Methods and apparatus to increase rigidity of printed circuit boards

An apparatus comprising:

• a stack of insulative layers, the stack including a first face and a second face opposite the first face;
• a plurality of conductive layers, ones of the conductive layers between adjacent ones of the insulative layers;
• and
• a metal stiffener extending along a perimeter of a first one of the insulative layers, the metal stiffener having a thickness in a direction perpendicular to the first face, the thickness being less than a distance between the first and second faces, the metal stiffener having a width in a direction parallel to the first face and extending away from the first insulative layer, the width being greater than the thickness of the metal stiffener.

An apparatus comprising:

• a stack of insulative layers, the stack including a first face and a second face opposite the first face;
• a plurality of conductive layers, ones of the conductive layers between adjacent ones of the insulative layers;
• and
• a metal stiffener extending along a perimeter of a first one of the insulative layers, the metal stiffener having a thickness in a direction perpendicular to the first face, the thickness being less than a distance between the first and second faces, the metal stiffener electrically coupled to a first conductive layer in contact with the first insulative layer.

An apparatus comprising:

• a stack of insulative layers, the stack including a first face and a second face opposite the first face;
• a plurality of conductive layers, ones of the conductive layers between adjacent ones of the insulative layers;
• and
• a metal stiffener extending along a perimeter of a subset of the insulative layers, the subset including at least two of the insulative layers but less than all of the insulative layers, the metal stiffener having a thickness in a direction perpendicular to the first face, the thickness being less than a distance between the first and second faces.