Method for manufacturing a multi-layer circuit board

1. A method for manufacturing a multi-layer circuit board, comprising:

providing three copper dad laminates, each copper clad laminate including a first copper layer, a second copper layer and an insulating layer arranged between the first copper layer and the second copper layer;

selectively removing portions of the first copper layer of each copper clad laminate to obtain a first trace layer, and selectively removing portions of second copper layer of each copper clad laminate to obtain a second trace layer, thereby obtaining three first circuit substrates;

laminating a dielectric layer on each first trace layer of two of the first circuit substrates, thereby obtaining two second circuit substrates;

forming a first metal bump on the first trace layer and a second metal bump on the second trace layer of the remaining one of the three first circuit substrate, thereby obtaining a third circuit substrate;

stacking and laminating the third circuit substrate between the two second circuit substrates, the dielectric layers of the second circuit substrates adjacent to the third circuit substrate, the first metal bump and the second metal bump passing through the dielectric layers and electrically connected to the first trace layers of the second circuit substrates.

2. The method of claim 1 , wherein the dielectric layers are in B-stage after laminating on each first trace layer of two of the first circuit substrates.

3. The method of claim 1 , wherein the first metal bump comprises a first copper layer and a first tin layer, the second metal bump comprises a second copper layer and a second tin layer, a method for forming the first metal bump and the second metal bump comprising;

forming a first photo resist layer and a second photo resist layer on two opposite surfaces of the first circuit substrate;

defining a first hole in the first photo resist layer, and defining a second hole in the second photo resist layer, thereby, a portion of the first trace layer being exposed in the first hole, a portion of the second trace layer being exposed in the second hole;

forming a first copper layer in the first hole and forming a second copper layer in the second hole;

forming a first tin layer on the first copper layer and forming a second tin layer on the second copper layer, and

removing the first photo resist layer and the second photo resist layer.

4. The method of claim 1 , further comprising melting the first tin layer and the second tin layer to bond the first tin liner and the second tin layer with the first trace layers using a reflow soldering process after stacking and laminating the third circuit substrate between the two second circuit substrates.

5. The method of claim 4 , further comprising curing the dielectric layer after the first tin layer and the second tin layer are melted and bonded with the first trace layers.

6. The method of claim 1 , wherein the dielectric layer is Ajinomoto build-up film.

7. A method for manufacturing a multi-layer circuit board, comprising:

providing 2N+3 copper clad laminates, each copper clad laminate including a first copper layer, a second copper layer and an insulating layer arranged between the first copper layer and the second copper layer, wherein N is a natural number and not less than 1;

forming a first trace layer by selectively removing portions of first copper layer of each copper clad laminate, and forming a second trace layer by selectively removing portions of second copper layer of each copper clad laminate, thereby obtaining 2N+3 first circuit substrates;

laminating a dielectric layer on each first trace layer of two first circuit substrates, thereby obtaining two second circuit substrates;

forming a first metal bump on the first trace layer and a second metal bump on the second trace layer of each of the 2N+1 first circuit substrates, thereby obtaining 2N+1 third circuit substrates;

laminating a dielectric layer on each first trace layer and each second trace layer of the remaining N first circuit substrates, thereby obtaining N fourth circuit substrates;

stacking and laminating N+1 third circuit substrates and N fourth circuit substrates between the two second circuit substrates, only one of the fourth circuit substrates being arranged between two neighbor third circuit substrates, only one of the third circuit substrates arranged between two neighbor fourth circuit substrates, the dielectric layer of each of the second circuit substrates adjacent to a third circuit substrate, each first metal bump passing through adjacent dielectric layer and electrically connected with the first trace layer of the second or fourth circuit substrate, each second metal bump passing through adjacent dielectric layer and electrically connected with the first trace layer of the second or fourth circuit substrate.

8. The method of claim 7 , wherein the dielectric, layers are in B-stage when laminating on each first trace layer of two of the first circuit substrates.

9. The method of claim 7 , wherein the first metal bump comprises a first copper layer and a first tin layer, the second metal bump comprises a second copper layer and a second tin layer, a method for forming the first metal bump and the second metal bump comprising:

forming a first photo resist layer and a second photo resist layer on two opposite surfaces of the first circuit substrate;

defining a first hole in the first photo resist layer, and defining a second hole in the second photo resist layer, thereby, a portion of the first trace layer being exposed in the first hole, a portion of the second trace layer being exposed in the second hole;

forming a first copper layer in the first hole and forming a second copper layer in the second hole using a plating process;

forming a first tin layer on the first copper layer and forming a second tin layer on the second copper layer using a plating process; and

removing the first photo resist layer and the second photo resist layer.

10. The method of claim 7 , further comprising melting the first tin layer and the second tin layer to bond the first tin layer and the second tin layer with the first trace layers using a reflow soldering process after stacking and laminating the third circuit substrate between the two second circuit substrates.

11. The method of claim 10 , farther comprising curing the dielectric layer after the first tin layer and the second tin layer are melted and bonded with the first trace layers.

12. The method of claim 7 , wherein the dielectric layer is composed of an Ajinomoto build-up film.