.g. motherboard, heat sink, and the like). The
stiffening frame (220) provides mechanical support for the carrier
(206) and may be particular advantageous in those applications
where the carrier (206) is relatively thin (e.g. coreless, thin
core, and the like). The stiffening frame (220) may be made
utilizing materials with a desirable mechanical strength (e.g.
copper, nickel, stainless steel, titanium, aluminum, molded
plastics, ceramics, composites or combinations of each, and the
like). The stiffening frame (220) may be made utilizing materials
with a desirable coefficient of thermal expansion (`CTE`) (e.g.
similar CTE as carrier (206), and the like). The stiffening frame
(220) may be made by forging, plating, stamping, molding, casting,
machining, and the like. For example, the stiffening frame (220)
may be made from stainless steel sheet metal.
[0018] The stiffening frame (220) can also include a central
opening (226). In certain embodiments, the stiffening frame (220)
may be configured so that the opening (226) is generally arranged
so as to be substantially concentric with one or more IC chips, as
described in more detail below with reference to FIG. 3. The
stiffening frame (220) can also include a base portion (222) and
may further include one or more sets of opposing sidewalls (224).
An underside (199) of the base portion (222) may be attached to the
carrier (206). Sidewalls (224), if employed, can extend upward from
a topside (201) of the base portion (222) and provide additional
stiffening to in-plane bending of the overall assembly. In certain
embodiments, the stiffening frame (220) can include two sidewalls
(224), four sidewalls (224), and the like. The sidewall (224)
topside (201) surfaces may be substantially coplanar. In some
embodiments, opposing or opposite facing sidewall (224) topside
(201) surfaces are substantially coplanar.
[0019] FIG. 3 illustrates a second step in forming example IC chip
module (200), in accordance with certain embodiments of the present
disclosure. IC chip module (200) includes a semiconductor chip
(202). The semiconductor chip (202) may be an integrated circuit
chip, semiconductor die, processor, microchip, and the like.
Interconnects electrically connect the semiconductor chip (202) and
the topside (201) of the carrier (206). Such interconnects can
include a wire bond, solder bond, stud, conductive ball, conductive
button, and the like. An underfill may be electrically-insulating,
may substantially surround the interconnects, may isolate
individual interconnects, and may provide mechanical support
between the semiconductor chip (202) and the carrier (206).
Underfill may also prevent damage to individual interconnects due
to thermal expansion mismatches between the semiconductor chip
(202) and the carrier (206).
[0020] In some embodiments, the carrier (206) may include other
devices besides the semiconductor chip (202), for example, surface
mount devices (e.g. capacitors, resistors, and the like). The
semiconductor chip (202) may be for example a die, a microchip, a
microprocessor, a graphic processor, a combined processor and
graphics processor, an application specific integrated circuit
(`ASIC`), a system on a chip (`SOC`), a three dimensional
integrated circuit, a system on insulator ('SOI'), and the
like.
[0021] FIG. 4 illustrates a third step in forming an example IC
chip module (200), in accordance with certain embodiments of the
present disclosure. In some embodiments, the IC chip module (200)
can include a first directional heat spreader (210). The first
directional heat spreader (210) generally transfers heat relatively
efficiently in a first opposing bivector direction (213) as well as
through its thickness. An opposing bivector direction (213)
consists of two opposing vectors (e.g., 180-degrees relative to
each other). First directional heat spreader (210) may be made from
a directionally thermally conductive material such as graphite. For
example, the first directional heat spreader (210) may be
fabricated from Pyroid.RTM. HT manufactured by MINTEQ.RTM.
Pyrogenics Group. The first directional heat spreader (210) may
have a higher coefficient of thermal conductivity as compared to
copper in a first opposing bivector direction (213), resulting in
the desirability of its use in future generations of electronic
devices.
[0022] The first directional heat spreader (210) may thermally
contact the one or more semiconductor chip(s) (202), such that
efficient heat transfer between elements is achieved by the
reduction of air gaps there between. As described in more detail
below, the shape of the first directional heat spreader (210) may
be altered so as to reduce directional stress on the first
directional heat spreader (210). Furthermore, as described in more
detail below, the shape of the first directional heat spreader
(210) may be altered so as to improve the heat transfer between the
first directional heat spreader (210) and the semiconductor chip
(202).
