The invention may take form in various components and arrangements of components, and in various process operations and arrangements of process operations. The drawings are only for purposes of illustrating preferred embodiments and are not to be construed as limiting the invention. The drawings of the light emitting packages are not to scale.
With reference to
The chip carrier 14 is preferably substantially thermally conductive. At least the top principal surface 26 of the chip carrier 14 is substantially electrically insulating. The chip carrier 14 can be made of an electrically insulating material such as semi-insulating silicon, a ceramic, or a thermally conductive but electrically insulating plastic. Alternatively, the chip carrier 14 can be made of an electrically conductive material with an insulating layer or coating applied at least to the top principal surface 26. For example, the chip carrier 14 can be made of conductive silicon with a silicon dioxide layer disposed on the top principal surface 26, or the chip carrier 14 can be made of a metal with an insulator disposed on the top principal surface 26, or so forth.
The electrically conductive layers 20, 22 extend away from the die attach region where the light emitting chip 12 is flip chip bonded. Lead frame elements 40, 42, which are electrically conductive and electrically isolated from one another, are secured to and electrically contact portions of the electrically conductive layers 20, 22 distal from the die attach region. The lead frame 40, 42 is attached to the top principal surface 26 of the chip carrier 14. The lead frame element 40 includes an electrical lead 46 distal from the chip carrier 14 and a bend 48 such that the lead 46 is approximately coplanar with a bottom principal surface 50 of the chip carrier 14. Similarly, the lead frame element 42 includes an electrical lead 52 distal from the chip carrier 14 and a bend 54 such that the lead 52 is approximately coplanar with the bottom principal surface 50 of the chip carrier 14. Electrical and physical bonding of the lead frame elements 40, 42 to the top principal surface 26 of the chip carrier 14 is suitably achieved by solder bonds 54, 56. The lead frame 40, 42 is suitably made of copper or another highly conductive material.
An overmolding or encapsulant 60 is disposed over the light emitting chip 12 and the top principal surface 26 of the chip carrier 14, and also encapsulates a portion of the lead frame elements 40, 42 proximate to the chip carrier 14. The leads 46, 52 of the lead frame 40, 42 as well as the bottom principal surface 50 of the chip carrier 14 extend outside of the encapsulant 60. Optionally, a wavelength-converting phosphor layer 62 coats the encapsulant 60 and fluorescently or phosphorescently converts light emitted by the light emitting chip 12 to another wavelength or range or plurality of wavelengths.
The chip carrier 14 and the light emitting chip 12 and lead frame 40, 42 bonded to the top principal surface 26 of the chip carrier 14, together with the optional encapsulant 60 and phosphor layer 62, collectively define a surface mountable unit that is surface-mounted on a printed circuit board 70. In the example embodiment of
In one embodiment, the attachment bonding the leads 46, 52 to the terminals 80, 82 and the attachment bonding the bottom principal surface 50 of the chip carrier 14 to the thermal terminal 84 are the same. For example, these attachments can all be made by solder bonds in a single bonding process. Alternatively, a different type of attachment is used for bonding the bottom principal surface 50 of the chip carrier 14 to the thermal terminal 84 as compared with the type of attachment used for bonding the leads 46, 52 to the terminals 80, 82. In this latter approach, the thermal attachment of the chip carrier 14 and the electrical attachments of the leads 46, 52 can be separately optimized for thermal and electrical conductance, respectively.
As in the package 10, at least the top principal surface 126 of the chip carrier 114 is electrically insulating, while the chip carrier 114 can be either electrically insulating, or electrically conductive with an insulator layer providing the electrically insulating top principal surface 126. The chip carrier 114 is also preferably substantially thermally conductive. The lead frame 140, 142 is electrically conductive, and is suitably made of copper or another metal. The package 110 as illustrated does not include an encapsulant or phosphor; however, these components are optionally added. If an encapsulant is added, the bottom principal surface 150 of the chip carrier 114 and the leads 146, 152 of the leads should extend outside of the encapsulant.
Advantageously, the light emitting package 110 does not include wire bonds. Rather, electrical connection between the lead frame 140, 142 and the light emitting chip 112 is through the conductive layers 120, 122. As best seen in
With reference to
Lead frame elements 240, 242 are soldered or otherwise electrically contacted and mechanically bonded with the conductive layers 220, 222 disposed on the top principal surface of the chip carrier 214. Similarly to the corresponding lead frame elements of the packages 10, 110, the lead frame elements 240, 242 each include a bend 248, 254 so that electrical leads 246, 252 are approximately coplanar with a bottom principal surface of the chip carrier 214. Similarly to the package 10, an encapsulant 260 encapsulates the light emitting chip 212, the wire bond 290, the top principal surface of the chip carrier 214, and portions of the lead frame elements 240, 242, while the leads 246, 252 and the bottom principal surface of the chip carrier 214 extend outside of the encapsulant 260. Moreover, the light emitting package 210 includes a phosphor coating 262.
