Active solid-state devices (e.g. – transistors – solid-state diode – Combined with electrical contact or lead – Of specified configuration
Reexamination Certificate
1999-06-21
2001-12-04
Potter, Roy (Department: 2822)
Active solid-state devices (e.g., transistors, solid-state diode
Combined with electrical contact or lead
Of specified configuration
C257S701000
Reexamination Certificate
active
06326694
ABSTRACT:
FIELD OF THE INVENTION
This invention relates to a printed circuit board used for electronic devices, and further relates to a method of manufacturing the printed circuit board.
BACKGROUND OF THE INVENTION
Recently, following the tendency of electronic devices towards compact size and higher mounting density, multilayer printed circuit boards have been strongly demanded, not only for industrial but also for consumer use. This type of multilayer printed circuit boards requires employing inner-via-hole connections between a plurality of circuit patterns and also requires high reliability.
A conventional method of manufacturing a double sided printed circuit board is described as follows. FIGS.
8
(
a
) to (
e
) are cross-sectional views showing a method of manufacturing a conventional double sided printed circuit board. First, an insulating substrate
801
such as glass-epoxy is provided as shown in FIG.
8
(
a
). Then, copper foils
802
are applied on both sides of insulating substrate
801
as shown in FIG.
8
(
b
). Subsequently, insulating substrate
801
and copper foils
802
are bonded to each other through heating and pressurization. Thereafter, by using a conventional technique such as etching or the like, copper foils
802
are formed into a first circuit pattern
805
and a second circuit pattern
806
as illustrated in FIG.
8
(
c
). Next, as shown in FIG.
8
(
d
), through-holes
803
are drilled at places where first circuit pattern
805
and second circuit pattern
806
will be electrically connected. After that, conductive paste
804
is filled into through-holes
803
by a printing process as shown in FIG.
8
(
e
), and the paste is hardened.
In the manner as described above, first circuit pattern
805
and second circuit pattern
806
are connected by conductive paste
804
filled into through-holes
803
, and thus, a double sided printed circuit board
807
is obtained.
However, the above-mentioned conventional structure has the problem that adhesion between the conductive paste and the wall surface of the through-hole is poor. In addition, there is a gap in coefficient of thermal expansion between the conductive paste and the insulating substrate so that a boundary face of the conductive paste and the through-hole breaks due to the thermal shock of solder dipping. As a result, a failure in continuity occurs.
SUMMARY OF THE INVENTION
It is an objective of this invention to solve the above-noted problems in the conventional system by improving adhesion between the conductive resin compound and the wall surface of the through-hole in the substrate. Another object of this invention is to provide a printed circuit board with high reliability. A further object of this invention is to provide a method of manufacturing this printed circuit board.
In order to accomplish these and other objects and advantages, a printed circuit board of the first embodiment of the invention comprises a resin impregnate fiber sheet substrate with through-holes formed in the thickness direction and a conductive resin compound filled into the through-holes in the thickness direction for electrical connection, wherein the substrate and the conductive resin compound are bonded to each other chemically and physically.
It is preferable that the substrate and the conductive resin compound are bonded to each other such that the conductive resin compound penetrates into the substrate.
Furthermore, it is preferable that the conductive resin compound comprises metallic particulates and resin, and in addition, that the substrate and the conductive resin compound are bonded to each other through impregnation of the resin which is one component of the conductive resin compound that penetrates into the substrate.
It is also preferable that the substrate and the conductive resin compound are bonded to each other through covalent bonding, or self-adhesion between the resin which is one component of the conductive resin compound and the impregnate resin in the substrate.
Furthermore, it is preferable that the substrate and the conductive resin compound are bonded to each other such that the fiber of the substrate penetrates into the conductive resin compound.
It is preferable that the impregnate resin of the substrate and the resin which is one component of the conductive resin compound are both thermosetting resins.
It is also preferable that the thermosetting resin comprises at least one resin selected from the group consisting of epoxy resin, thermosetting polybutadiene resin, phenol resin, and polyimide resin.
Furthermore, it is preferable that the resin impregnate fiber sheet of the substrate comprises at least one fiber selected from the group consisting of heat-resisting synthetic fiber and glass fiber.
In addition, it is preferable in this example that the heat-resisting synthetic fiber comprises at least one fiber selected from the group consisting of aromatic polyamide fiber and polyimide fiber.
It is also preferable in this example that the resin impregnate fiber sheet of the substrate is a nonwoven fabric.
Furthermore, it is preferable that the metallic particulate in the conductive resin compound is at least one metal selected from the group consisting of gold, silver, copper, palladium, nickel, and an alloy thereof.
Furthermore, it is preferable that the metallic particulates in the conductive resin compound are present in an amount of from 80 to 92.5 percent by weight.
It is preferable that each metallic particulate in the conductive resin compound has an average diameter of from 0.2 to 20 &mgr;m. The average diameter can be measured using a microscopic method or a light scattering method.
In addition, it is preferable in this example that the average diameter of the through-hole filled with the conductive resin compound is from 50 to 300 &mgr;m.
Furthermore, it is preferable in this example that a circuit is formed on both the surface of the substrate and at the terminal of the conductive resin compound.
It is also preferable in this example that the substrate is either one sheet or a plurality of sheets.
A second embodiment of this invention is a method of manufacturing a printed circuit board comprising the steps of: laminating both sides of an uncured resin impregnate fiber sheet substrate material having inner holes or voids with cover films, forming through-holes in the substrate material in the thickness direction by laser irradiation, filling the through-holes with conductive paste, removing the cover films and applying a metal foil on at least one side of the substrate material, bonding the substrate material with the conductive paste by compressing and hardening the substrate material through heating and pressurization, and forming predetermined patterns on the metal foil. The above-mentioned “uncured resin” in the substrate material also includes semi-hardened resin.
It is preferable in this embodiment that metal foil is applied on both sides of the substrate material.
Furthermore, it is preferable in this embodiment that a method of manufacturing a printed circuit board comprises the steps of: laminating both sides of an uncured resin impregnate fiber sheet substrate material having inner holes or voids with cover films, forming through-holes in the substrate material in the thickness direction by laser irradiation, filling the through-holes with conductive paste, removing the cover films and applying a metal foil on one side of each sheet, thereby forming two sheets of intermediate, disposing the intermediates in a state in which the sides with metal foils face outside, holding at least two layers of circuit substrates with circuit patterns in a core, bonding the substrate material with the conductive paste by compressing and hardening with heating and pressurization, and forming predetermined patterns on the metal foils.
Furthermore, it is preferable in this embodiment that the method of manufacturing a printed circuit board comprises the steps of: laminating both sides of an uncured resin impregnate fiber sheet substrate material having inner holes or voids with cover film
Hatakeyama Akihito
Kawakita Kouji
Kojima Tamao
Nakatani Seiichi
Ogawa Tatsuo
Matsushita Electric - Industrial Co., Ltd.
Morrison & Foerster / LLP
Potter Roy
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