[0023] In some embodiments, a thermal interface material ("TIM")
may be applied to the top side (201) of the semiconductor chip
(202) and a first directional heat spreader (210) may be applied to
the top side (201) of the semiconductor chip (202) contacting the
TIM. The TIM may be a thermal grease, gel, and so on. For example,
the underside (199) of the first directional heat spreader (210)
thermally contacts the topside (201) of the semiconductor chip
(202) through the TIM.
[0024] When attached to the semiconductor chip (202), the first
directional heat spreader (210) may contact the stiffener base
portion (222) and/or the opposing sidewalls (224) of the stiffener
(220). As such, the length of the first directional heat spreader
(210) is approximately equal to the distance between the opposing
sidewalls (224). The first directional heat spreader (210) may be
press fit, interference fit, and the like, to the opposing
sidewalls of stiffener (220). The first directional heat spreader
(210) may also be attached via an adhesive, a silicone, and the
like, to the base portion (222) and/or the opposing sidewalls (224)
of the stiffener (220). For example, the underside (199) of the
first directional heat spreader (210) may be adhered to the topside
(201) of the stiffener base portion (222) using a silicone-based
adhesive.
[0025] In some embodiments, the first directional heat spreader
(210) may instead be loosely coupled to the stiffener (220) at an
area of stiffening frame proximal to the opposing sidewalls (224).
That is, the first directional heat spreader may be coupled to the
stiffener (220) in a relatively loose, mechanical coupling. This
may allow for some flexibility of movement within the first
directional heat spreader (210). As described in more detail above,
the shape of semiconductor chip (202) underlying the first
directional heat spread (210) may result in a fulcrum underneath
the first directional heat spreader (210), exacerbating limitations
in the mechanical stress properties of the first directional heat
spreader (210). By loosely coupling the first directional heat
spreader (210) to the stiffener (220) away from the underlying
fulcrum, some of this stress may be alleviated. In the same or
alternative embodiments, the first directional heat spreader (210)
may be loosely coupled to the opposing sidewalls (224) rather than
to the stiffener (220) for analogous reasons. As an example of the
relatively loose coupling, the first directional heat spreader
(210) may be coupled to the stiffener (220) with a relatively
low-strength bonding material such as the EA6700 silicone adhesive
offered by Dow Corning.RTM., at a thickness of approximately 140
.mu.m.
[0026] The first directional heat spreader (210) may be fabricated
such that the opposing bivector direction (213) may generally point
to the opposing sidewalls (224) of the stiffener (220). In an
embodiment, when attached to the semiconductor chip (202), a
topside (201) surface of the first directional heat spreader (210)
may be substantially coplanar with the topside (201) surface of the
stiffening frame (220). In alternative embodiments, when attached
to the semiconductor chip (202), a topside (201) surface of the
first directional heat spreader (210) may be raised relative to the
topside (201) surface of the stiffening frame (220).
[0027] In some embodiments, the first directional heat spreader
(210) may include a topside (201) recess (212). The recess (212)
may be to a depth approximately equal to half the overall height of
the first directional heat spreader (210). A top side (201) of the
recess (212) may generally be below the top side (201) of the first
directional heat spreader (210). A dimension "m" of first
directional heat spreader (210) may be equal to a dimension "n" of
recess (212). The recess (212) may be centered upon a dimension "1"
of the first directional heat spreader (210). Contacting the
stiffening frame (220) and being in thermal contact with the
semiconductor chip (202), the first directional heat spreader (210)
may transfer heat from the semiconductor chip (202) to the opposing
sidewalls (224) of the stiffener (220) along the bivector direction
(213).
