This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2000-159163, filed Mar. 31, 2000, the entire contents of which are incorporated herein by reference.
The present invention relates to a method of forming a composite member, in which a conductive portion is formed in an insulator, the composite member being used in, for example, a wiring board in the fields of electric appliances, electronic appliances and electric and electronic communication. The present invention also relates to a photosensitive composition and an insulating material that can be suitably used in the manufacturing method of the composite member. Further, the present invention relates to a composite member manufactured by the manufacturing method of the present invention and to a multi-layer wiring board and an electronic package including the particular composite member.
In recent years, increase in the degree of integration and miniaturization of various electric and electronic parts including a semiconductor device are being promoted. The particular tendency will be further promoted in the future without fail. In this connection, various measures are being proposed and tried in an attempt to apply a high density mounting to a printed circuit board including formation of a fine pattern and a fine pitch of a metal wiring and formation of a steric wiring.
Particularly, the steric wiring is indispensable to a high density mounting and, thus, various methods are being proposed in an attempt to manufacture a wiring board having a steric wiring. In general, the steric wirings are of a multi-layered structure such as a built-up wiring board prepared by laminating two dimensional printed wiring boards and a multi-layered wiring board. It is difficult to form a steric wiring having a free three dimensional shape. The built-up wiring board or the multi-layered wiring board has a structure that adjacent wiring layers are connected to each other by a conductive column called via. The via is formed by processing an insulating layer by a photolithography process using a photosensitive polyimide or resist, followed by selectively applying a plating to the via or by filling the via with a conductive paste. For forming a via by such a method, it is necessary to repeat a plurality of times the steps of resist coating, light exposure and etching, making the via formation highly laborious. In addition, it is difficult to improve the yield.
It is also possible to form the via by forming a through-hole (via hole) of a predetermined size in an insulating substrate constituting a printed wiring board by using a drill or a CO2 laser, followed by applying plating to the via hole or by filling the via hole with a conductive paste. In these methods, however, it is difficult to form freely a fine via having a size of scores of microns or less at a desired position.
In the method disclosed in Japanese Patent Disclosure No. 7-207450, a compound having a hydrophilic group is introduced into pores of three dimensional porous film such as a PTFE film. Under this condition, the film is subjected to a light exposure in a predetermined pattern by using a low pressure mercury lamp (wave lengths of 185 nm and 254 nm), thereby forming the hydrophilic group on the three dimensional porous film. Further, a metal plating is applied to the three dimensional porous film.
In the conventional method described above, however, the material forming the three dimensional porous film is deteriorated because a light beam having a short wavelength is used for the light exposure. Also, the light for the light exposure is absorbed by the three dimensional porous film and, thus, fails to reach the inner region of the porous body, resulting in failure to form fine vias.
Further, in the conventional method described above, the PTFE forming the three dimensional porous film reacts with the light for the light exposure so as to selectively form hydrophilic groups. However, PTFE is defective in that the molding workability is low and that PTFE is costly.
Another method of forming a via is disclosed in Japanese Patent Disclosure No. 11-24977. In this method, the entire surface of a porous insulating member is impregnated with a photosensitive composition containing, for example, a photosensitive reducing agent and a metal salt. Then, a light exposure is applied in a predetermined pattern to the impregnated insulating member so as to reduce the cation of the metal salt in the light exposed portion to a metal nucleus, followed by removing by washing the photosensitive composition in the non-light exposed portion. Further, an electroless plating or a soldering is applied to the residual metal nuclei so as to form vias of a predetermined pattern.
In the method described above, however, the entire surface of the porous insulating member is impregnated with a photosensitive composition containing a metal salt as described above, making it difficult to remove completely the metal salt adsorbed on the portion corresponding to the non-exposed portion after the light exposure step. As a result, a difficulty is brought about that the metal nuclei are precipitated on undesired portions in the subsequent reducing step. Such an abnormal deposition of the metal nuclei gives rise to a problem in terms of the insulating properties between adjacent vias and between adjacent wiring layers with progress in the fine pulverization of the pattern.
Also, in the via formed in the insulating substrate by the conventional method of manufacturing a wiring board, the insulating body and the conductive portion are brought into a direct contact. In this case, since the adhesion between the insulating body and the conductive portion is poor, a problem is generated that the conductive portion is peeled off the insulating substrate during the use.
Further, where a multi-layered wiring board is prepared by laminating a plurality of wiring boards manufactured by the conventional method of manufacturing a wiring board, it is required to further improve the electrical connection between the wiring layers of the wiring boards and the conductivity of the wiring.
An object of the present invention is to provide a method of manufacturing a composite member, which has a high degree of freedom in the design of a conductive circuit, in which deterioration of the insulating body is not brought about by the light exposure, and which is free from an abnormal deposition of a metal on the insulating body so as to form a conductive portion having a fine pattern.
