Active solid-state devices (e.g. – transistors – solid-state diode – Combined with electrical contact or lead – Flip chip
Reexamination Certificate
1998-04-06
2002-03-26
Whitehead, Jr., Carl (Department: 2822)
Active solid-state devices (e.g., transistors, solid-state diode
Combined with electrical contact or lead
Flip chip
C257S704000
Reexamination Certificate
active
06362530
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates generally to integrated circuit packages and more specifically to methods of manufacturing integrated circuit packages including flip chip integrated circuit die attached to a substrate.
In the integrated circuit packaging industry, there is continuous pressure to reduce the cost of manufacturing integrated circuit package. To accomplish this, a wide variety of package designs and assembly methods have been developed. One particular type of package currently being produced is referred to as a flip chip ball grid array package. This type of package can provide a very small, relatively cost effective package sometimes referred to as a flip chip or chip scale package. However, because of the very large numbers of this type of package currently being produced, and because of the competitive nature of the integrated circuit package industry, even a slight reduction in the costs of producing this type of package can provide a substantial advantage. Therefore, it is desirable to provide an improved, less costly method of manufacturing integrated circuit packages such as flip chip ball grid array packages.
For comparative purposes, a current method of manufacturing a slip chip ball grid array package, designated by reference numeral
100
, will be briefly described with reference to
FIGS. 1A-D
. As illustrated in
FIG. 1A
, package
100
includes an overall substrate
102
and a flip chip integrated circuit die
104
. Die
104
includes a plurality of contacts
106
for electrically connecting die
104
to substrate
102
. Typically, contacts
106
are provided in the form of solder balls.
Overall substrate
102
includes a stiffener
108
and an interconnecting substrate
110
. In this case, interconnecting substrate
110
is a conventional flex tape substrate such as a polyimide tape substrate. Stiffener
108
is provided as a layer of metal material having a window punched through its center to provide an open space for mounting die
104
to flex tape substrate
110
. Once stiffener
108
has been punched, it is attached to interconnecting substrate
110
as shown in FIG.
1
A. With overall substrate
102
assembled, it is positioned and prepared to being the assembly of package
100
. This is accomplished by fluxing interconnecting substrate
110
so that the contact points on interconnecting substrate
110
, indicated by reference numeral
112
, are ready to receive contacts
106
of die
104
as illustrated in FIG.
1
A.
As also shown in
FIG. 1A
, the next step involved in manufacturing integrated circuit package
100
is the step of positioning die
104
on substrate
102
using a conventional vacuum pickup tool. Die
104
is then attached to substrate
102
by reflowing solder ball contacts
106
. After die
104
is attached to substrate
102
, the assembly is typically cleaned to remove any excess flux. As illustrated in
FIG. 1B
, and if desired, die
104
may be underfilled at this point in order to stabilize and protect the connections between die
104
and interconnecting substrate
110
. This is accomplished using any conventional underfill technique.
Referring now to
FIG. 1C
, the next step of the prior art method being described involves attaching a plurality of solder ball contacts
114
for connecting integrated circuit package
100
to external elements. As shown in
FIG. 1C
, package
100
is turned over and fluxed so that the contact points on interconnecting substrate
110
, indicated by reference numeral
116
, are ready to receive solder ball contacts
114
. In a manner similar to that describe above for die
104
, solder ball contacts
114
are picked up and positioned on interconnecting substrate
110
using a conventional vacuum pickup tool. Once properly positioned on interconnecting substrate
110
, contacts
114
are attached to package
100
by reflowing solder ball contacts
114
. After contacts
114
are attached to package
100
, the assembly is typically cleaned to remove any excess flux remaining on the package. This step of cleaning the assembly completes the basic assembly of the package if additional heat dissipating elements are not required.
Although the above described method results in a useful package, it is desirable to provide this type of package at the lowest possible cost. The present invention provides a method of manufacturing a flip chip ball grid array package which eliminates some of the steps require to produce the package. By reducing the number of steps required to manufacture the package, the cost of producing the package may be reduced.
In certain situations in which additional heat dissipating characteristics are required, an additional heat sink
118
may be attached to the top of prior art package
100
as illustrated in FIG.
1
D. Although this configuration improves the heat dissipating characteristics of the package, it may not provide sufficient heat dissipating characteristics. Accordingly, it is desirable to provide a package configuration having even greater thermal dissipating characteristics than the above described configuration. The present invention provides arrangements and methods of producing integrated circuit packages which are capable of improved heat dissipating characteristics compared to the prior art configuration described above.
SUMMARY OF THE INVENTION
As will be described in more detail hereinafter, a method forming an integrated circuit package is disclosed herein. The method includes the step of providing a flip chip integrating circuit die having a first plurality of contacts for electrically connecting the die to other elements. A second plurality of contacts for electrically connecting the integrated circuit package to external elements is also provided. Initially, a substrate for supporting the flip chip die and the second plurality of contacts is prepared. The substrate includes a connecting arrangement for electrically connecting the first plurality of contacts on the die to the second plurality of contacts. With the substrate prepared, the flip chip integrated circuit die and the second plurality of contacts are positioned on the substrate. Wit the flip chip die and the second plurality of contacts in position, both the first plurality of contacts on the flip chip die and the second plurality of contacts are simultaneously attached to the substrate thereby electrically connecting the die and the second plurality of contacts to the substrate.
In one embodiment, the first and the second plurality of contacts are solder balls. In this embodiment, the step of attached both the first plurality of contacts on the flip chip die and the second plurality of contacts to the substrate includes the step of reflowing the solder balls.
In another embodiment, a vacuum pickup tool is used to pick up the die and the second plurality of contacts and to position the die and the second plurality of contacts on the substrate. The vacuum pickup tool includes a pickup head designed to pick up both the die and the second plurality of contacts and simultaneously position the die and the second plurality of contacts on the substrate.
In another embodiment, the substrate includes a heat conducting stiffener that supports the connecting arrangement on a first surface of the stiffener. Wit this configuration, the first plurality of contacts and the heat conducting stiffener provide a thermal path for dissipating heat away from the die. In one version of this embodiment, the connecting arrangement includes a layer of electrically insulating material deposited on the first surface of the stiffener and a pattern of electrically conductive traces formed on the insulating layer. These traces electrically connect the first plurality of contacts on the die to the second plurality of contacts. Alternatively, the connecting arrangement may include a thin flex tape substrate supported on the first surface of the stiffener. In order to further improve the heat dissipating characteristics of the package, a heat sink may be attached to a second surface of the stiffener.
Lee Shaw Wei
Takiar Hem P.
Jr. Carl Whitehead
National Semiconductor Corporation
Potter Roy
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