Warp compensated electronic assemblies
View Patent ↗An electronic panel assembly (EPA) includes one or more electronic devices with primary faces having electrical contacts, opposed rear faces and edges therebetween. The devices are mounted primary faces down in openings in a warp control sheet (WCS). Cured plastic encapsulation is formed at least between lateral edges of the devices and WCS openings. Undesirable panel warping during encapsulation is mitigated by choosing the WCS coefficient of thermal expansion (CTE) to be less than the encapsulation CTE. Thin film insulators and conductors couple electrical contacts on various devices to each other and to external terminals, thereby forming an integrated multi-device EPA.
1. An electronic assembly, comprising:
multiple electronic devices with primary faces where electrical contacts are located, opposed rear faces, and edges extending between the primary and rear faces;
a perforated warp control sheet having a first surface, an opposed second surface, and multiple openings therein sized to accept the multiple electronic devices and having a first coefficient of thermal expansion (CTE), wherein the multiple electronic devices are located in the multiple openings in the perforated warp control sheet so that gaps are located between the edges of the electronic devices and edges of the openings, wherein the primary faces of the electronic devices are substantially co-planar with the first surface of the perforated warp control sheet, and wherein the opposed rear faces of the multiple electronic devices are higher than the second surface of the perforated warp control sheet; and
cured plastic encapsulation material in the gaps and over the second surface of the perforated warp control sheet, wherein a characteristic of the plastic encapsulation material is that a second CTE of the plastic encapsulation material is different from the first CTE by 5% or more, so that a panel containing the multiple electronic devices and the perforated warp control sheet has a convex warp, wherein the primary faces are exposed at a first surface of the panel, and the first surface of the panel has a convex curve.
2. The assembly of claim 1 , wherein the perforated warp control sheet comprises nickel and iron.
3. The assembly of claim 1 , wherein the warp is less than 5% of a lateral extent of the panel.
4. The assembly of claim 3 , wherein the warp is less than about 2% of the lateral extent of the panel.
5. The assembly of claim 1 , wherein the first CTE in a range of 50-95% of the second CTE.
6. The assembly of claim 5 , wherein the first CTE in a range of 55-85% of the second CTE.
7. The assembly of claim 1 , wherein the first CTE is in a range of 6.5-12.4 ppm/° C.
8. The assembly of claim 1 , wherein the first CTE is in a range of 7.2-11.1 ppm/° C.
9. The assembly of claim 1 , further comprising:
one or more insulating layers at least over the primary electrical faces of the devices in the panel;
vias through some of the one or more insulating layers to various electrical contacts of the devices; and
conductors over one or more of the insulating layers and through one or more of the vias to interconnect various electrical contacts together or to external terminals or both, thereby providing an integrated electrical assembly.
10. An integrated electronic panel assembly (IEPA) having multiple electronic devices, comprising:
a warp control plane having a first surface, an opposed second surface, and openings therein adapted to receive multiple electronic devices, wherein the warp control plane has a first coefficient of thermal expansion (CTE) that is different from a second CTE by 5% or more;
the multiple electronic devices with first faces having bonding pads thereon, opposed rear faces, and edges extending between the first faces and rear faces, wherein the multiple electronic devices are located in the openings in the warp control plane with their bonding pads oriented toward the first surface, and wherein a gap separates the edges of each of the multiple electronic devices from each opening in the warp control plane;
cured plastic encapsulation having the second CTE over the opposed second surface of the warp control plane and between edges of the multiple electronic devices and the openings in the warp control plane, wherein the cured plastic encapsulation substantially fixes the multiple electronic devices and the warp control plane in the encapsulation, thereby forming a panel of multiple electronic devices that has a convex warp, wherein the first faces of the multiple electronic devices are exposed at a first surface of the panel, and the first surface of the panel has a convex curve.
11. The assembly of claim 10 , wherein the warp control plane comprises a nickel-iron alloy with between 40-52% nickel.
12. The assembly of claim 10 , wherein the first CTE is in a range of 50-95% of the second CTE.
13. The assembly of claim 10 , wherein the first CTE is in a range of 55-85% of the second CTE.
14. The assembly of claim 10 , wherein the warp control plane has an opposed second surface, and wherein the opposed rear faces of the multiple electronic devices are higher than the second surface of the warp control plane.
15. The assembly of claim 10 , further comprising:
one or more insulating layers at least over the first faces of the multiple electronic devices in the panel;
vias through some of the one or more insulating layers to various electrical contacts of the devices; and
conductors over one or more of the insulating layers and through one or more of the vias to interconnect various electrical contacts together or to external terminals or both, thereby providing the IEPA.