Active solid-state devices (e.g. – transistors – solid-state diode – Combined with electrical contact or lead – Bump leads
Reexamination Certificate
2002-04-22
2004-09-14
Chambliss, Alonzo (Department: 2827)
Active solid-state devices (e.g., transistors, solid-state diode
Combined with electrical contact or lead
Bump leads
C257S778000, C257S779000, C257S786000, C174S255000, C174S263000, C361S764000, C361S767000, C361S774000, C361S777000
Reexamination Certificate
active
06791186
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a mounting substrate and a structure having a semiconductor element mounted on the substrate and, more particularly, to a mounting substrate for mounting thereon a semiconductor element having a line of electrode terminals and a structure having a semiconductor element mounted on the substrate.
2. Description of the Related Art
A structure, in which a semiconductor element is mounted on a substrate by flip chip bonding, the semiconductor element comprising a plurality of electrode terminals arranged in two rows at the central portion of the surface thereof, is known.
FIG. 12
shows a method of mounting a semiconductor element
10
on a substrate
20
to provide such a structure. Electrode terminals (not shown) of the semiconductor element
10
are each provided with a protruded electrode
12
of a gold bump, and connection electrodes
22
are arranged, corresponding to the protruded electrodes
12
, on the surface of the substrate
20
on which the semiconductor element
10
is to be mounted. The connection electrodes
22
and the protruded electrodes
12
are aligned with each other, and the semiconductor element
10
is mounted on the substrate
20
. The surface of the connection electrodes
22
is deposited with solder (not shown). The semiconductor element
10
is heated to a temperature at which the solder is melted, and the protruded electrodes
12
are bonded under pressure to the connection electrodes
22
.
FIG. 13
is a sectional view showing a structure in which the semiconductor element
10
is mounted on the substrate
20
. The connection electrodes
22
arranged on the surface of the substrate
20
where the semiconductor element is to be mounted include solder deposited on the surface of a copper pattern
23
.
The protruded electrodes
12
of the semiconductor element
10
are arranged in two rows. The connection electrodes
22
are also arranged in two rows on the substrate
20
at positions corresponding to the protruded electrodes
12
. The connection electrodes
22
are exposed from the protective film
32
, such as a solder mask, covering the surface of the substrate
20
on which the semiconductor element is to be mounted. Actually, as shown in
FIG. 12
, the area of the surface of the substrate
20
, in which the semiconductor element
10
is to be mounted and the connection electrodes
22
are arranged, constitutes an exposed rectangular opening
30
. The solder
24
on the connection electrodes
22
is exposed in the opening
30
, while the portion other than the opening
30
is covered with a protective film
32
, such as a solder mask, as shown in FIG.
13
. The connection electrodes
22
are each connected with a wiring pattern
26
, which in turn is covered by the protective film
32
.
Apart from the structure as shown in
FIG. 12
in which the semiconductor element having protruded electrodes arranged in two rows is mounted by flip-chip bonding, there is a structure in which a product, such as a memory chip, having a plurality of protruded electrodes arranged in a single row substantially along the center line of the product is mounted. In the structure in which a product having the protruded electrodes arranged in a single row is mounted on a substrate, the connection electrodes of the substrate are also arranged in a single row at positions corresponding to the protruded electrodes.
In the case where a semiconductor element with protruded electrodes arranged in one row is mounted as described above, the problem described below is posed.
FIG. 14A
shows the substrate
20
aligned with the semiconductor element
10
having a protruded electrode
12
.
FIG. 14B
shows the state in which the protruded electrode
12
is brought into contact with the connection electrode
22
of the substrate
20
and heated under pressure to thereby bring the end surface of the protruded electrode
12
into contact with the surface of the connection electrode
22
. As the result of the protruded electrode
12
coming into contact with the connection electrode
22
, the connection electrode
22
and the substrate
20
are partially depressed.
FIG. 14C
shows the state in which the temperature is decreased until the solder
24
on the connection electrode
22
is solidified to thereby release the pressure imparted on the protruded electrode
12
.
Once the solder
24
is solidified and the pressure is released from the protruded electrode
12
, as shown in
FIG. 14C
, the semiconductor element
10
comes to be mounted at an angle to the surface of the substrate
20
by the elasticity of the substrate
20
and the connection electrode
22
. This is by reason of the fact that, in the case where the protruded electrodes
12
are arranged in two rows as shown in
FIG. 13
, the distortion imparted on the semiconductor element
10
is distributed equally between the right and left sides in the drawing, whereas in the case where the protruded electrodes
12
are aligned in one row as shown in
FIG. 14C
, the stress on the semiconductor element
10
loses balance and more strongly acts on one side.
In the case where the semiconductor element
10
is mounted obliquely on the substrate
20
as shown in
FIG. 14C
, the reliability of electrical connection between the protruded electrodes
12
and the connection electrodes
22
is deteriorated, or the underfill material
34
(
FIG. 13C
) fails to be sufficiently filled up between the semiconductor element
10
and the substrate
20
, thereby forming a void. This derives from the fact that when the semiconductor element
10
is mounted at an angle, the interval between the semiconductor element
10
and the substrate
20
is partially reduced to less than that required to allow the underfill material
34
to be adequately filled therein.
In the case where underfill material is filled after bonding the semiconductor element
10
to the substrate
20
, care must be taken not to generate any void in the sealed area. A resin material having a high fluidity is used as the underfill material
34
. Nevertheless, it is very difficult for the underfill material to flow sufficiently in the very narrow space between the semiconductor element
10
and the substrate
20
. Especially in the region where the protruded electrodes
12
and the connection electrodes
22
are connected with each other and where the underfill material
34
does not easily flow, a void is liable to occur.
SUMMARY OF THE INVENTION
The present invention has been achieved to obviate the aforementioned problems, and an object of the invention is to provide a highly reliable mounting substrate and a structure in which a semiconductor element having protruded electrodes arranged in a line substantially along the center line of a surface of the semiconductor element is mounted on a substrate by flip-chip bonding in such a manner that the protruded electrodes of the semiconductor element and the connection electrodes of the substrate are securely connected electrically to each other, with the underfill material being sufficiently filled in the space between the semiconductor element and the substrate.
According to one aspect of this invention, there is provided a mounting substrate, on which a semiconductor element is to be mounted by flip chip bonding, the semiconductor element having a surface on which a plurality of electrode terminals are formed so as to be arranged in a line, each of the electrode terminals having a protruded electrode formed thereon,
wherein the surface of the mounting substrate on which the semiconductor element is to be mounted is provided with a protective film having an opening corresponding to an area of the semiconductor element where the protruded electrodes are located, a plurality of connection electrodes being arranged in the opening, the connection electrodes being provided with a solder for bonding it to the protruded electrodes, and being arranged at the same interval as that of the protruded electrodes, and each of the connection electrodes being connecte
Sorimachi Haruo
Yoneda Yoshihiro
Chambliss Alonzo
Paul & Paul
Shinko Electric Industries Co. Ltd.
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