Another object of the present invention is to provide a method of manufacturing a composite member, which has a high degree of freedom in the design of a conductive circuit, which permits manufacturing a composite member at a low manufacturing cost without giving adverse effects to the selectivity of the material of the insulating portion and to the molding workability, and which is free from an abnormal deposition of a metal on the insulating body so as to form a conductive portion having a fine pattern.
Another object of the present invention is to provide a photosensitive composition and an insulating material used for the manufacturing method of a composite member described above.
Another object of the present invention is to provide a composite member manufactured by the method described above.
Another object of the present invention is to provide a multi-layered wiring board comprising a composite member manufactured by the method described above.
Still another object of the present invention is to provide an electronic package using a composite member or a multi-layered wiring board manufactured by the method described above.
According to a first aspect of the present invention, there is provided a method of manufacturing a composite member in which a conductive portion is selectively formed in an insulating body, comprising:
(1) forming a photosensitive composition layer within or on the surface of said insulating body, said photosensitive composition containing a compound forming an ion-exchange group upon irradiation with light having a wavelength not shorter than 280 nm;
(2) exposing selectively the photosensitive composition layer to light having a wavelength not shorter than 280 nm so as to form ion-exchange groups in the light exposed portion; and
(3) forming the conductive portion by bonding a metal ion or metal to the ion-exchange group formed in the light exposed portion by the exposing.
According to a second aspect of the present invention, there is provided a method of manufacturing a composite member in which a conductive portion is selectively formed in an insulating body, comprising:
(1) forming a photosensitive composition layer within or on the surface of said insulating body, said photosensitive composition containing a compound having an ion-exchange group;
(2) exposing selectively the photosensitive composition layer to light having a wavelength not shorter than 280 nm so as to cause ion-exchange groups in the light exposed portion to disappear and to cause the ion-exchange groups to remain in the unexposed portion; and
(3) forming the conductive portion by bonding a metal ion or metal to be bonded to the ion-exchange group remaining in the unexposed portion after the exposing.
According to a third aspect of the present invention, there is provided a method of manufacturing a composite member in which a conductive portion is selectively formed in an insulating body, comprising:
(1) forming a photosensitive composition layer within or on the surface of said insulating body, said photosensitive composition containing a compound forming an ion-exchange group upon irradiation with light, and said compound being selected from the group consisting of an onium salt derivative, a sulfonium ester derivative, a carboxylic acid derivative and a naphthoquinone diazide derivative;
(2) exposing selectively the photosensitive composition layer to light so as to form ion-exchange groups in the light exposed portion; and
(3) forming the conductive portion by bonding a metal ion or metal to the ion-exchange group formed in the light exposed portion by the exposing.
According to a fourth aspect of the present invention, there is provided a method of manufacturing a composite member in which a conductive portion is selectively formed in an insulating body, comprising:
(1) forming a photosensitive composition layer within or on the surface of said insulating body, said photosensitive composition containing a compound having an ion-exchange group;
(2) exposing selectively the photosensitive composition layer to light so as to cause ion-exchange groups in the light exposed portion to disappear and to cause the ion-exchange groups to remain in the unexposed portion; and
(3) forming the conductive portion by bonding a metal ion or metal to the ion-exchange group remaining in the unexposed portion after the light exposure in a pattern.
According to a further aspect of the present invention, there is provided a method of manufacturing a composite member in which a conductive portion is selectively formed in an insulating body, comprising:
(1) forming a photosensitive composition layer within or on the surface of said insulating body, said photosensitive composition containing a compound forming an ion-exchange group in the presence of acid and a photo acid generating agent;
(2) exposing selectively to light and heating the photosensitive composition layer so as to form ion-exchange group in the light exposed portion; and
(3) forming the conductive portion by bonding a metal ion or metal to the ion-exchange group formed in the light exposed portion by the exposing.
It is desirable for the method of the present invention to further comprise the step of applying an electroless plating to the surface of the conductive portion formed in the third step.
According to another embodiment of the present invention, there is provided a photosensitive composition used for manufacturing a composite member, the composition containing a naphthoquinone diazide derivative and a polycarbodiimide derivative.
According to another embodiment of the present invention, there is provided a porous insulating body having the inner surface of the pore covered with a photosensitive composition containing a naphthoquinone diazide derivative.
According to another embodiment of the present invention, there is provided a composite member having a conductive portion formed on at least one of the surface and the inner region of a porous insulating body via an organic compound, wherein the amount of the organic compound, which is present between the insulating body and the conductive portion, per unit area of the surface of the insulating body is larger than the amount of the organic compound that is not in contact with the conductive portion.
According to another embodiment of the present invention, there is provided a multi-layered wiring board including a plurality of substrates that are laminated one upon the other, wherein the substrate comprises a porous insulating body having fine pores and a conductive portion formed on at least one of the surface and the inner region of the fine pore of the porous insulating body, and a layer formed of a conductive body that does not contain the component of the insulating body is formed on the outermost surface of the conductive portion of each substrate.
Further, according to still another embodiment of the present invention, there is provided an electronic package comprising a wiring board consisting of the composite body described above or a multi-layered wiring board described above and an electronic part electrically connected to the wiring board.