Last July Nordson DIMA participated in a test case for potting SMT LED's for Osram Opto Semiconductors with one component RTV silicone material from Dow Corning®. The main purpose of the potting tests was to verify and test the suitability of the potting material concerning the use in LED video wall application, especially with low height SMT LEDs with a tight pitch.
Some extracts from the Test Case Appliation Note:
With the move into the digital age, outdoor signs and video walls are becoming more and more common. Nowadays these electronic signs can be seen in stadiums, as street bill boarding or advertising on buildings in cities, bus stops, gas stations, etc.As many of these applications have contact with the outdoor environment, protection of the electrical components including the LED leads is a must.
Numerous potting materials could be dispensed to protect the LED metal contacts from the environment, such as Polyurethane, Acrylic, Silicone, etc. The ever decreasing dimensions of LED packages allow smaller pitches and require different potting solutions.Of the many products available on the market the one-component black RTV silicone SE-9187L from Dow Corning® has been selected, based on its low viscosity for enhanced flow and self-leveling to achieve a homogenous and flat coating. Furthermore, the very low surface energy of silicone will allow the material to efficiently wet out the substrate into the tiniest corners of the components creating a good coverage.
The selection of the best possible equipment is based on the type of material (mainly one-component or two-component), the size of the products/title, the required accuracy and repeatability of the application and the required cycle time per product. Secondary the required investment should also not be forgotten - investment in the initial equipment, as well as daily maintenance costs. Here, the Nordson DIMA Dispense Master DD-500 in combination with the Nordson DIMA DD-5131 dispense valve were selected since small quantities but high varieties of different shapes have to be performed.
The machine was a good candidate for the test because it is flexible, the boards can be placed manually and it is an easy to operate desktop system. This desktop robot is a XYZ-system that is capable of handling boards up to 400 x 600 mm with a dispensing work area of 320 x 420 mm and a Z-stroke of 87 mm. The total size of the system is 700 x 700 x 550 mm (LxBxH). The maximum speed of the system is 80 mm/sec and the accuracy is at 150 microns. The Nordson DIMA DD-5131 dispense valve (suitable for 1K or 2K compounds) can be mounted to the gantry with a head that can move in the XYZ-direction. The camera is a standard feature in this machine that makes programming more user-friendly but it is not necessary for the process.
During the tests the camera helped to program the dispense positions. Other systems available on the market provide in-line capabilities, higher speed, better accuracy and a larger work envelope. The better machines for in-line capabilities, such as the Dispenser Elite line from Nordson DIMA provides higher speeds (10x faster dispensing as compared to the Dispense Master line), larger sample area and other technical features such as extremely good accuracy that provide fast in-line performance.
Read the complete Application Note below: