| abstract |
In the present invention, a bump pad is formed on a surface of a substrate corresponding to a cavity region, and a second insulating layer (for example, an insulating layer which can be etched by a sandblasting process such as a resin not containing glass fiber) , A copper foil barrier for protecting the second insulating layer is formed on the surface of the second insulating layer corresponding to the cavity region, a third insulating layer (for example, a prepreg) is laminated on the copper foil barrier, do. A mask exposing only the cavity region is formed on the copper foil circuit of the outer layer, and the third insulating layer whose surface is exposed is laser drilled to form the cavity. At this time, a copper foil barrier is provided at the lower end to prevent the laser from damaging the second insulating layer or the lower bump pad. After the laser drill is finished, the copper foil barrier is removed by a chemical wet etching method, and the second insulating layer whose surface is exposed at the bottom is removed by a sandblast method to expose the bump pad previously prepared. |