Copper-clad laminate
There is provided a copper-clad laminate in which transmission characteristics exhibited by a resin layer can be further improved while sufficient peel strength between a copper foil and the resin layer is ensured. The laminate includes a copper foil; an adhesive layer including a polyphenylene ether resin, a polyimide resin, an olefin-based resin, a liquid crystal polymer, a polyester resin, a polystyrene resin, a hydrocarbon elastomer, a benzoxazine resin, an active ester resin, a cyanate ester resin, a bismaleimide resin, a butadiene resin, a hydrogenated or non-hydrogenated styrene butadiene resin, an epoxy resin, a fluororesin, a vinyl-group-containing resin, or the like; and a resin layer. The maximum height Sz at a copper foil surface on the adhesive layer side is 6.8 μm or less. The dielectric loss tangent value of the adhesive layer at 1 GHz, δa, is equal to or less than that of the resin layer, δr.
1. A copper-clad laminate comprising:
a copper foil;
an adhesive layer provided on a surface of the copper foil and comprising one or more selected from the group consisting of an olefin resin, a liquid crystal polymer, a polyester resin, a benzoxazine resin, an active ester resin, a cyanate ester resin, and a fluororesin; and
a resin layer provided on a surface of the adhesive layer,
wherein the olefin resin is at least one selected from the group consisting of a polyethylene resin, a polypropylene resin, a polymethylpentene resin, and a cycloolefin resin,
wherein the surface of the copper foil on the adhesive layer side has a maximum height Sz of 6.8 μm or less as measured in accordance with ISO 25178, and the adhesive layer has a dielectric loss tangent value at a frequency of 1 GHz, δa, which is equal to or less than a dielectric loss tangent value of the resin layer at a frequency of 1 GHz, δr,
wherein the surface of the copper foil on the adhesive layer side has a kurtosis Sku of 2.0 or more and 3.5 or less as measured in accordance with ISO 25178 at the surface of the copper foil on the adhesive layer side, and
wherein the adhesive layer has a thickness of 0.1 μm or more and 20 μm or less.
2. The copper-clad laminate according to claim 1 , wherein the maximum height Sz at the surface of the copper foil on the adhesive layer side is 0.15 μm or more and 6.8 μm or less.
3. The copper-clad laminate according to claim 1 , wherein the dielectric loss tangent value of the adhesive layer at a frequency of 1 GHz, δa, is 0.0001 or more and 0.003 or less.
4. The copper-clad laminate according to claim 1 , wherein the dielectric loss tangent value of the resin layer at a frequency of 1 GHz, δr, is 0.0001 or more and 0.03 or less.
5. The copper-clad laminate according to claim 1 , wherein the adhesive layer comprises at least one selected from the group consisting of an olefin resin, a liquid crystal polymer, and a fluororesin in an amount of 10% by weight or more based on a total weight of the adhesive layer,
wherein the olefin resin is at least one selected from the group consisting of a polyethylene resin, a polypropylene resin, a polymethylpentene resin, and a cycloolefin resin.
6. The copper-clad laminate according to claim 1 , wherein the resin layer comprises a glass cloth and an insulating resin with which the glass cloth is impregnated.
7. The copper-clad laminate according to claim 1 , wherein the resin layer has a thickness of 5 μm or more and 5 mm or less.
8. The copper-clad laminate according to claim 1 , having a peel strength of the copper foil from the adhesive layer of 0.3 kN/m or more as measured in accordance with JIS C 6481-1996.
9. A method for manufacturing the copper-clad laminate according to claim 1 , comprising:
providing a copper foil having a surface having a maximum height Sz of 6.8 μm or less as measured in accordance with ISO 25178;
applying a resin varnish comprising an adhesive to a surface of the copper foil and drying the resin varnish to obtain an adhesive-attached copper foil, the adhesive comprising one or more selected from the group consisting of an olefin resin, a liquid crystal polymer, a polyester resin, a benzoxazine resin, an active ester resin, a cyanate ester resin, and a fluororesin, and, having a dielectric loss tangent value at a frequency of 1 GHz of δa after curing; and
bonding the adhesive-attached copper foil to a resin layer having a dielectric loss tangent value at a frequency of 1 GHz of δr to form a copper-clad laminate,
wherein the δa is equal to or less than the δr,
wherein the olefin resin is at least one selected from the group consisting of a polyethylene resin, a polypropylene resin, a polymethylpentene resin, and a cycloolefin resin,
and
wherein the adhesive layer has a thickness of 0.1 μm or more and 20 μm or less.