Flexible circuit board assembly with common heat spreader and method of manufacture

Claim 2

A flexible substrate for a circuit board, comprising: one or more flexible wiring layers of conductive metal; one or more flexible, dielectric layers including one separating any respective adjacent pair of the wiring layers and forming connected layers; means including one or more additional flexible metal wiring layers attached on only selected parts of one or more major exterior surfaces of the substrate to define thicker, stiffer areas of more complex circuitry with such additional layers and to define more flexible bend areas without such additional layers for bending the circuit board through only the flexible areas about a line; one or more metal heat spreader plates attached to the thicker sections; and conductive vias connecting between the wiring layers in the stiffer areas.

Claim 3

The substrate of claim 2 which is bent with a smaller radius at bend areas than in the functional islands.

Claim 4

The substrate of claim 2 or 3 in which the dielectric layers include polyimide film.

Claim 5

The substrate of claim 4 in which the polyimide film is about 0.025 mm thick.

Claim 6

The substrate of any one of claims 2 to 5 in which the dielectric layers are laminated to the wiring layers using an adhesive, preferably a film adhesive approximately 0.025 mm thick.

Claim 7

The substrate of any one of claims 2 to 6 in which metal wiring layers include copper foil of uniform thickness patterned to form electrical circuits.

Claim 8

The substrate of claim 7 in which the copper foil includes a foil approximately 0.018 mm thick.

Claim 9

The substrate of any one of claims 2 to 8 in which one of the additional wiring layers on the stiffer sections of each of two major exterior surfaces of the substrate consists of chemically or electrically deposited copper, preferably including layers approximately 0.025 mm thick.

Claim 10

The substrate of any one of claims 2 to 9 in which the conductive vias include one or more via holes made through the substrate being internally plated with chemically or electrically deposited copper.

Claim 11

The substrate of claim 10 in which the via holes include holes approximately 0.025 mm in diameter and are plated with the same deposited copper layer included in an outer wiring layer on each of two major surfaces of the substrate.

Claim 12

The substrate of any one of claims 2 to 11 further comprising an additional flexible dielectric layer for each additional wiring layer extending only on said stiffer functional islands.

Claim 13

The substrate of any one of the claims 2 to 12 in which the thicker areas include one or more arrays of electrical connections at an external dielectric layer for directly connecting a chip with a mirror image array of connection pads.

Claim 14

The substrate of any one of claims 2 to 12 in which the thicker areas include one or more rectangular windows through the thicker areas surrounded by wirebond connection pads for connecting a wirebond chip in the windows.

Claim 15

The substrate of any one of claims 2 to 14 further comprising: a core of polyimide film about 0.025 mm thick with two major surfaces; first layers of film adhesive about 0.025 mm thick on each on a major surface of the core; layers of copper film about 0.018 mm thick with first major surfaces of each connected by the first adhesive layers to each major surface of the core; second layers of film adhesive about 0.025 mm thick each on a second major surface of each copper layer; external layers of polyimide film about 0.025 mm thick each with a major internal surface connected by the second layers of film adhesive to each second major surface of the copper layers; holes formed through the substrate; a layer of copper, chemically or electrically deposited in the through holes, and about 0.018 mm thick selectively on a major external surface of each external layer of polyimide film and defining thicker, stiffer areas of the substrate and more flexible, thinner areas for bending the substrate; a layer of solder mask on an exterior major surface of each layer of deposited copper at the thicker areas; one or more arrays of electrical connections on at least one major surface of the substrate for connecting direct connection chips; and one or more linear rows of wirebond pads forming a rectangle about every wirebond window for connecting wirebond chips.

Claim 16

A circuit board comprising: a flexible substrate including: at least one flexible wiring layer; and at least one flexible dielectric layer including a layer to separate any adjacent pairs of wiring layer and an exterior dielectric layer with windows; and connector means at the windows in the dielectric for electrically connecting pins or leads to the wiring layer; one or more components of a first height on the exterior dielectric layer with leads connected to the connector means; one or more components of a second, greater height on the exterior dielectric layer with leads connected to connector means.

Claim 17

The circuit board of claim 16 in which the connection array of a chip is soldered to a connection array of the substrate, preferably by soldered flip chip interconnections.

Claim 18

The circuit board of claim 16 or 17 in which the connection between a chip and the substrate is encapsulated with electrically non-conductive plastic.

Claim 19

The circuit board of any one of claims 16 to 18 in which the heat sink includes an aluminum plate.

