Test socket of semiconductor device

Details Test socket of semiconductor device Test socket of semiconductor device

2001-04-23

2002-07-30

Nelms, David (Department: 2818)

Active solid-state devices (e.g., transistors, solid-state diode

Housing or package

Device held in place by clamping

Reexamination Certificate

active

06426553

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to a test socket of a semiconductor device to be used, for example, to connect a semiconductor package having a ball-shaped external terminal projected from the package bottom to test equipment.
A conventional test socket of a semiconductor device will be explained by referring to
FIGS. 1
to
3
.
Firstly, the first prior art will be explained referring to FIG.
1
.
FIG. 1
is a cross sectional view showing a basic constitution of a contact member
1
of a spring probe pin type test socket. The spring probe pin type test socket is a test socket for executing a characteristic evaluation test of, for example, an FBGA (flat package ball grid array) IC (integrated circuit)
2
in which many contact members
1
are installed in the test socket. Each of these contact members
1
is structured so as to receive a ball-shaped external terminal
3
made of solder projecting from a bottom of a package of IC
2
with a concavity at an upper end thereof being supported by a pin support member not shown in the drawing. The lower end thereof is in contact with a contact pad
5
of a test board
4
corresponding to the external terminal
3
of the IC
2
. External terminal
3
and pad
5
are thus connected to be conductible to each other, thereby DC characteristic evaluation or AC characteristic evaluation such as the high frequency characteristics and high-speed characteristics are carried out.
The contact member
1
has a metallic cylindrical case
6
with an upper end closed, a compression spring
7
housed in the case
6
for generating compression force in the axial direction, and a contact end
8
projecting downward from a lower end opening of the case
6
. An upper end of the contact end
8
is connected to a metallic plunger
9
, which is compressed by the spring
7
in the cylindrical case
6
. Furthermore, at the upper end of the case
6
, a concavity
10
is formed. The characteristic evaluation test of the IC
2
is executed under the condition that the external terminal
3
on the bottom of the IC
2
is pressed against the upper end concavity
10
of the contact member
1
installed to the test socket and that the contact end
8
of the plunger
9
projected downward is pressed against the contact pad
5
of the test board
4
of the test equipment at the same time.
However, the contact member
1
of the spring probe pin type test socket has a line length of, for example, 3 to 5 mm and has an inductance of 1 nH to 1.5 nH or so due to the structure in which the upper end concavity
10
and the contact end
8
are respectively pressed against the corresponding external terminal
3
and contact pad
5
so as to conduct to each other by the plunger
9
compressed by the spring
7
housed in the case
6
and connected. As a result, at the time of evaluation of the characteristics at a frequency of several GHz, the line length must be shorter. However, due to the structure of the spring probe pin type test socket, it is difficult to shorten the line length. Thus, a test socket for high frequency having a short line length and low inductance must be used which means a replacement of the test socket.
Next, the second prior art will be explained referring to FIG.
2
.
FIG. 2
is a cross sectional view showing a basic structure of a contact member
11
of a sheet type test socket. In
FIG. 2
, the contact member
11
is a test socket for executing the characteristic evaluation test of the IC
2
of the FBGA type described above, which is structured so that many metallic wires
13
are embedded overall a sheet-like insulating base
12
at a fine pitch and are inclined to a surface of the sheet.
At the time of conducting the DC characteristic evaluation or the AC characteristic evaluation such as the high frequency characteristics and high-speed characteristics, the contact member
11
of the test socket is arranged between the IC
2
and the test board
4
of the test equipment. The external terminal
3
of the IC
2
and the corresponding contact pad
5
of the test board
4
are arranged facing to each other across the contact member
11
. Thereafter, the external terminal
3
and the contact pad
5
are pressed against the contact member
11
. With the arrangement, a part of the wires
13
obliquely embedded in the insulating base
12
and in contact with the external terminal
3
are also in contact with the contact pad
5
and thereby being made conductive to each other.
In the contact member
11
of the test socket having the structure described, the length of the oblique metallic wires
13
, that is, the line length is about 1.1 mm when the thickness of the insulating base
12
is about 1 mm, for example, which is shorter than that of the first prior art and the inductance is 0.2 nH or less, which is also lower than that of the first prior art. As a result, characteristics at a frequency of several GHz can be evaluated.
However, in the test socket of the second prior art, solder dust or package dust adhered on the surface of the external terminal
3
is also adhered on the surface of the contact member
11
in contact with the external terminal
3
of the IC
2
when the IC
2
characteristic evaluation test is executed many times. When the characteristic evaluation test is continued further, the adhered dust remained and piled increases contamination, which impedes a result of the characteristic evaluation test. Therefore, whenever the contact count reaches about 1500 times, for example, the contact member
11
must be frequently cleaned for which a great deal of time is required.
In the test socket, on the other hand, the cost is very high due to the structure of the contact member
11
in which the metallic wires
13
are arranged regularly overall the insulating base
12
.
Next, the third prior art will be explained referring to FIG.
3
.
FIG. 3
is a cross sectional view showing the basic structure of a contact member
14
of a sheet type test socket for executing the characteristic evaluation test of the IC
2
of FBGA described above. The contact member
14
holds many conductive elastic contactors
16
at a position corresponding to the external terminal
3
on the bottom of the package of IC
2
of the sheet-like insulating base
15
. Each of the elastic contactors
16
is formed passing through the insulating base
15
and having an upper contact part
16
a
and a lower contact part
16
b
respectively projected from an upper and a lower surface of the insulating base
15
.
At the time of conducting the DC characteristic evaluation and the AC characteristic evaluation such as the high frequency characteristics and high speed characteristics, the contact member
14
of the test socket is arranged between the IC
2
, so that the test board
4
of the test equipment and the contact surface of the lower contact part
16
b
of the elastic contactor
16
is positioned right above the contact pad
5
of the test board
4
. Further, the corresponding the external terminal
3
of the IC
2
is positioned right above the contact surface of the upper contact part
16
a
of the elastic contactor
16
. Thereafter, the external terminal
3
is pressed against the contact surface of the upper contact part
16
a
of the elastic contactor
16
installed on the contact member
14
and the contact surface of the lower contact part
16
b
of the elastic contactors
16
is pressed against the top of the contact pad
5
of the test board
4
. With the arrangement, the external terminal
3
and the contact pad
5
are made conductive to each other via the elastic contactor
16
.
When the total height of the elastic contactor
16
held by the insulating base
15
, that is, the line length is selected as about 0.7 mm, for example, in the contact member
14
of the test socket having the structure described, it is shorter than that of the second prior art having such a low inductance as 1.0 nH. As a result, characteristics at a higher frequency than that of the second prior art can be evaluated.
However, in the test socket described,

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