U.S. patent application number 15/800155 was filed with the patent office on 2018-07-19 for reducing thermal cycling fatigue.
The applicant listed for this patent is International Business Machines Corporation. Invention is credited to Eric J. Campbell, Sarah K. Czaplewski, Jennifer I. Porto.
Application Number | 20180203496 15/800155 |
Document ID | / |
Family ID | 62838288 |
Filed Date | 2018-07-19 |
United States Patent
Application |
20180203496 |
Kind Code |
A1 |
Campbell; Eric J. ; et
al. |
July 19, 2018 |
REDUCING THERMAL CYCLING FATIGUE
Abstract
An approach to reduce thermal cycling fatigue associated with an
identified component in an electrical system. The approach includes
a controller determining power to the electrical system is turned
off and initiating power from an external power source to one or
more heating elements in a vicinity of the identified component.
The approach includes a controller receiving a first temperature
from one or more temperature sensors in the vicinity of the
identified component and determining whether the first temperature
is within a predetermined temperature range. Responsive to the
controller determining that the first temperature is not within the
predetermined temperature range, the approach includes the
controller adjusting a power level of the one or more heating
elements.
Inventors: |
Campbell; Eric J.;
(Rochester, MN) ; Czaplewski; Sarah K.;
(Rochester, MN) ; Porto; Jennifer I.; (Rochester,
MN) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
International Business Machines Corporation |
Armonk |
NY |
US |
|
|
Family ID: |
62838288 |
Appl. No.: |
15/800155 |
Filed: |
November 1, 2017 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
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15405850 |
Jan 13, 2017 |
|
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15800155 |
|
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
Y02P 70/50 20151101;
H01L 2224/32245 20130101; H01L 23/053 20130101; H05K 2201/10734
20130101; Y02D 10/00 20180101; H05K 1/0212 20130101; G06F 1/206
20130101; H01L 23/34 20130101; H05K 3/3436 20130101; H01L
2224/73253 20130101; H01L 23/345 20130101; G06F 1/266 20130101;
H01L 24/32 20130101; H01L 2224/131 20130101; H01L 2224/16227
20130101; H01L 23/367 20130101; H05K 1/0271 20130101; H05K
2201/10151 20130101; H01L 2224/131 20130101; H01L 2924/014
20130101; H01L 2924/00014 20130101 |
International
Class: |
G06F 1/26 20060101
G06F001/26; G06F 1/20 20060101 G06F001/20; H01L 23/00 20060101
H01L023/00; H05K 1/02 20060101 H05K001/02; H05K 1/18 20060101
H05K001/18; H01L 23/053 20060101 H01L023/053; H01L 23/34 20060101
H01L023/34; H01L 23/367 20060101 H01L023/367 |
Claims
1. A method to reduce thermal cycling fatigue associated with an
identified component in an electrical system, the method
comprising: determining, by a controller, power to the electrical
system is turned off, wherein determining power to the electrical
system includes maintaining power to the identified component from
an external power source without using the one or more heating
elements or the one or more temperature sensors; initiating, by the
controller, power from an external power source to one or more
heating elements in a vicinity of the identified component, wherein
the external power source is one of an alternating current source
or a direct current source, and wherein the direct current source
is a battery, and wherein the identified component is determined
sensitive to thermal cycling fatigue by one or more of mechanical
modeling, accelerated thermal cycling testing of the identified
component in an electronic assembly, analysis of field returns of
the identified component in the electrical system, an analysis of
historical data associated with thermal cycling of the identified
component, and engineering judgment; receiving, by the controller,
a first temperature from one or more temperature sensors in the
vicinity of the identified component, wherein the identified
component is determined sensitive to thermal cycling fatigue by one
or more of mechanical modeling, accelerated thermal cycling testing
of the identified component in an electronic assembly, analysis of
field returns of the identified component in the electrical system,
an analysis of historical data associated with thermal cycling of
the identified component, and engineering judgment; determining, by
the controller, whether the first temperature is within a
predetermined temperature range; responsive to determining that the
first temperature is not within the predetermined temperature
range, adjusting, by the controller, a power level of the one or
more heating elements, wherein the one or more heating elements are
embedded in at least a portion of a surface of at least one of: a
printed circuit board in the vicinity of the identified component,
a module substrate of the identified component, a semiconductor
chip in the identified component, a lid of the identified
component, and a heat sink for the identified component; responsive
to adjusting the power level of the one or more heating elements,
querying, by the controller, the one or more temperature sensors
for a second temperature; determining, by the controller, that the
second temperature is within the predetermined temperature range;
and monitoring, by the controller, the one or more temperature
sensors in the vicinity of the identified component to maintain the
second temperature within the predetermined temperature range,
wherein maintaining the second temperature includes reducing pump
out of a thermal interface material thermally coupling a
semiconductor chip to a module lid and a heat sink.
Description
BACKGROUND OF THE INVENTION
[0001] The present invention relates generally to the field of
electronic packaging, and more particularly to reducing thermal
cycling fatigue of components in computer systems and other
electrical systems.
[0002] Thermal cycling fatigue of interconnections such as solder
joints between various components composed of materials with
different coefficients of thermal expansion is a fundamental
problem in many electronic assembly applications used in many
different industries. In computer systems and other electrical
systems, frequent temperature cycling of the various components
such as semiconductor chips, module substrates, printed circuit
boards, connectors, and other associated hardware due to powering
off and on the system may result in thermal cycling fatigue
fails.
[0003] Energy sensitive computer users who power down computer
systems on a regular basis as an energy saving measure may create
an increase in thermal cycling experienced by computer components
and hardware. Additionally, a rise in the use of portable
electronics and portable computers such as tablets, smartphones,
and notebooks, which may experience multiple on/off cycles per day,
increases thermal cycling of components and associated
interconnections.
[0004] Mechanical modeling programs for predicting thermal cycling
fatigue in components and interconnections between various
components in an electrical system are commonly used to identify
components and associated interconnections most likely to
experience thermal fatigue fails in an electrical system.