[0028] FIG. 5 illustrates a fourth step in forming an example IC
chip module (200), in accordance with certain embodiments of the
present disclosure. In some embodiments, the IC chip module (200)
may include a second directional heat spreader (216). The second
directional heat spreader (216) generally transfers heat
efficiently in a second opposing bivector direction (215) as well
as through its thickness. The opposing bivector direction (215)
consists of two opposing vectors (i.e. 180 degrees relative to each
other). The opposing bivector direction (215) may be orthogonal to
the opposing bivector direction (213). The second directional heat
spreader (216) may be made from a directionally thermally
conductive material such as graphite. In a certain embodiment, the
first directional heat spreader (216) may be fabricated from
Pyroid.RTM. HT manufactured by MINTEQ.RTM. Pyrogenics Group. The
second directional heat spreader (216) may have a higher
coefficient of thermal conductivity as compared to copper in a
second opposing bivector direction (215).
[0029] The second directional heat spreader (216) may thermally
contact the first directional heat spreader (210). A thermal
interface material ("TIM") may be applied to the top side (201) of
the recess (212) and the second directional heat spreader (216) may
be applied to the top side (201) of the recess (212) contacting the
TIM. The TIM may be a thermal grease, gel, and so on. For example,
an underside (199) of the second directional heat spreader (216)
may thermally contact the topside (201) of the recess (212). More
specifically, an underside (199) of a recess (218) of the second
directional heat spreader (216) may thermally contact the topside
(201) of the recess (212).
[0030] When attached to the first directional heat spreader (210),
the second directional heat spreader (216) may contact the
stiffener base portion (222) and/or opposing sidewalls (224) of the
stiffener (220). As such, the length of the second directional heat
spreader (216) is approximately equal to the distance between the
opposing sidewalls (224). The second directional heat spreader
(216) may be press fit, interference fit, and the like, to the
opposing sidewalls of the stiffener (220). The second directional
heat spreader (216) may also be attached via adhesive, silicone,
and the like, to the base portion (222) and/or opposing sidewalls
(224) of the stiffener (220). For example, the underside (199) of
the second directional heat spreader (216) may thermally contact
the topside (201) of the base portion (222).
[0031] The second directional heat spreader (216) may be fabricated
such that the opposing bivector direction (215) may generally point
to the opposing sidewalls (224) of the stiffener (220). In some
embodiments, when attached to the first directional heat spreader
(210), the topside (201) surface of the second directional heat
spreader (216) may be substantially coplanar with the topside (201)
surface of the stiffening frame (220) and the topside (201) surface
of the first directional heat spreader (210). In alternative
embodiments, when attached to the first directional heat spreader
(210), the topside (201) surface of the second directional heat
spreader (216) may be raised relative to the topside (201) surface
of the stiffening frame (220) and may be substantially coplanar
with the topside (201) surface of the first directional heat
spreader (210).
[0032] The second directional heat spreader (216) may include an
underside (199) recess (218). The recess (218) may be to a depth
approximately equal to half the overall height of the second
directional heat spreader (216). An underside (199) recess (218) is
generally above the underside (199) of the second directional heat
spreader (216). A dimension "p" of the second directional heat
spreader (216) may be equal to a dimension "q" of recess (218). The
recess (218) may be centered upon a dimension "o" of the second
directional heat spreader (216).
[0033] Dimension "n" may be approximately equal to dimension "q"
and dimension "p" may equal dimension "m" such that the second
directional heat spreader (216) may juxtapose fit with the first
directional heat spreader (212) via the fitting, linking, slotting,
dovetailing, and the like, of recess (218) and recess (212),
respectively. The second directional heat spreader (216) may be
press fit, interference fit, adhered and the like, to the first
directional heat spreader (210). The second directional heat
spreader (216) may also thermally contact the first directional
heat spreader (210). For example, the dimensions of recess (212)
and/or recess (218) may be adjusted to allow for TIM material to
lay between the second directional heat spreader (216) and the
first directional heat spreader (210) upon recess (212) and recess
(218) surfaces. In this instance, the coplanarity of the topside
(201) surface of the second directional heat spreader (216) and the
topside (201) surface of first directional heat spreader (210) may
be substantially maintained.
[0034] Contacting the stiffening frame (220), and being in thermal
contact with the first directional heat spreader (210), the second
directional heat spreader (216) may transfer heat from the first
directional heat spreader (210) to the opposing sidewalls (224) and
base (222) of the stiffener (220) along the bivector direction
(215). As described in more detail above, the second directional
heat spreader (210) may also be loosely coupled to the stiffener
(220) and/or the sidewalls (224).
