Stacking multiple devices using flexible circuit
One embodiment of the invention includes a flexible circuit and a stiffener. The flexible circuit has first, second, and third portions. The first portion is folded on an upper surface of the third portion and has first contact elements attached to a first device. The second portion is folded on the first device and has second contact elements attached to a second device. The stiffener is attached to the upper surface of the third portion and located between the upper surface of the third portion and the first portion.
1. An apparatus comprising:
a flexible circuit having first, second, and third portions, the first portion being folded on an upper surface of the third portion and having first contact elements attached to a first device, the second portion being folded on the first device and having second contact elements attached to a second device, wherein at least one of the first and second contact elements comprise a plurality of solder pads; and
a stiffener attached to the upper surface of the third portion and located between the upper surface of the third portion and the first portion.
2. The apparatus of claim 1 further comprising:
an encapsulant to encapsulate the flexible circuit and the first and second devices.
3. The apparatus of claim 1 wherein the third portion has a lower surface having third contact elements.
4. The apparatus of claim 3 wherein the lower surface is attached to at least one of a printed circuit board and a third device via the third contact elements.
5. The apparatus of claim 4 wherein the first, second, and third portions include first, second, and third layer having signal traces mapped to the first, second, and third contact elements, respectively.
6. The apparatus of claim 3 wherein the third contact elements comprise a plurality or solder pads.
7. The apparatus of claim 3 wherein the stiffener is made of one of an insulating material, a polyimide film, a mica plate, a polyester film, and a polyaramid paper.
8. The apparatus of claim 1 wherein the first and second devices are identical devices having solder balls attached to the first and second contact elements, respectively.
9. The apparatus of claim 8 wherein the identical devices are memory devices.
10. A method comprising:
folding a flexible circuit having first, second, and third portions, the first portion being folded on an upper surface of the third portion and having first contact elements attached to a first device, the second portion being folded on the first device and having second contact elements attached to a second device, wherein at least one of the first and second contact elements comprise a plurality of solder pads; and
attaching a stiffener to the upper surface of the third portion and between the upper surface of the third portion and the first portion.
11. The method of claim 10 further comprising:
encapsulating the flexible circuit and the first and second devices by an encapsulant.
12. The method of claim 10 wherein the third portion has a lower surface having third contact elements.
13. The method of claim 12 further comprising attaching the lower surface to at least one of a printed circuit board and a third device via the third contact elements.
14. The method of claim 13 wherein the first, second, and third portions include first, second, and third layer having signal traces mapped to the first, second, and third contact elements, respectively.
15. The method of claim 12 wherein the third contact elements comprise a plurality of solder pads.
16. The method of claim 10 wherein the first and second devices are identical devices having solder balls attached to the first and second contact elements, respectively.
17. The method of claim 16 wherein the identical devices are memory devices.
18. The method of claim 10 wherein the stiffener is made of one of an insulating material, a polyimide film, a mica plate, a polyester film, and a polyaramid paper.
19. A module comprising:
a first device and a second device; and
a stacking element to stack the second device on the first device, the stacking element comprising:
a flexible circuit having first, second, and third portions, the first portion being folded on an upper surface of the third poition and having first contact elements attached to the first device, the second portion being folded on the first device and having second contact elements attached to the second device, wherein at least one of the first and second contact elements comprise a plurality of solder pads; and
a stiffener attached to the upper surface of the third portion and located between the upper surface of the third portion and the first portion.
20. The module of claim 19 wherein the stacking element further comprising:
an encapsulant to encapsulate the flexible circuit and the first and second devices.
21. The module of claim 19 wherein the third portion has a lower surface having third contact elements.
22. The module of claim 21 wherein the lower surface is attached to at least one of a printed circuit board and a third device via the third contact elements.
23. The module of claim 22 wherein the first, second, and third portions include first, second, and third layer having signal traces mapped to the first, second, and third contact elements, respectively.
24. The module of claim 21 wherein the third contact elements comprise a plurality of solder pads.
25. The module of claim 19 wherein the first and second devices are identical devices having solder balls attached to the first and second contact elements, respectively.
26. The module of claim 25 wherein the identical devices are memory devices.
27. The module of claim 25 wherein the stiffener is made of one of an insulating material, a polyimide film, a mica plate, a polyester film, and a polyaramid paper.