[Problem to be Solved] A multilayer flexible printed circuit board having a strip line advantageous to folding is provided. [Solution] A multilayer flexible printed circuit board 100 of an embodiment is a multilayer flexible printed circuit board having a strip line foldable at a folding part F1, the board including: a flexible insulative substrate 30; an inner layer circuit pattern 5 provided inside the flexible insulative substrate 30 and including a signal line 6 extending in a predetermined direction; a ground thin film 14a constituting a ground layer at least in the folding part F1 out of a ground layer of the strip line and constituted of a nonelectrolytic plating coat 14 formed on the flexible insulative substrate 30; and a protective layer 20 that covers the ground thin film 14a and is in close contact with an exposed part 19 from which the flexible insulative substrate 30 is exposed.

A surface-treated copper foil includes a bulk copper foil and a first surface treatment layer. The first surface treatment layer is disposed on a first surface of the bulk copper foil and includes a roughening layer, where the outermost surface of the first surface treatment layer is a treating surface of the surface-treated copper foil. The material volume (Vm) of the treating surface is 0.06 to 1.45 m.sup.3/m.sup.2, and the five-point peak height (S5p) of the treating surface is 0.15 to 2.00 m.

A metal foil that has a carrier and a preparation method thereof. The metal foil with a carrier comprises a carrier layer, a barrier layer, a striping layer, and a metal foil layer. The carrier layer, the barrier layer, the striping lay, and the metal foil layer are sequentially stacked, or the carrier layer, the striping layer, the barrier layer, and the metal foil layer are sequentially stacked. The diffusion depth of the carrier layer to the metal foil layer is less than or equal to 3 m and the diffusion depth of the metal foil layer toward the carrier layer is less than or equal to 3 m at a temperature of 20-400 C. By setting the barrier layer, the carrier layer and the metal foil layer are prevented from diffusing mutually to cause bonding at a high temperature, so that the carrier layer and the metal foil layer are easy to peel off.

A method of making a printed circuit board is disclosed. The method includes forming a plurality of layers. The method further includes forming a stack including the plurality of layers such that topmost and bottommost layers of the stack are copper layers and such that inner layers of the stack include resin layers and further copper layers. The method further includes thermocompressing the stack to form a panel such that the resin layers conform to the further copper layers and such that the copper layers bend around a perimeter of the inner layers. The method further includes separating a printed circuit board from the panel such that the printed circuit board's widest extent defines its final width.

A substrate for a printed circuit board includes a base film having an insulating property; a first conductive layer formed on at least one of surfaces of the base film by application of a conductive ink containing metal particles; and a second conductive layer formed, by plating, on a surface of the first conductive layer, the surface being on a side opposite to the base film, wherein a region near an interface between the base film and the first conductive layer contains a metal oxide species based on a metal of the metal particles and a metal hydroxide species based on the metal of the metal particles, the metal oxide species in the region near the interface between the base film and the first conductive layer has a mass per unit area of 0.1 g/cm.sup.2 or more and 10 g/cm.sup.2 or less, and a mass ratio of the metal oxide species to the metal hydroxide species is 0.1 or more.

Provided is a copper-clad laminate in which a copper foil and a resin are joined together with high heat-resistant adhesion force though a fluororesin is used. This copper-clad laminate includes a surface-treated copper foil including a copper foil and a zinc-containing layer on at least one surface of the copper foil; and a sheet-shaped fluororesin on the zinc-containing layer side of the surface-treated copper foil. The zinc-containing layer is composed of Zn and a transition element M having a melting point of 1200 C. or more. When the interface between the copper foil and the zinc-containing layer is subjected to elemental analysis by GD-OES, the emission intensity ratio I.sub.Zn/I.sub.Cu of the emission intensity of Zn to that of Cu is 3.010.sup.3 or less, and the emission intensity ratio I.sub.Zn/I.sub.M of the emission intensity of Zn to that of the transition element M is 0.30 to 0.50.

Disclosed is a copper foil for printed circuits prepared by forming a primary particle layer of copper on a surface of a copper foil, and then forming a secondary particle layer based on ternary alloy composed of copper, cobalt and nickel on the primary particle layer; in which the average particle size of the primary particle layer is 0.25 to 0.45 m, and the average particle size of the secondary particles layer based on ternary alloy composed of copper, cobalt and nickel is 0.05 to 0.25 m. Provided is a copper foil for printed circuits, in which powder fall from the copper foil can be reduced and the peeling strength and heat resistance can be improved by forming a primary particle layer of copper on a surface of a copper foil, and then forming a secondary particle layer based on copper-cobalt-nickel alloy plating on the primary particle layer.

Metal foil provided with an electrically resistive layer, characterized in that an alloy (in particular, a NiCrAlSi alloy) resistive layer containing 1 to 6 mass % of Si is formed on the metal foil controlled to have a ten-point average roughness Rz, which was measured by an optical method, of 4.0 to 6.0 m, and the variation in the resistance value of the electrically resistive layer is within 10%. Provided is a copper foil that allows embedding of a resistive material in a board by further forming an electrically resistive layer on the copper foil, and further allows improving the adhesiveness and suppressing the variation in resistance value within a certain range. As needed, metal foil provided in advance with a copper-zinc alloy layer formed on the surface thereof and a stabilizing layer composed of at least one component selected from zinc oxide, chromium oxide, and nickel oxide formed on the copper-zinc alloy layer is used.

A method of forming a stacked wiring includes forming a first adhesion layer on a substrate, forming a first wiring on the first adhesion layer, etching the first adhesion layer and the first wiring by the same first wet etching so that the first wiring is in a reverse trapezoid shape in which a first width of a top surface is larger than a second width of a bottom surface contacting the first adhesion layer as a cross-section in a direction intersecting with a first wiring extending direction, covering the top surface and a side surface of the first wiring with a second adhesion layer, forming a second wiring on the second adhesion layer, and etching the second adhesion layer and the second wiring by the same second wet etching so that the second adhesion layer and the second wiring remain on only the top surface of the first wiring.

A surface treated copper foil for a High-Frequency circuit as well as a corresponding method of treating a copper foil, the copper foil including two opposite sides, where a first side is coated with a treatment layer including, in this order: a first layer including oxides of Mo and of Zn deposited on the first side, where the first layer is free of Ni; a second layer of Cr oxide; and a coupling agent layer; where the first layer includes the oxides of Mo and of Zn in a quantity of between 5 and 30 mg/m.sup.2 calculated as Mo and Zn; where the treatment layer has a roughness Rz JIS of 0.7 m or less; and where the first side is free of roughening treatment.