Stacked ball grid array packages

• US 20060138630A1
• Filed: 12/21/2005
• Published: 06/29/2006
• Est. Priority Date: 12/28/2004
• Status: Abandoned Application

• Current Assignee: Netlist, Inc.
• Original Assignee: Netlist, Inc.
• Inventors: Bhakta, Jayesh R.
• Application Number:
  US11/314,968
• Publication Number:
  US 20060138630A1
• Time in Patent Office: Days
• US Class Current: 257/686
• CPC Class Codes: H01L 2224/0401 Bonding areas specifically adapted for bump connectors, e.g. under bump metallisation [UBM]
• CPC Class Codes: H01L 2224/16 of an individual bump connector
• CPC Class Codes: H01L 2225/107 Indirect electrical connections, e.g. via an interposer, a flexible substrate, using TAB
• CPC Class Codes: H01L 23/5387 Flexible insulating substrates H01L23/5388 takes precedence
• CPC Class Codes: H01L 25/105 the devices being of a type provided for in group H01L27/00
• CPC Class Codes: H01L 2924/00014 the subject-matter covered by the group, the symbol of which is combined with the symbol of this group, being disclosed without further technical details

Abstract

An arrangement of ball grid array packages includes a flexible circuit board having first and second opposed surfaces defining a central portion to which first and second side portions are flexibly attached. A first package has a first array of solder ball pins attached to the first surface of the circuit board in the central portion thereof. A second package has first and second opposed surfaces and a second array of solder ball pins on the first surface that are attached to the second surface of the circuit board in the central portion thereof. A third array of solder ball pins is provided on each of the side portions on the first surface thereof. The side portions are folded underneath the second package and attached to the second surface thereof, whereby the third array of solder ball pins is oriented for attachment to a motherboard.

Claims

1. A stacked arrangement of ball grid array (BGA) packages, the arrangement comprising:

a flexible circuit board having first and second opposed surfaces, a central portion, and a side portion extending from each of two opposed sides of the central portion;

a first array of contact pads on the first surface of the flexible circuit board and in the central portion thereof;

a second array of contact pads on the second surface of the flexible circuit board and in the central portion thereof;

a lower array of contact pads on the first surface of the flexible circuit board in each of the side portions thereof;

a first BGA package having an upper array of solder ball pins on a first surface thereof, each pin in the upper array of pins being fixed to a corresponding one of the contact pads in the first array of contact pads; and

a second BGA package having first and second opposed surfaces and a middle array of solder ball pins on the first surface thereof, each pin in the middle array of pins being fixed to a corresponding one of the contact pads in the second array of contact pads;

wherein side portions of the flexible circuit board are folded around the second BGA package so as to be fixed, at the second surface thereof, to the second surface of the second BGA package, whereby the lower array of contact pads is exposed for attachment to a mother board.

2. The arrangement of claim 1, wherein the flexible circuit board comprises a metal-plated lower polymer layer laminated to an upper polymer layer.

3. The arrangement of claim 2, wherein the polymer includes a polyamide.

4. The arrangement of claim 1, wherein each of the side portions of the flexible circuit board is joined to the central portion by a highly flexible transition portion.

5. The arrangement of claim 4, wherein the flexible circuit board includes an internal metal layer, wherein the metal layer is formed as a latticework in the transition portions.

6. A flexible circuit board for mounting first and second ball grid array (BGA) packages on a motherboard, comprising:

a first array of contact pads on a central portion of a first surface;

a second array of contact pads on a central portion of a second surface opposed to the first surface; and

an array of solder ball pins on each of two side portions of the first surface, the side portions extending from opposite sides of the central portion;

wherein the side portions are foldable relative to the central portion so as to bring the solder ball pins on the side portions directly underneath the central portion of the second surface so as to be attachable to the motherboard.

7. The flexible circuit board of claim 6, wherein the flexible circuit board comprises a metal-plated lower polymer layer laminated to an upper polymer layer.

8. The flexible circuit board of claim 7, wherein the polymer includes a polyamide.

9. The flexible circuit board of claim 6, wherein each of the side portions of the flexible circuit board is joined to the central portion by a highly flexible transition portion.

10. The flexible circuit board of claim 9, wherein the flexible circuit board includes an internal metal layer, wherein the metal layer is formed as a latticework in the transition portions.

11. An arrangement of ball grid array (BGA) packages, comprising:

a flexible circuit board having first and second opposed surfaces defining a central portion and first and second side portions extending from opposite sides of the central portion;

a first BGA package having a first array of solder ball pins on a first surface thereof that are conductively attached to the first surface of the flexible circuit board in the central portion thereof;

a second BGA package having first and second opposed surfaces and a second array of solder ball pins on the first surface thereof that are conductively attached to the second surface of the flexible circuit board in the central portion thereof; and

a third array of solder ball pins on each of the side portions of the flexible circuit board on the first surface thereof;

wherein the second surface of the flexible circuit board is attached at the side portions thereof to the second surface of the second BGA package, so as to orient the third array of solder ball pins for attachment to a motherboard.

12. The arrangement of claim 11, wherein the first array of solder ball pins is attached to a first array of contact pads on the first surface of the flexible circuit board, and the second array of solder ball pins is attached to a second array of contact pads on the second surface of the flexible circuit board.

13. The arrangement of claim 11, wherein the flexible circuit board comprises a metal-plated lower polymer layer laminated to an upper polymer layer.

14. The arrangement of claim 13, wherein the polymer includes a polyamide.

15. The arrangement of claim 11, wherein each of the side portions of the flexible circuit board is joined to the central portion by a highly flexible transition portion.

16. The arrangement of claim 15, wherein the flexible circuit board includes an internal metal layer, wherein the metal layer is formed as a latticework in the transition portions.