SUMMARY
[0005] Embodiments of the present invention provide a method and an
apparatus to reduce thermal cycling fatigue associated with an
identified component in an electrical system. The method includes a
controller determining power to the electrical system is turned off
and initiating power from an external power source to one or more
heating elements in a vicinity of the identified component. The
method includes determining, by a controller, power to the
electrical system is turned off, wherein determining power to the
electrical system includes maintaining power to the identified
component from an external power source without using the one or
more heating elements or the one or more temperature sensors. The
method includes initiating, by the controller, power from an
external power source to one or more heating elements in a vicinity
of the identified component, wherein the external power source is
one of an alternating current source or a direct current source,
and wherein the direct current source is a battery, and wherein the
identified component is determined sensitive to thermal cycling
fatigue by one or more of mechanical modeling, accelerated thermal
cycling testing of the identified component in an electronic
assembly, analysis of field returns of the identified component in
the electrical system, an analysis of historical data associated
with thermal cycling of the identified component, and engineering
judgment. The method includes receiving, by the controller, a first
temperature from one or more temperature sensors in the vicinity of
the identified component, wherein the identified component is
determined sensitive to thermal cycling fatigue by one or more of
mechanical modeling, accelerated thermal cycling testing of the
identified component in an electronic assembly, analysis of field
returns of the identified component in the electrical system, an
analysis of historical data associated with thermal cycling of the
identified component, and engineering judgment. The method includes
determining, by the controller, whether the first temperature is
within a predetermined temperature range. Responsive to determining
that the first temperature is not within the predetermined
temperature range, the method includes adjusting, by the
controller, a power level of the one or more heating elements,
wherein the one or more heating elements are embedded in at least a
portion of a surface of at least one of: a printed circuit board in
the vicinity of the identified component, a module substrate of the
identified component, a semiconductor chip in the identified
component, a lid of the identified component, and a heat sink for
the identified component. Responsive to adjusting the power level
of the one or more heating elements, the method includes querying,
by the controller, the one or more temperature sensors for a second
temperature. The method includes determining, by the controller,
that the second temperature is within the predetermined temperature
range. The method includes monitoring, by the controller, the one
or more temperature sensors in the vicinity of the identified
component to maintain the second temperature within the
predetermined temperature range, wherein maintaining the second
temperature includes reducing pump out of a thermal interface
material thermally coupling a semiconductor chip to a module lid
and a heat sink.
BRIEF DESCRIPTION OF THE DRAWINGS
[0006] FIG. 1 depicts a cross-sectional view of an electronic
assembly for reducing thermal cycling fatigue associated with a
sensitive component, in accordance with an embodiment of the
present invention.
[0007] FIG. 2A depicts a cross-sectional view of a sensitive
component with heating elements in a portion of a module substrate
for reducing thermal cycling fatigue, in accordance with an
embodiment of the present invention.
[0008] FIG. 2B depicts a cross-sectional view of a sensitive
component with heating elements in another portion of a module
substrate for reducing thermal cycling fatigue, in accordance with
an embodiment of the present invention.
[0009] FIG. 3 depicts a cross-sectional view of a sensitive
component with a heating element on a module lid for reducing
thermal cycling fatigue, in accordance with an embodiment of the
present invention.
[0010] FIG. 4 depicts a cross-sectional view of a sensitive
component with a heating element thermally coupled to a heat sink
for reducing thermal cycling fatigue, in accordance with an
embodiment of the present invention.
[0011] FIG. 5 is a flowchart depicting operational steps of one
example of a method to reduce thermal cycling fatigue associated
with a sensitive component in an electronic assembly as depicted in
FIG. 1, in accordance with an embodiment of the present
invention.
DETAILED DESCRIPTION
[0012] Detailed embodiments of the claimed structures and methods
are disclosed herein. The method steps described below do not form
a complete process flow for manufacturing packaging for integrated
circuits such as chip carrier packaging and second level packaging
assemblies using printed circuit boards (PCB). The present
embodiments can be practiced in conjunction with integrated circuit
fabrication, integrated circuit packaging for module assemblies,
and/or second level (e.g., PCB) assembly manufacture as may be used
in a computer system or other electrical system using techniques
currently used in the art. For illustrative purposes, the figures
and discussion include only a subset of the commonly practiced
process steps as are necessary for an understanding of the
described embodiments. The figures represent cross-section portions
of a semiconductor module and an assembled PCB with heating
elements in an electronic assembly in a computer system, however,
embodiments of the present invention are not limited to the
components, or the electronic assembly depicted, and the concepts
and methods described herein may be applied to other electronic
components and other types of electrical systems. The figures are
not drawn to scale, but instead are drawn to illustrate the
features of the described embodiments. Specific structural and
functional details disclosed herein are not to be interpreted as
limiting, but merely as a representative basis for teaching one
skilled in the art to variously employ the methods and structures
of the present disclosure. In the description, details of
well-known features and techniques may be omitted to avoid
unnecessarily obscuring the presented embodiments.
[0013] References in the specification to "one embodiment", "other
embodiment", "another embodiment", "an embodiment", etc., indicate
that the embodiment described may include a particular feature,
structure or characteristic, but every embodiment may not
necessarily include the particular feature, structure or
characteristic. Moreover, such phrases are not necessarily
referring to the same embodiment. Further, when a particular
feature, structure, or characteristic is described in connection
with an embodiment, it is understood that it is within the
knowledge of one skilled in the art to affect such feature,
structure or characteristic in connection with other embodiments,
whether or not explicitly described.
[0014] For purposes of the description hereinafter, the terms
"upper", "lower", "right", "left", "vertical", "horizontal", "top",
"bottom", and derivatives thereof shall relate to the disclosed
structures and methods, as oriented in the drawing figures. The
terms "overlying", "atop", "over", "on", "positioned on" or
"positioned atop" mean that a first element is present on a second
element wherein intervening elements, such as an interface
structure, may be present between the first element and the second
element. The term "direct contact" means that a first element and a
second element are connected without any intermediary conducting,
insulating or semiconductor layers at the interface of the two
elements.
