Facilitating heat transfer from an integrated circuit package

Details Facilitating heat transfer from an integrated circuit package Facilitating heat transfer from an integrated circuit package

2001-09-10

2003-11-25

Dang, Trung (Department: 2823)

Semiconductor device manufacturing: process

Packaging or treatment of packaged semiconductor

C438S122000, C438S124000, C438S127000

Reexamination Certificate

active

06653167

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to assembling an integrated circuit package. More specifically, the invention relates to facilitating heat and force transfer between the integrated circuit package after a silicon layer has been bonded to the substrate.
2. Description of the Related Art
Digital circuits, no matter how complex, are composed of a small group of identical building blocks. These blocks can be gates or special circuits or other structures for which gates are less suitable. But the majority of digital circuits are composed of gates or combinations of gates. Gates are combinations of high-speed electronic switches such as transistors.
A microprocessor is a central processing unit of a computer or other device using thousands (or millions) of gates, flip-flops and memory cells. Flip-flops and memory cells are modified versions of basic logic gates.
It is known to manufacture an integrated circuit using conductors separated by a semiconductor. Circuits are fabricated on a semiconductor by selectively altering the conductivity of the semiconductor material. Various conductivity levels correspond to elements of a transistor, diode, resistor, or small capacitor. Individual components such as transistors, diodes, resistors, and small capacitors are formed on small chips of silicon. These individual components are interconnected by wiring patterns (typically aluminum, copper or gold).
An integrated circuit is then included in a larger structure, known as integrated circuit package, that provides electrical connections between the integrated circuit and the next level assembly. The integrated circuit package also serves structural functions. Integrated circuit packages are then mounted on printed (or wired) circuit boards which are used to assemble electronic systems such as personal computers and other data processing equipment.
It is known to manufacture an integrated circuit package using a layer of silicon and a layer of a substrate. The substrate layer can be ceramic or another material with the necessary electrical insulating properties, such as a ceramic. Heat is applied during the manufacturing process to bond the silicon layer to the substrate layer. Uneven cooling of the silicon and substrate layers (sometimes referred to as the “package”) could produce failures in the package. Uniform cooling minimizes the number of failures in the package.
After bonding the silicon layer to the substrate layer a heat spreader (sometimes referred to as a “thermal lid” or simply a “lid”) is attached to the package. The thermal lid serves to conduct heat from the integrated circuit package to the environment and thus facilitates even cooling. The lid is typically formed from a metal due to the high thermal conductivity of metals. Typically, neither the thermal lid nor the silicon surface are sufficiently flat to provide an efficient heat exchange interface. Thus, imperfections in the surface of the thermal lid and the surface of the silicon prevent complete surface contact between the surface of the silicon and the surface of the thermal lid. The incomplete surface contact is an impediment to heat transfer which in turn causes failures of the package.
The lid can be used in conjunction with a heat sink. The heat sink is provided with fins or other external surfaces to increase contact with ambient air. The increased contact with the ambient air further facilitates heat transfer.
The lid also serves to promote even transfer of forces to the package. Even transfer of force to the package prevents force concentrations on the silicon layer, substrate or in some circumstances the printed circuit board. Even force transfer also reduces failures of the package.
To facilitate surface contact between the thermal lid and the silicon surface a thermal interface (sometimes referred to as a “die interface”) is employed. The die interface can be applied to the surface of the silicon before the thermal lid is attached. The die interface is not necessarily a solid and can conform to imperfections in the surface of the silicon. Similarly, the die interface can conform to imperfections in the surface of the thermal lid. Thus, using a die interface increases the surface contact between the silicon and the thermal lid and promotes heat transfer.
The increased surface contact between the silicon surface and lid has an additional benefit. When the lid is applied to the silicon layer a force is transferred. If the force is not uniformly transferred, imperfections in the silicon surface can result. Failures of the silicon surface can result in rejected packages or later failures.
When a heat sink is employed it is also known to utilize a heat sink interface. Similar in material characteristic to a die interface, a heat sink interface is not necessarily a solid but can also be a viscous liquid. Similar in function to a die interface, a heat sink interface also improves heat transfer properties by improving surface contact between the heat sink and the lid. Similar to the die interface the heat sink interface improves force transfer by increasing surface contact between the heat sink and the lid.
An example of a material that is suitable for use as an interface is manufactured by Thermagon of Cleveland, Ohio. This specific material, referred to as T-lma-60, has suitable thermal conductive properties and can be used as a thermal interface. T-lma-60 can have more than one layer and is a thermal conductive structure phase change material. T-lma-60 changes phase from solid to liquid at approximately 60° C. A thermal interface, such as T-lma-60 or other, can have a plurality of layers. For example, a thermal interface such as T-lma-60 can have three layers, one of which can be a metallic central layer.
FIG. 1A
depicts substrate
120
adjacent to printed circuit board (sometimes referred to as “pcb”)
110
. Silicon die
130
is bonded to substrate
120
as previously discussed. Die interface
150
is typically a non-solid used to facilitate heat transfer between silicon die
130
and lid
140
. Lid
140
contacts heat sink interface
160
as shown. Heat sink interface
160
contacts heat sink
170
as shown. Lid interface
180
is used to facilitate heat transfer between silicon die
130
and substrate
120
.
FIG. 1B
depicts a thermal lid with a cavity depth of zero. As depicted in
FIG. 1B
, lid interface
180
is not typically used for applications having a zero cavity thermal lid due to the lack of surface contact between thermal lid
140
and substrate
120
.
FIG. 2A
depicts the logical steps of placing die interface
150
on silicon die
130
. As shown in
FIG. 2A
, the method begins with start
210
. From start
210
the logical steps include providing substrate, providing silicon die
220
and providing thermal lid
240
. After providing silicon die
220
and providing substrate
230
the silicon die
130
and substrate
120
are bonded,
250
. Provide thermal lid
240
is shown occurring prior to bonding (
250
) silicon die
130
to substrate
120
but can occur later. After providing thermal lid
240
die interface is placed (
260
) on silicon die
130
. After die interface is placed on silicon die
130
lid interface
180
is placed (
265
) on substrate
120
. After lid interface is placed (
265
) on substrate, thermal lid
140
is placed on die interface
150
and lid interface
180
. In one method, after the thermal lid and thermal interface are placed on the silicon layer
270
, the process ends
295
.
Another embodiment represented in FIG.
2
B. In the embodiment represented in
FIG. 2B
, heat sink
170
is provided,
255
. When a heat sink is provided heat sink interface
160
is also provided,
265
. As shown in
FIG. 2B
, heat sink interface
160
is placed (
280
) on thermal lid
140
after the thermal lid is placed (
270
) on the silicon die. As further shown in
FIG. 2B
, heat sink
170
is placed (
290
) on thermal interface
160
after heat sink interface
160
is placed (
280
) on the thermal lid.
Although
FIG. 2B
depicts providing he

Affiliated with

Also associated with

Rating

Facilitating heat transfer from an integrated circuit package does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Facilitating heat transfer from an integrated circuit package, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Facilitating heat transfer from an integrated circuit package will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3154802