Multilayer printed circuit board

1. A multilayer printed circuit board, comprising:

a first printed circuit board;

a second printed circuit board; and

an adhesive film sandwiched between the first printed circuit board and the second printed circuit board, the adhesive film comprising a first surface and a second surface at an opposite side to the first surface; and

a function layer disposed between the first printed circuit board and the second printed circuit board and between the first surface and the second surface, the function layer configured for blocking water from passing therethrough and for screening electromagnetic interference between the first printed circuit board and the second printed circuit board.

2. The multilayer printed circuit board as claimed in claim 1 , wherein the function layer is an aluminum foil.

3. The multilayer printed circuit board as claimed in claim 1 , wherein the function layer is substantially flat and is parallel to the first surface and the second surface of the adhesive film.

4. The multilayer printed circuit board as claimed in claim 3 , wherein a thickness of the function layer is in a range from about 3 micrometers to about 25 micrometers.

5. The multilayer printed circuit board as claimed in claim 1 , wherein the function layer is wave-shaped, and is, as a whole, substantially parallel to the first surface and the second surface.

6. The multilayer printed circuit board as claimed in claim 5 , wherein an average thickness of the function layer is in a range from about 3 micrometers to about 25 micrometers.

7. The multilayer printed circuit board as claimed in claim 1 , wherein the function layer is disposed between the first printed circuit board and the adhesive film.

8. A multilayer printed circuit board, comprising:

a first printed circuit board comprising a first insulation layer and a first electrical trace formed on the first insulation layer;

a second printed circuit board comprising a second insulation layer and a second electrical trace formed on the second insulation layer; and

an adhesive film sandwiched between the first insulation layer of the first printed circuit board and the second insulation layer of the second printed circuit board, the adhesive film comprising an adhesive matrix and a function layer, the adhesive film comprising a first surface and a second surface at an opposite side to the first surface, the function layer disposed between the first surface and the second surface, the function layer being configured for screening electromagnetic interference between the first electrical trace and the second electrical trace.

9. The multilayer printed circuit board as claimed in claim 8 , wherein the function layer comprises an aluminum foil.

10. The multilayer printed circuit board as claimed in claim 8 , wherein the function layer is substantially flat and is parallel to the first surface and the second surface.

11. The multilayer printed circuit board as claimed in claim 10 , wherein a thickness of the function layer is in a range from about 3 micrometers to about 25 micrometers.

12. The multilayer printed circuit board as claimed in claim 8 , wherein the function layer is wave-shaped, and is, as a whole, substantially parallel to the first surface and the second surface.

13. The multilayer printed circuit board as claimed in claim 12 , wherein an average thickness of the function layer is in a range from about 3 micrometers to about 25 micrometers.

14. A multilayer printed circuit board, comprising:

a first printed circuit board comprising a first insulation layer and a first electrical trace formed on the first insulation layer;

a second printed circuit board comprising a second insulation layer and a second electrical trace formed on the second insulation layer;

a first adhesive film sandwiched between the first insulation layer and the second insulation layer, the first adhesive film comprising a first surface and a second surface at an opposite side to the first surface;

a first function layer disposed between the first surface and the second surface for screening electromagnetic interference between the first electrical trace and the second electrical trace;

a copper clad laminate comprising a third insulation layer and a copper trace formed on the third insulation layer;

a second adhesive film sandwiched between the second electrical trace and the third insulation layer, the second adhesive film comprising a third surface and a fourth surface at an opposite side to the third surface; and

a second function layer disposed between the third surface and the fourth surface for screening electromagnetic interference between the second electrical trace and the copper trace.