Electricity: measuring and testing – Fault detecting in electric circuits and of electric components – Of individual circuit component or element
Reexamination Certificate
2003-03-18
2004-10-26
Pert, Evan (Department: 2829)
Electricity: measuring and testing
Fault detecting in electric circuits and of electric components
Of individual circuit component or element
C324S1540PB
Reexamination Certificate
active
06809543
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to methods, that can be performed automatically in a chip tester, which prevent a chip from being thermally destroyed by a defective pressed joint between the chip and a temperature regulating component within the chip tester. As used herein, the term “chip” means any of the following items: 1) an integrated circuit that is encapsulated in a package, such as a plastic or ceramic packages; 2) an integrated circuit by itself without an encapsulating package; and 3) the integrated circuit of items 1) or 2) which is mounted on a substrate.
In the prior art, the structure of one chip tester is disclosed in U.S. Pat. No. 6,325,662. All of the teachings of that patent are herein incorporated by reference; however,
FIGS. 2 and 2A
in the patent show a portion of the chip tester that is most relevant to the present invention. Those figures are reproduced herein as
FIGS. 1 and 2
, and they are labeled prior art.
The above prior art chip tester includes a frame that has four vertical members, two of which are shown herein in
FIGS. 1 and 2
as items
11
e
and
11
f
. These members support multiple sets of: a chip holding subassembly, a power converter subassembly, a temperature regulating subassembly, and a pressing mechanism.
Each chip holding subassembly includes components
12
a
-
12
d
. From one to fourteen of these chip holding subassemblies are in the frame. Component
12
a
is a printed circuit board which has one face
12
a
-
1
and an opposite face
12
a
-
2
. Attached to face
12
a
-
1
are N sockets
12
b
, each of which holds one IC chip
12
c
that is to be tested. Here, N is any desired number, such as sixteen or thirty, for example. Attached to face
12
a
-
2
are N sets of electrical contacts
12
d
, and each set carries all of the electrical power and all signals for one of the chips
12
c
. Each socket
12
b
is connected to one set of contacts
12
d
by microscopic conductors (not shown) that pass thru the printed circuit board
12
a.
Each power converter subassembly includes components
13
a
-
13
c
. A separate power converter subassembly is supported by the frame above each chip holding subassembly. Component
13
a
is a printed circuit board which has one face
13
a
-
1
and an opposite face
13
a
-
2
. Attached to face
13
a
-
1
are N sets of electrical contacts
13
b
, each of which mates with one set of the contacts
12
d
on the chip holding subassembly. Attached to face
13
a
-
2
are N DC—DC power converters
13
c
. Each power converter
13
c
supplies power to one set of the contacts
13
b
, and it is connected to those contacts by microscopic conductors (not shown) that pass through the printed circuit board
13
a.
Each temperature regulating subassembly includes components
14
a
-
14
d
. A separate temperature regulating subassembly is in the frame below each chip holding assembly
12
. Component
14
a
is a flat rigid plate which has one face
14
a
-
1
and an opposite face
14
a
-
2
. Attached to face
14
a
-
2
are N springy components
14
b
, and each springy component
14
b
holds one temperature regulating component
14
c
such that it is aligned with one chip
12
c
in the chip holding assembly
12
.
The temperature regulating component
14
c
can be of a type which removes heat from the chips
12
c
by conduction, such as a heat sink; or it can be of a type which adds heat to the chips
12
c
by conduction, such as an electric resistive heater; or it can be a combination of both types. Several stops
14
d
are attached to the face
14
a
-
2
, and they are aligned with the spaces between the sockets
12
b
in the chip holding assembly. These stops
14
d
limit the force with which the temperature regulating components
14
c
can be pressed against the chips
12
c.
Each pressing mechanism includes components
15
a
-
15
g
. Component
15
a
is a rail which is rigidly attached to the frame columns
11
e
and
11
f
. This rail
15
a
lies below the temperature regulating subassembly and is parallel to face
14
a
-
1
of the plate
14
a
. Components
15
b
and
15
c
are a pair of arms that are coupled together with a pivotal joint
15
d
which presses against face
14
a
-
1
of the plate
14
a
. The arms
15
b
and
15
c
also have slidable joints
15
e
and
15
f
which slide on the rail
15
a
. Component
15
g
is a spring which is coupled between the slidable joint
15
f
and the frame. All of the components
15
b
-
15
g
are duplicated in the pressing mechanism as shown in FIG.
1
.
In operation, an actuator slides the arms
15
b
on the rail
15
a
to either an “open” position or a “closed” position. When the arms
15
b
are in the open position, the angle “A” between the arms
15
b
and
15
c
is large, and so the pivotal joints
15
d
have moved down. Consequently, each chip holding subassembly is spaced apart from its corresponding power converter subassembly and corresponding temperature regulating subassembly, as is shown in FIG.
1
.
Conversely, when the arms
15
b
are in the closed position, the angle “A” between the arms
15
b
and
15
c
is small, and so the pivotal joints
15
d
have moved up. Consequently, each chip holding subassembly is pressed against its corresponding power converter subassembly and corresponding temperature regulating subassembly, as is shown in FIG.
2
.
To test a set of chips with the tester of
FIGS. 1 and 2
, the following sequence of steps conventionally is performed. First, while the arms
15
b
are in the open position, each chip holding subassembly is placed in the tester between its corresponding power converter subassembly and corresponding temperature regulating subassembly. Next, the arms
15
b
are moved to the closed position, and in that position electrical power and test signals are sent to all of chips
12
c
. While this occurs, the temperature of the chips
12
c
is regulated by the temperature regulating components
14
c
. Then, after all of the test signals have been sent to the chips
12
c
, the electrical power to chips is turned off, the arms
15
b
are moved back to the open position, and each chip holding subassembly is removed from the tester.
However, a major drawback with the above sequence of steps is that when the arms
15
b
are in the closed position, a defect may be present in one or more of the pressed joints that occur between the chips
12
c
and the corresponding temperature regulating components
14
c
. Due to such a defect, the thermal resistance through the pressed joint can be so large that the temperature regulating component
14
c
is not able to prevent the chip
12
c
from overheating when electrical power is applied to chip.
One particular cause for a pressed joint being defective is that a chip
12
c
has been improperly inserted in its socket
12
b
. Another cause is that the surface of a temperature regulating component
14
c
which contacts a chip
12
c
has been oxidized by extended use, and thereby became too resistant. Still another cause is that a film of thermally resistant debris has been accidentally deposited on the surface of a chip
12
c
or the surface of a temperature regulating component
14
c
that gets pressed together.
The above problem is most serious for the latest state-of-the-art chips which dissipate extremely high levels of electrical power. Some of the latest chips dissipate over two-hundred watts of power, and at that power level a chip will rapidly destroy itself if it is not properly cooled. Starting at about 150 degrees centigrade, various materials that make up the chip can either improperly diffuse, or soften, or melt.
Accordingly, a primary object of the present invention is to overcome the above problem.
BRIEF SUMMARY OF THE INVENTION
The present invention is a method of preventing the thermal destruction of an integrated circuit chip in a tester that includes a temperature regulating component for contacting the chip through a pressed joint, which could be defective. This method begins with the step of pressing the chip and the temperature regulating component together wi
Babcock James Wittman
Tustaniwskyj Jerry Ihor
Fassbender Charles J.
Kobert Russell M.
Pert Evan
Rode Lise A.
Starr Mark T.
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