1. Field of the Invention
This invention relates to a surface mount light emitting diode (LED) and holder.
2. Description of Prior Art
a-c and
a-d show various views of a prior art through hole LED holder. Through hole LED holders are typically inserted into holes drilled into printed circuit boards (PCB) and mechanically joined to the PCB via a latch. Through hole LED holders need not, but may, be soldered to the PCB. While through hole mounting generally provides strong mechanical bonds, the drilling step results in additional manufacturing expense. Through hole mounting also limits the available routing area for signal traces on layers immediately below the top layer on multilayer boards since the holes must pass through all layers to the opposite side of the board.
A surface mounted LED and holder according to this invention includes a high temperature plastic holder surrounding an LED with improved wire bond strength resulting in thermal protection to survive the reflow soldering process.
A surface mounted LED according to a preferred embodiment of this invention includes an LED and a holder. The holder preferably includes a plurality of feet arranged at approximately equal intervals around the perimeter of a base of the holder. The feet are preferably positioned to correspond with a preferred solder pad layout for attaching the surface mount LED to a substrate using conventional reflow soldering techniques. In addition, the holder preferably includes a plurality of through holes permitting use in connection with a variety of two, three and four lead LEDs.
As manufacturing turns to surface mounted technology instead of traditional through hole technology, a demand is anticipated for reliable surface mounted LED assemblies. Relevant industries include automotive, telecommunications, industrial, signage and/or any other industry requiring incorporation of improved LED assemblies.
Costs savings may be realized by moving away from a through hole device to a surface mounted device. Additionally, wave soldering may be avoided through the use of the described configuration of the device. The device according to this invention will preferably withstand reflow soldering exposure to 255 degrees C. for 10 seconds.
The above-mentioned and other features and objects of this invention will be better understood from the following detailed description taken in conjunction with the drawings wherein:
a-c show a top view, a side view and a reflow profile of a prior art surface mount LED;
a-d show a perspective view, a top view, a side view and a top view of a PCB cutout for a prior art through hole LED holder;
LED 12 may be either a single-color or multi-color LED with any number of leads 13 but generally include two to four leads 13. Single-color LEDs generally include two leads 13 while multi-color LEDs generally include three or four leads 13. LED 12 should be able to withstand reflow soldering exposure to 255 degrees C. for 10 seconds. LED 12 may include a standard leadframe, alternatively LED 12 may include a leadframe with a smaller foot print. In one preferred embodiment, the leadframe has a 0.4×0.5 mm sq. foot print. To minimize failure of LED 12 during the reflow soldering process, pull strength of a bond wire of LED 12 may be improved. The pull strength can be improved with a thicker wire bond and/or by adding an extra ball bond on top of a wedge bond on the leadframe side.
Holder 14 preferably comprises a high temperature plastic and is preferably molded of a polyphenylene sulfide (PPS) material or similar material capable of withstanding high temperatures and impact. The high temperature plastic should preferably withstand reflow soldering exposure to 255 degrees C. for 10 seconds.
According to a preferred embodiment of this invention, base 16 further includes lower surface 18 and at least one and preferably a plurality of supports 19. In
According to a preferred embodiment of this invention, holder 14 includes at least one through hole 24, 34, 44, 54 and preferably a plurality of through holes permitting use in connection with a variety of two, three and four lead LEDs. Additionally, holder 14 preferably includes at least one channel 26, 36, 46, 56 and preferably a plurality of channels formed in lower surface 18. Each channel connects with either one or two through holes. Preferably, each channel is distinct and does not intersect with any other channel. Each channel preferably forms an opening in a side of holder 14 and adjacent to a corresponding wrap section.
In the embodiment shown in
In operation, an LED is inserted into holder 14 in advance of the reflow soldering operation.
Referring to
As a result of the described wrap, four contact points 21, 31, 41 and 51 are formed near each foot 20, 30, 40 and 50. These four contact points 21, 31, 41 and 51 correspond with a solder pad layout, shown in
As shown in
While in the foregoing specification this invention has been described in relation to certain preferred embodiments thereof, and many details have been set forth for purpose of illustration, it will be apparent to those skilled in the art that the LED holder is susceptible to additional embodiments and that certain of the details described herein can be varied considerably without departing from the basic principles of the invention.
This Application is based on International Application Number PCT/US2009/033028, filed Feb. 4, 2009, and claims priority from US Application No. 61/030,763, filed Feb. 22, 2008, the disclosures of which are hereby incorporated by reference herein in their entirety.
Filing Document | Filing Date | Country | Kind | 371c Date |
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PCT/US2009/033028 | 2/4/2009 | WO | 00 | 8/20/2010 |
Publishing Document | Publishing Date | Country | Kind |
---|---|---|---|
WO2009/105334 | 8/27/2009 | WO | A |
Number | Name | Date | Kind |
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4507718 | Bury | Mar 1985 | A |
5324962 | Komoto et al. | Jun 1994 | A |
6386733 | Ohkohdo et al. | May 2002 | B1 |
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6787435 | Gibb et al. | Sep 2004 | B2 |
7472565 | Heldoorn | Jan 2009 | B1 |
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Number | Date | Country |
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61-202484 | Sep 1986 | JP |
Entry |
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ISR for PCT/US2009/033028 mailed Mar. 16, 2009. |
Number | Date | Country | |
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20110147785 A1 | Jun 2011 | US |
Number | Date | Country | |
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61030763 | Feb 2008 | US |