LED connectors are not the “sexiest” of design components in a lighting fixture, but they can have a major impact on thermal path design, efficiency of production, and LED fixture certification time. Avnet’s Mark Mousseau shares design tips for better LED connector selection.
Design decisions in the eco-system of an LED fixture are numerous and have multiple positive and negative effects on the overall lighting system efficacy, functionality, and certification time. One of the areas most commonly overlooked in the design process of LED fixtures is the selection of the proper LED connectors. LED connectors are not the “sexiest” of design components in a lighting fixture, but their selection can have a major impact on thermal path design, efficiency of production, and LED fixture certification time.
LED connector selection can often be an afterthought of the modern LED fixture designer unless there are specific requirements outlined by an OEM’s end customer or within the installation code of the particular lighting fixture. Little thought is given to the time and money that can be saved in the certification process, design time, and time-to-market strategy of a project in an industry where LEDs and fixture efficiencies are changing on a quarterly basis. That’s a mistake because there are, in fact, savings to be had and efficiencies to be gained.
Thermal design is one of the most important constraints an engineer must conquer when designing an efficient LED lighting fixture. An efficient thermal design can minimize losses in luminous intensity and can maximize LED component life over time. Both of these factors lead to a successful and efficient LED fixture design. With the move in LED technology from discrete layout light engines to chip-on-board (CoB) LEDs, LED connector selection has become critical in the design process for most lighting engineers.
There is one critical design constraint that must be considered when selecting the proper LED connector solution for a CoB design – thermal transfer. A designer must select the connector that will maintain even pressure over the entire area of the LED to maximize thermal interface and conductive heat transfer from the LED to the thermal paste and heatsink. A poor thermal interface between these three components can lead to thermal spotting, loss of thermal interface, and catastrophic failure of the LED.
A good example of an LED connector solution designed to meet these criteria is the TE Connectivity Type 50 or Type 50Z CoB connector. These single-piece Zhaga-compliant connectors allow for even pressure over the entire upper mechanical surface of the LED because of the one-piece design and mechanical snap-in LED retention cavity. These features allow even pressure and complete interface between the CoB LED, the thermal paste, and the heatsink, creating an efficient conductive thermal path for transfer of heat away from the LED.
The selection of a connector for an LED fixture design can have a major impact on the production efficiency and assembly of a lighting fixture. Most LED lighting fixtures consist of a power supply, light engine, and heatsink, which all need to be connected. Maximizing the mechanical package in an LED lighting fixture is critically important, and the correct LED connector selection can help in this design step by reducing space while making assembly of the lighting fixture easier in production. An example of this would be the TE Connectivity Through-Board SMT connector, which allows the designer to mount the connector on the same side of board as the directional LEDs, while it still protrudes through the bottom of the LED board for connection to the wires from the power supply through the heatsink. The flat-top design will not interfere with secondary optics and makes ease of fixture assembly simpler in production while maximizing mechanical space.
The UL certification process of an LED fixture can be long and costly, and improper LED connector selection can lead to unforeseen engineering expenses, lengthen certification time, and cause a delay in new product introductions. It is no secret that most LED-designated connectors are actually repurposed electronics connectors that meet the design needs of the lighting market. This also means that not all of the LED connectors available for selection in lighting fixtures have the proper certification or recognitions needed for implementation in a UL-compliant lighting fixture. When selecting an LED connector for design into an LED fixture, make sure the manufacturer has obtained the proper certifications needed. An example of a product that would have these certifications is the AVX 9159 series board-to-board LED connector, which can be used to daisy-chain multiple LED boards and has UL approval up to 3A. Using a product like this will cut down on UL certification time and limit the need to track down material declarations during the certification process with a non-compliant component.
Tackling these three simple design considerations for LED connectors on the front end can help with thermal path design, efficiency of production, and LED fixture certification time when designing an LED fixture. They can also save time and money in the design process.
Mark Mousseau is senior illumineer at Avnet Electronics Marketing Americas.