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
2000-09-20
2003-03-04
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
C430S283100, C430S285100, C430S906000, C522S137000, C522S138000, C522S167000
Reexamination Certificate
active
06528236
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to a photosensitive resin composition having both ultraviolet-setting property and thermosetting property. More particularly, the present invention relates to a photosensitive resin composition that can be utilized in various fields such as the fields of coating materials, printing industry and electronics industry as an ultraviolet-setting coating material, a plate-making material or the like and is used as, in particular, an adhesive between circuit layers in, for example, printed wiring boards for livelihood and printed wiring boards for industry. In addition, the present invention relates to a multilayer printed wiring board comprising insulating layers of said photosensitive resin composition used as an adhesive between circuit layers, and a process for producing the multilayer printed wiring board.
In recent years, so-called “improvements for high-density packaging” involving the formation of a fine pattern and multiple layers of wiring have proceeded in printed wiring boards, with a reduction in size and an improvement in performance characteristics of electronic machines. As high-density printed wiring boards such as those for mounting semiconductor chips, multilayer printed wiring boards have been widely used which are produced by a build-up method comprising laminating insulating layers and wiring layers alternately on a substrate.
The insulating layers of the multilayer printed wiring board produced by the conventional build-up method are formed not by impregnating a core material such as glass cloth with an insulating material, but by applying a photosensitive resin composition on a substrate without a core material and light-curing and heat-curing the composition. Properties required of the photosensitive resin composition in this production process are, for example, as follows: the composition can form a uniform coating film having no void, on an internal circuit layer having a certain degree of unevenness; the composition is photosensitive and developable and has a sufficient resolution to form desirable via holes; the composition is resistant to chemicals such as a plating solution and a surface-treating agent; and the composition is flexible for preventing the formation of cracks by application of force in a production and construction process using a thin substrate obtained by coating a substrate.
The printed wiring board produced is required to have electrical insulating properties and heat resistance for soldering in mounting of parts. When a semiconductor is directly mounted, the printed wiring board is required to have, for example, resistance to wire bonding and resistance to heat cycle. For attaining these heat resistances, it is necessary to use a photosensitive resin composition having a high glass transition temperature. However, there is no photosensitive resin composition having the various properties described above.
At present, so-called photo-solder resists are known as photosensitive insulating materials and are often used as an adhesive between circuit layers. For example, JP-A-4(1992)-148590 discloses a multilayer wiring board obtained by forming photo-via holes by using a photosensitive epoxy resin. In addition, there is, for example, a composition comprising a phenolic resin having acryloyl groups or methacryloyl groups, a polyfunctional epoxy compound and a photopolymerization initiator (JP-B-7(1995)-49464). However, when such a photosensitive epoxy resin is used as a main constituent, the resulting composition is disadvantageous in that it has a low glass transition temperature, resulting in many limitations on a method for mounting of parts.
In general, properties such as dynamic visco-elastic modulus, thermal expansion coefficient and dielectric constant of the insulating layer of a printed wiring board markedly change at the glass transition point of the insulating layer. Therefore, when the insulating layer is heated to a temperature higher than the glass transition point, there is a fear that ply separation may be caused between a substrate and the insulating layer or between the insulating layer and a wiring layer. There is also a fear of marked change in the electric characteristics of the insulating layer.
When a part to be mounted such as a semiconductor chip is mounted on a multilayer printed wiring board produced by the build-up method, the glass transition temperature should be about 150° C. or higher in order that the printed wiring board can withstand thermal stress in a heating step.
However, a printed wiring board produced by the build-up method by the use of a conventional photosensitive resin composition is disadvantageous in that it does not satisfy the above requirement because the glass transition temperature of its insulating layer is about 130° C.
An electroconductive layer on the inner surface of each via hole formed in either a wiring layer on the insulating layer of a printed wiring board produced by the build-up method or the insulating layer is formed by a plating method. The peel strength of a plating layer on the insulating layer should be 800 N/m or more in practice in order that the plating layer may not peel off owing to heat history.
Conventional printed wiring boards, however, are disadvantageous in that they do not satisfy the above requirement because the peel strength of a plating layer on the insulating layer of the printed wiring board is about 600 N/m.
SUMMARY OF THE INVENTION
The present invention has been accomplished as a result of earnest investigation carried out in view of the problems described above. An object of the present invention is to provide a photosensitive resin composition for an adhesive between circuit layers which can be developed with an aqueous developing solution containing no organic solvent, has various characteristics required of a internal-layer material for a multilayer wiring board, such as a high adhesion to a substrate, i.e., a high peel strength for a wiring layer, and has an especially excellent heat resistance, and to provide a highly reliable printed wiring board obtained by using said resin composition and a process for producing the printed wiring board.
The present inventors found that a photosensitive resin composition comprising an unsaturated imide compound as an essential constituent has a high glass transition temperature by virtue of the rigid structure of the unsaturated imide compound.
The present inventors also found the following. Particularly when the unsaturated imide compound is a bismaleimide type compound, it does not produce a substituent that is subject to oxidative cleavage, even when it is reacted with a phenolic hydroxyl group. Therefore, an epoxy compound capable of producing a hydroxyethylene group by reaction with a phenolic hydroxyl group is used together with the unsaturated imide compound to facilitate oxidative cleavage. Thus, when a wiring layer is formed on a resin layer, fine anchors are formed in the resin layer, resulting in a high peel strength between the resin layer and the wiring layer.
The present inventors also found the following. When the unsaturated imide compound contains a maleimide type addition compound, the presence of functional groups such as carboxyl group, unsaturated imide group and amide group in the maleimide type addition compound is advantageous in that the photosensitive resin composition has, of course, a high glass transition temperature, is soluble in an alkaline aqueous solution, and has an excellent resolution. In addition, the photosensitive resin composition can be expected to have a high adhesion to a substrate. Furthermore, treatment of the photosensitive resin composition with a permanganate or the like before plating exposes the functional groups good in plate adhesion, resulting in strong binding to a plating layer, and hence a high peel strength can be attained between the photosensitive resin composition and a wiring layer. The present invention has been accomplished on the basis of the above findings.
That is, the present invention
Amano Koji
Fujiwara Makoto
Fukase Toshimitsu
Hamilton Cynthia
Smith , Gambrell & Russell, LLP
Sumitomo Bakelite Co. Ltd.
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