Circuit board structure

A circuit board structure, comprising:

• a first substrate comprising a first dielectric layer, a first external circuit layer, a first conductive through hole, and a first inner circuit layer, wherein the first external circuit layer and the first inner circuit layer are respectively located on opposite sides of the first dielectric layer, and the first conductive through hole penetrates through the first dielectric layer and connects the first external circuit layer and the first internal circuit layer electrically;
• a second substrate comprising a second dielectric layer, a second external circuit layer, a second conductive through hole, and a second inner circuit layer, wherein the second external circuit layer and the second inner circuit layer are respectively located on opposite sides of the second dielectric layer, and the second conductive through hole penetrates through the second dielectric layer and connects the second external circuit layer and the second inner circuit layer electrically;
• a third dielectric layer covering the first inner circuit layer;
• a fourth dielectric layer covering the second inner circuit layer;
• a first annular retaining wall disposed in the third dielectric layer and electrically connected to the first internal circuit layer, wherein an orthographic projection of the first annular retaining wall on the first substrate surrounds the first conductive through hole;
• and
• a second annular retaining wall disposed in the fourth dielectric layer and electrically connected to the second inner circuit layer, wherein an orthographic projection of the second annular retaining wall on the second substrate surrounds the second conductive through hole, the third dielectric layer is connected to the fourth dielectric layer, and part of the first annular retaining wall is connected to part of the second annular retaining wall, such that the first substrate is butted to the second substrate.