Reflective solder mask layer for LED phosphor package
A mounting substrate ( 40 ) has a patterned metal layer defining a plurality of top metal bond pads for bonding to bottom metal bond pads of LED dies. A solder mask layer ( 52 ) is formed over the mounting substrate, where the mask has openings that expose the top metal bond pads and protects metal traces on the substrate. The mask layer is a highly reflective white paint. The exposed top metal bond pads are then wetted with solder. The LED dies' bottom metal bond pads are then soldered to the exposed top metal bond pads, such that the mask layer surrounds each LED die to reflect light. A reflective ring ( 60 ) is affixed to the substrate to surround the LED dies. A viscous phosphor material ( 62 ) then partially fills the ring and is cured. All downward light by the LED dies and phosphor is reflected upward by the ring and solder mask layer.
1. A light emitting device comprising:
a light emitting diode (LED) die having a plurality of electrodes formed thereon;
a mounting substrate having a patterned metal layer defining at least one metal bond pad;
a dielectric solder mask layer disposed on the at least one metal bond pad of the mounting substrate, the mask layer having a plurality of openings that expose portions of the at least one bond pad, the mask layer being formed of a reflective material that reflects at least 90% of visible light and restricts deposited molten solder to the plurality of openings;
solder disposed in the plurality of openings of the mask layer and in contact with the at least one metal bond pad of the mounting substrate and respective electrodes of the plurality of electrodes of the LED die such that the at least one metal bond pad of the LED die is soldered to the at least one other metal bond pad, wherein the mask layer completely surrounds the LED die and is disposed under the LED die between the plurality of electrodes to reflect light;
a pre-formed ring that is affixed to the solder mask layer, the ring having reflective internal walls that extend above the height of the first LED die and surround the LED die;
a wavelength conversion material at least partially filling the ring such that the wavelength conversion material covers the LED die and a portion of the mask layer; and
a lens disposed over the LED die that separates the wavelength conversion layer from the LED die.
2. The device of claim 1 , wherein the LED die comprises LED semiconductor layers mounted on a submount.
3. The device of claim 1 , wherein the first wavelength conversion material comprises a phosphor.
4. The device of claim 1 , wherein the wavelength conversion material comprises quantum dots.
5. The device of claim 1 , wherein the reflective ring serves as a mold for the wavelength conversion material.
6. The device of claim 1 , wherein the reflective material comprises a white paint.
7. The device of claim 1 , wherein the reflective material comprises reflective particles in a binder.
8. The device of claim 1 , further comprising:
a plurality of other LED dies having associated metal bond pads,
wherein the patterned metal layer on the mounting substrate defines a plurality of metal bond pads corresponding to the metal bond pads of the other LED dies,
wherein the mask layer has a plurality of openings that expose at least a portion of each of the plurality of metal bond pads of the mounting substrate corresponding to the metal bond pads of the other LED dies, and
wherein the plurality of metal bond pads of the plurality of other LED dies are bonded to the exposed at least the portion of the plurality of metal bonds pads of the mounting substrate corresponding to the metal bond pads of the other LED dies, such that the mask layer surrounds each of the plurality of other LED dies.
9. The device of claim 8 , wherein the patterned metal layer interconnects the LED die and the plurality of other LED dies and is covered by the mask layer.
10. A method of forming a light emitting structure comprising:
providing a mounting substrate having a patterned metal layer defining a plurality of metal bond pads;
depositing a dielectric solder mask layer on the plurality of metal bond pads, the mask layer having a plurality of openings that expose at least a portion of each of the plurality of metal bond pads, the mask layer being formed of a reflective material that reflects at least 90% of visible light and restricts deposited molten solder to the plurality of openings; and
bonding a respective electrode of a plurality of electrodes of associated light emitting diode (LED) dies to the exposed at least a portion of each of the plurality of metal bond pads of the mounting substrate by applying molten solder to fill the plurality of openings in the mask layer such that the mask layer completely surrounds each of the plurality of LED dies and is disposed under the LED die between the plurality of electrodes to reflect light;
providing a pre-formed ring having reflective internal walls;
affixing the pre-formed ring to the solder mask layer, such that the reflective internal walls of the ring extend above the height of the LED dies and surround the LED dies;
at least partially filling the ring with a wavelength conversion material such that the wavelength conversion material covers the LED dies and a portion of the mask layer; and
providing a lens over the LED die that separates the wavelength conversion material from the LED die.