Electricity: conductors and insulators – Conduits – cables or conductors – Preformed panel circuit arrangement
Reexamination Certificate
2001-09-14
2004-10-05
Cuneo, Kamand (Department: 2827)
Electricity: conductors and insulators
Conduits, cables or conductors
Preformed panel circuit arrangement
C174S250000, C174S254000, C174S261000, C361S774000, C257S737000
Reexamination Certificate
active
06800816
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a wiring circuit board having bumps, where the bumps are of a uniform height, and a method of manufacturing the same.
2. Description of the Related Art
Microscopic bumps (for example, bumps being a diameter of 50 &mgr;m and a height of 30 &mgr;m) are widely used when connecting electronic components such as a semiconductor device and a liquid crystal display device to a wiring circuit board, or when connecting the layers of a multi-layer wiring board.
A typical method of forming bumps of this size is shown in
FIGS. 5A
to
5
E.
Specifically, first, as shown in
FIG. 5A
, a 2 layer flexible board
53
is made up of a polyimide film
51
on a copper toil
52
, and copper toil
52
is patterned by photolithography to form a wiring circuit
54
(FIG.
5
B).
Next, a cover coat layer
55
is formed on wiring circuit
54
in accordance with conventional methods (FIG.
5
C). For example, cover coat layer
55
can be formed by forming a polyamic acid layer on wiring circuit
54
, patterning by photolithography, and imidization. Alternatively, a resist ink may also be printed thereon.
Next, the area on polyimide film
51
that corresponds to wiring circuit
54
is irradiated with laser light to form bump holes
56
(FIG.
5
D). Then, after covering cover coat layer
55
with a protective film as needed (not shown in the Figures), microscopic bumps are formed by growing metal bumps
57
by means or electrolytic plating on the portions of wiring circuit
54
that are exposed in the bottom of bump holes
56
(FIG.
5
E).
However, when opening bump holes
56
by means of laser irradiation, there is a problem with variations in open space due to variations in the amount of smear adhered to the bottom of bump holes
56
, and as a result, there is a problem with large variations developing in the height of metal bumps
57
. Because of this, stable bump connections are difficult. In particular, connecting semiconductor devices to the wiring circuit in one batch by means of ultrasound is difficult. In addition, a plating pre-treatment Is essential in order to improve the strength of the adherence between wiring circuit
54
and the metal bumps
57
formed thereon.
SUMMARY OF THE INVENTION
An object of the present invention is to solve the aforementioned problems in the prior art, make stable bump connections possible, and to provide a method of manufacturing a wiring circuit board with bumps that makes complex operations such as plating pre-treatment unnecessary.
The present inventor has discovered that bumps with a uniform height and a surface roughness on the tip faces thereof of 0.2 to 20 &mgr;m can be formed by half etching a metal foil with a surface roughness of 0.2 to 20 &mgr;m and a thickness that is the sum of the thickness corresponding to the height of the metal bumps and the thickness of the wiring circuit layer, to a depth corresponding to the desired thickness of the metal bumps, without performing complex operations such as plating pre-treatment, and thus stable bump connections can be realized. The present inventor has finally achieved the present invention.
Specifically, the present invention provides a wiring circuit board having bumps in which a cover coat layer is formed on a first side of a wiring circuit, an insulating layer is formed on a second side of the wiring circuit, and bumps in continuity with the wiring circuit are formed such that they project from said insulating layer, wherein the wiring circuit and bumps are integrally formed from one metal foil, and a surface roughness of the tip faces of the bumps is 0.2 to 20 &mgr;m.
In this wiring circuit board having bumps, it is preferred that a metallic thin film layer consisting of a metal different from the metal foil is provided between a bump formation surface on the wiring circuit and the insulating layer, in order to improve the adhesive strength between the insulating layer and the metal foil. In particular, in the event that the insulating layer is a polyimide layer imidized from a polyimide precursor layer, it is preferred that the metallic thin film layer exhibits an adhesive strength to the polyimide precursor layer that is higher than the metal foil. In this way, the adhesiveness with the polyimide precursor layer (and the imidized layer) can be improved. A combination of copper foil for the metal foil, and a thin film of Ni, Zn, Sn or Ni—Co alloy and the like for the metallic thin film layer can be preferably mentioned as a combination for this type of metal foil and metallic thin film layer.
In addition, it is preferred that the cover coat layer has a connection aperture that allows access to the wiring circuit from the cover coat side.
In addition, the present invention provides a method of manufacturing a wiring circuit board having bumps in which the bumps formed on the wiring circuit have a surface roughness on the tip fares thereof of 0.2 to 20 &mgr;m, the manufacturing method comprising the steps of:
(a) laminating a protective film on a bump formation surface of a metal foil having a surface roughness of 0.2 to 20 &mgr;m and a thickness which is the sum of a thickness of the wiring circuit and a height of the bumps to be formed on the wiring circuit, and forming an etching mask for wiring circuit formation on a wiring circuit formation surface of the metal foil;
(b) half etching the metal foil from the side of the etching mask for wiring circuit formation to form a wiring circuit with a desired thickness;
(c) providing a cover coat layer on the wiring circuit after removing the etching mask for wiring circuit formation;
(d) forming an etching mask for bump formation on the bump formation surface after removing the protective film provided on the bump formation surface of the metal foil;
(e) half etching the metal foil from the side of the etching mask for bump formation to form bumps of the desired height;
(f) forming a polyimide precursor layer to cover the bumps after removing the etching mask for bump formation; and
(g) etching back the polyimide precursor layer and imidizing the same to form an insulating layer with a desired thickness. In this method of manufacturing, the wiring circuit is formed before bump formation.
In step (f) of this method of manufacturing, it is preferred that a metallic thin film consisting of a metal different from the metal foil (in particular, a metal having an adhesiveness to the polyimide precursor layer that is higher than the metal foil) is formed after the etching mask for bump formation is removed, and a polyimide precursor layer to cover the bumps is formed on the metallic thin film layer. In this way, the adhesiveness with the polyimide precursor layer (and the imidized layer) can be improved.
The present invention also provides a method of manufacturing a wiring circuit board having bumps in which the bumps formed on the wiring circuit have a surface roughness on the tip face thereof of 0.2 to 20 &mgr;m, the manufacturing method comprising the steps of:
(aa) laminating a protective film on the wiring circuit formation surface of the metal foil which has a surface roughness of 0.2 to 20 &mgr;m and having a thickness which is the sum of a thickness of the wiring circuit and a height of the bumps to be formed on the wiring circuit, and forming an etching mask for bump formation on a bump formation surface of the metal foil;
(bb) half etching the metal foil from the side of the etching mask for bump formation to form bumps of the desired height;
(cc) forming a polyimide precursor layer to cover the bumps after removing the etching mask for bump formation:
(dd) half etching the polyimide precursor layer and imidizing the same to form an insulating layer with a desired thickness;
(ee) forming an etching mask for wiring circuit formation on a wiring circuit formation surface after removing the protective film provided on the wiring circuit formation surface of the metal foil;
(ff) half etching the metal foil from the side of the etching mask for wiring circuit formation to form
Cuneo Kamand
Patel I B
Sony Chemicals Corp
LandOfFree
Wiring circuit board having bumps and method of producing same does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Wiring circuit board having bumps and method of producing same, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Wiring circuit board having bumps and method of producing same will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3268028