Dummy wafer

A dummy wafer comprising a wafer substrate including a carbon fiber reinforced plastic, wherein

• said wafer substrate has two skin layers each located on principal surface side, and a core layer located between said two skin layers;
• both of said two skin layers have a plurality of one-dimensionally reinforced CFRP layers, said one-dimensionally reinforced CFRP layer being a layer consisting of a carbon fiber reinforced plastic consisting of a cured and shaped product of a unidirectional prepreg in which carbon fibers are oriented in one direction;
• when the orientation direction of carbon fibers in one of the two outermost CFRP layers, which are one-dimensionally reinforced CFRP layers located closest to the principal surface side in each of said two skin layers, is made to be a reference direction, the orientation direction of carbon fibers in the other outermost CFRP layer falls within an angle range from −20° to +20° with respect to the reference direction;
• the tensile modulus of carbon fibers in both the two outermost CFRP layers is 200 GPa to 600 GPa;
• both the two skin layers have a one-dimensionally reinforced CFRP layer containing carbon fibers oriented in an angle range from +75° to +90° with respect to the reference direction and having a tensile modulus 1.5 times to 3.0 times that of carbon fibers of the outermost CFRP layer contained in the skin layer, and/or a one-dimensionally reinforced CFRP layer containing carbon fibers oriented in an angle range from −75° to −90° with respect to the reference direction and having a tensile modulus 1.5 times to 3.0 times that of carbon fibers of the outermost CFRP layer contained in the skin layer;
• said core layer has a one-dimensionally reinforced CFRP layer containing carbon fibers oriented in an angle range from −20° to +20° with respect to the reference direction and having a tensile modulus of 200 GPa to 400 GPa;
• and
• said core layer also has a one-dimensionally reinforced CFRP layer containing carbon fibers oriented in an angle range from +75° to +90° with respect to the reference direction and having a tensile modulus of 200 GPa to 400 GPa and/or a one-dimensionally reinforced CFRP layer containing carbon fibers oriented in an angle range from −75° to −90° with respect to the reference direction and having a tensile modulus of 200 GPa to 400 GPa.

A dummy wafer substrate comprising:

• an upper skin layer comprising an outermost layer and another layer, each composed of a cured unidirectional prepre sheet made of a one-dimensionally reinforced CFRP including oriented carbon fibers, wherein the carbon fibers of the outermost layer and those of the other layer are oriented in different angles, and the other layer has a higher tensile strength than that of the outermost layer;
• a lower skin layer comprising an outermost layer and another layer, each composed of a cured unidirectional prepre sheet made of a one-dimensionally reinforced CFRP including oriented carbon fibers, wherein the carbon fibers of the outermost layer and those of the other layer are oriented in different angles, and the other layer has a higher tensile strength than that of the outermost layer;
• and
• a core layer interposed between the upper skin layer and the lower skin layer, said core layer made of one-dimensionally reinforced CFRP including oriented carbon fibers.