Testing IC socket

Details Testing IC socket Testing IC socket

1999-02-16

2001-08-21

Metjahic, Safet (Department: 2858)

Electricity: measuring and testing

Fault detecting in electric circuits and of electric components

Of individual circuit component or element

C324S765010, C439S069000

Reexamination Certificate

active

06278284

ABSTRACT:

BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an IC socket, and more specifically an IC socket for testing a grid array package.
2. Description of Related Art
In general, an IC socket comprising a resin body and a plurality of metallic contacts each including a connecting terminal for electrically connecting to a corresponding lead or bump of a semiconductor package and a lead formed integrally with the connecting terminal and adapted to be inserted into a corresponding through-hole of a printed circuit board.
FIGS. 9A and 9B
are diagrammatic sectional views illustrating the structure of conventional IC sockets. As shown in these drawings, an IC socket is assembled by forcibly inserting a contact
1
into a contact fixing hole
3
of an IC socket body
2
.
Recently, a variety of semiconductor packages have appeared, and in order to minimize the size of the semiconductor packages, the package is gradually shifting from a quad flat package (QFP) comprising a number of leads
13
outward extending from a periphery of a package body
12
as shown in
FIG. 10
, to a grid array package such as a ball grid array (BGA) package
14
having a number of solder bumps
15
formed in the form of a matrix on a lower surface of the package to constitute electric contacts of the package, as shown in
FIGS. 11A and 11B
, a pin grid array (PGA) package, and a land grid array (LGA) package, since these grid array packages can be used at a relatively low cost in place of QFP.
An IC socket used for testing an electric characteristics of the grid array packages such as BGA, PGA and LGA packages, has contacts of a spring structure so that the contacts are brought into pressure-contact with the electric contacts of the package such as leads or solder bumps. Because the contacts of the IC socket are pressure-contacted with the lead or solder bumps of the package, there occurs a phenomenon that a material of the electric contacts of the package is transferred to the contacts of the IC socket, with the result that an electrical contacting condition becomes poor, and therefore, it becomes necessary to frequently exchange the IC socket.
In the prior art, it was a general practice to fix an IC socket
2
to a test board
6
, as shown in
FIG. 12
, by inserting contact pins id extending from the IC socket body
2
, into through-holes
6
a
of the test board
6
from one surface of the test board
6
, and then by soldering a tip end portion of the contact pins
1
d
projected from the other surface of the test board
6
, by a solder
19
. However, since it is difficult to exchange the IC socket under this practice, it has been proposed to make the IC socket detachable, as shown in
FIG. 13
, by providing an adapter socket
7
having a corresponding number of pin sockets
8
, by soldering the pin sockets
8
to the test board
6
by a solder
19
, and on the other hand, by inserting the contact pins
1
d
of the IC socket body
2
in the pin sockets
8
so that the contact pin
1
d
is grasped by a contact spring
8
a
in the inside of the pin socket
8
.
However, in the IC socket shown in
FIG. 13
, if a fixing and grasping force for the contact
1
in the IC socket is inferior to an insertion pressure of the contact pin
1
d
into the pin socket
8
applied when the IC socket body
2
is fixed to the adapter socket
7
, the contact pins are often deviated from each other, and in an extreme case, the contact falls away from the IC socket body.
FIG. 14
is a diagrammatic enlarged partial view of the contact
1
and the IC socket body
2
. When the contact
1
is inserted in and fixed to the contact fixing hole
3
of the IC socket body
2
, the fixing and grasping force F
0
acts on the contact
1
from the contact fixing hole
3
, and the insertion pressure F
1
acts on the contact
1
from a lower position, as shown in FIG.
15
. When the relation between these forces becomes F
0
<F
1
, the contact
1
falls out from the IC socket
2
, as designated by Reference Numeral
20
in FIG.
16
.
In order to prevent the falling-out of the contact, Japanese Patent Application Pre-examination Publication No. JP-A-07-058250 discloses a technology in which, as shown in
FIG. 2
of JP-A-07-058250, a barb
10
b
is formed on each of opposite side surfaces of a contact pin
10
, so that when the contact pin
10
is inserted into a through hole of an IC socket body
9
, the contact pin
10
is prevented from falling out from the IC socket body
9
by action of a wedge effect of the barb
10
b
. In this proposal, however, it is impossible to exchange the contact.
There has been also disclosed an IC socket for a plat package such as the QFP having a number of connection leads extending outward from the periphery of the package, the IC socket being configured to firmly hold the contacts by a hold-down plate, as another means for preventing the contact from falling out from the IC socket body.
For example, Japanese Utility Model Application Pre-examination
Publication No. JP-A-07U025594 discloses an IC socket including an upper plate member and a lower plate member and having a structure in which, as shown in
FIG. 3
of JP-A-07U025594, a fixing contact
31
in the form of a wedge having a lead
32
to be inserted into a through hole of a printed board
61
is driven into the lower plate member
11
, and on the other hand, the upper plate member
21
is provided with a movable contact
35
which can be moved dependently upon the kind of the IC package.
In this IC socket, however, the fixing of the movable contact
35
by the upper plate member
21
is achieved by depressing opposite ends of a stationary contact portion
36
of the movable contact
35
by means of the upper plate member
21
. Therefore, the size of the movable contact becomes large, with the result that this IC socket cannot be applied to an IC socket for the grid array package such as BGA package. Japanese Utility Model Application Post-examination Publication No. JP-B-04U000553 discloses an IC socket having, as shown in
FIG. 2
of JP-B-04U000553, a number of turned contact pins
5
arranged and aligned on a base plate
1
and a hold-down plate
7
put on a base portion of the turned contact pins
5
, the hold-down plate
7
being depressed by a body member
3
, so that the contact pins
5
are fixed by the body member
3
through the intermediary of hold-down plate
7
. However, this IC socket can be applied for only the flat packet, and cannot be applied to a high density package such as the grid array package having a number of contacts arranged on a bottom surface of the package.
SUMMARY OF THE INVENTION
Accordingly, it is an object of the present invention to provide an IC socket which has overcome the above mentioned problems of the prior art.
Another object of the present invention is to provide an IC socket for testing the grid array package such as BGA package.
The above and other objects of the present invention are achieved in accordance with the present invention by an IC socket for testing a grid array package, the IC socket being configured to be fitted with an adapter socket mounted on a test board, the IC socket including an IC socket body having a bottom plate formed with a number of contact holding holes penetrating through the bottom plate and arranged in the form of a matrix, a number of contacts each having a contacting end, a spring portion, a fixing base portion and a contacting pin which are arranged in the named order, the fixing base portion of each of the contacts being inserted into a corresponding contact holding hole of the IC socket body from the upperside of the bottom plate, and a fixing plate having a corresponding number of fixing apertures and fixed on an upper surface of the bottom plate of the IC socket body by passing the contacts through the fixing apertures, respectively, the fixing base portion of the contact being fixed between the bottom plate of the IC socket body and an edge portion of the fixing aperture of the fixing plate.
In a preferred embodiment of the IC socket

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