[0015] In the interest of not obscuring the presentation of the
embodiments of the present invention, in the following detailed
description, some of the processing steps or operations that are
known in the art may have been combined together for presentation
and for illustration purposes, and in some instances may not have
been described in detail. In other instances, some processing steps
or operations that are known may not be described. It should be
understood that the following description is rather focused on the
distinctive features or elements of the various embodiments of the
present invention.
[0016] Embodiments of the present invention provide a method and an
apparatus to reduce thermal cycling fatigue in an electronic
assembly. Embodiments of the present invention provide a method to
reduce thermal cycling fatigue associated with one or more
identified components, such as a semiconductor module, sensitive to
temperature cycling fatigue. Embodiments of the present invention
include the use of one or more heating elements located in or
thermally coupled to one or more identified components in an
electronic assembly to reduce thermal cycling fatigue by reducing a
range of a temperature change experienced by the identified
components and/or interconnections associated with the identified
component during a thermal cycle due to a system power off/on
cycle. Embodiments of the present invention provide a method and an
apparatus to reduce thermal cycling fatigue associated with an
identified component in an electronic assembly by maintaining a
temperature associated with the identified component in a desired
temperature range during normal operation of a powered electronic
assembly.
[0017] Embodiments of the present invention propose a method to
reduce thermal cycling fatigue associated with one or more
identified components by providing power to the identified
component from an external power source when an associated
electrical system, such as a computer system, is turned off.
Maintaining power to the identified components sensitive to thermal
cycling fatigue, when the identified components include active or
passive devices capable sustaining heat in the identified
components, reduces thermal cycling fatigue by reducing the range
of temperature excursion experienced by the identified components
and associated interconnections to the identified components,
thereby reducing thermal cycling fatigue.
[0018] Furthermore, embodiments of the present invention provide a
method to reduce pumping out of a thermal interface material in
semiconductor modules with a lid and/or a heat sink that thermally
connects the semiconductor chip to the lid and/or the heat sink.
Pump out is a phenomenon, known to one skilled in the art, that
occurs during thermal cycling as a semiconductor chip and a lid
and/or a heat sink thermally coupled to the semiconductor chip bow
in opposite directions during thermal expansion and contraction
extruding the thermal interface material out from a center portion
of semiconductor chip. Pump out reduces the amount of the thermal
interface material in contact with the semiconductor chip thereby
reducing thermal conductivity between the semiconductor chip and
the lid and/or the heat sink. Embodiments of the present invention
reduces the range of a temperature excursion experienced by the
identified component during a power off/on cycle and reduces the
movement of the lid and/or heat sink in contact with the thermal
interface material and the movement of the semiconductor chip
covered by the thermal interface material thereby, reducing pump
out of the thermal interface material associated with the
semiconductor chip.
[0019] FIG. 1 depicts a cross-sectional view of an electronic
assembly 100 for reducing thermal cycling fatigue associated with
sensitive component 120 in accordance with an embodiment of the
present invention. As depicted, FIG. 1 includes electronic assembly
100, with thermal interface material 101, chip 102, lid 103, module
substrate 104, interconnects 105, heating elements 106, PCB 107,
temperature sensor 108, battery 109, controller 110, and sensitive
component 120. Electronic assembly 100 may be any known type of
assembly of electronic components and/or other components used in
an electrical circuit in an electrical system. For example,
electronic assembly 100 may be used in a computer system, a game
system, or an aerospace application.
[0020] In various embodiments, sensitive component 120 includes
thermal interface material 101, chip 102, lid 103, module substrate
104, and interconnects 105. In some embodiments, one or more of
thermal interface material 101, chip 102, and lid 103 are not
present. In various embodiments, sensitive component 120 is an
active component, such as a semiconductor module. In an embodiment,
sensitive component 120 is a passive component, such as a
connector, cable, capacitor, or the like. Sensitive component 120
may include, but is not limited to a ceramic module (e.g., ceramic
ball grid array module, ceramic column grid array module, a ceramic
leadless module, pin-in-hole module, etc.), a lead frame module, a
plastic module (e.g., a PCB ball grid array, a flex film module,
etc.,), a silicon-on-insulator module, a photosensitive device
module (e.g., LED or solar cell), a surface mount module, a
connector, a cable, or other electrical component capable of
experiencing fatigue failures associated with thermal cycling. In
some embodiments, sensitive component 120 includes one or more of
the following chip 102, heating elements 106, temperature sensor
108, battery 109, and controller 110. In some embodiments, more
than one sensitive component 120 is present in electronic assembly
100.
[0021] Sensitive component 120 is any component in an electrical
system such as a computer system, aerospace system, a consumer
system, and the like that is determined to be at risk for thermal
cycling fatigue. Identifying or determining one or more components
as a component at risk for thermal cycling fatigue includes
determining a component is sensitive or prone to thermal cycling
fatigue. A sensitivity of thermal cycling fatigue may be
ddetermined for a component by one the following methods but is not
limited to, mechanical modeling, accelerated thermal cycling tests,
an analysis of field returns, an analysis of previous historical
data on similar or the same component in other similar electrical
systems, and engineering judgment. For example, a sensitivity to
thermal cycling fatigue for sensitive component 120 is determined
by an accelerated thermal cycling test of sensitive component 120
on a PCB in a test chamber simulating the computer system power
ON/OFF cycles. The accelerated thermal cycling test may identify
the possibility of a thermal cycling fatigue fail associated with
sensitive component 120 occurring during a predicted life of the
computer system.
[0022] Thermal interface material 101 is any known thermally
conductive material for conducting heat from chip 102 to lid 103
and/or to a heat sink (not depicted in FIG. 1) attached to lid 103
or attached directly to chip 102 (not depicted). Thermal interface
material 101 may be a thermal grease, a thermal putty, a thermal
oil, a thermal pad, a thermal gap filler, and the like residing
between chip 102 and lid 103, which may be an integrated heat sink.
