Prepregs including UV curable resins useful for manufacturing semi-flexible PCBs

A method of preparing a laminate sheet comprising the steps of:

• (a) applying a mask to a first prepreg including a UV curable resin layer and a thermally curable resin layer wherein the mask is applied to the UV curable resin layer, the mask including at least one UV light transparent portion and at least one UV light opaque portion;
• (b) directing UV light at the mask for a period of time sufficient to cure the UV curable resin layer underlying the UV light transparent portion of the mask to form a UV light treated first prepreg having at least one cured UV resin portion and at least one uncured UV resin portion;
• (c) contacting a core layer with the UV light treated first prepreg such that the at least one cured UV resin portion and the at least one uncured UV resin portion contact the core layer to form a layup;
• and
• (d) applying heat and/or pressure to the lay-up to form a laminated layup including a semi-flexible core having a rest material portion that overlies the at least one cured UV resin portion where the semi-flexible core layer is not substantially laminated to the at least one cured UV resin portion.