Semiconductor device manufacturing: process – Packaging or treatment of packaged semiconductor – Making plural separate devices
Reexamination Certificate
1999-10-01
2001-09-18
Chaudhari, Chandra (Department: 2813)
Semiconductor device manufacturing: process
Packaging or treatment of packaged semiconductor
Making plural separate devices
C257S692000, C257S693000
Reexamination Certificate
active
06291269
ABSTRACT:
BACKGROUND OF THE INVENTION
1 . Field of the Invention
The present invention generally relates to a semiconductor bare chip and a method of manufacturing the semiconductor bare chip and particularly relates to a mounting structure of the semiconductor bare chip, which allows reduced mounting area.
2 . Description of the Related Art
Because of the recent miniaturization of portable electronic devices, there is a need for a higher density when mounting a semiconductor on a mounting board. In order to achieve high-density mounting, a technology has been developed which utilizes the flip-chip method. With the flip-chip method, a semiconductor bare chip, which is a chip that is not packaged, is directly mounted on the mounting board. Thus, a reduced mounting area is achieved, since no additional area is necessary around the semiconductor bare chip.
FIG. 1
shows a partially enlarged view of a semiconductor bare chip
10
of the related art.
FIGS. 2A-2B
are diagrams showing the semiconductor bare chip
10
of the related art which is mounted on a printed board
20
.
As shown in
FIG. 1
, the semiconductor bare chip is constructed such that a stud bump
13
made of Au (gold) is formed on each electrode
12
on a bottom surface
11
a
of a semiconductor bare chip body 11 which has been cut-out from a wafer. The semiconductor bare chip is also constructed such that a conductive adhesive agent
14
is provided so as to cover the head of the stud bump
13
.
The stud bump includes a seat
13
a
and a head
13
b
. The seat
13
a
has a shape of a squeezed sphere. The head
13
b
is substantially cylindrical. The head
13
b
has a diameter d
2
, which is smaller than a diameter d
1
of the seat
13
a
. The head
13
b
protrudes from the seat
13
a
by a length a. The head
13
b
is formed so that a predetermined amount of conductive adhesive agent
14
will be provided thereon, and that the stud bump
13
can be easily pressed against an electrode
21
on a printed board
20
.
As shown in
FIG. 2A
, the electrodes
21
are formed on the printed board
20
. The electrodes
21
have a thickness b. The electrodes
21
have a rectangular shape with a side length c of approximately 40 &mgr;m. The stud bumps
13
and the electrodes
21
are positioned so as to correspond to each other.
As shown in
FIG. 2A
, the semiconductor bare chip
10
is mounted using a flip-chip method of the press joint type. That is, the head
13
b
of the stud bump
13
is pressed against the electrode
21
and is stuck on the electrode
21
using the conductive adhesive agent
14
. Also, the semiconductor bare chip body
11
is stuck on the printed board
20
by a thermosetting adhesive agent
31
. Since the thermosetting adhesive agent
31
is provided within a gap
30
between the semiconductor bare chip body
11
and the printed board
20
and has been thermoset, the entire bottom surface
11
a
of the semiconductor bare chip body
11
is stuck on the printed board
20
. Also, because the thermosetting adhesive agent
31
is thermoset and contracted, the entire bottom surface
11
a
of the semiconductor bare chip body
11
is pulled towards the printed board
20
with a force F
1
. With this force F
1
, the head
13
b
of the stud bump
13
is pressed against the electrode
21
.
Here, the head
13
b
is formed such that a height a is approximately 30 &mgr;m so that a sufficient amount of the conductive adhesive agent
14
adheres thereto.
The thickness b of the electrode
21
on the printed board
20
is reduced along with the refinement of the patterning, and is approximately 20 &mgr;m.
The relationship between the height a of the head and the thickness b of the electrode
21
can be expressed as a>b.
If the semiconductor bare chip
10
is displaced from the predetermined position when mounting the semiconductor bare chip
10
by the flip-chip method, the head
13
b
will slip off from the electrode
21
as shown in FIG.
2
B. That is, the head
13
b
touches the top surface of the printed board
20
and the shoulder of the seat
13
a
does not come in contact with the electrode
21
. Because of this, there will be no electrical connection between the stud bump
13
and the electrode
21
.
In the following, a size which allows the semiconductor bare chip
10
to be displaced from a predetermined position P in either one of the directions X
1
and X
2
is referred to as an allowable size e. When mounting the semiconductor bare chip
10
by the flip-chip method, the allowable size e is determined such that the head
13
b
touches an edge of the electrode
21
. The allowable size e is generally (c/2)+(d
2
/2), and is as small as approximately 30 &mgr;m. This requires higher accuracy of a positioning process when mounting the semiconductor bare chip
10
by the flip-chip method. This makes it difficult to mount the semiconductor bare chip
10
. Therefore, a problem arises that the possibility of poor mounting may occur and that of mounting production may be reduced.
SUMMARY OF THE INVENTION
Accordingly, it is a general object of the present invention to provide a semiconductor bare chip, a method of manufacturing a semiconductor bare chip and a mounting structure of a semiconductor bare chip which can solve the problems described above.
It is another and more specific object of the invention to provide a semiconductor bare chip which can achieve an improved yield of production in the mounting process.
In order to achieve the above objects according to the present invention, a semiconductor bare chip includes a plurality of stud bumps provided on the surface of the semiconductor bare chip body, each of the stud bumps including a seat and a head protruding from the seat, wherein a height of the head is less than a thickness of electrodes provided on a board on which the semiconductor bare chip is mounted.
In the semiconductor bare chip described above, the height of the head of the stud bump is determined so as to be smaller than the thickness of the electrode on the board on which the semiconductor bare chip is mounted. When mounting the semiconductor bare chip with each stud bump connected to a corresponding electrode on the board, the semiconductor bare chip may be displaced from its predetermined position. This results in the head slipping of f from the electrode. Even in such a case, the shoulder of the seat touches the electrode, enabling the connection at the seat. Therefore, an allowable amount of displacement of the semiconductor bare chip from the predetermined position can be increased compared to the related art. Thereby, an improved yield of production in mounting process is achieved.
It is still another object of the present invention to provide a method of manufacturing a semiconductor bare chip which can achieve an accurate determination of the thickness of the head of each stud bump.
In order to achieve the above object according to the present invention, a method of manufacturing a semiconductor bare chip which comprises a semiconductor bare chip body and a plurality of stud bumps provided on a surface of said semiconductor bare chip body, each of said stud bumps comprising a seat and a head protruding from said seat, said method comprising the steps of:
a) pressing the semiconductor bare chip against a plate so as to cause a deformation of an end portion of said head; and
b) making an adjustment to a height of said head so that said height of said head is less than a thickness of electrodes provided on a board, said semiconductor bare chip being mounted on said board, said adjustment being achieved by controlling a force exerted by the pressing of step a).
In the method described above, the stud bumps are provided on the surface of the semiconductor bare chip body by wire bonding. A height of the head is adjusted so as to be smaller than a thickness of electrodes on the board. This adjustment is carried out by suitably determining the force exerted when pressing the semiconductor bare chip against the plate. Thereby, the thickness of the head of each stud bump can be determined as a whole wit
Baba Shunji
Fukui Kiyoshi
Kira Hidehiko
Tsunoi Kazuhisa
Armstrong Westerman Hattori McLeland & Naughton LLP
Berezny Nema
Chaudhari Chandra
Fujitsu Limited
LandOfFree
Semiconductor bare chip, method of manufacturing... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Semiconductor bare chip, method of manufacturing..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Semiconductor bare chip, method of manufacturing... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2438091