While phosphor-coated encapsulants are shown in
With reference to
Lead frame elements 340, 342 are soldered or otherwise electrically contacted and mechanically bonded with the conductive layers 320, 322 disposed on the top principal surface of the chip carrier 314. Similarly to the corresponding lead frame elements of the packages 10, 110, the lead frame elements 340, 342 each include a bend 348, 354 so that electrical leads 346, 352 are approximately coplanar with a bottom principal surface of the chip carrier 314, so that the light emitting chip package 310 can be surface mounted by soldering or otherwise connecting the leads 346, 352 of the lead frame elements 340, 342 to a printed circuit board or other support. Preferably, the surface mounting also includes forming a solder bond or other thermal contact between the bottom principal surface of the chip carrier 314 and the printed circuit board or other support. Although no encapsulant or phosphor is included in the light emitting package 310, it will be appreciated that an encapsulant, phosphor, optical components, or the like are optionally included.
In another embodiment, the light emitting chips 312B, 312D are replaced by zener diodes connected across the gaps 328, 330, respectively. The zener diodes provide electrostatic discharge protection for the light emitting chips 312A, 312C. Moreover, it will be appreciated that other electronic components can be similarly added along with interconnecting circuitry defined by conductive areas on the top principal surface of the chip carrier 314. Such other electronic components can regulate behavior of the light emitting chips, for example by providing input voltage conditioning, current limiting, or the like.
With reference to
Lead frame elements 440, 442 are soldered or otherwise electrically contacted and bonded with the conductive layers 420, 422 disposed on the top principal surface of the chip carrier 414. Similarly to the corresponding lead frame elements of the packages 10, 110, the lead frame elements 440, 442 each include a bend 448, 454 so that electrical leads 446, 452 are approximately coplanar with a bottom principal surface of the chip carrier 414, so that the light emitting chip package 410 can be surface mounted by soldering or otherwise connecting the leads 446, 452 to a printed circuit board or other support. Preferably, the surface mounting also includes forming a solder bond or other thermal contact between the bottom principal surface of the chip carrier 414 and the printed circuit board or other support. Although no encapsulant or phosphor is included in the light emitting package 410, it will be appreciated that an encapsulant, phosphor, optical components, or the like are optionally included.
In
The light emitting packages described herein are suitably constructed using electronic packaging processes. One example process is as follows. The process preferably starts with a chip carrier wafer which will be diced to produce a large number of light emitting packages each including a chip carrier diced from the chip carrier wafer. If the chip carrier is electrically conductive, it is preferably coated, oxidized, or otherwise processed to form an electrically insulating layer at least on the top principal surface. Two or more patterned conductive layers are formed on the top principal surface of the chip carrier using metal evaporation, electroplating, or the like in conjunction with lithographic techniques that define the electrically isolating gaps between the conductive layers. These patterned conductive layers are the electrical terminal conductive layers, such as the layers 20, 22 of the package of
Each chip carrier produced by the dicing is processed in the example process as follows. The top principal surface of the chip carrier is soldered to the lead frame. Preferably, the two lead frame elements are secured together by tabs or other fasteners during this soldering, and in one embodiment a number of such lead frames are secured together in a linear or two-dimensional array to facilitate automated processing. A transfer molding process is used to form the encapsulant over the light emitting chips, the top principal surface of the chip carrier, and portions of the lead frame. The molding die is designed so that the leads and the bottom principal surface of the chip carrier extend outside the molded encapsulant. The tabs of the lead frames are then cut or trimmed to electrically separate the lead frame elements to produce the final light emitting package that is suitable for surface mounting by soldering or the like.
The invention has been described with reference to the preferred embodiments. Obviously, modifications and alterations will occur to others upon reading and understanding the preceding detailed description. It is intended that the invention be construed as including all such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.
This application claims the benefit of U.S. provisional application Ser. No. 60/527,969 filed on Dec. 9, 2003.
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/US04/41392 | 12/9/2004 | WO | 00 | 3/29/2007 |
Number | Date | Country | |
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60527969 | Dec 2003 | US |