In various embodiments, thermal interface material 101 is a
compliant material and/or a material that moves and experiences
pump out during thermal cycling. In some embodiments, thermal
interface material 101 is not present.
[0023] Chip 102 is any known semiconductor device. Chip 102 may
include microprocessors, application-specific integrated circuits
(ASICs), silicon-on-insulator devices and photosensitive devices
such as light emitting diodes (LEDs), solar cells, and the like. In
various embodiments, chip 102 is electrically connected or coupled
to module substrate 104 using any known interconnection method such
as solder bumps, wire bonds, and the like (not depicted). In an
embodiment, chip 102 is connected directly to PCB 107 or another
element capable of connecting to chip 102 (e.g., a flex cable,
etc.) using known interconnection methods such as wire bonding,
solder bumps, and the like. In various embodiments, chip 102 may be
thermally connected or coupled to lid 103 and/or a heat sink (not
depicted) by thermal interface material 101. In an embodiment, chip
102 is not thermally connected to lid 103 or a heat sink. In an
embodiment, chip 102 includes one or more heating elements (not
depicted) that may cover a portion of a layer of chip 102. In one
embodiment, controller 110 is included in a portion of chip
102.
[0024] Lid 103 is any known lid, module cover and/or heat sink. In
various embodiments, lid 103 is coupled to chip 102, module
substrate 104, and thermal interface material 101. In some
embodiments, lid 103 is thermally coupled to a heat sink and chip
102 by thermal interface material 101. In an embodiment, lid 103 is
a heat sink using thermal interface material 101 as a thermal
conduit transmitting heat from chip 102 to lid 103. In some
embodiments, thermal interface material 101 is not present. In one
embodiment, lid 103 is an encapsulation material for chip 102
(e.g., glob top). In an embodiment, lid 103 includes one or more
heating elements in or on a portion of a surface of lid 103. In one
embodiment, lid 103 may not be present. In one embodiment, battery
109 resides on lid 103.
[0025] Module substrate 104 represents any known module substrate.
Module substrate 104 may be a ceramic module substrate, a laminate
or PCB module substrate, a flexible film substrate, a metal
substrate, or the like, used to interconnect chip 102 with other
circuit components, for example, in a computer system. As depicted,
module substrate 104 is connected to chip 102 by interconnects (not
depicted) and to PCB 107 by interconnects 105. In an embodiment,
module substrate 104 is not present. In various embodiments, module
substrate 104 includes one or more heating elements 106. In an
embodiment, one or both of controller 110 and battery 109 are
coupled with module substrate 104.
[0026] Interconnects 105 are any known interconnection method
between various levels of electronic packaging or between various
types of electrical components, for example, between sensitive
component 120 and PCB 107 and/or between chip 102 and module
substrate 104 (not depicted in FIG. 1). As depicted, interconnects
105 are solder balls used to create solder joints that connect
module substrate 104 of sensitive component 120 to PCB 107,
however, interconnects 105 are not limited to solder balls or to
connections between module substrate 104 and PCB 107. Interconnects
105 may include any known interconnect method such as wire bonds,
solder joints including solder balls, solder columns, pins,
J-leads, or leadless interconnections, adhesive based
interconnections, other metal based interconnections (e.g., between
a semiconductor chip or LED and a carrier), pad to pad connections,
connector connections, and the like. In various embodiments,
interconnects 105 are associated with sensitive component 120
(e.g., connect sensitive component 120 to another component such as
PCB 107).
[0027] Heating elements 106 are any known heating elements capable
of providing heat to one or more of the various components in the
vicinity of sensitive component 120. Heating elements 106 may be a
resistive thick or thin film, a resistor, a resistive wire, a
resistive line, a thermistor, a resistive metal, a capacitor, and
the like capable of being embedded in, attached on, or under one or
more of the components of electronic assembly 100 and generating
heat when receiving electrical power or current. As depicted in
FIG. 1, heating elements 106 are embedded in PCB 107 under the
peripheral rows of interconnects 105 of sensitive component 120 but
are not limited to this location. In various embodiments, one or
more heating elements may reside in, on, or under a portion of a
next level carrier of sensitive component 120 such as PCB 107, in,
on, or under a portion of sensitive component 120 (depicted in FIG.
2), in, on, or under a portion of chip 102 (not depicted), in, on,
or under a portion of lid 103 (depicted in FIG. 3) or a heat sink
(depicted in FIG. 4). For example, heating elements 106 are located
on PCB 107 within 25 mm of sensitive component 120. Heating
elements 106 are electrically coupled to controller 110 and an
external power source such as battery 109.
[0028] In various embodiments, heating elements 106 receive power
from battery 109 or an alternating current power source, such as a
standard wall plug-in. In an embodiment, heating elements 106
provide a level of heat to maintain a temperature associated to
sensitive component 120 within a desired temperature range when the
electrical system is powered on (e.g., maintains a temperature
determined in or in the vicinity of sensitive component 120 within
a desired range during a normal power on operation of the
electrical system). In one embodiment, heating elements 106 may not
be present. For example, when power is turned off to an electrical
system including sensitive component 120, the electrical circuits
of sensitive component 120 receive power from battery 109 or
another external power source as determined by controller 110 to
maintain a temperature in the vicinity of sensitive component 120
within a desired temperature range.
[0029] PCB 107 is any known carrier for sensitive component 120
(e.g., a next level carrier or second level of electronic packaging
for sensitive module 120 in electronic assembly 100). As depicted
PCB 107 is a printed circuit board. In various embodiments, PCB 107
is composed of one or more laminated layers of non-conductive
materials (not depicted) between one or more layers of conductive
materials (not depicted) to provide lines or traces in a signal
layer(s) and/or power plane layers in PCB 107. For example, PCB 107
may be composed of one or more layers of non-conductive materials
(e.g., epoxy/glass not depicted), one or more layer of conductive
layers (e.g., copper layers or layer of copper lines or traces not
depicted), and one or more heating elements 106, which may be
embedded in one or more portions of a layer or layers of PCB 107 or
on a surface of PCB 107 (not depicted). In various embodiments, PCB
107 is any next level carrier (e.g., card, flex cable, flexible
film carrier, silicon carrier, another semiconductor carrier, metal
carrier, etc.) capable of coupling with sensitive component 120 by
interconnects 105 and including one or more heating elements 106.
