Patent Application
20130001596
The present application relates generally to providing electrostatic discharge (ESD) protection on printed circuit boards, and, more particularly, to providing such protection in light emitting diode (LED) systems.
Damage to electronic components resulting from electrostatic discharge can pose a serious problem for high technology companies. The financial cost of such damages can sometimes exceed ten percent of annual gross sales by some estimates and can affect productivity and product reliability across a broad spectrum of the electronics industry.
LEDs are one type of electronic component subject to damage by ESD. ESD damage can occur during manufacturing, handling, packaging or installation. Large numbers of LEDs are often aggregated onto modules to create lighting systems which require ESD protection. What is needed, therefore, is an ESD protection mechanism that can be incorporated into these modules with minimal impact on the complexity and cost of the manufacturing process while simultaneously providing a high degree of protection and reliability.
Reference should be made to the following detailed description which should be read in conjunction with the following figures, wherein like numerals represent like parts:
Light emitting diodes (LEDs), a type of optoelectronic device, are vulnerable to damage by electrostatic discharge (ESD). One method of protecting these devices is to place a reversed diode in parallel with a single LED, a string of LEDs or even an array of LEDs.
Directly depositing ESD diodes, in the form of conductive polymers, onto the flexible substrate PCB also simplifies the ability to handle minor modifications to the LED layout or module design after a PCB design has been finalized.
The ESD diodes may be deposited on the flexible substrate in a thin film array comprising a structure of multiple layers. As will be understood by those skilled in the art, each physical vapor deposition process includes a plurality of associated parameters whose nominal values may be selected and/or adjusted to yield a thin film structure with one or more desired properties. As used herein, use of the term “nominal” or “nominally” when referring to an amount means a designated or theoretical amount that may vary from the actual amount. For example, process parameters associated with pulsed laser deposition include temperature, deposition pressure, laser repetition rate, total number of laser pulses, and the gas environment to grow the films, e.g. N2, H2, Ar or forming gas. The nominal value(s) of one or more parameters chosen may depend on the substrate material, a desired thickness of the thin film structure and/or a desired surface characteristic (e.g., uniform or non-uniform) of the thin film structure. Nominal value(s) of the parameters may be adjusted during the deposition process to thereby change one or more characteristics of the thin film structure.
Providing the ability to deposit ESD diodes directly on a substrate allows the PCB designer to place as many ESD protection points as needed, thereby protecting all LEDs and electronic devices on the circuit.
According to one aspect of the disclosure, there is provided a method of providing electro-static discharge (ESD) protection to a plurality of light emitting diodes (LEDs) wherein the plurality of LEDs are deposited on a flexible substrate, the method including: providing an ESD diode; and depositing the ESD diode on the flexible substrate in proximity to the plurality of LEDs. The deposition process may be a chemical vapor deposition, metalorganic chemical vapor deposition, pulsed laser deposition, atomic layer deposition, spatial atomic layer deposition, direct writing via positive displacement dispensing, ink-jet or aerosol jetting. The proximity of placement the ESD diode to the LED as well as the number of ESD diodes to be deposited may be determined by the degree of ESD protection required. The ESD diodes may be fabricated from conductive polymers.
According to another aspect of the disclosure, there is provided a light source including: a module comprising a flexible substrate; a plurality of light emitting diodes (LEDs) deposited on the module; and an electrostatic discharge (ESD) diode deposited on the module in proximity to the plurality of LEDs.
While the principles of the invention have been described herein, it is to be understood by those skilled in the art that this description is made only by way of example and not as a limitation as to the scope of the invention. Other embodiments are contemplated within the scope of the present invention in addition to the exemplary embodiments shown and described herein. Modifications and substitutions by one of ordinary skill in the art are considered to be within the scope of the present invention, which is not to be limited except by the following claims.
