Adhesive bonding and miscellaneous chemical manufacture – Differential fluid etching apparatus – For liquid etchant
Reexamination Certificate
2001-03-27
2003-02-11
Mills, Gregory (Department: 1763)
Adhesive bonding and miscellaneous chemical manufacture
Differential fluid etching apparatus
For liquid etchant
Reexamination Certificate
active
06517666
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to automatic decapsulators and more particularly to the device protection unit utilized in such decapsulators.
BACKGROUND OF THE INVENTION
Automatic decapsulators are used to expose the die in any plastic package or device by etching away the die's plastic covering. Either fuming sulfuric, fuming nitric, or mixed fuming nitric and sulfuric acids may be used as an etchant. Decapsulation is a fast and safe process that produces a clean, uncorroded die surface. When fuming nitric acid is used as the etchant, there is little or no damage to the die surface or bond pads. Fuming sulfuric acid is normally used at an elevated temperature to remove the plastics that are not compatible with fuming nitric acid. The etching process is performed under pressure in an inert atmosphere to reduce metal oxidation and to reduce the production of harmful fumes.
FIG. 1
a
illustrates a side view of a typical system for automatic decapsulation of a device. The system
10
includes a safety cover
11
which is coupled to an etch plate
13
. The system
10
also includes a positioning fixture
12
coupled to the etch plate
13
which is typically metal and is aligned with a package
16
and a gasket
14
, typically made of rubber. The gasket
14
is positioned under the device
16
with an etch window in the gasket's center. During decapsulation, the device holder
20
presses down on the device
16
, which presses down upon the rubber gasket
14
, creating a tight seal with the etch head
18
. The etchant is then provided by the etch head
18
through the etch window to the device
16
.
For many current plastic packages, such as plastic ball grid array (PBGA) or fine ball grid array (FBGA) packages, solder balls are disposed on the backside of the package, i.e., on the face opposite to that exposed to the etchant. Decapsulating such packages is a challenge because the decapsulation temperature exceeds the melting point of the solder balls, and the solder balls can be deformed by the device holder. Moreover, some packages, like FBGA packages, can be as small as 5 mm on each side, thereby presenting alignment problems.
Co-pending U.S. patent application Ser. No. 09/680,558 entitled, “Automatic Decapsulation System Utilizing An Acid Resistant, High Heat Endurance and Flexible Sheet Coupled to a Rubber Gasket and Method of Use,” filed on Oct. 5, 2000, and assigned to the assignee of the present invention, addresses some of the challenges faced when decapsulating ball grid array packages. According to one embodiment of the co-pending patent application, a spacer and a protection plate are disposed between the device and the device holder so that the device holder does not come in direct contact with the backside of the device. The spacer makes contact with the backside of the device only in areas without solder balls. Accordingly, the spacer prevents the protection plate from deforming the solder balls during decapsulation.
FIG. 2
a
illustrates a side view of the automatic decapsulation system
100
in accordance with the above-referenced co-pending application. The system
100
is similar to the system
10
of
FIG. 1
, and includes a safety cover
11
′ which is coupled to an etch plate
13
′. As is seen, a spacer
108
is inserted between the backside of the package
110
and the protection plate
106
. A rubber gasket
104
is placed between a gasket plate
102
and a head etch
18
′. The spacer
108
is preferably made of a TEFLON sheet having a thickness of at least the height of the solder balls. TEFLON® is well known in the art. The generic term for TEFLON is polytetrafluoroethylene (PTFE).
FIG. 2
b
illustrates a top view of the backside of the device
110
with the spacer
108
in accordance with the present embodiment. As is shown, a window is cut out of a sheet (not shown) to form the spacer
108
, which surrounds and protects the solder balls. Accordingly, when the protection plate
106
is placed on top of the spacer
108
, the plate
106
does not come in contact with the backside of the device
110
, and the solder balls are protected from being crushed.
Although the above-described system in the co-pending patent application functions for its intended purpose, one of ordinary skill in the art will readily recognize that it would be desirable to improve the way in which the backside of the device is protected. For instance, it would be desirable to simplify the placement of the spacer, such that alignment with a very small device, such as a FBGA package, is accomplished with relative ease. It also would be desirable to devise a system in which the protection plate is easily put in place and kept in place during decapsulation. In addition, it would be desirable to reduce the cost and labor associated with manufacturing different spacers having different sizes to match the various package sizes.
Accordingly, what is needed is a system and method to overcome the above-identified problems. The system and method should be cost effective and easy to implement with existing processes and equipment. The present invention addresses such a need.
SUMMARY OF THE INVENTION
An automatic decapsulation system for a device is disclosed. The system comprises an etch plate, an etch head, a sheet coupled to the etch head, a rubber gasket disposed between the etch head and the sheet, and an integrated spacer and protection plate for securing the device without damaging the backside of the device during decapsulation. In one embodiment of the present invention, the integrated spacer and protection plate is adjustable to accommodate devices of varying sizes.
The integrated spacer and protection plate of the present invention automatically aligns the spacer with the device, thereby reducing the amount of time taken to otherwise align the spacer. In addition, because the spacer and protection plate are integrated, the protection plate is put in place and kept in place automatically. In a preferred embodiment, the integrated spacer and protection plate is manufactured from a TEFLON sheet, thereby providing a highly durable and cost efficient solution.
REFERENCES:
patent: 4826556 (1989-05-01), Kobayashi
patent: 5252179 (1993-10-01), Ellerson et al.
patent: 5443675 (1995-08-01), Wensink
patent: 5766496 (1998-06-01), Martin
patent: 5783098 (1998-07-01), Martin et al.
patent: 5792305 (1998-08-01), Winsemius et al.
patent: 5855727 (1999-01-01), Martin et al.
Hulog Jose
Li Xia
Massoodi Mohammad
Advanced Micro Devices , Inc.
Crowell Michelle
Mills Gregory
Sawyer Law Group LLP
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