Test socket

Details Test socket Test socket

2000-05-16

2002-09-10

Sherry, Michael (Department: 2829)

Electricity: measuring and testing

Fault detecting in electric circuits and of electric components

Of individual circuit component or element

C324S760020

Reexamination Certificate

active

06448803

ABSTRACT:

TECHNICAL FIELD
The present invention relates to an electric connection structure between an integrated circuit (IC) device and a printed circuit board, and in particular, to a structure of a test socket for testing an integrated circuit.
BACKGROUND ART
An integrated circuit fabricated through complicated processes is subject to various electric tests for a characteristics measurement or quality inspection. In this respect, a socket is frequently used in order to electrically connect a test circuit of a printed circuit board installed at a test equipment to an external terminal (outer lead) of the IC device. That is, for testing the IC device, the socket serves as an interface for electrically connecting the printed circuit board of the test equipment and an IC device.
A conventional test socket structure will now be described with reference to accompanying drawings.
Generally, as shown in
FIG. 1
, a test socket of an IC device includes a socket housing
10
and a plurality of contact fingers (contact terminals)
11
. The contact finger is formed curved in a semicircle shape so as to have a spring elastic force by a downward pressing pressure. Reference numeral
12
denotes a fixing pin for fixing the IC device so that the electrical connection between the contact finger and the outer lead of the semiconductor device is not be unstable while the IC device is being tested.
FIG. 2
shows a device under test (DUT)
14
as mounted on the socket. The device under test
14
is mounted on the socket in a manner that an outer lead
15
of the device under test
14
is contacted by an upper terminal
11
a
of the contact finger
11
. For performing the test, the lower terminal
11
b
of the contact finger
11
is mounted to be necessarily contacted on a printed circuit (not shown) of the printed circuit board of the test equipment.
Thereafter, the device under test
14
is pressed down by a pressing unit (not shown), so that the outer lead of the device under test and the upper terminal
11
a
of the contact pin of the socket are electrically connected by the press-down contact, and the lower terminal
11
b
of the contact pin and a circuit pattern (not shown) formed on the surface of the board of the test equipment are also electrically connected by the press-down contact.
The device pressing unit (not shown) renders the overall outer leads of the device under test mounted on the socket to be contacted to the upper terminal of the contact fingers, and at this time, the downward pressure has a great value. Accordingly, if such a strong downward pressure is applied thereto in every testing, the frequency of the testing becomes higher, resulting in that the spring elastic force of the contact finger of the socket is deteriorated or there possibly occurs difference in spring elastic force with respect to each contact finger.
With those problem occurring, eventually, a contact finger having a weakened spring elastic force among the plural contact fingers would cause a contact inferiority or a contact instability over such connection between the device under test and the external terminal, even though the device under test is pressed down by the pressing pressure.
Such a contact finger having the weakened spring elastic force must be replaced by a new normal one. In this respect, in case of a socket having the contact finger and the socket housing as an incorporated one, even if there occurs a contact deterioration or contact instability for a single contact finger, the high-priced socket itself needs to be replaced by a new one, which inevitably incurs a heavy expense for testing with a prodigal waste.
In order to resolve such a problem, the U.S. Pat. No. 5,634,801 discloses a test socket having a structure that a defective contact pin is individually replaced, as illustrated in
FIGS. 3A and 3B
, details of which will now be described.
The socket shown in
FIG. 3A
includes a housing
30
, a plurality of contact pin receiving slots
31
each arranged in parallel at predetermined intervals within the housing
30
, an upper and a lower cavities
32
a
and
32
b
each formed at an upper surface and a lower surface of the housing. The upper cavity
32
a
formed at the upper surface of the housing
30
and the lower cavity
32
b
formed at the lower surface of the housing
30
are positioned at marginal portions in mutually opposite side of the slot.
Elastomer
33
a
and
33
b
are respectively installed within the upper and lower cavities
32
a
and
32
b
. Inside each of the contact pin receiving slot
31
, S-shaped contact pins
34
are respectively inserted, of which an upper end portion and a lower end portion are respectively rested on the elastomers.
Reference numeral
35
denotes a printed circuit board of the test equipment, and reference numeral
36
denotes a circuit pattern formed on the printed circuit board, which is connected to the lower surface of the contact pin
34
.
FIG. 3B
is a longitudinal-sectional view taken along line IV—IV of FIG.
3
A.
As described above, the conventional socket has an advantage in that since each contact pin
34
is individually installed in each contact pin receiving slot
31
, any defective contact pin can be replaced by a normal one whenever it occurs.
Nevertheless, it also has disadvantages in the following aspects.
First, in case that plural contact pins
34
are defective, each contact pin should be replaced one by one, causing inconvenience and taking much time for replacing the contact pins.
Secondly, in order to perform testing, when the IC device (not shown) is pressed downwardly (‘a’ direction) as is mounted on the upper portion of the contact pin, the lower surface portion
34
a
of the contact pin
34
moves in the horizontal direction to the circuit pattern, that is, in a ‘b’ direction toward inside the socket, while being contacted with the circuit pattern
36
of the printed circuit board.
In addition, after finishing the testing, when the semiconductor device is raised upward (‘c’ direction), the lower surface portion
34
a
of the contact pin
34
moves in the horizontal direction, that is, ‘d’ direction opposite to the ‘b’ direction.
Accordingly, if the testing of the semiconductor device is repeatedly done, the lower surface portion
34
a
of the contact pin
34
always contacts the circuit pattern
36
whenever it moves in the ‘b’ and ‘d’ directions. Consequently, repeated movement of the lower surface portion
34
a
causes an abrasion on the part of the circuit pattern
36
where the contact pin is continuously contacted thereto, creating a problem of deterioration on the printed circuit board of the high-priced test equipment.
Fabricating method of the contact pin or the contact finger of the conventional test socket is as follows.
As shown in
FIG. 4A
, a metal plate
40
having straight grains
41
in one direction is formed by extrusion molding. And, As shown in
FIG. 4B
, a contact pin or contact finger
42
in patterns such as ‘C’-shape or ‘S’-shape is drawn. And then, as shown in
FIG. 4C
, a pattern shaped in a contact finger is cut out therefrom, to thereby form a contact finger
42
.
In this respect, however, the contact finger made by that method is easily broken along the metal grains during the testing, as up and down movement is repeated by hundreds and thousands of times.
In addition, as the movement in the direction perpendicular to the direction of the metal grain is repeated, its spring elastic force is weakened, so that the contact finger is easily deformed, resulting in that a durability of the socket is shortened.
DISCLOSURE OF THE INVENTION
Therefore, it is an object of the present invention to provide a test socket structure in which a contact pin of a defective socket is replaced by block unit.
Another object of the present invention is to provide a test socket structure in which a pattern of a printed circuit board of a testing equipment is not abraded during testing of a semiconductor device.
Still another object of the present invention is to provide a test socket in which an elastomer is installed

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