[0035] The first directional heat spreader (210) and the second
directional heat spreader (216) may be packaged together prior to
thermally contacting the first directional heat spreader (210) with
the semiconductor chip (202). For example, the first directional
heat spreader (210) and the second directional heat spreader (216)
may be packaged together (e.g., via contacting, via thermally
contacting, and the like), and a thermally conductive,
adhesion-promoting coating, such as Nickel plating, and the like,
may be deposited upon the first directional heat spreader (210) and
the second directional heat spreader (216) package.
[0036] Generally because of the increased directional coefficient
of thermal conductivity, the first directional heat spreader (210)
and/or the second directional heat spreader (216) may remove heat
from the semiconductor chip (202) more efficiently as compared to a
traditional lid and assist in the efficient heat removal from IC
chip module (200) to an external heat sink by spreading heat more
evenly over top sides (201) of first directional heat spreader
(210) and/or second directional heat spreader (216).
[0037] The various TIMs referenced herein, may be similar or
dissimilar. The TIMs generally reduces air gaps between elements,
thereby increasing heat transfer there between. The TIMs may be a
thermal gel, thermal compound, thermal paste, heat paste, and the
like. In various embodiments, each semiconductor chip (202) of IC
chip module (200) may be thermally joined to an associated cover
with the same thickness of thermal interface material. In other
embodiments, the various thermal interface materials may be of
differing thicknesses.
[0038] IC chip module (200) may be packaged with higher level
electronic device components, such as a motherboard and/or a heat
sink, according to various embodiments of the present invention.
The electronic device may be for example a computer, server, mobile
device, tablet, and the like. The IC chip module (200) may be
connected to a motherboard via interconnects. Motherboard may be
the main printed circuit board of the electronic device and
includes electronic components, such as a graphics processing unit,
memory, and the like, and provides connectors for other
peripherals. The interconnects electrically connect the carrier
(206) to the motherboard and may be a wire bond, solder bond, stud,
conductive ball, conductive button, and the like. The interconnects
may be larger and more robust than the interconnects that connect
the Semiconductor chip (202) with the carrier (206). When the IC
chip module (200) is seated upon motherboard a second reflow
process may be performed to join interconnects to electrical
contacts of both the carrier (206) and motherboard. Alternately, a
mechanical pressurized interconnect may be established.
[0039] To assist in the removal of heat from the semiconductor chip
(202) a heat sink may thermally contact the IC chip module (200)
via a TIM. The heat sink may be a passive heat exchanger (e.g. pin
heat sink, electronic device chassis, and the like) that cools the
semiconductor chip (202) by dissipating heat into the surrounding
air. The heat sink may also be an active heat exchanger (i.e.
forced air, forced liquid cooling system, and the like). More
specifically, the heat sink may thermally contact the topside (201)
surfaces of the first directional heat spreader (210) and the
second directional heat spreader (216). As such, during operation
of electronic device, a thermal path exists from Semiconductor chip
(202) to the first directional heat spreader (210) and the second
directional heat spreader (216). The thermal path may continue by
transferring heat from the topsides (201) of the first directional
heat spreader (210) and the second directional heat spreader (216)
to the heat sink.
[0040] In alternative embodiments, an IC chip module may be
configured to reduce directional stress in the orthotropic
encapsulation member, in accordance with certain embodiments of the
present disclosure. As described in more detail above, the use of
new materials in electronic device packaging may present new
difficulties. For example, graphite, as an orthotropic material,
has reduced material strength in its out-of-plane dimension (e.g.,
dimensions orthogonal to opposing bivector direction (213)). As a
result, electronic devices incorporating such materials may be
shaped in such a way so as to reduce or diffuse these out-of-plane
stresses.