In one embodiment, chip 102 is attached directly to PCB 107 (e.g.,
wire bond direct chip attach). In various embodiments, PCB 107
includes heating elements 106, which may be either in embedded or
on a surface of PCB 107. In various embodiments, controller 110 and
battery 109 are included in, on, or under PCB 107.
[0030] Temperature sensor 108 is a known temperature-sensing
device, such as a thermocouple, capable of determining a
temperature of various elements or components in the vicinity of
sensitive component 120. As depicted, temperature sensor 108 is on
PCB 107 within the vicinity of sensitive component 120 (e.g.,
within 3 cm of sensitive component 120). In other embodiments,
temperature sensor 108 may reside in sensitive component 120, in
PCB 107, in the vicinity of sensitive component 120, or on a
surface of sensitive component 120. In various embodiments, one or
more temperature sensors 108 are present in electronic assembly 100
in the vicinity of or in sensitive component 120. For example, two
temperature sensors 108 may be present on PCB 107 in the vicinity
of sensitive component 120. In one embodiment, one or more
temperature sensors 108 are located in or on more than one
component in electronic assembly 100. For example, a temperature
sensor 108 may be present under module substrate 104 and on PCB
107.
[0031] Battery 109 is electrically connected to controller 110 and
heating elements 106. Battery 109 is any type of battery capable of
providing power to heating elements 106. Battery 109 may be a
rechargeable battery as used in a smartphone, a smart battery, a
battery pack, or the like. As depicted, battery 109 may be external
to sensitive component 120, for example on PCB 107. In other
embodiments, battery 109 may be embedded in or on a surface of
sensitive component 120, on lid 103, or in another location within
an electrical system. In some embodiments, battery 109 may reside
in another location outside of electronic assembly 100 within an
electrical system or may reside external to the electrical system
(e.g., external to a computer system). In various embodiments,
battery 109 is capable of initiating power to heating elements 106
based instructions from controller 110 when an electrical system or
a computer system with electronic assembly 100 is turned off. In
some embodiments, for example, when controller 110 maintains power
to heating elements 106 from an alternating current (AC) external
power source (e.g., not depicted) such as a standard wall
connection during a computer system power down, battery 109 may not
be present.
[0032] Controller 110 is a controller, such as a
proportional-integral-derivative (PID) controller, one or more
microprocessors or other similar devices known to one skilled in
the art, used in applications to monitor and control temperature of
a portion of electronic assembly 100. In various embodiments,
controller 110 monitors and maintains a desired temperature or a
desired temperature range in a portion of sensitive component 120
or in a portion of PCB 107 in the vicinity of sensitive component
120. In various embodiments, controller 110 resides in, on, or
under one of PCB 107, module substrate 104, chip 102, or another
location in the electrical system (not depicted), or external to
the electrical system. As depicted, controller 110 resides on PCB
107 in the vicinity of an outer row of interconnects 105 however,
in other embodiments, controller 110 resides in another location in
the electrical system. For example, controller 110 resides on
module substrate 104. In an embodiment, controller 110 resides
outside of the electrical system. In various embodiments,
controller 110 in electronic assembly 100 is electrically coupled
to or connected to heating elements 106, temperature sensors 108,
and battery 109.
[0033] In various embodiments, controller 110 determines when power
is turned off to an electrical system that includes sensitive
component 120 and, in response, controller 110 initiates power to
heating elements 106 using an external power source, such as
battery 109. Controller 110 is configured to query temperature
sensor 108 for a temperature of a portion of electronic assembly
100 in the vicinity of sensitive component 120 or within sensitive
component 120 when power is turned off to electronic assembly 100.
Controller 110 is configured to maintain the temperature of a
portion of PCB 107 in the vicinity of sensitive component 120 or in
a portion of sensitive component 120 within a desired or
predetermined temperature range. In various embodiments, controller
110, using an external power source (e.g., battery 109), adjusts
the power level and heat emitted by heating elements 106 when the
power to electronic assembly 100 is turned off. In various
embodiments, controller 110 compares a received temperature
associated with sensitive component 120, as detected by one or more
of temperature sensors 108, to a predetermined or desired
temperature range to monitor and maintain the temperature
associated with sensitive component 120 within the predetermined
temperature range by adjusting the heat emitted by heating elements
106.
[0034] In one embodiment, controller 110 determines that power to
electronic assembly 100 is turned off, and in response, controller
110 initiates power from an external power source to sensitive
component 120. For example, when controller 110 determines a
computer system is powered down or turned off, controller 110
initiates external power to sensitive component 120 by one of
battery 109 or other external power source. In this example,
heating elements 106 are not present and/or do not receive power
when the electrical system is powered down. By providing power from
an external power source (e.g., battery 109) to sensitive component
120 when sensitive component 120 includes one or more active or
passive devices, such as a chip 102, capable of maintaining a level
of heat generation, controller 110 reduces the temperature change
experienced by sensitive component 120 when the computer system is
turned off. Reducing the change of temperature of sensitive
component 120 when a computer system is powered down reduces
thermal cycling fatigue associated with sensitive component
120.
[0035] FIG. 2A depicts a cross-sectional view of sensitive
component 220A with heating elements 206A in a portion of module
substrate 204A for reducing thermal cycling fatigue in accordance
with an embodiment of the present invention. As depicted, FIG. 2A
includes thermal interface material 101, chip 102, lid 103, module
substrate 204A, heating elements 206A, and interconnects 105. In an
embodiment, one or more of thermal interface material 101 and lid
103 are not present. Sensitive component 220A with module substrate
204A and heating elements 206A may include some similar components
as depicted and discussed with respect to FIG. 1 to provide a
reduction in thermal cycling fatigue in electronic assembly 100.
