Substrate or panel with releasable core

A method of making a core panel comprising:

• providing a releasable core including a first recess in a first side of a cured prepreg material and a second recess in a second side of the prepreg material, the second side opposite the first side, the releasable core including a first copper foil integrally coupled with the prepreg material in the first recess and a second copper foil integrally coupled with the prepreg material in the second recess;
• releasably coupling a third copper foil to the first copper foil through a first temporary adhesive layer coupled to the first copper foil, the first temporary adhesive layer at least partially situated in the first recess;
• the first temporary adhesive layer including a first width and the third copper foil including a second width, the first width less than the second width;
• and
• releasably coupling a fourth copper foil to the second copper foil through a second temporary adhesive layer coupled to the fourth copper foil.