# US 9,883,580 B1 · Printed circuit board that provides a direct thermal path between components and a thermal layer and method for assembly

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- Number: US 9,883,580 B1
- Document ID: US9883580B1
- Status: Granted
- Kind: B1
- Application number: 14/684,245
- Filed: 2015-04-10
- Granted: 2018-01-30
- Earliest claimed: 2014-04-11
- Assignees: Adura Led Solutions, LLC
- Applicants: SinkPAD, LLC
- Inventors: Kalu K. Vasoya
- Web page: https://patentgrep.com/patent/US9883580B1

## CPC

- H05K 1/0207: {using internal conductor planes parallel to the surface for thermal conduction, e.g. power planes}
- H05K 3/3452: Solder masks
- F21K 9/20: Light sources comprising attachment means
- F21K 9/90: Methods of manufacture
- H05K 1/0204: {using means for thermal conduction connection in the thickness direction of the substrate (H05K1/0207 takes precedence)}
- H05K 1/0206: {by printed thermal vias}
- H05K 1/0209: {External configuration of printed circuit board adapted for heat dissipation, e.g. lay-out of conductors, coatings}
- H05K 1/111: {Pads for surface mounting, e.g. lay-out}
- H05K 1/181: associated with surface mounted components
- H05K 3/301: {by means of a mounting structure (H05K3/325 takes precedence)}
- H10H 20/857: Interconnections, e.g. lead-frames, bond wires or solder balls
- H10W 90/00: Package configurations
- F21Y 2101/00: Point-like light sources
- H05K 2201/10106: Light emitting diode [LED]
- H05K: PRINTED CIRCUITS; CASINGS OR CONSTRUCTIONAL DETAILS OF ELECTRIC APPARATUS; MANUFACTURE OF ASSEMBLAGES OF ELECTRICAL COMPONENTS
- F21K: NON-ELECTRIC LIGHT SOURCES USING LUMINESCENCE; LIGHT SOURCES USING ELECTROCHEMILUMINESCENCE; LIGHT SOURCES USING CHARGES OF COMBUSTIBLE MATERIAL; LIGHT SOURCES USING SEMICONDUCTOR DEVICES AS LIGHT-GENERATING ELEMENTS; LIGHT SOURCES NOT OTHERWISE PROVIDED FOR
- H10H: INORGANIC LIGHT-EMITTING SEMICONDUCTOR DEVICES HAVING POTENTIAL BARRIERS
- H10W: GENERIC PACKAGES, INTERCONNECTIONS, CONNECTORS OR OTHER CONSTRUCTIONAL DETAILS OF DEVICES COVERED BY CLASS H10
- F21Y: INDEXING SCHEME ASSOCIATED WITH SUBCLASSES F21K, F21L, F21S and F21V, RELATING TO THE FORM OR THE KIND OF THE LIGHT SOURCES OR OF THE COLOUR OF THE LIGHT EMITTED

## Abstract

A method of assembling a component to a printed circuit board that includes a thermal layer and a circuit layer separated by a dielectric layer. The circuit layer includes circuit pads that correspond to terminal surfaces on the component. The dielectric layer includes an aperture that exposes a portion of the thermal layer that correspond to a thermal pad on the component. Solder paste is applied to the circuit pads and the exposed thermal layer. Lower surfaces of the solder paste are in contact with the circuit pads and the thermal layer and upper surfaces of the solder paste are substantially coplanar. The component is placed on the solder paste. The printed circuit board and the component are heated to create solder joints between the terminal surfaces on the component and the circuit pads and between the thermal pad on the component and the thermal layer.

## Claims

### Claim 1

A method of assembling a plurality of surface mount components to a printed circuit board, the method comprising:
providing the printed circuit board that includes
a circuit layer including circuit pads that correspond to terminal surfaces on the plurality of surface mount components,
a thermal layer that provides a thermal surface to be joined to a thermal pad on each of the plurality of surface mount components, the thermal surface being recessed from the circuit pads,
a dielectric layer having a first side coupled to the circuit layer and an opposing second side coupled to the thermal layer, the dielectric layer including an aperture that exposes a portion of the thermal layer, and
a solder mask layer that coats portions of the circuit layer, the first side of the dielectric layer, and the exposed portion of the thermal layer, the solder mask layer coating the exposed portion of the thermal layer to create a plurality of small apertures that expose portions of the thermal layer in the dielectric layer aperture, each of the plurality of small apertures corresponding to the thermal pad on one of the plurality of surface mount components;
applying a solder paste to the circuit pads and the portion of the thermal layer exposed by the aperture;
placing the plurality of surface mount components on the solder paste; and
heating the printed circuit board and the plurality of surface mount components to create solder joints.

### Claim 2 (depends on 1)

The method of claim 1, wherein lower surfaces of the solder paste are in contact with the circuit pads and the thermal layer and upper surfaces of the solder paste are substantially coplanar.

### Claim 3 (depends on 1)

The method of claim 1, wherein the solder joints are between the terminal surfaces on the plurality of surface mount components and the circuit pads and between the thermal pad on each of the plurality of surface mount components and the thermal layer.