Module substrate 204A includes one or more heating elements 206A.
In various embodiments, heating elements 206A are embedded in a
portion of one or more layers of module substrate 204A and/or in
one or more layers of module substrate 204A. For example, heating
elements 206A are in an outer portion of a layer such as between
interconnects 105 at outer edges or periphery of module substrate
204A (as depicted) but are not limited to this location. Heating
elements 206A receive power from an external power source (e.g.,
battery 109 in FIG. 1), as determined by controller 110 (depicted
in FIG. 1) when power is turned off during an electrical system or
computer system power down.
[0036] FIG. 2B depicts a cross-sectional view of sensitive
component 220B with heating elements 206B in a portion of module
substrate 204B, other than that depicted in FIG. 2A, for reducing
thermal cycling fatigue in accordance with an embodiment of the
present invention. In another example, heating elements 206B may be
a thick film resistor in a layer or a portion of one or more layers
embedded in module substrate 204B or on an outer surface or a
portion of an outer surface of module substrate 204B (e.g., a layer
of a thick or a thin film resistor material on module substrate
204B). The location of heating elements 206A and heating elements
206B (depicted in FIG. 2B) may be determined as result of
mechanical modeling, analysis of thermal cycling fatigue fails, an
analysis of field returns, engineering judgment, or other
analysis.
[0037] FIG. 3 depicts a cross-sectional view of sensitive component
320 with heating element 306 on lid 303 for reducing thermal
cycling fatigue in accordance with an embodiment of the present
invention. Sensitive component 320 with heating elements 306 on lid
303 may include some similar components as depicted and discussed
with respect to FIG. 1 to provide a reduction in thermal cycling
fatigue in electronic assembly 100. As depicted, FIG. 3 includes
thermal interface material 101, chip 102, heating element 306, lid
303, module substrate 104, and interconnects 105. In various
embodiments, heating element 306 is on the top of lid 30, is under
lid 303, or is embedded in lid 303 . Heating element 306 receives
power from an external power source (e.g., battery 109 in FIG. 1)
when initiated by controller 110 (depicted in FIG. 1) when power to
an electrical system or a computer system containing sensitive
component 306 is turned off. Heating element 306 may transmit heat
to chip 102 and/or through lid 103 to module substrate 104 and
interconnects 105 to reduce thermal cycling fatigue of sensitive
component 320 when the power is turned off.
[0038] FIG. 4 depicts a cross-sectional view of sensitive component
420 with heating element 406 thermally coupled to heat sink 403 for
reducing thermal interface material pump out in accordance with an
embodiment of the present invention. Sensitive component 420 with
heating elements 406 associated with heat sink 403 may include some
similar components as depicted and discussed with respect to FIG. 1
to provide a reduction in thermal cycling fatigue in electronic
assembly 100. FIG. 4 includes the various elements thermal
interface material 101, chip 102, lid 103, module substrate 104, as
previously discussed in detail with respect to FIG. 1, along with
thermal interface material 401, heat sink 403, interconnects 405A,
interconnects 405B, and heating element 406. FIG. 4 depicts one
embodiment of sensitive component 420 with heating element 406
included as a layer, such as a thin resistive metal layer, on a
surface of heat sink 403. In various embodiments, heating element
406 resides in one or more other locations on, in, or under a
portion of heat sink 403. For example, heating element 406 may be a
number of resistive wires residing the valleys between each of the
heat sink fins (e.g., on the horizontal surface of heat sink 403
between or adjacent to the vertical elements or fins).
Interconnects 405A coupling module substrate 104 to PCB 107 (not
depicted) are pins as may be used in in a pinned sensitive module
420, which may be soldered to or joined with PCB 107 by a
pin-in-hole connector. Interconnects 405B, as depicted, connect
chip 102 to module substrate 104, for example by solder connections
however, interconnects 405B may be another type of chip 102 to
module substrate 104 connection (e.g., wire bonds, etc.).
[0039] Heating elements 406, and/or heating elements 106, 206A,
206B, 306, or heating elements in chip 102 (not depicted, and as
discussed with respect to FIGS. 1, 2A, 2B, and 3) may reduce pump
out of thermal interface material 401 from between the heat sink
403 and lid 103 and/or from between lid 103 and chip 102. For
example, using the method discussed below in detail with respect to
FIG. 5, the effect of the thermal expansion differences in chip
102, lid 103, and heat sink 403 that cause pump out can be
minimized. For example, as known to one skilled in the art, chip
102 and heat sink 403 may bow in opposing directions due to
differences in thermal expansion and contraction of the various
materials used in sensitive module 420. Reducing the temperature
excursions experienced by chip 102, lid 103, and heat sink 403 by
using one or more of heating elements 106, 206A, 206B, 306, or 406
reduces the extrusion or pump out of thermal interface material
401. Less bowing of chip 102, lid 103, and heat sink 403 reduces
extrusion or the loss of thermal interface material between the
center portion of lid 103 corresponding to chip 102 and a center
portion of heat sink 403 (e.g., corresponding to chip 102).
[0040] FIG. 5 is a flowchart 500 depicting operational steps of one
example of a method to reduce thermal cycling fatigue associated
with sensitive component 120 in an electronic assembly 100 as
depicted in FIG. 1, in accordance with an embodiment of the present
invention. As depicted, FIG. 5 includes one example of a method to
reduce thermal fatigue cycling in interconnects 105 connecting
sensitive component 120 and PCB 107 in an electrical system. The
method discussed with respect to PCB 107 connected by interconnects
105 to module substrate 104, however, various embodiments of the
present invention are not limited to reducing thermal cycling
fatigue associated to sensitive component 120, but, may be applied
to other components in the computer system, to components in other
electrical systems (e.g., chip 102 to PCB 107 in consumer
applications). Additionally, the method discussed in flowchart 500
may be applied to other embodiments of the present invention
discussed above. For example, the method discussed with respect to
flowchart 500 may be applied with the various embodiments of the
present invention discussed with respect to FIGS. 2A, 2B, 3, and
4.
