Stress management in BGA packaging
The present semiconductor structure includes a substrate having a planar surface, a semiconductor chip attached to the planar surface of the substrate, the chip preferably being of the same thickness as or thinner than the substrate, and a package body attached to the substrate and to the semiconductor chip. The semiconductor chip and substrate are sufficiently rigidly attached so that substantial force applied parallel to the planar surface of the substrate may be transmitted therebetween, reducing temperature-change stress on solder balls which connect the substrate with a PCB. The semiconductor chip with advantage is thinned to reduce the stress on the solder balls.
1 . A semiconductor structure comprising:
a substrate having a planar surface;
a semiconductor chip attached to the planar surface of the substrate;
a package body attached to the substrate and to the semiconductor chip;
the semiconductor chip and substrate being sufficiently rigidly attached so that substantial force applied parallel to the planar surface of the substrate may be transmitted therebetween.
2 . The semiconductor structure of claim 1 wherein the semiconductor chip and substrate have substantially different coefficients of thermal expansion.
3 . The semiconductor structure of claim 2 wherein the substrate has a substantially higher coefficient of thermal expansion than the coefficient of thermal expansion of the semiconductor chip.
4 . The semiconductor structure of claim 1 wherein the area of the semiconductor chip is more than 60% of the area of the substrate.
5 . The semiconductor structure of claim 1 wherein the area of the semiconductor chip is more than 80% of the area of the substrate.
6 . The semiconductor structure of claim 1 wherein the coefficient of thermal expansion of the package body is similar to the coefficient of thermal expansion of the substrate.
7 . The semiconductor structure of claim 6 wherein the substrate has a substantially higher coefficient of thermal expansion than the coefficient of thermal expansion of the semiconductor chip.
8 . The semiconductor structure of claim 1 and further comprising an attachment layer for attaching the semiconductor chip and the substrate, the attachment layer having a modulus of elasticity of approximately 1.0 GPa or more.
9 . The semiconductor structure of claim 1 wherein the thickness of the semiconductor chip is equal to or less than the thickness of the substrate.
10 . The semiconductor structure of claim 1 and further comprising a plurality of conductors attached to the substrate, and a board, the conductors attached to the substrate being attached to the board.
11 . The semiconductor structure of claim 10 wherein the conductors are solder balls.
12 . The semiconductor structure of claim 11 wherein the substrate has a substantially higher coefficient of thermal expansion than the coefficient of thermal expansion of the semiconductor chip.
13 . The semiconductor structure of claim 12 wherein the coefficient of thermal expansion of the board is similar to the coefficient of thermal expansion of the substrate.
14 . A semiconductor structure comprising:
a substrate;
a semiconductor chip attached to the substrate;
a package body attached to the substrate and to the semiconductor chip;
wherein the thickness of the semiconductor chip is equal to or less than the substrate.
15 . The structure of claim 14 wherein the thickness of the semiconductor chip is less than 75% of the thickness of the substrate.
16 . The structure of claim 14 wherein the thickness of the semiconductor chip is less than 50% of the thickness of the substrate.
17 . The structure of claim 14 wherein the thickness of the semiconductor chip is less than 25% of the thickness of the substrate.
18 . The semiconductor structure of claim 14 wherein the area of the semiconductor chip is more than 60% of the area of the substrate.
19 . The semiconductor structure of claim 14 wherein the area of the semiconductor chip is more than 80% of the area of the substrate.
20 . A semiconductor structure comprising:
a substrate having a planar surface;
a first semiconductor chip attached to the planar surface of the substrate;
a second semiconductor chip attached to the first semiconductor chip;
a package body attached to the substrate and to the first and second semiconductor chips;
the first semiconductor chip and substrate being sufficiently rigidly attached so that substantial force applied parallel to the planar surface of the substrate may be transmitted therebetween.
21 . The semiconductor structure of claim 20 wherein the first and second semiconductor chips have similar coefficients of thermal expansion, and the substrate has a coefficient of thermal expansion substantially different from that of the first semiconductor chip.
22 . The semiconductor of structure of claim 21 and further comprising a plurality of conductors attached to the substrate, and a board, the conductors attached to the substrate being attached to the board.
23 . The semiconductor structure of claim 22 wherein the conductors are solder balls.
24 . The semiconductor structure of claim 23 and further comprising an attachment layer for attaching the first semiconductor chip and the substrate, the attachment layer having a modulus of elasticity of approximately 1.0 GPa or more.
25 . A semiconductor structure comprising:
a substrate having a planar surface;
a first semiconductor chip attached to the planar surface of the substrate;
a spacer attached to the first semiconductor chip;
a second semiconductor chip attached to the spacer;
a package body attached to the substrate and to the first and second semiconductor chips;
the first semiconductor chip and substrate being sufficiently rigidly attached so that substantial force applied parallel to the planar surface of the substrate may be transmitted therebetween.
26 . The semiconductor structure of claim 25 wherein the first and second semiconductor chips have similar coefficients of thermal expansion, and the substrate has a coefficient of thermal expansion substantially different from that of the first semiconductor chip.
27 . The semiconductor of structure of claim 26 and further comprising a plurality of conductors attached to the substrate, and a board, the conductors attached to the substrate being attached to the board.
28 . The semiconductor structure of claim 27 wherein the conductors are solder balls.
29 . The semiconductor structure of claim 28 and further comprising an attachment layer for attaching the first semiconductor chip and the substrate, the attachment layer having a modulus of elasticity of approximately 1.0 GPa or more.
30 . The method of claim 1 and further comprising said semiconductor structure incorporated in a system.
31 . The method of claim 30 wherein the system is selected from the group consisting of a hand-held device, a vehicle, and a computer.