Circuit board assembly and method of manufacturing the same

A method of manufacturing a circuit board assembly, comprising:

• providing an electronic component stacking structure, wherein the electronic component stacking structure has a sidewall;
• providing a base, wherein the base has a surface and a hole;
• disposing the electronic component stacking structure in the hole;
• after the electronic component stacking structure is disposed in the hole, attaching a photoresist layer to the surface;
• forming a first opening and a second opening in the photoresist layer exposing the sidewall;
• forming a first conductive pillar in the first opening and a first conductive portion in the second opening;
• after the first conductive pillar and the first conductive portion are formed, forming a second conductive portion in the second opening connected to the first conductive portion to form a second conductive pillar, wherein the first conductive pillar and the second conductive pillar are connected to the sidewall, and a length of the second conductive pillar is greater than a length of the first conductive pillar;
• providing an initial circuit board, wherein the initial circuit board has a stepped opening and comprises a first connection wiring layer and a second connection wiring layer;
• and
• disposing the electronic component stacking structure, the first conductive pillar and the second conductive pillar in the stepped opening, wherein the first conductive pillar is electrically connected to the first connection wiring layer, and the second conductive pillar is electrically connected to the second connection wiring layer.