[0041] Controller 110 determines the electrical system power is
turned off (502). Controller 110 identifies that the power to an
operating electrical system, for example, the power to a computer
system, is disconnected or turned off. When power is turned off in
an operating electrical system, a cooling portion of a thermal
cycle is initiated. In some embodiments, controller 110 does not
determine if a power source is disconnected or turned off to an
electrical system or a computer system that includes sensitive
component 120.
[0042] Controller 110 turns on one or more heating elements 106
(504). In an embodiment, controller 110 initiates power to heating
elements 106 in PCB 107 using an external power source such as
battery 109. For example, controller 110 initiates external power
from battery 109 to heating elements 106 when controller 110
determines an electrical system power is turned off. In one
embodiment, depicted in FIG. 1, heating elements 106 may be in or
on an outer layer of PCB 107 in the vicinity or under of the outer
row interconnects 105 on the periphery of sensitive component 120.
Heating elements 106 are in the vicinity of sensitive component 120
and interconnects 105. As previously discussed with respect to
FIGS. 1 and 2B, heating elements 106 may be located in one or more
positions in a portion of PCB 107 or in a portion of sensitive
component 120. For example, one or more heating elements 206B may
be in or on a portion of a top surface of module substrate 204B
(depicted in FIG. 2B). In one embodiment, controller 110 powers on
heating elements 106 residing in chip 102 when power is turned off
to an electrical system. For example, one or more heating elements
106 may reside in an outer portion of a layer of a semiconductor
device such as chip 102 or in a layer of chip 102, for example, in
a layer deposited during or before the back end of the line (BEOL)
semiconductor processes.
[0043] In an embodiment, controller 110 initiates an external power
source to supply power or turn on heating elements 106 on either
lid 103 and/or on a module heat sink (e.g., heat sink 403 in FIG.
4) associated with sensitive component 120. For example, heating
elements 306 may reside on a portion of lid 303 (depicted in FIG.
3) coupled to sensitive module 320 (e.g., by thermal interface
material 101). For example, one or more heating elements 306 (not
depicted) may cover a portion of lid 303 along the periphery or
outer edges where lid 303 attaches to module substrate 104. In some
embodiments, controller 110 does not automatically turn on or
initiate power to heating elements 106 using an external power
source such as battery 109.
[0044] In one embodiment, controller 110 turns on heating elements
106 associated with sensitive component 120 located in more than
one component in electronic assembly 100. For example, using an
external power source such as an alternating current source or
battery 109, controller 110 may initiate power to heating elements
106 in PCB 107 (depicted in FIG. 1) and heating elements 206B in
module substrate 204B (depicted in FIG. 2B) when power is turned
off to electronic assembly 100 in a computer system. Initiating
power to heating elements 106 and heating elements 206B on both a
module substrate 204B and PCB 107 allows controller 110 to
precisely control the temperature in the vicinity of sensitive
component 120 and/or reduce a temperature drop experienced by
interconnects 105 and an identified component, such as sensitive
component 220B, during a cool down portion of a thermal cycle
during a computer system or other electrical system power down.
[0045] In an embodiment, controller 110 turns on or initiates power
to sensitive component 120 from an external power source when
controller 110 determines that power to the electronic system
associated with sensitive component 120 is turned off. For example,
controller 110, upon determining the power is turned off in a
computer system, may initiate power to sensitive component 120
using one of a direct power (DC) power source such as battery 109
or an external power source such as alternating power (AC) source.
When controller 110 initiates an external power source to maintain
power to sensitive component 120 and when sensitive component 120
contains active or passive devices capable of generating heat, a
reduction in the range of the temperature excursion during power
off/on experienced by sensitive component 120 occurs. When
controller 110 supplies external power to sensitive component 120,
which has active or passive devices capable of continued heat
generation, thermal cycling fatigue of interconnects 105 associated
with sensitive component 120 is reduced due to a smaller
temperature change during a power off/on thermal cycle.
[0046] Controller 110 measures one or more temperatures associated
with a sensitive component (506). In various embodiments,
controller 110 queries temperature sensor 108 in one or more
locations in the vicinity of sensitive component 120 (e.g., on a
surface of PCB 107 within 25 mm of sensitive component 120). In
various embodiments, controller 110 queries temperatures associated
with one or more temperature sensors 108 in one or more locations
that may be in, on, or under sensitive component 120. For example,
controller 110 queries two temperature sensors 108 (not depicted in
FIG. 1) present on lid 103 of sensitive component 120 for a current
temperature.
[0047] Controller 110 determines whether the temperature is in a
desired range (decision 508). Controller 110 compares the
temperature measured in the vicinity of or in sensitive component
120 to a desired temperature range to determine if the current
temperature associated with sensitive component 120 is within the
desired temperature range. In various embodiments, controller 110
is configured with a predetermined or desired temperature
range.
[0048] The predetermined temperature range may be determined, for
example, based on one or more of the following known methods. The
predetermined temperature range or a desired temperature range may
be determined, for example, by mechanical modelling predicting
thermal cycling fatigue associated with sensitive module 120 (e.g.,
finite element modelling or the like using various temperature
ranges), analysis of fatigue fails of sensitive component 120 from
field returns of computer systems or other electrical systems in
various environments and/or operating conditions, analysis of
thermal profiles of other components similar to sensitive component
120 in other similar system environments, engineering judgment, or
the like.
[0049] Responsive to controller 110 determining that the
temperature is not in the desired temperature range (no branch of
decision 508), controller 110 adjusts heating elements 106 (510).
Controller 110 may adjust or change the power level or the
temperature of heating elements 106 using known methods, for
example, by changing the current or power supplied to heating
elements 106. If the current temperature of sensitive component 120
or the temperature in the vicinity of interconnects 105 to
sensitive component 120 (e.g., a temperature of PCB 107 near an
outer row of interconnects 105) is below the desired temperature
range, controller 110 may increase power to heating elements 106.
