Electricity: measuring and testing – Fault detecting in electric circuits and of electric components – Of individual circuit component or element
Reexamination Certificate
2000-08-16
2002-09-03
Karlsen, Ernest (Department: 2829)
Electricity: measuring and testing
Fault detecting in electric circuits and of electric components
Of individual circuit component or element
C324S765010
Reexamination Certificate
active
06445201
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to an IC package testing device for evaluating electrical characteristics of an IC package, particularly BGA (ball grid array), and a method for testing an IC package using the testing device. More particularly, the present invention relates to a handling device and a handling method for properly abutting solder balls of an IC package respectively on a plurality of measurement contact pins provided in a socket in the testing device.
1. Description of the Related Art
In recent years, as the number of pins provided in an IC package increases, BGA has been used more widely. First, a general structure of a BGA will be described.
FIG. 1A
is a side view of a BGA, and
FIG. 1B
is a plan view thereof. The BGA
1
is a semiconductor component having a rectangular shape. The BGA
1
is about 5 to 50 mm long along each side and about 0.5 to 3 mm thick. A plurality of solder balls
2
are provided on one surface of the BGA
1
. An LSI (large-scale integrated circuit)
3
is buried in the central part of the BGA
1
. Each electrode (not shown) of the LSI
3
is connected to a respective one of the solder balls
2
via a respective one of thin lines (not shown) running through the inside of the BGA
1
. As a method for mounting the BGA
1
on a printed board (not shown), the surface of the BGA
1
having the solder balls
2
provided thereon is placed on the printed board and the solder balls
2
are melted so that the BGA
1
is integrated into the printed board as a circuit.
As shown in
FIG. 1B
, the BGA
1
includes a number of solder balls
2
arranged in a grid pattern which extends along the periphery thereof. Each solder ball
2
has a generally hemispherical shape and protrudes from the surface of the BGA
1
. Each of the solder balls
2
has a diameter as small as about 0.3 mm. Recently, a single BGA
1
has some hundreds to one thousand or more of the solder balls
2
, with a pitch of grid as small as about 0.5 mm. Recently, the degree of integration of an LSI has been increased. Along with that, the number of the solder balls
2
needs to be further increased. Meanwhile, a high-density mounting onto the printed board is also demanded. Therefore, it is difficult to increase the size of the BGA
1
itself. Thus, the density of the array of the solder balls
2
tends to be further increased.
Next, a method for measuring electrical characteristics of the BGA
1
will be described. FIG.
2
A through
FIG. 2D
are cross-sectional views sequentially illustrating the steps of a method for testing electrical characteristics of the BGA
1
using a conventional socket
4
p
. In general, a jig (hereinafter, referred to as a socket) including a group of contact pins
5
p
having an array identical to that of the solder balls
2
is used for the measurement. The contact pins
5
p
can be compressed and expanded by a certain amount. When compressed and expanded, a predetermined spring pressure is applied to the point of contact. As the solder balls
2
are pressed against the tips of the contact pins
5
p
, the contact pins
5
p
are electrically connected to the solder balls
2
, thereby making it possible to measure various kinds of electrical characteristics of the BGA
1
. The contact pins
5
p
shown in
FIG. 2A
are, for example, of a type which includes a compression spring (not shown) under each pin, and generates a spring pressure according to the amount of compression thereof.
The steps of the method for measuring electrical characteristics of the BGA
1
will be sequentially described below. First, the BGA
1
is positioned with respect to the socket
4
p
based on the outer shape of the BGA
1
as shown in FIG.
1
B. Thereafter, a suction head
6
p
sucks onto a surface of the BGA
1
which is opposite to the surface including the solder balls
2
, and carries the BGA
1
over the socket
4
p.
Next, as shown in
FIG. 2A
, the suction head
6
p
inserts the BGA
1
into the socket
4
p
. The socket
4
p
includes many contact pins
5
p
on the bottom. Each side wall of the socket
4
p
is formed of two portions, i.e., a tapered section
40
and a straight section
41
. The tapered section
40
adjoins the opening of the socket
4
p
. The side wall of the tapered section
40
is tapered such that it flares upwardly. If the BGA
1
has a square shape as shown in
FIG. 1B
, the side wall of the tapered section
40
has four tapered sides. The straight section
41
adjoins the bottom of the socket
4
p
, and has a vertical side wall.
Next, after the suction head
6
p
carries the BGA
1
to the tapered section
40
, suction is ceased so as to release and drop the BGA
1
off from the suction head
6
p
as shown in FIG.
2
B. Then, BGA
1
slides down along the tapered surfaces of the tapered section
40
and into the straight section
41
.
As shown in
FIG. 2C
, each of the solder balls
2
is loaded on a respective one of the contact pins
5
p
at the bottom of the socket
4
p
, and the falling down of the BGA
1
is stopped. The shape of the straight section
41
is set to be slightly larger than the outer shape of the BGA
1
, thereby making it possible to abut the BGA
1
on the respective contact pins
5
p
based on the outer shape of the BGA
1
.
Next, as shown in
FIG. 2D
, the suction head
6
p
is lowered by a predetermined amount so as to press the BGA
1
. As a result, the contact pins
5
p
are pressed down by a certain amount via the BGA
1
. Consequently, each of the contact pins
5
p
is electrically connected to a respective one of the solder balls
2
. Thus, using a measuring instrument (not shown) which is connected to each of the contact pins
5
p
via a cable or the like (not shown), various kinds of electrical characteristics are measured. After the measurement, the suction head
6
p
is raised while sucking onto the BGA
1
again, and carries the BGA
1
to a predetermined position for the next step to be performed.
However, the conventional IC package testing device and testing method have problems as follows. First of all, the socket has a structural problem. As described above, when the BGA
1
slides down along the tapered section
40
in the opening of the socket
4
p
, the BGA
1
does not always slides down smoothly. Sometimes, the BGA
1
is stuck halfway through.
FIG. 3A
is a cross-sectional view showing a case where the BGA
1
is stuck halfway through the tapered section
40
. The suction head
6
p
carries the BGA
1
to a predetermined position within the opening of the socket
4
p
, and then the suction is ceased so as to drop the BGA
1
. However, while the BGA
1
is sliding down off from the suction-head
6
p
, a part of the BGA
1
is stuck in the tapered section
40
, thereby preventing the BGA
1
from properly falling down from the suction head
6
p
. As shown in
FIG. 3B
, however, the suction head
6
p
is lowered by a predetermined amount even in such a state, whereby an excessive amount of external force is applied to the BGA
1
from above, damaging the BGA
1
.
Moreover, the force applied by the suction head
6
p
is also applied to the contact pins
5
p
. This force is applied not only in the direction along which the contact pins
5
p
are compressed and expanded (i.e., the vertical direction) but also in the lateral direction. As described above, each of the contact pins
5
p
can be compressed and expanded due to the compression spring included therein. However, the maximum spring pressure during its compression and expansion is as small as about 10 g, and the size of the tip portion of the contact pin
5
p
is as small as about &phgr;0.3 mm which is about the same as that of the solder ball
2
. Thus, the contact pin
5
p
is a component which is extremely thin and fragile. As a result, when an external force in the lateral direction is applied thereto, the contact pin
5
p
is easily bent. If even only one contact pin
5
p
among many is bent and thus can no longer be compressed and expanded smoothly. As a result, the remaining contact pins
5
Horimoto Akio
Simizu Jun
Karlsen Ernest
McGinn & Gibb PLLC
NEC Machinery Corporation
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