Electricity: conductors and insulators – Conduits – cables or conductors – Preformed panel circuit arrangement
Reexamination Certificate
1999-07-21
2001-07-10
Gaffin, Jeffrey (Department: 2841)
Electricity: conductors and insulators
Conduits, cables or conductors
Preformed panel circuit arrangement
C174S262000, C174S263000, C174S267000, C257S738000, C257S778000, C257S780000, C361S771000, C361S774000, C361S767000, C361S768000, C356S370000, C356S370000
Reexamination Certificate
active
06259038
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a circuit board for mounting a semiconductor chip (hereinafter referred to as a circuit board), wherein conductor bumps to be electrically connected to electrodes of the semiconductor carried on a substrate of the circuit board are formed on conductor pads formed on a surface of the substrate of the circuit board, and a method for inspecting the same.
2. Description of the Related Art
As examples of such a circuit board as described above, there are a first circuit board shown in
FIGS. 14
to
16
and
17
to
19
and a second circuit board shown in
FIGS. 20
to
22
.
In the first circuit board, a circuit pattern
20
is formed on a surface of a substrate
10
thereof. A conductor pad
30
of a disc shape or other is formed on the circuit pattern
20
. The substrate
10
is made of insulating material such as resin or ceramic. The circuit pattern
20
and the conductor pad
30
are formed by etching a copper foil adhered to the surface of the substrate
10
or by etching a metal skin applied to the surface of an insulating resin layer by a build-up system on the substrate
10
.
A resist layer
40
comprised of insulating resin or the like is broadly formed on the surface of the substrate
10
for the purpose of preventing solder from sticking to the surface of the substrate
10
.
The first circuit board shown in
FIGS. 14
to
16
has an opening
50
in the resist layer
40
, in which are consecutively exposed the conductor pad
30
, the circuit pattern
20
adjacent thereto and a surface of a portion of the substrate
10
therearound.
The first circuit board shown in
FIGS. 17
to
19
has an opening
50
in the resist layer
40
, in which is exposed a central portion of the conductor pad
30
.
A conductor bump
60
is formed on the conductor pad
30
exposed in the opening
50
, which is of a sermispherical shape and constituted by conductive resin plated with solder or Au or mixed with conductive filler.
On the other hand, a metallized conductor pad
30
of a disc shape is provided on the surface of the substrate
10
made of ceramic or the like in the second circuit board. The conductor pad
30
is connected to the upper end of a column-like metallized conductor via
22
pierced through the substrate
10
in the thickness direction. The conductor via
22
constitutes a circuit pattern.
A resist layer
40
formed of insulating resin or the like is broadly formed on the surface of the substrate
10
for the purpose of preventing solder from sticking thereto. A circular opening
50
is formed in the resist layer
40
so that a central portion of the conductor pad
30
is exposed therein.
A conductor bump
60
is formed on the conductor pad
30
exposed in the opening
50
and is of a semispherical shape and is constituted by conductive resin plated with solder or Au or mixed with conductive filler.
In the prior art, when the first circuit board and the second circuit board are inspected, as shown in
FIG. 16
,
19
or
22
, a height hl from the surface of the resist layer
40
to a top of the conductor bump
60
is measured by means of an optical detector using a laser beam or a visible ray (hereinafter referred merely to a “photometer”) or a CCD (which is an abridgement of Charge Coupled Device) camera. Then, based on this measured value, a height h
2
from the surface of the substrate
10
to the top of the conductor bump
60
or a height h
3
from the upper surface of the conductor pad
30
to the top of conductor bump
60
are estimated. Next, based on this estimated value, a variation of heights of the conductor bumps is determined. Finally, based on this variation, it is determined whether or not the above-mentioned first and second circuit boards are acceptable.
The determination of whether or not the first and second circuit boards are acceptable is important because, if a large variation exists in height of the respective conductor bump
60
formed on the conductor pad
30
exposed in each of a plurality of openings
50
formed in the resist layer
40
in a matrix manner as shown in
FIGS. 23 and 24
, there might be a risk in that when a plurality of conductor bumps
90
formed on electrodes arranged in correspondence to the conductor pads
30
on one side of a semiconductor chip
80
in a matrix manner are pressed onto the plurality of conductor bumps
60
at a predetermined pressure so that both the conductor bumps
60
,
90
are at once welded or pressbonded together, all of the conductor bumps
60
and
90
may not be electrically connected to each other in a reliable manner.
According to the above-mentioned determination in the prior art wherein the height h
1
is first measured, then the heights h
2
and h
3
are estimated thereby, and finally the variation of the height of the conductor bump
60
is calculated from the estimated values, it is impossible to correctly obtain the actual variation of the height of the conductor bump
60
.
This reason therefor is as follows.
There are two methods for forming the resist layer
40
; one method wherein a resist liquid is coated broadly on the surface of the substrate
10
, which is then dried at a high temperature, and another method wherein a dry film of resist formed in a sheet form is adhered onto the surface of the substrate
10
, which is then dried at a high temperature.
The surface of the resist layer
40
formed broadly on the surface of the substrate
10
by these methods is not evenly flat but tends to undulate up and down, causing a variation in height everywhere on the surface of the resist layer
40
.
Therefore, it impossible to use the surface of the resist layer
40
formed on the surface of the substrate
10
in the above-mentioned manner as a reference surface for the correct estimation of the height h
2
or h
3
.
To solve such a problem, two methods are proposed; a first one wherein the height h
2
is directly measured by an optical detector or a CCD camera while using, as a reference surface, the surface of the substrate
10
in the vicinity of the conductor bump
50
exposed in the opening
50
, and a second one wherein the height h
3
is directly measured by an optical detector or a CCD camera.
According to the first or second method, it is believed that the variation f a height of the conductor bump
60
formed on the substrate
10
is correctly determined.
The first and second methods, however, could not be applied to the above-mentioned first or second circuit board of the prior art.
The reason why the height h
2
from the surface of the substrate
10
to the top of the conductor bump
60
could not be measured by the first method is that a gap between the conductor bump
60
and the inner wall of the opening
50
is too narrow as shown in
FIGS. 15 and 16
, and therefore a width of the surface area of the substrate
10
exposed in the gap is also too small. When one wishes to directly measure the height h
2
from the surface of the substrate
10
in the vicinity of the bump
60
exposed in the opening
50
to the top of the conductor bump
60
by the first method while using the optical detector, it is necessary to emit a laser beam or a visible ray from the optical detector disposed above the resist layer
40
onto the surface of the substrate
10
and reflect or diffuse the same to be directed to the optical detector. Such a reflected or diffused ray, however, is difficult to make incident upon the optical detector due to the interference with the conductor bump
60
or the resist layer
40
. on the other hand, if a CCD camera is used to directly measure the height from the surface of the substrate
10
in the vicinity of the bump
60
exposed in the opening
50
to the top of the conductor bump
60
by the first method, it is also difficult to focus the CCD camera on the surface of the substrate
10
of a narrow width.
To enable the height h
2
to be directly measured by the first method while using an optical detector, a CCD camera or the like, it is suggested to provide a large opening
50
in the re
Arai Kenkichi
Koizumi Naoyuki
Sakaguchi Hideaki
Gaffin Jeffrey
Patel I B
Pennie & Edmonds LLP
Shinko Electric Industries Co. Ltd.
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