### Claim 4 (depends on 1)

The method of claim 1, wherein the plurality of surface mount components are placed on the solder paste such that the terminal surfaces on the plurality of surface mount components are in contact with the solder paste applied to the circuit pads and the thermal pad on each of the plurality of surface mount components are in contact with the solder paste applied to the thermal layer.

### Claim 5 (depends on 1)

The method of claim 1, wherein a first side of the thermal layer is a layer of copper and the first side of the thermal layer is coupled to the second side of the dielectric layer.

### Claim 6 (depends on 5)

The method of claim 5, wherein a layer of aluminum is coupled to the layer of copper on a second side of the layer of copper opposite the first side of the layer of copper.

### Claim 7 (depends on 1)

The method of claim 1, wherein the dielectric layer has a thickness of less than 75 micrometers (μm).

### Claim 8 (depends on 1)

The method of claim 1, wherein the solder paste is applied with a stencil having a thickness of between 120 and 160 micrometers (μm).

### Claim 9 (depends on 1)

The method of claim 1, wherein the solder paste is applied with a stencil having a thermal pad opening that is at least 95% of an area of the aperture that exposes the portion of the thermal layer.

### Claim 10 (depends on 9)

The method of claim 9, wherein the stencil has circuit pad openings with areas that are no more than 75% of areas of the corresponding circuit pads.

### Claim 11 (depends on 1)

The method of claim 1, wherein a perpendicular distance between the second side of the dielectric layer and a side of the circuit layer furthest from the dielectric layer is less than 130 micrometers (μm).

### Claim 12 (depends on 1)

The method of claim 1, wherein the terminal surfaces and the thermal pad on each of the plurality of surface mount components provide substantially coplanar surfaces that are placed on the solder paste.

### Claim 13 (depends on 1)

The method of claim 1, wherein the plurality of surface mount components are each an LED (light emitting diode).

### Claim 14

A printed circuit board comprising:
a circuit layer including circuit pads that correspond to terminal surfaces on a plurality of surface mount components;
a thermal layer that provides a thermal surface to be joined to a thermal pad on each of the plurality of surface mount components, the thermal surface being recessed from the circuit pads;
a dielectric layer having a first side coupled to the circuit layer and an opposing second side coupled to the thermal layer, the dielectric layer including an aperture that exposes a portion of the thermal layer; and
a solder mask layer that coats portions of the circuit layer, the first side of the dielectric layer, and the exposed portion of the thermal layer, the solder mask layer coating the exposed portion of the thermal layer to create a plurality of small apertures that expose portions of the thermal layer in the dielectric layer aperture, each of the plurality of small apertures corresponding to the thermal pad on one of the plurality of surface mount components.

### Claim 15 (depends on 14)

The printed circuit board of claim 14, wherein the thermal layer includes a layer of copper that is coupled to the second side of the dielectric layer.

### Claim 16 (depends on 15)

The printed circuit board of claim 15, wherein the thermal layer further includes a layer of aluminum that is coupled to the layer of copper on an opposite side from the dielectric layer.

### Claim 17 (depends on 14)

The printed circuit board of claim 14, wherein the dielectric layer has a thickness of less than 75 micrometers (μm).

### Claim 18

An LED (light emitting diode) assembly comprising:
a plurality of surface mount LED components, each having one or more terminal surfaces and a thermal pad;
a printed circuit board that includes
a circuit layer including circuit pads that correspond to the terminal surfaces on the plurality of surface mount LED components,
a thermal layer that provides a thermal surface to be joined to the thermal pad on each of the plurality of surface mount LED components, the thermal surface being recessed from the circuit pads,
a dielectric layer having a first side coupled to the circuit layer and an opposing second side coupled to the thermal layer, the dielectric layer including an aperture that exposes a portion of the thermal layer, and
a solder mask layer that coats portions of the circuit layer, the first side of the dielectric layer, and the exposed portion of the thermal layer, the solder mask layer coating the exposed portion of the thermal layer to create a plurality of small apertures that expose portions of the thermal layer in the dielectric layer aperture, each of the plurality of small apertures corresponding to the thermal pad on one of the plurality of surface mount LED components;
a first solder layer that directly couples the circuit pads to the terminal surfaces on the plurality of surface mount LED components; and
a second solder layer that directly couples the thermal layer to the thermal pad on each of the plurality of surface mount LED components, the second solder layer being thicker than the first solder layer.

### Claim 19 (depends on 18)

The LED assembly of claim 18, wherein the thermal layer includes a layer of copper that is coupled to the second side of the dielectric layer.

### Claim 20 (depends on 19)

The LED assembly of claim 19, wherein the thermal layer further includes a layer of aluminum that is coupled to the layer of copper on an opposite side from the dielectric layer.

### Claim 21 (depends on 18)

The LED assembly of claim 18, wherein the dielectric layer has a thickness of less than 75 micrometers (μm).

### Claim 22 (depends on 18)

The LED assembly of claim 18, wherein a perpendicular distance between the second side of the dielectric layer and a side of the circuit layer furthest from the dielectric layer is less than 130 micrometers (μm).