Semiconductor device manufacturing: process – Packaging or treatment of packaged semiconductor – Metallic housing or support
Reexamination Certificate
2000-05-12
2002-04-16
Nelms, David (Department: 2818)
Semiconductor device manufacturing: process
Packaging or treatment of packaged semiconductor
Metallic housing or support
C438S106000
Reexamination Certificate
active
06372551
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to integrated circuit (IC) packaging technology, and more particularly, to an Integrated Circuit packaging method for packaging an Integrated Circuit chip of an optically-sensitive type, such as an image-sensor Integrated Circuit chip, which can help prevent resin flash on lead frame and help increase wire bondability.
2. Description of Related Art
Integrated Circuit packaging technology is used to pack one or more Integrated Circuit chips in a single module. Typically, the Integrated Circuit chip or chips are enclosed within an opaque encapsulating body, and thus is invisible from the outside. However, for image-sensor Integrated Circuit chips, it is required to allow them to detect outside light to serve their function. For this reason, a special Integrated Circuit package configuration is used to pack Integrated Circuit chips of optically-sensitive types.
One problem to the manufacture of the image-sensor Integrated Circuit chips, however, is that the resin used to form the package body could easily flash onto the lead frame surface, which would then undesirably degrade the quality of the die attachment and wire bonding on the lead frame surface in subsequent processes. Conventionally, various Integrated Circuit packaging methods have been proposed to eliminate the flash problem, including, for example, the U.S. Pat. No. 5,070,041 and the U.S. Pat. No. 5,523,608.
The U.S. Pat. No. 5,070,041 discloses an Integrated Circuit packaging method for manufacturing a single-chip image-sensor Integrated Circuit package, which is briefly depicted in the following with reference to
FIGS. 1A-1D
.
Referring to
FIG. 1A
, by the U.S. Pat. No. 5,070,041, the first step is to prepare a lead frame
110
of the type having a die-pad portion
111
and a finger portion
112
. To prevent flash, a polymer precoating
120
is formed over the die-pad portion
111
and the inner end of the finger portion
112
.
Referring further to
FIG. 1B
, in the next step, a molding process is performed to form a top package body
121
and a bottom package body
122
. The top package body
121
is centrally-hollowed for die attachment. During this molding process, however, the resin used to form the top and bottom package bodies
121
,
122
would undesirably flash onto the die-pad portion
111
and the inner end of the finger portion
112
of the lead frame
110
(the flashed resin is here pointed out by the reference numeral
130
). Since these lead frame portions are pre-coated with the polymer precoating
120
, the flashed resin
130
thereon can be subsequently removed by using a special solvent.
Referring further to
FIG. 1C
, in the next step, a die-attachment process is performed to attach an image-sensor Integrated Circuit chip
140
on the die-pad portion
111
of the lead frame
110
. Subsequently, with the bottom package body
122
being fixed over a heat block
150
, a wire-bonding process is performed to apply a set of bonding wires
160
for electrically coupling the image-sensor Integrated Circuit chip
140
to the inner end of the finger portion
112
of the lead frame
110
.
Referring further to
FIG. 1D
, in the next step, a lidding process is performed to cover a transparent lid
170
onto the top opening of the top package body
121
to thereby hermetically seal the image-sensor Integrated Circuit chip
140
. This completes the manufacture of the single-chip image-sensor Integrated Circuit package.
The foregoing Integrated Circuit packaging method, however, has two drawbacks. First, it is quite costly to implement the forming of the polymer precoating
120
and the subsequent solvent cleaning of the flashed resin
130
over the polymer precoating
120
, which makes the overall manufacture process quite cost-ineffective. Second, during the wire-bonding process, since the heat block
150
is in direct thermal contact with the resin-made bottom package body
122
rather than with the lead frame
110
, the heat transfer from the heat block
150
to the lead frame
110
would be inadequate, thus undesirably resulting in a poor bondability to the bonding wires
160
. There exists therefore a need for a new Integrated Circuit packaging method that can eliminate the flash problem in a more cost-effective way and also allows a better heat transfer to the die pad during the wire-bonding process.
The U.S. Pat. No. 5,523,608 discloses an Integrated Circuit packaging method used to manufacture a dual-chip image-sensor Integrated Circuit package, which is briefly depicted in the following with reference to
FIGS. 2A-2D
.
Referring to
FIG. 2A
, by the U.S. Pat. No. 5,523,608, the first step is to prepare a lead frame
210
of the type having a die-pad portion
211
and a finger portion
212
. Next, a first die-attachment process is performed to attach a first Integrated Circuit chip
241
on the back side of the die-pad portion
211
of the lead frame
210
. After this, a first wire-bonding process is performed to apply a first set of bonding wires
261
for electrically coupling the first Integrated Circuit chip
241
to the back side of the inner end of the finger portion
212
of the lead frame
210
.
Referring further to
FIG. 2B
, in the next step, a molding process is performed to form a top package body
221
and a bottom package body
222
. The top package body
221
is centrally-hollowed for die attachment. During this molding process, however, the resin used to form the top and bottom package bodies
221
,
222
would undesirably flash onto the front side of the die-pad portion
211
and the inner end of the finger portion
212
of the lead frame
210
(the flashed resin is here pointed out by the reference numeral
230
). A blast process is then performed by the use of a blaster
231
to clean the flashed resin
230
away.
Referring further to
FIG. 2C
, in the next step, a second die-attachment process is performed to attach a second Integrated Circuit chip
242
(image-sensor Integrated Circuit chip) on the front side of the die-pad portion
211
of the lead frame
210
. Subsequently, with the bottom package body
222
being fixed over a heat block
250
, a second wire-bonding process is performed to apply a second set of bonding wires
262
for electrically coupling the second Integrated Circuit chip
242
to the front side of the inner end of the finger portion
212
of the lead frame
210
.
Referring further to
FIG. 2D
, in the next step, a lidding process is performed to cover a transparent lid
270
onto the top opening of the top package body
221
to thereby hermetically seal the second Integrated Circuit chip
242
. This completes the manufacture of the dual-chip image-sensor Integrated Circuit package.
The foregoing Integrated Circuit packaging method, however, also has two drawbacks. First, it is quite costly to implement the blast process to clean the flashed resin, which makes the overall manufacture process quite cost-ineffective. Second, during the second wire-bonding process, since the heat block
250
is in direct thermal contact with the resin-made bottom package body
222
rather than with the lead frame
210
, the heat transfer from the heat block
250
to the lead frame
210
would be inadequate, thus undesirably resulting in a poor bondability to the second set of bonding wires
262
. There exists therefore a need for a new Integrated Circuit packaging method that can eliminate the flash problem in a more cost-effective way and also allows a better heat transfer to the die pad during the second wire-bonding process.
SUMMARY OF THE INVENTION
It is the primary objective of this invention to provide a new Integrated Circuit packaging method which can help solve the above-mentioned flash problem.
It is another objective of this invention to provide a new Integrated Circuit packaging method which allows the lead frame to come in direct thermal contact with the heat block during wire-bonding process.
In accordance with the foregoing and other objectives, the invention proposes a new Integrated Circu
Corless Peter F.
Dang Phuc T.
Edwards & Angell LLP
Jensen Steven M.
Nelms David
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