Claim 20

The circuit board of any one of claims 16 to 19 further comprising: one or more rectangular windows extending through the substrate at a heat sink; wirebond pads in rectangular rows encircle the windows on the surface of the substrate opposite from the heat sink; a chip with wirebond pads on a first major surface and positioned in the window with a second major surface of the chip bonded to the heat sink; bonded wires connecting between respective wirebond pads of the chip and substrate; and a plastic encapsulant encapsulating the bonded wires, wirebond pads on the substrate and the wirebond chip.

Claim 21

A circuit board comprising: a flexible substrate including: multiple wiring layers; multiple dielectric layers including a layer to separate each adjacent pair of wiring layer and an exterior dielectric layer on a first major surface of the substrate; a rectangular window extending through the substrate; and wirebond pads in a rectangular row encircling the window on a second major surface of the substrate opposite the first major surface; a heat sink with a first major surface laminated to a part of the first major surface of the substrate at the window; a wirebond chip extending through the window with a first major surface adhesively attached to the first major surface of the heat sink and with wirebond pads on a second major surface of the chip opposite to the first major surface of the chip; wires connecting between wirebond pads of the chip and substrate; and plastic encapsulant covering the wires, wirebond pads of the substrate and second major surface of the chip.

Claim 22

The circuit board of claim 21 in which an adhesive between the wirebond chip and the heat sink is a thermally conductive plastic.

Claim 23

A circuit board, comprising: a substrate including: multiple flexible wiring layers of conductive metal; one or more flexible dielectric layers including one separating each adjacent pair of the wiring layers forming a substrate of connected layers; one or more additional flexible metal wiring layers attached on only selected parts of one or more major exterior surfaces of the substrate and which define thicker, stiffer areas of more complex circuitry with such additional layers and define more flexible bend areas without such additional layers through which the circuit board can be bent about a line; conductive vias connecting between wiring layers in the stiffer areas; and one or more additional flexible dielectric layers attached on only the thicker stiffer areas; components connected to each of the thicker, stiffer areas of the substrate; two heat sink plates each with a first major surface attached on a first surface of the substrate to each of two adjacent thicker, stiffer areas of the substrate separated by a bend area for allowing the substrate to bend to move the heat sink plates together with a second major surface of each heat sink plate in adjacent confronting position; means for connecting the heat sinks together to form a single structure with a second major surface of each heat sink plate in adjacent confronting position; and means for attaching the heat sink structure to a frame for conducting heat out of the heat sink structure.

Claim 24

The circuit board of claim 23 in which means for connecting the heat sinks together include: a first heat sink plate has one or more threaded holes in one edge; and a second heat sink plate which includes: an edge flange with respective through holes through which screws can be inserted to screw into the threaded holes of the first heat sink to connect the heat sinks together; and one or more threaded holes in one edge for connection to perpendicular frame member.

Claim 25

A flexible substrate for a circuit board, comprising: a lamellar structure with multiple flexible metal wiring layers and multiple flexible dielectric layers including a dielectric layer between each adjacent wiring layer; via holes through the substrate in parts selected to be thicker, stiffer areas; metal plating the through holes and forming one or more additional flexible metal wiring layers only on selected parts of the major exterior of the substrate which define thicker, stiffer areas of more complex circuitry with such additional layers and more flexible bend areas without such additional layers and through which the substrate can be bent about a line; and a metal heat spreader plate attached to one of the thicker, stiffer areas.

Claim 26

The substrate of claim 25 in which the lamellar structure further comprises: a layer of film adhesive positioned between adjacent metal wiring and dielectric layers.

Claim 27

The substrate of claim 25 or 26 further comprising one or more additional dielectric layers deposited only on the thicker, stiffer areas of the substrate.

Claim 28

The substrate of any one of claims 25 to 27, further comprising copper foils patterned to produce the wiring layers.

Claim 29

The substrate of any one of claims 25 to 28, further comprising rectangular windows through the substrate and in which the additional wiring layers include an external wiring layer with wirebond pads in rectangular lines about the windows.

Claim 30

A flexible circuit board, comprising: a flexible circuit board substrate with multiple wiring layers and windows through the circuit board with wirebond connection pads near the window; and a heat sink plate laminated to the circuit board at the windows; wirebond chips positioned in the windows and bonded onto the heat sink plate; bonding wires extending between pads on the wirebond chip and wirebond pads on the circuit board at the window; and encapsulant enclosing the wirebond chip bonding wires, and wirebond pads with an organic material.