Build-up printed wiring board substrate having a core layer that is part of a circuit
View Patent ↗Integrated circuits and processes for manufacturing integrated circuits are described that use printed wiring board substrates having a core layer that is part of the circuit of the printed wiring board. In a number of embodiments, the core layer is constructed from a carbon composite. In several embodiments, techniques are described for increasing the integrity of core layers in designs calling for high density clearance hole drilling. One embodiment of the invention includes a core layer that includes electrically conductive material and at least one build-up wiring portion formed on an outer surface of the core layer. In addition, the build-up portion comprises at least one micro wiring layer including a circuit that is electrically connected to the electrically conductive material in the core layer via a plated through hole.
1. A printed wiring board substrate, comprising:
a core layer that includes a carbon plate;
a layer of metal that is clad by resin to one side of the carbon plate and thereby defines the outer surface of the core layer;
wherein the layer of metal includes an interior surface from which protrusions (dendrites) extend, and a plurality of the protrusions (dendrites) contact the carbon plate; and
at least one build-up wiring portion formed on the layer of metal;
wherein the build-up portion includes a dielectric layer comprising non-reinforced dielectric formed on the layer of metal; and
wherein the build-up portion comprises at least one micro wiring layer including a circuit that is electrically connected to the carbon plate in the core layer via a plated through hole.
2. The printed wiring board substrate of claim 1 , wherein the coefficient of thermal expansion of the core layer is lower than the coefficient of thermal expansion of the at least one build-up portion.
3. The printed wiring board substrate of claim 1 , wherein the core layer is configured to act as a ground plane.
4. The printed wiring board substrate of claim 1 , wherein the core layer is configured to act as a power plane.
5. The printed wiring board substrate of claim 1 , wherein the core layer is configured to act as a split power and ground plane.
6. The printed wiring board substrate of claim 1 , wherein the core layer comprises a first electrically conductive layer that is bonded to a second electrically conductive layer by a dielectric layer that electrically isolates the first layer from the second layer.
7. The printed wiring board substrate of claim 1 , wherein:
a second layer of metal is clad onto a second side of the carbon plate;
a second build-up wiring portion is formed on the second layer of metal;
a plated through hole connects a circuit on a micro wiring layer in the first build up wiring portion with a circuit on a micro wiring layer in the second build up wiring portion; and
the plated through hole is electrically isolated form the electrically conductive material in the core layer by a resin filled clearance hole.
8. The printed wiring board substrate of claim 1 , wherein the core layer has a coefficient of thermal expansion of between 0 ppm/° C. and 12 ppm/° C. in the surface spreading direction.
9. The printed wiring board substrate of claim 8 , wherein the core layer has a coefficient of thermal expansion of between 0 ppm/° C. and 9 ppm/° C. in the surface spreading direction.
10. The printed wiring board substrate of claim 1 , wherein the core layer has a thermal conductivity of between 2 W/m·K and 500 W/m·K in the surface spreading direction.
11. The printed wiring board substrate of claim 1 , wherein the core layer has a thermal conductivity of between 50 W/m·K and 1000 W/m·K in the surface spreading direction.
12. The printed wiring board substrate of claim 1 , wherein the core layer has a tensile modulus of between 5 msi and 35 msi in the surface spreading direction.
13. The printed wiring board substrate of claim 1 , wherein the core layer has a tensile modulus of between 10 msi and 40 msi in the surface spreading direction.
14. The printed wiring board substrate of claim 1 , wherein the core layer has a dielectric constant that is greater than 6.0 at 1 MHz.
15. The printed wiring board of claim 1 , wherein the core layer has a thickness that is at least 30% of the thickness of the printed wiring board substrate.
16. The printed wiring board of claim 1 , wherein the layer of metal includes an exterior surface that is planar.