Radiation imagery chemistry: process – composition – or product th – Imaging affecting physical property of radiation sensitive... – Radiation sensitive composition or product or process of making
Reexamination Certificate
1998-11-25
2001-07-17
Hamilton, Cynthia (Department: 1752)
Radiation imagery chemistry: process, composition, or product th
Imaging affecting physical property of radiation sensitive...
Radiation sensitive composition or product or process of making
C430S285100, C430S906000, C430S325000, C430S311000
Reexamination Certificate
active
06261741
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a photosensitive heat-resistant resin composition. The present invention also relates to a method of patterning a heat-resistant insulating film made of such a resin composition. The present invention further relates to a patterned heat-resistant insulating film.
More specifically, a photosensitive heat-resistant resin composition according to the present invention contains a polyamideimide and an acrylic resin as main components. The polyamideimide is excellent in heat-resistance, electrical insulation and toughness, whereas the acrylic resin has a nature of polymerizing or hardening under light irradiation. Thus, the resin composition of the present invention may be used as a photo-curing adhesive or for providing a minutely patterned insulating layer in a high-density printed circuit board (including a build-up multilayer circuit board) or in high-density electronic devices.
2. Description of the Related Art
Due to recent demand for size reduction, higher performance and lower cost with respect to electronic apparatuses, there has been a rapid development toward sophistication of printed circuit boards and high-density packaging of electronic devices, which has led to an active study as to a build-up multilayer wiring structure. In a build-up multilayer wiring structure, an insulating film is interposed between different wiring conductor layers, and the insulating film is minutely patterned to have via-holes for establishing electrical conduction between the different wiring conductor layers.
For the convenience of explanation, reference is now made to
FIGS. 1 and 2
of the accompanying drawings for more specifically describing the build-up multilayer wiring structure.
FIG. 1
is a fragmentary sectional view showing a conventional build-up multilayer wiring structure, whereas
FIG. 2
is a perspective view showing a glass mask used for making such a multilayer wiring structure.
Referring first to
FIG. 1
, the conventional build-up multilayer wiring structure includes a first wiring conductor pattern
2
formed on each surface of a core substrate
1
which is provided with through-holes
1
a
(only one shown in FIG.
1
). The first wiring conductor pattern
2
on one surface of the core substrate
1
is electrically connected to the first wiring conductor pattern on the opposite surface of the core substrate by way of the through-holes
1
a.
Each surface of the core substrate
1
is also formed with an insulating film
3
which is suitably patterned to have via-holes
3
a
. Further, the surface of the insulating film
3
is formed with a second wiring conductor pattern
4
which partially extends into the respective via-holes
3
a
into electrical conduction with the first wiring conductor pattern
1
. Depending on a particular need, an additional insulating film (or films) similarly formed with additional via-holes and an additional wiring conductor pattern may be provided to enhance the degree of circuit integration in the thickness direction without increasing the two-dimensional size (i.e., width and length).
The build-up multilayer wiring structure described above may be made by the following process.
First, a core substrate
1
is prepared which is provided with through-holes
1
a
and a first wiring conductor pattern
2
. Each of the through-holes
1
a
is filled with an insulating resin
5
.
Then, a photosensitive resin is uniformly applied to each surface of the core substrate
1
for forming a photosensitive resin layer
3
.
Then, as shown in
FIG. 2
, a glass mask
6
is held in contact with the applied photosensitive resin layer
3
(which is not cured yet), and the photosensitive resin layer is irradiated with light. The glass mask
6
has impervious spots
6
a
, so that the portions of the photosensitive resin layer
3
corresponding to the impervious spots
6
a
are not exposed to light and therefore does not harden.
Then, the resin layer
3
is developed with a developer liquid and thereafter heat-treated for removal the developer liquid. As a result, via-holes
3
a
are formed at the portions of the resin layer
3
(insulating film) corresponding to the impervious spots
6
a
of the glass mask
6
by removal of the non-cured photosensitive resin.
Then, a conductor layer is formed on the patterned insulating film
3
by electroless plating or electroplating.
Then, the conductor layer is suitably etched to form a second wiring conductor pattern
4
.
The degree of circuit integration may be increased by repeating the above process steps.
As a material for forming an insulating film in a build-up multilayer wiring structure or the like, a photosensitive resin composition is known which contains bisphenol epoxy acrylate, a photosensitivity enhancer, an epoxy compound and a curing agent for example (see JP-A-50-144431 and JP-A-51-40451). However, such a resin composition requires a large quantity of an organic solvent for development, so that sufficient care needs to be taken for avoiding environmental pollution and a risk of fires.
Recently, therefore, use is made of a photosensitive resin composition which can be developed with a dilute alkaline water solution in place of an organic solvent. For instance, JP-A-56-40329 and JP-A-57-45785 disclose an alkaline-developing type photosensitive resin composition containing, as a base polymer, the reaction product of an epoxy resin and an unsaturated monocarboxylic acid, to which is added a polybasic acid anhydride. Further, JP-A-61-243869 discloses an alkaline-developing type photosensitive resin composition containing novolak epoxy, this resin composition providing a good chemical resistance.
However, the epoxy-based photosensitive resin composition of the prior art described above has a glass transition temperature (Tg) of no higher than 150° C., so that it fails to provide a sufficient heat-resistance. Further, since the prior art resin composition also contains a filler such as calcium carbonate in a proportion of no less than 10 wt % relative to the epoxy resin, it may fail to provide a sufficient electrical insulation if the insulating film made of the resin composition is thin or if the intervals between the wires of the wiring conductor pattern are narrow (i.e., if the wiring conductor pattern is formed excessively fine).
SUMMARY OF THE INVENTION
It is, therefore, an object of the present invention is to provide a photosensitive heat-resistant resin composition which is excellent in photosensitivity and heat resistance for suitably forming an insulating film in a build-up printed circuit board.
Another object of the present invention is to provide a method of patterning an insulating film made of such a resin composition.
A further object of the present invention is to provide a patterned insulating film obtained by such a method.
According to a first aspect of the present invention, there is provided a photosensitive heat-resistant resin composition comprising a polyamideimide resin, an organic solvent for dissolving the polyamideimide, an acrylic monomer or oligomer having at least two polymerizable double bonds, and a photoreaction initiator for initiating polymerization of the acrylic monomer or oligomer by photochemical reaction.
The resin composition described above, when irradiated with light, hardens due to photochemical polymerization of the acrylic monomer or oligomer, and the acrylic polymer and the polyamideimide coexist in the hardened portion. Further, the resulting insulating film exhibits an excellent heat resistance due to the presence of the polyamideimide.
Preferably, the resin composition may further comprise a photosensitivity enhancer for enhancing the photochemical polymerization of the acrylic monomer or oligomer.
According to a second aspect of the present invention, there is provided a method of patterning a heat-resistant insulating film which is made of the photosensitive heat-resistant resin composition described above. Specifically, the method comprises the steps of: applying the resin compo
Hayashi Nobuyuki
Machida Hiroyuki
Tani Motoaki
Armstrong Westerman Hattori McLeland & Naughton LLP
Fujitsu Limited
Hamilton Cynthia
LandOfFree
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