Increasing power to heating elements 106 in or on PCB 107 maintains
or reduces the temperature loss in the vicinity of sensitive
component 120 when the electrical system or a computer system is
powered down. After completing an adjustment to heating elements
106, controller 110 measures the temperature of sensitive component
120 (506). As previously discussed, controller 110 queries one or
more temperature sensors 108 in the vicinity of or in sensitive
component 120.
[0050] Responsive to controller 110 determining that the
temperature is in the desired temperature range (yes branch of
decision 508), controller 110 determines whether an electrical
system is turned on (decision 512). When controller 110 determines
that current temperature of sensitive component 120 is within the
predetermined, desired temperature, controller 110 verifies that
the electrical system has been turned on (yes branch of decision
512). Responsive to determining the electrical system is turned on,
controller 110 turns off the external power (e.g., battery 109) to
heating elements 106 (514). As the power of the electrical system
is turned on, the various components such as chip 102 receive power
and begin generating heat. As the various components such as chip
102 receive power and begin generating heat, the temperature delta
or the range of the temperature change experienced in a thermal
cycle is decreased, resulting in less stress and strain on
interconnects 105 associated with sensitive component 120 during
thermal cycling, thereby reducing resulting thermal cycling
fatigue. Controller 110 halts external power to heating elements
106 until controller 110 determines power is not provided to the
electrical system (e.g., the electrical system is powered off
again).
[0051] Responsive to controller 110 determining the electrical
system is not turned on (no branch of decision 512), controller 110
measures one or more temperatures associated with sensitive
component 120 (506). As previously discussed, controller 110
monitors one or more temperatures in the vicinity of and/or in
sensitive component 120 using one or more temperature sensors 108
to maintain the temperature within the desired temperature range in
decision 508.
[0052] In one embodiment, controller 110 may be configured with a
predetermined delay time for heating element turn off after the
electrical system resumes receiving power (e.g., a delay in turning
off external power to heating elements 106 when a system is turned
back on). For example, based on thermal fatigue models and
previously recorded temperature excursions of sensitive component
120 in the electrical system during powering on a delay of five
minutes may be configured in controller 110 for turning off heating
elements 106 after the electrical system is turned on again. For
example, a reduction in the thermal cycling fatigue can occur due
to a reduction in the temperature change observed by sensitive
component 120 and interconnects 105 (e.g., solder joints). As
sensitive component 120 heats up due to re-applied power to chip
102, maintaining power to heating elements 106 for a short period
time after the system is turned on minimizes temperature changes
occurring at sensitive component 120 and interconnects 105.
[0053] In another embodiment, controller 110 determines that the
power to the electrical system including sensitive component 120 is
turned on (e.g., the electrical system is operating) and queries
temperature sensors 108 to measure one or more temperatures
associated with sensitive component 120 (as discussed in step 506).
Controller 110 continuously, on a predetermined interval, requests
the temperature associated with sensitive component 120. For
example, controller 110 may query temperature sensor 108 on PCB 107
that is 15 mm from an outer row of interconnects 105 (as depicted
in FIG. 1) every minute to monitor the current temperature
associated with sensitive component 120. Controller 110 compares
the current received temperature to a predetermined or desired
temperature range.
[0054] Controller 110 determines whether the current received
temperature is in the desired temperature range. Responsive to
controller 110 determining the current received temperature is not
within the desired temperature range, controller 110 initiates
power to heating elements 106 using either power provided from the
electrical system or from an external power source (e.g., battery
109). Upon initiating power to heating elements 106, controller 110
continues to monitor the temperature associated with sensitive
component 120 by querying temperature sensors 108 for a current
temperature and in response to receiving a current temperature,
determines whether the received current temperature is within the
desired temperature range. Responsive to determining the received
current temperature is not within the desired temperature range,
controller 110 adjusts heating elements 106 as previously discussed
with respect to decision 508.
[0055] Responsive to controller 110 determining the current
temperature is within the desired temperature range, then
controller 110 turns off heating elements 106 and continues to
monitor the temperature associated with sensitive component 120. In
one embodiment, controller 110 continues to monitor and adjust the
temperature associated with sensitive component 120 to maintain a
current temperature within the desired temperature range until a
command to stop monitoring is received by controller 110 from a
user input on any known user interface capable of communicating
with controller 110. In various embodiments, when controller 110
determines that the power is no longer turned on in the electrical
system, controller 110 turns on one or more heating elements (step
504) and continues executing steps 506 through 514 as previously
discussed with respect to FIG. 5.
[0056] In one embodiment, controller 110 may monitor and maintain a
temperature associated with sensitive module 120 when an electrical
system is powered on (e.g., receiving power to the electrical
system or computer). For example, controller 110 continuously
monitors and maintains a temperature associated with sensitive
component 120 in the desired temperature range regardless of
whether the power is supplied to the electrical system (i.e.,
controller 110 monitors and maintains a temperature in the vicinity
of sensitive component 120 in both electrical system power ON and
power OFF situations so steps 502 and 504 maybe skipped). In this
embodiment discussed with respect to sensitive component 120,
controller 110 executes step 506 to measure one or more
temperatures associated with sensitive component 120 and determines
whether the temperature is in the desired range (decision step
508), and responsive to determining that the temperature is not in
the desired range, adjusts heating elements (step 510). However, if
the temperature is within the desired range, controller 110 returns
to step 506 to monitor the temperature associated with sensitive
component 120.
[0057] The descriptions of the various embodiments of the present
invention have been presented for purposes of illustration, but are
not intended to be exhaustive or limited to the embodiments
disclosed. Many modifications and variations will be apparent to
those of ordinary skill in the art without departing from the scope
and spirit of the described embodiments. The terminology used
herein was chosen to best explain the principles of the
embodiments, the practical application or technical improvement
over technologies found in the marketplace, or to enable others of
ordinary skill in the art to understand the embodiments disclosed
herein.
* * * * *