Semiconductor device manufacturing: process – Including control responsive to sensed condition – Optical characteristic sensed
Reexamination Certificate
2001-08-30
2003-04-01
Fourson, George (Department: 2823)
Semiconductor device manufacturing: process
Including control responsive to sensed condition
Optical characteristic sensed
C438S069000
Reexamination Certificate
active
06541284
ABSTRACT:
FIELD OF THE INVENTION
The invention relates generally to the field of image sensing IC chip packages and methods of making same.
BACKGROUND OF THE INVENTION
An image sensing integrated circuit chip
23
, shown in
FIG. 1
, is at the center of all electronic, i.e. digital, cameras. Typically, IC chip package
23
is ceramic and has a glass window
25
covering an image sensitive integrated circuit die
29
. As it is known in the art, image sensitive circuit die
29
may include an array of light sensitive charge coupled devices that produce an electronic image when exposed to light. Glass window
25
is part of a standard “cover” or “lid” for the IC chip
23
and has the sole function of providing a hermetic seal to protect circuit die
29
from the environment while permitting it to be exposed to light. Image sensing IC chip package
23
, however, is only a small part of an electronic camera.
With reference to
FIG. 2
, the imaging module
9
of a typical electronic camera incorporates several components and sub-components. The components are assembled into a carrier package for the individual sub-components.
FIG. 2
provides a cut-out view of a typical image module assembly, or carrier package,
9
. As shown, carrier package
9
includes a lens assembly
11
, a mounting plate
15
and a ceramic, IC chip package
19
housing a solid state image sensitive die
22
. As explained above, ceramic chip
19
has a glass window
21
over the image sensitive die
22
. The cavity
13
of lens assembly
11
typically includes such elements as an aperture, an optical lens, and an IR filter. A recessed barrel
11
b
of lens assembly
11
would be fitted into an opening in mounting plate
15
, which in turn would have multiple reference locators
17
for mating with concentric mounting holes
24
in ceramic chip package
19
. The assembly of carrier package
9
is further complicated by the requirement that the optical lens be kept at a critical “focal distance” to the surface of the image sensitive die
22
. A further discussion on some of the difficulties associated with construction of such imaging modules can be found in U.S. Pat. No. 5,998,878.
In addition to the complexity of imaging module
9
, the image sensing IC chip package
19
can place additional obstacles to the construction of an electronic camera. As explained above, IC chip package
19
is typically ceramic, which makes it considerably more expensive than other IC chip packages. Attempts to reduce the cost of packaging an image sensitive die has lead to the use of plastic chip packages in electronic cameras.
FIG. 3
shows an example of a plastic chip package
31
for housing an image sensitive die
33
discussed in U.S. Pat. No. 5,534,745. Image sensitive die
33
is attached to a substrate paddle
35
. As it would be understood in the art, the light sensitive charge coupled devices, CCD, would be arranged in an array pattern in the middle of the surface of die
33
. For illustrative purposes, the side-view of the section of die
33
representing the CCD array is shown as a rectangular shape
39
along the top surface of die
33
. In the present example, a film wall
41
of polyamide having adhesive on both its upper and lower sides is placed surrounding the image sensitive area
39
of die
33
. A glass cover
43
is then attached onto the film wall
41
over the image sensitive area
39
of die
33
. Wire leads
37
are then bonded to the bond pads on die
33
. Finally, the entire assembly is encased in a molding step to form plastic package
31
.
A second approach to produce a plastic chip package for an image sensitive die is discussed in U.S. Pat. No. 5,753,857. With reference to
FIG. 4
, an IC chip package
51
in accordance with the '857 patent consists of two interlocking, plastic components; a support-base component
53
and a lid component
55
. The image sensitive die
57
is attached to base component
53
. The lid component
55
includes solder bumps
59
coupled to wire leads
61
. As the lid component
55
is coupled to the support-base component
53
, the solder bumps
59
line up with the bond pads on image sensitive die
57
. The lid component
55
also has an opening on top exposing the CCD array
58
of die
57
. Once the lid component
55
and support-base component
53
have been assembled, a glass top
63
is adhered to lid component
55
.
None of the preceding examples, however, attempt to simplify the basic imaging module assembly
9
shown in FIG.
2
. One approach toward simplifying a imaging module assembly is to incorporate one of the sub-components of the lens assembly into an IC chip package itself. U.S. Pat. No. 5,340,420 is an example of this approach.
With reference to
FIG. 5
, the approach described in the '420 patent is to incorporate a color separation filter
65
into an image sensitive, IC chip package
67
. Image sensitive die
69
is placed within chip package
67
and wire bonds
71
couple bond pads on die
69
to wire leads within chip package
67
. Following this, an optical coupling composition
73
is uniformly coated on top of image sensitive die
69
. A color separation filter
65
is then placed on composition
73
. Filter
65
is pressed down to form uniform spreading of composition
73
, and is then aligned using alignment targets, as is known in the art. Once the die
69
and filter
65
assembly has been checked for debris and bubble entrapment, very small amounts of ultraviolet curable adhesive is placed at each end of filter
65
to set it in place. A black epoxy is then dispensed along the periphery of filter
65
to encapsulate the separation interface between filter
65
and die
69
. Lastly, a glass cover
75
is placed on IC chip package
67
.
In spite of the incorporation of the filter into the IC package, as shown in
FIG. 5
, one is still required to construct a larger imaging module assembly
9
, as shown in
FIG. 2
, to house all the other necessary sub-components of the lens module
11
and to attach the lens module to the chip package. What is needed is an IC chip package that minimizes the need for construction of a modular imaging assembly.
It is an object of the present invention to provide an imaging module assembly of reduced complexity.
It is a second object of the present invention to reduce the cost associated with the construction of an imaging module assembly.
It is still a third object of the present invention to provide a method of miniaturizing the imaging assembly of an electronic camera.
SUMMARY OF THE INVENTION
The above objects have been met in a one-piece, chip module cover design that integrates all the critical functional elements of the imaging module of an electronic camera. The electronic camera module of the present invention provides reduced piece parts and assembly costs by integration of all the individual sub-components of an imaging module and their respective mounting features into a single cover design for an IC chip package. As a result, the present invention also provides a higher reliability for the overall imaging module assembly of the camera.
The IC chip package of the present invention constitutes a complete imaging module for an electronic camera, and is preferably constructed from injection molded plastic to further reduce cost. A molded plastic cover is first constructed. The molded plastic cover holds an IR filter, holds an optical lens within proper focal distance, provides an aperture function for the optical lens, and provides protection for an image sensitive die, which it covers. Preferably the cover also has a metal coat, such as electroless nickel plating, to provide EMI shielding. The process begins by attaching the image sensitive die, or image sensor die, to a substrate carrier using a die attach epoxy. A wire bond operation is then executed to connect I/O bond pads on the die to substrate carrier bond fingers. A partially assembled, one piece molded chip cover is then attached to the substrate carrier using epoxy. UV cure adhesive is applied to a lens shelf constructed within the molded ch
Atmel Corporation
Fourson George
Schneck Thomas
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