[0041] In some embodiments, the shape of directional heat spreader
may be formed in such a way so as to reduce out-of-plane stresses
by tapering an end of the directional heat spreader proximal to one
of the opposing sidewalls such that an area of the directional heat
spreader in contact with a portion of one of the opposing sidewalls
is less than an area of the directional heat spreader distal from
one of the opposing sidewalls. In some configurations of the IC
chip module, a directional heat spreader may be shaped such that
its outer dimensions substantially conform to the shape outlined by
taper lines.
[0042] By tapering the directional heat spreader, mechanical
bending stress may be concentrated along the long dimension of
directional heat spreader (e.g., in the same direction as bivector
direction (213)). By decreasing and centering the adhered surface
area of directional heat spreader to the stiffener, the associated
mechanical stresses in the out-of-plane dimension (e.g., orthogonal
to bivector direction (213)) may be reduced.
[0043] In the same or alternative embodiments, the shape of the
directional heat spreader may be formed in such a way so as to
reduce critical stresses by forming one or more hole(s) in the
directional heat spreader in an area of the directional heat
spreader proximal to one of the opposing sidewalls. Such holes may
be formed in any appropriate manner, including drilling. Each hole
may then form a container which may be filled resulting in the
formation of an elastomeric column of adhesive within the
directional heat spreader. In some embodiments, this column may be
used as an attachment point to some portion of the stiffener. By
attaching the directional heat spreader to the stiffener via an
elastomeric column of adhesive, a centerline-aligned, flexible,
mechanical coupling mechanism may be introduced to focus mechanical
stresses along an in-plane dimension of directional heat spreader
(e.g., in the same direction as bivector direction (213)).
[0044] In some embodiments, directional heat spreader may be shaped
in such a way so as to reduce out-of-plane stresses both by
tapering and by forming one or more hole(s) in the directional heat
spreader. By incorporating both shaping mechanisms, stress
reduction may be additionally reduced.
[0045] FIG. 6 illustrates an example underside of a directional
heat spreader (210) configured to reduce directional stress in the
orthotropic encapsulation member, in accordance with certain
embodiments of the present disclosure. In some embodiments, the IC
chip module (200) can include an attach structure (801) on the
surface of the directional heat spreader (210) operable to increase
a contact radius (807) between a center area of the directional
heat spreader (210) and the semiconductor chip (202). As described
in more detail above, the shape of the semiconductor chip (202)
underlying the directional heat spreader (210) may form a
near-point contact fulcrum over which lies the directional heat
spreader (210). As a result of contact with this fulcrum, the
contact radius is at a minimum and thus mechanical stresses on the
directional heat spreader (210) may be concentrated and increased
in the directional heat spreader (210) out-of-plane dimension.
[0046] One approach to reducing the out-of-plane stresses is to
increase the effective contact area between the directional heat
spreader (210) and the fulcrum portion of the semiconductor chip
(202) with a structure that increases the contact radius (307). For
the purposes of this disclosure, the term "contact radius" may be
understood to be the distance between the concentric center of the
semiconductor chip (202) and the effective contact point(s) with a
bottom portion of the directional heat spreader (210) surface
through a thermal interface material previously described.
[0047] In some embodiments, increasing the contact radius (807) may
be accomplished by forming a groove, channel, recess, divot, or
other structure in a bottom portion of the directional heat
spreader (210) proximal to the semiconductor chip (202). For
example, FIG. 6 illustrates an indentation (804) in a bottom
portion of the directional heat spreader (210) proximal to the
semiconductor chip (202). FIG. 6 illustrates an area boundary (802)
generally corresponding to the portion of the directional heat
spreader (210) overlying the semiconductor chip (202). In the
example directional heat spreader (210), the indentation (804) has
been made in directional heat spreader in order to reduce the
contact between the directional heat spreader (210) and the
semiconductor chip (202). In some embodiments, the indentation
(804) is made into the directional heat spreader (210) at a
relatively shallow depth that credits the surface curvature of the
semiconductor chip (202) but does not go all the way through the
directional heat spreader (210).
[0048] In the example directional heat spreader (210), the
indentation (804) is made only over an area boundary (802)
generally corresponding to the portion of the directional heat
spreader (210) overlying the semiconductor chip (202). In
alternative configurations, the indentation (804) may be a channel
running the length of the directional heat spreader (210), larger
than the area boundary (802) overlying the semiconductor chip (202)
(e.g., to account for manufacturing ease and simplification).
