Stock material or miscellaneous articles – Structurally defined web or sheet – Discontinuous or differential coating – impregnation or bond
Reexamination Certificate
1999-04-23
2001-07-03
Lam, Cathy (Department: 1775)
Stock material or miscellaneous articles
Structurally defined web or sheet
Discontinuous or differential coating, impregnation or bond
C428S322700, C428S323000, C428S418000, C428S901000, C174S258000
Reexamination Certificate
active
06254971
ABSTRACT:
TECHNICAL FIELD
This invention relates to metal foil having provided on one side thereof a thermosetting resin film which is for use in a multilayered wiring board, a process for producing the resin-having metal foil, a multilayered wiring board having the resin-having metal foil, and an electronic device having an electronic component electrically connected to the multilayered wiring board. The multilayered wiring board according to the present invention has practically the same distance between wiring layers irrespective of the in-plane positions of the multilayered wiring board, showing small variation in characteristic impedance. Therefore, it exhibits very excellent characteristics as a wiring board for ultrahigh-speed digital circuits. The electronic device according to the present invention has excellent stability of the characteristic impedance and, with a digital semiconductor mounted as an electronic element, allows the digital semiconductor to operate at a higher speed and, with a semiconductor having an analog portion mounted as an electronic element, can handle signals of higher frequency because crosstalks of the signals are reduced. Where a resin having a glass transition temperature of 180° C. or higher after heat curing is used, the multilayered wiring board and the electronic device according to the present invention have very high reliability. Since a thermosetting resin having a relative dielectric constant of not higher than 3.3 at a frequency range of not lower than 1 MHz before heat curing is used, the multilayered wiring board of the present invention in which such a thermosetting resin is used as cured is excellent in stability of characteristic impedance, high-speed signal transmission properties, and low crosstalk properties. The electronic device using this multilayered wiring board allows a digital semiconductor to operate at its highest speed or a semiconductor dealing with analog signals to operate at its highest frequency.
BACKGROUND ART
Copper foil with an epoxy resin is known as metal foil having a thermosetting resin film. However, when such a conventional metal foil with resin is applied to production of a multilayered wiring board (sequentially multilayered wiring board) by a so-called lamination build-up process in which sheets of metal foil with resin are sequentially laminated, it has been difficult to even the film thickness of the thermosetting resin, which functions as an electrical insulator, all over the wiring board thereby to make the characteristic impedance of the wiring fall within a given range. Further, as the thermosetting resin is not intended to be applied to high-speed circuits or high-frequency analog circuits, the dielectric characteristics and heat resistance of the thermosetting resin are insufficient for such uses. In the conventional metal foil having an epoxy resin used in the production of copper-clad laminates, the dielectric constant of the resin is 3.6 to 3.9, and the glass transition temperature of the cured resin is as low as 120 to 150° C.
In the field of electric wiring boards, it is a matter of urgency to establish a lamination build-up process that will form denser wiring than a through-hole plating process. However, there has not been a suitable resin-having metal foil for use in multilayered wiring board that can be used in high-speed digital circuits and high-frequency analog circuits. It is an object of the present invention to provide a multilayered wiring board which can be used for high-speed digital circuits and high-frequency analog circuits and an electronic device using the same, in which metal foil having provided on one side thereof a film of a thermosetting resin is used, the thermosetting resin having a specific resin flow, a specific relative dielectric constant, and a specific glass transition temperature after curing.
DISCLOSURE OF THE INVENTION
As a result of extensive investigation, the inventors of the present invention have reached discovery of resin-having metal foil. The present invention consists of the following 13 embodiments.
Firstly, the present invention provides resin-having metal foil for a sequentially multilayered wiring board, which comprises metal foil having provided on one side thereof a film of a thermosetting resin having a relative dielectric constant of not higher than 3.3 at a frequency range of not lower than 1 MHz and having a resin flow of 1 to 50%.
Secondly, the present invention provides resin-having metal foil for a sequentially multilayered wiring board which comprises metal foil having on one side thereof a film of a thermosetting resin having a relative dielectric constant of not higher than 3.3 at a frequency range of not lower than 1 MHz and having a resin flow of 5 to 50%.
Thirdly, the present invention provides the resin-having metal foil for a sequentially multilayered wiring board according to claim
1
or
2
, wherein the thermosetting resin contains an inorganic filler.
Fourthly, the present invention provides the resin-having metal foil for a multilayered wiring board according to claim
1
,
2
or
3
, wherein the thermosetting resin has a glass transition temperature of not lower than 180° C. after it cures.
Fifthly, the present invention provides the resin-having metal foil for a sequentially multilayered wiring board according to claim
1
,
2
,
3
or
4
, wherein the thermosetting resin is a thermosetting polyphenylene ether resin.
Sixthly, the present invention provides the resin-having metal foil for a sequentially multilayered wiring board according to claim
5
, wherein the thermosetting resin is a thermosetting polyphenylene ether resin containing a styrene polymer.
Seventhly, the present invention provides a process for producing resin-having metal foil for a sequentially multilayered wiring board according to claim
5
or
6
, which comprises coating metal foil with a resin varnish comprising a thermosetting polyphenylene ether resin and a solvent, and drying the coating film, wherein the drying is carried out under such a condition that the rate of evaporation of the solvent be not higher than 0.10 g/cm
2
-min.
Eighthly, the present invention provides a process for producing resin-having metal foil for a sequentially multilayered wiring board according to claim
5
or
6
, which comprises coating metal foil with a resin varnish comprising a thermosetting polyphenylene ether resin and a solvent, and drying the coating film, wherein the drying is carried out under such a condition that the rate of evaporation of the solvent be not higher than 0.10 g/cm
2
·min until the residual solvent concentration of the coating film is reduced to 200,000 ppm.
Ninethly, the present invention provides a process for producing resin-having foil for a sequentially multilayered wiring board according to claim
5
or
6
, which comprises melt-extruding a thermosetting polyphenylene ether resin under a condition that does not substantially cause the resin to decompose.
Tenthly, the present invention provides the resin-having metal foil for a sequentially multilayered wiring board according to any one of claims
1
to
6
, having an easily strippable sheet for protecting the resin surface.
Eleventhly, the present invention provides a sequentially multilayered wiring board, wherein the wiring layers are formed by sequentially laminating sheets of resin-having metal foil for a sequentially multilayered wiring board according to claim
1
,
2
,
3
,
4
or
5
.
Twelfthly, the present invention provides an electronic device comprising a sequentially multilayered wiring board according to the above described 11th embodiment and an electronic element connected thereto via a wiring means .
Thirteenthly, the present invention provides the electronic device according to the above described 12th embodiment, comprising a sequentially multilayered wiring board according to the above described 11th embodiment which achieves a speed of electrical signal transmission of 16.5 cm
sec or higher and has a heat resistance of not lower than 180° C., and an electronic element
Arai Takeshi
Katayose Teruo
Kinoshita Shozo
Asahi Kasei Kabushiki Kaisha
Lam Cathy
Pennie & Edmonds LLP
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