Additionally, the example indentation (804) is illustrated as being
generally rectangular in shape to aid in understanding. However,
other shapes (e.g., ovular, circular, semicircular, domed, complex
combinations, etc.) would be available to one of ordinary skill in
the art without departing from the present disclosure.
[0049] In some embodiments, the attach structure (801) may also
include one or more protrusion(s) (806) from the side of the
directional heat spreader (210) proximal to the semiconductor chip
(202). Protrusions (806) may be located to simultaneously increase
the contact radius (807) and preferentially contact some portion of
the semiconductor chip (202) at a semiconductor chip hot spot. For
the purposes of this disclosure, a "hot spot" may refer to any
portion of the semiconductor chip (202) for which a designer of the
semiconductor chip (202) may want to particularly alleviate a
concentrated heat generation. For example, different portions of
the semiconductor device (202) may generate heat at different rates
and in different amounts. Therefore, in order to best alleviate
local heat generation, the attach structure (801) may be shaped in
such a way so as to make specific contact with those hot spots. For
example, FIG. 6 illustrates a plurality of protrusions (806) (e.g.,
columns or pillars) extending from the directional heat spreader
(210), through the indentation (804) so as to make contact with the
semiconductor chip (202). By including protrusions (806), the
design of the directional heat spreader (210) may be tailored to
increase the contact radius (807) and address the specific heat
generation mitigation needs of the particular semiconductor chip
(202) with which it is associated.
[0050] Although FIG. 6 illustrates protrusions (806) as being
generally rectangular, other shapes (e.g., ovular, circular, point,
triangular, etc.) may be available to one of ordinary skill in the
art without departing from the scope of the present disclosure.
Further, although FIG. 6 illustrates protrusions (806) as being
generally singular and evenly spaced, other configurations (e.g.,
rails, different spacing, targeted spacing, etc.) may be available
to one of ordinary skill in the art without departing from the
scope of the present disclosure. The attach structure (801)
including recesses (804) and/or protrusions (806) on a bottom
surface of the heat spreader may be formed by machining, pressing,
annealing, molding, surface treatment (e.g., plating), etc. For
example, the attach structure (801) may be formed by a two-step
nickel plating operation.
[0051] FIG. 7 depicts a flow chart illustrating an example method
(900) for reducing directional stress in an orthotropic
encapsulation member (e.g., directional heat spreader (210)) of an
electronic package, in accordance with certain embodiments of the
present disclosure. In some embodiments, method (900) includes
attaching (902) a stiffening frame (220) to a carrier (206), the
stiffening frame (220) comprising a central opening (226) to accept
a semiconductor chip (202), a base portion (222), and a plurality
of opposing sidewalls (224). As described in more detail above with
reference to FIGS. 2-8, stiffening frame (220) and carrier (206)
provide the structure into which semiconductor chip (202) and
directional heat spreader (210) fit, wherein directional heat
spreader (210) is shaped to reduce a directional stress along the
opposing bivector direction (213).
[0052] Method (900) also includes electrically coupling (904)
semiconductor chip (202) to carrier (206) concentrically arranged
within the central opening (226). In some embodiments, when being
attached, stiffening frame (220) may be aligned with carrier (206)
such that opening (226) is substantially concentric with
semiconductor chip (202) or, if semiconductor chip (202) is not yet
installed, with locations to which semiconductor chip (202) will be
attached to carrier (206). An adhesive may be applied to the
underside (199) of stiffening frame (220) or to topside (201) of
carrier (206). Depending upon the type of adhesive, a curing
process may be needed to cure the adhesive.
[0053] In some embodiments, semiconductor chip (202) is attached to
carrier (206) by way of interconnects and underfill is applied. In
certain embodiments semiconductor chip (202) is attached using a
solder bump processes including a solder reflow. Underfill may be
applied around a portion of the perimeter of semiconductor chip
(202) and drawn thereunder by capillary action. In some
embodiments, underfill may be subject to a curing process. The
curing of underfill may or may not coincide with the curing of the
adhesive connecting the stiffening frame (220) and the carrier
(206). In some embodiments, this process may occur prior to
attaching stiffening frame (220) to carrier (206).
[0054] In some embodiments, an adhesive may be applied to
stiffening frame (220). For example, adhesive may be applied to
base portion (222) of stiffening frame (220) and/or inner surfaces
of sidewalls (224). If polymeric, the adhesive may be applied by
brush, dispenser, and the like. The adhesive may also consist of a
b-staged epoxy or adhesive preform and may be pre-attached to
stiffener (220). In some embodiments, the directional heat spreader
(210) is shaped to modify adhesion forces to reduce a directional
stress along the opposing bivector direction (213). In such cases,
the adhesive may be preferentially located along the heat spreader
(210) centerline or form elastomeric columns within holes (716) in
heat spreader (210) proximal to one or more of the opposing
sidewalls (224).
[0055] Method (900) also includes thermally contacting (906)
directional heat spreader (210) to semiconductor chip (202), the
directional heat spreader (210) transferring heat from
semiconductor chip (202) in an opposing bivector direction (213)
towards opposing sidewalls (224), wherein directional heat spreader
(210) is shaped to reduce a directional stress along the opposing
bivector direction (213). In various embodiments, thermal interface
material may be applied to semiconductor chip (202) and/or the
underside of directional heat spreader (210). Directional heat
spreader (210) is attached to stiffening frame (202) and thermally
contacts semiconductor chip (202). In various embodiments, another
thermal interface material may be applied to the topside (201) of
directional heat spreader recess (212) or the underside (199)
second directional heat spreader recess (218). In some embodiments,
second directional heat spreader (216) may be attached to first
heat spreader (210).
[0056] FIG. 8 depicts a flow chart illustrating an example method
of usage (1000) of an electronic package within an electronic
device, in accordance with certain embodiments of the present
disclosure. In some embodiments, method (1000) includes
electrically connecting (1002) an IC chip module (200) to a
motherboard (706). As described in more detail above, IC chip
module (200) includes: a carrier (206) comprising a top surface
(702) and a bottom surface (704) configured to be electrically
connected to a motherboard (706); a stiffening frame (22) attached
to carrier top surface (702), stiffening frame (220) comprising a
central opening (226) that accepts a semiconductor chip (202), a
base portion (222), and a plurality of opposing sidewalls (224);
semiconductor chip (202) electrically connected to the carrier top
surface (702) and concentrically arranged within central opening
(226), and directional heat spreader (210) thermally contacting
semiconductor chip (202), the directional heat spreader (210)
transferring heat from semiconductor chip (202) in an opposing
bivector direction (213) towards opposing sidewalls (224), wherein
directional heat spreader (210) is shaped to reduce a directional
stress along the opposing bivector direction (213).
[0057] Example method (1000) also includes thermally contacting
(1004) a heat sink (e.g., heat sink (104) to IC chip module (200).
In some embodiments, a thermal interface material may be applied to
IC chip module (200). For example, thermal interface material may
be injected, painted, spread, placed on or otherwise applied to the
topside (201) surfaces of directional heat spreader (210). The heat
sink may be attached utilizing thermal interface material, thermal
tape, epoxy, preform, and the like. Generally, a force may be
applied to secure the heat sink to IC chip module (200). A heat
transfer path exists generally between semiconductor chip (202) and
the heat sink via directional heat spreader (210) (and, if present,
second directional heat spreader (216)).
[0058] Certain embodiments of the present disclosure are described
herein with reference to flowchart illustrations and/or block
diagrams of methods, apparatus (systems), and other program
products. It will be understood that each block of the flowchart
illustrations and/or block diagrams, and combinations of blocks in
the flowchart illustrations and/or block diagrams, can be
implemented by computer readable program instructions.
[0059] It will be understood from the foregoing description that
modifications and changes may be made in various embodiments
without departing from its true spirit. The descriptions in this
specification are for purposes of illustration only and are not to
be construed in a limiting sense. The scope of the present
disclosure is limited only by the language of the following
claims.
* * * * *